International Journal of Exergy (26 papers in press)
Exergoeconomic Optimization of an Air Cooled Heat Exchanger with Copper Oxide Additives
by Nader Javani
Abstract: In the current study, the effect of suspended CuO nanoparticles in a fluid on the exergoeconomic and thermoeconomic properties of an air cooled heat exchanger (ACHE) is investigated. Multi-objective particle swarm optimization algorithm is employed for this purpose. Nine design parameters are selected and two sets of objective functions including the exergy efficiency versus total annual cost (exergoeconomic optimization) and effectiveness versus total annual cost (thermoeconomic optimization) are taken into account. In each case, the results are compared with the base fluid which has no nanoparticles. Results show that nanoparticles have not a meaningful effect on the exergoeconomic improvement of ACHE while a significant improvement is observed for the thermoeconomic optimization. It is also shown that adding CuO nanoparticle into the base fluid for a specified effectiveness, decreases the heat exchanger total annual cost (TAC). If a fixed annual cost is considered, the base fluid mixed with nanoparticles will increase the heat exchanger effectiveness. A value of 9.5% improvement in effectiveness is found for the nanoparticle additives compared with the base fluid for a fixed value of 140$ total annual cost. On the other hand, 20.7% improvement in total annual cost is obtained for the nanoparticle additives compared to the base fluid for the same effectiveness of the 0.7.
Keywords: Air cooled heat exchanger; Exergy efficiency; Exergoeconomics; Nanoparticle; Optimization.
Thermodynamic assessment of the use of alternative metabolic energy resources on work performance efficiency of spontaneous rat myometrium contractions
by Gulnihal Selay Varicioglu, Sinem Ethemoglu, Ali Bahadir Olcay, Bayram Yilmaz, Mustafa Ozilgen
Abstract: Uterine smooth muscles (myometrium) are employed during labour to expel fetus (infant) out of the uterus. Exergy efficiency of the rat myometrium muscle contractions were assessed with the data collected in organ bath experiments in Krebs solutions. The major energy source, glucose, of the Krebs solution was substituted with sucrose, sodium pyruvate and calcium and lactate to assess the effect of the metabolic energy source on the exergy efficiency of work performance. Force versus time graphs were correlated with the work done during the contractions. Muscle contraction exergy efficiency was calculated as the ratio of work done by a muscle strip to the total exergy supplied. Exergy efficiency of the contractions was the highest, 36.7 %, when lactate was the metabolic energy source and it was followed by 35.3 % when pyruvate was the metabolic energy source. Exergy efficiencies of the cases with glucose and sucrose were 34.1 % and 23.5 %, respectively. The findings of this study may open way to further studies which may eventually help women give birth to babies with less pain by increasing exergy efficiency of the process.
Keywords: Myometrium; muscle work performance; exergy efficiency; energy source.
Energy, Exergy and Exergoeconomic Analyses of a Solar Refrigeration Cycle Using Nanofluid
by Hossein Asgharian, Ehsan Baniasadi, C. Ozgur Colpan
Abstract: In this paper, energy, exergy and exergoeconomic analyses of a solar absorption refrigeration cycle with energy storage are conducted. In this cycle, nanofluid is used as the heat transfer fluid (HTF) in a flat plate collector to improve the performance of the cycle. Based on the results of the analyses, the type of nanofluid and working conditions that lead to lower cost of cooling effect and higher COP and exergy efficiency of the cycle are found. The results show that utilization of CuO and Al2O3 nanofluids with 5% volume fraction increases the COP of the solar cycle by 17.98% and 14.51%, respectively, whereas the exergy-based cost rate of cooling decreases by 10.25% and 5.48%, respectively. Utilization the CuO nanofluid as the HTF is found to be more favorable for improving the performance of the cycle and decreasing the exergy-based cost of cooling.
Keywords: Solar absorption refrigeration cycle; Exergoeconomic analysis; Exergy efficiency; Cooling effect; Nanofluid; Energy storage.
