Entropy, exergy, and cost analyses of solar driven cogeneration systems using supercritical CO_2 Brayton cycles and MEE-TVC desalination system

International Nuclear Information System (INIS)

Kouta, Amine; Al-Sulaiman, Fahad; Atif, Maimoon; Marshad, Saud Bin

2016-01-01

Highlights: • The entropy, exergy, and cost analyses for two solar cogeneration configurations are conducted. • The recompression cogeneration cycle achieves lower LCOE as compared to the regeneration cogeneration cycle. • The solar tower is the largest contributor to entropy generation in both configurations reaching almost 80%. • The specific entropy generation in the MEE-TVC decreases with decreasing the fraction. - Abstract: In this study, performance and cost analyses are conducted for a solar power tower integrated with supercritical CO_2 (sCO_2) Brayton cycles for power production and a multiple effect evaporation with a thermal vapor compression (MEE-TVC) desalination system for water production. The study is performed for two configurations based on two different supercritical cycles: the regeneration and recompression sCO_2 Brayton cycles. A two-tank molten salt storage is utilized to ensure a uniform operation throughout the day. From the entropy analysis, it was shown that the solar tower is the largest contributor to entropy generation in both configurations, reaching almost 80% from the total entropy generation, followed by the MEE-TVC desalination system, and the sCO_2 power cycle. The entropy generation in the two-tank thermal storage is negligible, around 0.3% from the total generation. In the MEE-TVC system the highest contributing component is the steam jet ejector, which is varying between 50% and 60% for different number of effects. The specific entropy generation in the MEE-TVC decreases as the fraction of the input heat to the desalination system decreases; while the specific entropy generation of the sCO_2 cycle remains constant. The cost analysis performed for different regions in Saudi Arabia and the findings reveal that the regions characterized by the highest average solar irradiation throughout the year have the lowest LCOE and LCOW values. The region achieving the lowest cost is Yanbu, followed by Khabt Al-Ghusn in the second

Exergetic analysis of the operation of a petrochemical pole cogeneration system; Analise exergetica da operacao de uma planta de cogeracao de um polo petroquimico

Energy Technology Data Exchange (ETDEWEB)

Torres, Ednildo A. [Bahia Univ., Salvador, BA (Brazil). Escola Politecnica]. E-mail: ednildo@ufba.br; Gallo, Waldyr L. R. [Universidade Estadual de Campinas, SP (Brazil). Faculdade de Engenharia Mecanica. Dept. de Energia]. E-mail: gallo@unicamp.br

2000-07-01

This work presents an exergy analysis for a petrochemical cogeneration system (the greater operating in Brazil). The system is described, the method employed to simulate the system is presented, and the exergy efficiencies are defined. The analysis presents the exergy efficiencies and irreversibility for each sub-system. The results obtained from real data were used to compare operation strategies which are not clear from energy balances. (author)

Energy and Exergy Analysis of Cogeration System with Biogas Engines

OpenAIRE

Doseva, Nadezhda; Chakyrova, Daniela

2015-01-01

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

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

Energy Technology Data Exchange (ETDEWEB)

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

2012-07-01

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

Modelling of a chemisorption refrigeration and power cogeneration system

International Nuclear Information System (INIS)

Bao, Huashan; Wang, Yaodong; Roskilly, Anthony Paul

2014-01-01

Highlights: • An adsorption cogeneration was proposed and simulated for cooling and electricity. • A dynamic model was built and studied to demonstrate the variability of the system. • A dynamic model included the complex coupling of thermodynamic and chemical kinetic. • Mutual constrains between main components and optimisation methods were discussed. • The highest theoretical COP and exergy efficiency of cogeneration is 0.57 and 0.62. - Abstract: The present work for the first time explores the possibility of a small-scale cogeneration unit by combining solid–gas chemisorption refrigeration cycle and a scroll expander. The innovation in this work is the capability of producing refrigeration and electricity continuously and simultaneously without aggravating the energy scarcity and environmental impact. Individual modelling for each component, which has been validated by experimental data, was firstly investigated in order to identify the proper operation condition for the cogeneration mode achieving 1000 W power output. Subsequently, with the integrated modelling of two components the cogeneration performance was studied to demonstrate the viability of this concept. However, because of the mutual constraint between the chemisorption and the expansion when they link in series, the power output of the cogeneration mode was only around one third of the original expectation under the same condition identified in the individual modelling. Methods of improving the global performance including the selection of reactive mediums were also discussed and would be of referable value for the future practical investigation

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

International Nuclear Information System (INIS)

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

2004-01-01

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

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.

Exergy and economic analysis of organic rankine cycle hybrid system utilizing biogas and solar energy in rural area of China

DEFF Research Database (Denmark)

Zhao, Chunhua; Zheng, Siyu; Zhang, Ji

2017-01-01

circuits. The cogeneration supplied the power to the air-condition in summer condition and hot water, which is heated in the condenser, in winter condition. The system performance under the subcritical pressures has been assessed according to the energy-exergy and economic analysis with the organic working......℃. The exergy efficiency of organic Rankine cycle (ORC) system increases from 35.2% to 38.2%. Moreover, an economic analysis of the system is carried out. The results demonstrate that the profits generated from the reduction of biogas fuel and electricity consumption can lead to a significant saving, resulting...

Energy and exergy utilizations of the Chinese urban residential sector

International Nuclear Information System (INIS)

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

2014-01-01

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

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

Science.gov (United States)

Goncalves, Pedro Manuel Ferreira

supply options are proposed and assessed as primary energy demand and exergy efficiency, showing it as a possible benchmarking method for future legislative frameworks regarding the energy performance assessment of buildings. Case study IV proposes a set of complementary indicators for comparing cogeneration and separate heat and electricity production systems. It aims to identify the advantages of exergy analysis relative to energy analysis, giving particular examples where these advantages are significant. The results demonstrate that exergy analysis can reveal meaningful information that might not be accessible using a conventional energy analysis approach, which is particularly evident when cogeneration and separated systems provide heat at very different temperatures. Case study V follows the exergy analysis method to evaluate the energy and exergy performance of a desiccant cooling system, aiming to assess and locate irreversibilities sources. The results reveal that natural gas boiler is the most inefficient component of the plant in question, followed by the chiller and heating coil. A set of alternative heating supply options for desiccant wheel regeneration is proposed, showing that, while some renewables may effectively reduce the primary energy demand of the plant, although this may not correspond to the optimum level of exergy efficiency. The thermal and chemical exergy components of moist air are also evaluated, as well as, the influence of outdoor environmental conditions on the energy/exergy performance of the plant. This research provides knowledge that is essential for the future development of complementary energy- and exergy-based indicators, helping to improve the current methodologies on performance assessments of buildings, cogeneration and desiccant cooling systems. The significance of exergy analysis is demonstrated for different types of buildings, which may be located in different climates (reference states) and be supplied by different types

Proposal of a combined heat and power plant hybridized with regeneration organic Rankine cycle: Energy-Exergy evaluation

International Nuclear Information System (INIS)

Anvari, Simin; Jafarmadar, Samad; Khalilarya, Shahram

2016-01-01

Highlights: • A new thermodynamic cogeneration system is proposed. • Energy and exergy analysis of the considered cycle were performed. • An enhancement of 2.6% in exergy efficiency compared to that of baseline cycle. - Abstract: Among Rankine cycles (simple, reheat and regeneration), regeneration organic Rankine cycle demonstrates higher efficiencies compared to other cases. Consequently, in the present work a regeneration organic Rankine cycle has been utilized to recuperate gas turbine’s heat using heat recovery steam generator. At first, this cogeneration system was subjected to energy and exergy analysis and the obtained results were compared with that of investigated cogeneration found in literature (a cogeneration system in which a reheat organic Rankine cycle for heat recuperation of gas turbine cycle was used with the aid of heat recovery steam generator). Results indicated that the first and second thermodynamic efficiencies in present cycle utilizing regeneration cycle instead of reheat cycle has increased 2.62% and 2.6%, respectively. In addition, the effect of thermodynamic parameters such as combustion chamber’s inlet temperature, gas turbine inlet temperature, evaporator and condenser temperature on the energetic and exergetic efficiencies of gas turbine-heat recovery steam generator cycle and gas turbine-heat recovery steam generator cycle with regeneration organic Rankine cycle was surveyed. Besides, parametric analysis shows that as gas turbine and combustion chamber inlet temperatures increase, energetic and exergetic efficiencies tend to increase. Moreover, once condenser and evaporator temperature raise, a slight decrement in energetic and exergetic efficiency is expected.

Integrated and visual performance evaluation model for thermal systems and its application to an HTGR cogeneration system

International Nuclear Information System (INIS)

Qi, Zhang; Yoshikawa, Hidekazu; Ishii, Hirotake; Shimoda, Hiroshi

2010-01-01

An integrated and visual model EXCEM-MFM (EXergy, Cost, Energy and Mass - Multilevel Flow Model) has been proposed in this study to comprehensively analyze and evaluate the performances of thermal systems by coupling two models: EXCEM model and MFM. In the EXCEM-MFM model, MFM is used to provide analysis frameworks for exergy, cost, energy and mass four parameters, and EXCEM is used to calculate the flow values of these four parameters for MFM based on the provided framework. In this study, we used the tools and technologies of computer science and software engineering to materialize the model. Moreover, the feasibility and application potential of this proposed EXCEM-MFM model has been demonstrated by the example application of a comprehensive performance study of a typical High Temperature Gas Reactor (HTGR) cogeneration system by taking into account the thermodynamic and economic perspectives. (author)

Exergy analysis for Generation IV nuclear plant optimization

International Nuclear Information System (INIS)

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

2010-01-01

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

Exergy analysis for Generation IV nuclear plant optimization

Energy Technology Data Exchange (ETDEWEB)

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

2010-07-01

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

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

International Nuclear Information System (INIS)

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

2013-01-01

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

Investigation on an innovative cascading cycle for power and refrigeration cogeneration

International Nuclear Information System (INIS)

Jiang, Long; Lu, Huitong; Wang, Ruzhu; Wang, Liwei; Gong, Lixia; Lu, Yiji; Roskilly, Anthony Paul

2017-01-01

Highlights: • A novel cascading cycle for power and refrigeration cogeneration is proposed and investigated. • Pumpless ORC and sorption refrigeration cycle act as the first and second stage. • The highest power and refrigeration output are able to reach 232 W and 4.94 kW, respectively. • The exergy efficiency of heat utilization ranges from 30.1% to 41.8%. - Abstract: In order to further realize efficient utilization of low grade heat, an innovative cascading cycle for power and refrigeration cogeneration is proposed. Pumpless Organic Rankine Cycle (ORC) acts as the first stage, and the refrigerant R245fa is selected as the working fluid. Sorption refrigeration cycle serves as the second stage in which silica-gel/LiCl composite sorbent is developed for the improved sorption characteristic. The concerning experimental system is established, and different hot water inlet temperatures from 75 °C to 95 °C are adopted to investigate the cogeneration performance. It is indicated that the highest power and refrigeration output are able to reach 232 W and 4.94 kW, respectively under the condition of 95 °C hot water inlet temperature, 25 °C cooling water temperature and 10 °C chilled water outlet temperature. For different working conditions, the total energy and exergy efficiency of the cascading system range from 0.236 to 0.277 and 0.101 to 0.132, respectively. For cascading system the exergy efficiency of heat utilization ranges from 30.1% to 41.8%, which is 144% and 60% higher than that of pumpless ORC and sorption chiller when the hot water inlet temperature is 95 °C.

Experimental study on a resorption system for power and refrigeration cogeneration

International Nuclear Information System (INIS)

Jiang, L.; Wang, L.W.; Liu, C.Z.; Wang, R.Z.

2016-01-01

Energy conversion technologies, especially for power generation and refrigeration technologies driven by the low temperature heat, are gathering the momentum recently. This paper presents a novel resorption system for electricity and refrigeration cogeneraion. Compared with adsorption refrigeration system, resorption refrigeration is characterized as safety and simple structure since there is no ammonia liquid in the system. The cogeneration system is mainly composed of three HTS (high temperature salt) unit beds; three LTS (low temperature salts) unit beds, one expander, three ammonia valves, two oil valves, four water valves and connection pipes. Chemical working pair of MnCl 2 –CaCl 2 –NH 3 is selected. Since scroll expander is suitable for small type power generation system, it is chosen for expansion process. 4.8 kg MnCl 2 and 3.9 kg CaCl 2 impregnated in expanded natural graphite treated with sulfuric acid (ENG-TSA) are filled in the cogeneration system. Experimental results show that maximum cooling power 2.98 kW is able to be obtained while maximum shaft power is about 253 W with 82.3 W average value. The cogeneration system can be utilized for the heat source temperature lower than 170 °C. Total energy efficiency increases from 0.293 to 0.417 then decreases to 0.407 while exergy efficiency increases from 0.12 to 0.16. - Highlights: • A resorption system for power and refrigeration cogeneration is established and investigated. • ENG-TSA as the additive improves the heat and mass performance of composite adsorbent. • The highest shaft power and refrigeration power are 253 W and 2.98 kW, respectively. • Total energy efficiency of the system increases from 0.293 to 0.417 then decreases to 0.407.

Improving bioethanol production from sugarcane: evaluation of distillation, thermal integration and cogeneration systems

International Nuclear Information System (INIS)

Dias, Marina O.S.; Modesto, Marcelo; Ensinas, Adriano V.; Nebra, Silvia A.; Filho, Rubens Maciel; Rossell, Carlos E.V.

2011-01-01

Demand for bioethanol has grown considerably over the last years. Even though Brazil has been producing ethanol from sugarcane on a large scale for decades, this industry is characterized by low energy efficiency, using a large fraction of the bagasse produced as fuel in the cogeneration system to supply the process energy requirements. The possibility of selling surplus electricity to the grid or using surplus bagasse as raw material of other processes has motivated investments on more efficient cogeneration systems and process thermal integration. In this work simulations of an autonomous distillery were carried out, along with utilities demand optimization using Pinch Analysis concepts. Different cogeneration systems were analyzed: a traditional Rankine Cycle, with steam of high temperature and pressure (80 bar, 510 o C) and back pressure and condensing steam turbines configuration, and a BIGCC (Biomass Integrated Gasification Combined Cycle), comprised by a gas turbine set operating with biomass gas produced in a gasifier that uses sugarcane bagasse as raw material. Thermoeconomic analyses determining exergy-based costs of electricity and ethanol for both cases were carried out. The main objective is to show the impact that these process improvements can produce in industrial systems, compared to the current situation.

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

International Nuclear Information System (INIS)

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

2006-01-01

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

Thermodynamic performance analysis of a novel electricity-heating cogeneration system (EHCS) based on absorption heat pump applied in the coal-fired power plant

International Nuclear Information System (INIS)

Zhang, Hongsheng; Li, Zhenlin; Zhao, Hongbin

2015-01-01

Highlights: • Presented a novel waste heat recovery method for Combined Heat and Power system. • Established models of the integrated system based on energy and exergy analysis. • Adopted both design and actual data ensuring the reliability of analysis results. - Abstract: A novel electricity-heating cogeneration system (EHCS) which is equipped with an absorption heat pump (AHP) system to recover waste heat from exhaust steam of the steam turbines in coal-fired thermal power plants is proposed to reduce heating energy consumption and improve the utilization of the fossil fuels in existing CHP (Combined Heat and Power) systems. According to the first and second thermodynamic law, the changes of the performance evaluation indicators are analyzed, and exergy analyses for key components of the system are carried out as well as changes of exergy indexes focusing on 135 MW direct air cooling units before and after modification. Compared with the conventional heating system, the output power increases by about 3.58 MW, gross coal consumption rate and total exergy loss respectively reduces by 11.50 g/kW h and 4.649 MW, while the total thermal and exergy efficiency increases by 1.26% and 1.45% in the EHCS when the heating load is 99,918 kJ at 75% THA condition. Meanwhile, the decrement of total exergy loss and increment of total exergy efficiency increase with the increasing of the heating load. The scheme cannot only bring great economic benefits but also save fossil resources, which has a promising market application potential.

AMBIENT CONDITIONS EFFECTS ON PERFORMANCE OF GAS TURBINE COGENERATION POWER PLANTS

OpenAIRE

Necmi Ozdemir*

2016-01-01

In this study, the performances of a simple and an air preheated cogeneration cycles in ambient conditions are compared with each other. A computer program written by the author in FORTRAN codes is used for the calculation of the enthalpy and entropy values of the streams, Exergy analysis is done and compared for the simple and the air preheated cogeneration cycles for different ambient conditions. The two cogeneration cycles are evaluated in terms of heat powers and electric, electrical to h...

Exergy analysis of a gas-hydrate cool storage system

International Nuclear Information System (INIS)

Bi, Yuehong; Liu, Xiao; Jiang, Minghe

2014-01-01

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

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.

Analysis and assessment of a new organic Rankine based heat engine system with/without cogeneration

International Nuclear Information System (INIS)

Hogerwaard, Janette; Dincer, Ibrahim; Zamfirescu, Calin

2013-01-01

A low-temperature heat driven heat engine is proposed as a cost-effective system for power and heat production for small scale applications. The external heat source allows flexibility in the design; the system may be coupled with various available renewable sources including biomass/biofuel/biogas combustion, geothermal heat, concentrated solar radiation, and industrial waste heat, by selecting appropriate off-the-shelf components from the HVAC (heating, ventilation, and air conditioning), refrigeration, and automotive industries for use in an ORC (organic Rankine cycle). A theoretical analysis and an experimental study are carried out for an ORC with R134a as the working fluid, utilizing a low-temperature heat source (T source < 150 °C), with focus on the expansion and boiling processes. The complete ORC model is comprised of models for the expander, working fluid pump, boiler, and condenser. Thermodynamic and heat transfer models are developed to calculate the local and averaged heat transfer coefficient of the working fluid throughout the boiling process, based on the geometry of the selected heat exchanger. Data collected for the experimental ORC test bench are used to validate the expander and boiler models. A case study is performed for the proposed ORC, for cogeneration of power and heat in a residential application. The results of the case study analysis for the proposed ORC system indicate a cycle efficiency of 0.05, exergy efficiency of 0.17, and energy and exergy cogeneration efficiency of 0.87, and 0.35, respectively. - Highlights: • Development and investigation of a scroll based Rankine heat engine operating with R134a. • Thermodynamic analyses of the system and its components. • Heat transfer analyses of boiler and condenser. • Dynamic analysis of expander. • Model validation through performed experiments on an ORC test bench

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

International Nuclear Information System (INIS)

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

1994-01-01

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

Exergoeconomic analysis and optimization of a model cogeneration system; Analise exergoeconomica e otimizacao de um modelo de sistema de cogeracao

Energy Technology Data Exchange (ETDEWEB)

Vieira, Leonardo S.R. [Centro de Pesquisas de Energia Eletrica, Rio de Janeiro, RJ (Brazil). Area de Conhecimento de Materiais e Mecanica]. E-mail: lsrv@cepel.br; Donatelli, Joao L.M. [Espirito Santo Univ., Vitoria, ES (Brazil). Dept. de Engenharia Mecanica]. E-mail: donatelli@lttc.com.ufrj.br; Cruz, Manuel E.C. [Universidade Federal, Rio de Janeiro, RJ (Brazil). Dept. de Engenharia Mecanica]. E-mail: manuel@serv.com.ufrj.br

2000-07-01

In this paper we perform exergetic and exergoeconomic analyses, a mathematical optimization and an exergoeconomic optimization of a gas turbine-heat recovery boiler cogeneration system with fixed electricity and steam production rates. The exergy balance is calculated with the IPSE pro thermal system simulation program. In the exergetic analysis, exergy destruction rates, exergetic efficiencies and structural bond coefficients for each component are evaluated as functions of the decision variables of the optimization problem. In the exergoeconomic analysis the cost for each exergetic flow is determined through cost balance equations and additional auxiliary equations from cost partition criteria. Mathematical optimization is performed by the metric variable method (software EES - Engineering Equation Solver) and by the successive quadratic programming (IMSL library - Fortran Power Station). The exergoeconomic optimization is performed on the basis of the exergoeconomic variables. System optimization is also performed by evaluating the derivative of the objective function through finite differences. This paper concludes with a comparison between the four optimization techniques employed. (author)

Energy and exergy analyses of the diffusion absorption refrigeration system

International Nuclear Information System (INIS)

Yıldız, Abdullah; Ersöz, Mustafa Ali

2013-01-01

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

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.

Controlling systems of cogeneration blocks

International Nuclear Information System (INIS)

Suriansky, J.; Suriansky, J. Ml.; Puskajler, J.

2007-01-01

In this article the main parts of cogeneration unit control system are described. Article is aimed on electric power measurement with electricity protection as with temperature system regulation. In conclusion of the article, the control algorithm with perspective of cogeneration solve is indicated. (authors)

Advanced exergy analyses of an ejector expansion transcritical CO_2 refrigeration system

International Nuclear Information System (INIS)

Bai, Tao; Yu, Jianlin; Yan, Gang

2016-01-01

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

Cogeneration system simulation/optimization

International Nuclear Information System (INIS)

Puppa, B.A.; Chandrashekar, M.

1992-01-01

Companies are increasingly turning to computer software programs to improve and streamline the analysis o cogeneration systems. This paper introduces a computer program which originated with research at the University of Waterloo. The program can simulate and optimize any type of layout of cogeneration plant. An application of the program to a cogeneration feasibility study for a university campus is described. The Steam and Power Plant Optimization System (SAPPOS) is a PC software package which allows users to model any type of steam/power plant on a component-by-component basis. Individual energy/steam balances can be done quickly to model any scenario. A typical days per month cogeneration simulation can also be carried out to provide a detailed monthly cash flow and energy forecast. This paper reports that SAPPOS can be used for scoping, feasibility, and preliminary design work, along with financial studies, gas contract studies, and optimizing the operation of completed plants. In the feasibility study presented, SAPPOS is used to evaluate both diesel engine and gas turbine combined cycle options

The application of exergy to human-designed systems

Science.gov (United States)

Hamilton, P.

2012-12-01

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

Coal to SNG: Technical progress, modeling and system optimization through exergy analysis

International Nuclear Information System (INIS)

Li, Sheng; Ji, Xiaozhou; Zhang, Xiaosong; Gao, Lin; Jin, Hongguang

2014-01-01

synthesis process will increase sharply, which causes a decrease in overall system efficiency. Keeping the conversion ratio of the first synthesis reaction between 0.78 and 0.90 not only avoids the rapid increase of exergy destruction in the SNG synthesis process but also produces the SNG product with a high CH 4 purity (>94.0%), and the catalyst can be maintained with a high activity. When the split ratio of the recycle gas is approximately 0.85, the best coupling/balance between SNG production and power generation can be attained and thus the highest overall system efficiency of approximately 62% is achieved, much higher than approximately 55% efficiency in a traditional coal to SNG plant. The findings presented in this paper are important steps for future improvements of coal to SNG systems, especially the SNG and power cogeneration systems, integration in the future

Energy system analysis of a pilot net-zero exergy district

International Nuclear Information System (INIS)

Kılkış, Şiir

2014-01-01

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

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

International Nuclear Information System (INIS)

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

2016-01-01

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

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

Directory of Open Access Journals (Sweden)

Xiao Chen

2015-04-01

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

Exergeoconomic analysis and optimization of a novel cogeneration system producing power and refrigeration

International Nuclear Information System (INIS)

Akbari Kordlar, M.; Mahmoudi, S.M.S.

2017-01-01

Highlights: • A novel combined cooling and power cogeneration system is proposed. • Thermodynamic and exergoeconomic analyses are performed. • Optimizations are performed considering thermodynamics and economics. • An increase in turbine inlet pressure is in favor of the system performance. • Five parameters influence the total product unit cost. - Abstract: A novel combined cooling and power cogeneration system driven by geothermal hot water is proposed. The system, which is a combination of an organic Rankine cycle and an absorption refrigeration cycle, is analyzed and optimized from the viewpoints of thermodynamics and economics. The working fluid in organic Rankine cycle is ammonia and in the refrigeration cycle is an ammonia-water solution. Parametric studies are performed to identify decision parameters prior to optimization. In optimizing the system performance three design cases i.e. designs for maximum first law efficiency (case1), maximum second law efficiency (case2) and minimum total product unit cost (case3) are considered. The results show that the total products unit cost in case3 is around 20.4% and 24.3% lower than the corresponding value in case1 and 2, respectively. The lower product unit cost in case3 is accompanied with an expense of 10.21% and 4.5% reduction in the first and second law efficiencies, compared to case1 and 2, respectively. The results also indicate that concerning the costs associated with capital and exergy destruction costs of components, the priority of components for modifications are the turbine, condenser and absorber. The last component in this order are the two pumps in the system.

Enhancement of exergy efficiency in combustion systems using flameless mode

International Nuclear Information System (INIS)

Hosseini, Seyed Ehsan; Wahid, Mazlan Abdul

2014-01-01

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

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.

