WorldWideScience

Sample records for exergy

  1. Exergy analysis

    DEFF Research Database (Denmark)

    Dovjak, M.; Simone, Angela; Kolarik, Jakub

    2011-01-01

    al. (1998). The effect of different levels of RH, Ta and effective clothing insulation on human body exergy balance chain, changes in human body exergy consumption rate (hbExCr) and predicted mean vote (PMV) index were analyzed. The results show that thermal comfort conditions do not always results....... Hot and dry and cold and dry conditions have similar hbExCr. The difference appears, if the whole human body exergy balance chain is taken into consideration. To maintain comfortable conditions it is important that exergy consumption and stored exergy are at optimal values with a rational combination...

  2. Exergy sustainability.

    Energy Technology Data Exchange (ETDEWEB)

    Robinett, Rush D. III (.; ); Wilson, David Gerald; Reed, Alfred W.

    2006-05-01

    Exergy is the elixir of life. Exergy is that portion of energy available to do work. Elixir is defined as a substance held capable of prolonging life indefinitely, which implies sustainability of life. In terms of mathematics and engineering, exergy sustainability is defined as the continuous compensation of irreversible entropy production in an open system with an impedance and capacity-matched persistent exergy source. Irreversible and nonequilibrium thermodynamic concepts are combined with self-organizing systems theories as well as nonlinear control and stability analyses to explain this definition. In particular, this paper provides a missing link in the analysis of self-organizing systems: a tie between irreversible thermodynamics and Hamiltonian systems. As a result of this work, the concept of ''on the edge of chaos'' is formulated as a set of necessary and sufficient conditions for stability and performance of sustainable systems. This interplay between exergy rate and irreversible entropy production rate can be described as Yin and Yang control: the dialectic synthesis of opposing power flows. In addition, exergy is shown to be a fundamental driver and necessary input for sustainable systems, since exergy input in the form of power is a single point of failure for self-organizing, adaptable systems.

  3. Human Body Exergy Metabolism

    OpenAIRE

    Mady, Carlos Eduardo Keutenedjian

    2013-01-01

    The exergy analysis of the human body is a tool that can provide indicators of health and life quality. To perform the exergy balance it is necessary to calculate the metabolism on an exergy basis, or metabolic exergy, although there is not yet consensus in its calculation procedure. Hence, the aim of this work is to provide a general method to evaluate this physical quantity for human body based on indirect calorimetry data. To calculate the metabolism on an exergy basis it is necessary to d...

  4. Quantifying global exergy resources

    International Nuclear Information System (INIS)

    Hermann, Weston A.

    2006-01-01

    Exergy is used as a common currency to assess and compare the reservoirs of theoretically extractable work we call energy resources. Resources consist of matter or energy with properties different from the predominant conditions in the environment. These differences can be classified as physical, chemical, or nuclear exergy. This paper identifies the primary exergy reservoirs that supply exergy to the biosphere and quantifies the intensive and extensive exergy of their derivative secondary reservoirs, or resources. The interconnecting accumulations and flows among these reservoirs are illustrated to show the path of exergy through the terrestrial system from input to its eventual natural or anthropogenic destruction. The results are intended to assist in evaluation of current resource utilization, help guide fundamental research to enable promising new energy technologies, and provide a basis for comparing the resource potential of future energy options that is independent of technology and cost

  5. Pitfalls of Exergy Analysis

    Science.gov (United States)

    Vágner, Petr; Pavelka, Michal; Maršík, František

    2017-04-01

    The well-known Gouy-Stodola theorem states that a device produces maximum useful power when working reversibly, that is with no entropy production inside the device. This statement then leads to a method of thermodynamic optimization based on entropy production minimization. Exergy destruction (difference between exergy of fuel and exhausts) is also given by entropy production inside the device. Therefore, assessing efficiency of a device by exergy analysis is also based on the Gouy-Stodola theorem. However, assumptions that had led to the Gouy-Stodola theorem are not satisfied in several optimization scenarios, e.g. non-isothermal steady-state fuel cells, where both entropy production minimization and exergy analysis should be used with caution. We demonstrate, using non-equilibrium thermodynamics, a few cases where entropy production minimization and exergy analysis should not be applied.

  6. EXERGY OF TEXTILE MATERIALS

    Directory of Open Access Journals (Sweden)

    V. N. Romaniuk

    2015-01-01

    Full Text Available The article presents solution for the task of evaluating exergy of the substance in the flow for textile and woven fabrics based on thermodynamic analysis of the corresponding technical systems. The exergy method allows estimating the energy effectiveness for the most problematic heat-technological systems of substance transformation and thus outlining the ways for decreasing the electric-power component in the production prime cost. The actuality of the issue stems from the renowned scenario alteration on the world energy market and is aggravated by necessity of retaining and building up the export potential of the light industry as an important component of the republic national-economic complex. The exergy method has been here for quite a long time and saw the interest fading and appearing again with periodicity of the research-generations alternation. Cooling down of every new generation towards the specified method is explained mostly by unresolved problem of the exergy evaluation for diverse materials, which poses a problem in the course of analysis of the substance transformation systems. The specified problem as a general rule does not create obstacles for energyconversion systems. However, the situation with substance-transformation systems is by far more complicated primarily due to diversity of the materials and respectively of the specification peculiarities of such component of the substance exergy in the flow as chemical component. Abeyance of conclusion in finding the chemical component of the substance exergy does not allow performing thermodynamic valuation of the energy provision for the heat-technological process in full measure. Which complicates the matters of decision-making and finding a medium for reduction of their energy consumption. All stated above relates to the textile industry and in the first instance to the finishing production departments.The authors present the exergy-evaluation problem solution for the

  7. Exergy destruction in ammonia scrubbers

    NARCIS (Netherlands)

    Zisopoulos, Filippos K.; Goot, van der Atze Jan; Boom, Remko M.

    2018-01-01

    A theoretical ammonia scrubbing process by sulfuric acid solution is assessed with the concept of exergy. The exergy destruction of chemical neutralization is mainly (75–94%) due to changes in the chemical exergy of streams and thermal effects from the reaction while mixing effects have a limited

  8. Molar exergy and flow exergy of pure chemical fuels

    International Nuclear Information System (INIS)

    Zanchini, Enzo; Terlizzese, Tiziano

    2009-01-01

    Expressions of the molar exergy and of the molar flow exergy of a pure chemical fuel are deduced rigorously from the basic principles of thermodynamics. It is shown that molar exergy and molar flow exergy coincide when the temperature T and the pressure p of the fuel are equal to the temperature T B and the pressure p B of the environment; a general relation between exergy and flow exergy is proved as a consequence. The deduction of the expression of the molar exergy of a chemical fuel for non-standard values of T B and p B is clarified. For hydrogen, carbon dioxide and several hydrocarbons, tables are reported to allow a simple calculation of the molar exergy of the fuel for any value of the temperature T B and the relative humidity φ B of the environment, in the range 268.15 K ≤ T B ≤ 313.15 K and 0.1 ≤ φ B ≤ 1, with reference to the standard atmospheric pressure. Additional tables are provided to evaluate the difference between the exergy or the flow exergy of the fuel in its given initial state and the exergy at T = T B and p = p B . In these tables, it is assumed that fuel and environment have the same temperature and that the fuel pressure varies in the range 1.01325 bar ≤ p ≤ 200 bar; the fuel may be gas or liquid.

  9. Exergy in School?

    Directory of Open Access Journals (Sweden)

    Tomaž Kranjc

    2017-04-01

    Full Text Available Students at all levels of physics instruction have difficulties dealing with energy, work and heat in general and, in particular, with the concepts of efficiency and ideal heat engine, and the maximum performance of refrigerators and heat pumps (Cochran & Heron, 2006; Bucher, 1986. The reason for the difficulties is an insufficient understanding of the second law of thermodynamics (Kesidou & Duit, 1992. In order to make these topics less difficult, the concept of exergy — well established as a powerful analytical tool in technical thermodynamics — describing the “quality” of energy, seems in our judgment to be worthy of inclusion in the physics curriculum at all levels. Its introduction does not add another law. It facilitates the understanding of irreversibilities (as the destruction of exergy and gives a deeper meaning to the second law. In the treatment of heat engines the second-law efficiency throws a new light on the notions of an ideal and a real engine (similarly for a refrigerator or a heat pump. Exergy introduces, in a natural way, a distinction between various forms of energy according to its quality — availability for performing work. “Energy reserves”, which can be better understood with the help of exergy, are of practical interest. From the thermodynamic point of view, a more correct term would be “availability reserves”; all around us, there are huge quantities of energy (in atmosphere, in oceans etc, but of very limited availability, i.e., of limited exergy. In order to identify common misconceptions and difficulties encountered by students in the learning of the first and second law of thermodynamics, particularly in connection with heat engines and similar cyclic devices, we conducted a combined research among students of the Primary School Education at the Faculty of Education (UPR PeF and of Biodiversity, Bioinformatics and Mediterranean Agriculture at the Faculty of Mathematics, Natural Sciences and

  10. The Exergy of Lift and Aircraft Exergy Flow Diagrams

    OpenAIRE

    Paulus, Jr., David; Gaggioli, Richard

    2010-01-01

    Aside from incidental, auxiliary loads, in level flight the principal load on the aircraft propulsion engine is the power required to provide the continuous lift. To construct an exergy flow diagram for an aircraft – for example, for the purpose of pinpointing inefficiencies and for costing – an expression is needed for the exergy delivered to and by the wings. That is, an expression is needed for the exergy of lift. The purpose of this paper is to present an expression de...

  11. Modeling the exergy behavior of human body

    International Nuclear Information System (INIS)

    Keutenedjian Mady, Carlos Eduardo; Silva Ferreira, Maurício; Itizo Yanagihara, Jurandir; Hilário Nascimento Saldiva, Paulo; Oliveira Junior, Silvio de

    2012-01-01

    Exergy analysis is applied to assess the energy conversion processes that take place in the human body, aiming at developing indicators of health and performance based on the concepts of exergy destroyed rate and exergy efficiency. The thermal behavior of the human body is simulated by a model composed of 15 cylinders with elliptical cross section representing: head, neck, trunk, arms, forearms, hands, thighs, legs, and feet. For each, a combination of tissues is considered. The energy equation is solved for each cylinder, being possible to obtain transitory response from the body due to a variation in environmental conditions. With this model, it is possible to obtain heat and mass flow rates to the environment due to radiation, convection, evaporation and respiration. The exergy balances provide the exergy variation due to heat and mass exchange over the body, and the exergy variation over time for each compartments tissue and blood, the sum of which leads to the total variation of the body. Results indicate that exergy destroyed and exergy efficiency decrease over lifespan and the human body is more efficient and destroys less exergy in lower relative humidities and higher temperatures. -- Highlights: ► In this article it is indicated an overview of the human thermal model. ► It is performed the energy and exergy analysis of the human body. ► Exergy destruction and exergy efficiency decreases with lifespan. ► Exergy destruction and exergy efficiency are a function of environmental conditions.

  12. Exergy conversion in the Japanese society

    International Nuclear Information System (INIS)

    Wall, G.

    1989-01-01

    In this paper exergy concept is reviewed as a tool for resource accounting. Conversions of energy and material resources in the Japanese society are described in terms of exergy. Necessary concepts and conventions are introduced. Exergy losses in transformations of material resources and in conversions of various forms of energy are described in some detail

  13. Exergy Evaluation of Desalination Processes

    Directory of Open Access Journals (Sweden)

    Veera Gnaneswar Gude

    2018-06-01

    Full Text Available Desalination of sea or brackish water sources to provide clean water supplies has now become a feasible option around the world. Escalating global populations have caused the surge of desalination applications. Desalination processes are energy intensive which results in a significant energy portfolio and associated environmental pollution for many communities. Both electrical and heat energy required for desalination processes have been reduced significantly over the recent years. However, the energy demands are still high and are expected to grow sharply with increasing population. Desalination technologies utilize various forms of energy to produce freshwater. While the process efficiency can be reported by the first law of thermodynamic analysis, this is not a true measure of the process performance as it does not account for all losses of energy. Accordingly, the second law of thermodynamics has been more useful to evaluate the performance of desalination systems. The second law of thermodynamics (exergy analysis accounts for the available forms of energy in the process streams and energy sources with a reference environment and identifies the major losses of exergy destruction. This aids in developing efficient desalination processes by eliminating the hidden losses. This paper elaborates on exergy analysis of desalination processes to evaluate the thermodynamic efficiency of major components and process streams and identifies suitable operating conditions to minimize exergy destruction. Well-established MSF, MED, MED-TVC, RO, solar distillation, and membrane distillation technologies were discussed with case studies to illustrate the exergy performances.

  14. Exergy analysis for combined regenerative Brayton and inverse Brayton cycles

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Zelong; Chen, Lingen; Sun, Fengrui [College of Naval Architecture and Power, Naval University of Engineering, Wuhan 430033 (China)

    2012-07-01

    This paper presents the study of exergy analysis of combined regenerative Brayton and inverse Brayton cycles. The analytical formulae of exergy loss and exergy efficiency are derived. The largest exergy loss location is determined. By taking the maximum exergy efficiency as the objective, the choice of bottom cycle pressure ratio is optimized by detailed numerical examples, and the corresponding optimal exergy efficiency is obtained. The influences of various parameters on the exergy efficiency and other performances are analyzed by numerical calculations.

  15. Exergy analysis for combined regenerative Brayton and inverse Brayton cycles

    OpenAIRE

    Zelong Zhang, Lingen Chen, Fengrui Sun

    2012-01-01

    This paper presents the study of exergy analysis of combined regenerative Brayton and inverse Brayton cycles. The analytical formulae of exergy loss and exergy efficiency are derived. The largest exergy loss location is determined. By taking the maximum exergy efficiency as the objective, the choice of bottom cycle pressure ratio is optimized by detailed numerical examples, and the corresponding optimal exergy efficiency is obtained. The influences of various parameters on the exergy efficien...

  16. Exergy method technical and ecological applications

    CERN Document Server

    Szargut, J

    2005-01-01

    The exergy method makes it possible to detect and quantify the possibilities of improving thermal and chemical processes and systems. The introduction of the concept ""thermo-ecological cost"" (cumulative consumption of non-renewable natural exergy resources) generated large application possibilities of exergy in ecology. This book contains a short presentation on the basic principles of exergy analysis and discusses new achievements in the field over the last 15 years. One of the most important issues considered by the distinguished author is the economy of non-renewable natural exergy.

  17. Exergy analysis of the LFC process

    International Nuclear Information System (INIS)

    Li, Qingsong; Lin, Yuankui

    2016-01-01

    Highlights: • Mengdong lignite was upgraded by liquids from coal (LFC) process at a laboratory-scale. • True boiling point distillation of tar was performed. • Basing on experimental data, the LFC process was simulated in Aspen Plus. • Amounts of exergy destruction and efficiencies of blocks were calculated. • Potential measures for improving the LFC process are suggested. - Abstract: Liquid from coal (LFC) is a pyrolysis technology for upgrading lignite. LFC is close to viability as a large-scale commercial technology and is strongly promoted by the Chinese government. This paper presents an exergy analysis of the LFC process producing semicoke and tar, simulated in Aspen Plus. The simulation included the drying unit, pyrolysis unit, tar recovery unit and combustion unit. To obtain the data required for the simulation, Mengdong lignite was upgraded using a laboratory-scale experimental facility based on LFC technology. True boiling point distillation of tar was performed. Based on thermodynamic data obtained from the simulation, chemical exergy and physical exergy were determined for process streams and exergy destruction was calculated. The exergy budget of the LFC process is presented as a Grassmann flow diagram. The overall exergy efficiency was 76.81%, with the combustion unit causing the highest exergy destruction. The study found that overall exergy efficiency can be increased by reducing moisture in lignite and making full use of physical exergy of pyrolysates. A feasible method for making full use of physical exergy of semicoke was suggested.

  18. Exergy analysis of HTGR-GT

    International Nuclear Information System (INIS)

    Cao Jianhua; Wang Jie; Yang Xiaoyong; Yu Suyuan

    2005-01-01

    The High Temperature Gas-cooled Reactor (HTGR) coupled with gas turbine for high efficiency in electricity production is supposed to be one of the candidates for the future nuclear power plants. The HTGR gas turbine cycle is theoretically based on the Brayton cycle with recuperated, intercooled and precooled sub-processes. In this paper, an exergy analysis of the Brayton Cycle on HTGR is presented. The analyses were done for four typical reactor outlet temperatures and the exergy loss distribution and exergy loss ratio of each sub-process was quantified. The results show that more than a half of the exergy loss takes place in the reactor, while the low pressure compressor (LPC), the high pressure compressor (HPC) and the intercooler denoted by compress system together, play a much small role in the contribution of exergy losses. With the rise of the reactor outlet temperature, both the exergy loss and exergy loss ratio of the reactor can be greatly cut down, so is the total exergy loss of the cycle; while the exergy loss ratios of the recuperator and precooler have a small rise. The total exergy efficiency of the cycle is quite high (50% more or less). (authors)

  19. Exergy accounting - the energy that matters

    Energy Technology Data Exchange (ETDEWEB)

    Fachina, V. [Petroleo do Brasil S.A. (PETROBRAS), Rio de Janeiro, RJ (Brazil)], E-mail: vicentefachina@petrobras.com.br

    2009-07-01

    The exergy concept is introduced by utilizing a general framework on which are based the model equations. An exergy analysis is performed on a case study: a control volume for a power module is created by comprising gas turbine, reduction gearbox, AC generator, exhaustion ducts and heat regenerator. The implementation of the equations is carried out by collecting test data of the equipment data sheets from the respective vendors. By utilizing an exergy map, one proposes both mitigating and contingent countermeasures for maximizing the exergy efficiency. An exergy accounting is introduced by showing how the exergy concept might eventually be brought up to the traditional money accounting. At last, one devises a unified approach for efficiency metrics in order to bridge the gaps between the physical and the economical realms. (author)

  20. Energy, Exergy and Advanced Exergy Analysis of a Milk Processing Factory

    DEFF Research Database (Denmark)

    Bühler, Fabian; Nguyen, Tuong-Van; Jensen, Jonas Kjær

    2016-01-01

    integration, an exergy analysis pinpoints the locations, causes and magnitudes of thermodynamic losses. The advanced exergy analysis further identifies the real potential for thermodynamic improvements of the system by splitting exergy destruction into its avoidable and unavoidable parts, which are related......, cream and milk powder. The results show the optimisation potential based on 1st and 2nd law analyses. An evaluation and comparison of the applicability of exergy methods, including advanced exergy methods, to the dairy industry is made. The comparison includes typical energy mappings conducted onsite......, and discusses the benefits and challenges of applying advanced thermodynamic methods to industrial processes....

  1. Exergy. Concept, challenges and usages for industry

    International Nuclear Information System (INIS)

    2013-04-01

    The increasing pressure on natural resources makes reduction of energy consumption a critical stake. The exergy concept offers a global, standard and rigorous framework to energy systems analysis, and as such, contributes to tackle the energy challenge. ENEA has released a publication that popularizes the exergy concept, explains its application within the energy efficiency field, and highlights its value for industrial actors

  2. Regional and global exergy and energy efficiencies

    Energy Technology Data Exchange (ETDEWEB)

    Nakicenovic, N; Kurz, R [International Inst. for Applied Systems Analysis, Laxenburg (Austria). Environmentally Compatible Energy Strategies (Ecuador) Project; Gilli, P V [Graz Univ. of Technology (Austria)

    1996-03-01

    We present estimates of global energy efficiency by applying second-law (exergy) analysis to regional and global energy balances. We use a uniform analysis of national and regional energy balances and aggregate these balances first for three main economic regions and subsequently into world totals. The procedure involves assessment of energy and exergy efficiencies at each step of energy conversion, from primary exergy to final and useful exergy. Ideally, the analysis should be extended to include actual delivered energy services; unfortunately, data are scarce and only rough estimates can be given for this last stage of energy conversion. The overall result is that the current global primary to useful exergy efficiency is about one-tenth of the theoretical maximum and the service efficiency is even lower. (Author)

  3. Exergy analysis of encapsulation of photochromic dye by spray drying

    Science.gov (United States)

    Çay, A.; Akçakoca Kumbasar, E. P.; Morsunbul, S.

    2017-10-01

    Application of exergy analysis methodology for encapsulation of photochromic dyes by spray drying was presented. Spray drying system was investigated considering two subsystems, the heater and the dryer sections. Exergy models for each subsystem were proposed and exergy destruction rate and exergy efficiency of each subsystem and the whole system were computed. Energy and exergy efficiency of the system were calculated to be 5.28% and 3.40%, respectively. It was found that 90% of the total exergy inlet was destroyed during encapsulation by spray drying and the exergy destruction of the heater was found to be higher.

  4. Exergy analysis of a MSF distillation plant

    International Nuclear Information System (INIS)

    Kahraman, Nafiz; Cengel, Yunus A.

    2005-01-01

    In this paper, a large MSF distillation plant in the gulf area is analyzed thermodynamically using actual plant operation data. Exergy flow rates are evaluated throughout the plant, and the exergy flow diagram is prepared. The rates of exergy destruction and their percentages are indicated on the diagram so that the locations of highest exergy destruction can easily be identified. The highest exergy destruction (77.7%) occurs within the MSF unit, as expected, and this can be reduced by increasing the number of flashing stages. The exergy destruction in the pumps and motors account for 5.3% of the total, and this also can be reduced by using high efficiency motors and pumps. The plant is determined to have a second law efficiency of just 4.2%, which is very low. This indicates that there are major opportunities in the plant to reduce exergy destruction and, thus, the amount of electric and thermal energy supplied, making the operation of the plant more cost effective

  5. EXERGY ANALYSIS OF PRODUCTION LINE CANDIED FRUIT

    Directory of Open Access Journals (Sweden)

    V. D. Dem'шanov

    2014-01-01

    Full Text Available Summary. The task of exergy analysis - evaluation based on the second law of thermodynamics, thermodynamic degree of technical perfection of the whole system, as well as to identify those stages of a technical process, which contains the bulk of the loss of exergy in order to improve its efficiency. Using exergy analysis allows to solve a wide range of technical problems on the basis of a unified thermodynamic methods. Exergy analysis was performed by the method whereby thermotechnological system candied fruit production, conventionally separated from the environment of the closed control surface. Exchange scheme under consideration thermotechnological candied fruit production material, thermal and energy flows to the environment, as well as between the control surfaces. Exergy in external input material streams: air and water and citric acid, as well as output streams without having increment Shih-exergy in the process of passing through the reference surface - of running air-water and after washing, are in thermodynamic equilibrium with the surroundings is zero. In the total number of internal exergy losses include losses from the final result of the temperature difference in the heat exchange between the raw material to be dried and heated air electromechanical arising from irreversible alteration of structural and mechanical properties of the product, and the hydraulic loss due to the sudden increase of the specific volume of air as it enters the working chamber dryer. The resulting exergy efficiency is 8.87 %, which is 3.7 % higher than when using the technology of the prototype based on solar air-dried product. This indicates an increase in the degree of perfection of the thermodynamic system by using microwave heating of the product in combination with the removal of moisture in the atmosphere low temperature coolant, which precludes significant outside exergy loss on drying step.

  6. Critical of the concept of exergy

    International Nuclear Information System (INIS)

    Mora Casal, Rene Alejandro

    2015-01-01

    Exergy is a concept that, since its invention sixty years ago, has gained popularity and has extended beyond engineering applications. However, a deep study of this concept reveals problems and inconsistencies, both of theoretical type and of application. Six problems are identified and discussed: ambiguous notation, ambiguous reference states, applicability to real processes, redundancy with respect to other thermodynamic properties, inconsistency between the concepts of exergy and lost work, and applicability of the exergetic analysis results. Some roads to solution for these problems are proposed, being the fifth one the most difficult to solve, as it requires a redefinition of exergy. (author) [es

  7. Exergy energy, environment and sustainable development

    CERN Document Server

    Dincer, Ibrahim; Rosen, Marc A

    2007-01-01

    This book deals with exergy and its applications to various energy systems and applications as a potential tool for design, analysis and optimization, and its role in minimizing and/or eliminating environmental impacts and providing sustainable development. In this regard, several key topics ranging from the basics of the thermodynamic concepts to advanced exergy analysis techniques in a wide range of applications are covered as outlined in the contents. - Comprehensive coverage of exergy and its applications - Connects exergy with three essential areas in terms of energy, environment and sustainable development - Presents the most up-to-date information in the area with recent developments - Provides a number of illustrative examples, practical applications, and case studies - Easy to follow style, starting from the basics to the advanced systems.

  8. Characterization and Exergy Analysis of Triphenyl Borate

    International Nuclear Information System (INIS)

    Acarali, N. B.

    2015-01-01

    In this study, unlike from the literature, boron oxide, borax decahydrate, boric acid and borax pentahydrate as boron sources were used to synthesize Triphenyl Borate (TPB). The reactions of TPB were carried out by using both phenol and various boron sources in inert water-immiscible organic solvent successfully. On the basis of analyzes (FT-IR, SEM, TGA/DSC) obtained, it was seen that phenol acted as a support to borate structure framework and thermal characterisation of the amorphous solid under determined conditions suggested that usage of different boron sources had effects for glass transition temperature in TPB production. The exergy analysis was performed to the TPB production to determine efficiency. The exergy analysis showed that the highest exergy efficiency was obtained by using boron oxide as a boron source. Consequently, all analyses results showed that TPB was produced successfully. Accordingly, characterization and exergy analysis supported each other. (author)

  9. Exergy Analysis of Complex Ship Energy Systems

    Directory of Open Access Journals (Sweden)

    Pierre Marty

    2016-04-01

    Full Text Available With multiple primary and secondary energy converters (diesel engines, steam turbines, waste heat recovery (WHR and oil-fired boilers, etc. and extensive energy networks (steam, cooling water, exhaust gases, etc., ships may be considered as complex energy systems. Understanding and optimizing such systems requires advanced holistic energy modeling. This modeling can be done in two ways: The simpler approach focuses on energy flows, and has already been tested, approved and presented; a new, more complicated approach, focusing on energy quality, i.e., exergy, is presented in this paper. Exergy analysis has rarely been applied to ships, and, as a general rule, the shipping industry is not familiar with this tool. This paper tries to fill this gap. We start by giving a short reminder of what exergy is and describe the principles of exergy modeling to explain what kind of results should be expected from such an analysis. We then apply these principles to the analysis of a large two-stroke diesel engine with its cooling and exhaust systems. Simulation results are then presented along with the exergy analysis. Finally, we propose solutions for energy and exergy saving which could be applied to marine engines and ships in general.

  10. Exergy of partially coherent thermal radiation

    International Nuclear Information System (INIS)

    Wijewardane, S.; Goswami, Yogi

    2012-01-01

    Exergy of electromagnetic radiation has been studied by a number of researchers for well over four decades in order to estimate the maximum conversion efficiencies of thermal radiation. As these researchers primarily dealt with solar and blackbody radiation, which have a low degree of coherence, they did not consider the partial coherence properties of thermal radiation. With the recent development of surface structures, which can emit radiation with high degree of coherence, the importance of considering the partial coherent properties in exergy calculation has become a necessity as the coherence properties directly influence the entropy of the wave field. Here in this paper we derive an expression for the exergy of quasi-monochromatic radiation using statistical thermodynamics and show that it is identical with the expressions derived using classical thermodynamics. We also present a method to calculate the entropy, thereby the exergy of partially coherent radiation using statistical thermodynamics and a method called matrix treatment of wave field. -- Highlights: ► Considered partial coherence of radiation for the first time to calculate exergy. ► The importance of this method is emphasized with energy conversion examples. ► Derived an expression for the exergy of radiation using statistical thermodynamics. ► Adopted a method to calculate intensity of statistically independent principle wave.

  11. Exergy analysis of industrial ammonia synthesis

    International Nuclear Information System (INIS)

    Kirova-Yordanova, Zornitza

    2004-01-01

    Exergy consumption of ammonia production plants depends strongly on the ammonia synthesis loop design. Due to the thermodynamically limited low degree of conversion of hydrogen-nitrogen mixture to ammonia, industrial ammonia synthesis is implemented as recycle process (so-called 'ammonia synthesis loop'). Significant quantities of reactants are recycled back to reactor, after the removal of ammonia at low temperatures. Modern ammonia synthesis plants use well-developed heat- and cold recovery to improve the reaction heat utilisation and to reduce the refrigeration costs. In this work, the exergy method is applied to estimate the effect of the most important process parameters on the exergy efficiency of industrial ammonia synthesis. A specific approach, including suitable definitions of the system boundaries and process parameters, is proposed. Exergy efficiency indexes are discussed in order to make the results applicable to ammonia synthesis loops of various designs. The dependence of the exergy losses on properly selected independent process parameters is studied. Some results from detailed exergy analysis of the most commonly used ammonia synthesis loop design configurations at a wide range of selected parameters values are shown

  12. Energy and exergy utilizations of the Chinese urban residential sector

    International Nuclear Information System (INIS)

    Liu, Yanfeng; Li, Yang; Wang, Dengjia; Liu, Jiaping

    2014-01-01

    Highlights: • The energy and exergy use in China’s urban residential sector between 2002 and 2011 are analyzed. • The primary locations and causes of energy and exergy losses in the CURS are identified. • The large gap between the energy and exergy efficiencies implies great potential for energy saving. • The exergy utilization can be improved by using appropriate technology, management and policy. - Abstract: In this paper, the energy and exergy utilizations in the Chinese urban residential sector (CURS) are analyzed by considering the energy and exergy flows for the years between 2002 and 2011. The energy and exergy efficiencies of this sector are calculated to examine the potential for advancing the ‘true’ energy efficiency and determine the real energy losses. The results demonstrate large differences between the overall energy efficiencies (62.8–70.2%) and the exergy efficiencies (11.0–12.2%) for the years analyzed. The sizable gap between the energy and exergy efficiencies implies a high potential for energy savings in the CURS. Future energy saving strategies should pay more attention to the improvement in exergy efficiencies. Moreover, it is found that direct fuel use constituted the primary exergy losses of the CURS; coal-fired boiler heating systems cause approximately 35% of the total exergy losses. Gas stoves, cogeneration systems, coal stoves and gas water heaters constitute 15.3%, 15%, 5.5% and 4.9% of the total exergy losses, respectively

  13. Exergy performance of human body under physical activities

    International Nuclear Information System (INIS)

    Mady, Carlos Eduardo Keutenedjian; Albuquerque, Cyro; Fernandes, Tiago Lazzaretti; Hernandez, Arnaldo José; Saldiva, Paulo Hilário Nascimento; Yanagihara, Jurandir Itizo; Oliveira, Silvio de

    2013-01-01

    The aim of this work is to apply performance indicators for individuals under physical activity based on the concepts of exergy destroyed and exergy efficiency. The cardiopulmonary exercise test is one of the most used tests to assess the functional capacity of individuals with varying degrees of physical training. To perform the exergy analysis during the test, it is necessary to calculate heat and mass flow rates, associated with radiation, convection, vaporization and respiration, determined from the measurements and some relations found in the literature. The energy balance allowed the determination of the internal temperature over time and the exergy variation of the body along the experiment. Eventually, it was possible to calculate the destroyed exergy and the exergy efficiency from the exergy analysis. The exergy rates and flow rates are dependent of the exercise level and the body metabolism. The results show that the relation between the destroyed exergy and the metabolism is almost constant during the test, furthermore its value has a great dependence of the subject age. From the exergy analysis it was possible to divide the subjects according to their training level, for the same destroyed exergy, subjects with higher lactate threshold can perform more work. - Highlights: • Exergy analysis was applied to the human body under physical activities. • Concept of maximum available work from ATP hydrolysis was compared with exergy analysis results. • For the same destroyed exergy, subjects with higher lactate threshold can perform more work. • Runners during physical activities tend to a state of minimum destroyed exergy and maximum exergy efficiency

  14. Adopting exergy analysis for use in aerospace

    Science.gov (United States)

    Hayes, David; Lone, Mudassir; Whidborne, James F.; Camberos, José; Coetzee, Etienne

    2017-08-01

    Thermodynamic analysis methods, based on an exergy metric, have been developed to improve system efficiency of traditional heat driven systems such as ground based power plants and aircraft propulsion systems. However, in more recent years interest in the topic has broadened to include applying these second law methods to the field of aerodynamics and complete aerospace vehicles. Work to date is based on highly simplified structures, but such a method could be shown to have benefit to the highly conservative and risk averse commercial aerospace sector. This review justifies how thermodynamic exergy analysis has the potential to facilitate a breakthrough in the optimization of aerospace vehicles based on a system of energy systems, through studying the exergy-based multidisciplinary design of future flight vehicles.

  15. Exergy analysis of photovoltaic solar collector

    International Nuclear Information System (INIS)

    Sopian, K.; Othman, M.Y.Hj.

    1998-01-01

    The exergy analysis (availability or second law analysis) is applied to the photovoltaic thermal solar collector. Photovoltaic thermal collector is a special type of solar collector where electricity and heat are produced simultaneously. The electricity produced from the photovoltaic thermal collector is all converted into useful work. The available quantity of the heat collected can readily be determined by taking into account both the quantity (heat quantity) and quality ( a function of temperature) of the thermal energy. Therefore, using the concept of exergy allows heat produced from the thermal collector and the electricity generated from the photovoltaic cells to be compared or to be evaluated on the basis of a common measure such as the effectiveness on solar energy collection or the total amount of available energy. In this paper, the effectiveness of solar energy collection is called combined photovoltaic thermal exergy efficiency. An experimental setup of a double pas photovoltaic thermal solar collector has been deigned, fabricated and tested. (author)

  16. Exergy outcomes associated with the greenhouse effects

    International Nuclear Information System (INIS)

    Valero, A.; Arauzo, I.

    1991-01-01

    In this paper the effect on the exergy of the Earth's fossil fuels if natural environmental conditions are changed due to the greenhouse effect is studied. The change considered here is a temperature rise produced as a result of increased CO 2 concentration. The temperature change due to the increase in CO 2 concentration is modeled in accordance with the most recent studies on the greenhouse effect. The result is that the ''average fossil fuel'', based on estimates of proven reserves, will lose 0.3% of its exergy if the atmospheric concentration of CO 2 doubles. Assuming that CO 2 concentration will double over the next hundred years, this 0.3% exergy loss of proven reserves means that we will lose as much capacity to produce work as primary energy was consumed in USA and Canada during 1988

  17. An exergy method for compressor performance analysis

    Energy Technology Data Exchange (ETDEWEB)

    McGovern, J A; Harte, S [Trinity Coll., Dublin (Ireland)

    1995-07-01

    An exergy method for compressor performance analysis is presented. The purpose of this is to identify and quantify defects in the use of a compressor`s shaft power. This information can be used as the basis for compressor design improvements. The defects are attributed to friction, irreversible heat transfer, fluid throttling, and irreversible fluid mixing. They are described, on a common basis, as exergy destruction rates and their locations are identified. The method can be used with any type of positive displacement compressor. It is most readily applied where a detailed computer simulation program is available for the compressor. An analysis of an open reciprocating refrigeration compressor that used R12 refrigerant is given as an example. The results that are presented consist of graphs of the instantaneous rates of exergy destruction according to the mechanisms involved, a pie chart of the breakdown of the average shaft power wastage by mechanism, and a pie chart with a breakdown by location. (author)

  18. Advances in exergy analysis: a novel assessment of the Extended Exergy Accounting method

    International Nuclear Information System (INIS)

    Rocco, M.V.; Colombo, E.; Sciubba, E.

    2014-01-01

    Highlights: • General overview of exergy-based methods for system analysis is presented. • Taxonomy for exergy-based methods classification is proposed. • Theoretical foundations and details of Extended Exergy Accounting are described. - Abstract: Objective: This paper presents a theoretical reassessment of the Extended Exergy Accounting method (EEA in the following), a comprehensive exergy-based analytical paradigm for the evaluation of the total equivalent primary resource consumption in a generic system. Our intent in this paper was to rigorously review the EEA theory and to highlight its double “valence” as a resource quantifier and to clarify its operative potential. On the one side, EEA can be properly regarded as a general “costing” theory based on a proper knowledge of the cumulative exergy consumption of different supply chains, economic systems and labour market: it is indeed the only method that translates externalities (capital, labour and environmental remediation) into cumulative exergetic costs and thus allows for their rigorous inclusion in a comprehensive resource cost assessment. Indeed, the extended exergy cost eec reflects both the thermodynamic “efficiency” of the production chain and the “hidden” resource costs for the society as a whole. From another, perhaps even more innovative, perspective, EEA can be viewed as a space and time dependent methodology since economic and labour costs can only be included in the Extended Exergy balance via their exergy equivalents (via two rigorously defined postulates). Since the equivalent exergy cost of the externalities depends both on the type of society and on the time window of the analysis, the extended exergy cost eec reflects in a very real sense both the thermodynamic “efficiency” of the machinery and the “conversion efficiency” of the specific society within which the analysis is performed. We argue that these two intrinsic features of the EEA method provide both

  19. Cumulative exergy losses associated with the production of lead metal

    Energy Technology Data Exchange (ETDEWEB)

    Szargut, J [Technical Univ. of Silesia, Gliwice (PL). Inst. of Thermal-Engineering; Morris, D R [New Brunswick Univ., Fredericton, NB (Canada). Dept. of Chemical Engineering

    1990-08-01

    Cumulative exergy losses result from the irreversibility of the links of a technological network leading from raw materials and fuels extracted from nature to the product under consideration. The sum of these losses can be apportioned into partial exergy losses (associated with particular links of the technological network) or into constituent exergy losses (associated with constituent subprocesses of the network). The methods of calculation of the partial and constituent exergy losses are presented, taking into account the useful byproducts substituting the major products of other processes. Analyses of partial and constituent exergy losses are made for the technological network of lead metal production. (author).

  20. Energy and exergy utilization in transportation sector of Saudi Arabia

    International Nuclear Information System (INIS)

    Dincer, I.; Hussain, M.M.; Al-Zaharnah, I.

    2004-01-01

    In this paper we present an analysis of energy and exergy utilization in the transportation sector of Saudi Arabia by considering the sectoral energy and exergy flows for the years of 1990-2001. Energy and exergy analyses are conducted for its three subsectors, namely road, air and marine, and hence the energy and exergy efficiencies are obtained for comparison. Road subsector appears to be the most efficient one compared to air and marine subsectors. It is found that the energy efficiencies in air and marine subsectors are found to be equal to the corresponding exergy efficiencies due to the values of exergy grade function. A comparison of the overall energy and exergy efficiencies of Saudi Arabian transportation sector with the Turkish transportation sector is also presented for the year 1993 based on the data available. Although the sectoral coverage is not same for both countries, it is still useful to illustrate the situation on how subsectoral energy and exergy efficiencies vary over the years. Turkish transportation sector appears to be a bit more efficient for that particular year. It is believed that the present technique is practical and useful for analyzing sectoral energy and exergy utilization to determine how efficient energy and exergy are used in transportation sector. It is also be helpful to establish standards, based on exergy, to facilitate applications in industry and in other planning processes such as energy planning

  1. Exergy analysis of the energy use in Greece

    International Nuclear Information System (INIS)

    Koroneos, Christopher J.; Nanaki, Evanthia A.; Xydis, George A.

    2011-01-01

    In this work, an analysis is being done on the concept of energy and exergy utilization and an application to the residential and industrial sector of Greece. The energy and exergy flows over the period from 1990 to 2004 were taken into consideration. This period was chosen based on the data reliability. The energy and exergy efficiencies are calculated for the residential and industrial sectors and compared to the findings of a previous study concerning the exergy efficiency of the Greek transport sector. The residential energy and exergy efficiencies for the year 2003 were 22.36% and 20.92%, respectively, whereas the industrial energy and exergy efficiencies for the same year were 53.72% and 51.34%, respectively. The analysis of energy and exergy utilization determines the efficiency of the economy as a whole. The results can play an important role in the establishment of efficiency standards of the energy use in various economy sectors. These standards could be utilized by energy policy makers. - Research highlights: → This work analyzes energy and exergy utilization in the energy sector of Greece by considering the energy and exergy flows for the years of 1990-2004. → Energy and exergy analyses and hence efficiencies for the residential and industrial sector are then obtained and compared to transport energy and exergy efficiencies. → The industrial sector appears to be the most energy and exergy efficient one. → It should be noted that due to non-availability of data concerning the fuel energy consumption of the appliances as well as of industrial processes, a general methodology was employed in order to calculate the energy and exergy efficiencies. → It may also be concluded that the exergy analysis offers constructive suggestions for the optimization and improvement of the energy utilization effectiveness of the sectors under study.

  2. The analysis of exergy and cash flow

    International Nuclear Information System (INIS)

    Weimin, H.

    1989-01-01

    The paper presents the analysis of the economic content of exergy parameter and the thermodynamical analogy of the analysis of cash flow, and gives out the reasonable foundations of the analysis of heat economy. The thoughts of optimum design of the combination of heat economic analysis and investment policy are also put forward

  3. Exergy analysis in industrial food processing

    NARCIS (Netherlands)

    Zisopoulos, F.K.

    2016-01-01

    The sustainable provision of food on a global scale in the near future is a very serious challenge. This thesis focuses on the assessment and design of sustainable industrial food production chains and processes by using the concept of exergy which is an objective metric based on the first and

  4. Solar and wind exergy potentials for Mars

    International Nuclear Information System (INIS)

    Delgado-Bonal, Alfonso; Martín-Torres, F. Javier; Vázquez-Martín, Sandra; Zorzano, María-Paz

    2016-01-01

    The energy requirements of the planetary exploration spacecrafts constrain the lifetime of the missions, their mobility and capabilities, and the number of instruments onboard. They are limiting factors in planetary exploration. Several missions to the surface of Mars have proven the feasibility and success of solar panels as energy source. The analysis of the exergy efficiency of the solar radiation has been carried out successfully on Earth, however, to date, there is not an extensive research regarding the thermodynamic exergy efficiency of in-situ renewable energy sources on Mars. In this paper, we analyse the obtainable energy (exergy) from solar radiation under Martian conditions. For this analysis we have used the surface environmental variables on Mars measured in-situ by the Rover Environmental Monitoring Station onboard the Curiosity rover and from satellite by the Thermal Emission Spectrometer instrument onboard the Mars Global Surveyor satellite mission. We evaluate the exergy efficiency from solar radiation on a global spatial scale using orbital data for a Martian year; and in a one single location in Mars (the Gale crater) but with an appreciable temporal resolution (1 h). Also, we analyse the wind energy as an alternative source of energy for Mars exploration and compare the results with those obtained on Earth. We study the viability of solar and wind energy station for the future exploration of Mars, showing that a small square solar cell of 0.30 m length could maintain a meteorological station on Mars. We conclude that the low density of the atmosphere of Mars is responsible of the low thermal exergy efficiency of solar panels. It also makes the use of wind energy uneffective. Finally, we provide insights for the development of new solar cells on Mars. - Highlights: • We analyse the exergy of solar radiation under Martian environment • Real data from in-situ instruments is used to determine the maximum efficiency of radiation • Wind

  5. Exergy Steam Drying and Energy Integration

    Energy Technology Data Exchange (ETDEWEB)

    Verma, Prem; Muenter, Claes (Exergy Engineering and Consulting, SE-417 55 Goeteborg (Sweden)). e-mail: verma@exergyse.com

    2008-10-15

    Exergy Steam Drying technology has existed for past 28 years and many new applications have been developed during this period. But during past few years the real benefits have been exploited in connection with bio-fuel production and energy integration. The steam dryer consists of a closed loop system, where the product is conveyed by superheated and pressurised carrier steam. The carrier steam is generated by the water vapours from the product being dried, and is indirectly superheated by another higher temperature energy source such as steam, flue gas, thermal oil etc. Besides the superior heat transfer advantages of using pressurised steam as a drying medium, the energy recovery is efficient and simple as the recovered energy (80-90%) is available in the form of steam. In some applications the product quality is significantly improved. Examples presented in this paper: Bio-Combine for pellets production: Through integration of the Exergy Steam Dryer for wood with a combined heat and power (CHP) plant, together with HP steam turbine, the excess carrier steam can be utilised for district heating and/or electrical power production in a condensing turbine. Bio-ethanol production: Both for first and second generation of ethanol can the Exergy process be integrated for treatment of raw material and by-products. Exergy Steam Dryer can dry the distillers dark grains and solubles (DDGS), wood, bagasse and lignin. Bio-diesel production: Oil containing seeds and fruits can be treated in order to improve both the quality of oil and animal feed protein, thus minimizing further oil processing costs and increasing the sales revenues. Sewage sludge as bio-mass: Municipal sewage sludge can be considered as a renewable bio-fuel. By drying and incineration, the combustion heat value of the sludge is sufficient for the drying process, generation of electrical energy and production of district heat. Keywords; Exergy, bio-fuel, bio-mass, pellets, bio-ethanol, biodiesel, bio

  6. Application of exergy as thermodynamic indicator in ecology

    International Nuclear Information System (INIS)

    Jorgensen, S.E.; Nors Nielsen, Soren

    2007-01-01

    We introduce a modified form of exergy named eco-exergy as an ecological indicator. Exergy of detritus and of various organisms are found based upon the definition of eco-exergy. Eco-exergy measures a system's deviation from chemical equilibrium. It is, therefore, crucial to find the concentration of detritus and the various organisms at chemical equilibrium which is possible by the calculation of the probability to form detritus and the various organisms by chemical equilibrium. It implies that the probability to form proteins with the right amino acid sequence must be determined by the use of the amount of coding genes. It is stressed that what we determine by this method of exergy calculation is a relative eco-exergy index. It is not possible to find the eco-exergy of entire ecosystems, because they are far too complex to allow us to know all the details of an ecosystem. The eco-exergy indices have been found in a few cases to demonstrate the usefulness of the method and to show how the exergy indices can be translated to applicable ecological information

  7. Exergy Analysis of Operating Lignite Fired Thermal Power Plant

    Directory of Open Access Journals (Sweden)

    K. Murugesan

    2009-01-01

    Full Text Available The energy assessment must be made through the energy quantity as well as the quality. But the usual energy analysisevaluates the energy generally on its quantity only. However, the exergy analysis assesses the energy on quantity as well asthe quality. The aim of the exergy analysis is to identify the magnitudes and the locations of real energy losses, in order toimprove the existing systems, processes or components. The present paper deals with an exergy analysis performed on anoperating 50MWe unit of lignite fired steam power plant at Thermal Power Station-I, Neyveli Lignite Corporation Limited,Neyveli, Tamil Nadu, India. The exergy losses occurred in the various subsystems of the plant and their components havebeen calculated using the mass, energy and exergy balance equations. The distribution of the exergy losses in several plantcomponents during the real time plant running conditions has been assessed to locate the process irreversibility. The Firstlaw efficiency (energy efficiency and the Second law efficiency (exergy efficiency of the plant have also been calculated.The comparison between the energy losses and the exergy losses of the individual components of the plant shows that themaximum energy losses of 39% occur in the condenser, whereas the maximum exergy losses of 42.73% occur in the combustor.The real losses of energy which has a scope for the improvement are given as maximum exergy losses that occurredin the combustor.

  8. Energy and exergy analyses of the diffusion absorption refrigeration system

    International Nuclear Information System (INIS)

    Yıldız, Abdullah; Ersöz, Mustafa Ali

    2013-01-01

    This paper describes the thermodynamic analyses of a DAR (diffusion absorption refrigeration) cycle. The experimental apparatus is set up to an ammonia–water DAR cycle with helium as the auxiliary inert gas. A thermodynamic model including mass, energy and exergy balance equations are presented for each component of the DAR cycle and this model is then validated by comparison with experimental data. In the thermodynamic analyses, energy and exergy losses for each component of the system are quantified and illustrated. The systems' energy and exergy losses and efficiencies are investigated. The highest energy and exergy losses occur in the solution heat exchanger. The highest energy losses in the experimental and theoretical analyses are found 25.7090 W and 25.4788 W respectively, whereas those losses as to exergy are calculated 13.7933 W and 13.9976 W. Although the values of energy efficiencies obtained from both the model and experimental studies are calculated as 0.1858, those values, in terms of exergy efficiencies are found 0.0260 and 0.0356. - Highlights: • The diffusion absorption refrigerator system is designed manufactured and tested. • The energy and exergy analyses of the system are presented theoretically and experimentally. • The energy and exergy losses are investigated for each component of the system. • The highest energy and exergy losses occur in the solution heat exchanger. • The energy and the exergy performances are also calculated

  9. Unsteady exergy destruction of the neuron under dynamic stress conditions

    International Nuclear Information System (INIS)

    Genc, S.; Sorguven, E.; Ozilgen, M.; Aksan Kurnaz, I.

    2013-01-01

    Just like all physical systems, biological systems also obey laws of thermodynamics, and as such the useful work potential of a biological system is its exergy. In some studies, exergy of living systems is considered with respect to work performance of humans in offices or buildings; however the exergy analysis of biochemical reactions in a cell as a closed system goes largely untouched. In this study, exergy analysis was applied to glucose metabolism of a model neuron, and dynamic exergy destructions were calculated for four different conditions, namely normoxia, hypoxia, glucose starvation and excess glucose. Our results showed that neuronal metabolism achieved a new steady state under each condition within 5 min. This dynamic model predicts that, both exergy destruction and work potential rates increase with increasing blood glucose concentration. The ratio of exergy destruction rate to work potential rate increases logarithmically with increasing blood glucose concentration. The neuronal metabolism is thus found to function in an efficient way and switches to lower exergy destruction under stress conditions such as glucose starvation. This behavior seen in this exergy analysis study confirms the assumption of minimum entropy production in living systems. - Highlights: • Unsteady exergy analysis of glucose metabolism of a model neuron is performed. • Dynamic exergy losses were calculated for four different conditions: normoxia, hypoxia, glucose starvation and excess glucose. • Neuronal metabolism achieved a new steady state under each condition within 5 min. • Both exergy loss and work potential rates increase with increasing blood glucose concentration. • Neuronal metabolism functions in an efficient way and switches to lower exergy loss under stress conditions

  10. Selection of Optimum Working Fluid for Organic Rankine Cycles by Exergy and Exergy-Economic Analyses

    Directory of Open Access Journals (Sweden)

    Kamyar Darvish

    2015-11-01

    Full Text Available The thermodynamic performance of a regenerative organic Rankine cycle that utilizes low temperature heat sources to facilitate the selection of proper organic working fluids is simulated. Thermodynamic models are used to investigate thermodynamic parameters such as output power, and energy efficiency of the ORC (Organic Rankine Cycle. In addition, the cost rate of electricity is examined with exergo-economic analysis. Nine working fluids are considered as part of the investigation to assess which yields the highest output power and exergy efficiency, within system constraints. Exergy efficiency and cost rate of electricity are used as objective functions for system optimization, and each fluid is assessed in terms of the optimal operating condition. The degree of superheat and the pressure ratio are independent variables in the optimization. R134a and iso-butane are found to exhibit the highest energy and exergy efficiencies, while they have output powers in between the systems using other working fluids. For a source temperature was equal to 120 °C, the exergy efficiencies for the systems using R134a and iso-butane are observed to be 19.6% and 20.3%, respectively. The largest exergy destructions occur in the boiler and the expander. The electricity cost rates for the system vary from 0.08 USD/kWh to 0.12 USD/kWh, depending on the fuel input cost, for the system using R134a as a working fluid.

  11. On the Reference State for Exergy when Ambient Temperature Fluctuates

    OpenAIRE

    Michel Pons

    2009-01-01

    Exergy (availability) is the amount of mechanical work that could be produced by reversible processes. This notion is revisited in the case when ambient temperature fluctuates. Simple examples are first considered, and then a theoretical approach is developed. It results that the most reliable way for combining entropy and total energy into an exergy function is a linear combination where entropy is multiplied by a constant temperature. It results that ambient air has non-zero exergy, but tha...

  12. Exergy analysis of a gas-hydrate cool storage system

    International Nuclear Information System (INIS)

    Bi, Yuehong; Liu, Xiao; Jiang, Minghe

    2014-01-01

    Based on exergy analysis of charging and discharging processes in a gas-hydrate cool storage system, the formulas for exergy efficiency at the sensible heat transfer stage and the phase change stage corresponding to gas-hydrate charging and discharging processes are obtained. Furthermore, the overall exergy efficiency expressions of charging, discharging processes and the thermodynamic cycle of the gas-hydrate cool storage system are obtained. By using the above expressions, the effects of number of transfer units, the inlet temperatures of the cooling medium and the heating medium on exergy efficiencies of the gas-hydrate cool storage system are emphatically analyzed. The research results can be directly used to evaluate the performance of gas-hydrate cool storage systems and design more efficient energy systems by reducing the sources of inefficiency in gas-hydrate cool storage systems. - Highlights: • Formulas for exergy efficiency at four stages are obtained. • Exergy efficiency expressions of two processes and one cycle are obtained. • Three mainly influencing factors on exergy efficiencies are analyzed. • With increasing the inlet temperature of cooling medium, exergy efficiency increases. • With decreasing the inlet temperature of heating medium, exergy efficiency increases

  13. Collective systems:physical and information exergies.

    Energy Technology Data Exchange (ETDEWEB)

    Robinett, Rush D. III (.; ); Wilson, David Gerald

    2007-04-01

    Collective systems are typically defined as a group of agents (physical and/or cyber) that work together to produce a collective behavior with a value greater than the sum of the individual parts. This amplification or synergy can be harnessed by solving an inverse problem via an information-flow/communications grid: given a desired macroscopic/collective behavior find the required microscopic/individual behavior of each agent and the required communications grid. The goal of this report is to describe the fundamental nature of the Hamiltonian function in the design of collective systems (solve the inverse problem) and the connections between and values of physical and information exergies intrinsic to collective systems. In particular, physical and information exergies are shown to be equivalent based on thermodynamics and Hamiltonian mechanics.

  14. Modeling and Exergy Analysis of District Cooling

    DEFF Research Database (Denmark)

    Nguyen, Chan

    in the gas cooler, pinch temperature in the evaporator and effectiveness of the IHX. These results are complemented by the exergy analysis, where the exergy destruction ratio of the CO2 system’s component is found. Heat recovery from vapour compression heat pumps has been investigated. The heat is to be used...... consists of a combined heat and power (CHP) plant with a separate refrigeration plant, where its condenser heat is rejected to the environment. The recovery system consists of the same CHP plant but with a heat pump, where the condensation heat is recovered. Five different refrigerants (R717, R600a, R290...... and surrounding temperature has been carried out. It has been demonstrated that the two methods yield significantly different results. Energy costing prices the unit cost of heating and cooling equally independent of the quality of the heat transfer, and it tends to overprice the cost of cooling in an irrational...

  15. Sensitivity analysis of exergy destruction in a real combined cycle power plant based on advanced exergy method

    International Nuclear Information System (INIS)

    Boyaghchi, Fateme Ahmadi; Molaie, Hanieh

    2015-01-01

    Highlights: • The advanced exergy destruction components of a real CCPP are calculated. • The TIT and r c variation are investigated on exergy destruction parts of the cycle. • The TIT and r c growth increase the improvement potential in the most of components. • The TIT and r c growth decrease the unavoidable part in some components. - Abstract: The advanced exergy analysis extends engineering knowledge beyond the respective conventional methods by improving the design and operation of energy conversion systems. In advanced exergy analysis, the exergy destruction is splitting into endogenous/exogenous and avoidable/unavoidable parts. In this study, an advanced exergy analysis of a real combined cycle power plant (CCPP) with supplementary firing is done. The endogenous/exogenous irreversibilities of each component as well as their combination with avoidable/unavoidable irreversibilities are determined. A parametric study is presented discussing the sensitivity of various performance indicators to the turbine inlet temperature (TIT), and compressor pressure ratio (r c ). It is observed that the thermal and exergy efficiencies increase when TIT and r c rise. Results show that combustion chamber (CC) concentrates most of the exergy destruction (more than 62%), dominantly in unavoidable endogenous form which is decreased by 11.89% and 13.12% while the avoidable endogenous exergy destruction increase and is multiplied by the factors of 1.3 and 8.6 with increasing TIT and r c , respectively. In addition, TIT growth strongly increases the endogenous avoidable exergy destruction in high pressure superheater (HP.SUP), CC and low pressure evaporator (LP.EVAP). It, also, increases the exogenous avoidable exergy destruction of HP.SUP and low pressure steam turbine (LP.ST) and leads to the high decrement in the endogenous exergy destruction of the preheater (PRE) by about 98.8%. Furthermore, r c growth extremely rises the endogenous avoidable exergy destruction of gas

  16. An innovative application of extended exergy analysis into an industrial park.

    Science.gov (United States)

    Fan, Yupeng; Qiao, Qi; Fang, Lin

    2017-04-01

    Exergy is a thermodynamic term used to account all possible useful work theoretically throughout one process when it is brought into equilibrium with its environment. It however cannot directly incorporate non-physical flows, which can be accounted by extensions of the exergy consumption method. Extended exergy, which builds a bridge between thermal and anthropic dimensions, can both measure resource consumption and economic system. In this study, we applied extended exergy analysis to analyze an industrial park, including material consumption, social investment, and environmental influence. The total extended exergy consumption in the study park amounts to 2.52 EJ. The material-based exergy occupies the largest exergy consumption, followed by capital exergy, environmental remediation exergy, and labor exergy in decreasing order. The exergy capacity was proposed to depict the conversion ability from exergy consumption into economic benefits. In the study area, electronic information industry has the largest exergy capacity with a value of 70 RMB/GJ, indicating a high conversion power from exergy to money. New energy vehicles and parts manufacturing occupies bottom rung in terms of exergy capacity. From the view of material consumption, other industry consumed a lot more exergy compared to electronic information industry; for the environmental remediation, other industry has the lowest exergy capacity, indicating it discharged more pollutants than other clusters to output the same amount of money. Therefore, other industry needs to be urgently transformed and upgraded. The study could help to optimize industrial structure and environmental management in industrial parks.

  17. Exergy analysis of gas turbine with air bottoming cycle

    International Nuclear Information System (INIS)

    Ghazikhani, M.; Khazaee, I.; Abdekhodaie, E.

    2014-01-01

    In this paper, the exergy analysis of a conventional gas turbine and a gas turbine with air bottoming cycle (ABC) is presented in order to study the important parameters involved in improving the performance characteristics of the ABC based on the Second Law of thermodynamics. In this study, work output, specific fuel consumption (SFC) and the exergy destruction of the components are investigated using a computer model. The variations of the ABC cycle exergy parameters are comprehensively discussed and compared with those of the simple gas turbine. The results indicate that the amount of the exhaust exergy recovery in different operating conditions varies between 8.6 and 14.1% of the fuel exergy, while the exergy destruction due to the extra components in the ABC makes up only 4.7–7.4% of the fuel exergy. This is the reason why the SFC of the ABC is averagely 13.3% less and the specific work 15.4% more than those of the simple gas turbine. The results also reveal that in the ABC cycle, at a small value of pressure ratio, a higher specific work with lower SFC can be achieved in comparison with those of the simple gas turbine. - Highlights: • Exhaust exergy recovery in ABC gas turbine varies with 8.6–14.1% of the fuel exergy. • Irreversibility of the extra devices in ABC makes up 4.7–7.4% of the fuel exergy. • SFC in ABC is poor due to exergy recovery more than extra devices irreversibility. • At the same TIT and R c , specific work in the ABC is more than simple gas turbine. • The recuperator has the largest contribution in the irreversibility of the ABC

  18. Energy and exergy analysis of solar power tower plants

    International Nuclear Information System (INIS)

    Xu Chao; Wang Zhifeng; Li Xin; Sun Feihu

    2011-01-01

    Establishing the renewable electricity contribution from solar thermal power systems based on energy analysis alone cannot legitimately be complete unless the exergy concept becomes a part of that analysis. This paper presents a theoretical framework for the energy analysis and exergy analysis of the solar power tower system using molten salt as the heat transfer fluid. Both the energy losses and exergy losses in each component and in the overall system are evaluated to identify the causes and locations of the thermodynamic imperfection. Several design parameters including the direct normal irradiation (DNI), the concentration ratio, and the type of power cycle are also tested to evaluate their effects on the energy and exergy performance. The results show that the maximum exergy loss occurs in the receiver system, followed by the heliostat field system, although main energy loss occurs in the power cycle system. The energy and exergy efficiencies of the receiver and the overall system can be increased by increasing the DNI and the concentration ratio, but that increment in the efficiencies varies with the values of DNI and the concentration ratio. It is also found that the overall energy and exergy efficiencies of the solar tower system can be increased to some extent by integrating advanced power cycles including reheat Rankine cycles and supercritical Rankine cycles. - Highlights: →We presented a theoretical framework for the energy and exergy analysis of the solar tower system. →We tested the effects of several design parameters on the energy and exergy performance. →The maximum exergy loss occurs in the receiver system, followed by the heliostat field system. →Integrating advanced power cycles leads to increases in the overall energy and exergy efficiencies.

  19. Exergy analysis of a combined power and cooling cycle

    International Nuclear Information System (INIS)

    Fontalvo, Armando; Pinzon, Horacio; Duarte, Jorge; Bula, Antonio; Quiroga, Arturo Gonzalez; Padilla, Ricardo Vasquez

    2013-01-01

    This paper presents a comprehensive exergy analysis of a combined power and cooling cycle which combines a Rankine and absorption refrigeration cycle by using ammonia–water mixture as working fluid. A thermodynamic model was developed in Matlab ® to find out the effect of pressure ratio, ammonia mass fraction at the absorber and turbine efficiency on the total exergy destruction of the cycle. The contribution of each cycle component on the total exergy destruction was also determined. The results showed that total exergy destruction decreases when pressure ratio increases, and reaches a maximum at x ≈ 0.5, when ammonia mass fraction is varied at absorber. Also, it was found that the absorber, the boiler and the turbine had the major contribution to the total exergy destruction of the cycle, and the increase of the turbine efficiency reduces the total exergy destruction. The effect of rectification cooling source (external and internal) on the cycle output was investigated, and the results showed that internal rectification cooling reduces the total exergy destruction of the cycle. Finally, the effect of the presence or absence of the superheater after the rectification process was determined and it was obtained that the superheated condition reduces the exergy destruction of the cycle at high turbine efficiency values. Highlights: • A parametric exergy analysis of a combined power and cooling cycle is performed. • Two scenarios for rectifier cooling (internal and external) were studied. • Internal cooling source is more exergetic efficient than external cooling source. • The absorber and boiler have the largest total exergy destruction. • Our results show that the superheater reduces the exergy destruction of the cycle

  20. Enhancement of exergy efficiency in combustion systems using flameless mode

    International Nuclear Information System (INIS)

    Hosseini, Seyed Ehsan; Wahid, Mazlan Abdul

    2014-01-01

    Highlights: • Exergy efficiency in flameless combustion mode is 13% more than conventional combustion. • The maximum exergy efficiency in flameless combustion mode is achieved when oxidizer contains 10% oxygen. • Exergy destruction of flameless combustion is maximized when CO 2 is used for dilution of oxidizer. - Abstract: An exergitic-based analysis of methane (CH 4 ) conventional and flameless combustion in a lab-scale furnace is performed to determine the rate of pollutant formation and the effective potential of a given amount of fuel in the various combustion modes. The effects of inlet air temperature on exergy efficiency and pollutant formation of conventional combustion in various equivalence ratios are analyzed. The rate of exergy destruction in different conditions of flameless combustion (various equivalence ratios, oxygen concentration in the oxidizer and the effects of diluent) are computed using three-dimensional (3D) computational fluid dynamic (CFD). Fuel consumption reduction and exergy efficiency augmentation are the main positive consequences of using preheated air temperature in conventional combustion, however pollutants especially NO x formation increases dramatically. Low and moderate temperature inside the chamber conducts the flameless combustion system to low level pollutant formation. Fuel consumption and exergy destruction reduce drastically in flameless mode in comparison with conventional combustion. Exergy efficiency of conventional and flameless mode is 75% and 88% respectively in stoichiometric combustion. When CO 2 is used for dilution of oxidizer, chemical exergy increases due to high CO 2 concentration in the combustion products and exergy efficiency reduces around 2% compared to dilution with nitrogen (N 2 ). Since the rate of irreversibilities in combustion systems is very high in combined heat and power (CHP) generation and other industries, application of flameless combustion could be effective in terms of pollutant

  1. Addressing Different Approaches for Evaluating Low-Exergy Communities

    NARCIS (Netherlands)

    Jansen, S.C.; Meggers, Forrest; Heiselberg, Per Kvols

    2016-01-01

    The IEA Annex 64 focusing on low-ex communities aims at the improvement of energy conversion chains on a community scale, using exergy analysis as the primary evaluation mode. Within this Annex the participants discuss important aspects and available methods for energy and exergy assessment as well

  2. Comparison between exergy and energy analysis for biodiesel production

    International Nuclear Information System (INIS)

    Amelio, A.; Van de Voorde, T.; Creemers, C.; Degrève, J.; Darvishmanesh, S.; Luis, P.; Van der Bruggen, B.

    2016-01-01

    This study investigates the exergy concept for use in chemical engineering applications, and compares the energy and exergy methodology for the production process of biodiesel. A process for biodiesel production was suggested and simulated in view of the energy and exergy analysis. A method was developed to implement the exergy concept in Aspen Plus 7.3. A comparison between the energy and the exergy approach reveals that the concepts have similarities but also some differences. In the exergy study, the reaction section has the largest losses whereas in the energy study separation steps are the most important. An optimization, using both concepts, was carried out using the same parameters. The optimized results were different depending on the objective function. It was concluded that exergy analysis is crucial during the design or redesign step in order to investigate thermodynamic efficiencies in each part of the process. - Highlights: • New flowsheet for the production of biodiesel simulated with Aspen Plus. • Calculation of the exergetic costs and several interesting indexes. • Comparison of exergy and energy analysis for the process studied.

  3. The correlation of energy with entropy and exergy; Die Vernetzung der Energie mit Entropie und Exergie

    Energy Technology Data Exchange (ETDEWEB)

    Weber, Gernot (Dr. Gernot Weber, Energie-Gebaeudetechnik, Kleinostheim)

    2011-07-01

    Thermodynamics generally is regarded as one of the most difficult fields of knowledge. This may be particularly due to the difficulties and due to the often very complicated described correlations between the terms energy, entropy and exergy in the technical literature. The contribution under consideration tries to explain these correlations to the (scientifically trained) technically interested readers understandable.

  4. Energy and Exergy Analysis of the Danish Industry Sector

    DEFF Research Database (Denmark)

    Bühler, Fabian; Nguyen, Tuong-Van; Elmegaard, Brian

    2015-01-01

    % to 56% in 2012. Industries with high-temperature processes, such as the cement and metal production sectors, present the highest exergy efficiencies but the lowest energy ones. The opposite conclusion is drawn for the food, paper and chemical industries. The exergy losses, which indicate the potential......A detailed analysis of the Danish industry is presented in this paper using the energy, exergy and embodied exergy methods. The 22 most energy-intensive process industries, which represent about 80% of the total primary energy use of the industry, were modelled and analysed in details for the years...... is not seen with the embodied exergy efficiency, which remains at around 29% for the Danish industry. This analysis shows that there are still large potentials to recover waste heat in most Danish industrial sectors and thus to increase their efficiencies....

  5. Energy and exergy analyses of solar drying process of pistachio

    International Nuclear Information System (INIS)

    Midilli, A.; Kucuk, H.

    2003-01-01

    This paper is concerned with the energy and exergy analyses of the drying process of shelled and unshelled pistachios using a solar drying cabinet. Using the first law of thermodynamics, energy analysis was carried to estimate the amounts of energy gained from solar air collectors and the ratios of energy utilization. However, exergy analysis was accomplished to determine the location, type, and magnitude of exergy losses during the solar drying process by applying the second law of thermodynamics. It was deduced that the exergy losses took place mostly in the 15th shelf where the available energy was less utilized. Moreover, the shelled and unshelled pistachios are sufficiently dried in the ranges between 40 and 60 deg. C and 37 and 62% of relative humidity at 1.23 m s -1 of drying air velocity in 6 h despite the exergy losses of 0.15-3.08 kJ kg -1

  6. Energy and exergy analyses of solar drying process of pistachio

    Energy Technology Data Exchange (ETDEWEB)

    Midilli, A [University of Nigde (Turkey). Dept. of Mechanical Engineering; Kucuk, H [Karadeniz Technical Univ., Trabzon (Turkey). Dept. of Mechanical Engineering

    2003-05-01

    This paper is concerned with the energy and exergy analyses of the drying process of shelled and unshelled pistachios using a solar drying cabinet. Using the first law of thermodynamics, energy analysis was carried to estimate the amounts of energy gained from solar air collectors and the ratios of energy utilization. However, exergy analysis was accomplished to determine the location, type, and magnitude of exergy losses during the solar drying process by applying the second law of thermodynamics. It was deduced that the exergy losses took place mostly in the 15th shelf where the available energy was less utilized. Moreover, the shelled and unshelled pistachios are sufficiently dried in the ranges between 40 and 60{sup o}C and 37 and 62% of relative humidity at 1.23 m s{sup -1} of drying air velocity in 6 h despite the exergy losses of 0.15-3.08 kJ kg{sup -1}. (Author)

  7. Exergy Flows inside a One Phase Ejector for Refrigeration Systems

    Directory of Open Access Journals (Sweden)

    Mohammed Khennich

    2016-03-01

    Full Text Available The evaluation of the thermodynamic performance of the mutual transformation of different kinds of exergy linked to the intensive thermodynamic parameters of the flow inside the ejector of a refrigeration system is undertaken. Two thermodynamic metrics, exergy produced and exergy consumed, are introduced to assess these transformations. Their calculation is based on the evaluation of the transiting exergy within different ejector sections taking into account the temperature, pressure and velocity variations. The analysis based on these metrics has allowed pinpointing the most important factors affecting the ejector’s performance. A new result, namely the temperature rise in the sub-environmental region of the mixing section is detected as an important factor responsible for the ejector’s thermodynamic irreversibility. The overall exergy efficiency of the ejector as well as the efficiencies of its sections are evaluated based on the proposed thermodynamic metrics.

  8. ENERGY AND EXERGY ANALYSIS OF A POWDER DETERGENT UNIT

    International Nuclear Information System (INIS)

    G. Bektas; F. Balkan

    2008-01-01

    In the recent years, there is a growing interest on minimization of energy utilization in various plants and thereby improving the performance. As an efficient tool for examining the processes, the exergy analysis gains importance. In the present work, the application of exergy analysis to powder detergent unit of a powder detergent production plant located at Izmir, Turkey were performed y using actual plant operational data. Also the energy analyses were considered for comparison. Although there are a number of energy and exergy analyses in various areas of industry, this study will be likely the first one for powder detergent production. The energy and exergy efficiencies of the equipments were calculated and it was concluded that according to the overall balance around the unit, the energy efficiency was 0.76 and the exergy efficiency was 0.40

  9. ENERGY AND EXERGY ANALYSIS OF A POWDER DETERGENT UNIT

    Energy Technology Data Exchange (ETDEWEB)

    G. Bektas; F. Balkan [Ege University, Chemical Engineering Department, Izmir (Turkey)

    2008-09-30

    In the recent years, there is a growing interest on minimization of energy utilization in various plants and thereby improving the performance. As an efficient tool for examining the processes, the exergy analysis gains importance. In the present work, the application of exergy analysis to powder detergent unit of a powder detergent production plant located at Izmir, Turkey were performed y using actual plant operational data. Also the energy analyses were considered for comparison. Although there are a number of energy and exergy analyses in various areas of industry, this study will be likely the first one for powder detergent production. The energy and exergy efficiencies of the equipments were calculated and it was concluded that according to the overall balance around the unit, the energy efficiency was 0.76 and the exergy efficiency was 0.40.

