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Sample records for exergy

  1. 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.

  2. Exergy analysis

    DEFF Research Database (Denmark)

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

    2011-01-01

    Exergy analysis enables us to make connections among processes inside the human body and processes in a building. So far, only the effect of different combinations of air temperatures and mean radiant temperatures have been studied, with constant relative humidity in experimental conditions...... 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...

  3. Exergy representations in thermodynamics

    OpenAIRE

    Favrat, Daniel; Maréchal, François

    2015-01-01

    The paper reviews various representations of exergy and exergy losses in energy systems going from simple heat exchanger (heat transfer, dissipation and embedded exergy) to the exergy of full energy systems from fossil or non fossil resources (including the diffusion exergy). The systems shown include shell in tube heat exchangers, thermal power cycles, cogeneration, heat pump direct heating systems and cryogenic systems. The representations include simple gravitational analogies to extended ...

  4. Human Body Exergy Metabolism

    OpenAIRE

    Mady, Carlos

    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...

  5. Pitfalls of exergy analysis

    CERN Document Server

    Vágner, Petr; Maršík, František

    2016-01-01

    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 and Sustainability

    NARCIS (Netherlands)

    Stougie, L.; Van der Kooi, H.J.

    2009-01-01

    A thorough qualitative investigation of the relation between exergy losses and environmental problems has been conducted. Environmental effects being taken into account include climate change, acidification, eutrophication, disposal and dissipation. It is concluded that almost all environmental

  7. 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

  8. Exergy Analysis of Rocket Systems

    Science.gov (United States)

    Gilbert, Andrew; Mesmer, Bryan; Watson, Michael D.

    2015-01-01

    Exergy is defined as the useful work available from a system in a specified environment. Exergy analysis allows for comparison between different system designs, and allows for comparison of subsystem efficiencies within system designs. The proposed paper explores the relationship between the fundamental rocket equation and an exergy balance equation. A previously derived exergy equation related to rocket systems is investigated, and a higher fidelity analysis will be derived. The exergy assessments will enable informed, value-based decision making when comparing alternative rocket system designs, and will allow the most efficient configuration among candidate configurations to be determined.

  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. Fractal Representation of Exergy

    Directory of Open Access Journals (Sweden)

    Yvain Canivet

    2016-02-01

    Full Text Available We developed a geometrical model to represent the thermodynamic concepts of exergy and anergy. The model leads to multi-scale energy lines (correlons that we characterised by fractal dimension and entropy analyses. A specific attention will be paid to overlapping points, rising interesting remarks about trans-scale dynamics of heat flows.

  11. The Exergy of Lift and Aircraft Exergy Flow Diagrams

    OpenAIRE

    Richard A. Gaggioli; David M. Paulus, Jr.

    2003-01-01

    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...

  12. Exergy Analysis for Energy Systems

    Science.gov (United States)

    2006-09-01

    AFRL-VA-WP-TM-2007-3095 EXERGY ANALYSIS FOR ENERGY SYSTEMS Dr. Rama S.R. Gorla Gorla Consultants, Inc. SEPTEMBER 2006 Final...IN-HOUSE 5b. GRANT NUMBER 4. TITLE AND SUBTITLE EXERGY ANALYSIS FOR ENERGY SYSTEMS 5c. PROGRAM ELEMENT NUMBER 0602201 5d. PROJECT NUMBER

  13. Exergy based analysis of economic sustainability”

    OpenAIRE

    Reis, A. Heitor

    2006-01-01

    Exergy is presented here as the physical prime-mover of economic systems, and an exergy based concept of value is proposed in this paper. The main exergy fluxes are identified as those carried by raw exergy (primary sources), raw materials, usable exergy and exergy embodied in manufactured commodities. It is shown how efficiency of exergy use is the physical basis for competitiveness and how exergy content (value)can be assigned to skillfulness and expertise. Sustainability of econom...

  14. Exergy efficiency from staple food ingredients to body metabolism

    NARCIS (Netherlands)

    Rodriguez-Illera, Marta; Nikiforidis, Constantinos V.; Goot, van der Atze Jan; Boom, Remko M.

    2017-01-01

    One of the methods to evaluate the efficiency in the production of foods is using exergy, the share of useful energy, and exergy analysis. In this paper, we propose a link between exergy analysis and nutrition to account for the exergy efficiency (exergy of output per exergy of input) in the

  15. Exergy production, cost and renewability

    CERN Document Server

    Junior, Silvio de Oliveira

    2012-01-01

    Exergy is a powerful analytical tool bridging the conceptual gap between the Second Law of Thermodynamics and applied engineering. This volume shows how it can be deployed in a range of scenarios from power plants to petroleum production and refining.

  16. Exergy analysis of thermal comfort

    OpenAIRE

    Prek, Matjaž

    2015-01-01

    Traditional methods of human thermal comfort are based on the first law of thermodynamics. These methods use an energy balance of the human body to determine heat transfer between the body and its environment. By contrast, thesecond law of thermodynamics introduces the concept of exergy. It enables the determination of exergy consumption within the human body dependent on personal and environmental factors. We show that the existing methods of comfort assessment could be further expanded by t...

  17. Exergy use in the Swedish society 1994

    Energy Technology Data Exchange (ETDEWEB)

    Wall, G.

    1997-07-01

    The exergy concept is reviewed as a tool for resource accounting. Conversions of energy and material resources in the Swedish society in 1994 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 into heat are described in some detail

  18. 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...

  19. 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.

  20. 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.

  1. 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)

  2. Exergy Based Methods for Multidisciplinary Analysis & Design

    Science.gov (United States)

    2011-05-01

    Exergy Based Methods for Multidisciplinary Analysis & Design José A. Camberos, David J. Moorhouse, &tc Multidisciplinary Science & Technology...SUBTITLE Exergy Based Methods for Multidisciplinary Analysis & Design 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) 5d...of Exergy Case Studies 3 MULTIDISCIPLINARY SCIENCE & TECHNOLOGY AFRL Air Vehicles In-House Research Centers 4 Multidisciplinary Science

  3. Recovery of thermomechanical exergy from cryofuels

    Energy Technology Data Exchange (ETDEWEB)

    Fyke, A.; Crane, P.; Scott, D.S. [University of Victoria, British Columbia (Vatican City State, Holy See). Inst. for Integrated Energy Systems; Li, D. [Alberta Univ., Edmonton, AB (Canada). Dept. of Mechanical Engineering

    1997-04-01

    Low carbon fuels can be stored as cryogenic liquids in transportation applications. The vehicle`s primary energy conversion device exploits the chemical exergy of such fuels. Due to their low temperatures, however, they contain thermochemical exergy which is almost always wasted by the energy conversion power train. Thermo-mechanical exergy has two components: one due to temperature and one due to pressure. In cryogens the thermal component is dominant. Recovering the thermomechanical exergy of cryofuels such as LNG or LH{sub 2} can increase the overall systemic efficiency of vehicle power trains. We define a system which recovers the thermomechanical exergy of a cryogen a CERS (Cryogen Exergy Recovery System). However, a system which synergistically utilizes both the exergy of a cryofuel and the exergy of the waste heat of a chemical exergy utilization process (e.g. fuel cell or heat engine) we call an ECERS (Enhanced Cryogen Recovery System). This paper presents the conceptual design of an ECERS using the Ballard fuel cell bus as a ``case study``; however, the emphasis of the paper is on the use of these technologies in a broad context. (Author)

  4. EXERGY AND FISHER INFORMATION AS ECOLOGICAL INDEXES

    Science.gov (United States)

    Ecological indices are used to provide summary information about a particular aspect of ecosystem behavior. Many such indices have been proposed and here we investigate two: exergy and Fisher Information. Exergy, a thermodynamically based index, is a measure of maximum amount o...

  5. Exergy Analysis of Cryogenic Air Separation

    NARCIS (Netherlands)

    Cornelissen, Rene; Hirs, Gerard

    1998-01-01

    An exergy analysis is performed to analyse the possibilities of fuel saving in the cryogenic distillation process, which is the main method of air separation. It is shown that more than half of the exergy loss takes place in the liquefaction unit and almost one-third in the air compression unit.

  6. Interpretation of the exergy equation for steady-flow processes

    NARCIS (Netherlands)

    Siemons, R.V.

    1986-01-01

    We define and discuss the terms in exergy equations, with particular reference to the role of chemical terms in the exergy loss for steady-flow processes. Although there is a chemical contribution to exergy, exergy losses of steady-flow processes may be calculated by using a simple expression for

  7. Advanced exergy analysis of transcritical CO2 heat pump system ...

    Indian Academy of Sciences (India)

    Conventional exergy analysis identifies component exergy destruction, however, does not give clear picture whether occurs because of component itself or due to remaining components and then the advanced exergy analysis is emphasized. The main purpose of this study is to apply advanced exergy analysis to the ...

  8. Exergy analysis of a MSF distillation plant

    Energy Technology Data Exchange (ETDEWEB)

    Kahraman, Nafiz [Department of Mechanical Engineering, Erciyes University, Kayseri (Turkey)]. E-mail: nafiz@erciyes.edu.tr; Cengel, Yunus A. [Department of Mechanical Engineering/312, University of Nevada, Reno, NV 89557 (United States)

    2005-09-15

    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.

  9. 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.

  10. Exergy analysis of nutrient recovery processes.

    Science.gov (United States)

    Hellström, D

    2003-01-01

    In an exergy analysis, the actual consumption of resources in physical and chemical processes is calculated. Energy and chemical elements are not consumed in the processes--they are only transformed into other forms with lower quality. The principals of exergy analysis are illustrated by comparing different wastewater treatment systems for nutrient recovery. One system represents an end-of-pipe structure, whereas other systems include source separation of grey water, black water, and urine. The exergy flows analysed in this paper are those related to management and treatment of organic matter and nutrients. The study shows that the total exergy consumption is lowest for the system with source separation of urine and faeces and greatest for the conventional wastewater treatment system complemented by processes for nutrient recovery.

  11. 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.

  12. Performance of the Dutch Energy Sector based on energy, exergy and Extended Exergy Accounting

    Energy Technology Data Exchange (ETDEWEB)

    Ptasinski, K.J. [Eindhoven University of Technology (Netherlands). Department of Chemical Engineering; Koymans, M.N. [Statistics Netherlands, Voorburg (Netherlands); Verspagen, H.H.G. [Eindhoven University of Technology (Netherlands). Department of Technology Management

    2006-12-15

    The performance of the Dutch Energy Sector is analyzed using the Standard Exergy Analysis as well as Extended Exergy Accounting (EEA) method. Performance indicators based on energy, exergy and cumulative exergy consumption (CExC) are evaluated for three subsectors: exploitation, transformation, and distribution of energy. It is shown that performance indicators based on CExC are much lower than those based on energy and exergy concepts. The EEA method is applied for analysis of four branches: cokeries and refineries, refineries, central electricity production, and distribution and decentral electricity production. The EEA method originally proposed by Sciubba is modified by evaluating the cost-to-exergy conversion factor from the monetary value and CExC of the feedstock. It was found that the monetary equivalent of extended exergy is higher than the respective product sales. Finally, it is shown that performance indicators of selected energy branches based on extended exergy are much lower than those based on the CExC. (author)

  13. The relation between exergy and sustainability according to literature

    NARCIS (Netherlands)

    Stougie, L.; Van der Kooi, H.J.

    2011-01-01

    A thorough investigation of literature about the relation between exergy and sustainability was conducted in September 2010. An overview of opinions and methods in the field of exergy analysis and sustainability is briefly presented. Exergy analysis has several advantages compared to energy

  14. Modeling and Exergy Analysis of District Cooling

    DEFF Research Database (Denmark)

    Nguyen, Chan

    In this thesis energy, exergy and exergoeconomic analysis has been carried out on a different number of co-generation energy systems involving cooling. The models and methods developed can be used as a frame work to improve the district heating and cooling system thermodynamically and/or economic......In this thesis energy, exergy and exergoeconomic analysis has been carried out on a different number of co-generation energy systems involving cooling. The models and methods developed can be used as a frame work to improve the district heating and cooling system thermodynamically and....../or economically which is the objective of the PhD project. A thermodynamic (energy and exergy) model of a transcritical CO2 cooling and heating system has been developed. The coefficient of performance (COP) of the system is the characteristic of interest. A sensitivity analysis of the parameters: compressor...... manner. Energy costing will also not encourage rational heating and cooling temperature demand and thus will not promote efficient use of resources. These flaws are not seen with exergy costing, since it has taken the quality of heat transfer in to account. Consequently the exergy costing method is found...

  15. System-level responses of lake ecosystems to chemical stresses using exergy and structural exergy as ecological indicators.

    Science.gov (United States)

    Xu, Fu-Liu; Dawson, R W; Tao, Shu; Li, Ben-Gang; Cao, Jun

    2002-01-01

    This paper presents the system-level responses of experimental lake ecosystems to three chemical stresses (acidification, copper and pesticide contamination) using exergy and structural exergy as ecological indicators. The results indicate that the doses or toxicity of the three chemical stressors contributed to changes in both exergy and structural exergy. Remarkable changes in exergy and structural exergy occurred under acidic conditions and in the presence of Dursban, 24D-DMA, permethrin, bifenthrin, Carbaryl, TCP, PCP, trichlorethylene, benzene, and high doses of Cu, oil, and hexazinone. This seemed to indicate that the subject ecosystems were seriously contaminated by these chemical stressors. For low doses of Cu, oil, atrazine, HCBP, and hexazinone, exergy and structural exergy were either unchanged or only slightly changed, suggesting that the lake ecosystems were not significantly impacted by these chemical stressors. Discussion of the relationships between ecosystem-level changes and structural and functional changes in stressed lake ecosystems indicates that the above-mentioned ecosystem-level changes were in accordance with the changes in structure and function. The observed changes in exergy and structural exergy were also consistent with Odum's predictions of shortened food chains, reduced resource use efficiency, poor stability, low information, and high entropy in stressed aquatic ecosystems. The findings lead the authors to conclude that it is feasible for exergy and structural exergy to serve as ecological indicators when characterizing the system-level responses of experimental lake ecosystems to chemical stress. These results for experimental lake ecosystems would be extrapolated to actual lakes.

  16. Estimating exergy prices for energy carriers in heating systems: Country analyses of exergy substitution with capital expenditures

    NARCIS (Netherlands)

    Muller, A.; Kranzl, L.; Tuominen, P.; Boelman, E.; Molinari, M.; Entrop, Alexis Gerardus

    2011-01-01

    Exergy represents the ability of an energy carrier to perform work and can be seen as a core indicator for measuring its quality. In this article we postulate that energy prices reflect the exergy content of the underlying energy carrier and that capital expenditures can substitute for exergy to

  17. Exergy analysis for a freeze-drying process

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Yongzhong; Zhao, Yanfei; Feng, Xiao [Department of Chemical Engineering, Xi' an Jiaotong University, 28, Xianning West Road, Xi' an, Shaanxi 710049 (China)

    2008-05-15

    A mathematical model for exergy loss analysis of a freeze-drying process was established to evaluate the exergy losses in the individual operations and the distribution of exergy losses in a freeze-dryer. The exergy losses of five operations, namely, freezing, primary drying, secondary drying and vapor condensation as well as vacuum pumping were included in the model. The unique feature of the model is the incorporation of dynamics into the expressions of the exergy loss analyses for freezing, primary drying and secondary drying stages. The distribution of exergy losses at various operating parameters of freeze-drying was investigated using this model. Take freeze dying beef for an example. The effects of various operation conditions on the exergy losses in the three stages were investigated. The results show that the exergy consumption in the primary drying reaches 35.69% of the total exergy input, while exergy consumption in vapor condensing is 31.76% of the total exergy input. In the vacuum pumping 23.29% of the total exergy input is consumed. In contrast the exergy consumption in the freezing and the secondary drying is only 3.56% and 5.71% of the total exergy input, respectively. The exergy analyses based on various operating parameters show that the exergy losses of the drying process can be remarkably reduced by increasing the temperature of the cooling source in the vapor condenser. In this study, when the temperature of the cooling source in the vapor condenser increases from -70 C to -25 C, it leads to the total exergy losses reducing from 1409 kJ/kg(moist basis) to 604 kJ/kg(moist basis). It indicates that increasing the temperature of vapor condensation is an effective way to reduce the total exergy losses of the system, as long as the conditions of drying dynamics are satisfied during drying. Moreover, there is an optimal surface temperature corresponding to the minimum total exergy losses during the primary and secondary drying stages. If the surface

  18. 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.

  19. 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...... 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...

  20. 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

  1. 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.

  2. Exergy assessment of future energy transition scenarios with application to Switzerland

    OpenAIRE

    Codina Gironès, Victor; Allais, Matteo; Favrat, Daniel; Vuille, François; Maréchal, François

    2017-01-01

    Using an exergy based indicator is highly desirable to compare future national energy strategies. A new web- based information platform called energyscope.ch, informing the general public on the Swiss energy transition was presented at ECOS2016. This paper presents a new extension of the approach that we plan to call exergyscope.ch, clearly stating exergy and distinguishing between primary exergy, final exergy and useful exergy. This allows for a graphical interpretation of the exergy efficie...

  3. 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...... 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...... the performance of the floor heating and the whole system. The exergy input to auxiliary components plays a significant role in the overall exergy performance of systems, and its effects become even more significant for low temperature heating systems....

  4. Exergy analysis of ventilation systems with energy recovery

    OpenAIRE

    I.O. Sukhodub; V.I. Deshko

    2014-01-01

    Thermal, mechanical and chemical components of room air exergy and its change depending on the outside air parameters (temperature, humidity and pressure) have been examined for different periods of the year, using the climatic data for Kiev (IWEC). In winter the thermal component dominates, whereas in summer the chemical one prevails. Various approaches to exergy efficiency definition of ventilation systems with energy recovery (namely, a universal, functional and maximum exergy efficien...

  5. Energy and Exergy Analyses of the Danish Industry Sector

    DEFF Research Database (Denmark)

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

    2016-01-01

    with data for the years 2006 and 2012. The sectoral energy and exergy losses, as well as the exergy destruction, were further established to quantify the potential for recovering and valorising heat otherwise lost. By also considering transformation processes occurring in the utility sector, the impact...... analyses. The exergy losses amounted to 3800 TJ for the same year. Meanwhile, the complete exergy losses, including the central production of heat and power, exceeded 8700 TJ. This analysis illustrates for the case study of Denmark how waste heat recovery potentials in the industrial sectors are found...

  6. 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.

  7. 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.

  8. 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

    to technological limitations, and into its endogenous and exogenous parts, which illustrate the interactions between the different sub-systems. This analysis is based on actual factory data from one of Europe’s largest dairy producers: the complete production line is modelled, and includes the production of milk......, 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....

  9. Steady–State Exergy Analysis of a Simple Solar Still

    Directory of Open Access Journals (Sweden)

    G. Cervantes–de Gortari.

    2010-01-01

    Full Text Available This paper presents a steady–state, theoretical exergy analysis of a solar still, focused on the exergy flows in the components of the still: collector plate, brine and glass cover. The analytical approach states an energy balance for each component resulting in three coupled equations where three parameters –solar irradiance, ambient temperature and insulation thickness– are studied. The energy balances are solved to find temperatures of each component; these temperatures are used to compute energy and exergy flows. Results in the steady–state regime show that the collector transports 13% of incident radiation exergy to the heat the brine, while in the brine the evaporation exergy accounts for the 6% of total exergy. Exergy/energy ratio shows that the most efficient component is the brine reaching more than 90% for almost any value of the parameters under study, while the collector has a 23% exergy/energy ratio for a 1,000 W/m2 solar energy input. The solar still is a device that uses efficiently the heating of a collector and the general discussion about its promotion should not, as it must be with almost every other solar device, be about thermodynamic limitations.

  10. 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

  11. 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.

  12. Energy and Exergy Analysis of the Danish Industry Sector

    DEFF Research Database (Denmark)

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

    2015-01-01

    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......% 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...... for recovering and valorising heat, amounted to 3,800 TJ for the same year. Meanwhile, the embodied exergy losses, from the central production of heat and power, exceeded 8,700 TJ. The comparison of the embodied energy efficiencies from 2006 to 2012 shows a clear increase of 4.2%-points, but this trend...

  13. 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.

  14. 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

  15. 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.

  16. Extended-exergy analysis of the Chinese society

    Energy Technology Data Exchange (ETDEWEB)

    Chen, G.Q. [National Laboratory for Turbulence and Complex Systems, Department of Mechanics, Peking University, Beijing 100871 (China); Chen, B. [National Laboratory for Turbulence and Complex Systems, Department of Mechanics, Peking University, Beijing 100871 (China); State Key Joint Laboratory of Environmental Science and Pollution Control, School of Environment, Beijing Normal University, Beijing 100875 (China)

    2009-09-15

    Extended-exergy analysis (EEA) for Chinese society was carried out in this paper to present a benchmarking case for future comparative studies in social systems ecology based on exergetic biophysics. For the EEA as an extension of labor theory of value and a possible sustainability metric, exergetic values were assigned to the production factors including labor, capital and environmental remediation costs. Also, the conversion coefficient of households sector was evaluated with the consideration of working hours, which significantly supplements the traditional energy and exergy accounting. The Chinese societal system was classified into seven sectors including the extraction, conversion, agriculture, industry, transportation, tertiary and households. The calculations of capital exergy and labor exergy were modified according to the special social-economic situation of China. A detailed accounting for the total societal extended-exergy use of China 2005 was conducted. Meanwhile, comparison of the net input exergy resources, extended-exergy capital, and labor of the total Chinese society during 2000-2005 was made to reveal the temporal changes using EEA. Finally, the EEA performances of China were compared with those of Norway, UK, Italy and the province of Siena to present solid foundation for energy strategy and identification of sustainable development mode. (author)

  17. 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.

  18. Analyzing the international exergy flow network of ferrous metal ores.

    Science.gov (United States)

    Qi, Hai; An, Haizhong; Hao, Xiaoqing; Zhong, Weiqiong; Zhang, Yanbing

    2014-01-01

    This paper employs an un-weighted and weighted exergy network to study the properties of ferrous metal ores in countries worldwide and their evolution from 2002 to 2012. We find that there are few countries controlling most of the ferrous metal ore exports in terms of exergy and that the entire exergy flow network is becoming more heterogeneous though the addition of new nodes. The increasing of the average clustering coefficient indicates that the formation of an international exergy flow system and regional integration is improving. When we contrast the average out strength of exergy and the average out strength of currency, we find both similarities and differences. Prices are affected largely by human factors; thus, the growth rate of the average out strength of currency has fluctuated acutely in the eleven years from 2002 to 2012. Exergy is defined as the maximum work that can be extracted from a system and can reflect the true cost in the world, and this parameter fluctuates much less. Performing an analysis based on the two aspects of exergy and currency, we find that the network is becoming uneven.

  19. Exergy: its potential and limitations in environmental science and technology.

    Science.gov (United States)

    Dewulf, Jo; Van Langenhove, Herman; Muys, Bart; Bruers, Stijn; Bakshi, Bhavik R; Grubb, Geoffrey F; Paulus, D M; Sciubba, Enrico

    2008-04-01

    New technologies, either renewables-based or not, are confronted with both economic and technical constraints. Their development takes advantage of considering the basic laws of economics and thermodynamics. With respect to the latter, the exergy concept pops up. Although its fundamentals, that is, the Second Law of Thermodynamics, were already established in the 1800s, it is only in the last years that the exergy concept has gained a more widespread interest in process analysis, typically employed to identify inefficiencies. However, exergy analysis today is implemented far beyond technical analysis; it is also employed in environmental, (thermo)economic, and even sustainability analysis of industrial systems. Because natural ecosystems are also subjected to the basic laws of thermodynamics, it is another subject of exergy analysis. After an introduction on the concept itself, this review focuses on the potential and limitations of the exergy conceptin (1) ecosystem analysis, utilized to describe maximum storage and maximum dissipation of energy flows (2); industrial system analysis: from single process analysis to complete process chain analysis (3); (thermo)economic analysis, with extended exergy accounting; and (4) environmental impact assessment throughout the whole life cycle with quantification of the resource intake and emission effects. Apart from technical system analysis, it proves that exergy as a tool in environmental impact analysis may be the most mature field of application, particularly with respect to resource and efficiency accounting, one of the major challenges in the development of sustainable technology. Far less mature is the exergy analysis of natural ecosystems and the coupling with economic analysis, where a lively debate is presently going on about the actual merits of an exergy-based approach.

  20. 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...

  1. Energy and Exergy Analysis of an Annular Thermoelectric Heat Pump

    Science.gov (United States)

    Kaushik, S. C.; Manikandan, S.; Hans, Ranjana

    2016-07-01

    In this paper, the concept of an annular thermoelectric heat pump (ATEHP) has been introduced. An exoreversible thermodynamic model of the ATEHP considering the Thomson effect in conjunction with Peltier, Joule and Fourier heat conduction has been investigated using exergy analysis. New expressions for dimensionless heating power, optimum current at the maximum energy, exergy efficiency conditions and dimensionless irreversibilities in the ATEHP are derived. The results show that the heating power, energy and exergy efficiency of the ATEHP are lower than the flat-plate thermoelectric heat pump. The effects of annular shape parameter ( S r = r 2 /r 1), dimensionless temperature ratio ( θ = T h /T c) and the electrical contact resistances on the heating power, energy/exergy efficiency of an ATEHP have been studied. This study will help in the designing of actual ATEHP systems.

  2. Exergy-Based Efficiency Analysis of Pyrometallurgical Processes

    Science.gov (United States)

    Klaasen, Bart; Jones, Peter-Tom; Durinck, Dirk; Dewulf, Jo; Wollants, Patrick; Blanpain, Bart

    2010-12-01

    Exergy-based efficiency analysis provides a powerful tool for optimizing industrial processes. In this article, the use of this technique for pyrometallurgical applications is explored in four steps. First, the exergy concept is introduced, the outline of exergy calculations is presented, and the role of a reference state is discussed. Second, it is shown that an unambiguous exergy calculation for pyrometallurgical streams with a complex, unknown phase composition is not straightforward. Hence, a practical methodology is proposed in which a suitable phase-based stream description is estimated prior to the actual exergy calculation. For this, the equilibrium phase composition is calculated, whereas all known stream properties are incorporated as boundary conditions. Third, the proposed methodology is validated by recalculating literature results. This reveals significant deviations for exergy values of the same pyrometallurgical streams. Our results are probably more accurate because of the incorporation of additional phase-related information. And fourth, a full analysis of a zinc-recycling process is presented. In a base case scenario, the total exergetic efficiency turns out to be only 1.2 pct. Based on this result, different process modifications are suggested and evaluated quantitatively. We find that significant efficiency gains are possible.

  3. Efficiency dilution: long-term exergy conversion trends in Japan.

    Science.gov (United States)

    Williams, Eric; Warr, Benjamin; Ayres, Robert U

    2008-07-01

    This analysis characterizes century-scale trends in exergy efficiency in Japan. Exergy efficiency captures the degree to which energy inputs (such as coal) are converted into useful work (such as electricity or power to move a vehicle). This approach enables the estimation of net efficiencies which aggregate different technologies. Sectors specifically analyzed are electricity generation, transport, steel production, and residential space heating. One result is that the aggregate exergy efficiency of the Japanese economy declined slightly over the last half of the 20th century, reaching a high of around 38% in the late 1970s and falling to around 33% by 1998. The explanation for this is that while individual technologies improved dramatically over the century, less exergy-efficient ones were progressively adopted, yielding a net stabilization or decline. In the electricity sector, for instance, adoption of hydropower was followed by fossil-fired plants and then by nuclear power, each technology being successively less efficient from an exergy perspective. The underlying dynamic of this trend is analogous to declining ore grades in the mining sector. Increasing demand for exergy services requires expended utilization of resources from which it is more difficult to extract utility (e.g., falling water versus coal). We term this phenomenon efficiency dilution.

  4. Exergy in near-field electromagnetic heat transfer

    Science.gov (United States)

    Iizuka, Hideo; Fan, Shanhui

    2017-09-01

    The maximum amount of usable work extractable from a given radiative heat flow defines the exergy. It was recently noted that the exergy in near-field radiative heat transfer can exceed that in the far-field. Here, we derive a closed form formula of exergy in the near-field heat transfer between two parallel surfaces. This formula reveals that, for a given resonant frequency, the maximum exergy depends critically on the resonant linewidth, and there exists an optimal choice of the linewidth that maximizes the exergy. Guided by the analytical result, we show numerically that with a proper choice of doping concentration, the heat flow between two properly designed SiC-coated heavily doped silicon regions can possess exergy that is significantly higher compared to the heat flow between two SiC regions where the heat flow is carried out by phonon-polaritons. Our work indicates significant opportunities for either controlling material properties or enhancing the fundamental potential for near-field heat transfer in thermal energy conversion through the approach of meta-material engineering.

  5. 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...

  6. Analysis of seasonal exergy efficiency of an air handling unit

    Science.gov (United States)

    StreckienÄ--, G.; Martinaitis, V.; Bielskus, J.

    2017-09-01

    Ventilation systems play an important role for providing suitable indoor climate in buildings. Improving these systems allows promoting energy efficiency in building sector, which is responsible for a large percentage of global energy consumption. Therefore, this work focuses on assessment of ventilation air handling unit (AHU) using thermodynamics. The exergy analysis is used to evaluate the performance of an AHU. Special attention is made about seasonally varying exergy flows of a system. As efficiency of a ventilation system is closely linked to local climate, especially to the varying reference temperature. The paper presents an approach for calculating the seasonal exergy efficiency and gives the results of the AHU analysis. The case study reveals that the highest exergy consumption is when the outdoor temperature is -2.5 °C. The AHU case with heat recovery and water heater is the most efficient comparing to other cases investigated. The use of this methodology may be extended for determining of the seasonal exergy efficiency of any other HVAC equipment.

  7. 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.

  8. 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

  9. Energy and exergy analysis of a cruise ship

    DEFF Research Database (Denmark)

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

    2015-01-01

    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...... to its final use on board. To illustrate this, we perform ed an analysis of the energy and exergy flow rates of a cruise ship sailing in the Baltic Sea based on a combination of available measurements from ship operations and of mechanistic knowledge of the system . The energy analys is allows...

  10. Exergy and extended exergy accounting of very large complex systems with an application to the province of Siena, Italy.

    Science.gov (United States)

    Sciubba, Enrico; Bastianoni, Simone; Tiezzi, Enzo

    2008-01-01

    This paper describes the application of exergy and extended exergy analyses to large complex systems. The system to be analysed is assumed to be at steady state, and the input and output fluxes of matter and energy are expressed in units of exergy. Human societies of any reasonable extent are indeed Very Large Complex Systems and can be represented as interconnected networks of N elementary "components", their Subsystems; the detail of the disaggregation depends on the type and quality of the available data. The structural connectivity of the "model" of the System must correctly describe the interactions of each mass or energy flow with each sector of the society: since it is seldom the case that all of these fluxes are available in detail, some preliminary mass- and energy balances must be completed and constitute in fact a part of the initial assumptions. Exergy accounting converts the total amount of resources inflow into their equivalent exergetic form with the help of a table of "raw exergy data" available in the literature. The quantification of each flow on a homogeneous exergetic basis paves the way to the evaluation of the efficiency of each energy and mass transfer between the N sectors and makes it possible to quantify the irreversible losses and identify their sources. The advantage of the EEA, compared to a classical exergy accounting, is the inclusion in the system balance of the exergetic equivalents of three additional "Production Factors": human Labour, Capital and Environmental Remediation costs. EEA has an additional advantage: it allows for the calculation of the efficiency of the domestic sector (impossible to evaluate with any other energy- or exergy-based method) by considering the working hours as its product. As implied in the title, an application of the method was made to a model of the province of Siena (on a year 2000 database): the results show that the sectors of this Province have values of efficiency close to the Italian average

  11. Exergy analysis of a passive direct methanol fuel cell

    Energy Technology Data Exchange (ETDEWEB)

    Bahrami, Hafez; Faghri, Amir [Department of Mechanical Engineering, University of Connecticut, Storrs, CT 06269 (United States)

    2011-02-01

    An analytical, one-dimensional, steady state model is employed to solve for overpotentials at the catalyst layers along with the liquid water and methanol distributions at the anode, and oxygen transport at the cathode. An iterative method is utilized to calculate the cell temperature at each cell current density. A comprehensive exergy analysis considering all possible species inside the cell during normal operation is presented. The contributions of different types of irreversibilities including overpotentials at the anode and cathode, methanol crossover, contact resistance, and proton conductivity of the membrane are investigated. Of all losses, overpotentials in conjunction with the methanol crossover are considered as the major exergy destruction sources inside the cell during the normal operation. While the exergy losses due to electrochemical reactions are more significant at higher current densities, exergy destruction by methanol crossover at the cathode plays more important role at lower currents. It is also found that the first-law efficiency of a passive direct methanol fuel cell increases as the methanol solution in the tank increases in concentration from 1 M to 3 M. However, this is not the case with the second-law efficiency which is always decreasing as the concentration of the methanol solution in the tank increases. (author)

  12. 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.

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

    DEFF Research Database (Denmark)

    Li, Hongwei; Svendsen, Svend

    . 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...

  14. 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 ...

  15. Energy and exergy optimization of food waste pretreatment and incineration.

    Science.gov (United States)

    Tang, Yuanjun; Dong, Jun; Chi, Yong; Zhou, Zhaozhi; Ni, Mingjiang

    2017-08-01

    With the aim of upgrading current food waste (FW) management strategy, a novel FW hydrothermal pretreatment and air-drying incineration system is proposed and optimized from an energy and exergy perspective. Parameters considered include the extracted steam quality, the final moisture content of dehydrated FW, and the reactor thermal efficiency. Results show that optimal working condition can be obtained when the temperature and pressure of extracted steam are 159 °C and 0.17 MPa, the final moisture content of dehydrated FW is 10%, and the reactor thermal efficiency is 90%. Under such circumstance, the optimal steam energy and exergy increments reach 194.92 and 324.50 kJ/kg-FW, respectively. The novel system is then applied under the local conditions of Hangzhou, China. Results show that approximately 2.7 or 11.6% (from energy or exergy analysis perspective) of electricity can be additionally generated from 1 ton of MSW if the proposed novel FW system is implemented. Besides, comparisons between energy and exergy analysis are also discussed.

  16. 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)

  17. 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...

  18. 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...

  19. 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...

  20. 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

    system required 53% lower auxiliary exergy input than the air cooling system, showing a clear benefit for the water-based systems over the air-based systems. The auxiliary energy and exergy input to different systems is an important parameter for the whole system performance. Its effects become more...... pronounced and can be studied better in terms of exergy than energy. The required exergy input to the power plant for space heating and cooling purposes are comparable to the required exergy input for auxiliary components. The exergy input to auxiliary components should be minimized to fully benefit from...... the water-based low temperature heating and high temperature cooling systems, and in general in heating and cooling systems, and to integrate effectively the renewable energy resources to building heating and cooling systems....

  1. 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...

  2. 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...... exergy losses amount to 22.3 MW. The gas lifting train and the production-separation module are the most exergy-destructive operations of the oil and gas processing system, consuming 8.83 MW and 8.17 MW respectively, while the power generation system alone is responsible for 46.7 MW. The exergetic...

  3. Low-grade coal and biomass co-combustion on fluidized bed: exergy analysis

    Energy Technology Data Exchange (ETDEWEB)

    Martin, C.; Villamanan, M.A.; Chamorro, C.R.; Segovia, J.J. [University of Valladolid (Spain). Dept. of Energy; Otero, J.; Cabanillas, A. [Environment and Technology Ciemat, Madrid (Spain). Dept. of Fossil Fuels

    2006-03-01

    The purpose of this work is to prove the technical feasibility of the bubbling fluidized bed co-combustion, using biomass and low-grade coal mixtures and applying the exergy method. The pilot plant modelled is an atmospheric bubbling fluidized bed combustion chamber with a nominal capacity of 1 MWth. We have applied the mass balance, the energy balance and the exergy balance to the plant in nine experiments, which have been performed at different operation conditions. The exergy analysis includes the calculation of the exergy destruction and the exergetic efficiency of the plant for these experiments. An estimation of the irreversibility cost is also evaluated. (author)

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

    DEFF Research Database (Denmark)

    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...... 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...

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

    DEFF Research Database (Denmark)

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

    in a two-step system consisting of a waste-to-energy process and a consequent bottom ash treatment. B) An aluminum-pre-sorting step takes place prior to the thermal treatment. In case of B, an additional exergy is spent on pre-sorting, but, in return, a metal of higher quality is obtained. The discussion......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...... 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. On exergy analysis and entropy production minimisation in industrial ecology

    OpenAIRE

    Zvolinschi, Anita

    2006-01-01

    The objective of this thesis is to improve the basis for applying industrial ecology to the evaluation of material and energy resource use and transformation in industrial systems. The underlying hypothesis was that when the second law of thermodynamics is applied it improves the basis for using industrial ecology for the evaluation of the use and transformation of resources in industrial systems. Exergy analysis and entropy production calculation and minimisation of industrial processes are ...

  7. Exergy Analysis of a Reactive Distillation MTBE Unit

    OpenAIRE

    Garcia, M.; Ricardo Rivero

    2001-01-01

    In this paper application of exergy analysis to the reactive distillation system of a Methyl TerButyl Ether (MTBE) production unit of a crude oil refinery is presented. In a refinery, the MTBE is obtained from methanol, and butanes (isobutylenes) produced in the fluidized catalytic cracking (FCC) unit. The reactives (isobutylenes) after purification are introduced to the main reaction system, the products of which are sent to the reactive distillation system to complete the reaction....

  8. Expanding exergy analysis to account for ecosystem products and services.

    Science.gov (United States)

    Hau, Jorge L; Bakshi, Bhavik R

    2004-07-01

    Exergy analysis is a thermodynamic approach used for analyzing and improving the efficiency of chemical and thermal processes. It has also been extended for life cycle assessment and sustainability evaluation of industrial products and processes. Although these extensions recognize the importance of capital and labor inputs and environmental impact, most of them ignore the crucial role that ecosystems play in sustaining all industrial activity. Decisions based on approaches that take nature for granted continue to cause significant deterioration in the ability of ecosystems to provide goods and services that are essential for every human activity. Accounting for nature's contribution is also important for determining the impact and sustainablility of industrial activity. In contrast, emergy analysis, a thermodynamic method from systems ecology, does account for ecosystems, but has encountered a lot of resistance and criticism, particularly from economists, physicists, and engineers. This paper expands the engineering concept of Cumulative Exergy Consumption (CEC) analysis to include the contribution of ecosystems, which leads to the concept of Ecological Cumulative Exergy Consumption (ECEC). Practical challenges in computing ECEC for industrial processes are identified and a formal algorithm based on network algebra is proposed. ECEC is shown to be closely related to emergy, and both concepts become equivalent if the analysis boundary, allocation method, and approach for combining global energy inputs are identical. This insight permits combination of the best features of emergy and exergy analysis, and shows that most of the controversial aspects of emergy analysis need not hinder its use for including the exergetic contribution of ecosystems. Examples illustrate the approach and highlight the potential benefits of accounting for nature's contribution to industrial activity.

  9. 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.

  10. Exergy optimization in a steady moving bed heat exchanger.

    Science.gov (United States)

    Soria-Verdugo, A; Almendros-Ibáñez, J A; Ruiz-Rivas, U; Santana, D

    2009-04-01

    This work provides an energy and exergy optimization analysis of a moving bed heat exchanger (MBHE). The exchanger is studied as a cross-flow heat exchanger where one of the phases is a moving granular medium. The optimal MBHE dimensions and the optimal particle diameter are obtained for a range of incoming fluid flow rates. The analyses are carried out over operation data of the exchanger obtained in two ways: a numerical simulation of the steady-state problem and an analytical solution of the simplified equations, neglecting the conduction terms. The numerical simulation considers, for the solid, the convection heat transfer to the fluid and the diffusion term in both directions, and for the fluid only the convection heat transfer to the solid. The results are compared with a well-known analytical solution (neglecting conduction effects) for the temperature distribution in the exchanger. Next, the analytical solution is used to derive an expression for the exergy destruction. The optimal length of the MBHE depends mainly on the flow rate and does not depend on particle diameter unless they become very small (thus increasing sharply the pressure drop). The exergy optimal length is always smaller than the thermal one, although the difference is itself small.

  11. 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.

  12. Exergy and Its Efficiency Calculations in Ferrochrome Production

    Science.gov (United States)

    Ramakrishna, G.; Kadrolkar, Ameya; Srikakulapu, N. Gurulaxmi

    2015-04-01

    Ferrochrome production is a high energy intensive process consuming around 3000 to 3500 kWh/t of electrical energy. Ferrochrome is produced by smelting of different grades of chromite ore with coke and fluxing agents such as lime, dolomite, and quartz in a submerged arc furnace (SAF). Apart from the production of ferrochrome, co-products that are produced during the process include carbon monoxide rich off-gas and slag. The slag is cooled with high pressure jet water which results in the formation of slag granules. In the present practice, off-gas generated from the SAF is used for ladle preheating, as fuel in sinter plant, while the remaining is unutilized. Approximately 34 to 40 pct of heat from off-gas is utilized, while the remaining 60 to 66 pct of the off-gas can be utilized for generating electricity by gas combustion turbine. The concept of exergy is applied to monitor the existing process and to understand the feasibility of modification. In the present study, comparison of exergy efficiency for existing process and two adapted case studies has been performed, involving utilization of off-gas for sintering and power generation and waste heat utilization from dry slag granulation. It is observed that there was considerable increase in exergy efficiency for waste heat utilization by dry granulation case study when compared with other two case studies.

  13. 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

  14. 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

    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...... exergy input of air-based systems was significantly larger than the water-based systems. The use of available cool exergy in the crawl-space resulted in 54% and 29% smaller exergy input to the power plant for the air-based and water-based cooling systems, respectively. For floor cooling, the exergy input...... to the power plant can be reduced by 90% and 93%, with the use of ground, and use of the ground and the air in the crawl-space, respectively. A new approach to exergy efficiency was introduced and used to prove that the exergy supply from the ground matches well with the low exergy demand of the floor cooling...

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

    African Journals Online (AJOL)

    HOD

    environmental or dead state temperature, there were no appreciable changes in the values of exergy efficiency of the boiler/steam generator. The outcomes of this work provide the exergy consumption and distribution profiles of the thermal power plant, making it possible to adopt effective energy-saving measures.