Energy, exergy and exergoeconomic analysis of high temperature short time milk pasteurization plant
by Gurjeet Singh, Gurjeet Singh, P.J. Singh, P.J. Singh, V.V. Tyagi, V.V. Tyagi, P. Barnwal, P. Barnwal, A.K. Pandey, A.K. Pandey
Abstract: India produces 19.54% of the total annual milk production of the entire world (819 MT) with a yearly rise of 3.6%. However, a gloomy picture is portrayed by its limited processing capabilities (35%) which are responsible for its meager share (0.68%) in world trade. The motivation for the present work emerges from the fact that specific manufacturing cost of pasteurised milk as well as cost rate of exergy destruction in production of pasteurised milk in a dairy food processing plant had not been determined in any of the studies performed in the past. Therefore, present work concentrates primarily upon exergoeconomic evaluation of High-Temperature Short-Time Milk Pasteurisation Plant so as to achieve cost optimization and enhancement of overall profitability in the existing milk plant setup. Further, exergy gauge registered an exergy efficiency of 68.84%, with an exergy improvement potential of 48.14%, accompanied by specific exergy destruction of 32.21 kJ/kg of pasteurised skim milk. The thermoeconomic analysis revealed that specific manufacturing cost of pasteurised skim milk was calculated to be 2.75 R/kg along with cumulative cost rate of exergy destruction amounting to Rs. 14266.88 R/H. The high and low values of exergoeconomic factor magnify the role of capital investment and thermodynamic inefficiencies respectively. The former was reported to be most significant in case of holding coil (62.45%), heat exchanger (49.25%) and regeneration-1(20.18%), whereas the latter was diagnosed to be prominent in pumping and cream separation unit. Additionally, the total operating cost rate was estimated to be highest for the subunits regeneration-2 (6108.20 R/H) followed by a heating section (2153.63 R/H) and final chiller (2000.28 R/H) of dairy food processing plant.
Keywords: Energy; exergoeconomic; exergy; milk processing; milk pasteurization plant.
ENTROPY ANALYSIS FOR THERMALLY DISTURBED THIN FILMS
by Bekir Sami Yilbas, Saad Bin Mansoor
Abstract: Entropy generation rate during phonon transport across consecutively placed two thin films is examined. The films are thermal disturbed via setting the temperature differential at the edges. The Boltzmann transport equation is introduced to model the micro/nano scale heat transfer across the films. Thermal resistance is incorporated at the edges and at the interface of the films to model the boundary scattering. Thermodynamic irreversibility in association with the entropy generation rate is formulated in the films while adopting the phonon intensity distribution. The thermal conductivity predictions are validated incorporating the previous data. It is demonstrated that the thermal conductivity data predicted and obtained from the experiments are in good agreement. The phonon scattering at the film edges and at the interface results in temperature jump in these regions. As the film thickness reduces, the entropy generation rate becomes large, which is related to the thermodynamic irreversibility caused by temperature jump. The entropy generation rate predicted through the Fourier heating model remains significantly larger than that obtained from the phonon radiative transport model, which is more pronounced for the small film thicknesses
Keywords: Phonon transport; thin films; entropy generation; boundary scattering.
Exergy Analysis of a Natural Gas Fuelled Gas Turbine Based Cogeneration Cycle
by Yildiz Koc, Ozkan Kose, Huseyin Yagli
Abstract: In this paper, the monthly based annual performance of a natural gas fuelled gas turbine based cogeneration cycle was analysed. The performance analysis of the system was investigated in three steps. First, the real system parameters like temperature, pressure and power production were measured during a year. The measured parameters were compared with theoretical calculations. After which exergy based annual analysis of the system was performed for both system components and the overall system. Finally, the exergy analysis of the maximum and minimum power generated months (December and February) were compared with each other to show differences between the endpoints. As a result of the study, during the year, the maximum thermal and exergy efficiency of the simple gas turbine was calculated as 36.45% and 50.50% for the real case and 43.82% and 60.70% for the theoretical case, respectively. Moreover, the maximum thermal and exergy efficiency of the cogeneration system was determined as 79.00% and 94.19% for the real case and 83.92% and 91.64% for the theoretical case.
Keywords: Gas turbine; cogeneration cycle; real and theoretical comparison; annual analysis; performance analysis; exergy.