  10. Exergy Rate Profile of Multicomponent Distillation System

    Directory of Open Access Journals (Sweden)

    Kehinde Adewale Adesina

    2016-07-01

    Full Text Available Exergy rate profiles, exergetic efficiency and irreversibility were used to examine the driving forces in multicomponent distillation system with the view to identifying feasible and efficient operating parameters. The mixture used comprised of 5% propane, 15% iso-butane, 25% nbutane, 20% iso-pentane and 35% n-pentane. Operating variables were feed temperature (-30 oC and -80 oC, pressure (800 kPa and 1200 kPa, and reflux-ratio (2 and 6. Stage-by-stage system exergy analysis was estimated. Column profiles of base case -30 oC, -80 oC, -30 oC-reflus ratio 6, -80 oC reflux ratio 6 and base case reflux ratio 6 did not crossed thus are thermodynamically feasible. Base case -30 oC-reflux ratio 2, -80 oC-reflux ratio 2, and base case-reflux ratio 2 were crossed and constricted and are infeasible. Base case results gave efficiency of 81.7% at depropanizer and 65.2% at debutanizer. Base cases sensitivity results with -30 oC, -80 oC and reflux ratio 6, efficiency range 57.40 – 70% and 65.20% - 54.90% for depropanizer and debutanizer respectively. Spitted cases gave 81.7% and 62.20% with more scatter profiles. Splitted feed base case -30 oC design gave the lowest overall system exergy loss rate of 1.12E+6 and efficiency of 95.70%. Design feasible parameters, system efficiency and irreversibility which form basis

  11. The Tenuous Use of Exergy as a Measure of Resource Value or Waste Impact

    Directory of Open Access Journals (Sweden)

    Roydon A. Fraser

    2009-12-01

    Full Text Available Exergy is a thermodynamic concept that has been widely promoted for assessing and improving sustainability, notably in the characterization of resources and wastes. Despite having many notable benefits, exergy is often misused by authors who tend to apply it as an intrinsic characteristic of an object (i.e., as a static thermodynamic variable. Using both theoretical and empirical evidence the authors present five key limitations that must be overcome before exergy can be applied to characterize objects: (1 the incompatibility between exergy quality and resource quality; (2 the inability of exergy to characterize non work-producing resources via the concentration exergy; (3 the constraints placed on the derivation of exergy; (4 problems with the exergy reference environment; and (5 the multiple perspectives applied to exergy analysis. Until the limitations are addressed, exergy should only be used for its original purpose as a decision making tool for engineering systems analysis.

  12. Systems Engineering in Terms of Exergy

    Directory of Open Access Journals (Sweden)

    José A. Camberos

    2009-01-01

    Full Text Available We address the design of a flight vehicle from the viewpoint of a system of systems and we discuss the integration of the individual technical disciplines. Then a conceptual fundamental methodology and tools required for the analysis, design, and optimization of aerospace vehicles in terms of the efficient use of on-board energy are discussed. This suggests changing the design paradigm to the optimization of a system of energy systems. We propose a foundation for system-level design with optimization based on minimum exergy destruction.

  13. Comparative exergy analyses of gasoline and hydrogen fuelled ices

    International Nuclear Information System (INIS)

    Nieminen, J.; Dincer, I.; Yang, Y.

    2009-01-01

    Comparative exergy models for naturally aspirated gasoline and hydrogen fuelled spark ignition internal combustion engines were developed according to the second laws of thermodynamics. A thorough graphical analysis of heat transfer, work, thermo mechanical, and intake charge exergy functions was made. An irreversibility function was developed as a function of entropy generation and graphed. A second law analysis yielded a proportional exergy distribution as a fraction of the intake charge exergy. It was found that the hydrogen fuelled engine had a greater proportion of the intake charge exergy converted into work exergy, indicating a second law efficiency of 50.13% as opposed to 44.34% for a gasoline fuelled engine. The greater exergy due to heat transfer or thermal availability associated with the hydrogen fuelled engine is postulated to be a part of the reason for decreased work output of a hydrogen engine. Finally, a second law analysis of both hydrogen and gasoline combustion reactions indicate a greater combustion irreversibility associated with gasoline combustion. A percentage breakdown of the combustion irreversibilities were also constructed according to information found in literature searches. (author)

  14. Understanding the Sustainability of Fuel from the Viewpoint of Exergy

    Directory of Open Access Journals (Sweden)

    Yaning Zhang

    2018-01-01

    Full Text Available At the same time of providing a huge amount of energy to the world population (social sustainability and global economy (economic sustainability, the fuel itself also releases a great amount of emissions to the environment the world people live in in the forms of gaseous pollutants (SOx, NOx, CO, CO2, CH4, etc. and ash compositions (Al2O3, CaO, Fe2O3, K2O, MgO, MnO, Na2O, P2O5, SO3, SiO2, TiO2, etc., seriously impacting the environment (environmental sustainability for the world population and global economy. Sustainability generally encompasses economic sustainability, environmental sustainability, and social sustainability, and all of these are significantly related to the energy/resource sustainability. This study addresses the sustainability of fuel from the viewpoint of exergy. It is demonstrated that the energy of a fuel is best evaluated by its chemical exergy, and the environmental impact of a fuel can be assessed through the chemical exergy of its emissions (the specific impacts such as toxicity or greenhouse effect are not detailed. Then, the sustainability of fuel can be understood from the viewpoint of exergy through three ways: (a high chemical exergy of the fuel, (b high exergy efficiency of the fuel conversion process, and (c low chemical exergy of the emissions.

  15. Exergy costs analysis of groundwater use and water transfers

    International Nuclear Information System (INIS)

    Carrasquer, Beatriz; Uche, Javier; Martínez-Gracia, Amaya

    2016-01-01

    Highlights: • A methodology to estimate the unit exergy cost of water supply alternatives is provided. • Two alternatives (water transfers and groundwaters) are defined. • The unit exergy costs are given as a function of design and operating parameters. • Unit exergy cost of groundwaters go from 1.01 to 2.67 and from 1 to 4.06 in water transfers. • Unit exergy costs are calculated and contrasted for the medium course of the Ebro. - Abstract: In the search for new alternatives to meet the water demands, it is interesting to analyze the cost of using alternatives different from those such as desalination and pumping. The exergy cost analysis can be a useful tool to estimate costs of those alternatives as a function of its energy efficiency and its relative abundance with respect to existing resources in their surroundings. This study proposes a methodology for assessing the costs of groundwaters and water transfers from surplus basins within the exergy perspective. An equation to assess the exergy costs of these alternatives is proposed. System boundaries are first identified to the assessment of input and output currents to the system in exergy values for the design and certain operating conditions. Next, an equation to assess water supply costs depending on design and operational parameters is proposed, from the analysis of different examples. Pumping efficiency, altitude gap and flow among other features are introduced in the calculations as those characteristics parameters. In the developed examples, unit exergy costs of groundwaters go from 1.01 to 2.67, and from 1 to 4.06 in case of water transfers. Maximum values, as expected within this perspective, are found at high pumped/transferred flows and high pumping levels and/or low pumping efficiency if pumping is required.

  16. Exergy analysis of a crude oil atmospheric distillation unit

    International Nuclear Information System (INIS)

    Rivero, R.; Gonzalez, G.V.; Garcia, V.H.; Pulido, R.; Escarcega, C.A.

    1989-01-01

    This paper deals with the application of an exergy analysis to an existing and operating crude oil atmospheric distillation unit. The objective of such an analysis is to fully understand where energy inefficiencies and real energy losses are located and where modifications should be implemented to improve the overall utilization of energy in the plant. First, the description of the process and the block diagram are presented. After that, the calculating procedure to obtain the exergy balance, the exergy losses, the effectiveness and the improvement potential for each plant component is described and the corresponding results are shown. Finally, the component and overall evaluations are discussed

  17. Exergy-based comparison of two Greek industries

    DEFF Research Database (Denmark)

    Xydis, George; Koroneos, C.; Naniki, E.

    2011-01-01

    In this work, the potential of the increase in exergy and energy efficiency of the Greek construction and Food, Drink and Tobacco (FDT) industries has been examined using energy and exergy analysis methodology. These two industries play a vital role towards sustainable development of the country....... The continuous increase in energy use in these two industries during the years 1971–2000 shows that both remain steadily in an ascendant orbit. The aim was to analyse and compare the energy use and exergy consumption in the Greek construction and FDT industries to gain insights into each sector's efficiency...

  18. Biomass boiler energy conversion system analysis with the aid of exergy-based methods

    International Nuclear Information System (INIS)

    Li, Changchun; Gillum, Craig; Toupin, Kevin; Donaldson, Burl

    2015-01-01

    Highlights: • Conventional exergy analysis and advanced exergy analysis are performed. • The combustion process dominates the exergy destruction. • Increase excess air will decrease the overall boiler exergy efficiency. • Increase the SH temperatures will increase the overall boiler exergy efficiency. • The avoidable exergy destructions in the air heaters are very small. - Abstract: The objective of this paper is to establish a theoretical framework for the exergy analysis and advanced exergy analysis of a real biomass boiler. These analyses can be used for both the diagnosis and optimization of a biomass boiler as well as for the design of a new biomass boiler. Conventional exergy analysis is performed to recognize the source(s) of inefficiency and irreversibility and identify exergy destruction in different components of the biomass boiler. An advanced exergy analysis is performed to provide comprehensive information about the avoidable exergy destruction and real fuel-saving potential for each component, as well as the overall system. Sensitivity studies of several design parameters including the excess air, biomass moisture and steam parameters were evaluated. The results show that the maximum exergy destruction occurs in the combustion process, followed by the Water Walls (WW) & Radiant Superheater (RSH) and the Low Temperature Superheater (LTSH). The fuel-saving and exergy efficiency improvement strategies for different components are discussed in this paper

  19. Exergy performance of different space heating systems: A theoretical study

    DEFF Research Database (Denmark)

    Kazanci, Ongun Berk; Shukuya, Masanori; Olesen, Bjarne W.

    2016-01-01

    , the effects of floor covering resistance on the whole system performance were studied using two heat sources; a natural gas fired condensing boiler and an air-source heat pump. The heating systems were also compared in terms of auxiliary exergy use for pumps and fans. The low temperature floor heating system......Three space heating systems (floor heating with different floor covering resistances, radiator heating with different working temperatures, warm-air heating with and without heat recovery) were compared using a natural gas fired condensing boiler as the heat source. For the floor heating systems...... performed better than other systems in terms of exergy demand. The use of boiler as a heat source for a low-exergy floor heating system creates a mismatch in the exergy supply and demand. Although an air-source heat pump could be a better heat source, this depends on the origin of the electricity supplied...

  20. Energy and exergy analysis of the silicon production process

    International Nuclear Information System (INIS)

    Takla, M.; Kamfjord, N.E.; Tveit, Halvard; Kjelstrup, S.

    2013-01-01

    We used energy and exergy analysis to evaluate two industrial and one ideal (theoretical) production process for silicon. The industrial processes were considered in the absence and presence of power production from waste heat in the off-gas. The theoretical process, with pure reactants and no side-reactions, was used to provide a more realistic upper limit of performance for the others. The energy analysis documented the large thermal energy source in the off-gas system, while the exergy analysis documented the potential for efficiency improvement. We found an exergetic efficiency equal to 0.33 ± 0.02 for the process without power production. The value increased to 0.41 ± 0.03 when waste heat was utilized. For the ideal process, we found an exergetic efficiency of 0.51. Utilization of thermal exergy in an off-gas of 800 °C increased this exergetic efficiency to 0.71. Exergy destructed due to combustion of by-product gases and exergy lost with the furnace off-gas were the largest contributors to the thermodynamic inefficiency of all processes. - Highlights: • The exergetic efficiency for an industrial silicon production process when silicon is the only product was estimated to 0.33. • With additional power production from thermal energy in the off-gas we estimated the exergetic efficiency to 0.41. • The theoretical silicon production process is established as the reference case. • Exergy lost with the off-gas and exergy destructed due to combustion account for roughly 75% of the total losses. • With utilization of the thermal exergy in the off-gas at a temperature of 800 °C the exergetic efficiency was 0.71

  1. Exergy Analysis of a Solar Humidification- Dehumidification Desalination Unit

    OpenAIRE

    Mohammed A. Elhaj; Jamal S. Yassin

    2013-01-01

    This paper presents the exergy analysis of a desalination unit using humidification-dehumidification process. Here, this unit is considered as a thermal system with three main components, which are the heating unit by using a solar collector, the evaporator or the humidifier, and the condenser or the dehumidifier. In these components the exergy is a measure of the quality or grade of energy and it can be destroyed in them. According to the second law of thermodynamics thi...

  2. Exergy analysis of the energy use in Greece

    DEFF Research Database (Denmark)

    Koroneos, C.J.; Nanaki, E.A.; Xydis, George

    2011-01-01

    In this work, an analysis is being done on the concept of energy and exergy utilization and an application to the residential and industrial sector of Greece. The energy and exergy flows over the period from 1990 to 2004 were taken into consideration. This period was chosen based on the data...... of the energy use in various economy sectors. These standards could be utilized by energy policy makers....

  3. Exergy method of analysis and its application to a helium cryorefrigerator

    International Nuclear Information System (INIS)

    Thirumaleshwar, M.

    1979-01-01

    Concepts of Exergy, Exergy balance, Exergy function and Exergetic efficiency are reviewed. Curves for the Exergetic efficiency of an ideal isobaric source system for the generalised case of an ideal gas, as well as for the specific case of Helium, are presented. An Enthalpy-Exergy diagram for Helium with a pressure range of 1 atm to 150 atm and temperature range of 10 K to 300 K is drawn. Use of this chart is illustrated by analysing a modified Brayton Cycle Cryorefrigerator system with reference to each of its components. Finally, the exergy balance indicates the fraction of the total exergy supplied which is 'lost' in each of the components. (author)

  4. Exergy analysis of waste emissions from gas flaring

    Directory of Open Access Journals (Sweden)

    Olawale Saheed ISMAIL

    2016-07-01

    Full Text Available Gas flaring produces a stream of waste gases at high temperature and pressure which contains carbon monoxide, Hydrogen Sulphide etc. The resultant effect of which is detrimental to our planet and, consequently, to the life of both the living and the non-living things. It’s well known that gas flaring contributes in no small measure to the global warming. Exergy analysis is applied in this work to analyze waste emissions from gas flaring so as to have a model through which impact of gas flaring can be measured. The study considers both the thermo-mechanical exergy and the chemical exergy of these gases. Relevant data on gas flaring activities in the Niger-Delta region of Nigeria between the periods of fifteen (15 years was obtained from the Nigerian National Petroleum Corporation (NNPC. A computer program (Exergy Calculator was developed based on the equations generated in the Model. Exergy associated with gas flaring activities in Nigeria between the periods of 1998 through 2012 was calculated. The results show that 1 mscf (in thousand cubic feet of flared gases generate 0.000041 MWh of energy leading to a value of 440158.607 MWh of energy for the period under review.The analysis provides important conclusions and recommendations for improving oil platforms operationsin in order to safeguard the environment, health of the populace, and maximize recovered exergy from gas flaring.

  5. Energy and exergy analyses of Angra-2 nuclear power plant

    Energy Technology Data Exchange (ETDEWEB)

    Marques, João G.O.; Costa, Antonella L.; Pereira, Claubia; Fortini, Ângela, E-mail: jgabrieloliveira2010@bol.com.br, E-mail: antonella@nuclear.ufmg.br, E-mail: claubia@nuclear.ufmg.br, E-mail: fortini@nuclear.ufmg.br [Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, MG (Brazil). Departamento de Engenharia Nuclear

    2017-07-01

    Nuclear Power Plants (NPPs) based on Pressurized Water Reactors (PWRs) technology are considered an alternative to fossil fuels plants due to their reliability with low operational cost and low CO{sub 2} emissions. An example of PWR plant is Angra-2 built in Brazil. This NPP has a nominal electric power output of 1300 MW and made it possible for the country save its water resources during electricity generation from hydraulic plants, and improved Brazilian knowledge and technology in nuclear research area. Despite all these benefits, PWR plants generally have a relatively low thermal efficiency combined with a large amount of irreversibility generation or exergy destruction in their components, reducing their capacity to produce work. Because of that, it is important to assess such systems to understand how each component impacts on system efficiency. Based on that, the aim of this work is to evaluate Angra-2 by performing energy and exergy analyses to quantify the thermodynamic performance of this PWR plant and its components. The methodology consists in the development of a mathematical model in EES (Engineering Equation Solver) software based on thermodynamic states in addition to energy and exergy balance equations. According to the results, Angra 2 has energy efficiency of 36.18% and exergy efficiency of 49.24%. Reactor core is the most inefficient device in the NPP; it has exergy efficiency of 67.16% and is responsible for 63.88% of all exergy destroyed in Angra-2. (author)

  6. Energy and exergy utilizations of the Jordanian SMEs industries

    International Nuclear Information System (INIS)

    Al-Ghandoor, A.; Al Salaymeh, M.; Al-Abdallat, Y.; Al-Rawashdeh, M.

    2013-01-01

    Highlights: ► We analyze the energy and exergy utilizations of the Jordanian SMEs industries. ► We developed an energy balance for the Jordanian SMEs industries. ► The low efficiencies values suggest that many opportunities for better industrial energy utilizations still exist. - Abstract: This study presents detailed analysis of the energy and exergy utilizations of the Jordanian Small-Medium Enterprises (SMEs) by considering the flows of energy and exergy through the main end uses in the Jordanian industrial sector. To achieve this purpose, a survey covering 180 facilities was conducted and energy consumption data was gathered to establish detailed end-use balance for the Jordanian industrial sector. The energy end-use balance provides a starting point to estimate the site and embodied energy and exergy efficiencies. The average site energy and exergy efficiencies of the Jordanian SMEs industries sector are estimated as 78.3% and 37.9% respectively, while the embodied energy and exergy efficiencies are estimated as 58.9% and 21.2% respectively. The low efficiencies values suggest that many opportunities for better industrial energy utilizations still exist.

  7. New exergy analysis of a regenerative closed Brayton cycle

    International Nuclear Information System (INIS)

    Naserian, Mohammad Mahdi; Farahat, Said; Sarhaddi, Faramarz

    2017-01-01

    Highlights: • The maximum power is studied relating to time and size constraints variations. • The influence of time and size constraints on exergy destruction are investigated. • The definitions of heat exergy, and second law efficiency are modified. - Abstract: In this study, the optimal performance of a regenerative closed Brayton cycle is sought through power maximization. Optimization is performed on the output power as the objective function using genetic algorithm. In order to take into account the time and the size constraints in current problem, the dimensionless mass-flow parameter is used. The influence of the unavoidable exergy destruction due to finite-time constraint is taken into account by developing the definition of heat exergy. Finally, the improved definitions are proposed for heat exergy, and the second law efficiency. Moreover, the new definitions will be compared with the conventional ones. For example, at a specified dimensionless mass-flow parameter, exergy overestimation in conventional definition, causes about 31% lower estimation of the second law efficiency. These results could be expected to be utilized in future solar thermal Brayton cycle assessment and optimization.

  8. Thermal performance of gas turbine power plant based on exergy analysis

    International Nuclear Information System (INIS)

    Ibrahim, Thamir K.; Basrawi, Firdaus; Awad, Omar I.; Abdullah, Ahmed N.; Najafi, G.; Mamat, Rizlman; Hagos, F.Y.

    2017-01-01

    Highlights: • Modelling theoretical framework for the energy and exergy analysis of the Gas turbine. • Investigated the effects of ambient temperature on the energy and exergy performance. • The maximum exergy loss occurs in the gas turbine components. - Abstract: This study is about energy and exergy analysis of gas turbine power plant. Energy analysis is more quantitatively while exergy analysis is about the same but with the addition of qualitatively. The lack quality of the thermodynamic process in the system leads to waste of potential energy, also known as exergy destruction which affects the efficiency of the power plant. By using the first and second law of thermodynamics, the model for the gas turbine power plant is built. Each component in the thermal system which is an air compressor, combustion chamber and gas turbine play roles in affecting the efficiency of the gas turbine power plant. The exergy flow rate for the compressor (AC), the combustion chamber (CC) and the gas turbine (GT) inlet and outlet are calculated based on the physical exergy and chemical exergy. The exergy destruction calculation based on the difference between the exergy flow in and exergy flow out of the component. The combustion chamber has the highest exergy destruction. The air compressor has 94.9% and 92% of exergy and energy efficiency respectively. The combustion chamber has 67.5% and 61.8% of exergy and energy efficiency respectively while gas turbine has 92% and 82% of exergy and energy efficiency respectively. For the overall efficiency, the plant has 32.4% and 34.3% exergy and energy efficiency respectively. To enhance the efficiency, the intake air temperature should be reduced, modify the combustion chamber to have the better air-fuel ratio and increase the capability of the gas turbine to receive high inlet temperature.

  9. Energy and exergy evaluation of a 220MW thermal power plant ...

    African Journals Online (AJOL)

    Energy and exergy evaluation of a 220MW thermal power plant. ... Nigerian Journal of Technology ... At the variation of environmental or dead state temperature, ther e were no appreciable changes in the values of exergy efficiency of the ...

  10. Exergy analysis of heating, refrigerating and air conditioning methods and applications

    CERN Document Server

    Dincer, Ibrahim

    2015-01-01

    Improve and optimize efficiency of HVAC and related energy systems from an exergy perspective. From fundamentals to advanced applications, Exergy Analysis of Heating, Air Conditioning, and Refrigeration provides readers with a clear and concise description of exergy analysis and its many uses. Focusing on the application of exergy methods to the primary technologies for heating, refrigerating, and air conditioning, Ibrahim Dincer and Marc A. Rosen demonstrate exactly how exergy can help improve and optimize efficiency, environmental performance, and cost-effectiveness. The book also discusses the analysis tools available, and includes many comprehensive case studies on current and emerging systems and technologies for real-world examples. From introducing exergy and thermodynamic fundamentals to presenting the use of exergy methods for heating, refrigeration, and air conditioning systems, this book equips any researcher or practicing engineer with the tools needed to learn and master the application of exergy...

  11. Energy and exergy analysis of low temperature district heating network

    International Nuclear Information System (INIS)

    Li, Hongwei; Svendsen, Svend

    2012-01-01

    Low temperature district heating with reduced network supply and return temperature provides better match of the low quality building heating demand and the low quality heating supply from waste heat or renewable energy. In this paper, a hypothetical low temperature district heating network is designed to supply heating for 30 low energy detached residential houses. The network operational supply/return temperature is set as 55 °C/25 °C, which is in line with a pilot project carried out in Denmark. Two types of in-house substations are analyzed to supply the consumer domestic hot water demand. The space heating demand is supplied through floor heating in the bathroom and low temperature radiators in the rest of rooms. The network thermal and hydraulic conditions are simulated under steady state. A district heating network design and simulation code is developed to incorporate the network optimization procedure and the network simultaneous factor. Through the simulation, the overall system energy and exergy efficiencies are calculated and the exergy losses for the major district heating system components are identified. Based on the results, suggestions are given to further reduce the system energy/exergy losses and increase the quality match between the consumer heating demand and the district heating supply. -- Highlights: ► Exergy and energy analysis for low and medium temperature district heating systems. ► Different district heating network dimensioning methods are analyzed. ► Major exergy losses are identified in the district heating network and the in-house substations. ► Advantages to apply low temperature district heating are highlighted through exergy analysis. ► The influence of thermal by-pass on system exergy/energy performance is analyzed.

  12. An exergy analysis on the performance of a counterflow wet cooling tower

    International Nuclear Information System (INIS)

    Muangnoi, Thirapong; Asvapoositkul, Wanchai; Wongwises, Somchai

    2007-01-01

    Cooling towers are used to extract waste heat from water to atmospheric air. An energy analysis is usually used to investigate the performance characteristics of cooling tower. However, the energy concept alone is insufficient to describe some important viewpoints on energy utilization. In this study, an exergy analysis is used to indicate exergy and exergy destruction of water and air flowing through the cooling tower. Mathematical model based on heat and mass transfer principle is developed to find the properties of water and air, which will be further used in exergy analysis. The model is validated against experimental data. It is noted from the results that the amount of exergy supplied by water is larger than that absorbed by air, because the system produces entropy. To depict the utilizable exergy between water and air, exergy of each working fluid along the tower are presented. The results show that water exergy decreases continuously from top to bottom. On the other hand, air exergy is expressed in terms of convective and evaporative heat transfer. Exergy of air via convective heat transfer initially loses at inlet and slightly recovers along the flow before leaving the tower. However, exergy of air via evaporative heat transfer is generally high and able to consume exergy supplied by water. Exergy destruction is defined as the difference between water exergy change and air exergy change. It reveals that the cooling processes due to thermodynamics irreversibility perform poorly at bottom and gradually improve along the height of the tower. The results show that the lowest exergy destruction is located at the top of the tower

  13. Advanced exergy analysis for a bottoming organic rankine cycle coupled to an internal combustion engine

    International Nuclear Information System (INIS)

    Galindo, J.; Ruiz, S.; Dolz, V.; Royo-Pascual, L.

    2016-01-01

    Highlights: • Advanced exergy analysis were carried out using experimental data of an ORC. • Exergy destruction analyzed as endogenous/exogenous and unavoidable/avoidable. • Exergy destruction was estimated by considering technological restrictions. - Abstract: This paper deals with the evaluation and analysis of a bottoming ORC cycle coupled to an IC engine by means of conventional and advanced exergy analysis. Using experimental data of an ORC coupled to a 2 l turbocharged engine, both conventional and advanced exergy analysis are carried out. Splitting the exergy in the advanced exergy analysis into unavoidable and avoidable provides a measure of the potential of improving the efficiency of this component. On the other hand, splitting the exergy into endogenous and exogenous provides information between interactions among system components. The result of this study shows that there is a high potential of improvement in this type of cycles. Although, from the conventional analysis, the exergy destruction rate of boiler is greater than the one of the expander, condenser and pump, the advanced exergy analysis suggests that the first priority of improvement should be given to the expander, followed by the pump, the condenser and the boiler. A total amount of 3.75 kW (36.5%) of exergy destruction rate could be lowered, taking account that only the avoidable part of the exergy destruction rate can be reduced.

  14. Exergy transfer and parametric study of counter flow wet cooling towers

    International Nuclear Information System (INIS)

    Wang Li; Li Nianping

    2011-01-01

    A thermodynamic analysis of the counter flow wet cooling tower (CWCT) is performed in this paper. Both energy and exergy formulations are developed and validated for the system. Four types of exergy transfer processes occurring inside the CWCT are investigated schematically. A parametric study is conducted under various operating conditions in order to investigate the effects of thermal efficiency and water-to-air ratio on the exergy performance of the CWCT. Unlike past studies, the transiting exergy contained in the inlet and outlet water is not considered. It is found that the exergy efficiency is always less than 25%. The exergy parameters including evaporation water loss, exergy efficiency, exergy input, internal and external exergy losses are very sensitive to the thermal efficiency when it is very close to 1.0 at lower water-to-air ratios. - Research highlights: → We model counter flow wet cooling towers and make a detailed exergy analysis. → Four types of exergy transfer processes are investigated schematically. → Only a small part of exergy input, less than 25%, is effectively utilized.

  15. Advanced exergy analyses of an ejector expansion transcritical CO_2 refrigeration system

    International Nuclear Information System (INIS)

    Bai, Tao; Yu, Jianlin; Yan, Gang

    2016-01-01

    Highlights: • Advanced exergy analyses are performed on CO_2 EERC cycle. • Compressor should be improved first, followed by ejector, evaporator and gas cooler. • Interactions among the system components are assessed with advanced exergy analysis. • Real potential for exergy destruction reduction of the system is 43.44%. - Abstract: This paper presents a thermodynamic investigation on an ejector expansion transcritical CO_2 refrigeration system with advanced exergy analysis. By splitting the exergy destruction into endogenous/exogenous and unavoidable/avoidable parts, more valuable information of the interactions among the system components and the components improvement potential is provided. The results indicate that the compressor with largest avoidable endogenous exergy destruction possesses the highest priority of improvement, followed by the ejector, evaporator and gas cooler. The system exergy destruction is dominantly endogenous, and 43.44% of the total exergy destruction can be avoided by improving the system components. The evaporator has a serious impact on the exogenous exergy destruction within the compressor and ejector, and its own exergy destruction is entirely belongs to endogenous part. The effects of the discharge pressure, compressor efficiency and ejector efficiency on the system exergetic performance are discussed. There is an optimal discharge pressure with respect to the minimum endogenous exergy destruction in the compressor. Avoidable endogenous exergy destruction rates of the compressor and ejector are respectively reduced by 93.6% and 81.7% when the corresponding component efficiency varies from 0.5 to 0.9.

  16. Energy and exergy analysis of industrial fluidized bed drying of paddy

    International Nuclear Information System (INIS)

    Sarker, Md. Sazzat Hossain; Ibrahim, Mohd Nordin; Abdul Aziz, Norashikin; Punan, Mohd Salleh

    2015-01-01

    This paper presents energy and exergy analysis of industrial fluidized bed paddy drying. The maximum design capacity of the dryer was 22 t/h. Existing energy and exergy models developed applying the First and Second law of Thermodynamics are employed to estimate the amounts of energy used, the ratios of energy utilization, magnitude of exergy losses and exergy efficiencies during the drying process. The analysis shows that energy usage and (EUR) energy utilization ratios vary between 38.91 kJ/s to 132.00 kJ/s and 5.24–13.92 %, respectively while exergy efficiency vary from 46.99 to 58.14%. A simple exergy balance reveals that only 31.18–37.01 % exergy are utilized for drying of paddy and the remaining large amount of exergy are wasted. Exergy can be increased through providing sufficient insulation on dryer body and recycling the exhaust air which need to be studied further for investigating the economic feasibility. - Highlights: • Energy and exergy analysis of industrial fluidized bed paddy drying are presented. • Energy usage varies from 38.91 kJ/s to 132.00 kJ/s. • Energy usage ratio is found to vary between 5.24 and 13.38%. • Exergy efficiency varies from 41.30 to 58.14%. • Only 31.18–37.01 % exergy are utilized in the paddy drying system

  17. Exergy Analysis of Serpentine Thermosyphon Solar Water Heater

    Directory of Open Access Journals (Sweden)

    Muhammad Faisal Hasan

    2018-03-01

    Full Text Available The performance of a solar hot water system is assessed for heat pump and domestic heating applications. Thermodynamic analysis on a serpentine-type thermosyphon flat-plate solar heater is conducted using the Second Law of thermodynamics. Exergetic optimization is first performed to determine the parameters for the maximum exergy efficiency using MATLAB optimization toolbox. Geometric parameters (collector surface area, dimensions, and pipe diameter, optical parameters (transmittance absorptance product, ambient temperature, solar irradiation and operating parameters (mass flow rate, fluid temperature, and overall heat transfer (loss coefficient are accounted for in the optimization scheme. The exergy efficiency at optimum condition is found to be 3.72%. The results are validated using experimental data and found to be in good agreement. The analysis is further extended to the influence of various operating parameters on the exergetic efficiency. It is observed that optical and thermal exergy losses contribute almost 20%, whereas approximately 77% exergy destruction is contributed by the thermal energy conversion. Exergy destruction due to pressure drop is found negligible. The result of this analysis can be used for designing and optimization of domestic heat pump system and hot water application.

  18. Minimization of local impact of energy systems through exergy analysis

    International Nuclear Information System (INIS)

    Cassetti, Gabriele; Colombo, Emanuela

    2013-01-01

    Highlights: • The model proposed aims at minimizing local impact of energy systems. • The model is meant to minimize the impact starting from system thermodynamics. • The formulation combines exergy analysis and quantitative risk analysis. • The approach of the model is dual to Thermoeconomics. - Abstract: For the acceptability of energy systems, environmental impacts are becoming more and more important. One primary way for reducing impacts related to processes is by improving efficiency of plants. A key instrument currently used to verify such improvements is exergy analysis, extended to include also the environmental externalities generated by systems. Through exergy-based analyses, it is possible indeed to evaluate the overall amount of resources consumed along all the phases of the life cycle of a system, from construction to dismantling. However, resource consumption is a dimension of the impact of a system at global level, while it may not be considered a measure of its local impact. In the paper a complementary approach named Combined Risk and Exergy Analysis (CRExA) to assess impacts from major accidents in energy systems is proposed, based on the combination of classical exergy analysis and quantitative risk analysis (QRA). Impacts considered are focused on effects on human health. The approach leads to the identification of solutions to minimize damages of major accidents by acting on the energy system design

  19. The application of exergy to human-designed systems

    Science.gov (United States)

    Hamilton, P.

    2012-12-01

    Exergy is the portion of the total energy of a system that is available for conversion to useful work. Exergy takes into account both the quantity and quality of energy. Heat is the inevitable product of using any form of high-quality energy such as electricity. Modern commercial buildings and industrial facilities use large amounts of electricity and so produce huge amounts of heat. This heat energy typically is treated as a waste product and discharged to the environment and then high-quality energy sources are consumed to satisfy low-quality energy heating and cooling needs. Tens of thousands of buildings and even whole communities could meet much of their heating and cooling needs through the capture and reuse of heat energy. Yet the application of exergy principles often faces resistance because it challenges conventions about how we design, construct and operate human-engineered systems. This session will review several exergy case studies and conclude with an audience discussion of how exergy principles may be both applied and highlighted in formal and informal education settings.

  20. Energy, Entropy and Exergy in Communication Networks

    Directory of Open Access Journals (Sweden)

    Slavisa Aleksic

    2013-10-01

    Full Text Available The information and communication technology (ICT sector is continuously growing, mainly due to the fast penetration of ICT into many areas of business and society. Growth is particularly high in the area of technologies and applications for communication networks, which can be used, among others, to optimize systems and processes. The ubiquitous application of ICT opens new perspectives and emphasizes the importance of understanding the complex interactions between ICT and other sectors. Complex and interacting heterogeneous systems can only properly be addressed by a holistic framework. Thermodynamic theory, and, in particular, the second law of thermodynamics, is a universally applicable tool to analyze flows of energy. Communication systems and their processes can be seen, similar to many other natural processes and systems, as dissipative transformations that level differences in energy density between participating subsystems and their surroundings. This paper shows how to apply thermodynamics to analyze energy flows through communication networks. Application of the second law of thermodynamics in the context of the Carnot heat engine is emphasized. The use of exergy-based lifecycle analysis to assess the sustainability of ICT systems is shown on an example of a radio access network.

  1. Exergy analysis of a cogeneration power plant

    International Nuclear Information System (INIS)

    Núñez Bosch, Osvaldo Manuel

    2015-01-01

    In the following study exergetic evaluation of a cogeneration power plant in operation with installed electrical capacity of 24 MW and process heat demand of 190 MW it is performed. The main objective of the research was to determine the influence of the increase in power generation capacity, raising the superheated steam parameters and the number of regenerative heaters on the second law efficiency and irreversibilities in the different components of the plant. To study the power plant was divided into subsystems: steam generator blowdown expander, main steam pipe, steam turbine regenerative heaters, reduction system, deaerator and pumps. The study results show that exergy losses and irreversibilities differ widely from one subsystem to another. In general, the total irreversibility accounted for 70.7% of primary fuel availability. The steam generator subsystem had the highest contribution to the irreversibility of the plant by 54%. It was determined that the increased steam parameters helps reduce the irreversibility and increase the exergetic efficiency of installation. The suppression of the reduction and incorporation of extraction-condensing turbine produce the same effect and helps to reduce power consumption from the national grid. Based on the results recommendations for improving plant efficiency are made. (full text)

  2. Exergy analysis of a 1000 MW double reheat ultra-supercritical power plant

    International Nuclear Information System (INIS)

    Si, Ningning; Zhao, Zhigang; Su, Sheng; Han, Pengshuai; Sun, Zhijun; Xu, Jun; Cui, Xiaoning; Hu, Song; Wang, Yi; Jiang, Long; Zhou, Yingbiao; Chen, Gang; Xiang, Jun

    2017-01-01

    Highlights: • Set up a simple and effective method to analysis the performance of double reheat USC unit. • Exergy loss distribution of the double reheat USC unit was declared. • The sensitivity variations of the unit’s exergy efficiency has been revealed. • Provide the foundation for the operation optimization of double reheat USC unit. - Abstract: This study evaluates the performance of a 1000 MW double reheat ultra-supercritical power plant. An exergy analysis was performed to direct the energy loss distribution of this system. Based on the exergy balance equation, together with exergy efficiency, exergy loss coefficient, and exergy loss rate, the exergy distribution and efficiency of the unit were determined. Results show that the highest exergy loss in furnace is as high as 85%, which caused by the combustion of fuel and heat exchange of water wall. The VHP and the two LPs suffer the highest exergy losses, namely 1.86%, 2.04% and 2.13% respectively. The regenerative heating system has an exergy loss rate of 2.3%. The condenser suffers a heat loss of 999 MW, but its exergy is as low as 20.49 MW. The sensitivity variations of the unit’s exergy efficiency with load, feedwater temperature, main steam temperature and pressure, the twice reheat steam temperatures, and steam exhaust pressure were also analyzed, indicating that load, feedwater temperature, and steam exhaust pressure influence the exergy efficiency of this unit than other elements. The overall exergy efficiency decreases along with the gradual increase of steam exhaust pressure at any constant outlet boiler temperature, but it increases as the load, feedwater temperature, main steam temperature and pressure, and twice reheat steam temperatures increase at fixed steam exhaust pressure.

  3. Comprehensive exergy analysis of a commercial tomato paste plant with a double-effect evaporator

    International Nuclear Information System (INIS)

    Mojarab Soufiyan, Mohamad; Dadak, Ali; Hosseini, Seyed Sina; Nasiri, Farshid; Dowlati, Majid; Tahmasebi, Maryam; Aghbashlo, Mortaza

    2016-01-01

    In this study, a detailed exergy evaluation of a commercial tomato paste plant with a double-effect evaporator was conducted in order to provide information on the system thermodynamic inefficiencies. Using energy and exergy balance equations, all components of the plant were analyzed individually and their exergetic parameters were calculated on the basis of actual operational data. The required data were obtained from Nazchin tomato paste factory located in Tehran, Iran. In addition, it was attempted to quantify the exergy utilized for processing a given amount of the tomato paste. The results showed that over 82% of the total destroyed exergy in the plant occurred in the boiler combination as the main component wasting exergy. Furthermore, exergy analysis introduced this combination as the main equipment rejecting exergy to the ambient where 4.79% of its total exergy input was lost. The rational exergy efficiency of the first- and second-effect evaporative units was found to be 65.33% and 56.60%, respectively. The specific exergy consumption of the tomato paste production was also determined as 16.83 MJ/kg. Generally, exergy concept and its extensions could be served as a powerful assessment technique to optimize the design and performance of multiple-effect evaporation systems employed in food industry. - Highlights: • Exergy analysis of a tomato paste plant with a double-effect evaporator was done. • 82% of the total exergy destruction rate occurred in the boiler combination. • 16.83 MJ exergy was utilized for production of 1 kg tomato paste. • Optimal number of effects could be potentially found using exergy-based approaches.

  4. Assessing exergy of forest ecosystem using airborne and satellite data

    Science.gov (United States)

    Brovkina, Olga; Fabianek, Tomas; Lukes, Petr; Zemek, Frantisek

    2017-04-01

    Interactions of the energy flows of forest ecosystem with environment are formed by a suite of forest structure, functions and pathways of self-control. According to recent thermodynamic theory for open systems, concept of exergy of solar radiation has been applied to estimate energy consumptions on evapotranspiration and biomass production in forest ecosystem or to indicate forest decline and human land use impact on ecosystem stability. However, most of the methods for exergy estimation in forest ecosystem is not stable and its physical meaning remains on the surface. This study was aimed to contribute to understanding the exergy of forest ecosystem using combination of remote sensing (RS) and eddy covariance technologies, specifically: 1/to explore exergy of solar radiation depending on structure of solar spectrum (number of spectral bands of RS data), and 2/to explore the relationship between exergy and flux tower eddy covariance measurements. Two study forest sites were located in Western Beskids in the Czech Republic. The first site was dominated by young Norway spruce, the second site was dominated by mature European beech. Airborne hyperspectral data in VNIR, SWIR and TIR spectral regions were acquired 9 times for study sites during a vegetation periods in 2015-2016. Radiometric, geometric and atmospheric corrections of airborne data were performed. Satellite multispectral Landsat-8 cloud-free 21 scenes were downloaded and atmospherically corrected for the period from April to November 2015-2016. Evapotranspiration and latent heat fluxes were collected from operating flux towers located on study sites according to date and time of remote sensing data acquisition. Exergy was calculated for each satellite and airborne scene using various combinations of spectral bands as: Ex=E^out (K+ln E^out/E^in )+R, where Ein is the incoming solar energy, Eout is the reflected solar energy, R = Ein-Eout is absorbed energy, Eout/Ein is albedo and K is the Kullback increment

  5. Exergy analysis of aluminum recovery from municipal solid waste incineration

    DEFF Research Database (Denmark)

    Vyzinkarova, Dana; Allegrini, Elisa; Laner, D.

    Two main challenges, associated with the recovery of aluminum from state-of-the-art municipal solid waste (MSW) incineration plants, are yield as well as quality losses of metallic aluminum due to particle surface oxidation and presence of impurities. Yet, in the framework of life cycle assessment...... (LCA) a direct measure for expressing the quality of primary and secondary resources is missing. In view of a possible solution, exergy has been proposed as a concept to evaluate the quality of resources. In this paper, LCA and exergy analyses for two waste treatment approaches are conducted...... in parallel to each other, with a goal to evaluate the added value of exergy for LCA studies in the resource recovery context. The functional unit is the treatment of 1 ton MSW. Two alternative approaches for recovering aluminum from MSW directed to a waste-to-energy plant are considered. A) MSW is treated...

  6. Energy and Exergy Analyses of the Danish Industry Sector

    DEFF Research Database (Denmark)

    Bühler, Fabian; Nguyen, Tuong-Van; Elmegaard, Brian

    2016-01-01

    A detailed analysis of the Danish industry is presented in this paper using the energy and exergy methods. For the 22 most energy-intensive process industries, which represent about 80% of the total primary energy use of the industrial sector, detailed end-use models were created and analysed...... of using electricity and district heat in the industry is shown. The exergy efficiencies for each process industry were found to be in the range of 12% to 56% in 2012. However variations in the efficiencies within the sectors for individual process industries occur, underlining the need for detailed......, by determining the sectors losses and exergy destruction. In addition the importance of applying a system analysis is shown, which corrects the site efficiencies for electricity and district heating use. The use of 22 industries,further highlights differences amongst industries belonging to the same sector....

  7. Exergy analysis of biomass organic Rankine cycle for power generation

    Science.gov (United States)

    Nur, T. B.; Sunoto

    2018-02-01

    The study examines proposed small biomass-fed Organic Rankine Cycle (ORC) power plant through exergy analysis. The system consists of combustion burner unit to utilize biomass as fuel, and organic Rankine cycle unit to produce power from the expander. The heat from combustion burner was transfered by thermal oil heater to evaporate ORC working fluid in the evaporator part. The effects of adding recuperator into exergy destruction were investigated. Furthermore, the results of the variations of system configurations with different operating parameters, such as the evaporating pressures, ambient temperatures, and expander pressures were analyzed. It was found that the largest exergy destruction occurs during processes are at combustion part, followed by evaporator, condenser, expander, and pump. The ORC system equipped with a recuperator unit exhibited good operational characteristics under wide range conditions compared to the one without recuperator.

  8. Exergy analysis for Generation IV nuclear plant optimization

    International Nuclear Information System (INIS)

    Gomez, A.; Azzaro-Pantel, C.; Domenech, S.; Pibouleau, L.; Latge, Ch.; Haubensack, D.; Dumaz, P.

    2010-01-01

    This paper deals with the application of the exergy concept to an energy production system involving a very high temperature reactor coupled with an innovative electricity-generating cycle. The objective is to propose a general approach to quantify exergy destruction of the involved process components, modelled by a thermodynamic simulator (Proceedings of the Conference on High Temperature Reactors, Beijing, China, 22-24 September 2004, International Atomic Agency, Vienna (Austria), HTR-2004; 1-11). The minimization of exergy destruction is then identified as the optimization criterion used in an optimization framework based on a genetic algorithm, in which the model is embedded. Finally, the approach is applied to electrical production by a Brayton-Rankine combined cycle connected to a nuclear reactor. Some typical results are presented. The perspectives of this work including the cogeneration of hydrogen and electricity are highlighted. (authors)

  9. Exergy analysis for Generation IV nuclear plant optimization

    Energy Technology Data Exchange (ETDEWEB)

    Gomez, A.; Azzaro-Pantel, C.; Domenech, S.; Pibouleau, L. [Univ Toulouse, Lab Genie Chim, CNRS, UMR 5503, F-31700 Toulouse 1 (France); Latge, Ch. [CEA Cadarache DEN DTN DIR, St Paul Les Durance, (France); Haubensack, D.; Dumaz, P. [CEA Cadarache DEN DER SESI LCSI, St Paul Les Durance (France)

    2010-07-01

    This paper deals with the application of the exergy concept to an energy production system involving a very high temperature reactor coupled with an innovative electricity-generating cycle. The objective is to propose a general approach to quantify exergy destruction of the involved process components, modelled by a thermodynamic simulator (Proceedings of the Conference on High Temperature Reactors, Beijing, China, 22-24 September 2004, International Atomic Agency, Vienna (Austria), HTR-2004; 1-11). The minimization of exergy destruction is then identified as the optimization criterion used in an optimization framework based on a genetic algorithm, in which the model is embedded. Finally, the approach is applied to electrical production by a Brayton-Rankine combined cycle connected to a nuclear reactor. Some typical results are presented. The perspectives of this work including the cogeneration of hydrogen and electricity are highlighted. (authors)

  10. EXERGY ANALYSIS OF GEOTHERMAL POWER PLANT KAMOJANG 68, 3 MW IN CAPACITY

    OpenAIRE

    Aziz, Amiral

    2018-01-01

    The importance of exergy analysis in preliminary design of geothermal power has been proven. An exergy analysis was carried out and the locations and quantities of exergy losses, wastes and destructions in the different processes of the plan were pinpointed. The obtained results show that the total exergy available from production wells KMJ 68 was calculated to be 6967.55 kW. The total exergy received from wells which is connected during the analysis and enter into the separator was found to ...

  11. Exergy analysis of the FIGUEIRA thermal power plant operation - state of Parana, Brazil

    Energy Technology Data Exchange (ETDEWEB)

    Stanescu, George; Lima, Joao E. [Parana Univ., Curitiba, PR (Brazil). Dept. de Engenharia Mecanica]. E-mails: stanescu@demec.ufpr.br; joeduli@demec.ufpr.br; Andrade, Carlos de [FIGUEIRA Thermal Power Plant, Figueira, PR (Brazil)]. E-mail: ccarlosaandrade@zipmail.com.br

    2000-07-01

    Exergy analysis is a powerful tool to evaluate, design and improve the thermal systems. The method of exergy analysis or availability analysis is well suited for furthering the goal of increasing the efficiency of existing power generation systems, and the capability of more effective energy resource use. Exergy analysis of the FIGUEIRA thermal power plant is presented. Exergy losses occurring in various components are considered and the exergy balance is shown in tabular form. Results clearly reveal that the steam generator is the principal site of thermodynamic losses, while the condenser is relatively unimportant. (author)

  12. Exergy analysis of a solar-powered vacuum membrane distillation unit using two models

    International Nuclear Information System (INIS)

    Miladi, Rihab; Frikha, Nader; Gabsi, Slimane

    2017-01-01

    A detailed exergy analysis of a solar powered VMD unit was performed using two models: the ideal mixture model and the model using the thermodynamics properties of seawater. The exergy flow rates of process steam, given by the two models differed of about 18%, on average. Despite these differences, the two models agree that during the step of condensation, the most important fraction of exergy was destroyed. Moreover, in this work, two forms of exergy efficiency are calculated. The overall exergy efficiency of the unit with reference to the exergy collected by the solar collector was 3.25% and 2.30% according to Cerci and Sharqawy models, respectively. But, it was 0.182% and 0.128%, when referenced to the exergy of solar radiation, according to Cerci and Sharqawy models, respectively. Besides, the utilitarian exergy efficiency was 9.96%. Since the heat exchanger, the hollow-fiber module and the condenser have a very high exergy performance, then it can be concluded that the enhancement or reduction of exergy losses will be mainly by recovering heat lost in brine discharges and in the rejection of the cooling water. In addition, the influence of the rejection rate on exergy efficiencies was studied. - Highlights: • Two exergy models were compared using a VMD plant dataset. • Two forms of exergy efficiency were evaluated and discussed. • The components responsible for the biggest losses in the system were identified. • The direction for performance enhancement of the desalination device was pointed out. • The influence of the rejection rate on exergy efficiencies was studied.

  13. Exergy analysis of wine production: Red wine production process as a case study

    International Nuclear Information System (INIS)

    Genc, Mahmut; Genc, Seda; Goksungur, Yekta

    2017-01-01

    Highlights: • Red wine production process was studied thermodynamically by exergy analysis method. • The first study on exergetic analysis of a red wine production process. • Energetic and exergetic efficiencies are calculated as 57.2 and 41.8%, respectively. • Cumulative exergy loss is computed as 2692.51 kW for 1 kg/s grape. • Specific exergy loss is found as 5080.20 kW/kg wine. - Abstract: This paper performs exergy analysis of a red wine production line and defines the exergy destruction rates to assess the system performance in terms of sustainability. A model study with necessary data is chosen for the calculations. The total exergy destruction rate of the overall system was determined to be 344.08 kW while the greatest destruction rate of the exergy in the whole system occurred in the open fermenter (333.6 kW). The system thermal efficiency was obtained to be 57.2% while the exergy efficiency was calculated as 41.8%. The total exergy destruction rate of the overall system increases with the increase both in the grape flow rate and the reference temperature when the reference pressure is assumed as 101.325 kPa. Furthermore, the chemical exergy of streams was found much higher than the physical exergy for each stream. The exergy results were illustrated through the Grassmann diagram. Furthermore, cumulative exergy loss and specific exergy loss values were determined as 2692.51 kW/1 kg/s grape processed and 5080.20 kW/kg wine, respectively.

  14. More efficient mushroom canning through pinch and exergy analysis

    NARCIS (Netherlands)

    Paudel, Ekaraj; Sman, van der Ruud G.M.; Westerik, Nieke; Awasthi, Ashutosh; Dewi, Belinda P.C.; Boom, Remko M.

    2017-01-01

    Conventional production of canned mushrooms involves multiple processing steps as vacuum hydration, blanching, sterilization, etc. that are intensive in energy and water usage. We analyzed the current mushroom processing technique plus three alternative scenarios via pinch and exergy analysis.

  15. Thermodynamic optimization of heat exchanger tanks by exergy ...

    African Journals Online (AJOL)

    The paper introduces heat exchanger tanks, detailing their dominant thermodynamic relations to obtain the exergy analysis relations of heat exchanger tanks. Heat exchanger tank is examined under various laboratory conditions, including the power of heat element inside the tank, mass flow rate of cooling water of tank ...

  16. Exergy analysis of an IGCC design configuration for Plant Wansley

    International Nuclear Information System (INIS)

    Tsatsaronis, G.; Tawfik, T.; Lin, L.; Gallaspy, D.T.

    1989-01-01

    An integrated gasification-combined-cycle power plant design was developed for Georgia Power Company's Plant Wansley. This paper discusses the plant configuration and presents the most important results obtained from a detailed exergy analysis of the plant design. This analysis will be completed in a subsequent paper through an exergoeconomic analysis to identify design improvements for reducing the electricity cost

  17. Evaluation of seasonal exergy efficiency of air handing unit

    Directory of Open Access Journals (Sweden)

    Kęstutis Genys

    2015-10-01

    Full Text Available The article deals with the air handling unit seasonal exergy efficiency. TRNSYS simulation tool is used to evaluate it. The object of research is air treatment device used to treat an air for the ventilation of laboratory. The mathematical model of air handling unit using TRNSYS simulation tool was developed when the technical parameters of air handling unit and energy exchange in it were analysed. The developed model according to the made observations during the warm and cold periods was tested and validation of elements was performed. The simulation of air handling unit operation after the verification of reliability and permitted tolerances was performed. The control mechanisim which allows simulating the operation of air handling unit during cold and warm periods of the year was made. The mathematical algorithm for calculation of air handling unit exergy efficiency coefficient applying the principles of exergy analysis was developed. The seasonal exergy efficiency of air handling unit equal to 3.94 percent during the simulation was obtained.

  18. Energy and Exergy Performance of three FPSO Operational Modes

    DEFF Research Database (Denmark)

    Sánchez, Yamid Alberto Carranza; Junior, Silvio de Oliveira; da Silva, Julio Augusto Mendes

    2015-01-01

    by the FPSO operator. Energy and exergy criteria have been applied to evaluate and compare the performance of components and systems of the three operational modes of the FPSO. The processing and utilities plants have been modeled and simulated by using Aspen HYSYS®. Results indicate that higher oil content...

  19. Exergy optimization of cooling tower for HGSHP and HVAC applications

    International Nuclear Information System (INIS)

    Singh, Kuljeet; Das, Ranjan

    2017-01-01

    Highlights: • Development of new correlations for outlet parameters with all inlet parameters. • Simultaneous achievement of required heat load and minimum exergy destruction. • Multiple combinations of parameters found for same heat load at minimized exergy. • Study useful for optimum control of cooling tower under varying ambient conditions. • Generalized optimization study can be implemented for any mechanical cooling tower. - Abstract: In the present work, a constrained inverse optimization method for building cooling applications is proposed to control the mechanical draft wet cooling tower by minimizing the exergy destruction and satisfying an imposed heat load under varying environmental conditions. The optimization problem is formulated considering the cooling dominated heating, ventilation and air conditioning (HVAC) and hybrid ground source heat pump (HGSHP). As per the requirement, new second degree correlations for the tower outlet parameters (water temperature, air dry and wet-bulb temperatures) with five inlet parameters (dry-bulb temperature, relative humidity, water inlet temperature, water and air mass flow rates) are developed. The Box–Behnken design response surface method is implemented for developing the correlations. Subsequently, the constrained optimization problem is solved using augmented Lagrangian genetic algorithm. This work further developed optimum inlet parameters operating curves for the HGSHP and the HVAC systems under varying environmental conditions aimed at minimizing the exergy destruction along with the fulfillment of the required heat load.

  20. Energy and exergy analyses of malt drink production in Nigeria

    International Nuclear Information System (INIS)

    Fadare, D.A.; Nkpubre, D.O.; Oni, A.O.; Falana, A.; Waheed, M.A.; Bamiro, O.A.

    2010-01-01

    Energy requirements and exergy inefficiencies for processing of malt drink were estimated for a Nigerian brewery. The process was divided into twenty-one basic unit operations and grouped into four main group operations: silo house, brew house, filter room and packaging house. The energy intensity for processing a batch of 9.8 tonnes brew grains to 562 hl of malt drink was estimated as 261.63 MJ/hl consisting of electrical (41.01%), thermal (58.81%) and manual (0.19%) of the total energy. The most energy intensive group operation was the Packaging House operation, followed by the Brew House operation with energy intensities of 223.19 and 35.94 MJ/hl, respectively. The exergy analysis revealed that the packaging house operation was responsible for most of the inefficiency (92.16%) followed by brew house operation (7.17%) and the silo house and filter room operations with less than 1% of the total exergy lost. The most exergy loss took place in the pasteurizer, which accounted for 59.75% of the overall system inefficiency. Modification in the pasteurizer and use of spent grains as alternate source of energy in the steam boiler were recommended to improve the energy efficiency of the system.

  1. Energy and exergy analyses of malt drink production in Nigeria

    Energy Technology Data Exchange (ETDEWEB)

    Fadare, D.A.; Nkpubre, D.O.; Oni, A.O.; Falana, A.; Bamiro, O.A. [Mechanical Engineering Department, University of Ibadan, P. M.B. 1, Ibadan, Oyo State (Nigeria); Waheed, M.A. [Mechanical Engineering Department, University of Agriculture, P. M.B. 2240, Abeokuta, Ogun State (Nigeria)

    2010-12-15

    Energy requirements and exergy inefficiencies for processing of malt drink were estimated for a Nigerian brewery. The process was divided into twenty-one basic unit operations and grouped into four main group operations: silo house, brew house, filter room and packaging house. The energy intensity for processing a batch of 9.8 tonnes brew grains to 562 hl of malt drink was estimated as 261.63 MJ/hl consisting of electrical (41.01%), thermal (58.81%) and manual (0.19%) of the total energy. The most energy intensive group operation was the Packaging House operation, followed by the Brew House operation with energy intensities of 223.19 and 35.94 MJ/hl, respectively. The exergy analysis revealed that the packaging house operation was responsible for most of the inefficiency (92.16%) followed by brew house operation (7.17%) and the silo house and filter room operations with less than 1% of the total exergy lost. The most exergy loss took place in the pasteurizer, which accounted for 59.75% of the overall system inefficiency. Modification in the pasteurizer and use of spent grains as alternate source of energy in the steam boiler were recommended to improve the energy efficiency of the system. (author)

  2. Sugarcane exergy calculation; Calculo de la exergia de la cana de azucar

    Energy Technology Data Exchange (ETDEWEB)

    Fernandez P, Maria I.; Nebra P, Silvia A. [Universidade Estadual de Campinas, SP (Brazil). Faculdade de Engenharia Mecanica. Dept. de Energia]. E-mails: mariai@fem.unicamp.br.; sanebra@fem.unicamp.br; Martinez R, Arnaldo [Universidade de Oriente, Santiago de Cuba (Cuba). Facultad de Ingenieria Mecanica. Centro de Estudios de Refrigeracion Luis Fernando Brossard Perez]. E-mail: arnaldo@fim.ceefe.uo.edu.cu

    2000-07-01

    This paper presents a sugarcane exergy calculation, carried out considering the material as constituted by dry fiber and juice, being the last one that includes all the sucrose and water present in sugarcane. The variation intervals of sugarcane chemical composition and consequently the chemical composition of fibre and juice were obtained from a bibliography research. the finals results show that, the fibre exergy, as was considered totally dry and without sucrose, is a function of it chemical composition only. The quotient between the exergy and low calorific value has a middle value of 1,14 and the middle value of it exergy was 2329 kJ/kg of cane. Based on the environmental reference proposed by Szargut for the sugarcane juice exergy determination, it was obtained that the mixture component of the juice exergy has no piratical influence in the total exergy juice value, being the value of the reactive exergy component the determining of a middle value of sugarcane juice exergy of 2814,25 kJ/kg of juice and 2380Kj/Kg of cane. The sugarcane exergy value obtained for 8-18% of fiber, 75-82% of water and 14.5-22% of sucrose was 4709Kj/kg of cane. (author)

  3. Energy and exergy analysis of an annular shaft kiln with opposite burners

    International Nuclear Information System (INIS)

    Rong, Wenjie; Li, Baokuan; Qi, Fengsheng; Cheung, Sherman C.P.

    2017-01-01

    Highlights: • An OBASK is investigated for the energy and exergy performance. • The energy and exergy efficiency of the OBASK is of 63.6% and 35.7%, respectively. • The exergy destruction accounts for 44.5% of the total exergy input. - Abstract: Annular shaft kilns with opposite burners (OBASK) has been widely adopted due to the advantages of cost saving and easy controlling. Nonetheless, compared with the traditional annular shaft kiln, the OBASK is not favorable in terms of thermal performance and energy efficiency. Aiming to improve the thermal performance, a comprehensive energy and exergy analysis of an OBASK has been conducted based on the actual operational data obtained from on-site measurements. For making a thorough thermal analysis of the OBASK, special attentions have been focused in considering magnesium decomposition reaction and moisture in limestone in the methodology. The energy and exergy efficiencies are determined to be 63.6% and 35.7%, respectively. The exergy destruction is 44.0% of total exergy input of which fuel combustion causes 56.6% of the exergy destruction. Furthermore, the effects of CaO and moisture contents in limestone on energy and exergy efficiencies are analyzed. The results have demonstrated the potential energy saving of the OBASK and identified three proposed energy conservation measures. Improvement and effect of the three proposed measures on the thermal performance are verified via further analysis.

  4. Advanced exergy analysis on a modified auto-cascade freezer cycle with an ejector

    International Nuclear Information System (INIS)

    Bai, Tao; Yu, Jianlin; Yan, Gang

    2016-01-01

    This paper presents a study on a modified ejector enhanced auto-cascade freezer cycle with conventional thermodynamic and advanced exergy analysis methods. The energetic analysis shows that the modified cycle exhibits better performance than the conventional auto-cascade freezer cycle, and the system COP and volumetric refrigeration capacity could be improved by 19.93% and 28.42%. Furthermore, advanced exergy analysis is adopted to better evaluate the performance of the proposed cycle. The exergy destruction within a system component is split into endogenous/exogenous and unavoidable/avoidable parts in the advanced exergy analysis. The results show that the compressor with the largest avoidable endogenous exergy destruction has highest improvement priority, followed by the condenser, evaporator and ejector, which is different from the conclusion obtained from the conventional exergy analysis. The evaporator/condenser greatly affects the exogenous exergy destruction within the system components, and the compressor has large impact on the exergy destruction within the condenser. Improving the efficiencies of the compressor efficiency and the ejector could effectively reduce the corresponding avoidable endogenous exergy destruction. The exergy destruction within the evaporator almost entirely belongs to the endogenous part, and reducing the temperature difference at the evaporator is the main approach of reducing its exergy destruction. - Highlights: • A modified ejector enhanced auto-cascade freezer cycle is proposed. • Conventional and advanced exergy analyses are performed in this study. • Compressor should be firstly improved first, followed by condenser and evaporator. • Interactions among the system components are assessed with advanced exergy analysis.

  5. Role of exergy in increasing efficiency and sustainability and reducing environmental impact

    International Nuclear Information System (INIS)

    Rosen, Marc A.; Dincer, Ibrahim; Kanoglu, Mehmet

    2008-01-01

    The use of exergy is described as a measure for identifying and explaining the benefits of sustainable energy and technologies, so the benefits can be clearly understood and appreciated by experts and non-experts alike, and the utilization of sustainable energy and technologies can be increased. Exergy can be used to assess and improve energy systems, and can help better understand the benefits of utilizing green energy by providing more useful and meaningful information than energy provides. Exergy clearly identifies efficiency improvements and reductions in thermodynamic losses attributable to more sustainable technologies. A new sustainability index is developed as a measure of how exergy efficiency affects sustainable development. Exergy can also identify better than energy the environmental benefits and economics of energy technologies. The results suggest that exergy should be utilized by engineers and scientists, as well as decision and policy makers, involved in green energy and technologies in tandem with other objectives and constraints

  6. Analysis of cumulative exergy losses in the chains of technological processes

    International Nuclear Information System (INIS)

    Szargut, J.

    1989-01-01

    This paper reports on cumulative exergy consumption (CExC) which characterizes the chain of technological processes leading from natural resources to the final product under consideration. The difference of CExC and exergy of material or energy carrier expresses the cumulative exergy loss (CExL) in the mentioned technological chain. Two apportionment methods of CExL have been proposed. Partial exergy losses appear in particular links of the technological chain and characterize the influence of irreversibility of these links. Constituent exergy losses express the influence of thermodynamic imperfection of constituent technological chains leading to the final link of the total technological chain. Analysis of the partial and constituent exergy losses informs about the possibilities of improvement of the technological chains

  7. Subjective thermal sensation and human body exergy consumption rate: analysis and correlation

    DEFF Research Database (Denmark)

    Simone, Angela; Dovjak, M.; Kolarik, Jakub

    2011-01-01

    , it is reasonable to consider both the exergy flows in building and those within the human body. There is a need to verify the human-body exergy model with the Thermal-Sensation (TS) response of subjects exposed to different combinations of indoor climate parameters (temperature, humidity, etc.). First results...... available on the relation between human-body exergy consumption rates and subjectively assessed thermal sensation showed that the minimum human body exergy consumption rate is associated with thermal sensation votes close to thermal neutrality, tending to slightly cool side of thermal sensation. By applying...... the exergy concept to the built indoor environment, additional results are going to be explored. By using the data available so far of operative temperature (to), the human body exergy consumption rates increase as to increases above 24°C or decreases below 22°C at relative humidity (RH) lower than 50...

  8. An investigation on the assessed thermal sensation and human body exergy consumption rate

    DEFF Research Database (Denmark)

    Simone, Angela; Kolarik, Jakub; Iwamatsu, Toshiya

    2010-01-01

    perception of the indoor environment is rare. As the building should provide healthy and comfortable environment for its occupants, it is reasonable to consider both the exergy flows in the building and within the human body. A relatively new approach of the relation between the exergy concept and the built......-environment research has been explored in the present work. The relationship of subjectively assessed thermal sensation data, from earlier thermal comfort studies, to the calculated human-body exergy consumption has been analysed. The results show that the minimum human body exergy consumption rate was related......The exergy concept helps to optimize indoor climate conditioning systems to meet the requirements of sustainable building design. While the exergy approach to design and operation of indoor climate conditioning systems is relatively well established, its exploitation in connection to human...

  9. A relation between calculated human body exergy consumption rate and subjectively assessed thermal sensation

    DEFF Research Database (Denmark)

    Simone, Angela; Kolarik, Jakub; Iwamatsu, Toshiya

    2011-01-01

    occupants, it is reasonable to consider both the exergy flows in building and those within the human body. Until now, no data have been available on the relation between human-body exergy consumption rates and subjectively assessed thermal sensation. The objective of the present work was to relate thermal...... sensation data, from earlier thermal comfort studies, to calculated human-body exergy consumption rates. The results show that the minimum human body exergy consumption rate is associated with thermal sensation votes close to thermal neutrality, tending to the slightly cool side of thermal sensation....... Generally, the relationship between air temperature and the exergy consumption rate, as a first approximation, shows an increasing trend. Taking account of both convective and radiative heat exchange between the human body and the surrounding environment by using the calculated operative temperature, exergy...

  10. Framework for analysis of solar energy systems in the built environment from an exergy perspective

    OpenAIRE

    Torio, H.; Schmidt, D.

    2010-01-01

    Exergy analysis is a more powerful tool than mere energy analysis for showing the improvement potential of energy systems. Direct use of solar radiation instead of degrading other high quality energy resources found in nature is advantageous. Yet, due to physical inconsistencies present in the exergy analysis framework for assessing direct-solar systems commonly found in literature, high exergy losses arise in the conversion process of solar radiation in direct-solar systems. However, these l...

  11. Performance analysis of ventilation systems with desiccant wheel cooling based on exergy destruction

    International Nuclear Information System (INIS)

    Tu, Rang; Liu, Xiao-Hua; Hwang, Yunho; Ma, Fei

    2016-01-01

    Highlights: • Ventilation systems with desiccant wheel were analyzed from exergy destruction. • Main performances influencing factors for ventilation systems are put forward. • Improved ventilation systems with lower exergy destruction are suggested. • Performances of heat pumps driven ventilation systems are greatly increased. - Abstract: This paper investigates the performances of ventilation systems with desiccant wheel cooling from the perspective of exergy destructions. Based on the inherent influencing factors for exergy destructions of heat and mass transfer and heat sources, provide guidelines for efficient system design. First, performances of a basic ventilation system are simulated, which is operated at high regeneration temperature and low coefficient of performance (COP). Then, exergy analysis of the basic ventilation system shows that exergy destructions mainly exist in the heat and mass transfer components and the heat source. The inherent influencing factors for the heat and mass transfer exergy destruction are heat and mass transfer capacities, which are related to over dehumidification of the desiccant wheel, and unmatched coefficients, which represent the uniformity of the temperature or humidity ratio differences fields for heat and mass transfer components. Based on these findings, two improved ventilation systems are suggested. For the first system, over dehumidification is avoided and unmatched coefficients for each component are reduced. With lower heat and mass transfer exergy destructions and lower regeneration temperature, COP and exergy efficiency of the first system are increased compared with the basic ventilation system. For the second system, a heat pump, which recovers heat from the process air to heat the regeneration air, is adopted to replace the electrical heater and cooling devices. The exergy destruction of the heat pump is considerably reduced as compared with heat source exergy destruction of the basic ventilation

  12. Energy–exergy analysis and optimisation of a model sugar factory in Turkey

    International Nuclear Information System (INIS)

    Taner, Tolga; Sivrioglu, Mecit

    2015-01-01

    This study is related to the energy and exergy analysis of a model sugar factory in Turkey. In this study, energy efficiency issue in food industries are investigated within a general context to provide energy saving by reducing energy – exergy losses in the sugar production process. The aim of this study is to determine the best energy and exergy efficiency with the mass and energy balances according to design parameters for a sugar factory. Energy savings that can be applied in food industries are examined. Appropriate scenarios are prepared, and optimization results are compared. As a result of thermodynamics calculations made according to the 1st and 2nd Laws of Thermodynamics, energy and exergy efficiencies of a factory were calculated. Factory total energy efficiency and exergy efficiency were found to be 72.2% and 37.4%, respectively, and according to these results, energy quality was found to be 0.64. In conclusion, the current turbine power process energy and exergy efficiencies were 46.4% and 27.7%, respectively, and the optimized turbine power process energy and exergy efficiencies were 48.7% and 31.7%, respectively. This study performs an attitude to the problem of exergy optimization of the turbine power plant. An overall assessment of the energy and exergy efficiency calculations is performed and is focused on how they should be. - Highlights: • The energy and exergy efficiency of a sugar plant depends more on steam than process. • Energy and exergy efficiencies of a factory increase when the turbine power increases, as in a sugar factory. • Statistical analysis demonstrates the precision of data. • Thermoeconomic analysis of the energy and exergy efficiency of the Çumra Sugar Integrated Plant is performed.

  13. General methodology for exergy balance in ProSimPlus® process simulator

    International Nuclear Information System (INIS)

    Ghannadzadeh, Ali; Thery-Hetreux, Raphaële; Baudouin, Olivier; Baudet, Philippe; Floquet, Pascal; Joulia, Xavier

    2012-01-01

    This paper presents a general methodology for exergy balance in chemical and thermal processes integrated in ProSimPlus ® as a well-adapted process simulator for energy efficiency analysis. In this work, as well as using the general expressions for heat and work streams, the whole exergy balance is presented within only one software in order to fully automate exergy analysis. In addition, after exergy balance, the essential elements such as source of irreversibility for exergy analysis are presented to help the user for modifications on either process or utility system. The applicability of the proposed methodology in ProSimPlus ® is shown through a simple scheme of Natural Gas Liquids (NGL) recovery process and its steam utility system. The methodology does not only provide the user with necessary exergetic criteria to pinpoint the source of exergy losses, it also helps the user to find the way to reduce the exergy losses. These features of the proposed exergy calculator make it preferable for its implementation in ProSimPlus ® to define the most realistic and profitable retrofit projects on the existing chemical and thermal plants. -- Highlights: ► A set of new expressions for calculation of exergy of material streams is developed. ► A general methodology for exergy balance in ProSimPlus ® is presented. ► A panel of solutions based on exergy analysis is provided to help the user for modifications on process flowsheets. ► The exergy efficiency is chosen as a variable in a bi-criteria optimization.

  14. Sustainability Indicators for the Use of Resources—The Exergy Approach

    DEFF Research Database (Denmark)

    Koroneos, Christopher J.; Nanaki, Evanthia A.; Xydis, George

    2012-01-01

    , trends, and impacts. New thinking and research with regard to indicator frameworks, methodologies, and actual indicators are also needed. The value of the overall indicators depends on the production procedure of each material, and indicates their environmental impact. The use of “exergy indicators......” based on the exergy content of materials and the use of the second law of thermodynamics in this work presents the relationship between exergy content and environmental impact....

  15. Exergy analysis of the solar still integrated nano composite phase change materials

    International Nuclear Information System (INIS)

    Methre, V.K.; Eswaramoorthy, M.