  16. Exergy costing analysis and performance evaluation of selected gas turbine power plants

    Directory of Open Access Journals (Sweden)

    S.O. Oyedepo

    2015-12-01

    Full Text Available In this study, exergy costing analysis and performance evaluation of selected gas turbine power plants in Nigeria are carried out. The results of exergy analysis confirmed that the combustion chamber is the most exergy destructive component compared to other cycle components. The exergetic efficiency of the plants was found to depend significantly on a change in gas turbine inlet temperature (GTIT. The increase in exergetic efficiency with the increase in turbine inlet temperature is limited by turbine material temperature limit. This was observed from the plant efficiency defect curve. As the turbine inlet temperature increases, the plant efficiency defect decreases to minimum value at certain GTIT (1,200 K, after which it increases with GTIT. This shows degradation in performance of gas turbine plant at high turbine inlet temperature. Exergy costing analysis shows that the combustion chamber has the greatest cost of exergy destruction compared to other components. Increasing the GTIT, both the exergy destruction and the cost of exergy destruction of this component are found to decrease. Also, from exergy costing analysis, the unit cost of electricity produced in the power plants varies from cents 1.99/kWh (N3.16/kWh to cents 5.65/kWh (N8.98/kWh.

  17. Exergy Accounting: A Quantitative Comparison of Methods and Implications for Energy-Economy Analysis

    Directory of Open Access Journals (Sweden)

    Jack Miller

    2016-11-01

    Full Text Available Assessments of the feasibility of decoupling energy consumption from economic growth could benefit from an improved understanding of the size, nature and value of different energy flows. This understanding may be enhanced by focusing upon so-called “useful exergy”—a measure of both the quantity and “quality” of energy (defined here as its thermodynamic ability to perform physical work at the “useful” stage of the energy conversion chain. Useful exergy flows within national economies are increasingly being quantified and their role in economic activity explored. However, this so-called “exergy economics” field currently lacks a consistent methodology. This paper contributes to the development of a more consistent approach. By constructing a “useful exergy account” for the United Kingdom covering the period 1960–2012, we explore how different methodological choices influence estimates of useful exergy for different categories of end-use as well as estimates of total national useful exergy consumption. Specifically, we evaluate the sensitivity of estimates to: (a the method of estimating the exergy efficiency of different end-uses; (b the boundaries between end-use categories; and (c the method of estimating the primary exergy associated with renewable electricity. We also improve upon the current method of accounting for industrial uses of heat. This leads to suggestions for best practice when constructing useful exergy accounts, and the identification of areas where further methodological development is required.

  18. Patterning exergy of benthic macroinvertebrate communities using self-organizing maps

    NARCIS (Netherlands)

    Park, Y.S.; Lek, S.; Scardi, M.; Verdonschot, P.F.M.; Jørgensen, S.E.

    2006-01-01

    Exergy is a measure of the free energy of a system with contributions from all components including the energy of organisms, and it is used as an ecological indicator. In this study, we implemented a self-organizing map (SOM) for patterning exergy of benthic macroinvertebrate communities. The

  19. 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 ...

  20. 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 (i...

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

    African Journals Online (AJOL)

    At the variation of environmental or dead state temperature, ther e were no appreciable changes in the values of exergy efficiency of the boiler/steam generator. The outcomes of this work provide the exergy consumption and distribution profile s of the thermal power plant, making it possible to adopt effective energy - saving ...

  2. On the exergy disaggregation for thermoeconomic analysis of a gas turbine cogeneration system

    Energy Technology Data Exchange (ETDEWEB)

    Santos, Jose Joaquim Conceicao Soares [Federal University of Espirito Santo - UFES/DEM, Goiabeiras, Vitoria, ES (Brazil); Silva, Julio Augusto Mendes da [University of Sao Paulo, Sao Paulo, SP (Brazil)], e-mail: jams@usp.br; Palacio, Jose Carlos Escobar [Federal University of Itajuba, Itajuba, MG (Brazil); Moreira, Hugo Lima [Federal Rural University of Amazonia, Belem, PA (Brazil)

    2010-07-01

    Most analysts agree that exergy, instead of enthalpy only, is the most adequate thermodynamic quantity to associate with cost. Therefore, all thermoeconomic methodologies use the exergy to define productive structure. Sometimes, under a thermoeconomic analysis point of view, it is necessary to consider a mass or an energy flow rate consisting of several exergy components, for example thermal, mechanical and chemical components. Most analysts agree that by considering separate exergy forms the accuracy of the results is improved in thermoeconomics. However, these analysts recognize that the disaggregation of physical exergy might not be always reasonably because of the increase in the computational efforts. Thus, the main questions are: Is this improvement often marginal? Is exergy disaggregation necessary for extracting the main conclusions? This paper aims at answering these questions for the case of external fuel (natural gas) exergy allocation to the two final products (heat and power) of a gas turbine cogeneration system, by applying four different productive structures based on different kind and level of physical exergy disaggregation. The paper also shown that the model that uses enthalpy together with sintropy presents the closest result in relation to the total disaggregated model, showing the rationality of this methodology that intrinsically allocate the residues to the components of the cycle using the entropy variation in each component as a weighting factor. (author)

  3. Exergy analysis : a tool to study the sustainability of food supply chains

    NARCIS (Netherlands)

    Apaiah, R.K.; Linnemann, A.R.; Kooi, van der H.J.

    2006-01-01

    This paper explores the potential of using exergy analysis to study and compare the environmental impact of food supply chains. The method identifies the links where exergy destruction takes place and shows where improvements are possible to minimize this destruction. The supply chains of three

  4. Review of an energy and exergy analysis of a fuel cell system

    Science.gov (United States)

    van den Oosterkamp, P. F.; Goorse, A. A.; Blomen, L. J. M. J.

    A review of an energy and exergy analysis of the KTI 25 kW fuel cell system is described. This system consists of a fuel cell and a fuel processor. An examination of the system's integration concept is done with the aim of pinpointing the existing losses. The exergy calculations are performed with the Aspen Plus programme using a Fortran extension. Energy and energy calculations are presented in a Sankey and Grassmann diagram, respectively. The system's major energy losses are involved with off-gases, while the system's major exergy losses are associated with internal process irreversibilities. It is concluded that the exergy calculations pinpoint the losses accurately and that the exergy analysis gives a better insight of the system's process.

  5. 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.

  6. 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.

  7. 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

    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. lithe 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...

  8. Energy and exergy of potato drying process via cyclone type dryer

    Energy Technology Data Exchange (ETDEWEB)

    Kavak Akpinar, E. [Department of Mechanical Engineering, Firat University, 23279 Elazig (Turkey)]. E-mail: eakpinar@firat.edu.tr; Midilli, A. [Energy Division, Department of Mechanical Engineering, Nigde University, 51200 Nigde (Turkey); Bicer, Y. [Department of Mechanical Engineering, Firat University, 23279 Elazig (Turkey)

    2005-09-15

    This paper is concerned with the energy and exergy analyses of the single layer drying process of potato slices via a cyclone type dryer. Using the first law of thermodynamics, an energy analysis was performed to estimate the ratios of energy utilization. An exergy analysis was accomplished to determine the location, type and magnitude of the exergy losses during the drying process by applying the second law of thermodynamics. It was concluded that the exergy losses took place mostly in the 1st tray where the available energy was less utilized during the single layer drying process of potato slices. It is emphasized that the potato slices are sufficiently dried in the ranges between 60 and 80 deg. C and 20-10% relative humidity at 1 and 1.5 ms{sup -1} of drying air velocity during 10-12 h despite the exergy losses of 0-1.796 kJ s{sup -1}.

  9. Energy and exergy of potato drying process via cyclone type dryer

    Energy Technology Data Exchange (ETDEWEB)

    Akpinar, E. Kavak; Bicer, Y. [Firat Univ., Dept. of Mechanical Engineering, Elazig (Turkey); Midilli, A. [Nigde Univ., Dept. of Mechanical Engineering, Nigde (Turkey)

    2005-09-01

    This paper is concerned with the energy and exergy analyses of the single layer drying process of potato slices via a cyclone type dryer. Using the first law of thermodynamics, an energy analysis was performed to estimate the ratios of energy utilization. An exergy analysis was accomplished to determine the location, type and magnitude of the exergy losses during the drying process by applying the second law of thermodynamics. It was concluded that the exergy losses took place mostly in the 1st tray where the available energy was less utilized during the single layer drying process of potato slices. It is emphasized that the potato slices are sufficiently dried in the ranges between 60 and 80 deg C and 20-10% relative humidity at 1 and 1.5 ms{sup -1} of drying air velocity during 10-12 h despite the exergy losses of 0-1.796 kJ s{sup -1}. (Author)

  10. Exergy analysis for resource conversion of the Chinese Society 1993 under the material product system

    Energy Technology Data Exchange (ETDEWEB)

    Chen, B.; Chen, G.Q. [National Laboratory for Complex Systems and Turbulence, Department of Mechanics and Engineering Science, Peking University, Beijing 100871 (China)

    2006-07-15

    The resource exergy conversion in Chinese society in 1993 under the material product system (MPS) was investigated. Major resources that entered the society were divided into subgroups and analyzed in detail. The end use was broken down into ten end-use sectors: the forestry industry, food industry, iron and steel industry, nonferrous metal industry, chemical industry, textile industry, transportation, households, commerce, other industry. The total exergy input was 62.9EJ, which was 53.3GJ/cap. The total exergy output contained 11.66EJ or 9.88GJ/cap, which was 19% of the total exergy input. One RMB (Chinese Renminbi) yuan ($ 0.17) corresponded to 3.37MJ resource exergy output. (author)

  11. 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.

  12. Exergy Analysis of Human Respiration Under Physical Activity

    OpenAIRE

    Jurandir Itizo Yanagihara; Silvio de Oliveira Jr; Maurício Silva Ferreira; Luiz Felipe Pellegrini; Cyro Albuquerque Neto

    2010-01-01

    This paper presents an exergy analysis of the human body under physical activity. A model of the respiratory system and a model of the thermal system were used for this purpose. These models consider heat and mass transfers in lungs, tissues and blood. Each component of these models is repr...

  13. 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. .

  14. Modelling of Split Condenser Heat Pump: Optimization and Exergy Analysis

    DEFF Research Database (Denmark)

    Christensen, Stefan Wuust; Elmegaard, Brian; Markussen, Wiebke Brix

    2017-01-01

    This paper presents a numerical study of a split condenser heat pump (SCHP). The SCHP setup differs from a traditional heat pump (THP) setup in the way that two separate water streams on the secondary side of the condenser are heated in parallel to different temperature levels, whereas only one s...... unit. For a water temperature of 40°C/85°C and an evaporating temperature of 5°C, the total area of the two plate heat exchangers was reduced by 3%. When using the SCHP setup the exergy destruction was slightly smaller compared to the THP....

  15. Exergy analysis of an HCFC-22 and HC-290 operated air conditioning system

    Science.gov (United States)

    Ahamed, Jamal Uddin; Raiyan, Muhammad Ferdous; Salam, Md. Abdus

    2017-06-01

    The present work discusses exergy analysis of a split type air conditioning system. Typical domestic air conditioners use R22 which is a Hydrochloroflurocarbon (HCFC) refrigerant. Due to its destructive impact on ozone layer, search for alternative refrigerants is going on. Propane (R290), a pure Hydrocarbon (HC) is considered here along with R22 to make different blends of refrigerants. Two HCFC-22 and HC-290 mixtures (P1 and P2) were prepared with mass ratios of (R22:R290) 90:10 and 85:15 respectively. Using experimentally obtained data of pressure and temperature, other properties in the vapor compression system were found by REFPROP 7 software. Finally, exergy analysis was done for all the refrigerants (R22, P1 and P2). Exergy destruction in each component was also inspected. Total exergy loss of mixture P2 was found to be greater than the exergy loss of R22 and P1. Variations in exergy losses were observed with respect to evaporator temperature at two different ambient conditions. In all cases, exergy destruction in condenser was found to be the highest among the four main components of the cycle.

  16. Energy- and exergy analysis of rape seed oil methyl ester (RME) production under Swedish conditions

    Energy Technology Data Exchange (ETDEWEB)

    Hovelius, K.; Hansson, P. [Swedish University of Agricultural Sciences, Uppsala (Sweden). Dept. of Agricultural Engineering

    1999-10-01

    In this study the rape seed oil methyl ester (RME) production chain was analysed with respect to its energy- and exergy efficiencies. The differences between results from an ordinary energy analysis and an exergy analysis of the production were also quantified and discussed. The sensitivity of the results to changes in some of the most important input parameters were then analysed in order to find production strategies that increase the exergy efficiency. The study was applied to rape seed cultivation situated in southern Sweden. The rape seed oil was hot pressed in a large-scale plant, and the RME was esterified in the same factory as that in which the rape seed oil was pressed. Both direct and indirect energy and exergy flows used for RME production were included. The analysis showed that a large part of the energy and exergy used to produce RME was related to nitrogen fertilizers and diesel fuels. Another important conclusion was that the exergy efficiency of the production in general is higher than the energy efficiency. A third conclusion was that it is possible, by using alternative production strategies, to improve the exergy efficiency without decreasing the energy efficiency.

  17. An improved calculation of the exergy of natural resources for exergetic life cycle assessment (ELCA).

    Science.gov (United States)

    De Meester, Bram; Dewulf, Jo; Janssens, Arnold; Van Langenhove, Herman

    2006-11-01

    The focus in environmental research is shifting from emission abatement to critical process analysis, including assessment of resource consumption. The exergy theory offers a thermodynamic methodology to account for the consumption of natural resources. However, exergy data on mineral resources available in the literature are inadequate to apply to exergetic life cycle analysis, due to incompleteness, inconsistencies, and a dated thermochemical basis. An uncertainty assessment of the data has to be performed as well. In this work, three recent thermochemical databases were applied to evaluate the chemical exergy of 85 elements and 73 minerals, 21 of which had not yet been quantified in the literature. The process required the choice of a new reference species for aluminum. Muscovite was selected, giving rise to a chemical exergy of 809.4 kJ/mol for aluminum. The theory proved to be robust for the exergy of chemical elements, as exergy values differing by 1.2% on average from most recent literature were found. On the contrary, the exergy values for minerals differed by factors up to 14 from literature values, due to the application of recent thermochemical values and consistently selected reference species. The consistent dataset of this work will enable straightforward resource intake evaluation through an exergetic life cycle assessment.

  18. 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......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...... exergy values are assigned to all flows, allowing for quantifying various types of exergy losses. The exergy losses determined here are those caused by (1) oxidative changes in the thermal process (irreversible exergy destruction), (2) material losses (low recovery efficiencies), and (3) mixing of metals...

  19. Exergy analysis of the performance of low-temperature district heating system with geothermal heat pump

    Science.gov (United States)

    Sekret, Robert; Nitkiewicz, Anna

    2014-03-01

    Exergy analysis of low temperature geothermal heat plant with compressor and absorption heat pump was carried out. In these two concepts heat pumps are using geothermal water at 19.5 oC with spontaneous outflow 24 m3/h as a heat source. The research compares exergy efficiency and exergy destruction of considered systems and its components as well. For the purpose of analysis, the heating system was divided into five components: geothermal heat exchanger, heat pump, heat distribution, heat exchanger and electricity production and transportation. For considered systems the primary exergy consumption from renewable and non-renewable sources was estimated. The analysis was carried out for heat network temperature at 50/40 oC, and the quality regulation was assumed. The results of exergy analysis of the system with electrical and absorption heat pump show that exergy destruction during the whole heating season is lower for the system with electrical heat pump. The exergy efficiencies of total system are 12.8% and 11.2% for the system with electrical heat pump and absorption heat pump, respectively.

  20. 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)

  1. Exergy Analysis of Solid Fuel-Fired Heat and Power Plants: A Review

    Directory of Open Access Journals (Sweden)

    Francis Chinweuba Eboh

    2017-02-01

    Full Text Available The growing demand for energy is particularly important to engineers with respect to how the energy produced by heat and power plants can be used efficiently. Formerly, performance evaluation of thermal power plants was done through energy analysis. However, the energy method does not account for irreversibilities within the system. An effective method to measure and improve efficiency of thermal power plant is exergy analysis. Exergy analysis is used to evaluate the performance of a system and its main advantage is enhancement of the energy conversion process. It helps identify the main points of exergy destruction, the quantity and causes of this destruction, as well as show which areas in the system and components have potential for improvements. The current study is a comprehensive review of exergy analyses applied in the solid fuels heat and power sector, which includes coal, biomass and a combination of these feedstocks as fuels. The methods for the evaluation of the exergy efficiency and the exergy destruction are surveyed in each part of the plant. The current review is expected to advance understanding of exergy analysis and its usefulness in the energy and power sectors: it will assist in the performance assessment, analysis, optimization and cost effectiveness of the design of heat and power plant systems in these sectors.

  2. 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.

  3. Exergy efficiency in industry: where do we stand?

    Science.gov (United States)

    Ayres, Robert U; Talens Peiró, Laura; Villalba Méndez, Gara

    2011-12-15

    Efficiency is a term generally used to determine how well a system performs. However, efficiency can have different meanings and, unaccompanied by a formal definition or taken out of context, can lead to serious misconceptions. In many official publications, efficiency is calculated as the ratio of useful output to energy input. This measure reflects the first law of thermodynamics (conservation of energy) but does not reflect the potential for improvement. A better measure, that also reflects the second law of thermodynamics, is the ratio of the potential useful (exergy) output to the potential useful (exergy) input. We estimate second law efficiencies for the inorganic and organic chemical industries to be 29% and 35% respectively. We also estimate the efficiency of the U.S. industry sector as a whole to be 37.6%, as compared to only 7.7% for the overall U.S. economy. These figures are far lower than the "first law" figures published by the U.S. Department of Energy (80% for industry and 42.5% overall) and they imply a significant potential for improvement.

  4. 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.

  5. 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.

  6. Eco-exergy and emergy based self-organization of three forest plantations in lower subtropical China.

    Science.gov (United States)

    Lu, Hongfang; Fu, Fangyan; Li, Hao; Campbell, Daniel E; Ren, Hai

    2015-10-21

    The bio-thermodynamic structures of a mixed native species plantation, a conifer plantation and an Acacia mangium plantation in Southern China were quantified over a period of 15 years based on eco-exergy methods. The efficiencies of structural development and maintenance were quantified through an integrated application of eco-exergy and emergy methods. The results showed that the storage of eco-exergy increased over 3 times in all three plantations, as predicted by the maximum eco-exergy principle. This trend was primarily seen due to the accumulation of biomass, instead of an increase in the specific eco-exergy (eco-exergy per unit biomass), although species richness did increase. The eco-exergy to emergy and eco-exergy to empower ratios of the three plantations generally increased during the study period, but the rate of increase slowed down after 20 years. The dominant trees are the largest contributors to the eco-exergy stored in the plantations, and thus, the introduction of suitable indigenous tree species should be considered after the existing trees pass through their period of most rapid growth or around 20 years after planting. The combined application of C-values and suggested weighting factors in the eco-exergy calculation can imply opposite results, but may also supply useful information for forest management.

  7. Energy and exergy analyses of drying of eggplant slices in a cyclone type dryer

    Energy Technology Data Exchange (ETDEWEB)

    Akpinar, E. Kavak [Firat University, Elazig (Turkmenistan)

    2005-02-01

    In this paper, the energy and exergy analyses of the drying process of thin layer of eggplant slices are investigated. Drying experiments were conducted at inlet temperatures of drying air of 55, 65 and 75 .deg. C and at drying air velocities of 1 and 1.5 ms{sup -1} in a cyclone type dryer. Using the first law of thermodynamics, energy analysis was carried to estimate the ratios of energy utilization. However, exergy analysis was accomplished to determine type and magnitude of exergy losses during the drying process by applying the second law of thermodynamics. It was deduced that eggplant slices are sufficiently dried in the ranges between 55-75 .deg. C of drying air temperature and at 1 and 1.5 ms{sup -1} of drying air velocity during 12000-21600s despite the exergy losses of 0-0.739 kJs{sup -1}.

  8. 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...

  9. Reduced Exergy Method for Heat-Electricity Cost Allocation in Combined Heat and Power Plants

    Directory of Open Access Journals (Sweden)

    Xue-min Ye

    2003-12-01

    Full Text Available Abstract: Although the cost allocation method does not change the total benefits of CHP, the use of various cost allocation methods generally results in significant differences in costs allocated for CHP products. In order to overcome the inadequacy of existing cost allocating methods in theory and in practice, according to the different roles of anergy and exergy in heat supply process of CHP plant, the reduced exergy method for cost allocation is formulated by introducing the concepts of the available anergy and reduced exergy. The contribution of the available anergy is expressed with a user factor, which can reflect different utilization for different practical conditions. Some practical conditions for typical CHP units are computed and compared with existing methods. Calculations show that the cost allocation by using the reduced exergy model is more rational and practical than those by using existing models in terms of embodying the physical meaning.

  10. Energy and Exergy Analyses of CO2/HFE7000 Cascade Cooling System

    Directory of Open Access Journals (Sweden)

    Fatih YILMAZ

    2017-10-01

    Full Text Available In this study, a new refrigerant HFE7000, has been investigated thermodynamically in the cascade cooling system. Energy (COP and exergy efficiency of cascade cooling system with CO2/HFE7000 refrigerants are performed. In this regard, the impacts of various parameters on the COP and exergy efficiency and exergy destruction rate of CCS are studied. Moreover, the CO2 refrigerant is used in the low-temperature circuit and HFE7000 is used in the high-temperature circuit. The COP and exergy efficiency of cascade cooling system are found as 2.313 and 0.5482, for cooling application. In the last section, comparison with R134a refrigerant is done, which is widely used in cascade cooling system.

  11. EXERGY-BASED ECOLOGICAL ANALYSIS OF GENERALIZED IRREVERSIBLE HEAT PUMP SYSTEM

    Directory of Open Access Journals (Sweden)

    GOVIND MAHESHWARI

    2011-10-01

    Full Text Available A reverse Carnot cycle forms the basis of all heat-pump cycles in providing heating and cooling loads. The optimal exergy-based Ecological analysis of an irreversible Heat-pump system with the losses of heat resistance, heat leak and internal irreversibility has been carried out by taking into account Exergy based ecological function (E as an objective in the viewpoint of Finite-Time-Thermodynamics (FTT or Entropy Generation Minimization (EGM. Exergy is defined here as the power required minus the lost power. The effects of irreversibilities along with internal heat leakage on coefficient on the performance of the system are investigated. The exergy based Ecological function decreases steadily with irreversibilites and heat leakages in the system. COP in such a system increases with the cycle temperature ratio. If a heat pump cycle is optimized with above mentioned criterion, there is a trade-off between its coefficient of Performance and the heating load it provides.

  12. Nearly Net-Zero Exergy Districts as Models for Smart Energy Systems

    National Research Council Canada - National Science Library

    Şiir Kilkiş

    2017-01-01

    ... Östra Sala backe, which will have a new energy concept. The latter is analysed based on proposals for two phases that aim to reach a net-zero district target based on the quality of energy (exergy...

  13. Exergy Analysis of a Parallel-Plate Active Magnetic Regenerator with Nanofluids

    National Research Council Canada - National Science Library

    Ibai Mugica; Steven Roy; Sebastien Poncet; Jonathan Bouchard; Hakim Nesreddine

    2017-01-01

    .... A 1D numerical model has been extensively used to quantify the exergy performance of a system composed of a parallel-plate regenerator, magnetic source, pump, heat exchangers and control valves...

  14. The challenge of introducing an exergy indicator in a local low on energy

    OpenAIRE

    Favrat, Daniel; Maréchal, François; Epelly, Olivier

    2006-01-01

    Extending the idea of exergy 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 submitted for acceptance of large projects. This paper summarizes the problem definition, a clarification of the...

  15. The effect of altitude and intensity of physical activity on the exergy efficiency of respiratory system

    OpenAIRE

    Henriques, Izabela Batista; Mady, Carlos Eduardo Keutenedjian; Albuquerque Neto, Cyro; Yanagihara,Jurandir Itizo; Oliveira Junior, Silvio

    2013-01-01

    The effect of altitude on exercise performance of lowlanders has long been discussed, but it is still unclear whether the performance reduction is related to inefficiency of the respiratory system, body tissues or both. In the present work, exergy analysis was applied to the human body in order to compare its exergy efficiency under basal conditions and during physical activity at sea level and high altitudes for different periods of acclimatization. Two control volumes were analyzed: respira...

  16. Exergy Methods for the Generic Analysis and Optimization of Hypersonic Vehicle Concepts

    OpenAIRE

    Markell, Kyle Charles

    2005-01-01

    This thesis work presents detailed results of the application of exergy-based methods to highly dynamic, integrated aerospace systems such as hypersonic vehicle concepts. In particular, an exergy-based methodology is compared to a more traditional based measure by applying both to the synthesis/design and operational optimization of a hypersonic vehicle configuration comprised of an airframe sub-system and a propulsion sub-system consisting of inlet, combustor, and nozzle components. A numbe...

  17. 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.

  18. 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.

  19. Exergy analysis of an industrial-scale ultrafiltrated (UF) cheese production plant: a detailed survey

    Science.gov (United States)

    Nasiri, Farshid; Aghbashlo, Mortaza; Rafiee, Shahin

    2017-02-01

    In this study, a detailed exergy analysis of an industrial-scale ultrafiltrated (UF) cheese production plant was conducted based on actual operational data in order to provide more comprehensive insights into the performance of the whole plant and its main subcomponents. The plant included four main subsystems, i.e., steam generator (I), above-zero refrigeration system (II), Bactocatch-assisted pasteurization line (III), and UF cheese production line (IV). In addition, this analysis was aimed at quantifying the exergy destroyed in processing a known quantity of the UF cheese using the mass allocation method. The specific exergy destruction of the UF cheese production was determined at 2330.42 kJ/kg. The contributions of the subsystems I, II, III, and IV to the specific exergy destruction of the UF cheese production were computed as 1337.67, 386.18, 283.05, and 323.51 kJ/kg, respectively. Additionally, it was observed through the analysis that the steam generation system had the largest contribution to the thermodynamic inefficiency of the UF cheese production, accounting for 57.40 % of the specific exergy destruction. Generally, the outcomes of this survey further manifested the benefits of applying exergy analysis for design, analysis, and optimization of industrial-scale dairy processing plants to achieve the most cost-effective and environmentally-benign production strategies.

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

    Directory of Open Access Journals (Sweden)

    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.

  1. 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

  2. Energy and exergy analyses of thermal power plants: A review

    Energy Technology Data Exchange (ETDEWEB)

    Kaushik, S.C.; Reddy, V.S.; Tyagi, S.K. [Indian Institute of Technology Delhi, New Delhi (India). Centre for Energy Studies

    2011-05-15

    The energy supply to demand narrowing down day by day around the world, the growing demand of power has made the power plants of scientific interest, but most of the power plants are designed by the energetic performance criteria based on first law of thermodynamics only. The real useful energy loss cannot be justified by the fist law of thermodynamics, because it does not differentiate between the quality and quantity of energy. The present study deals with the comparison of energy and exergy analyses of thermal power plants stimulated by coal and gas. This article provides a detailed review of different studies on thermal power plants over the years. This review would also throw light on the scope for further research and recommendations for improvement in the existing thermal power plants.

  3. 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

  4. Use of Exergy Analysis to Quantify the Effect of Lithium Bromide Concentration in an Absorption Chiller

    Directory of Open Access Journals (Sweden)

    Andrew Lake

    2017-04-01

    Full Text Available Absorption chillers present opportunities to utilize sustainable fuels in the production of chilled water. An assessment of the steam driven absorption chiller at the University of Idaho, was performed to quantify the current exergy destruction rates. Measurements of external processes and flows were used to create a mathematical model. Using engineering equation solver to analyze and identify the major sources of exergy destruction within the chiller. It was determined that the absorber, generator and condenser are the largest contribution to the exergy destruction at 30%, 31% and 28% of the respectively. The exergetic efficiency is found to be 16% with a Coefficient of performance (COP of 0.65. Impacts of weak solution concentration of lithium bromide on the exergy destruction rates were evaluated using parametric studies. The studies reveled an optimum concentration that could be obtained by increasing the weak solution concentration from 56% to 58.8% a net decrease in 0.4% of the exergy destruction caused by the absorption chiller can be obtained. The 2.8% increase in lithium-bromide concentration decreases the exergy destruction primarily within the absorber with a decrease of 5.1%. This increase in concentration is shown to also decrease the maximum cooling capacity by 3% and increase the exergy destruction of the generator by 4.9%. The study also shows that the increase in concentration will change the internal temperatures by 3 to 7 °C. Conversely, reducing the weak solution concentration results is also shown to increase the exergetic destruction rates while also potentially increasing the cooling capacity.

  5. THIS ARTICLE HAS BEEN RETRACTED Exergy as an ecological application used in the recovery process of benthic communities.

    Science.gov (United States)

    Zhang, Feijun; Tong, Chunfu; Xie, Zhifa; Lu, Jianjian

    2007-03-01

    Exergy, the thermodynamic function that represents the distance of an open system from equilibrium, is proposed as an ecological indicator for summarizing the complex dynamics occurring in a disturbed community during its recovery processes. These complex dynamics can be difficult to capture by using classical indices. In this study, we sampled macrobenthos using the BACI scheme (before versus after; control versus impact) in tidal wetlands of west Chongming Island, China, an area that has been disturbed by ecological engineering measures. Exergy storage is estimated for benthic communities. The control area is proposed as dynamic reference for estimating local exergy storage of the benthic community. Three different methods were used for estimating exergy on the basis of coefficients: (a) taken for taxa groups; (b) estimated from coding genes given for broad taxonomic groups; and (c) estimated from genome size taken as close as possible to the taxonomic level of the species, providing a basis for inferring similarities. We found a decrease of local exergy content in the disturbed area 9 days after the disturbance. Subsequently, the reference exergy of the benthic community increased (i.e. in the surrounding control area) in accordance with the proposed hypothesis regarding the dynamics of exergy storage during a system's development. Estimates of local exergy arrived at using the three methods provided comparable results. Based on this, we then discuss the feasibility of using the more readily available genome size data for estimating exergy. This result may have important implications for broader application of this indicator to biological systems. Moreover, the adjacent control samples seem to represent an appropriate dynamic reference for estimating the local exergy of disturbed communities. We found that exergy was a useful indicator that integrates the processes underlying the recovery of the benthic community after disturbance.

  6. Exergy in the built environment. The added value of exergy in the assessment and development of energy systems for the built environment.

    NARCIS (Netherlands)

    Jansen, S.C.

    2013-01-01

    This doctoral research studied the added value of exergy for the assessment and development of energy systems for the built environment, aiming at a reduced need for high-quality energy input. Currently the analysis and development of energy systems for the built environment is based on the energy

  7. 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...

  8. Investigation of the effect of packing location on performance of closed wet cooling tower based on exergy analysis

    Science.gov (United States)

    Qasim, S. M.; Hayder, M. J.

    2016-08-01

    In this paper, the effect of packing location on thermal performance of Closed Wet Cooling Tower (CWCT) based on exergy analysis has been studied. The experimental study incorporates design, manufacture and testing of a modified counter flow forced draft CWCT prototype. The modification based on addition packing to the conventional CWCT. The variation of spray water temperature, air dry bulb temperature, air wet bulb temperature, enthalpy and relative humidity of air for different position along the tower are measured experimentally. Applying the exergy destruction method for the cooling tower; exergy destruction, exergy efficiency, exergy of water and air were calculated for two cases: CWCT with packing below the heat exchanger and CWCT with packing above the heat exchanger. It is highly important to analyze the exergy along the cooling tower height. Therefore, the exergy analysis of different elements along the height of the tower is carried out. Results show that the total exergy destruction of modified CWCT is higher when the heat exchanger is located above the packing at the highest point of the tower.

  9. Mathematical model for exergy in the system NaCl-H2O

    Directory of Open Access Journals (Sweden)

    Ninković Rozalija R.

    2004-01-01

    Full Text Available In this work mathematical models for the exergy and relative enthalpy of the water solution of sodium-chloride and the pure crystalline sodium-chloride where derived. The environment was defined with the temperature 20 °C, pressure 101,325 kPa and with liquid water and crystalline sodium-chloride, both having at the defined environmental conditions the value of exergy equal zero. The obtained mathematical model is valid in the temperature interval from 0 to 170°C and for the all compositions of solution, until to saturation. The derived mathematical model for the exergy is based on the Pitzer's ion interaction equation which satisfactory represents the dependence of the osmotic coefficient and the mean ionic activity coefficient on the composition of solution. The calculated values of exergy using the mathematical model were compared with the appropriate diagram for the exergy constructed using the table values of activity coefficients, osmotic coefficients and partial molar enthalpies.

  10. 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 .

  11. 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.

  12. 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.

  13. 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.

  14. 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...

  15. 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

    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...... 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....

  16. 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.

  17. 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

    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...... of structurally dynamic models (SDMs). The limitations and possible future applications of the approach are also addressed. (C) 2009 Elsevier B.V. All rights reserved....... 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...

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

    Energy Technology Data Exchange (ETDEWEB)

    Oladiran, M.T. [Department of Mechanical Engineering, University of Botswana, P/Bag 0061, Gaborone (Botswana)]. E-mail: Oladiran@mopipi.ub.bw; Meyer, J.P. [Department of Mechanical and Aeronautical Engineering, University of Pretoria, Pretoria (South Africa)]. E-mail: jmeyer@up.ac.za

    2007-10-15

    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.

  19. Energy and exergy analysis of heat pump using R744/R32 refrigerant mixture

    Directory of Open Access Journals (Sweden)

    Wang Fang

    2014-01-01

    Full Text Available An energy and exergy analysis of heat pump with blends of refrigerant mixture R744/R32 was carried out. The coefficient of performance and exergy efficiency of the system were studied with different mass fraction of R744 in the blends and different heat source temperatures. The volumetric heat capacity, condensing pressure, discharge temperature, and compression ratio were also investigated. The results indicate that at a certain concentration (15/85 by mass, the blends achieve better performance, and are superior to those of R22, the results also show that the new refrigerant mixture is an attractive option for promising alternative refrigerant.

  20. Exergy analysis of air cooling systems in buildings in hot humid climates

    Energy Technology Data Exchange (ETDEWEB)

    Alpuche, M.G. [UNAM, Temixco, Morelos (Mexico). Posgrado en Ingenieria; Heard, C. [Instituto Mexicano del Petroleo, Mexico DF (Mexico); Best, R.; Rojas, J. [UNAM, Temixco, Morelos (Mexico). Centro de Investigacion en Energia

    2005-03-01

    The purpose of this study is to analyze the influence of using air cooling desiccant systems on reaching thermal comfort conditions in the interior of a building, supposing this to be an open system. Exergy analysis has been carried out for the different design temperatures and relative humidity conditions within those established for ASHRAE summer thermal comfort conditions. The climatic conditions of a hot humid climate such as Villahermosa, Tabasco, Mexico, are used as an example. A novel reference state has been used for the exergy analysis, since this varies according to the fluctuation of the ambient temperature and humidity. (author)

  1. Energy, Entropy and Exergy Concepts and Their Roles in Thermal Engineering

    Directory of Open Access Journals (Sweden)

    Yunus A. Cengel

    2001-08-01

    Full Text Available 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 the aspects of energy, entropy and exergy and their roles in thermal engineering.

  2. Thermal Analysis of Hypersonic Inlet Flow with Exergy-Based Design Methods

    OpenAIRE

    Moorhouse, David J.; Prendergast, James P.; Hoke, Charles M.

    2002-01-01

    This paper presents results of work that has been done in developing use of the Second Law of Thermodynamics and methods such as exergy and thermoeconomics into a system-level analysis and design methodology. The application of these methods to the design of a complete flight vehicle is illustrated by considering an integrated airframe/propulsion system as a device to do work. This shows how system-level consideration of exergy applies to all vehicle systems in consistent terms. For the hyper...

  3. Biomass gasification with preheated air: Energy and exergy analysis

    Directory of Open Access Journals (Sweden)

    Karamarkovic Rade M.

    2012-01-01

    Full Text Available Due to the irreversibilities that occur during biomass gasification, gasifiers are usually the least efficient units in the systems for production of heat, electricity, or other biofuels. Internal thermal energy exchange is responsible for a part of these irreversibilities and can be reduced by the use of preheated air as a gasifying medium. The focus of the paper is biomass gasification in the whole range of gasification temperatures by the use of air preheated with product gas sensible heat. The energetic and exergetic analyses are carried with a typical ash-free biomass feed represented by CH1.4O0.59N0.0017 at 1 and 10 bar pressure. The tool for the analyses is already validated model extended with a heat exchanger model. For every 200 K of air preheating, the average decrease of the amount of air required for complete biomass gasification is 1.3% of the amount required for its stoichiometric combustion. The air preheated to the gasification temperature on the average increases the lower heating value of the product gas by 13.6%, as well as energetic and exergetic efficiencies of the process. The optimal air preheating temperature is the one that causes gasification to take place at the point where all carbon is consumed. It exists only if the amount of preheated air is less than the amount of air at ambient temperature required for complete gasification at a given pressure. Exergy losses in the heat exchanger, where the product gas preheats air could be reduced by two-stage preheating.

  4. 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)

  5. Energy and exergy evaluation of an integrated solar heat pipe wall ...

    Indian Academy of Sciences (India)

    The rate of increasing in temperature of air becomes negligible after 30 heat pipes and the trend of the thermal efficiency is descending with increasing heat pipes. The results also indicate that at a cold winter day of January, the proposed system with a 20 heat pipe collector shows maximum energy and exergy efficiency of ...

  6. Energy and exergy analysis in double-pass solar air heater

    Indian Academy of Sciences (India)

    In this study, an attempt is made to improve the energy and exergy performance of solar air heater by employing double pass with different absorber surface geometries (roughened, finned, and v-corrugated wire ... Department of Mechanical Engineering, Annamalai University, Annamalai Nagar 608002, Tamilnadu, India ...

  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 in double-pass solar air heater

    Indian Academy of Sciences (India)

    P VELMURUGAN

    Abstract. In this study, an attempt is made to improve the energy and exergy performance of solar air heater by employing double pass with different absorber surface geometries (roughened, finned, and v-corrugated wire mesh) in the second pass, and also by mounting longitudinal fins in the back side of the absorber plate ...

  9. 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.

  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. 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...

  12. Exergy analysis in the assessment of the sustainability of waste gas treatment systems.

    Science.gov (United States)

    Dewulf, J; Van Langenhove, H; Dirckx, J

    2001-06-12

    This study focuses on the sustainability of different technological options for the treatment of waste gases from a waste water treatment plant loaded with volatile organic compounds. The options considered are biofiltration, active carbon adsorption and catalytic and thermal oxidation. The amount of resources and utilities to construct and operate each system have been investigated from the point of view of the Second Law of thermodynamics. The unit in which all resources are treated is Joules of exergy. It was concluded that biofiltration was the most exergetically efficient system. The cumulative exergy consumption of the resources and utilities for construction and operation have been quantified in exergy terms. Further on, the requirements for the abatement of emissions generated by operating the waste gas treatment systems and the amount of renewables have been taken into account in the assessment of the sustainability of the waste gas treatment technologies. Finally, a comparison between exergy analysis and life cycle analysis in assessing the sustainability of the waste gas treatment options, is presented.

  13. Mass balance, energy and exergy analysis of bio-oil production by fast pyrolysis

    Science.gov (United States)

    Mass, energy and exergy balances are analyzed for bio-oil production in a bench scale fast pyrolysis system developed by the USDA’s Agricultural Research Service (ARS) for the processing of commodity crops to fuel intermediates. Because mass balance closure is difficult to achieve due, in part, to ...

  14. COMPARISON OF ENERGY AND EXERGY EFFICIENCIES OF ABSORPTION REFRIGERATION SYSTEM WITH MECHANICAL COMPRESSION REFRIGERATION SYSTEM

    Directory of Open Access Journals (Sweden)

    Gülay YAKAR

    2005-02-01

    Full Text Available In this study, energy and exergy analysis of absorption refrigeration system using LiBr- water and mechanical compression refrigeration system using R134-a were performed at different evaporation temperatures. The results are presented in tables and figures.

  15. 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)

  16. Exergy analysis of hypersonic propulsion systems: Performance comparison of two different scramjet configurations at cruise conditions

    Energy Technology Data Exchange (ETDEWEB)

    Amati, V.; Bruno, C.; Simone, D.; Sciubba, E. [Department of Mechanical and Aeronautical Engineering, University of Roma 1 ' ' La Sapienza' ' , Via Eudossiana 18, 00184 Roma (Italy)

    2008-02-15

    An exergy analysis of an advanced hypersonic vehicle, a scramjet, is presented and discussed with a twofold scope. First, to perfect the exergy approach to the design and optimization of aerospace propulsion systems: the exergy flow diagram can provide aircraft engineers and system designers with additional insight on the avoidable and unavoidable systemic losses, thus allowing for effective design improvements. Second, to explore limits and merits of two different fuelling solutions for a scramjet-powered aircraft. Two configurations are critically compared: one with a direct H{sub 2} injection and one with an on-board kerosene reformer. The present study treats the scramjet-propelled plane as a Large Complex Energy System ('LCES'), and applies system balances (mass, energy, exergy) to calculate the relevant losses. The exergy analysis confirms that the introduction of an on-board reformer is advantageous from the point of view of the thrust efficiency (with a gain of 3 percentage points with respect to the H{sub 2}-fuelled engine) and, more importantly, from the point of view of a more correct use of the available resources (the fuel in the tanks). Another advantage of the on-board reforming is that the higher value of the volumetric-specific impulse allows for reducing the fuel tank size. All calculations have been performed with CAMEL {sup registered}, a modular simulator for energy conversion processes conceived and developed in the last decade by the Authors' group at the Mechanical and Aeronautical Engineering Department of the University of Roma 1 'La Sapienza'. Some additional component models have been studied and implemented, and a specific tool dedicated to the analysis of propulsion systems has been created and integrated in the simulation package. (author)

  17. 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

    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...... 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.......-state thermal environments. Therefore, the first objective of the current paper was to compare a recently introduced unsteady-state model with previously used steady-state model using data obtained under both constant and transient temperature conditions. The second objective was to explore a relationship...

  18. Effect of Variation of Operational Regimes in Building Environment on Results of its Energy and Exergy Assessments

    Science.gov (United States)

    Voloshchuk, Volodymyr

    2017-03-01

    For further development of the dynamic exergy analysis within built environment the work proposes to take into account stochastic nature of variations of operational regimes. Using the probability theory and statistics methods, the set of parameters considered as relevant for uncertainty conditions are presented. It is shown that characteristics of buildings (insulation, window performance, heat recovery, etc.) and type of the heating system have undoubtedly a strong influence not only on the energy/exergy demand and consumption but also on the sensitivity of the energy/exergy parameters to variations of external conditions. According to the results obtained after implementations of energy efficient solutions coefficient of variation of energy/exergy-based parameters can be increased up to two times.