Exergy performance of different space heating systems: A theoretical study

DEFF Research Database (Denmark)

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

2016-01-01

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

Energy and exergy analyses of an integrated solar heat pump system

International Nuclear Information System (INIS)

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

2014-01-01

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

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

International Nuclear Information System (INIS)

Joybari, Mahmood Mastani; Haghighat, Fariborz

2016-01-01

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

Minimization of local impact of energy systems through exergy analysis

International Nuclear Information System (INIS)

Cassetti, Gabriele; Colombo, Emanuela

2013-01-01

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

Cogeneration Systems; Sistemas de Cogeneracion

Energy Technology Data Exchange (ETDEWEB)

Fernandez M, Manuel F; Huante P, Liborio; Romo M, Cesar A [Instituto de Investigaciones Electricas, Cuernavaca, Morelos (Mexico)

2006-07-01

The present article deals on relevant aspects on the subject of cogeneration within the Mexican territorial limits. In the first place it is presented the role of Mexico in terms of its cogeneration potential, the type of service that has obtained from this predominant modality of cogeneration for self-supplying, the most propitious sectors to develop it, its legislations on the matter, the projects made for the implementation of cogeneration plants, as well as the existing cogeneration schemes for its respective optimization proposals. Without leaving out the analysis on the different types of evaluation on the efficiency of cogeneration systems and the aspects to consider for the election of a generation cycle. [Spanish] El presente articulo trata sobre aspectos relevantes en materia de cogeneracion dentro de los limites territoriales de la nacion mexicana. Se muestra en primer lugar el papel de Mexico en terminos de su potencial de cogeneracion, el tipo de servicio que ha obtenido de esta predominantemente (modalidad de cogeneracion para autoabastecimiento), los sectores mas propicios para desarrollarla, sus legislaciones al respecto, los proyectos realizados para la implementacion de plantas de cogeneracion, asi como los esquemas de cogeneracion existentes con sus respectivas propuestas de optimizacion. Sin dejar de lado el analisis sobre los distintos tipos de evaluacion de la eficiencia de sistemas de cogeneracion y los aspectos a considerar para la eleccion de un ciclo de generacion.

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

DEFF Research Database (Denmark)

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

2016-01-01

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

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.

The role of cogeneration systems in sustainability of energy

International Nuclear Information System (INIS)

Çakir, Uğur; Çomakli, Kemal; Yüksel, Fikret

2012-01-01

Highlights: ► Energy source on the world is tending to run out day by day while the energy need of humanity is increasing simultaneously. ► There are two ways to overcome this problem; one of them is renewable energy sources like solar or wind energy systems. ► The other way is like cogeneration systems. ► Cogeneration system is one of the ways to save the energy and use the energy efficiently. ► A case study is made for a hospital to present the sustainability aspects of cogeneration systems. - Abstract: Cogeneration system (CHP) is one of the ways to save the energy and use the energy efficiently. When compared to separate fossil-fired generation of heat and electricity, CHP may result in a consistent energy conservation (usually ranging from 10% to 30%) while the avoided CO 2 emissions are, as a first approximation, similar to the amount of energy saving. In terms of sustainability, one of the primary considerations is energy efficiency. Sustainable energy is considered as a kind of energy which is renewable and continuous, meaning that the use of such energy can potentially be kept up well into the future without causing harmful repercussions for future generations. In this study, environmental benefits and sustainability aspects of cogeneration systems and importance of those systems to the use of sustainable energy are underlined. To support this idea, first we have referred some scientific studies previously made on cogeneration systems and then we have used our own case study. The case study made on gas engined cogeneration system was applied for a hospital to show the sustainability aspects of cogeneration systems.

Cogeneration and local authorities; Cogeneration et collectivites territoriales

Energy Technology Data Exchange (ETDEWEB)

NONE

1996-07-01

This conference is composed of 15 communications concerning cogeneration systems and applications in local communities. The main themes are: the regulation context and administrative procedures for cogeneration projects in France; legal aspects, risk covering, financing and sellback conditions for cogeneration systems; examples of cogeneration and tri-generation (with refrigeration energy) in different cities, airport, hospitals, campus, combined with the upgrading of district heating systems or municipal waste incineration plants. Impacts on energy savings and air pollution are also discussed

Residential cogeneration systems: review of the current technology

International Nuclear Information System (INIS)

Onovwiona, H.I.; Ugursal, V.I.

2006-01-01

There is a growing potential for the use of micro-cogeneration systems in the residential sector because they have the ability to produce both useful thermal energy and electricity from a single source of fuel such as oil or natural gas. In cogeneration systems, the efficiency of energy conversion increases to over 80% as compared to an average of 30-35% for conventional fossil fuel fired electricity generation systems. This increase in energy efficiency can result in lower costs and reduction in greenhouse gas emissions when compared to the conventional methods of generating heat and electricity separately. Cogeneration systems and equipment suitable for residential and small-scale commercial applications like hospitals, hotels or institutional buildings are available, and many new systems are under development. These products are used or aimed for meeting the electrical and thermal demands of a building for space and domestic hot water heating, and potentially, absorption cooling. The aim of this paper is to provide an up-to-date review of the various cogeneration technologies suitable for residential applications. The paper considers the various technologies available and under development for residential, i.e. single-family ( e ) and multi-family (10-30kW t ) applications, with focus on single-family applications. Technologies suitable for residential cogeneration systems include reciprocating internal combustion engine, micro-turbine, fuel cell, and reciprocating external combustion Stirling engine based cogeneration systems. The paper discusses the state of development and the performance, environmental benefits, and costs of these technologies. (author)

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.

Gas cogeneration system in Sapporo Therme

Energy Technology Data Exchange (ETDEWEB)

Kanematsu, Michihiko

1988-06-01

Sapporo Therme is a multi-purpose resort including a hot-water jumbo swimming pool having an area of about 130,000m/sup 2/ and a circumference of 800 m, 13 additional swimming pools with additional sizes, a hot-water slider, 16 types of saunas, an artificial sunbathing system, an athletic system, a restaurant, a cinema, tennis courts, and other outdoor facilities. Sapporo Therme uses a cogeneration system consisting of using LP gas(95% or more propane gas) to drive a 1,200 PS gas engine and supply motive power and lightening. At the same time, the cogeneration system collects gas engine waste heat and combines this heat with that from hot-water and steam boilers to supply hot water to swimming pools, roads, and room heaters. The ratio of waste heat collection rate to power generation efficiency is about 5.0. Sapporo Therme is thus the optimal facilities for cogeneration. (1 figs, 3 photos)

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

International Nuclear Information System (INIS)

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

2015-01-01

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

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

International Nuclear Information System (INIS)

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

2014-01-01

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

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.

Thermoeconomic analysis of Biomass Integrated Gasification Gas Turbine Combined Cycle (BIG GT CC) cogeneration plant

Energy Technology Data Exchange (ETDEWEB)

Arrieta, Felipe Raul Ponce; Lora, Electo Silva [Escola Federal de Engenharia de Itajuba, MG (Brazil). Nucleo de Estudos de Sistemas Termicos]. E-mails: aponce@iem.efei.br; electo@iem.efei.br; Perez, Silvia Azucena Nebra de [Universidade Estadual de Campinas, SP (Brazil). Faculdade de Engenharia Mecanica. Dept. de Energia]. E-mail: sanebra@fem. unicamp.br

2000-07-01

Using thermoeconomics as a tool to identify the location and magnitude of the real thermodynamic losses (energy waste, or exergy destruction and exergy losses) it is possible to assess the production costs of each product (electric power and heat) and the exergetic and exergoeconomic cost of each flow in a cogeneration plant to assist in decision-marketing procedures concerning to plant design, investment, operation and allocations of research funds. Thermo economic analysis of Biomass Integrated Gasification Gas Turbine Combined Cycle (BIG GT CC) cogeneration plant for its applications in sugar cane mills brings the following results: the global exergetic efficiency is low; the highest irreversibilities occur in the following equipment, by order: scrubber (38%), gas turbine (16%), dryer (12%), gasifier and HRSG (6%); due to the adopted cost distribution methodology, the unit exergetic cost of the heat (4,11) is lower than electricity (4,71); the lower market price of biomass is one of the most sensible parameter in the possible implementation of BIG-GT technology in sugar cane industry; the production costs are 31 US$/MWh and 32 US$/MWh for electricity and heat, respectively. The electricity cost is, after all, competitive with the actual market price. The electricity and heat costs are lower or almost equal than other values reported for actual Rankine cycle cogeneration plants. (author)

Exergy analysis of a novel CHP–GSHP coupling system

International Nuclear Information System (INIS)

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

2016-01-01

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

Community Design Parameters and the Performance of Residential Cogeneration Systems

Directory of Open Access Journals (Sweden)

Hazem Rashed-Ali

2012-11-01

Full Text Available The integration of cogeneration systems in residential and mixed-use communities has the potential of reducing their energy demand and harmful emissions and can thus play asignificant role in increasing their environmental sustainability. This study investigated the impact of selected planning and architectural design parameters on the environmental and economic performances of centralized cogeneration systems integrated into residential communities in U.S.cold climates. Parameters investigated include: 1 density, 2 use mix, 3 street configuration, 4 housing typology, 5 envelope and building systems’ efficiencies, and 6 passive solar energyutilization. The study integrated several simulation tools into a procedure to assess the impact of each design parameter on the cogeneration system performance. This assessment procedure included: developing a base-line model representing typical design characteristics of U.S. residential communities; assessing the cogeneration system’s performance within this model using three performance indicators: percentage of reduction in primary energy use, percentage of reduction in CO2 emissions; and internal rate of return; assessing the impact of each parameter on the system performance through developing 46 design variations of the base-line model representing potential changes in each parameter and calculating the three indicators for each variation; and finally, using a multi-attribute decision analysis methodology to evaluate the relative impact of each parameter on the cogeneration system performance. The study results show that planning parameters had a higher impact on the cogeneration system performance than architectural ones. Also, a significant correlation was found between design characteristics identified as favorable for the cogeneration system performance and those of sustainable residential communities. These include high densities, high use mix, interconnected street networks, and mixing of

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

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

Allocating resources and products in multi-hybrid multi-cogeneration: What fractions of heat and power are renewable in hybrid fossil-solar CHP?

International Nuclear Information System (INIS)

Beretta, Gian Paolo; Iora, Paolo; Ghoniem, Ahmed F.

2014-01-01

A general method for the allocation of resources and products in multi-resource/multi-product facilities is developed with particular reference to the important two-resource/two-product case of hybrid fossil and solar/heat and power cogeneration. For a realistic case study, we show how the method allows to assess what fractions of the power and heat should be considered as produced from the solar resource and hence identified as renewable. In the present scenario where the hybridization of fossil power plants by solar-integration is gaining increasing attention, such assessment is of great importance in the fair and balanced development of local energy policies based on granting incentives to renewables resources. The paper extends to the case of two-resource/two-product hybrid cogeneration, as well as to general multi-resource/multi-generation, three of the allocation methods already available for single-resource/two-product cogeneration and for two-resource/single-product hybrid facilities, namely, the ExRR (Exergy-based Reversible-Reference) method, the SRSPR (Single Resource Separate Production Reference) method, and the STALPR (Self-Tuned-Average-Local-Productions-Reference) method. For the case study considered we show that, unless the SRSPR reference efficiencies are constantly updated, the differences between the STALPR and SRSPR methods become important as hybrid and cogeneration plants take up large shares of the local energy production portfolio. - Highlights: • How much of the heat and power in hybrid solar-fossil cogeneration are renewable? • We define and compare three allocation methods for hybrid cogeneration. • Classical and exergy allocation are based on prescribed reference efficiencies. • Adaptive allocation is based on the actual average efficiencies in the local area. • Differences among methods grow as hybrid CHP (heat and power cogeneration) gains large market fractions

Benefit Analysis of Emergency Standby System Promoted to Cogeneration System

Directory of Open Access Journals (Sweden)

Shyi-Wen Wang

2016-07-01

Full Text Available Benefit analysis of emergency standby system combined with absorption chiller promoted to cogeneration system is introduced. Economic evaluations of such upgraded projects play a major part in the decisions made by investors. Time-of-use rate structure, fuel cost and system constraints are taken into account in the evaluation. Therefore, the problem is formulated as a mixed-integer programming problem. Using two-stage methodology and modified mixed-integer programming technique, a novel algorithm is developed and introduced here to solve the nonlinear optimization problem. The net present value (NPV method is used to evaluate the annual benefits and years of payback for the cogeneration system. The results indicate that upgrading standby generators to cogeneration systems is profitable and should be encouraged, especially for those utilities with insufficient spinning reserves, and moreover, for those having difficulty constructing new power plants.

Quantifying global exergy resources

International Nuclear Information System (INIS)

Hermann, Weston A.

2006-01-01

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

Exergy analysis of HTGR-GT

International Nuclear Information System (INIS)

Cao Jianhua; Wang Jie; Yang Xiaoyong; Yu Suyuan

2005-01-01

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

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

International Nuclear Information System (INIS)

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

2016-01-01

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

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

OpenAIRE

Pankaj Yadav; Brijesh Tripathi; Manoj Kumar

2013-01-01

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

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 .

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

International Nuclear Information System (INIS)

Zmeureanu, Radu; Yu Wu, Xin

2007-01-01

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

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

International Nuclear Information System (INIS)

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

2014-01-01

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

Development of a proton exchange membrane fuel cell cogeneration system

Energy Technology Data Exchange (ETDEWEB)

Hwang, Jenn Jiang; Zou, Meng Lin [Department of Greenergy, National University of Tainan, Tainan 700 (China)

2010-05-01

A proton exchange membrane fuel cell (PEMFC) cogeneration system that provides high-quality electricity and hot water has been developed. A specially designed thermal management system together with a microcontroller embedded with appropriate control algorithm is integrated into a PEM fuel cell system. The thermal management system does not only control the fuel cell operation temperature but also recover the heat dissipated by FC stack. The dynamic behaviors of thermal and electrical characteristics are presented to verify the stability of the fuel cell cogeneration system. In addition, the reliability of the fuel cell cogeneration system is proved by one-day demonstration that deals with the daily power demand in a typical family. Finally, the effects of external loads on the efficiencies of the fuel cell cogeneration system are examined. Results reveal that the maximum system efficiency was as high as 81% when combining heat and power. (author)

Development of Residential SOFC Cogeneration System

International Nuclear Information System (INIS)

Ono, Takashi; Miyachi, Itaru; Suzuki, Minoru; Higaki, Katsuki

2011-01-01

Since 2001 Kyocera has been developing 1kW class Solid Oxide Fuel Cell (SOFC) for power generation system. We have developed a cell, stack, module and system. Since 2004, Kyocera and Osaka Gas Co., Ltd. have been developed SOFC residential co-generation system. From 2007, we took part in the 'Demonstrative Research on Solid Oxide Fuel Cells' Project conducted by New Energy Foundation (NEF). Total 57 units of 0.7kW class SOFC cogeneration systems had been installed at residential houses. In spite of residential small power demand, the actual electric efficiency was about 40%(netAC,LHV), and high CO2 reduction performance was achieved by these systems. Hereafter, new joint development, Osaka Gas, Toyota Motors, Kyocera and Aisin Seiki, aims early commercialization of residential SOFC CHP system.

Development of Residential SOFC Cogeneration System

Science.gov (United States)

Ono, Takashi; Miyachi, Itaru; Suzuki, Minoru; Higaki, Katsuki

2011-06-01

Since 2001 Kyocera has been developing 1kW class Solid Oxide Fuel Cell (SOFC) for power generation system. We have developed a cell, stack, module and system. Since 2004, Kyocera and Osaka Gas Co., Ltd. have been developed SOFC residential co-generation system. From 2007, we took part in the "Demonstrative Research on Solid Oxide Fuel Cells" Project conducted by New Energy Foundation (NEF). Total 57 units of 0.7kW class SOFC cogeneration systems had been installed at residential houses. In spite of residential small power demand, the actual electric efficiency was about 40%(netAC,LHV), and high CO2 reduction performance was achieved by these systems. Hereafter, new joint development, Osaka Gas, Toyota Motors, Kyocera and Aisin Seiki, aims early commercialization of residential SOFC CHP system.

Multi-objective optimization for the maximization of the operating share of cogeneration system in District Heating Network

International Nuclear Information System (INIS)

Franco, Alessandro; Versace, Michele

2017-01-01

Highlights: • Combined Heat and Power plants and civil/residential energy uses. • CHP plant supported by auxiliary boilers and thermal energy storage. • Definition of optimal operational strategies for cogeneration plants for District Heating. • Optimal-sized Thermal Energy Storage and a hybrid operational strategy. • Maximization of cogeneration share and reduction of time of operation of auxiliary boilers. - Abstract: The aim of the paper is to define optimal operational strategies for Combined Heat and Power plants connected to civil/residential District Heating Networks. The role of a reduced number of design variables, including a Thermal Energy Storage system and a hybrid operational strategy dependent on the storage level, is considered. The basic principle is to reach maximum efficiency of the system operation through the utilization of an optimal-sized Thermal Energy Storage. Objective functions of both energetic and combined energetic and economic can be considered. In particular, First and Second Law Efficiency, thermal losses of the storage, number of starts and stops of the combined heat and power unit are considered. Constraints are imposed to nullify the waste of heat and to operate the unit at its maximum efficiency for the highest possible number of consecutive operating hours, until the thermal tank cannot store more energy. The methodology is applied to a detailed case study: a medium size district heating system, in an urban context in the northern Italy, powered by a combined heat and power plant supported by conventional auxiliary boilers. The issues involving this type of thermal loads are also widely investigated in the paper. An increase of Second Law Efficiency of the system of 26% (from 0.35 to 0.44) can be evidenced, while the First Law Efficiency shifts from about 0.74 to 0.84. The optimization strategy permits of combining the economic benefit of cogeneration with the idea of reducing the energy waste and exergy losses.

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

International Nuclear Information System (INIS)

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

2012-01-01

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

Molar exergy and flow exergy of pure chemical fuels

International Nuclear Information System (INIS)

Zanchini, Enzo; Terlizzese, Tiziano

2009-01-01

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

Biomass cogeneration: A business assessment

Science.gov (United States)

Skelton, J. C.

1981-11-01

The biomass cogeneration was reviewed. The business assessment is based in part on discussions with key officials from firms that have adopted biomass cogeneration systems and from organizations such as utilities, state and federal agencies, and banks directly involved in a biomass cogeneration project. The guide is organized into five chapters: biomass cogeneration systems, biomass cogeneration business considerations, biomass cogeneration economics, biomass cogeneration project planning, and case studies.

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

DEFF Research Database (Denmark)

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

2014-01-01

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

Exergy analysis of building integrated semitransparent photovoltaic thermal (BiSPVT system

Directory of Open Access Journals (Sweden)

Neha Gupta

2017-02-01

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

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.

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...

Stirling based micro co-generation system for single households

Energy Technology Data Exchange (ETDEWEB)

Ribberink, J.S.; Zutt, J.G.M.; Rabou, L.P.L.M.; Beckers, G.J.J. [ECN Clean Fossil Fuels, Petten (Netherlands); Baijens, C.A.W.; Luttikholt, J.J.M. [ATAG Verwarming, Lichtenvoorde (Netherlands)

2000-04-01

This paper describes the progress made in the ENATEC development program for a free piston Stirling engine based micro co-generation system that serves the supply of up to 1 kW{sub e} and up to 24 kW heat for domestic heating and/or for hot tap water production for single households at overall system efficiencies of 96%. Experiments show that the free piston Stirling engines from Stirling Technology Company run very reliably and controllably, and that the efficiency targets for the 1 kW{sub e} micro co-generation system are feasible. A ceramic foam burner with good heat transfer characteristics and low NOx emissions was developed. A demonstration micro co-generation unit was built and successfully presented. A 1 kW{sub e} free piston Stirling engine for the European market was developed. High efficiencies at full load and at part load, low emissions, low noise, and minimum maintenance make the Stirling engine based micro co-generation system an attractive candidate for the next generation of domestic boilers in Europe. 5 refs.

Energetic and exergetic analysis of cogeneration power combined cycle and ME-TVC-MED water desalination plant: Part-1 operation and performance

International Nuclear Information System (INIS)

Almutairi, Abdulrahman; Pilidis, Pericles; Al-Mutawa, Nawaf; Al-Weshahi, Mohammed

2016-01-01

Highlights: • Develop a comprehensive model for a very advanced cogeneration plant using real data. • Evaluate ME-TVC-MED unit using the latest thermodynamic properties of seawater. • Evaluate the desalination unit contribution to the overall efficiency. • Evaluate the stage exergetic efficiency in the ME-TVC-MED unit. • Numerous possibilities have been suggested to improve the proposed system. - Abstract: A comprehensive model of cogeneration plant for electrical power and water desalination has been developed based on energetic and exergetic analyses using real operational data. The power side is a combined cycle power plant (CCPP), while the desalination side is a multi-effect thermal vapour compression plant coupled with a conventional multi-effect plant (ME-TVC-MED). IPSEpro software was utilized to model the process, which shows good agreement with the manufacturer's data and published research. The thermodynamic properties of saline water were obtained from the latest published data in the literature. The performance of the cogeneration plant was examined for different ambient temperatures, pressure ratios, loads, feed water temperatures, number of effects and entrainment ratios. The results show that gas turbine engines produce the highest level of useful work in the system at around 34% of the total fuel input. At the same time, they constitute a major source of irreversibility, which accounts for 84% of the total exergy destruction in the plant, while the lowest source of irreversibility is in the steam turbine of 3.3% due to the type of working fluid and reheating system. In the ME-TVC-MED desalination unit, the highest source of irreversibilities occurs in the effects and in the thermo-compressor. The first two effects in the ME-TVC parallel section were responsible for about 40.6% of the total effect exergy destruction, which constitutes the highest value among all the effects. Operating the system at full load while reducing ambient

Exergy analysis

DEFF Research Database (Denmark)

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

2011-01-01

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

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

International Nuclear Information System (INIS)

Wijewardane, S.; Goswami, Yogi

2014-01-01

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

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

International Nuclear Information System (INIS)

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

2015-01-01

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

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.

Energy and exergy analysis of solar power tower plants

International Nuclear Information System (INIS)

Xu Chao; Wang Zhifeng; Li Xin; Sun Feihu

2011-01-01

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

Exergy analysis of encapsulation of photochromic dye by spray drying

Science.gov (United States)

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

2017-10-01

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

A novel evaluation of heat-electricity cost allocation in cogenerations based on entropy change method

International Nuclear Information System (INIS)

Ye, Xuemin; Li, Chunxi

2013-01-01

As one of the most significant measures to improve energy utilization efficiency and save energy, cogeneration or combined heat and power (CHP) has been widely applied and promoted with positive motivations in many countries. A rational cost allocation model should indicate the performance of cogenerations and balance the benefits between electricity generation and heat production. Based on the second law of thermodynamics, the present paper proposes an entropy change method for cost allocation by choosing exhaust steam entropy as a datum point, and the new model works in conjunction with entropy change and irreversibility during energy conversion processes. The allocation ratios of heat cost with the present and existing methods are compared for different types of cogenerations. Results show that the allocation ratios with the entropy change method are more rational and the cost allocation model can make up some limitations involved in other approaches. The future energy policies and innovational directions for cogenerations and heat consumers should be developed. - Highlights: • A rational model of cogeneration cost allocation is established. • Entropy change method integrates the relation of entropy change and exergy losses. • The unity of measuring energy quality and quantity is materialized. • The benefits between electricity generation and heat production are balanced

Utilizing the Exergy Concept to Address Environmental Challenges of Electric Systems

Directory of Open Access Journals (Sweden)

Carmen A. Bulucea

2012-10-01

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

Thermal-economic analysis of cogeneration systems

International Nuclear Information System (INIS)

Walter, A.C.S.; Bajay, S.V.

1992-01-01

Approximately 80 countries produce sugar, and fortuitously alcohol, from sugar cane. In all these countries the cogeneration technology of steam turbines is utilized, although almost always inefficient. The greater potential of cogeneration in Brazil is in sugar and alcohol sector, because of the use of sugar cane bagasse as combustible. This work applies the techniques of simulation and economic analysis to different configuration of plants, to determine power generation and associated costs of each alternative. The application of the same procedure at operating condition of several configurations in transient system permits the determination of production profile of exceeding during one day. (C.M.)