    2015-01-01

    This paper communicates the exergy analysis of solar still integrated with nano composite phase change materials for design and operating parameters. Al_2O_3 nano materials (50 nm) is dispersed by weight ratio in paraffin wax at melting state and its thermophysical properties are evaluated using developed correlation. Exergy balance equation for basin liner, thermal energy storage, glass cover and saline water is developed and exergy efficiency is analysed. It is found that exergy efficiency is improved by higher weight ratio of Al_2O_3 nano materials with paraffin wax alone. (author)

  16. Exergy Analysis of a Ground-Coupled Heat Pump Heating System with Different Terminals

    Directory of Open Access Journals (Sweden)

    Xiao Chen

    2015-04-01

    Full Text Available In order to evaluate and improve the performance of a ground-coupled heat pump (GCHP heating system with radiant floors as terminals, an exergy analysis based on test results is performed in this study. The system is divided into four subsystems, and the exergy loss and exergy efficiency of each subsystem are calculated using the expressions derived based on exergy balance equations. The average values of the measured parameters are used for the exergy analysis. The analysis results show that the two largest exergy losses occur in the heat pump and terminals, with losses of 55.3% and 22.06%, respectively, and the lowest exergy efficiency occurs in the ground heat exchange system. Therefore, GCHP system designers should pay close attention to the selection of heat pumps and terminals, especially in the design of ground heat exchange systems. Compared with the scenario system in which fan coil units (FCUs are substituted for the radiant floors, the adoption of radiant floors can result in a decrease of 12% in heating load, an increase of 3.24% in exergy efficiency of terminals and an increase of 1.18% in total exergy efficiency of the system. The results may point out the direction and ways of optimizing GCHP systems.

  17. The influence of Thomson effect in the energy and exergy efficiency of an annular thermoelectric generator

    International Nuclear Information System (INIS)

    Kaushik, S.C.; Manikandan, S.

    2015-01-01

    Highlights: • Exergy analysis in the annular thermoelectric generator (ATEG) system is proposed. • Analytical expressions for the power output, exergy efficiency of an ATEG is derived. • The effects of S r , R L , and θ in P out and exergy efficiency of an ATEG is studied. • The influence of Thomson effect in P out and exergy efficiency of an ATEG is studied. - Abstract: The exoreversible thermodynamic model of an annular thermoelectric generator (ATEG) considering Thomson effect in conjunction with Peltier, Joule and Fourier heat conduction has been investigated using exergy analysis. New expressions for optimum current at the maximum power output and maximum energy, exergy efficiency conditions, and dimensionless irreversibilities in the ATEG are derived. The modified expression for figure of merit of a thermoelectric generator considering the Thomson effect has also been obtained. The results show that the power output, energy and exergy efficiency of the ATEG is lower than the flat plate thermoelectric generator. The effects of annular shape parameter (S r = r 2 /r 1 ), load resistance (R L ), dimensionless temperature ratio (θ = T h /T c ) and the thermal and electrical contact resistances in power output, energy/exergy efficiency of the ATEG have been studied. It has also been proved that because of the influence of Thomson effect, the power output and energy/exergy efficiency of the ATEG is reduced. This study will help in the designing of the actual annular thermoelectric generation systems

  18. Exergy analysis of a turbofan engine for an unmanned aerial vehicle during a surveillance mission

    International Nuclear Information System (INIS)

    Şöhret, Yasin; Dinç, Ali; Karakoç, T. Hikmet

    2015-01-01

    In this study, an exergy analysis of a turbofan engine, being the main power unit of an UAV (unmanned aerial vehicle) over the course of a surveillance mission flight, is presented. In this framework, an engine model is firstly developed, based upon engine design parameters and conditions using a genuine code. Next, the exergy analysis is performed according to thermodynamic laws. At the end of the study, the combustion chamber is identified as the most irreversible component of the engine, while the high pressure turbine and compressor are identified as the most efficient components throughout the flight. The minimum exergy efficiency is 58.24% for the combustion chamber at the end of the ingress flight phase, while the maximum exergy efficiency is found to be 99.09% for the high pressure turbine at the start of the ingress flight phase and landing loiter. The highest exergy destruction within the engine occurs at landing loiter, take-off and start of climb, with rates of 16998.768 kW, 16820.317 kW and 16564.378 kW respectively. - Highlights: • This study reveals the exergy parameters of a turbofan engine for an UAV. • Exergy analysis is conducted for a complete surveillance mission flight. • Variation of exergy parameters of engine components during the flight is presented. • The impact of the environment conditions on exergy parameters is proven.

  19. Dynamic Exergy Analysis for the Thermal Storage Optimization of the Building Envelope

    Directory of Open Access Journals (Sweden)

    Valentina Bonetti

    2017-01-01

    Full Text Available As a measure of energy “quality”, exergy is meaningful for comparing the potential for thermal storage. Systems containing the same amount of energy could have considerably different capabilities in matching a demand profile, and exergy measures this difference. Exergy stored in the envelope of buildings is central in sustainability because the environment could be an unlimited source of energy if its interaction with the envelope is optimised for maintaining the indoor conditions within comfort ranges. Since the occurring phenomena are highly fluctuating, a dynamic exergy analysis is required; however, dynamic exergy modelling is complex and has not hitherto been implemented in building simulation tools. Simplified energy and exergy assessments are presented for a case study in which thermal storage determines the performance of seven different wall types for utilising nocturnal ventilation as a passive cooling strategy. Hourly temperatures within the walls are obtained with the ESP-r software in free-floating operation and are used to assess the envelope exergy storage capacity. The results for the most suitable wall types were different between the exergy analysis and the more traditional energy performance indicators. The exergy method is an effective technique for selecting the construction type that results in the most favourable free-floating conditions through the analysed passive strategy.

  20. Nonimaging optics maximizing exergy for hybrid solar system

    Science.gov (United States)

    Winston, Roland; Jiang, Lun; Abdelhamid, Mahmoud; Widyolar, Bennett K.; Ferry, Jonathan; Cygan, David; Abbasi, Hamid; Kozlov, Alexandr; Kirk, Alexander; Elarde, Victor; Osowski, Mark

    2016-09-01

    The project team of University of California at Merced (UC-Merced), Gas Technology Institute (GTI) and MicroLink Devices Inc. (MicroLink) are developing a hybrid solar system using a nonimaging compound parabolic concentrator (CPC) that maximizes the exergy by delivering direct electricity and on-demand heat. The hybrid solar system technology uses secondary optics in a solar receiver to achieve high efficiency at high temperature, collects heat in particles and uses reflective liftoff cooled double junction (2J) InGaP/GaAs solar cells with backside infrared (IR) reflectors on the secondary optical element to raise exergy efficiency. The nonimaging optics provides additional concentration towards the high temperature thermal stream and enables it to operate efficiently at 650 °C while the solar cell is maintained at 40 °C to operate as efficiently as possible.

  1. Energy and Exergy Analysis of Cogeration System with Biogas Engines

    OpenAIRE

    Doseva, Nadezhda; Chakyrova, Daniela

    2015-01-01

    In this paper, an existing cogeneration system driven by biogas internal combustion engines (ICE) is a subject of an investigation by energy and exergy analyses. The system is installed in the Varna Wastewater Treatment Plant (Varna WWTP), Bulgaria and its purpose is to utilize the methane produced as a byproduct of the solids stabilization process at Varna WWTP. Otherwise, the produced methane would pollute the environment. The presented paperhas been organised in the following way: first, i...

  2. Exergy analysis of an experimental heat transformer for water purification

    International Nuclear Information System (INIS)

    Rivera, W.; Huicochea, A.; Martinez, H.; Siqueiros, J.; Juarez, D.; Cadenas, E.

    2011-01-01

    First and second law of thermodynamics have been used to analyze the performance of an experimental heat transformer used for water purification. The pure water is produced in the auxiliary condenser delivering an amount of heat, which is recycled into the heat transformer increasing the heat source temperatures and also the internal, external and exergy coefficients of performance. The theoretical and experimental study was divided into two parts. In the first part, a second law analysis was carried out to the experimental system showing that the absorber and the condenser are the components with the highest irreversibilities. In the second part, with the results obtained from the second law analysis, new test runs were carried out at similar conditions than the former but varying only one selected temperature at the time. Comparing the COP (coefficient of performance) between the old and new test runs, it was shown that higher internal, external and exergy coefficients of performance were obtained in all the new test runs. Also it was shown that the ECOP (exergy coefficient of performance) increases with an increment of the amount of the purified water produced and with the decrease of the flow ratio. -- Research highlights: → By the first time an experimental results of a heat transformer for water purification with heat recycling has been presented. → An exergy analysis has been carried out in order to identify the irreversibilities in the main components of the system. → With the results obtained of the second law analysis new experimental test runs were carried out minimizing the system irreversibilities and furthermore increasing the system efficiency.

  3. The concept 'environment' in exergy analysis Some special cases

    International Nuclear Information System (INIS)

    Serova, E.N.; Brodianski, V.M.

    2004-01-01

    The concept 'environment' is of considerable importance in present-day engineering thermodynamics. Introduction of this concept in operation brings not only simplification of the methods of solving classical thermodynamic problems, but also gives the exergy method which forms the major new part of thermodynamics, including some parts of biology, economics and other fields of science. But practice shows that it is necessary to define the concept 'environment' more precisely in some cases

  4. The exergy fields in transport processes: Their calculation and use

    Energy Technology Data Exchange (ETDEWEB)

    Lior, N.; Sarmiento-Darkin, W.; Al-Sharqawi, H.S. [University of Penn, Philadelphia, PA (United States). Dept. of Mechanical Engineering & Applied Mechanics

    2006-04-15

    This paper is a brief review of the method for analyzing the space and time dependent exergy and irreversibility fields in processes. It presents the basic equations, the method for their use, major literature sources, and three examples from the authors' work: flow desiccation, combustion of oil droplets, and combustion of pulverized coal. Conclusions from this Second Law analysis are used to attempt process improvement suggestions.

  5. Ecological accounting based on extended exergy: a sustainability perspective.

    Science.gov (United States)

    Dai, Jing; Chen, Bin; Sciubba, Enrico

    2014-08-19

    The excessive energy consumption, environmental pollution, and ecological destruction problems have gradually become huge obstacles for the development of societal-economic-natural complex ecosystems. Regarding the national ecological-economic system, how to make explicit the resource accounting, diagnose the resource conversion, and measure the disturbance of environmental emissions to the systems are the fundamental basis of sustainable development and coordinated management. This paper presents an extended exergy (EE) accounting including the material exergy and exergy equivalent of externalities consideration in a systematic process from production to consumption, and China in 2010 is chosen as a case study to foster an in-depth understanding of the conflict between high-speed development and the available resources. The whole society is decomposed into seven sectors (i.e., Agriculture, Extraction, Conversion, Industry, Transportation, Tertiary, and Domestic sectors) according to their distinct characteristics. An adaptive EE accounting database, which incorporates traditional energy, renewable energy, mineral element, and other natural resources as well as resource-based secondary products, is constructed on the basis of the internal flows in the system. In addition, the environmental emission accounting has been adjusted to calculate the externalities-equivalent exergy. The results show that the EE value for the year 2010 in China was 1.80 × 10(14) MJ, which is greatly increased. Furthermore, an EE-based sustainability indices system has been established to provide an epitomized exploration for evaluating the performance of flows and storages with the system from a sustainability perspective. The value of the EE-based sustainability indicator was calculated to be 0.23, much lower than the critical value of 1, implying that China is still developing in the stages of high energy consumption and a low sustainability level.

  6. ANALYSIS OF EXERGY PARAMETERS OF BIOGAS POWER PLANT

    Directory of Open Access Journals (Sweden)

    Denysova A.E.

    2014-08-01

    Full Text Available The techniques of an exergy analysis concerning various circuits of biogas units, which allows replacing traditional energy resources and improving environmental conditions, has been presented. The heat schemes of biogas units were proposed, and analysis of their effectiveness was made. The comparison of different cycle parameters of various biogas units (i.e. a combustion turbine unit, a combined cycle gas turbine unit with gas discharges into the boiler and a combined cycle gas turbine with a high-temperature vapor generator and a reheating stage was made, and the comparison of their exergy characteristics was carried out. The results of exergy analysis had demonstrated that the cycle of biogas CCGT (combined cycle gas turbine with a reheating stage and using a high-pressure steam generator is the most effective, that can be explained by the fact that the thermal energy proportions of combustion products, accounting for the steam cycle and the gas cycle are approximately equal, comparing to conventional combined cycle gas turbine units.

  7. Energy, exergy, and economic analysis of a geothermal power plant

    Directory of Open Access Journals (Sweden)

    Hamid Kazemi

    2018-04-01

    Full Text Available The current study aimed at designing a geothermal power plant in the Nonal area in Damavand district for simultaneous generation of thermal energy the electric power in the network of Damavand City and a part of Tehran province, the organic working fluid for the above cycle is R245fa which is a non-flammable fluid of dry type. The values of energy efficiency, exergy, the net rate of entropy change, and the specific output power were calculated as 18.2%, 21.3%, 172.97 kW/K, and 31.43 kJ/kg, respectively. The cost of drilling a well, as well as designing and construction of Damavand’s geothermal power plant, were calculated to be 4.2 and 521.5 million (USD, respectively. Also, the cost per generation of each kW/h of power in Damavand power plant was 17 cents. The estimated payback time is calculated as 15 years. The analysis of the cycle in different months of the year showed that exergy efficiency has little change. The only significant effect of temperature changes was on the exergy efficiency as approximately a change of 2% can be seen during a year.

  8. Energy-, exergy- and emergy analysis of biomass production

    Energy Technology Data Exchange (ETDEWEB)

    Hovelius, K.

    1997-11-01

    In this report, results from analyzing salix-, winter wheat-, and winter rape cultivations from energy, exergy, and EMERGY perspectives are presented. The exchange in terms of energy for this Salix cultivation is 28 times , but if instead an exergy analysis is done the exchange for exactly the same process is 36 times. The energy analysis gives an energy exchange of 8.1 for winter wheat cultivation, and 5.7 for winter rape cultivation. Corresponding exchanges for the exergy analysis are 9.3 for winter wheat and 6.6 for winter rape. The EMERGY analysis gives a transformity for salix of 1.04E+11 sej/kg DM, for winter wheat 3.85E+11 sej/kg DM, and for winter rape 1.03E+12 sej/kg DM. Thus, the EMERGY need is bigger for rape cultivation than for winter wheat and salix cultivations. The NEYR is the ratio between the EMERGY yield and the EMERGY invested from society (economy, services and other resources), and it is 1.10 for this salix cultivation, and 0.66 for both the winter wheat and the winter rape cultivations. The EIR is the ratio between the EMERGY invested from society and the EMERGY invested from the environment, and it is 2.23 for this salix cultivation, 11.5 for the winter wheat cultivation , and 11.8 for the winter rape cultivation. 26 refs, 11 figs, 25 tabs

  9. Exergy Losses in the Szewalski Binary Vapor Cycle

    Directory of Open Access Journals (Sweden)

    Tomasz Kowalczyk

    2015-10-01

    Full Text Available In this publication, we present an energy and exergy analysis of the Szewalski binary vapor cycle based on a model of a supercritical steam power plant. We used energy analysis to conduct a preliminary optimization of the cycle. Exergy loss analysis was employed to perform a comparison of heat-transfer processes, which are essential for hierarchical cycles. The Szewalski binary vapor cycle consists of a steam cycle bottomed with an organic Rankine cycle installation. This coupling has a negative influence on the thermal efficiency of the cycle. However, the primary aim of this modification is to reduce the size of the power unit by decreasing the low-pressure steam turbine cylinder and the steam condenser. The reduction of the “cold end” of the turbine is desirable from economic and technical standpoints. We present the Szewalski binary vapor cycle in addition to a mathematical model of the chosen power plant’s thermodynamic cycle. We elaborate on the procedure of the Szewalski cycle design and its optimization in order to attain an optimal size reduction of the power unit and limit exergy loss.

  10. Exergy analysis of a novel CHP–GSHP coupling system

    International Nuclear Information System (INIS)

    Kang, Shushuo; Li, Hongqiang; Liu, Lifang; Lei, Jing; Zhang, Guoqiang

    2016-01-01

    Highlights: • Exergy loss distributions and efficiency of the novel system are carried out and discussed. • Essential energy saving character of the novel system is revealed. • Influences of key operation parameter on thermodynamic performance are investigated. - Abstract: A novel natural gas based combined heating and power (CHP) and ground source heat pump (GSHP) coupling system has been suggested and analyzed in terms of first law of thermodynamics. In this paper, the performance of the novel system is investigated from the perspective of second law of thermodynamics, and the calculations are completed by the combination of Aspen plus simulation and theoretical derivation. The research results show that, the novel system can obtain total exergy efficiency 22.58%, about 3.7% higher than the reference system. So as to reveal the essential energy saving character about the novel system, the exergy loss distribution differences between the novel and reference system are discussed. Moreover, the key operation parameter which will affect the performance of the novel system is also investigated. The final research results show that, the novel integration approach will provide a good reference for the other similar high-efficiency energy system.

  11. Avoidable and unavoidable exergy destructions of a fluidized bed coal combustor and a heat recovery steam generator

    International Nuclear Information System (INIS)

    Callak, Meliha; Balkan, Firuz; Hepbasli, Arif

    2015-01-01

    Highlights: • Performing advanced exergy analysis of a fluidized-bed combustion for the first time. • Comparing conventional and modified exergy efficiencies of the subsystems. • Deducting inefficiencies of the system components for possible improvements. - Abstract: Advanced exergy analysis was performed using the actual operational data taken from a fluidized bed coal combustor (FBCC) and a heat recovery steam generator (HRSG) in a textile plant located at Torbalı, Izmir. First, the conventional exergy analysis of the units was carried out. The exergetic efficiencies of the units were found to be 44.2% and 46.2%, respectively. Advanced exergy analysis was then performed by splitting the exergy destructions of the units into avoidable and unavoidable parts. The avoidable exergy destruction rates of the FBCC and the HRSG were determined to be 2999 kW and 760 kW according to the measurements. Correspondingly, the exergy efficiencies were modified to 53.1% and 48.1%, respectively

  12. Advantages and limitations of exergy indicators to assess sustainability of bioenergy and biobased materials

    International Nuclear Information System (INIS)

    Maes, Dries; Van Passel, Steven

    2014-01-01

    Innovative bioenergy projects show a growing diversity in biomass pathways, transformation technologies and end-products, leading to complex new processes. Existing energy-based indicators are not designed to include multiple impacts and are too constrained to assess the sustainability of these processes. Alternatively, indicators based on exergy, a measure of “qualitative energy”, could allow a more holistic view. Exergy is increasingly applied in analyses of both technical and biological processes. But sustainability assessments including exergy calculations, are not very common and are not generally applicable to all types of impact. Hence it is important to frame the use of exergy for inclusion in a sustainability assessment. This paper reviews the potentials and the limitations of exergy calculations, and presents solutions for coherent aggregation with other metrics. The resulting approach is illustrated in a case study. Within the context of sustainability assessment of bioenergy, exergy is a suitable metric for the impacts that require an ecocentric interpretation, and it allows aggregation on a physical basis. The use of exergy is limited to a measurement of material and energy exchanges with the sun, biosphere and lithosphere. Exchanges involving services or human choices are to be measured in different metrics. This combination provides a more inclusive and objective sustainability assessment, especially compared to standard energy- or carbon-based indicators. Future applications of this approach in different situations are required to clarify the potential of exergy-based indicators in a sustainability context. -- Highlights: • Innovative bioenergy projects require more advanced sustainability assessments to incorporate all environmental impacts. • Exergy-based indicators provide solutions for objective and robust measurements. • The use of exergy in a sustainability assessment is limited to material exchanges, excluding exchanges with society

  13. Improvement potential of a real geothermal power plant using advanced exergy analysis

    International Nuclear Information System (INIS)

    Gökgedik, Harun; Yürüsoy, Muhammet; Keçebaş, Ali

    2016-01-01

    The main purpose of this paper is to quantitatively evaluate thermodynamic performance of a geothermal power plant (GPP) from potential for improvement point of view. Thus, sources of inefficiency and irreversibilities can be determined through exergy analysis. The advanced exergy analysis is more appropriate to determine real potential for thermodynamic improvements of the system by splitting exergy destruction into unavoidable and avoidable portions. The performance critical components and the potential for exergy efficiency improvement of a GPP were determined by means of the advanced exergy analysis. This plant is the Bereket GPP in Denizli/Turkey as a current operating system. The results show that the avoidable portion of exergy destruction in all components except for the turbines is higher than the unavoidable value. Therefore, much can be made to lessen the irreversibilities for components of the Bereket GPP. The total exergy efficiency of the system is found to be 9.60%. Its efficiency can be increased up to 15.40% by making improvements in the overall components. Although the heat exchangers had lower exergy and modified exergy efficiencies, their exergy improvement potentials were high. Finally, in the plant, the old technology is believed to be one of the main reasons for low efficiencies. - Highlights: • Evaluation of potential for improvement of a GPP using advanced exergy analysis. • Efficiency can be increased up to 15.40% by making improvements in the components. • Heat exchangers are the highest avoidable values, making them the least efficient components in plant. • The main reasons for low efficiencies are believed to be the old technology.

  14. Feasibility study of microalgal and jatropha biodiesel production plants: Exergy analysis approach

    International Nuclear Information System (INIS)

    Ofori-Boateng, Cynthia; Keat, Teong Lee; JitKang, Lim

    2012-01-01

    The exergy analyses performed in this study are based on three thermodynamic performance parameters namely exergy destruction, exergy efficiency and thermodynamic improvement potentials. After mathematical analysis with Aspen Plus software, the results showed that 64% and 44% of the total exergy content of the input resources into microalgal methyl ester (MME) and jatropha methyl ester (JME) production plants were destroyed respectively for 1 ton of biodiesel produced. This implies that only 36% and 56% (for MME and JME production plants respectively) useful energy in the products is available to do work. The highest and lowest exergy destructions were recorded in the oil extraction units (38% and 39% of the total exergy destroyed for MME and JME plants respectively) and transesterification units (5% and 2% of total exergy destroyed for MME and JME plants respectively) respectively for 1 ton biodiesel produced. Since sustainable biodiesel production depends on cultivation of feedstock, oil extraction and transesterification processes, exergy analysis which is carried out on only the transesterification unit cannot justify the thermodynamic feasibility of the whole biodiesel production plant unless a complete thermodynamic assessment has been done for the whole plant. Thus, according to this study which considers all the biodiesel production processes, MME and JME production plants are not thermodynamically feasible. - Highlights: ► 64% of exergy content of input resources into MME production plant is destroyed. ► 44% of exergy content of input resources into JME production plant is destroyed. ► Exergetic efficiencies of MME and JME production plants are far less than 1. ► Thermodynamically, MME and JME production plants are unsustainable. ► Exergy loss can be reduced by using heat integrated reactive distillation process.

  15. Exergy analysis of a gas turbine power plant | Oko | Journal of ...

    African Journals Online (AJOL)

    Exergy analysis of a 100MW gas turbine power plant that works on the. Brayton cycle is presented. The average increase in the thermodynamic degradation of the plant over the period of six (6) years at three different levels of load was assessed. The exergy analysis of the plant was done on two sets of data: one from the ...

  16. Thermodynamic evaluation of a kerosene pre- Fraction unit using energy and exergy analysis

    Directory of Open Access Journals (Sweden)

    Ehsan Ghasemi

    2017-09-01

    Full Text Available This work applies the method of energy and exergy analysis over first step of linear alkyl benzene (LAB production namely kerosene pre fraction plant, to determine unit energy and exergy performance and loss, besides of opportunities for improvement based on operational data. For this purpose macroscopic energy and exergy balance was developed over main equipment including electro pumps, heat exchangers, air coolers, and distillation columns. The results shows that total energy performance of plant is 92.62% by 19.76 MW energy lost, while from exergy perspective, unit performance is 78.08% by 17.92 MW exergy lost. Maximum local exergy lost occurs in the feed pre heater exchanger by 27% performance which is designed to recover energy from top product of second column, furthermore results shows that upgrading low quality energy in air coolers based on heat pump concept would protect energy and exergy emission to the environment and reduce 40% of total lost energy and 16% of total lost exergy in plant.

  17. A relation between calculated human body exergy consumption rate and subjectively assessed thermal sensation

    Energy Technology Data Exchange (ETDEWEB)

    Simone, Angela; Kolarik, Jakub; Olesen, Bjarne W. [ICIEE/BYG, Technical University of Denmark (Denmark); Iwamatsu, Toshiya [Faculty of Urban Environmental Science, Tokyo Metropolitan University (Japan); Asada, Hideo [Architech Consulting Co., Tokyo (Japan); Dovjak, Mateja [Faculty of Civil and Geodetic Engineering, University of Ljubljana (Slovenia); Schellen, Lisje [Eindhoven University of Technology, Faculty of Architecture Building and Planning (Netherlands); Shukuya, Masanori [Laboratory of Building Environment, Tokyo City University, Yokohama (Japan)

    2011-01-15

    Application of the exergy concept to research on the built environment is a relatively new approach. It helps to optimize climate conditioning systems so that they meet the requirements of sustainable building design. As the building should provide a healthy and comfortable environment for its occupants, it is reasonable to consider both the exergy flows in building and those within the human body. Until now, no data have been available on the relation between human-body exergy consumption rates and subjectively assessed thermal sensation. The objective of the present work was to relate thermal sensation data, from earlier thermal comfort studies, to calculated human-body exergy consumption rates. The results show that the minimum human body exergy consumption rate is associated with thermal sensation votes close to thermal neutrality, tending to the slightly cool side of thermal sensation. Generally, the relationship between air temperature and the exergy consumption rate, as a first approximation, shows an increasing trend. Taking account of both convective and radiative heat exchange between the human body and the surrounding environment by using the calculated operative temperature, exergy consumption rates increase as the operative temperature increases above 24 C or decreases below 22 C. With the data available so far, a second-order polynomial relationship between thermal sensation and the exergy consumption rate was established. (author)

  18. An application of energy and exergy analysis in agricultural sector of Malaysia

    International Nuclear Information System (INIS)

    Ahamed, J.U.; Saidur, R.; Masjuki, H.H.; Mekhilef, S.; Ali, M.B.; Furqon, M.H.

    2011-01-01

    Thermodynamic losses usually take place in machineries used for agricultural activities. Therefore, it is important to identify and quantify the losses in order to devise strategies or policies to reduce them. An exergy analysis is a tool that can identify the losses occurred in any sector. In this study, an analysis has been carried out to estimate energy and exergy consumption of the agricultural sector in Malaysia. Energy and exergy efficiencies have been determined for the devices used in the agricultural sector of Malaysia, where petrol, diesel and fuel oil are used to run the machineries. Energy and exergy flow diagrams for the overall efficiencies of Malaysian agricultural sector are presented as well. The average overall energy and exergy efficiencies of this sector were found to be 22% and 20.728%, respectively, within the period from 1991 to 2009. These figures were found to be lower than those of Norway but higher than Turkey. - Highlights: ► Highest exergy efficiency was found about 20.7% for the year 2007. ► The exergy efficiency of the agro-sector in Malaysia was lower than that of energy efficiency. ► It was also found that this sector of Malaysia is less efficient than Saudi Arabia and Norway. ► Energy and exergy losses were identified through this analysis. ► Part of the losses can be reduced using appropriate technology, management and policy.

  19. Exergy analysis of offshore processes on North Sea oil and gas platforms

    DEFF Research Database (Denmark)

    Nguyen, Tuong-Van; Pierobon, Leonardo; Elmegaard, Brian

    2012-01-01

    generation. In this paper, the most thermodynamically inefficient processes are identified by performing an exergy analysis, based on models built with the simulation tools Aspen Plus®, DNA and Aspen HYSYS®. Results reveal that the total exergy destruction of the system amounts to 69.4 MW, while the total...

  20. Exergy analysis of a circulating fluidized bed boiler cogeneration power plant

    International Nuclear Information System (INIS)

    Gürtürk, Mert; Oztop, Hakan F.

    2016-01-01

    Highlights: • Analysis of energy and exergy for a cogeneration power plant have been performed. • This plant has circulating fluidized bed boiler. • Energy and exergy efficiencies of the boiler are obtained as 84.65% and 29.43%, respectively. • Exergy efficiency of the plant was calculated as 20%. - Abstract: In this study, energy and exergy analysis of a cogeneration power plant have been performed. The steam which is produced by the cogeneration power plant is used for salt production and most important part of the cogeneration power plant is the circulation fluidized bed boiler. Energy and exergy efficiency of the circulation fluidized bed boiler were found as 84.65% and 29.43%, respectively. Exergy destruction of the circulation fluidized bed boiler was calculated as 21789.39 kW and 85.89% of exergy destruction in the plant. The automation system of the cogeneration power plant is insufficient. Exergy efficiency of the plant was calculated as 20%. Also, some design parameters increasing energy losses were determined.

  1. Energy and advanced exergy analysis of an existing hydrocarbon recovery process

    International Nuclear Information System (INIS)

    Mehrpooya, Mehdi; Lazemzade, Roozbeh; Sadaghiani, Mirhadi S.; Parishani, Hossein

    2016-01-01

    Highlights: • Advanced exergoeconomic analysis is performed for propane refrigerant system. • Avoidable/unavoidable & endogenous/exogenous irreversibilities were calculated. • Advanced exergetic analysis identifies the potentials for improving the system. - Abstract: An advanced exergy analysis of the Ethane recovery plant in the South Pars gas field is presented. An industrial refrigeration cycle with propane refrigerant is investigated by the exergy analysis method. The equations of exergy destruction and exergetic efficiency for the main cycle units such as evaporators, condensers, compressors, and expansion valves are developed. Exergetic efficiency of the refrigeration cycle is determined to be 33.9% indicating a high potential for improvements. The simulation results reveal that the exergy loss and exergetic efficiencies of the air cooler and expansion sections respectively are the lowest among the compartments of the cycle. The coefficient of performance (COP) is obtained as 2.05. Four parts of irreversibility (avoidable/unavoidable) and (endogenous/exogenous) are calculated for the units with highest inefficiencies. The advanced exergy analysis reveals that the exergy destruction has two major contributors: (1) 59.61% of the exergy is lost in the unavoidable form in all units and (2) compressors contribute to 25.47% of the exergy destruction. So there is a high potential for improvement for these units, since 63.38% of this portion is avoidable.

  2. Energy and exergy use in public and private sector of Saudi Arabia

    Energy Technology Data Exchange (ETDEWEB)

    Dincer, I. E-mail: idincer@kfupm.edu.sa; Hussain, M.M.; Al-Zaharnah, I

    2004-09-01

    In this paper, we deal with the analysis of energy and exergy utilization in the public and private sector of Saudi Arabia by considering the energy and exergy flows for the years between 1990 and 2001. Energy and exergy analyses for the public and private sector are undertaken to study the energy and exergy efficiencies. These sectoral efficiencies are then compared, and energy and exergy flow diagrams for the public and private sector over the years are presented, respectively. Energy and exergy efficiencies of the public and private sector are compared for its six sub-sectors, namely commercial, governmental, streets, Mosques, hospitals and charity associations, particularly illustrated for the year 2000. Hospital sub-sector appears to be the most energy efficient sector and government sub-sector the most exergy efficient one. The results presented here provide insights into the sectoral energy use that may assist energy policy makers for the country. It is believed that the present techniques are useful for analyzing sectoral energy and exergy utilization, and that they provide Saudi Arabia with energy savings through energy efficiency and/or energy conservation measures. It is also be helpful to establish standards to facilitate application in industry and in other planning processes such as energy planning.

  3. Assessment of the Turkish utility sector through energy and exergy analyses

    International Nuclear Information System (INIS)

    Utlu, Zafer; Hepbasli, Arif

    2007-01-01

    The present study deals with evaluating the utility sector in terms of energetic and exergetic aspects. In this regard, energy and exergy utilization efficiencies in the Turkish utility sector over a wide range of period from 1990 to 2004 are assessed in this study. Energy and exergy analyses are performed for eight power plant modes, while they are based on the actual data over the period studied. Sectoral energy and exergy analyses are conducted to study the variations of energy and exergy efficiencies for each power plants throughout the years, and overall energy and exergy efficiencies are compared for these power plants. The energy utilization efficiencies for the overall Turkish utility sector range from 32.64% to 45.69%, while the exergy utilization efficiencies vary from 32.20% to 46.81% in the analyzed years. Exergetic improvement potential for this sector are also determined to be 332 PJ in 2004. It may be concluded that the methodology used in this study is practical and useful for analyzing sectoral and subsectoral energy and exergy utilization to determine how efficient energy and exergy are used in the sector studied. It is also expected that the results of this study will be helpful in developing highly applicable and productive planning for energy policies

  4. energy and exergy evaluation of a 220mw thermal power plant

    African Journals Online (AJOL)

    HOD

    The outcomes of this work provide the exergy consumption and distribution profiles of the thermal power plant ... power plant with post-combustion CO2 capture. The once-through boiler exhibited the highest exergy destruction of all the plants ...

  5. Energy and exergy use in public and private sector of Saudi Arabia

    International Nuclear Information System (INIS)

    Dincer, I.; Hussain, M.M.; Al-Zaharnah, I.

    2004-01-01

    In this paper, we deal with the analysis of energy and exergy utilization in the public and private sector of Saudi Arabia by considering the energy and exergy flows for the years between 1990 and 2001. Energy and exergy analyses for the public and private sector are undertaken to study the energy and exergy efficiencies. These sectoral efficiencies are then compared, and energy and exergy flow diagrams for the public and private sector over the years are presented, respectively. Energy and exergy efficiencies of the public and private sector are compared for its six sub-sectors, namely commercial, governmental, streets, Mosques, hospitals and charity associations, particularly illustrated for the year 2000. Hospital sub-sector appears to be the most energy efficient sector and government sub-sector the most exergy efficient one. The results presented here provide insights into the sectoral energy use that may assist energy policy makers for the country. It is believed that the present techniques are useful for analyzing sectoral energy and exergy utilization, and that they provide Saudi Arabia with energy savings through energy efficiency and/or energy conservation measures. It is also be helpful to establish standards to facilitate application in industry and in other planning processes such as energy planning

  6. An application of energy and exergy analysis in residential sector of Malaysia

    International Nuclear Information System (INIS)

    Saidur, R.; Masjuki, H.H.; Jamaluddin, M.Y.

    2007-01-01

    In this paper, the useful concept of energy and exergy utilization is defined, analyzed and applied to the residential sector of Malaysia by taking into account the energy and exergy flows for a period of 8 years from the year 1997 to 2004. The energy and exergy efficiencies are determined for the devices used in this sector and found to be 70% and 28%, respectively. Energy and exergy flow diagrams for the overall efficiencies of Malaysian residential sector are also illustrated in this paper. It is found that the current methodology applied in Saudi Arabia is suitable to analyze energy and exergy use in Malaysian residential sector. It has been found that the exergy efficiency of the Malaysian residential sector appears to be much lower than its corresponding energy efficiency. It has been observed that about 21% of total exergy losses are caused by refrigerator-freezer and 12% of total loss is caused by air conditioner. Washing machine, fan and rice cooker contribute about 11%, 10% and 8% of total exergy losses, respectively

  7. Energy system analysis of a pilot net-zero exergy district

    International Nuclear Information System (INIS)

    Kılkış, Şiir

    2014-01-01

    Highlights: • Östra Sala backe is analyzed as a pilot district for the net-zero exergy target. • An analysis tool is developed for proposing an energy system for Östra Sala backe. • A total of 8 different measures are included and integrated in the energy system. • The exergy produced on-site is 49.7 GW h, the annual exergy consumed is 54.3 GW h. • The average value of the level of exergy match in the supply and demand is 0.84. - Abstract: The Rational Exergy Management Model (REMM) provides an analytical model to curb primary energy spending and CO 2 emissions by means of considering the level of match between the grade/quality of energy resources (exergy) on the supply and demand sides. This model is useful for developing forward-looking concepts with an energy systems perspective. One concept is net-zero exergy districts, which produce as much energy at the same grade or quality as consumed on an annual basis. This paper analyzes the district of Östra Sala backe in Uppsala Municipality in Sweden as a pilot, near net-zero exergy district. The district is planned to host 20,000 people at the end of four phases. The measures that are considered include an extension of the combined heat and power based district heating and cooling network, heat pumps driven on renewable energy, district heating driven white goods, smart home automation, efficient lighting, and bioelectricity driven public transport. A REMM Analysis Tool for net-zero exergy districts is developed and used to analyze 5 scenarios based on a Net-Zero Exergy District Option Index. According to the results, a pilot concept for the first phase of the project is proposed. This integrates a mix of 8 measures considering an annual electricity load of 46.0 GW h e and annual thermal load of 67.0 GW h t . The exergy that is produced on-site with renewable energy sources is 49.7 GW h and the annual exergy consumed is 54.3 GW h. The average value of the level of match between the demand and supply of

  8. Energy and exergy analysis at the utility and commercial sectors of Malaysia

    International Nuclear Information System (INIS)

    Saidur, R.; Sattar, M.A.; Masjuki, H.H.; Abdessalam, H.; Shahruan, B.S.

    2007-01-01

    In this paper, sectoral energy and exergy analysis model is applied to the utility and commercial sectors of Malaysia by considering the energy and exergy flows from 1990 to 2003. The energy and exergy efficiencies are determined for the sub-sectors and devices used in these two sectors. It has been found the hydroelectric power plant sub-sector is more energy and exergy efficient compared to the thermal power plant sub-sector. The energy and exergy efficiencies of utility and commercial sectors of Malaysia are compared with a few other countries around the world as well. The utility and commercial sectors of Malaysia are found to be more efficient than that of Thailand, Brunei, China, and Vietnam in 1999

  9. Exergy losses of resource recovery from a waste-to-energy plant

    DEFF Research Database (Denmark)

    Vyzinkarova, Dana; Laner, D.; Astrup, Thomas Fruergaard

    2013-01-01

    Metal resources recovered from waste incineration bottom ash (BA) are of lower quality as compared to primary resources, but to date no framework for expressing the quality losses exists. Exergy is a concept that may have the potential to evaluate the resource quality in waste management....... In this study, focusing on recovery from waste-to-energy plants with basic and advanced BA treatment, the goal is to give an indication about quality of selected recovered resources (Fe, Al, and Cu) by means of exergy analysis. Metal flows are modeled through both incineration scenarios, and then chemical....... The results indicate that exergy losses due to mixing are insignificant as compared to chemical exergies of metals in all flows. Total exergy losses for Fe, Al, and Cu recovery in the two WtE systems range from 38% to 90%....

  10. WEXA: exergy analysis for increasing the efficiency of air/water heat pumps - Final report

    Energy Technology Data Exchange (ETDEWEB)

    Gasser, L.; Wellig, B.; Hilfiker, K.

    2008-04-15

    This comprehensive final report for the Swiss Federal Office of Energy (SFOE) presents the results of a study at the made by the Engineering and Architecture department at the Lucerne University of Applied Sciences and Arts. The subject of the WEXA study (Waermepumpen-Exergie-Analyse - heat pump exergy analysis) is the analysis of the operation of air/water heat-pumps using exergy analysis methods. The basic thermodynamics of heating systems using heat-pumps is discussed. The exergy analyses and exergy balances for the various components and processes of an air/water heat-pump are presented and discussed. Comparisons are presented for heat-pumps with on/off and continuous control systems for their compressors and fans. The paper is concluded with a collection of appendices on the subject.

  11. Numerical Analysis of Exergy for Air-Conditioning Influenced by Ambient Temperature

    Directory of Open Access Journals (Sweden)

    Jing-Nang Lee

    2014-07-01

    Full Text Available The article presents numerical analysis of exergy for air-conditioning influenced by ambient temperature. The model of numerical simulation uses an integrated air conditioning system exposed in varied ambient temperature to observe change of the four main devices, the compressor, the condenser, the capillary, and the evaporator in correspondence to ambient temperature. The analysis devices of the four devices’s exergy influenced by the varied ambient temperature and found that the capillary has unusual increasing exergy loss vs. increasing ambient temperature in comparison to the other devices. The result shows that reducing exergy loss of the capillary influenced by the ambient temperature is the key for improving working efficiency of an air-conditioning system when influence of the ambient temperature is considered. The higher ambient temperature causes the larger pressure drop of capillary and more exergy loss.

  12. On the definition of exergy efficiencies for petroleum systems: Application to offshore oil and gas processing

    DEFF Research Database (Denmark)

    Nguyen, Tuong-Van; Voldsund, Mari; Elmegaard, Brian

    2014-01-01

    Exergy-based efficiencies are measures of the thermodynamic perfection of systems and processes. A meaningful formulation of these performance criteria for petroleum systems is difficult because of (i) the high chemical exergy of hydrocarbons, (ii) the large variety of chemical components, and (iii....... They showed a low sensitivity to performance improvements, gave inconsistent results, or favoured facilities operating under certain con-ditions. We suggest an alternative formulation, called the component-by-component exergy efficiency, which builds on the decomposition of the exergy ows at the level...... the highest performance (29.6%). A more realistic measure of the technical potential for improving these systems can be carried out by splitting further the exergy destruction into its avoidable and unavoidable parts....

  13. Current and future energy and exergy efficiencies in the Iran’s transportation sector

    International Nuclear Information System (INIS)

    Zarifi, F.; Mahlia, T.M.I.; Motasemi, F.; Shekarchian, M.; Moghavvemi, M.

    2013-01-01

    Highlights: • The overall energy and exergy efficiencies of the sector were calculated. • The overall efficiencies were compared to other countries. • The overall energy and exergy efficiencies have been predicted by scenario approach. • A summary of recommendations to improve the sector is provided. - Abstract: Transportation is the second largest energy consumer sector in Iran which accounts for 24% of total energy consumption in 2009. This large percentage (almost a quarter) of energy consumption necessitates the determination of energy and exergy flows and their respective losses, which will enable the reduction of both energy growth and its consequent environmental impacts in the near future. This paper attempts to analyze and investigate the energy and exergy utilization of the transportation sector in Iran for the period of 1998–2009. Additionally, the total energy consumption in each subsector and the overall energy and exergy efficiencies are predicted via scenario approach. A comparison of the overall energy and exergy efficiencies of Iran with six other countries is also presented. The results show that the overall energy and exergy efficiencies of transportation sector in Iran is higher than China and Norway, while it is lower than Saudi Arabia, Jordan, Turkey, and Malaysia for the year 2000. Road appears to be the most efficient subsector. The overall energy efficiency is determined to be in the range of 22.02% in 1998, to 21.49% in 2009, while the overall exergy efficiency is determine to be in the range of 21.47% in 1998, to 21.19% in 2009. The energy consumption in each subsector is predicted from 2010 to 2035. It was discovered that the overall energy and exergy efficiencies possesses an upward trend during this time period. Finally, some recommendations vis-à-vis the improvement of the energy and exergy efficiencies in Iranian transportation sector in the future was provided and duly discussed

  14. Exergy and exergoeconomic analyses of a supercritical CO_2 cycle for a cogeneration application

    International Nuclear Information System (INIS)

    Wang, Xurong; Yang, Yi; Zheng, Ya; Dai, Yiping

    2017-01-01

    Detailed exergy and exergoeconomic analyses are performed for a combined cogeneration cycle in which the waste heat from a recompression supercritical CO_2 Brayton cycle (sCO_2) is recovered by a transcritical CO_2 cycle (tCO_2) for generating electricity. Thermodynamic and exergoeconomic models are developed on the basis of mass and energy conservations, exergy balance and exergy cost equations. Parametric investigations are then conducted to evaluate the influence of key decision variables on the sCO_2/tCO_2 performance. Finally, the combined cycle is optimized from the viewpoint of exergoeconomics. It is found that, combining the sCO_2 with a tCO_2 cycle not only enhances the energy and exergy efficiencies of the sCO_2, but also improves the cycle exergoeconomic performance. The results show that the most exergy destruction rate takes place in the reactor, and the components of the tCO_2 bottoming cycle have less exergy destruction. When the optimization is conducted based on the exergoeconomics, the overall exergoeconomic factor, the total cost rate and the exergy destruction cost rate are 53.52%, 11243.15 $/h and 5225.17 $/h, respectively. The optimization study reveals that an increase in reactor outlet temperature leads to a decrease in total cost rate and total exergy destruction cost rate of the system. - Highlights: • Exergy and exergoeconomic analyses of a combined sCO_2/tCO_2 cycle were performed. • Exergoeconomic optimization of the sCO_2/tCO_2 cycle was presented. • The reactor had the highest exergy loss among sCO_2/tCO_2 cycle components. • The overall exergoeconomic factor was up to 53.5% for the optimum case.

  15. Exergy analysis of single effect absorption refrigeration systems: The heat exchange aspect

    International Nuclear Information System (INIS)

    Joybari, Mahmood Mastani; Haghighat, Fariborz

    2016-01-01

    Highlights: • Exergy analysis of LiBr/H 2 O absorption systems with identical COP was carried out. • Exergy destruction rank: absorber followed by generator, condenser and evaporator. • Lower heat source and chilled water inlet temperature reduced exergy destruction. • Higher cooling water inlet temperature reduced exergy destruction. • Lower HTF mass flow rate increased exergy efficiency even for fixed system COP. - Abstract: The main limitation of conventional energy analysis for the thermal performance of energy systems is that this approach does not consider the quality of energy. On the other hand, exergy analysis not only provides information about the systems performance, but also it can specify the locations and magnitudes of losses. A number of studies investigated the effect of parameters such as the component temperature, and heat transfer fluid (HTF) temperature and mass flow rate on the exergetic performance of the same absorption refrigeration system; thus, reported different coefficient of performance (COP) values. However, in this study, the system COP was considered to remain constant during the investigation. This means comparing systems with different heat exchanger designs (based on HTF mass flow rate and temperature) having the same COP value. The effect of HTF mass flow rate and inlet temperature of the cooling water, chilled water and heat source on the outlet specific exergy and exergy destruction rate of each component was investigated. It was found that the lower HTF mass flow rate decreased exergy destruction of the corresponding component. Moreover, the lower temperature of heat source and chilled water inlet increased the system exergetic efficiency. That was also the case for the higher cooling water inlet temperature. Based on the analysis, since the absorber and condenser accounted for a large portion of the total exergy destruction, cooling tower modification with lower cooling water mass flow rate is recommended

  16. Environmental emissions by Chinese industry: Exergy-based unifying assessment

    International Nuclear Information System (INIS)

    Bo Zhang; Chen, G.Q.; Xia, X.H.; Li, S.C.; Chen, Z.M.; Xi Ji

    2012-01-01

    Based on chemical exergy as an objective measure for the chemical deviation between the emission and the environment, a unifying assessment is carried out for major environmental emissions covering COD, ammonia nitrogen, SO 2 , soot, dust, NO x and solid waste by Chinese industry over 1997–2006, with emphasis on the sectoral and regional levels in 2006. Of the total emission in exergy up to 274.1 PJ in 2006, 67.7% is estimated from waste gases, 29.9% from waste water and 2.4% from solid waste. Five of 40 sectors and 12 of 30 regions are responsible for 72.7% and 65.5% of the total emission, respectively. SO 2 is the leading emission type in 9 sectors and 25 regions, and COD in another 28 sectors and 5 regions. Some pollution-intensive sectors such as Production and Distribution of Electric Power and Heat Power and Manufacture of Paper and Paper Products, and western and inland regions such as Guangxi and Ningxia with high emission intensities are identified. By clustering and disjoint principal component analysis with intensities of emissions and fuel coal use as variables, three principal components are extracted, and four statistically significant clusters are pinpointed in the sectoral and regional analysis. Corresponding policy-making implications are addressed. - Highlights: ► A chemical exergy-based unifying assessment for industrial emissions is performed. ► The emissions at the sectoral/regional levels in 2006 are systematically revealed. ► The main principal components and clusters for emission intensities are pinpointed.

  17. Energy and exergy assessments for an enhanced use of energy in buildings

    Science.gov (United States)

    Goncalves, Pedro Manuel Ferreira

    Exergy analysis has been found to be a useful method for improving the conversion efficiency of energy resources, since it helps to identify locations, types and true magnitudes of wastes and losses. It has also been applied for other purposes, such as distinguishing high- from low-quality energy sources or defining the engineering technological limits in designing more energy-efficient systems. In this doctoral thesis, the exergy analysis is widely applied in order to highlight and demonstrate it as a significant method of performing energy assessments of buildings and related energy supply systems. It aims to make the concept more familiar and accessible for building professionals and to encourage its wider use in engineering practice. Case study I aims to show the importance of exergy analysis in the energy performance assessment of eight space heating building options evaluated under different outdoor environmental conditions. This study is concerned with the so-called "reference state", which in this study is calculated using the average outdoor temperature for a given period of analysis. Primary energy and related exergy ratios are assessed and compared. Higher primary exergy ratios are obtained for low outdoor temperatures, while the primary energy ratios are assumed as constant for the same scenarios. The outcomes of this study demonstrate the significance of exergy analysis in comparison with energy analysis when different reference states are compared. Case study II and Case study III present two energy and exergy assessment studies applied to a hotel and a student accommodation building, respectively. Case study II compares the energy and exergy performance of the main end uses of a hotel building located in Coimbra in central Portugal, using data derived from an energy audit. Case study III uses data collected from energy utilities bills to estimate the energy and exergy performance associated to each building end use. Additionally, a set of energy

  18. Emergy and exergy analyses: Complementary methods or irreducible ideological options?

    International Nuclear Information System (INIS)

    Sciubba, Enrico; Ulgiati, Sergio

    2005-01-01

    The paper discusses the similarities and the incompatibilities between two forms of Energy Analysis (exergy and emergy, 'EXA' and 'EMA' in the following), both of which try to represent the behavior of physical systems by means of cumulative energy input/output methods that result in a double integration over space and time domains. Theoretical background, definitions and balance algebra are discussed first, in a 'statement-counterstatement' format that helps pinpointing differences and similarities. A significant, albeit simplified, benchmark case (ethanol production from corn) is used to compare the results and analytically assess the merits of each approach as well as possible synergic aspects. Corn production, transport and industrial conversion to ethanol are included in the analysis. First, mass balance and energy accounting are performed in each step of the process, then, exergy and emergy evaluations are carried out separately to lead to a set of performance indicators, the meaning of which is discussed with reference to their proper scale of application. The Authors underline that each method has its own preferred field of application and conclude that the two approaches appear to be characterized not much as different (and therefore competing) tools, but as different paradigms, whose meta-levels (their 'philosophies') substantially differ. In particular, EXA is found to provide the most correct and insightful assessment of thermodynamic features of any process and to offer a clear quantitative indication of both the irreversibilities and the degree of matching between the used resources and the end-use material or energy flows. EXA combined with costing considerations results in Thermo-Economics (TE), presently the best engineering method for System optimization. One of EXA recent extensions, Extended Exergy Accounting (EEA) includes all externalities in the exergy resource accounting, thus providing a more complete picture of how a process is interacting

  19. Energy and exergy analysis of a cruise ship

    DEFF Research Database (Denmark)

    Baldi, Francesco; Ahlgren, Fredrik; Nguyen, Tuong-Van

    2015-01-01

    but increasing share of the industry. The complexity of the energy system of a s hip where the energy required by propulsion is no longer the trivial main contributor to the whole energy use thus makes this kind of ship of particular interest for the analysis of how energy is converted from its original form...... destruction is generated in the Diesel engines and in the oil - fired boilers) and in the sea water cooler (5.4%) ; the main exergy losses happen instead in the exhaust gas, mostly from the main engines (6 7% of total losses) and particularly from those not equipped with heat recovery devices . The improved...

  20. Energy and exergy analysis of counter flow wet cooling towers

    Directory of Open Access Journals (Sweden)

    Saravanan Mani

    2008-01-01

    Full Text Available Cooling tower is an open system direct contact heat exchanger, where it cools water by both convection and evaporation. In this paper, a mathematical model based on heat and mass transfer principle is developed to find the outlet condition of water and air. The model is solved using iterative method. Energy and exergy analysis infers that inlet air wet bulb temperature is found to be the most important parameter than inlet water temperature and also variation in dead state properties does not affect the performance of wet cooling tower. .

  1. An attempt to introduce dynamics into generalised exergy considerations

    International Nuclear Information System (INIS)

    Grubbstroem, Robert W.

    2007-01-01

    In previous research, the author developed a general abstract framework for the exergy content of a system of finite objects [Grubbstroem RW. Towards a generalized exergy concept. In: van Gool W, Bruggink JJC, editors. Energy and time in the economic and physical sciences. Amsterdam: North-Holland; 1985. p. 41-56]. Each such object is characterised by its initial extensive properties and has an inner energy written as a function of these properties. It was shown that if these objects were allowed to interact, there is a maximum amount of work that can be extracted from the system as a whole, and a general formula for this potential was provided. It was also shown that if one of the objects was allowed to be of infinite magnitude initially, taking on the role as an environment having constant intensive properties, then the formula provided took on the same form as the classical expression for exergy. As a side result, the theoretical considerations demonstrated that the second law of thermodynamics could be interpreted as the inner energy function being a (weakly) convex function of its arguments, when these are chosen as the extensive properties. Since exergy considerations are based on the principle that total entropy is conserved when extracting work, these processes would take an infinite time to complete. In the current paper, instead, a differential-equation approach is introduced to describe the interaction in finite time between given finite objects of a system. Differences in intensive properties between the objects provide a force enabling an exchange of energy and matter. An example of such an interaction is heat conduction. The resulting considerations explain how the power extracted from the system will be limited by the processes being required to perform within finite-time constraints. Applying finite-time processes, in which entropy necessarily is generated, leads to formulating a theory for a maximal power output from the system. It is shown that

  2. A METHOD FOR EXERGY ANALYSIS OF SUGARCANE BAGASSE BOILERS

    Directory of Open Access Journals (Sweden)

    CORTEZ L.A.B.

    1998-01-01

    Full Text Available This work presents a method to conduct a thermodynamic analysis of sugarcane bagasse boilers. The method is based on the standard and actual reactions which allows the calculation of the enthalpies of each process subequation and the exergies of each of the main flowrates participating in the combustion. The method is presented using an example with real data from a sugarcane bagasse boiler. A summary of the results obtained is also presented together based on the 1st Law of Thermodynamics analysis, the exergetic efficiencies, and the irreversibility rates. The method presented is very rigorous with respect to data consistency, particularly for the flue gas composition.

  3. Optimization of operating parameters in a hybrid wind–hydrogen system using energy and exergy analysis: Modeling and case study

    International Nuclear Information System (INIS)

    Fakehi, Amir Hossein; Ahmadi, Somayeh; Mirghaed, Mohammad Rezaie

    2015-01-01

    Highlights: • The exergy analysis of a hybrid system of a wind turbine and PEM electrolyzer/fuel-cell has been performed. • Effects of various operating parameters on the exergy efficiency have been investigated. • The exergy and energy efficiency in each of hybrid system’s components have been compared. - Abstract: In this study, hybrid renewable energy system based on wind/electrolyzer/PEM fuel cell are conceptually modeled, and also, exergy and energy analysis are performed. The energy and exergy flows are investigated by the proposed model for Khaf region-Iran with high average wind speed and monsoon. Exergy and energy analysis framework is made based on thermodynamic, electro-chemical and mechanical model of the different component of hybrid system. Also, the effects of various operating parameters in exergy efficiency are calculated. The results show an optimum wind speed where the exergy efficiency and power coefficient is at maximum level, and also, when the ambient temperature start to be increased in wind turbine, the efficiencies decrease by a great deal for constant wind speeds. Also, the optimum temperature is calculated by exergy analysis in electrolyzer and fuel cell as 353 and the exergy efficiency of electrolyzer decreases by increasing the membrane thickness. Furthermore, pressure changes affect exergy and energy efficiency in PEM fuel cell. Finally, the electrolyzer and fuel cell efficiencies are calculated as 68.5% and 47% respectively.

  4. Diagnosis of an alternative ammonia process technology to reduce exergy losses

    International Nuclear Information System (INIS)

    Ghannadzadeh, Ali; Sadeqzadeh, Majid

    2016-01-01

    Highlights: • Pinpointed non-efficient units by visualized exergetic ammonia process flowsheets. • Recommended ways towards sustainable ammonia productions based on exergy-loss sources. • Demonstrated applicability of the exergetic solutions panel on an ammonia process. - Abstract: Ammonia production through more efficient technologies can be achieved using exergy analysis. Ammonia production is one of the most important but also one of most energy consuming processes in the chemical industry. Based on a panel of solutions previously developed, this study helps to identify potential areas of improvement using an exergy analysis that covers all aspects of conventional ammonia synthesis and separation. The total internal and external exergy losses are calculated as 3,152 and 6,364 kJ/kg, respectively. The process is then divided into five main functional blocks based on their exergy losses. The reforming block contains the largest exergy loss (3,098 kJ/kg) and thus the largest potential for improvement including preheating cold feed through an economizer, developing technology towards isobaric mixing, and pressure drop reduction in the secondary reformer as the main contributors to the irreversibility (1,302 kJ/kg) in this block. The second largest exergy loss resides in the ammonia synthesis block (3,075 kJ/kg) where solutions such as reduced temperature rise across the compressor, proper compressor isolation, reducing undesired components such as argon in the reactor feed, and using lower temperatures for reactor outlet streams, are proposed to decrease the exergy losses. Throttling process in the syngas separator is the key contributing mechanism for the irreversibility (1,635 kJ/kg exergy losses) in the gas upgrading block. The exergy losses in the residual ammonia removal block (833 kJ/kg exergy losses) are mainly due to the stripper and the absorber column where a modified column design might be helpful. The highest exergy loss in the preheating block

  5. Human Body Exergy Balance: Numerical Analysis of an Indoor Thermal Environment of a Passive Wooden Room in Summer

    Directory of Open Access Journals (Sweden)

    Koichi Isawa

    2015-09-01

    Full Text Available To obtain a basic understanding of the resultant changes in the human body exergy balance (input, consumption, storage, and output accompanying outdoor air temperature fluctuations, a “human body system and a built environmental system” coupled with numerical analysis was conducted. The built environmental system assumed a wooden room equipped with passive cooling strategies, such as thermal insulation and solar shading devices. It was found that in the daytime, the cool radiation exergy emitted by surrounding surfaces, such as walls increased the rate of human body exergy consumption, whereas the warm radiant exergy emitted by the surrounding surfaces at night decreased the rate of human body exergy consumption. The results suggested that the rates and proportions of the different components in the exergy balance equation (exergy input, consumption, storage, and output vary according to the outdoor temperature and humidity conditions.

  6. The role of an exergy-based building stock model for exploration of future decarbonisation scenarios and policy making

    International Nuclear Information System (INIS)

    García Kerdan, Iván; Raslan, Rokia; Ruyssevelt, Paul; Morillón Gálvez, David

    2017-01-01

    State-of-the-art research suggests that energy systems are best evaluated using exergy analysis, as exergy represents the real value of an energy source, demonstrating it to be the only rational basis for evaluation. After discovering the lack of thermodynamic integration into stock modelling, this paper presents the development of an exergy-based building stock model. The aim of this paper is twofold. Firstly, to investigate the impact of large-scale future energy retrofit scenarios in the English and Welsh (E&W) non-domestic sector, and secondly, to determine the potential of exergy analysis in improving sectoral efficiency and its potential implications on exergy-oriented policy making. The research explores seven different large-scale future retrofit scenarios that encompass typical, low-carbon, and low-exergy approaches. Modelling results show that by 2050, current regulations have the potential to reduce carbon emissions by up to 49.0±2.9% and increasing sector thermodynamic efficiency from 10.7% to 13.7%. On the other hand, a low-exergy oriented scenario based on renewable electricity and heat pumps is able to reduce carbon emissions by 88.2±2.4%, achieving a sectoral exergy efficiency of 19.8%. This modelling framework can provide energy policy makers with new insights on policy options based on exergy indicators and the assessment of their potential impact. - Highlights: • A bottom-up exergy-based model was developed to analyse the UK non-domestic sector. • Different low-carbon and low-exergy large-scale retrofit scenarios were assessed. • The UK non-domestic sector as a whole has an exergy efficiency of 10.7±4.06%. • Exergy-based retrofits could reduce sectoral carbon emissions by 88±2.4% for 2050. • Exergy oriented policies are required to obtain a sustainable building sector.

  7. Process analysis using the concept of intrinsic and extrinsic exergy losses

    International Nuclear Information System (INIS)

    Chang Hsuan; Chuang, S.-C.

    2003-01-01

    This paper introduces a two-level idealization concept and decomposes the exergy losses of processing operations into the intrinsic part and the extrinsic part. The first level idealization is the reversible operation and the second level idealization is the thermodynamic equilibrium operation. The exergy losses arising from the deviations from the first level idealization only, caused by configuration constraints, are defined as the intrinsic exergy losses. The extra exergy losses which arise from further deviations from the second level idealization, caused by transport rate limitations, are defined as the extrinsic exergy losses. Demonstrated by several example cases of different complex levels, the analysis results can pinpoint what and where to focus on for improvements: (1) design configurations or transport rate limitations, and (2) the specific locations within the operations or processes. As an example, for a de-ethanizer, the improvement measures on configuration-related and transport rate-related design conditions result in a 11.42% reduction of overall column intrinsic exergy loss and a 81.74% reduction of total individual stage extrinsic exergy loss

  8. Exergy and exergoeconomic analysis of a petroleum refinery utilities plant using the condensing to power method

    Energy Technology Data Exchange (ETDEWEB)

    Mendes da Silva, Julio Augusto; Pellegrini, Luiz Felipe; Oliveira Junior, Silvio [Polytechnic School of the University of Sao Paulo, SP (Brazil)], e-mails: jams@usp.br, luiz.pellegrini@usp.br, soj@usp.br; Plaza, Claudio; Rucker, Claudio [Petrobras - Petroleo Brasileiro S.A., Rio de Janeiro, RJ (Brazil)], e-mails: claudioplaza@petrobras.com.br, rucker@petrobras.com.br

    2010-07-01

    In this paper a brief description of the main processes present in a modern high capacity refinery is done. The methodology used to evaluate, through exergy analysis, the performance of the refinery's utilities plant since it is responsible for a very considerable amount of the total exergy destruction in a refinery is presented. The utilities plant products: steam, electricity, shaft power and high pressure water had their exergy unit cost determined using exergoeconomic approach. A simple and effective method called condensing to power was used to define the product of the condensers in exergy basis. Using this method it is possible to define the product of the condenser without the use of negentropy concept nor the aggregation of condensers to the steam turbines. By using this new approach, the costs obtained for the plant's products are exactly the same costs obtained when the condenser is aggregated to the steam turbine but with the advantage that the information about the stream between condenser and the steam turbine is not lost and the condenser can be evaluated singly. The analysis shows that the equipment where attention and resources should be focused are the boilers followed by the gas turbine, that together, are responsible for 80% of total exergy destruction in the utilities plant. The total exergy efficiency found for the utilities plant studied is 35% while more than 280 MW of exergy is destroyed in the utilities processes. (author)

  9. Energy and exergy assessments of a perlite expansion furnace in a plaster plant

    International Nuclear Information System (INIS)

    Gürtürk, Mert; Oztop, Hakan F.; Hepbaslı, Arif

    2013-01-01

    Highlights: • Importance of energy efficiency on perlite process is discussed. • Effects of perlite production on 3E, namely, energy, environment and economics is presented. • The system must be replaced with the developed technology and the return of the investment would be less than 18 months. - Abstract: In this study, energy and exergy assessments of a perlite expansion furnace in a plaster factory are performed. Chemical properties of the perlite and its application areas are described. Energy and exergy relations according to the First and Second Law of Thermodynamics are derived. Energy and exergy efficiencies, losses and exergy destructions are calculated based on the measurements obtained from the system. Evaluations of environmental impact, energy management and economic are finally generalized according to the obtained results. Energy and exergy efficiencies of the furnace are determined to be 66% and 26%, respectively. Reference temperature effects on exergy efficiency, destruction and sustainability index are also presented. The results showed that the furnace has not been well designed in terms of thermal aspects due to high energy and exergy losses and the manufacturer producing the perlite expanded should establish an energy management structure

  10. Modeling of chemical exergy of agricultural biomass using improved general regression neural network

    International Nuclear Information System (INIS)

    Huang, Y.W.; Chen, M.Q.; Li, Y.; Guo, J.

    2016-01-01

    A comprehensive evaluation for energy potential contained in agricultural biomass was a vital step for energy utilization of agricultural biomass. The chemical exergy of typical agricultural biomass was evaluated based on the second law of thermodynamics. The chemical exergy was significantly influenced by C and O elements rather than H element. The standard entropy of the samples also was examined based on their element compositions. Two predicted models of the chemical exergy were developed, which referred to a general regression neural network model based upon the element composition, and a linear model based upon the high heat value. An auto-refinement algorithm was firstly developed to improve the performance of regression neural network model. The developed general regression neural network model with K-fold cross-validation had a better ability for predicting the chemical exergy than the linear model, which had lower predicted errors (±1.5%). - Highlights: • Chemical exergies of agricultural biomass were evaluated based upon fifty samples. • Values for the standard entropy of agricultural biomass samples were calculated. • A linear relationship between chemical exergy and HHV of samples was detected. • An improved GRNN prediction model for the chemical exergy of biomass was developed.

  11. An exergy approach to efficiency evaluation of desalination

    KAUST Repository

    Ng, Kim Choon

    2017-05-02

    This paper presents an evaluation process efficiency based on the consumption of primary energy for all types of practical desalination methods available hitherto. The conventional performance ratio has, thus far, been defined with respect to the consumption of derived energy, such as the electricity or steam, which are susceptible to the conversion losses of power plants and boilers that burned the input primary fuels. As derived energies are usually expressed by the units, either kWh or Joules, these units cannot differentiate the grade of energy supplied to the processes accurately. In this paper, the specific energy consumption is revisited for the efficacy of all large-scale desalination plants. In today\\'s combined production of electricity and desalinated water, accomplished with advanced cogeneration concept, the input exergy of fuels is utilized optimally and efficiently in a temperature cascaded manner. By discerning the exergy destruction successively in the turbines and desalination processes, the relative contribution of primary energy to the processes can be accurately apportioned to the input primary energy. Although efficiency is not a law of thermodynamics, however, a common platform for expressing the figures of merit explicit to the efficacy of desalination processes can be developed meaningfully that has the thermodynamic rigor up to the ideal or thermodynamic limit of seawater desalination for all scientists and engineers to aspire to.

  12. Exergy storage to exploit solar energy in air conditioning

    Energy Technology Data Exchange (ETDEWEB)

    Navarrete-Gonzalez, J.J.; Torres-Reyes, E. [Guanajuato Univ., Guanajuato (Mexico). Inst. de Investigaciones Cientificas; Cervantes-de Gortari, J.G. [Univ. of Cuidad, Mexico City (Mexico). Dept. de Termoenergia y Mejoramiento Ambiental

    2006-07-01

    A thermodynamic procedure was developed to analyze the exergy of a rock bed thermal storage unit that used solar power to acclimatize a pig farm. Thermal behaviour was described by means of a control volume that included the entire system and assumed a unidirectional air flow and an adiabatic process. The thermodynamic properties of the system were determined as a function of the experimental temperature profiles developed during thermal storage from solar to thermal energy conversion provided by a solar collector at a fixed mass rate of air flow. Experimental data were used to calculate the energy yield and to determine the entropy generation inside the system. The aim of the study was to determine how well the thermodynamic model matched the real data obtained experimentally during normal operating conditions. Results indicated that an exergy accumulation existed inside the control volume, which was the net result of the energy gain during the heating process. However, entropy generation due to irreversibilities was studied for just 1 air flow. Further research is needed to establish a semi-empirical model of the process with the minimum of entropy generation. It was concluded that the thermal energy storage system was suitable for use in pig farms. 5 refs., 8 figs.

  13. A general exergy-based environmental impact index

    International Nuclear Information System (INIS)

    Diaz-Mendez, Sosimo E.; Rodriguez-Lelis, Jose Maria; Hernandez-Guerrero, Abel

    2011-01-01

    An ecosystem is a complex system in which biotic and abiotic factors interact and influence each other both directly and indirectly. Each of these factors has to comply with a specific function in the different processes that occur inside the ecosystem, whether transporting or transforming energy or both. When anthropogenic emissions are produced, part of the useful energy of the ecosystem is used to assimilate or absorb those emissions, and the energy spent, loses its function and becomes lost work in accordance with the Gouy-Stodola theorem. Thus, the work that an ecosystem can carry out varies as a function of the lost work produced by anthropogenic sources. The permanency or loss of the ecosystem depends on how many irreversibilities it can support. The second law of thermodynamics through a systematic use of the exergy and lost work is the basis of this paper where a general environmental impact index, based on exergy, is proposed. For the purpose of this work, the ecosystem is divided in subsystems--water, soil, atmosphere, organisms and society- -all of them inter-related. The ideal work variation can be obtained from each subsystem within the selected ecosystem, and a global index can be determined by adding the partial lost work of each subsystem. This global index is then used to determine the trend followed by the ecosystem from its pristine, original or environmental line base state. This environmental impact index applicability is presented for a simple combustion example

  14. An exergy approach to efficiency evaluation of desalination

    Science.gov (United States)

    Ng, Kim Choon; Shahzad, Muhammad Wakil; Son, Hyuk Soo; Hamed, Osman A.

    2017-05-01

    This paper presents an evaluation process efficiency based on the consumption of primary energy for all types of practical desalination methods available hitherto. The conventional performance ratio has, thus far, been defined with respect to the consumption of derived energy, such as the electricity or steam, which are susceptible to the conversion losses of power plants and boilers that burned the input primary fuels. As derived energies are usually expressed by the units, either kWh or Joules, these units cannot differentiate the grade of energy supplied to the processes accurately. In this paper, the specific energy consumption is revisited for the efficacy of all large-scale desalination plants. In today's combined production of electricity and desalinated water, accomplished with advanced cogeneration concept, the input exergy of fuels is utilized optimally and efficiently in a temperature cascaded manner. By discerning the exergy destruction successively in the turbines and desalination processes, the relative contribution of primary energy to the processes can be accurately apportioned to the input primary energy. Although efficiency is not a law of thermodynamics, however, a common platform for expressing the figures of merit explicit to the efficacy of desalination processes can be developed meaningfully that has the thermodynamic rigor up to the ideal or thermodynamic limit of seawater desalination for all scientists and engineers to aspire to.

  15. Exergy Analysis of the Revolving Vane Compressed Air Engine

    Directory of Open Access Journals (Sweden)

    Alison Subiantoro

    2016-01-01

    Full Text Available Exergy analysis was applied to a revolving vane compressed air engine. The engine had a swept volume of 30 cm3. At the benchmark conditions, the suction pressure was 8 bar, the discharge pressure was 1 bar, and the operating speed was 3,000 rev·min−1. It was found that the engine had a second-law efficiency of 29.6% at the benchmark conditions. The contributors of exergy loss were friction (49%, throttling (38%, heat transfer (12%, and fluid mixing (1%. A parametric study was also conducted. The parameters to be examined were suction reservoir pressure (4 to 12 bar, operating speed (2,400 to 3,600 rev·min−1, and rotational cylinder inertia (0.94 to 2.81 g·mm2. The study found that a higher suction reservoir pressure initially increased the second-law efficiency but then plateaued at about 30%. With a higher operating speed and a higher cylinder inertia, second-law efficiency decreased. As compared to suction pressure and operating speed, cylinder inertia is the most practical and significant to be modified.

  16. Exergy analysis of a distillation tower for crude oil fractionation

    International Nuclear Information System (INIS)

    Rivero, R.