  19. Effect of Variation of Operational Regimes in Building Environment on Results of its Energy and Exergy Assessments

    Directory of Open Access Journals (Sweden)

    Voloshchuk Volodymyr

    2017-03-01

    Full Text Available For further development of the dynamic exergy analysis within built environment the work proposes to take into account stochastic nature of variations of operational regimes. Using the probability theory and statistics methods, the set of parameters considered as relevant for uncertainty conditions are presented. It is shown that characteristics of buildings (insulation, window performance, heat recovery, etc. and type of the heating system have undoubtedly a strong influence not only on the energy/exergy demand and consumption but also on the sensitivity of the energy/exergy parameters to variations of external conditions. According to the results obtained after implementations of energy efficient solutions coefficient of variation of energy/exergy-based parameters can be increased up to two times.

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

    Energy Technology Data Exchange (ETDEWEB)

    Tchanche, B.F.; Lambrinos, Gr.; Frangoudakis, A.; Papadakis, G. [Department of Natural Resources and Agricultural Engineering, Agricultural University of Athens, 75 Iera Odos Street, 11855 Athens (Greece)

    2010-04-15

    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

  1. A detailed study of desalination exergy models and their application to a semi-conductor ultra-pure water plant

    OpenAIRE

    Fitzsimons, Lorna

    2011-01-01

    Ultra-Pure Water (UPW) is a high energy raw material used in the semiconductor manufacturing industry. However, to date, the production of UPW has received little focus in terms of energy consumption mitigation. Exergy analysis is perhaps the most powerful tool available in the search for industrial energy efficiency. The objective of this research was to develop an approach for the exergy analysis of Semiconductor UPW plants in an effort to characterise energy consumption. However, following...

  2. Energy and Exergy Performances of Air-Based vs. Water-Based Heating and Cooling Systems: A Case Study of a Single-Family House

    DEFF Research Database (Denmark)

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

    2016-01-01

    , in terms of energy and exergy. In addition to the energy and exergy input required at the heating and cooling plants, the energy use of auxiliary components (fans and pumps) also vary depending on the chosen terminal unit. In order to study the energy and exergy performances of air-based and water...... energy and exergy inputs to the system, energy and exergy inputs to the auxiliary components were also studied. Both heating and cooling cases were considered and three climatic zones were studied; Copenhagen (Denmark), Yokohama (Japan), and Ankara (Turkey). The analysis showed that the water......-based radiant heating and cooling system performed better than the air-based system both in terms of energy and exergy input to the heating/cooling plant. The relative benefits of the water-based system over the air-based system vary depending on the climatic zone. The air-based system also requires higher...

  3. Effects of abiotic factors on ecosystem health of Taihu Lake, China based on eco-exergy theory.

    Science.gov (United States)

    Wang, Ce; Bi, Jun; Fath, Brian D

    2017-02-21

    A lake ecosystem is continuously exposed to environmental stressors with non-linear interrelationships between abiotic factors and aquatic organisms. Ecosystem health depicts the capacity of system to respond to external perturbations and still maintain structure and function. In this study, we explored the effects of abiotic factors on ecosystem health of Taihu Lake in 2013, China from a system-level perspective. Spatiotemporal heterogeneities of eco-exergy and specific eco-exergy served as thermodynamic indicators to represent ecosystem health in the lake. The results showed the plankton community appeared more energetic in May, and relatively healthy in Gonghu Bay with both higher eco-exergy and specific eco-exergy; a eutrophic state was likely discovered in Zhushan Bay with higher eco-exergy but lower specific eco-exergy. Gradient Boosting Machine (GBM) approach was used to explain the non-linear relationships between two indicators and abiotic factors. This analysis revealed water temperature, inorganic nutrients, and total suspended solids greatly contributed to the two indicators that increased. However, pH rise driven by inorganic carbon played an important role in undermining ecosystem health, particularly when pH was higher than 8.2. This implies that climate change with rising CO2 concentrations has the potential to aggravate eutrophication in Taihu Lake where high nutrient loads are maintained.

  4. Effects of abiotic factors on ecosystem health of Taihu Lake, China based on eco-exergy theory

    Science.gov (United States)

    Wang, Ce; Bi, Jun; Fath, Brian D.

    2017-02-01

    A lake ecosystem is continuously exposed to environmental stressors with non-linear interrelationships between abiotic factors and aquatic organisms. Ecosystem health depicts the capacity of system to respond to external perturbations and still maintain structure and function. In this study, we explored the effects of abiotic factors on ecosystem health of Taihu Lake in 2013, China from a system-level perspective. Spatiotemporal heterogeneities of eco-exergy and specific eco-exergy served as thermodynamic indicators to represent ecosystem health in the lake. The results showed the plankton community appeared more energetic in May, and relatively healthy in Gonghu Bay with both higher eco-exergy and specific eco-exergy; a eutrophic state was likely discovered in Zhushan Bay with higher eco-exergy but lower specific eco-exergy. Gradient Boosting Machine (GBM) approach was used to explain the non-linear relationships between two indicators and abiotic factors. This analysis revealed water temperature, inorganic nutrients, and total suspended solids greatly contributed to the two indicators that increased. However, pH rise driven by inorganic carbon played an important role in undermining ecosystem health, particularly when pH was higher than 8.2. This implies that climate change with rising CO2 concentrations has the potential to aggravate eutrophication in Taihu Lake where high nutrient loads are maintained.

  5. The Use of Exergy and Decomposition Techniques in the Development of Generic Analysis, and Optimization Methodologies Applicable to the Synthesis/Design of Aircraft/Aerospace Systems

    Science.gov (United States)

    2006-04-21

    The Use of Exergy and Decomposition Techniques in the Development of Generic Analysis and Optimization Methodologies Applicable to the Synthesis...The Use of Exergy and Decomposition Techniques in the 5a. CONTRACT NUMBER Development of Generic Analysis and Optimization Methodologies Applicable...NUMBER Functions/Figures of Merit on the Analysis and Optimization of High Performance Aircraft System Synthesis/Design; Thesis #2: Exergy Methods for

  6. Quantitative assessment of solid waste treatment systems in the industrial ecology perspective by exergy analysis.

    Science.gov (United States)

    Dewulf, Jo P; Van Langenhove, Herman R

    2002-03-01

    Solid waste treatment options (recycling, incineration, and landfilling; the two latter processes both with co-generation of heat and electricity) have been studied for cardboard, newspaper, polyethylene, poly(ethylene terephthalate), polypropylene, polystyrene, and poly(vinyl chloride) waste. The conversion processes have been analyzed in terms of the second law of thermodynamics. The analysis allows calculating the exergy (useful energy) embodied in conversion products that can be obtained from the required inputs for the treatment processes. Taking into account the waste materials and the resources to convert them, it proved that recycling is the most efficient option for polyethylene with an efficiency of 62.5% versus 43.6% for incineration and 0.9% for landfilling. Next, waste treatment has been put into the broader perspective of industrial ecology. Exergetic efficiencies of industrial metabolic options have been calculated. Here resources for manufacturing and converting solid products have been considered. Furthermore, selection of one type of conversion excludes the generation of other potential conversion products. Therefore, it has to be taken into account that these latter products still have to be produced starting from virgin resources. Recycling proved to be the most efficient strategy: the ratio eta between exergy embodied in all delivered products on one hand, and all exergy withdrawn from the ecosphere or from waste materials on the other hand, is the highest. For polyethylene, eta proved to be 0.568, whereas eta is 0.503 and 0.329 for incineration and landfilling, respectively. On the other hand, if R the ratio between exergy of delivered products on one hand and exergy of virgin materials on the other hand is calculated, the differences between the industrial metabolic options are larger. Recycling polyethylene showed a ratio R of 0.936, whereas ratios of 0.772 and 0.531 were found for incineration and landfilling, respectively. It has been

  7. 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

  8. Exergy efficiency analysis of a flat plate solar collector using graphene based nanofluid

    Science.gov (United States)

    Said, Z.; Alim, M. A.; Janajreh, Isam

    2015-10-01

    The thermal efficiency of a flat plate solar thermal collector is largely affected by the thermal conductivity of the fluid used. In this paper, we theoretically analyzed the heat transfer performance, the entropy generation rate, and the exergy efficiency of the two different graphene based nanofluids (graphene/Acetone and graphene/water). From the analyses, it is revealed that by inserting a small amount of graphene nanoparticles in water, exergy efficiency could be enhanced by 21%, comparing to conventional fluids and entropy generation is decreased by 4%. However, the graphene/water nanofluid shows a lower entropy generation. This characteristic suggests that graphene/water nanofluid is a better candidate for flat solar thermal application.

  9. 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

    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...... 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...

  10. 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

    of an integrated system in which steam extracted from an existing combined heat and power unit is used for covering the heating demand of a lignocellulosic ethanol production facility. The integration solution was designed and optimized using already existing steam extraction points in the combined heat and power...... 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......Integrating second generation bioethanol production in combined heat and power units is expected to increase system energy efficiencies while producing sustainable fuel for the transportation sector at a competitive price. By applying exergy analysis, this study assessed the efficiency...

  11. 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

    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...... coefficient of performance). This requires higher electricity input to the heat pump, corresponding to an increased exergy demand and consumption, to achieve the same space heating or cooling. The required exergy input to the system (power plant where the electricity is generated) increased by 14% and 5...

  12. Energy and exergy analyses of a biomass-based hydrogen production system.

    Science.gov (United States)

    Cohce, M K; Dincer, I; Rosen, M A

    2011-09-01

    In this paper, a novel biomass-based hydrogen production plant is investigated. The system uses oil palm shell as a feedstock. The main plant processes are biomass gasification, steam methane reforming and shift reaction. The modeling of the gasifier uses the Gibbs free energy minimization approach and chemical equilibrium considerations. The plant, with modifications, is simulated and analyzed thermodynamically using the Aspen Plus process simulation code (version 11.1). Exergy analysis, a useful tool for understanding and improving efficiency, is used throughout the investigation, in addition to energy analysis. The overall performance of the system is evaluated, and its efficiencies become 19% for exergy efficiency and 22% energy efficiency while the gasifier cold gas efficiency is 18%. Copyright © 2011 Elsevier Ltd. All rights reserved.

  13. 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

    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...... 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...... 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...

  14. 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...... 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...... 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...

  15. 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.

  16. Theoretical Energy and Exergy Analyses of Proton Exchange Membrane Fuel Cell by Computer Simulation

    OpenAIRE

    I. D. Gimba; Abdulkareem, A. S.; Jimoh, A.; A. S. Afolabi

    2016-01-01

    A mathematical model of a proton exchange membrane fuel cell (PEMFC) was developed to investigate the effects of operating parameters such as temperature, anode and cathode pressures, reactants flow rates, membrane thickness, and humidity on the performance of the modelled fuel cell. The developed model consisted of electrochemical, heat energy and exergy components which were later simulated using a computer programme. The simulated model for the voltage output of the cell showed good confor...

  17. [Thermodynamics of life from the point of view of technical thermodynamics and exergy].

    Science.gov (United States)

    Grassmann, P

    1984-07-01

    All living beings are, from the thermodynamic point of view, open, well regulated, and optimized systems with considerable internal irreversibilities. However scientific research is mainly based on closed systems. The theory of open systems is very well developed in engineering thermodynamics. Here the concept of "exergy"--the thermodynamic potential related to given surroundings--clearly distinguishes between the two concepts of the word "energy".

  18. Exergy Methods for the Mission-Level Analysis and Optimization of Generic Hypersonic Vehicles

    OpenAIRE

    Brewer, Keith Merritt

    2006-01-01

    Though the field of hypersonic vehicle design is thriving again, few studies to date demonstrate the technology through a mission in which multiple flight conditions and constraints are encountered. This is likely due to the highly integrated and sensitive nature of hypersonic vehicle components. Consequently, a formal Mach 6 through Mach 10 flight envelope is explored which includes cruise, acceleration/climb, deceleration/descend and turn mission segments. An exergy approach to the vehic...

  19. Exergy Assessment of Recovery Solutions from Dry and Moist Gas Available at Medium Temperature

    Directory of Open Access Journals (Sweden)

    Fadhel Ayachi

    2012-03-01

    Full Text Available The Agence Nationale de la Recherche (ANR-EESI ENERGY ReCOvery from Low Temperature heat sources (ENERCO_LT project is a waste heat recovery project that aims to reduce energy consumption in industrial gas production sites, by producing electrical power from exothermic processes discharges at low and medium temperature. Two promising thermal sources, consisting of: (i almost dry gas flow at 165 °C and (ii moist gas flow at 150 °C with a dew point at 60 °C, were then investigated. In this paper, the challenge was to discern suitable recovery solutions facing resource specificities and their thermodynamic constraints, in order to minimize the overall exergy destruction, i.e., to move up the exergy efficiency of the entire system. In this spirit, different designs, including Organic Rankine Cycles (ORCs and CO2 transcritical cycles, operating as simple and cascade cycles, were investigated. Combined exergy analysis and pinch optimization was performed to identify the potential of various working fluids, by their properties, to overcome the global irreversibility according to the studied resource. Supercritical parameters of various working fluids are investigated too, and seem to bring promising results regarding system performances.

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

    Directory of Open Access Journals (Sweden)

    George A. Xydis

    2012-08-01

    Full Text Available Global carbon dioxide (CO2 emissions reached an all-time high in 2010, rising 45% in the past 20 years. The rise of peoples’ concerns regarding environmental problems such as global warming and waste management problem has led to a movement to convert the current mass-production, mass-consumption, and mass-disposal type economic society into a sustainable society. The Rio Conference on Environment and Development in 1992, and other similar environmental milestone activities and happenings, documented the need for better and more detailed knowledge and information about environmental conditions, 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.

  1. 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.

  2. 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.

  3. The exergy of a phase shift: Ecosystem functioning loss in seagrass meadows of the Mediterranean Sea

    Science.gov (United States)

    Montefalcone, Monica; Vassallo, Paolo; Gatti, Giulia; Parravicini, Valeriano; Paoli, Chiara; Morri, Carla; Bianchi, Carlo Nike

    2015-04-01

    Sustained functioning of ecosystems is predicted to depend upon the maintenance of their biodiversity, structure and integrity. The large consensus achieved in this regard, however, faces to the objective difficulty of finding appropriate metrics to measure ecosystem functioning. Here, we aim at evaluating functional consequence of the phase shift occurring in meadows of the Mediterranean seagrass Posidonia oceanica, a priority habitat that is undergoing regression in many coastal areas due to multiple human pressures. Structural degradation of the P. oceanica ecosystem, consequent to increasing coastal exploitation and climate change, may result in the progressive replacement of this seagrass by opportunistic macrophytes, either native or alien. Reviewing published information and our personal records, we measured changes in biological habitat provisioning, species richness and biomass associated to each of the alternative states characterizing the phase shift. Then, ecosystem functioning was assessed by computing the exergy associated to each state, exergy being a state variable that measures the ecosystem capacity to produce work. Phase shift was consistently shown to imply loss in habitat provision, species richness, and biomass; structural and compositional loss was parallelled by a reduction of exergy content, thus providing for the first time an objective and integrative measure of the loss of ecosystem functioning following the degradation of healthy seagrass meadows.

  4. An Exergy-Based Model for Population Dynamics: Adaptation, Mutualism, Commensalism and Selective Extinction

    Directory of Open Access Journals (Sweden)

    Enrico Sciubba

    2012-10-01

    Full Text Available Following the critical analysis of the concept of “sustainability”, developed on the basis of exergy considerations in previous works, an analysis of possible species “behavior” is presented and discussed in this paper. Once more, we make use of one single axiom: that resource consumption (material and immaterial can be quantified solely in terms of exergy flows. This assumption leads to a model of population dynamics that is applied here to describe the general behavior of interacting populations. The resulting equations are similar to the Lotka-Volterra ones, but more strongly coupled and intrinsically non-linear: as such, their solution space is topologically richer than those of classical prey-predator models. In this paper, we address an interesting specific problem in population dynamics: if a species assumes a commensalistic behavior, does it gain an evolutionary advantage? And, what is the difference, in terms of the access to the available exergy resources, between mutualism and commensalism? The model equations can be easily rearranged to accommodate both types of behavior, and thus only a brief discussion is devoted to this facet of the problem. The solution space is explored in the simplest case of two interacting populations: the model results in population curves in phase space that can satisfactorily explain the evolutionistic advantages and drawbacks of either behavior and, more importantly, identify the presence or absence of a “sustainable” solution in which both species survive.

  5. Data on energy, exergy analysis and optimisation for a sugar factory.

    Science.gov (United States)

    Taner, Tolga; Sivrioglu, Mecit

    2015-12-01

    A huge amount of energy is consumed during sugar production in the food industry. The large amount of steam used and the power of the turbine power plant are key factors. This makes energy and exergy analysis important in sugar factories. The data given in the following paper are related to input and output information of the paper entitled Energy - exergy analysis and optimisation of a model sugar factory in Turkey by Taner and Sivrioglu (2015) [1]. Factory total energy efficiency and exergy efficiency are found to be η enT=72.2% and η exT=37.4%, respectively, and according to these results, the total energy quality ∅ T=0.64. These results indicate higher efficiency than similar studies (Vuckovic et al., 2014; Pellegrini and Oliviera Junior, 2011; Deshmukh et al., 2013; Palacios-Bereche et al., 2015) [2], [3], [4], [5]. This study can be a model for these similar factories by Taner and Sivrioglu (2015) [1].

  6. Data on energy, exergy analysis and optimisation for a sugar factory☆

    Science.gov (United States)

    Taner, Tolga; Sivrioglu, Mecit

    2015-01-01

    A huge amount of energy is consumed during sugar production in the food industry. The large amount of steam used and the power of the turbine power plant are key factors. This makes energy and exergy analysis important in sugar factories. The data given in the following paper are related to input and output information of the paper entitled Energy – exergy analysis and optimisation of a model sugar factory in Turkey by Taner and Sivrioglu (2015) [1]. Factory total energy efficiency and exergy efficiency are found to be ηenT=72.2% and ηexT=37.4%, respectively, and according to these results, the total energy quality ∅T=0.64. These results indicate higher efficiency than similar studies (Vuckovic et al., 2014; Pellegrini and Oliviera Junior, 2011; Deshmukh et al., 2013; Palacios-Bereche et al., 2015) [2], [3], [4], [5]. This study can be a model for these similar factories by Taner and Sivrioglu (2015) [1]. PMID:26958601

  7. Divergence of trends in US and UK aggregate exergy efficiencies 1960-2010.

    Science.gov (United States)

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

    2014-08-19

    National exergy efficiency analysis relates the quality of primary energy inputs to an economy with end useful work in sectoral energy uses such as transport, heat and electrical devices. This approach has been used by a range of authors to explore insights to macroscale energy systems and linkages with economic growth. However, these analyses use a variety of calculation methods with sometimes coarse assumptions, inhibiting comparisons. Therefore, building on previous studies, this paper first contributes toward a common useful work accounting framework, by developing more refined methodological techniques for electricity end use and transport exergy efficiencies. Second, to test this more consistent and granular approach, these advances are applied to the US and UK for 1960 to 2010. The results reveal divergent aggregate exergy efficiencies: US efficiency remains stable at around 11%, while UK efficiency rises from 9% to 15%. The US efficiency stagnation is due to "efficiency dilution", where structural shifts to lower efficiency consumption (e.g., air-conditioning) outweigh device-level efficiency gains. The results demonstrate this is an important area of research, with consequent implications for national energy efficiency policies.

  8. Nearly Net-Zero Exergy Districts as Models for Smart Energy Systems

    Directory of Open Access Journals (Sweden)

    Şiir Kilkiş

    2017-03-01

    Full Text Available The planning of urban settlements requires a targeted approach towards more sustainable energy, water, and environment systems. This research work analyses the city of Uppsala and a district that is an urban renewal project at the site of former high voltage power lines, namely Östra Sala backe, which will have a new energy concept. The latter is analysed based on proposals for two phases that aim to reach a net-zero district target based on the quality of energy (exergy. An indicator set with five main categories is introduced based on per capita values to enable a comparable basis between the scales of the city and the district, including exergy per capita as a new indicator. The present status of Uppsala is further analysed based on Sankey diagrams to provide insight into the present urban metabolism of the city. The results indicate that the best practice values of Östra Sala backe based on phase two can achieve significant savings in per capita values, which include 5.5 MWh of energy usage, 6.1 MWh of exergy consumption, 33 m3 of water consumption, 22 kg of waste generation, and 4.2 tonnes of carbon dioxide (CO2 emissions. Additional scenarios for Uppsala indicate that the district can be about 10 years ahead of the city’s existing performance.

  9. Data on energy, exergy analysis and optimisation for a sugar factory

    Directory of Open Access Journals (Sweden)

    Tolga Taner

    2015-12-01

    Full Text Available A huge amount of energy is consumed during sugar production in the food industry. The large amount of steam used and the power of the turbine power plant are key factors. This makes energy and exergy analysis important in sugar factories. The data given in the following paper are related to input and output information of the paper entitled Energy – exergy analysis and optimisation of a model sugar factory in Turkey by Taner and Sivrioglu (2015 [1]. Factory total energy efficiency and exergy efficiency are found to be ηenT=72.2% and ηexT=37.4%, respectively, and according to these results, the total energy quality ∅T=0.64. These results indicate higher efficiency than similar studies (Vuckovic et al., 2014; Pellegrini and Oliviera Junior, 2011; Deshmukh et al., 2013; Palacios-Bereche et al., 2015 [2–5]. This study can be a model for these similar factories by Taner and Sivrioglu (2015 [1].

  10. Exergy analysis of an integrated solid oxide fuel cell and organic Rankine cycle for cooling, heating and power production

    Energy Technology Data Exchange (ETDEWEB)

    Al-Sulaiman, Fahad A. [Mechanical and Aerospace Engineering Department, Carleton University 1125 Colonel By Drive, Ottawa, Ontario (Canada); Dincer, Ibrahim [Faculty of Engineering and Applied Science, University of Ontario Institute of Technology 2000 Simcoe Street North, Oshawa, Ontario (Canada); Hamdullahpur, Feridun [Mechanical and Mechatronics Engineering Department, University of Waterloo, 200 University Avenue West, Waterloo, Ontario (Canada)

    2010-04-15

    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. (author)

  11. 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.

  12. 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

    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...

  13. Exergy and Thermoeconomic Analyses of Central Receiver Concentrated Solar Plants Using Air as Heat Transfer Fluid

    Directory of Open Access Journals (Sweden)

    Claudia Toro

    2016-10-01

    Full Text Available The latest developments in solar technologies demonstrated that the solar central receiver configuration is the most promising application among concentrated solar power (CSP plants. In CSPs solar-heated air can be used as the working fluid in a Brayton thermal cycle and as the heat transfer fluid for a Rankine thermal cycle as an alternative to more traditional working fluids thereby reducing maintenance operations and providing the power section with a higher degree of flexibility To supply thermal needs when the solar source is unavailable, an auxiliary burner is requested. This configuration is adopted in the Julich CSP (J-CSP plant, operating in Germany and characterized by a nominal power of 1.5 MW, the heat transfer fluid (HTF is air which is heated in the solar tower and used to produce steam for the bottoming Rankine cycle. In this paper, the J-CSP plant with thermal energy storage has been compared with a hybrid CSP plant (H-CSP using air as the working fluid. Thermodynamic and economic performances of all the simulated plants have been evaluated by applying both exergy analysis and thermoeconomic analysis (TA to determine the yearly average operation at nominal conditions. The exergy destructions and structure as well as the exergoeconomic costs of products have been derived for all the components of the plants. Based on the obtained results, the thermoeconomic design evaluation and optimization of the plants has been performed, allowing for improvement of the thermodynamic and economic efficiency of the systems as well as decreasing the exergy and exergoeconomic cost of their products.

  14. Exergy Analysis and Second Law Efficiency of a Regenerative Brayton Cycle with Isothermal Heat Addition

    Directory of Open Access Journals (Sweden)

    Naser M. Jubeh

    2005-07-01

    Full Text Available Abstract: The effect of two heat additions, rather than one, in a gas turbine engine is analyzed from the second law of thermodynamics point of view. A regenerative Brayton cycle model is used for this study, and compared with other models of Brayton cycle. All fluid friction losses in the compressor and turbine are quantified by an isentropic efficiency term. The effect of pressure ratio, turbine inlet temperature, ambient temperature, altitude, and altitude with variable ambient temperature on irreversibility "exergy destroyed" and second law efficiency was investigated and compared for all models. The results are given graphically with the appropriate discussion and conclusion.

  15. 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

    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 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...

  16. Nearly Net-Zero Exergy Districts as Models for Smart Energy Systems

    OpenAIRE

    Şiir Kilkiş

    2017-01-01

    The planning of urban settlements requires a targeted approach towards more sustainable energy, water, and environment systems. This research work analyses the city of Uppsala and a district that is an urban renewal project at the site of former high voltage power lines, namely Östra Sala backe, which will have a new energy concept. The latter is analysed based on proposals for two phases that aim to reach a net-zero district target based on the quality of energy (exergy). An indicator s...

  17. Evaluation of the cryogenic helium recovery process from natural gas based on flash separation by advanced exergy cost method - Linde modified process

    Science.gov (United States)

    Ansarinasab, Hojat; Mehrpooya, Mehdi; Parivazh, Mohammad Mehdi

    2017-10-01

    In this paper, exergy cost analysis method is used to evaluate a new cryogenic Helium recovery process from natural gas based on flash separation. Also advanced exergoeconomic analysis was made to determine the amount of avoidable exergy destruction cost of the process component. This proposed process can extract Helium from a feed gas stream with better efficiency than other existing processes. The results indicate that according to the avoidable endogenous exergy destruction cost C-4 (287.2/hr), C-5 (257.3/hr) and C-6 (181.6/hr) compressors should be modified first, respectively. According to the endogenous investment and exergy destruction cost, the interactions between the process components are not strong. In compressors, a high proportion of the cost of exergy destruction is avoidable while in these components, investment costs are unavoidable. In heat exchangers and air coolers, a high proportion of the exergy destruction cost is unavoidable while in these components, investment costs are avoidable. Finally, three different strategies are suggested to improve performance of each component, and the sensitivity of exergoeconomic factor and cost of exergy destruction to operating variables of the process are studied.

  18. 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

  19. Simulation, exergy analysis and application of diabatic distillation to a tertiary amyl methyl ether production unit of a crude oil refinery

    Energy Technology Data Exchange (ETDEWEB)

    Rivero, R.; Garcia, M.; Urquiza, J

    2004-03-01

    This paper presents the results of a detailed exergy analysis of a tertiary amyl methyl ether (TAME) unit of a crude oil refinery and the application of diabatic distillation to the depentanizer tower of the unit. Diabatic distillation is a separation process in which heat is not only supplied to the reboiler and extracted from the condenser [as in a conventional (adiabatic) distillation column], but is also transferred inside the column. The process enables operation to approach equilibrium conditions, thus reducing exergy losses and increasing exergy effectiveness. In a TAME unit of a refinery, isoamylenes are converted to TAME. Before transforming the isoamylenes in the reactors, it is necessary to recover them from a catalytic gasoline stream by a depentanization process. The exergy losses of this depentanization process represent about 70% of the total exergy losses of the unit. The results of the exergy analysis of the TAME unit are presented and a detailed exergy analysis of the conventional adiabatic depentanizer column is conducted for comparison purposes. Then, the application of diabatic distillation to the system is evaluated by using cooling water circulating in series from tray to tray in the rectification section and by making the steam emanating from the reboiler circulate in series from tray to tray in the stripping section. The results in terms of the reduction of exergy losses, heating and cooling media flow rates, and cost effectiveness of the diabatic option for the depentanizer section of the plant are compared to the original adiabatic system, and the effect of the diabatization on the overall exergy performance parameters of the depentanizer section and on the whole TAME unit, are presented in this paper.

  20. Comparative exergy analysis of direct alcohol fuel cells using fuel mixtures

    Science.gov (United States)

    Leo, Teresa J.; Raso, Miguel A.; Navarro, Emilio; Sánchez-de-la-Blanca, Emilia

    Within the last years there has been increasing interest in direct liquid fuel cells as power sources for portable devices and, in the future, power plants for electric vehicles and other transport media as ships will join those applications. Methanol is considerably more convenient and easy to use than gaseous hydrogen and a considerable work is devoted to the development of direct methanol fuel cells. But ethanol has much lower toxicity and from an ecological viewpoint ethanol is exceptional among all other types of fuel as is the only chemical fuel in renewable supply. The aim of this study is to investigate the possibility of using direct alcohol fuel cells fed with alcohol mixtures. For this purpose, a comparative exergy analysis of a direct alcohol fuel cell fed with alcohol mixtures against the same fuel cell fed with single alcohols is performed. The exergetic efficiency and the exergy loss and destruction are calculated and compared in each case. When alcohol mixtures are fed to the fuel cell, the contribution of each fuel to the fuel cell performance is weighted attending to their relative proportion in the aqueous solution. The optimum alcohol composition for methanol/ethanol mixtures has been determined.

  1. 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.

  2. Dynamic Exergy Method for Evaluating the Control and Operation of Oxy-Combustion Boiler Island Systems.

    Science.gov (United States)

    Jin, Bo; Zhao, Haibo; Zheng, Chuguang; Liang, Zhiwu

    2017-01-03

    Exergy-based methods are widely applied to assess the performance of energy conversion systems; however, these methods mainly focus on a certain steady-state and have limited applications for evaluating the control impacts on system operation. To dynamically obtain the thermodynamic behavior and reveal the influences of control structures, layers and loops, on system energy performance, a dynamic exergy method is developed, improved, and applied to a complex oxy-combustion boiler island system for the first time. The three most common operating scenarios are studied, and the results show that the flow rate change process leads to less energy consumption than oxygen purity and air in-leakage change processes. The variation of oxygen purity produces the largest impact on system operation, and the operating parameter sensitivity is not affected by the presence of process control. The control system saves energy during flow rate and oxygen purity change processes, while it consumes energy during the air in-leakage change process. More attention should be paid to the oxygen purity change because it requires the largest control cost. In the control system, the supervisory control layer requires the greatest energy consumption and the largest control cost to maintain operating targets, while the steam control loops cause the main energy consumption.

  3. Energy and exergy evaluation of a tri-generation system driven by the geothermal energy

    Energy Technology Data Exchange (ETDEWEB)

    Akrami, Ehsan; Mahmoudi, S. M. S. [Faculty of Mechanical Engineering, University of Tabriz, Tabriz (Iran, Islamic Republic of); Chitsaz, Ata [Faculty of Mechanical Engineering, Urmia University, Urmia (Iran, Islamic Republic of); Ghamari, Pooria [Faculty of Mechanical Engineering, Urmia University of Technology Urmia (Iran, Islamic Republic of)

    2017-01-15

    In this paper, a geothermal-based tri-generation energy system with three useful outputs is clearly developed to produce electricity, heating and hydrogen. To have a better view of the thermodynamic performance of the present integrated system, parametric studies upon the effects of geofluid mass flow rate, turbine inlet temperature and pressure on the energy and exergy efficiencies of the system are undertaken. Under the specified circumstances, the related efficiencies of energy and exergy for the overall system are estimated around 26.14 % and 44.45 %, respectively, while these efficiencies for this system with electricity and heating generation, amount to 25.32 % and 39.75 %, and these amounts for solely electricity generation are 6 % and 33.47 %, respectively. Also the amount of net electricity power and heating generation in specific design parameter values are estimated around 43.47 (kW) and 149.8 (kW), respectively. In addition, for every 10.4 kW of electrical energy consumption in the electrolysis unit, pure hydrogen will be produced at a rate of 0.2 kg/hour.

  4. 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%.

  5. Exergy diagnosis of coal fired CHP plant with application of neural and regression modelling

    Directory of Open Access Journals (Sweden)

    Stanek Wojciech

    2012-01-01

    Full Text Available Mathematical models of the processes, that proceed in energetic machines and devices, in many cases are very complicated. In such cases, the exact analytical models should be equipped with the auxiliary empirical models that describe those parameters which are difficult to model in a theoretical way. Regression or neural models identified basing on measurements are rather simple and are characterized by relatively short computation time. For this reason they can be effectively applied for simulation and optimization of steering and regulation processes, as well as, for control and thermal diagnosis of operation (eq. power plants or CHP plants. In the paper regression and neural models of thermal processes developed for systems of operation control of thermal plants are presented. Theoretical-empirical model of processes proceeding in coal fired CHP plant have been applied. Simulative calculations basing on these models have been carried out. Results of simulative calculations have been used for the exergetic evaluation of considered power plant. The diagnosis procedure let to investigate the formation of exergy costs in interconnected components of the system of CHP, as well as, investigate the influence of defects in operation of components on exergy losses and on the exergetic cost in other components. [Acknowledgment. The paper has been prepared within the RECENT project (REsearch Center for Energy and New Technologies supported by 7th Framework Programme, Theme 4, Capacities.

  6. 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.

  7. High temperature solid oxide fuel cell integrated with novel allothermal biomass gasification. Part II: Exergy analysis

    Science.gov (United States)

    Panopoulos, K. D.; Fryda, L.; Karl, J.; Poulou, S.; Kakaras, E.

    Biomass gasification derived gas is a renewable fuel, which can be used for SOFC applications. This work investigates the integration of a near atmospheric solid oxide fuel cell (SOFC) with a novel allothermal biomass steam gasification process into a combined heat and power (CHP) system of less than MW e range. Heat for steam gasification is supplied from SOFC depleted fuel in a fluidised bed (FB) combustor via high temperature sodium heat pipes. In the first paper, the integrated system was modelled in Aspen Plus™ and critical aspects for its feasibility were identified. The aim of this second part is the evaluation of the integrated system in exergy terms. Satisfying allothermal gasification heat demand is illustrated by examining each sub-process involved separately as well as combined. For a relatively low STBR = 0.6, the SOFC fuel utilisation for which the system operates under optimum conditions is U f = 0.7. Above that value additional biomass has to be used in the FB combustor to provide gasification heat with considerable exergy losses. For SOFC operation at current density 2500 A m -2, the system uses 90 kg h -1 biomass, operates with electrical exergetic efficiency 32% producing 140 kW e, while the combined electrical and thermal exergetic efficiency is 35%.

  8. HEAT PUMP GAS COOLER CONTROL USING CRITERION OF MINIMUM OF EXERGY LOSSSES

    Directory of Open Access Journals (Sweden)

    Sit M.L.

    2014-08-01

    Full Text Available This paper focuses on the development of the criterion of optimality of transients of the control system, based on the minimum of exergy losses in the gas cooler of carbon dioxide heat pump. It is noted that the exergy quality criterion has a clear physical meaning, as compared with the integral quadratic criterion in which the choice of the coefficients in the integrand is not justified. Mathematic model of heat exchanger is obtained using the method of solving differential equations, without going to the irrational transfer functions. The model is reduced to transfer functions of the first and second order with the delay. The continuous temperature control system of heat pump gas cooler is considered. It is shown, that one of the versions of the control system for the minimization of the proposed criterion can be a combined control system using both the principle of the negative feedback and the principle of the invariance related to a number of disturbances affecting the processes of heat transfer in the heat exchanger.

  9. 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.

  10. 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.

  11. 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.

  12. Eco-exergy and emergy based self-organization of three forest plantations in lower subtropical China

    Science.gov (United States)

    The bio-thermodynamic structures of a mixed native species plantation, a conifer plantation and an Acacia mangium plantation in Southern China were quantified over a period of 15 years based on eco-exergy methods. The efficiencies of structural development and maintenance were qu...

  13. Cumulative exergy extraction from the natural environment (CEENE): a comprehensive life cycle impact assessment method for resource accounting.

    Science.gov (United States)

    Dewulf, J; Bösch, M E; De Meester, B; Van der Vorst, G; Van Langenhove, H; Hellweg, S; Huijbregts, M A J

    2007-12-15

    The objective of the paper is to establish a comprehensive resource-based life cycle impact assessment (LCIA) method which is scientifically sound and that enables to assess all kinds of resources that are deprived from the natural ecosystem, all quantified on one single scale, free of weighting factors. The method is based on the exergy concept. Consistent exergy data on fossils, nuclear and metal ores, minerals, air, water, land occupation, and renewable energy sources were elaborated, with well defined system boundaries. Based on these data, the method quantifies the exergy "taken away" from natural ecosystems, and is thus called the cumulative exergy extraction from the natural environment (CEENE). The acquired data set was coupled with a state-of-the art life cycle inventory database, ecoinvent. In this way, the method is able to quantitatively distinguish eight categories of resources withdrawn from the natural environment: renewable resources, fossil fuels, nuclear energy, metal ores, minerals, water resources, land resources, and atmospheric resources. Third, the CEENE method is illustrated for a number of products that are available in ecoinvent, and results are compared with common resource oriented LCIA methods. The application to the materials in the ecoinvent database showed that fossil resources and land use are of particular importance with regard to the total CEENE score, although the other resource categories may also be significant.

  14. 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.

  15. Energy and exergy analysis of cookstove by using Cedrus deodara (deodar wood) and saccharum officinarum (sugar cane) waste

    Science.gov (United States)

    Chouhan, A. P. Singh; Yaseen, S.; Pruthi, A.

    2017-07-01

    Deodar (Cedrus deodara) wood collected from the Kashmir region in India. This study is focused on energy and exergy analysis of cook stove by using deodar wood, demand of a cookstove is higher in rural areas. In ancient time U-shaped and three stone cook stove was used, but they emitted greenhouse gases CO and CO2 in the environment and these toxic emissions are also dangerous for human being and the environment. Sampada model cook stove used for the analysis of energy an exergy by using water boiling test with using deodar wood and bagasse samples and a mixture of wood and bagasse also used. Wood and bagasse characterized for the ultimate, proximate, calorific value before the water boiling test of the cookstove. Results carried out that the efficiency of cook stove with deodar wood was 33.33 % and exergy calculated 2.1 % and energy efficiency and energy efficiency by using bagasse were 23.23 % and 0.43 %, respectively, and wood and bagasse mixture ratio given energy and exergy efficiencies for ratios 75:25 is the best ratio of energy production. These results indicated that deodar wood is more stable because thermal stability of wood is greater than bagasse. Deodar is a suitable source for the combustion purposes of higher energy production.

  16. 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

  17. The Use of Exergy and Decomposition Techniques in the Development of Generic Analysis, and Optimization Methodologies Applicable to the Synthesis/Design of Aircraft/Aerospace Systems

    National Research Council Canada - National Science Library

    von Spakovsky, Michael R; Periannan, Vijayanand; Markell, Kyle C; Brewer, Keith M

    2006-01-01

    In M.S. thesis #1, advantages of applying exergy-based analysis and optimization methods to the synthesis/design and operation of aircraft systems is demonstrated using a supersonic aircraft fighter flown over an entire mission...

  18. 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

  19. Exergy analysis of a counter flow Ranque-Hilsch vortex tube for different cold orifice diameters, L/D ratios and exit valve angles

    Science.gov (United States)

    Devade, Kiran D.; Pise, Ashok T.

    2017-06-01

    An experimental investigation is made to find out the effects of the cold end orifice diameters, length to diameter ratio and exit valve angles on the heating and cooling performance of the counter flow Ranque-Hilsch vortex tube with air as a working fluid. The tube and cold end orifices used at these experiments are made of brass. Three cold end orifices (5, 6 and 7 mm) have been manufactured and are used five different L/D ratios (15 plain tube, 15-18 with 4° divergence angle) and exit valve angles (30°-90°). Inlet pressures were adjusted from 200 to 600 kPa with 100 kPa increments, and the exergy loss, exergy efficiency was determined. As a result of the experimental study, it is determined that the exergy loss between the hot and cold fluid is decreased with increasing of the cold end orifice diameter. Exergy efficiency decreases with increase in L/D ratio. It is also concluded that diverging vortex tube produces lower exergy loss as compared to plain tube. Valve angles have significant effect on hot end exergy loss of the vortex tube.

  20. 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..

  1. 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...

  2. 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.

  3. 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)

  4. Second-generation bio-ethanol (SGB) from Malaysian palm empty fruit bunch: energy and exergy analyses.

    Science.gov (United States)

    Tan, Hui Teng; Lee, Keat Teong; Mohamed, Abdul Rahman

    2010-07-01

    Recently, second-generation bio-ethanol (SGB), which utilizes readily available lignocellulosic biomass has received much interest as another potential source of liquid biofuel comparable to biodiesel. Thus the aim of this paper is to determine the exergy efficiency and to compare the effectiveness of SGB and palm methyl ester (PME) processes. It was found that the production of bio-ethanol is more thermodynamically sustainable than that of biodiesel as the net exergy value (NExV) of SGB is 10% higher than that of PME. Contrarily, the former has a net energy value (NEV) which is 9% lower than the latter. Despite this, SGB is still strongly recommended as a potential biofuel because SGB production can help mitigate several detrimental impacts on the environment. Copyright (c) 2010 Elsevier Ltd. All rights reserved.

  5. Evaluation of heat transfer and exergy loss in a concentric double pipe exchanger equipped with helical wires

    Energy Technology Data Exchange (ETDEWEB)

    Akpinar, Ebru Kavak [Mechanical Engineering Department, Firat University, TR-23119 Elazig (Turkey)

    2006-11-15

    In this study, the effects on heat transfer, friction factor and dimensionless exergy loss were investigated experimentally by mounting helical (spring shaped) wires of different pitch in the inner pipe in a double pipe heat exchanger. In the experiments, hot (air) and cold (water) fluids flowed through the inner pipe and annulus, respectively. The experiments were performed for both parallel and counter current flow modes of the fluids at Reynolds numbers between 6500 and 13,000. An augmentation of up to 2.64 times in Nusselt number compared to the empty pipe was obtained in the helical system. The increase in friction factor was about 2.74 times that of the empty pipe, depending on Reynolds number and the pitch or helical number. An augmentation of up to 1.16 times in the dimensionless exergy loss compared to the empty pipe was obtained in the helical system. Some empirical correlations expressing the results were also derived and discussed. (author)

  6. Exergy analysis of the Chartherm process for energy valorization and material recuperation of chromated copper arsenate (CCA) treated wood waste.