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

International Nuclear Information System (INIS)

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

2011-01-01

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

Nonimaging optics maximizing exergy for hybrid solar system

Science.gov (United States)

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

2016-09-01

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

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

International Nuclear Information System (INIS)

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

2012-01-01

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

DDACE cogeneration systems : 10 case studies

Energy Technology Data Exchange (ETDEWEB)

NONE

2009-07-01

DDACE Power Systems are experts in green energy power generation and provide solutions that deal with waste and industrial by-products. The company develops practical energy solutions that address environmental and financial concerns facing both industrial and municipal customers. The following 10 case studies are examples of the installations that DDACE Power Systems have completed in recent years: (1) a combined heat and emergency power installation on the roof of a 19 storey apartment building on Bloor Street in Toronto, Ontario. The cogeneration package provides electricity and heat to the entire building, replacing an old diesel generator, (2) a combined heat and emergency power installation at the Villa Colombo extended care facility in Vaughan, Ontario. The cogeneration system provides heat and power to the building, as well as emergency power, (3) emergency standby power with demand response capabilities at Sobeys Distribution Warehouse in Vaughan, Ontario. The primary purpose of the 2.4 MW low emission, natural gas fuelled emergency standby generator is to provide emergency power to the building in the event of a grid failure, (4) a dual fuel combined heat and power installation at the Queensway Carleton Hospital in Ottawa, Ontario that provides electricity, hot water and steam to all areas of the hospital, (5) a tri-generation installation at the Ontario Police College in Aylmer, Ontario which provides power and heat to the building as well as emergency power in the event of a grid failure. An absorption chiller provides cooling in the summer and an exhaust emission control system reduces NOx emissions, (6) a biomass gasification installation at Nexterra Energy in Kamloops, British Columbia. The 239 kW generator is fueled by synthesis gas, (7) biogas utilization at Fepro Farms in Cobden, Ontario for treatment of the facility's waste products. The biogas plant uses cow manure, as well as fats, oil and grease from restaurants to produce electricity and

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

Energy Technology Data Exchange (ETDEWEB)

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

2011-07-01

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

Unsteady exergy destruction of the neuron under dynamic stress conditions

International Nuclear Information System (INIS)

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

2013-01-01

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

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

International Nuclear Information System (INIS)

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

2015-01-01

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

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

Directory of Open Access Journals (Sweden)

Kamyar Darvish

2015-11-01

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

Stirling engine based micro co-generation system for single households

Energy Technology Data Exchange (ETDEWEB)

Ribberink, H.; Zutt, S.; Rabou, L.; Beckers, G. [Netherlands Energy Research Foundation (ECN), Petten (Netherlands); Baijens, K.; Luttikholt, J. [Atag Verwarming BV (Netherlands)

2000-07-01

This paper describes the progress made in the ENATEC development program for a free piston Stirling engine based micro co-generation system that serves the supply of up to 1 kW{sub e} and up to 24 kW heat for domestic heating and/or for hot tap water production for single households at overall system efficiencies of 96%: Experiments show that the free piston Stirling engines from Stirling Technology Company run very reliably and controllably, and that the efficiency targets for the 1 kW{sub e} micro co-generation system are feasible. A ceramic foam burner with good heat transfer characteristics and low NOx emissions was developed. A demonstration micro co-generation unit was built and successfully presented. A 1 kW{sub e} free piston Stirling engine for the European market was developed. High efficiencies at full load and at part load, low emissions, low noise, and minimum maintenance make the Stirling engine based micro co-generation system an attractive candidate for the next generation of domestic boilers in Europe. (orig.)

Exergy energy, environment and sustainable development

CERN Document Server

Dincer, Ibrahim; Rosen, Marc A

2007-01-01

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

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

International Nuclear Information System (INIS)

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

2014-01-01

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

Biomass based optimal cogeneration system for paper industry

Energy Technology Data Exchange (ETDEWEB)

Ashok, S.; Jayaraj, S. [National Inst. of Technology, Calicut (India)

2008-07-01

A mathematical model of a biomass supported steam turbine cogeneration system was presented. The multi-time interval non-linear model used genetic algorithms to determine optimal operating costs. The cogeneration system consisted of steam boilers; steam headers at different pressure levels; steam turbines operating at different capacities; and other auxiliary devices. System components were modelled separately to determine constraints and costs. Total costs were obtained by summing up costs corresponding to all equipment. Cost functions were fuel cost; grid electricity cost; grid electricity export revenues; start-up costs; and shut-down costs. The non-linear optimization model was formulated by considering equal intervals of 1-hour intervals. A case study of a typical paper industry plant system was considered using coal, black liquor, and groundnut shells. Results of the study showed that the use of groundnut shells as a fuel resulted in a savings of 11.1 per cent of the total monthly operating costs while delivering 48.6 MWh daily to the electricity grid after meeting the plant's total energy requirements. It was concluded that the model can be used to optimize cogeneration systems in paper plants. 14 refs., 3 tabs., 3 figs.

Performance analysis of a stationary fuel cell thermoelectric cogeneration system

Energy Technology Data Exchange (ETDEWEB)

Kuo, J.K.; Hwang, J.J.; Lin, C.H. [Department of Greenergy, National University of Tainan, Tainan, 70005 (China)

2012-12-15

The main purpose of our study was to use an experimental method and system dynamic simulation technology to examine a proton exchange membrane fuel cell thermoelectric cogeneration system that provides both high-quality electric power and heated water. In the second part of our study, we experimentally verified the development of key components of the fuel cell and conducted a comprehensive analysis of the subsystems, including the fuel cell module, hydrogen supply subsystem, air supply subsystem, humidifier subsystem, and heat recovery subsystem. Finally, we integrated all of the subsystems into a PEM fuel cell thermoelectric cogeneration system and performed efficiency tests and analysis of power generation, heat recovery, and thermoelectric cogeneration. After comparing this system's efficiency results using simulation and experimentation, we determined that the accuracy of the simulation values when compared to the experimental values was >95%, showing that this system's simulation nearly approached the efficiency of the actual experiment, including more than 53% for power generation efficiency, more than 39% for heat recovery efficiency, and more than 93% for thermoelectric cogeneration combined efficiency. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Introduction to cogeneration; Introducao a cogeracao

Energy Technology Data Exchange (ETDEWEB)

Nogueira, Luiz Augusto Horta; Martins, Andre Luiz Silva [Escola Federal de Engenharia de Itajuba, MG (Brazil)

1997-07-01

This work presents a general view of cogeneration. The paper approaches the development of cogeneration, technological aspects, the cogeneration in Brazil, economical aspects, performance of cogeneration systems, viability, costs, cogeneration potentials and technological trends.

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

International Nuclear Information System (INIS)

Boyaghchi, Fateme Ahmadi; Molaie, Hanieh

2015-01-01

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

Exergy analysis for stationary flow systems with several heat exchange temperatures

Energy Technology Data Exchange (ETDEWEB)

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

1995-07-01

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

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

International Nuclear Information System (INIS)

Yan, Linbo; Yue, Guangxi; He, Boshu

2015-01-01

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

Effect of cycle coupling-configuration on energy cascade utilization for a new power and cooling cogeneration cycle

International Nuclear Information System (INIS)

Jing, Xuye; Zheng, Danxing

2014-01-01

Highlights: • A new power and cooling cogeneration cycle was proposed. • The thermophysical properties and the performance of the new cycle were calculated. • Different cycle coupling-configurations were analyzed. • The energy efficiency boosting mechanism of the new cycle was elucidated. - Abstract: To recover mid-low grade heat, a new power/cooling cogeneration cycle was proposed by combining the Kalina cycle and the double-effect ammonia–water absorption refrigeration (DAAR) cycle together, and the equivalent heat-to-power and exergy efficiencies of the cogeneration cycle reached 41.18% and 58.00%, respectively. To determine the effect of cycle coupling-configuration on energy cascade utilization for the new cycle, the cycle coupling-configuration of the Kalina and DAAR cycles were first analyzed, after which the cycle coupling-configuration of the new cycle was analyzed. Analysis results showed that the cycle coupling-configuration of the new cycle enhanced the energy cascade utilization. Furthermore, the energy efficiency boosting mechanism of the new cycle was elucidated

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.

Application of exergy as thermodynamic indicator in ecology

International Nuclear Information System (INIS)

Jorgensen, S.E.; Nors Nielsen, Soren

2007-01-01

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

Exergy analysis and optimisation of a marine molten carbonate fuel cell system in simple and combined cycle configuration

International Nuclear Information System (INIS)

Dimopoulos, George G.; Stefanatos, Iason C.; Kakalis, Nikolaos M.P.

2016-01-01

Highlights: • Process modelling and optimisation of an integrated marine MCFC system. • Component-level and spatially distributed exergy analysis and balances. • Optimal simple cycle MCFC system with 45.5% overall exergy efficiency. • Optimal combined cycle MCFC system with 60% overall exergy efficiency. • Combined cycle MCFC system yields 30% CO_2 relative emissions reduction. - Abstract: In this paper we present the exergy analysis and design optimisation of an integrated molten carbonate fuel cell (MCFC) system for marine applications, considering waste heat recovery options for additional power production. High temperature fuel cells are attractive solutions for marine energy systems, as they can significantly reduce gaseous emissions, increase efficiency and facilitate the introduction of more environmentally-friendly fuels, like LNG and biofuels. We consider an already installed MCFC system onboard a sea-going vessel, which has many tightly integrated sub-systems and components: fuel delivery and pre-reforming, internal reforming sections, electrochemical conversion, catalytic burner, air supply and high temperature exhaust gas. The high temperature exhaust gasses offer significant potential for heat recovery that can be directed into both covering the system’s auxiliary heat requirements and power production. Therefore, an integrated systems approach is employed to accurately identify the true sources of losses in the various components and to optimise the overall system with respect to its energy efficiency, taking into account the various trade-offs and subject to several constraints. Here, we present a four-step approach: a. dynamic process models development of simple and combined-cycle MCFC system; b. MCFC components and system models calibration via onboard MCFC measurements; c. exergy analysis, and d. optimisation of the simple and combined-cycle systems with respect to their exergetic performance. Our methodology is based on the

Methodology for the optimal design of an integrated first and second generation ethanol production plant combined with power cogeneration.

Science.gov (United States)

Bechara, Rami; Gomez, Adrien; Saint-Antonin, Valérie; Schweitzer, Jean-Marc; Maréchal, François

2016-08-01

The application of methodologies for the optimal design of integrated processes has seen increased interest in literature. This article builds on previous works and applies a systematic methodology to an integrated first and second generation ethanol production plant with power cogeneration. The methodology breaks into process simulation, heat integration, thermo-economic evaluation, exergy efficiency vs. capital costs, multi-variable, evolutionary optimization, and process selection via profitability maximization. Optimization generated Pareto solutions with exergy efficiency ranging between 39.2% and 44.4% and capital costs from 210M$ to 390M$. The Net Present Value was positive for only two scenarios and for low efficiency, low hydrolysis points. The minimum cellulosic ethanol selling price was sought to obtain a maximum NPV of zero for high efficiency, high hydrolysis alternatives. The obtained optimal configuration presented maximum exergy efficiency, hydrolyzed bagasse fraction, capital costs and ethanol production rate, and minimum cooling water consumption and power production rate. Copyright © 2016 Elsevier Ltd. All rights reserved.

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

International Nuclear Information System (INIS)

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

2016-01-01

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

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

Exergy analysis of industrial ammonia synthesis

International Nuclear Information System (INIS)

Kirova-Yordanova, Zornitza

2004-01-01

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

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

International Nuclear Information System (INIS)

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

2014-01-01

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

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...

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

International Nuclear Information System (INIS)

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

2014-01-01

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

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

International Nuclear Information System (INIS)

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

2010-01-01

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

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

International Nuclear Information System (INIS)

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

2015-01-01

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

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.

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.

An HTR cogeneration system for industrial application

International Nuclear Information System (INIS)

Haverkate, B.R.W.; Van Heek, A.I.; Kikstra, J.F.

1999-01-01

Because of its favourable characteristics of safety and simplicity the high-temperature reactor (HTR) could become a competitive heat source for a cogeneration unit. The Netherlands is a world leading country in the field of cogeneration. As nuclear energy remains an option for the medium and long term in this country, systems for nuclear cogeneration should be explored and developed. Hence, ECN Nuclear Research is developing a conceptual design of an HTR for Combined generation of Heat and Power (CHP) for the industry in and outside the Netherlands. The design of this small CHP-unit for industrial applications is mainly based on a pre-feasibility study in 1996, performed by a joint working group of five Dutch organisations, in which technical feasibility was shown. The concept that was subject of that study, INCOGEN, used a 40 MW thermal pebble bed HTR and produced a maximum amount of electricity plus low temperature heat. The system has been improved to produce industrial quality heat, and has been renamed ACACIA. The output of this installation is 14 MW electricity and 17 tonnes of steam per hour, with a pressure of 10 bar and a temperature of 220C. The economic characteristics of this installation turned out to be much more favourable using modern cost data. 15 refs

Human Body Exergy Metabolism

OpenAIRE

Mady, Carlos Eduardo Keutenedjian

2013-01-01

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

The performance of a temperature cascaded cogeneration system producing steam, cooling and dehumidification

KAUST Repository

Myat, Aung; Thu, Kyaw; Kim, Youngdeuk; Ng, K. C.

2013-01-01

This paper discusses the performance of a temperature-cascaded cogeneration plant (TCCP), equipped with an efficient waste heat recovery system. The TCCP, also called a cogeneration system, produces four types of useful energy-namely, (i

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.

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.

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.

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

International Nuclear Information System (INIS)

Kaynakli, Omer; Saka, Kenan; Kaynakli, Faruk

2015-01-01

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

The Exergy of Lift and Aircraft Exergy Flow Diagrams

OpenAIRE

Paulus, Jr., David; Gaggioli, Richard

2010-01-01

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

Application of information theory for the analysis of cogeneration-system performance

International Nuclear Information System (INIS)

Takahashi, Kazuki; Ishizaka, Tadashi

1998-01-01

Successful cogeneration system performance depends critically upon the correct estimation of load variation and the accuracy of demand prediction. We need not only aggregated annual heat and electricity demands, but also hourly and monthly patterns in order to evaluate a cogeneration system's performance by computer simulation. These data are usually obtained from the actual measurements of energy demand in existing buildings. However, it is extremely expensive to collect actual energy demand data and store it over a long period for many buildings. However we face the question of whether it is really necessary to survey hourly demands. This paper provides a sensitivity analysis of the influence of demand-prediction error upon the efficiency of cogeneration system, so as to evaluate the relative importance of various demand components. These components are annual energy demand, annual heat-to-electricity ratio, daily load factor and so forth. Our approach employs the concept of information theory to construct a mathematical model. This analysis provides an indication of the relative importances of demand indices, and identifies what may become a good measure of assessing the efficiency of the cogeneration system for planning purposes. (Author)

Exergy in School?

Directory of Open Access Journals (Sweden)

Tomaž Kranjc

2017-04-01

Information Technologies (UPR FAMNIT of the University of Primorska. Based on interviews and questionnaires given to two groups of students — an experimental and a control group — in the beginning and the end of the semester, we investigated the influence (and possible advantages of the introduction of the concept of exergy and the second-law ficiency. In the presentation, we show a few examples that were treated with the experimental group in order to motivate the students and to make them familiar with the concept of exergy: the “energy losses” of a car engine and an analysis of improvements still allowed by nature; exergy loss associated with heat conduction; a simple exergy analysis of a heating house system (considering energy and exergy fluxes. We list some of the problems encountered by the students and the most common misconceptions as could be identified from the tests, questionnaires and interviews. An additional goal of the investigation is to test a longer-term knowledge of students. From our research it would appear that exergy and the second-law efficiency are useful concepts which make it possible for students to get a better grasp of the material and to not only obtain a clearer understanding and knowledge of standard topics like heat engines, but also a broader view and insight into the meaning of energy and both the first and the second law, and their interrelation.

Implementation of gas district cooling and cogeneration systems in Malaysia; Mise en oeuvre de systemes de gas district cooling et de cogeneration en Malaisie

Energy Technology Data Exchange (ETDEWEB)

Haron, S. [Gas District Cooling, M, Sdn Bhd (Malaysia)

2000-07-01

With its energy demand in the early 1990's growing at a high rate due to the country's strong economic growth, Malaysia studied various options to improve the efficiency of its energy use. Since its natural gas reserves are almost four times that of its crude oil reserves, efforts were therefore centered on seeking ways to boost the use of natural gas to mitigate the growing domestic energy need. PETRONAS, the national oil company, subsequently studied and chose the District Cooling System using natural gas as the primary source of fuel. The Kuala Lumpur City Center development, which houses the PETRONAS Twin Towers, was subsequently chosen as the first project to use the Gas District Cooling (GDC) System. To acquire the technology and implement this project, PETRONAS created a new subsidiary, Gas District Cooling (Malaysia) Sendirian Berhad (GDC(M)). In the process of improving the plant's efficiency, GDC(M) discovered that the GDC system's efficiency and project economics would be significantly enhanced if its is coupled to a Cogeneration system. Having proven the success of the GDC/Cogeneration system, GDC(M) embarked on a campaign to aggressively promote and seek new opportunities to implement the system, both in Malaysia-and abroad. Apart from enhancing efficiency of energy use, and providing better project economics, the GDC/Cogeneration system also is environment friendly. Today, the GDC/Cogeneration systems is the system of choice for several important developments in Malaysia, which also includes the country's prestigious projects such as the Kuala Lumpur International Airport and the New Federal Government Administrative Center in Putrajaya. (author)

Performance Optimization of Unglazed Nanofluid Photovoltaic/Thermal System: Energy and Exergy Analyses

Directory of Open Access Journals (Sweden)

M. Imtiaz Hussain

2018-01-01

Full Text Available The focus of this paper is to predict the transient response of a nanoengineered photovoltaic thermal (PV/T system in view of energy and exergy analyses. Instead of a circular-shaped receiver, a trapezoidal-shaped receiver is employed to increase heat transfer surface area with photovoltaic (PV cells for improvement of heat extraction and thus achievement of a higher PV/T system efficiency. The dynamic mathematical model is developed using MATLAB® software by considering real-time heat transfer coefficients. The proposed model is validated with experimental data from a previous study. Negligible discrepancies were found between measured and predicted data. The validated model was further investigated in detail using different nanofluids by dispersing copper oxide (CuO and aluminum oxide (Al2O3 in pure water. The overall performance of the nanoengineered PV/T system was compared to that of a PV/T system using water only, and optimal operating conditions were determined for maximum useful energy and exergy rates. The results indicated that the CuO/water nanofluid has a notable impact on the energy and exergy efficiencies of the PV/T system compared to that of Al2O3/water nanofluid and water only cases.

Exergy method of analysis and its application to a helium cryorefrigerator

International Nuclear Information System (INIS)

Thirumaleshwar, M.

1979-01-01

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

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

International Nuclear Information System (INIS)

Genc, Mahmut; Genc, Seda; Goksungur, Yekta

2017-01-01

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

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.

Cogeneration techniques; Les techniques de cogeneration

Energy Technology Data Exchange (ETDEWEB)

NONE

1999-10-01

This dossier about cogeneration techniques comprises 12 parts dealing successively with: the advantages of cogeneration (examples of installations, electrical and thermal efficiency); the combustion turbine (principle, performances, types); the alternative internal combustion engines (principle, types, rotation speed, comparative performances); the different configurations of cogeneration installations based on alternative engines and based on steam turbines (coal, heavy fuel and natural gas-fueled turbines); the environmental constraints of combustion turbines (pollutants, techniques of reduction of pollutant emissions); the environmental constraints of alternative internal combustion engines (gas and diesel engines); cogeneration and energy saving; the techniques of reduction of pollutant emissions (pollutants, unburnt hydrocarbons, primary and secondary (catalytic) techniques, post-combustion); the most-advanced configurations of cogeneration installations for enhanced performances (counter-pressure turbines, massive steam injection cycles, turbo-chargers); comparison between the performances of the different cogeneration techniques; the tri-generation technique (compression and absorption cycles). (J.S.)

Thermal performance of gas turbine power plant based on exergy analysis

International Nuclear Information System (INIS)

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

2017-01-01

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

Urban Integrated Industrial Cogeneration Systems Analysis. Phase II final report

Energy Technology Data Exchange (ETDEWEB)

1984-01-01

Through the Urban Integrated Industrial Cogeneration Systems Analysis (UIICSA), the City of Chicago embarked upon an ambitious effort to identify the measure the overall industrial cogeneration market in the city and to evaluate in detail the most promising market opportunities. This report discusses the background of the work completed during Phase II of the UIICSA and presents the results of economic feasibility studies conducted for three potential cogeneration sites in Chicago. Phase II focused on the feasibility of cogeneration at the three most promising sites: the Stockyards and Calumet industrial areas, and the Ford City commercial/industrial complex. Each feasibility case study considered the energy load requirements of the existing facilities at the site and the potential for attracting and serving new growth in the area. Alternative fuels and technologies, and ownership and financing options were also incorporated into the case studies. Finally, site specific considerations such as development incentives, zoning and building code restrictions and environmental requirements were investigated.

Cogeneration

International Nuclear Information System (INIS)

Derbentli, Taner

2006-01-01

Cogeneration is the combined production of power and heat. Cogeneration aims to utilize the waste heat of power plants. The waste heat may be utilized for process heating, district heating, drying and cooling. In this way the primary energy is utilized more efficiently. Furthermore due to use of lesser amounts of fuel, emissions and carbon dioxide production is reduced. This is important from the viewpoint of controlling global warming. Cogeneration is used worldwide in industry and in conjunction with district heating.The prime movers used for this purpose are gas turbines, Diesel or natural gas engines and steam power plants. There are several parameters used for characterizing cogeneration. First of all capacity shows the power produced by the cogeneration plant. Most of the cogeneration plants used in industry have capacities between 3 and 20 MW. However there are plants having capacities as large as 200 MW and capacities smaller than 1 MW. The latter are known as micro cogeneration plants. Power to heat ratio is another parameter characterizing cogeneration. It gives the ratio of power produced to heat produced in a cogeneration plant. For gas turbine plants this is around 0.6, for gas engines it is about 1. For steam power plants, power to heat ratio is smaller than 0.4. The total efficiency or fuel utilization efficiency is defined as the total useful output of the plant as power and heat to energy input as fuel. The higher this value, the better is the cogeneration application. In a well designed plant this value may be as high as eighty to ninety percent. Cogeneration started as self power production in Turkey to provide continuous and top quality electric power to industrial plants in the 1990s. Now approximately 20 % of the power production capacity of Turkey is provided by the cogeneration plants. Turkey imports most of its primary energy demand, therefore it is important to increase the use of cogeneration to reduce the demand. There are studies which

Performance investigation of a cogeneration plant with the efficient and compact heat recovery system

KAUST Repository

Myat, Aung; Thu, Kyaw; Kim, Young-Deuk; Choon, Ng Kim

2011-01-01

This paper presents the performance investigation of a cogeneration plant equipped with an efficient waste heat recovery system. The proposed cogeneration system produces four types of useful energy namely: (i) electricity, (ii) steam, (iii) cooling

Analysis of an optimal resorption cogeneration using mass and heat recovery processes

International Nuclear Information System (INIS)

Lu, Yiji; Wang, Yaodong; Bao, Huashan; Yuan, Ye; Wang, Liwei; Roskilly, Anthony Paul

2015-01-01

Highlights: • Resorption cogeneration for electricity and refrigeration generation. • Mass and heat recovery to further improve the performance. • The first and second law analysis. - Abstract: This paper presents an optimised resorption cogeneration using mass and heat recovery to improve the performance of a novel resorption cogeneration fist proposed by Wang et al. This system combines ammonia-resorption technology and expansion machine into one loop, which is able to generate refrigeration and electricity from low-grade heat sources such as solar energy and industrial waste heat. Two sets of resorption cycle are designed to overcome the intermittent performance of the chemisorption and produce continuous/simultaneous refrigeration and electricity. In this paper, twelve resorption working pairs of salt complex candidates are analysed by the first law analysis using Engineering Equation Solver (EES). The optimal resorption working pairs from the twelve candidates under the driven temperature from 100 °C to 300 °C are identified. By applying heat/mass recovery, the coefficient of performance (COP) improvement is increased by 38% when the high temperature salt (HTS) is NiCl 2 and by 35% when the HTS is MnCl 2 . On the other hand, the energy efficiency of electricity has also been improved from 8% to 12% with the help of heat/mass recovery. The second law analysis has also been applied to investigate the exergy utilisation and identify the key components/processes. The highest second law efficiency is achieved as high as 41% by the resorption working pair BaCl 2 –MnCl 2 under the heat source temperature at 110 °C.

Comments on derivation of an index for evaluating economics of cogeneration systems and its applications

Energy Technology Data Exchange (ETDEWEB)

Banerjee, R [Indian Inst. of Tech., Bombay (India). Dept. of Mechanical Engineering

1990-04-01

Industrial cogeneration systems usually must satisfy a power load and heat loads at different temperatures. The limitations of the economic index proposed by Pak and Suzuki for such cogeneration systems is discussed in this paper. The importance of a rational exergetic basis for evaluation of different grades of energy is emphasised. Thermodynamic criteria, e.g. the exergetic efficiency, relative fuel savings and fuel chargeable to power, are shown to provide useful information regarding cogeneration options. Any assessment scheme for cogeneration schemes must incorporate thermodynamic criteria in addition to economic criteria. (author).

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

DEFF Research Database (Denmark)

Gullo, Paride; Elmegaard, Brian; Cortella, Giovanni

2016-01-01

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

Feasibility study for retrofitting biogas cogeneration systems to district heating in South Korea.

Science.gov (United States)

Chung, Mo; Park, Hwa-Choon

2015-08-01

A feasibility study was performed to assess the technical and economic merits of retrofitting biogas-based cogeneration systems to district heating networks. Three district heating plants were selected as candidates for accommodating heat recovery from nearby waste treatment stations, where a massive amount of biogas can be produced on a regular basis. The scenario involves constructing cogeneration systems in each waste treatment station and producing electricity and heat. The amounts of biogas production for each station are estimated based on the monthly treatment capacities surveyed over the most recent years. Heat produced by the cogeneration system is first consumed on site by the waste treatment system to keep the operating temperature at a proper level. If surplus heat is available, it will be transported to the nearest district heating plant. The year-round operation of the cogeneration system was simulated to estimate the electricity and heat production. We considered cost associated with the installation of the cogeneration system and piping as initial investments. Profits from selling electricity and recovering heat are counted as income, while costs associated with buying biogas are expenses. Simple payback periods of 2-10 years were projected under the current economic conditions of South Korea. We found that most of the proposed scenarios can contribute to both energy savings and environmental protection. © The Author(s) 2015.

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

International Nuclear Information System (INIS)

Tan, Mehmet; Keçebaş, Ali

2014-01-01

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

Exergy transfer and parametric study of counter flow wet cooling towers

International Nuclear Information System (INIS)

Wang Li; Li Nianping

2011-01-01

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

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

International Nuclear Information System (INIS)

Bai, Tao; Yu, Jianlin; Yan, Gang

2016-01-01

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

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

International Nuclear Information System (INIS)

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

2015-01-01

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

Cogeneration. Energy efficiency - Micro-cogeneration; La Cogeneration. Efficacite Energetique - Micro-cogeneration

Energy Technology Data Exchange (ETDEWEB)

Boudellal, M.