    1990-01-01

    In this paper the application of the exergy method to a crude oil atmospheric distillation tower is presented. The fundamentals and procedures are presented as well as the main parameters used to describe the thermodynamic performance of the system, such as Exergy Losses, Effectiveness and Improvement Potential. A parametric analysis of the influence on the effectiveness of the tower is then performed as a function of the number of trays, the amount of stripping steam, the use of reboilers and the operation pressure. The results obtained are discussed. As expected, the effectiveness of the tower increases with the overall number of trays in the tower and in the stripping columns for a constant operation pressure and a constant amount of stripping steam but there is a limit at which the pressure drop across the trays and the stripping steam requirements make the effectiveness decrease. The use of reboilers in the stripping columns adjacent to the main tower allows an increase in the effectiveness basically due to a greater heat integration. Finally, the increase in the operation pressure of the tower produces an increase of the effectiveness but also an increase in the stripping steam requirements

  17. Parametric study of an absorption refrigeration machine using advanced exergy analysis

    International Nuclear Information System (INIS)

    Gong, Sunyoung; Goni Boulama, Kiari

    2014-01-01

    An advanced exergy analysis of a water–lithium bromide absorption refrigeration machine was conducted. For each component of the machine, the proposed analysis quantified the irreversibility that can be avoided and the irreversibility that is unavoidable. It also identified the irreversibility originating from inefficiencies within the component and the irreversibility that does not originate from the operation of the considered component. It was observed that the desorber and absorber concentrated most of the exergy destruction. Furthermore, the exergy destruction at these components was found to be dominantly endogenous and unavoidable. A parametrical study has been presented discussing the sensitivity of the different performance indicators to the temperature at which the heat source is available, the temperature of the refrigerated environment, and the temperature of the cooling medium used at the condenser and absorber. It was observed that the endogenous avoidable exergy destruction at the desorber, i.e. the portion of the desorber irreversibility that could be avoided by improving the design and operation of the desorber, decreased when the heat source or the temperature at which the cooling effect was generated increased, and it decreased when the heat sink temperature increased. The endogenous avoidable exergy destruction at the absorber displayed the same variations, though it was observed to be less affected by the heat source temperature. Contrary to the aforementioned two components, the exergy destruction at the evaporator and condenser were dominantly endogenous and avoidable, with little sensitivity to the cycle operating parameters. - Highlights: • Endogenous, exogenous, avoidable and unavoidable irreversibilities were calculated for a water–LiBr absorption machine. • Overall, desorber and absorber concentrated most of the exergy destruction of the cycle. • The exergy destruction was mainly endogenous and unavoidable for the desorber and

  18. Thermodynamic energy and exergy analysis of three different engine combustion regimes

    International Nuclear Information System (INIS)

    Li, Yaopeng; Jia, Ming; Chang, Yachao; Kokjohn, Sage L.; Reitz, Rolf D.

    2016-01-01

    Highlights: • Energy and exergy distributions of three different combustion regimes are studied. • CDC demonstrates the highest utilization efficiency of heat transfer and exhaust. • HCCI achieves the highest energy and exergy efficiencies over CDC and RCCI. • HCCI and RCCI demonstrate lower exergy destruction than CDC. • Combustion temperature, rate, duration and regime affect exergy destruction. - Abstract: Multi-dimensional models were coupled with a detailed chemical mechanism to investigate the energy and exergy distributions of three different combustion regimes in internal combustion engines. The results indicate that the 50% heat release point (CA50) considerably affects fuel efficiency and ringing intensity (RI), in which RI is used to quantify the knock level. Moreover, the burn duration from the 10% heat release point (CA10) to CA50 dominates RI, and the position of 90% heat release point (CA90) affects fuel efficiency. The heat transfer losses of conventional diesel combustion (CDC) strongly depend on the local temperature gradient, while it is closely related to the heat transfer area for homogeneous charge compression ignition (HCCI) and reactivity controlled compression ignition (RCCI). Among the three combustion regimes, CDC has the largest utilization efficiency for heat transfer and exhaust energy due to its higher temperature in the heat transfer layer and higher exhaust pressure and temperature. The utilization efficiency of heat transfer and exhaust in RCCI is less affected by the variation of CA50 compared to those in CDC and HCCI. Exergy destruction is closely related to the homogeneity of in-cylinder temperature and equivalence ratio during combustion process, the combustion temperature, the chemical reaction rate, and the combustion duration. Under the combined effect, HCCI and RCCI demonstrate lower exergy destruction than CDC at the same load. Overall, the variations of the exergy distribution for the three combustion regimes

  19. Exergy costing for energy saving in combined heating and cooling applications

    DEFF Research Database (Denmark)

    Nguyen, Chan; Veje, Christian T.; Willatzen, Morten

    2014-01-01

    . In the first method, referred to as energy costing, a conventional thermoeconomic analysis is used. Here the ammonia heat pump is subject to a thermodynamic analysis with mass and energy balance equations. In the second method referred to as exergy costing, an exergy based economic analysis is used, where...... exergy balance equations are used in conjunction with mass and energy balance equations. In both costing methods the thermodynamic analysis is followed by an economic analysis which includes investment and operating costs. For both methods the unit costs of heating and cooling are found and compared...

  20. Application of eco-exergy for assessment of ecosystem health and development of structurally dynamic models

    DEFF Research Database (Denmark)

    Zhang, J.; Gürkan, Zeren; Jørgensen, S.E.

    2010-01-01

    are developed using eco-exergy as the goal function, have been applied in explaining and exploring ecosystem properties and changes in community structure driven by biotic and abiotic factors. In this paper, we review the application of eco-exergy for the assessment of ecosystem health and development......Eco-exergy has been widely used in the assessment of ecosystem health, parameter estimations, calibrations, validations and prognoses. It offers insights into the understanding of ecosystem dynamics and disturbance-cl riven changes. Particularly, structurally dynamic models (SDMs), which...

  1. Analysis on exergy consumption patterns for space heating in Slovenian buildings

    DEFF Research Database (Denmark)

    Dovjak, Mateja; Shukuya, Masanori; Olesen, Bjarne W.

    2010-01-01

    and demand is taken into consideration. Exergy calculations enable us to analyze how much exergy is consumed in which part, from boiler to building envelope. They also reveal how much energy is supplied for the purpose of heating. Results show that insulation has much bigger effect than effect of boiler...... efficiency. However, the most effective solution is to improve building envelope together with boiler efficiency. Better thermal insulation also makes an important contribution to the improvement of thermal comfort conditions. It causes higher surface temperatures resulting in a larger warm radiant exergy...... emission rate and consequently better thermal comfort....

  2. Exergy, Energy, and Dynamic Parameter Analysis of Indigenously Developed Low-Concentration Photovoltaic System

    OpenAIRE

    Pankaj Yadav; Brijesh Tripathi; Manoj Kumar

    2013-01-01

    Piecewise linear parabolic trough collector (PLPTC) is designed and developed to concentrate solar radiation on monocrystalline silicon based photovoltaic module. A theoretical model is used to perform electrical energy and exergy analysis of low-concentration photovoltaic (LCPV) system working under actual test conditions (ATC). The exergy efficiency of LCPV system is in the range from 5.1% to 4.82% with increasing rate of input exergy rate from 30.81 W to 96.12 W, when conce...

  3. Application of exergy analysis to the thermodynamical study of operation cycles of diesel engines

    Energy Technology Data Exchange (ETDEWEB)

    Zellat, M

    1987-01-01

    To simulate the operation cycle of a diesel engine a general methodology is proposed, called as exergy theory, based on the simultaneous application of the first and second principles of thermodynamics. This analysis accounts for the exergy losses in function of what can be recovered from the second principle and give a more fruitful representation than the pure energy analysis which takes into account only the first principle. The concept of a recovery power turbine RPT, linked to the driving shaft and declutchable is described. The yield increase in nominal power and at half-charge when the RPT is disconnected, is explained by exergy analysis.

  4. The calculation of the chemical exergies of coal-based fuels by using the higher heating values

    International Nuclear Information System (INIS)

    Bilgen, Selcuk; Kaygusuz, Kamil

    2008-01-01

    This paper demonstrates the application of exergy to gain a better understanding of coal properties, especially chemical exergy and specific chemical exergy. In this study, a BASIC computer program was used to calculation of the chemical exergies of the coal-based fuels. Calculations showed that the chemical composition of the coal influences strongly the values of the chemical exergy. The exergy value of a coal is closely related to the H:C and O:C ratios. High proportions of hydrogen and/or oxygen, compared to carbon, generally reduce the exergy value of the coal. High contents of the moisture and/or the ash cause to low values of the chemical exergy. The aim of this paper is to calculate the chemical exergy of coals by using equations given in the literature and to detect and to evaluate quantitatively the effect of irreversible phenomena increased the thermodynamic imperfection of the processes. In this paper, the calculated exergy values of the fuels will be useful for energy experts studied in the coal mining area and coal-fired powerplants

  5. Studies on the Exergy Transfer Law for the Irreversible Process in the Waxy Crude Oil Pipeline Transportation

    Directory of Open Access Journals (Sweden)

    Qinglin Cheng

    2018-04-01

    Full Text Available With the increasing demand of oil products in China, the energy consumption of pipeline operation will continue to rise greatly, as well as the cost of oil transportation. In the field of practical engineering, saving energy, reducing energy consumption and adapting to the international oil situation are the development trends and represent difficult problems. Based on the basic principle of non-equilibrium thermodynamics, this paper derives the field equilibrium equations of non-equilibrium thermodynamic process for pipeline transportation. To seek the bilinear form of “force” and “flow” in the non-equilibrium thermodynamics of entropy generation rate, the oil pipeline exergy balance equation and the exergy transfer pipeline dynamic equation of the irreversibility were established. The exergy balance equation was applied to energy balance evaluation system, which makes the system more perfect. The exergy flow transfer law of the waxy oil pipeline were explored deeply from the directions of dynamic exergy, pressure exergy, thermal exergy and diffusion exergy. Taking an oil pipeline as an example, the influence factors of exergy transfer coefficient and exergy flow density were analyzed separately.

  6. Numerical study of cullet glass subjected to microwave heating and SiC susceptor effects. Part II: Exergy transfer analysis

    International Nuclear Information System (INIS)

    Acevedo, Luis; Usón, Sergio; Uche, Javier

    2015-01-01

    Highlights: • Exergy transfer analysis is proposed for the analysis of microwave glass heating. • Distribution of exergy transferred, accumulated and destroyed is quantified. • The method is applied to the comparison of different susceptor positions. - Abstract: The mathematical model of exergy transfer in cullet glass heated by microwave inside of a cubical cavity with the aid of a susceptor is presented. Part I of this paper presented a numerical combined electromagnetic and heat transfer model by applying both transient Maxwell’s equations and heat transfer equations. Then, the electromagnetic and temperature fields were used to obtain the exergy transfer analysis in the oven. Exergy transfer analysis informs us about the efficiency of energy transformations taking place during the heating process, since it explains how the quality of the energy behaves along the heating process. The rate of internal exergy, exergy flowing and destroyed exergy were obtained and presented for this transient process. Part I showed that the susceptor location could change the temperature fields of cullet glass. So, an exergy analysis is important to understand the irreversibilities produced by a susceptor during preheating (microwaves activation) and heating process of the cullet glass, and how they could be minimized. Exergy transfer analysis shows how both, electromagnetic and heat transfer, are responsible of the irreversibilities generated in the heating process

  7. Emergy and Eco-exergy Evaluation of Four Forest Restoration Modes

    Science.gov (United States)

    Four different forest restoration modes (Acacia mangium plantation, mixed-native species plantation, conifer plantation and Eucalyptus plantation) were evaluated using Energy System Theory and the emergy synthesis method. In addition, the eco-exergies of the four forest restorati...

  8. The thermodynamic properties of the upper continental crust: Exergy, Gibbs free energy and enthalpy

    International Nuclear Information System (INIS)

    Valero, Alicia; Valero, Antonio; Vieillard, Philippe

    2012-01-01

    This paper shows a comprehensive database of the thermodynamic properties of the most abundant minerals of the upper continental crust. For those substances whose thermodynamic properties are not listed in the literature, their enthalpy and Gibbs free energy are calculated with 11 different estimation methods described in this study, with associated errors of up to 10% with respect to values published in the literature. Thanks to this procedure we have been able to make a first estimation of the enthalpy, Gibbs free energy and exergy of the bulk upper continental crust and of each of the nearly 300 most abundant minerals contained in it. Finally, the chemical exergy of the continental crust is compared to the exergy of the concentrated mineral resources. The numbers obtained indicate the huge chemical exergy wealth of the crust: 6 × 10 6 Gtoe. However, this study shows that approximately only 0.01% of that amount can be effectively used by man.

  9. Exergy costs analysis of water desalination and purification techniques by transfer functions

    International Nuclear Information System (INIS)

    Carrasquer, Beatriz; Martínez-Gracia, Amaya; Uche, Javier

    2016-01-01

    Highlights: • A procedure to estimate the unit exergy cost of water treatment techniques is provided. • Unit exergy costs of water purification and desalination are given as a function of design and operating parameters. • Unit exergy costs range from 3.3 to 6.8 in purification and from 2 to 26 in desalination. • They could be used in their preliminary design as good indicators of their energy efficiency. - Abstract: The unit exergy costs of desalination and purification, which are two alternatives commonly used for water supply and treatment, have been characterized as a function of the energy efficiency of the process by combining the Exergy Cost Analysis with Transfer Function Analysis. An equation to assess the exergy costs of these alternatives is then proposed as a quick guide to know the energy efficiency of any water treatment process under different design and operating conditions. This combination, was satisfactory applied to groundwaters and water transfers. After identifying the boundaries of the system, input and output flows are calculated in exergy values. Next, different examples are analyzed in order to propose a generic equation to assess the exergy cost of the water restoration technologies, attending to their main features. Recovery ratio, energy requirements and salts concentrations (for desalination), and plant capacity and organic matter recovery (for water purification) are introduced in the calculations as their main endogenous parameters. Values obtained for typical operation ranges of commercial plants showed that unit exergy costs of water purification ranged from 3.3 to 6.8; maximum values, as expected, were found at low plant capacities and high organic matter removal ratios. For water desalination, values varied from 2 to 7 in membrane technologies and from 10 to 26 in thermal processes. The recovery ratio and salts concentration in raw water increased the unit exergy costs in membrane techniques. In distillation processes

  10. Energy and exergy analyses of native cassava starch drying in a tray dryer

    International Nuclear Information System (INIS)

    Aviara, Ndubisi A.; Onuoha, Lovelyn N.; Falola, Oluwakemi E.; Igbeka, Joseph C.

    2014-01-01

    Energy and exergy analyses of native cassava starch drying in a tray dryer were carried out to assess the performance of the system in terms of energy utilization, energy utilization ratio, energy efficiency, exergy inflow and outflow, exergy loss and exegetic efficiency. The results indicated that for the starch with ash content of 0.76%, 0.85% crude protein, 0.16% crude fat, negligible amount of fiber, average granule size of 14.1 μm, pH of 5.88, amylose content of 23.45% and degree of crystallinity of 22.34%, energy utilization and energy utilization ratio increased from 1.93 to 5.51 J/s and 0.65 to 0.6 as the drying temperature increased from 40 to 60 °C. Energy efficiency increased from 16.036 to 30.645%, while exergy inflow, outflow and losses increased from 0.399 to 2.686, 0.055 to 0.555 and 0.344 to 2.131 J/s respectively in the above temperature range. Exergetic efficiency increased with increase in both drying air temperature and energy utilization and was lower than energy efficiency. Exergetic improvement potential also increased with increase in drying air temperature. Model equations that could be used to express the energy and exergy parameters as a function of drying temperature were established. - Highlights: • Energy and exergy analyses of cassava starch drying in a tray dryer were carried out. • Energy utilization increased with drying temperature. • Energy efficiency was higher than exergy efficiency. • Energy and exergy efficiencies increased with increase in temperature. • Improvement potential increased with increase in temperature

  11. Overall energy, exergy and carbon credit analysis by different type of hybrid photovoltaic thermal air collectors

    International Nuclear Information System (INIS)

    Agrawal, Sanjay; Tiwari, G.N.

    2013-01-01

    Highlights: ► Comparative study of PVT air collectors. ► CO 2 analysis of all type of PVT air collectors. ► Study of thermal energy, exergy gain and exergy efficiency. ► Exergy efficiency of unglazed hybrid PVT tiles air collector is most efficient. - Abstract: In this paper, comparative analysis of different type of photovoltaic thermal (PVT) air collector namely: (i) unglazed hybrid PVT tiles, (ii) glazed hybrid PVT tiles and (iii) conventional hybrid PVT air collectors have been carried out for the composite climate of Srinagar (India). The comparative study has been carried out in terms of overall thermal energy and exergy gain, exergy efficiency and carbon credit earned by different type of hybrid PVT air collectors. It has been observed that overall annual thermal energy and exergy gain of unglazed hybrid PVT tiles air collector is higher by 27% and 29.3% respectively as compared to glazed hybrid PVT tiles air collector and by 61% and 59.8% respectively as compared to conventional hybrid PVT air collector. It has also been observed that overall annual exergy efficiency of unglazed and glazed hybrid PVT tiles air collector is higher by 9.6% and 53.8% respectively as compared to conventional hybrid PVT air collector. On the basis of comparative study, it has been concluded that CO 2 emission reduction per annum on the basis of overall thermal energy gain of unglazed and glazed hybrid PVT tiles air collector is higher by 62.3% and 27.7% respectively as compared to conventional hybrid PVT air collector and on the basis of overall exergy gain it is 59.7% and 22.7%.

  12. Energy and exergy utilization efficiencies and emission performance of Canadian transportation sector, 1990–2035

    International Nuclear Information System (INIS)

    Motasemi, F.; Afzal, Muhammad T.; Salema, Arshad Adam; Moghavvemi, M.; Shekarchian, M.; Zarifi, F.; Mohsin, R.

    2014-01-01

    Transportation sector of Canada is the second largest energy consuming sector which accounts for 30% of the total energy consumption of the country in 2009. The purpose of this work was to analyze the energy, exergy, and emission performance for four different modes of transport (road, air, rail, and marine) from the year 1990–2035. For historical period, the estimated overall energy efficiency ranges from 22.41% (1991) to 22.55% (2006) with a mean of 22.48 ± 0.07% and the overall exergy efficiency ranges from 21.61% (2001) to 21.87 (2006) with a mean of 21.74 ± 0.13%. Energy and exergy efficiencies may reach 20.95% and 20.97% in the year 2035 respectively based on the forecasted data. In comparison with other countries, we found that in the year 2000 the overall energy and exergy efficiencies for Canadian transportation sector were higher than Jordan, China, Norway, and Saudi Arabia but lower than Turkey and Malaysia. Between the year 1990–2009, the highest amount of emission produced in each subsector was: road CO 2 (80%), NO x (72%), and CO (carbon monoxide) (96%); air SO 2 (86%); rail NO x (6%) and marine NO x (7%). The road subsector produced the highest amount of emissions. - Highlights: • Energy, exergy and emission performance for Canadian transport was analyzed. • Maximum energy and exergy efficiencies were 22.55% and 21.87% in 2006 respectively. • Energy and exergy efficiencies may decrease in the year 2035. • CO 2 was the largest pollutant emitted followed by CO, NO x , and SO 2 . • Utilization of green fuels can improve exergy and emission performance

  13. Integrated assessment of exergy, energy and carbon dioxide emissions in an iron and steel industrial network

    International Nuclear Information System (INIS)

    Wu, Junnian; Wang, Ruiqi; Pu, Guangying; Qi, Hang

    2016-01-01

    Highlights: • Exergy, energy and CO_2 emissions assessment of iron and steel industrial network. • Effects of industry symbiosis measures on exergy, energy and CO_2 emissions. • Exploring the environmental impact from exergy losses. • The overall performance indexes are proposed for iron and steel industrial network. • Sinter strand and the wet quenching process have the lowest exergy efficiency. - Abstract: Intensive energy consumption and high pollution emissions in the iron and steel industry have caused problems to the energy system, in the economy, and in the environment. Iron and steel industrial network as an example of energy conservation and emissions reduction, require better analysis and assessment. The present study comprehensively assesses an iron and steel industrial network and its environmental performance with respect to exergy, energy and CO_2 emissions. The results show that the sinter strand needs to be greatly improved and the wet quenching process needs to be completely redesigned. The overall exergy efficiency and energy efficiency can be improved by adopting industrial symbiosis (IS) measures. We found that adjusting the energy structure to use renewable energy and recycling solid waste can greatly reduce CO_2 emissions. Moreover, the maximum exergy losses occurred in the blast furnace with the maximum CO_2 emissions. The iron making plant exerted a strong effect on the environment based on the equivalent CO_2 emission potentials. Many performance indicators of the entire industrial network were also examined in this work. It can be seen that integrated evaluation of energy and CO_2 emissions with exergy is necessary to help to mitigate adverse environmental impacts and more effectively fulfill the goals for energy conservation and emissions reduction.

  14. Exergy analysis for stationary flow systems with several heat exchange temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Lampinen, M J; Heikkinen, M A [Helsinki Univ. of Technology, Espoo (Finland). Dept. of Energy Engineering

    1995-07-01

    A thermodynamic theory of exergy analysis for a stationary flow system having several heat inputs and outputs at different temperature levels is presented. As a new result a relevant reference temperature of the surroundings is derived for each case. Also a general formula which combines exergy analysis with a modified Carnot efficiency is derived. The results are illustrated by numerical examples for mechanical multi-circuit heat pump cycles, for a Brayton process and for an absorption heat pump. (Author)

  15. Exergy analysis of parabolic trough solar collectors integrated with combined steam and organic Rankine cycles

    International Nuclear Information System (INIS)

    Al-Sulaiman, Fahad A.

    2014-01-01

    Highlights: • As the solar irradiation increases, the exergetic efficiency increases. • The R134a combined cycle has best exergetic performance, 26%. • The R600a combined cycle has the lowest exergetic efficiency, 20%. • The main source of exergy destruction is the solar collector. • There is an exergetic improvement potential of 75% in the systems considered. - Abstract: In this paper, detailed exergy analysis of selected thermal power systems driven by parabolic trough solar collectors (PTSCs) is presented. The power is produced using either a steam Rankine cycle (SRC) or a combined cycle, in which the SRC is the topping cycle and an organic Rankine cycle (ORC) is the bottoming cycle. Seven refrigerants for the ORC were examined: R134a, R152a, R290, R407c, R600, R600a, and ammonia. Key exergetic parameters were examined: exergetic efficiency, exergy destruction rate, fuel depletion ratio, irreversibility ratio, and improvement potential. For all the cases considered it was revealed that as the solar irradiation increases, the exergetic efficiency increases. Among the combined cycles examined, the R134a combined cycle demonstrates the best exergetic performance with a maximum exergetic efficiency of 26% followed by the R152a combined cycle with an exergetic efficiency of 25%. Alternatively, the R600a combined cycle has the lowest exergetic efficiency, 20–21%. This study reveals that the main source of exergy destruction is the solar collector where more than 50% of inlet exergy is destructed, or in other words more than 70% of the total destructed exergy. In addition, more than 13% of the inlet exergy is destructed in the evaporator which is equivalent to around 19% of the destructed exergy. Finally, this study reveals that there is an exergetic improvement potential of 75% in the systems considered

  16. Exergy efficient production, storage and distribution of solar energy

    Energy Technology Data Exchange (ETDEWEB)

    Sandnes, Bjoernar

    2003-07-01

    There are two main themes in this thesis. 1) Exergy efficient utilization of solar energy, where the introduction of alternative technologies such as photovoltaic/thermal collectors and phase change energy storage in a low temperature solar system is investigated. 2) The possibility of storing thermal energy in supercooled liquids is investigated. The introductory chapters introduce the concept of exergy, and focus on the use of solar heat as an inherently low quality source for covering low quality demands associated with space heating and hot water. The different stages of solar energy production, storage, and distribution of heat is discussed, with emphasis on exergy relevant issues. With the low temperature solar heating system as background, the introduction of some additional technologies that are investigated. A section of this thesis presents a study of a small scale PV/T collector as a possible component in a low temperature system. In another section the instrumentation that has been built for studies of full-size PV and thermal systems is described, and the possibility of using the PV unit outputs as parameters for controlling the thermal system operation is briefly discussed. It is suggested that the design of the PV/T unit in terms of whether priority should be given to electricity or heat production should be based on how consumption of high quality auxiliary energy is minimized, and not on adding up the combined exergy which is being produced. Solar combisystems require larger heat storage capacities compared to the more common solar hot water systems. Increased volumetric heat storage capacity can be achieved by latent heat storage systems where thermal energy is stored as heat of fusion in phase change materials (PCMs). A section presents a study where spherically encapsulated PCM is incorporated in a solar heat store. Solar combisystems are often complex, and have a relatively large number of interacting components. Another section describes a

  17. Exergy recovery during LNG regasification: Electric energy production - Part two

    International Nuclear Information System (INIS)

    Dispenza, Celidonio; Dispenza, Giorgio; Rocca, Vincenzo La; Panno, Giuseppe

    2009-01-01

    In liquefied natural gas (LNG) regasification facilities, for exergy recovery during regasification, an option could be the production of electric energy recovering the energy available as cold. In a previous paper, the authors propose an innovative process which uses a cryogenic stream of LNG during regasification as a cold source in an improved combined heat and power (CHP) plant. Considering the LNG regasification projects in progress all over the World, an appropriate design option could be based on a modular unit having a mean regasification capacity of 2 x 10 9 standard cubic meters/year. This paper deals with the results of feasibility studies, developed by the authors at DREAM in the context of a research program, on ventures based on thermodynamic and economic analysis of improved CHP cycles and related innovative technology which demonstrate the suitability of the proposal

  18. Exergy and Energy Analysis of Low Temperature District Heating Network

    DEFF Research Database (Denmark)

    Li, Hongwei; Svendsen, Svend

    is in line with a pilot project that is carrying out in Denmark with network supply/return temperature at 55oC/25 oC. The consumer domestic hot water (DHW) demand is supplied with a special designed district heating (DH) storage tank. The space heating (SH) demand is supplied with a low temperature radiator......Low temperature district heating (LTDH) with reduced network supply and return temperature provides better match of the low quality building thermal demand and the low quality waste heat supply. In this paper, an exemplary LTDH network was designed for 30 low energy demand residential houses, which....... The network thermal and hydraulic conditions were simulated under steady state with an in-house district heating network design and simulation code. Through simulation, the overall system energetic and exergetic efficiencies were calculated and the exergy losses for the major district heating system...

  19. Energy and exergy analysis of low temperature district heating network

    DEFF Research Database (Denmark)

    Li, Hongwei; Svendsen, Svend

    2012-01-01

    is designed to supply heating for 30 low energy detached residential houses. The network operational supply/return temperature is set as 55 °C/25 °C, which is in line with a pilot project carried out in Denmark. Two types of in-house substations are analyzed to supply the consumer domestic hot water demand...... energy/exergy losses and increase the quality match between the consumer heating demand and the district heating supply.......Low temperature district heating with reduced network supply and return temperature provides better match of the low quality building heating demand and the low quality heating supply from waste heat or renewable energy. In this paper, a hypothetical low temperature district heating network...

  20. Energy and exergy analyses of electrolytic hydrogen production

    Energy Technology Data Exchange (ETDEWEB)

    Rosen, M A [Ryerson Polytechnic Univ., Toronto, ON (Canada). Dept. of Mechanical Engineering

    1995-07-01

    The thermodynamic performance is investigated of a water-electrolysis process for producing hydrogen, based on current-technology equipment. Both energy and exergy analyses are used. Three cases are considered in which the principal driving energy inputs are (i) electricity, (ii) the high-temperature heat used to generate the electricity, and (iii) the heat source used to produce the high-temperature heat. The nature of the heat source (e.g.) fossil fuel, nuclear fuel, solar energy, (etc.) is left as general as possible. The analyses indicate that, when the main driving input is the hypothetical heat source, the principal thermodynamic losses are associated with water splitting, electricity generation and heat production; the losses are mainly due to the irreversibilities associated with converting a heat source to heat, and heat transfer across large temperature differences. The losses associated with the waste heat in used cooling water, because of its low quality, are not as significant as energy analysis indicates. (Author)

  1. Numerical analysis and field study of time dependent exergy-energy of a gas-steam combined cycle

    Directory of Open Access Journals (Sweden)

    Barari Bamdad

    2012-01-01

    Full Text Available In this study, time dependent exergy analysis of the Fars Combined Power Plant Cycle has been investigated. Exergy analysis has been used for investigating each part of actual combined cycle by considering irreversibility from Apr 2006 to Oct 2010. Performance analysis has been done for each part by evaluating exergy destruction in each month. By using of exergy analysis, aging of each part has been evaluated respect to time duration. In addition, the rate of lost work for each month has been calculated and variation of this parameter has been considered as a function of aging rate. Finally, effects of exergy destruction of each part have been investigated on exergy destruction of whole cycle. Entire analysis has been done for Unit 3 and 4 of gas turbine cycle which combined by Unit B of steam cycle in Fars Combined Power Plant Cycle located in Fars province in Iran.

  2. Evaluation of Working Fluids for Organic Rankine Cycle Based on Exergy Analysis

    Science.gov (United States)

    Setiawan, D.; Subrata, I. D. M.; Purwanto, Y. A.; Tambunan, A. H.

    2018-05-01

    One of the crucial aspects to determine the performance of Organic Rankine Cycle (ORC) is the selection of appropriate working fluids. This paper describes the simulative performance of several organic fluid and water as working fluid of an ORC based on exergy analysis with a heat source from waste heat recovery. The simulation was conducted by using Engineering Equation Solver (EES). The effect of several parameters and thermodynamic properties of working fluid was analyzed, and part of them was used as variables for the simulation in order to determine their sensitivity to the exergy efficiency changes. The results of this study showed that water is not appropriate to be used as working fluid at temperature lower than 130 °C, because the expansion process falls in saturated area. It was also found that Benzene had the highest exergy efficiency, i.e. about 10.49%, among the dry type working fluid. The increasing turbine inlet temperature did not lead to the increase of exergy efficiency when using organic working fluids with critical temperature near heat source temperature. Meanwhile, exergy efficiency decreasing linearly with the increasing condenser inlet temperature. In addition, it was found that working fluid with high latent heat of vaporization and specific heat exert in high exergy efficiency.

  3. Exergy Analysis of a Pilot Parabolic Solar Dish-Stirling System

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    Ehsan Gholamalizadeh

    2017-09-01

    Full Text Available Energy and exergy analyses were carried out for a pilot parabolic solar dish-Stirling System. The system was set up at a site at Kerman City, located in a sunny desert area of Iran. Variations in energy and exergy efficiency were considered during the daytime hours of the average day of each month in a year. A maximum collector energy efficiency and total energy efficiency of 54% and 12.2%, respectively, were predicted in July, while during the period between November and February the efficiency values were extremely low. The maximum collector exergy efficiency was 41.5% in July, while the maximum total exergy efficiency reached 13.2%. The values of energy losses as a percentage of the total losses of the main parts of the system were also reported. Results showed that the major energy and exergy losses occurred in the receiver. The second biggest portion of energy losses occurred in the Stirling engine, while the portion of exergy loss in the concentrator was higher compared to the Stirling engine. Finally, the performance of the Kerman pilot was compared to that of the EuroDish project.

  4. Exergy analysis of integrated waste management in the recovery and recycling of used cooking oils.

    Science.gov (United States)

    Talens Peiró, Laura; Villalba Méndez, Gara; Gabarrell i Durany, Xavier

    2008-07-01

    Used cooking oil (UCO) is a domestic waste generated daily by food industries, restaurants, and households. It is estimated that in Europe 5 kg of UCO are generated per inhabitant, totalling 2.5 million metric tons per year. Recovering UCO for the production of biodiesel offers a way of minimizing and avoiding this waste and related pollution. An exergy analysis of the integrated waste management (IWM) scheme for UCO is used to evaluate such a possibility by accounting for inputs and outputs in each stage, calculating the exergy loss and the resource input and quantifying the possible improvements. The IWM includes the collection, pretreatment, and delivery of UCO and the production of biodiesel. The results show that the greatest exergy loss occurs during the transport stages (57%). Such exergy loss can be minimized to 20% by exploiting the full capacity of collecting vans and using biodiesel in the transport stages. Further, the cumulative exergy consumption helps study how the exergy consumption of biodiesel can be further reduced by using methanol obtained from biogas in the transesterification stage. Finally, the paper discusses how increasing the collection of UCO helps minimize uncontrolled used oil disposal and consequently provides a sustainable process for biodiesel production.

  5. Energy and exergy utilization efficiencies in the Japanese residential/commercial sectors

    International Nuclear Information System (INIS)

    Kondo, Kumiko

    2009-01-01

    Unlike the manufacturing sector, the residential/commercial sectors of Japan struggle to meet their environmental requirements. For instance, their CO 2 emission levels have increased tremendously since 1990. This research estimates energy and 'exergy (available energy)' efficiencies in Japan's residential/commercial sectors during the period 1990-2006. Since an exergy analysis reveals 'available energy losses', it is an effective tool to achieve sustainable societies. The primary objective of this paper is to examine the potential for advancing the 'true' energy efficiency in Japan's residential/commercial sectors-by observing energy and exergy efficiency disparities. The results show large differences between the overall energy and exergy efficiencies in the residential (60.12%, 6.33%)/commercial sectors (51.78%, 5.74%) in 2006. This implies great potential for energy savings in both sectors. Furthermore, this research suggests that the residential sector may face more difficulties than the commercial sector, although the latter appears to be less energy-efficient, according to recent statistics. This is because the disparity between energy and exergy efficiencies has expanded in the residential sector since 2000. This study illustrates the importance of exergy analyses in promoting sustainable energy policies and new adaptation strategies.

  6. Exergy analysis, parametric analysis and optimization for a novel combined power and ejector refrigeration cycle

    International Nuclear Information System (INIS)

    Dai Yiping; Wang Jiangfeng; Gao Lin

    2009-01-01

    A new combined power and refrigeration cycle is proposed, which combines the Rankine cycle and the ejector refrigeration cycle. This combined cycle produces both power output and refrigeration output simultaneously. It can be driven by the flue gas of gas turbine or engine, solar energy, geothermal energy and industrial waste heats. An exergy analysis is performed to guide the thermodynamic improvement for this cycle. And a parametric analysis is conducted to evaluate the effects of the key thermodynamic parameters on the performance of the combined cycle. In addition, a parameter optimization is achieved by means of genetic algorithm to reach the maximum exergy efficiency. The results show that the biggest exergy loss due to the irreversibility occurs in heat addition processes, and the ejector causes the next largest exergy loss. It is also shown that the turbine inlet pressure, the turbine back pressure, the condenser temperature and the evaporator temperature have significant effects on the turbine power output, refrigeration output and exergy efficiency of the combined cycle. The optimized exergy efficiency is 27.10% under the given condition.

  7. Extended exergy concept to facilitate designing and optimization of frequency-dependent direct energy conversion systems

    International Nuclear Information System (INIS)

    Wijewardane, S.; Goswami, Yogi

    2014-01-01

    Highlights: • Proved exergy method is not adequate to optimize frequency-dependent energy conversion. • Exergy concept is modified to facilitate the thermoeconomic optimization of photocell. • The exergy of arbitrary radiation is used for a practical purpose. • The utility of the concept is illustrated using pragmatic examples. - Abstract: Providing the radiation within the acceptable (responsive) frequency range(s) is a common method to increase the efficiency of the frequency-dependent energy conversion systems, such as photovoltaic and nano-scale rectenna. Appropriately designed auxiliary items such as spectrally selective thermal emitters, optical filters, and lenses are used for this purpose. However any energy conversion method that utilizes auxiliary components to increase the efficiency of a system has to justify the potential cost incurred by those auxiliary components through the economic gain emerging from the increased system efficiency. Therefore much effort should be devoted to design innovative systems, effectively integrating the auxiliary items and to optimize the system with economic considerations. Exergy is the widely used method to design and optimize conventional energy conversion systems. Although the exergy concept is used to analyze photovoltaic systems, it has not been used effectively to design and optimize such systems. In this manuscript, we present a modified exergy method in order to effectively design and economically optimize frequency-dependent energy conversion systems. Also, we illustrate the utility of this concept using examples of thermophotovoltaic, Photovoltaic/Thermal and concentrated solar photovoltaic

  8. Analysis on exergy consumption patterns for space heating in Slovenian buildings

    International Nuclear Information System (INIS)

    Dovjak, Mateja; Shukuya, Masanori; Olesen, Bjarne W.; Krainer, Ales

    2010-01-01

    Problem of high energy use for heating in Slovenian buildings is analyzed with exergy and energy analysis. Results of both are compared and discussed. Three cases of exterior building walls are located in three climatic zones in winter conditions. Results of energy analyses show that the highest heating energy demand appears in the case with less thermal insulation, especially in colder climate. If the comparison is made only on the energy supply and exergy supply, the results of exergy analysis are the same as those of energy analysis. The main difference appears, if the whole chain of supply and demand is taken into consideration. Exergy calculations enable us to analyze how much exergy is consumed in which part, from boiler to building envelope. They also reveal how much energy is supplied for the purpose of heating. Results show that insulation has much bigger effect than effect of boiler efficiency. However, the most effective solution is to improve building envelope together with boiler efficiency. Better thermal insulation also makes an important contribution to the improvement of thermal comfort conditions. It causes higher surface temperatures resulting in a larger warm radiant exergy emission rate and consequently better thermal comfort.

  9. Exergy-based assessment for waste gas emissions from Chinese transportation

    International Nuclear Information System (INIS)

    Ji Xi; Chen, G.Q.; Chen, B.; Jiang, M.M.

    2009-01-01

    As an effective measure for environmental impact associated with the waste emissions, exergy is used to unify the assessment of the waste gases of CO, NO x , and SO 2 emitted from fossil fuel consumption by the transportation system in China. An index of emission exergy intensity defined as the ratio of the total chemical exergy of the emissions and the total converted turnover of the transportation is proposed to quantify the environmental impact per unit of traffic service. Time series analyses are presented for the emission exergy and emission exergy intensity of the whole Chinese transportation as well as for its four sectors of highways, railways, waterways and civil aviation from 1978 to 2004. For the increasing emission exergy with CO taking the largest share, the highways sector was the major contributor, while the railways sector initially standing as the second main contributor developed into the least after 1995. The temporal and structural variations of the emissions are illustrated against the transition of the transportation system in a socio-economic perspective, with emphasis on policy-making implications.

  10. Assessing the Exergy Costs of a 332-MW Pulverized Coal-Fired Boiler

    Directory of Open Access Journals (Sweden)

    Victor H. Rangel-Hernandez

    2016-08-01

    Full Text Available In this paper, we analyze the exergy costs of a real large industrial boiler with the aim of improving efficiency. Specifically, the 350-MW front-fired, natural circulation, single reheat and balanced draft coal-fired boiler forms part of a 1050-MW conventional power plant located in Spain. We start with a diagram of the power plant, followed by a formulation of the exergy cost allocation problem to determine the exergy cost of the product of the boiler as a whole and the expenses of the individual components and energy streams. We also define a productive structure of the system. Furthermore, a proposal for including the exergy of radiation is provided in this study. Our results show that the unit exergy cost of the product of the boiler goes from 2.352 to 2.5, and that the maximum values are located in the ancillary electrical devices, such as induced-draft fans and coil heaters. Finally, radiation does not have an effect on the electricity cost, but affects at least 30% of the unit exergy cost of the boiler’s product.

  11. Energy and exergy analyses of an integrated solar heat pump system

    International Nuclear Information System (INIS)

    Suleman, F.; Dincer, I.; Agelin-Chaab, M.

    2014-01-01

    An integrated solar and heat pump based system for industrial heating is developed in this study. The system comprises heat pump cycle for process heating water and solar energy for another industrial heating process. Comprehensive energy and exergy analyses are performed on the system. These analyses generated some compelling results as expected because of the use of green and environmentally friendly energy sources. The results show that the energy efficiency of the process is 58% while the exergy efficiency is 75%. Energetic COP of the heat pump cycle is 3.54 whereas the exergy efficiency is 42.5%. Moreover, the energetic COP of the system is 2.97 and the exergy efficiency of the system is 35.7%. In the parametric study, a different variation such as changing the temperature and pressure of the condenser also shows positive results. - Highlights: • An integrated system is analysed using renewable energy source which can be used in textile industry. • Energy losses and exergy destructions are calculated at all major components. • Energy and exergy efficiencies of all subunits, subsystems and overall system are determined. • A parametric study shows the effect of environment and operating conditions on efficiencies. • Solar energy for heating in textile industry is efficient and environmentally friendly

  12. Energy and exergy prices of various energy sources along with their CO2 equivalents

    International Nuclear Information System (INIS)

    Caliskan, Hakan; Hepbasli, Arif

    2010-01-01

    Various types of energy sources are used in the residential and industrial sectors. Choosing the type of sources is important. When an energy source is selected, its CO 2 equivalent and energy and exergy prices must be known for a sustainable future and for establishing energy policies. These prices are based on their energy values. Exergy analysis has been recently applied to a wide range of energy-related systems. Thus, obtaining the exergy values has become more meaningful for long-term planning. In this study, energy and exergy prices of various energy sources along with CO 2 equivalents are calculated and compared for residential and industrial applications in Turkey. Energy sources considered include coal, diesel oil, electricity, fuel oil, liquid petroleum gas (LPG), natural gas, heat pumps and geothermal, and their prices were obtained over a period of 18 months, from January 2008 to June 2009. For the residential and industrial sectors, minimum energy and exergy prices were found for ground source heat pumps, while maximum energy and exergy prices belong to LPG for both sectors.

  13. Exergy analysis and evolutionary optimization of boiler blowdown heat recovery in steam power plants

    International Nuclear Information System (INIS)

    Vandani, Amin Mohammadi Khoshkar; Bidi, Mokhtar; Ahmadi, Fatemeh

    2015-01-01

    Highlights: • Heat recovery of boiler blow downed water using a flash tank is modeled. • Exergy destruction of each component is calculated. • Exergy efficiency of the whole system is optimized using GA and PSO algorithms. • Utilizing the flash tank increases the net power and efficiency of the system. - Abstract: In this study, energy and exergy analyses of boiler blowdown heat recovery are performed. To evaluate the effect of heat recovery on the system performance, a steam power plant in Iran is selected and the results of implementation of heat recovery system on the power plant are investigated. Also two different optimization algorithms including GA and PSO are established to increase the plant efficiency. The decision variables are extraction pressure from steam turbine and temperature and pressure of boiler outlet stream. The results indicate that using blowdown recovery technique, the net generated power increases 0.72%. Also energy and exergy efficiency of the system increase by 0.23 and 0.22, respectively. The optimization results show that temperature and pressure of boiler outlet stream have a higher effect on the exergy efficiency of the system in respect to the other decision variables. Using optimization methods, exergy efficiency of the system reaches to 30.66% which shows a 1.86% augmentation with regard to the situation when a flash tank is implemented.

  14. Evolutionary synthesis of optimum light ends recovery unit with exergy analysis application

    International Nuclear Information System (INIS)

    Khalili-Garakani, Amirhossein; Ivakpour, Javad; Kasiri, Norollah

    2016-01-01

    Highlights: • Presenting an evolutionary synthesis algorithm. • Reducing configuration nominees based on exergy loss diagram of distillation columns. • Reduction of search space without decreasing the comprehensiveness and precision of the synthesis algorithm. • Rigorous simulation and optimization of sequences. - Abstract: Exergy analysis proved to be important in understanding of regions with poor energy efficiency and improve the design of distillation processes. In this study a new method based on exergy analysis is developed for the synthesis of a light ends recovery unit. The algorithm is some kinds of evolutionary one which employ total exergy loss diagrams of distillation columns for limiting the search space and reducing configuration nominees. The new method presented here for the light end separation unit, applies exergy loss diagrams as a powerful tool in locating the weak spot in the distillation columns of the Brugma sequence (as a first guess) and change the structure of the sequence step by step to achieve the best sequence. The results show that the new method could reduce the amount of calculations between 16% and 55% of the cases considered in this case study. The reduction of the search space takes place without decreasing the comprehensiveness and precision of the synthesis algorithm. Besides the amount of reduction in total annual cost and exergy loss of the optimum sequence is considerable.

  15. Rethinking exergy efficiency in favor of exergy sustainability as a criteria for design. Paper no. IGEC-1-ID12

    International Nuclear Information System (INIS)

    Seager, T.P.

    2005-01-01

    'Full text:' Engineering design in power generation or conversion has typically focused on minimizing exergy losses (entropy gains), or maximizing economic returns. Both entropy minimization and profit maximization are readily obtainable and acceptable objective criteria for design of thermodynamic processes. However, alternative criteria are imaginable. This research presents a framework for considering minimal environmental impact or maximum renewability as alternative design criteria. In the environmental case, fuel source is based upon an exergetic environmental metric called pollution potential. In the case of renewability, a life-cycle metric describing the replacement time frame of the fuel source is employed. When coupled, the two metrics together partially assess the overall sustainability of the design. (author)

  16. Resource recovery from residual household waste: An application of exergy flow analysis and exergetic life cycle assessment.

    Science.gov (United States)

    Laner, David; Rechberger, Helmut; De Soete, Wouter; De Meester, Steven; Astrup, Thomas F

    2015-12-01

    Exergy is based on the Second Law of thermodynamics and can be used to express physical and chemical potential and provides a unified measure for resource accounting. In this study, exergy analysis was applied to four residual household waste management scenarios with focus on the achieved resource recovery efficiencies. The calculated exergy efficiencies were used to compare the scenarios and to evaluate the applicability of exergy-based measures for expressing resource quality and for optimizing resource recovery. Exergy efficiencies were determined based on two approaches: (i) exergy flow analysis of the waste treatment system under investigation and (ii) exergetic life cycle assessment (LCA) using the Cumulative Exergy Extraction from the Natural Environment (CEENE) as a method for resource accounting. Scenario efficiencies of around 17-27% were found based on the exergy flow analysis (higher efficiencies were associated with high levels of material recycling), while the scenario efficiencies based on the exergetic LCA lay in a narrow range around 14%. Metal recovery was beneficial in both types of analyses, but had more influence on the overall efficiency in the exergetic LCA approach, as avoided burdens associated with primary metal production were much more important than the exergy content of the recovered metals. On the other hand, plastic recovery was highly beneficial in the exergy flow analysis, but rather insignificant in exergetic LCA. The two approaches thereby offered different quantitative results as well as conclusions regarding material recovery. With respect to resource quality, the main challenge for the exergy flow analysis is the use of exergy content and exergy losses as a proxy for resource quality and resource losses, as exergy content is not per se correlated with the functionality of a material. In addition, the definition of appropriate waste system boundaries is critical for the exergy efficiencies derived from the flow analysis, as it

  17. Avoidable and unavoidable exergy destruction and exergoeconomic evaluation of the thermal processes in a real industrial plant

    Directory of Open Access Journals (Sweden)

    Vučković Goran D.

    2012-01-01

    Full Text Available Exergy analysis is a universal method for evaluating the rational use of energy. It can be applied to any kind of energy conversion system or chemical process. An exergy analysis identifies the location, the magnitude and the causes of thermodynamic inefficiencies and enhances understanding of the energy conversion processes in complex systems. Conventional exergy analyses pinpoint components and processes with high irreversibility. To overcome the limitations of the conventional analyses and to increase our knowledge about a plant, advanced exergy-based analyses are developed. These analyses provide additional information about component interactions and reveal the real potential for improvement of each component constituting a system, as well as of the overall system. In this paper, a real industrial plant is analyzed using both conventional and advanced exergy analyses, and exergoeconomic evaluation. Some of the exergy destruction in the plant components is unavoidable and constrained by technological, physical and economic limitations. Calculations related to the total avoidable exergy destruction caused by each component of the plant supplement the outcome of the conventional exergy analysis. Based on the all-reaching analysis, by improving the boiler operation (elimination of approximately 1 MW of avoidable exergy destruction in the steam boiler the greatest improvement in the efficiency of the overall system can be achieved.

  18. Energy-exergy analysis of compressor pressure ratio effects on thermodynamic performance of ammonia water combined cycle

    International Nuclear Information System (INIS)

    Mohtaram, Soheil; Chen, Wen; Zargar, T.; Lin, Ji

    2017-01-01

    Highlights: • Energy exergy analysis is conducted to find the effects of RP. • EES software is utilized to perform the detailed energy-exergy analyses. • Effects investigated through energy and exergy destruction, enthalpy, yields, etc. • Detailed results are reported showing the performance of gas and combined cycle. - Abstract: The purpose of this study is to investigate the effect of compressor pressure ratio (RP) on the thermodynamic performances of ammonia-water combined cycle through energy and exergy destruction, enthalpy temperature, yields, and flow velocity. The energy-exergy analysis is conducted on the ammonia water combined cycle and the Rankine cycle, respectively. Engineering Equation Solver (EES) software is utilized to perform the detailed analyses. Values and ratios regarding heat drop and exergy loss are presented in separate tables for different equipments. The results obtained by the energy-exergy analysis indicate that by increasing the pressure ratio compressor, exergy destruction of high-pressure compressors, intercooler, gas turbine and the special produced work of gas turbine cycle constantly increase and the exergy destruction of recuperator, in contrast, decreases continuously. In addition, the least amount of input fuel into the combined cycle is observed when the pressure ratio is no less than 7.5. Subsequently, the efficiency of the cycle in gas turbine and combined cycle is reduced because the fuel input into the combined cycle is increased.

  19. Evolution of the decrease in mineral exergy throughout the 20th century. The case of copper in the US

    International Nuclear Information System (INIS)

    Valero, Alicia; Valero, Antonio; Arauzo, Inmaculada

    2008-01-01

    A mineral deposit is a natural resource whose exergy can be calculated from a defined reference environment (RE). This RE can be compared to a thermodynamically dead planet, where all materials have reacted, dispersed and mixed. Like any substance, a mine is characterized by its quantity, chemical composition and concentration (ore grade). The mine's exergy measures the minimum (reversible) energy to extract and concentrate the materials from the RE to the conditions in the mine. And the mine's exergy replacement cost accounts for the actual exergy required to accomplish this, with available technologies. The exergy assessment of the natural resource wealth of the Earth defined from a RE is named as exergoecology. The aim of this paper is to prove the usefulness of these two indicators for assessing the degradation of mineral deposits over history. As an example, the exergy decrease of US copper mines due to copper extraction throughout the 20th century has been determined. The results indicate that the exergy decrease was 65.4 Mtoe, while the exergy replacement cost 889.9 Mtoe. During the past century, the US extracted the equivalent of 2.5 and 1.2 times of its current national exergy reserves and base reserve of copper, respectively

  20. Energy and exergy analyses of a biomass trigeneration system using an organic Rankine cycle

    International Nuclear Information System (INIS)

    Al-Sulaiman, Fahad A.; Dincer, Ibrahim; Hamdullahpur, Feridun

    2012-01-01

    In this study, energy and exergy analyses of a biomass trigeneration system using an organic Rankine cycle (ORC) are presented. Four cases are considered for analysis: electrical-power, cooling-cogeneration, heating-cogeneration and trigeneration cases. The results obtained reveal that the best performance of the trigeneration system considered can be obtained with the lowest ORC evaporator pinch temperature considered, T pp = 20 K, and the lowest ORC minimum temperature, T 9 = 345 K. In addition, this study reveals that there is a significant improvement when trigeneration is used as compared to only electrical power production. This study demonstrates that the fuel utilization efficiency increases, in average, from 12% for electrical power to 88% for trigeneration. Moreover, the maximum exergy efficiency of the ORC is 13% and, when trigeneration is used, it increases to 28%. Furthermore, this study reveals that the electrical to cooling ratio can be controlled through changing the ORC evaporator pinch point temperature and/or the pump inlet temperature. In addition, the study reveals that the biomass burner and the ORC evaporator are the main two sources of exergy destruction. The biomass burner contributes to 55% of the total destructed exergy whereas the ORC evaporator contributes to 38% of the total destructed exergy. -- Highlights: ► The best performance can be obtained with the lowest ORC evaporator pinch temperature and the lowest ORC minimum temperature. ► There is, on average, 75 % gain in energy efficiency for trigeneration compared to electrical system. ► There is, on average, 17% gain in exergy efficiency when trigeneration is used as compared to electrical system. ► The electrical to cooling ratio is sensitive to the variation of the pinch point temperature and pump inlet temperature. ► The two main sources of the exergy destruction are the biomass burner with 55% and the ORC evaporator with 38%.

  1. Exergy and environmental comparison of the end use of vehicle fuels: The Brazilian case

    International Nuclear Information System (INIS)

    Flórez-Orrego, Daniel; Silva, Julio A.M.; Oliveira Jr, Silvio de

    2015-01-01

    Highlights: • Total and non-renewable exergy costs of Brazilian transportation service are evaluated. • Specific CO 2 emissions of the Brazilian transportation service are determined. • Overall exergy efficiency of the end use of vehicle fuels in transportation sector is calculated. • A comparative extended analysis of the production and end use of transportation fuels is presented. - Abstract: In this work, a comparative exergy and environmental analysis of the vehicle fuel end use is presented. This analysis comprises petroleum and natural gas derivatives (including hydrogen), biofuels (ethanol and biodiesel), and their mixtures, besides of the electricity generated in the Brazilian electricity mix, intended to be used in plug in electric vehicles. The renewable and non-renewable unit exergy costs and CO 2 emission cost are proposed as suitable indicators for assessing the renewable exergy consumption intensity and the environmental impact, and for quantifying the thermodynamic performance of the transportation sector. This allows ranking the energy conversion processes along the vehicle fuels production routes and their end use, so that the best options for the transportation sector can be determined and better energy policies may be issued. It is found that if a drastic CO 2 emissions abatement of the sector is pursued, a more intensive utilization of ethanol in the Brazilian transportation sector mix is advisable. However, as the overall exergy conversion efficiency of the sugar cane industry is still very low, which increases the unit exergy cost of ethanol, better production and end use technologies are required. Nonetheless, with the current scenario of a predominantly renewable Brazilian electricity mix, based on more than 80% of renewable sources, this source consolidates as the most promising energy source to reduce the large amount of greenhouse gas emissions which transportation sector is responsible for

  2. Understanding China’s past and future energy demand: An exergy efficiency and decomposition analysis

    International Nuclear Information System (INIS)

    Brockway, Paul E.; Steinberger, Julia K.; Barrett, John R.; Foxon, Timothy J.

    2015-01-01

    Highlights: • We complete the first time series exergy and useful work study of China (1971–2010). • Novel exergy approach to understand China’s past and future energy consumption. • China’s exergy efficiency rose from 5% to 13%, and is now above US (11%). • Decomposition finds this is due to structural change not technical leapfrogging. • Results suggests current models may underestimate China’s future energy demand. - Abstract: There are very few useful work and exergy analysis studies for China, and fewer still that consider how the results inform drivers of past and future energy consumption. This is surprising: China is the world’s largest energy consumer, whilst exergy analysis provides a robust thermodynamic framework for analysing the technical efficiency of energy use. In response, we develop three novel sub-analyses. First we perform a long-term whole economy time-series exergy analysis for China (1971–2010). We find a 10-fold growth in China’s useful work since 1971, which is supplied by a 4-fold increase in primary energy coupled to a 2.5-fold gain in aggregate exergy conversion efficiency to useful work: from 5% to 12.5%. Second, using index decomposition we expose the key driver of efficiency growth as not ‘technological leapfrogging’ but structural change: i.e. increasing reliance on thermodynamically efficient (but very energy intensive) heavy industrial activities. Third, we extend our useful work analysis to estimate China’s future primary energy demand, and find values for 2030 that are significantly above mainstream projections

  3. Exergy costing for energy saving in combined heating and cooling applications

    International Nuclear Information System (INIS)

    Nguyen, Chan; Veje, Christian T.; Willatzen, Morten; Andersen, Peer

    2014-01-01

    Highlights: • We investigate the basis for cost apportioning of simultaneous heating and cooling. • Two thermoeconomic methods based on energy and exergy costing is demonstrated. • The unit cost of heating and cooling for a heat pump system is found and compared. • Energy costing may obstruct efficient use of energy. • Exergy costing provides the most rational cost apportioning for energy saving. - Abstract: The aim of this study is to provide a price model that motivates energy saving for a combined district heating and cooling system. A novel analysis using two thermoeconomic methods for apportioning the costs to heating and cooling provided simultaneously by an ammonia heat pump is demonstrated. In the first method, referred to as energy costing, a conventional thermoeconomic analysis is used. Here the ammonia heat pump is subject to a thermodynamic analysis with mass and energy balance equations. In the second method referred to as exergy costing, an exergy based economic analysis is used, where exergy balance equations are used in conjunction with mass and energy balance equations. In both costing methods the thermodynamic analysis is followed by an economic analysis which includes investment and operating costs. For both methods the unit costs of heating and cooling are found and compared. The analysis shows that the two methods yield significantly different results. Rather surprisingly, it is demonstrated that the exergy costing method results in about three times higher unit cost for heating than for cooling as opposed to equal unit costs when using the energy method. Further the exergy-based cost for heating changes considerably with the heating temperature while that of cooling is much less affected

  4. Operation optimization of a distributed energy system considering energy costs and exergy efficiency

    International Nuclear Information System (INIS)

    Di Somma, M.; Yan, B.; Bianco, N.; Graditi, G.; Luh, P.B.; Mongibello, L.; Naso, V.

    2015-01-01

    Highlights: • Operation optimization model of a Distributed Energy System (DES). • Multi-objective strategy to optimize energy cost and exergy efficiency. • Exergy analysis in building energy supply systems. - Abstract: With the growing demand of energy on a worldwide scale, improving the efficiency of energy resource use has become one of the key challenges. Application of exergy principles in the context of building energy supply systems can achieve rational use of energy resources by taking into account the different quality levels of energy resources as well as those of building demands. This paper is on the operation optimization of a Distributed Energy System (DES). The model involves multiple energy devices that convert a set of primary energy carriers with different energy quality levels to meet given time-varying user demands at different energy quality levels. By promoting the usage of low-temperature energy sources to satisfy low-quality thermal energy demands, the waste of high-quality energy resources can be reduced, thereby improving the overall exergy efficiency. To consider the economic factor as well, a multi-objective linear programming problem is formulated. The Pareto frontier, including the best possible trade-offs between the economic and exergetic objectives, is obtained by minimizing a weighted sum of the total energy cost and total primary exergy input using branch-and-cut. The operation strategies of the DES under different weights for the two objectives are discussed. The operators of DESs can choose the operation strategy from the Pareto frontier based on costs, essential in the short run, and sustainability, crucial in the long run. The contribution of each energy device in reducing energy costs and the total exergy input is also analyzed. In addition, results show that the energy cost can be much reduced and the overall exergy efficiency can be significantly improved by the optimized operation of the DES as compared with the

  5. The utility of environmental exergy analysis for decision making in energy

    International Nuclear Information System (INIS)

    Simpson, Adam P.; Edwards, Chris F.

    2013-01-01

    The analysis framework discussed and employed in this paper utilizes the recent recognition that exergy is a form of environmental free energy to provide a fundamental basis for valuing environmental interactions independent from their secondary impacts. The framework is comprised of two separate components: (1) environmental exergy analysis and (2) anthropocentric sensitivity analysis. Environmental exergy analysis is based on fundamental thermodynamic principles and analysis techniques. It extends the principles of technical exergy analysis to the environment in order to quantify the location, magnitudes, and types of environmental impact—state change, alteration of natural transfers, and destruction change. Anthropocentric sensitivity analysis is based on the concepts of anthropocentric value and anthropocentric sensitivity. It enables the results of environmental exergy analysis to be interpreted for decision making, but at the expense of introducing some subjectivity into the framework. A key attribute of the framework is its ability to evaluate the environmental performance of energy systems on a level playing field, regardless of the specifics of the systems—i.e., resources consumed, products and by-products produced, or system size and time scale. The utility of the analysis framework for decision making is demonstrated in this paper through application to three example energy systems. - Highlights: ► Utilizes the recognition that exergy is a form of environmental free energy. ► Combines environmental exergy analysis and anthropocentric sensitivity analysis. ► Evaluates/compares environmental performance of systems on a level playing field. ► Independence from the system specifics—resources, by-products, sizes, time scales. ► Utility for decision making is demonstrated using real and notional energy systems

  6. Breakdown and assessment of cumulative exergy losses for a turbojet over a flight

    Energy Technology Data Exchange (ETDEWEB)

    Rosen, M. [Univ. of Ontario Inst. of Technology, Oshawa, ON (Canada). Faculty of Engineering and Applied Science

    2007-07-01

    This paper presented an exergy analysis conducted to evaluate the contribution of exhaust emissions from the engine of a turbojet to the craft's total exergy losses. The aim of the study was to understand the most significant exergy losses in aerospace engines in order to increase energy efficiency. The analysis was also conducted to further break down components of the exhaust's emissions as well as to assess the sensitivity of the results in relation to their reference environment. The exergy analysis formed part of a series of analyses conducted on a turbojet over a complete flight. Results of the study demonstrated that the use of a constant reference environment resulted in errors as high as 52 per cent when compared with results obtained using a reference environment that changed at the same time as the operating environment. The error was dependent on the distance flow. When the constant reference environment was set at the cruising altitude, the error was reduced as the flight distance increased. It was concluded that any constant reference environment produced false trends when cumulative exergy losses were examined over a flight cycle. 19 refs., 5 figs.

  7. Exergetic Analysis, Optimization and Comparison of LNG Cold Exergy Recovery Systems for Transportation

    Directory of Open Access Journals (Sweden)

    Paweł Dorosz

    2018-01-01

    Full Text Available LNG (Liquefied Natural Gas shares in the global energy market is steadily increasing. One possible application of LNG is as a fuel for transportation. Stricter air pollution regulations and emission controls have made the natural gas a promising alternative to liquid petroleum fuels, especially in the case of heavy transport. However, in most LNG-fueled vehicles, the physical exergy of LNG is destroyed in the regasification process. This paper investigates possible LNG exergy recovery systems for transportation. The analyses focus on “cold energy” recovery systems as the enthalpy of LNG, which may be used as cooling power in air conditioning or refrigeration. Moreover, four exergy recovery systems that use LNG as a low temperature heat sink to produce electric power are analyzed. This includes single-stage and two-stage direct expansion systems, an ORC (Organic Rankine Cycle system, and a combined system (ORC + direct expansion. The optimization of the above-mentioned LNG power cycles and exergy analyses are also discussed, with the identification of exergy loss in all components. The analyzed systems achieved exergetic efficiencies in the range of 20 % to 36 % , which corresponds to a net work in the range of 214 to 380 kJ/kg L N G .

  8. Exergy Analysis of the Supply of Energy and Material Resources in the Swedish Society

    Directory of Open Access Journals (Sweden)

    Mei Gong

    2016-09-01

    Full Text Available Exergy is applied to the Swedish energy supply system for the period 1970–2013. Exergy flow diagrams for the systems of electricity and district heating as well as for the total supply system of energy and material resources for 2012 are presented. The share of renewable use has increased in both electricity and district heat production. The resource use is discussed in four sectors: residential and service, transportation, industry and agriculture. The resource use is also analyzed with respect to exergy efficiency and renewable share. The total exergy input of energy and material resources amounts to about 2700 PJ of which about 530 PJ was used for final consumption in 2012. The results are also compared with similar studies. Even though the share of renewable resource use has increased from 42% in 1980 to 47% in 2012, poor efficiency is still occurring in transportation, space heating, and food production. A strong dependence on fossil and nuclear fuels also implies a serious lack of sustainability. A more exergy efficient technology and a higher renewable energy share are needed in order to become a more sustainable society.

  9. Thermodynamic exergy analysis for small modular reactor in nuclear hybrid energy system - 15110

    International Nuclear Information System (INIS)

    Boldon, L.; Liu, L.; Sabharwall, P.; Rabiti, C.; Bragg-Sitton, S.M.

    2015-01-01

    To assess the inherent value of energy in a thermal system, it is necessary to understand both the quantity and quality of energy available or the exergy. We study the case where nuclear energy through a small modular reactor (SMR) is supplementing the available wind energy through storage to meet the needs of the electrical grid. Nuclear power is also being used for the production of hydrogen via high temperature steam electrolysis. For a SMR exergy analysis, both the physical and economic environments must be considered. The physical environment incorporates the energy, raw materials, and reference environment, where the reference environment refers to natural resources available without limit and without cost. This paper aims to explore the use of exergy analysis methods to estimate and optimize SMR resources and costs for individual subsystems, based on thermodynamic principles-resource utilization and efficiency. The paper will present background information on exergy theory; identify the core subsystems in an SMR plant coupled with storage systems in support of renewable energy and hydrogen production; perform a thermodynamic exergy analysis; determine the cost allocation among these subsystems; and calculate unit 'exergetic' costs, unit 'exergo-economic' costs, and first and second law efficiencies. Exergetic and 'exergo-economic' costs ultimately determine how individual subsystems contribute to overall profitability and how efficiencies and consumption may be optimized to improve profitability, making SMRs more competitive with other generation technologies

  10. A Thermorisk framework for the analysis of energy systems by combining risk and exergy analysis

    International Nuclear Information System (INIS)

    Cassetti, G.; Colombo, E.; Zio, E.

    2016-01-01

    Highlights: • An exergy based analysis for improving efficiency and safety of energy systems is presented. • The relation between thermodynamic parameters and the safety characteristics is identified. • Possible modifications in the process are indicated to improve the safety of the system. - Abstract: The impact of energy production, transformation and use on the environmental resources encourage to understand the mechanisms of resource degradation and to develop proper analyses to reduce the impact of the energy systems on the environment. At the technical level, most attempts for reducing the environmental impact of energy systems focus on the improvement of process efficiency. One way toward an integrated approach is that of adopting exergy analysis for assessing efficiency and test improving design and operation solutions. The paper presents an exergy based analysis for improving efficiency and safety of energy systems, named Thermorisk analysis. The purpose of the Thermorisk analysis is to supply information to control, and eventually reduce, the risk of the systems (i.e. risk of accidents) by acting on the thermodynamic parameters and safety characteristics in the same frame. The proper combination of exergy and risk analysis allows monitoring the effects of efficiency improvement on the safety of the systems analyzed. A case study is presented, showing the potential of the analysis to identify the relation between the exergy efficiency and the risk of the system analyzed, and the contribution of inefficiencies on the safety of the process. Possible modifications in the process are indicated to improve the safety of the system.

  11. Estimating the energy and exergy utilization efficiencies for the residential-commercial sector: an application

    International Nuclear Information System (INIS)

    Utlu, Zafer; Hepbasli, Arif

    2006-01-01

    The main objectives in carrying out the present study are twofold, namely to estimate the energy and exergy utilization efficiencies for the residential-commercial sector and to compare those of various countries with each other. In this regard, Turkey is given as an illustrative example with its latest figures in 2002 since the data related to the following years are still being processed. Total energy and exergy inputs in this year are calculated to be 3257.20 and 3212.42 PJ, respectively. Annual fuel consumptions in space heating, water heating and cooking activities as well as electrical energy uses by appliances are also determined. The energy and exergy utilization efficiency values for the Turkish residential-commercial sector are obtained to be 55.58% and 9.33%, respectively. Besides this, Turkey's overall energy and exergy utilization efficiencies are found to be 46.02% and 24.99%, respectively. The present study clearly indicates the necessity of the planned studies toward increasing exergy utilization efficiencies in the sector studied

  12. Exergy analysis of synthetic biofuel production via fast pyrolysis and hydroupgrading

    International Nuclear Information System (INIS)

    Peters, Jens F.; Petrakopoulou, Fontina; Dufour, Javier

    2015-01-01

    This paper presents the first assessment of the exergetic performance of a biorefinery process based on catalytic hydroupgrading of bio-oil from fast pyrolysis. Lignocellulosic biomass is converted into bio-oil through fast pyrolysis, which is then upgraded to synthetic fuels in a catalytic hydrotreating process. The biorefinery process is simulated numerically using commercial software and analyzed using exergetic analysis. Exergy balances are defined for each component of the plant and the exergetic efficiencies and exergy destruction rates are calculated at the component, section and plant level, identifying thermodynamic inefficiencies and revealing the potential for further improvement of the process. The overall biofuel process results in an exergetic efficiency of 60.1%, while the exergetic efficiency of the upgrading process in the biorefinery alone is 77.7%. Within the biorefinery, the steam reforming reactor is the main source of inefficiencies, followed by the two hydrotreating reactors. In spite of the high operating pressures in the hydrotreating section, the compressors have little impact on the total exergy destruction. Compared to competing lignocellulosic biofuel processes, like gasification with Fischer–Tropsch synthesis or lignocellulosic ethanol processes, the examined system achieves a significantly higher exergetic efficiency. - Highlights: • Exergetic analysis of a biorefinery for bio-oil hydroupgrading. • Detailed simulation model using 83 model compounds. • Exergy destruction quantified in each component of the plant. • Exergetic efficiency and potential for improvement determined on component level. • Highest exergy destruction in the pyrolysis plant and the steam reformer

  13. Exergy efficiency enhancement of MSF desalination by heat recovery from hot distillate water stages

    International Nuclear Information System (INIS)

    Al-Weshahi, Mohammed A.; Anderson, Alexander; Tian, Guohong

    2013-01-01

    This detailed exergy analysis of a 3800 m 3 /h Multi-Stage Flash (MSF) desalination plant is based on the latest published thermodynamics properties of water and seawater. The parameters of the study were extracted from a validated model of MSF desalination using IPSEpro software. The results confirmed that the overall exergy efficiency of the unit is lower than would be desirable at only 5.8%. Exergy inputs were destroyed by 55%, 17%, 10%, 4.3%, and 14% respectively, in the heat recovery stages, brine heater, heat rejection stages, pumps and brine streams disposal. Moreover, the detail of the study showed that the lowest exergy destruction occurs in the first stage, increasing gradually in heat recovery stages and sharply in heat rejection stages. The study concludes that recovering the heat from the hot distillate water stages can improve unit exergy efficiency from its low 5.8% to a more economical 14%, with the hot water parameters suitable for powering other thermal systems such as absorption chiller and multi-effect desalination

  14. Exergy optimization for a novel combination of organic Rankine cycles, Stirling cycle and direct expander turbines

    Science.gov (United States)

    Moghimi, Mahdi; Khosravian, Mohammadreza

    2018-06-01

    In this paper, a novel combination of organic Rankine cycles (ORCs), Stirling cycle and direct expander turbines is modeled and optimized using the genetic algorithm. The Exergy efficiency is considered as an objective function in the genetic algorithm. High efficiency is the main advantage of Stirling cycle, however, it needs nearly isothermal compressor and turbine. Therefore, an argon ORC and a R14 ORC are placed before and after the Striling cycle along with two expander turbines at the end of the line. Each component and cycle of the proposed plant in this article is verified by the previous works available in the literature and good agreement is achieved. The obtained results reveal that 27.98%, 20.86% and 12.90% of the total cold exergy are used by argon ORC, Stirling cycle and R14 ORC, respectively. Therefore, utilization of the Stirling cycle is a good idea for the LNG line cold exergy. The maximum exergy destruction occurs in the heat exchanger after the argon ORC (85.786 kJ/s per one kg/s LNG) due to the wasted cold exergy, which can be used for air conditioning systems in the plant. Finally, it would be shown that the maximum efficiency of the proposed plant is 54.25% and the maximum output power is 355.72 kW.

  15. Residential solar air conditioning: Energy and exergy analyses of an ammonia–water absorption cooling system

    International Nuclear Information System (INIS)

    Aman, J.; Ting, D.S.-K.; Henshaw, P.

