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In the present study, firstly, the power production, thermal and exergy efficiencies were calculated for the simple and recuperative gas turbine cycles at constant power production (50 MW) and turbine outlet temperature (450 degrees C). The system was analysed for the cases of using both natural gas and pure hydrogen as a fuel for simple and recuperative gas turbine systems. After analyses, the efficiencies of the recuperative gas turbine cycle were higher than the simple gas turbine cycle up to 18 bar pressure for both natural gas and H-2. At the pressure of 18 bar and above, the efficiency of the simple gas turbine cycle found higher than the recuperative gas turbine cycle since the compressor outlet temperature is higher than the turbine outlet temperature. Despite the higher cost of H-2 for unit power production, the H-2 used gas turbine cycles has more advantageous than natural gas in terms of performance, environment and CO2 emission. For the cases of using H-2 and natural gas as fuel, the minimum fuel cost was calculated as 0.345 $/kWh and 0.075 $/kWh at 20 bar for simple gas turbine cycle, while they were found as 0.322 $/kWh and 0.071 $/kWh at 4 bar for recuperative gas turbine cycle, respectively. The CO2 emission of the 50 MW gas turbine was found between 46.27 tones-CO2/h and 71.15 tones-CO2/h for natural gas using simple and recuperative gas turbine systems, besides zero CO2 emission of using H-2. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

This work presents a thermodynamic evaluation of an operating geothermal ORC power plant. The model is realized by using measured data of AFJET geothermal power plant which has 3MWe net power output capacity. Thermodynamic assessment of the system is conducted to see the energy and exergy efficiencies of each component, and the whole plant. Additionally, a parametric study is conducted to understand the effects of various operating conditions on the system performance. Different from previous studies, daily and annual net power output profile of the plant was investigated with considering ambient temperature fluctuations. Results revealed that net power output can drop as significant as 36% from winter to summer months. Also, between nighttime to daytime, the net power expectation may decrease by 5%. The exergy destruction rate of re-injection process constitutes the most significant part (38.1%) of the total exergy destruction of the plant. The conversion and exergy efficiencies of the system are calculated as 11.24% and 39.03%, respectively. Also, to enhance the performance of the plant, an internal heat recovery system is recommended. The analyses show that the implementation of an internal heat recovery system improves the energy and exergy efficiencies of the plant by 15%.

Thermoelectric generator (TEG) has great potential in low-grade waste heat recovery and there is some research on the influence of the Peltier effect on it. However, most of them only consider the total performance changes, such as the variation of power and efficiency due to the Peltier effect, and ignore the impact of the Peltier effect on the temperature of TEGs, which is the core reason of performance changes. To investigate how the Peltier effect affects the temperature loss at the two sides of TEGs, respectively, an experimental setup is built and an analytical model is derived. The result shows that the temperature loss at the cold side is less than that of the hot side. The power loss has a linear relation with the product of the temperature difference and temperature loss. The maximum loss of power, energy efficiency, and exergy efficiency occurs at a particular load range. Within that range, power, energy efficiency, and exergy efficiency reach the maximum, respectively. According to the results, the suggestion of thermal resistance optimization for TEGs is provided.

© 2021 Hydrogen Energy Publications LLCIn the presented paper, energy and exergy analysis is performed for thermochemical hydrogen (H2) production facility based on solar power. Thermal power used in thermochemical cycles and electricity production is obtained from concentrated solar power systems. In order to investigate the effect of thermochemical cycles on hydrogen production, three different cycles which are low temperature Mg–Cl, H2SO4 and UT-3 cycles are compared. Reheat-regenerative Rankine and recompression S–CO2 Brayton power cycles are considered to supply electricity needed in the Mg–Cl and H2SO4 thermochemical cycles. Furthermore, the effects of instant solar radiation and concentration ratio on the system performance are investigated. The integration of S–CO2 Brayton power cycle instead of reheat-regenerative Rankine enhances the system performance. The maximum exergy efficiency which is obtained in the system with Mg–Cl thermochemical and recompression S–CO2 Brayton power cycles is 27%. Although the energy and exergy efficiencies decrease with the increase of the solar radiation, they increase with the increase of the concentration ratio. The highest exergy destruction occurred in the solar energy unit.