    Science.gov (United States)

    Bosmans, A; Auweele, M Vanden; Govaerts, J; Helsen, L

    2011-04-01

    The Chartherm process (Thermya, Bordeaux, France) is a thermochemical conversion process to treat chromated copper arsenate (CCA) impregnated wood waste. The process aims at maximum energy valorization and material recuperation by combining the principles of low-temperature slow pyrolysis and distillation in a smart way. The main objective of the exergy analysis presented in this paper is to find the critical points in the Chartherm process where it is necessary to apply some measures in order to reduce exergy consumption and to make energy use more economic and efficient. It is found that the process efficiency can be increased with 2.3-4.2% by using the heat lost by the reactor, implementing a combined heat and power (CHP) system, or recuperating the waste heat from the exhaust gases to preheat the product gas. Furthermore, a comparison between the exergetic performances of a 'chartherisation' reactor and an idealized gasification reactor shows that both reactors destroy about the same amount of exergy (i.e. 3500kWkg(wood)(-1)) during thermochemical conversion of CCA-treated wood. However, the Chartherm process possesses additional capabilities with respect to arsenic and tar treatment, as well as the extra benefit of recuperating materials. Copyright © 2010 Elsevier Ltd. All rights reserved.

  7. Investigation of heat transfer and exergy loss in a concentric double pipe exchanger equipped with swirl generators

    Energy Technology Data Exchange (ETDEWEB)

    Kavak Akpinar, Ebru; Bicer, Yasar [Mechanical Engineering Department, Firat University, 23279 Elazig (Turkey)

    2005-06-01

    In this study, the effect on heat transfer rates, friction factor and exergy loss of swirl generators with holes for the entrance of fluid were investigated by placing them at the entrance section of inner pipe of heat exchanger. Various swirl generators having circular holes at different number and diameter were used. Hot air and cold water were passed through the inner pipe and annulus, respectively. Experiments were carried out for both parallel and counter flow models of the fluids at Reynolds numbers between 8500-17 500. Heat transfer, friction factor and exergy analyses were made for the conditions with and without swirl generators and compared to each other. Some empirical correlations expressing the results were also derived and discussed. It was observed that the Nusselt number could increase up to 130% at a value of about 2.9 times increase in the friction factor by giving rotation to the air with the help of the swirl elements. The increase the dimensionless exergy loss was about 1.25 times in comparison with that for the inner pipe without swirl generators. (authors)

  8. Energy and exergy analyses on a novel hybrid solar heating, cooling and power generation system for remote areas

    Energy Technology Data Exchange (ETDEWEB)

    Zhai, H.; Dai, Y.J.; Wu, J.Y.; Wang, R.Z. [Institute of Refrigeration and Cryogenics, Shanghai Jiao Tong University, Shanghai 200240 (China)

    2009-09-15

    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)

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. Sun-to-Wheels Exergy Efficiencies for Bio-Ethanol and Photovoltaics.

    Science.gov (United States)

    Williams, Eric; Sekar, Ashok; Matteson, Schuyler; Rittmann, Bruce E

    2015-06-02

    The two main paths to power vehicles with sunlight are to use photosynthesis to grow biomass, converting to a liquid fuel for an internal combustion engine or to generate photovoltaic electricity that powers the battery of an electric vehicle. While the environmental attributes of these two paths have been much analyzed, prior studies consider the current state of technology. Technologies for biofuel and photovoltaic paths are evolving; it is critical to consider how progress might improve environmental performance. We address this challenge by assessing the current and maximum theoretical exergy efficiencies of bioethanol and photovoltaic sun-to-wheels process chains. The maximum theoretical efficiency is an upper bound stipulated by physical laws. The current net efficiency to produce motive power from silicon photovoltaic modules is estimated at 5.4%, much higher than 0.03% efficiency for corn-based ethanol. Flat-plate photovoltaic panels also have a much higher theoretical maximum efficiency than a C4 crop plant, 48% versus 0.19%. Photovoltaic-based power will always be vastly more efficient than a terrestrial crop biofuel. Providing all mobility in the U.S. via crop biofuels would require 130% of arable land with current technology and 20% in the thermodynamic limit. Comparable values for photovoltaic-based power are 0.7% and 0.081%, respectively.

  15. Exergy analysis of the Szewalski cycle with a waste heat recovery system

    Directory of Open Access Journals (Sweden)

    Kowalczyk Tomasz

    2015-09-01

    Full Text Available The conversion of a waste heat energy to electricity is now becoming one of the key points to improve the energy efficiency in a process engineering. However, large losses of a low-temperature thermal energy are also present in power engineering. One of such sources of waste heat in power plants are exhaust gases at the outlet of boilers. Through usage of a waste heat regeneration system it is possible to attain a heat rate of approximately 200 MWth, under about 90 °C, for a supercritical power block of 900 MWel fuelled by a lignite. In the article, we propose to use the waste heat to improve thermal efficiency of the Szewalski binary vapour cycle. The Szewalski binary vapour cycle provides steam as the working fluid in a high temperature part of the cycle, while another fluid – organic working fluid – as the working substance substituting conventional steam over the temperature range represented by the low pressure steam expansion. In order to define in detail the efficiency of energy conversion at various stages of the proposed cycle the exergy analysis was performed. The steam cycle for reference conditions, the Szewalski binary vapour cycle as well as the Szewalski hierarchic vapour cycle cooperating with a system of waste heat recovery have been comprised.

  16. 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.

  17. Exergy analysis of an integrated fuel processor and fuel cell (FP-FC) system

    Energy Technology Data Exchange (ETDEWEB)

    Delsman, E.R. [Department of Chemical Engineering and Chemistry, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven (Netherlands); Uju, C.U. [Department of Chemical Engineering and Chemistry, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven (Netherlands); Croon, M.H.J.M. de [Department of Chemical Engineering and Chemistry, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven (Netherlands); Schouten, J.C. [Department of Chemical Engineering and Chemistry, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven (Netherlands); Ptasinski, K.J. [Department of Chemical Engineering and Chemistry, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven (Netherlands)]. E-mail: k.j.ptasinski@tue.nl

    2006-12-15

    Fuel cells have great application potential as stationary power plants, as power sources in transportation, and as portable power generators for electronic devices. Most fuel cells currently being developed for use in vehicles and as portable power generators require hydrogen as a fuel. Chemical storage of hydrogen in liquid fuels is considered to be one of the most advantageous options for supplying hydrogen to the cell. In this case a fuel processor is needed to convert the liquid fuel into a hydrogen-rich stream. This paper presents a second-law analysis of an integrated fuel processor and fuel cell system. The following primary fuels are considered: methanol, ethanol, octane, ammonia, and methane. The maximum amount of electrical work and corresponding heat effects produced from these fuels are evaluated. An exergy analysis is performed for a methanol processor integrated with a proton exchange membrane fuel cell, for use as a portable power generator. The integrated FP-FC system, which can produce 100 W of electricity, is simulated with a computer model using the flow-sheeting program Aspen Plus. The influence of various operating conditions on the system efficiency is investigated, such as the methanol concentration in the feed, the temperature in the reformer and in the fuel cell, as well as the fuel cell efficiency. Finally, it is shown that the calculated overall exergetic efficiency of the FP-FC system is higher than that of typical combustion engines and rechargeable batteries.

  18. 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.

  19. 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%.

  20. Exergy performance analysis of the conceptual district energy network system with heat pump

    Energy Technology Data Exchange (ETDEWEB)

    Shin, Seung Won; Chung, Ha Seung [Hongik University, Seoul (Korea, Republic of); Kim, Min Sung [Korea Institute of Energy Research, Daejeon (Korea, Republic of)

    2014-08-15

    To increase the efficiency of a district heating system, we propose a district energy network concept which combines several heating resources with additional electric heat pump and thermal energy storage. With help of thermal energy storage, a heat pump can be operated at maximum efficiency at all the time. Electricity generated with less CO{sub 2} emission makes the proposed system much more environmentally friendly. Even though the proposed concept can be applied to any given situation, a specific target area was chosen to show the effectiveness of the newly proposed energy network concept more clearly. Several constraints were applied for the selection process and a simplified model used for quantitative comparison between the existing and the developed concept. Exergy analysis showed the increased performance of proposed energy network system. The result showed that the newly proposed concept generates less CO{sub 2} emission by 46% at maximum compared to the existing system. By using additional renewable energy sources, we can reduce CO{sub 2} emission even further.

  1. Conceptual design and exergy analysis of an integrated structure of natural gas liquefaction and production of liquid fuels from natural gas using Fischer-Tropsch synthesis

    Science.gov (United States)

    Niasar, Malek Shariati; Amidpour, Majid

    2018-01-01

    In this paper, utilizing absorption refrigeration system as an alternative to compression refrigeration system of MFC refrigeration cycle in an integrated superstructure with the main aim of reduction in required energy is investigated. High-energy consumption in such units is reduced because of the removal of a stage of the compression system, while the possibility of using waste energy through employing of absorption refrigeration system can be provided. A superstructure including cogeneration of heating, cooling and power for LNG production and liquid fuels using Fischer-Tropsch synthesis are investigated. Exergy analysis shows that the greatest amount of exergy destruction of equipment is related to the compressors by 28.99% and the lowest exergy destruction is related to the gas turbine by 0.17%. Integrated structure has overall thermal efficiency of 90% and specific power of 0.1988 kW h/(kg LNG)-1.

  2. A Nearly Net-Zero Exergy District as a Model for Smarter Energy Systems in the Context of Urban Metabolism

    OpenAIRE

    Kılkış, Şiir

    2017-01-01

    The planning of urban settlements requires a targeted approach towards more sustainable energy, water, and environment systems. This research work analyses the city of Uppsala and a district that is an urban renewal project at the site of former high voltage power lines, namely Östra Sala backe, which will have a new energy concept. The latter is analysed based on proposals for two phases that aim to reach a net-zero district target based on the quality of energy (exergy). An indicator set...

  3. Energy and exergy analysis of a two pass photovoltaic –thermal (PV/T) air heater

    Energy Technology Data Exchange (ETDEWEB)

    Srinivas, M.; Jayaraj, S. [Department of Mechanical Engineering, National Institute of Technology, Calicut-673601 (India)

    2013-07-01

    A double pass hybrid solar air (PV/T) heater with slats is designed and fabricated to study elaborately its thermal and electrical performance corresponding to the warm and humid environment. Air as a heat removing fluid is made to flow through upper and lower channels of the collector. The collector is designed in such way that the absorber plate is partially covered by solar cells. Thin metallic strips (called slats) are attached longitudinally at the bottom side of the absorber plate to improve the overall system performance (by increasing the cooling rate of the absorber plate). Thermal and electrical performances of the whole system at different cooling rates are presented. The exergy analysis of double pass hybrid solar air (PV/T) heater with slats has also been carried out. The instantaneous overall energy and overall exergy efficiency of the double pass hybrid (PV/T) solar air heater varies between 29 – 37 percent and 14-17 percent respectively. These obtained values are comparable with that of published results.

  4. 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.

  5. 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

    Full Text Available Fossil fuels are still widely used for power generation. Nevertheless, it is possible to attain a short- and medium-term substantial reduction of greenhouse gas emissions to the atmosphere through a sequestration of the CO2 produced in fuels’ oxidation. The chemical-looping combustion (CLC technique is based on a chemical intermediate agent, which gets oxidized in an air reactor and is then conducted to a separated fuel reactor, where it oxidizes the fuel in turn. Thus, the oxidation products CO2 and H2O are obtained in an output flow in which the only non-condensable gas is CO2, allowing the subsequent sequestration of CO2 without an energy penalty. Furthermore, with shrewd configurations, a lower exergy destruction in the combustion chemical transformation can be achieved. This paper focus on a second law analysis of a CLC combined cycle power plant with CO2 sequestration using syngas from coal and biomass gasification as fuel. The key thermodynamic parameters are optimized via the exergy method. The proposed power plant configuration is compared with a similar gas turbine system with a conventional combustion, finding a notable increase of the power plant efficiency. Furthermore, the influence of syngas composition on the results is investigated by considering different H2-content fuels.

  6. Explanation of the observed structure of functional feeding groups of aquatic macro-invertebrates by an ecological model and the maximum exergy principle

    NARCIS (Netherlands)

    Jorgensen, S.E.; Verdonschot, P.F.M.; Lek, S.

    2002-01-01

    The maximum exergy principle presumes that an ecosystem with its species composition tends to move as far away from thermodynamic equilibrium as possible under the prevailing conditions. If this principle is valid, the species composition (or rather their properties) found in any ecosystem represent

  7. Energy, economy and exergy evaluations of the solutions for supplying domestic hot water from low-temperature district heating in Denmark

    DEFF Research Database (Denmark)

    Yang, Xiaochen; Li, Hongwei; Svendsen, Svend

    2016-01-01

    . Evaluation models were built to investigate the energy, economy and exergy performances of the proposed domestic hot water systems in various configurations. The configurations of the devised domestic hot water substations were optimised to fit well with both low and ultra-low-temperature district heating...

  8. Energy and exergy analyses of an integrated gasification combined cycle power plant with CO2 capture using hot potassium carbonate solvent.

    Science.gov (United States)

    Li, Sheng; Jin, Hongguang; Gao, Lin; Mumford, Kathryn Anne; Smith, Kathryn; Stevens, Geoff

    2014-12-16

    Energy and exergy analyses were studied for an integrated gasification combined cycle (IGCC) power plant with CO2 capture using hot potassium carbonate solvent. The study focused on the combined impact of the CO conversion ratio in the water gas shift (WGS) unit and CO2 recovery rate on component exergy destruction, plant efficiency, and energy penalty for CO2 capture. A theoretical limit for the minimal efficiency penalty for CO2 capture was also provided. It was found that total plant exergy destruction increased almost linearly with CO2 recovery rate and CO conversion ratio at low CO conversion ratios, but the exergy destruction from the WGS unit and the whole plant increased sharply when the CO conversion ratio was higher than 98.5% at the design WGS conditions, leading to a significant decrease in plant efficiency and increase in efficiency penalty for CO2 capture. When carbon capture rate was over around 70%, via a combination of around 100% CO2 recovery rate and lower CO conversion ratios, the efficiency penalty for CO2 capture was reduced. The minimal efficiency penalty for CO2 capture was estimated to be around 5.0 percentage points at design conditions in an IGCC plant with 90% carbon capture. Unlike the traditional aim of 100% CO conversion, it was recommended that extremely high CO conversion ratios should not be considered in order to decrease the energy penalty for CO2 capture and increase plant efficiency.

  9. An exergy based assessment of the production and conversion of switchgrass, equine waste and forest residue to bio-oil using fast pyrolysis

    Science.gov (United States)

    The resource efficiency of biofuel production via biomass pyrolysis is evaluated using exergy as an assessment metric. Three feedstocks, important to various sectors of US agriculture, switchgrass, forest residue and equine waste are considered for conversion to bio-oil (pyrolysis oil) via fast pyro...

  10. Exergy Analysis of a Two-Pass Reverse Osmosis (RO Desalination Unit with and without an Energy Recovery Turbine (ERT and Pressure Exchanger (PX

    Directory of Open Access Journals (Sweden)

    Nuri M. Eshoul

    2015-07-01

    Full Text Available This paper presents an exergy analysis of an actual two-pass (RO desalination system with the seawater solution treated as a real mixture and not an ideal mixture. The actual 127 ton/h two pass RO desalination plant was modeled using IPSEpro software and validated against operating data. The results show that using the (ERT and (PX reduced the total power consumption of the SWRO desalination by about 30% and 50% respectively, whereas, the specific power consumption for the SWRO per m3 water decreased from 7.2 kW/m3 to 5.0 kW/m3 with (ERT and 3.6 kW/m3 with (PX. In addition, the exergy efficiency of the RO desalination improved by 49% with ERT and 77% with PX and exergy destruction was reduced by 40% for (ERT and 53% for (PX. The results also showed that, when the (ERT and (PX were not in use, accounted for 42% of the total exergy destruction. Whereas, when (ERT and (PX are in use, the rejected seawater account maximum is 0.64%. Moreover, the (PX involved the smallest area and highest minimum separation work.

  11. The effect of injection timing on energy and exergy analysis of a diesel engine with biodiesel fuel

    Directory of Open Access Journals (Sweden)

    A Farhadi

    2017-05-01

    Full Text Available Introduction Nowadays, due to higher environmental pollution and decreasing fossil fuels many countries make decisions to use renewable fuels and restrict using of fossil fuels. Renewable fuels generally produce from biological sources. Biodiesel is an alternative diesel fuel derived from the transesterification of vegetable oils, animal fats, or waste frying oils. Considering the differences between diesel and biodiesel fuels, engine condition should be modified based on the fuel or fuel blends to achieve optimum performance. One of the simplest and yet the most widely used models is the thermodynamic model. After verification of the data obtained by model with experimental data it is possible to generalize the extracted data to an unlimited number of functional conditions or unlimited number of fuel types which saves time and reduces costs for experimental engine tests. Using the second law of thermodynamics, it is possible to calculate and analyze the exergy of the engine.4 Materials and Methods In this work, the zero-dimensional model was used to account for internal energy variations, pressure work, heat transfer losses to the solid walls and heat release. The applied assumptions include: The cylinder mixture temperature, pressure and composition were assumed uniform throughout the cylinder. Furthermore, the one-zone thermodynamic model assumes instantaneous mixing between the burned and unburned gases. The cylinder gases were assumed to behave as an ideal gas mixture, Gas properties, include enthalpy, internal energy modeled using polynomial equations associated with temperature. In this research, the equations 1 to 20 were used in Fortran programming language. The results of incylinder pressure obtained by the model were validated by the results of experimental test of OM314 engine. Then the effects of injection timing on Energy and Exergy of the engine were analyzed for B20 fuel. Results and Discussion Comparing the results of the model

  12. Energy and exergy analysis of the Kalina cycle for use in concentrated solar power plants with direct steam generation

    DEFF Research Database (Denmark)

    Knudsen, Thomas; Clausen, Lasse Røngaard; Haglind, Fredrik

    2014-01-01

    In concentrated solar power plants using direct steam generation, the usage of a thermal storage unit based only on sensible heat may lead to large exergetic losses during charging and discharging, due to a poor matching of the temperature profiles. By the use of the Kalina cycle, in which...... with direct steam generation. The following two scenarios were addressed using energy and exergy analysis: generating power using heat from only the receiver and using only stored heat. For each of these scenarios comparisons were made for mixture concentrations ranging from 0.1 mole fraction of ammonia to 0.......9, and compared to the conventional Rankine cycle. This comparison was then also carried out for various turbine inlet pressures (100 bar to critical pressures). The results suggest that there would be no benefit from using a Kalina cycle instead of a Rankine cycle when generating power from heat taken directly...

  13. 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

    Due to the existing huge biogas resource in the rural area of China, biogas is widely used for production and living. Cogeneration system provides an opportunity to realize the balanced utilization of the renewable energy such as biogas and solar energy. This paper presented a numerical...... investigation of a hybrid energy-driven organic Rankine cycle (ORC) cogeneration system, involving a solar organic Rankine cycle and a biogas boiler. The biogas boiler with a module of solar Parabolic-Trough Collectors (PTC) is employed to provide heat source to the ORC via two distinct intermediate pressurized...... 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...

  14. A Critical Interpretation and Quantitative Extension of the Sama-Szargut Second Law Rules in an Extended Exergy Perspective

    Directory of Open Access Journals (Sweden)

    Enrico Sciubba

    2014-08-01

    Full Text Available Twenty-five years ago, Gaggioli, Sama and Qian published a series of 10 “second law guidelines” for design and process engineers, nicknamed at that time “the Gaggioli-Sama rules”. These guidelines, some of them previously published by Sama between 1980 and 1983, are a compilation of “second law errors” to avoid in the design of energy conversion systems. The list was rearranged several times, until a revised version containing 21 rules was published by Sama and Szargut in 1995. Ever since, these guidelines came to be known as “the Sama-Szargut rules”. The rules are a series of well-formulated and insightful suggestions that reflect a thermodynamicist’s idea that the “best design” is the one that minimizes the overall irreversibility in a process or plant, under the prescribed technological constraints. Characteristically, the concept of “optimal system” is completely absent, the emphasis being on the extensive inclusion of second law reasoning into design decisions. A critical analysis of the rules would suggest that all of them be routinely implemented both in new designs and most important in retrofit projects. A survey of some of the current most common energy conversion installations shows that, quite on the contrary, most of the rules are disregarded in practical applications. This paper argues that the reason for this incongruency is the neglection in the engineering design decision of the real cost of installation, operation and decommissioning of a plant, and proposes a rephrasing of the rules in an extended exergy perspective: if the production cost, including the externalities, is measured in units of equivalent primary exergy, the Sama-Szargut rules can be directly interpreted in this sense, and abidance by the rules results in the reduction of the resource cost for any given objective.

  15. 2D Temperature Analysis of Energy and Exergy Characteristics of Laminar Steady Flow across a Square Cylinder under Strong Blockage

    Directory of Open Access Journals (Sweden)

    M. Ozgun Korukcu

    2015-05-01

    Full Text Available Energy and exergy characteristics of a square cylinder (SC in confined flow are investigated computationally by numerically handling the steady-state continuity, Navier-Stokes and energy equations in the Reynolds number range of Re = 10–50, where the blockage ratio (β = B/H is kept constant at the high level of β = 0.8. Computations indicated for the upstream region that, the mean non-dimensional streamwise (u/Uo and spanwise (v/Uo velocities attain the values of u/Uo = 0.840®0.879 and v/Uo = 0.236®0.386 (Re = 10®50 on the front-surface of the SC, implying that Reynolds number and blockage have stronger impact on the spanwise momentum activity. It is determined that flows with high Reynolds number interact with the front-surface of the SC developing thinner thermal boundary layers and greater temperature gradients, which promotes the thermal entropy generation values as well. The strict guidance of the throat, not only resulted in the fully developed flow character, but also imposed additional cooling; such that the analysis pointed out the drop of duct wall (y = 0.025 m non-dimensional temperature values (ζ from ζ = 0.387®0.926 (Re = 10®50 at xth = 0 mm to ζ = 0.002®0.266 at xth = 40 mm. In the downstream region, spanwise thermal disturbances are evaluated to be most inspectable in the vortex driven region, where the temperature values show decrease trends in the spanwise direction. In the corresponding domain, exergy destruction is determined to grow with Reynolds number and decrease in the streamwise direction (xds = 0®10 mm. Besides, asymmetric entropy distributions as well were recorded due to the comprehensive mixing caused by the vortex system.

  16. Energy and Exergy Analyses of a Diesel Engine Fuelled with Biodiesel-Diesel Blends Containing 5% Bioethanol

    Directory of Open Access Journals (Sweden)

    Bahar Sayin Kul

    2016-10-01

    Full Text Available In this study, energy and exergy analysis were performed for a single cylinder, water-cooled diesel engine using biodiesel, diesel and bioethanol blends. Each experiment was performed at twelve different engine speeds between 1000 and 3000 rev/min at intervals of 200 rev/min for four different fuel blends. The fuel blends, prepared by mixing biodiesel and diesel in different proportions fuel with 5% bioethanol, are identified as D92B3E5 (92% diesel, 3% biodiesel and 5% bioethanol, D85B10E5 (85% diesel, 10% biodiesel and 5% bioethanol, D80B15E5(80% diesel, 15% biodiesel and 5% bioethanol and D75B20E5 (75% diesel, 20% biodiesel and 5% bioethanol. The effect of blends on energy and exergy analysis was investigated for the different engine speeds and all the results were compared with effect of D100 reference fuel. The maximum thermal efficiencies obtained were 31.42% at 1500 rev/min for D100 and 31.42%, 28.68%, 28.1%, 28% and 27.18% at 1400 rev/min, respectively, for D92B3E5, D85B10E5, D80B15E5, D75B20E5. Maximum exergetic efficiencies were also obtained as 29.38%, 26.8%, 26.33%, 26.15% and 25.38%, respectively, for the abovementioned fuels. As a result of our analyses, it was determined that D100 fuel has a slightly higher thermal and exergetic efficiency than other fuel blends and all the results are quite close to each other.

  17. Exergy applied to the heat conduction analysis in glass covers of a solar cooker box-type with internal and external reflectors

    Science.gov (United States)

    Terres, H.; Lizardi, A.; Chávez, S.; López, R.; Vaca, M.

    2017-01-01

    In this work, an exergy evaluation to determine the energy availability across to glass covers, place where the solar radiation enters toward a solar cooker box-type is done. Considering the heating process of water, the energy not used is quantified by means of exergy. The results allow identifying the glasses in the cover as the zone where the solar cooker could be improved. The conduction heat transfer losses for the glasses is most big than 75%. Because the values for the conduction heat losses are around 90%, which are very important, this allows to identify the cover glass as the area where improvements could be made in this type of solar cookers.

  18. Trends in Austrian Resource Efficiency: An Exergy and Useful Work Analysis in Comparison to Material Use, CO2 Emissions, and Land Use.

    Science.gov (United States)

    Eisenmenger, Nina; Warr, Benjamin; Magerl, Andreas

    2017-10-01

    In the past few years, resource use and resource efficiency have been implemented in the European Union (EU) environmental policy programs as well as international sustainable development programs. In their programs, the EU focuses on four resource types that should be addressed: materials, energy (or carbon dioxide [CO2] emissions), water, and land. In this article, we first discuss different perspectives on energy use and present the results of a long-term exergy and useful work analysis of the Austrian economy for the period 1900-2012, using the methodology developed by Ayres and Warr. Second, we discuss Austrian resource efficiency by comparing the presented exergy and useful work data with material use, CO2 emissions, and land-use data taken from statistical sources. This comparison provides, for the first time, a long-term analysis of Austrian resource efficiency based on a broad understanding thereof and evaluates Austrian development in relation to EU and Austrian policy targets.

  19. Exergy and thermoeconomic evaluation of hydrogen production from natural gas; Avaliacao exergetica e termo-economica da producao de hidrogenio a partir do gas natural

    Energy Technology Data Exchange (ETDEWEB)

    Cruz, Flavio Eduardo da [PROMON Engenharia Ltda., Sao Paulo, SP (Brazil); Oliveira Junior, Silvio de [Universidade de Sao Paulo (USP), SP (Brazil). Escola Politecnica

    2008-07-01

    Some specific processes are required to obtain pure hydrogen and the most usual one is the natural gas reforming, where natural gas reacts with superheated steam producing H{sub 2}, CO, CO{sub 2} and H{sub 2}O. This paper presents exergy and thermoeconomic analysis of a complete hydrogen production unit of a petroleum refinery. The hydrogen production unit analysed in this paper has to supply 550,000 Nm{sup 3} of hydrogen per day to purify diesel oil. Based on a synthesis plant of the hydrogen production unit, the exergy efficiency of each component and of the overall plant are calculated. The hydrogen production cost is determined by means of a thermoeconomic analysis in which the equality cost partition method is employed, including capital and operational costs, in order to determine the production cost of hydrogen and other products of the plant.(author)

  20. Compliance of secondary production and eco-exergy as indicators of benthic macroinvertebrates assemblages' response to canopy cover conditions in Neotropical headwater streams.

    Science.gov (United States)

    Linares, Marden Seabra; Callisto, Marcos; Marques, João Carlos

    2018-02-01

    Riparian vegetation cover influences benthic assemblages structure and functioning in headwater streams, as it regulates light availability and autochthonous primary production in these ecosystems.Secondary production, diversity, and exergy-based indicators were applied in capturing how riparian cover influences the structure and functioning of benthic macroinvertebrate assemblages in tropical headwater streams. Four hypotheses were tested: (1) open canopy will determine the occurrence of higher diversity in benthic macroinvertebrate assemblages; (2) streams with open canopy will exhibit more complex benthic macroinvertebrate communities (in terms of information embedded in the organisms' biomass); (3) in streams with open canopy benthic macroinvertebrate assemblages will be more efficient in using the available resources to build structure, which will be reflected by higher eco-exergy values; (4) benthic assemblages in streams with open canopy will exhibit more secondary productivity. We selected eight non-impacted headwater streams, four shaded and four with open canopy, all located in the Neotropical savannah (Cerrado) of southeastern Brazil. Open canopy streams consistently exhibited significantly higher eco-exergy and instant secondary production values, exemplifying that these streams may support more complex and productive benthic macroinvertebrate assemblages. Nevertheless, diversity indices and specific eco-exergy were not significantly different in shaded and open canopy streams. Since all the studied streams were selected for being considered as non-impacted, this suggests that the potential represented by more available food resources was not used to build a more complex dissipative structure. These results illustrate the role and importance of the canopy cover characteristics on the structure and functioning of benthic macroinvertebrate assemblages in tropical headwater streams, while autochthonous production appears to play a crucial role as food

  1. Energy-Exergy, Environmental and Economic Criteria in Combined Heat and Power (CHP Plants: Indexes for the Evaluation of the Cogeneration Potential

    Directory of Open Access Journals (Sweden)

    Marco F. Torchio

    2013-05-01

    Full Text Available In the first part of this work, combined heat and power (CHP criteria pertaining to energy, exergy, environmental (pollutant emission and economic aspects, have been investigated and compared. Although the constraints in legislation usually refer to energy efficiency, primary energy savings and greenhouse gas savings, other criteria should also be taken into account in order to obtain a better evaluation of a cogeneration plant. Here particular attention has been paid to saving indexes for both an individual CHP-unit and for a CHP-system, that is the complete system with all the cogeneration units and the auxiliary plants necessary to cover the users’ demand. Five indexes, named potential indexes, have been introduced to evaluate the cogeneration potential: one for energy saving, one for exergy, two for environmental aspects (global and local scale and one for economic aspects. Finally, some indexes analysed in the paper have been applied to a case study concerning a district heating cogeneration system, and the different behaviour of the energy-exergy, environmental and economic aspects has been discussed.

  2. Energy and exergy analysis of a new flat-plate solar air heater having different obstacles on absorber plates

    Energy Technology Data Exchange (ETDEWEB)

    Akpinar, Ebru Kavak; Kocyigit, Fatih [Mechanical Engineering Department, Firat University, 23279 Elazig (Turkey)

    2010-11-15

    This study experimentally investigates performance analysis of a new flat-plate solar air heater (SAH) with several obstacles (Type I, Type II, Type III) and without obstacles (Type IV). Experiments were performed for two air mass flow rates of 0.0074 and 0.0052 kg/s. The first and second laws of efficiencies were determined for SAHs and comparisons were made among them. The values of first law efficiency varied between 20% and 82%. The values of second law efficiency changed from 8.32% to 44.00%. The highest efficiency were determined for the SAH with Type II absorbent plate in flow channel duct for all operating conditions, whereas the lowest values were obtained for the SAH without obstacles (Type IV). The results showed that the efficiency of the solar air collectors depends significantly on the solar radiation, surface geometry of the collectors and extension of the air flow line. The largest irreversibility was occurring at the SAH without obstacles (Type IV) collector in which collector efficiency is smallest. At the end of this study, the energy and exergy relationships are delivered for different SAHs. (author)

  3. Energy, exergy and environmental quality of hard coal and natural gas in whole life cycle concerning home heating

    Directory of Open Access Journals (Sweden)

    Pikon Krzysztof

    2016-01-01

    Full Text Available The use of coal is suspected to have high environmental impact. Natural gas is treated as more environmentally friendly with high methane content and lower emission factors. In order to calculate the environmental impact in the whole life cycle associated with combustion of coal and natural gas all stages from “cradle to grave” should be taken into account. In particular, the transportation stage, especially in the case of life cycle analysis of gas, seems to be crucial. The distance of transmission of gas from gas fields, for instance located in Siberia, could be mainly associated with high diffuse emission of methane. The comparison of environmental impact assessment of coal and natural gas utilization for heating purposes is presented in the paper. The additional factor taken into account is localisation of boilers. In the analysis the coal is sombusted in combined heat and power plants equipped with flue gas treatment units is that released emissions are relatively remote from an urban area. In contrast, the natural gas is burned in small domestic installations with no additional FGT systems. The results of the analysis are given in 6 major impact categories. Moreover, the results of the life cycle analysis were brought into comprehensive thermo-ecological cost index, which is a cumulated exergy consumption of non-renewable resources. The results presented in the paper refer to the contemporary problem of the choice of energy sources in the context of its overall environmental efficiency.

  4. Quantifying Systemic Efficiency using Exergy and Energy Analysis for Ground Source Heat Pumps: Domestic Space Conditioning and Water Heating Applications.

    Energy Technology Data Exchange (ETDEWEB)

    Ally, Moonis Raza [ORNL; Baxter, Van D [ORNL; Gehl, Anthony C [ORNL; Munk, Jeffrey D [ORNL

    2017-01-01

    Although air temperatures over land surfaces show wide seasonal and daily variations, the ground, approximately 10 meters below the earth s surface, remains relatively stable in temperature thereby serving as an energy source or sink. Ground source heat pumps can heat, cool, and supply homes with hot water efficiently by utilizing the earth s renewable and essentially inexhaustible energy resources, saving fossil fuels, reducing greenhouse gas emissions, and lowering the environmental footprint. In this paper, evidence is shown that ground source heat pumps can provide up to 79%-87% of domestic hot water energy needs, and up to 77% of space heating needs with the ground s thermal energy resources. The case refers to a 12-month study conducted at a 253 m2 research house located in Oak Ridge, Tennessee, 36.01 N 84.26 W in a mixed-humid climate with HDD of 2218 C-days and CDD of 723 C-days under simulated occupancy conditions. A single 94.5m vertical bore interfaced the heat pump with the ground. The research shows that this technology is capable of achieving US DOE targets of 25 % and 35% energy savings in HVAC, and in water heating, respectively by 2030. It is also a viable technology to meet greenhouse gas target emissions under the IECC 2012 Standard, as well as the European Union (EU) 2020 targets of using renewable energy resources. The paper quantifies systemic efficiencies using Exergy analysis of the major components, clearly pointing areas for further improvement.

  5. Sustainability Efficiency Factor: Measuring Sustainability in Advanced Energy Systems through Exergy, Exergoeconomic, Life Cycle, and Economic Analyses

    Science.gov (United States)

    Boldon, Lauren

    (NHES) reference case studies to (1) introduce sustainability metrics, such as life cycle assessment, (2) demonstrate the methods behind exergy and exergoeconomic analyses, (3) provide an economic analysis of the potential for SMR development from first-of-a-kind (FOAK) to nth-of-a-kind (NOAK), thereby illustrating possible cost reductions and deployment flexibility for SMRs over large conventional nuclear reactors, (4) assess the competitive potential for incorporation of storage and hydrogen production in NHES and in regulated and deregulated electricity markets, (5) compare an SMR-hydrogen production plant to a natural gas steam methane reforming plant using the SEF, and (6) identify and review the social considerations which would support future nuclear development domestically and abroad, such as public and political/regulatory needs and challenges. The Global Warming Potential (GWP) for the SMR (300 MWth)-wind (60 MWe)-high temperature steam electrolysis (200 tons Hydrogen per day) system was calculated as approximately 874 g CO2-equivalent as part of the life cycle assessment. This is 92.6% less than the GWP estimated for steam methane reforming production of hydrogen by Spath and Mann. The unit exergetic and exergoeconomic costs were determined for each flow within the NHES system as part of the exergy/exergoeconomic cost analyses. The unit exergetic cost is lower for components yielding more meaningful work like the one exiting the SMR with a unit exergetic cost of 1.075 MW/MW. In comparison, the flow exiting the turbine has a very high unit exergetic cost of 15.31, as most of the useful work was already removed through the turning of the generator/compressor shaft. In a similar manner, the high unit exergoeconomic cost of 12.45/MW*sec is observed for the return flow to the reactors, because there is very little exergy present. The first and second law efficiencies and the exergoeconomic factors were also determined over several cases. For the first or base SMR

  6. A Comparative Study on Energy and Exergy Analyses of a CI Engine Performed with Different Multiple Injection Strategies at Part Load: Effect of Injection Pressure

    Directory of Open Access Journals (Sweden)

    Muammer Özkan

    2015-01-01

    Full Text Available In this study, a four stroke four cylinder direct injection CI engine was run using three different injection pressures. In all measurements, the fuel quantity per cycle, the pre injection and main injection timing, the boost pressure and the engine speed were kept constant. The motor tests were performed under 130, 140 and 150 MPa rail pressure. During the theoretical part of the study, combustion, emission, energy and exergy analysis were made using the test results. An increase in the injection pressure increases combustion efficiency. The results show that combustion efficiency is not enough by itself, because the increase in the power need of the injection pump, decreases the thermal efficiency. The increase in the combustion temperature, increases the cooling loss and decreases the exergetic efficiency. In addition, the NOx emissions increased by 12% and soot emissions decreased 44% via increasing injection pressure by 17%. The thermal and exergetic efficiencies are found inversely proportional with injection pressure. Exergy destruction is found independent of the injection pressure and its value is obtained as ~6%.

  7. Process development and exergy cost sensitivity analysis of a hybrid molten carbonate fuel cell power plant and carbon dioxide capturing process

    Science.gov (United States)

    Mehrpooya, Mehdi; Ansarinasab, Hojat; Moftakhari Sharifzadeh, Mohammad Mehdi; Rosen, Marc A.

    2017-10-01

    An integrated power plant with a net electrical power output of 3.71 × 105 kW is developed and investigated. The electrical efficiency of the process is found to be 60.1%. The process includes three main sub-systems: molten carbonate fuel cell system, heat recovery section and cryogenic carbon dioxide capturing process. Conventional and advanced exergoeconomic methods are used for analyzing the process. Advanced exergoeconomic analysis is a comprehensive evaluation tool which combines an exergetic approach with economic analysis procedures. With this method, investment and exergy destruction costs of the process components are divided into endogenous/exogenous and avoidable/unavoidable parts. Results of the conventional exergoeconomic analyses demonstrate that the combustion chamber has the largest exergy destruction rate (182 MW) and cost rate (13,100 /h). Also, the total process cost rate can be decreased by reducing the cost rate of the fuel cell and improving the efficiency of the combustion chamber and heat recovery steam generator. Based on the total avoidable endogenous cost rate, the priority for modification is the heat recovery steam generator, a compressor and a turbine of the power plant, in rank order. A sensitivity analysis is done to investigate the exergoeconomic factor parameters through changing the effective parameter variations.

  8. The analysis of different processes of extraction: yield of extracts obtained from Aloe Vera (Aloe barbadensis Miller and Sweet Bay (Laurus nobilis L. and the exergy analysis of applied processes

    Directory of Open Access Journals (Sweden)

    Jasna Ivanović

    2009-10-01

    Full Text Available The present study was aimed to investigate and compare the efficiency of different methods for the isolation extract from a plant material. Extracts from dried leaves of Aloe vera (A. barbadensis Mill. and Sweet Bay (Laurus nobilis L. were obtained applying the following techniques: supercritical carbon dioxide (SC CO2 extraction at 30 MPa and 100 °C, a combined ultrasonic extraction and pre-treatment using SC CO2 (US-SCCO2, and a conventional ultrasonic extraction (US with 96% ethanol. US-SCCO2 resulted in much higher yields of extracts of aloe and bay compared to SC CO2 extraction. Determined extract’s yield was used for calculating the maximum useful work and exergy loss as a measure of irreversibility of the extraction process. Calculated maximum useful work per 1 kg of the extract was ranged from 0.7 to 226 kJ while estimated values of the exergy loss were from 48 to 416 kJ per 1 kg of the extract. The maximum useful work and exergy loss have the largest value for SCE much more than for other processes of extraction (US and US-SCCO2. The pre-treatment of the plant material with SC CO2 before an ultrasound-assisted extraction or the decrease of a particle size used for ultrasound-assisted extraction of Aloe vera has led to the decrease of maximum useful work and exergy loss. Unlike, pre-treatment with SC CO2 followed by ultrasound-assisted extraction increased the exergy loss when bay was used as the plant material.

  9. Energy and exergy analysis of alternating injection of oxygen and steam in the low emission underground gasification of deep thin coal

    DEFF Research Database (Denmark)

    Eftekhari, Ali Akbar; Wolf, Karl Heinz; Rogut, Jan

    2017-01-01

    Recent studies have shown that by coupling the underground coal gasification (UCG) with the carbon capture and storage (CCS), the coal energy can be economically extracted with a low carbon footprint. To investigate the effect of UCG and CCS process parameters on the feasibility of the UCG....... Additionally, we show that the zero-emission conversion of unmineable deep thin coal resources in a coupled UCG-CCS process, that is not practical with the current state of technology, can be realized by increasing the energy efficiency of the carbon dioxide capture process....... to conduct an energy and exergy analysis of the UCG process. We study the effect of various process parameters on the efficiency of the UCG process, the zero-emission recovery factor of coal, and the total CO2 emission of the process. Moreover, we compare the alternating injection of air...

  10. Exergy analysis and performance of a counter flow Ranque-Hilsch vortex tube having various nozzle numbers at different inlet pressures of oxygen and air

    Energy Technology Data Exchange (ETDEWEB)

    Kirmaci, Volkan [Bartin University, Faculty of Engineering, Mechanical Engineering Department, 74100 Bartin (Turkey)

    2009-11-15

    An experimental investigation is made to determine the effects of the orifice nozzle number and the inlet pressure on the heating and cooling performance of the counter flow Ranque-Hilsch vortex tube when air and oxygen used as a fluid. The orifices used at these experiments are made of the polyamide plastic material. The thermal conductivity of polyamide plastic material is 0.25 W/m C. Five orifices with nozzle numbers of 2, 3, 4, 5 and 6 have been manufactured and used during the experiments. For each one of the orifices (nozzle numbers) when used with two different fluids, inlet pressures were adjusted from 150 kPa to 700 kPa with 50 kPa increments, and the exergy efficiency was determined. During the experiments, a vortex tube is used with an L/D ratio of 15, and cold mass fraction is held constant at 0.5. As a result of the experimental study, it is determined that the temperature gradient between the hot and cold fluid is decreased with increasing of the orifice nozzle number. (author)

  11. Transformation toward a Secure and Precaution-Oriented Energy System with the Guiding Concept of Resilience—Implementation of Low-Exergy Solutions in Northwestern Germany

    Directory of Open Access Journals (Sweden)

    Urte Brand

    2015-07-01

    Full Text Available Climate changes, incidents like nuclear disasters, and associated political objectives call for significant changes to the current energy system. Despite these far-reaching transformation processes, within the intended changes security of supply and precautions against the possible consequences of climate change must be ensured. Consequently, the question arises how to direct energy systems. In this context the processes of guiding orientations with the help of the guiding concept of “resilient systems” and feasible and addressee-oriented guiding design principles can be an option to provide guidance in transformation processes. However, it is questionable whether and how such processes are effective in the long term and if they are able to give direction by doing so. Within the framework of empirical studies of a regional guiding orientation process for the energy system of Northwestern Germany, the long-term effectiveness of the process and its spread resilient guiding design principles of “low-exergy solutions” and “climate-adapted and energy-efficient refrigeration” has been confirmed. Such effectiveness requires the implementation of a four-phase guiding orientation process which takes content-related and process-related effectiveness factors into account. Therefore, the study shows how regional energy systems can be designed toward the major challenges of ensuring security and precaution.