    2014-01-01

    Large scale heat-driven absorption cooling systems are available in the marketplace for industrial applications but the concept of a solar driven absorption chiller for air-conditioning applications is relatively new. Absorption chillers have a lower efficiency than compression refrigeration systems, when used for small scale applications and this restrains the absorption cooling system from air conditioning applications in residential buildings. The potential of a solar driven ammonia–water absorption chiller for residential air conditioning application is discussed and analyzed in this paper. A thermodynamic model has been developed based on a 10 kW air cooled ammonia–water absorption chiller driven by solar thermal energy. Both energy and exergy analyses have been conducted to evaluate the performance of this residential scale cooling system. The analyses uncovered that the absorber is where the most exergy loss occurs (63%) followed by the generator (13%) and the condenser (11%). Furthermore, the exergy loss of the condenser and absorber greatly increase with temperature, the generator less so, and the exergy loss in the evaporator is the least sensitive to increasing temperature. -- Highlights: • 10 kW solar thermal driven ammonia–water air cooled absorption chiller is investigated. • Energy and exergy analyses have been done to enhance the thermal performance. • Low driving temperature heat sources have been optimized. • The efficiencies of the major components have been evaluated

  16. Exergy Analysis of Air-Gap Membrane Distillation Systems for Water Purification Applications

    Directory of Open Access Journals (Sweden)

    Daniel Woldemariam

    2017-03-01

    Full Text Available Exergy analyses are essential tools for the performance evaluation of water desalination and other separation systems, including those featuring membrane distillation (MD. One of the challenges in the commercialization of MD technologies is its substantial heat demand, especially for large scale applications. Identifying such heat flows in the system plays a crucial role in pinpointing the heat loss and thermal integration potential by the help of exergy analysis. This study presents an exergetic evaluation of air-gap membrane distillation (AGMD systems at a laboratory and pilot scale. A series of experiments were conducted to obtain thermodynamic data for the water streams included in the calculations. Exergy efficiency and destruction for two different types of flat-plate AGMD were analyzed for a range of feed and coolant temperatures. The bench scale AGMD system incorporating condensation plate with more favorable heat conductivity contributed to improved performance parameters including permeate flux, specific heat demand, and exergy efficiency. For both types of AGMD systems, the contributions of the major components involved in exergy destruction were identified. The result suggested that the MD modules caused the highest fraction of destructions followed by re-concentrating tanks.

  17. Energy and exergy analyses of an ice-on-coil thermal energy storage system

    International Nuclear Information System (INIS)

    Ezan, Mehmet Akif; Erek, Aytunç; Dincer, Ibrahim

    2011-01-01

    In this study, energy and exergy analyses are carried out for the charging period of an ice-on-coil thermal energy storage system. The present model is developed using a thermal resistance network technique. First, the time-dependent variations of the predicted total stored energy, mass of ice, and outlet temperature of the heat transfer fluid from a storage tank are compared with the experimental data. Afterward, performance of an ice-on-coil type latent heat thermal energy storage system is investigated for several working and design parameters. The results of a comparative study are presented in terms of the variations of the heat transfer rate, total stored energy, dimensionless energetic/exergetic effectiveness and energy/exergy efficiency. The results indicate that working and design parameters of the ice-on-coil thermal storage tank should be determined by considering both energetic and exergetic behavior of the system. For the current parameters, storage capacity and energy efficiency of the system increases with decreasing the inlet temperature of the heat transfer fluid and increasing the length of the tube. Besides, the exergy efficiency increases with increasing the inlet temperature of the heat transfer fluid and increasing the length of the tube. -- Highlights: ► A comprehensive study on energy and exergy analyses of an ice-on-coil TES system. ► Determination of irreversibilities and their potential sources. ► Evaluation of both energy and exergy efficiencies and their comparisons.

  18. Comparison of exergy of emissions from two energy conversion technologies, considering the potential for environmental impact

    International Nuclear Information System (INIS)

    Crane, P.; Scott, D.S.; Rosen, M.A.

    1992-01-01

    There is a reference state in which substances exist in a stable form in the environment (atmosphere, hydrosphere, lithosphere) for all elements. Substances which are out of equilibrium with the environmental reference state, either in terms of chemical composition, concentration, pressure or temperature represent an opportunity to do work as they pass through processes which bring them to the environmental reference state and hence into equilibrium with the environment. The degree to which a substance is out of equilibrium with the environment is represented by its exergy. For an unconstrained emission, the exergy, or potential to do work, of a substance is dissipated in the environment as the substance is brought to the reference state of the environment. Hence, exergy may be considered a measure of the potential of the substance to impact the environment. This paper examines emissions from two alternate automobile power trains: (i) methanol-fuelled spark ignition engines, and (ii) hydrogen-fuelled fuel cells. It is shown that the exergy of emissions from the methanol engine is high (and thus indicative of greater impact on the environment), whereas emissions from a hydrogen/air fuel cell are lower in exergy (thus indicating a system better synchronised with the environment). These results are as expected. Thus, the methodology presented for evaluation of potential for environmental impact, which is both general and quantitative, appears promising. (Author)

  19. Exergy analysis on throttle reduction efficiency based on real gas equations

    International Nuclear Information System (INIS)

    Luo, Yuxi; Wang, Xuanyin

    2010-01-01

    This paper proposes an approach to calculate the efficiency of throttling in which the exergy (available energy) is used to evaluate the energy conversion processes. In the exergy calculation for real gases, a difficult part of integration can be removed by judiciously advised thermodynamic paths; the compressibility factor is calculated by using Peng-Robinson (P-R) equation. It is found that the largest deviation between the exergies calculated by the real gas equation and ideal gas assumption is about 1%. Because the exergy is a function of the pressure and temperature, the Joule-Thomson coefficients are used to calculate the temperature changes of throttling, based on the compressibility factors of the Soave-Redlich-Kwong (S-R-K) and P-R equations, and the temperature decreases are compared with those calculated by empirical formula. The result shows that the heat exergy contributes very little in throttling. The simple equation of ideal gas is suggested to calculate the efficiency of throttling for air at atmospheric temperatures.

  20. Multi-objective exergy-based optimization of a polygeneration energy system using an evolutionary algorithm

    International Nuclear Information System (INIS)

    Ahmadi, Pouria; Rosen, Marc A.; Dincer, Ibrahim

    2012-01-01

    A comprehensive thermodynamic modeling and optimization is reported of a polygeneration energy system for the simultaneous production of heating, cooling, electricity and hot water from a common energy source. This polygeneration system is composed of four major parts: gas turbine (GT) cycle, Rankine cycle, absorption cooling cycle and domestic hot water heater. A multi-objective optimization method based on an evolutionary algorithm is applied to determine the best design parameters for the system. The two objective functions utilized in the analysis are the total cost rate of the system, which is the cost associated with fuel, component purchasing and environmental impact, and the system exergy efficiency. The total cost rate of the system is minimized while the cycle exergy efficiency is maximized by using an evolutionary algorithm. To provide a deeper insight, the Pareto frontier is shown for multi-objective optimization. In addition, a closed form equation for the relationship between exergy efficiency and total cost rate is derived. Finally, a sensitivity analysis is performed to assess the effects of several design parameters on the system total exergy destruction rate, CO 2 emission and exergy efficiency.

  1. Comparison of exergy of emissions from two energy conversion technologies, considering the potential for environmental impact

    Energy Technology Data Exchange (ETDEWEB)

    Crane, P; Scott, D S [Victoria Univ., BC (Canada). Dept. of Mechanical Engineering; Rosen, M A [Ryerson Polytechnical Inst., Toronto, ON (Canada). Dept. of Mechanical Engineering

    1992-05-01

    There is a reference state in which substances exist in a stable form in the environment (atmosphere, hydrosphere, lithosphere) for all elements. Substances which are out of equilibrium with the environmental reference state, either in terms of chemical composition, concentration, pressure or temperature represent an opportunity to do work as they pass through processes which bring them to the environmental reference state and hence into equilibrium with the environment. The degree to which a substance is out of equilibrium with the environment is represented by its exergy. For an unconstrained emission, the exergy, or potential to do work, of a substance is dissipated in the environment as the substance is brought to the reference state of the environment. Hence, exergy may be considered a measure of the potential of the substance to impact the environment. This paper examines emissions from two alternate automobile power trains: (i) methanol-fuelled spark ignition engines, and (ii) hydrogen-fuelled fuel cells. It is shown that the exergy of emissions from the methanol engine is high (and thus indicative of greater impact on the environment), whereas emissions from a hydrogen/air fuel cell are lower in exergy (thus indicating a system better synchronised with the environment). These results are as expected. Thus, the methodology presented for evaluation of potential for environmental impact, which is both general and quantitative, appears promising. (Author).

  2. Exergy analysis of transcritical carbon dioxide refrigeration cycle with an expander

    International Nuclear Information System (INIS)

    Yang Junlan; Ma Yitai; Li Minxia; Guan Haiqing

    2005-01-01

    In this paper, a comparative study is performed for the transcritical carbon dioxide refrigeration cycles with a throttling valve and with an expander, based on the first and second laws of thermodynamics. The effects of evaporating temperature and outlet temperature of gas cooler on the optimal heat rejection pressure, the coefficients of performance (COP), the exergy losses, and the exergy efficiencies are investigated. In order to identify the amounts and locations of irreversibility within the two cycles, exergy analysis is employed to study the thermodynamics process in each component. It is found that in the throttling valve cycle, the largest exergy loss occurs in the throttling valve, about 38% of the total cycle irreversibility. In the expander cycle, the irreversibility mainly comes from the gas cooler and the compressor, approximately 38% and 35%, respectively. The COP and exergy efficiency of the expander cycle are on average 33% and 30% higher than those of the throttling valve cycle, respectively. It is also concluded that an optimal heat rejection pressure can be obtained for all the operating conditions to maximize the COP. The analysis results are of significance to provide theoretical basis for optimization design and operation control of the transcritical carbon dioxide cycle with an expander

  3. Exergy optimization for a novel combination of organic Rankine cycles, Stirling cycle and direct expander turbines

    Science.gov (United States)

    Moghimi, Mahdi; Khosravian, Mohammadreza

    2018-01-01

    In this paper, a novel combination of organic Rankine cycles (ORCs), Stirling cycle and direct expander turbines is modeled and optimized using the genetic algorithm. The Exergy efficiency is considered as an objective function in the genetic algorithm. High efficiency is the main advantage of Stirling cycle, however, it needs nearly isothermal compressor and turbine. Therefore, an argon ORC and a R14 ORC are placed before and after the Striling cycle along with two expander turbines at the end of the line. Each component and cycle of the proposed plant in this article is verified by the previous works available in the literature and good agreement is achieved. The obtained results reveal that 27.98%, 20.86% and 12.90% of the total cold exergy are used by argon ORC, Stirling cycle and R14 ORC, respectively. Therefore, utilization of the Stirling cycle is a good idea for the LNG line cold exergy. The maximum exergy destruction occurs in the heat exchanger after the argon ORC (85.786 kJ/s per one kg/s LNG) due to the wasted cold exergy, which can be used for air conditioning systems in the plant. Finally, it would be shown that the maximum efficiency of the proposed plant is 54.25% and the maximum output power is 355.72 kW.

  4. Application of the Stirling engine driven with cryogenic exergy of LNG (liquefied natural gas) for the production of electricity

    International Nuclear Information System (INIS)

    Szczygieł, Ireneusz; Stanek, Wojciech; Szargut, Jan

    2016-01-01

    LNG (liquefied natural gas) delivered by means of sea-ships is pressurized and then regasified before its introduction to the system of pipelines. The utilization of cryogenic exergy of LNG for electricity production without combustion of any its portion is analyzed. For the conversion of LNG cryogenic exergy into electricity, the Stirling engine is proposed to be applied. The theoretical thermodynamic model of Stirling engine has been applied. This model is used to investigate the influence of pinch temperature in heat exchangers, engine compression ratio and dead volumes ratios on the thermodynamic parameters of the Stirling engine. The results of simulation represent the input data for investigations of thermodynamic performance of the proposed system. In order to evaluate the thermodynamic performance of the proposed process, an exergy analysis has been applied. The exergy efficiency and influence of design and operational parameters on exergy losses are determined for each of the proposed system configurations. The obtained results represent the background for advanced exergy-based analyses, including thermo-ecological cost. - Highlights: • Application of Stirling engine in LNG regasification. • Thermodynamic model of Stirling engine for cryogenic exergy recovery is applied. • Sensitivity analysis of operational parameters on system behaviour is applied. • Exergy analysis is conducted.

  5. An estimation of the energy and exergy efficiencies for the energy resources consumption in the transportation sector in Malaysia

    International Nuclear Information System (INIS)

    Saidur, R.; Sattar, M.A.; Masjuki, H.H.; Ahmed, S.; Hashim, U.

    2007-01-01

    The purpose of this work is to apply the useful energy and exergy analysis models for different modes of transport in Malaysia and to compare the result with a few countries. In this paper, energy and exergy efficiencies of the various sub-sectors are presented by considering the energy and exergy flows from 1995 to 2003. Respective flow diagrams to find the overall energy and exergy efficiencies of Malaysian transportation sector are also presented. The estimated overall energy efficiency ranges from 22.74% (1999) to 22.98% (1998) with a mean of 22.82+/-0.06% and that of overall exergy efficiency ranges from 22.44% (2000) to 22.82% (1998) with a mean of 22.55+/-0.12%. The results are compared with respect to present energy and exergy efficiencies in each sub-sector. The transportation sector used about 40% of the total energy consumed in 2002. Therefore, it is important to identify the energy and exergy flows and the pertinent losses. The road sub-sector has appeared to be the most efficient one compared to the air and marine sub-sectors. Also found that the energy and exergy efficiencies of Malaysian transportation sector are lower than that of Turkey but higher than Norway

  6. The Characteristics of the Exergy Reference Environment and Its Implications for Sustainability-Based Decision-Making

    Directory of Open Access Journals (Sweden)

    Stephen Murphy

    2012-07-01

    Full Text Available In the energy realm there is a pressing need to make decisions in a complex world characterized by biophysical limits. Exergy has been promoted as a preferred means of characterizing the impacts of resource consumption and waste production for the purpose of improving decision-making. This paper provides a unique and critical analysis of universal and comprehensive formulations of the chemical exergy reference environment, for the purpose of better understanding how exergy can inform decision-making. Four related insights emerged from the analysis, notably: (1 standard and universal chemical exergy reference environments necessarily encounter internal inconsistencies and even contradictions in their very formulations; (2 these inconsistencies are a result of incompatibility between the exergy reference environment and natural environment, and the desire to model the exergy reference environment after the natural environment so as to maintain analytical relevance; (3 the topics for which exergy is most appropriate as an analytical tool are not well served by comprehensive reference environments, and (4 the inconsistencies point to a need for deeper reflection of whether it is appropriate to adopt a thermodynamic frame of analysis for situations whose relevant characteristics are non-thermodynamic (e.g., to characterize scarcity. The use of comprehensive reference environments may lead to incorrect recommendations and ultimately reduce its appeal for informing decision-making. Exergy may better inform decision-making by returning to process dependent reference states that model specific processes and situations for the purpose of engineering optimization.

  7. Energy and exergy analysis of an organic Rankine for power generation from waste heat recovery in steel industry

    International Nuclear Information System (INIS)

    Kaşka, Önder

    2014-01-01

    Highlights: • Analysis of a waste heat driven Organic Rankine Cycle (ORC). • Irreversibility determination of subcomponents in ORC. • Using pinch point analysis in the evaporator of ORC. • Calculating energy and exergy efficiency for two different actual cases. • Optimum net power output for ORC. - Abstract: Energy, in conjunction with exergy, analysis of a waste heat driven Organic Rankine Cycle (ORC) is performed. Using actual plant data, performance of the cycle and pinpoint sites of primary exergy destruction are assessed. Furthermore, variations of energy and exergy efficiencies of the system with evaporator/condenser pressures, superheating and subcooling are illustrated. It is observed from the analysis that, the energy and exergy efficiencies of the system are 10.2%; 48.5% and 8.8%; 42.2%, respectively, for two different actual cases. Exergy destruction of subcomponents is also quantified. The components with greater exergy destructions to lower one can be listed as evaporator, turbine, condenser and pump. Evaporation pressure has significant effect on both energy and exergy efficiencies. Pinch-point analysis is, also performed to determine effects of heat exchange process, in the evaporator, on the net power production

  8. The role of exergy in increasing utilization of green energy and technologies. Paper no. IGEC-1-Keynote-Rosen

    International Nuclear Information System (INIS)

    Rosen, M.A.

    2005-01-01

    The use of exergy is described as a measure for identifying and explaining the benefits of green energy and technologies, so the benefits can be clearly understood and appreciated by experts and non-experts alike, and the utilization of green energy and technologies can be increased. Exergy can be used to assess and improve energy systems, and can help better understand the benefits of utilizing green energy by providing more useful and meaningful information than energy provides. Exergy clearly identifies efficiency improvements and reductions in thermodynamic losses attributable to green technologies. Exergy can also identify better than energy the environmental benefits and economics of energy technologies. Exergy should be utilized to engineers and scientists, as well as decision and policy makers, involved in green energy and technologies. (author)

  9. Unsteady-state human-body exergy consumption rate and its relation to subjective assessment of dynamic thermal environments

    DEFF Research Database (Denmark)

    Schweiker, Marcel; Kolarik, Jakub; Dovjak, Mateja

    2016-01-01

    of the present study confirmed previously indicated trends that lowest human body exergy consumption rate is associated with thermal sensation close to neutrality. Moreover, higher acceptability was in general associated with lower human body exergy consumption rate. (C) 2016 Elsevier B.V. All rights reserved.......Few examples studied applicability of exergy analysis on human thermal comfort. These examples relate the human-body exergy consumption rate with subjectively obtained thermal sensation votes and had been based on steady-state calculation methods. However, humans are rarely exposed to steady...... between the human-body exergy consumption rate and subjective assessment of thermal environment represented by thermal sensation as well as to extend the investigation towards thermal acceptability votes. Comparison of steady-state and unsteady-state model showed that results from both models were...

  10. New exergy criterion in the 'multi-criteria' context: a life cycle assessment of two plaster products

    International Nuclear Information System (INIS)

    Beccali, Giorgio; Cellura, Maurizio; Mistretta, Marina

    2003-01-01

    This paper deals with the exergy analysis (EXA) of plaster materials and ranks the environmental burdens due to the production of such materials. The calculation of the exergy loss during the whole examined process represents a relevant index, looking at the technology improvement of a process, as a suitable tool in aid of the trade-off of alternative materials in the decision making. A life cycle inventory is performed for building plaster products and the matrix method is used. The authors extend the application of EXA to life cycle assessment, conducting an exergetic life cycle assessment, and propose an exergetic index in the framework of multi-criteria decision making. An exergy balance, accounting for energy and material flows, is applied to calculate the exergy losses and efficiencies for each stage of the examined processes: resources extraction, materials processing, transport and product manufacturing. Furthermore, exergy values are calculated for the pollutants and wastes

  11. Resource recovery from residual household waste: An application of exergy flow analysis and exergetic life cycle assessment

    DEFF Research Database (Denmark)

    Laner, David; Rechberger, Helmut; De Soete, Wouter

    2015-01-01

    Exergy is based on the Second Law of thermodynamics and can be used to express physical and chemical potential and provides a unified measure for resource accounting. In this study, exergy analysis was applied to four residual household waste management scenarios with focus on the achieved resource...... of the waste treatment system under investigation and (ii) exergetic life cycle assessment (LCA) using the Cumulative Exergy Extraction from the Natural Environment (CEENE) as a method for resource accounting. Scenario efficiencies of around 17-27% were found based on the exergy flow analysis (higher...... with the functionality of a material. In addition, the definition of appropriate waste system boundaries is critical for the exergy efficiencies derived from the flow analysis, as it is constrained by limited information available about the composition of flows in the system as well as about secondary production...

  12. A novel human body exergy consumption formula to determine indoor thermal conditions for optimal human performance in office buildings

    DEFF Research Database (Denmark)

    Wu, Xiaozhou; Zhao, Jianing; Olesen, Bjarne W.

    2013-01-01

    In this paper, a novel human body exergy consumption formula was derived strictly according to Gagge's two-node thermal transfer model. The human body exergy consumption calculated by the formula was compared with values calculated using Shukuya's formula for a typical office environment....... The results show that human body exergy consumption calculated by either of these formulas reaches a minimum under the same thermal condition. It is shown that this is in accordance with expectation. The relation between human performance and human body exergy consumption was studied by analyzing the data...... obtained in simulated office environments in winter. The results show that human body exergy consumption and human performance are inversely as operative temperature changes from 17 to 28°C or human thermal sensation changes from −1.0 to +1.4, and that optimum thermal comfort cannot be expected to lead...

  13. Exergy characteristics of a ceiling-type residential air conditioning system operating under different climatic conditions

    Energy Technology Data Exchange (ETDEWEB)

    Ozbek, Arif [Dept. of Mechanical Engineering, Ceyhan Engineering Faculty, Cukurova University, Adana (Turkmenistan)

    2016-11-15

    In this study an energy and exergy analysis of a Ceiling-type residential air conditioning (CTRAC) system operating under different climatic conditions have been investigated for provinces within the different geographic regions of Turkey. Primarily, the hourly cooling load capacities of a sample building (Q{sub evap}) during the months of April, May, June, July, August and September were determined. The hourly total heat gain of the sample building was determined using the Hourly analysis program (HAP). The Coefficient of performance (COP), exergy efficiency (η) and exergy destruction (Ex{sub dest}) values for the whole system and for each component were obtained. The results showed that lower atmospheric temperature (T{sub atm}) influenced the performance of the system and each of its components.

  14. Energy and exergy analyses of energy consumptions in the industrial sector in South Africa

    International Nuclear Information System (INIS)

    Oladiran, M.T.; Meyer, J.P.

    2007-01-01

    The energy-utilization over a 10-year period (1994-2003) has been analysed for the South African industrial sector, which consumes more primary energy than any other sector of the economy. Four principal sub-sectors, namely iron and steel, chemical and petrochemical, mining and quarrying, and non-ferrous metals/non-metallic minerals were considered in this study. Primary-energy utilization data were used to calculate the weighted mean energy and exergy efficiencies for the sub-sectors and then overall values for the industrial sector were obtained. The results indicate that exergy efficiency is considerably lower than energy efficiency in all the sub-sectors, particularly in mining and quarrying processes, for which the values were approximately 83% and 16%, respectively. The performance of exergy utilization in the industrial sector can be improved by introducing various conservation strategies. Results from this study were compared with those for other countries

  15. Exergy analysis of thermal management system for range-extended electric vehicles

    Energy Technology Data Exchange (ETDEWEB)

    Hamut, H. S.; Dincer, I.; Naterer, G. F. [Faculty of Engineering and Applied Science, University of Ontario Institute of Technology (Canada)], email: Ibrahim.Dincer@uoit.ca

    2011-07-01

    In the last few decades, the energy crisis, increasing gas prices and concerns over environmental pollution have encouraged the development of electric vehicle (EV) and hybrid electric vehicle (HEV) technologies. In this paper, a thermal management system (TMS) installed in a range-extended electric vehicle is examined and is found to have a substantial impact on battery efficiency and vehicle performance. An exergy analysis was conducted on the refrigeration and coolant circuits and the Coefficient of Performance (COP) of the baseline system was determined to be 2.0 with a range of 1.8 to 2.4. The overall exergy was found to be 32% with a range of 26% to 39%. Ambient temperature had the largest impact on overall exergy efficiency but there is a need to further investigate temperature effects on battery efficiency, since the battery's performance has such a high impact on vehicle performance overall.

  16. Cycle Design of Reverse Brayton Cryocooler for HTS Cable Cooling Using Exergy Analysis

    Science.gov (United States)

    Gupta, Sudeep Kumar; Ghosh, Parthasarathi

    2017-02-01

    The reliability and price of cryogenic refrigeration play an important role in the successful commercialization of High Temperature Superconducting (HTS) cables. For cooling HTS cable, sub-cooled liquid nitrogen (LN2) circulation system is used. One of the options to maintain LN2 in its sub-cooled state is by providing refrigeration with the help of Reverse Brayton Cryo-cooler (RBC). The refrigeration requirement is 10 kW for continuously sub-cooling LN2 from 72 K to 65 K for cooling 1 km length of HTS cable [1]. In this paper, a parametric evaluation of RBC for sub-cooling LN2 has been performed using helium as a process fluid. Exergy approach has been adopted for this analysis. A commercial process simulator, Aspen HYSYS® V8.6 has been used for this purpose. The critical components have been identified and their exergy destruction and exergy efficiency have been obtained for a given heat load condition.

  17. Advanced exergy-based analyses applied to a system including LNG regasification and electricity generation

    Energy Technology Data Exchange (ETDEWEB)

    Morosuk, Tatiana; Tsatsaronis, George; Boyano, Alicia; Gantiva, Camilo [Technische Univ. Berlin (Germany)

    2012-07-01

    Liquefied natural gas (LNG) will contribute more in the future than in the past to the overall energy supply in the world. The paper discusses the application of advanced exergy-based analyses to a recently developed LNG-based cogeneration system. These analyses include advanced exergetic, advanced exergoeconomic, and advanced exergoenvironmental analyses in which thermodynamic inefficiencies (exergy destruction), costs, and environmental impacts have been split into avoidable and unavoidable parts. With the aid of these analyses, the potentials for improving the thermodynamic efficiency and for reducing the overall cost and the overall environmental impact are revealed. The objectives of this paper are to demonstrate (a) the potential for generating electricity while regasifying LNG and (b) some of the capabilities associated with advanced exergy-based methods. The most important subsystems and components are identified, and suggestions for improving them are made. (orig.)

  18. Energy efficiency analysis of styrene production by adiabatic ethylbenzene dehydrogenation using exergy analysis and heat integration

    Directory of Open Access Journals (Sweden)

    Ali Emad

    2018-03-01

    Full Text Available Styrene is a valuable commodity for polymer industries. The main route for producing styrene by dehydrogenation of ethylbenzene consumes a substantial amount of energy because of the use of high-temperature steam. In this work, the process energy requirements and recovery are studied using Exergy analysis and Heat Integration (HI based on Pinch design method. The amount of steam plays a key role in the trade-off between Styrene yield and energy savings. Therefore, optimizing the operating conditions for energy reduction is infeasible. Heat integration indicated an insignificant reduction in the net energy demand and exergy losses, but 24% and 34% saving in external heating and cooling duties, respectively. When the required steam is generated by recovering the heat of the hot reactor effluent, a considerable saving in the net energy demand, as well as the heating and cooling utilities, can be achieved. Moreover, around 68% reduction in the exergy destruction is observed.

  19. Advanced exergy analysis of a R744 booster refrigeration system with parallel compression

    DEFF Research Database (Denmark)

    Gullo, Paride; Elmegaard, Brian; Cortella, Giovanni

    2016-01-01

    In this paper, the advanced exergy analysis was applied to a R744 booster refrigeration system with parallel compression taking into account the design external temperatures of 25 degrees C and 35 degrees C, as well as the operating conditions of a conventional European supermarket. The global...... efficiencies of all the chosen compressors were extrapolated from some manufactures' data and appropriated optimization procedures of the performance of the investigated solution were implemented.According to the results associated with the conventional exergy evaluation, the gas cooler/condenser, the HS (high...... stage) compressor and the MT (medium temperature) display cabinet exhibited the highest enhancement potential. The further splitting of their corresponding exergy destruction rates into their different parts and the following assessment of the interactions among the components allowed figuring out...

  20. Performance Analysis of 20MW gas turbine power plant by Energy and Exergy Methods

    International Nuclear Information System (INIS)

    Lebele-Alawa, B. T.; Asuo, J. M.

    2013-01-01

    Energy and exergy analysis were conducted to evaluate the optimal performance of a 20 MW gas turbine power plant. The energy analysis was based on First Law of Thermodynamics, while the exergy method used both First and Second Laws of Thermodynamics. The locations and magnitude of losses which inhibited the performance of the power plant were identified by balance system equations. The internal losses associated with each plant component were estimated for improvement to be made to such component for maximum power output. The energy efficiency was 20.73 %, while the exergeric efficiency was 16.39 %; but the exergy loss of 38.62 % in the combustor was the largest among the components of plant. (au)

  1. Exergy and Energy Analysis of Combustion of Blended Levels of Biodiesel, Ethanol and Diesel Fuel in a DI Diesel Engine

    International Nuclear Information System (INIS)

    Khoobbakht, Golmohammad; Akram, A.; Karimi, Mahmoud; Najafi, G.

    2016-01-01

    Highlights: • Exergy analysis showed that thermal efficiency of diesel engine was 36.61%. • Energy loss and work output rates were 71.36 kW and 41.22 kW, respectively. • Exergy efficiency increased with increasing engine load and speed. • Exergy efficiency increased with increasing biodiesel and bioethanol. • 0.17 L of biodiesel, 0.08 L of ethanol in 1 L of diesel at 1900 rpm and 94% load had maximum exergy efficiency. - Abstract: In this study, the first and second laws of thermodynamics are employed to analyze the energy and energy in a four-cylinder, direct injection diesel engine using blended levels of biodiesel and ethanol in diesel fuel. Also investigated the effect of operating factors of engine load and speed as well as blended levels of biodiesel and ethanol in diesel fuel on the exergy efficiency. The experiments were designed using a statistical tool known as Design of Experiments (DoE) based on central composite rotatable design (CCRD) of response surface methodology (RSM). The resultant quadratic models of the response surface methodology were helpful to predict the response parameter (exergy efficiency) further to identify the significant interactions between the input factors on the responses. The results depicted that the exergy efficiency decreased with increasing percent by volume biodiesel and ethanol fuel. The fuel blend of 0.17 L biodiesel and 0.08 L of ethanol added to 1 L of diesel (equivalent with D80B14E6) at 1900 rpm and 94% load was realized have the most exergy efficiency. The results of energy and exergy analyses showed that 43.09% of fuel exergy was destructed and the average thermal efficiency was approximately 36.61%, and the exergetic efficiency was approximately 33.81%.

  2. Comparative energy and exergy performance assessments of a microcogenerator unit in different electricity mix scenarios

    International Nuclear Information System (INIS)

    Gonçalves, Pedro; Angrisani, Giovanni; Roselli, Carlo; Gaspar, Adélio R.; Gameiro da Silva, Manuel

    2013-01-01

    Highlights: • Experimental and energy–exergy modelling of a 6 kW micro-combined heat and power unit. • Evaluation of energy and exergy efficiencies for performance assessment. • Use of exergy and energy indicators for comparison with a reference system. • Use of different renewables supply options into the electric and heat reference system. • The electric grid mix of Portugal and Italy is used and discussed. - Abstract: The Directive 2004/8/EC on the promotion of cogeneration proposes a comparative indicator based on primary energy savings, neglecting some important thermodynamic aspects, such as exergy. This study aims to compare and discuss the usefulness of a set of complementary indicators for performance assessments of cogeneration systems, concerning thermodynamic principles based on first and second law (the exergy approach). As case study, a 6 kW electric output micro-combined heat and power unit was experimentally tested and a model of the unit was developed in TRNSYS. Considering as reference a set of different heat and electricity scenarios, including the actual electric mixes of Portugal and Italy, the indicators case incon (PES) and Primary and Total Irreversibilities Savings (PIS and TIS), as well as energy and exergy renewability ratios were assessed and discussed. The results show that the use of MCHP has higher advantages for the Italian electric grid, than an equivalent scenario considering the Portuguese electric network as reference. As result, for a particular scenario analysed, PES and PIS have 3% and 6% for Portugal, and 10% and 18% for Italy, respectively. Furthermore, for one particular scenario evaluated, the indicators energetic and exergetic renewability ratios have 23% and 14%, respectively for the Portuguese electric grid, and 19% and 10% for the Italian electric system

  3. Determination of uncertainties in energy and exergy analysis of a power plant

    International Nuclear Information System (INIS)

    Ege, Ahmet; Şahin, Hacı Mehmet

    2014-01-01

    Highlights: • Energy and exergy efficiency uncertainties in a large thermal power plant examined. • Sensitivity analysis shows importance of basic measurements on efficiency analysis. • A quick and practical approach is provided for determining efficiency uncertainties. • Extreme case analysis characterizes maximum possible boundaries of uncertainties. • Uncertainty determination in a plant is a dynamic process with real data. - Abstract: In this study, energy and exergy efficiency uncertainties of a large scale lignite fired power plant cycle and various measurement parameter sensitivities were investigated for five different design power outputs (100%, 85%, 80%, 60% and 40%) and with real data of the plant. For that purpose a black box method was employed considering coal flow with Lower Heating Value (LHV) as a single input and electricity produced as a single output of the plant. The uncertainty of energy and exergy efficiency of the plant was evaluated with this method by applying sensitivity analysis depending on the effect of measurement parameters such as LHV, coal mass flow rate, cell generator output voltage/current. In addition, an extreme case analysis was investigated to determine the maximum range of the uncertainties. Results of the black box method showed that uncertainties varied between 1.82–1.98% for energy efficiency and 1.32–1.43% for exergy efficiency of the plant at an operating power level of 40–100% of full power. It was concluded that LHV determination was the most important uncertainty source of energy and exergy efficiency of the plant. The uncertainties of the extreme case analysis were determined between 2.30% and 2.36% for energy efficiency while 1.66% and 1.70% for exergy efficiency for 40–100% power output respectively. Proposed method was shown to be an approach for understanding major uncertainties as well as effects of some measurement parameters in a large scale thermal power plant

  4. Exergy analysis of Portuguese municipal solid waste treatment via steam gasification

    International Nuclear Information System (INIS)

    Couto, Nuno; Silva, Valter; Monteiro, Eliseu; Rouboa, Abel

    2017-01-01

    Highlights: • Evaluation of Portuguese municipal solid waste gasification was conducted. • Previously studied biomass substrate was used as benchmark. • Numerical model built upon a reliable set of experimental runs was used. • Thermodynamic analysis on steam as gasifying agent was showed. • A CFD model was combined with RSM to optimize exergy efficiency. - Abstract: The presented study focuses on a thermodynamic analysis conducted on steam gasification of Portuguese municipal solid wastes (MSW). Current literature addressing this issue is extremely scarce due to the complexity in handling MSW’s heterogeneity. To fill this significant gap, a mathematical model built upon a reliable set of experimental runs from a semi-industrial gasifier was used to evaluate the effects of reactor temperature and steam-to-biomass ratio (SBR) on produced gas and tar content. Results from a previously studied biomass substrate were used as benchmark. Numerical results were validated with both experimental results and existing literature. Increase in gasification temperature led to a clear increase in both exergy values and exergy efficiency. On the other hand, increase in SBR led to a sharp increase in the exergy values when steam was first introduced, leading to relatively constant values when SBR was further increased. Regarding exergy efficiency, SBR led to a clear maximum value, which in the case of forest residues was found at SBR = 1, while for MSW at 1.5. In order to promote a more hydrogen-rich gas, data obtained from the numerical model was used to design an exergy efficiency optimization model based on the response surface method. Maximum hydrogen efficiency was found at 900 °C with a SBR of 1.5 for MSW and 1 for forest residues. Surprisingly, forest residues and MSW presented virtually the same maximum hydrogen efficiency.

  5. Energy and exergy analyses of a bi-evaporator compression/ejection refrigeration cycle

    International Nuclear Information System (INIS)

    Geng, Lihong; Liu, Huadong; Wei, Xinli; Hou, Zhonglan; Wang, Zhenzhen

    2016-01-01

    Highlights: • A bi-evaporator compression/ejection refrigeration cycle was studied experimentally. • Experiments were operated at the same external conditions and cooling capacities. • COP improvement was 16.94–30.59% higher than that of the conventional system. • The exergy efficiency of the R134a cycle was improved by 7.57–28.29%. - Abstract: Aiming to reduce the throttling loss in the vapor compression refrigeration cycle, a bi-evaporator compression/ejection refrigeration cycle (BCERC) using an ejector as the expansion device was experimentally investigated with R134a refrigerant. The effects of the compressor frequency and the operating conditions on the coefficient of performance (COP) and the amount of exergy destruction of each component were studied. The results were compared with that of the conventional vapor compression refrigeration cycle under the same external operating conditions and cooling capacities. Results showed that the refrigeration cycle with an ejector as the expansion device exhibited lower irreversibility for each component and total system in comparison with the conventional vapor compression refrigeration cycle. The COP and the exergy efficiency of the BCERC were higher than that of the conventional system. The COP and exergy efficiency improvements became more significant as the condenser water temperature increased, the evaporator water temperature decreased and the compressor frequency increased. In the BCERC with a constant frequency compressor, the COP and the exergy efficiency could be improved by 16.94–30.59%, 7.57–28.29%, respectively. The COP and the exergy efficiency of the BCERC with a variable frequency compressor could increase by around 32.64% and 23.32%, respectively.

  6. Exergy metrication of radiant panel heating and cooling with heat pumps

    International Nuclear Information System (INIS)

    Kilkis, Birol

    2012-01-01

    Highlights: ► Rational Exergy Management Model analytically relates heat pumps and radiant panels. ► Heat pumps driven by wind energy perform better with radiantpanels. ► Better CO 2 mitigation is possible with wind turbine, heat pump, radiant panel combination. ► Energy savings and thermo-mechanical performance are directly linked to CO 2 emissions. - Abstract: Radiant panels are known to be energy efficient sensible heating and cooling systems and a suitable fit for low-exergy buildings. This paper points out the little known fact that this may not necessarily be true unless their low-exergy demand is matched with low-exergy waste and alternative energy resources. In order to further investigate and metricate this condition and shed more light on this issue for different types of energy resources and energy conversion systems coupled to radiant panels, a new engineering metric was developed. Using this metric, which is based on the Rational Exergy Management Model, true potential and benefits of radiant panels coupled to ground-source heat pumps were analyzed. Results provide a new perspective in identifying the actual benefits of heat pump technology in curbing CO 2 emissions and also refer to IEA Annex 49 findings for low-exergy buildings. Case studies regarding different scenarios are compared with a base case, which comprises a radiant panel system connected to a natural gas-fired condensing boiler in heating and a grid power-driven chiller in cooling. Results show that there is a substantial CO 2 emission reduction potential if radiant panels are optimally operated with ground-source heat pumps driven by renewable energy sources, or optimally matched with combined heat and power systems, preferably running on alternative fuels.

  7. Exergy analysis of a combined heat and power plant with integrated lignocellulosic ethanol production

    International Nuclear Information System (INIS)

    Lythcke-Jørgensen, Christoffer; Haglind, Fredrik; Clausen, Lasse R.

    2014-01-01

    Highlights: • We model a system where lignocellulosic ethanol production is integrated with a combined heat and power (CHP) plant. • We conduct an exergy analysis for the ethanol production in six different system operation points. • Integrated operation, district heating (DH) production and low CHP loads all increase the exergy efficiency. • Separate operation has the largest negative impact on the exergy efficiency. • Operation is found to have a significant impact on the exergy efficiency of the ethanol production. - Abstract: Lignocellulosic ethanol production is often assumed integrated in polygeneration systems because of its energy intensive nature. The objective of this study is to investigate potential irreversibilities from such integration, and what impact it has on the efficiency of the integrated ethanol production. An exergy analysis is carried out for a modelled polygeneration system in which lignocellulosic ethanol production based on hydrothermal pretreatment is integrated in an existing combined heat and power (CHP) plant. The ethanol facility is driven by steam extracted from the CHP unit when feasible, and a gas boiler is used as back-up when integration is not possible. The system was evaluated according to six operation points that alternate on the following three different operation parameters: Load in the CHP unit, integrated versus separate operation, and inclusion of district heating production in the ethanol facility. The calculated standard exergy efficiency of the ethanol facility varied from 0.564 to 0.855, of which the highest was obtained for integrated operation at reduced CHP load and full district heating production in the ethanol facility, and the lowest for separate operation with zero district heating production in the ethanol facility. The results suggest that the efficiency of integrating lignocellulosic ethanol production in CHP plants is highly dependent on operation, and it is therefore suggested that the

  8. Assessment of a closed thermochemical energy storage using energy and exergy methods

    International Nuclear Information System (INIS)

    Abedin, Ali Haji; Rosen, Marc A.

    2012-01-01

    Highlights: ► Thermodynamics assessments are reported for a general closed thermochemical thermal energy storage system. ► Energy and exergy efficiencies of various processes in a closed thermochemical TES are evaluated and compared. ► Understanding is enhanced of thermochemical TES technologies and their potential implementations. ► Exergy analysis is observed to be useful when applied to thermochemical TES, with or in place of energy analysis. - Abstract: Thermal energy storage (TES) is an important technology for achieving more efficient and environmentally benign energy systems. Thermochemical TES is a type of TES with the potential for high energy density and is only recently being considered intensively. To improve understanding of thermochemical TES systems and their implementation, energy and exergy analyses are beneficial. Here, thermodynamics assessments are presented for a general closed thermochemical TES system, including assessments and comparisons of the efficiencies of the overall thermochemical TES cycle and its charging, storing and discharging processes. Locations and causes of thermodynamic losses in thermochemical TES systems are being specified using exergy analysis. The analytical methodology applied in this study identifies that energy and exergy efficiencies differ for thermochemical TESs, e.g. the energy efficiency for a case study is approximately 50% while the exergy efficiency is about 10%. Although the focus is to evaluate thermodynamic efficiencies, other design parameters such as cost, and environmental impact also need to be examined in assessing thermochemical storage. The efficiencies for thermochemical TES provided here should be helpful for designing these energy systems and enhancing their future prospects.

  9. On the definition of exergy efficiencies for petroleum systems: Application to offshore oil and gas processing

    International Nuclear Information System (INIS)

    Nguyen, Tuong-Van; Voldsund, Mari; Elmegaard, Brian; Ertesvåg, Ivar Ståle; Kjelstrup, Signe

    2014-01-01

    Exergy-based efficiencies are measures of the thermodynamic perfection of systems and processes. A meaningful formulation of these performance criteria for petroleum systems is difficult because of (i) the high chemical exergy of hydrocarbons, (ii) the large variety of chemical components, and (iii) the differences in operating conditions between facilities. This work focuses on offshore processing plants, considering four oil platforms that differ by their working conditions and designs. Several approaches from the scientific literature for similar processes are presented and applied to the four cases. They showed a low sensitivity to performance improvements, gave inconsistent results, or favoured facilities operating under certain conditions. We suggest an alternative formulation, called the component-by-component exergy efficiency, which builds on the decomposition of the exergy flows at the level of the chemical compounds. It allows therefore for sound comparisons of separation systems, while it successfully evaluates their theoretical improvement potentials. The platform displaying the lowest efficiency (1.7%) is characterised by little pumping and compression works, at the opposite of the one displaying the highest performance (29.6%). A more realistic measure of the technical potential for improving these systems can be carried out by splitting further the exergy destruction into its avoidable and unavoidable parts. - Highlights: • Different exergy efficiency definitions for petroleum systems are reviewed. • These definitions are applied to four oil and gas platforms and are revealed to be inapplicable. • A new formulation, namely the component-by-component efficiency, is proposed. • The performance of the offshore platforms under study varies between 1.7% and 29.6%

  10. Thoughts about future power generation systems and the role of exergy analysis in their development

    International Nuclear Information System (INIS)

    Lior, Noam

    2002-01-01

    In the face of the likely doubling of the world population and perhaps tripling of the power demand over the next 50 years, this paper (1) presents some thoughts on the possible ways to meet the power demands under the constraints of increased population and land use while holding the environmental impact to a tolerable one, and (2) outlines the ways exergy analysis may be effectively used in the conception and development of such processes. To effectively develop the innovative power generation systems needed in the 21st century, irreversibility and exergy analysis should be much more focused on the intrinsic process details. (Author)

  11. On exergy analysis of industrial plants and significance of ambient temperature

    Energy Technology Data Exchange (ETDEWEB)

    Rian, Berit

    2011-07-01

    The exergy analysis has been a relatively mature theory for more than 30 years. However, it is not that developed in terms of procedures for optimizing systems, which partly explains why it is not that common. Misconceptions and prejudices, even among scientists, are also partly to blame.The main objective of this work was to contribute to the development of an understanding and methodology of the exergy analysis. The thesis was mainly based on three papers, two of which provided very different examples from existing industrial systems in Norway, thus showing the societal perspective in terms of resource utilization and thermodynamics. The last paper and the following investigation were limited to certain aspects of ambient conditions. Two Norwegian operational plants have been studied, one operative for close to 30 years (Kaarstoe steam production and distribution system), while the other has just started its expected 30 years of production (Snoehvit LNG plant). In addition to mapping the current operational status of these plants, the study of the Kaarstoe steam production and distribution system concluded that the potential for increasing the thermodynamic performance by rather cautious actions was significant, whereas the study of the Snoehvit LNG plant showed the considerable profit which the Arctic location provided in terms of reduced fuel consumption. The significance of the ambient temperature led to the study of systems with two ambient bodies (i.e. ambient water and ambient air) of different temperatures, here three different systems were investigated: A regenerative steam injection gas turbine (RSTIG), a simple Linde air liquefaction plant (Air Liq) and an air-source heat pump water heater (HPWH). In particular, the effect of the chosen environment on exergy analysis was negligible for RSTIG, modest for Air Liq and critical for HPWH. It was found that the amount of exergy received from the alternative ambient body, compared to the main exergy flow of

  12. Analysis of exergy loss of gasoline surrogate combustion process based on detailed chemical kinetics

    International Nuclear Information System (INIS)

    Sun, Hongjie; Yan, Feng; Yu, Hao; Su, W.H.

    2015-01-01

    Highlights: • We explored the exergy loss sources of gasoline engine like combustion process. • The model combined non-equilibrium thermodynamics with detailed chemical kinetics. • We explored effects of initial conditions on exergy loss of combustion process. • Exergy loss decreases 15% of fuel chemical exergy by design of initial conditions. • Correspondingly, the second law efficiency increases from 38.9% to 68.9%. - Abstract: Chemical reaction is the most important source of combustion irreversibility in premixed conditions, but details of the exergy loss mechanisms have not been explored yet. In this study numerical analysis based on non-equilibrium thermodynamics combined with detailed chemical kinetics is conducted to explore the exergy loss mechanism of gasoline engine like combustion process which is simplified as constant volume combustion. The fuel is represented by the common accepted gasoline surrogates which consist of four components: iso-octane (57%), n-heptane (16%), toluene (23%), and 2-pentene (4%). We find that overall exergy loss is mainly composed of three peaks along combustion generated from chemical reactions in three stages, the conversion from large fuel molecules into small molecules (as Stage 1), the H 2 O 2 loop-related reactions (as Stage 2), and the violent oxidation reactions of CO, H, and O (as Stage 3). The effects of individual combustion boundaries, including temperature, pressure, equivalence ratio, oxygen concentration, on combustion exergy loss have been widely investigated. The combined effects of combustion boundaries on the total loss of gasoline surrogates are also investigated. We find that in a gasoline engine with a compression ratio of 10, the total loss can be reduced from 31.3% to 24.3% using lean combustion. The total loss can be further reduced to 22.4% by introducing exhaust gas recirculation and boosting the inlet charge. If the compression ratio is increased to 17, the total loss can be decreased to

  13. Reinforcement learning for optimal control of low exergy buildings

    International Nuclear Information System (INIS)

    Yang, Lei; Nagy, Zoltan; Goffin, Philippe; Schlueter, Arno

    2015-01-01

    Highlights: • Implementation of reinforcement learning control for LowEx Building systems. • Learning allows adaptation to local environment without prior knowledge. • Presentation of reinforcement learning control for real-life applications. • Discussion of the applicability for real-life situations. - Abstract: Over a third of the anthropogenic greenhouse gas (GHG) emissions stem from cooling and heating buildings, due to their fossil fuel based operation. Low exergy building systems are a promising approach to reduce energy consumption as well as GHG emissions. They consists of renewable energy technologies, such as PV, PV/T and heat pumps. Since careful tuning of parameters is required, a manual setup may result in sub-optimal operation. A model predictive control approach is unnecessarily complex due to the required model identification. Therefore, in this work we present a reinforcement learning control (RLC) approach. The studied building consists of a PV/T array for solar heat and electricity generation, as well as geothermal heat pumps. We present RLC for the PV/T array, and the full building model. Two methods, Tabular Q-learning and Batch Q-learning with Memory Replay, are implemented with real building settings and actual weather conditions in a Matlab/Simulink framework. The performance is evaluated against standard rule-based control (RBC). We investigated different neural network structures and find that some outperformed RBC already during the learning phase. Overall, every RLC strategy for PV/T outperformed RBC by over 10% after the third year. Likewise, for the full building, RLC outperforms RBC in terms of meeting the heating demand, maintaining the optimal operation temperature and compensating more effectively for ground heat. This allows to reduce engineering costs associated with the setup of these systems, as well as decrease the return-of-invest period, both of which are necessary to create a sustainable, zero-emission building

  14. Exergy, exergoeconomic and environmental analyses and evolutionary algorithm based multi-objective optimization of combined cycle power plants

    International Nuclear Information System (INIS)

    Ahmadi, Pouria; Dincer, Ibrahim; Rosen, Marc A.

    2011-01-01

    A comprehensive exergy, exergoeconomic and environmental impact analysis and optimization is reported of several combined cycle power plants (CCPPs). In the first part, thermodynamic analyses based on energy and exergy of the CCPPs are performed, and the effect of supplementary firing on the natural gas-fired CCPP is investigated. The latter step includes the effect of supplementary firing on the performance of bottoming cycle and CO 2 emissions, and utilizes the first and second laws of thermodynamics. In the second part, a multi-objective optimization is performed to determine the 'best' design parameters, accounting for exergetic, economic and environmental factors. The optimization considers three objective functions: CCPP exergy efficiency, total cost rate of the system products and CO 2 emissions of the overall plant. The environmental impact in terms of CO 2 emissions is integrated with the exergoeconomic objective function as a new objective function. The results of both exergy and exergoeconomic analyses show that the largest exergy destructions occur in the CCPP combustion chamber, and that increasing the gas turbine inlet temperature decreases the CCPP cost of exergy destruction. The optimization results demonstrates that CO 2 emissions are reduced by selecting the best components and using a low fuel injection rate into the combustion chamber. -- Highlights: → Comprehensive thermodynamic modeling of a combined cycle power plant. → Exergy, economic and environmental analyses of the system. → Investigation of the role of multiobjective exergoenvironmental optimization as a tool for more environmentally-benign design.

  15. Exergy based methods for economic and risk design optimization of energy systems: Application to a gas turbine

    International Nuclear Information System (INIS)

    Cassetti, G.; Rocco, M.V.; Colombo, E.

    2014-01-01

    Exergy based analyses are considered by the scientific community appropriate tools for the design and the performance evaluation and improvements of energy systems. Moreover, they are today recognized as proper instruments to assess economic, environmental and social externalities of energy systems. This paper presents the results of a study in which different exergy analysis methods are adopted to determine the optimal design configuration of a gas turbine operating in simple Joule Brayton cycle. Standard exergy and Thermoeconomic analyses are performed to identify the highest thermodynamic efficiency and minimum economic cost configurations of the system, while for the environmental analysis Authors propose an innovative method in which the exergy analysis is combined with a Risk Analysis. With this method the total risk associated to the system is used as objective function in the same way as monetary cost is for standard Thermoeconomic analysis. These three methods aims therefore to determine the optimal design configurations of the system with respect to their specific objective functions, respectively: exergy cost (J/J), monetary (exergoeconomic) cost (€/J) and risk (injured/J) of the product. Results lead to three different optimal design parameters for the system, according to the objective of each analysis procedure. - Highlights: • An original implementation of Thermoeconomic framework is proposed. • Standard Exergy and Thermoeconomic analysis are performed on a case study. • A new model using exergy as allocation criteria for Risk Analysis is performed. • Different optimal configurations are obtained and compared

  16. Exergy and economic analysis of a pyramid-shaped solar water purification system: Active and passive cases

    International Nuclear Information System (INIS)

    Kianifar, Ali; Zeinali Heris, Saeed; Mahian, Omid

    2012-01-01

    An exergy analysis has been conducted to show the effect of a small fan on the exergy efficiency in a pyramid-shaped solar still. The tests were carried out in Mashhad (36° 36′ N), for two solar still systems. One of them was equipped with a small fan (active system), to enhance the evaporation rate while the other one was tested in passive condition (no fan). To examine the effects of radiation and water depth on exergy efficiency, experiments in two seasons and two different depths of water in the solar still basin were performed. The results show that during summer, active unit has higher exergy efficiency than passive one while in winter there is no considerable difference between the exergy efficiency of the units. Results also reveal that the exergy efficiency is higher when the water depth in the basin is lower. Finally, the economic analysis shows a considerable reduction in production cost of the water (8–9%) when the active system is used. -- Highlights: ► Using a small fan in the solar still; reduces the productive cost of fresh water up to 9%. ► Effects of the fan and basin depth on the exergy efficiency during summer and winter were examined. ► Utilizing an active system will increase the daily productivity of fresh water by 20%.

  17. An exergy-based multi-objective optimisation model for energy retrofit strategies in non-domestic buildings

    International Nuclear Information System (INIS)

    García Kerdan, Iván; Raslan, Rokia; Ruyssevelt, Paul

    2016-01-01

    While the building sector has a significant thermodynamic improvement potential, exergy analysis has been shown to provide new insight for the optimisation of building energy systems. This paper presents an exergy-based multi-objective optimisation tool that aims to assess the impact of a diverse range of retrofit measures with a focus on non-domestic buildings. EnergyPlus was used as a dynamic calculation engine for first law analysis, while a Python add-on was developed to link dynamic exergy analysis and a Genetic Algorithm optimisation process with the aforementioned software. Two UK archetype case studies (an office and a primary school) were used to test the feasibility of the proposed framework. Different measures combinations based on retrofitting the envelope insulation levels and the application of different HVAC configurations were assessed. The objective functions in this study are annual energy use, occupants' thermal comfort, and total building exergy destructions. A large range of optimal solutions was achieved highlighting the framework capabilities. The model achieved improvements of 53% in annual energy use, 51% of exergy destructions and 66% of thermal comfort for the school building, and 50%, 33%, and 80% for the office building. This approach can be extended by using exergoeconomic optimisation. - Highlights: • Integration of dynamic exergy analysis into a retrofit-oriented simulation tool. • Two UK non-domestic building archetypes are used as case studies. • The model delivers non-dominated solutions based on energy, exergy and comfort. • Exergy destructions of ERMs are optimised using GA algorithms. • Strengths and limitations of the proposed exergy-based framework are discussed.

  18. Modelling the energy and exergy utilisation of the Mexican non-domestic sector: A study by climatic regions

    International Nuclear Information System (INIS)

    García Kerdan, Iván; Morillón Gálvez, David; Raslan, Rokia; Ruyssevelt, Paul

    2015-01-01

    This paper presents the development of a bottom-up stock model to perform a holistic energy study of the Mexican non-domestic sector. The current energy and exergy flows are shown based on a categorisation by climatic regions with the aim of understanding the impact of local characteristics on regional efficiencies. Due to the limited data currently available, the study is supported by the development of a detailed archetype-based stock model using EnergyPlus as a first law analysis tool combined with an existing exergy analysis method. Twenty-one reference models were created to estimate the electric and gas use in the sector. The results indicate that sectoral energy and exergy annual input are 95.37 PJ and 94.28 PJ, respectively. Regional exergy efficiencies were found to be 17.8%, 16.6% and 23.2% for the hot-dry, hot-humid and temperate climates, respectively. The study concludes that significant potential for improvements still exists, especially in the cases of space conditioning, lighting, refrigeration, and cooking where most exergy destructions occur. Additionally, this work highlights that the method described may be further used to study the impact of large-scale refurbishments and promote national regulations and standards for sustainable buildings that takes into consideration energy and exergy indicators. - Highlights: • A bottom-up physics model was developed to analyse the Mexican commercial stock. • A detailed energy analysis by climate, buildings and end-uses is presented. • The Mexican non-domestic sector as a whole has an exergy efficiency of 19.7%. • The lowest regional exergy efficiency is found at the hot-humid region with 16.6%. • By end use, the highest exergy destructions are caused by HVAC and lighting

  19. Investigating the effect of several thermodynamic parameters on exergy destruction in components of a tri-generation cycle

    International Nuclear Information System (INIS)

    Salehzadeh, A.; Khoshbakhti Saray, R.; JalaliVahid, D.

    2013-01-01

    Multiple energy generating cycles such as tri-generation cycles, which produce heat and cold in addition to power through burning of a primary fuel, have increasingly been used in recent decades. On the other hand, advanced exergy analysis of thermodynamic systems by splitting exergy destruction into endogenous and exogenous parts identifies internal irreversibilities of each of the components and the effect of these irreversibilities on the performance of other components. Therefore, main sources of exergy destruction in cycles can be highlighted and useful recommendations in order to improve the performance of thermodynamic cycles can be presented. In the present work, a tri-generation cycle with 100 MW power production, 70 MW heat and 9 MW cooling capacity is considered. For this tri-generation cycle, effects of various thermodynamic parameters on the amount of endogenous and exogenous exergy destructions, exergy loss and the amount of fuel consumption, are investigated. The results indicate that, increasing compressor pressure ratio, pre-heater outlet temperature and excess air leads to better combustion and lower exergy loss and fuel consumption. Increasing the mass flow rate of steam generator, while keeping the cycle outlet temperature constant and considering cooling capacity variable, lead to increase the first- and second-law efficiencies of the cycle. - Highlights: ► Advanced exergy analysis is used to analyze a tri-generation cycle. ► Increasing compressor pressure ratio leads to lower exergy loss and fuel consumption. ► Exergy loss is lowered by increasing pre-heater outlet temperature. ► Increasing the air flow rate of the cycle improves the performance of the cycle

  20. Application of the exergy concept in the petroleum refining and petrochemical industry

    Energy Technology Data Exchange (ETDEWEB)

    Rivero, Ricardo [Instituto Mexicano del Petroleo, Grupo de Exergia, Mexico City (Mexico)

    2002-08-01

    In this paper, the past, present and future applications of the exergy concept in applied process research, development and engineering projects in the petroleum refining and petrochemical industry, conducted at the Mexican Petroleum Institute (IMP), are described. These applications are the result of a clear recognition of the challenge represented by the reduction of energy degradation, i.e. the application of the second law of thermodynamics, through the exergy concept, which allows to simultaneously consider the three E's model: energy-economy-ecology. Applications can be grouped in two complementary directions: the first, methodological, direction consists in integrating within general simulation, analysis and optimization programs, the subroutines required to conduct exergy analyses, in order to get a quick and precise manner, all information required to integrally optimize chemical processes through detailed exergoeconomic and exergoecologic studies. The second direction refers to research and technological development of specific systems and processes, integrally optimum, of which the justification lies on the exergy analysis, i.e. on its capacity to simultaneously consider energy, economy and ecology aspects, such as diabatic distillation, absorption heat pumps, coking-gasification-combined cycle co- and tri-generation, fuel cells, etc. (Author)

  1. Theoretical analysis of the performance of different cooling strategies with the concept of cool exergy

    DEFF Research Database (Denmark)

    Kazanci, Ongun Berk; Shukuya, Masanori; Olesen, Bjarne W.

    2016-01-01

    The whole chains of exergy flows for different cooling systems were compared. The effects of cooling demand (internal vs. external solar shading), space cooling method (floor cooling vs. air cooling with ventilation system), and the availability of a nearby natural heat sink (intake air for the v......The whole chains of exergy flows for different cooling systems were compared. The effects of cooling demand (internal vs. external solar shading), space cooling method (floor cooling vs. air cooling with ventilation system), and the availability of a nearby natural heat sink (intake air...... for the ventilation system being outdoor air vs. air from the crawl-space, and air-to-water heat pump vs. ground heat exchanger as cooling source) on system exergy performance were investigated. It is crucial to minimize the cooling demand because it is possible to use a wide range of heat sinks (ground, lake, sea......-water, etc.) and indoor terminal units, only with a minimized demand. The water-based floor cooling system performed better than the air-based cooling system; when an air-to-water heat pump was used as the cooling source, the required exergy input was 28% smaller for the floor cooling system. The auxiliary...

  2. Exergy analysis of a combined heat and power plant with integrated lignocellulosic ethanol production

    DEFF Research Database (Denmark)

    Lythcke-Jørgensen, Christoffer Ernst; Haglind, Fredrik; Clausen, Lasse Røngaard

    2013-01-01

    produces ethanol, solid biofuel, molasses, and is able to produce district heating hot water. Considering all products equally valuable, the exergy efficiency of the ethanol facility was found to be 0.790 during integrated operation with zero district heating production, and 0.852 during integrated...

  3. An application of the extended exergy accounting method to the Turkish society, year 2006

    International Nuclear Information System (INIS)

    Seckin, C.; Sciubba, E.; Bayulken, A.R.

    2012-01-01

    The Turkish society is analyzed, on the basis of a 2006 database, by means of the EEA (Extended Exergy Accounting) method. A brief synthesis of EEA is also presented, with the purpose of clarifying some of the issues related to its accounting technique. The system to be analyzed is assumed to be at steady state, and the input and output fluxes of matter and energy are expressed in terms of their respective exergy content. This study is intended to provide support for possible structural interventions aimed at the improvement of the degree of sustainability of the Country: since EEA allows for the conversion of the so-called “externalities”, i.e., of the immaterial fluxes of labour, capital and environmental remediation, into their exergetic equivalents, a more comprehensive and deeper insight of the resource consumption and of the environmental impact becomes possible. As usual in EEA analyses, the Turkish society has been modelled as an open thermodynamic system interacting with two “external” systems, namely “Environment” and “Abroad”, and consisting itself of seven internal subsystems: Extraction-, Conversion-, Transportation-, Agricultural-, Industrial-, Tertiary- and Domestic sector. -- Highlights: ► Extended Exergy Accounting Application to Turkish society 2006. ► Exergy transfers between sectors, environment and abroad. ► Exergetic equivalent of labour and capital fluxes. ► Environmental remediation cost computing for different sectors in Turkey. ► Sectoral efficiencies.

  4. The challenge of introducing an exergy indicator in a local law on energy

    International Nuclear Information System (INIS)

    Favrat, D.; Marechal, F.; Epelly, O.

    2008-01-01

    Extending the exergy concept to practitioners and policy makers is still a major challenge. Recently the 'Canton of Geneva' in Switzerland introduced a new law governing the procedures of attribution of building permits for new or retrofitted city areas. Authorities were asked to define a procedure including the calculation of an exergy indicator to be quantified in each file concerning large projects submitted for acceptance. This paper summarizes the problem definition, a clarification of the limits expected from the exergy indicator as well as the spreadsheet tool and the tables used to facilitate this quantification both for heating and air conditioning. For simplification the overall system was divided into a superstructure formed by four subsystems including the room convector, the plant of the building, a possible district heating and cooling plant and an external power plant. Three temperature ranges were considered for the building distribution networks both in heating and cooling. Ten different technology combinations were considered ranking from the lowest heating exergy efficiency with nuclear electricity and joule heating to the best efficiency with hydroelectricity and District heating electric heat pumps using lake water

  5. Experimental investigation and exergy analysis of a triple fluid vapor absorption refrigerator

    International Nuclear Information System (INIS)

    Jemaa, Radhouane Ben; Mansouri, Rami; Boukholda, Ismail; Bellagi, Ahmed

    2016-01-01

    Highlights: • Experimental study on a commercial triple fluid vapor absorption refrigerator performed. • An Aspen-hysys model developed and validated with experimental measurements. • Exergy analysis of the unit performed and discussed. • Absorber identified as largest source of irreversibility, followed by solution heat exchanger. - Abstract: This paper presents an energy and exergy analyses of a triple fluid vapor absorption refrigerator working with ammonia as refrigerant, water as absorbent and hydrogen as auxiliary gas. The experimental setup is constituted of a commercial unit equipped with the appropriate metrology. The temperature at the inlet and outlet of every component of the machine, as well as the cabinet and ambient temperature are continuously measured and monitored. A simulation model of the machine is developed using the process simulator Aspen-Hysys. The thermodynamic analysis includes energy and exergy efficiency calculations, destroyed exergy evaluation and degradation of the coefficient of performance (COP) in each component of the refrigerator. The results indicate that the absorber exhibits the largest source of irreversibility followed by the solution heat exchanger. These two components alone are at the origin of 63% of the total degradation of COP.

  6. Exergy analysis of thermochemical ethanol production via biomass gasification and catalytic synthesis

    NARCIS (Netherlands)

    van der Heijden, H.H.J.L.; Ptasinski, K.J.

    2012-01-01

    In this paper an exergy analysis of thermochemical ethanol production from biomass is presented. This process combines a steam-blown indirect biomass gasification of woody feedstock, with a subsequent conversion of produced syngas into ethanol. The production process involves several process

  7. Numerical Calculation and Exergy Equations of Spray Heat Exchanger Attached to a Main Fan Diffuser

    Science.gov (United States)

    Cui, H.; Wang, H.; Chen, S.

    2015-04-01

    In the present study, the energy depreciation rule of spray heat exchanger, which is attached to a main fan diffuser, is analyzed based on the second law of thermodynamics. Firstly, the exergy equations of the exchanger are deduced. The equations are numerically calculated by the fourth-order Runge-Kutta method, and the exergy destruction is quantitatively effected by the exchanger structure parameters, working fluid (polluted air, i.e., PA; sprayed water, i.e., SW) initial state parameters and the ambient reference parameters. The results are showed: (1) heat transfer is given priority to latent transfer at the bottom of the exchanger, and heat transfer of convection and is equivalent to that of condensation in the upper. (2) With the decrease of initial temperature of SW droplet, the decrease of PA velocity or the ambient reference temperature, and with the increase of a SW droplet size or initial PA temperature, exergy destruction both increase. (3) The exergy efficiency of the exchanger is 72.1 %. An approach to analyze the energy potential of the exchanger may be provided for engineering designs.

  8. Energy and Exergy Analysis of 210 MW Jamshoro Thermal Power Plant

    Directory of Open Access Journals (Sweden)

    Muhib Ali Rajper

    2016-04-01

    Full Text Available In this paper, thermodynamic analysis of 210 MW dual-fire, subcritical, reheat steam power plant, situated near Jamshoro, Pakistan has been performed. Firstly, the plant is modeled by EES (Engineering Equation Solver software. Moreover; a parametric study is performed to assess the impacts of various operating parameters on the performance. The net power output, energy efficiency and exergy efficiency are considered as performance parameters of the plant whereas, condenser pressure, main steam pressure and main steam temperature are nominated as operating parameters. According to the results, the net power output, energy efficiency and exergy efficiency are determined as 186.5 MW, 31.37% and 30.41% respectively, under design operating conditions. The condenser contributed a major share in the total energy loss i.e. 280 MW (68.7% followed by boiler with 89 MW (21.8%. The major exergy destructing area is found in the boiler with 350 MW (82.11% of the total exergy destruction followed by turbine with 43.1 MW (10.12% and condenser 12 MW (5.74 %. According to the parametric study, variation in operating parameters had great influence on the plant performance

  9. Development of an exergy-electrical analogy for visualizing and modeling building integrated energy systems

    International Nuclear Information System (INIS)

    Saloux, E.; Teyssedou, A.; Sorin, M.

    2015-01-01

    Highlights: • The exergy-electrical analogy is developed for energy systems used in buildings. • This analogy has been developed for a complete set of system arrangement options. • Different possibilities of inter-connections are illustrated using analog switches. • Adaptability and utility of the diagram over traditional ones are emphasized. - Abstract: An exergy-electrical analogy, similar to the heat transfer electrical one, is developed and applied to the case of integrated energy systems operating in buildings. Its construction is presented for the case of space heating with electric heaters, heat pumps and solar collectors. The proposed analogy has been applied to a set of system arrangement options proposed for satisfying the building heating demand (space heating, domestic hot water); different alternatives to connect the units have been presented with switches in a visualization scheme. The analogy for such situation has been performed and the study of a solar assisted heat pump using ice storage has been investigated. This diagram directly permits energy paths and their associated exergy destruction to be visualized; hence, sources of irreversibility are identifiable. It can be helpful for the comprehension of the global process and its operation as well as for identifying exergy losses. The method used to construct the diagram makes it easily adaptable to others units or structures or to others models depending on the complexity of the process. The use of switches could be very useful for optimization purposes

  10. Exergy Analysis of a Subcritical Reheat Steam Power Plant with Regression Modeling and Optimization

    Directory of Open Access Journals (Sweden)

    MUHIB ALI RAJPER

    2016-07-01

    Full Text Available In this paper, exergy analysis of a 210 MW SPP (Steam Power Plant is performed. Firstly, the plant is modeled and validated, followed by a parametric study to show the effects of various operating parameters on the performance parameters. The net power output, energy efficiency, and exergy efficiency are taken as the performance parameters, while the condenser pressure, main steam pressure, bled steam pressures, main steam temperature, and reheat steam temperature isnominated as the operating parameters. Moreover, multiple polynomial regression models are developed to correlate each performance parameter with the operating parameters. The performance is then optimizedby using Direct-searchmethod. According to the results, the net power output, energy efficiency, and exergy efficiency are calculated as 186.5 MW, 31.37 and 30.41%, respectively under normal operating conditions as a base case. The condenser is a major contributor towards the energy loss, followed by the boiler, whereas the highest irreversibilities occur in the boiler and turbine. According to the parametric study, variation in the operating parameters greatly influences the performance parameters. The regression models have appeared to be a good estimator of the performance parameters. The optimum net power output, energy efficiency and exergy efficiency are obtained as 227.6 MW, 37.4 and 36.4, respectively, which have been calculated along with optimal values of selected operating parameters.

  11. Energy and exergy performance of residential heating systems with separate mechanical ventilation

    International Nuclear Information System (INIS)

    Zmeureanu, Radu; Yu Wu, Xin

    2007-01-01

    The paper brings new evidence on the impact of separate mechanical ventilation system on the annual energy and exergy performance of several design alternatives of residential heating systems, when they are designed for a house in Montreal. Mathematical models of residential heating, ventilation and domestic hot water (HVAC-DHW) systems, which are needed for this purpose, are developed and furthermore implemented in the Engineering Equation Solver (EES) environment. The Coefficient of Performance and the exergy efficiency are estimated as well as the entropy generation and exergy destruction of the overall system. The equivalent greenhouse gas emissions due to the on-site and off-site use of primary energy sources are also estimated. The addition of a mechanical ventilation system with heat recovery to any HVAC-DHW system discussed in the paper increases the energy efficiency; however, it decreases the exergy efficiency, which indicates a potential long-term damaging impact on the natural environment. Therefore, the use of a separate mechanical ventilation system in a house should be considered with caution, and recommended only when other means for controlling the indoor air quality cannot be applied

  12. An Innovative Use of Renewable Ground Heat for Insulation in Low Exergy Building Systems

    Directory of Open Access Journals (Sweden)

    Hansjürg Leibundgut

    2012-08-01

    Full Text Available Ground heat is a renewable resource that is readily available for buildings in cool climates, but its relatively low temperature requires the use of a heat pump to extract it for heating. We developed a system that uses low temperature ground heat directly in a building wall to reduce transmission heat losses. The Active Low Exergy Geothermal Insulation Systems (ALEGIS minimizes exergy demand and maximizes the use of renewable geothermal heat from the ground. A fluid is pumped into a small pipe network in an external layer of a wall construction that is linked to a ground heat source. This decouples the building from the outside temperature, therefore eliminating large peak demands and reducing the primary energy demand. Our steady-state analysis shows that at a design temperature of −10 °C the 6 cm thick active insulation system has equivalent performance to 11 cm of passive insulation. Our comparison of heating performance of a building with our active insulation system versus a building with static insulation of the same thickness shows a 15% reduction in annual electricity demand, and thus exergy input. We present an overview of the operation and analysis of our low exergy concept and its modeled performance.