In this paper, thermodynamic and thermoeconomic analyses, and also optimization of an organic Rankine cycle (ORC) were performed. The system was adapted to an existing solid waste power plant with a 5.66 MW installed power capacity in order to produce additional power from the exhaust gas. The actual operating data of the plant were utilized during all stages of the analyses. The originality of this paper is based on the analysis of the possibility of the energy conversion of an exhaust gas with a temperature of 566 & #x000B0;C into the electricity by utilizing an ORC system in the concept of waste-to-energy. Four different working fluids: toluene, octamethyltrisiloxane (MDM), octamethyl cyclotetrasiloxane (D4) and n-decane were considered and analyzed for the current system. This is also another novelty of this study due to lack of such a study, in the open literature, that deals with an ORC utilized for a typical municipal solid waste power plant. According to the thermoeconomic analyses, toluene was found to be the optimum working fluid with the maximum power output of 584.6 kW and the exergy efficiency of 15.69%. The optimization of the cycle was performed by using the non-dominated sorting genetic algorithm method (NSGA-II) in MATLAB software environment. The optimization results were compared and the deviations of the net power output and the total cost rate were evaluated as & #x2212;5.89%, & #x2212;3.51 & #x00024;/h for toluene; 0.96%, & #x2212;3.60 & #x00024;/h for MDM; 8.45%, & #x2212;2.04 & #x00024;/h for D4 and 2.00%, & #x2212;5.54 & #x00024;/h for n-decane, respectively. © 2018 Elsevier Ltd

In the literature, energetic and exergetic performance of Organic Rankine Cycle (ORC) were investigated by various researchers. The working parameters affecting the cycle's performance were determined but the impact weights and the order of importance of these parameters were not discussed with a statistical approach. In this context, nine fundamental process parameters such as working fluid type, pinch point temperature differences in the evaporator and condenser, superheating temperature, evaporation and condensation temperatures, heat exchanger effectiveness, turbine and pump efficiencies have been selected for the statistical evaluation. A comprehensive statistical analysis has been carried out to observe the effect of the parameters on the first and second law efficiencies of the ORC. The impact ratios and order of importance of these parameters on the system's performance indicators have been determined. While Taguchi method is performed to determine the optimum levels of each parameter, ANOVA method is used to obtain the impact weights of the parameters on objective functions. In addition to these methods, Grey Relational Analysis (GRA) method is used to optimize the multi-objective function. Evaporator temperature, turbine efficiency, effectiveness of heat exchanger, condenser temperature are obtained as main process parameters on the multiple performance characteristics of ORC and the impact ratios of these parameters are calculated as 31.37%, 19.53%, 16.64%, and 16.61%, respectively. The best condition for the multiple performance characteristics is determined as A(1)B(1)C(3)D(3)E(3)F(3)G(1)H(3)I(3) and under these operating conditions, the first and second law efficiencies of the system are found as 18.1% and 65.52%, respectively.

In this study, the advantages of the ORC were used to improve overall performance of a simple gas turbine (GT) located in a wood production facility. In addition to ORC, a steam boiler (SB) is also coupled with the GT to improve overall performance and to produce needed steam. During study, benzene, cyclohexane, hexane, R11, R123, R600, R601 and toluene were used as working fluid. During parametric optimisation of ORC, entering pressure of turbine rose from 10 bar to 35 bar, while entering pressure of turbine rose from saturated steam temperature to fluid’s maximal temperature. The best performing working fluid was found as benzene for ORC turbine inlet pressure between 10 bar and 25 bar. Above 25 bar ORC-turbine inlet pressure, R123 showed the highest performance. The maximum ORC net power production, thermal and exergy efficiencies were found as 1076.76 kW, 21.14% and 47.00% for ORC used R123 at 230 °C and 35 bar. However, although ORC with R123 has the highest net power production, the payback periods of ORC with R11 is minimum (2.5 years). At this ORC turbine inlet parameters, performance parameters of the cogeneration system were found the highest as thermal efficiency 69.19% and exergy efficiency 75.51%.