2010-07-01

Depletion of natural resources and of non-renewable energy sources, pollution, greenhouse effect, increasing energy needs: energy efficiency is a major topic implying a better use of the available primary energies. In front of these challenges, cogeneration - i.e. the joint production of electricity and heat, and, at a local or individual scale, micro-cogeneration - can appear as interesting alternatives. This book presents in a detailed manner: the present day and future energy stakes; the different types of micro-cogeneration units (internal combustion engines, Stirling engine, fuel cell..), and the available models or the models at the design stage; the different usable fuels (natural gas, wood, biogas..); the optimization rules of a facility; the costs and amortizations; and some examples of facilities. (J.S.)

Pitfalls of Exergy Analysis

Science.gov (United States)

Vágner, Petr; Pavelka, Michal; Maršík, František

2017-04-01

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

Optimum design of cogeneration system for nuclear seawater desalination - 15272

International Nuclear Information System (INIS)

Jung, Y.H.; Jeong, Y.H.

2015-01-01

A nuclear desalination process, which uses the energy released by nuclear fission, has less environmental impact and is generally cost-competitive with a fossil-fuel desalination process. A reference cogeneration system focused on in this study is the APR-1400 coupled with a MED (multi-effect distillation) process using the thermal vapor compression (TVC) technology. The thermal condition of the heat source is the most crucial factor that determines the desalination performance, i.e. energy consumption or freshwater production, of the MED-TVC process. The MED-TVC process operating at a higher motive steam pressure clearly shows a higher desalination performance. However, this increased performance does not necessarily translate to an advantage over processes operated at lower motive steam pressures. For instance, a higher motive steam pressure will increase the heat cost resulting from larger electricity generation loss, and thus may make this process unfavorable from an economic point of view. Therefore, there exists an optimum design point in the coupling configuration that makes the nuclear cogeneration system the most economical. This study is mainly aimed at investigating this optimum coupling design point of the reference nuclear cogeneration system using corresponding analysis tools. The following tools are used: MEE developed by the MEDRC for desalination performance analysis of the MED-TVC process, DE-TOP and DEEP developed by the IAEA for modeling of coupling configuration and economic evaluation of the nuclear cogeneration system, respectively. The results indicate that steam extraction from the MS exhaust and condensate return to HP FWHTR 5 is the most economical coupling design

The Optimal Operation Criteria for a Gas Turbine Cogeneration System

Directory of Open Access Journals (Sweden)

Atsushi Akisawa

2009-04-01

Full Text Available The study demonstrated the optimal operation criteria of a gas turbine cogeneration system based on the analytical solution of a linear programming model. The optimal operation criteria gave the combination of equipment to supply electricity and steam with the minimum energy cost using the energy prices and the performance of equipment. By the comparison with a detailed optimization result of an existing cogeneration plant, it was shown that the optimal operation criteria successfully provided a direction for the system operation under the condition where the electric power output of the gas turbine was less than the capacity

Electricity transport regimes: their impact on cogeneration

Energy Technology Data Exchange (ETDEWEB)

Cotard, Erwan [COGEN, Europe (Belgium)

2000-12-01

In many cases the main product of cogeneration is heat and the surplus electricity is sold to the grid. However, the economics of cogeneration can be influenced by transport networks (transmission and distribution): the structure of network pricing is relatively new. In a recent note from COGEN Europe it was recommended that cogenerators who use only the local distribution system should not pay for the transmission system and that tariffs should be structured in sufficient detail for the advantages of decentralisation to be realised. The article is presented under the sub-headings of (i) why is this important? (the omission of the transmission element reduces the overall price of cogeneration); (ii) the advantages of decentralised cogeneration; (iv) the theory - the different systems (the European Directive on electricity market liberalization); (v) the options for transport fees; (vi) current regimes in some EU states (vii) the case of transborder transport; impact of each system on cogeneration; recommendations to policymakers; (viii) the Netherlands and (ix) the UK.

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.

Optimization of a novel carbon dioxide cogeneration system using artificial neural network and multi-objective genetic algorithm

International Nuclear Information System (INIS)

Jamali, Arash; Ahmadi, Pouria; Mohd Jaafar, Mohammad Nazri

2014-01-01

In this research study, a combined cycle based on the Brayton power cycle and the ejector expansion refrigeration cycle is proposed. The proposed cycle can provide heating, cooling and power simultaneously. One of the benefits of such a system is to be driven by low temperature heat sources and using CO 2 as working fluid. In order to enhance the understanding of the current work, a comprehensive parametric study and exergy analysis are conducted to determine the effects of the thermodynamic parameters on the system performance and the exergy destruction rate in the components. The suggested cycle can save the energy around 46% in comparison with a system producing cooling, power and hot water separately. On the other hand, to optimize a system to meet the load requirement, the surface area of the heat exchangers is determined and optimized. The results of this section can be used when a compact system is also an objective function. Along with a comprehensive parametric study and exergy analysis, a complete optimization study is carried out using a multi-objective evolutionary based genetic algorithm considering two different objective functions, heat exchangers size (to be minimized) and exergy efficiency (to be maximized). The Pareto front of the optimization problem and a correlation between exergy efficiency and total heat exchangers length is presented in order to predict the trend of optimized points. The suggested system can be a promising combined system for buildings and outland regions. - Highlights: •Energy and exergy analysis of a novel CHP system are reported. •A comprehensive parametric study is conducted to enhance the understanding of the system performance. •Apply a multi-objective optimization technique based on a code developed in the Matlab software program using an evolutionary algorithm

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.

Global environment and cogeneration

International Nuclear Information System (INIS)

Miyahara, Atsushi

1992-01-01

The environment problems on global scale have been highlighted in addition to the local problems due to the rapid increase of population, the increase of energy demand and so on. The global environment summit was held in Brazil. Now, global environment problems are the problems for mankind, and their importance seems to increase toward 21st century. In such circumstances, cogeneration can reduce carbon dioxide emission in addition to energy conservation, therefore, attention has been paid as the countermeasure for global environment. The background of global environment problems is explained. As to the effectiveness of cogeneration for global environment, the suitability of city gas to environment, energy conservation, the reduction of carbon dioxide and nitrogen oxides emission are discussed. As for the state of spread of cogeneration, as of March, 1992, those of 2250 MW in terms of power generation capacity have been installed in Japan. It is forecast that cogeneration will increase hereafter. As the future systems of cogeneration, city and industry energy center conception, industrial repowering, multiple house cogeneration and fuel cells are described. (K.I.)

Carbon exergy tax (CET): its impact on conventional energy system design and its contribution to advanced systems utilisation

International Nuclear Information System (INIS)

Massardo, A.F.; Santarelli, M.; Borchiellini, R.

2003-01-01

A proposed analytical procedure for a charge on CO 2 emissions is used to determine its impact on the design process of different conventional energy systems. The charge on CO 2 emissions is defined as a Carbon Exergy Tax (CET). The CET utilises the concept of Efficiency Penalty of the energy system coupled with the Index of CO 2 Emissions, which connects the amount of the CO 2 emitted by the plant with the Second Law efficiency of the plant itself. The aim is to reward the efficient use of energy resources, both from a resource and environmental standpoint, and to penalise plants inefficient in this respect. The CET and the conventional Carbon Tax (CT, based on energy policy considerations and imposed on the mass of emitted CO 2 ) are applied to different conventional energy systems (a gas turbine simple cycle; a regenerative cogeneration gas turbine; a three pressure levels combined cycle) in order to determine their impact on the design of the plants. The effects of the CET and CT are investigated for different scenarios (pressure ratio, fuel cost, etc.). The results are presented using useful representations: the cost of electricity vs. efficiency, the cost of electricity vs. specific work, and the cost of electricity vs. plant design parameters (e.g., pressure ratio). Finally, ways that the use of the CET can contribute to the widespread utilization of advanced energy systems, which are more efficient and less polluting, is discussed. In particular, the CET and CT influence is presented and discussed for a solid oxide fuel cell (SOFC) and gas turbine combined cycle

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

International Nuclear Information System (INIS)

Gökgedik, Harun; Yürüsoy, Muhammet; Keçebaş, Ali

2016-01-01

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

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.

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

International Nuclear Information System (INIS)

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

2017-01-01

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

A novel nuclear combined power and cooling system integrating high temperature gas-cooled reactor with ammonia–water cycle

International Nuclear Information System (INIS)

Luo, Chending; Zhao, Fuqiang; Zhang, Na

2014-01-01

Highlights: • We propose a novel nuclear ammonia–water power and cooling cogeneration system. • The high temperature reactor is inherently safe, with exhaust heat fully recovered. • The thermal performances are improved compared with nuclear combined cycle. • The base case attains an energy efficiency of 69.9% and exergy efficiency of 72.5%. • Energy conservation and emission reduction are achieved in this cogeneration way. - Abstract: A nuclear ammonia–water power and refrigeration cogeneration system (NAPR) has been proposed and analyzed in this paper. It consists of a closed high temperature gas-cooled reactor (HTGR) topping Brayton cycle and a modified ammonia water power/refrigeration combined bottoming cycle (APR). The HTGR is an inherently safe reactor, and thus could be stable, flexible and suitable for various energy supply situation, and its exhaust heat is fully recovered by the mixture of ammonia and water in the bottoming cycle. To reduce exergy losses and enhance outputs, the ammonia concentrations of the bottoming cycle working fluid are optimized in both power and refrigeration processes. With the HTGR of 200 MW thermal capacity and 900 °C/70 bar reactor-core-outlet helium, the system achieves 88.8 MW net electrical output and 9.27 MW refrigeration capacity, and also attains an energy efficiency of 69.9% and exergy efficiency of 72.5%, which are higher by 5.3%-points and 2.6%-points as compared with the nuclear combined cycle (NCC, like a conventional gas/steam power-only combined cycle while the topping cycle is a closed HTGR Brayton cycle) with the same nuclear energy input. Compared with conventional separate power and refrigeration generation systems, the fossil fuel saving (based on CH 4 ) and CO 2 emission reduction of base-case NAPR could reach ∼9.66 × 10 4 t/y and ∼26.6 × 10 4 t/y, respectively. The system integration accomplishes the safe and high-efficiency utilization of nuclear energy by power and refrigeration

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.

Exergy Analysis of Serpentine Thermosyphon Solar Water Heater

Directory of Open Access Journals (Sweden)

Muhammad Faisal Hasan

2018-03-01

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

Exergy costs analysis of groundwater use and water transfers

International Nuclear Information System (INIS)

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

2016-01-01

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

Exergy-based assessment for waste gas emissions from Chinese transportation

International Nuclear Information System (INIS)

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

2009-01-01

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

Exergy analysis of the LFC process

International Nuclear Information System (INIS)

Li, Qingsong; Lin, Yuankui

2016-01-01

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

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

Energy Technology Data Exchange (ETDEWEB)

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

2000-07-01

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

Exergy Evaluation of Desalination Processes

Directory of Open Access Journals (Sweden)

Veera Gnaneswar Gude

2018-06-01

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

Energy, exergy, economic and environmental (4E) analysis of a solar desalination system with humidification-dehumidification

International Nuclear Information System (INIS)

Deniz, Emrah; Çınar, Serkan

2016-01-01

Highlights: • Possibility of suppling all energy consumption from solar energy was tested. • Air and water-heated humidification-dehumidification desalination system was proposed. • Energy, exergy, economic and environmental analysis were performed. • Productivity and performance of the desalination system was analyzed. • Various operational parameters were investigated. - Abstract: A novel humidification-dehumidification (HDH) solar desalination system is designed and tested with actual conditions and solar energy was used to provide both thermal and electrical energy. Energy-exergy analyses of the system are made and economic and enviro-economic properties are investigated using data obtained from experimental studies. In this way, economic and environmental impacts of the HDH solar desalination systems have also been determined. The maximum daily energy efficiency of the system was calculated as 31.54% and the maximum exergy efficiency was found as 1.87%. The maximum fresh water production rate is obtained as 1117.3 g/h. The estimated cost of fresh water produced through the designed HDH system is 0.0981 USD/L and enviro-economic parameter is 2.4041 USD/annum.

Modeling the exergy behavior of human body

International Nuclear Information System (INIS)

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

2012-01-01

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

Energy and exergy analysis of low temperature district heating network

International Nuclear Information System (INIS)

Li, Hongwei; Svendsen, Svend

2012-01-01

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

General methodology for exergy balance in ProSimPlus® process simulator

International Nuclear Information System (INIS)

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

2012-01-01

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

Energy and exergy analysis of multi-effects distillation with thermo vapour compressor (MED-TVC) desalination system

Energy Technology Data Exchange (ETDEWEB)

Saffari, A.; Sayyaadi, H. [Khaje Nasir Toosi Univ. of Technology, Tehran (Iran, Islamic Republic of). Faculty of Mechanical Engineering, Energy Division; Alishiri, M. [Fan Niroo Co., Tehran (Iran, Islamic Republic of). Desalination and Water Solutions

2008-07-01

Countries around the world have a significant need for high-quality water. The desalination industry is especially important in ensuring the supply of high-quality water, especially the countries around the Persian Gulf such as Iran. A multiple-effect distiller (MED) with thermal vapor compression (TVC) system is more attractive than other thermal systems due to its effectiveness, easier operation and maintenance, and good economics. This paper presented a heat and mass balance relation and comprehensive exergy analysis of a typical MED with a thermal vapour compression desalination system. The purpose of the study was to provide a cost-effective tool that could be applied in the design, development and optimization of thermal desalination plants. The paper discussed the energy simulation, with particular reference to the temperatures for each effect; the condenser, gain output ratio, distillate production rate, brine outlet and feed water rates for each effect; steam consumption; coolant sea water and total sea water inlet rate; pressure distribution in the evaporators; and the entertained vapour rate at TVC. Exergy analysis revealed that the steam ejector and evaporators are the main sources of exergy destruction. It was also shown that lowering the temperature difference can minimize exergy losses. 21 refs., 4 tabs., 16 figs.

Application of the Pinch analysis for the design of a cogeneration system in a paper mill; Aplicacion del analisis Pinch para el diseno de un sistema de cogeneracion en una industria papelera

Energy Technology Data Exchange (ETDEWEB)

Mani Gonzalez, A. G.; Arriola Medellin, A. [Instituto de Investigaciones Electricas, Cuernavaca (Mexico)

1997-12-31

The Pinch Analysis is a set of principles, tools and rules for the design that allow the engineer find the best way to configure the elements of a process. In the last ten years it has been utilized for the design of new processes as well as in the energy optimization of existing processes. In this paper the tools utilized for the integration of a cogeneration system in a process for the production of paper is presented. It is also presented how the combined treatment of the Pinch Analysis and the exergy concept allows to define, before the detailed design, the cogeneration potential, the fuel consumption and the amount of pollutant emissions for different cogeneration schemes. [Espanol] El analisis Pinch es un conjunto de principios, herramientas y reglas de diseno que permiten al ingeniero encontrar la mejor manera de configurar los elementos de un proceso. En los ultimos diez anos se ha utilizado para el diseno de procesos nuevos asi como en la optimacion energetica de procesos existentes. En el presente articulo se presentan las herramientas utilizadas para la integracion de un sistema de cogeneracion en un proceso de produccion de papel. Se muestra tambien como el tratamiento combinado del analisis Pinch y el concepto de energia permite definir, antes del diseno detallado, el potencial de cogeneracion, el consumo de combustible y la cantidad de emisiones contaminantes para diferentes esquemas de cogeneracion.

Application of the Pinch analysis for the design of a cogeneration system in a paper mill; Aplicacion del analisis Pinch para el diseno de un sistema de cogeneracion en una industria papelera

Energy Technology Data Exchange (ETDEWEB)

Mani Gonzalez, A G; Arriola Medellin, A [Instituto de Investigaciones Electricas, Cuernavaca (Mexico)

1998-12-31

The Pinch Analysis is a set of principles, tools and rules for the design that allow the engineer find the best way to configure the elements of a process. In the last ten years it has been utilized for the design of new processes as well as in the energy optimization of existing processes. In this paper the tools utilized for the integration of a cogeneration system in a process for the production of paper is presented. It is also presented how the combined treatment of the Pinch Analysis and the exergy concept allows to define, before the detailed design, the cogeneration potential, the fuel consumption and the amount of pollutant emissions for different cogeneration schemes. [Espanol] El analisis Pinch es un conjunto de principios, herramientas y reglas de diseno que permiten al ingeniero encontrar la mejor manera de configurar los elementos de un proceso. En los ultimos diez anos se ha utilizado para el diseno de procesos nuevos asi como en la optimacion energetica de procesos existentes. En el presente articulo se presentan las herramientas utilizadas para la integracion de un sistema de cogeneracion en un proceso de produccion de papel. Se muestra tambien como el tratamiento combinado del analisis Pinch y el concepto de energia permite definir, antes del diseno detallado, el potencial de cogeneracion, el consumo de combustible y la cantidad de emisiones contaminantes para diferentes esquemas de cogeneracion.

An HTR cogeneration system for industrial applications

International Nuclear Information System (INIS)

Haverkate, B.R.W.; Heek, A.I. van; Kikstra, J.F.

2001-01-01

Because of its favourable characteristics of safety and simplicity the high-temperature reactor (HTR) could become a competitive heat source for a cogeneration unit. The Netherlands is a world leading country in the field of cogeneration. As nuclear energy remains an option for the medium and long term in this country, systems for nuclear cogeneration should be explored and developed. Hence, ECN Nuclear Research is developing a conceptual design of an HTR for Combined generation of Heat and Power (CHP) for the industry in and outside the Netherlands. The design of this small CHP-unit for industrial applications is mainly based on a pre-feasibility study in 1996, performed by a joint working group of five Dutch organisations, in which technical feasibility was shown. The concept that was subject of this study, INCOGEN, used a 40 MW thermal pebble bed HTR and produced a maximum amount of electricity plus low temperature heat. The system has been improved to produce industrial quality heat, and has been renamed ACACIA. The output of this installation is 14 MW electricity and 17 tonnes of steam per hour, with a pressure of 10 bar and a temperature of 220 deg. C. The economic characteristics of this installation turned out to be much more favourable using modern data. The research work for this installation is embedded in a programme that has links to the major HTR projects in the world. Accordingly ECN participates in several IAEA Co-ordinated Research Programmes (CRPs). Besides this, ECN is involved in the South African PBMR-project. Finally, ECN participates in the European Concerted Action on Innovative HTR. (author)

Exergy destruction in ammonia scrubbers

NARCIS (Netherlands)

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

2018-01-01

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

Exergy. Concept, challenges and usages for industry

International Nuclear Information System (INIS)

2013-04-01

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

A comparative thermodynamic analysis of ORC and Kalina cycles for waste heat recovery: A case study for CGAM cogeneration system

Directory of Open Access Journals (Sweden)

Arash Nemati

2017-03-01

Full Text Available A thermodynamic modeling and optimization is carried out to compare the advantages and disadvantages of organic Rankine cycle (ORC and Kalina cycle (KC as a bottoming cycle for waste heat recovery from CGAM cogeneration system. Thermodynamic models for combined CGAM/ORC and CGAM/KC systems are performed and the effects of some decision variables on the energy and exergy efficiency and turbine size parameter of the combined systems are investigated. Solving simulation equations and optimization process have been done using direct search method by EES software. It is observed that at the optimum pressure ratio of air compressor, produced power of bottoming cycles has minimum values. Also, evaporator pressure optimizes the performance of cycle, but this optimum pressure level in ORC (11 bar is much lower than that of Kalina (46 bar. In addition, ORC's simpler configuration, higher net produced power and superheated turbine outlet flow, which leads to a reliable performance for turbine, are other advantages of ORC. Kalina turbine size parameter is lower than that of the ORC which is a positive aspect of Kalina cycle. However, by a comprehensive comparison between Kalina and ORC, it is concluded that the ORC has significant privileges for waste heat recovery in this case.

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

OpenAIRE

Abbasi, Yasser; Baniasadi, Ehsan; Ahmadikia, Hossein

2016-01-01

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

Energy and exergy analysis of industrial fluidized bed drying of paddy

International Nuclear Information System (INIS)

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

2015-01-01

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

Energy and advanced exergy analysis of an existing hydrocarbon recovery process

International Nuclear Information System (INIS)

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

2016-01-01

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

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.

The utility of environmental exergy analysis for decision making in energy

International Nuclear Information System (INIS)

Simpson, Adam P.; Edwards, Chris F.

2013-01-01

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

Cogeneration for Brazil

International Nuclear Information System (INIS)

Anon.

2000-01-01

Almost all the electric power in Brazil comes from large-scale hydroelectric plants: only about 3% comes from cogeneration. But, now that the barriers which discouraged cogeneration are being removed, there will be more and more investment in cogeneration and distributed generation. The circumstances which have brought about these changes are described. It is expected that cogeneration will be responsible for producing 10-15% of Brazil's electricity by 2010 and the demand for cogeneration will reach 11-17 GW. It is concluded that Brazil represents one of the world's most attractive market for cogeneration and distributed generation

Improving the Efficiency of a Nucler Power Plant Using a Thermoelectric Cogeneration System

Directory of Open Access Journals (Sweden)

Rauf Terzi

2018-02-01

Full Text Available The efficiencies of nuclear power plants are rather poor having the ratio %30 by using the conventional energy/exergy tools. According to that information, large amount of energy is wasted during condensation and thrown out to the environment. Thermoelectric generator (TEG system has a potential to be used as a heat exchanging technology to produce power with a relatively low efficiency (about 5% and it can transform the temperature difference into electricity and generate clean electrical energy. In the present study, we offer a novel system to recover the waste heat from a VVER-1000 nuclear power plant. The heat transfer of the TEG is analyzed numerically with respect to the various temperature ranges and constant mass flow rate of the exhaust steam entering the system. In the analyses, different hot temperature ranges (35ºC, 45ºC and 55ºC and a constant cold temperature (i.e. 18ºC are used for a HZ-20 thermoelectric module and it has been proven that the designed TEG can produce the maximum output power of 76,956 MW for a temperature difference ∆T=37 and the conversion efficiency of 3,854% sits. The TEG is designed for the condenser of a 1000 MW nuclear power plant. It's shown that about 2,0% increasing in the power plant efficiency is expected by using the selected thermoelectric generator in the condensation cycle. Article History: Received: July 15th 2017; Received:  October 17th 2017; Accepted: February 13rd 2018; Available online How to Cite This Article: Terzi, R. and Kurt, E. (2018, Improving the efficiency of a nuclear power plant using a thermoelectric cogeneration system, Int. Journal of Renewable Energy Development, 7(1, 77-84. https://doi.org/10.14710/ijred.7.1.77-84

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.

Exergy performance of human body under physical activities

International Nuclear Information System (INIS)

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

2013-01-01

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

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.

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)

Global and local emission impact assessment of distributed cogeneration systems with partial-load models

International Nuclear Information System (INIS)

Mancarella, Pierluigi; Chicco, Gianfranco

2009-01-01

Small-scale distributed cogeneration technologies represent a key resource to increase generation efficiency and reduce greenhouse gas emissions with respect to conventional separate production means. However, the diffusion of distributed cogeneration within urban areas, where air quality standards are quite stringent, brings about environmental concerns on a local level. In addition, partial-load emission worsening is often overlooked, which could lead to biased evaluations of the energy system environmental performance. In this paper, a comprehensive emission assessment framework suitable for addressing distributed cogeneration systems is formulated. Local and global emission impact models are presented to identify upper and lower boundary values of the environmental pressure from pollutants that would be emitted from reference technologies, to be compared to the actual emissions from distributed cogeneration. This provides synthetic information on the relative environmental impact from small-scale CHP sources, useful for general indicative and non-site-specific studies. The emission models are formulated according to an electrical output-based emission factor approach, through which off-design operation and relevant performance are easily accounted for. In particular, in order to address the issues that could arise under off-design operation, an equivalent load model is incorporated within the proposed framework, by exploiting the duration curve of the cogenerator loading and the emissions associated to each loading level. In this way, it is possible to quantify the contribution to the emissions from cogeneration systems that might operate at partial loads for a significant portion of their operation time, as for instance in load-tracking applications. Suitability of the proposed methodology is discussed with respect to hazardous air pollutants such as NO x and CO, as well as to greenhouse gases such as CO 2 . Two case study applications based on the emission

HTGR-steam cycle/cogeneration plant economic potential

International Nuclear Information System (INIS)

1981-05-01

The cogeneration of heat and electricity provides the potential for improved fuel utilization and corresponding reductions in energy costs. In the evaluation of the cogeneration plant product costs, it is advantageous to develop joint-product cost curves for alternative cogeneration plant models. The advantages and incentives for cogeneration are then presented in a form most useful to evaluate the various energy options. The HTGR-Steam Cycle/Cogeneration (SC/C) system is envisioned to have strong cogeneration potential due to its high-quality steam capability, its perceived nuclear siting advantages, and its projected cost advantages relative to coal. The economic information presented is based upon capital costs developed during 1980 and the economic assumptions identified herein

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

International Nuclear Information System (INIS)

Muangnoi, Thirapong; Asvapoositkul, Wanchai; Wongwises, Somchai

2007-01-01

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

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

International Nuclear Information System (INIS)

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

2016-01-01

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

Smart intermittency-friendly cogeneration: Techno-economic performance of innovative double storage concept for integrating compression heat pumps in distributed cogeneration

DEFF Research Database (Denmark)

Blarke, Morten

2011-01-01

cogeneration plants rather than central power plants are giving way for wind power in the electricity mix. Could intermittent renewables be a threat to the system-wide energy, economic and environmental benefits that distributed cogeneration have to offer? This paper investigates how existing cogeneration...... plants may adapt their plant design and operational strategy to improve the co-existence between cogeneration and intermittent renewables. A novel intermittency-friendly and super-efficient concept in cogeneration is presented that involves integrating a high-pressure compression heat pump using heat...