  13. Combined solar organic Rankine cycle with reverse osmosis desalination process: Energy, exergy, and cost evaluations

    Energy Technology Data Exchange (ETDEWEB)

    Nafey, A.S.; Sharaf, M.A. [Department of Engineering Science, Faculty of Petroleum and Mining Engineering, Suez Canal University, Suez (Egypt)

    2010-11-15

    Organic Rankine cycles (ORC) have unique properties that are well suited to solar power generation. In this work design and performance calculations are performed using MatLab/SimuLink computational environment. The cycle consists of thermal solar collectors (Flat Plate Solar Collector (FPC), or Parabolic Trough Collector (PTC), or Compound Parabolic Concentrator (CPC)) for heat input, expansion turbine for work output, condenser unit for heat rejection, pump unit, and Reverse Osmosis (RO) unit. Reverse osmosis unit specifications used in this work is based on Sharm El-Shiekh RO desalination plant. Different working fluids such as: butane, isobutane, propane, R134a, R152a, R245ca, and R245fa are examined for FPC. R113, R123, hexane, and pentane are investigated for CPC. Dodecane, nonane, octane, and toluene are allocated for PTC. The proposed process units are modeled and show a good validity with literatures. Exergy and cost analysis are performed for saturation and superheated operating conditions. Exergy efficiency, total exergy destruction, thermal efficiency, and specific capital cost are evaluated for direct vapor generation (DVG) process. Toluene and Water achieved minimum results for total solar collector area, specific total cost and the rate of exergy destruction. (author)

  14. Exergy analysis of building integrated semitransparent photovoltaic thermal (BiSPVT system

    Directory of Open Access Journals (Sweden)

    Neha Gupta

    2017-02-01

    Full Text Available In this paper, an exergy analysis of building integrated semitransparent photovoltaic thermal (BiSPVT system has been carried out. In the proposed system, the room below building integrated semitransparent photovoltaic thermal system has been considered as an air-conditioned (constant room temperature. Energy balance equation for each components namely semitransparent photovoltaic roof, floor and room air have been given. Based on energy balance, an analytical expression for room air, solar cell and room floor temperatures have been derived along with solar cell electrical efficiency. Further by considering the day lighting parameters, an overall exergy of the proposed system has been derived for different number of air change between the room and ambient air. It has been observed that there is reduction in room air and solar cell temperatures with an increase of number of air changes. However, solar cell electrical efficiency increases with decrease in temperature of solar cell. Further, it is found that an electrical power and illumination inside the room are more dominating in comparison with thermal exergy. An increase of 1.15% in an overall exergy is observed for the number of air changes varies from 0 to 4. Experimental validation of theoretical model has also been carried out.

  15. Benefits of Exergy-Based Analysis for Aerospace Engineering Applications—Part I

    Directory of Open Access Journals (Sweden)

    John H. Doty

    2009-01-01

    Full Text Available This paper compares the analysis of systems from two different perspectives: an energy-based focus and an exergy-based focus. A complex system was simply modeled as interacting thermodynamic systems to illustrate the differences in analysis methodologies and results. The energy-based analysis had combinations of calculated states that are infeasible. On the other hand, the exergy-based analyses only allow feasible states. More importantly, the exergy-based analyses provide clearer insight to the combination of operating conditions for optimum system-level performance. The results strongly suggest changing the analysis/design paradigm used in aerospace engineering from energy-based to exergy-based. This methodology shift is even more critical in exploratory research and development where previous experience may not be available to provide guidance. Although the models used herein may appear simplistic, the message is very powerful and extensible to higher-fidelity models: the 1st Law is only a necessary condition for design, whereas the 1st and 2nd Laws provide the sufficiency condition.

  16. Exergy Analysis of the Musculoskeletal System Efficiency during Aerobic and Anaerobic Activities

    Directory of Open Access Journals (Sweden)

    Gabriel Marques Spanghero

    2018-02-01

    Full Text Available The first and second laws of thermodynamics were applied to the human body in order to evaluate the quality of the energy conversion during muscle activity. Such an implementation represents an important issue in the exergy analysis of the body, because there is a difficulty in the literature in evaluating the performed power in some activities. Hence, to have the performed work as an input in the exergy model, two types of exercises were evaluated: weight lifting and aerobic exercise on a stationary bicycle. To this aim, we performed a study of the aerobic and anaerobic reactions in the muscle cells, aiming at predicting the metabolic efficiency and muscle efficiency during exercises. Physiological data such as oxygen consumption, carbon dioxide production, skin and internal temperatures and performed power were measured. Results indicated that the exergy efficiency was around 4% in the weight lifting, whereas it could reach values as high as 30% for aerobic exercises. It has been shown that the stationary bicycle is a more adequate test for first correlations between exergy and performance indices.

  17. Enviro-exergy sustainability analysis of boiler evolution in district energy system

    International Nuclear Information System (INIS)

    Compton, M.; Rezaie, B.

    2017-01-01

    Investigations into energy resources are important from the point of energy sustainability. The principal objective of this study is to investigate the evolution of the operating boilers at the University of Idaho (UI) district energy plant through an exergy analysis. The biomass boiler uses western red cedar chips from nearby lumber mills and provides 95% of the steam requirements of the main campus of UI in Moscow, ID, USA. Thermodynamic analysis reveals a thermal efficiency of 76% and an exergy efficiency of 24% for the biomass boiler. A combustion model is developed to determine the primary emissions products of both the bone dry wood chips and natural gas fuels. CO 2 comprises 26% of the bone dry biomass emissions and 8% of the natural gas emissions products. Testing results of the biomass boiler exhaust stack show CO 2 emissions of 14% when an average moisture content of 33% is accounted for. An overview of the evolution of the energy plant is discussed, showing the generational differences in each boiler. By using a biomass fuel source, the cost per 1000 kg of steam produced is on average 63% lower than using natural gas, resulting in savings of over $1 million annually. - Highlights: • Exergy efficiency comparison of biomass and natural gas boilers. • Moisture content in biomass reduces average heating value and exergy efficiency. • Local sustainable energy sources can result in economic savings over fossil fuels. • Older boilers can have comparable efficiencies with newer ones after improvements.

  18. Tetra-combined cogeneration system. Exergy and thermo economic evaluation; Sistema tetra combinado de cogeracao. Avaliacao exergetica e termoeconomica

    Energy Technology Data Exchange (ETDEWEB)

    Arriola, Domingo Wilson Garagatti [Sao Paulo Univ., SP (Brazil). Escola Politecnica. Dept. de Engenharia Mecanica]. E-mail: wgarriol@usp.br; Oliveira Junior, Silvio de [Instituto de Pesquisas Tecnologicas (IPT), Sao Paulo, SP (Brazil)]. E-mail: olivsilj@ipt.br

    2000-07-01

    This paper presents the description and the exergy and thermo economic evaluation of a new cogeneration system, called tetra-combined cogeneration system, that generates electricity and chilled water (for air conditioning purposes) and eventually steam. This system is composed of a gas turbine, a heat recovery steam generator, a condensation/extraction steam turbine and a hybrid absorption/steam ejection chiller. The exergy and thermo economic performance (exergy based costs of electricity, steam and chilled water production) of this system is compared with the performances of conventional cogeneration systems, pointing out the advantages and disadvantages of this new system. (author)

  19. Tetra-combined cogeneration system. Exergy and thermoeconomic evaluation; Sistema tetra combinado de cogeracao. Avaliacao exergetica e termoeconomica

    Energy Technology Data Exchange (ETDEWEB)

    Arriola, Domingo Wilson Garagatti [Sao Paulo Univ., SP (Brazil). Escola Politecnica. Dept. de Engenharia Mecanica]. E-mail: wgarriol@usp.br; Oliveira Junior, Silvio de [Instituto de Pesquisas Tecnologicas (IPT), Sao Paulo, SP (Brazil)]. E-mail: olivsilj@ipt.br

    2000-07-01

    The description and the exergy and thermo economic evaluation of a new cogeneration system, called tetra-combined cogeneration system, that generates electricity and chilled water (for air conditioning purposes) and eventually steam is presented. This system is composed of a gas turbine, a heat recovery steam generator, a condensation/extraction steam turbine and a hybrid absorption/steam ejection chiller.The exergy and thermo economic performance (exergy based costs of electricity, steam and chilled water production) of this system is compared with the performances of conventional cogeneration systems, pointing out the advantages and disadvantages of this new system. (author)

  20. Exergy analysis and optimization of a thermal management system with phase change material for hybrid electric vehicles

    International Nuclear Information System (INIS)

    Javani, N.; Dincer, I.; Naterer, G.F.; Yilbas, B.S.

    2014-01-01

    In the present study, energy and exergy analyses are conducted to investigate a new cooling system of hybrid electric vehicles (HEVs). A latent heat thermal energy storage system is integrated with an active refrigeration cycle where octadecane is selected as the phase change material (PCM). The liquid cooling system flows through the chiller following a conventional vapor compression cooling cycle. The latent heat shell and the tube heat exchanger operate in parallel with the chiller and a fraction of coolant enters the heat exchanger and, therefore, decreases the heat load of the chiller, leading to a lower work required by the compressor. The exergy destruction rate and the exergy efficiency of each component in a hybrid thermal management system (TMS) are calculated. In addition, the effects of parameters such as the fraction of coolant entering the heat storage system (PCM mass fraction), evaporator temperature, and compressor pressure ratio on the system performance are investigated. The findings of the exergy analysis reveal that the overall exergy efficiency of the system with PCM presence is 31%, having the largest exergy destruction rate of 0.4 kW and the heat exchangers have lower exergy efficiency as compared to other components. In addition, the results of the parametric study show that an increase in PCM mass fraction results in an increase in exergy efficiency of the system. An environmental impact assessment is also conducted and the results show that an increase in exergy efficiency of the cooling system reduces greenhouse gasses and also increases the sustainability of the system. Moreover, a multi-objective optimization using the genetic algorithm is performed by incorporating two objective functions, namely exergy efficiency to be maximized and total cost rate of the system to be minimized. A Pareto frontier is obtained and a single desirable optimal solution is selected based on LINMAP decision-making process. The results show that the maximum

  1. Energy and exergy analysis of a double effect absorption refrigeration system based on different heat sources

    International Nuclear Information System (INIS)

    Kaynakli, Omer; Saka, Kenan; Kaynakli, Faruk

    2015-01-01

    Highlights: • Energy and exergy analysis was performed on double effect series flow absorption refrigeration system. • The refrigeration system runs on various heat sources such as hot water, hot air and steam. • A comparative analysis was carried out on these heat sources in terms of exergy destruction and mass flow rate of heat source. • The effect of heat sources on the exergy destruction of high pressure generator was investigated. - Abstract: Absorption refrigeration systems are environmental friendly since they can utilize industrial waste heat and/or solar energy. In terms of heat source of the systems, researchers prefer one type heat source usually such as hot water or steam. Some studies can be free from environment. In this study, energy and exergy analysis is performed on a double effect series flow absorption refrigeration system with water/lithium bromide as working fluid pair. The refrigeration system runs on various heat sources such as hot water, hot air and steam via High Pressure Generator (HPG) because of hot water/steam and hot air are the most common available heat source for absorption applications but the first law of thermodynamics may not be sufficient analyze the absorption refrigeration system and to show the difference of utilize for different type heat source. On the other hand operation temperatures of the overall system and its components have a major effect on their performance and functionality. In this regard, a parametric study conducted here to investigate this effect on heat capacity and exergy destruction of the HPG, coefficient of performance (COP) of the system, and mass flow rate of heat sources. Also, a comparative analysis is carried out on several heat sources (e.g. hot water, hot air and steam) in terms of exergy destruction and mass flow rate of heat source. From the analyses it is observed that exergy destruction of the HPG increases at higher temperature of the heat sources, condenser and absorber, and lower

  2. Energy and exergy efficiencies in Turkish transportation sector, 1988-2004

    International Nuclear Information System (INIS)

    Ediger, Volkan S.; Camdali, Unal

    2007-01-01

    This study aims at examining energy and exergy efficiencies in Turkish transportation sector. Unlike the previous studies, historical data is used to investigate the development of efficiencies of 17 years period from 1988 to 2004. The energy consumption values in tons-of-oil equivalent for eight transport modes of four transportation subsectors of the Turkish transportation sector, including hard coal, lignite, oil, and electricity for railways, oil for seaways and airways, and oil and natural gas for highways, are used. The weighted mean energy and exergy efficiencies are calculated for each mode of transport by multiplying weighting factors with efficiency values of that mode. They are then summed up to calculate the weighted mean overall efficiencies for a particular year. Although the energy and exergy efficiencies in Turkish transport sector are slightly improved from 1988 to 2004, the historical pattern is cyclic. The energy efficieny is found to range from 22.16% (2002) to 22.62% (1998 and 2004) with a mean of 22.42±0.14% and exergy efficiency to range from 22.39% (2002) to 22.85% (1998 and 2004) with a mean of 22.65±0.15%. Overall energy and exergy efficiencies of the transport sector consist mostly of energy and exergy efficiencies of the highways subsector in percentages varying from 81.5% in 2004 to 91.7% in 2002. The rest of them are consisted of other subsectors such as railways, seaways, and airways. The overall efficiency patterns are basically controlled by the fuel consumption in airways in spite of this subsector's consisting only a small fraction of total. The major reasons for this are that airways efficiencies and the rate of change in fuel consumption in airways are greater than those of the others. This study shows that airway transportation should be increased to improve the energy and exergy efficiencies of the Turkish transport sectors. However, it should also be noted that no innovations and other advances in transport technologies are

  3. Energy and exergy recovery in a natural gas compressor station – A technical and economic analysis

    International Nuclear Information System (INIS)

    Kostowski, Wojciech J.; Kalina, Jacek; Bargiel, Paweł; Szufleński, Paweł

    2015-01-01

    Highlights: • Energy and exergy flow in a natural gas compressor station. • Operational efficiency only 18.3% vs. 35.1% nominal. • 3 energy/exergy recovery systems proposed. • Up to 168.9 GW h/y electricity and 6.5 GW h/y heat recoverable. • Legal obstacles: operators not allowed to produce electricity. - Abstract: The paper presents possible solutions to improve the thermodynamic performance of a natural gas compressor station equipped with various type of compressor units and operated at part-load conditions. A method for setting a simplified energy and exergy balance based on the available metering information has been presented. For a case study plant, it has been demonstrated that the current part-load operation leads to a significant decrease in energy and exergy efficiency compared to the nominal state of machinery. Three alternative improvement strategies have been proposed: (1) installation of a heat recovery hot water generator for covering the existing heat demand of the plant; (2) installation of a heat recovery thermal oil heater for covering the existing heat demand and driving an organic Rankine cycle (ORC) for electricity generation; (3) installation of a heat recovery thermal oil heater with and ORC and gas expanders for switching into full-load operation of the gas turbine unit. Energy and exergy performance of the proposed strategies as well as their economic feasibility have been analyzed. The second scenario involving an ORC unit provides the highest local energy savings, however, its economic feasibility is not achieved under the current part-load operating conditions. A hypothetic scenario of the same station operated at full-load due to an increased gas transmission capacity demonstrate the economic feasibility (possible under optimistic price conditions). Finally, it has been shown that the possibility of waste energy recovery from natural gas transmission systems (in particular, from compressor stations) depends on legal

  4. Comparative exergy analyses of Jatropha curcas oil extraction methods: Solvent and mechanical extraction processes

    International Nuclear Information System (INIS)

    Ofori-Boateng, Cynthia; Keat Teong, Lee; JitKang, Lim

    2012-01-01

    Highlights: ► Exergy analysis detects locations of resource degradation within a process. ► Solvent extraction is six times exergetically destructive than mechanical extraction. ► Mechanical extraction of jatropha oil is 95.93% exergetically efficient. ► Solvent extraction of jatropha oil is 79.35% exergetically efficient. ► Exergy analysis of oil extraction processes allow room for improvements. - Abstract: Vegetable oil extraction processes are found to be energy intensive. Thermodynamically, any energy intensive process is considered to degrade the most useful part of energy that is available to produce work. This study uses literature values to compare the efficiencies and degradation of the useful energy within Jatropha curcas oil during oil extraction taking into account solvent and mechanical extraction methods. According to this study, J. curcas seeds on processing into J. curcas oil is upgraded with mechanical extraction but degraded with solvent extraction processes. For mechanical extraction, the total internal exergy destroyed is 3006 MJ which is about six times less than that for solvent extraction (18,072 MJ) for 1 ton J. curcas oil produced. The pretreatment processes of the J. curcas seeds recorded a total internal exergy destructions of 5768 MJ accounting for 24% of the total internal exergy destroyed for solvent extraction processes and 66% for mechanical extraction. The exergetic efficiencies recorded are 79.35% and 95.93% for solvent and mechanical extraction processes of J. curcas oil respectively. Hence, mechanical oil extraction processes are exergetically efficient than solvent extraction processes. Possible improvement methods are also elaborated in this study.

  5. Utilizing the Exergy Concept to Address Environmental Challenges of Electric Systems

    Directory of Open Access Journals (Sweden)

    Carmen A. Bulucea

    2012-10-01

    Full Text Available Theoretically, the concepts of energy, entropy, exergy and embodied energy are founded in the fields of thermodynamics and physics. Yet, over decades these concepts have been applied in numerous fields of science and engineering, playing a key role in the analysis of processes, systems and devices in which energy transfers and energy transformations occur. The research reported here aims to demonstrate, in terms of sustainability, the usefulness of the embodied energy and exergy concepts for analyzing electric devices which convert energy, particularly the electromagnet. This study relies on a dualist view, incorporating technical and environmental dimensions. The information provided by energy assessments is shown to be less useful than that provided by exergy and prone to be misleading. The electromagnet force and torque (representing the driving force of output exergy, accepted as both environmental and technical quantities, are expressed as a function of the electric current and the magnetic field, supporting the view of the necessity of discerning interrelations between science and the environment. This research suggests that a useful step in assessing the viability of electric devices in concert with ecological systems might be to view the magnetic flux density B and the electric current intensity I as environmental parameters. In line with this idea the study encompasses an overview of potential human health risks and effects of extremely low frequency electromagnetic fields (ELF EMFs caused by the operation of electric systems. It is concluded that exergy has a significant role to play in evaluating and increasing the efficiencies of electrical technologies and systems. This article also aims to demonstrate the need for joint efforts by researchers in electric and environmental engineering, and in medicine and health fields, for enhancing knowledge of the impacts of environmental ELF EMFs on humans and other life forms.

  6. Environmental and exergy benefit of nanofluid-based hybrid PV/T systems

    International Nuclear Information System (INIS)

    Hassani, Samir; Saidur, R.; Mekhilef, Saad; Taylor, Robert A.

    2016-01-01

    Highlights: • Environmental and ExPBT analysis of different PV/T configurations is presented. • The exergy payback time of nanofluid-based hybrid PV/T system is about 2 years. • Nanofluid-based hybrid PV/T system is a reliable solution for pollution prevention. • Nanofluid-based hybrid PV/T system is highly recommended at high solar concentration. - Abstract: Photovoltaic/thermal (PV/T) solar systems, which produce both electrical and thermal energy simultaneously, represent a method to achieve very high conversion rates of sunlight into useful energy. In recent years, nanofluids have been proposed as efficient coolants and optical filter for PV/T systems. Aim of this paper is to theoretically analyze the life cycle exergy of three different configurations of nanofluids-based PV/T hybrid systems, and compare their performance to a standard PV and PV/T system. Electrical and thermal performance of the analyzed solar collectors was investigated numerically. The life cycle exergy analysis revealed that the nanofluids-based PV/T system showed the best performance compared to a standard PV and PV/T systems. At the optimum value of solar concentration C, nanofluid-based PV/T configuration with optimized optical and thermal properties produces ∼1.3 MW h/m 2 of high-grade exergy annually with the lowest exergy payback time of 2 years, whereas these are ∼0.36, ∼0.79 MW h/m 2 and 3.48, 2.55 years for standard PV and PV/T systems, respectively. In addition, the nanofluids-based PV/T system can prevent the emissions of about 448 kg CO 2 eq m −2 yr −1 . Overall, it was found that the nanofluids-based PV/T with optimized optical and thermal properties has potential for further development in a high-concentration solar system.

  7. Energy and exergy analysis of integrated system of ammonia–water Kalina–Rankine cycle

    International Nuclear Information System (INIS)

    Chen, Yaping; Guo, Zhanwei; Wu, Jiafeng; Zhang, Zhi; Hua, Junye

    2015-01-01

    The integrated system of AWKRC (ammonia–water Kalina–Rankine cycle) is a novel cycle operated on KC (Kalina cycle) for power generation in non-heating seasons and on AWRC (ammonia–water Rankine cycle) for cogeneration of power and heating water in winter. The influences of inlet temperatures of both heat resource and cooling water on system efficiencies were analyzed based on the first law and the second law of thermodynamics. The calculation is based on following conditions that the heat resource temperature keeps 300 °C, the cooling water temperature for the KC or AWRC is respectively 25 °C or 15 °C; and the temperatures of heating water and backwater are respectively 90 °C and 40 °C. The results show that the evaluation indexes of the power recovery efficiency and the exergy efficiency of KC were respectively 18.2% and 41.9%, while the composite power recovery efficiency and the composite exergy efficiency of AWRC are respectively 21.1% and 43.0% accounting both power and equivalent power of cogenerated heating capacity, including 54.5% heating recovery ratio or 12.4% heating water exergy efficiency. The inventory flow diagrams of both energy and exergy gains and losses of the components operating on KC or AWRC are also demonstrated. - Highlights: • An integrated system of AWKRC (ammonia–water Kalina–Rankine cycle) is investigated. • NH_3–H_2O Rankine cycle is operated for cogenerating power and heating-water in winter. • Heating water with 90 °C and capacity of 54% total reclaimed heat load is cogenerated. • Kalina cycle is operated for power generation in other seasons with high efficiency. • Energy and exergy analysis draw similar results in optimizing the system parameters.

  8. Extended exergy-based sustainability accounting of a household biogas project in rural China

    International Nuclear Information System (INIS)

    Yang, J.; Chen, B.

    2014-01-01

    Biogas has been earmarked as one of the leading renewable energy sources capable of mitigating environmental emissions in rural areas. Thus, developing an accounting technique is of particular importance in coping with increasing problems related to renewable agriculture and rural energy supply. In this study, extended exergy was generalised for the sustainability evaluation of biogas projects. Furthermore, a series of extended exergy-based indicators was presented as benchmarking from the perspectives of resources, economics and greenhouse gas (GHG) emissions. The sustainability of a “Three-in-One” biogas production system in southern China was thereby evaluated based on the proposed framework. The results show that economic costs concentrate in the construction phase. GHG emissions are mainly derived from bricks and cement, with proportions of 36.23% and 34.91%, respectively. The largest resource depletion occurs during the consumption of feedstock (87.06%) in the operation phase. Compared with other renewable energy conversion systems, the biogas project has a higher renewability (0.925) and economic return on investment ratio (6.82) and a lower GHG emission intensity (0.012). With the merit of bridging thermodynamics and externality, the extended exergy-based approach presented in this study may effectively appraise the energy and environmental performance of biogas projects. - Highlights: • Extended exergy is used to describe the sustainability level of biogas projects. • A set of extended exergy based sustainability indicator is established. • Biogas project has high renewability and greenhouse gas emission abatement potential. • Multiple utilization of biogas digestate is a promising way to improve sustainability

  9. Thermodynamic and economic evaluations of a geothermal district heating system using advanced exergy-based methods

    International Nuclear Information System (INIS)

    Tan, Mehmet; Keçebaş, Ali

    2014-01-01

    Highlights: • Evaluation of a GDHS using advanced exergy-based methods. • Comparison of the results of the conventional and advanced exergy-based methods. • The modified exergetic efficiency and exergoeconomic factor are found as 45% and 13%. • Improvement and total cost-savings potentials are found to be 3% and 14%. • All the pumps have the highest improvement potential and total cost-savings potential. - Abstract: In this paper, a geothermal district heating system (GDHS) is comparatively evaluated in terms of thermodynamic and economic aspects using advanced exergy-based methods to identify the potential for improvement, the interactions among system components, and the direction and potential for energy savings. The actual operational data are taken from the Sarayköy GDHS, Turkey. In the advanced exergetic and exergoeconomic analyses, the exergy destruction and the total operating cost within each component of the system are split into endogenous/exogenous and unavoidable/avoidable parts. The advantages of these analyses over conventional ones are demonstrated. The results indicate that the advanced exergy-based method is a more meaningful and effective tool than the conventional one for system performance evaluation. The exergetic efficiency and the exergoeconomic factor of the overall system for the Sarayköy GDHS were determined to be 43.72% and 5.25% according to the conventional tools and 45.06% and 12.98% according to the advanced tools. The improvement potential and the total cost-savings potential of the overall system were also determined to be 2.98% and 14.05%, respectively. All of the pumps have the highest improvement potential and total cost-savings potential because the pumps were selected to have high power during installation at the Sarayköy GDHS

  10. Experimental investigation and exergy analysis of the performance of a counter flow Ranque-Hilsch vortex tube with regard to nozzle cross-section areas

    Energy Technology Data Exchange (ETDEWEB)

    Dincer, K.; Avci, A.; Berber, A. [Dept. of Mechanical Eng., Fac. of Eng. and Architecture, Selcuk Univ., Selcuklu, Konya (Turkey); Baskaya, S. [Dept. of Mechanical Eng., Fac. of Eng. and Architecture, Gazi Univ., Maltepe, Ankara (Turkey)

    2010-08-15

    Exergy analysis and performance of a Ranque-Hilsch Vortex Tube (RHVT) with various nozzle cross-section areas (NCSA = 3 x 3, 4 x 4, 5 x 5 mm{sup 2}) were determined under inlet pressures (P{sub i}) of 260, 300 kPa (absolute) pressurized air. The maximum difference in the temperatures of hot output and cold output streams was obtained for NCSA = 3 x 3 mm{sup 2}. The total inlet exergy (sum E{sub i}), total outlet exergy (sum E{sub O}), total lost exergy (sum E{sub Lost}) and exergy efficiency ({eta}, %) were calculated. It was determined that the exergy efficiency of the system, varied between 1% and 39%, and the highest exergy efficiency was obtained for NCSA = 3 x 3 mm{sup 2}. The exergy efficiency strongly depends on the level of P{sub i}, {xi} and v{sub cold}. Variation of the exergy efficiency decreased with decreasing P{sub i}, {xi}, v{sub cold} and the highest and lowest exergy efficiencies were found when the values of P{sub i}, {xi}, v{sub cold} reached maximum and minimum levels, respectively. (author)

  11. Splitting the exergy destruction into avoidable and unavoidable parts of a gas engine heat pump (GEHP) for food drying processes based on experimental values

    International Nuclear Information System (INIS)

    Gungor, Aysegul; Erbay, Zafer; Hepbasli, Arif; Gunerhan, Huseyin

    2013-01-01

    Highlights: • Advanced exergy analysis of a gas engine heat pump drying system for the first time. • Varying exergy efficiency values from 79.71% to 81.66% for the overall drying system. • Obtaining modified exergy efficiencies of 84.50–86.00% for the overall drying system. - Abstract: Some limitations in a conventional exergy analysis may be significantly reduced through an advanced exergy analysis. In this regard, the latter is a very useful tool to assess the real potential for improving a system component by splitting the exergy destruction into unavoidable and avoidable parts. This may provide a realistic measure to deduct the improvement potential for the thermodynamic efficiency of a component. For this purpose, improvement efforts are then made by focusing only on these avoidable parts. In this paper, a gas engine heat pump (GEHP) drying system was analyzed using both conventional and advanced exergy analyses. Three medicinal and aromatic plants (Foeniculum vulgare, Malva sylvestris L. and Thymus vulgaris) were dried in a pilot scale GEHP drier, which was designed, constructed and installed in Ege University, Izmir, Turkey. Drying experiments were performed at an air temperature of 45 °C with an air velocity of 1 m/s. For each system component, avoidable and unavoidable exergy destructions, modified exergy efficiency values and modified exergy destruction ratios were determined. Except for the compressor, the evaporator and the drying cabinet, most of the exergy destructions in the system components were avoidable and these avoidable parts can be reduced by design improvements. For the HP unit and the overall drying system, the values for exergy efficiency were obtained to be in the range of 82.51–85.11% and 79.71–81.66% while those for the modified exergy efficiency were calculated to be in the range of 85.70–89.26% and 84.50–86.00%, respectively

  12. Exergy analysis of the biogas sorption-enhanced chemical looping reforming process integrated with a high-temperature proton exchange membrane fuel cell

    International Nuclear Information System (INIS)

    Kasemanand, Sarunyou; Im-orb, Karittha; Tippawan, Phanicha; Wiyaratn, Wisitsree; Arpornwichanop, Amornchai

    2017-01-01

    Highlights: • A biogas reforming and fuel cell integrated process is considered. • Energy and exergy analyses of the integrated process are performed. • Increasing the nickel oxide-to-biogas ratio decreases the exergy efficiency. • The exergy destruction of the fuel cell increases with increasing cell temperature. • The exergy efficiency of the process is improved when heat integration is applied. - Abstract: A biogas sorption-enhanced chemical looping reforming process integrated with a high-temperature proton exchange membrane fuel cell is analyzed. Modeling of such an integrated process is performed by using a flowsheet simulator (Aspen plus). The exergy analysis is performed to evaluate the energy utilization efficiency of each unit and that of the integrated process. The effect of steam and nickel oxide to biogas ratios on the exergetic performance of the stand-alone biogas sorption-enhanced chemical looping reforming process is investigated. The total exergy destruction increases as the steam or nickel oxide to biogas ratio increases. The main exergy destruction is found at the air reactor. For the high-temperature proton exchange membrane fuel cell, the main exergy destruction is found at the cathode. The total exergy destruction increases when cell temperature increases, whereas the inverse effect is found when the current density is considered as a key parameter. Regarding the exergy efficiency, the results show opposite trend to the exergy destruction. The heat integration analysis is performed to improve the exergetic performance. It is found that the integrated process including the heat integration system can improve the exergy destruction and exergy efficiency of 48% and 60%, respectively.

  13. Exergy destruction and losses on four North Sea offshore platforms: A comparative study of the oil and gas processing plants

    DEFF Research Database (Denmark)

    Voldsund, Mari; Nguyen, Tuong-Van; Elmegaard, Brian

    2014-01-01

    The oil and gas processing plants of four North Sea offshore platforms are analysed and compared, based on the exergy analysis method. Sources of exergy destruction and losses are identified and the findings for the different platforms are compared. Different platforms have different working...... conditions, which implies that some platforms need less heat and power than others. Reservoir properties and composition vary over the lifetime of an oil field, and therefore maintaining a high efficiency of the processing plant is challenging. The results of the analysis show that 27%-57% of the exergy...... destruction take place in the gas treatment sections, 13%-29% take place in the gas recompression sections and 10%-24% occur in the production manifolds. The exergy losses with flared gas are significant for two of the platforms. The exact potential for energy savings and for enhancing system performances...

  14. Exergy analysis of micro-organic Rankine power cycles for a small scale solar driven reverse osmosis desalination system

    International Nuclear Information System (INIS)

    Tchanche, B.F.; Lambrinos, Gr.; Frangoudakis, A.; Papadakis, G.

    2010-01-01

    Exergy analysis of micro-organic Rankine heat engines is performed to identify the most suitable engine for driving a small scale reverse osmosis desalination system. Three modified engines derived from simple Rankine engine using regeneration (incorporation of regenerator or feedliquid heaters) are analyzed through a novel approach, called exergy-topological method based on the combination of exergy flow graphs, exergy loss graphs, and thermoeconomic graphs. For the investigations, three working fluids are considered: R134a, R245fa and R600. The incorporated devices produce different results with different fluids. Exergy destruction throughout the systems operating with R134a was quantified and illustrated using exergy diagrams. The sites with greater exergy destruction include turbine, evaporator and feedliquid heaters. The most critical components include evaporator, turbine and mixing units. A regenerative heat exchanger has positive effects only when the engine operates with dry fluids; feedliquid heaters improve the degree of thermodynamic perfection of the system but lead to loss in exergetic efficiency. Although, different modifications produce better energy conversion and less exergy destroyed, the improvements are not significant enough and subsequent modifications of the simple Rankine engine cannot be considered as economically profitable for heat source temperature below 100 °C. As illustration, a regenerator increases the system's energy efficiency by 7%, the degree of thermodynamic perfection by 3.5% while the exergetic efficiency is unchanged in comparison with the simple Rankine cycle, with R600 as working fluid. The impacts of heat source temperature and pinch point temperature difference on engine's performance are also examined. Finally, results demonstrate that energy analysis combined with the mathematical graph theory is a powerful tool in performance assessments of Rankine based power systems and permits meaningful comparison of different

  15. Thermodynamic analysis of a novel power plant with LNG (liquefied natural gas) cold exergy exploitation and CO_2 capture

    International Nuclear Information System (INIS)

    Romero Gómez, Manuel; Romero Gómez, Javier; López-González, Luis M.; López-Ochoa, Luis M.

    2016-01-01

    The LNG (liquefied natural gas) regasification process is a source of cold exergy that is suitable to be recovered to improve the efficiency of thermal power plants. In this paper, an innovative power plant with LNG (liquefied natural gas) exergy utilisation and the capture of CO_2 proceeding from the flue gases is presented. It is characterised by the recovery of LNG cold exergy in a closed Brayton cycle and through direct expansion in an expander coupled to an electrical generator. Moreover, this novel power plant configuration allows CO_2 capture, through an oxy-fuel combustion system and a Rankine cycle that operates with the flue gases themselves and in quasi-critical conditions. The greatest advantage of this plant is that all the recoverable LNG exergy is used to increase the efficiency of the CBC (closed Brayton cycle) and in direct expansion whereas, in other power cycles found in literature that associate LNG regasification and CO_2 capture, part of the LNG exergy is used for condensing flue gas CO_2 for its subsequent capture. As a result, a high efficiency power plant is achieved, exceeding 65%, with almost zero greenhouse gas emissions. - Highlights: • LNG cold exergy can be recovered to improve the efficiency of power plants. • High efficiency power plant with almost zero greenhouse gas emissions. • CO_2 capture through an oxy-fuel combustion system and a Rankine cycle. • Sensitivity analysis of key parameters to evaluate the effect on the efficiency. • The exergy available in the LNG represents 34.79% of the fuel exergy.

  16. Performance Assessment of a Hybrid Solar-Geothermal Air Conditioning System for Residential Application: Energy, Exergy, and Sustainability Analysis

    OpenAIRE

    Abbasi, Yasser; Baniasadi, Ehsan; Ahmadikia, Hossein

    2016-01-01

    This paper investigates the performance of a ground source heat pump that is coupled with a photovoltaic system to provide cooling and heating demands of a zero-energy residential building. Exergy and sustainability analyses have been conducted to evaluate the exergy destruction rate and SI of different compartments of the hybrid system. The effects of monthly thermal load variations on the performance of the hybrid system are investigated. The hybrid system consists of a vertical ground sour...

  17. Industrial and ecological cumulative exergy consumption of the United States via the 1997 input-output benchmark model

    International Nuclear Information System (INIS)

    Ukidwe, Nandan U.; Bakshi, Bhavik R.

    2007-01-01

    This paper develops a thermodynamic input-output (TIO) model of the 1997 United States economy that accounts for the flow of cumulative exergy in the 488-sector benchmark economic input-output model in two different ways. Industrial cumulative exergy consumption (ICEC) captures the exergy of all natural resources consumed directly and indirectly by each economic sector, while ecological cumulative exergy consumption (ECEC) also accounts for the exergy consumed in ecological systems for producing each natural resource. Information about exergy consumed in nature is obtained from the thermodynamics of biogeochemical cycles. As used in this work, ECEC is analogous to the concept of emergy, but does not rely on any of its controversial claims. The TIO model can also account for emissions from each sector and their impact and the role of labor. The use of consistent exergetic units permits the combination of various streams to define aggregate metrics that may provide insight into aspects related to the impact of economic sectors on the environment. Accounting for the contribution of natural capital by ECEC has been claimed to permit better representation of the quality of ecosystem goods and services than ICEC. The results of this work are expected to permit evaluation of these claims. If validated, this work is expected to lay the foundation for thermodynamic life cycle assessment, particularly of emerging technologies and with limited information

  18. Thermodynamic evaluation of distillation columns using exergy loss profiles: a case study on the crude oil atmospheric distillation column

    Energy Technology Data Exchange (ETDEWEB)

    Tarighaleslami, Amir Hossein [Mahshahr Branch, Islamic Azad University, Chemical Engineering Faculty, Mahshar, Khouzestan (Iran, Islamic Republic of); Omidkhah, Mohammad Reza [Tarbiat Modares University, Chemical Engineering Department, Faculty of Engineering, Tehran (Iran, Islamic Republic of); Ghannadzadeh, Ali [University of Toulouse, Department of Process and System Engineering, Chemical Engineering Laboratory, Toulouse (France); Hoseinzadeh Hesas, Roozbeh [University of Malaya, Chemical Engineering Department, Faculty of Engineering, Kuala Lumpur (Malaysia)

    2012-06-15

    This paper presents a case study on the crude oil atmospheric distillation column of Tabriz refinery plant to show the applicability of exergy loss profiles in thermodynamic examination of the different retrofit options. The atmospheric distillation column of Tabriz refinery has been revamped as a consequence of increase of the plant capacity to 100,000 bpd. To cover the deficit of feedstock of the revamped unit, a blend of the existing feedstock with imported crude oil is used as a feedstock. However, to investigate how the blend of these two different types of crudes as a feedstock has an influence on the operating conditions, the examination of the column is needed. Exergy as a comprehensive thermodynamic property which translates the temperature, pressure and composition change into a common unit has been chosen to evaluate the distillation column thermodynamically. Furthermore, the exergy loss profile of the base case serves as a scoping tool to pinpoint the source of inefficiencies. Then, the exergy loss profile as a screening tool has found the retrofit options which are likely to yield greatest energy saving from a list of retrofit options proposed by the industrial partner. In the presented case study, the exergy loss profile identifies the best retrofit option with 17.16% reduction in exergy losses, which finally lead to 3.6% reduction of primary fuel demand. (orig.)

  19. Application of the exergy method to the environmental impact estimation: The nitric acid production as a case study

    International Nuclear Information System (INIS)

    Kirova-Yordanova, Zornitza

    2011-01-01

    In this work the exergy method is used to compare various methods for removal of NO x from waste (tail) gas released into the atmosphere from nitric acid production plants with respect to their overall environmental impact. Three basic methods for NO x abatement are analysed: selective catalytic reduction (SCR), non-selective catalytic reduction (NSCR) and extended absorption. The positive and negative effects and the net effect from the NO x abatement are calculated. The following exergy-based indicators are used for comparing the energy efficiency and the environmental impact of different treatment processes as a result from pollutants removal: reduction of the exergy of the emissions from the whole process route (ammonia and nitric acid production units); exergy of the additional emissions, arising as a result of the treatment process; total net reduction of the exergy consumption, Cumulative Energy Consumption (CEnC) and Cumulative Exergy Consumption (CExC) of natural resources as a result of the waste flows treatment. -- Highlights: → A thermodynamic study of the effects of three NO x abatement methods. → A comparison of the positive, negative and overall net effects of the three methods. → The best overall results are obtained for the extended absorption method. → The selective catalytic reduction method is estimated as unsatisfactory. → The non-selective catalytic reduction method could benefit from improved catalysts.

  20. Greenhouse gas emission and exergy analyses of an integrated trigeneration system driven by a solid oxide fuel cell

    International Nuclear Information System (INIS)

    Chitsaz, Ata; Mahmoudi, S. Mohammad S.; Rosen, Marc A.

    2015-01-01

    Exergy and greenhouse gas emission analyses are performed for a novel trigeneration system driven by a solid oxide fuel cell (SOFC). The trigeneration system also consists of a generator-absorber heat exchanger (GAX) absorption refrigeration system and a heat exchanger to produce electrical energy, cooling and heating, respectively. Four operating cases are considered: electrical power generation, electrical power and cooling cogeneration, electrical power and heating cogeneration, and trigeneration. Attention is paid to numerous system and environmental performance parameters, namely, exergy efficiency, exergy destruction rate, and greenhouse gas emissions. A maximum enhancement of 46% is achieved in the exergy efficiency when the SOFC is used as the primary mover for the trigeneration system compared to the case when the SOFC is used as a standalone unit. The main sources of irreversibility are observed to be the air heat exchanger, the SOFC and the afterburner. The unit CO 2 emission (in kg/MWh) is considerably higher for the case in which only electrical power is generated. This parameter is reduced by half when the system is operates in a trigeneration mode. - Highlights: • A novel trigeneration system driven by a solid oxide fuel cell is analyzed. • Exergy and greenhouse gas emission analyses are performed. • Four special cases are considered. • An enhancement of up to 46% is achieved in exergy efficiency. • The CO 2 emission drops to a relatively low value for the tri-generation case

  1. Exergy assessment and optimization of a cogeneration system based on a solid oxide fuel cell integrated with a Stirling engine

    International Nuclear Information System (INIS)

    Hosseinpour, Javad; Sadeghi, Mohsen; Chitsaz, Ata; Ranjbar, Faramarz; Rosen, Marc A.

    2017-01-01

    Highlights: • A novel cogeneration system driven by a SOFC and Stirling engine is proposed. • Energy and exergy assessments are reported of a novel cogeneration system. • The energy efficiency of the combined system can be achieved 75.88%. • The highest exergy destruction occurs in the air heat exchanger. - Abstract: A cogeneration system based on a methane-fed solid oxide fuel cell (SOFC) integrated with a Stirling engine is analyzed from the viewpoints of energy and exergy. The effects on the system performance are investigated of varying four key system parameters: current density, SOFC inlet temperature, compression ratio and regenerator effectiveness. The energy efficiency of the combined system is found to be 76.32% which is about 24.61% more than that of a stand-alone SOFC plant under the same conditions. Considering exergy efficiency as the only objective function, it is found that, as the SOFC inlet temperature increases, the exergy efficiency of the cogeneration system rises to an optimal value of 56.44% and then decreases. The second law analysis also shows that the air heat exchanger has the greatest exergy destruction rate of all system components. The cooling water of the engine also can supply the heating needs for a small home.

  2. Thermodynamic exergy analysis for small modular reactor in nuclear hybrid energy system

    Directory of Open Access Journals (Sweden)

    Boldon Lauren

    2016-01-01

    Full Text Available Small modular reactors (SMRs provide a unique opportunity for future nuclear development with reduced financial risks, allowing the United States to meet growing energy demands through safe, reliable, clean air electricity generation while reducing greenhouse gas emissions and the reliance on unstable fossil fuel prices. A nuclear power plant is comprised of several complex subsystems which utilize materials from other subsystems and their surroundings. The economic utility of resources, or thermoeconomics, is extremely difficult to analyze, particularly when trying to optimize resources and costs among individual subsystems and determine prices for products. Economics and thermodynamics cannot provide this information individually. Thermoeconomics, however, provides a method of coupling the quality of energy available based on exergy and the value of this available energy – “exergetic costs”. For an SMR exergy analysis, both the physical and economic environments must be considered. The physical environment incorporates the energy, raw materials, and reference environment, where the reference environment refers to natural resources available without limit and without cost, such as air input to a boiler. The economic environment includes market influences and prices in addition to installation, operation, and maintenance costs required for production to occur. The exergetic cost or the required exergy for production may be determined by analyzing the physical environment alone. However, to optimize the system economics, this environment must be coupled with the economic environment. A balance exists between enhancing systems to improve efficiency and optimizing costs. Prior research into SMR thermodynamics has not detailed methods on improving exergetic costs for an SMR coupled with storage technologies and renewable energy such as wind or solar in a hybrid energy system. This process requires balancing technological efficiencies and

  3. Exergy analysis of a coal/biomass co-hydrogasification based chemical looping power generation system

    International Nuclear Information System (INIS)

    Yan, Linbo; Yue, Guangxi; He, Boshu

    2015-01-01

    Power generation from co-utilization of coal and biomass is very attractive since this technology can not only save the coal resource but make sufficient utilization of biomass. In addition, with this concept, net carbon discharge per unit electric power generation can also be sharply reduced. In this work, a coal/biomass co-hydrogasification based chemical looping power generation system is presented and analyzed with the assistance of Aspen Plus. The effects of different operating conditions including the biomass mass fraction, R_b, the hydrogen recycle ratio, R_h_r, the hydrogasification pressure, P_h_g, the iron to fuel mole ratio, R_i_f, the reducer temperature, T_r_e, the oxidizer temperature, T_o_x, and the fuel utilization factor, U_f of the SOFC (solid oxide fuel cell) on the system operation results including the energy efficiency, η_e, the total energy efficiency, η_t_e, the exergy efficiency, η_e_x, the total exergy efficiency, η_t_e_x and the carbon capture rate, η_c_c, are analyzed. The energy and exergy balances of the whole system are also calculated and the corresponding Sankey diagram and Grassmann diagram are drawn. Under the benchmark condition, exergy efficiencies of different units in the system are calculated. η_t_e, η_t_e_x and η_c_c of the system are also found to be 43.6%, 41.2% and 99.1%, respectively. - Highlights: • A coal/biomass co-hydrogasification based chemical looping power generation system is setup. • Sankey and Grassmann diagrams are presented based on the energy and exergy balance calculations. • Sensitivity analysis is done to understand the system operation characteristics. • Total energy and exergy efficiencies of this system can be 43.6% and 41.2%, respectively. • About 99.1% of the carbon contained in coal and biomass can be captured in this system.

  4. A net-zero building application and its role in exergy-aware local energy strategies for sustainability

    International Nuclear Information System (INIS)

    Kılkış, Şiir

    2012-01-01

    Highlights: ► Net-zero exergy targets are put forth for more energy-sufficient buildings and districts. ► A premier building that is the first LEED Platinum building in Turkey exemplifies this target. ► The building integrates low-exergy measures with PV/BIPV, CHP, GSHP, solar collectors and TES. ► Two districts in the south heating network of Stockholm are compared with this technology bundle. ► Net-zero exergy targets are related to a re-structuring of an exergy-aware energy value chain. - Abstract: Based on two case studies, this paper explores the nexus of exergy, net-zero targets, and sustainable cities as a means of analyzing the role of exergy-aware strategies at the building and district level. The first case study is a premier building in Ankara that is ready to meet the net-zero exergy target. It is also the first building in Turkey to receive the highest Platinum rating in Leadership in Energy and Environmental Design. A net-zero exergy building (NZEXB) is a building that has an annual sum of net-zero exergy transfer across the building-district boundary. This new target is made possible by lowered annual exergy consumption, (AEXC), and increased on-site production from a bundle of sustainable energy technologies. The modeled results of the building indicate that the reduced AEXC of 60 kW h/m 2 yr is met with on-site production of 62 kW h/m 2 yr. On-site production includes PV and building integrated PV, a micro-wind turbine, combined heat and power, GSHP, and solar collectors. Diversified thermal energy storage tanks further facilitate the exergy supply to meet with the exergy demand. The results of this case study provide key lessons to structure an energy value chain that is more aware of exergy, which are up-scalable to the district level when the bundle of sustainable energy technologies is zoomed out across a larger spatial area. These key lessons are then compared with the second case study of two districts in the south heating network

  5. Application of the exergy index as ecological indicator of organically enrichment areas in the Mar Menor lagoon (south-eastern Spain)

    Energy Technology Data Exchange (ETDEWEB)

    Salas, F.; Marques, J.C. [University of Coimbra (Portugal). Dept. of Zoology; Marcos, C.; Perez-Ruzafa, A. [University of Murcia (Spain). Dept. of Ecology and and Hidrology

    2005-10-01

    The increase of stress induced changes in marine environments caused by different types of marine pollution made necessary the search for indicators that assist in assessing pollution effects at the community level. The main goals, with a view to an effective management, are the early detection and evaluation of environmental responses to pollution and to avoid or mitigate negative impacts that different uses may generate. Exergy has been considered as a promising indicator of ecosystem integrity, acquiring a considerable interest in the context of systems ecology. In this research we have tested the capability of exergy (both the exergy index and specific exergy) alongside other diversity indices (Shannon and Margalef indices) of distinguishing organically enriched areas in a Mediterranean coastal lagoon (El Mar Menor). Results show that the exergy index and specific exergy were able to give useful information on community structure, although they were not capable of distinguishing high and poor organically enriched areas or affected by any other type of pollution. Diversity indices were more sensitive to organic pollution. We may say that the exergy and specific exergy are still not applicable as the only ecological indicators in a generalized way in the field of environmental management. Therefore, they still require further application in a wider range of geographical areas and in different conditions in order to study more widely the properties of exergy as an ecological indicator. (author)

  6. Analysis of first and second law of an engine operating with Bio diesel from palm oil. Part 2: global exergy balance

    International Nuclear Information System (INIS)

    Agudelo, John R; Agudelo, Andres F; Cuadrado, Ilba G

    2006-01-01

    An exergy analysis of a diesel engine operating with palm oil bio diesel and its blends with diesel fuel is presented. Measurements were carried out in a test bench under stationary conditions varying engine load at constant speed and vice versa. The variation in exergy distribution and second law efficiency were obtained under several operating points. It was found that fuel type do not affect exergy distribution but it does affect the second law efficiency, which is slightly higher for diesel fuel. In contrast with energy balance results, exergy flows of exhaust and coolant streams are low, specially for the latter. This result is relevant for the implementation of cogeneration systems.

  7. Energy and Exergy Analysis and Optimization of Combined Heat and Power Systems. Comparison of Various Systems

    Directory of Open Access Journals (Sweden)

    Monica Costea

    2012-09-01

    Full Text Available The paper presents a comparison of various CHP system configurations, such as Vapour Turbine, Gas Turbine, Internal Combustion Engine, External Combustion Engine (Stirling, Ericsson, when different thermodynamic criteria are considered, namely the first law efficiency and exergy efficiency. Thermodynamic optimization of these systems is performed intending to maximize the exergy, when various practical related constraints (imposed mechanical useful energy, imposed heat demand, imposed heat to power ratio or main physical limitations (limited heat availability, maximum system temperature allowed, thermo-mechanical constraints are taken into account. A sensitivity analysis to model parameters is given. The results have shown that the various added constraints were useful for the design allowing to precise the influence of the model main parameters on the system design. Future perspective of the work and recommendations are stated.

  8. Basis of combined Pinch Technology and exergy analysis and its application to energy industry in Mexico

    International Nuclear Information System (INIS)

    Rodriguez T, M.A.; Rangel D, H.

    1994-01-01

    The energy industry scheme in Mexico has an enormous potential to do re adaptations with the intention of increase the efficiency in the use of energy. One of the most modern engineering tools to make such re adaptations consist in a suitable combination of analysis of exergy and Pinch technology. In this work, the basis of this new technology are presented, besides the potential areas of application in the Mexican energy industry are also considered. So then, it is shown that a combined analysis of exergy and Pinch technology (ACETP) is useful to analyze, in a conceptual and easy to understand way, systems that involve heat and power. The potential areas of application of ACETP are, cryogenic processes, power generation systems and cogeneration systems. (Author)

  9. Engineering design and exergy analyses for combustion gas turbine based power generation system

    International Nuclear Information System (INIS)

    Sue, D.-C.; Chuang, C.-C.

    2004-01-01

    This paper presents the engineering design and theoretical exergetic analyses of the plant for combustion gas turbine based power generation systems. Exergy analysis is performed based on the first and second laws of thermodynamics for power generation systems. The results show the exergy analyses for a steam cycle system predict the plant efficiency more precisely. The plant efficiency for partial load operation is lower than full load operation. Increasing the pinch points will decrease the combined cycle plant efficiency. The engineering design is based on inlet air-cooling and natural gas preheating for increasing the net power output and efficiency. To evaluate the energy utilization, one combined cycle unit and one cogeneration system, consisting of gas turbine generators, heat recovery steam generators, one steam turbine generator with steam extracted for process have been analyzed. The analytical results are used for engineering design and component selection

  10. Comparative study of the sources of exergy destruction on four North Sea oil and gas platforms

    DEFF Research Database (Denmark)

    Voldsund, Mari; Nguyen, Tuong-Van; Elmegaard, Brian

    2013-01-01

    temperatures and pressures, gas- and water-to-oil ratios in the feed, crude oil properties, product specifications and recovery strategies. These differences imply that some platforms naturally need less power for oil and gas processing than others. Reservoir properties and composition also vary over......In this paper, the oil and gas processing systems on four North Sea offshore platforms are reported and discussed. Sources of exergy destruction are identified and the findings for the different platforms are compared. Different platforms have different working conditions, such as reservoir...... the lifetime of an oil field, and to maintain the efficiency of an offshore platform is therefore challenging. In practice, variations in the process feed result in the use of control strategies such as anti-surge recycling, which cause additional power consumption and exergy destruction. For all four...

  11. Further optimization of a parallel double-effect organosilicon distillation scheme through exergy analysis

    International Nuclear Information System (INIS)

    Sun, Jinsheng; Dai, Leilei; Shi, Ming; Gao, Hong; Cao, Xijia; Liu, Guangxin

    2014-01-01

    In our previous work, a significant improvement in organosilicon monomer distillation using parallel double-effect heat integration between a heavies removal column and six other columns, as well as heat integration between methyltrichlorosilane and dimethylchlorosilane columns, reduced the total exergy loss of the currently running counterpart by 40.41%. Further research regarding this optimized scheme demonstrated that it was necessary to reduce the higher operating pressure of the methyltrichlorosilane column, which is required for heat integration between the methyltrichlorosilane and dimethylchlorosilane columns. Therefore, in this contribution, a challenger scheme is presented with heat pumps introduced separately from the originally heat-coupled methyltrichlorosilane and dimethylchlorosilane columns in the above-mentioned optimized scheme, which is the prototype for this work. Both schemes are simulated using the same purity requirements used in running industrial units. The thermodynamic properties from the simulation are used to calculate the energy consumption and exergy loss of the two schemes. The results show that the heat pump option further reduces the flowsheet energy consumption and exergy loss by 27.35% and 10.98% relative to the prototype scheme. These results indicate that the heat pumps are superior to heat integration in the context of energy-savings during organosilicon monomer distillation. - Highlights: • Combine the paralleled double-effect and heat pump distillation to organosilicon distillation. • Compare the double-effect with the heat pump in saving energy. • Further cut down the flowsheet energy consumption and exergy loss by 27.35% and 10.98% respectively

  12. Exergy and exergoeconomic analysis of a Compressed Air Energy Storage combined with a district energy system

    International Nuclear Information System (INIS)

    Bagdanavicius, Audrius; Jenkins, Nick

    2014-01-01

    Highlights: • CAES and CAES with thermal storage systems were investigated. • The potential for using heat generated during the compression stage was analysed. • CAES-TS has the potential to be used both as energy storage and heat source. • CAES-TS could be a useful tool for balancing overall energy demand and supply. - Abstract: The potential for using heat generated during the compression stage of a Compressed Air Energy Storage system was investigated using exergy and exergoeconomic analysis. Two Compressed Air Energy Storage systems were analysed: Compressed Air Energy Storage (CAES) and Compressed Air Energy Storage combined with Thermal Storage (CAES-TS) connected to a district heating network. The maximum output of the CAES was 100 MWe and the output of the CAES-TS was 100 MWe and 105 MWth. The study shows that 308 GW h/year of electricity and 466 GW h/year of fuel are used to generate 375 GW h/year of electricity. During the compression of air 289 GW h/year of heat is generated, which is wasted in the CAES and used for district heating in the CAES-TS system. Energy efficiency of the CAES system was around 48% and the efficiency of CAES-TS was 86%. Exergoeconomic analysis shows that the exergy cost of electricity generated in the CAES was 13.89 ¢/kW h, and the exergy cost of electricity generated in the CAES-TS was 11.20 ¢/kW h. The exergy cost of heat was 22.24 ¢/kW h in the CAES-TS system. The study shows that CAES-TS has the potential to be used both as energy storage and heat source and could be a useful tool for balancing overall energy demand and supply

  13. Exergy analysis of vapor compression refrigeration cycle with two-stage and intercooler

    Energy Technology Data Exchange (ETDEWEB)

    Kilic, Bayram [Mehmet Akif Ersoy University, Bucak Emin Guelmez Vocational School, Bucak, Burdur (Turkey)

    2012-07-15

    In this study, exergy analyses of vapor compression refrigeration cycle with two-stage and intercooler using refrigerants R507, R407c, R404a were carried out. The necessary thermodynamic values for analyses were calculated by Solkane program. The coefficient of performance, exergetic efficiency and total irreversibility rate of the system in the different operating conditions for these refrigerants were investigated. The coefficient of performance, exergetic efficiency and total irreversibility rate for alternative refrigerants were compared. (orig.)

  14. Energy utilization, carbon dioxide emission, and exergy loss in flavored yogurt production process

    International Nuclear Information System (INIS)

    Sorgüven, Esra; Özilgen, Mustafa

    2012-01-01

    This paper investigates the impact of food production processes on the environment in terms of energy and exergy utilization and carbon dioxide emission. There are three different energy utilization mechanisms in food production: Utilization of solar energy by plants to produce agricultural goods; feed consumption by herbivores to produce meat and milk; fossil fuel consumption by industrial processes to perform mixing, cooling, heating, etc. Production of strawberry-flavored yogurt, which involves these three mechanisms, is investigated here thermodynamically. Analysis starts with the cultivation of the ingredients and ends with the transfer of the final product to the market. The results show that 53% of the total exergy loss occurs during the milk production and 80% of the total work input is consumed during the plain yogurt making. The cumulative degree of perfection is 3.6% for the strawberry-flavored yogurt. This value can rise up to 4.6%, if renewable energy resources like hydropower and algal biodiesel are employed instead of fossil fuels. This paper points the direction for the development of new technology in food processing to decrease waste of energy and carbon dioxide accumulation in the atmosphere. -- Highlights: ► Energy and exergy utilization and carbon dioxide emission during strawberry-flavored yogurt production. ► Cumulative degree of perfection of strawberry-flavored yogurt is 3.6%. ► 53% of the total exergy loss occurs during the milk production. ► 80% of the total work input is consumed during the plain yogurt making.

  15. Exergy Based Performance Analysis of Double Flow Solar Air Heater with Corrugated Absorber

    OpenAIRE

    S. P. Sharma; Som Nath Saha

    2017-01-01

    This paper presents the performance, based on exergy analysis of double flow solar air heaters with corrugated and flat plate absorber. A mathematical model of double flow solar air heater based on energy balance equations has been presented and the results obtained have been compared with that of a conventional flat-plate solar air heater. The double flow corrugated absorber solar air heater performs thermally better than the flat plate double flow and conventional flat-plate solar air heate...

  16. Exergy analysis of a centralized air conditioning system for ice water

    International Nuclear Information System (INIS)

    Armas, Juan C; Lapido, Margarita J; Castellanos, Juan A

    2006-01-01

    An exergetic analysis of a centralized system of air conditioning, based on a vapor compression refrigeration cycle, appears in this article. The investigation allows to calculate the irreversibilities (exergy destruction) in the main components of the refrigeration cycle as well as to evaluate the sensitivity of this indicator when the operating conditions changes. As main result the most sensible components of the cycle are identified, information that will be useful in order to define strategies of operation focused to the power efficiency increase.

  17. Energy, Entropy and Exergy Concepts and Their Roles in Thermal Engineering

    OpenAIRE

    Dincer, Ibrahim; Cengel, Yunus A.

    2001-01-01

    Abstract: Energy, entropy and exergy concepts come from thermodynamics and are applicable to all fields of science and engineering. Therefore, this article intends to provide background for better understanding of these concepts and their differences among various classes of life support systems with a diverse coverage. It also covers the basic principles, general definitions and practical applications and implications. Some illustrative examples are presented to highlight the importance of t...

  18. Exergy analysis and parameter study on a novel auto-cascade Rankine cycle

    International Nuclear Information System (INIS)

    Bao, Junjiang; Zhao, Li

    2012-01-01

    A novel auto-cascade Rankine cycle (ARC) is proposed to reduce thermodynamics irreversibility and improve energy utilization. Like the Kalina cycle, the working fluid for the ARC is zeotropic mixture, which can improve the system efficiency due to the temperature slip that zeotropic mixtures exhibit during phase change. Unlike the Kalina cycle, two expanders are included in the ARC rather than a expander and a throttling valve in the Kalina cycle, which means more work can be obtained. Using the exhaust gas as the heat source and water as the heat sink, a program is written by Matlab 2010a to carry out exergy analysis and parameter study on the ARC. Results show that the R245fa mass fraction in the primary circuit exists an optimum value with respect to the minimum total cycle irreversibility. The largest exergy loss occurs in evaporator, followed by the superheater, condenser, regenerator and IHE (Internal heat exchanger). As the R245fa mass fraction increases, the exergy losses of different components vary diversely. With the evaporation pressure rises, the total cycle irreversibility decreases and work output increases. Separator temperature has a greater influence on the system performance than superheating temperature. Compared with ORC (organic Rankine cycle) and Kalina cycle in the literature, the ARC has proven to be thermodynamically better. -- Highlights: ► We have proposed a novel auto-cascade Rankine cycle (ARC) system. ► The zeotropic mixture Isopentane/R245fa is employed in this system. ► Exergy analysis and parameter study on the ARC are presented. ► Compared with ORC and Kalina cycle in the literature, the ARC has proven to be thermodynamically better.

  19. Energetic and Exergy Efficiency of a Heat Storage Unit for Building Heating

    International Nuclear Information System (INIS)

    Hazami, Mejdi; Kooli, Sami; Lazaar, Meriem; Farhat, Abdelhamid; Belghith, Ali

    2009-01-01

    This paper deals with a numerical and experimental investigation of a daily solar storage system conceived and built in Laboratoire de Maitrise des Technologies de l Energie (LMTE, Borj Cedria). This system consists mainly of the storage unit connected to a solar collector unit. The storage unit consists of a wooden case with dimension of 5 m 3 (5 m x 1m x 1m) filed with fin sand. Inside the wooden case was buried a network of a polypropylene capillary heat exchanger with an aperture area equal to 5 m 2 . The heat collection unit consisted of 5 m 2 of south-facing solar collector mounted at a 37 degree tilt angle. In order to evaluate the system efficiency during the charging period (during the day) and discharging period (during the night) an energy and exergy analyses were applied. Outdoor experiments were also carried out under varied environmental conditions for several consecutive days. Results showed that during the charging period, the average daily rates of thermal energy and exergy stored in the heat storage unit were 400 and 2.6 W, respectively. It was found that the net energy and exergy efficiencies in the charging period were 32 pour cent and 22 pour cent, respectively. During the discharging period, the average daily rates of the thermal energy and exergy recovered from the heat storage unit were 2 kW and 2.5 kW, respectively. The recovered heat from the heat storage unit was used for the air-heating of a tested room (4 m x 3 m x 3 m). The results showed that 30 pour cent of the total heating requirement of the tested room was obtained from the heat storage system during the whole night in cold seasons

  20. Exergy and Environmental Impact Assessment between Solar Powered Gas Turbine and Conventional Gas Turbine Power Plant

    OpenAIRE

    Rajaei, Ali; Barzegar Avval, Hasan; Eslami, Elmira

    2016-01-01

    Recuperator is a heat exchanger that is used in gas turbine power plants to recover energy from outlet hot gases to heat up the air entering the combustion chamber. Similarly, the combustion chamber inlet air can be heated up to temperatures up to 1000 (°C) by solar power tower (SPT) as a renewable and environmentally benign energy source. In this study, comprehensive comparison between these two systems in terms of energy, exergy, and environmental impacts is carried out. Thermodynamic simul...

  1. Proposing a novel combined cycle for optimal exergy recovery of liquefied natural gas

    Energy Technology Data Exchange (ETDEWEB)

    Salimpour, M.R.; Zahedi, M.A. [Isfahan University of Technology (Iran, Islamic Republic of). Department of Mechanical Engineering

    2012-08-15

    The effective utilization of the cryogenic exergy associated with liquefied natural gas (LNG) vaporization is important. In this paper, a novel combined power cycle is proposed which utilizes LNG in different ways to enhance the power generation of a power plant. In addition to the direct expansion in the appropriate expander, LNG is used as a low-temperature heat sink for a middle-pressure gas cycle which uses nitrogen as working fluid. Also, LNG is used to cool the inlet air of an open Brayton gas turbine cycle. These measures are accomplished to improve the exergy recovery of LNG. In order to analyze the performance of the system, the influence of several key parameters such as pressure ratio of LNG turbine, ratio of the mass flow rate of LNG to the mass flow rate of air, pressure ratio of different compressors, LNG pressure and inlet pressure of nitrogen compressor, on the thermal efficiency and exergy efficiency of the offered cycle is investigated. Finally, the proposed combined cycle is optimized on the basis of first and second laws of thermodynamics. (orig.)

  2. Exergy Analysis of a Subcritical Refrigeration Cycle with an Improved Impulse Turbo Expander

    Directory of Open Access Journals (Sweden)

    Zhenying Zhang

    2014-08-01

    Full Text Available The impulse turbo expander (ITE is employed to replace the throttling valve in the vapor compression refrigeration cycle to improve the system performance. An improved ITE and the corresponding cycle are presented. In the new cycle, the ITE not only acts as an expansion device with work extraction, but also serves as an economizer with vapor injection. An increase of 20% in the isentropic efficiency can be attained for the improved ITE compared with the conventional ITE owing to the reduction of the friction losses of the rotor. The performance of the novel cycle is investigated based on energy and exergy analysis. A correlation of the optimum intermediate pressure in terms of ITE efficiency is developed. The improved ITE cycle increases the exergy efficiency by 1.4%–6.1% over the conventional ITE cycle, 4.6%–8.3% over the economizer cycle and 7.2%–21.6% over the base cycle. Furthermore, the improved ITE cycle is also preferred due to its lower exergy loss.

  3. Nonlinear Slewing Spacecraft Control Based on Exergy, Power Flow, and Static and Dynamic Stability

    Science.gov (United States)

    Robinett, Rush D.; Wilson, David G.

    2009-10-01

    This paper presents a new nonlinear control methodology for slewing spacecraft, which provides both necessary and sufficient conditions for stability by identifying the stability boundaries, rigid body modes, and limit cycles. Conservative Hamiltonian system concepts, which are equivalent to static stability of airplanes, are used to find and deal with the static stability boundaries: rigid body modes. The application of exergy and entropy thermodynamic concepts to the work-rate principle provides a natural partitioning through the second law of thermodynamics of power flows into exergy generator, dissipator, and storage for Hamiltonian systems that is employed to find the dynamic stability boundaries: limit cycles. This partitioning process enables the control system designer to directly evaluate and enhance the stability and performance of the system by balancing the power flowing into versus the power dissipated within the system subject to the Hamiltonian surface (power storage). Relationships are developed between exergy, power flow, static and dynamic stability, and Lyapunov analysis. The methodology is demonstrated with two illustrative examples: (1) a nonlinear oscillator with sinusoidal damping and (2) a multi-input-multi-output three-axis slewing spacecraft that employs proportional-integral-derivative tracking control with numerical simulation results.

  4. Exergy analysis on industrial boiler energy conservation and emission evaluation applications

    Science.gov (United States)

    Li, Henan

    2017-06-01

    Industrial boiler is one of the most energy-consuming equipments in china, the annual consumption of energy accounts for about one-third of the national energy consumption. Industrial boilers in service at present have several severe problems such as small capacity, low efficiency, high energy consumption and causing severe pollution on environment. In recent years, our country in the big scope, long time serious fog weather, with coal-fired industrial boilers is closely related to the regional characteristics of high strength and low emissions [1]. The energy-efficient and emission-reducing of industry boiler is of great significance to improve China’s energy usage efficiency and environmental protection. Difference in thermal equilibrium theory is widely used in boiler design, exergy analysis method is established on the basis of the first law and second law of thermodynamics, by studying the cycle of the effect of energy conversion and utilization, to analyze its influencing factors, to reveal the exergy loss of location, distribution and size, find out the weak links, and a method of mining system of the boiler energy saving potential. Exergy analysis method is used for layer combustion boiler efficiency and pollutant emission characteristics analysis and evaluation, and can more objectively and accurately the energy conserving potential of the mining system of the boiler, find out the weak link of energy consumption, and improve equipment performance to improve the industrial boiler environmental friendliness.

  5. Exergetic evaluation on photovoltaic/thermal hybrid panel; Taiyoko netsu hybrid panel no exergy hyoka

    Energy Technology Data Exchange (ETDEWEB)

    Iwaki, H; Morita, Y; Fujisawa, T; Tani, T [Science University of Tokyo, Tokyo (Japan)

    1996-10-27

    The photovoltaic/thermal hybrid panel (PV/T) is an energy converter that was designed for the composite use of electricity and heat. In this paper, the validity of PV/T designed for trial was evaluated based on an exergetic theory. As the result of an experiment, the electric exergetic value of PV/T and PV is each 65.8 kWh/m{sup 2} and 58.6 kWh/m{sup 2}. The former is higher than the latter by 11.2%. The total exergetic value of PV/T is also 1.2 and 8.2 times as high as those of a PV and solar collector (SC), respectively. The calculation result of the optimum temperature operation showed that the exergetic value of PV/T is 3.1 times as high as the electric exergetic value. Therefore, the operation must be performed with the electric and thermal exergetic values set in a ratio of 3.1 to 1. In this paper, the operating mode is handled in which importance was more attached to the electric exergy than the thermal exergy. The flow rate of a heating medium on PV/T is not thus the flow control that maximizes the PV/T exergy. In the future, studies including these points will be promoted. 7 refs., 7 figs., 3 tabs.

  6. Exergy and Environmental Impact Assessment between Solar Powered Gas Turbine and Conventional Gas Turbine Power Plant

    Directory of Open Access Journals (Sweden)

    Ali Rajaei

    2016-01-01

    Full Text Available Recuperator is a heat exchanger that is used in gas turbine power plants to recover energy from outlet hot gases to heat up the air entering the combustion chamber. Similarly, the combustion chamber inlet air can be heated up to temperatures up to 1000 (°C by solar power tower (SPT as a renewable and environmentally benign energy source. In this study, comprehensive comparison between these two systems in terms of energy, exergy, and environmental impacts is carried out. Thermodynamic simulation of both cycles is conducted using a developed program in MATLAB environment. Exergetic performances of both cycles and their emissions are compared and parametric study is carried out. A new parameter (renewable factor is proposed to evaluate resources quality and measure how green an exergy loss or destruction or a system as a whole is. Nonrenewable exergy destruction and loss are reduced compared to GT with recuperator cycle by 34.89% and 47.41%, respectively. Reductions in CO2, NOx, and CO compared to GT with recuperator cycle by 49.92%, 66.14%, and 39.77%, respectively, are in line with renewable factor value of around 55.7 which proves the ability of the proposed green measure to evaluate and compare the cycles performances.

  7. Performance Optimization of Unglazed Nanofluid Photovoltaic/Thermal System: Energy and Exergy Analyses

    Directory of Open Access Journals (Sweden)

    M. Imtiaz Hussain

    2018-01-01

    Full Text Available The focus of this paper is to predict the transient response of a nanoengineered photovoltaic thermal (PV/T system in view of energy and exergy analyses. Instead of a circular-shaped receiver, a trapezoidal-shaped receiver is employed to increase heat transfer surface area with photovoltaic (PV cells for improvement of heat extraction and thus achievement of a higher PV/T system efficiency. The dynamic mathematical model is developed using MATLAB® software by considering real-time heat transfer coefficients. The proposed model is validated with experimental data from a previous study. Negligible discrepancies were found between measured and predicted data. The validated model was further investigated in detail using different nanofluids by dispersing copper oxide (CuO and aluminum oxide (Al2O3 in pure water. The overall performance of the nanoengineered PV/T system was compared to that of a PV/T system using water only, and optimal operating conditions were determined for maximum useful energy and exergy rates. The results indicated that the CuO/water nanofluid has a notable impact on the energy and exergy efficiencies of the PV/T system compared to that of Al2O3/water nanofluid and water only cases.

  8. Inferring community properties of benthic macroinvertebrates in streams using Shannon index and exergy

    Science.gov (United States)

    Nguyen, Tuyen Van; Cho, Woon-Seok; Kim, Hungsoo; Jung, Il Hyo; Kim, YongKuk; Chon, Tae-Soo

    2014-03-01

    Definition of ecological integrity based on community analysis has long been a critical issue in risk assessment for sustainable ecosystem management. In this work, two indices (i.e., Shannon index and exergy) were selected for the analysis of community properties of benthic macroinvertebrate community in streams in Korea. For this purpose, the means and variances of both indices were analyzed. The results found an extra scope of structural and functional properties in communities in response to environmental variabilities and anthropogenic disturbances. The combination of these two parameters (four indices) was feasible in identification of disturbance agents (e.g., industrial pollution or organic pollution) and specifying states of communities. The four-aforementioned parameters (means and variances of Shannon index and exergy) were further used as input data in a self-organizing map for the characterization of water quality. Our results suggested that Shannon index and exergy in combination could be utilized as a suitable reference system and would be an efficient tool for assessment of the health of aquatic ecosystems exposed to environmental disturbances.