In the present study, optimization of two parabolic trough solar thermal power plants integrated with thermal energy storage (TES), and fuel backup system (FBS) has been performed. The first plant uses Therminol VP-1 as heat transfer fluid in the solar field and the second plant uses molten salt. The optimization is carried out with solar multiple (SM) and full load hours of TES as the parameters, with an objective of minimizing the levelized cost of electricity (LCOE) and maximizing the annual energy yield. A 4E (energy-exergy-environment-economic) comparison of the optimized plants alongside the Andasol 1 as reference plant is studied. The molten salt plant resulting as the best technology, from the optimization and 4E comparative study has been chosen for the viability analysis of ten locations in Algeria with semi-arid and arid climatic conditions. The results indicate that Andasol 1 reference plant has the highest mean annual energy efficiency (17.25%) and exergy efficiency (23.30%). Whereas, the highest capacity factor (54.60%) and power generation (236.90 GW h) are exhibited by the molten salt plant. The molten salt plant has least annual water usage of about 800,482 m3, but demands more land for the operation. Nevertheless the oil plant emits the lowest amount of CO2 gas (less than 40.3 kilo tonnes). From the economic viewpoint, molten salt seems to be the best technology compared to other plants due to its lowest investment cost (less than 360 million dollars) and lower levelized cost of electricity (LCOE) (8.48 �/kW h). The viability study proposes Tamanrasset, as the best location for erection of a parabolic trough solar thermal power plant with a low LCOE of 7.55 �/kW h, and a high annual power generation (more than 266 GW h). According to the feasibility analysis, the semi-arid and arid Algerian sites are suitable for realization of PTSTPP with integrated TES and FBS, especially the southern locations (19 N-32 N, 8 W-12 E). � 2015 Elsevier Ltd. All rights reserved.

Due to increasing energy demand and decreasing fossil resources, the optimisation of existing systems has a critical role to minimise energy consumption and diminish the adverse effect of power systems on the environment. Therefore, the main interest of researchers is mainly focused on developing a new combined system to use energy sources more efficient. In the present study, a KC was integrated into an existing burner, which uses waste chips as fuel for producing steam and drying moist fibre. The KC was analysed based on the first and second law of thermodynamics and thermally optimised. After detailed analyses for varying turbine inlet temperature at 50 bar (up to 330 degrees C) and water-ammonium concentrations (from X = 20% to X = 80%), maximum net power, thermal and exergy efficiencies of KC were found as 348.73 kW, 22.7% and 52.7% at T = 330 degrees C and X = 80%, respectively. For the overall cogeneration system, the maximum thermal and exergy efficiencies were calculated as 71.77% and 77.86% at X = 80%, respectively.

The exergoeconomic analysis of an urban area is introduced in this study, performed in an annual energy interaction basis. The investigated period covers the year of 2016, and indoor and outdoor temperatures, construction properties, and annual energy consumptions for heating purposes were all taken into account during the analysis. The selected urban area is the campus housings of Van Yuzuncu Yil University, which were constructed in 2012 after the Van earthquakes. Known as an important tool in understanding the cost structure of energy-intensive sectors, the exergoeconomic analysis was introduced as part of the planning concept in the study, and the analysis involves the results of 'exergetic cost' and 'exergy efficiency' analyses for the case area. Considering the urban nature of the study location, annual meteorological and domestic values were fully covered in the calculations. The results show that, despite being a well-designed and constructed urban area, certain specific design considerations were not met, and there is plenty of space for improvement in cost-reduction, particularly so for a location with such a cold climate.

WOS: 000498072600067, The wastes in wood industries (waste chips) are commonly used as fuel for burners to produce steam and to use the remaining heat in the drying process. However, in spite of that, there is a considerable amount of heat evaluated from the burn of waste chips still released to the atmosphere without use. Therefore, in the present study, a cogeneration cycle design by used of ORC was designed and parametrically optimised for six organic working fluids (acetone, ethanol, R11, RE245fa2, R365mfc and R601a). During the ORC optimisation, the ORC turbine inlet temperature was changed from the saturated steam temperature of the fluid to the maximum temperature of the fluid. The ORC turbine inlet pressure was increased from 7.5 bar to the critical pressure of the fluid. As a result of the study, the maximum net power, net thermal efficiency and exergy efficiency of the ORC were found as 453.91 kW, 30.01% and 67.56% at 340 degrees C and 62.5 bar from the ORC with ethanol. This means that almost 30% of the waste heat could be recovered by use of the ORC with ethanol. By using the designed cogeneration system, it was calculated that the thermal efficiency of the system can be increased up to 74.01%.