An Evaluation of Multi-Effect Desalination with a Thermal Vapor Compression System in Terms of Thermo-economics
by Mehmet Tontu, Besir Sahin, Mehmet Bilgili
Abstract: In this study, a multi-effect distillation system (MEDTVC) that is presently in use in a thermal power plant was analyzed. The operating data of an existing MEDTVC (2000 m3/day) desalination process is used for the present analysis. The analysis of the considered system was performed based on the energy, exergy and thermoeconomic approach. Also, the effect of operating plant load, seawater temperatures and upper brine temperatures on the performance of the desalination plant was investigated. The gain output ratio and exergy efficiency increased with increasing production load and seawater temperature. When the production load and seawater temperatures were 100% and 33oC, respectively, the gain output ratio and exergy efficiency obtained was 7.73 and 2% respectively. In addition, the exergy analysis showed that the vast majority of the exergy destruction in the system occurred in the steam jet ejector. The results showed that the steam ejector was responsible for about 45% of the total exergy destruction. The thermoeconomic analysis shows that the unit product cost of the distilled water at the full load was calculated by 1.7 $/m3.
Keywords: Desalination; Energy; Exergy destruction; Exergy efficiency; Multi-effect; Thermal vapor compression.
Energy and Exergy Analyses of Using Natural Gas Compressor Station Waste Heat for Cogeneration Power and Fresh Water
by Mahdi Deymi-Dashtebayaz, Amir Ebrahimi Fizik, Sajjad Valipour Namanlo
Abstract: The feasibility of employing waste heat of the natural gas compressor station (NGCS) for providing the heat and power required in the multi stage flashing (MSF) water distillation system has been studied. The proposed system provides the possibility of reducing the outlet natural gas temperature from the NGCS. In this paper, a thermodynamic simulation is developed based on energy and exergy analysis for evaluating the features in the proposed system including combined power generation, water distillation and natural gas cooling cycle. The Faruj NGCS in Iran is selected as a case study to evaluate the proposed system. Based on exergy analysis for the overall system, the share of the exergy destruction rate for natural gas cooling, the MSF distillation and power generation cycles is calculated 48.76%, 48.39% and 2.85%, respectively. Moreover, in the MSF distillation cycle, consisting of HRS, HRJS and brine heater, the exergy destruction rate of the HRS unit with 25 flashing stages is obtained 71%. Due to the fact that a large number of NGCSs are operating in the western and southern regions of Iran and also due to the lack of water in these areas, the results of a comparative study show that by using waste heat from these stations, about 3,760,000 m3/day distilled water could be produced.
Keywords: NGCS station; Waste heat; MSF; Power generation; Energy and exergy analysis.
Energy and Exergy Evaluations of Catalytic Dry Reforming of Methane for Syngas Production in Fixed-bed Reactors
by Reiyu Chein, Wen-Huai Hsu
Abstract: Dry reforming of methane (DRM) is one of the most attractive ways to produce syngas because it simultaneously reduces two greenhouse gases. Moreover, DRM is a highly endothermic process, it is suitable for high temperature energy storage methods via thermochemical reaction. The energy and exergy characteristics of DRM were numerically studied in this study in a tubular fixed-bed reactor under heat supply from uniform temperature furnace or uniform wall heat flux. For both cases, variations in enthalpy, entropy and exergy were computed based on non-equilibrium thermodynamics for chemical reactions. The heat supply, heat of chemical reaction and entropy generation due to irreversibility were the sources that caused changes in enthalpy, entropy and exergy between the reactor inlet and outlet. Based on the simulated results it was found that the chemical reaction is the most dominant factor for entropy generation. It was also found that exergy at reactor outlet depends on the heat supply and a minimum value can be found due to contribution variations from the gas species involved in DRM. Based on the resulting lower heating value and syngas exergy (CO and H2) at the reactor outlet, it was found that the chemical energy and exergy efficiencies can be over 100% when the reaction temperature or the wall heat flux is high.
Keywords: Syngas; dry reforming of methane (DRM); uniform temperature furnace; uniform wall heat flux; chemical energy and exergy efficiencies.
Exergetic performance analysis of heat pumps: two alternative approaches
by Henrik Holmberg, Timo Laukkanen
Abstract: This paper evaluates the performance of a compressor driven and an absorption heat pump on the basis of exergy analysis using two different approaches. Approach 1 is based on the calculation of the effective heat absorbing and emitting temperatures and the entropy generation rate. Approach 2 is based on the commonly used exergy analysis where the real ambient temperature is used. The main goal is to analyze how these two approaches differ from each other. Approach 1 gives the exact improvement potential (Wreal - Wmin) of the heat pump while Approach 2 underestimates it. The average flow temperature also approximates the correct improvement potential with sufficient accuracy when temperature change of the flow is relatively small. Both approaches can be used when performances of heat pumps are compared. Both approaches also give a more realistic view of the performance than the commonly used COP, especially regarding the absorption heat pump.