  12. Preliminary analysis of dry-steam geothermal power plant by employing exergy assessment: Case study in Kamojang geothermal power plant, Indonesia

    Directory of Open Access Journals (Sweden)

    Bayu Rudiyanto

    2017-09-01

    Full Text Available The objectives of this study are to perform the exergy analysis and ambient temperature optimization of the Kamojang geothermal power plant by employing Engineering Equation Solver (EES. The geothermal capacity is 55 MW and the field is vapor-dominated reservoir with temperature 245 °C. In the initial state temperature, pressure and mass flow data are collected from the plant operation. The study results show that system has overall efficiency of 35.86% which means that only 111,138.92 kW electrical power can be extracted from 309,000 kW thermal power being produced by 10 production wells of Kamojang. This low efficiency is due to irreversibility associated with different processes and components in the system. The largest irreversibility occurs in condenser due to which 53% of total energy is disposed into the environment. Ambient temperature at Kamojang varies from 17 to 20 °C. The effect of this variation in temperature is also investigated and it is observed that higher temperature does not have any significant impact on system efficiency.

  13. Energy and Exergy Analysis for Improving the Energy Performance of Air-Cooled Liquid Chillers by Different Condensing-Coil Configurations

    Directory of Open Access Journals (Sweden)

    Tzong-Shing Lee

    2012-03-01

    Full Text Available This study constructed a parameter analysis for improving the energy performance of air-cooled water chillers by altering the angle configuration of the condenser coils. The mathematical models for energy and exergy analyses of the individual components and overall system of air-cooled water chillers are presented. This study investigated the potential enhancement of performance efficiency in air-cooled chillers and the energy conversion efficiency of each component, in order to determine how the angle configuration of condenser coils influences chiller performance. This study found that the overall performance of an air-cooled chiller could be improved by approximately 3.4%, and the total irreversibility could be reduced by approximately 2.7%. With each 1% increase in average wind speed over the condenser coils, the overall performance of an air‑cooled chiller was found to be enhanced by approximately 0.43%, and its total irreversibility was reduced by approximately 0.35%. The results of this study can be effectively applied to air-cooled condenser units, and can provide an important basis of reference for developing and enhancing the energy efficiency of air-cooled chillers.

  14. Exergy Analysis and Exergo-Economic Optimization of Industrial Processes Optimisation des procédés industriels par analyse exergétique et exergo-économique

    Directory of Open Access Journals (Sweden)

    Le Goff P.

    2006-11-01

    Full Text Available The overall evaluation of a process can be made by exergy accounting or by financial accounting. In all cases, a process can be optimized by determining the best compromise between the various input fluxes. L'évaluation globale d'un procédé peut être faite soit au moyen d'un bilan exergétique, soit par l'intermédiaire d'un bilan économique. Dans tous les cas, un procédé peut être optimisé en déterminant le meilleur compromis entre les différents flux mis en jeu.

  15. The Process Synthesis Pyramid: Conceptual design of a Liquefied Energy Chain using Pinch Analysis,Exergy Analysis,Deterministic Optimization and Metaheuristic Searches

    Energy Technology Data Exchange (ETDEWEB)

    Aspelund, Audun

    2012-07-01

    Process Synthesis (PS) is a term used to describe a class of general and systematic methods for the conceptual design of processing plants and energy systems. The term also refers to the development of the process flowsheet (structure or topology), the selection of unit operations and the determination of the most important operating conditions.In this thesis an attempt is made to characterize some of the most common methodologies in a PS pyramid and discuss their advantages and disadvantages as well as where in the design phase they could be used most efficiently. The thesis shows how design tools have been developed for subambient processes by combining and expanding PS methods such as Heuristic Rules, sequential modular Process Simulations, Pinch Analysis, Exergy Analysis, Mathematical Programming using Deterministic Optimization methods and optimization using Stochastic Optimization methods. The most important contributions to the process design community are three new methodologies that include the pressure as an important variable in heat exchanger network synthesis (HENS).The methodologies have been used to develop a novel and efficient energy chain based on stranded natural gas including power production with carbon capture and sequestration (CCS). This Liquefied Energy Chain consists of an offshore process a combined gas carrier and an onshore process. This energy chain is capable of efficiently exploiting resources that cannot be utilized economically today with minor Co2 emissions. Finally, a new Stochastic Optimization approach based on a Tabu Search (TS), the Nelder Mead method or Downhill Simplex Method (NMDS) and the sequential process simulator HYSYS is used to search for better solutions for the Liquefied Energy Chain with respect to minimum cost or maximum profit. (au)

  16. Integral programs of energy conservation (exergy) in the petroleum industry; Programas integrales de ahorro de energia (exergia) en la industria petrolera

    Energy Technology Data Exchange (ETDEWEB)

    Rivero Rodriguez, R. [Instituto Mexicano del Petroleo (IMP), Mexico, D. F. (Mexico)

    1995-12-31

    This paper presents some of the fundamental issues related to energy conservation programs in general and to the petroleum industry in particular with the purpose of integrating them both, that is, considering not only the energy issues, but also the ecological and economical aspects. This is achieved by using the two fundamental laws of thermodynamics (the science that studies energy, its characteristics, and its transformations) through the use of the exergy concept, which is a measure of the energy quality and of its withdrawal with respect to the environment. The origins of the present-day technologies, regarding energy conservation, the short, medium and long term general strategies and the implementation stages of the integral programs of energy conservation are presented, and it concludes with a series of general policies aimed at making the energy conservation programs more congruent with the maintenance of a sustainable development. [Espanol] En este trabajo se presentan algunos aspectos fundamentales relacionados con los programas de ahorro de energia en general, y en la industria petrolera en particular, con objeto de lograr que los mismos sean integrales, es decir que consideren no solo los aspectos puramente energeticos, sino tambien los aspectos ecologicos y economicos. Esto se logra utilizando conjuntamente las dos leyes fundamentales de la termodinamica (la ciencia que estudia la energia, sus caracteristicas y sus transformaciones), mediante la utilizacion del concepto de exergia, que es una medida de la calidad de la energia y de su alejamiento con respecto al medio ambiente. Se presentan los origenes de las tendencias tecnologicas actuales en materia de ahorro de energia, las estrategias generales a corto, mediano y largo plazos y las etapas en la implementacion de programas integrales de ahorro de energia, para concluir con una serie de politicas generales tendientes a lograr que los programas de ahorro de energia sean congruentes con el

  17. DEVELOPMENT OF THE SCHEME AND EXERGY ANALYSIS OF THE EGS WITH THE POSSIBILITY OF THE SIMULTANEOUS PRODUCTION OF ELECTRICITY AND "DEEP COLD"

    Directory of Open Access Journals (Sweden)

    V. Ia Gubarev

    2014-01-01

    Full Text Available One of the areas of energy conservation is the use of an expander-generator sets, that convert pressurized natural gas into electricity. In applying the expander-generator set for using gas pressure power generation gas flow necessary to heat, as as a result of expansion of the gas in an expander and a corresponding lowering of the temperature, the formation of condensate and hydrates in gas pipelines and fittings, piping and, as a consequence, their blockage or obstruction. In connection with this gas before detander-generating set to be heated so that at its exit gas temperature was at least 0 0C. A scheme in which the heater is replaced by adsorption drying, which makes it possible to use an expander-generator set at low temperatures without the risk of it or after it, mist and hydrates. Gas adsorption drying - process is selective absorption of the surface pores of the solid adsorbent of water molecules from the gas, and then extract them from the pores by applying external influences. The process of adsorption drying gas can achieve dew point – 90 0C. Including this unit, or equivalent, in the scheme with the DHA, get simultaneous generation of electricity and "deep cold". Area of application "deep cold" is very broads. Along with all energy and chemical industries, he is in demand in the food industry, plants for the production of beer and soft drinks. Chill needed for freezing and for subsequent storage products in refrigeration terminals and warehouses. This article contains diagrams of the adsorption unit, unit the receipt of "deep cold", a description of their work and exergy analysis of the developed scheme.

  18. Energy Rebound as a Potential Threat to a Low-Carbon Future: Findings from a New Exergy-Based National-Level Rebound Approach

    Directory of Open Access Journals (Sweden)

    Paul E. Brockway

    2017-01-01

    Full Text Available 150 years ago, Stanley Jevons introduced the concept of energy rebound: that anticipated energy efficiency savings may be “taken back” by behavioural responses. This is an important issue today because, if energy rebound is significant, this would hamper the effectiveness of energy efficiency policies aimed at reducing energy use and associated carbon emissions. However, empirical studies which estimate national energy rebound are rare and, perhaps as a result, rebound is largely ignored in energy-economy models and associated policy. A significant difficulty lies in the components of energy rebound assessed in empirical studies: most examine direct and indirect rebound in the static economy, excluding potentially significant rebound of the longer term structural response of the national economy. In response, we develop a novel exergy-based approach to estimate national energy rebound for the UK and US (1980–2010 and China (1981–2010. Exergy—as “available energy”—allows a consistent, thermodynamic-based metric for national-level energy efficiency. We find large energy rebound in China, suggesting that improvements in China’s energy efficiency may be associated with increased energy consumption (“backfire”. Conversely, we find much lower (partial energy rebound for the case of the UK and US. These findings support the hypothesis that producer-sided economies (such as China may exhibit large energy rebound, reducing the effectiveness of energy efficiency, unless other policy measures (e.g., carbon taxes are implemented. It also raises the prospect we need to deploy renewable energy sources faster than currently planned, if (due to rebound energy efficiency policies cannot deliver the scale of energy reduction envisaged to meet climate targets.

  19. Valoración económica de las pérdidas de exergía de las operaciones térmicas en la industria azucarera de caña Economic value of exergy losses in heating operations in cane sugar mills

    Directory of Open Access Journals (Sweden)

    Dora Paz

    2005-12-01

    Full Text Available Tomando como base los resultados del análisis exergético de las operaciones térmicas: Calentamiento- Evaporación-Cristalización (CEC de un ingenio de Tucumán, realizado por Paz y Cárdenas en 2005, se procedió a determinar el valor económico de las pérdidas de exergía. Dichas pérdidas de exergía representan potencias eléctricas equivalentes que dejaron de producirse, por lo que el daño causado por las mismas puede ser calculado directamente a partir del precio de la energía eléctrica. Esta original metodología propuesta para determinar ahorros monetarios, basada en la reducción de exergía perdida, se comparó con los resultados obtenidos con la metodología tradicional (basada en el ahorro de vapor vivo. Los ahorros monetarios logrados con las propuestas A y B fueron de $1,05 x 10(6 (0,35 x 10(6 USD y $1,92 x 10(6 (0,64 x 10(6 USD por zafra, determinándose Tasas Internas de Retorno (TIR de 191% y 20,8%, respectivamente.This paper is based on the results of previous work done by Paz and Cárdenas in 2005, in which exergy losses in thermal operations: Heating-Evaporation-Crystallization (H-E-C of a cane sugar mill located in Tucumán, were evaluated. Exergy losses represent equivalent non-produced electric power; therefore, the resulting damage can be calculated directly from the price of the electric energy. Results obtained with this novel methodology (exergy loss reduction were compared with those obtained with the traditional method (live steam saving when evaluating monetary savings. In fact, monetary savings in A and B proposals were $1,05 x 10(6 (0,35 x 10(6 USD and $1,92 x 10(6 (0,64 x 10(6 USD per season, respectively. Internal Rates of Return (IRR were 191% and 20,8%, respectively.

  20. Exergy Efficient Application of LNG Cold

    NARCIS (Netherlands)

    Stougie, L.; Van der Kooi, H.J.

    2010-01-01

    The worldwide demand for Liquefied Natural Gas (LNG) is growing, which results in numerous LNG import terminals being under construction. In the interest of sustainable development, it is important to decide carefully upon which technology to apply for evaporating the LNG to natural gas. Three

  1. Sustainability assessment of salmonid feed using energy, classical exergy and eco-exergy analysis

    NARCIS (Netherlands)

    Draganovic, V.; Jorgensen, S.E.; Boom, R.M.; Jonkers, J.; Goot, van der A.J.

    2013-01-01

    Reduction of the environmental impact of feed products is of paramount importance for salmon farming. This article explores the potential to compare three thermodynamically based ecological indicators. The environmental impact of partial replacement of fish meal (FM) and fish oil with alternative

  2. Exergy and Sustainability : Insights into the Value of Exergy Analysis in Sustainability Assessment of Technological Systems

    NARCIS (Netherlands)

    Stougie, L.

    2014-01-01

    A major challenge in striving for a more sustainable society is the selection of technological systems. Given the capital intensity of industrial production plants, power generation systems and infrastructure, investment decisions create path dependencies for decades to come. It is difficult to know

  3. Exergy-based efficiency and renewability assessment of biofuel production.

    Science.gov (United States)

    Dewulf, J; Van Langenhove, H; Van De Velde, B

    2005-05-15

    This study presents an efficiency and renewability analysis of the production of three biofuels: rapeseed methyl ester (RME), soybean methyl ester (SME) and corn-based ethanol (EtOH). The overall production chains have been taken into account: not only the agricultural crop production and the industrial conversion into biofuel, but also production of the supply of agricultural resources (pesticides, fertilizers, fuel, seeding material) and industrial resources (energy and chemicals) to transform the crops into biofuel. Simultaneously, byproducts of the agricultural and industrial processes have been taken into account when resources have to be allocated to the biofuels. The technical analysis via the second law of thermodynamics revealed that corn-based EtOH results in the highest production rate with an exergetic fuel content of 68.8 GJ ha(-1) yr(-1), whereas the RME and SME results were limited to 47.5 and 16.4 GJ ha(-1) yr(-1). The allocated nonrenewable resource input to deliver these biofuels is significant: 16.5, 15.4, and 5.6 MJ ha(-1) yr(-1). This means that these biofuels, generally considered as renewable resources, embed a nonrenewable fraction of one-quarter for EtOH and even one-third for RME and SME. This type of analysis provides scientifically sound quantitative information that is necessarywith respect to the sustainability analysis of so-called renewable energy.

  4. Mass balance and exergy analysis of a fast pyrolysis system

    Science.gov (United States)

    Mass balance closure and exergetic efficiency is evaluated for a bench scale fast pyrolysis system. The USDA Agricultural Research Service (ARS) has developed this system for processing energy crops and agricultural residues for bio-oil (pyrolysis oil or pyrolysis liquids) production. Mass balance c...

  5. 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

    Floating, Production, Storage and Offloading (FPSO) is a floating facility used in primary petroleum processing. In Brazil, most FPSOs have been installed in Campos Basin and new facilities may be implemented in the pre-salt area are projected to boost the Brazilian oil production. Crude oil comp...

  6. Sustainable energy systems : Limitations and challenges based on exergy analysis

    NARCIS (Netherlands)

    Verkooijen, A.H.M.; Woudstra, N.

    General There is a general understanding that the so-called “developed countries” have to change their way of life including their energy supply into a more sustainable way. But even in the case of unanimity with regard to the direction, there are still many opinions about the way to follow. This

  7. Application of the Exergy UCG technology in international UCG projects

    Science.gov (United States)

    Blinderman, M. S.

    2017-07-01

    Underground Coal Gasification is a subject of continuing global interest in the energy sector. While the international scenario in UCG is promising, it is deeply desirable that advances in this area are seen in India as well. This is particularly so with the Paris Climate Agreement bringing in more stringent challenges for clean energy development. India has many potential coal basins which may be suitable for UCG deployment. India is in dire need of indigenous source of gaseous and liquid hydrocarbons that could compete with imported products. It is also the country with exceptionally large and diverse coal and lignite resources, large part of which could not be mined due to geological complexity and prohibitive cost. Thus, there is a rationale that the εUCG™ technology plays a decisive role in realizing the potential of Indian coal resources for the benefit of Indian industry and population. This article has been adapted by Dr. Ajay K. Singh from a lecture delivered at the “Workshop on Challenges and Opportunities of Underground Coal Gasification”, Vigyan Bhawan, New Delhi on 14 February 2017.

  8. Sustainable energy systems: Limitations and challenges based on exergy analysis

    OpenAIRE

    Woudstra, N.

    2012-01-01

    General There is a general understanding that the so-called “developed countries” have to change their way of life including their energy supply into a more sustainable way. But even in the case of unanimity with regard to the direction, there are still many opinions about the way to follow. This thesis discusses problems and possibilities of more sustainable energy systems first of all for the energy supply of the Netherlands. The “trias energetica” is used to distinguish the steps that have...

  9. Sustainable energy systems : Limitations and challenges based on exergy analysis

    NARCIS (Netherlands)

    Woudstra, N.

    2012-01-01

    General There is a general understanding that the so-called “developed countries” have to change their way of life including their energy supply into a more sustainable way. But even in the case of unanimity with regard to the direction, there are still many opinions about the way to follow. This

  10. Measurement and investigation into air source heat pump exergy

    Science.gov (United States)

    Cho, Hung-Pin; Hsu, Ching-Wei; Jwo, Ching-Song; Tsai, Meng-Ying; Chen, Sih-Li

    2011-12-01

    This study applies the second law of thermodynamics to analyze the irreversibility of air source heat pump systems. By using both T type thermocouple wires to measure the inlet and outlet temperatures of key components in the system and using pressure transmitters to measure the high and low pressure of the experiment systems, we collect data and use two control volume(CV) models to calculate the generative volume and irreversibility of entropy for each system component. According to the experiment results for both CV models (the CV of the refrigerant section and the CV of the whole control), the heat exchanger is found to have the largest irreversibility. The irreversibility error of the condenser is 4.6% and the irreversibility error of the evaporator is up to 21%. By applying the results of this study it is possible to improve the function of air source heat pump systems through improving the heat exchanger, achieving both cost and energy savings.

  11. Exergy analysis for a proposed binary geothermal power plant in Nisyros Island, Greece

    DEFF Research Database (Denmark)

    Koroneos, Christopher; Polyzakis, A.; Xydis, George

    2017-01-01

    and a measure of the quality of the different forms of energy in relation to given environmental conditions. In this paper, data from an experimental geothermal drill in the Greek Island of Nisyros, located in the south of the Aegean Sea, have been used in order to estimate the maximum available work...... resulted supporting technical feasibility of the proposed geothermal plant....

  12. Energy and exergy analysis of PV/T air collectors connected in series

    NARCIS (Netherlands)

    Dubey, Swapnil; Solanki, S.C.; Tiwari, A.

    2009-01-01

    In this paper an attempt has been made to derive the analytical expressions for N hybrid photovoltaic/thermal (PV/T) air collectors connected in series. The performance of collectors is evaluated by considering the two different cases, namely, Case I (air collector is fully covered by PV module

  13. Comparative exergy analysis of direct alcohol fuel cells using fuel mixtures

    OpenAIRE

    Leo Mena, Teresa de Jesus; Raso García, Miguel Ángel; Navarro Arevalo, Emilio; Sánchez de la Blanca, Emilia

    2011-01-01

    Within the last years there has been increasing interest in direct liquid fuel cells as power sources for portable devices and, in the future, power plants for electric vehicles and other transport media as ships will join those applications. Methanol is considerably more convenient and easy to use than gaseous hydrogen and a considerable work is devoted to the development of direct methanol fuel cells. But ethanol has much lower toxicity and from an ecological viewpoint ethanol is exceptiona...

  14. Is bioethanol a sustainable energy source? An energy-, exergy-, and emergy-based thermodynamic system analysis

    NARCIS (Netherlands)

    Liao, Wenjie; Heijungs, Reinout; Huppes, Gjalt

    2011-01-01

    Biofuels are widely seen as substitutes for fossil fuels to offset the imminent decline of oil production and to mitigate the emergent increase in GHG emissions. This view is, however, based on too simple an analysis, focusing on only one piece in the whole mosaic of the complex biofuel

  15. Exergy landscapes: Exploration of second-law thinking towards sustainable landscape design

    NARCIS (Netherlands)

    Stremke, S.; Dobbelsteen, van den A.; Koh, J.

    2011-01-01

    Depletion of fossil fuels and climate change necessitate a transition to sustainable energy systems that make efficient use of renewable energy sources. During recent decades, the Second Law of Thermodynamics has helped to increase energy efficiencies. More recently, the disciplines of building

  16. Resource metabolism of the construction sector an application of material and exergy flow analysis

    OpenAIRE

    Rashedul Hoque, Mohammad

    2013-01-01

    Ésta tesis tiene como objetivo evaluar el consumo de recursos del sector de la construcción, los residuos y las emisiones generadas por el sector. Ésto está motivado por el hecho de que el sector de la construcción es responsable de una gran cantidad de consumo de recursos y representa casi el 9% el valor bruto añadido al producto interno bruto del mundo. La evaluación considera la perspectiva del ciclo de vida, desde la extracción de materias primas, a través de la construcción y fabricación...

  17. Energy and Exergy analysis of a light duty diesel engine operating at different altitudes

    OpenAIRE

    John Agudelo; Andrés Agudelo; Juan Pérez

    2009-01-01

    La densidad del aire disminuye con el aumento de la altitud sobre el nivel del mar, este aspecto afecta el proceso de combustión, la formación de emisiones contaminantes y por tanto el desempeño del motor. En este trabajo se presenta el diagnóstico del proceso de combustión de un motor diesel de automoción turbo-alimentado, mediante la medición de presión en cámara operando en tres alturas diferentes sobre el nivel del mar, bajo condiciones estacionarias, utilizando diesel convencional (acpm)...

  18. 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

    Global carbon dioxide (CO2) emissions reached an all-time high in 2010, rising 45% in the past 20 years. The rise of peoples’ concerns regarding environmental problems such as global warming and waste management problem has led to a movement to convert the current mass-production, mass-consumptio......Global carbon dioxide (CO2) emissions reached an all-time high in 2010, rising 45% in the past 20 years. The rise of peoples’ concerns regarding environmental problems such as global warming and waste management problem has led to a movement to convert the current mass-production, mass......-consumption, and mass-disposal type economic society into a sustainable society. The Rio Conference on Environment and Development in 1992, and other similar environmental milestone activities and happenings, documented the need for better and more detailed knowledge and information about environmental conditions...

  19. High-speed engine/component performance assessment using exergy and thrust-based methods

    Science.gov (United States)

    Riggins, D. W.

    1996-01-01

    This investigation summarizes a comparative study of two high-speed engine performance assessment techniques based on energy (available work) and thrust-potential (thrust availability). Simple flow-fields utilizing Rayleigh heat addition and one-dimensional flow with friction are used to demonstrate the fundamental inability of conventional energy techniques to predict engine component performance, aid in component design, or accurately assess flow losses. The use of the thrust-based method on these same examples demonstrates its ability to yield useful information in all these categories. Energy and thrust are related and discussed from the stand-point of their fundamental thermodynamic and fluid dynamic definitions in order to explain the differences in information obtained using the two methods. The conventional definition of energy is shown to include work which is inherently unavailable to an aerospace Brayton engine. An engine-based energy is then developed which accurately accounts for this inherently unavailable work; performance parameters based on this quantity are then shown to yield design and loss information equivalent to the thrust-based method.

  20. Mass, Energy, Entropy and Exergy Rate Balance in a Ranque-Hilsh Vortex Tube

    Science.gov (United States)

    Carrascal Lecumberri, Edorta; Sala Lizarraga, José María

    2013-01-01

    The objective of this paper is to present a laboratory program designed for the Thermodynamics course offered in the Department of Thermal Engineering at the University of the Basque Country. With reference to one of the examples given in the textbook by Moran, Shapiro, Boettner and Bailey (2012), the balances of mass, energy, entropy and exergy…

  1. Exergy Based Analysis for the Environmental Control and Life Support Systems of the International Space Station

    Science.gov (United States)

    Clem, Kirk A.; Nelson, George J.; Mesmer, Bryan L.; Watson, Michael D.; Perry, Jay L.

    2016-01-01

    When optimizing the performance of complex systems, a logical area for concern is improving the efficiency of useful energy. The energy available for a system to perform work is defined as a system's energy content. Interactions between a system's subsystems and the surrounding environment can be accounted for by understanding various subsystem energy efficiencies. Energy balance of reactants and products, and enthalpies and entropies, can be used to represent a chemical process. Heat transfer energy represents heat loads, and flow energy represents system flows and filters. These elements allow for a system level energy balance. The energy balance equations are developed for the subsystems of the Environmental Control and Life Support (ECLS) system aboard the International Space Station (ISS). The use of these equations with system information would allow for the calculation of the energy efficiency of the system, enabling comparisons of the ISS ECLS system to other systems as well as allows for an integrated systems analysis for system optimization.

  2. Exergy Analysis of a CO2 Recovery Plant for a Brewery

    DEFF Research Database (Denmark)

    Nielsen, Daniel Rønne; Elmegaard, Brian; Bang-Møller, Christian

    2012-01-01

    efficiencies for processes and the different utility plants. One considerable utility plant is the CO2 recovery plant, which purifies/purges the CO2 generated in the fermentation process in order to reuse it in the brewery site or sell it to customers who demand high quality CO2. In the paper a detailed model...

  3. Exergy Assessment of Single Stage Solar Adsorption Refrigeration System Using ANN

    National Research Council Canada - National Science Library

    Baiju, V; Muraleedharan, C

    2012-01-01

    ... which are considered major cause for ozone layer depletion. From this context the adsorption refrigeration system attains a considerable attention in 1970s due to the energy crisis and ecological problems related to the use of CFCs and HFCs. Research has proved that the adsorption refrigeration technology has a promising potential for competing w...

  4. Exergy and Thermoeconomic Analyses of Central Receiver Concentrated Solar Plants Using Air as Heat Transfer Fluid

    OpenAIRE

    Claudia Toro; Rocco, Matteo V; Emanuela Colombo

    2016-01-01

    The latest developments in solar technologies demonstrated that the solar central receiver configuration is the most promising application among concentrated solar power (CSP) plants. In CSPs solar-heated air can be used as the working fluid in a Brayton thermal cycle and as the heat transfer fluid for a Rankine thermal cycle as an alternative to more traditional working fluids thereby reducing maintenance operations and providing the power section with a higher degree of flexibility To suppl...

  5. The wind chill temperature effect on a large-scale PV plant—an exergy approach

    DEFF Research Database (Denmark)

    Xydis, George

    2013-01-01

    disregarded atmospheric variables in planning new PV plants, in fact, do play a significant role on the plant's overall exergetic efficiency as wind chill temperature. The solar potential around a windy coastal hilly area was studied and presented on the basis of field measurements and simulations...

  6. Energy use in the production of unrefined sugar in Colombia (exergy analysis

    Directory of Open Access Journals (Sweden)

    Héctor Velásquez

    2011-01-01

    Full Text Available El objetivo de este estudio es determinar cómo se usan los recursos energéticos en la producción de panela en Colombia. Para este fi n, se realizaron mediciones en ocho trapiches que representan los procesos productivos típicos de la panela. Con los datos experimentales se obtuvieron los balances de primera y segunda ley de la termodinámica, a partir de los cuales se calcularon las efi ciencias y algunos indicadores del uso de la energía. La comparación de los trapiches mostró que las mejoras tecnológicas permiten aumentar la efi ciencia energética a niveles aceptables debido a un mejor proceso de combustión y a la reducción de las pérdidas energéticas asociadas con los gases de escape y la transferencia de calor a través de las paredes. El efecto de dichas mejoras sobre la efi ciencia de segunda ley no es signifi cativo, lo cual sugiere que se deberían implementar sistemas de cogeneración en los procesos de producción a gran escala con el fi n de hacer un uso más racional de los recursos energéticos.

  7. Exergy analysis of biogas production from a municipal solid waste landfill

    DEFF Research Database (Denmark)

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

    2013-01-01

    In the energy area, intensive efforts are being made over the last years to bridge the supply area with renewable energy sources and the demand side with energy conservation. Energy recovery from municipal solid waste landfills can play a contributing role in the solution of problems of both waste...

  8. Energy and Exergy analysis of a light duty diesel engine operating at different altitudes

    Directory of Open Access Journals (Sweden)

    John Agudelo

    2009-01-01

    Full Text Available La densidad del aire disminuye con el aumento de la altitud sobre el nivel del mar, este aspecto afecta el proceso de combustión, la formación de emisiones contaminantes y por tanto el desempeño del motor. En este trabajo se presenta el diagnóstico del proceso de combustión de un motor diesel de automoción turbo-alimentado, mediante la medición de presión en cámara operando en tres alturas diferentes sobre el nivel del mar, bajo condiciones estacionarias, utilizando diesel convencional (acpm como combustible. A medida que aumenta la altura sobre el nivel del mar se incrementa la relación combustible/ aire (mezcla más rica y con ello el consumo específico de combustible, la duración de la combustión, la combustión en fase premezclada, la temperatura máxima, el calor transferido a los gases y la exergía destruida, mientras que el rendimiento térmico efectivo del motor, la presión máxima y la exergía en el cilindro disminuyen. Sin embargo, la eficiencia mecánica y el tiempo de inyección se mantienen aproximadamente constantes. Las diferencias encontradas en la exergía destruida se deben a las variaciones del proceso de combustión, ya que no se encontraron efectos significativos en las carreras de compresión y expansión. La mayor irreversibilidad debida al aumento de la altura se debe a la baja calidad de la energía de los gases de escape.

  9. 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

    and simulation environment based on the Modelica programming language. The system was tested on two single office rooms. In order to evaluate potential energy savings, the energy performance of the novel system was compared with the one of a conventional system for three typical weeks during winter, spring...... and summer. Simulation results showed that the novel system was able to maintain comfortable levels of indoor air temperature in both rooms for all the three typical weeks. In addition, the novel system used approximately 35% and 7% less energy than the conventional system, respectively for the typical...

  10. Framework for the Economic Analysis of Hybrid Systems Based on Exergy Consumption

    Energy Technology Data Exchange (ETDEWEB)

    Rabiti, Cristian [Idaho National Lab. (INL), Idaho Falls, ID (United States); Cherry, Robert S. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Deason, Wesley R. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Sabharwall, Piyush [Idaho National Lab. (INL), Idaho Falls, ID (United States); Bragg-Sitton, Shannon M. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Boardman, Richard D. [Idaho National Lab. (INL), Idaho Falls, ID (United States)

    2014-08-01

    Starting from an overview of the dynamic behavior of the electricity market the need of the introduction of energy users that will provide a damping capability to the system is derived as also a qualitative analysis of the impact of uncertainty, both in the demand and supply side, is performed. Then it follows an introduction to the investment analysis methodologies based on the discounting of the cash flow, and then work concludes with the illustration and application of the exergonomic principles to provide a sound methodology for the cost accounting of the plant components to be used in the cash flow analysis.

  11. Selection and Exergy Analysis of Fuel Cell System to Meet all Energy Needs of Residential Buildings

    OpenAIRE

    G.R. Ashari; N.Hedayat; S. Shalbaf; E.Hajidavalloo

    2011-01-01

    In this paper a polymer electrolyte membrane (PEM) fuel cell power system including burner, steam reformer, heat exchanger and water heater has been considered to meet the electrical, heating, cooling and domestic hot water loads of residential building which in Tehran. The system uses natural gas as fuel and works in CHP mode. Design and operating conditions of a PEM fuel cell system is considered in this study. The energy requirements of residential building and the num...

  12. Energy and exergy analyses of homogeneous charge compressin ignition (HCCI engine

    Directory of Open Access Journals (Sweden)

    Fatehi Ghahfarokhi Rasool

    2013-01-01

    Full Text Available In the present investigation, a single-cylinder, four-stroke cycle, TD43 engine has been used to evaluate the first and second laws of thermodynamics terms. To this aim, the first law analysis is done by using a thermo-kinetic model. The results show a good agreement with the experimental data. Also for the second law analysis, a developed in house computational code is applied. Behaviors of the results have a good accordance with the literature. The result show that an increase in the inlet charge temperature causes the maximum pressure, indicated work availability and entropy generation per cycle be reduced and the in-cylinder temperature, heat loss availability and total availability be increased. Also the results show that an increase in the engine speed causes the total availability be increased and the heat loss availability be decreased. When the engine speed increases, reduction in the duration of cycle evolution causes the reduction of heat transfer.

  13. The available-enthalpy (flow-exergy) cycle. Part-II: applications to idealized baroclinic waves

    CERN Document Server

    Marquet, Pascal

    2014-01-01

    The local available-enthalpy cycle proposed in Part I of this paper is applied to document energetics of three numerical simulations, representing life cycles of idealized baroclinic waves. An improved temporal numerical scheme defined in Part I is used in this study, together with the Arpege-IFS model using a T42 triangular truncation. A 45{\\deg}N and 200 hPa dry unstable jet is constructed with the most unstable mode at zonal wave number 8. Energetic impacts of both horizontal and vertical diffusion schemes are determined separately. The role of ageostrophic winds within the Ekman layer is investigated, leading to an explanation for large observed values for the dissipation terms and to a new formulation of the potential-energy conversions. The magnitudes of these new conversion terms are compared with those of the usual barotropic and baroclinic conversions. A new version for the available-enthalpy cycle is proposed. It is suitable for open systems and it includes explicitly the potential-energy component ...

  14. Sustainability Assessment of Power Generation Systems by Applying Exergy Analysis and LCA Methods

    NARCIS (Netherlands)

    Stougie, L.; van der Kooi, H.J.; Valero Delgado, A.

    2015-01-01

    The selection of power generation systems is important when striving for a more sustainable society. However, the results of environmental, economic and social sustainability assessments are subject to new insights into the calculation methods and to changing needs, economic conditions and societal

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

    National Research Council Canada - National Science Library

    Boldon, Lauren; Sabharwall, Piyush; Rabiti, Cristian; Bragg-Sitton, Shannon M; Liu, Li

    2016-01-01

    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...

  16. Workshop on Constructal Theory of the Generation of Optimal Flow Configurations Held in Rome, Italy on 17-18 March 2005

    Science.gov (United States)

    2005-04-01

    14. SUBJECT TERMS EOARD, Optimization, Energy conversion, Constructal theory, Exergy 15. NUMBER OF PAGES 16. PRICE...Ex,fuel fuel exergy Boeing C-17 Airlifter (Cargo Aircraft) o· destroyed during combustion destroyed during energy conversion...mass)1/6 fuel mass, or destroyed exergy exergy destroyed by the system exergy destroyed for flying the system °oO

  17. Exergoeconomic optimization of tetra-combined trigeneration system

    National Research Council Canada - National Science Library

    Juan Carlos Burbano Jaramillo; Silvio de Oliveira

    2015-01-01

    .... The performance evaluation of systems is carried out by the application of exergy and exergoeconomic analysis of the proposed alternatives in order to determine exergy efficiency and exergy based...

  18. A conceptual exergy-based framework for assessing, monitoring, and designing a resource efficient agri-food sector

    NARCIS (Netherlands)

    Zisopoulos, Filippos K.; Overmars, Lisa; Goot, van der Atze Jan

    2017-01-01

    The sustainable development goals (SDGs) are a set of global goals, targets, and indicators set by the member states of the United Nations and which are to be followed by governments, the private sector, and the civil society for the next 15 years. Here, we present a framework in the form of a

  19. Experimental and numerical study of nanofluid in heat exchanger fitted by modified twisted tape: exergy analysis and ANN prediction model

    Science.gov (United States)

    Maddah, Heydar; Ghasemi, Nahid; Keyvani, Bahram; Cheraghali, Ramin

    2017-04-01

    Present study provides an experimental investigation of the exergetic efficiency due to the flow and heat transfer of nanofluids in different geometries and flow regimes of the double pipe heat exchangers. The experiments with different Geometrical Progression Ratio (GPR) of twists as the new modified twisted tapes and different nanofluid concentration were performed under similar operation condition. Pitch length of the proposed twisted tapes and consequently the twist ratios changed along the twists with respect to the Geometrical Progression Ratio (GPR) whether reducer (RGPR 1). Regarding the experimental data, utilization of RGPR twists together with nanofluids tends to increase exergetic efficiency. Since the Prediction of exergetic efficiency from experimental process is complex and time consuming, artificial neural networks for identification of the relationship, which may exist between the thermal and flow parameters and exergetic efficiency, have been utilized. The network input consists of five parameters ({Re} ,\\Pr ,φ, Tr, GPR) that crucially dominate the heat transfer process. The results proved that the introduced ANN model is reliable and capable in proposing a proper development plan for a heat exchanger and/or to determine the optimal plan of operation for heat transfer process.

  20. Energy and Exergy Analyses of a New Combined Cycle for Producing Electricity and Desalinated Water Using Geothermal Energy

    Directory of Open Access Journals (Sweden)

    Mehri Akbari

    2014-04-01

    Full Text Available A new combined cogeneration system for producing electrical power and pure water is proposed and analyzed from the viewpoints of thermodynamics and economics. The system uses geothermal energy as a heat source and consists of a Kalina cycle, a LiBr/H2O heat transformer and a water purification system. A parametric study is carried out in order to investigate the effects on system performance of the turbine inlet pressure and the evaporator exit temperature. For the proposed system, the first and second law efficiencies are found to be in the ranges of 16%–18.2% and 61.9%–69.1%, respectively. For a geothermal water stream with a mass flow rate of 89 kg/s and a temperature of 124 °C, the maximum production rate for pure water is found to be 0.367 kg/s.

  1. 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

    A hybrid plant producing combined heat and power (CHP) from biomass by use of a two-stage gasification concept, solid oxide fuel cells (SOFC) and a micro gas turbine was considered for optimization. The hybrid plant represents a sustainable and efficient alternative to conventional decentralized...

  2. Possibilities and consequences of the Total Cumulative Exergy Loss method in improving the sustainability of power generation

    NARCIS (Netherlands)

    Stougie, L.; van der Kooi, H.J.

    2016-01-01

    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

  3. Sustainability assessment of power generation in combination with lng evaporation : A comparison of lca methods and exergy analysis

    NARCIS (Netherlands)

    Stougie, L.; Van der Kooi, H.J.

    2013-01-01

    Several options exist for power generation, but it is difficult to determine which option is the most sustainable. When assessing the sustainability of an option or system, it is important to consider the environmental, economic and social aspects of sustainability and to take a life-cycle point of

  4. Exergy analysis of heat exchangers in the copper-chlorine thermochemical cycle to enhance thermal effectiveness and cycle efficiency

    National Research Council Canada - National Science Library

    Orhan, Mehmet F; Dincer, Ibrahim; Rosen, Marc A

    2011-01-01

    .... For this temperature level, the copper-chlorine (Cu-Cl) cycle is one of the most promising cycles that can be integrated with nuclear reactors for hydrogen production by decomposing water into its constituents...

  5. Taguchi Method for Investigating the Performance Parameters and Exergy of a Diesel Engine Using Four Types of Diesel Fuels

    Directory of Open Access Journals (Sweden)

    Dara K. Khidir

    2016-05-01

    Full Text Available The effects of changes in engine operating parameters, i.e., engine speed, throttle and water temperature, for four types of diesel fuel (A, B, C and D of different specific gravities, as supplied from local market and refineries, were studied and simultaneously optimized. The experiment design was based on Taguchi’s “L' 16” orthogonal table, and the engine was put to test at different engine speeds, throttling opening percentages and water temperatures, using different fuels. The data were analyzed using S/N (signal to noise ratio for each factor. The obtained results show that the optimum operating conditions for minimum BSFC (brake specific fuel consumption are achieved when the engine speed is 2500 rpm, the throttle is placed at 75% of full throttling, the water temperature is 80 oC and the engine is using fuel type D. Also, results of S/N ratio reveal that the throttle has significant influence on brake thermal and exergic efficiencies. Water temperature is the second most effective factor and then comes the influence of engine speed. The least effective factor among the studied parameters for the types of fuel considered in this experiment is the fuel type.

  6. Exergy analysis of integrated photovoltaic thermal solar water heater under constant flow rate and constant collection temperature modes

    NARCIS (Netherlands)

    Tiwari, A.; Dubey, Swapnil; Sandhu, G.S.; Sodha, M.S.; Anwar, S.I.

    2009-01-01

    In this communication, an analytical expression for the water temperature of an integrated photovoltaic thermal solar (IPVTS) water heater under constant flow rate hot water withdrawal has been obtained. Analysis is based on basic energy balance for hybrid flat plate collector and storage tank,

  7. Thermodynamic optimisation of a heat exchanger

    NARCIS (Netherlands)

    Cornelissen, Rene; Hirs, Gerard

    1999-01-01

    The objective of this paper is to show that for the optimal design of an energy system, where there is a trade-off between exergy saving during operation and exergy use during construction of the energy system, exergy analysis and life cycle analysis should be combined. An exergy optimisation of a

  8. National Energy Security and Reliance on Foreign Oil

    Science.gov (United States)

    2009-02-12

    st session, 19 December 2007). Exergy Flow Chart. http://gcep.stanford.edu/pdfs/GCEP_Exergy_Poster_web.pdf (accessed 8 November 2008). Geis...369. http://en.wikipedia.org/wiki/Solar_power. 20 Exergy Flow Chart. http://gcep.stanford.edu/pdfs/GCEP_Exergy_Poster_web.pdf. 21 Travis Bradford

  9. Methods to Optimize for Energy Efficiency

    Science.gov (United States)

    2011-05-01

    Prototype Representation & Design Exploration Methods 7 EXERGY -BASED METHODS Feature Presentation Historically: • Energy always an implicit...thermal components Exergy -Based Design Methods: Specify all vehicle design requirements as work potential ( exergy destruction, entropy...PS, ECS, and AFS-A Optimal Vehicles Predicted for Four Optimization Metrics Traditional: • Minimize Gross Takeoff Weight Exergy Methods

  10. THERMOECONOMIC ANALYSIS AND OPTIMIZATION OF GAS TURBINE POWER PLANT

    OpenAIRE

    Siahaya, Yusuf

    2009-01-01

    A gas turbine power plant, which will be located in Jakarta, will analyzed with the aid of exergy, exergoeconomics and optimization. An exergy analysis identifies the real thermodynacs inefficiency due to irreversibility destroyed within a gas turbine power plant system. An exergoeconomics or thermodynamic analysis consists of an exergy, an economic, an exergy costing, an exergoeconomic, and an exergoeconomic optimization aims at minimizing the thermodynamic inefficiencies (exergy...

  11. Energy and exergy analysis of chemical looping combustion technology and comparison with pre-combustion and oxy-fuel combustion technologies for CO2 capture

    OpenAIRE

    Mukherjee, Sanjay; Kumar, Prashant; Yang, Aidong; Fennell, Paul

    2015-01-01

    Abstract Carbon dioxide (CO2) emitted from conventional coal-based power plants is a growing concern for the environment. Chemical looping combustion (CLC), pre-combustion and oxy-fuel combustion are promising CO2 capture technologies which allow clean electricity generation from coal in an integrated gasification combined cycle (IGCC) power plant. This work compares the characteristics of the above three capture technologies to those of a conventional IGCC plant without CO2 capture. CLC tech...