In this study, we designed a multifunctional heat pump system using just one scroll compressor and which can be run in four different modes, namely air to air, air to water, water to water and water to air, in order to make an experimental energetic and exergetic performance comparison. Experimental system consists of two condensers and two evaporators and uses R22 as working fluid. One of the evaporators and condensers uses water and the others use air as heat source/sink. Heating capacities of four heat pump types are equal to each other. It is realized by adjusting the mass flow rate and temperature level of external fluid of condenser. Results show that the heat pump unit which has the maximum COP (coefficient of performance) value is water to air type with 3.94 and followed by water to water type with 3.73, air to air type with 3.54 and air to water type with 3.40. Ranking of four heat pump types with respect to their mean exergy efficiency is as follows; water to air type with 30.23%, air to air type with 30.22%, air to water type with 24.77% and water to water type with 24.01%. Exergy destruction rates of the systems were investigated in this study and the results revealed that the heat pump type which has the maximum exergy destruction is air to air type with 2.93 kW. The second highest one is air to water type with 2.84 kW. The third highest one is water to air type with 2.64 kW and last one is water to water type with 2.55 kW. It is understood that the temperature of the evaporator external fluid affects the exergetic efficiency of the system more than the mass flow rate. In contrast to the previous, the dominant parameter which has more important effect on the exergy destruction of the heat pump unit is the mass flow rate of evaporator external fluid. (C) 2013 Elsevier Ltd. All rights reserved.

In this paper, effects of the ambient conditions on performance of cogeneration cycles are analyzed by using exergy analysis method. These cogeneration cycles are the simple cycle, the air preheating cycle, the air-fuel preheating cycle and the inlet air cooling cycle. Also, these cycles are evaluated thermodynamically for different air and fuel mass ratio and the performance of these cycles are compared. The electrical power generation increases about 10-15 % by decreasing the inlet air temperature of the compressor from 25 0C to 0 0C. However, the thermal power decreases about 10 % with decreasing inlet air temperature. During the summer, the electric power can be easily increased 2-7 % by injecting water into the inlet air of the compressor. The exergetic efficiency of cycles is decreased 11-13 %, by decreasing the compressor inlet air pressure from 101.3 kPa to 70.18 kPa. But this change decreases the electric power generation about 25 %. The highest exergy efficiency is obtained for the air-fuel preheated cycle. The simple cycle is the best among the four cycles to obtain high heat rate and heat exergy. The effects of all ambient conditions on these cycles are considered simultaneously, analyzed and compared with each other in this study. © 2017 TIBTD Printed in Turkey.

This paper presents a thermoeconomic analysis and assessment of a municipal solid waste power plant system in Gaziantep. The operation of an existing municipal solid waste power plant is described in detail and a thermoeconomical methodology based on exergoeconomic relations and specific exergy costing (SPECO) method is provided to allocate cost flows through subcomponents of the plant. SPECO method is based on a step by step procedure which begins from identification of energy and exergy values of all states defined in the present system through fuel (F) and product (P) approach and ends at the point of establishing related exergy based cost balance equations together with auxiliary equations. The actual exergy efficiency of the solid waste power plant is determined to be 47.84% which shows that 52.16% of the total exergy input to the plant is destroyed. The net electrical power output of the Gaziantep municipal solid waste power plant is 5.655 MW. The total cost rate of the power plant is evaluated as 18.44$/h as a result of thermoeconomic analyses.