Techno-economic assessment and optimization of stirling engine micro-cogeneration systems in residential buildings

Energy Technology Data Exchange (ETDEWEB)

Alanne, Kari; Soederholm, Niklas; Siren, Kai [Dept. of Energy Technology, Helsinki University of Technology, P.O. Box 4100, 02015 TKK (Finland); Beausoleil-Morrison, Ian [Dept. of Mechanical and Aerospace Engineering, Carleton University, Ottawa (Canada)

2010-12-15

Micro-cogeneration offers numerous potential advantages for the supply of energy to residential buildings in the sense of improved energy efficiency and reduced environmental burdens. To realize these benefits, however, such systems must reduce energy costs, primary energy consumption, and CO{sub 2} emissions relative to conventional heating systems. In this paper, we search for optimized strategies for the integration of a Stirling engine-based micro-cogeneration system in residential buildings by comparing the performance of various system configurations and operational strategies with that of a reference system, i.e. hydronic heating and a low temperature gas boiler in standard and passive house constructions located in different climates. The IDA-ICE whole-building simulation program is employed with the Stirling engine micro-cogeneration model that was developed by IEA/ECBCS Annex 42. In this way the dynamic effects of micro-cogeneration devices, such as warm-ups and shutdowns, are accounted for. This study contributes to the research by addressing hourly changes in the fuel mix used for central electricity generation and the utilization of thermal exhaust through heat recovery. Our results suggest that an optimally operated micro-cogeneration system encompassing heat recovery and appropriate thermal storage would result in a 3-5% decrease in primary energy consumption and CO{sub 2} emissions when compared to a conventional hydronic heating system. Moreover, this configuration is capable of delivering annual savings in all the combinations of electricity and fuel price between 0.05 and 0.15 EUR kW h{sup -1}. As can be expected, these results are sensitive to the electrical energy supply mix, building type, and climate. (author)

Techno-economic assessment and optimization of Stirling engine micro-cogeneration systems in residential buildings

International Nuclear Information System (INIS)

Alanne, Kari; Soederholm, Niklas; Siren, Kai; Beausoleil-Morrison, Ian

2010-01-01

Micro-cogeneration offers numerous potential advantages for the supply of energy to residential buildings in the sense of improved energy efficiency and reduced environmental burdens. To realize these benefits, however, such systems must reduce energy costs, primary energy consumption, and CO 2 emissions relative to conventional heating systems. In this paper, we search for optimized strategies for the integration of a Stirling engine-based micro-cogeneration system in residential buildings by comparing the performance of various system configurations and operational strategies with that of a reference system, i.e. hydronic heating and a low temperature gas boiler in standard and passive house constructions located in different climates. The IDA-ICE whole-building simulation program is employed with the Stirling engine micro-cogeneration model that was developed by IEA/ECBCS Annex 42. In this way the dynamic effects of micro-cogeneration devices, such as warm-ups and shutdowns, are accounted for. This study contributes to the research by addressing hourly changes in the fuel mix used for central electricity generation and the utilization of thermal exhaust through heat recovery. Our results suggest that an optimally operated micro-cogeneration system encompassing heat recovery and appropriate thermal storage would result in a 3-5% decrease in primary energy consumption and CO 2 emissions when compared to a conventional hydronic heating system. Moreover, this configuration is capable of delivering annual savings in all the combinations of electricity and fuel price between 0.05 and 0.15 Euro kW h -1 . As can be expected, these results are sensitive to the electrical energy supply mix, building type, and climate.

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...

Exergy based parametric analysis of a combined reheat regenerative thermal power plant and water–LiBr vapor absorption refrigeration system

International Nuclear Information System (INIS)

Gogoi, T.K.; Talukdar, K.

2014-01-01

Highlights: • Exergy analysis of a combined power–absorption cooling system is provided. • Exergetic efficiency of the power cycle and absorption cooling system are calculated. • Irreversibility in each component and total system irreversibility are calculated. • Effect of operating parameters on exergetic performance and irreversibility is analyzed. • Optimum operating parameters are identified based on energy and exergy based results. - Abstract: In this paper, exergy analysis of a combined reheat regenerative steam turbine (ST) based power cycle and water–LiBr vapor absorption refrigeration system (VARS) is presented. Exergetic efficiency of the power cycle and VARS, energy utilization factor (EUF) of the combined system (CS) and irreversibility in each system component are calculated. The effect of fuel flow rate, boiler pressure, cooling capacity and VARS components’ temperature on performance, component and total system irreversibility is analyzed. The second law based results indicate optimum performance at 150 bar boiler pressure and VARS generator, condenser, evaporator and absorber temperature of 80 °C, 37.5 °C, 15 °C and 35 °C respectively. The present exergy based results conform well to the first law based results obtained in a previous analysis done on the same combined system. Irreversibility distribution among various power cycle components shows the highest irreversibility in the cooling tower. Irreversibility of the exhaust flue gas leaving the boiler and the boiler are the next major contributors. Among the VARS components, exergy destruction in the generator is the highest followed by irreversibility contribution of the absorber, condenser and the evaporator

Modeling of a Cogeneration System with a Micro Gas Turbine Operating at Partial Load Conditions

Directory of Open Access Journals (Sweden)

José Carlos Dutra

2017-06-01

Full Text Available The integration of absorption chillers in micro-cogeneration systems based on micro-gas turbines can be useful as an appropriate strategy to increase the total system energy efficiency. Since it is an area intensive in technology, it is necessary to develop and use models of simulation, which can predict the behavior of the whole system and of each component individually, at different operating conditions. This work is part of a research project in high efficiency cogeneration systems, whose purpose at this stage is to model a micro-cogeneration system, which is composed of a micro gas turbine, Capstone C30, a compact cross flow finned tube heat exchanger and an absorption chiller. The entire model is composed of specifically interconnected models, developed and validated for each component. The simulation of the microturbine used a thermodynamic analytic model, which contains a procedure used to obtain the micro turbine characteristic performance curves, which is closed with the thermodynamic Brayton cycle model. In the cogeneration system discussed in this paper, the compact heat exchanger was used to heat thermal oil, which drives an absorption chiller. It was designed, characterized and installed in a cogeneration system installed at the Centre d'Innovació Tecnològica en Revalorització Energètica i Refrigeració, Universtat Rovira i Virgili. Its design led to the heat exchanger model, which was coupled with the micro turbine model. Presented in this work is a comparison between the data from the model and the experiments, demonstrating good agreement between both results.

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.

A technical analysis for cogeneration systems with potential applications in twelve California industrial plants. [energy saving heat-electricity utility systems

Science.gov (United States)

Moretti, V. C.; Davis, H. S.; Slonski, M. L.

1978-01-01

In a study sponsored by the State of California Energy Resources Conservation and Development Commission, 12 industrial plants in five utility districts were surveyed to assess the potential applications of the cogeneration of heat and electricity in California industry. Thermodynamic calculations were made for each plant in determining the energy required to meet the existing electrical and steam demands. The present systems were then compared to conceptual cogeneration systems specified for each plant. Overall energy savings were determined for the cogeneration applications. Steam and gas turbine topping cycle systems were considered as well as bottoming cycle systems. Types of industries studied were: pulp and paper, timber, cement, petroleum refining, enhanced oil recovery, foods processing, steel and glass

Cogeneration: a win-win option for Cadbury Nigeria

International Nuclear Information System (INIS)

Dayo, Felix; Bogunjoko, S.B.; Sobanwa, A.C.

2001-01-01

Like most developing countries, Nigeria is looking to cogeneration as a sustainable and reliable means of overcoming its present unreliable supply of energy. The article focuses on the efforts of the food company Cadbury Nigeria which uses cogeneration for all its steam and power requirements within its own factory. The Company recently decided to upgrade further by switching from liquid fossil fuels to natural gas. Diagrams show the existing system as well as the systems for cogeneration with natural gas. Some of the obstacles to be overcome to improve the viability of cogeneration in developing countries are listed. It is hoped that the outcome of the COP6 meeting to be held in April 2001 will offer encouragement for cogeneration

Cogeneration: a win-win option for Cadbury Nigeria

Energy Technology Data Exchange (ETDEWEB)

Dayo, Felix [Triple ' E' Systems Associates Ltd. (Nigeria); Bogunjoko, S.B.; Sobanwa, A.C. [Cadbury Nigeria plc. (Nigeria)

2001-02-01

Like most developing countries, Nigeria is looking to cogeneration as a sustainable and reliable means of overcoming its present unreliable supply of energy. The article focuses on the efforts of the food company Cadbury Nigeria which uses cogeneration for all its steam and power requirements within its own factory. The Company recently decided to upgrade further by switching from liquid fossil fuels to natural gas. Diagrams show the existing system as well as the systems for cogeneration with natural gas. Some of the obstacles to be overcome to improve the viability of cogeneration in developing countries are listed. It is hoped that the outcome of the COP6 meeting to be held in April 2001 will offer encouragement for cogeneration.

Cogeneration for small SAGD projects

Energy Technology Data Exchange (ETDEWEB)

Albion, Stuart [AMEC BDR Limited (United Kingdom)

2011-07-01

As many SAGD projects are being developed in remote locations, the supply of a steady source of power to them becomes an important question. Connecting these remote facilities to a grid can often be difficult and costly. This presentation, by AMEC BDR Limited, promotes the use of cogeneration in small SAGD projects. Cogeneration is the generation of two forms of energy from one fuel source. In this particular case, the energy forms would be electricity and heat. In many SAGD projects, a gas turbine system is used to generate the electricity, while a heat recovery system is utilized to generate steam. The use of cogeneration systems in SAGD projects, as opposed to using separate heat and electricity systems, has the potential to significantly reduce the amount of energy lost, the amount of emissions and power costs, in addition to ensuring that there is a reliable supply of steam and electricity.

Exergy analysis of the energy use in Greece

International Nuclear Information System (INIS)

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

2011-01-01

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

Exergy analysis of a MSF distillation plant

International Nuclear Information System (INIS)

Kahraman, Nafiz; Cengel, Yunus A.

2005-01-01

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

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

International Nuclear Information System (INIS)

Miladi, Rihab; Frikha, Nader; Gabsi, Slimane

2017-01-01

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

Exergy and exergoeconomic analysis of a Compressed Air Energy Storage combined with a district energy system

International Nuclear Information System (INIS)

Bagdanavicius, Audrius; Jenkins, Nick

2014-01-01

Highlights: • CAES and CAES with thermal storage systems were investigated. • The potential for using heat generated during the compression stage was analysed. • CAES-TS has the potential to be used both as energy storage and heat source. • CAES-TS could be a useful tool for balancing overall energy demand and supply. - Abstract: The potential for using heat generated during the compression stage of a Compressed Air Energy Storage system was investigated using exergy and exergoeconomic analysis. Two Compressed Air Energy Storage systems were analysed: Compressed Air Energy Storage (CAES) and Compressed Air Energy Storage combined with Thermal Storage (CAES-TS) connected to a district heating network. The maximum output of the CAES was 100 MWe and the output of the CAES-TS was 100 MWe and 105 MWth. The study shows that 308 GW h/year of electricity and 466 GW h/year of fuel are used to generate 375 GW h/year of electricity. During the compression of air 289 GW h/year of heat is generated, which is wasted in the CAES and used for district heating in the CAES-TS system. Energy efficiency of the CAES system was around 48% and the efficiency of CAES-TS was 86%. Exergoeconomic analysis shows that the exergy cost of electricity generated in the CAES was 13.89 ¢/kW h, and the exergy cost of electricity generated in the CAES-TS was 11.20 ¢/kW h. The exergy cost of heat was 22.24 ¢/kW h in the CAES-TS system. The study shows that CAES-TS has the potential to be used both as energy storage and heat source and could be a useful tool for balancing overall energy demand and supply

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

Directory of Open Access Journals (Sweden)

Vučković Goran D.

2012-01-01

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

Energy and exergy analysis of the silicon production process

International Nuclear Information System (INIS)

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

2013-01-01

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

Diagnosis of an alternative ammonia process technology to reduce exergy losses

International Nuclear Information System (INIS)

Ghannadzadeh, Ali; Sadeqzadeh, Majid

2016-01-01

belongs to the compressors (518 kJ/kg exergy losses) where a lower inlet temperature and better system isolation could help to reduce losses.

Exergy conversion in the Japanese society

International Nuclear Information System (INIS)

Wall, G.

1989-01-01

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

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

Directory of Open Access Journals (Sweden)

Valentina Bonetti

2017-01-01

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

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

International Nuclear Information System (INIS)

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

2013-01-01

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

Cogeneration technologies, optimisation and implementation

CERN Document Server

Frangopoulos, Christos A

2017-01-01

Cogeneration refers to the use of a power station to deliver two or more useful forms of energy, for example, to generate electricity and heat at the same time. This book provides an integrated treatment of cogeneration, including a tour of the available technologies and their features, and how these systems can be analysed and optimised.

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

Directory of Open Access Journals (Sweden)

Gabriel Marques Spanghero

2018-02-01

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

Extra cogeneration step seen boosting output 20%

Energy Technology Data Exchange (ETDEWEB)

Burton, P.

1984-10-08

Cogenerators can now buy a prototype 6.5 MW, pre-packaged cogeneration system that incorporates an added step to its cycle to reduce fuel use by 21%. Larger, custom-designed systems will be on the market in 1985. Fayette Manufacturing Co. will offer the Kalina Cycle system at a discount price of $8.2 million (1200/kW) until the systems are competitive with conventional units. The system varies from conventional cogeneration systems by adding a distillation step, which permits the use of two fluids for the turbine steam and operates at a higher thermodynamic efficiency, with boiling occuring at high temperature and low pressure. Although theoretically correct, DOE will withhold judgment on the system's efficiency until the first installation is operating.

A framework for the exergy analysis of future transport pathways: Application for the United Kingdom transport system 2010–2050

International Nuclear Information System (INIS)

Byers, Edward A.; Gasparatos, Alexandros; Serrenho, André C.

2015-01-01

Exergy analysis has been used to quantify the historical resource use efficiency and environmental impact of transport systems. However, few exergy studies have explored future transport pathways. This study aims to, (a) develop a conceptual framework for the exergy analysis of multiple future transport and electricity pathways, (b) apply this framework to quantify future resource consumption and service delivery patterns, (c) discuss the policy-relevant results that exergy studies of future transport systems can offer. Multiple transport and electricity pathways developed by the UK Government are used to explore changes in energy use, useful work delivery and greenhouse gas emissions. In passenger transport, ambitious electrification results in a 20% increase of useful work delivery, whilst reducing GHG emissions and energy consumption by 65%. For freight, international shipping and aviation, smaller exergy efficiency improvements make useful work delivery and greenhouse gas emissions highly dependent on transport demand. Passenger transport electrification brings a step-change in useful work delivery, which if accompanied by low-carbon electricity, significantly reduces greenhouse gas emissions. The efficiency of low-carbon electricity systems is significant for useful work delivery, but not dominant across the scenarios explored. High penetration of renewables and electrified transport is the most resource-efficient combination in this context. - Highlights: • Develop an exergy analysis framework of future transport pathways and apply it to UK. • Electrification of personal transport brings step change in useful work delivery. • Efficiency of electricity supply becomes significant once transport is electrified. • High electrification increases useful work (+20%) and reduces emissions (−65%). • High penetration of renewables and electrified transport is most resource efficient

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

International Nuclear Information System (INIS)

Abedin, Ali Haji; Rosen, Marc A.

2012-01-01

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

Energy and exergy analyses of Angra-2 nuclear power plant

Energy Technology Data Exchange (ETDEWEB)

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

2017-07-01

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

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.

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.

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

DEFF Research Database (Denmark)

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

2013-01-01

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

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

Directory of Open Access Journals (Sweden)

Qinglin Cheng

2018-04-01

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

Cogeneration in Taiwan

Energy Technology Data Exchange (ETDEWEB)

Cotard, E. [International Cogeneration Alliance (United States)

2000-10-01

The short article discusses pollution abatement and the potential role of cogeneration in Taiwan. A diagram shows the contributions of various energy sources (coal, oil etc.) from 1979-1999 and the growth of cogeneration between 1979 and 1999. The lack of natural gas or diesel does not help the cause of cogeneration in Taiwan, nor does the structure of the local electricity market. Nevertheless, if the proposed new LNG facilities are built in the North, then the opportunities for cogeneration will be very good.

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

Directory of Open Access Journals (Sweden)

John H. Doty

2009-01-01

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

Thermal systems; Systemes thermiques

Energy Technology Data Exchange (ETDEWEB)

Lalot, S. [Valenciennes Univ. et du Hainaut Cambresis, LME, 59 (France); Lecoeuche, S. [Ecole des Mines de Douai, Dept. GIP, 59 - Douai (France)]|[Lille Univ. des Sciences et Technologies, 59 - Villeneuve d' Ascq (France); Ahmad, M.; Sallee, H.; Quenard, D. [CSTB, 38 - Saint Martin d' Heres (France); Bontemps, A. [Universite Joseph Fourier, LEGI/GRETh, 38 - Grenoble (France); Gascoin, N.; Gillard, P.; Bernard, S. [Laboratoire d' Energetique, Explosion, Structure, 18 - Bourges (France); Gascoin, N.; Toure, Y. [Laboratoire Vision et Robotique, 18 - Bourges (France); Daniau, E.; Bouchez, M. [MBDA, 18 - Bourges (France); Dobrovicescu, A.; Stanciu, D. [Bucarest Univ. Polytechnique, Faculte de Genie Mecanique (Romania); Stoian, M. [Reims Univ. Champagne Ardenne, Faculte des Sciences, UTAP/LTM, 51 (France); Bruch, A.; Fourmigue, J.F.; Colasson, S. [CEA Grenoble, Lab. Greth, 38 (France); Bontemps, A. [Universite Joseph Fourier, LEGI/GRETh, 38 - Grenoble (France); Voicu, I.; Mare, T.; Miriel, J. [Institut National des Sciences Appliquees (INSA), LGCGM, IUT, 35 - Rennes (France); Galanis, N. [Sherbrooke Univ., Genie Mecanique, QC (Canada); Nemer, M.; Clodic, D. [Ecole des Mines de Paris, Centre Energetique et Procedes, 75 (France); Lasbet, Y.; Auvity, B.; Castelain, C.; Peerhossaini, H. [Nantes Univ., Ecole Polytechnique, Lab. de Thermocinetiquede Nantes, UMR-CNRS 6607, 44 (France)

2005-07-01

This session about thermal systems gathers 26 articles dealing with: neural model of a compact heat exchanger; experimental study and numerical simulation of the thermal behaviour of test-cells with walls made of a combination of phase change materials and super-insulating materials; hydraulic and thermal modeling of a supercritical fluid with pyrolysis inside a heated channel: pre-dimensioning of an experimental study; energy analysis of the heat recovery devices of a cryogenic system; numerical simulation of the thermo-hydraulic behaviour of a supercritical CO{sub 2} flow inside a vertical tube; mixed convection inside dual-tube exchangers; development of a nodal approach with homogenization for the simulation of the brazing cycle of a heat exchanger; chaotic exchanger for the cooling of low temperature fuel cells; structural optimization of the internal fins of a cylindrical generator; a new experimental approach for the study of the local boiling inside the channels of exchangers with plates and fins; experimental study of the flow regimes of boiling hydrocarbons on a bundle of staggered tubes; energy study of heat recovery exchangers used in Claude-type refrigerating systems; general model of Carnot engine submitted to various operating constraints; the free pistons Stirling cogeneration system; natural gas supplied cogeneration system with polymer membrane fuel cell; influence of the CRN coating on the heat flux inside the tool during the wood unrolling process; transport and mixture of a passive scalar injected inside the wake of a Ahmed body; control of a laser welding-brazing process by infrared thermography; 2D self-adaptative method for contours detection: application to the images of an aniso-thermal jet; exergy and exergy-economical study of an 'Ericsson' engine-based micro-cogeneration system; simplified air-conditioning of telephone switching equipments; parametric study of the 'low-energy' individual dwelling; brief synthesis of

Dynamic Simulation and Exergo-Economic Optimization of a Hybrid Solar–Geothermal Cogeneration Plant

Directory of Open Access Journals (Sweden)

Francesco Calise

2015-04-01

Full Text Available This paper presents a dynamic simulation model and a parametric analysis of a solar-geothermal hybrid cogeneration plant based on an Organic Rankine Cycle (ORC powered by a medium-enthalpy geothermal resource and a Parabolic Trough Collector solar field. The fluid temperature supplying heat to the ORC varies continuously as a function of the solar irradiation, affecting both the electrical and thermal energies produced by the system. Thus, a dynamic simulation was performed. The ORC model, developed in Engineering Equation Solver, is based on zero-dimensional energy and mass balances and includes specific algorithms to evaluate the off-design system performance. The overall simulation model of the solar-geothermal cogenerative plant was implemented in the TRNSYS environment. Here, the ORC model is imported, whereas the models of the other components of the system are developed on the basis of literature data. Results are analyzed on different time bases presenting energetic, economic and exergetic performance data. Finally, a rigorous optimization has been performed to determine the set of system design/control parameters minimizing simple payback period and exergy destruction rate. The system is profitable when a significant amount of the heat produced is consumed. The highest irreversibilities are due to the solar field and to the heat exchangers.

A new dynamism for the cogeneration of 2000 - from the medium to the mini-cogeneration; Une nouvelle dynamique pour la cogeneration en l'an 2000 - de la moyenne vers le mini-cogeneration

Energy Technology Data Exchange (ETDEWEB)

NONE

2001-07-01

In the framework of the Eco-Industries 2000 meeting, the ATEE organized a colloquium on the medium and mini-cogeneration market. This book presents the fourteen papers proposed at this colloquium bringing information on the cogeneration technology for the medium and mini-systems. The state of the art concerning the turbines and examples of dual systems (heating and warm water) are provided. Some economical aspects are also presented with the international and national market, the contracts management with EDF and the investments. (A.L.B.)

Towards an intermittency-friendly energy system: Comparing electric boilers and heat pumps in distributed cogeneration

International Nuclear Information System (INIS)

Blarke, Morten B.

2012-01-01

Highlights: ► We propose an “intermittency-friendly” energy system design. ► We compare intermittency-friendly concepts in distributed cogeneration. ► We investigate a new concept involving a heat pump and intermediate cold storage. ► We find significant improvements in operational intermittency-friendliness. ► Well-designed heat pump concepts are more cost-effective than electric boilers. -- Abstract: Distributed cogeneration has played a key role in the implementation of sustainable energy policies for three decades. However, increasing penetration levels of intermittent renewables is challenging that position. The paradigmatic case of West Denmark indicates that distributed operators are capitulating as wind power penetration levels are moving above 25%; some operators are retiring cogeneration units entirely, while other operators are making way for heat-only boilers. This development is jeopardizing the system-wide energy, economic, and environmental benefits that distributed cogeneration still has to offer. The solution is for distributed operators to adapt their technology and operational strategies to achieve a better co-existence between cogeneration and wind power. Four options for doing so are analysed including a new concept that integrates a high pressure compression heat pump using low-temperature heat recovered from flue gasses in combination with an intermediate cold storage, which enables the independent operation of heat pump and cogenerator. It is found that an electric boiler provides consistent improvements in the intermittency-friendliness of distributed cogeneration. However, well-designed heat pump concepts are more cost-effective than electric boilers, and in future markets where the gas/electricity price ratio is likely to increase, compression heat pumps in combination with intermediate thermal storages represent a superior potential for combining an intermittency-friendly pattern of operation with the efficient use of

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

International Nuclear Information System (INIS)

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

2015-01-01

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

Decision making based on data analysis and optimization algorithm applied for cogeneration systems integration into a grid

Science.gov (United States)

Asmar, Joseph Al; Lahoud, Chawki; Brouche, Marwan

2018-05-01

Cogeneration and trigeneration systems can contribute to the reduction of primary energy consumption and greenhouse gas emissions in residential and tertiary sectors, by reducing fossil fuels demand and grid losses with respect to conventional systems. The cogeneration systems are characterized by a very high energy efficiency (80 to 90%) as well as a less polluting aspect compared to the conventional energy production. The integration of these systems into the energy network must simultaneously take into account their economic and environmental challenges. In this paper, a decision-making strategy will be introduced and is divided into two parts. The first one is a strategy based on a multi-objective optimization tool with data analysis and the second part is based on an optimization algorithm. The power dispatching of the Lebanese electricity grid is then simulated and considered as a case study in order to prove the compatibility of the cogeneration power calculated by our decision-making technique. In addition, the thermal energy produced by the cogeneration systems which capacity is selected by our technique shows compatibility with the thermal demand for district heating.