  9. Exergy analysis on the irreversibility of rotary air preheater in thermal power plant

    International Nuclear Information System (INIS)

    Wang Hongyue; Zhao Lingling; Zhou Qiangtai; Xu Zhigao; Kim, Hyung Taek

    2008-01-01

    Energy recovery devices can have a substantial impact on process efficiency and their relevance to the problem of conservation of energy resources is generally recognized to be beyond dispute. One type of such a device, which is commonly used in thermal power plants and air conditioning systems, is the rotary air preheater. A major disadvantage of the rotary air preheater is that there is an unavoidable leakage due to carry over and pressure difference. There are gas streams involved in the heat transfer and mixing processes. There are also irreversibilities, or exergy destruction, due to mixing, pressure losses and temperature gradients. Therefore, the purpose of this research paper is based from the second law of thermodynamics, which is to build up the relationship between the efficiency of the thermal power plant and the total process of irreversibility in the rotary air preheater using exergy analysis. For this, the effects of the variation of the principal design parameters on the rotary air preheater efficiency, the exergy efficiency, and the efficiency of the thermal power plant are examined by changing a number of parameters of rotary air preheater. Furthermore, some conclusions are reached and recommendations are made so as to give insight on designing some optimal parameters

  10. Enhanced performance of solid oxide electrolysis cells by integration with a partial oxidation reactor: Energy and exergy analyses

    International Nuclear Information System (INIS)

    Visitdumrongkul, Nuttawut; Tippawan, Phanicha; Authayanun, Suthida; Assabumrungrat, Suttichai; Arpornwichanop, Amornchai

    2016-01-01

    Highlights: • Process design of solid oxide electrolyzer integrated with a partial oxidation reactor is studied. • Effect of key operating parameters of partial oxidation reactor on the electrolyzer performance is presented. • Exergy analysis of the electrolyzer process is performed. • Partial oxidation reactor can enhance the solid oxide electrolyzer performance. • Partial oxidation reactor in the process is the highest exergy destruction unit. - Abstract: Hydrogen production without carbon dioxide emission has received a large amount of attention recently. A solid oxide electrolysis cell (SOEC) can produce pure hydrogen and oxygen via a steam electrolysis reaction that does not emit greenhouse gases. Due to the high operating temperature of SOEC, an external heat source is required for operation, which also helps to improve SOEC performance and reduce operating electricity. The non-catalytic partial oxidation reaction (POX), which is a highly exothermic reaction, can be used as an external heat source and can be integrated with SOEC. Therefore, the aim of this work is to study the effect of operating parameters of non-catalytic POX (i.e., the oxygen to carbon ratio, operating temperature and pressure) on SOEC performance, including exergy analysis of the process. The study indicates that non-catalytic partial oxidation can enhance the hydrogen production rate and efficiency of the system. In terms of exergy analysis, the non-catalytic partial oxidation reactor is demonstrated to be the highest exergy destruction unit due to irreversible chemical reactions taking place, whereas SOEC is a low exergy destruction unit. This result indicates that the partial oxidation reactor should be improved and optimally designed to obtain a high energy and exergy system efficiency.

  11. Applicability of entropy, entransy and exergy analyses to the optimization of the Organic Rankine Cycle

    International Nuclear Information System (INIS)

    Zhu, Yadong; Hu, Zhe; Zhou, Yaodong; Jiang, Liang; Yu, Lijun

    2014-01-01

    Graphical abstract: Fig. 3a. Variations of the evaluation parameters with evaporation temperature in the case of prescribed hot and cold streams for R123. Fig. 3(a) indicates that among the seven parameters, the minimum entropy generation rate, exergy destruction rate, entransy efficiency, revised entropy generation number and the maximum entransy loss rate are corresponding to the maximum output power. However, the minimum entransy dissipation rate does not associate with the output power variation, it can be explained as follow: the entransy dissipation is one part of the entransy loss rate besides entransy variation (work entransy) or does not consider the influence of work output on the change of entransy. - Highlights: • Theories of entropy, exergy and entransy are applied to the optimization of the ORC. • Two commonly utilized working fluids – R123 and N-pentane are chosen for comparison. • Variable evaporation temperature, hot stream temperature and mass flow rate are considered. • 3-D coordinates are utilized to observe the global variation of parameters. • The concept of entransy loss rate is appropriate for all the cases discussed in this paper. - Abstract: Based on the theories of entropy, entransy and exergy, the concepts of entropy generation rate, revised entropy generation number, exergy destruction rate, entransy loss rate, entransy dissipation rate and entransy efficiency are applied to the optimization of the Organic Rankine Cycle. Cycles operating on R123 and N-pentane have been compared in three common cases which are variable evaporation temperature, hot stream temperature and hot stream mass flow rate. The optimization goal is to produce maximum output power. Some numerical analyses and simulations are presented, and the results show that when both the hot and cold stream conditions are fixed, all the entropy principle, the exergy theory, the entransy loss rate and the entransy efficiency are applicable to the optimization of the

  12. [Application of extended exergy method in driving mechanism and efficiency of regional eco-economy].

    Science.gov (United States)

    Fan, Xin Gang; Mi, Wen Bao; Hou, Jing Wei

    2017-01-01

    To analyze social-economic causes of the regional ecological degradation, and avoid such problems as the complex circulation network and difficulty to identify laws caused by extended exergy analysis (EEA) previously applied at the national scale, this paper reduced spatial scale to the county scale and took Pengyang County in Ningxia as an example. Eco-economic system in Peng-yang County was divided into seven interrelated sectors. The exergy value of circulations in the eco-economic system including materials, labor and capital were calculated respectively to analyze the extended exergy characteristics of the driving sectors, factors and paths and evaluate their ecological efficiency. The results showed that agriculture and households were the main driving sectors of the eco-economic system in Pengyang County. The average exergy value of 31 flow paths among the sectors was 0.80 PJ. There were only 8 flow paths whose exergy values were higher than the average value. Eco-economic system in Pengyang County development was driven by two continuous flow paths, labor output of the households sector and demands of the households sector supported by other sectors. The mineral resources were massively exploited, and then directly exported to the outside, which could not promote the local development from the inside, but, on the contrary, increase the ecological environment pressure because of the over-exploitation. The eco-efficiency of Pengyang County in 2014 was 68.1%, almost equivalent to the by-level of the national scale at home and abroad ten years ago, mainly because of the lower eco-efficiencies of the service sector and households sector. EEA had the advantage of networking and structuring, could specify the sectors, factors and driven paths, and break through the bottleneck of driving mechanism research of the eco-economic system. EEA had certain adaptability to explore the operational principle and optimal pattern of the regional eco-economic system. Compared

  13. Possibilities and consequences of the Total Cumulative Exergy Loss method in improving the sustainability of power generation

    International Nuclear Information System (INIS)

    Stougie, Lydia; Kooi, Hedzer J. van der

    2016-01-01

    Highlights: • The TCExL method can be applied to all kinds of technological systems. • All exergy losses during the lifetime of a technological system are considered. • The results of the TCExL method are independent of time and weighting factors. • Applying the TCExL method can improve the sustainability of power generation. • The system with the lowest TCExL score is not always economically favourable. - Abstract: It is difficult to decide which power generation system is the most sustainable when environmental, economic and social sustainability aspects are taken into account. Problems with conventional environmental sustainability assessment methods are that no consensus exists about the applied models and weighting factors and that exergy losses are not considered. Economic sustainability assessment methods do not lead to results that are independent of time because they are influenced by market developments, while social sustainability assessment methods suffer from the availability and qualitative or semi-quantitative nature of data. Existing exergy analysis methods do not take into account all exergy losses and/or are extended with factors or equations that are not commonly accepted. The new Total Cumulative Exergy Loss (TCExL) method is based on fundamental thermodynamic equations and takes into account all exergy losses caused by a technological system during its life cycle, i.e. internal exergy losses, exergy losses caused by emission abatement and exergy losses related to land use. The development of the TCExL method is presented as well as the application of this method and environmental, economic and social sustainability assessment methods to two case studies: power generation in combination with LNG evaporation and Fossil versus renewable energy sources for power generation. According to the results of the assessments, large differences exist between the environmental sustainability assessment and TCExL methods in the sense that different

  14. Exergy analysis of an integrated solid oxide fuel cell and organic Rankine cycle for cooling, heating and power production

    Science.gov (United States)

    Al-Sulaiman, Fahad A.; Dincer, Ibrahim; Hamdullahpur, Feridun

    The study examines a novel system that combined a solid oxide fuel cell (SOFC) and an organic Rankine cycle (ORC) for cooling, heating and power production (trigeneration) through exergy analysis. The system consists of an SOFC, an ORC, a heat exchanger and a single-effect absorption chiller. The system is modeled to produce a net electricity of around 500 kW. The study reveals that there is 3-25% gain on exergy efficiency when trigeneration is used compared with the power cycle only. Also, the study shows that as the current density of the SOFC increases, the exergy efficiencies of power cycle, cooling cogeneration, heating cogeneration and trigeneration decreases. In addition, it was shown that the effect of changing the turbine inlet pressure and ORC pump inlet temperature are insignificant on the exergy efficiencies of the power cycle, cooling cogeneration, heating cogeneration and trigeneration. Also, the study reveals that the significant sources of exergy destruction are the ORC evaporator, air heat exchanger at the SOFC inlet and heating process heat exchanger.

  15. Performance Assessment of a Hybrid Solar-Geothermal Air Conditioning System for Residential Application: Energy, Exergy, and Sustainability Analysis

    Directory of Open Access Journals (Sweden)

    Yasser Abbasi

    2016-01-01

    Full Text Available This paper investigates the performance of a ground source heat pump that is coupled with a photovoltaic system to provide cooling and heating demands of a zero-energy residential building. Exergy and sustainability analyses have been conducted to evaluate the exergy destruction rate and SI of different compartments of the hybrid system. The effects of monthly thermal load variations on the performance of the hybrid system are investigated. The hybrid system consists of a vertical ground source heat exchanger, rooftop photovoltaic panels, and a heat pump cycle. Exergetic efficiency of the solar-geothermal heat pump system does not exceed 10 percent, and most exergy destruction takes place in photovoltaic panel, condenser, and evaporator. Although SI of PV system remains constant during a year, SI of GSHP varies depending on cooling and heating mode. The results also show that utilization of this hybrid system can reduce CO2 emissions by almost 70 tons per year.

  16. Effect of reference environment on the turbofan engine with the aid of specific-exergy based methods

    Energy Technology Data Exchange (ETDEWEB)

    Turan, Onder [Anadolu University, School of Civil Aviation (Turkey)], e-mail: onderturan@anadolu.edu.tr

    2011-07-01

    Research is being carried out in the aeronautics sector on improving engine efficiency, and thereby increasing engine power, while reducing fuel consumption. The aim of this study was to determine the performance and efficiency of a turbofan engine and assess the impact of altitude on its performance. An exergetic analysis was carried out at different altitudes on a simple turbofan engine composed of inlet, fan, high pressure compressor and turbine, fan nozzle, compression chamber and exhaust. Exergy analysis allows the loss locations to be assessed and efficiencies evaluated in a meaningful way. Results showed that the turbofan engine has an efficiency of 25.68% to 28.11% and an exergy efficiency of 48.91% to 50.34%. It was found, moreover, that the combustion chamber was where the greatest efficiency losses occurred. This study permitted the exergy performance of a turbofan engine to be determined and identified the components where the greater losses occurred.

  17. Renewable and non-renewable exergy costs and CO2 emissions in the production of fuels for Brazilian transportation sector

    International Nuclear Information System (INIS)

    Flórez-Orrego, Daniel; Silva, Julio A.M. da; Velásquez, Héctor; Oliveira, Silvio de

    2015-01-01

    An exergy and environmental comparison between the fuel production routes for Brazilian transportation sector, including fossil fuels (natural gas, oil-derived products and hydrogen), biofuels (ethanol and biodiesel) and electricity is performed, and the percentage distribution of exergy destruction in the different units of the processing plants is characterized. An exergoeconomy methodology is developed and applied to properly allocate the renewable and non-renewable exergy costs and CO 2 emission cost among the different products of multiproduct plants. Since Brazilian electricity is consumed in the upstream processing stages of the fuels used in the generation thereof, an iterative calculation is used. The electricity mix comprises thermal (coal, natural gas and oil-fired), nuclear, wind and hydroelectric power plants, as well as bagasse-fired mills, which, besides exporting surplus electricity, also produce sugar and bioethanol. Oil and natural gas-derived fuels production and biodiesel fatty acid methyl-esters (FAME) derived from palm oil are also analyzed. It was found that in spite of the highest total unit exergy costs correspond to the production of biofuels and electricity, the ratio between the renewable to non-renewable invested exergy (cR/cNR) for those fuels is 2.69 for biodiesel, 4.39 for electricity, and 15.96 for ethanol, whereas for fossil fuels is almost negligible. - Highlights: • Total and non-renewable exergy costs of Brazilian transportation fuels are evaluated. • Specific CO 2 emissions in the production of Brazilian transportation fuels are determined. • Representative production routes for fossil fuels, biofuels and electricity are reviewed. • Exergoeconomy is used to distribute costs and emissions in multiproduct processes

  18. Application of artificial neural network method to exergy and energy analyses of fluidized bed dryer for potato cubes

    International Nuclear Information System (INIS)

    Azadbakht, Mohsen; Aghili, Hajar; Ziaratban, Armin; Torshizi, Mohammad Vahedi

    2017-01-01

    Drying the samples was performed in the inlet temperatures of 45, 50, and 55 °C, air velocity of 3.2, 6.8, and 9.1 m s"−"1, and bed depth of 1.5, 2.2, and 3 cm. The effects of these parameters were evaluated on energy utilization, energy efficiency and utilization ratio and exergy loss and efficiency. Furthermore, artificial neural network was employed in order to predict the energy and exergy parameters, and simulation of thermodynamic drying process was carried out, using the ANN created. A network was constructed from learning algorithms and transfer functions that could predict, with good accuracy, the exergy and energy parameters related to the drying process. The results revealed that energy utilization, efficiency, and utilization ratio increased by increasing the air velocity and depth of the bed; however, energy utilization and efficiency were augmented by increasing the temperature; additionally, energy utilization ratio decreased along with the rise in temperature. Also was found that exergy loss and efficiency improved by increasing the air velocity, temperature, and depth of the bed. Finally, the results of the statistical analyses indicated that neural networks can be utilized in intelligent drying process which has a large share of energy utilization in the food industry. - Highlights: • Energy utilization increased by increasing temperature, air velocity and depth of the bed. • Exergy loss increased with increasing the air velocity, temperature and depth of the bed. • Prediction by a trained neural network is faster than usual mathematical models. • ANN it is a suitable method to predict the energy and exergy in various driers.

  19. A framework for the exergy analysis of future transport pathways: Application for the United Kingdom transport system 2010–2050

    International Nuclear Information System (INIS)

    Byers, Edward A.; Gasparatos, Alexandros; Serrenho, André C.

    2015-01-01

    Exergy analysis has been used to quantify the historical resource use efficiency and environmental impact of transport systems. However, few exergy studies have explored future transport pathways. This study aims to, (a) develop a conceptual framework for the exergy analysis of multiple future transport and electricity pathways, (b) apply this framework to quantify future resource consumption and service delivery patterns, (c) discuss the policy-relevant results that exergy studies of future transport systems can offer. Multiple transport and electricity pathways developed by the UK Government are used to explore changes in energy use, useful work delivery and greenhouse gas emissions. In passenger transport, ambitious electrification results in a 20% increase of useful work delivery, whilst reducing GHG emissions and energy consumption by 65%. For freight, international shipping and aviation, smaller exergy efficiency improvements make useful work delivery and greenhouse gas emissions highly dependent on transport demand. Passenger transport electrification brings a step-change in useful work delivery, which if accompanied by low-carbon electricity, significantly reduces greenhouse gas emissions. The efficiency of low-carbon electricity systems is significant for useful work delivery, but not dominant across the scenarios explored. High penetration of renewables and electrified transport is the most resource-efficient combination in this context. - Highlights: • Develop an exergy analysis framework of future transport pathways and apply it to UK. • Electrification of personal transport brings step change in useful work delivery. • Efficiency of electricity supply becomes significant once transport is electrified. • High electrification increases useful work (+20%) and reduces emissions (−65%). • High penetration of renewables and electrified transport is most resource efficient

  20. Exergy evaluation of a typical 330 MW solar-hybrid coal-fired power plant in China

    International Nuclear Information System (INIS)

    Peng, Shuo; Wang, Zhaoguo; Hong, Hui; Xu, Da; Jin, Hongguang

    2014-01-01

    Highlights: • Exergy analysis of solar-hybrid coal-fired power plant has been processed. • EUD method is utilized to obtain detailed information on the exergy destruction in each process. • Off-design thermodynamic performances are discussed to identify the advantages. • Exergy destruction of several parts under varying solar radiation is examined. - Abstract: This study discusses the thermodynamic performance of a solar-hybrid coal-fired power plant that uses solar heat with temperature lower than 300 °C to replace the extracted steam from a steam turbine to heat the feed water. Through this process, the steam that was to be extracted can efficiently expand in the steam turbine to generate electricity. The flow rate of steam returning to the turbine retains only a small part of the main stream, allowing the steam turbine to run close to design conditions for all DNI. A solar-only thermal power plant without storage is also discussed to illustrate the advantages of a solar-hybrid coal-fired power plant. The off-design performances of both plants are compared based on the energy-utilization diagram method. The exergy destruction of the solar-hybrid coal-fired power plant is found to be lower than that of the solar-only thermal power plant. The comparison of two plants, which may provide detailed information on internal phenomena, highlights several advantages of the solar-hybrid coal-fired power plant in terms of off-design operation: lower exergy destruction in the solar feed water heater and steam turbine and higher exergy and solar-to-electricity efficiency. Preliminary technological economic performances of both plants are compared. The results obtained in this study indicate that a solar-hybrid coal-fired power plant could achieve better off-design performance and economic performance than a solar-only thermal power plant

  1. Energy and exergy analyses of medium temperature latent heat thermal storage with high porosity metal matrix

    International Nuclear Information System (INIS)

    Kumar, Ashish; Saha, Sandip K.

    2016-01-01

    Graphical abstract: I. Metal matrix is used as the thermal conductivity enhancers (TCE) in PCM-based TES. II. Time evolution second law analysis is evaluated for different porosities and pore diameters. III. Reduction in fluctuation in HTF temperature is significantly affected by the change in porosity (ε) shown in figure. IV. Maximum energy and exergy efficiencies are obtained for porosity of 0.85. V. Effect of pore diameter on first law and second law efficiencies is found to be marginal. - Abstract: Thermal energy storage system in a concentrating solar plant (CSP) reduces the gap between energy demand and supply caused by the intermittent behaviour of solar radiation. In this paper, detailed exergy and energy analyses of shell and tube type latent heat thermal storage system (LHTES) for medium temperature solar thermal power plant (∼200 °C) are performed to estimate the net useful energy during the charging and discharging period in a cycle. A commercial-grade organic phase change material (PCM) is stored inside the annular space of the shell and the heat transfer fluid (HTF) flows through the tubes. Thermal conductivity enhancer (TCE) in the form of metal matrix is embedded in PCM to augment heat transfer. A numerical model is developed to investigate the fluid flow and heat transfer characteristics using the momentum equation and the two-temperature non-equilibrium energy equation coupled with the enthalpy method to account for phase change in PCM. The effects of storage material, porosity and pore-diameter on the net useful energy that can be stored and released during a cycle, are studied. It is found that the first law efficiency of sensible heat storage system is less compared to LHTES. With the decrease in porosity, the first law and second law efficiencies of LHTES increase for both the charging and discharging period. There is no significant variation in energy and exergy efficiencies with the change in pore-diameter of the metal matrix.

  2. Energy and exergy analysis of a new ejector enhanced auto-cascade refrigeration cycle

    International Nuclear Information System (INIS)

    Yan, Gang; Chen, Jiaheng; Yu, Jianlin

    2015-01-01

    Highlights: • A new ejector enhanced auto-cascade refrigeration cycle using R134a/R23 is proposed. • The performance of new and basic cycles is compared by simulation method. • The new cycle outperforms the basic cycle in both energetic and exergy aspects. • Both cycles have optimum mixture compositions to obtain optimal performance. - Abstract: A new ejector enhanced auto-cascade refrigeration cycle using R134a/R23 refrigerant mixture is proposed in this paper. In the new cycle, an ejector is used to recover part of the work that would otherwise be lost in the throttling processes. The performance comparison between the new cycle and a basic auto-cascade refrigeration cycle is carried out based on the first and second laws of thermodynamics. The simulation results show that both the coefficient of performance and exergy efficiency of the new cycle can be improved by 8.42–18.02% compared with those of the basic cycle at the same operation conditions as the ejector has achieved pressure lift ratios of 1.12–1.23. It is found that in the new cycle, the highest exergy destruction occurs in the compressor followed by the condenser, cascade condenser, expansion valve, ejector and evaporator. The effect of some main parameters on the cycle performance is further investigated. The results show that for the new cycle, the achieved performance improvement over the basic cycle is also dependent on the mixture composition and the vapor quality at the condenser outlet. The coefficient of performance improvement of the new cycle over the basic cycle degrades with increasing vapor quality. In addition, there exists an optimum mixture composition to obtain the maximum coefficient of performance for the new cycle when other operation conditions are given. The optimum mixture composition of both cycles may be fixed at about 0.5 under the given evaporating temperature.

  3. Low temperature techniques for natural gas purification and LNG production: An energy and exergy analysis

    International Nuclear Information System (INIS)

    Baccanelli, Margaret; Langé, Stefano; Rocco, Matteo V.; Pellegrini, Laura A.; Colombo, Emanuela

    2016-01-01

    Highlights: • Low-temperature processes for of high CO_2 content natural gas have been modelled. • Energy and exergy analyses have been performed. • The Dual Pressure distillation scheme has the best thermodynamic performances. • There is a synergy between cryogenic natural gas purification and LNG production. - Abstract: Due to the rapid increase of the World’s primary energy demand of the last decades, low-temperature processes for the purification of natural gas streams with high carbon dioxide content has gained interest, since they allow to make profitable exploitation of low-quality gas reserves. Low temperature purification processes allow the direct production of a methane stream at high purity and at low-temperature, suitable conditions for the direct synergistic integration with natural gas cryogenic liquefaction processes, while CO_2 is obtained in liquid phase and under pressure. In this way, it can be pumped for transportation, avoiding significant compression costs as for classical CO_2 capture units (where carbon dioxide is discharged in gas phase and at atmospheric pressure), and further uses such as Enhanced Oil Recovery (EOR) or underground storage. In this paper, the three most common natural gas low-temperature purification techniques have been modelled and their performances have been evaluated through energy and exergy analyses. Specifically, the dual pressure low-temperature distillation process, the anti-sublimation process and a hybrid configuration have been considered. It is found that the dual pressure low-temperature distillation scheme reach the highest thermodynamic performances, resulting in the best values of exergy efficiency and equivalent methane requirements with respect to the other configurations. This is mainly due to the distributed temperature profile along a distillation column, resulting in a less irreversible heat exchanging process.

  4. Comparative study of two weir type cascade solar stills with and without PCM storage using energy and exergy analysis

    International Nuclear Information System (INIS)

    Sarhaddi, Faramarz; Farshchi Tabrizi, Farshad; Aghaei Zoori, Halimeh; Mousavi, Seyed Amir Hossein Seyed

    2017-01-01

    Highlights: • Performance evaluation of cascade solar stills with PCM storage is carried out. • Model of cascade solar still is weir type. • Present study is based on numerical simulation. • Effect of operating parameters is studies on yield, energy and exergy efficiencies. - Abstract: In this paper, the comparative study of energy and exergy performance of two weir type cascade solar stills with and without PCM storage in sunny and semi-cloudy days is carried out. The governing equations of energy analysis include a set of nonlinear equations which is obtained by writing energy balance for the various components of a solar still (i.e. glass cover, brackish water, absorber plate, phase change materials). A detailed exergy analysis is carried out and various irreversibility rates in the solar still system and its exergy efficiency are introduced. In order to solve the governing equations a computer simulation program is developed. The results of a numerical simulation of the present study are in good agreement with the experimental data of previous literatures. The numerical results of the present study show that the energy and exergy performance of solar still without PCM storage is better than the solar still with PCM storage in sunny days. On the other hand, the solar still with PCM storage is preferred for semi-cloudy days due to its better energy and exergy performance. The maximum value of the energy and exergy efficiencies of the solar still without PCM for a typical sunny day are 76.69% and 6.53%, respectively. While, the maximum energy and exergy efficiencies of the solar still with PCM for a sample semi-cloudy day are 74.35% and 8.59%, respectively. Furthermore, it is observed that the highest irreversibility rate belongs to the absorber plate and its value for the solar still without PCM on typical sunny day and the solar still with PCM on semi-cloudy days is 83.1% and 78.8% of the whole of system irreversibility rates, respectively. Whereas, the

  5. Exergy and economic analysis of organic rankine cycle hybrid system utilizing biogas and solar energy in rural area of China

    DEFF Research Database (Denmark)

    Zhao, Chunhua; Zheng, Siyu; Zhang, Ji

    2017-01-01

    circuits. The cogeneration supplied the power to the air-condition in summer condition and hot water, which is heated in the condenser, in winter condition. The system performance under the subcritical pressures has been assessed according to the energy-exergy and economic analysis with the organic working......℃. The exergy efficiency of organic Rankine cycle (ORC) system increases from 35.2% to 38.2%. Moreover, an economic analysis of the system is carried out. The results demonstrate that the profits generated from the reduction of biogas fuel and electricity consumption can lead to a significant saving, resulting...

  6. Modeling of a Novel Low-Exergy System for Office Buildings with Modelica

    DEFF Research Database (Denmark)

    Maccarini, Alessandro; Afshari, Alireza; Hultmark, Göran

    2016-01-01

    This paper aims to investigate the thermal behavior of a novel low-exergy system for office buildings. The main characteristic of the system is its ability to provide simultaneous heating and cooling by operating one water circuit. Inlet water temperature of about 22 °C is delivered to all...... the thermal zones in the building, no matter whether a single zone needs heating or cooling. This approach clearly differs from conventional systems where simultaneous heating and cooling is provided by two separated water circuits. A detailed model of the novel system was developed with Dymola, a modeling...

  7. Distillation of a Complex Mixture. Part II: Performance Analysis of a Distillation Column Using Exergy

    Directory of Open Access Journals (Sweden)

    Ouadjenia Fatima

    2007-09-01

    Full Text Available To analyze the performance of the separation process, we have introduced thethermodynamic concept of exergy through the exergetic efficiency of the column. Thesimulation results show that the exergetic output is relatively low and that the producedirreversibility fluxes are distributed throughout the whole column in a non-uniform manner.They are particularly significant in the condenser, boiler and tray feed. The influence of thevarious operating parameters (temperature, concentration and irreversibility in both sectionsof the column is also established. To emphasize the results, the relation in equation 17, ispresented graphically to evaluate the cumulative irreversibilities from the overhead to thebottom. This presentation is equivalent to the Grassmann diagram.

  8. Advanced exergy analysis of a R744 booster refrigeration system with parallel compression

    DEFF Research Database (Denmark)

    Gullo, Paride; Elmegaard, Brian; Cortella, Giovanni

    2016-01-01

    efficiencies of all the chosen compressors were extrapolated from some manufactures' data and appropriated optimization procedures of the performance of the investigated solution were implemented.According to the results associated with the conventional exergy evaluation, the gas cooler/condenser, the HS (high...... the real achievable improvements. The avoidable irreversibilities of the HS compressor and that of the MT evaporator were mainly and completely endogenous, respectively. On the other hand, the gas cooler/condenser could be predominantly improved by decreasing the inefficiencies of the MT evaporator...

  9. Exergy analysis and optimisation of a marine molten carbonate fuel cell system in simple and combined cycle configuration

    International Nuclear Information System (INIS)

    Dimopoulos, George G.; Stefanatos, Iason C.; Kakalis, Nikolaos M.P.

    2016-01-01

    Highlights: • Process modelling and optimisation of an integrated marine MCFC system. • Component-level and spatially distributed exergy analysis and balances. • Optimal simple cycle MCFC system with 45.5% overall exergy efficiency. • Optimal combined cycle MCFC system with 60% overall exergy efficiency. • Combined cycle MCFC system yields 30% CO_2 relative emissions reduction. - Abstract: In this paper we present the exergy analysis and design optimisation of an integrated molten carbonate fuel cell (MCFC) system for marine applications, considering waste heat recovery options for additional power production. High temperature fuel cells are attractive solutions for marine energy systems, as they can significantly reduce gaseous emissions, increase efficiency and facilitate the introduction of more environmentally-friendly fuels, like LNG and biofuels. We consider an already installed MCFC system onboard a sea-going vessel, which has many tightly integrated sub-systems and components: fuel delivery and pre-reforming, internal reforming sections, electrochemical conversion, catalytic burner, air supply and high temperature exhaust gas. The high temperature exhaust gasses offer significant potential for heat recovery that can be directed into both covering the system’s auxiliary heat requirements and power production. Therefore, an integrated systems approach is employed to accurately identify the true sources of losses in the various components and to optimise the overall system with respect to its energy efficiency, taking into account the various trade-offs and subject to several constraints. Here, we present a four-step approach: a. dynamic process models development of simple and combined-cycle MCFC system; b. MCFC components and system models calibration via onboard MCFC measurements; c. exergy analysis, and d. optimisation of the simple and combined-cycle systems with respect to their exergetic performance. Our methodology is based on the

  10. Nature of macroeconomic equilibrium and driving force of economic cycles in the light of difference between money and exergy forms in cost estimations

    Energy Technology Data Exchange (ETDEWEB)

    Bandura, A.V. [National Politechnical Univ., Kiev (Ukraine); Brodianskii, V.M. [Moscow Power Engineering Inst. Technical Univ. (Russian Federation)

    1996-11-01

    The main problem of exergy application directly in economic analysis is to find valid correlation between money-based cost and exergy based one (including exergy expenses of labour) and to define exergy cost as an economic category among the existing traditional economic ones. The present report is aimed to search the way for this macroeconomic problems` solution. It is demonstrated that exergy-based cost can be recalculated in a monetary form using a coefficient, defined as a ratio between money supply and the total exergy of all natural resources involved in production process, i.e. as a ratio between monetary and exergy bases. The difference between `natural` and current prices (P) can be used directly both for general quantitative characteristics of an economic cycles driving force and for control of market relationship imperfection. It is shown that for the period of time with the positive P, that is, current price is lower than a `natural` one, the recoveries in business cycles are observed. For the period of time with the negative P, that is, current price is higher than a natural one, economic recessions are observed. The moment of time when P = 0 corresponds to the turning point of a business cycle. In such a way the possibility to predict the turning points of business cycles is demonstrated. 14 refs, 2 figs, 2 tabs

  11. Theoretical energy and exergy analyses of solar assisted heat pump space heating system

    Directory of Open Access Journals (Sweden)

    Atmaca Ibrahim

    2014-01-01

    Full Text Available Due to use of alternative energy sources and energy efficient operation, heat pumps come into prominence in recent years. Especially in solar-assisted heat pumps, sizing the required system is difficult and arduous task in order to provide optimum working conditions. Therefore, in this study solar assisted indirect expanded heat pump space heating system is simulated and the results of the simulation are compared with available experimental data in the literature in order to present reliability of the model. Solar radiation values in the selected region are estimated with the simulation. The case study is applied and simulation results are given for Antalya, Turkey. Collector type and storage tank capacity effects on the consumed power of the compressor, COP of the heat pump and the overall system are estimated with the simulation, depending on the radiation data, collector surface area and the heating capacity of the space. Exergy analysis is also performed with the simulation and irreversibility, improvement potentials and exergy efficiencies of the heat pump and system components are estimated.

  12. Liquid air fueled open-closed cycle Stirling engine and its exergy analysis

    International Nuclear Information System (INIS)

    Wang, Jia; Xu, Weiqing; Ding, Shuiting; Shi, Yan; Cai, Maolin; Rehman, Ali

    2015-01-01

    An unconventional Stirling engine is proposed and its theoretical analysis is performed. The engine belongs to a “cryogenic heat engine” that is fueled by cryogenic medium. Conventional “cryogenic heat engine” employs liquid air as a pressure source, but disregards its heat-absorbing ability. Therefore, its efficiency can only be improved by increasing vapor pressure, accordingly increasing the demand on pressure resistance and sealing. In the proposed engine, a closed cycle structure of Stirling engine is added to combine with the open cycle structure of a conventional cryogenic heat engine to achieve high efficiency and simplicity by utilizing the heat-absorbing ability of liquid air. Besides, the theoretical analysis of the proposed engine is performed. The Schmidt theory is modified to model temperature variation in the cold space of the engine, and irreversible characteristic of regenerator is incorporated in the thermodynamic model. The modeling results show that under the same working pressure, the efficiency of the proposed engine is potentially higher than that of conventional ones and to achieve the same efficiency, the working pressure could be lower with the new mechanism. Composition of exergy loss in the proposed engine is analyzed. - Highlights: • Cryogenic energy is better exploited by the open-closed cycle Stirling mechanism. • The Schmidt theory is modified to model temperature variation. • Irreversible characteristics are incorporated in the thermodynamic model. • Composition of exergy loss in proposed engine is analyzed.

  13. Energy and Exergy Analysis of Ocean Compressed Air Energy Storage Concepts

    Directory of Open Access Journals (Sweden)

    Vikram C. Patil

    2018-01-01

    Full Text Available Optimal utilization of renewable energy resources needs energy storage capability in integration with the electric grid. Ocean compressed air energy storage (OCAES can provide promising large-scale energy storage. In OCAES, energy is stored in the form of compressed air under the ocean. Underwater energy storage results in a constant-pressure storage system which has potential to show high efficiency compared to constant-volume energy storage. Various OCAES concepts, namely, diabatic, adiabatic, and isothermal OCAES, are possible based on the handling of heat in the system. These OCAES concepts are assessed using energy and exergy analysis in this paper. Roundtrip efficiency of liquid piston based OCAES is also investigated using an experimental liquid piston compressor. Further, the potential of improved efficiency of liquid piston based OCAES with use of various heat transfer enhancement techniques is investigated. Results show that adiabatic OCAES shows improved efficiency over diabatic OCAES by storing thermal exergy in thermal energy storage and isothermal OCAES shows significantly higher efficiency over adiabatic and diabatic OCAES. Liquid piston based OCAES is estimated to show roundtrip efficiency of about 45% and use of heat transfer enhancement in liquid piston has potential to improve roundtrip efficiency of liquid piston based OCAES up to 62%.

  14. Optimal selection among different domestic energy consumption patterns based on energy and exergy analysis

    International Nuclear Information System (INIS)

    Lu, S.; Wu, J.Y.

    2010-01-01

    In China market, people have many choices for air conditioning of their apartments, including heat-pump systems or gas-fired boilers for heating and air conditioners for cooling. Domestic hot water is usually provided by domestic water heaters making use of electricity or natural gas, which are known for their great energy costs. These systems consume much energy and increase the total cost of required domestic energy. A novel system combining heat pump with water heater is proposed in this paper, and it is named domestic energy system. The system can realize the provision of space heating, cooling and domestic hot water throughout a year. Based on different types of air conditioners, space heating equipments and water heaters, domestic energy consumption patterns are concluded to be eight categories. This study describes and compares the eight domestic energy consumption patterns by economic analysis and prime energy analysis method. Results show that the domestic energy system can provide good economy and save energy significantly. Furthermore, exergy analysis method is employed to compare the exergy efficiencies of different energy consumption systems. The results show that the domestic energy system has the highest energy conversion efficiency and can make remarkable contribution to social energy saving.

  15. Preliminary Assessment of Noise Pollution Prevention in Wind Turbines Based on an Exergy Approach

    Directory of Open Access Journals (Sweden)

    Ofelia A. Jianu

    2017-06-01

    Full Text Available Most existing methods for energy transformation and use are inadvertently contaminating our watersupplies, releasing greenhouse gasses into the atmosphere, emitting compounds that diminish the earth'sprotective blanket of ozone, and depleting the earth's crust of natural resources. As a result, scientists andengineers are increasingly pursuing sustainable technologies so that costs associated with global warmingcan be minimized and adverse impact on living organisms can be prevented. A promising sustainablemethod is to harness energy from the wind via wind turbines. However, the noise generated by wind turbinesproves to be one of the most significant hindrances to the extensive use of wind turbines. In this study,noise generation produced by flow over objects is investigated to characterize the noise generated due toflow-structure interaction and aeroacoustics. As a benchmark, flow over a cylinder has been chosen for thisstudy, with the aim of correlating three main characteristics in noise generation. Hence, the generated soundpressure level, exergy destroyed and the normal flow velocity (∪ ∞ are employed to characterize the systemin order to relate the exergy destruction to the noise generated in the flow. The correlation has the potentialto be used in wind turbine designs to minimize noise pollution due to aerodynamic noise.

  16. The exergy underground coal gasification technology for power generation and chemical applications

    Energy Technology Data Exchange (ETDEWEB)

    Blinderman, M.S. [Ergo Exergy Technologies Inc., Montreal, PQ (Canada)

    2006-07-01

    Underground coal gasification (UCG) is a gasification process carried out in non-mined coal seams using injection and production wells drilled from the surface, converting coal in situ into a product gas usable for chemical processes and power generation. The UCG process developed, refined and practised by Ergo Exergy Technologies is called the Exergy UCG Technology or {epsilon}UCG{trademark} technology. This paper describes the technology and its applications. The {epsilon}UCG technology is being applied in numerous power generation and chemical projects worldwide, some of which are described. These include power projects in South Africa, India, Pakistan and Canada, as well as chemical projects in Australia and Canada. A number of {epsilon}UCG{trademark} based industrial projects are now at a feasibility usage in India, New Zealand, USA and Europe. An {epsilon}UCG{trademark} IGCC power plant will generate electricity at a much lower cost than existing fossil fuel power plants. CO{sub 2} emissions of the plant can be reduced to a level 55% less than those of a supercritical coal-fired plant and 25% less than the emissions of NG CC. 10 refs., 8 figs.

  17. Exergy analysis of an ejector-absorption heat transformer using artificial neural network approach

    International Nuclear Information System (INIS)

    Soezen, Adnan; Arcaklioglu, Erol

    2007-01-01

    This paper proposes artificial neural networks (ANNs) technique as a new approach to determine the exergy losses of an ejector-absorption heat transformer (EAHT). Thermodynamic analysis of the EAHT is too complex due to complex differential equations and complex simulations programs. ANN technique facilitates these complicated situations. This study is considered to be helpful in predicting the exergetic performance of components of an EAHT prior to its setting up in a thermal system where the working temperatures are known. The best approach was investigated using different algorithms with developed software. The best statistical coefficient of multiple determinations (R 2 -value) for training data equals to 0.999715, 0.995627, 0.999497, and 0.997648 obtained by different algorithms with seven neurons for the non-dimensional exergy losses of evaporator, generator, absorber and condenser, respectively. Similarly these values for testing data are 0.999774, 0.994039, 0.999613 and 0.99938, respectively. The results show that this approach has the advantages of computational speed, low cost for feasibility, rapid turnaround, which is especially important during iterative design phases, and easy of design by operators with little technical experience

  18. A critical review on energy, exergy, exergoeconomic and economic (4-E analysis of thermal power plants

    Directory of Open Access Journals (Sweden)

    Ravinder Kumar

    2017-02-01

    Full Text Available The growing energy supply, demand has created an interest towards the plant equipment efficiency and the optimization of existing thermal power plants. Also, a thermal power plant dependency on fossil fuel makes it a little bit difficult, because of environmental impacts has been always taken into consideration. At present, most of the power plants are going to be designed by the energetic performance criterion which is based on the first law of thermodynamics. Sometimes, the system energy balance is not sufficient for the possible finding of the system imperfections. Energy losses taking place in a system can be easily determined by using exergy analysis. Hence, it is a powerful tool for the measurement of energy quality, thereby helps to make complex thermodynamic systems more efficient. Nowadays, economic optimization of plant is also a big problem for researchers because of the complex nature. At a viewpoint of this, a comprehensive literature review over the years of energy, exergy, exergoeconomic and economic (4-E analysis and their applications in thermal power plants stimulated by coal, gas, combined cycle and cogeneration system have been done thoroughly. This paper is addressed to those researchers who are doing their research work on 4-E analysis in various thermal power plants. If anyone extracts an idea for the development of the concept of 4-E analysis using this article, we will achieve our goal. This review also indicates the scope of future research in thermal power plants.

  19. Energy and exergy analyses of Photovoltaic/Thermal flat transpired collectors: Experimental and theoretical study

    International Nuclear Information System (INIS)

    Gholampour, Maysam; Ameri, Mehran

    2016-01-01

    Highlights: • A Photovoltaic/Thermal flat transpired collector was theoretically and experimentally studied. • Performance of PV/Thermal flat transpired plate was evaluated using equivalent thermal, first, and second law efficiencies. • According to the actual exergy gain, a critical radiation level was defined and its effect was investigated. • As an appropriate tool, equivalent thermal efficiency was used to find optimum suction velocity and PV coverage percent. - Abstract: PV/Thermal flat transpired plate is a kind of air-based hybrid Photovoltaic/Thermal (PV/T) system concurrently producing both thermal and electrical energy. In order to develop a predictive model, validate, and investigate the PV/Thermal flat transpired plate capabilities, a prototype was fabricated and tested under outdoor conditions at Shahid Bahonar University of Kerman in Kerman, Iran. In order to develop a mathematical model, correlations for Nusselt numbers for PV panel and transpired plate were derived using CFD technique. Good agreement was obtained between measured and simulated values, with the maximum relative root mean square percent deviation (RMSE) being 9.13% and minimum correlation coefficient (R-squared) 0.92. Based on the critical radiation level defined in terms of the actual exergy gain, it was found that with proper fan and MPPT devices, there is no concern about the critical radiation level. To provide a guideline for designers, using equivalent thermal efficiency as an appropriate tool, optimum values for suction velocity and PV coverage percent under different conditions were obtained.

  20. Multidimensional modeling of the effect of Exhaust Gas Recirculation (EGR) on exergy terms in an HCCI engine fueled with a mixture of natural gas and diesel

    International Nuclear Information System (INIS)

    Jafarmadar, Samad; Nemati, Peyman; Khodaie, Rana

    2015-01-01

    Highlights: • The exergy efficiency decreases by 41.3%. • The irreversibility increases by 46.80%. • The cumulative heat loss exergy decreases by 68.10%. • The cumulative work exergy decreases by 63.4%. • The exhaust losses exergy increases by 28.79%. - Abstract: One of the most important issues in HCCI engines is auto-ignition timing control. EGR introduction into intake charge can be a method to control combustion phasing and its duration. In the current study, a FORTRAN-based code which includes 10 species (O_2, N_2, H_2O, CO_2, CO, H_2, OH, O, N, NO) associated with combustion products was employed to study the exergy analysis in a dual fuel (natural gas + diesel) HCCI engine at four EGR (exhaust gas recirculation) mass fractions (0%, 10%, 20%, and 30%) while the diesel fuel amount was held constant. In order to achieve this task, a 3-D CFD code was employed to model the energy balance during a closed cycle of running engine simulation. Moreover, an efficient Extend Coherent Flame Model-Three Zone model (ECFM-3Z) method was employed to analyze the combustion process. With crank positions at different EGR mass fractions, the exergy terms were identified and calculated separately. It was found that as EGR mass fraction increased from 0% to 30% (in 10% increment steps), exergy efficiency decreased from 48.9% to 28.7%. Furthermore, with the change in EGR mass fraction, the cumulative heat loss exergy decreased from 10.1% to 5.64% of mixture fuels chemical exergy.

  1. Impact of Ambient Conditions of Arab Gulf Countries on the Performance of Gas Turbines Using Energy and Exergy Analysis

    Directory of Open Access Journals (Sweden)

    Saleh S. Baakeem

    2017-01-01

    Full Text Available In this paper, energy and exergy analysis of typical gas turbines is performed using average hourly temperature and relative humidity for selected Gulf cities located in Saudi Arabia, Kuwait, United Arab Emirates, Oman, Bahrain and Qatar. A typical gas turbine unit of 42 MW is considered in this study. The electricity production, thermal efficiency, fuel consumption differences between the ISO conditions and actual conditions are determined for each city. The exergy efficiency and exergy destruction rates for the gas turbine unit and its components are also evaluated taking ISO conditions as reference conditions. The results indicate that the electricity production losses occur in all cities during the year, except in Dammam and Kuwait for the period between November and March. During a typical day, the variation of the power production can reach 4 MW. The rate of exergy destruction under the combined effect of temperature and humidity is significant in hot months reaching a maximum of 12 MW in July. The presented results show also that adding inlet cooling systems to the existing gas turbine units could be justified in hot periods. Other aspects, such as the economic and environmental ones, should also be investigated.

  2. Exergy analysis of biomass-to-synthetic natural gas (SNG) process via indirect gasification of various biomass feedstock

    NARCIS (Netherlands)

    Vitasari, C.R.; Jurascik, M.; Ptasinski, K.J.

    2011-01-01

    This paper presents an exergy analysis of SNG production via indirect gasification of various biomass feedstock, including virgin (woody) biomass as well as waste biomass (municipal solid waste and sludge). In indirect gasification heat needed for endothermic gasification reactions is produced by

  3. Energy and Exergy Analysis of Kalina Cycle for the Utilization of Waste Heat in Brine Water for Indonesian Geothermal Field

    Directory of Open Access Journals (Sweden)

    Nasruddin Nasruddin

    2015-04-01

    Full Text Available The utilization of waste heat in a power plant system—which would otherwise be released back to the environment—in order to produce additional power increases the efficiency of the system itself. The purpose of this study is to present an energy and exergy analysis of Kalina Cycle System (KCS 11, which is proposed to be utilized to generate additional electric power from the waste heat contained in geothermal brine water available in the Lahendong Geothermal power plant site in North Sulawesi, Indonesia. A modeling application on energy and exergy system is used to study the design of thermal system which uses KCS 11. To obtain the maximum power output and maximum efficiency, the system is optimized based on the mass fraction of working fluid (ammonia-water, as well as based on the turbine exhaust pressure. The result of the simulation is the optimum theoretical performance of KCS 11, which has the highest possible power output and efficiency. The energy flow diagram and exergy diagram (Grassman diagram was also presented for KCS 11 optimum system to give quantitative information regarding energy flow from the heat source to system components and the proportion of the exergy input dissipated in the various system components.

  4. Hydrogen Economy Model for Nearly Net-Zero Cities with Exergy Rationale and Energy-Water Nexus

    Directory of Open Access Journals (Sweden)

    Birol Kılkış

    2018-05-01

    Full Text Available The energy base of urban settlements requires greater integration of renewable energy sources. This study presents a “hydrogen city” model with two cycles at the district and building levels. The main cycle comprises of hydrogen gas production, hydrogen storage, and a hydrogen distribution network. The electrolysis of water is based on surplus power from wind turbines and third-generation solar photovoltaic thermal panels. Hydrogen is then used in central fuel cells to meet the power demand of urban infrastructure. Hydrogen-enriched biogas that is generated from city wastes supplements this approach. The second cycle is the hydrogen flow in each low-exergy building that is connected to the hydrogen distribution network to supply domestic fuel cells. Make-up water for fuel cells includes treated wastewater to complete an energy-water nexus. The analyses are supported by exergy-based evaluation metrics. The Rational Exergy Management Efficiency of the hydrogen city model can reach 0.80, which is above the value of conventional district energy systems, and represents related advantages for CO2 emission reductions. The option of incorporating low-enthalpy geothermal energy resources at about 80 °C to support the model is evaluated. The hydrogen city model is applied to a new settlement area with an expected 200,000 inhabitants to find that the proposed model can enable a nearly net-zero exergy district status. The results have implications for settlements using hydrogen energy towards meeting net-zero targets.

  5. Comparative effects of building envelope improvements and occupant behavioural changes on the exergy consumption for heating and cooling

    International Nuclear Information System (INIS)

    Schweiker, Marcel; Shukuya, Masanori

    2010-01-01

    Much focus is put on measures to improve the building envelope system performance to reduce the impact of the building sector on the global environmental degradation. This paper compares the potential of building envelope improvements to those of a change in the occupant's behavioural pattern. Three cases of improvements together with a base case were analysed using exergy analysis, because the exergy concept is useful to understand the underlying processes and the necessary adjustments to the calculation of the heat-pump system. The assumptions for the occupant behaviour were set up based on our field measurements conducted in a dormitory building and the calculation was for steady-state conditions. It was found that the potential of occupant behavioural changes for the reduction in exergy consumption is more affected by the outdoor temperature compared to building envelope improvements. The influence of occupant behaviour was highly significant (more than 90% decrease of exergy consumption) when the temperature difference between indoors and outdoors is small, which is the case for long periods in regions with moderate temperatures during summer and/or winter. Nevertheless, both measures combined lead to a reduction from 76% up to 95% depending on the outside conditions and should be the final goal.

  6. Energy and exergy analysis of multi-effects distillation with thermo vapour compressor (MED-TVC) desalination system

    Energy Technology Data Exchange (ETDEWEB)

    Saffari, A.; Sayyaadi, H. [Khaje Nasir Toosi Univ. of Technology, Tehran (Iran, Islamic Republic of). Faculty of Mechanical Engineering, Energy Division; Alishiri, M. [Fan Niroo Co., Tehran (Iran, Islamic Republic of). Desalination and Water Solutions

    2008-07-01

    Countries around the world have a significant need for high-quality water. The desalination industry is especially important in ensuring the supply of high-quality water, especially the countries around the Persian Gulf such as Iran. A multiple-effect distiller (MED) with thermal vapor compression (TVC) system is more attractive than other thermal systems due to its effectiveness, easier operation and maintenance, and good economics. This paper presented a heat and mass balance relation and comprehensive exergy analysis of a typical MED with a thermal vapour compression desalination system. The purpose of the study was to provide a cost-effective tool that could be applied in the design, development and optimization of thermal desalination plants. The paper discussed the energy simulation, with particular reference to the temperatures for each effect; the condenser, gain output ratio, distillate production rate, brine outlet and feed water rates for each effect; steam consumption; coolant sea water and total sea water inlet rate; pressure distribution in the evaporators; and the entertained vapour rate at TVC. Exergy analysis revealed that the steam ejector and evaporators are the main sources of exergy destruction. It was also shown that lowering the temperature difference can minimize exergy losses. 21 refs., 4 tabs., 16 figs.

  7. Two Examples of Exergy Optimization Regarding the “Thermo-Frigopump” and Combined Heat and Power Systems

    Directory of Open Access Journals (Sweden)

    Michel Feidt

    2013-02-01

    Full Text Available In a recent review an optimal thermodynamics and associated new upper bounds have been proposed, but it was only relative to power delivered by engines. In fact, it appears that for systems and processes with more than one utility (mainly mechanical or electrical power, energy conservation (First Law is limited for representing their efficiency. Consequently, exergy analysis combining the First and Second Law seems essential for optimization of systems or processes situated in their environment. For thermomechanical systems recent papers report on comparisons between energy and exergy analysis and corresponding optimization, but the proposed models mainly use heat transfer conductance modelling, except for internal combustion engine. Here we propose to reconsider direct and inverse configurations of Carnot machines, with two examples. The first example is concerned with “thermofrigo-pump” where the two utilities are hot and cold thermal exergies due to the difference in the temperature level compared to the ambient one. The second one is relative to a “combined heat and power” (CHP system. In the two cases, the model is developed based on the Carnot approach, and use of the efficiency-NTU method to characterize the heat exchangers. Obtained results are original thermodynamics optima, that represent exergy upper bounds for these two cases. Extension of the proposed method to other systems and processes is examined, with added technical constraints or not.

  8. Exergy and Exergoenvironmental Analysis of a CCHP System Based on a Parallel Flow Double-Effect Absorption Chiller

    Directory of Open Access Journals (Sweden)

    Ali Mousafarash

    2016-01-01

    Full Text Available A combined cooling, heating, and power (CCHP system which produces electricity, heating, and cooling is modeled and analyzed. This system is comprised of a gas turbine, a heat recovery steam generator, and a double-effect absorption chiller. Exergy analysis is conducted to address the magnitude and the location of irreversibilities. In order to enhance understanding, a comprehensive parametric study is performed to see the effect of some major design parameters on the system performance. These design parameters are compressor pressure ratio, gas turbine inlet temperature, gas turbine isentropic efficiency, compressor isentropic efficiency, and temperature of absorption chiller generator inlet. The results show that exergy efficiency of the CCHP system is higher than the power generation system and the cogeneration system. In addition, the results indicate that when waste heat is utilized in the heat recovery steam generator, the greenhouse gasses are reduced when the fixed power output is generated. According to the parametric study results, an increase in compressor pressure ratio shows that the network output first increases and then decreases. Furthermore, an increase in gas turbine inlet temperature increases the system exergy efficiency, decreasing the total exergy destruction rate consequently.

  9. Exergy analysis and optimization of a biomass gasification, solid oxide fuel cell and micro gas turbine hybrid system

    DEFF Research Database (Denmark)

    Bang-Møller, Christian; Rokni, Masoud; Elmegaard, Brian

    2011-01-01

    and exergy analyses were applied. Focus in this optimization study was heat management, and the optimization efforts resulted in a substantial gain of approximately 6% in the electrical efficiency of the plant. The optimized hybrid plant produced approximately 290 kWe at an electrical efficiency of 58...

  10. Experimental and numerical analysis of the optimized finned-tube heat exchanger for OM314 diesel exhaust exergy recovery

    International Nuclear Information System (INIS)

    Hatami, M.; Ganji, D.D.; Gorji-Bandpy, M.

    2015-01-01

    Highlights: • An optimized finned-tube heat exchanger is modeled. • Artificial Neural Networks and Genetic Algorithm are applied. • Exergy recovery from exhaust of a diesel engine is studied. - Abstract: In this research, a multi objective optimization based on Artificial Neural Network (ANN) and Genetic Algorithm (GA) are applied on the obtained results from numerical outcomes for a finned-tube heat exchanger (HEX) in diesel exhaust heat recovery. Thirty heat exchangers with different fin length, thickness and fin numbers are modeled and those results in three engine loads are optimized with weight functions for pressure drop, recovered heat and HEX weight. Finally, two cases of HEXs (an optimized and a non-optimized) are produced experimentally and mounted on the exhaust of an OM314 diesel engine to compare their results in heat and exergy recovery. All experiments are done for five engine loads (0%, 20%, 40%, 60% and 80% of full load) and four water mass flow rates (50, 40, 30 and 20 g/s). Results show that maximum exergy recovers occurs in high engine loads and optimized HEX with 10 fins have averagely 8% second law efficiency in exergy recovery

  11. Comparative study of different exhaust heat exchangers effect on the performance and exergy analysis of a diesel engine

    NARCIS (Netherlands)

    Hatami, M.; Boot, M.D.; Ganji, D.D.; Gorji-Bandpy, M.

    2015-01-01

    In this research, the effect of three designed heat exchangers on the performance of an OM314 diesel engine and its exergy balance is investigated. Vortex generator heat exchanger (HEX), optimized finned-tube HEX and non-optimized HEX are considered and mounted on the exhaust of diesel engine.

  12. A novel application of exergy analysis: Lean manufacturing tool to improve energy efficiency and flexibility of hydrocarbon processing

    International Nuclear Information System (INIS)

    Haragovics, Máté; Mizsey, Péter

    2014-01-01

    This work investigates the techniques used in evaluating distillation structures from lean manufacturing point of view. Oil and gas industry has already started adopting lean manufacturing principles in different types of processes from information flow to processing technologies. Generally, energy costs are the most important factors in processing hydrocarbons. Introducing flexibility desired by lean principles to the system may conflict energy efficiency of the system. However, this does not mean that the economic optimum is the energetic optimum. Therefore all possible changes due to temporarily stopped or not fully utilised plants have to be investigated, resulting in a large amount of cases that have to be evaluated. For evaluation exergy analysis can be used as it involves all energy types, and evaluation is straightforward. In this paper plain distillation structures are investigated, and the boundaries of the systems are set up according to the status of the site. Four component case studies are presented that show that the very same distillation structure can be more or less efficient depending on the status of the industrial site. It is also shown that exergy analysis used with different boundaries on the same system can show flexibility of the system and reveals potentials. - Highlights: • The article focuses on the flexibility aspect of lean manufacturing. • Exergy analysis of distillation scheme alternatives, energy efficiency. • Different boundaries define different scenarios of the same system is investigated. • The energy efficiency of distillation schemes also depends on their operating mode. • The exergy reserves of a distillation system can be revealed with exergy analysis

  13. A novel syngas-fired hybrid heating source for solar-thermal applications: Energy and exergy analysis

    International Nuclear Information System (INIS)

    Pramanik, Santanu; Ravikrishna, R.V.

    2016-01-01

    Highlights: • Biomass-derived syngas as a hybrid energy source for solar thermal power plants. • A novel combustor concept using rich-catalytic and MILD combustion technologies. • Hybrid energy source for a solar-driven supercritical CO 2 -based Brayton cycle. • Comprehensive energetic and exergetic analysis of the combined system. - Abstract: A hybrid heating source using biomass-derived syngas is proposed to enable continuous operation of standalone solar thermal power generation plants. A novel, two-stage, low temperature combustion system is proposed that has the potential to provide stable combustion of syngas with near-zero NO x emissions. The hybrid heating system consists of a downdraft gasifier, a two-stage combustion system, and other auxiliaries. When integrated with a solar cycle, the entire system can be referred to as the integrated gasification solar combined cycle (IGSCC). The supercritical CO 2 Brayton cycle (SCO 2 ) is selected for the solar cycle due to its high efficiency. The thermodynamic performance evaluation of the individual unit and the combined system has been conducted from both energy and exergy considerations. The effect of parameters such as gasification temperature, biomass moisture content, equivalence ratio, and pressure ratio is studied. The efficiency of the IGSCC exhibited a non-monotonic behavior. A maximum thermal efficiency of 36.5% was achieved at an overall equivalence ratio of 0.22 and pressure ratio of 2.75 when the gasifier was operating at T g = 1073 K with biomass containing 20% moisture. The efficiency increased to 40.8% when dry biomass was gasified at a temperature of 973 K. The exergy analysis revealed that the maximum exergy destruction occurred in the gasification system, followed by the combustion system, SCO 2 cycle, and regenerator. The exergy analysis also showed that 8.72% of the total exergy is lost in the exhaust; however, this can be utilized for drying of the biomass.

  14. Exergy analysis of an industrial unit of catalyst regeneration based on the results of modeling and simulation

    International Nuclear Information System (INIS)

    Toghyani, Mahboubeh; Rahimi, Amir

    2015-01-01

    An industrial process is synthesized and developed for decoking of de-hydrogenation catalyst, used in LAB (Linear Alkyl Benzene) production. A multi-tube fixed bed reactor, with short length tubes is designed for decoking of catalyst as the main equipment of the process. This study provides a microscopic exergy analysis for decoking reactor and a macroscopic exergy analysis for synthesized regeneration process. The dynamic mathematical modeling technique and the simulation of process by a commercial software are applied simultaneously. The used model was previously developed for performance analysis of decoking reactor. An appropriate exergy model is developed and adopted to estimate the enthalpy, exergetic efficiency and irreversibility. The model is validated with respect to some operating data measured in a commercial regeneration unit for variations in gas and particle characteristics along the reactor. In coke-combustion period, in spite of high reaction rate, the reactor has low exergetic efficiency due to entropy production during heat and mass transfer processes. The effects of inlet gas flow rate, temperature and oxygen concentration are investigated on the exergetic efficiency and irreversibilities. Macroscopic results indicate that the fan has the highest irreversibilities among the other equipment. Applying proper operating variables reduces the cycle irreversibilities at least by 20%. - Highlights: • A microscopic exergy analysis for a multi-tube fixed bed reactor is conducted. • Controlling the O_2 concentration upgrades the reactor exergetic performance. • A macroscopic exergy analysis for synthesized regeneration process is conducted. • The fan is one of the main sources of the regeneration cycle irreversibility. • The proposed strategies can reduce the cycle irreversibilities at least by 20%.

  15. Energy and Exergy Balances for Modern Diesel and Gasoline Engines Bilans d’énergie et d’exergie pour des moteurs Diesel et essence récents

    Directory of Open Access Journals (Sweden)

    Bourhis G.

    2009-11-01

    Full Text Available The aim is here to evaluate the difference between the energy and exergy (or available energy balances when heat recovery is considered in an internal combustion engine. In the first case, the entropy of the system is not taken into account so that, the maximum useful work recoverable from a system can not be estimated. Then, the second case is much more adapted to estimate heat recovery potential. In this paper, two modern engines are evaluated. First, an up-to-date gasoline engine: three-cylinder, downsized, low friction, then a modern common rail downsized Diesel engine. For each one, two energy and exergy balances are given for two different part-load operating points representative of the NEDC cycle using experimental data from steady state engine test benches. For the Diesel engine, it is shown that effective work represents around 30% and that around 55% of the energy introduced into the combustion chamber is lost (in the form of heat, especially in exhaust gas, in water coolant and oil. But when considering exergy balance, only 12% of the total exergy introduced through the fuel can be recovered, in order to produce useful work. Expecting a 25% exergy recovery efficiency, the effective engine efficiency could be increased by 10%. For the gasoline engine, the increase of the output work could be around 15%. L’objectif est ici d’évaluer la différence entre bilan d’énergie et d’exergie (ou énergie utile pour des moteurs à combustion interne lorsque la problématique de récupération d’énergie est prise en compte. Dans le premier cas, l’entropie du système n’est pas considérée, si bien que le travail utile maximal qu’il est possible de récupérer d’un système ne peut pas être estimé. Tandis que le second cas est bien mieux adapté pour estimer le potentiel de la récupération d’énergie. Dans cet article, deux moteurs modernes sont étudiés. Le premier est un moteur essence récent, 3 cylindres, de cylindr

  16. Exergy analysis in a space with ceiling shield; Analisis exegetico en un espacio con techo escudo

    Energy Technology Data Exchange (ETDEWEB)

    Laboratorio de Energia Solar, Universidad Nacional Autonoma de Mexico (Mexico)

    2009-07-15

    The Solar Laboratory of Energy (LES) of the Universidad Nacional Autonoma de Mexico (UNAM) was designed to be comfortable in spite of the extreme climate where it was built. One of the novel characteristics was the shield type ceiling used in cubicles. In order to compare the effect that had had with respect to the environmental conditions, one had to resort to an exergy analysis, since exergy is a measurement of the capacity of the energy to carry out a work. As a first system the data of the national meteorological system as initial conditions were used. The comparative system used as initial conditions the temperature and relative humidity measurements obtained in 1992 in a cubicle of the LES. Both systems were taken as open. The final conditions were settled at 25 Celsius degrees and 50% of relative humidity in a first case and variables (with respect to the perimeter a comfort zone) in a second case. The saving obtained was of 69% and 33% respectively. Although it is not possible to determine what percentage corresponds to the exclusive saving of the ceiling shield, we see that the cover all altogether, presents a significant exergy saving in respect to modifying the environmental conditions directly. [Spanish] El Laboratorio de Energia Solar (LES) de la Universidad Nacional Autonoma de Mexico (UNAM) fue disenado para ser confortable a pesar del clima extremoso donde fue construido. Una de las caracteristicas novedosas fue el uso de techo tipo escudo en cubiculo. Para comparar el efecto que se tuvo respecto a las condiciones ambientales, se recurrio a un analisis exergetico, ya que la exergia es una medida de la capacidad de la energia para realizar un trabajo. Como un primer sistema se utilizaron los datos del sistema meteorologico nacional como condiciones iniciales. El sistema comparativo utilizo como condiciones iniciales las mediciones de temperatura y humedad relativas obtenidas en 1992 en un cubiculo del LES. Ambos sistemas fueron tomados como abiertos

  17. Towards modeling of combined cooling, heating and power system with artificial neural network for exergy destruction and exergy efficiency prognostication of tri-generation components

    International Nuclear Information System (INIS)

    Taghavifar, Hadi; Anvari, Simin; Saray, Rahim Khoshbakhti; Khalilarya, Shahram; Jafarmadar, Samad; Taghavifar, Hamid

    2015-01-01

    The current study is an attempt to address the investigation of the CCHP (combined cooling, heating and power) system when 10 input variables were chosen to analyze 10 most important objective output parameters. Moreover, ANN (artificial neural network) was successfully applied on the tri-generation system on account of its capability to predict responses with great confidence. The results of sensitivity analysis were considered as foundation for selecting the most suitable and potent input parameters of the supposed cycle. Furthermore, the best ANN topology was attained based on the least amount of MSE and number of iterations. Consequently, the trainlm (Levenberg–Marquardt) training approach with 10-9-10 configuration has been exploited for ANN modeling in order to give the best output correspondence. The maximum MRE = 1.75% (mean relative error) and minimum R 2  = 0.984 represents the reliability and outperformance of the developed ANN over common conventional thermodynamic analysis carried out by EES (engineering equation solver) software. - Highlights: • Exergy analysis is undertaken for CCHP components based on operative factors. • ANN tool is applied to obtained database from thermodynamic analyses session. • The best ANN topology is detected at 10-9-10 with trainlm learning algorithm. • The input and output layer parameters were selected based on sensitivity analysis.

  18. Energy and exergy analysis of the turbo-generators and steam turbine for the main feed water pump drive on LNG carrier

    International Nuclear Information System (INIS)

    Mrzljak, Vedran; Poljak, Igor; Mrakovčić, Tomislav

    2017-01-01

    Highlights: • Two low-power steam turbines in the LNG carrier propulsion plant were investigated. • Energy and exergy efficiencies of both steam turbines vary between 46% and 62%. • The ambient temperature has a low impact on exergy efficiency of analyzed turbines. • The maximum efficiencies area of both turbines was investigated. • A method for increasing the turbo-generator efficiencies by 1–3% is presented. - Abstract: Nowadays, marine propulsion systems are mainly based on internal combustion diesel engines. Despite this fact, a number of LNG carriers have steam propulsion plants. In such plants, steam turbines are used not only for ship propulsion, but also for electrical power generation and main feed water pump drive. Marine turbo-generators and steam turbine for the main feed water pump drive were investigated on the analyzed LNG carrier with steam propulsion plant. The measurements of various operating parameters were performed and obtained data were used for energy and exergy analysis. All the measurements and calculations were performed during the ship acceleration. The analysis shows that the energy and exergy efficiencies of both analyzed low-power turbines vary between 46% and 62% what is significantly lower in comparison with the high-power steam turbines. The ambient temperature has a low impact on exergy efficiency of analyzed turbines (change in ambient temperature for 10 °C causes less than 1% change in exergy efficiency). The highest exergy efficiencies were achieved at the lowest observed ambient temperature. Also, the highest efficiencies were achieved at 71.5% of maximum developed turbo-generator power while the highest efficiencies of steam turbine for the main feed water pump drive were achieved at maximum turbine developed power. Replacing the existing steam turbine for the main feed water pump drive with an electric motor would increase the turbo-generator energy and exergy efficiencies for at least 1–3% in all analyzed

  19. Nonlinear Power Flow Control Design Utilizing Exergy, Entropy, Static and Dynamic Stability, and Lyapunov Analysis

    CERN Document Server

    Robinett III, Rush D

    2011-01-01

    Nonlinear Powerflow Control Design presents an innovative control system design process motivated by renewable energy electric grid integration problems. The concepts developed result from the convergence of three research and development goals: • to create a unifying metric to compare the value of different energy sources – coal-burning power plant, wind turbines, solar photovoltaics, etc. – to be integrated into the electric power grid and to replace the typical metric of costs/profit; • to develop a new nonlinear control tool that applies power flow control, thermodynamics, and complex adaptive systems theory to the energy grid in a consistent way; and • to apply collective robotics theories to the creation of high-performance teams of people and key individuals in order to account for human factors in controlling and selling power into a distributed, decentralized electric power grid. All three of these goals have important concepts in common: exergy flow, limit cycles, and balance between compe...

  20. Coal to SNG: Technical progress, modeling and system optimization through exergy analysis

    International Nuclear Information System (INIS)

    Li, Sheng; Ji, Xiaozhou; Zhang, Xiaosong; Gao, Lin; Jin, Hongguang

    2014-01-01

    Highlights: • Technical progresses of coal to SNG technologies are reported. • The entire coal to SNG system is modeled. • Coupling between SNG production and power generation is investigated. • Breakthrough points for further energy saving are determined. • System performance is optimized based on the first and second laws of thermodynamics. - Abstract: For both energy security and CO 2 emission reduction, synthetic natural gas (SNG) production from coal is an important path to implement clean coal technologies in China. In this paper, an overview of the progress of coal to SNG technologies, including the development of catalysts, reactor designs, synthesis processes, and systems integration, is provided. The coal to SNG system is modeled, the coupling between SNG production and power generation is investigated, the breakthrough points for further energy savings are determined, and the system performance is optimized based on the first and the second laws of thermodynamics. From the viewpoint of the first law of thermodynamics, the energy conversion efficiency of coal to SNG system can reach 59.8%. To reduce the plant auxiliary power, the breakthrough points are the development of low-energy-consumption oxygen production technology and gas purification technology or seeking new oxidants for coal gasification instead of oxygen. From the viewpoint of the second law of thermodynamics, the major exergy destruction in a coal to SNG system occurs in the coal gasification unit, SNG synthesis unit and the raw syngas cooling process. How to reduce the exergy destruction in these units is the key to energy savings and system performance enhancement. The conversion ratio of the first SNG synthesis reactor and the split ratio of the recycle gas are key factors that determine the performance of both the SNG synthesis process and the whole plant. A “turning point” phenomenon is observed: when the split ratio is higher than 0.90, the exergy destruction of the SNG

  1. EXERGY ANALYSIS OF THE CRYOGENIC HELIUM DISTRIBUTION SYSTEM FOR THE LARGE HADRON COLLIDER (LHC)

    International Nuclear Information System (INIS)

    Claudet, S.; Lebrun, Ph.; Tavian, L.; Wagner, U.

    2010-01-01

    The Large Hadron Collider (LHC) at CERN features the world's largest helium cryogenic system, spreading over the 26.7 km circumference of the superconducting accelerator. With a total equivalent capacity of 145 kW at 4.5 K including 18 kW at 1.8 K, the LHC refrigerators produce an unprecedented exergetic load, which must be distributed efficiently to the magnets in the tunnel over the 3.3 km length of each of the eight independent sectors of the machine. We recall the main features of the LHC cryogenic helium distribution system at different temperature levels and present its exergy analysis, thus enabling to qualify second-principle efficiency and identify main remaining sources of irreversibility.

  2. Effects of Floor Covering Resistance of a Radiant Floor on System Energy and Exergy Performances

    DEFF Research Database (Denmark)

    Kazanci, Ongun Berk; Shukuya, Masanori; Olesen, Bjarne W.

    2016-01-01

    Floor covering resistance (material and thickness) can be influenced by subjective choices (architectural design, interior design, texture, etc.) with significant effects on the performance of a radiant heating and cooling system. To study the effects of floor covering resistance on system...... performance, a water-based radiant floor heating and cooling system (dry, wooden construction) was considered to be coupled to an air-to-water heat pump, and the effects of varying floor covering resistances (0.05 m2K/W, 0.09 m2K/W and 0.15 m2K/W) on system performance were analyzed in terms of energy...... and exergy. In order to achieve the same heating and cooling outputs, higher average water temperatures are required in the heating mode (and lower temperatures in the cooling mode) with increasing floor covering resistance. These temperature requirements decrease the heat pump’s performance (lower...