Ammonia-water power cycles are important for efficient utilization of low temperature heat sources such as geothermal, solar, waste heat sources, etc. For some special conditions ammonia-water power cycle is an important and economical option. This paper presents an exergetic analysis of a combined power and cooling cycle that uses ammonia-water mixture as working fluid. Such cycles, use solar or geothermal energy or waste heat energy from a conventional power cycle. Ammonia-water power cycle can be used as independent cycles to provide power output and cooling. For a range (25–55 Bar) of boiler pressure the performance of the combined power and cooling cycle is investigated. The exergy of the boiler is very low compared to its energy. There is a boiling process and a heat transfer process at low temperature, both of which destruct the energy given to the boiler, so that the energy efficiency is low; however the exergy efficiency is higher than the energy efficiency. Increasing the turbine inlet pressure decreases the energy and exergy efficiencies.

Drying is a high-energy-intensive operation and an important step in the pasta production. In this study, exergy analysis of a four-step drying system in a farfalle pasta production line using actual operational data obtained from a plant located in Izmir, Turkey, was performed. Exergy loss rates, evaporation rates, exergy efficiencies, and improvement in potential rates for each dryer section were determined in this drying system. The exergy efficiency values varied between 0.25% and 5.27% from the predrying to the final drying section. The exergy efficiency value for the entire drying system was calculated to be 2.96%, and the highest exergetic improvement in potential rate was 165.54kW for the first dryer section. Copyright © 2013 John Wiley & Sons, Ltd. A four-step drying system in a farfalle pasta production line was exergetically analyzed for assessing and improving the efficiency of the drying process and the entire system along with its main components. Actual operational data were used in the analysis. The exergy efficiency values varied between 0.25% and 5.27% from the predrying to the final drying section, being 2.96% for the entire drying system. The highest exergetic improvement in potential rate (IP) was 165.54 kW for the first dryer section. © 2013 John Wiley & Sons, Ltd.

This study reveals an exergetic analysis of the reactive and pigment printing processes. Exergy models of the printing processes were formed and each step examined in terms of exergetic parameters. In the printing machine, the reactive printing process led to a higher specific exergy use due to the penetration requirement of the printing paste. The exergy efficiency in the subsequent drying after printing was found to be independent of the printing method, but affected by the fabric structure, which was calculated to be between 3.8% and 4.8%. In the fixation step, pigment printing provided the highest exergy efficiency, calculated to be 2.15%, due to the direct heating of the fixation air. It was observed for the fixation step that the boiler unit of the steaming process and the burner of the hot air fixation process led to the highest exergy destruction rates. The total exergy destruction rate in pigment printing was found to be higher than in the washing and final drying stages of reactive printing alone; thus, it was shown that the exergetic improvement of the post-washing and drying of reactive printing is of great importance.

International audience; Distillation columns are one of the main methods used for separating air components. Their inconvenient is their high energy consumption. The distillation process is simulated in three types of columns and the exergy losses in the different parts calculated. A sensitivity analysis is realized in order to optimize the geometric and the operational parameters of each type of column. A comparative exergy analysis between the distillation columns considered for cryogenic air separation shows that the exergy efficiency of a double diabatic column, with heat transfer all through the length of the column, is 23% higher than that of the conventional adiabatic double columns.

The specific refrigeration effect that can be obtained in a single stage mixed refrigerant Joule-Thomson refrigerator is strongly dependent on the composition of mixture used. Comprehensive methods have been developed over the last two decades to determine the mixture composition that results in the highest exergy efficiency or the refrigeration produced. However, what is not well known is the relationship between the mixture composition and the hardware, which ultimately decides the performance of the refrigerator. Experiments were conducted with seven different nitrogen-hydrocarbon mixtures in a single stage JT refrigerator to understand the effect of both composition and hardware on the performance of the refrigerator, the results of which are presented in this paper. � 2011 Elsevier Ltd. All rights reserved.