Multi-objective optimization of a pressurized solid oxide fuel cell – gas turbine hybrid system integrated with seawater reverse osmosis

International Nuclear Information System (INIS)

Eveloy, Valerie; Rodgers, Peter; Al Alili, Ali

2017-01-01

To improve the capacity and efficiency of distributed power and fresh water generation in coastal industrial facilities affected by regional water scarcity, a natural gas-fueled, pressurized solid oxide fuel cell-gas turbine (SOFC-GT) hybrid is integrated with a bottoming organic Rankine cycle (ORC) and seawater reverse osmosis (RO) desalination plant. This power and water co-generation system is optimized in terms of two objectives, maximum exergy efficiency and minimum cost rate, using a genetic algorithm. The exergetic and economic performance of three solutions representing maximum exergy efficiency, minimum cost rate, and a compromise between efficiency and cost rate, are compared. When imposing a water production requirement (reference case), the selected compromise multi-objective optimization solution delivers a net power output of 2.4 MWe and 636 m"3/day of permeate, at a co-generation exergy efficiency and cost rate of 71.3% and 0.0256 USD/s, respectively. The system payback time is estimated to be less than six years for typical economic parameters, but would become unprofitable in the most unfavorable economic scenario considered. Overall, the results indicate the thermodynamic and economic benefits of reverse osmosis over thermal desalination processes for integration with high-efficiency power generation systems in coastal regions impacted by domestic gas shortages and water scarcity. - Highlights: • Integration of a pressurized SOFC-GT hybrid system with a reverse osmosis unit. • Multi-objective, exergetic and economic optimization using a genetic algorithm. • Optimum solution delivers 2.4 MWe and 636 m"3/day of desalinated water. • Overall exergy efficiency and cost rate of 71.3% and 0.0256 USD/s, respectively. • System payback time estimated at less than six years for typical economic conditions.

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...

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

International Nuclear Information System (INIS)

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

2008-01-01

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

Subcooled compressed air energy storage system for coproduction of heat, cooling and electricity

International Nuclear Information System (INIS)

Arabkoohsar, A.; Dremark-Larsen, M.; Lorentzen, R.; Andresen, G.B.

2017-01-01

Highlights: •A new configuration of compressed air energy storage system is proposed and analyzed. •This system, so-called subcooled-CAES, offers cogeneration of electricity, heat and cooling. •A pseudo-dynamic energy, exergy and economic analysis of the system for an entire year is presented. •The annual power, cooling and heat efficiencies of the system are around 31%, 32% and 92%. •The overall energy and exergy performance coefficients of the system are 1.55 and 0.48, respectively. -- Abstract: Various configurations of compressed air energy storage technology have received attention over the last years due to the advantages that this technology offers relative to other power storage technologies. This work proposes a new configuration of this technology aiming at cogeneration of electricity, heat and cooling. The new system may be very advantageous for locations with high penetration of renewable energy in the electricity grid as well as high heating and cooling demands. The latter would typically be locations with district heating and cooling networks. A thorough design, sizing and thermodynamic analysis of the system for a typical wind farm with 300 MW capacity in Denmark is presented. The results show a great potential of the system to support the local district heating and cooling networks and reserve services in electricity market. The values of power-to-power, power-to-cooling and power-to-heat efficiencies of this system are 30.6%, 32.3% and 92.4%, respectively. The exergy efficiency values are 30.6%, 2.5% and 14.4% for power, cooling and heat productions. A techno-economic comparison of this system with two of the most efficient previous designs of compressed air energy storage system proves the firm superiority of the new concept.

Energy and cost saving results for advanced technology systems from the Cogeneration Technology Alternatives Study (CTAS)

Science.gov (United States)

Sagerman, G. D.; Barna, G. J.; Burns, R. K.

1979-01-01

An overview of the organization and methodology of the Cogeneration Technology Alternatives Study is presented. The objectives of the study were to identify the most attractive advanced energy conversion systems for industrial cogeneration applications in the future and to assess the advantages of advanced technology systems compared to those systems commercially available today. Advanced systems studied include steam turbines, open and closed cycle gas turbines, combined cycles, diesel engines, Stirling engines, phosphoric acid and molten carbonate fuel cells and thermionics. Steam turbines, open cycle gas turbines, combined cycles, and diesel engines were also analyzed in versions typical of today's commercially available technology to provide a base against which to measure the advanced systems. Cogeneration applications in the major energy consuming manufacturing industries were considered. Results of the study in terms of plant level energy savings, annual energy cost savings and economic attractiveness are presented for the various energy conversion systems considered.

Depletion of the non-renewable natural exergy resources as a measure of the ecological cost

International Nuclear Information System (INIS)

Szargut, Jan; Ziebik, Andrzej; Stanek, Wojciech

2002-01-01

The cumulative consumption of non-renewable exergy connected with the fabrication of particular products has been termed as their ecological cost. System of linear input-output equations determining the ecological costs have been formulated. The cogeneration processes have been considered using the principle of the avoided costs of fabrication of the products substituted by the by-products of the considered process. The ecological cost determined in a regional scope takes into account the ecological cost of the imported raw materials and semi-finished products. These quantities have been substituted by the economically equivalent export of own products. The deleterious effect of the rejection of waste products to the environment has been approximately determined by means of the monetary indices of harmfulness of waste products. It has been proved, that the ecological cost of human work cannot be introduced into the set of input-output equations. Exemplary calculations have been made for the products connected with the blast-furnace process. The influence of the injection of auxiliary fuels into the blast furnace on the ecological cost of pig iron has been analyzed too. (Author)

Regional and global exergy and energy efficiencies

Energy Technology Data Exchange (ETDEWEB)

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

1996-03-01

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

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.

Performance assessment of cogeneration and trigeneration systems for small scale applications

International Nuclear Information System (INIS)

Angrisani, Giovanni; Akisawa, Atsushi; Marrasso, Elisa; Roselli, Carlo; Sasso, Maurizio

2016-01-01

Highlights: • Indices and methods to assess the performance of polygeneration systems. • Index to evaluate the economic feasibility of trigeneration system is introduced. • Thermo-economic analysis is performed considering three commercial cogenerators. • Sensitivity analysis varying reference electric efficiency for European Countries. • Sensitivity analysis varying environmental and economic parameters. - Abstract: Cogeneration and trigeneration systems can contribute to the reduction of primary energy consumption and greenhouse gas emissions in residential and tertiary sectors, by reducing fossil fuels demand and grid losses with respect to conventional systems. To evaluate the performance of these systems, several indices and assessment methodologies can be used, due to the high complexity of such systems, which can consist of several energy conversion devices and can perform bidirectional interactions with external electric and thermal grids. In this paper, a review of the available indices and methodologies to assess the performances of polygeneration systems is provided. An index (TSS_t_r_i) aimed to assess the economic feasibility of a trigeneration system is also introduced and discussed. This activity started in the framework of the International Energy Agency Annex 54 project (“Integration of Micro-Generation and Related Energy Technologies in Buildings”), where research groups shared their expertise about methods applied in each Country to evaluate the performance of polygeneration systems. It was concluded that a thermo-economic analysis comparing the performance of a polygeneration system with those of a reference benchmark scenario, is a very suitable assessment method. Some of the reviewed methodologies are then applied to small scale commercial cogenerators. The sensitivity analysis is performed considering different reference average values of electric efficiency, unitary natural gas and electricity prices, and emission factors for

Assessment of energy and exergy efficiencies of a grate clinker cooling system through the optimization of its operational parameters

International Nuclear Information System (INIS)

Ahamed, J.U.; Madlool, N.A.; Saidur, R.; Shahinuddin, M.I.; Kamyar, A.; Masjuki, H.H.

2012-01-01

Grate coolers are widely used in cement industries to recover heat from hot clinker, coming out from the rotary kiln. This study focuses on improving the energy, exergy and recovery efficiencies of a grate cooling system through the optimization of its operational parameters such as masses of cooling air and clinker, cooling air temperature, and grate speed. It has been found that the energy and recovery energy efficiencies of a cooling system can be increased by 1.1% and 1.9%, respectively, with every 5% mass increases of cooling air. Similarly, it has been estimated that energy and recovery energy efficiencies can be increased by 2.0% and 0.4% with every 5% increase of cooling temperature. The exergy and its recovery efficiencies found to be increased by 3.6% and 2.2%, respectively, for the same condition. Energy efficiency and energy recovery efficiencies are increased by 3.5% and 1.4% with every 9.1% increase of grate speed. Using heat recovery from the exhaust air, energy and exergy recovery efficiencies of the cooling system found to be increased by 21.5% and 9.4%, respectively. It has been found that about 38.10% and 30.86% energy cost can be saved by changing mass flow rate of clinker and mass flow rate of cooling air, respectively. -- Highlights: ► The energy and exergy efficiencies of the base case clinker cooler are 81.2% and 53.7%, respectively. ► To increase 5% mass flow of cooling air, the energy and exergy efficiency increase 1.1% and 0.9%, respectively. ► Increase of grate speed and cooling air temperature cause to increase of all efficiencies. ► Heat recovery from the exhaust air experiences 21.5% and 9.4% in energy and exergy recovery efficiency, respectively. ► Reduction of clinker mass flow reduces the emission of NO x , CO, PM and CO 2 .

Exergy of partially coherent thermal radiation

International Nuclear Information System (INIS)

Wijewardane, S.; Goswami, Yogi

2012-01-01

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

District heating/cogeneration application studies for the Minneapolis-St Paul area. Executive summary; overall feasibility and economic viability for a district heating/new cogeneration system in Minneapolis-St. Paul

Energy Technology Data Exchange (ETDEWEB)

Margen, P.; Larsson, K.; Cronholm, L.A.; Marklund, J.E.

1979-08-01

A study was undertaken to determine the feasibility of introducing a large-scale, hot-water, district-heating system for the Minneapolis-St. Paul area. The analysis was based on modern European hot-water district-heating concepts in which cogeneration power plants supply the base-load thermal energy. Heat would be supplied from converted turbines of existing coal-fired power plants in Minneapolis and St. Paul. Toward the end of the 20-year development period, one or two new cogeneration units would be required. Thus, the district-heating system could use low-grade heat from either coal-fired or nuclear cogeneration power stations to replace the space-heating fuels currently used - natural gas and distillate oil. The following conclusions can be drawn: the concept is technically feasible, it has great value for fuel conservation, and with appropriate financing the system is economically viable.

On exergy analysis of industrial plants and significance of ambient temperature

Energy Technology Data Exchange (ETDEWEB)

Rian, Berit

2011-07-01

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

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

International Nuclear Information System (INIS)

Lior, Noam

2002-01-01

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

Exergy analysis of biomass organic Rankine cycle for power generation

Science.gov (United States)

Nur, T. B.; Sunoto

2018-02-01

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

Exergy costing for energy saving in combined heating and cooling applications

International Nuclear Information System (INIS)

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

2014-01-01

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

CDM potential of bagasse cogeneration in India

International Nuclear Information System (INIS)

Purohit, Pallav; Michaelowa, Axel

2007-01-01

So far, the cumulative capacity of renewable energy systems such as bagasse cogeneration in India is far below their theoretical potential despite government subsidy programmes. One of the major barriers is the high investment cost of these systems. The Clean Development Mechanism (CDM) provides industrialized countries with an incentive to invest in emission reduction projects in developing countries to achieve a reduction in CO 2 emissions at lowest cost that also promotes sustainable development in the host country. Bagasse cogeneration projects could be of interest under the CDM because they directly displace greenhouse gas emissions while contributing to sustainable rural development. This study assesses the maximum theoretical as well as the realistically achievable CDM potential of bagasse cogeneration in India. Our estimates indicate that there is a vast theoretical potential of CO 2 mitigation by the use of bagasse for power generation through cogeneration process in India. The preliminary results indicate that the annual gross potential availability of bagasse in India is more than 67 million tonnes (MT). The potential of electricity generation through bagasse cogeneration in India is estimated to be around 34 TWh i.e. about 5575 MW in terms of the plant capacity. The annual CER potential of bagasse cogeneration in India could theoretically reach 28 MT. Under more realistic assumptions about diffusion of bagasse cogeneration based on past experiences with the government-run programmes, annual CER volumes by 2012 could reach 20-26 million. The projections based on the past diffusion trend indicate that in India, even with highly favorable assumptions, the dissemination of bagasse cogeneration for power generation is not likely to reach its maximum estimated potential in another 20 years. CDM could help to achieve the maximum utilization potential more rapidly as compared to the current diffusion trend if supportive policies are introduced

A novel cogeneration system: A proton exchange membrane fuel cell coupled to a heat transformer

International Nuclear Information System (INIS)

Huicochea, A.; Romero, R.J.; Rivera, W.; Gutierrez-Urueta, G.; Siqueiros, J.; Pilatowsky, I.

2013-01-01

This study focuses on the potential of a novel cogeneration system which consists of a 5 kW proton exchange membrane fuel cell (PEMFC) and an absorption heat transformer (AHT). The dissipation heat resulting from the operation of the PEMFC would be used to feed the absorption heat transformer, which is integrated to a water purification system. Therefore, the products of the proposed cogeneration system are heat, electricity and distilled water. The study includes a simulation for the PEMFC as well as experimental results obtained with an experimental AHT facility. Based on the simulation results, experimental tests were performed in order to estimate the performance parameters of the overall system. This is possible due to the matching in power and temperatures between the outlet conditions of the simulated fuel cell and the inlet requirements of the AHT. Experimental coefficients of performance are reported for the AHT as well as the overall cogeneration efficiency for the integrated system. The results show that experimental values of coefficient of performance of the AHT and the overall cogeneration efficiency, can reach up to 0.256 and 0.571, respectively. This represents an increment in 12.4% of efficiency, compared to the fuel cell efficiency working individually. This study shows that the combined use of AHT systems with a PEMFC is possible and it is a very feasible project to be developed in the Centro de Investigación en Energía (Centre of Energy Research), México.

Cogeneration in the former Soviet Union

International Nuclear Information System (INIS)

Horak, W.C.

1997-01-01

The former Soviet Union made a major commitment to Cogeneration. The scale and nature of this commitment created a system conceptually different from Cogeneration in the west. The differences were both in scale, in political commitment, and in socio economic impact. This paper addresses some of the largest scale Cogeneration programs, the technology, and the residual impact of these programs. The integration of the Cogeneration and nuclear programs is a key focus of the paper. Soviet designed nuclear power plants were designed to produce both electricity and heat for residential and industrial uses. Energy systems used to implement this design approach are discussed. The significant dependence on these units for heat created an urgent need for continued operation during the winter. Electricity and heat are also produced in nuclear weapons production facilities, as well as power plants. The Soviets also had designed, and initiated construction of a number of nuclear power plants open-quotes ATETsclose quotes optimized for production of heat as well as electricity. These were canceled

Exergy metrication of radiant panel heating and cooling with heat pumps

International Nuclear Information System (INIS)

Kilkis, Birol

2012-01-01

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

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.

Utility-cogenerator game for pricing power sales and wheeling fees

International Nuclear Information System (INIS)

Kuwahata, Akeo; Asano, Hiroshi

1994-01-01

The authors studied an extensive game model of an electricity market where a cogenerator sells excess electricity to an electric utility or to an end user. They found that a buy-back system (the utility purchases cogenerated power) is as efficient as a cogenerator-customer wheeling system and that these two systems are more desirable than a monopoly system for the regulator. The buy-back rate should be equal to (LP bargaining solution) or less than (Nash bargaining solution) the marginal cost of the electric utility. They also conducted an analysis of a two-period electricity market in which they found that the cogenerator that can supply excess power during peak period obtains the market advantage

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

International Nuclear Information System (INIS)

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

2016-01-01

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

Energy, exergy and sustainability analyses of hybrid renewable energy based hydrogen and electricity production and storage systems: Modeling and case study

International Nuclear Information System (INIS)

Caliskan, Hakan; Dincer, Ibrahim; Hepbasli, Arif

2013-01-01

In this study, hybrid renewable energy based hydrogen and electricity production and storage systems are conceptually modeled and analyzed in detail through energy, exergy and sustainability approaches. Several subsystems, namely hybrid geothermal energy-wind turbine-solar photovoltaic (PV) panel, inverter, electrolyzer, hydrogen storage system, Proton Exchange Membrane Fuel Cell (PEMFC), battery and loading system are considered. Also, a case study, based on hybrid wind–solar renewable energy system, is conducted and its results are presented. In addition, the dead state temperatures are considered as 0 °C, 10 °C, 20 °C and 30 °C, while the environment temperature is 30 °C. The maximum efficiencies of the wind turbine, solar PV panel, electrolyzer, PEMFC are calculated as 26.15%, 9.06%, 53.55%, and 33.06% through energy analysis, and 71.70%, 9.74%, 53.60%, and 33.02% through exergy analysis, respectively. Also, the overall exergy efficiency, ranging from 5.838% to 5.865%, is directly proportional to the dead state temperature and becomes higher than the corresponding energy efficiency of 3.44% for the entire system. -- Highlights: ► Developing a three-hybrid renewable energy (geothermal–wind–solar)-based system. ► Undertaking a parametric study at various dead state temperatures. ► Investigating the effect of dead state temperatures on exergy efficiency

Cogeneration: One way to use biomass efficiently

International Nuclear Information System (INIS)

Gustavsson, L.; Johansson, B.

1993-01-01

Cogeneration in district heating systems is the most energy-efficient way to convert biomass into heat and electricity with current or nearly commercial technologies. Methanol produced from biomass and used in vehicles instead of petrol or diesel could reduce carbon dioxide emissions nearly as much per unit of biomass as if the biomass were used to replace natural gas for cogeneration, but at some higher cost per unit of carbon dioxide reduction. The most energy-efficient way to use biomass for cogeneration appears to be combined cycle technology, and the world's first demonstration plant is now being built. Potentially, this technology can be used for electricity production in Swedish district heating systems to provide nearly 20% of current Swedish electricity production, while simultaneously reducing carbon dioxide emissions from the district heating systems by some 55%. The heat costs from cogeneration with biomass are higher than the heat costs from fossil fuel plants at current fuel prices. Biomass can only compete with fossil fuel if other advantages, for example a lower environmental impact are considered. (au) (35 refs.)

Exergy analysis of a combined vapor power cycle and boiler flue gas driven double effect water–LiBr absorption refrigeration system

International Nuclear Information System (INIS)

Talukdar, K.; Gogoi, T.K.

2016-01-01

Highlights: • A combined vapor power and double effect water–LiBr absorption refrigeration system is proposed. • The flue gas of the power cycle boiler is the heat source for the double effect refrigeration system. • Energy and exergy analyses are performed to evaluate performance of the combined system. • Effect of high pressure generator temperature on combined system performance is highlighted. • Comparison is provided with a single effect absorption system integrated combined system. - Abstract: A combined vapor power cycle (PC) and double effect water–LiBr absorption refrigeration system (ARS) is proposed in this study. The boiler leaving flue gas of the PC is the heat source for the high pressure generator (HPG) of the double effect ARS. Exergy analysis of the proposed system is performed to show the performance variation of both the topping PC and the bottoming ARS with changing HPG temperature from 120 °C to 150 °C. Further the performance of double effect ARS integrated combined power and cooling system is compared with a similar system integrated with a single effect ARS. HPG temperature of the double effect ARS and generator temperature of the single effect ARS are considered as 120 °C and 80 °C respectively. Results show that the power and efficiency of the topping PC decreases with HPG temperature due to reduction in steam generation rate in the boiler. COP and exergy efficiency of the double effect ARS also reduces with increasing HPG temperature. The irreversible losses in the PC components decrease while the total irreversibility of the combined power and cooling system increases with HPG temperature due to increase in exergy loss with the HPG leaving flue gas and irreversibility of the ARS components. PC performance does not vary much due to replacement of the double effect ARS with the single effect ARS, however higher COP and exergy efficiency of the double effect system are achieved with much lower irreversible losses in the

Techno-Economic Assessment of Redundancy Systems for a Cogeneration Plant

Directory of Open Access Journals (Sweden)

Majid Mohd Amin Abd

2014-07-01

Full Text Available The use of distributed power generation has advantage as well as disadvantage. One of the disadvantages is that the plant requires a dependable redundancy system to provide back up of power during failure of its power generation equipment. This paper presents a study on techno-economic assessment of redundancy systems for a cogeneration plant. Three redundancy systems were investigated; using public utility, generator set and gas turbine as back up during failures. Results from the analysis indicate that using public utility provides technical as well as economic advantages in comparison to using generator set or turbine as back up. However, the economic advantage of the public utility depends on the frequency of failures the plant will experience as well on the maximum demand charge. From the break even analysis of the understudied plant, if the number of failures exceeds 3 failures per year for the case of maximum demand charge of RM56.80, it is more economical to install a generator set as redundancy. The study will be useful for the co-generator operators to evaluate the feasibility of redundancy systems.

Gaz de France and cogeneration: a story which goes on; Gaz de France et la cogeneration: une histoire qui se poursuit

Energy Technology Data Exchange (ETDEWEB)

NONE

2001-09-15

This document presents the principle of natural gas cogeneration (gas turbine and gas engine) and gives a general overview of the cogeneration market in France since 1991 and up to 2001 (development factors, results). The perspectives and opportunities of cogeneration are analyzed with respect to the development of new technologies like fuel cells (principle, advantages and future) and to the future energy markets. Follows a compilation and an analysis of French regulation texts about cogeneration systems, their connection to the power grid, and the tariffs of electricity re-purchase by Electricite de France (EdF). (J.S.)

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.

Comparison between exergy and energy analysis for biodiesel production

International Nuclear Information System (INIS)

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

2016-01-01

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

Industrial cogeneration optimization program. Final report, September 1979

Energy Technology Data Exchange (ETDEWEB)

Davis, Jerry; McWhinney, Jr., Robert T.

1980-01-01

This study program is part of the DOE Integrated Industry Cogeneration Program to optimize, evaluate, and demonstrate cogeneration systems, with direct participation of the industries most affected. One objective is to characterize five major energy-intensive industries with respect to their energy-use profiles. The industries are: petroleum refining and related industries, textile mill products, paper and allied products, chemicals and allied products, and food and kindred products. Another objective is to select optimum cogeneration systems for site-specific reference case plants in terms of maximum energy savings subject to given return on investment hurdle rates. Analyses were made that define the range of optimal cogeneration systems for each reference-case plant considering technology applicability, economic factors, and energy savings by type of fuel. This study also provides guidance to other parts of the program through information developed with regard to component development requirements, institutional and regulatory barriers, as well as fuel use and environmental considerations. (MCW)

Sustainability assessment of cogeneration sector development in Croatia

International Nuclear Information System (INIS)

Liposcak, Marko; Afgan, Naim H.; Duic, Neven; Graca Carvalho, Maria da

2006-01-01

The effective and rational energy generation and supply is one of the main presumptions of sustainable development. Combined heat and power production, or co-generation, has clear environmental advantages by increasing energy efficiency and decreasing carbon emissions. However, higher investment cost and more complicated design and maintenance sometimes-present disadvantages from the economical viability point of view. As in the case of most of economies in transition in Central and Eastern Europe, Croatia has a strong but not very efficient co-generation sector, delivering 12% of the final energy consumption. District heating systems in the country's capital Zagreb and in city of Osijek represent the large share of the overall co-generation capacity. Besides district heating, co-generation in industry sector is also relatively well developed. The paper presents an attempt to assess the sustainability of Croatian co-generation sector future development. The sustainability assessment requires multi-criteria assessment of specific scenarios to be taken into consideration. In this respect three scenarios of Croatian co-generation sector future development are taken into consideration and for each of them environmental, social and economic sustainability indicators are defined and calculated. The assessment of complex relationships between environmental, social and economic aspects of the system is based on the multi-criteria decision-making procedure. The sustainability assessment is based on the General Sustainability Index rating for different cases reflecting different criteria and their priority. The method of sustainability assessment is applied to the Croatian co-generation sector contributing to the evaluation of different strategies and definition of a foundation for policy related to the sustainable future cogeneration sector development

Demystifying the use of cogeneration in mine cooling applications

Energy Technology Data Exchange (ETDEWEB)

Del Castillo, D.O. [Hatch, Johannesburg (South Africa)

2010-07-01

A study was conducted in 2009 to determine the feasibility of having cogeneration in South African mines using diesel generators for large cooling installations. The study included a cost comparison between a conventional mechanical vapour-compression system and the proposed cogeneration system under different fuel prices and electric power cost scenarios. Both capital and operating costs were considered and the use of gas turbines was also examined. The cogeneration system consisted of four 3.75 MW diesel generators. The exhaust gases and the water from the jacket-coolers were used to drive 4 single-effect LiBr-water absorption refrigeration machines having a cooling capacity of 3.75 MW(R). The study showed that in most cases, cogeneration would not be economically feasible if specifically installed to produce cooling. Cogeneration would only be economically viable if both the power costs were to increase significantly and fuel prices were to drop considerably. The environmental issues associated with the exhaust gases were not addressed in this study. 3 refs., 4 tabs., 4 figs.

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

International Nuclear Information System (INIS)

Compton, M.; Rezaie, B.

2017-01-01

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

Aeroderivative gas turbines for cogeneration

International Nuclear Information System (INIS)

Horner, M.W.; Thames, J.M.

1988-01-01

Aircraft jet engine derivative gas turbines have gained acceptance for cogeneration applications through impressive advances in technology and especially in maintainability and reliability. The best advantages of heavy industrial turbines and of reliable commercial airline jet engines have been successfully joined to meet the requirements for industrial cogeneration service. The next generation is under development and offers improved thermal efficiencies, alternate fuel capabilities, low environmental emissions, flexibility of operation and improved competitive system economics. This paper summarizes the current aero-derivative engine features and advantages with various systems, and discusses advanced features under consideration at this time

Tax issues in structuring effective cogeneration vehicles

International Nuclear Information System (INIS)

Ebel, S.R.