Keywords: Rational ratio; exergy efficiency; irreversibility rate; COP; absorption heat pump; compressor driven heat pump.
Thermodynamic assessment and optimization of a biomass energy based combined system for multigeneration
by Nejat Tukenmez, Yunus Emre Yuksel, Murat Ozturk
Abstract: In this study, an integrated energy plant is designed for multi-generation and a parametric study is performed for integrated energy plant design. At the same time, optimization studies of integrated energy plant with parametric assessment are carried out. The energetic and exergetic performances of integrated system have been computed as 51.28% and 46.67%. Thermodynamic analysis data show that some parameters in the system are more effective on system efficiency and cost than other parameters. By using parametric study, these parameters are determined as biomass flow rate, gas turbine inlet temperature, gas turbine inlet pressure and air compressor compression ratio. These parameters are used as the decision variable in the optimization study. Optimal points of the integrated energy system are shown on the Pareto front.
Keywords: biomass gasification; multigeneration; energy; exergy; optimization.
Experimental exergoeconomic performance assessment of a wastewater source heat pump system
by Mustafa Araz, Arif Hepbasli, Huseyin Gunerhan
Abstract: This study aims at experimentally analyzing and assessing the performance of a wastewater source heat pump system (WWSHP) in cooling mode, which was installed at Yasar University, Izmir, Turkey through exergetic and thermoeconomic (exergoeconomic) analysis methods. Within this context, first, conventional exergy analysis was performed based on the actual experimental data, where exergy efficiencies, destructions and relative irreversibilities of each element were determined to indicate improvements. Then, these results were combined with the cost data of the system to make exergoeconomic analysis. Functional exergy efficiencies of the entire system and the WWSHP were obtained to be 7.56% and 11.77%, respectively. The compressor had the biggest relative irreversibility, which was followed by the fan-coil. The exergoeconomic factor values of the condenser, WW heat exchanger (WWHE) and fan-coil unit were lower than 0.5, indicating that the exergy destruction costs associated with these components were higher than the capital investments.
Keywords: wastewater; wastewater source heat pumps; waste to energy; exergy; thermoeconomic; exergoeconomic.
Exergy Analysis of Heating Options for Buildings in the Pacific Northwest
by Heather Dillon, Rachel Dzombak, Chrissi Antonopoulos
Abstract: A framework for quantifying environmental impact in future energy codes is explored based on exergy analysis. An example exergy analysis is performed that quantifies the environmental impact of electric resistance heating with exergetic efficiency of only 13% compared to 30% and 40% for air source and ground source heat pumps. This provides motivation for removing electric resistance as a space heating option in future energy codes in the Northwest.
Keywords: exergy; building energy codes; exergy policy; sustainability.
Special Issue on: GCGW2018 Exergetic Solutions for Better Performance
Comparative Thermodynamic Performance Assessment of Two-Stage Cycle for Various Refrigerants
by Fatih Yilmaz, Murat ÖZTURK, Resat SELBAS
Abstract: In this paper, the thermodynamic performance evaluations of the two-stage cooling cycle are investigated comparatively for different refrigerants under the same operating conditions. Due to their environmentally friendly properties, CO2, R600, R600a, R161, and R134a are selected as the refrigerants. The change in energy performance coefficient (COPen) and exergy performance coefficient (COPex) of the defined cycle are investigated according to the various indicators, such as reference temperature, gas cooler outlet temperature and pressure. Results are shown that, at the evaporator temperature of -5 oC and the gas cooler outlet temperature of 40 oC , the COPen of the cooling cycle are 1.644, 1.603, 1.452, 2.0356 and 1.928 for the refrigerants CO2, R600, R600a, R161 and R134a, respectively. Furthermore, COPex of the cycle are computed as 25.94%, 15.57%, 14.07%, 19.73% and 18.68% for the same refrigerants in the same order. In addition, the overall exergy destruction rate of the cooling cycle for CO2 refrigerant is calculated as 145.69 kW.
Keywords: CO2; energy; exergy; cooling; refrigerants.