This article deals with the exergy analysis and evaluation of broccoli in three different drying systems. The effects of drying air temperature on the exergy destruction, exergy efficiency, and exergetic improvement potential of the drying process were investigated. The exergy destruction rate for the drying chamber increased with the rise in the drying air temperature at 1.5 m/s, both in the tray and the heat pump dryer. The highest exergy efficiency value was obtained as 90.86% in the fluid bed dryer in comparison to the other two drying systems and the improvement potential rate was the highest in the heat pump dryer during drying of broccoli at the drying air temperature of 45°C and the drying air velocity of 1.0 m/s. © 2010 Taylor & Francis Group, LLC., TÜBİTAK project no: 106M482

In this paper, we undertake a study to investigate the performance of a hybrid photovoltaic-hydrogen system through energy and exergy efficiencies, improvement potential. This will help identify the irreversibilities (exergy destructions) for performance improvement purposes. Energetic and exergetic renewability ratios are also introduced for grid dependent hybrid energy systems. A case study is presented to highlight the importance of the thermodynamic parameters and show them using some actual and theoretical data. Three different energy demand options from photovoltaic panels to the consumer are identified and considered for the analysis. The minimum and maximum overall energy and exergy efficiencies of the system are calculated based on these options. It is found that the overall energy efficiency values of the system vary between 0.88% and 9.7% while minimum and maximum overall exergy efficiency values of the system are 0.77% and 9.3%, respectively. The monthly improvement potential of the system is also studied to investigate the seasonal performance. Copyright © 2008 by ASME.

There are several methods for producing hydrogen from solar energy. Currently, the most widely used solar hydrogen production method is to obtain hydrogen by electrolyzing the water at low temperature. In this study, solar hydrogen production methods, and their current status, are assessed. Solar-hydrogen/fuel cell hybrid energy systems for stationary applications, up to the present day are also discussed, and preliminary energy and exergy efficiency analyses are performed for a photovoltaic-hydrogen/fuel cell hybrid energy system in Denizli, Turkey. Three different energy demand paths - from photovoltaic panels to the consumer - are considered. Minimum and maximum overall energy and exergy efficiencies of the system are calculated based on these paths. It is found that the overall energy efficiency values of the system vary between 0.88% and 9.7%, while minimum and maximum overall exergy efficiency values of the system are between 0.77% and 9.3% as a result of selecting various energy paths. More importantly, the hydrogen path appears to be the least efficient one due to the addition of the electrolyzer, the fuel cells and the second inverter for hydrogen production and utilization. © 2008 Elsevier Ltd. All rights reserved.

Exergy analysis is often performed statically, for given system conditions and reference state. Dynamic exergy analyses, considering the variation of system operation and ambient conditions, would obviously be more time consuming. Therefore comparing the results of the two approaches helps understand when the dynamic methodology should be preferred. In this paper the yearly behaviour of a reversible Air Source Heat Pump (ASHP) is dynamically simulated with TRNSYS. At every time step the exergy delivered and consumed by the ASHP is calculated. Dynamic exergy efficiencies are then compared with steady state values and some useful considerations regarding the differences are performed.

In this study, exergy analysis and environmental impact assessment of a Photovoltaic (PV)-hydrogen production system and its components are carried out. Actual data measured in the system are employed for analysis purposes. Daily hydrogen production amount from solar energy through water electrolysis is 4.43 kg. The average system exergy efficiency is determined to be 3.18%. It is found that the highest exergy destruction occurs in the PVs. In the PVs, 93.3% of the total exergy input (incoming solar exergy) is destroyed. The second highest exergy destruction is from the electrolyser as 4.76% of the total exergy destruction. The average percent exergy destructions are 1.29% and 1.94% for charge controllers-inverter and batteries, respectively. Copyright © 2011 Inderscience Enterprises Ltd.

This work describes the energy and exergy analysis of a diesel engine integrated with a PCM based energy storage system, and provides more realistic and meaningful assessment than the conventional energy analysis. Using actual system data, the assessments of energy and exergy saved, and energy and exergy efficiencies are done. The exergy saved in the overall system is quantified and illustrated using an exergy flow diagram. Also, energy and exergy flow diagrams are compared. It is observed through the analysis that 6.13% of the total energy of the fuel is saved using the TES system. From the exergy analysis, it is identified that only 0.47% of the chemical availability of the fuel is saved. The energy efficiency of the integrated system is found to be varying between 3.19% and 34.15%. In contrast, the exergy efficiency, which incorporates the second law of thermodynamics for the integrated system, ranges from 0.25% to 27.41%.