  12. Application of exergy balances for the analysis of an oil plant; Aplicacion de balances de exergia para el analisis de una planta de petroleo

    Energy Technology Data Exchange (ETDEWEB)

    Rodriguez Toral, Miguel Angel; Rangel Davalos, Humberto [Instituto Mexicano del Petroleo (Mexico)

    1996-07-01

    The Mexican oil industry requires of the technological modernization, for this purpose it is planning the optimization of its operations of primary production, among which it stands out the separation and the stabilization. These operations take place in an oil complex which has been planned to be installed in the Mexican Southeastern. This paper shows some of the advances in the installation of the complex of separation, compression and stabilization of crude oil, which was analyzed at the light of the concepts of energy saving and of the second law of thermodynamics. [Spanish] La industria petrolera mexicana requiere de modernizacion tecnologica, para ello se esta planeando la optimizacion de sus operaciones de produccion primaria, entre las que destaca la separacion y estabilizacion. Dichas operaciones se efectuan en un complejo petrolero, mismo que se tiene planeado instalar en el sureste mexicano. Este trabajo muestra algunos de los avances en la instalacion del complejo de separacion, compresion y estabilizacion de petroleo crudo, el cual se analizo a la luz de los conceptos de ahorro de energia y de la segunda ley de la termodinamica.

  13. Solar Equivalences of the Earth’s Primary Exergy inflows and the Theoretical Basis for Secondary and Tertiary Emergy Flows of the Geobiosphere: New Calculations of Transformities

    Science.gov (United States)

    Brown et al. (2016) published a synthesis paper in which evidence was presented supporting a new value of the Earth’s geobiosphere baseline, 12.0E+24 seJ/y (solar equivalent joules per year) from which the emergy of all the Earth’s products and processes can be calcul...

  14. Exergy-based ecological performance of an irreversible Otto cycle with temperature-linear-relation variable specific heat of working fluid

    Science.gov (United States)

    Ge, Yanlin; Chen, Lingen; Qin, Xiaoyong; Xie, Zhihui

    2017-05-01

    Considering internal irreversibility loss (IIL), friction loss (FL) and heat transfer loss (HTL), an irreversible Otto cycle (IOC) model is built up by using air standard (AS) assumption. Based on finite-time thermodynamics (FTT), computing entropy generation rate (EGR) by using the irreversible losses in the cycle, the ecological function (EF) performance of the cycle is optimized when the specific heat (SH) of the working fluid (WF) varies with temperature with linear relation. Some important expressions, including efficiency, power output, EGR and EF, are obtained. Moreover, the effects of variable SH of WF and three losses on cycle performance are investigated. The research conclusion can provide some guidelines for the actual Otto cycle engine performance optimization.

  15. Energy, Exergy and Economic Evaluation Comparison of Small-Scale Single and Dual Pressure Organic Rankine Cycles Integrated with Low-Grade Heat Sources

    Directory of Open Access Journals (Sweden)

    Armando Fontalvo

    2017-09-01

    Full Text Available Low-grade heat sources such as solar thermal, geothermal, exhaust gases and industrial waste heat are suitable alternatives for power generation which can be exploited by means of small-scale Organic Rankine Cycle (ORC. This paper combines thermodynamic optimization and economic analysis to assess the performance of single and dual pressure ORC operating with different organic fluids and targeting small-scale applications. Maximum power output is lower than 45 KW while the temperature of the heat source varies in the range 100–200 °C. The studied working fluids, namely R1234yf, R1234ze(E and R1234ze(Z, are selected based on environmental, safety and thermal performance criteria. Levelized Cost of Electricity (LCOE and Specific Investment Cost (SIC for two operation conditions are presented: maximum power output and maximum thermal efficiency. Results showed that R1234ze(Z achieves the highest net power output (up to 44 kW when net power output is optimized. Regenerative ORC achieves the highest performance when thermal efficiency is optimized (up to 18%. Simple ORC is the most cost-effective among the studied cycle configurations, requiring a selling price of energy of 0.3 USD/kWh to obtain a payback period of 8 years. According to SIC results, the working fluid R1234ze(Z exhibits great potential for simple ORC when compared to conventional R245fa.

  16. 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

    Based on a nonlinear mathematical programming model, the sizes and operating conditions of the process units of single-effect absorption refrigeration systems operating with a LiBr–H2O solution are optimized for a specified cooling capacity by minimizing three single objective functions: the tota...

  17. Fuel cell electric vehicle as a power plant and SOFC as a natural gas reformer : An exergy analysis of different system designs

    NARCIS (Netherlands)

    Fernandes, A.A.; Woudstra, T.; van Wijk, A.J.M.; Verhoef, L.A.; Purushothaman Vellayani, A.

    2016-01-01

    Delft University of Technology, under its "Green Village" programme, has an initiative to build a power plant (car parking lot) based on the fuel cells used in vehicles for motive power. It is a trigeneration system capable of producing electricity, heat, and hydrogen. It comprises three main

  18. Analyzing Carbohydrate-Based Regenerative Fuel Cells as a Power Source for Unmanned Aerial Vehicles

    Science.gov (United States)

    2008-03-01

    have 24 hours of daylight, this means that it must be able to store enough exergy (the total amount of energy that can theoretically be converted to...useful work, differentiated from useful energy by the efficiency of converting energy to work) to function during the time when exergy consumption is...greater than exergy collection. For example, if we assume that the aircraft begins operations at a given time, it must produce enough excess exergy during

  19. Exergetic efficiency optimization for an irreversible heat pump ...

    Indian Academy of Sciences (India)

    temperature heat reservoirs by taking exergetic efficiency as the optimization objective combining exergy concept with finite-time thermodynamics (FTT). Exergetic efficiency is defined as the ratio of rate of exergy output to rate of exergy input of the system ...

  20. Exergetic optimisation of a heat exchanger, Engergy Conversion and Management

    NARCIS (Netherlands)

    Cornelissen, Rene; Hirs, Gerard

    1997-01-01

    Abstract The objective of this paper is to show that for the optimal design of an energy system, where there is a trade-off between exergy saving during operation and exergy use during construction of the energy system, exergy analysis and life cycle analysis should be combined. The two methods are

  1. An Investigation of Certain Thermodynamic Loses in Miniature Cryocoolers

    Science.gov (United States)

    2006-03-06

    looking at the loss of exergy in terms of entropy creation. The Gouy-Stodola (ref. 7) theorem states that the loss of exergy and hence work dissipated is...the Gouy-Stodola theorem (ref. 7) already referred to above. This states that the loss of exergy and hence lost work associated with any entropy

  2. Numerical Investigation of Second-Law Characteristics of Ramjet Throttling

    Science.gov (United States)

    2012-01-01

    subsystems across an aircraft. This common loss metric is provided by analyzing exergy destruction or entropy generation [4] [5] ; exergy destruction...25 th International Congress of the Aeronautical Sciences, 2006. [6] Marley, C., and Riggins, D., “The Thermodynamics of Exergy Losses and

  3. EXERGETIC MODELLING OF RGETIC MODELLING OF OIL ...

    African Journals Online (AJOL)

    eobe

    Steam boilers are widely applied for process heating, sterilization, drying, material conditioning and ... Exergy is destroyed whenever an irreversible process takes place. Exergy destruction is a measure of the ..... between the energy and exergy efficiencies of an adiabatic combustion unit of a steam boiler can be expressed ...

  4. Feasibility Study Of Maisotsenko Indirect Evaporative Air Cooling Cycle In Iran

    Directory of Open Access Journals (Sweden)

    Rezaee Vahid

    2015-06-01

    Full Text Available This paper presents energy and exergy analysis of air cooling cycle based on novel Maisotsenko indirect evaporative cooling cycle. Maisotsenko cycle (M-cycle provides desired cooling condition above the dew point and below the wet bulb temperature. In this study, based on average annual temperature, The Iran area is segmented into eleven climates. In energy analysis, wet-bulb and dew point effectiveness, cooling capacity rate and in exergy analysis, exergy input rate, exergy destruction rate, exergy loss, exergy efficiency, exergetic COP and entropy generation rate for Iran's weather conditions in the indicated climates are calculated. Moreover, a feasibility study based on water evaporation rate and Maisotsenko cycle was presented. Energy and exergy analysis results show that the fifth, sixth, seventh and eighth climates are quite compatible and Rasht, Sari, Ramsar and Ardabile cities are irreconcilable with the Maisotsenko cycle.

  5. Strategic Art and Energy: An Alternative Ends-Ways-Means View

    Science.gov (United States)

    2007-05-09

    the earth, but it is very diffuse and disorganized, and is therefore difficult to concentrate and use. The concept of exergy speaks directly to this...need for assessing the quality of the energy being used. Exergy is the part of an energy stream that can be converted into other forms of energy...and is therefore highly usable.11 Thermal energy has low exergy (i.e., the potential to convert energy into useful work), making it a poor candidate

  6. Soldier System Power Sources

    Science.gov (United States)

    2006-12-31

    Powered Battery Chargers 17 Exergy minimization 19 Use of secondary cells as temporary energy repositories 19 Design an automatic energy optimization...mission based on likely equipment use scenarios. The fourth was exergy minimization analysis that can be used to identify specific schemes for energy...34 Exergy minimization " An intelligent scheduling of the use of specific batteries in specific equipment was designed. "o Energy reclamation from

  7. The Scaling of Performance and Losses in Miniature Internal Combustion Engines

    Science.gov (United States)

    2010-01-01

    course of the interaction of the system with the environment is also defined as exergy . In the case of reciprocating engines, these irreversible...fuel and air, throttling of intake air are some of the engine processes that contribute to the destruction of availability and result in exergy ... Exergy is quantified by performing a second–law analysis and has been widely applied to internal combustion engines. 136 137 A second law analysis of

  8. Effect of Accessory Power Take-off Variation on a Turbofan Engine Performance

    Science.gov (United States)

    2012-09-26

    Figure ‎II.7. Effect of 0 to 7500 kW Exergy off-take in the form of bleed air or electrical energy, on the thrust and specific fuel consumption... exergy : mf = 0.35 lbm/s, Mach = 0.8, Alt = 35 kft on standard day...93 Figure C.2. TSFC versus exergy : mf = 0.35 lbm/s, Mach = 0.8, Alt = 35 kft on standard day

  9. Efficiency assessment of an integrated gasifier/boiler system for hydrogen production with different biomass types

    Energy Technology Data Exchange (ETDEWEB)

    Kalinci, Yildiz [Department of Technical Programs, Izmir Vocational High School, Dokuz Eylul University, Education Campus Buca, Izmir (Turkey); Hepbasli, Arif [Department of Mechanical Engineering, Faculty of Engineering, Ege University, 35100 Izmir (Turkey); Dincer, Ibrahim [Faculty of Engineering and Applied Science, University of Ontario Institute of Technology, 2000 Simcoe Street North, Oshawa, Ontario (Canada)

    2010-05-15

    In this study, we utilize some experimental data taken from the literature, especially on the air-blown gasification characteristics of six different biomass fuels, namely almond shell (ASF), walnut pruning (WPF), rice straw (RSF), whole tree wood chips (WWF), sludge (SLF) and non-recyclable waste paper (NPF) in order to study the thermodynamic performance of an integrated gasifier-boiler power system for its hydrogen production. In this regard, both energy and exergy efficiencies of the system are investigated. The exergy contents of different biomass fuels are calculated to be ranging from 15.89 to 22.07 MJ/kg, respectively. The hydrogen concentrations based on the stack gases at the cyclone exit are determined to be between 7 and 18 (%v/v) for NPF and ASF. Also, percentages of combustible vary from 30% to 46%. The stack gas has physical and chemical exergies. The total specific exergy rates are calculated and illustrated. These values change from 3.54 to 6.41 MJ/kg. Then, two types of exergy efficiencies are calculated, such as that exergy efficiency 1 is examined via all system powers, exergy and efficiency 2 is calculated according to specific exergy rates of biomass fuels and product gases. While the exergy efficiencies 1 change between 4.33% and 11.89%, exergy efficiencies 2 vary from 18.33% to 39.64%. Also, irreversibilities range from 9.76 to 18.02 MJ/kg. Finally, we investigate how nitrogen contents of biomass fuels affect on energy and exergy efficiencies. The SLF has the highest amount of nitrogen content as 5.64% db while the NPF has the lowest one as 0.14% db. The minimum and maximum exergetic efficiencies belong to the same fuels. Obviously, the higher the nitrogen content the lower the efficiency based on an inverse ratio between exergy efficiency and nitrogen content. (author)

  10. Thermodynamical analysis of human thermal comfort

    OpenAIRE

    Prek, Matjaž

    2015-01-01

    Traditional methods of human thermal comfort analysis are based on the first law of thermodynamics. These methods use an energy balance of the human body to determine heat transfer between the body and its environment. By contrast, the second law of thermodynamics introduces the useful concept of exergy. It enables the determination of the exergy consumption within the human body dependent on human and environmental factors. Human body exergy consumption varies with the combination of environ...

  11. The use of enzymes for beer brewing

    OpenAIRE

    Donkelaar, van, Laura H.G.; Mostert, Joost; Zisopoulos, Filippos K.; Boom, Remko M.; Goot, van der, Atze Jan

    2016-01-01

    The exergetic performance of beer produced by the conventional malting and brewing process is compared with that of beer produced using an enzyme-assisted process. The aim is to estimate if the use of an exogenous enzyme formulation reduces the environmental impact of the overall brewing process. The exergy efficiency of malting was 77%. The main exergy losses stem from the use of natural gas for kilning and from starch loss during germination. The exergy efficiency of the enzyme production p...

  12. Second law analysis of a conventional steam power plant

    Science.gov (United States)

    Liu, Geng; Turner, Robert H.; Cengel, Yunus A.

    1993-01-01

    A numerical investigation of exergy destroyed by operation of a conventional steam power plant is computed via an exergy cascade. An order of magnitude analysis shows that exergy destruction is dominated by combustion and heat transfer across temperature differences inside the boiler, and conversion of energy entering the turbine/generator sets from thermal to electrical. Combustion and heat transfer inside the boiler accounts for 53.83 percent of the total exergy destruction. Converting thermal energy into electrical energy is responsible for 41.34 percent of the total exergy destruction. Heat transfer across the condenser accounts for 2.89 percent of the total exergy destruction. Fluid flow with friction is responsible for 0.50 percent of the total exergy destruction. The boiler feed pump turbine accounts for 0.25 percent of the total exergy destruction. Fluid flow mixing is responsible for 0.23 percent of the total exergy destruction. Other equipment including gland steam condenser, drain cooler, deaerator and heat exchangers are, in the aggregate, responsible for less than one percent of the total exergy destruction. An energy analysis is also given for comparison of exergy cascade to energy cascade. Efficiencies based on both the first law and second law of thermodynamics are calculated for a number of components and for the plant. The results show that high first law efficiency does not mean high second law efficiency. Therefore, the second law analysis has been proven to be a more powerful tool in pinpointing real losses. The procedure used to determine total exergy destruction and second law efficiency can be used in a conceptual design and parametric study to evaluate the performance of other steam power plants and other thermal systems.

  13. Air Force Academy Aeronautics Digest - Fall/Winter 1981.

    Science.gov (United States)

    1982-06-01

    guarantees that it is conserved. ENEMY WILL COINISERVEO NAIDML LAW EMY I CONSERVED ENERGY = EXERGY + ANERGY Figure 12. An Issue Clarified in Aeronautics 312...Europ3 that is clarified by terms which will probably be creeping into our textbooks in the next few years. That is, energy is the sum of exergy and...anergy. What we want to conserve is exergy . Exergy is that portion of energy that is available to do work. When you turn off a light switch you are r~ally

  14. Modelling and analysis of offshore energy systems on North Sea oil and gas platforms

    DEFF Research Database (Denmark)

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

    2012-01-01

    export, and power generation. In this paper, a generic model of a North Sea oil and gas platform is described and the most thermodynamically inefficient processes are identified by performing an exergy analysis. Models and simulations are built and run with the tools Aspen Plus R, DNA and Aspen HYSYS R....... Results reveal that the total exergy destruction of the system is particularly sensitive to the gas-to-oil ratio and amounts to 55-65 MW, while the total exergy losses amount to 15-20 MW. The gas compression train and the production manifold module are the most exergy-destructive operations of the oil...

  15. Thermoeconomic and thermoenvironomic modeling and analysis of selected gas turbine power plants in Nigeria

    National Research Council Canada - National Science Library

    Oyedepo, Sunday O; Fagbenle, Richard O; Adefila, Samuel S; Alam, Md. Mahbub

    2015-01-01

    This study presents comprehensive thermoeconomic and thermoenvironomic modeling and analysis of selected gas turbine power plants in Nigeria using the first and second laws of thermodynamics (exergy) concept...

  16. Air Conditioning Systems from a 2nd Law Perspective

    Directory of Open Access Journals (Sweden)

    Luigi Marletta

    2010-04-01

    Full Text Available In this paper exergy analysis is used to assess the performance of the three most common air conditioning plant schemes: all-air, dual-duct and fan-coil systems. The results are presented in terms of flow diagrams to provide a clear picture of the exergy flow across the systems. The most relevant outcomes are that the air cooling and dehumidification is the process most responsible for the exergy loss and that the exergy efficiency of the overall systems is rather low; thus the quest for more appropriate technologies. Solar-assisted air-conditioning is also discussed, outlining the possibilities and the constraints.

  17. Does a small cost share reflect a negligible role for energy in economic production? Testing for aggregate production functions including capital, labor, and useful exergy through a cointegration-based method

    OpenAIRE

    Santos, João; Domingos, Tiago; Sousa, Tânia; St Aubyn, Miguel

    2017-01-01

    Trabajo presentado a Iberometrics VIII: Eight Iberian Cliometrics Workshop. Organizado por el Institute of Advanced Research in Business and Economics (INARBE) de la Universidad Pública de Navarra, en colaboración con Glocred y expertos de instituciones de España y Portugal. Celebrado en la Upna el 20-21 de abril de 2017. Neoclassical models disregard the role of energy in production, equating a factor's output elasticity with its cost share, but failing to explain growth without ...

  18. Heat exchange and heat exchangers. Systematics of construction - Series production - Tube oscillations - Economical optimization corresponding to manufacturing requirements due to exergy losses. Waermeaustausch und Waermeaustauscher. Konstruktionssystematik - Serienproduktion - Rohrschwingungen - Fertigungsgerechte wirtschaftliche Optimierung aufgrund von Exergieverlusten

    Energy Technology Data Exchange (ETDEWEB)

    Gregorig, R. (Technische Univ. Berlin (F.R. Germany). Fachbereich Verfahrenstechnik; Minas Gerais Univ., Belo Horizonte (Brazil). Escola de Engenharia)

    1973-01-01

    The author first gives a detailed description of the fundamental theories of heat exchange with special regard to the conditions for heat exchangers, followed by a systematic treatment of the constructional details, materials, and operation of heat exchangers. (DE)

  19. Thermodynamics of greenhouse systems for the northern latitudes: analysis, evaluation and prospects for primary energy saving.

    Science.gov (United States)

    Bronchart, Filip; De Paepe, Michel; Dewulf, Jo; Schrevens, Eddie; Demeyer, Peter

    2013-04-15

    In Flanders and the Netherlands greenhouse production systems produce economically important quantities of vegetables, fruit and ornamentals. Indoor environmental control has resulted in high primary energy use. Until now, the research on saving primary energy in greenhouse systems has been mainly based on analysis of energy balances. However, according to the thermodynamic theory, an analysis based on the concept of exergy (free energy) and energy can result in new insights and primary energy savings. Therefore in this paper, we analyse the exergy and energy of various processes, inputs and outputs of a general greenhouse system. Also a total system analysis is then performed by linking the exergy analysis with a dynamic greenhouse climate growth simulation model. The exergy analysis indicates that some processes ("Sources") lie at the origin of several other processes, both destroying the exergy of primary energy inputs. The exergy destruction of these Sources is caused primarily by heat and vapour loss. Their impact can be compensated by exergy input from heating, solar radiation, or both. If the exergy destruction of these Sources is reduced, the necessary compensation can also be reduced. This can be accomplished through insulating the greenhouse and making the building more airtight. Other necessary Sources, namely transpiration and loss of CO2, have a low exergy destruction compared to the other Sources. They are therefore the best candidate for "pump" technologies ("vapour heat pump" and "CO2 pump") designed to have a low primary energy use. The combination of these proposed technologies results in an exergy efficient greenhouse with the highest primary energy savings. It can be concluded that exergy analyses add additional information compared to only energy analyses and it supports the development of primary energy efficient greenhouse systems. Copyright © 2013 Elsevier Ltd. All rights reserved.

  20. Performance Evaluation of an Experimental Turbojet Engine

    Science.gov (United States)

    Ekici, Selcuk; Sohret, Yasin; Coban, Kahraman; Altuntas, Onder; Karakoc, T. Hikmet

    2017-11-01

    An exergy analysis is presented including design parameters and performance assessment, by identifying the losses and efficiency of a gas turbine engine. The aim of this paper is to determine the performance of a small turbojet engine with an exergetic analysis based on test data. Experimental data from testing was collected at full-load of small turbojet engine. The turbojet engine exhaust data contains CO2, CO, CH4, H2, H2O, NO, NO2, N2 and O2 with a relative humidity of 35 % for the ambient air of the performed experiments. The evaluated main components of the turbojet engine are the air compressor, the combustion chamber and the gas turbine. As a result of the thermodynamic analysis, exergy efficiencies (based on product/fuel) of the air compressor, the combustion chamber and the gas turbine are 81.57 %, 50.13 % and 97.81 %, respectively. A major proportion of the total exergy destruction was found for the combustion chamber at 167.33 kW. The exergy destruction rates are 8.20 %, 90.70 % and 1.08 % in the compressor, the combustion chamber and the gas turbine, respectively. The rates of exergy destruction within the system components are compared on the basis of the exergy rate of the fuel provided to the engine. Eventually, the exergy rate of the fuel is calculated to be 4.50 % of unusable due to exergy destruction within the compressor, 49.76 % unusable due to exergy destruction within the combustion chamber and 0.59 % unusable due to exergy destruction within the gas turbine. It can be stated that approximately 55 % of the exergy rate of the fuel provided to the engine can not be used by the engine.

  1. Exergetic analysis of breakfast cereal production in Nigeria ...

    African Journals Online (AJOL)

    The exergy analysis revealed that the roller dryer was responsible for most of the inefficiency (over 65.94%) followed by the wet mixer (27.40%). Suggestions for energy saving which will help in the reducing the high expenditure on energy and thus improve the profit margin were provided. Keywords : Energy, Exergy ...

  2. Exergetic comparison of food waste valorization in industrial bread production

    NARCIS (Netherlands)

    Zisopoulos, F.K.; Moejes, S.N.; Rossier Miranda, F.J.; Goot, van der A.J.; Boom, R.M.

    2015-01-01

    This study compares the thermodynamic performance of three industrial bread production chains: one that generates food waste, one that avoids food waste generation, and one that reworks food waste to produce new bread. The chemical exergy flows were found to be much larger than the physical exergy

  3. Advanced energy analysis of high temperature fuel cell systems

    NARCIS (Netherlands)

    Kouffeld, R.W.J.; Veringa, H.J.; De Groot, A.

    In this thesis the performance of high temperature fuel cell systems is studied using a new method of exergy analysis. The thesis consists of three parts: ⢠In the first part a new analysis method is developed, which not only considers the total exergy losses in a unit operation, but which

  4. Performance Analysis of Multipurpose Refrigeration System (MRS on Fishing Vessel

    Directory of Open Access Journals (Sweden)

    Ust Y.

    2016-04-01

    Full Text Available The use of efficient refrigerator/freezers helps considerably to reduce the amount of the emitted greenhouse gas. A two-circuit refrigerator-freezer cycle (RF reveals a higher energy saving potential than a conventional cycle with a single loop of serial evaporators, owing to pressure drop in each evaporator during refrigeration operation and low compression ratio. Therefore, several industrial applications and fish storage systems have been utilized by using multipurpose refrigeration cycle. That is why a theoretical performance analysis based on the exergetic performance coefficient, coefficient of performance (COP, exergy efficiency and exergy destruction ratio criteria, has been carried out for a multipurpose refrigeration system by using different refrigerants in serial and parallel operation conditions. The exergetic performance coefficient criterion is defined as the ratio of exergy output to the total exergy destruction rate (or loss rate of availability. According to the results of the study, the refrigerant R32 shows the best performance in terms of exergetic performance coefficient, COP, exergy efficiency, and exergy destruction ratio from among the other refrigerants (R1234yf, R1234ze, R404A, R407C, R410A, R143A and R502. The effects of the condenser, freezer-evaporator and refrigerator-evaporator temperatures on the exergetic performance coefficient, COP, exergy efficiency and exergy destruction ratios have been fully analyzed for the refrigerant R32.

  5. Evaluation de l'effectivite des machines frigorifiques a ammoniac a ...

    African Journals Online (AJOL)

    ... operating parameters significantly affect the efficiency of the refrigeration systems and their components. The analysis notes the degree of decrease in performance of these facilities per unit change its operating parameters. Keywords: Exergy, exergy analysis-single stage refrigeration system and dual stage, performance, ...

  6. Towards a Net Zero Building Cluster Energy Systems Analysis for US Army Installations

    Science.gov (United States)

    2011-05-01

    available technologies [2] related to the building envelope, ventilation, advanced “low exergy ” heating and cooling systems, central energy plants...built or retrofitted to “passive house” requirements and using advanced “low exergy ” systems to satisfy remaining heating and cooling needs. The

  7. Scramjet Fuel Injection Array Optimization Utilizing Mixed Variable Pattern Search With Kriging Surrogates

    Science.gov (United States)

    2008-03-01

    Experimental Attainment of Optimal Conditions,” Journal of the Royal Statistical Society, B(13): 1–38, 1951. 19. Brewer, K.M. Exergy Methods for the Mission... Exergy Methods for the Generic Analysis and Optimization of Hypersonic Vehicle Concepts. MS thesis. Virginia Polytechnic Institute and State

  8. Advanced energy analysis of high temperature fuel cell systems

    NARCIS (Netherlands)

    De Groot, A.

    2004-01-01

    In this thesis the performance of high temperature fuel cell systems is studied using a new method of exergy analysis. The thesis consists of three parts: ⢠In the first part a new analysis method is developed, which not only considers the total exergy losses in a unit operation, but which

  9. The development of the EXE-kas

    NARCIS (Netherlands)

    Bronchart, F.; Demeyer, P.; Linden, van der P.; Paepe, De M.; Vis, De R.; Wittemans, L.; Weel, Van P.A.; Cheret, E.; Malschaert, P.; Tassens, S.

    2017-01-01

    Different primary energy saving techniques for greenhouses have been tested in the past. Those systems were designed by using the first law. However, no attention was paid to the exergy destruction in the processes (second law). This exergy destruction is related to the driving potential of the

  10. Exergetic analysis of an aircraft turbojet engine with an afterburner

    Directory of Open Access Journals (Sweden)

    Ehyaei M.A.

    2013-01-01

    Full Text Available An exergy analysis is reported of a J85-GE-21 turbojet engine and its components for two altitudes: sea level and 11,000 meters. The turbojet engine with afterburning operates on the Brayton cycle and includes six main parts: diffuser, compressor, combustion chamber, turbine, afterburner and nozzle. Aircraft data are utilized in the analysis with simulation data. The highest component exergy efficiency at sea level is observed to be for the compressor, at 96.7%, followed by the nozzle and turbine with exergy efficiencies of 93.7 and 92.3%, respectively. At both considered heights, reducing of engine intake air speed leads to a reduction in the exergy efficiencies of all engine components and overall engine. The exergy efficiency of the turbojet engine is found to decrease by 0.45% for every 1°C increase in inlet air temperature.

  11. Eco-efficiency and control loop configuration for recycle systems

    Energy Technology Data Exchange (ETDEWEB)

    Munir, Muhammad Tajammal; Yu, Wei; Young, Brent P. [The University of Auckland, Auckland (New Zealand)

    2013-05-15

    To integrate measurements of eco-efficiency with control loop configuration has become an important topic since all industrial processes/plants are requested to increase their eco-efficiency. The exergy eco-efficiency factor, a new measure of eco-efficiency for control loop configuration, has been developed recently. The exergy eco-efficiency factor is based on the thermodynamic concept of exergy, which can be used to analyze a process in terms of its efficiency. The combination of the relative gain array (RGA), NI, CN, dynamic RGA, and the exergy eco-efficiency factor will help guide the process designer to find the optimal control design with low operating cost/eco-efficiency. In this paper, we validate the proposed exergy eco-efficiency factor for processes with recycles which are very common industrially.

  12. Determination of optimum pipe diameter along with energetic and exergetic evaluation of geothermal district heating systems. Modeling and application

    Energy Technology Data Exchange (ETDEWEB)

    Kalinci, Yildiz [Plumbing Technology, Department of Technical Programs, Izmir Vocational School, Dokuz Eyluel University, Education Campus Buca, Izmir (Turkey); Hepbasli, Arif [Department of Mechanical Engineering, Faculty of Engineering, Ege University, 35100 Bornova, Izmir (Turkey); Tavman, Ismail [Department of Mechanical Engineering, Faculty of Engineering, Dokuz Eyluel University, 35100 Bornova, Izmir (Turkey)

    2008-07-01

    This study deals with determination of optimum pipe diameters based on economic analysis and the performance analysis of geothermal district heating systems along with pipelines using energy and exergy analysis methods. In this regard, the Dikili geothermal district heating system (DGDHS) in Izmir, Turkey is taken as an application place, to which the methods presented here are applied with some assumptions. The system mainly consists of three cycles, namely (1) the transportation network, (2) the Danistay region, and (3) the Bariskent region. The thermal capacities of these regions are 21,025 and 7975 kW, respectively, while the supply (flow) and return temperature values of those are 80 and 50 C, respectively. Based upon the assessment of the transportation network using the optimum diameter analysis method, minimum cost is calculated to be US$ 561856.906 year{sup -1} for a nominal diameter of DN 300. The exergy destructions in the overall DGDHS are quantified and illustrated using exergy flow diagram. Furthermore, both energy and exergy flow diagrams are exhibited for comparison purposes. It is observed through analysis that the exergy destructions in the system particularly take place due to the exergy of the thermal water (geothermal fluid) reinjected, the heat exchanger losses, and all pumps losses, accounting for 38.77%, 10.34%, 0.76% of the total exergy input to the DGDHS. Exergy losses are also found to be 201.12817 kW and 1.94% of the total exergy input to the DGDHS for the distribution network. For the system performance analysis and improvement, both energy and exergy efficiencies of the overall DGDHS are investigated, while they are determined to be 40.21% and 50.12%, respectively. (author)

  13. Thermodynamic Optimization of a Geothermal- Based Organic Rankine Cycle System Using an Artificial Bee Colony Algorithm

    Directory of Open Access Journals (Sweden)

    Osman Özkaraca

    2017-10-01

    Full Text Available Geothermal energy is a renewable form of energy, however due to misuse, processing and management issues, it is necessary to use the resource more efficiently. To increase energy efficiency, energy systems engineers carry out careful energy control studies and offer alternative solutions. With this aim, this study was conducted to improve the performance of a real operating air-cooled organic Rankine cycle binary geothermal power plant (GPP and its components in the aspects of thermodynamic modeling, exergy analysis and optimization processes. In-depth information is obtained about the exergy (maximum work a system can make, exergy losses and destruction at the power plant and its components. Thus the performance of the power plant may be predicted with reasonable accuracy and better understanding is gained for the physical process to be used in improving the performance of the power plant. The results of the exergy analysis show that total exergy production rate and exergy efficiency of the GPP are 21 MW and 14.52%, respectively, after removing parasitic loads. The highest amount of exergy destruction occurs, respectively, in condenser 2, vaporizer HH2, condenser 1, pumps 1 and 2 as components requiring priority performance improvement. To maximize the system exergy efficiency, the artificial bee colony (ABC is applied to the model that simulates the actual GPP. Under all the optimization conditions, the maximum exergy efficiency for the GPP and its components is obtained. Two of these conditions such as Case 4 related to the turbine and Case 12 related to the condenser have the best performance. As a result, the ABC optimization method provides better quality information than exergy analysis. Based on the guidance of this study, the performance of power plants based on geothermal energy and other energy resources may be improved.

  14. COMPARATIVE ANALYSIS OF EXERGETIC BALANCE METHODS IN ALCOHOLIC DISTILLATION COLUMNS

    Directory of Open Access Journals (Sweden)

    Arletis Cruz Llerena

    2017-04-01

    Full Text Available The comparison between three methods to calculate the exergy of the currents involved in the exergetic balance of alcoholic distillation columns is presented. Exergy of the currents was considered as: 1 flow exergies, 2 heat exergies and 3 the sum of flow exergy and chemical exergy. The implementation of the exergetic analysis was examined as a key point to improve the efficiency of the process. A case study, where the methods are applied for the evaluation of the exergy is analyzed; differences among the methods were obtained between the 15% and 30 %. The influence of the studied columns in total work capacity loss was determined, concluding that regardless of the method, the distillation column has shown the higher loss. An economic analysis was made applying the first method to the case study, where the percentage of ethanol in wine increases from 5.8 ºGL to 9 ºGL, which led to a decrease of vapor consumption of 23.66%, an exergetic yield increase of 28.02 % and a combustion gas flow reduction of 24 627 034.4 m3/year.

  15. Thermodynamic analysis of fluidized bed drying of carrot cubes

    Energy Technology Data Exchange (ETDEWEB)

    Nazghelichi, Tayyeb; Kianmehr, Mohammad Hossein; Aghbashlo, Mortaza [Department of Agrotechnology, College of Abouraihan, University of Tehran, P.O. Box 33955-159, Pakdasht (Iran, Islamic Republic of)

    2010-12-15

    In this study, the energy and exergy analyses of fluidized bed drying of carrot cubes were investigated. Drying experiments were conducted at inlet air temperatures of 50, 60, and 70 C, BD (bed depths) of 30, 60, and 90 mm and square-cubed carrot dimensions of 4, 7, and 10 mm. The effects of drying variables on energy utilization, energy utilization ratio, exergy loss and exergy efficiency were studied. The energy utilization and energy utilization ratio varied between 0.105-1.949 kJ/s and 0.074-0.486, respectively. The exergy loss and exergy efficiency were found to be in the range of 0.206-1.612 kJ/s and 0.103-0.707, respectively. The results showed that small particles, deep beds and high inlet air temperatures increased energy utilization, energy utilization ratio, and exergy loss due to high value of heat and mass transfer. Also, the exergy efficiency had maximum value when higher drying air temperature, larger CS (cube size) and shorter BD were used for drying experiment. (author)

  16. Comparison Based on Exergetic Analyses of Two Hot Air Engines: A Gamma Type Stirling Engine and an Open Joule Cycle Ericsson Engine

    Directory of Open Access Journals (Sweden)

    Houda Hachem

    2015-10-01

    Full Text Available In this paper, a comparison of exergetic models between two hot air engines (a Gamma type Stirling prototype having a maximum output mechanical power of 500 W and an Ericsson hot air engine with a maximum power of 300 W is made. Referring to previous energetic analyses, exergetic models are set up in order to quantify the exergy destruction and efficiencies in each type of engine. The repartition of the exergy fluxes in each part of the two engines are determined and represented in Sankey diagrams, using dimensionless exergy fluxes. The results show a similar proportion in both engines of destroyed exergy compared to the exergy flux from the hot source. The compression cylinders generate the highest exergy destruction, whereas the expansion cylinders generate the lowest one. The regenerator of the Stirling engine increases the exergy resource at the inlet of the expansion cylinder, which might be also set up in the Ericsson engine, using a preheater between the exhaust air and the compressed air transferred to the hot heat exchanger.

  17. The use of exergetic indicators in the food industry - A review.

    Science.gov (United States)

    Zisopoulos, Filippos K; Rossier-Miranda, Francisco J; van der Goot, Atze Jan; Boom, Remko M

    2017-01-02

    Assessment of sustainability will become more relevant for the food industry in the years to come. Analysis based on exergy, including the use of exergetic indicators and Grassmann diagrams, is a useful tool for the quantitative and qualitative assessment of the efficiency of industrial food chains. In this paper, we review the methodology of exergy analysis and the exergetic indicators that are most appropriate for use in the food industry. The challenges of applying exergy analysis in industrial food chains and the specific features of food processes are also discussed.

  18. Towards a Net Zero Building Cluster Energy Systems Analysis for a Brigade Combat Team Complex

    Science.gov (United States)

    2010-05-01

    building enve- lope, ventilation, advanced “low exergy ” heating and cooling systems, central energy plants with co- This material is declared a work of the...from the mains increases from centralized to decentralized by 21% or 4.3 GWh/yr. The fact that heat is a local commodity with a lower exergy factor...and electricity is a non-local commod- ity with an exergy factor of 1 that cannot be stored easily like heat, indicates that this is a good path to

  19. Thermodynamics extends economics potentials

    Energy Technology Data Exchange (ETDEWEB)

    Bandura, Alexander V. [Kiev Technical Univ., Dept. of Marketing and Management, Kiev (Ukraine); Brodiansky, Victor M. [Moscow Energy Inst., Dept. of Cryogen Machines, Moscow (Russian Federation)

    2001-08-01

    In this paper we consider the use of exergy in economic valuation and its correlation with money. Exergy-based determination of production expenses provides a new base for 'natural' price determination. A new macroeconomic dynamics approach based on this correlation is proposed. This method is relatively general because it is not restricted by certain assumptions used in traditional economic analysis. The exergy model of macroeconomic dynamics was tested by utilizing data from the US economy. This test, covering a period of about 25 years, confirms this approach and opens new potentials in economic analysis. (Author)

  20. Thermodynamic Performance Indicators for Offshore Oil and Gas Processing: Application to Four North Sea Facilities

    DEFF Research Database (Denmark)

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

    2014-01-01

    achievable potential, they should evaluate the use of theoretical potential, and they should evaluate the total use of energy resources. The performance indicators are tested on four North Sea facilities, and the results are discussed. We recommend the use of a set of indicators for a thorough evaluation......Well-defined performance indicators can motivate optimal operation of offshore oil and gas platforms. We evaluate several thermodynamic performance indicators presented in the literature according to three criteria: Thermodynamic performance indicators should evaluate the use of technically...... of oil and gas platforms—the best-available-technology efficiency on an exergy basis, a task exergy efficiency, and the specific exergy destruction....

  1. Sustainability assessment of turbofan engine with mixed exhaust through exergetic approach

    Science.gov (United States)

    Saadon, S.; Redzuan, M. S. Mohd

    2017-12-01

    In this study, the theory, methods and example application are described for a CF6 high-bypass turbofan engine with mixed exhaust flow based on exergo-sustainable point of view. To determine exergetic sustainability index, the turbofan engine has to undergo detailed exergy analysis. The sustainability indicators reviewed here are the overall exergy efficiency of the system, waste exergy ratio, exergy destruction factor, environmental effect factor and the exergetic sustainability index. The results obtained for these parameters are 26.9%, 73.1%, 38.6%, 2.72 and 0.37, respectively, for the maximum take-off condition of the engine. These results would be useful to better understand the connection between the propulsion system parameters and their impact to the environment in order to make it more sustainable for future development.

  2. Exergetic analysis in petroleum primary separation plants; Analise exergetica em plantas de separacao primaria de petroleo

    Energy Technology Data Exchange (ETDEWEB)

    Ghiorzi, Telmo Machado

    1997-07-01

    This dissertation presents a method for evaluate the efficiency of primary petroleum separation plants off-shore, using the concept of exergy. This concept is presented as a thermodynamic property and one shows how to calculate its value. A bibliographic revision is done, as well as, the necessary adaptations and considerations foe exergy application on off-shore plants: It is presented a way to evaluate efficiency on plants which part of the products is used as the drive-force of the process and it is presented the exergy calculation for mixtures, through departure functions. This calculation deserves special attention due to Equilibrium-Liquid-Vapour behavior of the mixtures when brought to ambient conditions. Some hypothetical cases, carried out using the Process Simulator HYSIM, are analyzed. The conclusions and recommendations are related to design and operation of off-shore plants and perspectives to follow on the subject exergy and the petroleum industry. (author)

  3. Sustainability Metrics: The San Luis Basin Project

    Science.gov (United States)

    Sustainability is about promoting humanly desirable dynamic regimes of the environment. Metrics: ecological footprint, net regional product, exergy, emergy, and Fisher Information. Adaptive management: (1) metrics assess problem, (2) specific problem identified, and (3) managemen...

  4. Chemical Industry Bandwidth Study

    Energy Technology Data Exchange (ETDEWEB)

    none,

    2006-12-01

    The Chemical Bandwidth Study provides a snapshot of potentially recoverable energy losses during chemical manufacturing. The advantage of this study is the use of "exergy" analysis as a tool for pinpointing inefficiencies.

  5. Thermodynamic analyses of a biomass-coal co-gasification power generation system.

    Science.gov (United States)

    Yan, Linbo; Yue, Guangxi; He, Boshu

    2016-04-01

    A novel chemical looping power generation system is presented based on the biomass-coal co-gasification with steam. The effects of different key operation parameters including biomass mass fraction (Rb), steam to carbon mole ratio (Rsc), gasification temperature (Tg) and iron to fuel mole ratio (Rif) on the system performances like energy efficiency (ηe), total energy efficiency (ηte), exergy efficiency (ηex), total exergy efficiency (ηtex) and carbon capture rate (ηcc) are analyzed. A benchmark condition is set, under which ηte, ηtex and ηcc are found to be 39.9%, 37.6% and 96.0%, respectively. Furthermore, detailed energy Sankey diagram and exergy Grassmann diagram are drawn for the entire system operating under the benchmark condition. The energy and exergy efficiencies of the units composing the system are also predicted. Copyright © 2016 Elsevier Ltd. All rights reserved.

  6. Final Report: Evaluation of Alternative Technologies for Ethylene, Caustic-Chlorine, Ethylene Oxide, Ammonia, and Terephthalic Acid

    Energy Technology Data Exchange (ETDEWEB)

    none,

    2007-12-01

    This report evaluates alternative technologies for chemicals manufacturing which may present energy efficiency improvements compared to existing technologies. It is an extension of the Chemical Bandwidth Study, which evaluates energy and exergy losses in the U.S. chemicals industry.