1999-01-01

An overview of the Canadian income tax laws that apply to cogeneration projects was presented. Certain tax considerations could be taken into account in deciding upon ownership and financing structures for cogeneration projects, particularly those that qualify for class 43.1 capital cost allowance treatment. The tax treatment of project revenues and expenses were described. The paper also reviewed the 1999 federal budget proposals regarding the manufacturing and processing tax credit, the capital cost allowance system applicable to cogeneration assets and the treatment of the Canadian renewable conservation expense

Exergy analysis of a combined power and cooling cycle

International Nuclear Information System (INIS)

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

2013-01-01

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

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

International Nuclear Information System (INIS)

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

2016-01-01

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

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

Metamorphoses of cogeneration-based district heating in Romania: A case study

International Nuclear Information System (INIS)

Iacobescu, Flavius; Badescu, Viorel

2011-01-01

The paper presents the birth and evolution of the cogeneration-based district heating (DH) system in a medium size city in Romania (Targoviste). The evolution of the industrialization degree was the main factor which controlled the population growth and led to a continuous reconfiguration of the DH system. The DH system assisted by cogeneration emerged as a solution in a certain phase of the demographic development of the city. The political and social changes occurring in Romania after 1990 have had important negative consequences on the DH systems in small towns. In Targoviste the DH system survived but in 2001 the solution based on cogeneration became economically inefficient, due to the low technical quality of the existing equipment and the low gas prices, to the procedure of setting the DH tariffs and the service cost at consumer's level and to some bureaucratic problems. Energy policy measures taken at national and local levels in 2003 and 2005 led to the re-establishment of the cogeneration-based district heating in 2005. However, a different technical solution has been adopted. Details about the present (2009) cogeneration-based DH system in Targoviste are presented together with several technical and economical indicators. The main conclusion is that by a proper amendment of the technical solutions, cogeneration could be a viable solution for DH even in case of abrupt social and demographic changes, such as those occurring in Romania after 1990. - Research Highlights: →Birth and evolution of the cogeneration-based district heating system in a medium size city. →The industrialization degree is the main factor which controlled the reconfiguration of the district heating system. →Each stage of the evolution of district heating system has been a technological leap. →Cogeneration is a solution for district heating even in case of abrupt social changes.

Cogeneration in Australia. Situation and prospects

International Nuclear Information System (INIS)

1997-01-01

This Research Paper is mainly concerned with the status and prospects for cogeneration in Australia. An introductory chapter reviews the fundamentals of cogeneration, covering both technical and institutional aspects. A range of technologies are employed in cogeneration: these technologies and their efficiency and environmental impact effects are discussed in Chapter 2. The economics of cogeneration are a major factor in the profitability of current and potential plants. Potential factors affecting cogeneration economics are discussed .The status of cogeneration in Australia is reviewed for each State and Territory, and includes a number of case studies of existing plants. Government (federal, state, territory) policies that have a significant impact on the attractiveness of cogeneration are reviewed. Finally, the future prospects for cogeneration in Australia, drawing on the preceding chapters and a review of estimated potentials for cogeneration in Australia are presented

Load averaging system for co-generation plant; Jikayo hatsuden setsubi ni okeru fuka heijunka system

Energy Technology Data Exchange (ETDEWEB)

Ueno, Y. [Fuji Electric Co. Ltd., Tokyo (Japan)

1995-07-30

MAZDA Motor Corp. planed the construction of a 20.5MW co-generation plant in 1991 for responding to an increase in power demand due to expansion of the Hofu factory. On introduction of this co-generation plant, it was decided that the basic system would adopt the following. (1) A circulating fluidized bed boiler which can be operated by burning multiple kinds of fuels with minimum environmental pollution. (2) A heat accumulation system which can be operated through reception of a constant power from electric power company despite a sudden and wide range change in power demand. (3) A circulating-water exchange heat recovery system which recovers exhaust heat of the turbine plant as the hot water to be utilized for heating and air-conditioning of the factory mainly in winter. Power demand in MAZDA`s Hofu factory changes 15% per minute within a maximum range from 20MW to 8MW. This change is difficult to be followed even by an oil burning boiler excellent in load follow-up. The circulating Fluidized bed boiler employed this time is lower in the follow-up performance than the oil boiler. For the newly schemed plant, however, load averaging system named a heat accumulation system capable of responding fully to the above change has been developed. This co-generation plant satisfied the official inspection before commercial operation according the Ministerial Ordinance in 1993. Since then, with regard to the rapid load following, which was one of the initial targets, operation is now performed steadily. This paper introduces an outline of the system and operation conditions. 10 refs.

Exergy Analysis of a Solar Humidification- Dehumidification Desalination Unit

OpenAIRE

Mohammed A. Elhaj; Jamal S. Yassin

2013-01-01

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

Fuel cell-based cogeneration system covering data centers’ energy needs

International Nuclear Information System (INIS)

Guizzi, Giuseppe Leo; Manno, Michele

2012-01-01

The Information and Communication Technology industry has gone in the recent years through a dramatic expansion, driven by many new online (local and remote) applications and services. Such growth has obviously triggered an equally remarkable growth in energy consumption by data centers, which require huge amounts of power not only for IT devices, but also for power distribution units and for air-conditioning systems needed to cool the IT equipment. This paper is dedicated to the economic and energy performance assessment of a cogeneration system based on a natural gas membrane steam reformer producing a pure hydrogen flow for electric power generation in a polymer electrolyte membrane fuel cell. Heat is recovered from both the reforming unit and the fuel cell in order to supply the needs of an office building located near the data center. In this case, the cooling energy needs of the data center are covered by means of a vapor-compression chiller equipped with a free-cooling unit. Since the fuel cell’s output is direct current rather than alternate current, the possibility of further improving data centers’ energy efficiency adopting DC-powered data center equipment is also discussed. -- Highlights: ► Data centers' energy needs are discussed and possible savings from advanced energy management techniques are estimated. ► The thermal energy requirements of an office building close to the data center are added to the energy scenario. ► Significant energy and cost savings can be obtained by means of free-cooling, high-voltage direct current, and a cogeneration facility. ► The cogeneration system is based on a natural gas membrane reformer and a PEM fuel cell. ► Energy flows in the membrane reformer are analyzed and an optimal value of steam-to-carbon ratio is found in order to minimize the required membrane area.

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

Directory of Open Access Journals (Sweden)

Victor H. Rangel-Hernandez

2016-08-01

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

Exergy Steam Drying and Energy Integration

Energy Technology Data Exchange (ETDEWEB)

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

2008-10-15

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

Modular cogeneration for commercial light industrial sector

Energy Technology Data Exchange (ETDEWEB)

Sakhuja, R.

1984-01-01

An analysis of gas utilities' efforts to market small cogeneration systems could be helpful to entrepreneurs now venturing into this area. Orders have been placed with Thermo Electron, USA for 15 Tecogen modular cogeneration units. Applications range from an airline catering kitchen to a university swimming pool. 5 figures, 1 table.

Exergy analysis of gas turbine with air bottoming cycle

International Nuclear Information System (INIS)

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

2014-01-01

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

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...

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

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

International Nuclear Information System (INIS)

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

2016-01-01

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

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

International Nuclear Information System (INIS)

Kaushik, S.C.; Manikandan, S.

2015-01-01

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

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

International Nuclear Information System (INIS)

Szczygieł, Ireneusz; Stanek, Wojciech; Szargut, Jan

2016-01-01

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

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

DEFF Research Database (Denmark)

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

2015-01-01

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

Energy and exergy utilization in transportation sector of Saudi Arabia

International Nuclear Information System (INIS)

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

2004-01-01

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

Mini gas turbines. Study related to energy efficient cogeneration applications for new cogeneration markets. Appendix; Mini gasturbiner. Udredning vedr. energieffektive kraftvarmeapplikationer til nye kraftvarmemarkeder. Appendix

Energy Technology Data Exchange (ETDEWEB)

Mikkelsen, J.B.; Weel Hansen, M.; Astrupgaard, N.P.

2000-12-01

The aim of the project is to investigate, design and increase the energy efficiency in new cogeneration/cooling systems, which are based on new developed mini gas turbines. Hereby cogeneration can primarily based on natural gas and bio-fuels be spread to new market segments. The appendix presents further details related to gas turbine as burner; cogeneration with recuperation gas turbine; gas turbine for cogeneration/absorption refrigerator; the economic and operational basis used in the study. (EHS)

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.

An investigation of the techno-economic impact of internal combustion engine based cogeneration systems on the energy requirements and greenhouse gas emissions of the Canadian housing stock

International Nuclear Information System (INIS)

Asaee, S. Rasoul; Ugursal, V. Ismet; Beausoleil-Morrison, Ian

2015-01-01

This study provides a techno-economic evaluation of retrofitting internal combustion engine (ICE) based cogeneration systems in the Canadian housing stock (CHS). The study was conducted using the Canadian Hybrid Residential End-Use Energy and GHG Emissions Model (CHREM). CHREM includes close to 17,000 unique house files that are statistically representative of the Canadian housing stock. The cogeneration system performance was evaluated using a high resolution integrated building performance simulation software. It is assumed that the ICE cogeneration system is retrofitted into all houses that currently use a central space heating system and have a suitable basement or crawl space. The GHG emission intensity factor associated with marginal electricity generation in each province is used to estimate the annual GHG emissions reduction due to the cogeneration system retrofit. The results show that cogeneration retrofit yields 13% energy savings in the CHS. While the annual GHG emissions would increase in some provinces due to cogeneration retrofits, the total GHG emissions of the CHS would be reduced by 35%. The economic analysis indicates that ICE cogeneration system retrofits may provide an economically feasible opportunity to approach net/nearly zero energy status for existing Canadian houses. - Highlights: • Techno-economic evaluation ICE cogeneration systems for Canadian housing is reported. • ICE cogeneration retrofit could yield 13% annual energy savings in Canadian housing. • Annual GHG emissions of Canadian housing could decrease by 35% with ICE cogeneration. • But, in some provinces, GHG emissions would increase as a result of ICE cogeneration

Performance and operational economics estimates for a coal gasification combined-cycle cogeneration powerplant

Science.gov (United States)

Nainiger, J. J.; Burns, R. K.; Easley, A. J.

1982-01-01

A performance and operational economics analysis is presented for an integrated-gasifier, combined-cycle (IGCC) system to meet the steam and baseload electrical requirements. The effect of time variations in steam and electrial requirements is included. The amount and timing of electricity purchases from sales to the electric utility are determined. The resulting expenses for purchased electricity and revenues from electricity sales are estimated by using an assumed utility rate structure model. Cogeneration results for a range of potential IGCC cogeneration system sizes are compared with the fuel consumption and costs of natural gas and electricity to meet requirements without cogeneration. The results indicate that an IGCC cogeneration system could save about 10 percent of the total fuel energy presently required to supply steam and electrical requirements without cogeneration. Also for the assumed future fuel and electricity prices, an annual operating cost savings of 21 percent to 26 percent could be achieved with such a cogeneration system. An analysis of the effects of electricity price, fuel price, and system availability indicates that the IGCC cogeneration system has a good potential for economical operation over a wide range in these assumptions.

Energetic analysis of a novel vehicle power and cooling/heating cogeneration energy system using cascade cycles

International Nuclear Information System (INIS)

Yue, Chen; Han, Dong; Pu, Wenhao; He, Weifeng

2015-01-01

This study proposes and investigates a novel VCES (Vehicle power and cooling/heating Cogeneration Energy System), including a topping vehicle engine subsystem, and a bottoming waste-heat recovery subsystem which uses the zeotropic working fluid. The various grade exhaust and coolant waste-heat of the topping subsystem are cascade recovered by the bottoming subsystem, and slide-temperature thermal match in waste heat recovery heat exchangers and the condenser is considered also, obtaining power output and cooling/heating capacity. Based on the experimental data from an actual vehicle's energy demands and its waste-heat characteristics, the proposed VCES (vehicle cogeneration energy system) model is built and verified. Using ammonia-water as working fluid of the bottoming subsystem, integrated thermodynamic performances of the VCES are discussed through introducing three variables: an ambient temperature, the vehicle's velocity and the number of seated occupants. The influence of above three variables on the proposed VCES′ overall thermodynamic performance is analyzed by comparing it to a conventional VCES, and suitable operation conditions are recommended under cooling and heating conditions. - Highlights: • A novel vehicle cogeneration energy system is proposed. • Slide-temperature thermal match at two levels are considered. • Integration of the topping vehicle engine and bottoming waste heat recovery cycle is designed. • The cogeneration system model is built and verified based on experimental data. • Energy-saving potential of the proposed system is investigated

Modeling of a Novel Low-Exergy System for Office Buildings with Modelica

DEFF Research Database (Denmark)

Maccarini, Alessandro; Afshari, Alireza; Hultmark, Göran

2016-01-01

This paper aims to investigate the thermal behavior of a novel low-exergy system for office buildings. The main characteristic of the system is its ability to provide simultaneous heating and cooling by operating one water circuit. Inlet water temperature of about 22 °C is delivered to all...... the thermal zones in the building, no matter whether a single zone needs heating or cooling. This approach clearly differs from conventional systems where simultaneous heating and cooling is provided by two separated water circuits. A detailed model of the novel system was developed with Dymola, a modeling...

The effect of Ontario's transmission system policies on cogeneration projects

International Nuclear Information System (INIS)

Carr, J.

1999-01-01

The impact that the establishment of transmission tariffs would have on the viability of cogeneration projects in Ontario was discussed. The proposal to establish such tariffs on the basis of a 'postage stamp' rate would ensure that all electricity users have access to electricity at the same price. However, this would unfairly penalize short-haul transmission transactions and would possibly result in the inappropriate location of new generation facilities. Electricity users would ultimately be burdened with these inefficiencies. This presentation also discussed another public policy which proposes to determine what parts of the electricity system should have their costs recovered at postage stamp rates. The costs would include not only transmission charges but also distribution and generation costs. The restructuring of Ontario Hydro into the Ontario Power Generation Company (OPGC) and the Ontario Hydro Services Company (OHSC) and its impact on the cogeneration projects was also discussed

INCOGEN: Nuclear cogeneration in the Netherlands

International Nuclear Information System (INIS)

Heek, A.I. van

1997-01-01

A small heat and power cogeneration plant with a pebble bed high temperature reactor (HTR) is discussed. Cogeneration could be a new market for nuclear power and the HTR could be very suitable. The 40 MWth INCOGEN system is presented. Philosophy, layout, characteristics and performance are described. The lower power level, advanced component technologies and inherent safety features are used to obtain a maximally simplified system. Static and dynamic cycle analyses of the energy conversion system are discussed, as well as the behaviour of the reactor cavity cooling system. Although the cost study has not been finished yet, cost reduction trends are indicated. (author)

Critical of the concept of exergy

International Nuclear Information System (INIS)

Mora Casal, Rene Alejandro

2015-01-01

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

Technical overview of cogeneration: the hardware, the industries, the potential development

Energy Technology Data Exchange (ETDEWEB)

None

1977-12-01

Because the by-product heat from a power-conversion process is captured for productive use in a cogeneration system, instead of exhausted to the environment as it is in a conventional power plant, cogeneration represents an important energy-conservation technique. By cogenerating, an industrial plant can save the fuel that would have been needed to produce the amount of heat captured. Recognizing the significant energy-savings potential offered by cogeneration, DOE has undertaken a major R, D, and D program to investigate and promote cogeneration in industry. Resource Planning Associates, Inc. (RPA), has been working to accomplish four of the program's objectives: (1) survey current, near state-of-the-art, and future cogeneration equipment, and identify any gaps or deficiencies; (2) characterize the energy requirements of the manufacturing sectors of five of the country's most energy-intensive industries - chemical, petroleum refining, paper and pulp, textiles, and food; (3) identify principal targets for, and barriers to, the increased market development of cogeneration systems; and (4) estimate the potential maximum and the probable energy savings that could be achieved in the five selected industries through cogeneration. In investigating cogeneration hardware, three specific technologies - steam turbines, gas turbines, and diesel engines - were emphasized. It is estimated that the widespread application of cogeneration technology in the five industries studied could result in a maximum potential savings of 2.4 million barrels of oil equivalent per day (or a maximum incremental capacity of 140,000 MWe) by 1985.

Comparative exergy analyses of gasoline and hydrogen fuelled ices

International Nuclear Information System (INIS)

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

2009-01-01

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

Exergy analysis of a centralized air conditioning system for ice water

International Nuclear Information System (INIS)

Armas, Juan C; Lapido, Margarita J; Castellanos, Juan A

2006-01-01

An exergetic analysis of a centralized system of air conditioning, based on a vapor compression refrigeration cycle, appears in this article. The investigation allows to calculate the irreversibilities (exergy destruction) in the main components of the refrigeration cycle as well as to evaluate the sensitivity of this indicator when the operating conditions changes. As main result the most sensible components of the cycle are identified, information that will be useful in order to define strategies of operation focused to the power efficiency increase.

Experimental results and thermodynamic analysis of a natural gas small scale cogeneration plant for power and refrigeration purposes

International Nuclear Information System (INIS)

Bazzo, Edson; Nacif de Carvalho, Alvaro; Matelli, José Alexandre

2013-01-01

In this work, experimental results are reported for a small scale cogeneration plant for power and refrigeration purposes. The plant includes a natural gas microturbine and an ammonia/water absorption chiller fired by steam. The system was tested under different turbine loads, steam pressures and chiller outlet temperatures. An evaluation based on the 1st and 2nd Laws of Thermodynamics was also performed. For the ambient temperature around 24 °C and microturbine at full load, the plant is able to provide 19 kW of saturated steam at 5.3 bar (161 °C), corresponding to 9.2 kW of refrigeration at −5 °C (COP = 0.44). From a 2nd law point-of-view, it was found that there is an optimal chiller outlet temperature that maximizes the chiller exergetic efficiency. As expected, the microturbine presented the highest irreversibilities, followed by the absorption chiller and the HRSG. In order to reduce the plant exergy destruction, it is recommended a new design for the HRSG and a new insulation for the exhaust pipe. -- Highlights: • A small scale cogeneration plant for power and refrigeration is proposed and analyzed. • The plant is based on a microturbine and a modified absorption chiller. • The plant is analysed based on 1st and 2nd laws of thermodynamics. • Experimental results are found for different power and refrigeration conditions. • The plant proved to be technically feasible

Solar Cogeneration of Electricity and Hot Water at DoD Installations

Science.gov (United States)

2014-05-01

the cogeneration system displaces more energy (the impact is not 4-5X because the GHG intensity factors for offsetting electricity generation and...visibility to Army energy managers. Additional benefits of Cogenra’s solar cogeneration system are the engineering and design jobs at Cogenra’s...certification. Solar cogeneration can help earn LEED points in three areas: Optimizing Energy Efficiency Performance, On-Site Renewable Energy , and

Development of a Robust, Highly Efficient Oxygen-Carbon Monoxide Cogeneration System, Phase I

Data.gov (United States)

National Aeronautics and Space Administration — This small business innovation research is intended to develop a long-life, highly efficient O2-CO cogeneration system to support NASA's endeavors to pursue...

Energy and exergy analyses of malt drink production in Nigeria

Energy Technology Data Exchange (ETDEWEB)

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

2010-12-15

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

Energy and exergy analyses of malt drink production in Nigeria

International Nuclear Information System (INIS)

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

2010-01-01

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

The California cogeneration success story

International Nuclear Information System (INIS)

Neiggemann, M.F.

1992-01-01

This chapter describes the involvement of Southern California Gas Company(SoCalGas) in the promotion and demonstration of the benefits of cogeneration in California. The topics covered in this chapter are market strategy, cogeneration program objectives, cogeneration program, incentive cofunding, special gas rate, special service priority, special gas pressure and main options, advertising, promotional brochures and handbooks, technical support, program accomplishments, cogeneration outlook, and reasons for success of the program

Survey on construction of the database for new energy technology development. Cogeneration; Shin energy gijutsu kaihatsu kankei data shu sakusei chosa. Cogeneration

Energy Technology Data Exchange (ETDEWEB)

NONE

1997-03-01

As a part of the activity promoting use of new energy, the data related to cogeneration were systematically compiled. For new energy technology, such various policies for introducing new energy are in promotion with a progress of technological development as preparation of subsidy systems, field test business, and support advisory business for introducing new energy. For further effective promotion, integral systematic compilation of various data, and arrangement as basic data are necessary. Such latest announced data in a cogeneration field were collected and compiled as outline of new energy systems, concrete applications, subsidy systems, and approaches to new energy of various countries. Main data items are as follows: trend of cogeneration, outline of system, domestic and foreign concrete applications, prediction data on the use of new energy, overview of domestic and foreign policies for cogeneration, basic terminology, and tables of main related enterprises and organizations. This database is useful for the present activities promoting use of new energy, and preparation of the future vision. 29 figs., 33 tabs.

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

International Nuclear Information System (INIS)

Zhai, H.; Dai, Y.J.; Wu, J.Y.; Wang, R.Z.

2009-01-01

In this study, a small scale hybrid solar heating, chilling and power generation system, including parabolic trough solar collector with cavity receiver, a helical screw expander and silica gel-water adsorption chiller, etc., was proposed and extensively investigated. The system has the merits of effecting the power generation cycle at lower temperature level with solar energy more efficiently and can provide both thermal energy and power for remote off-grid regions. A case study was carried out to evaluate an annual energy and exergy efficiency of the system under the climate of northwestern region of China. It is found that both the main energy and exergy loss take place at the parabolic trough collector, amount to 36.2% and 70.4%, respectively. Also found is that the studied system can have a higher solar energy conversion efficiency than the conventional solar thermal power generation system alone. The energy efficiency can be increased to 58.0% from 10.2%, and the exergy efficiency can be increased to 15.2% from 12.5%. Moreover, the economical analysis in terms of cost and payback period (PP) has been carried out. The study reveals that the proposed system the PP of the proposed system is about 18 years under present energy price conditions. The sensitivity analysis shows that if the interest rate decreases to 3% or energy price increase by 50%, PP will be less than 10 years. (author)

Energy and Exergy Analyses of the Danish Industry Sector

DEFF Research Database (Denmark)

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

2016-01-01

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

The performance of residential micro-cogeneration coupled with thermal and electrical storage

Science.gov (United States)

Kopf, John

Over 80% of residential secondary energy consumption in Canada and Ontario is used for space and water heating. The peak electricity demands resulting from residential energy consumption increase the reliance on fossil-fuel generation stations. Distributed energy resources can help to decrease the reliance on central generation stations. Presently, distributed energy resources such as solar photovoltaic, wind and bio-mass generation are subsidized in Ontario. Micro-cogeneration is an emerging technology that can be implemented as a distributed energy resource within residential or commercial buildings. Micro-cogeneration has the potential to reduce a building's energy consumption by simultaneously generating thermal and electrical power on-site. The coupling of a micro-cogeneration device with electrical storage can improve the system's ability to reduce peak electricity demands. The performance potential of micro-cogeneration devices has yet to be fully realized. This research addresses the performance of a residential micro-cogeneration device and it's ability to meet peak occupant electrical loads when coupled with electrical storage. An integrated building energy model was developed of a residential micro-cogeneration system: the house, the micro-cogeneration device, all balance of plant and space heating components, a thermal storage device, an electrical storage device, as well as the occupant electrical and hot water demands. This model simulated the performance of a micro-cogeneration device coupled to an electrical storage system within a Canadian household. A customized controller was created in ESP-r to examine the impact of various system control strategies. The economic performance of the system was assessed from the perspective of a local energy distribution company and an end-user under hypothetical electricity export purchase price scenarios. It was found that with certain control strategies the micro-cogeneration system was able to improve the

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

International Nuclear Information System (INIS)

Kaşka, Önder

2014-01-01

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

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

International Nuclear Information System (INIS)

Callak, Meliha; Balkan, Firuz; Hepbasli, Arif

2015-01-01

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

Analysis of carbon dioxide emission of gas fuelled cogeneration plant

International Nuclear Information System (INIS)

Nordin, Adzuieen; Amin, M; Majid, A

2013-01-01

Gas turbines are widely used for power generation. In cogeneration system, the gas turbine generates electricity and the exhaust heat from the gas turbine is used to generate steam or chilled water. Besides enhancing the efficiency of the system, the process assists in reducing the emission of CO 2 to the environment. This study analyzes the amount of CO 2 emission by Universiti Teknologi Petronas gas fuelled cogeneration system using energy balance equations. The results indicate that the cogeneration system reduces the CO 2 emission to the environment by 60%. This finding could encourage the power plant owners to install heat recovery systems to their respective plants

Analysis of carbon dioxide emission of gas fuelled cogeneration plant

Science.gov (United States)

Nordin, Adzuieen; Amin, M.; Majid, A.

2013-12-01

Gas turbines are widely used for power generation. In cogeneration system, the gas turbine generates electricity and the exhaust heat from the gas turbine is used to generate steam or chilled water. Besides enhancing the efficiency of the system, the process assists in reducing the emission of CO2 to the environment. This study analyzes the amount of CO2 emission by Universiti Teknologi Petronas gas fuelled cogeneration system using energy balance equations. The results indicate that the cogeneration system reduces the CO2 emission to the environment by 60%. This finding could encourage the power plant owners to install heat recovery systems to their respective plants.

Energy and cost savings results for advanced technology systems from the Cogeneration Technology Alternatives Study /CTAS/

Science.gov (United States)

Sagerman, G. D.; Barna, G. J.; Burns, R. K.