  3. An energy and exergy study of a solar thermal air collector

    Directory of Open Access Journals (Sweden)

    Mohseni-Languri Ehsan

    2009-01-01

    Full Text Available A solar flat plate air collector was manufactured in the north of Iran, and connected to a room as the model to study the possibility of using such solar heating systems in the northern parts of Iran. This collector was tested as a solar air heater to see how good it could be for warming up the test room during the winter. The experimental data obtained through accurate measurements were analyzed using second law approach to find the optimum mass flow rate, which leads to the maximum exergy efficiency. It was found that for the test setup at the test location, a mass flow rate of 0.0011 kg/s is the optimum mass flow rate for tested conditions which leads to the highest second law efficiency.

  4. Exergy analysis of helium liquefaction systems based on modified Claude cycle with two-expanders

    Science.gov (United States)

    Thomas, Rijo Jacob; Ghosh, Parthasarathi; Chowdhury, Kanchan

    2011-06-01

    Large-scale helium liquefaction systems, being energy-intensive, demand judicious selection of process parameters. An effective tool for design and analysis of thermodynamic cycles for these systems is exergy analysis, which is used to study the behavior of a helium liquefaction system based on modified Claude cycle. Parametric evaluation using process simulator Aspen HYSYS® helps to identify the effects of cycle pressure ratio and expander flow fraction on the exergetic efficiency of the liquefaction cycle. The study computes the distribution of losses at different refrigeration stages of the cycle and helps in selecting optimum cycle pressures, operating temperature levels of expanders and mass flow rates through them. Results from the analysis may help evolving guidelines for designing appropriate thermodynamic cycles for practical helium liquefaction systems.

  5. Exergy analysis of a combined heat and power plant with integrated lignocellulosic ethanol production

    DEFF Research Database (Denmark)

    Lythcke-Jørgensen, Christoffer Ernst; Haglind, Fredrik; Clausen, Lasse Røngaard

    2014-01-01

    production. An exergy analysis is carried out for a modelled polygeneration system in which lignocellulosic ethanol production based on hydrothermal pretreatment is integrated in an existing combined heat and power (CHP) plant. The ethanol facility is driven by steam extracted from the CHP unit when feasible...... district heating production in the ethanol facility. The results suggest that the efficiency of integrating lignocellulosic ethanol production in CHP plants is highly dependent on operation, and it is therefore suggested that the expected operation pattern of such polygeneration system is taken......Lignocellulosic ethanol production is often assumed integrated in polygeneration systems because of its energy intensive nature. The objective of this study is to investigate potential irreversibilities from such integration, and what impact it has on the efficiency of the integrated ethanol...

  6. Exergy Analysis of the Cryogenic Helium Distribution System for the Large Hadron Collider (LHC)

    CERN Document Server

    Claudet, S; Tavian, L; Wagner, U

    2010-01-01

    The Large Hadron Collider (LHC) at CERN features the world’s largest helium cryogenic system, spreading over the 26.7 km circumference of the superconducting accelerator. With a total equivalent capacity of 145 kW at 4.5 K including 18 kW at 1.8 K, the LHC refrigerators produce an unprecedented exergetic load, which must be distributed efficiently to the magnets in the tunnel over the 3.3 km length of each of the eight independent sectors of the machine. We recall the main features of the LHC cryogenic helium distribution system at different temperature levels and present its exergy analysis, thus enabling to qualify second-principle efficiency and identify main remaining sources of irreversibility..

  7. Exergy analysis of components of integrated wind energy / hydrogen / fuel cell

    International Nuclear Information System (INIS)

    Hernandez Galvez, G.; Pathiyamattom, J.S.; Sanchez Gamboa, S.

    2009-01-01

    Exergy analysis is made of three components of an integrated wind energy to hydrogen fuel cell: wind turbine, fuel cell (PEMFC) and electrolyzer (PEM). The methodology used to assess how affect the second law efficiency of the electrolyzer and the FC parameters as temperature and operating pressure and membrane thickness. It develop methods to evaluate the influence of changes in the air density and height of the tower on the second law efficiency of the turbine. This work represents a starting point for developing the global availability analysis of an integrated wind / hydrogen / fuel cells, which can be used as a tool to achieve the optimum design of the same. The use of this system contribute to protect the environment

  8. Sensitivity of energy and exergy performances of heating and cooling systems to auxiliary components

    DEFF Research Database (Denmark)

    Kazanci, Ongun Berk; Shukuya, Masanori; Olesen, Bjarne W.

    2017-01-01

    . Different forms of energy (electricity and heat) are used in heating and cooling systems, and therefore, a holistic approach to system design and analysis is needed. In particular, distribution systems use electricity as a direct input to pumps and fans, and to other components. Therefore, exergy concept......Heating and cooling systems in buildings consist of three main subsystems: heating/cooling plant, distribution system, and indoor terminal unit. The choice of indoor terminal unit determines the characteristics of the distribution system and the heating and cooling plants that can be used...... should be used in design and analysis of the whole heating and cooling systems, in addition to the energy analysis. In this study, water-based (floor heating and cooling, and radiator heating) and air-based (air heating and cooling) heating and cooling systems were compared in terms of their energy use...

  9. Energy and Exergy Analysis of a Diesel Engine Fuelled with Diesel and Simarouba Biodiesel Blends

    Science.gov (United States)

    Panigrahi, Nabnit; Mohanty, Mahendra Kumar; Mishra, Sruti Ranjan; Mohanty, Ramesh Chandra

    2018-02-01

    This article intends to determine the available work and various losses of a diesel engine fuelled with diesel and SB20 (20 % Simarouba biodiesel by volume blended with 80 % diesel by volume). The energy and exergy analysis were carried out by using first law and second law of thermodynamics respectively. The experiments were carried out on a 3.5 kW compression ignition engine. The analysis was conducted on per mole of fuel basis. The energy analysis indicates that about 37.23 and 37.79 % of input energy is converted into the capacity to do work for diesel and SB20 respectively. The exergetic efficiency was 34.8 and 35 % for diesel and Simarouba respectively. Comparative study indicates that the energetic and exergetic performance of SB20 resembles with that of diesel fuel.

  10. Energy and Exergy Based Optimization of Licl-Water Absorption Cooling System

    Directory of Open Access Journals (Sweden)

    Bhargav Pandya

    2017-06-01

    Full Text Available This study presents thermodynamic analysis and optimization of single effect LiCl-H2O absorption cooling system. Thermodynamic models are employed in engineering equation solver to compute the optimum performance parameters. In this study, cut off temperature to operate system has been obtained at various operating temperatures. Analysis depicts that on 3.59 % rise in evaporator temperature, the required cut-off temperature decreased by 12.51%. By realistic comparison between thermodynamic first and second law analysis, optimum generator temperature relative to energy and exergy based prospective has been evaluated. It is found that optimum generator temperature is strong function of evaporator and condenser temperature. Thus, it is feasible to find out optimum generator temperature for various combinations of evaporator and condenser temperatures. Contour plots of optimum generator temperature for several combinations of condenser and absorber temperatures have been also depicted.

  11. Carbon exergy tax applied to biomass integrated gasification combined cycle in sugarcane industry

    International Nuclear Information System (INIS)

    Fonseca Filho, Valdi Freire da; Matelli, José Alexandre; Perrella Balestieri, José Antonio

    2016-01-01

    The development of technologies based on energy renewable sources is increasing worldwide in order to diversify the energy mix and satisfy the rigorous environmental legislation and international agreements to reduce pollutant emission. Considering specific characteristics of biofuels available in Brazil, studies regarding such technologies should be carried out aiming energy mix diversification. Several technologies for power generation from biomass have been presented in the technical literature, and plants with BIGCC (biomass integrated gasification combined cycle) emerge as a major technological innovation. By obtaining a fuel rich in hydrogen from solid biomass gasification, BIGCC presents higher overall process efficiency than direct burning of the solid fuel in conventional boilers. The objective of this paper is to develop a thermodynamic and chemical equilibrium model of a BIGCC configuration for sugarcane bagasse. The model embodies exergetic cost and CO_2 emission analyses through the method of CET (carbon exergy tax). An exergetic penalty comparison between the BIGCC technology (with and without CO_2 capture and sequestration), a natural gas combined cycle and the traditional steam cycle of sugarcane sector is then presented. It is verified that the BIGCC configuration with CO_2 capture and sequestration presents technical and environmental advantages when compared to traditional technology. - Highlights: • We compared thermal cycles with the exergetic carbon exergy tax. • Thermal cycles with and without carbon capture and sequestration were considered. • Burned and gasified sugarcane bagasse was assumed as renewable fuel. • Exergetic carbon penalty tax was imposed to all studied configurations. • BIGCC with carbon sequestration revealed to be advantageous.

  12. Experimental investigation and exergy analysis on thermal storage integrated micro-cogeneration system

    International Nuclear Information System (INIS)

    Johar, Dheeraj Kishor; Sharma, Dilip; Soni, Shyam Lal; Gupta, Pradeep K.; Goyal, Rahul

    2017-01-01

    Highlights: • Energy Storage System is integrated with Micro cogeneration system. • Erythritol is used as Phase Change Material. • Maximum energy saved is 15.2%. • Maximum exergy saved is 4.22%. • Combined systems are feasible to increase energy and exergy efficiency. - Abstract: This paper describes the performance of thermal storage integrated micro-cogeneration system based on single cylinder diesel engine. In addition to electricity generated from genset, waste heat from hot exhaust of diesel engine was used to heat water in a double pipe heat exchanger of 67.70 cm length with inside tube diameter of 3.81 cm and outside tube diameter of 5.08 cm. Additionally, a latent heat thermal energy storage system was also integrated with this cogeneration system. A shell and tube type heat exchanger of 346 mm diameter and 420 mm height with 45 tubes of 18 mm diameter each was designed and fabricated, to store thermal energy, in which Erythritol (C_4H_1_0O_4) was used as phase changing material. The test results show that micro capacity (4.4 kW), stationary, single cylinder, diesel engine can be successfully utilized to simultaneously produce power as well as heating, and to also store thermal energy. Slight decrease in engine performance was observed when double pipe heat exchanger and latent heat thermal energy storage system was integrated with engine but the amount of energy which could be recovered was significant. Maximum percentage of energy saved was obtained at a load of 3.6 kW and was 15.2%.

  13. Alternatives for power supply to natural-gas export compressors combined with heat production evaluated with respect to exergy utilization and CO2 emissions

    International Nuclear Information System (INIS)

    Woelneberg, Pia W.; Ertesvaag, Ivar S.

    2008-01-01

    The supply of process steam in combination with power for natural-gas export compressors was investigated using exergy analysis. The existing system with three 12.32 MW direct drive gas turbines each with a HRSG delivering 19.2 kg/s high-pressure steam was compared with an alternative where the gas turbines were replaced with new turbines. The exergy efficiencies were 46.7% and 48.6%, respectively, for the two cases. A second alternative with electric motors and a new CHP was investigated in three variants, all with some surplus electricity production. All variants gave higher exergy efficiencies than the other alternatives, from 51.5% to 53.6%. A third alternative with electric motors, stand-alone boilers and purchase of electricity was also analyzed, considering different origins of the electricity. This alternative gave the lowest exergy efficiencies, from 37.1% to 41.4% for different variants. In accordance with the exergy utilization, the CO 2 emissions per unit of exergy delivered were the lowest for the second alternative, while the total emissions were the highest for the third alternative. However, the domestic emissions, important in relation to international CO 2 agreements, were shown to be the lowest for the stand-alone boiler in combination with imported electricity. (author)

  14. Characteristic on photovoltaic/thermal hybrid collector. Evaluation of excergetic theory; Taiyoko netsu hybrid collector no tokusei. Exergy ni yoru hyoka

    Energy Technology Data Exchange (ETDEWEB)

    Iwawaki, H; Morita, Y; Fujisawa, T; Tani, T [Science University of Tokyo, Tokyo (Japan)

    1997-11-25

    Described herein are characteristics of photovoltaic (PV)/thermal hybrid collectors (PV/Ts), in which a PV module is combined with a plate-shape solar heat collector to simultaneously produce electric power and heat. Their efficiency is assessed by exergy. The test results indicate that the PV/T system gives a 1.07 times higher exergy than the PV system, 86.3 versus 80.7kWh. In terms of energy, the optimum values (OVs) are 5, 44 and 37% lower than the measuring values (MVs) for electrical energy, thermal energy and total exergy. In terms of exergy, on the other hand, OV is 5% lower than MV for electrical energy, but 893 times higher for thermal energy and 1.26 times higher for total exergy. As a result, the exergy level is 26% higher than that of a system which generates power as the main product and heat as the auxiliary product. 3 refs., 6 figs., 5 tabs.

  15. Universal exergy analysis method and its application%泛(火用)分析方法及其应用

    Institute of Scientific and Technical Information of China (English)

    蒋爱华; 梅炽; 时章明

    2011-01-01

    为分析和评价原材料、能源、资金、劳动力等不同类别的要素资源在生产过程中的综合利用情况,提出泛(火用)概念和泛(火用)分析方法,建立系统的泛(火用)分析和评价模型,定义泛(火用)利用系数和可持续发展指数等量化指标.利用泛(火用)分析方法和模型对SKS炼铅系统和太阳能光伏发电系统进行分析和评价.研究结果表明:SKS炼铅系统等冶金生产系统的泛(火用)利用系数很低,可持续发展性较差,节能措施应以降低这类生产系统的不可再生资源特别是不可再生能源的消耗为主;太阳能光伏系统的町持续发展性能优越,其节能工作应以降低太阳能电池的制造成本和设备安装成本为主.%To analyze the situation of comprehensive utilization of different kinds of resources such as material, energy,funds, labor force, the concept of uinversal exergy was defined and the universal exergy analysis method was put forward,some models for analysis and evaluation of universal exergy of systems were established, and some quantitative indicators such as utilization coefficient of universal exergy and sustainable development index were defined.Universal exergy analysis method and the models were used to evaluate a SKS lead smelting system and one of solar photovoltaic power generation systems.The results show that both the coefficient of utilization of universal exergy and the sustainable development index of metallurgical production systems like the SKS lead smelting system are lower, the energy-saving measures for such systems should be focused on reducing the consumption of unrenewable resources, especially unrenewable energy, and that solar photovoltaic power generation systems are very well in sustainable development, and the focus of the energy saving work is on reducing cost in manufacturing solar photovoltaic cells and the installation cost of the solar photovoltaic power systems.

  16. Assessment of energy and exergy efficiencies of a grate clinker cooling system through the optimization of its operational parameters

    International Nuclear Information System (INIS)

    Ahamed, J.U.; Madlool, N.A.; Saidur, R.; Shahinuddin, M.I.; Kamyar, A.; Masjuki, H.H.

    2012-01-01

    Grate coolers are widely used in cement industries to recover heat from hot clinker, coming out from the rotary kiln. This study focuses on improving the energy, exergy and recovery efficiencies of a grate cooling system through the optimization of its operational parameters such as masses of cooling air and clinker, cooling air temperature, and grate speed. It has been found that the energy and recovery energy efficiencies of a cooling system can be increased by 1.1% and 1.9%, respectively, with every 5% mass increases of cooling air. Similarly, it has been estimated that energy and recovery energy efficiencies can be increased by 2.0% and 0.4% with every 5% increase of cooling temperature. The exergy and its recovery efficiencies found to be increased by 3.6% and 2.2%, respectively, for the same condition. Energy efficiency and energy recovery efficiencies are increased by 3.5% and 1.4% with every 9.1% increase of grate speed. Using heat recovery from the exhaust air, energy and exergy recovery efficiencies of the cooling system found to be increased by 21.5% and 9.4%, respectively. It has been found that about 38.10% and 30.86% energy cost can be saved by changing mass flow rate of clinker and mass flow rate of cooling air, respectively. -- Highlights: ► The energy and exergy efficiencies of the base case clinker cooler are 81.2% and 53.7%, respectively. ► To increase 5% mass flow of cooling air, the energy and exergy efficiency increase 1.1% and 0.9%, respectively. ► Increase of grate speed and cooling air temperature cause to increase of all efficiencies. ► Heat recovery from the exhaust air experiences 21.5% and 9.4% in energy and exergy recovery efficiency, respectively. ► Reduction of clinker mass flow reduces the emission of NO x , CO, PM and CO 2 .

  17. Energy consumption, destruction of exergy and boil off during the process of liquefaction, transport and regasification of liquefied natural gas

    Energy Technology Data Exchange (ETDEWEB)

    Stradioto, Diogo Angelo; Schneider, Paulo Smith [Dept. of Mechanical Engineering. Universidade Federal do Rio Grande do Sul, Porto Alegre (Brazil)], e-mail: pss@mecanica.ufrgs.br

    2010-07-01

    A supply chain of Liquefied Natural Gas (LNG) is composed by several processes like extraction, purification, liquefaction, storage, transport, regasification and distribution. In all these stages, processes need of energy. The main objective of this work is to quantify the energy consumption, mass loss and exergy destruction occurred throughout the chain. Results show that the process of liquefaction is the largest consumer of energy. Storage and transport by ship are responsible for the bigger mass losses and regasification is the process of larger destruction of exergy. A case study is performed considering a stream of pure methane at the input of a liquefaction plant, and evaluates energy along the chain, ending up at the distribution of NG after its regasification. (author)

  18. Comparison based on energy and exergy analyses of the potential cogeneration efficiencies for fuel cells and other electricity generation devices

    Energy Technology Data Exchange (ETDEWEB)

    Rosen, M A [Ryerson Polytechnical Inst., Toronto, (CA). Dept. of Mechanical Engineering

    1990-01-01

    Comparisons of the potential cogeneration efficiencies are made, based on energy and exergy analyses, for several devices for electricity generation. The investigation considers several types of fuel cell system (Phosphoric Acid, Alkaline, Solid Polymer Electrolyte, Molten Carbonate and Solid Oxide), and several fossil-fuel and nuclear cogeneration systems based on steam power plants. In the analysis, each system is modelled as a device for which fuel and air enter, and electrical- and thermal-energy products and material and thermal-energy wastes exit. The results for all systems considered indicate that exergy analyses should be used when analysing the cogeneration potential of systems for electricity generation, because they weigh the usefulnesses of heat and electricity on equivalent bases. Energy analyses tend to present overly optimistic views of performance. These findings are particularly significant when large fractions of the heat output from a system are utilized for cogeneration. (author).

  19. Effects of varying composition of biogas on performance and emission characteristics of compression ignition engine using exergy analysis

    International Nuclear Information System (INIS)

    Verma, Saket; Das, L.M.; Kaushik, S.C.

    2017-01-01

    Highlights: • Different compositions of biogas have been studied in dual fuel mode using exergy analysis. • Diesel substitution by biogas decreases with higher CO_2 fractions in biogas. • Exergy efficiency decreases with higher CO_2 fractions in biogas. • With low CO_2 fractions in biogas equitable performance can be obtained in dual fuel mode. • Engine modifications are needed to utilize high CO_2 containing biogas. - Abstract: Growing energy demands and environmental degradation with uncontrolled exploitation of fossil fuels have compelled the world to look for the alternatives. In this context, biogas is a promising candidate, which can easily be utilized in IC engines for vehicular as well as decentralized power generation applications. Primary constituents of raw biogas are methane (CH_4) that defines its heating value, and carbon dioxide (CO_2) that acts like a diluent. This dilution effect reduces the flame speed and heating value of biogas, eventually deteriorating the engine performances. Present article focuses on experimental evaluation and quantification of these variations of the engine performance. Three compositions of biogas: BG93, BG84 and BG75 (containing 93%, 84% and 75% of CH_4 by volume respectively) were studied on a small CI engine in dual fuel mode. Moreover, to evaluate individual process inefficiencies, exergy analysis based on second-law of thermodynamics is implemented. Exergy balances for different compositions of biogas are presented. Biogas dual fuel operation showed 80–90% diesel substitution at lower engine loads. At higher loads, total irreversibility of the engine was increased from 59.56% for diesel operation to 61.44%, 64.18% and 64.64% for BG93, BG84 and BG75 biogas compositions respectively. Furthermore, combustion irreversibility was found to be decreasing with higher CO_2 concentrations in biogas. BG93 showed comparable results to that of diesel operation with 26.9% and 27.4% second-law efficiencies respectively.

  20. Energy and exergy analyses on a novel hybrid solar heating, cooling and power generation system for remote areas

    International Nuclear Information System (INIS)

    Zhai, H.; Dai, Y.J.; Wu, J.Y.; Wang, R.Z.

    2009-01-01

    In this study, a small scale hybrid solar heating, chilling and power generation system, including parabolic trough solar collector with cavity receiver, a helical screw expander and silica gel-water adsorption chiller, etc., was proposed and extensively investigated. The system has the merits of effecting the power generation cycle at lower temperature level with solar energy more efficiently and can provide both thermal energy and power for remote off-grid regions. A case study was carried out to evaluate an annual energy and exergy efficiency of the system under the climate of northwestern region of China. It is found that both the main energy and exergy loss take place at the parabolic trough collector, amount to 36.2% and 70.4%, respectively. Also found is that the studied system can have a higher solar energy conversion efficiency than the conventional solar thermal power generation system alone. The energy efficiency can be increased to 58.0% from 10.2%, and the exergy efficiency can be increased to 15.2% from 12.5%. Moreover, the economical analysis in terms of cost and payback period (PP) has been carried out. The study reveals that the proposed system the PP of the proposed system is about 18 years under present energy price conditions. The sensitivity analysis shows that if the interest rate decreases to 3% or energy price increase by 50%, PP will be less than 10 years. (author)

  1. Exergy Analyses of Fabricated Compound Parabolic Solar Collector with Evacuated Tubes at Different Operating Conditions: Indore (India)

    Science.gov (United States)

    Geete, Ankur; Dubey, Akash; Sharma, Ankush; Dubey, Anshul

    2018-05-01

    In this research work, compound parabolic solar collector (CPC) with evacuated tubes is fabricated. Main benefit of CPC is that there is no requirement of solar tracking system. With fabricated CPC; outlet temperatures of flowing fluid, instantaneous efficiencies, useful heat gain rates and inlet exergies (with and without considering Sun's cone angle) are experimentally found. Observations are taken at different time intervals (1200, 1230, 1300, 1330 and 1400 h), mass flow rates (1.15, 0.78, 0.76, 0.86 and 0.89 g/s), ambient temperatures and with various dimensions of solar collector. This research work is concluded as; maximum instantaneous efficiency is 69.87% which was obtained with 0.76 g/s flow rate of water at 1300 h and 42°C is the maximum temperature difference which was also found at same time. Maximum inlet exergies are 139.733 and 139.532 kW with and without considering Sun's cone angle at 1300 h, respectively. Best thermal performance from the fabricated CPC with evacuated tubes is found at 1300 h. Maximum inlet exergy is 141.365 kW which was found at 1300 h with 0.31 m aperture width and 1.72 m absorber pipe length.

  2. Energy, exergy, economic and environmental (4E) analysis of a solar desalination system with humidification-dehumidification

    International Nuclear Information System (INIS)

    Deniz, Emrah; Çınar, Serkan

    2016-01-01

    Highlights: • Possibility of suppling all energy consumption from solar energy was tested. • Air and water-heated humidification-dehumidification desalination system was proposed. • Energy, exergy, economic and environmental analysis were performed. • Productivity and performance of the desalination system was analyzed. • Various operational parameters were investigated. - Abstract: A novel humidification-dehumidification (HDH) solar desalination system is designed and tested with actual conditions and solar energy was used to provide both thermal and electrical energy. Energy-exergy analyses of the system are made and economic and enviro-economic properties are investigated using data obtained from experimental studies. In this way, economic and environmental impacts of the HDH solar desalination systems have also been determined. The maximum daily energy efficiency of the system was calculated as 31.54% and the maximum exergy efficiency was found as 1.87%. The maximum fresh water production rate is obtained as 1117.3 g/h. The estimated cost of fresh water produced through the designed HDH system is 0.0981 USD/L and enviro-economic parameter is 2.4041 USD/annum.

  3. Proposal of a combined heat and power plant hybridized with regeneration organic Rankine cycle: Energy-Exergy evaluation

    International Nuclear Information System (INIS)

    Anvari, Simin; Jafarmadar, Samad; Khalilarya, Shahram

    2016-01-01

    Highlights: • A new thermodynamic cogeneration system is proposed. • Energy and exergy analysis of the considered cycle were performed. • An enhancement of 2.6% in exergy efficiency compared to that of baseline cycle. - Abstract: Among Rankine cycles (simple, reheat and regeneration), regeneration organic Rankine cycle demonstrates higher efficiencies compared to other cases. Consequently, in the present work a regeneration organic Rankine cycle has been utilized to recuperate gas turbine’s heat using heat recovery steam generator. At first, this cogeneration system was subjected to energy and exergy analysis and the obtained results were compared with that of investigated cogeneration found in literature (a cogeneration system in which a reheat organic Rankine cycle for heat recuperation of gas turbine cycle was used with the aid of heat recovery steam generator). Results indicated that the first and second thermodynamic efficiencies in present cycle utilizing regeneration cycle instead of reheat cycle has increased 2.62% and 2.6%, respectively. In addition, the effect of thermodynamic parameters such as combustion chamber’s inlet temperature, gas turbine inlet temperature, evaporator and condenser temperature on the energetic and exergetic efficiencies of gas turbine-heat recovery steam generator cycle and gas turbine-heat recovery steam generator cycle with regeneration organic Rankine cycle was surveyed. Besides, parametric analysis shows that as gas turbine and combustion chamber inlet temperatures increase, energetic and exergetic efficiencies tend to increase. Moreover, once condenser and evaporator temperature raise, a slight decrement in energetic and exergetic efficiency is expected.

  4. Energy and exergy analyses of a copper-chlorine thermochemical water decomposition pilot plant for hydrogen production

    International Nuclear Information System (INIS)

    Orhan, M.F.; Dincer, I.; Rosen, M.A.

    2008-01-01

    Nuclear-based hydrogen production via thermochemical water decomposition using a copper-chlorine (Cu-Cl) cycle consists of a series of chemical reactions in which water is split into hydrogen and oxygen as the net result. This is accomplished through reactions involving intermediate copper and chlorine compounds, which are recycled. Energy and exergy analyses are reported here of a Cu-Cl pilot plant, including the relevant chemical reactions. The reference environment is taken to be at a temperature of 298.15 K and atmospheric pressure (1 atm). The chemical exergy of a substance, which is the maximum work that can be obtained from it by taking it to chemical equilibrium with the reference environment at constant temperature and pressure, is calculated with property data for the substance and the reference environment, with enthalpy and entropy values calculated using Shomate equations. The reaction heat, exergy destruction and efficiencies in each chemical reaction vary with the reaction temperature and reference-environment temperature. A parametric study with variable reaction and reference-environment temperatures is also presented. (author)

  5. Use of process steam in vapor absorption refrigeration system for cooling and heating applications: An exergy analysis

    Directory of Open Access Journals (Sweden)

    S. Anand

    2016-12-01

    Full Text Available The exponential increase in cost of conventional fuels shifts the interest toward the use of alternative as well waste energy sources for the operation of refrigeration and air-conditioning units. The present study therefore analyzes the performance of a process steam-operated vapor absorption system for cooling and heating applications using ammonia and water as working fluids based on first and second laws of thermodynamics. A mathematical model has been developed based on exergy analysis to investigate the performance of the system. The different performance parameters such as coefficient of performance (COP and exergetic efficiency of absorption system for cooling and heating applications are also calculated under different operating conditions. The results obtained show that cooling and heating COP along with second law efficiency (exergy efficiency increases with the heat source temperature at constant evaporator, condenser, and absorber temperature. Also, COP as well as exergy efficiency increases with an increase in the evaporator temperature at constant generator, condenser, and absorber temperature. The effect of ambient temperature on the exergetic efficiency for cooling and heating applications is also studied. The results obtained from the simulation studies can be used to optimize different components of the system so that the performance can be improved significantly.

  6. Performance, Emission, Energy, and Exergy Analysis of a C.I. Engine Using Mahua Biodiesel Blends with Diesel.

    Science.gov (United States)

    Panigrahi, Nabnit; Mohanty, Mahendra Kumar; Mishra, Sruti Ranjan; Mohanty, Ramesh Chandra

    2014-01-01

    This paper presents an experimental investigation on a four-stroke single cylinder diesel engine fuelled with the blends of Mahua oil methyl ester (MOME) and diesel. The performance emission, energy, and exergy analysis has been carried out in B20 (mixture of 80% diesel by volume with 20% MOME). From energy analysis, it was observed that the fuel energy input as well as energy carried away by exhaust gases was 6.25% and 11.86% more in case of diesel than that of B20. The unaccounted losses were 10.21% more in case of diesel than B20. The energy efficiency was 28%, while the total losses were 72% for diesel. In case of B20, the efficiency was 65.74 % higher than that of diesel. The exergy analysis shows that the input availability of diesel fuel is 1.46% more than that of B20. For availability in brake power as well as exhaust gases of diesel were 5.66 and 32% more than that of B20. Destructed availability of B20 was 0.97% more than diesel. Thus, as per as performance, emission, energy, and exergy part were concerned; B20 is found to be very close with that of diesel.

  7. Effect of the use of olive–pomace oil biodiesel/diesel fuel blends in a compression ignition engine: Preliminary exergy analysis

    International Nuclear Information System (INIS)

    López, I.; Quintana, C.E.; Ruiz, J.J.; Cruz-Peragón, F.; Dorado, M.P.

    2014-01-01

    Highlights: • Olive–pomace oil (OPO) biodiesel constitute a new second-generation biofuel. • Exergy efficiency and performance of OPO biodiesel, straight and blended with diesel fuel was evaluated. • OPO biodiesel, straight and blended, provided similar performance parameters. • OPO biodiesel, straight and blended, provided similar exergy efficiency compared to diesel fuel. • OPO biodiesel, straight and blended, provided no exergy cost increment compared to diesel fuel. - Abstract: Although biodiesel is among the most studied biofuels for diesel engines, it is usually produced from edible oils, which gives way to controversy between the use of land for fuel and food. For this reason, residues like olive–pomace oil are considered alternative raw materials to produce biodiesel that do not compete with the food industry. To gain knowledge about the implications of its use, olive–pomace oil methyl ester, straight and blended with diesel fuel, was evaluated as fuel in a direct injection diesel engine Perkins AD 3-152 and compared to the use of fossil diesel fuel. Performance curves were analyzed at full load and different speed settings. To perform the exergy balance of the tested fuels, the operating conditions corresponding to maximum engine power values were considered. It was found that the tested fuels offer similar performance parameters. When straight biodiesel was used instead of diesel fuel, maximum engine power decreased to 5.6%, while fuel consumption increased up to 7%. However, taking into consideration the Second Law of the Thermodynamics, the exergy efficiency and unitary exergetic cost reached during the operation of the engine under maximum power condition for the assessed fuels do not display significant differences. Based on the exergy results, it may be concluded that olive–pomace oil biodiesel and its blends with diesel fuel may substitute the use of diesel fuel in compression ignition engines without any exergy cost increment

  8. Exergy analysis of scroll compressors working with R22, R407C, and R417A as refrigerant for HVAC system

    Directory of Open Access Journals (Sweden)

    Kalaiselvam Sivakumar

    2009-01-01

    Full Text Available The rise in crisis of power enthralls the world economically and the options for conventional and non-conventional energy resources have been searched out. No system exists in this world with 100% efficiency due to several irreversibility's. If the output obtained from the system is maximum for a given input, maximum amount of energy can be saved globally. To understand the thermodynamic losses occurring in the system and to predict the available energy that can be tapped from the system, exergy plays a major role. Experimental study on exergy in a system can pave the way to understand the complete behavior of the system exergually. Conceptually exergy studies are based on simulation, to provide a new dimension to the concept of exergy experimental validation have been promoted. The analogy of exergy analysis of three refrigerants working in scroll compressors and their exergual features are explained in this paper. The refrigerants R22, R417A, and R407C and their thermo dynamical behavior, irreversibility were experimented in an air conditioning system with three scroll compressors, interaction between the system and the refrigerant in terms of pressure drop and heat transfer, friction has been implemented for the calculation of exergy. The entire system performance on the basis of refrigerant is validated in each part of the air conditioning system. The resultant coefficient of performance of R407C is 2.41% less than R22 in a R22 designed scroll compressor with minimal exergy losses. The second law efficiency of 50 to 55% obtained in R22 has fewer rules over R407C and R417A which has 48 to 52%. The diminutive deviation of results encourages R417A refrigerant to be used as a substitute for R22. Thus the exergual prediction of performance of refrigerant and second law efficiency can identify the use of eco-friendly refrigerant in scroll compressor.

  9. Comparison between regenerative organic Rankine cycle (RORC) and basic organic Rankine cycle (BORC) based on thermoeconomic multi-objective optimization considering exergy efficiency and levelized energy cost (LEC)

    International Nuclear Information System (INIS)

    Feng, Yongqiang; Zhang, Yaning; Li, Bingxi; Yang, Jinfu; Shi, Yang

    2015-01-01

    Highlights: • The thermoeconomic comparison of regenerative RORC and BORC is investigated. • The Pareto frontier solution with bi-objective compares with the corresponding single-objective solutions. • The three-objective optimization of the RORC and BORC is studied. • The RORC owns 8.1% higher exergy efficiency and 21.1% more LEC than the BORC under the Pareto-optimal solution. - Abstract: Based on the thermoeconomic multi-objective optimization by using non-dominated sorting genetic algorithm (NSGA-II), considering both thermodynamic performance and economic factors, the thermoeconomic comparison of regenerative organic Rankine cycles (RORC) and basic organic Rankine cycles (BORC) are investigated. The effects of five key parameters including evaporator outlet temperature, condenser temperature, degree of superheat, pinch point temperature difference and degree of supercooling on the exergy efficiency and levelized energy cost (LEC) are examined. Meanwhile, the Pareto frontier solution with bi-objective for maximizing exergy efficiency and minimizing LEC is obtained and compared with the corresponding single-objective solutions. Research demonstrates that there is a significant negative correlation between thermodynamic performance and economic factors. And the optimum exergy efficiency and LEC for the Pareto-optimal solution of the RORC are 55.97% and 0.142 $/kW h, respectively, which are 8.1% higher exergy efficiency and 21.1% more LEC than that of the BORC under considered condition. Highest exergy and thermal efficiencies are accompanied with lowest net power output and worst economic performance. Furthermore, taking the net power output into account, detailed investigation on the three-objective optimization for maximizing exergy efficiency, maximizing net power output and minimizing LEC is discussed

  10. Parametric exergy analysis of a tubular Solid Oxide Fuel Cell (SOFC) stack through finite-volume model

    International Nuclear Information System (INIS)

    Calise, F.; Ferruzzi, G.; Vanoli, L.

    2009-01-01

    This paper presents a very detailed local exergy analysis of a tubular Solid Oxide Fuel Cell (SOFC) stack. In particular, a complete parametric analysis has been carried out, in order to assess the effects of the synthesis/design parameters on the local irreversibilities in the components of the stack. A finite-volume axial-symmetric model of the tubular internal reforming Solid Oxide Fuel Cell stack under investigation has been used. The stack consists of: SOFC tubes, tube-in-tube pre-reformer and tube and shell catalytic burner. The model takes into account the effects of heat/mass transfer and chemical/electrochemical reactions. The model allows one to predict the performance of a SOFC stack once a series of design and operative parameters are fixed, but also to investigate the source and localization of inefficiency. To this scope, an exergy analysis was implemented. The SOFC tube, the pre-reformer and the catalytic burner are discretized along their longitudinal axes. Detailed models of the kinetics of the reforming, catalytic combustion and electrochemical reactions are implemented. Pressure drops, convection heat transfer and overvoltages are calculated on the basis of the work previously developed by the authors. The heat transfer model includes the contribution of thermal radiation, so improving the models previously used by the authors. Radiative heat transfer is calculated on the basis of the slice-to-slice configuration factors and corresponding radiosities. On the basis of this thermochemical model, an exergy analysis has been carried out, in order to localize the sources and the magnitude of irreversibilities along the components of the stack. In addition, the main synthesis/design variables were varied in order to assess their effect on the exergy destruction within the component to which the parameter directly refers ('endogenous' contribution) and on the exergy destruction of all remaining components ('exogenous' contribution). Then, this analysis

  11. Exergy Analysis and Optimization of an Alpha Type Stirling Engine Using the Implicit Filtering Algorithm

    Directory of Open Access Journals (Sweden)

    James A. Wills

    2017-12-01

    Full Text Available This paper presents the exergy analysis and optimization of the Stirling engine, which has enormous potential for use in the renewable energy industry as it is quiet, efficient, and can operate with a variety of different heat sources and, therefore, has multi-fuel capabilities. This work aims to present a method that can be used by a Stirling engine designer to quickly and efficiently find near-optimal or optimal Stirling engine geometry and operating conditions. The model applies the exergy analysis methodology to the ideal-adiabatic Stirling engine model. In the past, this analysis technique has only been applied to highly idealized Stirling cycle models and this study shows its use in the realm of Stirling cycle optimization when applied to a more complex model. The implicit filtering optimization algorithm is used to optimize the engine as it quickly and efficiently computes the optimal geometry and operating frequency that gives maximum net-work output at a fixed energy input. A numerical example of a 1,000 cm3 engine is presented, where the geometry and operating frequency of the engine are optimized for four different regenerator mesh types, varying heater inlet temperature and a fixed energy input of 15 kW. The WN200 mesh is seen to perform best of the four mesh types analyzed, giving the greatest net-work output and efficiency. The optimal values of several different engine parameters are presented in the work. It is shown that the net-work output and efficiency increase with increasing heater inlet temperature. The optimal dead-volume ratio, swept volume ratio, operating frequency, and phase angle are all shown to decrease with increasing heater inlet temperature. In terms of the heat exchanger geometry, the heater and cooler tubes are seen to decrease in size and the cooler and heater effectiveness is seen to decrease with increasing heater temperature, whereas the regenerator is seen to increase in size and effectiveness. In

  12. Energy and exergy analysis of a geothermal heat pump air conditioning system

    International Nuclear Information System (INIS)

    Baccoli, Roberto; Mastino, Costantino; Rodriguez, Giuseppe

    2015-01-01

    This paper considers the energy analysis of a heat pump system coupled to the ground by means of vertical exchangers, to verify which thermodynamic boundary conditions, in terms of thermal conductivity and diffusivity of the ground and the grout, make it competitive in comparison with other technologies harnessing atmospheric air as the heat source. The comparison is based on the maximum theoretical efficiency available in correspondence to the temperature effectively assumed by the thermal energy reservoirs in contact with the evaporator and the condenser during the operating conditions. The comparison of the two sources/sinks of heat, i.e. the ground and atmospheric air, represents the comparison between the time trend of the exergy of the two reservoirs required by an ideal GSHP and ASHP respectively. A fully transient heat transfer model able to handle on a time scale of a year or more and with a refinement of less than an hour is considered, since short term variations have significant effects on the overall performance of GSHP. In this paper the borehole heat transfer problem in the Laplace domain is solved for any trend and duration of thermal loads, taking into account an existing analytical approximation model of the full solution proposed by Lamarche and Beauchamp. A numerical inversion using the Inverse Discrete Fourier Transform is then applied to obtain the time domain solution. The method combines the flexibility and accuracy of the analytical model with the superior efficiency of the computational time offered by the numerical inversion if compared with that of methods based on the convolution scheme. - Highlights: • The energy and exergy analysis of a GSHP versus a ASHP system is considered. • The model works on a time scale of a year, with a refinement of less than an hour. • Flexibility and efficiency are combined by an analytical model and numerical inversion. • For which order of λ and α the GSHP is not competitive respect to ASHP is

  13. Detailed analysis of the effect of the turbine and compressor isentropic efficiency on the thermal and exergy efficiency of a Brayton cycle

    Directory of Open Access Journals (Sweden)

    Živić Marija

    2014-01-01

    Full Text Available Energy and exergy analysis of a Brayton cycle with an ideal gas is given. The irreversibility of the adiabatic processes in turbine and compressor is taken into account through their isentropic efficiencies. The net work per cycle, the thermal efficiency and the two exergy efficiencies are expressed as functions of the four dimensionless variables: the isentropic efficiencies of turbine and compressor, the pressure ratio, and the temperature ratio. It is shown that the maximal values of the net work per cycle, the thermal and the exergy efficiency are achieved when the isentropic efficiencies and temperature ratio are as high as possible, while the different values of pressure ratio that maximize the net work per cycle, the thermal and the exergy efficiencies exist. These pressure ratios increase with the increase of the temperature ratio and the isentropic efficiency of compressor and turbine. The increase of the turbine isentropic efficiency has a greater impact on the increase of the net work per cycle and the thermal efficiency of a Brayton cycle than the same increase of compressor isentropic efficiency. Finally, two goal functions are proposed for thermodynamic optimization of a Brayton cycle for given values of the temperature ratio and the compressor and turbine isentropic efficiencies. The first maximizes the sum of the net work per cycle and thermal efficiency while the second the net work per cycle and exergy efficiency. In both cases the optimal pressure ratio is closer to the pressure ratio that maximizes the net work per cycle.

  14. A method for energy and exergy analyses of product transformation processes in industry

    International Nuclear Information System (INIS)

    Abou Khalil, B.

    2008-12-01

    After a literature survey enabling the determination of the advantages and drawbacks of existing methods of assessment of the potential energy gains of an industrial site, this research report presents a newly developed method, named Energy and Exergy Analysis of Transformation Processes (or AEEP for Analyse energetique et exergetique des procedes de transformation), while dealing with actual industrial operations, in order to demonstrate the systematic character of this method. The different steps of the method are presented and detailed, one of them, the process analysis, being critical for the application of the developed method. This particular step is then applied to several industrial unitary operations in order to be a base for future energy audits in the concerned industry sectors, as well as to demonstrate its generic and systematic character. The method is the then applied in a global manner to a cheese manufacturing plant, all the different steps of the AEEP being applied. The author demonstrates that AEEP is a systematic method and can be applied to all energy audit levels, moreover to the lowest levels which have a relatively low cost

  15. Exergy, Economic and Environmental Analysis for Simple and Combined Heat and Power IC Engines

    Directory of Open Access Journals (Sweden)

    Mehdi Aliehyaei

    2015-04-01

    Full Text Available This study reports the results of exergy, economic and environmental analyses of simple and combined heat and power internal combustion engines. Values of entropy production, second law efficiency are calculated, and an objective function, including initial, operation, maintenance and fuel costs, as well as the external costs of environmental pollutants, such as CO2, CO and NOx, are presented for the flue gas of the internal combustion engine. The results show that entropy generation in the combined heat and power mode is 30% lower than that in the simple internal combustion engine. Also, by excessively increasing the air ratio, the system entropy generation decreases in both cases of simple and combined heat and power IC engines. The greatest portion of entropy generation is related to the combined heat and power internal combustion engine. The gas heat exchanger generates more entropy than the jacket heat exchanger. Lower values of electricity cost and external costs of air pollution are provided by higher values of molar air to fuel ratio. The environmental aspects depend on location of the system and time of engine operation.

  16. Energy and exergy analysis of electricity generation from natural gas pressure reducing stations

    International Nuclear Information System (INIS)

    Neseli, Mehmet Alparslan; Ozgener, Onder; Ozgener, Leyla

    2015-01-01

    Highlights: • Forecasting the recoverable energy from natural gas pressure reduction stations. • Electricity generation through pressure reduction stations via turboexpanders. • A thermodynamics analysis of PRS. - Abstract: Electricity generation or power recovery through pressure reduction stations (PRS) for general use has not been realized in Izmir. The main objective of the present study was to do a case study for calculating electricity to be recovered in one natural gas pressure reduction stations in Izmir. It is the first forecasting study to obtain energy from natural gas pressure-reducing stations in Izmir. Energy can be obtained from natural gas PRS with turbo-expanders instead of using throttle valves or regulators from the PRS. The exergy performance of PRS with TE is evaluated in this study. Exergetic efficiencies of the system and components are determined to assess their individual performances. Based upon pressure change and volumetric flow rate, it can be obtained by recovering average estimated installed capacity and annual energy 494.24 kW, 4113.03 MW h, respectively. In terms of estimated installed capacity power and annual energy, the highest level is 764.88 kW, approximately 6365.34 MW h, in Aliaga PRS. Also it can be seen that CO 2 emission factor average value is 295.45 kg/MW h

  17. Exergy analysis of large-scale helium liquefiers: Evaluating design trade-offs

    Science.gov (United States)

    Thomas, Rijo Jacob; Ghosh, Parthasarathi; Chowdhury, Kanchan

    2014-01-01

    It is known that higher heat exchanger area, more number of expanders with higher efficiency and more involved configuration with multi-pressure compression system increase the plant efficiency of a helium liquefier. However, they involve higher capital investment and larger size. Using simulation software Aspen Hysys v 7.0 and exergy analysis as the tool of analysis, authors have attempted to identify various trade-offs while selecting the number of stages, the pressure levels in compressor, the cold-end configuration, the heat exchanger surface area, the maximum allowable pressure drop in heat exchangers, the efficiency of expanders, the parallel/series connection of expanders etc. Use of more efficient cold ends reduces the number of refrigeration stages and the size of the plant. For achieving reliability along with performance, a configuration with a combination of expander and Joule-Thomson valve is found to be a better choice for cold end. Use of multi-pressure system is relevant only when the number of refrigeration stages is more than 5. Arrangement of expanders in series reduces the number of expanders as well as the heat exchanger size with slight expense of plant efficiency. Superior heat exchanger (having less pressure drop per unit heat transfer area) results in only 5% increase of plant performance even when it has 100% higher heat exchanger surface area.

  18. Using cryogenic exergy of liquefied natural gas for electricity production with the Stirling cycle

    International Nuclear Information System (INIS)

    Dong, Hui; Zhao, Liang; Zhang, Songyuan; Wang, Aihua; Cai, Jiuju

    2013-01-01

    Cryogenic generation is one of the most important ways to utilize cold energy during LNG (liquefied natural gas) regasification. This paper fundamentally investigates LNG cryogenic generation with the Stirling cycle method based on previous studies. A basic process of LNG cryogenic generation with the Stirling cycle was presented initially with seawater and LNG as heat source and heat sink. And its thermodynamic analysis was performed to verify the theoretical feasibility of the Stirling cycle method. The generating capacity, the exergy efficiency and the cold energy utilization efficiency of the basic process were also calculated. Subsequently, the influences of evaporation pressure on net work, equipment performance and comprehensive efficiency of cold energy utilization were discussed and the effect of LNG mass flow as well as the ambient temperature was also studied. Finally an improved process of LNG cryogenic generation with Stirling cycle method combined with an air liquefaction process is proposed as feasibility in improvements of the basic process. - Highlights: • We propose a basic process of LNG cryogenic generation with the Stirling cycle. • Seawater and LNG were applied as heat source and heat sink of the basic process. • The max generating capacity of the basic process is 51 kWh/tLNG. • The max cold energy utilization efficiency of the basic process is 0.56. • We also discussed some feasibilities of optimization of the basic cycle

  19. Assessment of maximum available work of a hydrogen fueled compression ignition engine using exergy analysis

    International Nuclear Information System (INIS)

    Chintala, Venkateswarlu; Subramanian, K.A.

    2014-01-01

    This work is aimed at study of maximum available work and irreversibility (mixing, combustion, unburned, and friction) of a dual-fuel diesel engine (H 2 (hydrogen)–diesel) using exergy analysis. The maximum available work increased with H 2 addition due to reduction in irreversibility of combustion because of less entropy generation. The irreversibility of unburned fuel with the H 2 fuel also decreased due to the engine combustion with high temperature whereas there is no effect of H 2 on mixing and friction irreversibility. The maximum available work of the diesel engine at rated load increased from 29% with conventional base mode (without H 2 ) to 31.7% with dual-fuel mode (18% H 2 energy share) whereas total irreversibility of the engine decreased drastically from 41.2% to 39.3%. The energy efficiency of the engine with H 2 increased about 10% with 36% reduction in CO 2 emission. The developed methodology could also be applicable to find the effect and scope of different technologies including exhaust gas recirculation and turbo charging on maximum available work and energy efficiency of diesel engines. - Highlights: • Energy efficiency of diesel engine increases with hydrogen under dual-fuel mode. • Maximum available work of the engine increases significantly with hydrogen. • Combustion and unburned fuel irreversibility decrease with hydrogen. • No significant effect of hydrogen on mixing and friction irreversibility. • Reduction in CO 2 emission along with HC, CO and smoke emissions

  20. Depletion of the non-renewable natural exergy resources as a measure of the ecological cost

    International Nuclear Information System (INIS)

    Szargut, Jan; Ziebik, Andrzej; Stanek, Wojciech

    2002-01-01

    The cumulative consumption of non-renewable exergy connected with the fabrication of particular products has been termed as their ecological cost. System of linear input-output equations determining the ecological costs have been formulated. The cogeneration processes have been considered using the principle of the avoided costs of fabrication of the products substituted by the by-products of the considered process. The ecological cost determined in a regional scope takes into account the ecological cost of the imported raw materials and semi-finished products. These quantities have been substituted by the economically equivalent export of own products. The deleterious effect of the rejection of waste products to the environment has been approximately determined by means of the monetary indices of harmfulness of waste products. It has been proved, that the ecological cost of human work cannot be introduced into the set of input-output equations. Exemplary calculations have been made for the products connected with the blast-furnace process. The influence of the injection of auxiliary fuels into the blast furnace on the ecological cost of pig iron has been analyzed too. (Author)

  1. Hydrogen from biomass gas steam reforming for low temperature fuel cell: energy and exergy analysis

    Directory of Open Access Journals (Sweden)

    A. Sordi

    2009-03-01

    Full Text Available This work presents a method to analyze hydrogen production by biomass gasification, as well as electric power generation in small scale fuel cells. The proposed methodology is the thermodynamic modeling of a reaction system for the conversion of methane and carbon monoxide (steam reforming, as well as the energy balance of gaseous flow purification in PSA (Pressure Swing Adsorption is used with eight types of gasification gases in this study. The electric power is generated by electrochemical hydrogen conversion in fuel cell type PEMFC (Proton Exchange Membrane Fuel Cell. Energy and exergy analyses are applied to evaluate the performance of the system model. The simulation demonstrates that hydrogen production varies with the operation temperature of the reforming reactor and with the composition of the gas mixture. The maximum H2 mole fraction (0.6-0.64 mol.mol-1 and exergetic efficiency of 91- 92.5% for the reforming reactor are achieved when gas mixtures of higher quality such as: GGAS2, GGAS4 and GGAS5 are used. The use of those gas mixtures for electric power generation results in lower irreversibility and higher exergetic efficiency of 30-30.5%.

  2. Mass, energy, entropy and exergy rate balance in a ranque-hilsh vortex tube

    Directory of Open Access Journals (Sweden)

    Edorta Carrascal

    2013-12-01

    Full Text Available The purpose of this paper is to exhibit a laboratory practicum designed for the subject of Thermodynamics at the Department of Thermal Engineering of the University of the Basque Country. With reference to one of the problems stated in the text of Moran, Shapiro, Boettner, Bailey (2012, the balances of mass, energy, entropy and exergy are applied in a particular Control Volume, and the ideal gas model is used. Using a Ranque-Hilsh vortex tube (Ranque, 1934, the division of a compressed air flow into two streams at a lower pressure is achieved; one hot  whose temperature can exceed 100 °C and another cold that can reach temperatures below -40 °C. Therefore an air flow is divided into two, one hot and one cold stream, without any thermal interaction with hot or cold focuses. The vortex tube operation can serve to expose the bases of the first and second law of thermodynamics. Even, this practical lab can be used to give sense to one of the most known theoretical experiments in thermodynamics, such as the one of Maxwell's demon (Lewins & Bejan, 1999; Liew, Zeegers, Kuerten & Michalek, 2012. On the other hand once a compressed air source is provided, the material needed to prepare the lab is simple and affordable and it has a very interesting and suggestive appeal.

  3. Energy and exergy analysis of an ethanol reforming process for solid oxide fuel cell applications.

    Science.gov (United States)

    Tippawan, Phanicha; Arpornwichanop, Amornchai

    2014-04-01

    The fuel processor in which hydrogen is produced from fuels is an important unit in a fuel cell system. The aim of this study is to apply a thermodynamic concept to identify a suitable reforming process for an ethanol-fueled solid oxide fuel cell (SOFC). Three different reforming technologies, i.e., steam reforming, partial oxidation and autothermal reforming, are considered. The first and second laws of thermodynamics are employed to determine an energy demand and to describe how efficiently the energy is supplied to the reforming process. Effect of key operating parameters on the distribution of reforming products, such as H2, CO, CO2 and CH4, and the possibility of carbon formation in different ethanol reformings are examined as a function of steam-to-ethanol ratio, oxygen-to-ethanol ratio and temperatures at atmospheric pressure. Energy and exergy analysis are performed to identify the best ethanol reforming process for SOFC applications. Copyright © 2014 Elsevier Ltd. All rights reserved.

  4. Energy and exergy analysis of photovoltaic-thermal collector with and without glass cover

    International Nuclear Information System (INIS)

    Chow, T.T.; Pei, G.; Fong, K.F.; Lin, Z.; Chan, A.L.S.; Ji, J.

    2009-01-01

    In photovoltaic-thermal (PV/T) technology, the use of glass cover on the flat-plate hybrid solar collector is favorable to the photothermic process but not to the photovoltaic process. Because of the difference in the usefulness of electricity and thermal energy, there is often no straight forward answer on whether a glazed or unglazed collector system is more suitable for a specific application. This glazing issue was tackled in this paper from the viewpoint of thermodynamics. Based on experimental data and validated numerical models, a study of the appropriateness of glass cover on a thermosyphon-based water-heating PV/T system was carried out. The influences of six selected operating parameters were evaluated. From the first law point of view, a glazed PV/T system is found always suitable if we are to maximize the quantity of either the thermal or the overall energy output. From the exergy analysis point of view however, the increase of PV cell efficiency, packing factor, water mass to collector area ratio, and wind velocity are found favorable to go for an unglazed system, whereas the increase of on-site solar radiation and ambient temperature are favorable for a glazed system

  5. Energy and exergy efficiency comparison of horizontal and vertical axis wind turbines

    Energy Technology Data Exchange (ETDEWEB)

    Pope, K.; Dincer, I.; Naterer, G.F. [Faculty of Engineering and Applied Science, University of Ontario Institute of Technology, 2000 Simcoe Street North, Oshawa, Ontario (Canada)

    2010-09-15

    In this paper, an energy and exergy analysis is performed on four different wind power systems, including both horizontal and vertical axis wind turbines. Significant variability in turbine designs and operating parameters are encompassed through the selection of systems. In particular, two airfoils (NACA 63(2)-215 and FX 63-137) commonly used in horizontal axis wind turbines are compared with two vertical axis wind turbines (VAWTs). A Savonius design and Zephyr VAWT benefit from operational attributes in wind conditions that are unsuitable for airfoil type designs. This paper analyzes each system with respect to both the first and second laws of thermodynamics. The aerodynamic performance of each system is numerically analyzed by computational fluid dynamics software, FLUENT. A difference in first and second law efficiencies of between 50 and 53% is predicted for the airfoil systems, whereas 44-55% differences are predicted for the VAWT systems. Key design variables are analyzed and the predicted results are discussed. The exergetic efficiency of each wind turbine is studied for different geometries, design parameters and operating conditions. It is shown that the second law provides unique insight beyond a first law analysis, thereby providing a useful design tool for wind power development. (author)

  6. NLP modeling for the optimization of LiBr-H2O absorption refrigeration systems with exergy loss rate, heat transfer area, and cost as single objective functions

    DEFF Research Database (Denmark)

    Mussati, Sergio F.; Gernaey, Krist; Morosuk, Tatiana

    2016-01-01

    exergy loss rate, the total heat transfer area, and the total annual cost of the system. It was found that the optimal solution obtained by minimization of the total exergy loss rate provides “theoretical” upper bounds not only for the total heat transfer area of the system but also for each process unit...... and all stream temperatures, while the optimal solution obtained by minimization of the total heat transfer area provides the lower bounds for these model variables, to solve a cost optimization problem. The minimization of the total exergy loss rate by varying parametrically the available total heat...... transfer area between these bounds was also performed, allowing to see how the optimal distribution of the available total heat transfer area among the system components, as well as the operating conditions (stream temperature, pressure, composition, and mass flow rate) and heat loads, vary qualitatively...

  7. Exergy analysis of a hydrogen fired combined cycle with natural gas reforming and membrane assisted shift reactors for CO2 capture

    International Nuclear Information System (INIS)

    Atsonios, K.; Panopoulos, K.D.; Doukelis, A.; Koumanakos, A.; Kakaras, Em.

    2012-01-01

    Highlights: ► Exergy analysis of NGCC with CCS. ► WGS-MR: exergetically efficient technology for CCS, less than 2% total exergy losses. ► 10% of total exergy dissipation in the ATR. ► Optimization of ATR operation and CO 2 stream treatment. - Abstract: Hydrogen production from fossil fuels together with carbon capture has been suggested as a means of providing a carbon free power. The paper presents a comparative exergetic analysis performed on the hydrogen production from natural gas with several combinations of reactor systems: (a) oxy or air fired autothermal reforming with subsequent water gas shift reactor and (b) membrane reactor assisted with shift catalysts. The influence of reactor temperature and pressure as well as operating parameter steam-to-carbon ratio, is also studied exergetically. The results indicate optimal power plant configurations with CO 2 capture, or hydrogen delivery for industrial applications.

  8. Energy, exergy, economic (3E) analyses and multi-objective optimization of vapor absorption heat transformer using NSGA-II technique

    International Nuclear Information System (INIS)

    Jain, Vaibhav; Sachdeva, Gulshan

    2017-01-01

    Highlights: • Study includes energy, exergy and economic analyses of absorption heat transformer. • It addresses multi-objective optimization study using NSGA-II technique. • Total annual cost and total exergy destruction are simultaneously optimized. • Results with multi-objective optimized design are more acceptable than other. - Abstract: Present paper addresses the energy, exergy and economic (3E) analyses of absorption heat transformer (AHT) working with LiBr-H 2 O fluid pair. The heat exchangers namely absorber, condenser, evaporator, generator and solution heat exchanger are designed for the size and cost estimation of AHT. Later, the effect of operating variables is examined on the system performance, size and cost. Simulation studies showed a conflict between thermodynamic and economic performance of the system. The heat exchangers with lower investment cost showed high irreversible losses and vice versa. Thus, the operating variables of systems are determined economically as well as thermodynamically by implementing non-dominated sort genetic algorithm-II (NSGA-II) technique of multi-objective optimization. In present work, if the cost based optimized design is chosen, total exergy destruction is 2.4% higher than its minimum possible value; whereas, if total exergy based optimized design is chosen, total annual cost is 6.1% higher than its minimum possible value. On the other hands, total annual cost and total exergy destruction are only 1.0% and 0.8%, respectively more from their minimum possible values with multi-objective optimized design. Thus, the multi-objective optimized design of the AHT is best outcome than any other single-objective optimized designs.

  9. Development of a correlation for parameter controlling using exergy efficiency optimization of an Al_2O_3/water nanofluid based flat-plate solar collector

    International Nuclear Information System (INIS)

    Shojaeizadeh, Ehsan; Veysi, Farzad

    2016-01-01

    Highlights: • Exergy efficiency optimization of a flat-plate collector with Al_2O_3 nanofluid is studied. • Solar radiation and ambient temperature are assumed to be uncontrollable. • Solar collector inlet temperature is influenced by the presence of reservoir tank. • A suitable exponential correlation is proposed for the optimized exergy efficiency. • This exponential correlation also is used for controlling independent parameters. - Abstract: The current study deals with the exergy efficiency optimization of an Al_2O_3/water nanofluid-based flat-plate solar collector according to a mathematical optimization (Sequential Quadratic Programming (SQP) method). This study takes into account exergy efficiency optimization when solar radiation and ambient temperature parameters are assumed to be uncontrollable and presented to a wide range of transient data of climatic conditions where these might take place during spring and summer seasons of Kermanshah (Iran), and perform two main cases as follows: (1) the fluid temperature at the inlet of solar collector, T_i, is independent of storage tank (open loop); (2) the fluid temperature at the inlet of solar collector, T_i, is influenced by the presence of storage tank (closed loop). In any conditions of each case studies (working fluid with and without nanoparticles), a suitable decreasing exponential correlation as function of T_a/G_t values (i.e. ambient temperature to solar radiation ratio) is developed for the optimized exergy efficiency and also well controlling independent parameters values (mass flow rate of fluid, nanoparticle volume concentration and collector inlet temperature). Also, it is concluded that each of optimized parameters and the optimum exergy efficiency is of a linear relation with each other.

  10. Energy and exergy performance analysis of a marine rotary desiccant air-conditioning system based on orthogonal experiment

    International Nuclear Information System (INIS)

    Zhu, Jun; Chen, Wu

    2014-01-01

    A novel marine rotary desiccant A/C (air-conditioning) system was developed and studied to improve energy utilization efficiency of ship A/C. The orthogonal experiment was first carried out to investigate the influence of various parameters of the marine rotary desiccant A/C system. During the orthogonal experiment the analysis of variance was used to exclude interference from the secondary influencing factor on system performance. The significant influencing factors of system were studied in great detail using the first and second laws of thermodynamics to find optimal setting parameters for best system performance. It is suggested from the analysis results that as regeneration temperature increases, the COP th (thermal coefficient of performance) and exergy efficiency of system (η e ) decreases by 46.9% and 38.8% respectively. They decrease in proportion to the increase of the temperature. η e reaches its maximum value of about 23.5% when the inlet humidity ratio of process air is 22 g/kg. Besides, the exergy loss of system concentrates on the regeneration air heater, the desiccant wheel and the regeneration air leaving the desiccant wheel, which account for 68.4%–81% of the total exergy loss. It can be concluded that applying the marine rotary desiccant A/C in high-temperature and high-humidity marine environment is advantageous. - Highlights: • Significant influencing factors of the system are found by the analysis of variance. • The change trends of the COP th and the η e are nearly proportional with the regeneration temperature. • The η e reaches its maximum value (about 23.5%) when the inlet humidity ratio of process air is 22 g/kg. • The contribution rate of the dry-bulb temperature of fresh air is up to 73.91% for the COP th . • Applying the marine rotary desiccant A/C in high-temperature and high-humidity marine environment is advantageous

  11. Energy and exergy analysis of a closed Brayton cycle-based combined cycle for solar power tower plants

    International Nuclear Information System (INIS)

    Zare, V.; Hasanzadeh, M.

    2016-01-01

    Highlights: • A novel combined cycle is proposed for solar power tower plants. • The effects of solar subsystem and power cycle parameters are examined. • The proposed combined cycle yields exergy efficiencies of higher than 70%. • For the overall power plant exergy efficiencies of higher than 30% is achievable. - Abstract: Concentrating Solar Power (CSP) technology offers an interesting potential for future power generation and research on CSP systems of all types, particularly those with central receiver system (CRS) has been attracting a lot of attention recently. Today, these power plants cannot compete with the conventional power generation systems in terms of Levelized Cost of Electricity (LCOE) and if a competitive LCOE is to be reached, employing an efficient thermodynamic power cycle is deemed essential. In the present work, a novel combined cycle is proposed for power generation from solar power towers. The proposed system consists of a closed Brayton cycle, which uses helium as the working fluid, and two organic Rankine cycles which are employed to recover the waste heat of the Brayton cycle. The system is thermodynamically assessed from both the first and second law viewpoints. A parametric study is conducted to examine the effects of key operating parameters (including solar subsystem and power cycle parameters) on the overall power plant performance. The results indicate that exergy efficiencies of higher than 30% are achieved for the overall power plant. Also, according to the results, the power cycle proposed in this work has a better performance than the other investigated Rankine and supercritical CO_2 systems operating under similar conditions, for these types of solar power plants.

  12. Application of exergy for the determination of the pro-ecological tax replacing the actual personal taxes

    International Nuclear Information System (INIS)

    Szargut, J.

    2002-01-01

    According to some published suggestions, taxes should not be a kind of penalty for positive effects of human activity (productivity, invention) but should burden negative effects, like the depletion of natural resources, and deleterious impacts on the environment. The consumption of non-renewable resources of exergy has been proposed in the present paper as a measure of the negative effects of human activity and a basis for a pro-ecological tax. A proposed course for determining this tax has been formulated. The method presented takes into account also the deleterious impact of waste products on the natural environment, the wear of machines and installations and the import of foreign products. (author)

  13. Performance of Loaded Thermal Storage Unit with a Commercial Phase Change Materials based on Energy and Exergy Analysis

    Directory of Open Access Journals (Sweden)

    Abdullah Nasrallh Olimat

    2017-11-01

    Article History: Received July 6th 2017; Received in revised form September 15th 2017; Accepted 25th Sept 2017; Available online How to Cite This Article: Olimat, A.N., Awad, A.S., Al-Gathain, F.M., and Shaban, N.A.. (2017 Performance of Loaded Thermal Storage Unit With A Commercial Phase Change Materials Based on Energy and Exergy Analysis. International Journal of Renewable Energy Develeopment, 6(3,283-290. https://doi.org/10.14710/ijred.6.3.283-290

  14. Energy and Exergy Analysis of Dual Channel Solar Air Collector with Different Absorber Plates Geometry

    Directory of Open Access Journals (Sweden)

    Najim A. Jassim

    2018-04-01

    Full Text Available Flat-plate collector considers most common types of collectors, for ease of manufacturing and low price compared with other collectors. The main aim of the present work is to increase the efficiency of the collector, which can be achieved by improving the heat transfer and minimize heat loss experimentally. Five types of solar air collectors have been tested, which conventional channel with a smooth absorber plate (model I, dual channel with a smooth absorber plate (model II, dual channel with perforating “V” corrugated absorber plate (model III, dual channel with internal attached wire mesh (model Ⅳ, and dual channel with absorber sheet of transparent honeycomb, (model Ⅴ. The dual channel collector used for increasing heat transfer area and heat removal factor to improve thermal performance. The outdoor test was conducted during the period December (2016 to February (2017 at different mass flow rates 0.0217 kg/s, 0.0271 kg/s and 0.0325 kg/s. The experiments were carried out from 8:30 AM to 3:00 PM for clear days. Experimental results show that the average thermal efficiency was (72.2 % for model (III, (40.2 % for model (I, (51.6 % for model (II, (65.1 % for model (Ⅳ and (59.7 % for model (Ⅴ. At the last part of the study, the exergy analyses were derived for both collectors. The results of this part showed that the conventional channel model (I is having largest irreversibility, and the dual channel collector model (III is having a greatest exergetic efficiency.

  15. The effect of ethanol-gasoline blends on performance and exhaust emissions of a spark ignition engine through exergy analysis

    International Nuclear Information System (INIS)

    Doğan, Battal; Erol, Derviş; Yaman, Hayri; Kodanli, Evren

    2017-01-01

    Highlights: • Examining the performance of ethanol-gasoline blend. • Evaluation of the exhaust emissions. • Energy and exergy analysis. • Calculation of irreversibility from cooling system and the exhaust resulting. - Abstract: Ethanol which is considered as an environmentally cleaner alternative to fossil fuels is used on its own or blended with other fuels in different ratios. In this study, ethanol which has high octane rating, low exhaust emission, and which is easily obtained from agricultural products has been used in fuels prepared by blending it with gasoline in various ratios (E0, E10, E20, and E30). Ethanol-gasoline blends have been used in a four-cylinder four-stroke spark ignition engine for performance and emission analysis under full load. In the experimental studies, engine torque, fuel and cooling water flow rates, and exhaust and engine surface temperature have been measured. Engine energy distribution, irreversible processes in the cooling system and the exhaust, and the exergy distribution have been calculated using the experimental data and the formulas for the first and second laws of thermodynamics. Experiments and theoretical calculations showed that ethanol added fuels show reduction in carbon monoxide (CO), carbon dioxide (CO_2) and nitrogen oxide (NO_X) emissions without significant loss of power compared to gasoline. But it was measured that the reduction of the temperature inside the cylinder increases the hydrocarbon (HC) emission.

  16. Exergy Analysis of an Intermediate Temperature Solid Oxide Fuel Cell-Gas Turbine Hybrid System Fed with Ethanol

    Directory of Open Access Journals (Sweden)

    Fotini Tzorbatzoglou

    2012-10-01

    Full Text Available In the present work, an ethanol fed Solid Oxide Fuel Cell-Gas Turbine (SOFC-GT system has been parametrically analyzed in terms of exergy and compared with a single SOFC system. The solid oxide fuel cell was fed with hydrogen produced from ethanol steam reforming. The hydrogen utilization factor values were kept between 0.7 and 1. The SOFC’s Current-Volt performance was considered in the range of 0.1–3 A/cm2 at 0.9–0.3 V, respectively, and at the intermediate operating temperatures of 550 and 600 °C, respectively. The curves used represent experimental results obtained from the available bibliography. Results indicated that for low current density values the single SOFC system prevails over the SOFC-GT hybrid system in terms of exergy efficiency, while at higher current density values the latter is more efficient. It was found that as the value of the utilization factor increases the SOFC system becomes more efficient than the SOFC-GT system over a wider range of current density values. It was also revealed that at high current density values the increase of SOFC operation temperature leads in both cases to higher system efficiency values.

  17. Exergy analysis of an adiabatic compressed air energy storage system using a cascade of phase change materials

    International Nuclear Information System (INIS)

    Tessier, Michael J.; Floros, Michael C.; Bouzidi, Laziz; Narine, Suresh S.

    2016-01-01

    Adiabatic compressed air energy storage is an emerging energy storage technology with excellent power and storage capacities. Currently, efficiencies are approximately 70%, in part due to the issue of heat loss during the compression stage. An exergy analysis is presented on a novel adiabatic compressed air energy storage system design utilizing a cascade of PCMs (phase change materials) for waste heat storage and recovery. The melting temperatures and enthalpies of the PCMs were optimized for this system and were shown to be dependent on the number of PCMs, the number of compression stages, and the maximum compression ratio. Efficiencies of storage and recovery using this approach are predicted to be as high as 85%, a 15% increase over current designs which do not incorporate PCMs. - Highlights: • A compressed air energy storage plant using phase change materials is proposed. • Increasing number of phase change materials increases roundtrip exergy efficiency. • A thermodynamic model allows melting points and latent heats required to be predicted.

  18. Energy and exergy analysis of a ground-coupled heat pump system with two horizontal ground heat exchangers

    Energy Technology Data Exchange (ETDEWEB)

    Esen, Hikmet; Esen, Mehmet [Department of Mechanical Education, Faculty of Technical Education, Firat University, 23119 Elazig (Turkey); Inalli, Mustafa; Pihtili, Kazim [Department of Mechanical Engineering, Faculty of Engineering, Firat University, 23119 Elazig (Turkey)

    2007-10-15

    In this paper we investigate of energetic and exergetic efficiencies of ground-coupled heat pump (GCHP) system as a function of depth trenches for heating season. The horizontal ground heat exchangers (HGHEs) were used and it were buried with in 1 m (HGHE1) and 2 m (HGHE2) depth trenches. The energy efficiency of GCHP systems are obtained to 2.5 and 2.8, respectively, while the exergetic efficiencies of the overall system are found to be 53.1% and 56.3%, respectively, for HGHE1 and HGHE2. The irreversibility of HGHE2 is less than of the HGHE1 as about 2.0%. The results show that the energetic and exergetic efficiencies of the system increase when increasing the heat source (ground) temperature for heating season. And the end of this study, we deal with the effects of varying reference environment temperature on the exergy efficiencies of HGHE1 and HGHE2. The results show that increasing reference environment temperature decreases the exergy efficiency in both HGHE1 and HGHE2. (author)

  19. Exergy Analysis of a Syngas-Fueled Combined Cycle with Chemical-Looping Combustion and CO2 Sequestration

    Directory of Open Access Journals (Sweden)

    Álvaro Urdiales Montesino

    2016-08-01