  7. Thermodynamic evaluation of the Kalina split-cycle concepts for waste heat recovery applications

    DEFF Research Database (Denmark)

    Nguyen, Tuong-Van; Knudsen, Thomas; Larsen, Ulrik

    2014-01-01

    of varying boundary conditions by conducting an exergy analysis. The design parameters of each configuration were determined by performing a multi-variable optimisation. The results indicate that the Kalina split-cycle with reheat presents an exergetic efficiency by 2.8% points higher than a reference Kalina...... and condenser, and indicates a reduction of the exergy destruction by about 23% in the heat recovery system compared to the baseline cycle....

  8. Analisis Eksergi Pada Unit Distilasi Atmosferik Dan Vakum Minyak Bumi

    OpenAIRE

    Zikri, Ahmad

    2014-01-01

    The atmospheric and vacuum distillations are the first plant in a crude oil refinery, in which several intermediate product are obtained through distillation of the crude oil mixture. To increase the thermodynamic efficiency, we need to use both the temperature-enthalpy and exergy losses together. It is important to determine the exergy losses profiles and to analyze the distribution losses in all stage of distillation column. Aspen Plus software is used as assi...

  9. Non-Intrusive Second Law Performance Evaluation of a Domestic Freezer

    OpenAIRE

    McGovern, Jim; Oladunjoye, S.

    2015-01-01

    This paper describes non-intrusive performance testing and second law, exergy-based, performance evaluation of a small, contemporary domestic freezer that used R600a refrigerant. The methodology presented is associated with logging of temperatures and the instantaneous power consumption. It gives a ‘second law of thermodynamics’ perspective on operating performance by providing rational efficiency values and by localizing and quantifying the instantaneous exergy destruction rates. This approa...

  10. Limits and Optimization of Power Input or Output of Actual Thermal Cycles

    OpenAIRE

    Emin Açıkkalp; Hasan Yamık

    2013-01-01

    In classical thermodynamic, maximum power obtained from system (or minimum power supplied to system) defined as availability (exergy), but availability term is only used for reversible systems. In reality, there is no reversible system, all systems are irreversible, because reversible cycles doesn’t include constrains like time or size and they operates in quasi-equilibrium state. Purpose of this study is to define limits of the all basic thermodynamic cycles and to provide finite-time exergy...

  11. Assessing the Robustness of Thermoeconomic Diagnosis of Fouled Evaporators: Sensitivity Analysis of the Exergetic Performance of Direct Expansion Coils

    Directory of Open Access Journals (Sweden)

    Antonio Piacentino

    2016-03-01

    Full Text Available Thermoeconomic diagnosis of refrigeration systems is a pioneering approach to the diagnosis of malfunctions, which has been recently proven to achieve good performances for the detection of specific faults. Being an exergy-based diagnostic technique, its performance is influenced by the trends of exergy functions in the “design” and “abnormal” conditions. In this paper the sensitivity of performance of thermoeconomic diagnosis in detecting a fouled direct expansion coil and quantifying the additional consumption it induces is investigated; this fault is critical due to the simultaneous air cooling and dehumidification occurring in the coil, that induce variations in both the chemical and thermal fractions of air exergy. The examined parameters are the temperature and humidity of inlet air, the humidity of reference state and the sensible/latent heat ratio (varied by considering different coil depths. The exergy analysis reveals that due to the more intense dehumidification occurring in presence of fouling, the exergy efficiency of the evaporator coil eventually increases. Once the diagnostic technique is based only on the thermal fraction of air exergy, the results suggest that the performance of the technique increases when inlet air has a lower absolute humidity, as evident from the “optimal performance” regions identified on a psychrometric chart.

  12. Assessing global resource utilization efficiency in the industrial sector.

    Science.gov (United States)

    Rosen, Marc A

    2013-09-01

    Designing efficient energy systems, which also meet economic, environmental and other objectives and constraints, is a significant challenge. In a world with finite natural resources and large energy demands, it is important to understand not just actual efficiencies, but also limits to efficiency, as the latter identify margins for efficiency improvement. Energy analysis alone is inadequate, e.g., it yields energy efficiencies that do not provide limits to efficiency. To obtain meaningful and useful efficiencies for energy systems, and to clarify losses, exergy analysis is a beneficial and useful tool. Here, the global industrial sector and industries within it are assessed by using energy and exergy methods. The objective is to improve the understanding of the efficiency of global resource use in the industrial sector and, with this information, to facilitate the development, prioritization and ultimate implementation of rational improvement options. Global energy and exergy flow diagrams for the industrial sector are developed and overall efficiencies for the global industrial sector evaluated as 51% based on energy and 30% based on exergy. Consequently, exergy analysis indicates a less efficient picture of energy use in the global industrial sector than does energy analysis. A larger margin for improvement exists from an exergy perspective, compared to the overly optimistic margin indicated by energy. Copyright © 2012 Elsevier B.V. All rights reserved.

  13. A comparative study of biomass integrated gasification combined cycle power systems: Performance analysis.

    Science.gov (United States)

    Zang, Guiyan; Tejasvi, Sharma; Ratner, Albert; Lora, Electo Silva

    2018-02-02

    The Biomass Integrated Gasification Combined Cycle (BIGCC) power system is believed to potentially be a highly efficient way to utilize biomass to generate power. However, there is no comparative study of BIGCC systems that examines all the latest improvements for gasification agents, gas turbine combustion methods, and CO 2 Capture and Storage options. This study examines the impact of recent advancements on BIGCC performance through exergy analysis using Aspen Plus. Results show that the exergy efficiency of these systems is ranged from 22.3% to 37.1%. Furthermore, exergy analysis indicates that the gas turbine with external combustion has relatively high exergy efficiency, and Selexol CO 2 removal method has low exergy destruction. Moreover, the sensitivity analysis shows that the system exergy efficiency is more sensitive to the initial temperature and pressure ratio of the gas turbine, whereas has a relatively weak dependence on the initial temperature and initial pressure of the steam turbine. Copyright © 2018 Elsevier Ltd. All rights reserved.

  14. Refining of wood waste from saw mills - a feasibility study for Alex sawmill; Foeraedling av saagverkens biprodukter - en oevergripande energi- och exergistudie oever Alex saag

    Energy Technology Data Exchange (ETDEWEB)

    Kullendorff, A.; Ryden, A. [SEP Scandinavian Energy Project AB (Sweden); Renstroem, R. [Karlstad Univ. (Sweden)

    1998-03-01

    An overall energy balance has been made for the Alex sawmill, with separate balances for the boiler and the timber dryer. Parallel to this energy balance, an exergy study has been compiled for the same systems. A heat demand has been identified from these balances and three different systems has been studied. Two of these imply a refinement of the by-products produced in the mill. System I: Hot water boiler as the present system; System II: Hot water boiler integrated with a back pressure dryer; System IIb: Hot water boiler integrated with a back pressure dryer and a plant for pelletizing the biofuel; System III: Steam boiler followed by power production integrated with a back pressure dryer; and System IIIb: Steam boiler followed by power production integrated with a back pressure dryer and a plant for pelletizing the biofuel. The study shows that System II seems to be the most interesting system from an energy and economical point of view with an additional revenue of about 15 MSEK/year. The dryer for this system is a newly developed not yet commercial atmospheric back pressure dryer especially suited for saw mills and small district heating companies. Other types of dryers could also be considered. Other types have not been evaluated here. The exergy study shows that the back pressure dryer almost double the yield of exergy, compared to the present situation. In addition to this, one has to take the fictitious 'profit in exergy' from the following combustion into account. If a steam boiler is installed instead of the hot water boiler, and power generation is added, then the exergy conservation will be improved even more compared to the system with the back pressure dryer. From an exergy point of view a system with power generation and back pressure drying will give an exergy yield of more than four times of that of todays system.

  15. Plant-wide control: eco-efficiency and control loop configuration.

    Science.gov (United States)

    Munir, M T; Yu, W; Young, B R

    2013-01-01

    Since the eco-efficiency of all industrial processes/plants has become increasingly important, engineers need to find a way to integrate the control loop configuration and the measurements of eco-efficiency. A new measure of eco-efficiency, the exergy eco-efficiency factor, for control loop configuration, is proposed in this paper. The exergy eco-efficiency factor is based on the thermodynamic concept of exergy which can be used to analyse a process in terms of its efficiency associated with the control configuration. The combination of control pairing configuration techniques (such as the relative gain array, RGA and Niederlinski index, NI) and the proposed exergy eco-efficiency factor will guide the process designer to reach the optimal control design with low operational cost (i.e., energy consumption). The exergy eco-efficiency factor is implemented in the process simulation case study and the reliability of the proposed method is demonstrated by dynamic simulation results. Copyright © 2012 ISA. Published by Elsevier Ltd. All rights reserved.

  16. Thermodynamic Analyses of Biomass Gasification Integrated Externally Fired, Post-Firing and Dual-Fuel Combined Cycles

    Directory of Open Access Journals (Sweden)

    Saeed Soltani

    2015-01-01

    Full Text Available In the present work, the results are reported of the energy and exergy analyses of three biomass-related processes for electricity generation: the biomass gasification integrated externally fired combined cycle, the biomass gasification integrated dual-fuel combined cycle, and the biomass gasification integrated post-firing combined cycle. The energy efficiency for the biomass gasification integrated post-firing combined cycle is 3% to 6% points higher than for the other cycles. Although the efficiency of the externally fired biomass combined cycle is the lowest, it has an advantage in that it only uses biomass. The energy and exergy efficiencies are maximized for the three configurations at particular values of compressor pressure ratios, and increase with gas turbine inlet temperature. As pressure ratio increases, the mass of air per mass of steam decreases for the biomass gasification integrated post-firing combined cycle, but the pressure ratio has little influence on the ratio of mass of air per mass of steam for the other cycles. The gas turbine exergy efficiency is the highest for the three configurations. The combustion chamber for the dual-fuel cycle exhibits the highest exergy efficiency and that for the post-firing cycle the lowest. Another benefit of the biomass gasification integrated externally fired combined cycle is that it exhibits the highest air preheater and heat recovery steam generator exergy efficiencies.

  17. Experimental studies on the thermal performance of a parabolic dish solar receiver with the heat transfer fluids SiC + water nano fluid and water

    Science.gov (United States)

    Rajendran, D. R.; Sundaram, E. Ganapathy; Jawahar, P.

    2017-06-01

    An experimental investigation has been carried out with aa point focusing dish reflector of 12 square meters aperture area, exposed to the average direct normal irradiations of 810 W/m2. This work focuses on enhancinge the energy and exergy efficiencies of the cavity receiver by minimizing the temperature difference between the wall and heat transfer fluids. Two heat transfer fluids Water and SiC + water nano fluid have been prepared from 50 nm particle size and 1% of volume fraction, and experimented separately for the flow rates of 0.2 lpm to 0.6 lpm with an interval of 0.1 lpm. The enhanced thermal conductivity of nano fluid is 0.800115 W/mK with the keff /kb ratio of 1.1759 determined by using the Koo and Kleinstreuer correlation. The maximum attained energy and exergy efficiencies are 29.14% and 24.82% for water, and 32.91% and 39.83% for SiC+water nano fluid. The nano fluid exhibits enhanced energy and exergy efficiency of 12.94% and 60.48% than that of water at the flow rate of 0.5 lpm. The result shows that the system with SiC+Water produces higher exergy efficiency as compared to energy efficiency; in the case of water alone, the energy efficiency is higher than exergy efficiency.

  18. Investigation of environmental and exergetic performance for a coal-preparing unit in cement processes

    Energy Technology Data Exchange (ETDEWEB)

    Sodut, Ziya [Technical Sciences Department, Military Academy (Turkey)], email: mzsogut@yahoo.com; Oktay, Zuhal [Mech. Engineering Dept, Faculty of Engineering, Balikesir University (Turkey)], email: zoktay@yahoo.com; Hikmet Karakoc, T. [School of Civil Aviation, Anadolu University (Turkey)], email: hkarakoc@anadolu.edu.tr; Hepbasli, A. [Mechanical Engineering Department, Faculty of Engineering, Ege University (Turkey)], email: arif.hepbasli@ege.edu.tr

    2011-07-01

    In recent years there has been an exponential increase in the use of energy and other resources in the industrial world and this has led to a diminishing supply of natural resources and a rise in the extent of damage done to the natural environment. The cement sector is one of the most important in Turkey's economy. This study presents energy and exergy analyses of a coal preparation unit in a cement plant. The changes in the exergy efficiency based on the dead state temperatures, exergy consumption, improvement potentials and emission effects of this process are investigated. The energy and exergy efficiencies of the process were calculated to be 74.03% and 21.36% respectively. And the average improvement and average exergy consumption potential were found to be 78.64% and 21.36% respectively. It is evident that there is a significant level of inefficiency in such thermal processes and the results of this type of analysis can be applied to help reduce CO2 emissions and foster a sustainable environment.

  19. EXERGETIC ANALYSIS OF A COGENERATION POWER PLANT

    Directory of Open Access Journals (Sweden)

    Osvaldo Manuel Nuñez Bosch

    2016-07-01

    Full Text Available Cogeneration power plants connected to industrial processes have a direct impact on the overall efficiency of the plant and therefore on the economic results. Any modification to the thermal outline of these plants must first include an exergetic analysis to compare the benefits it can bring the new proposal. This research is performed to a cogeneration plant in operation with an installed electrical capacity of 24 MW and process heat demand of 190 MW, it shows a study made from the Second Law of Thermodynamics. Exergetic evaluation of each component of the plant was applied and similarly modified cogeneration scheme was evaluated. The results illustrate that the exergy losses and irreversibilities are completely different from one subsystem to another. In general, the total exergy destruction represented 70,7% from the primary fuel exergy. Steam generator was the subsystem with the highest irreversibility of the plant with 54%. It was demonstrated that the increase of the steam parameters lead to reduce exergy destruction and exergy efficiency elevation. The suppression of the reduction system and the adding of an extraction-condensing steam turbine produce the same effect and contribute to drop off the electrical consumption from the grid.

  20. Performance evaluation and optimization of fluidized bed boiler in ethanol plant using irreversibility analysis

    Directory of Open Access Journals (Sweden)

    Nugroho Agung Pambudi

    2017-09-01

    Full Text Available This research aims to evaluate the performance of a fluidized bed boiler in an ethanol production plant through exergy and irreversibility analysis. The study also includes the optimization of the pre-heater and the deaerator in order to improve the system efficiency. Operational data from the ethanol production plant was collected between 2015 and early 2016. The total exergy derived from the fuel was determined to be 7783 kJ/s, while the exergy efficiency of the system was found to be 26.19%, with 2214 kJ/s used in steam production, while 71.55% was lost to component irreversibility and waste heat from the pre-heater. The exergy efficiencies of individual components of the system such as the boiler, deaerator, and pre-heater were found to be 25.82%, 40.13%, and 2.617%, respectively, with the pre-heater having the lowest efficiency. Thus, the pre-heater has the highest potential to significantly improve the efficiency of the boiler system. The optimization of the pre-heater shows that a rise in temperature in the outlet of the pre-heater positively affects the exergy efficiency of the deaerator.

  1. Thermodynamics analysis of refinery sludge gasification in adiabatic updraft gasifier.

    Science.gov (United States)

    Ahmed, Reem; Sinnathambi, Chandra M; Eldmerdash, Usama; Subbarao, Duvvuri

    2014-01-01

    Limited information is available about the thermodynamic evaluation for biomass gasification process using updraft gasifier. Therefore, to minimize errors, the gasification of dry refinery sludge (DRS) is carried out in adiabatic system at atmospheric pressure under ambient air conditions. The objectives of this paper are to investigate the physical and chemical energy and exergy of product gas at different equivalent ratios (ER). It will also be used to determine whether the cold gas, exergy, and energy efficiencies of gases may be maximized by using secondary air injected to gasification zone under various ratios (0, 0.5, 1, and 1.5) at optimum ER of 0.195. From the results obtained, it is indicated that the chemical energy and exergy of producer gas are magnified by 5 and 10 times higher than their corresponding physical values, respectively. The cold gas, energy, and exergy efficiencies of DRS gasification are in the ranges of 22.9-55.5%, 43.7-72.4%, and 42.5-50.4%, respectively. Initially, all 3 efficiencies increase until they reach a maximum at the optimum ER of 0.195; thereafter, they decline with further increase in ER values. The injection of secondary air to gasification zone is also found to increase the cold gas, energy, and exergy efficiencies. A ratio of secondary air to primary air of 0.5 is found to be the optimum ratio for all 3 efficiencies to reach the maximum values.

  2. Analysis and performance assessment of a new solar-based multigeneration system integrated with ammonia fuel cell and solid oxide fuel cell-gas turbine combined cycle

    Science.gov (United States)

    Siddiqui, Osamah; Dincer, Ibrahim

    2017-12-01

    In the present study, a new solar-based multigeneration system integrated with an ammonia fuel cell and solid oxide fuel cell-gas turbine combined cycle to produce electricity, hydrogen, cooling and hot water is developed for analysis and performance assessment. In this regard, thermodynamic analyses and modeling through both energy and exergy approaches are employed to assess and evaluate the overall system performance. Various parametric studies are conducted to study the effects of varying system parameters and operating conditions on the energy and exergy efficiencies. The results of this study show that the overall multigeneration system energy efficiency is obtained as 39.1% while the overall system exergy efficiency is calculated as 38.7%, respectively. The performance of this multigeneration system results in an increase of 19.3% in energy efficiency as compared to single generation system. Furthermore, the exergy efficiency of the multigeneration system is 17.8% higher than the single generation system. Moreover, both energy and exergy efficiencies of the solid oxide fuel cell-gas turbine combined cycle are determined as 68.5% and 55.9% respectively.

  3. Optimal Solutions for Load Sharing between Units of a Combined Heat and Power Plant

    Directory of Open Access Journals (Sweden)

    Shchinnikov P. A.

    2017-12-01

    Full Text Available The article presents the optimization method of load division between combined heat and power plant units. The method used the power unit division into functioning parts and the differential-exergy method. This method allowed presenting the unit as a structural diagram where exergetic subsystems are fuel supply, steam generator, turbine, generator and electrical equipment, water supply and regeneration, heat supply to the consumer. The differential-exergy method was based on a combination of exergy analysis and optimization method of economic efficiency criteria using uncertain Lagrange multipliers. The use of the exergy function of goal allowed avoiding the problem of division of fuel costs for each type of product that was important at optimization. The optimization criterion, its parameters and limitations were developed as well. These parameters can extend traditional technical and economic analysis of the combined heat and power plants operating mode, as they take into account thermodynamically rigorous division of fuel costs between heat and electric power at their complex production on the combined heat and power plants. The use of the differential-exergy method in optimizing the load distribution of the power units of the combined heat and power plants makes possible obtaining of fuel savings of 1.5 to 3%. It has been shown that if the parameters of power units deteriorate, the application of the method makes it possible to have the best performance of the power plant when it is compared with functioning of combined heat and power units at proportional loading.

  4. Thermodynamic analysis of a novel compact power generation and waste heat operated absorption, ejector-jet pump refrigeration cycle

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Anil; Kumar, Raj [YMCA University of Science and Technology, Faridabad (India)

    2014-09-15

    An R-152a ejector-jet pump refrigeration cycle and a LiBr-H{sub 2}O absorption refrigeration cycle have been integrated with a renewable energy power generator for making a proposed 'novel compact cogeneration cycle'. The exergy analysis of this proposed cycle leads to a possible performance improvement. Nearly 71.12% of the input exergy is destructed due to irreversibilities in the different components. The useful exergy output is around 7.12%. The exhaust exergy lost to the environment is 21.76%, which is lower than the exhaust energy lost 37.6% of the input energy, while the useful energy output is approximately 19.3%. The refrigerants used and the exhaust gas emissions samples are found to be favourable for reducing the global environmental related problems. The results also show that the coupling of the entrainment ratios of the ejector and jet pump has great effect on the exergy and energy efficiency.

  5. Energy Analysis and Multi-Objective Optimization of an Internal Combustion Engine-Based CHP System for Heat Recovery

    Directory of Open Access Journals (Sweden)

    Abdolsaeid Ganjehkaviri

    2014-10-01

    Full Text Available A comprehensive thermodynamic study is conducted of a diesel based Combined Heat and Power (CHP system, based on a diesel engine and an Organic Rankine Cycle (ORC. Present research covers both energy and exergy analyses along with a multi-objective optimization. In order to determine the irreversibilities in each component of the CHP system and assess the system performance, a complete parametric study is performed to investigate the effects of major design parameters and operating conditions on the system’s performance. The main contribution of the current research study is to conduct both exergy and multi-objective optimization of a system using different working fluid for low-grade heat recovery. In order to conduct the evolutionary based optimization, two objective functions are considered in the optimization; namely the system exergy efficiency, and the total cost rate of the system, which is a combination of the cost associated with environmental impact and the purchase cost of each component. Therefore, in the optimization approach, the overall cycle exergy efficiency is maximized satisfying several constraints while the total cost rate of the system is minimized. To provide a better understanding of the system under study, the Pareto frontier is shown for multi-objective optimization and also an equation is derived to fit the optimized point. In addition, a closed form relationship between exergy efficiency and total cost rate is derived.

  6. Experimental Studies on the Effect of Enhanced Thermal Conductivity of SiC+Water Nanofluid in the Performance of Small Scale Solar Parabolic Dish Receiver

    Science.gov (United States)

    Rajendran, D. R.; Sundaram, E. Ganapathy; Jawahar, P.

    In this experimental study, exergy efficiencies of water and SiC+water nanofluid, prepared from 50nm particle size and 1% of volume fraction were compared based on the effect of thermal conductivities by a dish reflector receiver system. The average temperature difference between the receiver walls and heat transfer fluids have been studied to understand the thermal performance of the system with respect to the important properties of thermal conductivities and specific heat capacities. The enhanced thermal conductivity of 0.800115W/mK with the Keff/Kb ratio of 1.1759 was determined by the Koo and Kleinstreuer correlation which is considering both the Maxwell correlation and Brownian motion. The attained higher average exergy efficiencies for water and SiC+water nanofluid are 21.08% and 37.06.%, respectively with the enhanced nanofluid exergy efficiency of 75.80% than that of water at the flow rate of 0.5lpm. The result also shows that the system with SiC+water nanofluid produced higher exergy efficiency, because the rates of energy and exergy carried by the nanofluid are 0.2378kW and 0.7593kW higher than that of water for all the flow rates except at 0.2lpm, due to the enhanced thermal conductivity of the nanofluid.

  7. Exergetic analysis and evaluation of a new application of gas engine heat pumps (GEHPs) for food drying processes

    Energy Technology Data Exchange (ETDEWEB)

    Gungor, Aysegul [Department of Mechanical Engineering, Faculty of Engineering, Gediz University, Izmir (Turkey); Erbay, Zafer [Department of Food Engineering, Faculty of Engineering, Ege University, 35100 Izmir (Turkey); Hepbasli, Arif [Department of Mechanical Engineering, Faculty of Engineering, Ege University, 35100 Izmir (Turkey)

    2011-03-15

    In this study, three medicinal and aromatic plants (Foeniculum vulgare, Malva sylvestris L. and Thymus vulgaris) were dried in a pilot scale gas engine driven heat pump 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. In this work, the performance of the drier along with its main components is evaluated using exergy analysis method. The most important component for improving the system efficiency is found to be the gas engine, followed by the exhaust air heat exchanger for the drying system. An exergy loss and flow diagram (the so-called Grassmann diagram) of the whole drying system is also presented to give quantitative information regarding the proportion of the exergy input dissipated in the various system components, while the sustainability index values for the system components are calculated to indicate how sustainability is affected by changing the exergy efficiency of a process. Gas engine, expansion valve and drying ducts account for more than 60% amount of exergy in the system. The exergetic efficiency values are in the range of 77.68-79.21% for the heat pump unit, 39.26-43.24% for the gas engine driven heat pump unit, 81.29-81.56% for the drying chamber and 48.24-51.28% for the overall drying system. (author)

  8. Exergoeconomic Evaluation of a Modern Ultra-Supercritical Power Plant

    Directory of Open Access Journals (Sweden)

    Lingnan Wu

    2012-09-01

    Full Text Available In this paper, the exergoeconomic analysis was conducted to an existing ultra-supercritical coal-fired power plant in China to understand the cost-formation process, to evaluate the economic performance of each component and to find possible solutions for more cost-effective designs. The total revenue requirement (TRR and the specific exergy costing (SPECO methods were applied for economic analysis and exergy costing, respectively. Quantitative balances of exergy and exergetic costs as well as necessary auxiliary equations for both individual component and the overall system were established. The results show that the exergoeconomic factors of the furnace and heat exchangers at low temperature levels, including air preheater and low-pressure feedwater preheaters, are rather small; while those of other components are relatively large. Moving more heat absorption into furnace to use the effective radiation heat transfer, increasing the air preheating temperature and adding more low pressure feedwater preheaters can be promising solutions for future design.

  9. Exergoeconomic analysis of an underground air tunnel system for greenhouse cooling system

    Energy Technology Data Exchange (ETDEWEB)

    Ozgener, Onder [Solar Energy Institute, Ege University, Bornova, Izmir 35100 (Turkey); Ozgener, Leyla [Department of Mechanical Engineering, Faculty of Engineering, Celal Bayar University, Muradiye, Manisa (Turkey)

    2010-08-15

    This paper investigates some exergoeconomic parameters for an underground air tunnel system based upon some operating conditions. The ratio of exergy loss rate to capital cost (R{sub ex}) changes between 0.052 and 0.552. The total exergy losses values are obtained to be from 0.26 kW to 2.50 kW for the system. The daily average maximum cooling coefficient of performances (COP) values for the system are also obtained to be 11.96 for experimental period, while the total average COP is found to be 5.89. The overall exergy efficiency value for the system on a product/fuel basis is found to be 56.9%. (author)

  10. Econophysics and bio-chemical engineering thermodynamics: The exergetic analysis of a municipality

    Science.gov (United States)

    Lucia, Umberto

    2016-11-01

    Exergy is a fundamental quantity because it allows us to obtain information on the useful work obtainable in a process. The analyses of irreversibility are important not only in the design and development of the industrial devices, but also in fundamental thermodynamics and in the socio-economic analysis of municipality. Consequently, the link between entropy and exergy is discussed in order to link econophysics to the bio-chemical engineering thermodynamics. Last, this link holds to the fundamental role of fluxes and to the exergy exchanged in the interaction between the system and its environment. The result consists in a thermodynamic approach to the analysis of the unavailability of the economic, productive or social systems. The unavailability is what the system cannot use in relation to its internal processes. This quantity result is interesting also as a support to public manager for economic decisions. Here, the Alessandria Municipality is analyzed in order to highlight the application of the theoretical results.

  11. Thermodynamic analysis of solar assisted multi-functional trigeneration system

    Directory of Open Access Journals (Sweden)

    Önder KIZILKAN

    2016-02-01

    Full Text Available In this study, modelling and thermodynamic analysis of solar assisted trigeneration system was carried out. The required thermal energy for gas and vapor cycles were supplied from solar tower which is a new concept for gas cycle applications. Additionally, an absorption refrigeration cycle, vapor production process, drying process and water heating process were integrated to the system. Energy and exergy efficiencies of the trigeneration system were determined by the application of first and second law analyses. The results showed that the gas cycle efficiency was found to be 31%, vapor cycle efficiency was found to be 28% and coefficient of performance (COP values of the refrigeration system was found to be 0.77. Also the highest exergy destruction rate was found to be 4154 kW in solar tower.Keywords: Solar tower, Trigeneration, Gas cycle, Vapor cycle, Energy, Exergy

  12. Influences of the Thomson Effect on the Performance of a Thermoelectric Generator-Driven Thermoelectric Heat Pump Combined Device

    Directory of Open Access Journals (Sweden)

    Yuanli Feng

    2018-01-01

    Full Text Available A thermodynamic model of a thermoelectric generator-driven thermoelectric heat pump (TEG-TEH combined device is established considering the Thomson effect and the temperature dependence of the thermoelectric properties based on non-equilibrium thermodynamics. Energy analysis and exergy analysis are performed. New expressions for heating load, maximum working temperature difference, coefficient of performance (COP, and exergy efficiency are obtained. The performance is analyzed and optimized using numerical calculations. The general performance, optimal performance, optimum variables, optimal performance ranges, and optimum variable ranges are obtained. The results show that the Thomson effect decreases the general performance and optimal performance, and narrows the optimal operating ranges and optimum variable ranges. Considering the Thomson effect, more thermoelectric elements should be allocated to the thermoelectric generator when designing the devices. The optimum design variables for the maximum exergy efficiency are different from those for the maximum COP. The results can provide more scientific guidelines for designing TEG-TEH devices.

  13. Appreciating the role of thermodynamics in LCA improvement analysis via an application to titanium dioxide nanoparticles.

    Science.gov (United States)

    Grubb, Geoffrey F; Bakshi, Bhavik R

    2011-04-01

    Although many regard it as the most important step of life cycle assessment, improvement analysis is given relatively little attention in the literature. Most available improvement approaches are highly subjective, and traditional LCA methods often do not account for resources other than fossil fuels. In this work exergy is evaluated as a thermodynamically rigorous way of identifying process improvement opportunities. As a case study, a novel process for producing titanium dioxide nanoparticles is considered. A traditional impact assessment, a first law energy analysis, and an exergy analysis are done at both the process and life cycle scales. The results indicate that exergy analysis provides insights not available via other methods, especially for identifying unit operations with the greatest potential for improvement. Exergetic resource accounting at the life cycle scale shows that other materials are at least as significant as fossil fuels for the production of TiO2 nanoparticles in this process.

  14. Theoretical Analysis for Heat Transfer Optimization in Subcritical Electrothermal Energy Storage Systems

    Directory of Open Access Journals (Sweden)

    Peng Hu

    2017-02-01

    Full Text Available Electrothermal energy storage (ETES provides bulk electricity storage based on heat pump and heat engine technologies. A subcritical ETES is described in this paper. Based on the extremum principle of entransy dissipation, a geometry model is developed for heat transfer optimization for subcritical ETES. The exergy during the heat transfer process is deduced in terms of entropy production. The geometry model is validated by the extremum principle of entropy production. The theoretical analysis results show that the extremum principle of entransy dissipation is an effective criterion for the optimization, and the optimum heat transfer for different cases with the same mass flux or pressure has been discussed. The optimum heat transfer can be achieved by adjusting the mass flux and pressure of the working fluid. It also reveals that with the increase of mass flux, there is a minimum exergy in the range under consideration, and the exergy decreases with the increase of the pressure.

  15. Thermodynamic analysis of lignocellulosic biofuel production via a biochemical process: guiding technology selection and research focus.

    Science.gov (United States)

    Sohel, M Imroz; Jack, Michael W

    2011-02-01

    The aim of this paper is to present an exergy analysis of bioethanol production process from lignocellulosic feedstock via a biochemical process to asses the overall thermodynamic efficiency and identify the main loss processes. The thermodynamic efficiency of the biochemical process was found to be 35% and the major inefficiencies of this process were identified as: the combustion of lignin for process heat and power production and the simultaneous scarification and co-fermentation process accounting for 67% and 27% of the lost exergy, respectively. These results were also compared with a previous analysis of a thermochemical process for producing biofuel. Despite fundamental differences, the biochemical and thermochemical processes considered here had similar levels of thermodynamic efficiency. Process heat and power production was the major contributor to exergy loss in both of the processes. Unlike the thermochemical process, the overall efficiency of the biochemical process largely depends on how the lignin is utilized. Copyright © 2010 Elsevier Ltd. All rights reserved.

  16. Applications of magnetic power production and its assessment - Annual report 2007

    Energy Technology Data Exchange (ETDEWEB)

    Kitanovski, A.; Vuarnoz, D.; Diebold, M.; Gonin, C.; Egolf, P. W.

    2007-07-01

    This annual report for the Swiss Federal Office of Energy (SFOE) takes a look at the work done at the University of Applied Sciences of Western Switzerland in 2007 on a project involving power production based on magnetic effects. In this annual report, a selection of feasible and economic magnetic power conversion systems is listed. Magnetic 'power generators' based on permanent and superconducting magnets are analysed for several heat source temperatures, magnetic field strengths and machine rotational frequencies. The analysis uses a newly derived model, which permits the determination of thermodynamic efficiency and exergy efficiency of a magnetic power-conversion system. This study shows that magnetic power conversion is better than conventional technologies in many aspects, such as, for example, for low exergy heat sources, where most of the conventional energy conversion technologies cannot even operate. The authors state that, in contrast, magnetic power generation technology leads to a high exergy efficiency of energy conversion for such sources.

  17. The environmental sustainability. The physical cost of replacement of mineral reserves; La sostenibilidad ambiental a escala planetaria. El coste fisico de reposicion del Capital Mineral de la Tierra

    Energy Technology Data Exchange (ETDEWEB)

    Valero, A.; Martinez, A.; Botero, E.

    2003-07-01

    In order to evaluate the physical value of mineral and water reserves, the concept of Exergy Replacement Cost has been defined as the energy required by the best available technologies to return a resource to the same conditions as it was delivered by the ecosystem. In the case of fossil fuel reserves, a new concept called exergy abatement cost has been proposed as a physical way of measuring the exergy cost of the best available technology for avoiding the environmental externalities associated with the use of fossil fuels. According to the results obtained, the physical value of mineral reserves is 15.4% of oil reserves. In the case of water reserves, 0,4 to 6,4 times the fossil energy consumed would be needed each year to supply only a part of the functions of the hydrological cycle. The global exegetic abatement costs would be 11,3% of the proven world exegetic reserves in fossil fuels. (Author)

  18. On organizing the working process in air-breathing engines

    Science.gov (United States)

    Latypov, A. F.

    2017-10-01

    Numerous experiments with ramjet and scramjet models reveal reconstruction of the initial supersonic flow during fuel combustion. This reconstruction is caused by violation of the entropy condition, which reads that the test gas entropy in each cross section of the engine duct should not exceed a certain maximum value calculated by the corresponding formula. With due allowance for this constraint, a functional mathematical model is developed for a combustion chamber with fuel injection in three sections, which ensures hypersonic scramjet operation in the range of flight Mach numbers M=6-12. The efficiency of this combustion chamber is estimated on the basis of the exergy of combustion products because the exergy determines the maximum velocity of gas exhaustion into the ambient medium and, hence, the maximum thrust of the engine. By calculating the engine thrust on the basis of the exergy values, the limiting Mach number for scramjet operation can be estimated from the cruising flight condition: M=12.

  19. Exergetic optimization of turbofan engine with genetic algorithm method

    Energy Technology Data Exchange (ETDEWEB)

    Turan, Onder [Anadolu University, School of Civil Aviation (Turkey)], e-mail: onderturan@anadolu.edu.tr

    2011-07-01

    With the growth of passenger numbers, emissions from the aeronautics sector are increasing and the industry is now working on improving engine efficiency to reduce fuel consumption. The aim of this study is to present the use of genetic algorithms, an optimization method based on biological principles, to optimize the exergetic performance of turbofan engines. The optimization was carried out using exergy efficiency, overall efficiency and specific thrust of the engine as evaluation criteria and playing on pressure and bypass ratio, turbine inlet temperature and flight altitude. Results showed exergy efficiency can be maximized with higher altitudes, fan pressure ratio and turbine inlet temperature; the turbine inlet temperature is the most important parameter for increased exergy efficiency. This study demonstrated that genetic algorithms are effective in optimizing complex systems in a short time.

  20. Optimization of a solar hydrogen storage system: Exergetic considerations

    Energy Technology Data Exchange (ETDEWEB)

    Lopez, E.; Isorna, F.; Rosa, F. [Instituto Nacional de Tecnica Aeroespacial, Ctra. S. Juan-Matalascanas, km.34, 21130 Mazagon (Huelva) (Spain)

    2007-07-15

    From production to end-users, the choice of suitable hydrogen delivery and storage systems will be essential to assure the adequate introduction and development of these facilities. This article describes the main options for hydrogen storage when produced from renewable energy, and explains different criteria to be considered in the design and building-up of stationary hydrogen storage systems, with special attention to exergy issues. An example of exergy analysis is done using data from the solar hydrogen storage facility of the Spanish Instituto Nacional de Tecnica Aeroespacial (INTA). As expected, the main conclusions of this analysis show the advantage of low pressure hydrogen in comparison with other available methods to store hydrogen. Another interesting option, from the exergy efficiency point of view, is the storage of hydrogen in metal hydride systems. The last option, and the most inefficient, is the high pressure hydrogen storage. (author)

  1. Implications of the modelling of stratified hot water storage tanks in the simulation of CHP plants

    Energy Technology Data Exchange (ETDEWEB)

    Campos Celador, A., E-mail: alvaro.campos@ehu.es [ENEDI Research Group-University of the Basque Country, Departamento de Maquinas y Motores Termicos, E.T.S.I. de Bilbao Alameda de Urquijo, s/n 48013 Bilbao, Bizkaia (Spain); Odriozola, M.; Sala, J.M. [ENEDI Research Group-University of the Basque Country, Departamento de Maquinas y Motores Termicos, E.T.S.I. de Bilbao Alameda de Urquijo, s/n 48013 Bilbao, Bizkaia (Spain)

    2011-08-15

    Highlights: {yields} Three different modelling approaches for simulation of hot water tanks are presented. {yields} The three models are simulated within a residential cogeneration plant. {yields} Small differences in the results are found by an energy and exergy analysis. {yields} Big differences between the results are found by an advanced exergy analysis. {yields} Results on the feasibility study are explained by the advanced exergy analysis. - Abstract: This paper considers the effect that different hot water storage tank modelling approaches have on the global simulation of residential CHP plants as well as their impact on their economic feasibility. While a simplified assessment of the heat storage is usually considered in the feasibility studies of CHP plants in buildings, this paper deals with three different levels of modelling of the hot water tank: actual stratified model, ideal stratified model and fully mixed model. These three approaches are presented and comparatively evaluated under the same case of study, a cogeneration plant with thermal storage meeting the loads of an urbanisation located in the Bilbao metropolitan area (Spain). The case of study is simulated by TRNSYS for each one of the three modelling cases and the so obtained annual results are analysed from both a First and Second-Law-based viewpoint. While the global energy and exergy efficiencies of the plant for the three modelling cases agree quite well, important differences are found between the economic results of the feasibility study. These results can be predicted by means of an advanced exergy analysis of the storage tank considering the endogenous and exogenous exergy destruction terms caused by the hot water storage tank.

  2. Análisis de la operación del horno alto mediante la exergía térmica

    OpenAIRE

    Babich, A.; García, L.; Vega, J.; Formoso, A.; Cores, A.

    1998-01-01

    In order to know the blast furnace thermic state, the thermic exergy can be used, which considers the temperatures level of the process. The magnitude analysis of thermic exergy for blast furnace operation using pulverized coal, natural gas and oxigen injection by tuyeres, shows that natural gas injection is less effective than pulverized coal and enriched blast with oxygen simultaneous injection.

    Para conocer el estado térmico del horno alto se puede utilizar la exergía té...

  3. Thermodynamic analysis of oil and gas platforms over various production profiles and feed compositions

    DEFF Research Database (Denmark)

    Nguyen, Tuong-Van; Junior, Silvio de Oliveira

    2017-01-01

    of energy and exergy. Feed compositions and production profiles, which correspond to data from actual fields, are used for calibrating the simulations. In a second step, the minimum energy and exergy losses of the platform are assessed by performing thermodynamic analyses, assuming an ideal scenario...... in which all processes are run at their design points. This approach proves to be useful for evaluating consistently different options for oil and gas production, and for determining, in a further step, the most promising solutions for minimising the energy use over a field lifetime....

  4. Thermodynamic Analysis of a Mixed-Mode Solar Dryer

    OpenAIRE

    I.A. Ikem; I.H. Iondover; O.E. Nyong; A.J. Adie

    2016-01-01

    Thermodynamic analysis of a mixed-mode solar dryer used for restaurant wastes is presented. This dryer is made up of up of flat-plat collector and a drying chamber. Thermodynamic properties of the working fluid were measured at input and exit points. Energy and exergy balance equations at the various segments of the dryer were formulated based on the balances in the solar grains dryer. The results show that energy and exergy efficiency are approximately in direct relation to the energy loss ...

  5. Integration of Decentralized Thermal Storages Within District Heating (DH) Networks

    Science.gov (United States)

    Schuchardt, Georg K.

    2016-12-01

    Thermal Storages and Thermal Accumulators are an important component within District Heating (DH) systems, adding flexibility and offering additional business opportunities for these systems. Furthermore, these components have a major impact on the energy and exergy efficiency as well as the heat losses of the heat distribution system. Especially the integration of Thermal Storages within ill-conditioned parts of the overall DH system enhances the efficiency of the heat distribution. Regarding an illustrative and simplified example for a DH system, the interactions of different heat storage concepts (centralized and decentralized) and the heat losses, energy and exergy efficiencies will be examined by considering the thermal state of the heat distribution network.

  6. Thermodynamic analysis of human heat and mass transfer and their impact on thermal comfort

    OpenAIRE

    Prek, Matjaž

    2015-01-01

    In this paper a thermodynamic analysis of human heat and mass transfer based on the 2nd law of thermodynamics in presented. For modelling purposes the two-node human thermal model was used. This model was improved in order to establish the exergy consumption within the human body as a consequence of heat and mass transfer and/or conversion. It is shown that the human body's exergy consumption in relation to selected human parameters exhibit a minimal value at certain combinations of environme...