1979-01-01

The Cogeneration Technology Alternatives Study (CTAS), a program undertaken to identify the most attractive advanced energy conversion systems for industrial cogeneration applications in the 1985-2000 time period, is described, and preliminary results are presented. Two cogeneration options are included in the analysis: a topping application, in which fuel is input to the energy conversion system which generates electricity and waste heat from the conversion system is used to provide heat to the process, and a bottoming application, in which fuel is burned to provide high temperature process heat and waste heat from the process is used as thermal input to the energy conversion system which generates energy. Steam turbines, open and closed cycle gas turbines, combined cycles, diesel engines, Stirling engines, phosphoric acid and molten carbonate fuel cells and thermionics are examined. Expected plant level energy savings, annual energy cost savings, and other results of the economic analysis are given, and the sensitivity of these results to the assumptions concerning fuel prices, price of purchased electricity and the potential effects of regional energy use characteristics is discussed.

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

International Nuclear Information System (INIS)

Al-Sulaiman, Fahad A.

2014-01-01

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

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.

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

Energy Technology Data Exchange (ETDEWEB)

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

2011-01-15

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

Development of cogeneration in Spain and financing methods

International Nuclear Information System (INIS)

Garcia, G.R.

1994-01-01

From 1980 there is in force in Spain a proper legal framework that could be considered a sound support to further cogeneration development. Despite this cogeneration law, a very few schemes were built. In 1986 IDAE, a state company attached to the Spanish Ministry of Industry and Energy, began a Cogeneration Programme focussed to a higher cogeneration utilisation. This programme has three main foundations: Technology dissemination; Technical support; Investment financing. As a result of these activities more than 1000 MW additional power schemes have been ordered all over the country and, as a consequence, cogenerated electricity will be multiplied by three in respect with the previous situation. A 20% of this new capacity has been developed directly by IDAE, that has invested approximately 90 million US Dollar through third party financing technics. The National Energy Plan 1991-2000 established the energy policy actuations in Spain for the present decade, giving importance to cogeneration development. This paper explains the way this development has been achieved, outlining IDAE's engagement to finance combined heat and power schemes through its comprehensive way of performing third party financing systems. (au)

Development of technology and systems for air-conditioned and cogenerations using natural gas; Desenvolvimento de tecnologia e sistemas para climatizaco e cogeracao usando gas natural

Energy Technology Data Exchange (ETDEWEB)

Santos, Carlos Antonio Cabral dos; Varani, Celina Maria Ribeiro [Universidade Federal da Paraiba (UFPB), Joao Pessoa, PB (Brazil). Lab. de Energia Solar; Campos, Michel Fabianski [PETROBRAS, Rio de Janeiro, RJ (Brazil)

2004-07-01

This preset work deal with a technological project that has as main objective the development of national technology in absorption refrigeration for application in the human thermal comfort with natural gas as energy source in direct fired or through energy recuperation of the combustion gases in cogeneration systems. This project makes part of the REDEGASENERGY and also receive financial support from CT-PETRO founds through FINEP, and also has as partner the local gas distributed company. The focus to be reached is the obtaining of a system of double effect using the solution pair Water-Lithium Bromide as work fluid to the capacity range of five to fifty tons of refrigeration. This range means a important branch on the market for minis-shopping, medical clinics, conveniences shopping, small hotels, motels, etc. The system is compound basically of heat exchangers: vapor generator, absorber, condenser, evaporator and intermediary exchanger. The design of the system is based on the thermodynamic, heat and mass analyses for each component. The concepts of exergy and irreversibility are used for through second thermodynamic law to realize the exegetic analysis and to identify the points of the most thermal lost. The correction on the identified components allows the improvements on the performance of each components and all system. As proposed steps to reach the final objective is established first the development of a single effect system operating in similar conditions of capacity and work fluid that the intended double effect system. (author)

Texasgulf solar cogeneration program. Mid-term topical report

Energy Technology Data Exchange (ETDEWEB)

1981-02-01

The status of technical activities of the Texasgulf Solar Cogeneration Program at the Comanche Creek Sulfur Mine is described. The program efforts reported focus on preparation of a system specification, selection of a site-specific configuration, conceptual design, and facility performance. Trade-off studies performed to select the site-specific cogeneration facility configuration that would be the basis for the conceptual design efforts are described. Study areas included solar system size, thermal energy storage, and field piping. The conceptual design status is described for the various subsystems of the Comanche Creek cogeneration facility. The subsystems include the collector, receiver, master control, fossil energy, energy storage, superheat boiler, electric power generation, and process heat subsystems. Computer models for insolation and performance are also briefly discussed. Appended is the system specification. (LEW)

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

International Nuclear Information System (INIS)

Caliskan, Hakan; Hepbasli, Arif

2010-01-01

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

Study of technical and economic feasibility of a cogeneration system in the tertiary sector; Estudo de viabilidade tecnica-economica de um sistema de cogeracao no setor terciario

Energy Technology Data Exchange (ETDEWEB)

Souza, Rodolffo Aquino de; Rocha, Carlos Roberto; Bortoni, Edson da Costa [Universidade Federal de Itajuba (EXCEN/UNIFEI), MG (Brazil). Centro de Excelencia em Eficiencia Energetica

2008-07-01

This study aims to examine the technical feasibility and financial cost for a cogeneration system in a company in the tertiary sector. For this, was studied the electromechanical and thermal characteristics of a shopping center, as well as the technologies associated with the proposed cogeneration system. From the modeling of electric and thermal loads it was determined the system of operation for the system and the possible surplus energy generated. For the analysis of economic viability compare operating costs without cogeneration and with the alternative of cogeneration chosen. Among the calculations are the costs of investment and operation of the system. Was encountered the attractiveness of a cogeneration system, which uses natural gas as fuel for alternative engines and, in turn, reject heat to the absorption chillers. The idealized cogeneration system was also evaluated positively with a view to qualification required for participation in policies to encourage the rational use of energy resources. (author)

The performance of a temperature cascaded cogeneration system producing steam, cooling and dehumidification

KAUST Repository

Myat, Aung

2013-02-01

This paper discusses the performance of a temperature-cascaded cogeneration plant (TCCP), equipped with an efficient waste heat recovery system. The TCCP, also called a cogeneration system, produces four types of useful energy-namely, (i) electricity, (ii) steam, (iii) cooling and (iv) dehumidification-by utilizing single fuel source. The TCCP comprises a Capstone C-30 micro-turbine that generates nominal capacity of 26 kW of electricity, a compact and efficient waste heat recovery system and a host of waste-heat-activated devices, namely (i) a steam generator, (ii) an absorption chiller, (iii) an adsorption chiller and (iv) a multi-bed desiccant dehumidifier. The performance analysis was conducted under different operation conditions such as different exhaust gas temperatures. It was observed that energy utilization factor could be as high as 70% while fuel energy saving ratio was found to be 28%. © 2013 Desalination Publications.

First Study of Helium Gas Purification System as Primary Coolant of Co-Generation Reactor

International Nuclear Information System (INIS)

Piping Supriatna

2009-01-01

The technological progress of NPP Generation-I on 1950’s, Generation-II, Generation-III recently on going, and Generation-IV which will be implemented on next year 2025, concept of nuclear power technology implementation not only for generate electrical energy, but also for other application which called cogeneration reactor. Commonly the type of this reactor is High Temperature Reactor (HTR), which have other capabilities like Hydrogen production, desalination, Enhanced Oil Recovery (EOR), etc. The cogeneration reactor (HTR) produce thermal output higher than commonly Nuclear Power Plant, and need special Heat Exchanger with helium gas as coolant. In order to preserve heat transfer with high efficiency, constant purity of the gas must be maintained as well as possible, especially contamination from its impurities. In this report has been done study for design concept of HTR primary coolant gas purification system, including methodology by sampling He gas from Primary Coolant and purification by using Physical Helium Splitting Membrane. The examination has been designed in physical simulator by using heater as reactor core. The result of study show that the of Primary Coolant Gas Purification System is enable to be implemented on cogeneration reactor. (author)

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...

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

International Nuclear Information System (INIS)

Stougie, Lydia; Kooi, Hedzer J. van der

2016-01-01

Highlights: • The TCExL method can be applied to all kinds of technological systems. • All exergy losses during the lifetime of a technological system are considered. • The results of the TCExL method are independent of time and weighting factors. • Applying the TCExL method can improve the sustainability of power generation. • The system with the lowest TCExL score is not always economically favourable. - Abstract: It is difficult to decide which power generation system is the most sustainable when environmental, economic and social sustainability aspects are taken into account. Problems with conventional environmental sustainability assessment methods are that no consensus exists about the applied models and weighting factors and that exergy losses are not considered. Economic sustainability assessment methods do not lead to results that are independent of time because they are influenced by market developments, while social sustainability assessment methods suffer from the availability and qualitative or semi-quantitative nature of data. Existing exergy analysis methods do not take into account all exergy losses and/or are extended with factors or equations that are not commonly accepted. The new Total Cumulative Exergy Loss (TCExL) method is based on fundamental thermodynamic equations and takes into account all exergy losses caused by a technological system during its life cycle, i.e. internal exergy losses, exergy losses caused by emission abatement and exergy losses related to land use. The development of the TCExL method is presented as well as the application of this method and environmental, economic and social sustainability assessment methods to two case studies: power generation in combination with LNG evaporation and Fossil versus renewable energy sources for power generation. According to the results of the assessments, large differences exist between the environmental sustainability assessment and TCExL methods in the sense that different

Thermoeconomic analysis and optimization of an ammonia–water power/cooling cogeneration cycle

International Nuclear Information System (INIS)

Zare, V.; Mahmoudi, S.M.S.; Yari, M.; Amidpour, M.

2012-01-01

The performance of an ammonia–water power/cooling cogeneration cycle is investigated and optimized paying more attention on the economic point of view. Thermodynamic and thermoeconomic models are developed in order to investigate the thermodynamic performance of the cycle and assess the unit cost of products. A parametric study is carried out and the cycle performance is optimized based on the thermal and exergy efficiencies as well as the sum of the unit costs of the system products. The results show that the sum of the unit cost of the cycle products obtained through thermoeconomic optimization is less than by around 18.6% and 25.9% compared to the cases when the cycle is optimized from the viewpoints of first and second laws of thermodynamics, respectively. It is also concluded that for each increase of $3/ton in unit cost of the steam as the heat source, the unit cost of the output power and cooling is increased by around $7.6/GJ and $15–19/GJ, respectively. -- Highlights: ► The theory of exergetic cost is applied to the case of ammonia–water power/cooling cycle. ► The cycle is optimized from the viewpoints of thermodynamics and economics. ► The economic optimization leads to a considerable reduction in the system product costs.

Economic study on compressed energy storage cogeneration system in urban areas

International Nuclear Information System (INIS)

Uchiyama, Youji

1991-01-01

Due to the concentration of functions into cities and the spread of room cooling facilities, the energy demand in cities increased rapidly especially in summer season. The improvement of load factor of electric power has become an important subject for electric power companies, and as the technology for positively improving it, there is electric power storage. As for compressed air energy storage (CAES) system, its introduction, has been investigated as the electric power storage technology for the future in electric power business, but since it is also gas turbine technology, it becomes a cogeneration system. If the waste heat of gas turbines and compressors can be utilized effectively, not only the load factor of electric power is improved, but also it contributes to the improvement of overall energy efficiency and the improvement of environmental problems. This research is to study on the feasibility of compressed air energy storage centering around its economical efficiency when it is installed in customer side as the cogeneration system in cities. The features of CAES, the tendency of the development in Japan and foreign countries, the introduction of CAES in new town districts and the economy are described. (K.I.)

Preliminary study of nuclear power cogeneration system using gas turbine process

International Nuclear Information System (INIS)

Fumizawa, Motoo; Inaba, Yoshitomo; Hishida, Makoto; Ogawa, Masuro; Ogata, Kann; Yamada, Seiya.

1995-12-01

The Nuclear power generation plant (NPGP) releases smaller amount of carbon dioxide than the fossil power plant for the generation of the unit electrical power. Thus, the NPGP is expected to contribute resolving the ecological problems. It is important to investigate the nuclear power cogeneration system using gas turbine process from the view point that it is better to produce electricity in high thermal efficiency from the high temperature energy. We carried out, in the current preliminary study, the survey and selection of the candidate cycles, then conducted the evaluation of cycle efficiency, the selection of R and D items to be solved for the decision of the optimum cycle. Following this, we evaluated nuclear heat application for intermediate and low temperature level released from gas turbine process and overall efficiency of cogeneration system. As a result, it was clarified that overall efficiency of the direct regenerative cycle was the highest in low temperature region below 200degC, and that of the direct regenerative inter cooling cycle was the highest in middle and high temperature region. (author)

Preliminary study of nuclear power cogeneration system using gas turbine process

Energy Technology Data Exchange (ETDEWEB)

Fumizawa, Motoo; Inaba, Yoshitomo; Hishida, Makoto [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment; Ogawa, Masuro; Ogata, Kann; Yamada, Seiya

1995-12-01

The Nuclear power generation plant (NPGP) releases smaller amount of carbon dioxide than the fossil power plant for the generation of the unit electrical power. Thus, the NPGP is expected to contribute resolving the ecological problems. It is important to investigate the nuclear power cogeneration system using gas turbine process from the view point that it is better to produce electricity in high thermal efficiency from the high temperature energy. We carried out, in the current preliminary study, the survey and selection of the candidate cycles, then conducted the evaluation of cycle efficiency, the selection of R and D items to be solved for the decision of the optimum cycle. Following this, we evaluated nuclear heat application for intermediate and low temperature level released from gas turbine process and overall efficiency of cogeneration system. As a result, it was clarified that overall efficiency of the direct regenerative cycle was the highest in low temperature region below 200degC, and that of the direct regenerative inter cooling cycle was the highest in middle and high temperature region. (author).

Electric power plants in cogeneration: a promising potential even in France

International Nuclear Information System (INIS)

Anon.

1995-01-01

Implantation of cogeneration power plants has increased in France since two years but stays below other countries such as northern Europe. Technical, economical, legal and financial aspects of cogeneration have been debated during the ''Euroforum'' seminar (June 14-16, 1995). The european association Cogen Europe, created in 1993 with the financial support of the SAVE european program, has analysed the barriers that restrain cogeneration development and their solutions. Advantages of cogeneration are undeniable at any scale (from small engines to huge industrial systems) if efficiency of energy used reaches 85%. Opinions of representatives from different industries implied in cogeneration technology are reported. (J.S.). 1 photo

Energy, exergy and economic assessments of a novel integrated biomass based multigeneration energy system with hydrogen production and LNG regasification cycle

International Nuclear Information System (INIS)

Taheri, M.H.; Mosaffa, A.H.; Farshi, L. Garousi

2017-01-01

In this work, a novel integrated biomass based multigeneration energy system is presented and investigated for power, cooling and hydrogen production. The proposed system consists of a combination of biomass integrated gasifier-gas turbine cycle, a Rankine cycle, a cascade organic Rankine cycle, an absorption refrigeration system and a PEM to produce hydrogen. This system uses cold energy of LNG as a thermal sink. Comprehensive thermodynamic and economic analyses as well as an optimization are performed. The effects of operating parameters on thermodynamic performance and total cost rate are investigated for overall system and subsystems. The results show that the fuel mass flow rate is the dominant factor affecting the variation of energy efficiency and total cost rate. An increase in fuel mass flow rate from 4 kg s"−"1 to 10 kg s"−"1 leads to a decrease of 8.5% and an increase of 122.8% overall energy efficiency and total cost rate, respectively. Also, the largest increase in exergy efficiency occurs when gas turbine inlet temperature increases. The results of optimization showed that the highest net power output, mass flow rate of natural gas delivered to city and the flue gas temperature discharged to the environment are obtained for the exergy efficiency optimal design. - Highlights: • A novel multigeneration system is investigated and optimized thermodynamically and economically. • This system is proposed for power, cooling and hydrogen production. • Proposed system uses LNG cold energy thermal sink that can generate power after vaporization. • The effects of operating parameters on energy and exergy efficiencies and total cost rate are investigated. • An optimization is applied based on the energy, exergy and economic viewpoints.

Energy, Exergy and Performance Analysis of Small-Scale Organic Rankine Cycle Systems for Electrical Power Generation Applicable in Rural Areas of Developing Countries

Directory of Open Access Journals (Sweden)

Suresh Baral

2015-01-01

Full Text Available This paper introduces the concept of installing a small-scale organic Rankine cycle system for the generation of electricity in remote areas of developing countries. The Organic Rankine Cycle Systems (ORC system uses a commercial magnetically-coupled scroll expander, plate type heat exchangers and plunger type working fluid feed pump. The heat source for the ORC system can be solar energy. A series of laboratory tests were conducted to confirm the cycle efficiency and expander power output of the system. Using the actual system data, the exergy destruction on the system components and exergy efficiency were assessed. Furthermore, the results of the variations of system energy and exergy efficiencies with different operating parameters, such as the evaporating and condensing pressures, degree of superheating, dead state temperature, expander inlet temperature and pressure ratio were illustrated. The system exhibited acceptable operational characteristics with good performance under a wide range of conditions. A heat source temperature of 121 °C is expected to deliver a power output of approximately 1.4 kW. In addition, the system cost analysis and financing mechanisms for the installation of the ORC system were discussed.

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

International Nuclear Information System (INIS)

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

2013-01-01

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

Energy and exergy utilizations of the Jordanian SMEs industries

International Nuclear Information System (INIS)

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

2013-01-01

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

New exergy analysis of a regenerative closed Brayton cycle

International Nuclear Information System (INIS)

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

2017-01-01

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

Characterization and Exergy Analysis of Triphenyl Borate

International Nuclear Information System (INIS)

Acarali, N. B.

2015-01-01

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

Cumulative exergy losses associated with the production of lead metal

Energy Technology Data Exchange (ETDEWEB)

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

1990-08-01

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

Characteristic on photovoltaic/thermal hybrid collector. Evaluation of excergetic theory; Taiyoko netsu hybrid collector no tokusei. Exergy ni yoru hyoka

Energy Technology Data Exchange (ETDEWEB)

Iwawaki, H; Morita, Y; Fujisawa, T; Tani, T [Science University of Tokyo, Tokyo (Japan)

1997-11-25

Described herein are characteristics of photovoltaic (PV)/thermal hybrid collectors (PV/Ts), in which a PV module is combined with a plate-shape solar heat collector to simultaneously produce electric power and heat. Their efficiency is assessed by exergy. The test results indicate that the PV/T system gives a 1.07 times higher exergy than the PV system, 86.3 versus 80.7kWh. In terms of energy, the optimum values (OVs) are 5, 44 and 37% lower than the measuring values (MVs) for electrical energy, thermal energy and total exergy. In terms of exergy, on the other hand, OV is 5% lower than MV for electrical energy, but 893 times higher for thermal energy and 1.26 times higher for total exergy. As a result, the exergy level is 26% higher than that of a system which generates power as the main product and heat as the auxiliary product. 3 refs., 6 figs., 5 tabs.

Grid integration policies of gas-fired cogeneration in Peninsular Malaysia: Fallacies and counterexamples

Energy Technology Data Exchange (ETDEWEB)

Shaaban, M., E-mail: m.shaaban@fke.utm.my [Centre of Electrical Energy Systems, Faculty of Electrical Engineering, Universiti Teknologi Malaysia, 81310 Johor Bahru (Malaysia); Azit, A.H. [Tenaga Nasional Berhad, Wisma TNB, Jalan Timur, 46200 Petaling Jaya, Selangor (Malaysia); Nor, K.M. [Centre of Electrical Energy Systems, Faculty of Electrical Engineering, Universiti Teknologi Malaysia, 81310 Johor Bahru (Malaysia)

2011-09-15

Despite the abundance of natural gas reserves in Malaysia coupled with serious government thrusts to promote cogeneration, its (cogeneration) development pace lags far off expectations. There are widespread fallacies among potential cogeneration developers and concerned professionals that cogeneration is uncompetitive in Malaysia due to existing policies of subsidized gas prices and grid-connection charges. This paper exposes these fallacies through counterexamples of practical cogeneration system design and evaluation of some segments of the industrial and service sectors in Peninsular Malaysia. The electrical and thermal characteristics of the cogeneration were modeled based on heat rate characteristics at partial loading patterns. A hierarchical mathematical programming approach that uses mixed-integer nonlinear optimization and dynamic programming principle, if necessary, is employed to determine the optimal size of cogeneration and its related auxiliary equipment as well as the optimal operation schedule. Financial assessment is integrated at a later stage to assess the economic viability of the system. Analyses of the cogeneration potential for several facilities of miscellaneous activities were carried out using various gas and electricity prices. Results obtained consistently rebuff the perpetuated fallacies and confirm that there is no real barrier to cogeneration development in Malaysia under current policies of gas prices and electricity tariffs. - Highlights: > Mixed-integer nonlinear programming and dynamic programming are used in the design. > Various loading levels are modeled and hourly operation schedule is determined. > Standby electricity charge has a minimal impact on cogeneration feasibility. > Gas and electricity prices are interrelated and affect cogeneration investment. > Under existing policies, there is no barrier to cogeneration adoption in Malaysia.

Grid integration policies of gas-fired cogeneration in Peninsular Malaysia: Fallacies and counterexamples

International Nuclear Information System (INIS)

Shaaban, M.; Azit, A.H.; Nor, K.M.

2011-01-01

Despite the abundance of natural gas reserves in Malaysia coupled with serious government thrusts to promote cogeneration, its (cogeneration) development pace lags far off expectations. There are widespread fallacies among potential cogeneration developers and concerned professionals that cogeneration is uncompetitive in Malaysia due to existing policies of subsidized gas prices and grid-connection charges. This paper exposes these fallacies through counterexamples of practical cogeneration system design and evaluation of some segments of the industrial and service sectors in Peninsular Malaysia. The electrical and thermal characteristics of the cogeneration were modeled based on heat rate characteristics at partial loading patterns. A hierarchical mathematical programming approach that uses mixed-integer nonlinear optimization and dynamic programming principle, if necessary, is employed to determine the optimal size of cogeneration and its related auxiliary equipment as well as the optimal operation schedule. Financial assessment is integrated at a later stage to assess the economic viability of the system. Analyses of the cogeneration potential for several facilities of miscellaneous activities were carried out using various gas and electricity prices. Results obtained consistently rebuff the perpetuated fallacies and confirm that there is no real barrier to cogeneration development in Malaysia under current policies of gas prices and electricity tariffs. - Highlights: → Mixed-integer nonlinear programming and dynamic programming are used in the design. → Various loading levels are modeled and hourly operation schedule is determined. → Standby electricity charge has a minimal impact on cogeneration feasibility. → Gas and electricity prices are interrelated and affect cogeneration investment. → Under existing policies, there is no barrier to cogeneration adoption in Malaysia.

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

International Nuclear Information System (INIS)

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

2014-01-01

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

Survey for making a data book related to the development of new energy technology. Cogeneration; 1999 nendo shin energy gijutsu kaihatsu kankei data shu sakusei chosa hokokusho. Cogeneration

Energy Technology Data Exchange (ETDEWEB)

NONE

2000-03-01

This is a report of 'A data book on cogeneration' surveyed by Japan Cogeneration Center under consignment from NEDO. Together with the advance of technology development, policies of new energy technology are being developed toward the introductory promotion in terms of preparation of subsidy system, field test project, advisory project for support of new energy introduction, etc. To promote the project for introducing/promoting new energy more effectively, it is necessary to arrange various data on new energy comprehensively/systematically and to prepare it as the basic data. Out of the technical fields of new energy, this report deals with the cogeneration field and collected/arranged the most up-to-date published data in terms mainly of a list of system, actual samples of introduction, subsidy system, situation of tackling it in each country, etc. The main items of data included in this report are shown below: (1) trend of cogeneration; (2) outline of system; (3) samples of introduction in Japan and abroad; (4) forecast of introduction; (5) policies on cogeneration in Japan; (6) basic technical terms. (NEDO)

Co-generation system with a linear concentrator and thermoelectric elements; Senkei shukokei to netsuden henkan soshi wo mochiita netsuden heikyu system

Energy Technology Data Exchange (ETDEWEB)

Kachi, E; Suzuki, A; Fujibayashi, K [Tokyo University of Agriculture and Technology, Tokyo (Japan)

1996-10-27

The co-generation system using a solar cell has the disadvantage that the performance of a cell element deteriorates when the temperature rises. Therefore, the co-generation system in which a BiTe thermoelectric element and linear Fresnel lens are used was constructed. Moreover, the basic characteristics were confirmed and the characteristics of a system model were analyzed. A thermoelectric element area must be reduced to improve the generating efficiency. The generating efficiency depends on the temperature difference between thermoelectric elements rather than the thermoelectric element area. As the thermoelectric area gets lower, the generating efficiency will get higher. This inclination is advantageous on the economic side. The generating efficiency becomes low during operation at high temperature. As a result, the temperature supplied to the thermal load is set to the lower position (100 to 200{degree}C) so as to advance the validity of the system. Even if the co-generation temperature is low, a heat supply capability of 150{degree}C is sufficient for an industrial heat supply system because it holds a large majority of the consumption demand for the whole industry. 3 refs., 8 figs., 3 tabs.

Exergy analysis of an experimental heat transformer for water purification

International Nuclear Information System (INIS)

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

2011-01-01

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

Analysis of gas turbine systems for sustainable energy conversion

Energy Technology Data Exchange (ETDEWEB)