  7. A Comparison of the Thermodynamic Efficiency of Vacuum Tube and Flat Plate Solar Collector Systems

    Directory of Open Access Journals (Sweden)

    Juozas Bielskus

    2013-12-01

    Full Text Available The article presents simulation based exergy analysis used for comparing solar thermal systems applied for preparing domestic hot water. The simulation of flat and vacuum tube solar collector systems was performed in TRNSYS simulation environment. A period of one year under Lithuanian climate conditions was chosen. Simulation was performed on 6 min time step resolution by calculating energy and exergy flows and creating balance calculation. Assessment results at system and element levels have been presented as monthly variation in efficiency. The conducted analysis has revealed that the systems designed to cover equal heat energy demand operates in different exergetic efficiencies.Article in Lithuanian

  8. Improved Engine Design Concepts Using the Second Law of Thermodynamics

    Energy Technology Data Exchange (ETDEWEB)

    None

    2009-09-30

    This project was aimed at developing and using numerical tools which incorporate the second law of thermodynamics to better understand engine operation and particularly the combustion process. A major activity of this project was the continual enhancement and use of an existing engine cycle simulation to investigate a wide range of engine parameters and concepts. The major motivation of these investigations was to improve engine efficiency. These improvements were examined from both the first law and second law perspective. One of the most important aspects of this work was the identification of the combustion irreversibilities as functions of engine design and operating parameters. The combustion irreversibility may be quantified in a number of ways but one especially useful way is by determining the destruction of exergy (availability) during the combustion process. This destruction is the penalty due to converting the fuel exergy to thermal energy for producing work. The engine cycle simulation was used to examine the performance of an automotive (5.7 liter), V-8 spark-ignition engine. A base case was defined for operation at 1400 rpm, stoichiometric, MBT spark timing with a bmep of 325 kPa. For this condition, the destruction of exergy during the combustion process was 21.0%. Variations of many engine parameters (including speed, load, and spark timing) did not alter the level of destruction very much (with these variations, the exergy destruction was within the range of 20.5-21.5%). Also, the use of turbocharging or the use of an over-expanded engine design did not significantly change the exergy destruction. The exergy destruction during combustion was most affected by increased inlet oxygen concentration (which reduced the destruction due to the higher combustion temperatures) and by the use of cooled EGR (which increased the destruction). This work has demonstrated that, in general, the exergy destruction for conventional engines is fairly constant ({approx

  9. energy and economic losses due to constant power outages in nigeria

    African Journals Online (AJOL)

    2012-07-02

    Jul 2, 2012 ... from Afam power station were assessed based on real data obtained through survey of companies, oral interview, individuals and also .... as Japan [7], Canada [8] and Brazil [9], respectively. Exergy calculation. By describing the .... Tasks such as space heating, heating in industrial furnaces, process steam ...

  10. Thermoeconomic Optimization of a Renewable Polygeneration System Serving a Small Isolated Community

    Directory of Open Access Journals (Sweden)

    Francesco Calise

    2015-01-01

    Full Text Available During the last years, special attention has been paid to renewable polygeneration technologies, able of simultaneously producing thermal, cooling, electrical energy and desalinated water from seawater. This paper focuses on an innovative polygeneration system driven by renewable energy sources, including the following technologies: hybrid photovoltaic/thermal collectors, concentrating parabolic trough (CPVT, a biomass heater, a single-stage absorption chiller and a multiple-effect distillation desalination system. The system is designed to cover the base load of an isolated small community. In previous papers, the dynamic simulation model about plant operation is discussed. In this paper, a detailed exergy, economic and environmental analysis of the plant is presented. In addition, the plant was optimized using different objective functions, applying the Design of Experiment (DoE methodology which evaluates the sensitivity of the different objective functions with respect to the selected design parameters. The results show that an increase of the storage volume is generally negative, whereas increasing the solar field area involves an increase of the exergy destruction rate, but also an improvement of the CPVT exergy output provided; the final result is an increase of both the exergy efficiency and the economic profitability of the polygeneration system.

  11. Thermodynamic Analysis of a Steam Power Plant with Double Reheat and Feed Water Heaters

    Directory of Open Access Journals (Sweden)

    M. M. Rashidi

    2014-03-01

    Full Text Available A steam cycle with double reheat and turbine extraction is presented. Six heaters are used, three of them at high pressure and the other three at low pressure with deaerator. The first and second law analysis for the cycle and optimization of the thermal and exergy efficiencies are investigated. An exergy analysis is performed to guide the thermodynamic improvement for this cycle. The exergy and irreversibility analyses of each component of the cycle are determined. Effects of turbine inlet pressure, boiler exit steam temperature, and condenser pressure on the first and second laws' efficiencies are investigated. Also the best turbine extraction pressure on the first law efficiency is obtained. The results show that the biggest exergy loss occurs in the boiler followed by the turbine. The results also show that the overall thermal efficiency and the second law efficiency decrease as the condenser pressure increases for any fixed outlet boiler temperature, however, they increase as the boiler temperature increases for any condenser pressure. Furthermore, the best values of extraction pressure from high, intermediate, and low pressure turbine which give the maximum first law efficiencies are obtained based on the required heat load corresponding to each exit boiler temperature.

  12. Exergetic and environmental impact assessments of an integrated organic Rankine cycle with a biomass combustor for combined cooling, heating and power production

    Energy Technology Data Exchange (ETDEWEB)

    Al-Sulaiman, F.A. [Carleton Univ., Ottawa, ON (Canada). Dept. of Mechanical and Aerospace Engineering; Hamdullahpur, F. [Waterloo Univ., ON (Canada). Dept. of Mechanical and Mechatronics Engineering; Dincer, I. [Univ. of Ontario Inst. of Technology, Oshawa, ON (Canada). Faculty of Engineering and Applied Science

    2010-07-01

    A trigeneration thermal system produces cooling, heating and power from the same source. In trigeneration plants, waste heat is used for heating and cooling. In this paper, exergetic and environmental impact analyses of a trigeneration system based on an integrated organic Rankine cycle (ORC) with a biomass combustor were conducted. The analyses were extended to include electrical-power, cooling-cogeneration and heating-cogeneration cases. The objective was to understand the working phenomena of the proposed system, and identify and quantify the sources of the irreversibilities in the system associated with each component. The environmental impact of the proposed system was also quantified. The exergy efficiency, exergy destruction rate and carbon dioxide (CO{sub 2}) emissions were examined under the variations of pump inlet temperature and turbine inlet pressure. The results showed that exergy efficiency increased to 27 per cent when trigeneration was used as compared 11 per cent when the electrical power system was used. The main two sources of exergy destruction were the biomass combustor and the ORC evaporator. Emissions of CO{sub 2} were much higher in the case of the the electrical-power system compared to the trigeneration system. 11 refs., 1 tab., 8 figs.

  13. exergetic analysis of breakfast cereal production in nigeria

    African Journals Online (AJOL)

    HOD

    This work comprehensively studied energy and exergy analyses of breakfast cereal production in Nigeria. The process analysis ... efficient [5, 6]. Energy consumption in food production/crop processing industry has been identified to be affected by factors like production scale; ..... Analysis of the Corn-Ethanol Cycle” Natural.

  14. Thermodynamics and sustainable development

    NARCIS (Netherlands)

    Cornelissen, Rene

    1997-01-01

    It is the objective of this thesis to demonstrate exergy analysis as a powerful instrument to obtain sustainable development. An important aspect of sustainable development is the minimisation of irreversibilities caused by the use of non-renewables. In order to limit the scope of this thesis

  15. Integration of oxygen membranes for oxygen production in cement plants

    DEFF Research Database (Denmark)

    Puig Arnavat, Maria; Søgaard, Martin; Hjuler, Klaus

    2015-01-01

    The present paper describes the integration of oxygen membranes in cement plants both from an energy, exergy and economic point of view. Different configurations for oxygen enrichment of the tertiary air for combustion in the pre-calciner and full oxy-fuel combustion in both pre-calciner and kiln...

  16. A review on recent developments in solar distillation units

    Indian Academy of Sciences (India)

    A review on recent developments in solar distillation units ... Solar still; absorber; fluoride; solar radiation; energy; exergy; heat transfer. Abstract. The solar still is gaining popularity among the scientific community for the production of distillate and fluoride free water due to its low cost and simple working principle. Continuous ...

  17. Determination of Performance Measuring Parameters of an Improved Dual Paraboloid Solar Cooker

    Directory of Open Access Journals (Sweden)

    Suhail Zaki Farooqui

    2017-01-01

    Full Text Available An experimental investigation into the performance evaluation of an improved dual reflector foldable paraboloid solar cooker has been reported, along with its energy and exergy analysis. The best attribute of this lightweight and low-cost solar cooker is its high performance coupled with the ease of handling. The cooker utilizes two paraboloid reflectors made out of Mylar-coated fiberglass dishes, each having a diameter of 90 cm and focal length of 105 cm. The total intercepted radiation energy is 1.08 kW under standard test conditions. Stagnation temperatures of up to 330°C and cooking temperatures of up to 290°C have been attained with load. Altogether, 9 experiments have been performed with and without load. Loaded tests have been conducted with water and vegetable oil. Results indicate an average cooking power of 485 W, peak exergy gain of 60.53 W, quality factor of 0.077, and a high product of temperature difference gap at half peak power to peak power of 4364.33 W·K. The maximum exergy output power attained was 70 W, while maximum exergy efficiency was 8–10%. All performance measuring parameters indicate that it is a high performance solar cooker for rural and urban communities and is suitable for all types of oil- and water-based cooking.

  18. Analysis of horizontal axis wind turbine blade using CFD

    African Journals Online (AJOL)

    A Pareto optimal multi-objective optimization for a horizontal axis wind turbine blade airfoil sections utilizing exergy analysis and neural networks. Journal of Wind Engineering and Industrial. Aerodynamics, Vol. 136, pp.62–72. Rajakumar S., Ravindran D. 2011 Iterative approach for optimising coefficient of power, coefficient ...

  19. Exergoeconomic analysis of a turboprop engine

    Energy Technology Data Exchange (ETDEWEB)

    Aydin, Hakan [TUSAS Motor Sanayi (Turkey)], e-mail: hakan.aydin@tei.com.tr; Turan, Onder; Hikmet Karakoc, T. [Anadolu University (Turkey)], e-mail: onderturan@anadolu.edu.tr, e-mail: hkarakoc@anadolu.edu.tr; Midilli, Adnan [Rize University (Turkey)], e-mail: amidilli@gmail.com

    2011-07-01

    The turboprop engine is an important component of short haul commuter and military transport aircraft when high speed is not critical. Using the turboprop engine could save operating costs in the aviation sector by reducing fuel consumption. The purpose of this research was to make an exergoeconomic analysis of a modern turboprop engine installed on a CN235 aircraft. This medium-range, twin-engined transport plane was developed to be a regional airliner and for military tasks, including maritime patrol, surveillance and air transport. The research focuses on the compressor, combustor, gas generator, power turbine and exhaust characteristics of the engine. The exergetic parameters were calculated along with exergoeconomic parameters such as the exergy cost rate and unit exergy cost rate of each turboprop engine component. Exergy analysis is more useful than energy analysis for investigating the efficiency and performance of these systems. Furthermore, exergoeconomic analysis is also very helpful for process improvement since it provides further information beyond that obtained from exergy analysis.

  20. Author Details

    African Journals Online (AJOL)

    Akpan, O.E. Vol 5, No 1 (2007) - Articles Exergy analysis of a gas turbine power plant. Abstract. ISSN: 1596-3497. AJOL African Journals Online. HOW TO USE AJOL... for Researchers · for Librarians · for Authors · FAQ's · More about AJOL · AJOL's Partners · Terms and Conditions of Use · Contact AJOL · News. OTHER ...

  1. The geobiosphere emergy baseline: A synthesis.

    Science.gov (United States)

    The concept of emergy defined as the available energy (or exergy) of one form used up directly and indirectly to produce an item or action (Odum, Environmental Accounting Emergy and Environmental Decision Making, John Wiley & Sons, Inc., 1996) requires the specification of a unif...

  2. Author Details

    African Journals Online (AJOL)

    ... Losses in a Gas-Turbine Plant Abstract · Vol 17, No 1-2 (2012) - Articles Temperature and thermal stress dependence on Fourier and Biot numbers during transient heating of a hollow cylinder. Abstract · Vol 18, No 1-2 (2013) - Articles Performance analysis of 20 MW gas turbine power plant by energy and exergy methods

  3. Increasing the thermal efficiency of boiler plant

    Directory of Open Access Journals (Sweden)

    Uyanchinov Evgeniy

    2017-01-01

    Full Text Available The thermal efficiency increase of boiler plant is actual task of scientific and technical researches. The optimization of boiler operating conditions is task complex, which determine by most probable average load of boiler, operating time and characteristics of the auxiliary equipment. The work purpose – the determination of thermodynamic efficiency increase ways for boiler plant with a gas-tube boiler. The tasks, solved at the research are the calculation of heat and fuel demand, the exergetic analysis of boilerhouse and heat network equipment, the determination of hydraulic losses and exergy losses due to restriction. The calculation was shown that the exergy destruction can be reduced by 2.39% due to excess air reducing to 10%; in addition the oxygen enrichment of air can be used that leads to reducing of the exergy destruction rate. The processes of carbon deposition from the side of flame and processes of scale formation on the water side leads to about 4.58% losses of fuel energy at gas-tube boiler. It was shown that the exergy losses may be reduced by 2.31% due to stack gases temperature reducing to 148 °C.

  4. Thermoeconomic Analysis and Optimization of a New Combined Supercritical Carbon Dioxide Recompression Brayton/Kalina Cycle

    Directory of Open Access Journals (Sweden)

    S. Mohammad S. Mahmoudi

    2016-10-01

    Full Text Available A new combined supercritical CO2 recompression Brayton/Kalina cycle (SCRB/KC is proposed. In the proposed system, waste heat from a supercritical CO2 recompression Brayton cycle (SCRBC is recovered by a Kalina cycle (KC to generate additional electrical power. The performances of the two cycles are simulated and compared using mass, energy and exergy balances of the overall systems and their components. Using the SPECO (Specific Exergy Costing approach and employing selected cost balance equations for the components of each system, the total product unit costs of the cycles are obtained. Parametric studies are performed to investigate the effects on the SCRB/KC and SCRBC thermodynamic and thermoeconomic performances of key decision parameters. In addition, considering the exergy efficiency and total product unit cost as criteria, optimization is performed for the SCRBC and SCRB/KC using Engineering Equation Solver software. The results indicate that the maximum exergy efficiency of the SCRB/KC is higher than that of the SCRBC by up to 10%, and that the minimum total product unit cost of the SCRB/KC is lower than that of the SCRBC by up to 4.9%.

  5. Thermo-feasibility optimization of multiple feed rate multicomponent ...

    African Journals Online (AJOL)

    Simulation was of a multicomponent distisllation system was carried out and the stage-by-stage system exergy analysis was carried out. Multiple feed rate base cases sensitivity results gave the most adequate and feasible thermo-exergetic rate profiles, efficiency ranges and destruction at the depropanizer and debutanizer.

  6. A resource efficiency assessment of the industrial mushroom production chain

    NARCIS (Netherlands)

    Zisopoulos, Filippos K.; Becerra Ramírez, Henry A.; Goot, van der Atze Jan; Boom, Remko M.

    2016-01-01

    We compare the exergetic performance of a conventional industrial mushroom production chain with a mushroom production chain where part of the compost waste is recycled and reused as raw material. The critical exergy loss points (CEPs) identified are the cooking-out process of the spent mushroom

  7. Second law efficiency for living cells.

    Science.gov (United States)

    Lucia, Umberto; Grisolia, Giulia

    2017-06-01

    The exergetic analysis of the biosystems is developed. It takes into account that cells are able to convert only part of the energy absorbed. The result is to highlight the fundamental role of the exergy as a quantity useful to develop considerations on the cells behavior in relation to normal or disease states.

  8. Part-Load Performance of a Wet Indirectly Fired Gas Turbine Integrated with an Organic Rankine Cycle Turbogenerator

    DEFF Research Database (Denmark)

    Pierobon, Leonardo; Nguyen, Tuong-Van; Mazzucco, Andrea

    2014-01-01

    ) fueled by woodchips and an organic Rankine cycle (ORC) turbogenerator. An exergy analysis is performed to identify the sources of inefficiencies, the optimal design variables, and the most suitable working fluid for the organic Rankine process. This step enables to parametrize the part-load model...

  9. Calorific values and combustion chemistry of animal manure

    Science.gov (United States)

    Combustion chemistry and calorific value analyses are the fundamental information for evaluating different biomass waste-to-energy conversion operations. Specific chemical exergy of manure and other biomass feedstock will provide a measure for the theoretically maximum attainable energy. The specifi...

  10. A rejoinder on energy versus impact indicators

    NARCIS (Netherlands)

    Leydesdorff, L.; Opthof, T.

    2012-01-01

    Citation distributions are so skewed that using the mean or any other central tendency measure is ill-advised. Unlike G. Prathap’s scalar measures (Energy, Exergy, and Entropy or EEE), the Integrated Impact Indicator (I3) is based on non-parametric statistics using the (100) percentiles of the

  11. A rejoinder on energy versus impact indicators

    NARCIS (Netherlands)

    Leydesdorff, Loet; Opthof, Tobias

    2012-01-01

    Citation distributions are so skewed that using the mean or any other central tendency measure is ill-advised. Unlike G. Prathap's scalar measures (Energy, Exergy, and Entropy or EEE), the Integrated Impact Indicator (I3) is based on non-parametric statistics using the (100) percentiles of the

  12. Low Emission Conversion of Fossil Fuels with Simultaneous or Consecutive Storage of Carbon Dioxide

    NARCIS (Netherlands)

    Eftekhari, A.A.

    2013-01-01

    This thesis evaluates the possibility of using underground coal gasification with a low CO2 footprint. The thesis consists of two parts. In the first part, by using the concept of exergy, a framework was constructed through which the practicality (feasibility) of an energy conversion/extraction

  13. The Use of Exergetic Indicators in the Food Industry – A Review

    NARCIS (Netherlands)

    Zisopoulos, F.K.; Rossier Miranda, F.J.; Goot, van der A.J.; Boom, R.M.

    2017-01-01

    Sustainability assessment will become more relevant for the food industry in the years to come. Analysis based on exergy including the use of exergetic indicators and Grassmann diagrams is a useful tool for the quantitative and qualitative assessment of the efficiency of industrial food chains. In

  14. Research Article Special Issue

    African Journals Online (AJOL)

    2016-05-15

    May 15, 2016 ... their range were evaluated using exergy analysis. This was meant to increase the efficiency and decrease the energy consumption. The results indicate that under thr circumstances of controlling mass flow rate of input cold water and power of heat element as well as the mixer speed, respectively, in their ...

  15. Sadhana | Indian Academy of Sciences

    Indian Academy of Sciences (India)

    Home; Journals; Sadhana. ABDELLAH SHAFIEIAN. Articles written in Sadhana. Volume 41 Issue 8 August 2016 pp 877-886. Energy and exergy evaluation of an integrated solar heat pipe wall system for space heating · ROONAK DAGHIGH ABDELLAH SHAFIEIAN · More Details Abstract Fulltext PDF. In this paper, an ...

  16. Comparative Exergoeconomic Analyses of Gas Turbine Steam Injection Cycles with and without Fogging Inlet Cooling

    Directory of Open Access Journals (Sweden)

    Hassan Athari

    2015-09-01

    Full Text Available The results are reported of exergoeconomic analyses of a simple gas turbine cycle without a fogging system (SGT, a simple steam injection gas turbine cycle (STIG, and a steam injection gas turbine cycle with inlet fogging cooler (FSTIG. The results show that (1 a gas-turbine cycle with steam injection and simultaneous cooling has a higher power output than the other considered cycle; (2 at maximum energy efficiency conditions the gas turbine has the highest exergy efficiency of the cycle components and the lowest value of exergy efficiency is calculated for the fog cooler, where the mixing of air and water at greatly different temperatures causes the high exergy destruction; and (3 utilization of the fogging cooler in the steam injection cycle increases the exergy destruction in the combustion chamber. Furthermore, the simple gas turbine cycle is found to be more economic as its relative cost difference, total unit product cost, and exergoeconomic factors are less than those for the two other configurations. However, its efficiency and net power output are notably lower than for the gas turbine with steam injection and/or fog cooling. The total unit product cost is highest for the simple gas turbine with steam injection.

  17. The value of the exergetic life cycle assessment besides the LCA

    NARCIS (Netherlands)

    Cornelissen, Rene; Hirs, Gerard

    2002-01-01

    In this paper the value of the exergetic life cycle assessment (ELCA) has been analysed. The ELCA uses the framework of the life cycle assessment (LCA) and can be seen as the exergy analysis of a complete life cycle. The value of the ELCA besides the LCA has been discussed. It is shown that the ELCA

  18. Performance Evaluation of a Small Scale Modular Solar Trigeneration System

    Directory of Open Access Journals (Sweden)

    Handong Wang

    2014-01-01

    Full Text Available In order to improve the efficiency of solar thermal power (STP system, a novel modular system combining cooling, heating, and power generation (CCHP is proposed and introduced in this work. This modular CCHP system can simultaneously provide 10 kW electricity, −15~5°C coolant, and 60°C hot water to meet the requirements of cooling, heating, and electricity in a general family or other fields. The flow chart and working process of the modular system are introduced, based on which the energy and exergy efficiencies at the CCHP and STP operation modes are primarily evaluated and discussed. The results show that when the output electricity is constant, the overall efficiencies of energy and exergy of the system operating at the CCHP mode are 9.37 times and 2.62 times as big as those of the system operating at the STP mode, respectively. Thus, the modular solar thermal CCHP system can improve the energy and exergy efficiencies. Furthermore, calculation shows that both the overall energy and exergy efficiencies decrease with increase of inlet vapor temperature at given inlet vapor pressure, but both the efficiencies increase with increase of inlet vapor pressure at given inlet temperature.

  19. Lowering the cost of large-scale energy storage: High temperature adiabatic compressed air energy storage

    Directory of Open Access Journals (Sweden)

    B. Cárdenas

    2017-06-01

    Full Text Available Compressed air energy storage is an energy storage technology with strong potential to play a significant role in balancing energy on transmission networks, owing to its use of mature technologies and low cost per unit of storage capacity. Adiabatic compressed air energy storage (A-CAES systems typically compress air from ambient temperature in the charge phase and expand the air back to ambient temperature in the discharge phase. This papers explores the use of an innovative operating scheme for an A-CAES system aimed at lowering the total cost of the system for a given exergy storage capacity. The configuration proposed considers preheating of the air before compression which increases the fraction of the total exergy that is stored in the form of high-grade heat in comparison to existing designs in which the main exergy storage medium is the compressed air itself. Storing a high fraction of the total exergy as heat allows reducing the capacity of costly pressure stores in the system and replacing it with cheaper thermal energy stores. Additionally, a configuration that integrates a system based on the aforementioned concept with solar thermal power or low-medium grade waste heat is introduced and thoroughly discussed.

  20. Numerical study of effect of oxygen fraction on local entropy ...

    Indian Academy of Sciences (India)

    R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22

    process in order to achieve higher combustion efficiency with a uniform exit temperature and allowable linear ... processes are accompanied by an irreversible increase in entropy, which leads to a decrease in exergy (available ... swirling jet impingement on an adiabatic wall (Shuja & Yilbas 2001b; 2003) and an imping-.

  1. optimal evaporating and condensing temperatures of organic

    African Journals Online (AJOL)

    user

    2017-01-01

    Jan 1, 2017 ... However, the study further showed that the evaporating temperature (ET) and condensing temperature (CT) affect the thermal performance and net power output of the cycles. Dai et al.[20]conducted parametric optimisation of ORC with exergy efficiency. He et al. [21] considered the optimisation of a simple.

  2. Energetic and Exergetic Analysis of an Ejector-Expansion Refrigeration Cycle Using the Working Fluid R32

    Directory of Open Access Journals (Sweden)

    Zhenying Zhang

    2015-07-01

    Full Text Available The performance characteristics of an ejector-expansion refrigeration cycle (EEC using R32 have been investigated in comparison with that using R134a. The coefficient of performance (COP, the exergy destruction, the exergy efficiency and the suction nozzle pressure drop (SNPD are discussed. The results show that the application of an ejector instead of a throttle valve in R32 cycle decreases the cycle’s total exergy destruction by 8.84%–15.84% in comparison with the basic cycle (BC. The R32 EEC provides 5.22%–13.77% COP improvement and 5.13%–13.83% exergy efficiency improvement respectively over the BC for the given ranges of evaporating and condensing temperatures. There exists an optimum suction nozzle pressure drop (SNPD which gives a maximum system COP and volumetric cooling capacity (VCC under a specified condition. The value of the optimum SNPD mainly depends on the efficiencies of the ejector components, but is virtually independent of evaporating temperature and condensing temperature. In addition, the improvement of the component efficiency, especially the efficiencies of diffusion nozzle and the motive nozzle, can enhance the EEC performance.

  3. Parametric optimization design for supercritical CO{sub 2} power cycle using genetic algorithm and artificial neural network

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Jiangfeng; Sun, Zhixin; Dai, Yiping [Institute of Turbomachinery, Xi' an Jiaotong University, No.28 Xianning West Road, Xi' an 710049 (China); Ma, Shaolin [Dongfang Steam Turbine Works, Deyang 618201 (China)

    2010-04-15

    Supercritical CO{sub 2} power cycle shows a high potential to recover low-grade waste heat due to its better temperature glide matching between heat source and working fluid in the heat recovery vapor generator (HRVG). Parametric analysis and exergy analysis are conducted to examine the effects of thermodynamic parameters on the cycle performance and exergy destruction in each component. The thermodynamic parameters of the supercritical CO{sub 2} power cycle is optimized with exergy efficiency as an objective function by means of genetic algorithm (GA) under the given waste heat condition. An artificial neural network (ANN) with the multi-layer feed-forward network type and back-propagation training is used to achieve parametric optimization design rapidly. It is shown that the key thermodynamic parameters, such as turbine inlet pressure, turbine inlet temperature and environment temperature have significant effects on the performance of the supercritical CO{sub 2} power cycle and exergy destruction in each component. It is also shown that the optimum thermodynamic parameters of supercritical CO{sub 2} power cycle can be predicted with good accuracy using artificial neural network under variable waste heat conditions. (author)

  4. Author Details

    African Journals Online (AJOL)

    Oko, C.O.C. Vol 5, No 1 (2007) - Articles Exergy analysis of a gas turbine power plant. Abstract. ISSN: 1596-3497. AJOL African Journals Online. HOW TO USE AJOL... for Researchers · for Librarians · for Authors · FAQ's · More about AJOL · AJOL's Partners · Terms and Conditions of Use · Contact AJOL · News. OTHER ...

  5. Techno-economic and Exergoeconomic Analysis of a micro cogeneration system for a residential use

    National Research Council Canada - National Science Library

    Alvaro Antonio Ochoa; José Carlos Charamba Dutra; Jorge Recarte Henríquez; Carlos Antonio Cabral dos Santos

    2016-01-01

    ...) and exergoeconomic analysis (exergy view). This system uses a natural gas-fueled 30 kW microturbine to generate electricity, and to produce hot water by recovering energy from the waste heat in the exhaust gases by using a heat exchanger...

  6. Performance evaluation of ejector expansion combined cooling and power cycles

    Science.gov (United States)

    Ghaebi, Hadi; Rostamzadeh, Hadi; Matin, Pouria Seyed

    2017-09-01

    This paper studies performance characteristics of a basic ejector expansion combined cooling and power cycle (EECCPC) as well as three modified ones. These modified cycles are EECCPC incorporating turbine bleeding, regenerative EECCP cycle, and EECCP cycle incorporating with both turbine bleeding and regeneration. The expansion valve has been replaced by a two-phase ejector-expander in the traditional CCP cycle to improve the first and second-law efficiencies. Furthermore, the exergy destruction for components of the systems as well as the whole systems has been calculated, leading to determination of the main source of irreversibility in different cycles. The results of the exergy analysis reveals that the generator has the major contribution role in the overall losses of the systems. The results also show that the EECCP cycle surpasses the TCCP cycle in terms of thermal and exergy efficiencies. As a matter of fact, the thermal and exergy efficiencies are improved by 6.02, and 5.44%, respectively, throughout this successive modification. At last, sensitivity analysis of different key parameters on performance of the cycles has been investigated. It is shown that one can obtain higher thermal efficiency by increasing of the generator and evaporator temperatures or decreasing of the condenser temperature.

  7. Exergetic Analysis of a Novel Solar Cooling System for Combined Cycle Power Plants

    Directory of Open Access Journals (Sweden)

    Francesco Calise

    2016-09-01

    Full Text Available This paper presents a detailed exergetic analysis of a novel high-temperature Solar Assisted Combined Cycle (SACC power plant. The system includes a solar field consisting of innovative high-temperature flat plate evacuated solar thermal collectors, a double stage LiBr-H2O absorption chiller, pumps, heat exchangers, storage tanks, mixers, diverters, controllers and a simple single-pressure Combined Cycle (CC power plant. Here, a high temperature solar cooling system is coupled with a conventional combined cycle, in order to pre-cool gas turbine inlet air in order to enhance system efficiency and electrical capacity. In this paper, the system is analyzed from an exergetic point of view, on the basis of an energy-economic model presented in a recent work, where the obtained main results show that SACC exhibits a higher electrical production and efficiency with respect to the conventional CC. The system performance is evaluated by a dynamic simulation, where detailed simulation models are implemented for all the components included in the system. In addition, for all the components and for the system as whole, energy and exergy balances are implemented in order to calculate the magnitude of the irreversibilities within the system. In fact, exergy analysis is used in order to assess: exergy destructions and exergetic efficiencies. Such parameters are used in order to evaluate the magnitude of the irreversibilities in the system and to identify the sources of such irreversibilities. Exergetic efficiencies and exergy destructions are dynamically calculated for the 1-year operation of the system. Similarly, exergetic results are also integrated on weekly and yearly bases in order to evaluate the corresponding irreversibilities. The results showed that the components of the Joule cycle (combustor, turbine and compressor are the major sources of irreversibilities. System overall exergetic efficiency was around 48%. Average weekly solar collector

  8. Investigation of intercooler-effectiveness on exergo-economic and exergo-sustainability parameters of modified Brayton cycles

    Directory of Open Access Journals (Sweden)

    Fidelis I. Abam

    2017-09-01

    Full Text Available The paper investigates the variants of intercooler effectiveness on exergo-economic and exergo-sustainability indicators of modified Brayton cycles. The objective is to ascertain how the variant in the intercooler effectiveness affects the exergy-based parameters. However, to achieve this, a component by component exergy-cost balances was established. The considered cycles include: the non-specific cycle (Case 1 comprising a gas turbine (GT, intercooler (IC, heat exchanger (HE and reheat system (REH, others include (GT+H+REH +ST, Case 2, (GT+HE +IC +REH +ST+FWH, Case 3 and (GT+HE+IC+REH +ST+2 FWH, Case 4. The calculated cycle efficiencies (Cases 1–4 varies from 17.59% to 28.84% for intercooler effectiveness of 0.75 and 0.95. The exergy destruction within this range was 0.97%, 1.26%, 0.89% and 1.23% (Cases 1, 2 3 and 4 respectively. The component exergy destruction cost (CEDC fluctuated between 3.85≤CEDC≤229.1$/hr,5.61E−06≤CEDC≤229.1$/h,1.46E−06≤CEDC≤229.1$/hr and 5.61E−06≤CEDC≤229.1$/hr for same order. Additionally, the exergo-sustainability indicators: exergy waste ratio (EWR, environmental effect factor (EFF and exergetic sustainability index (ESI were estimated between 17.59≤EEF≤28.84%,0.433≤EWR≤0.6359, 1.55≤ EFF ≤3.60 and 0.277≤ ESI ≤0.644. Conclusively, the intercooler and other modifications have a marginal effect but Cases 4 and 3 was most sustainable with considerable ESI.

  9. Thermoeconomic model of a commercial transcritical booster refrigeration system

    DEFF Research Database (Denmark)

    Ommen, Torben Schmidt; Elmegaard, Brian

    2011-01-01

    . The booster refrigeration plant consists of one refrigerant cycle supplying refrigerant for evaporators in both cooled and frozen display cases. The detailed numerical model of a refrigeration plant reflects that the trans- and subcritical operation criteria depends on heat rejection performance defined...... by ambient conditions. As two evaporation temperatures are produced from one exergy stream, thermoeconomic theory is used to establish the price of cooling at each individual temperature level based on operating costs. The analysis shows that exergy for cooling frozen displays has approximately double cost......For cooling applications in supermarkets, booster refrigeration systems operating in both transcritical and subcritical conditions are increasingly used. A thermodynamic model of a transcritical booster refrigeration plant is tailored to match the new generation of commercial refrigeration plants...

  10. Optimal Analysis of Irreversible Carnot Cycle Based on Entransy Dissipation

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Kyoung Hoon [Kumoh Nat’l Institute of Technology, Gumi (Korea, Republic of)

    2017-02-15

    The concept of entransy has been proposed recently as a potential heat transfer mechanism and could be useful in analyzing and optimizing the heat-work conversion systems. This work presents an entransy analysis for the irreversible Carnot cycle by systematic balance formulations of the entransy loss, work entransy, and entransy dissipations, which are consistent with exergy balances. Additionally, several forms of system efficiency are introduced based on entransy for the appreciation of the optimal system performance. The effects of the source temperature and irreversible efficiencies on the optimal conditions for system efficiencies are systematically investigated for both dumping and non-dumping cases of used source fluid. The results show different trends in entransy efficiencies when compared to the conventional efficiencies of energy and exergy, and represent another method to assess the effective use of heat source in power generation systems.

  11. Modeling of solar polygeneration plant

    Science.gov (United States)

    Leiva, Roberto; Escobar, Rodrigo; Cardemil, José

    2017-06-01

    In this work, a exergoeconomic analysis of the joint production of electricity, fresh water, cooling and process heat for a simulated concentrated solar power (CSP) based on parabolic trough collector (PTC) with thermal energy storage (TES) and backup energy system (BS), a multi-effect distillation (MED) module, a refrigeration absorption module, and process heat module is carried out. Polygeneration plant is simulated in northern Chile in Crucero with a yearly total DNI of 3,389 kWh/m2/year. The methodology includes designing and modeling a polygeneration plant and applying exergoeconomic evaluations and calculating levelized cost. Solar polygeneration plant is simulated hourly, in a typical meteorological year, for different solar multiple and hour of storage. This study reveals that the total exergy cost rate of products (sum of exergy cost rate of electricity, water, cooling and heat process) is an alternative method to optimize a solar polygeneration plant.

  12. Towards harmonizing natural resources as an area of protection in life cycle impact assessment

    DEFF Research Database (Denmark)

    Sonderegger, Thomas; Dewulf, Jo; Fantke, Peter

    2017-01-01

    categories, nor do existing methods and models addressing different natural resource categories do so in a consistent way across categories. Exceptions are exergy and solar energy-related methods, which cover the widest range of resource categories. However, these methods do not link exergy consumption...... to changes in availability or provisioning capacity of a specific natural resource (e.g., mineral, water, land etc.). So far, there is no agreement in the scientific community on the most relevant type of future resource indicators (depletion, increased energy use or cost due to resource extraction, etc......In this paper, we summarize the discussion and present the findings of an expert group effort under the umbrella of the United Nations Environment Programme (UNEP)/Society of Environmental Toxicology and Chemistry (SETAC) Life Cycle Initiative proposing natural resources as an Area of Protection...

  13. A study on the solar hydrogen production techniques

    Energy Technology Data Exchange (ETDEWEB)

    Bozoglan, Elif [Department of Management, Taris Olive Oil, Agricultural, Industrial and Commercial Company, (Turkey); Midilli, Adnan [Energy Technologies, Turgut Kiran Maritime College, Marine Engineering, Rize University (Turkey); Hepbasli, Arif [Department of Mechanical Engineering, College of Engineering, King Saud University (Saudi Arabia)

    2011-07-01

    With the depletion of fossil fuels and the rising concerns about the environment, interest in green energy, which is both sustainable and clean, is growing. Among the different techniques, solar energy based hydrogen production appears to be one of the simpler and more convenient methods. Several solar hydrogen production methods exist and the aim of this paper is to determine the environmental and sustainability performances of an electrolyser. A solar hydrogen system was designed to meet the demands of 100 families in Misurata, Libya, whose average consumption is 268 kW and an exergy analysis was performed on the system. Results showed that the exergy destruction factor was 0.14 and the environmental destruction factor was 0.16. This study demonstrated that producing hydrogen using solar energy is an environmentally friendly and sustainable method which does not generate any greenhouse gases in the operating stage.

  14. Performance Analysis of Cold Energy Recovery from CO2 Injection in Ship-Based Carbon Capture and Storage (CCS

    Directory of Open Access Journals (Sweden)

    Hwalong You

    2014-11-01

    Full Text Available Carbon capture and storage (CCS technology is one of the practical solutions for mitigating the effects of global warming. When captured CO2 is injected into storage sites, the CO2 is subjected to a heating process. In a conventional CO2 injection system, CO2 cold energy is wasted during this heating process. This study proposes a new CO2 injection system that takes advantage of the cold energy using the Rankine cycle. The study compared the conventional system with the new CO2 injection system in terms of specific net power consumption, exergy efficiency, and life-cycle cost (LCC to estimate the economic effects. The results showed that the new system reduced specific net power consumption and yielded higher exergy efficiency. The LCC of the new system was more economical. Several cases were examined corresponding to different conditions, specifically, discharge pressure and seawater temperature. This information may affect decision-making when CCS projects are implemented.

  15. A software algorithm/package for control loop configuration and eco-efficiency.

    Science.gov (United States)

    Munir, M T; Yu, W; Young, B R

    2012-11-01

    Software is a powerful tool to help us analyze industrial information and control processes. In this paper, we will show our recently development of a software algorithm/package which can help us select the more eco-efficient control configuration. Nowadays, the eco-efficiency of all industrial processes/plants has become more and more important; engineers need to find a way to integrate control loop configuration and measurements of eco-efficiency. The exergy eco-efficiency factor; a new measure of eco-efficiency for control loop configuration has been developed. This software algorithm/package will combine a commercial simulator, VMGSim, and Excel together to calculate the exergy eco-efficiency factor. Copyright © 2012 ISA. Published by Elsevier Ltd. All rights reserved.

  16. Entropy generation and thermodynamic analysis of solar air heaters with artificial roughness on absorber plate

    Directory of Open Access Journals (Sweden)

    Prasad Radha K.

    2017-09-01

    Full Text Available This paper presents mathematical modelling and numerical analysis to evaluate entropy generation analysis (EGA by considering pressure drop and second law efficiency based on thermodynamics for forced convection heat transfer in rectangular duct of a solar air heater with wire as artificial roughness in the form of arc shape geometry on the absorber plate. The investigation includes evaluations of entropy generation, entropy generation number, Bejan number and irreversibilities of roughened as well as smooth absorber plate solar air heaters to compare the relative performances. Furthermore, effects of various roughness parameters and operating parameters on entropy generation have also been investigated. Entropy generation and irreversibilities (exergy destroyed has its minimum value at relative roughness height of 0.0422 and relative angle of attack of 0.33, which leads to the maximum exergetic efficiency. Entropy generation and exergy based analyses can be adopted for the evaluation of the overall performance of solar air heaters.

  17. Integration of Decentralized Thermal Storages Within District Heating (DH Networks

    Directory of Open Access Journals (Sweden)

    Schuchardt Georg K.

    2016-12-01

    Full Text Available Thermal Storages and Thermal Accumulators are an important component within District Heating (DH systems, adding flexibility and offering additional business opportunities for these systems. Furthermore, these components have a major impact on the energy and exergy efficiency as well as the heat losses of the heat distribution system. Especially the integration of Thermal Storages within ill-conditioned parts of the overall DH system enhances the efficiency of the heat distribution. Regarding an illustrative and simplified example for a DH system, the interactions of different heat storage concepts (centralized and decentralized and the heat losses, energy and exergy efficiencies will be examined by considering the thermal state of the heat distribution network.

  18. Integrated optimization of fish oil microencapsulation process by spray drying.

    Science.gov (United States)

    Aghbashlo, Mortaza; Mobli, Hossien; Madadlou, Ashkan; Rafiee, Shahin

    2012-01-01

    An integrated approach through coupling response surface method (RSM) and genetic algorithm (GA) was applied to optimize the spray dryer operational condition for production of fish oil microcapsules. The inlet drying air temperature, aspirator rate, and peristaltic pump rate were independent and encapsulation efficiency (EE) and exergy efficiency were dependent variables. RSM was applied to establish the relationship between the independent and dependent variables followed by integrating the developed models using three mathematical approaches and measure the fitness value of GA. Consequently, the optimal drying condition for microencapsulation of fish oil was: inlet drying air temperature = 177.23°C, aspirator rate = 63.93%, and peristaltic pump rate = 14.04% yielding exergy efficiency of 8.10% and EE of 79.14%. The results of confirmation experiments for selected drying condition proved the capability of utilized approach for determination of sustainable and qualified process in fish oil microencapsulation by spray drying.

  19. Biodiesel production process from microalgae oil by waste heat recovery and process integration.

    Science.gov (United States)

    Song, Chunfeng; Chen, Guanyi; Ji, Na; Liu, Qingling; Kansha, Yasuki; Tsutsumi, Atsushi

    2015-10-01

    In this work, the optimization of microalgae oil (MO) based biodiesel production process is carried out by waste heat recovery and process integration. The exergy analysis of each heat exchanger presented an efficient heat coupling between hot and cold streams, thus minimizing the total exergy destruction. Simulation results showed that the unit production cost of optimized process is 0.592$/L biodiesel, and approximately 0.172$/L biodiesel can be avoided by heat integration. Although the capital cost of the optimized biodiesel production process increased 32.5% and 23.5% compared to the reference cases, the operational cost can be reduced by approximately 22.5% and 41.6%. Copyright © 2015 Elsevier Ltd. All rights reserved.

  20. Optimisation énergétique des procédés de séparation en raffinage et en traitement de gaz naturel Optimal Use of Energy in Separation Processes for Refining and Natural Gas Treatment

    Directory of Open Access Journals (Sweden)

    Rojey A.

    2006-11-01

    Full Text Available Cet article présente une méthode d'optimisation des procédés de séparation basée sur une analyse thermodynamique. Cette analyse s'appuie sur un bilan exergétique qui est établi dans le cas général d'un système quelconque opérant en régime permanent. Les facteurs qui conditionnent le rendement exergétique d'un procédé de séparation sont ensuite examinés. Il en résulte une méthode d'optimisation basée sur une réduction des irréversibilités thermodynamiques. Des exemples concrets d'application en raffinage et en traitement de gaz naturel sont présentés, et on montre comment cette analyse peut déboucher sur la conception de procédés innovants. The optimization of separation units in refining and natural-gas processing must take into consideration new needs and constraints that may seem incompatible. New installations must be designed not only on the basis of energy optimization but also by seeking to minimize investments and to respect new rules concerning environmental protection. The optimization described in this article is based on a thermodynamic analysis of different material and energy exchanges, The energybalance provides a suitable basis for making this analysis. It leads to the defining of an exergy efficiency that is all the higher as the thermodynamic irreversibilities are reduced, and that tends toward one for an ideal reversible system. For a separation process, a separation exergyterm is defined that correspond to the minimum separation work . Distillation is the basic separation operation. The exergy efficiency of this operation is low, and we show that, even in a relatively favorable cas, it is no greater than a value of about 6%. For an atmospheric distillation operation of crude oil, the exergy efficiency is about 4%. This overall exergy efficiency is the product of an external exergy efficiency and an internal exergy efficiency. The external exergy efficiency can be improved by better thermal