Energy, Exergy, Exergoeconomic, and Exergoenvironmental study of a parabolic trough collector using a converging-diverging receiver tube.
by Eric Chekwube Okonkwo, Tahir Abdul Hussain RATLAMWALA, Muhammad ABID
Abstract: This study presents a novel energy, exergy, exergoeconomic and exergoenvironmental analysis of a parabolic trough solar collector operating with a converging-diverging absorber tube design. The collector is modeled thermally after the experimental results of the Sandia National Laboratory LS-2 collector test using the engineering equation solver. The results of the analysis show that the converging-diverging geometry obtained a mean enhancement in thermal efficiency of 1.13% and 0.49% in exergetic efficiency when compared to the conventional absorber tube. The optical losses with 24.5% accounted for the highest source of exergetic losses while the exergy destruction due to heat transfer between the sun and the absorber accounted for 59.7% at inlet temperatures of 350 K. The exergoeconomic study shows that the cost rate of exergy destruction is seen to decrease from 3.4 - 0.35 $/hr as the inlet temperature increases from 323-650 K. The environmental study yielded an exergoenvironmental impact factor of 0.31 with the values of 2.61, 0.82 and 1.22 for the exergoenvironmental impact coefficient, impact index and impact improvement respectively.
Keywords: parabolic trough collector; converging-diverging; energy; exergy; exergy destruction; exergy loss; exergoeconomic; exergoenvironmental; thermal efficiency; heat transfer.
First and second law analyses of wastewater cooled condenser for a refrigeration system
by Ibrahim Karacayli, Lutfiye Altay, Arif Hepbasli
Abstract: In this study, a vapor compression refrigeration (VCR) system with a wastewater (WW) cooled condenser at a temperature range of 27 29 oC was designed. The cooling capacity of the system using R134a as the refrigerant was 1.09 kW. The condenser consisted of a coaxial heat exchanger with a capacity of 1 kW. This paper dealt with energy and exergy analyses of the VCR system using WW, as a heat sink. Experiments were performed in order to evaluate the energetic and exergetic performances of the wastewater-cooled condenser (WWC) and the overall system. The convective heat transfer coefficient of WW and refrigerant in the condenser, overall heat transfer coefficient of the WWC, total amount of heat removed by WW, amount of cooling effect, coefficient of performance (COP), exergy destruction rate, and second law efficiencies of the WWC and VCR system were calculated under different WW temperatures and flowrates. Increasing volumetric flowrate of WW from 200 L/h to 400 L/h caused 4.4% improvement in COP, 12.0% reduction in exergy destruction, and 10.3% increase in exergy efficiency.
Keywords: wastewater; refrigeration; energy; exergy; coefficient of performance; second law efficiency.
Energy, Exergy and Thermoeconomic Analyses of Biomass and Solar Powered Organic Rankine Cycles
by Özüm Çallı, C. Ozgur Colpan, Huseyin Gunerhan
Abstract: In this paper, energy, exergy and thermoeconomic analyses of three different integrated systems consisting of an organic Rankine cycle (ORC) are presented. These systems differ from each other in terms of the energy technology providing the heat transfer to the ORC. For this purpose, biomass burner, parabolic trough solar collector (PTSC), and a combination of those are used. For analyses, numerous control volumes surrounding the system components are first formed. Then, applying energy, exergy and thermoeconomic balance equations around these control volumes, the thermodynamic properties of each state, work and heat transfer interactions, and exergy and cost per unit of exergy are calculated. As a result of these analyses, the electrical and exergy efficiencies of the system, as well as the specific cost of the electricity (per unit of exergy) are found. The effects of biomass type and solar irradiation on the performance and cost are assessed. The energy and exergy-based performance and electricity cost of these systems are also compared with each other for the baseline conditions and different number of PTSCs. The results show that biomass-based ORC system yields the highest electrical (10.61%) and exergetic efficiencies (9.18%) and the lowest cost (30.37 $/GJ). In addition, the system having PTSC and biomass burner is thermoeconomically advantageous when this system has 4 or fewer collectors compared to the solar based ORC system having 12 collectors.
Keywords: Organic Rankine cycle; energy; exergy; thermoeconomic; renewable energy.
Thermoeconomic assessment of a solar based ejector absorption cooling system with thermal energy storage: A case study for al-Jofra city in Libya
by Salem Yosaf, Hasan Ozcan
Abstract: Libya lying in one of the warmest regions in the world, a continuous cooling is required for domestic and industrial needs. In this study, a concentrated solar photovoltaic energy (CSPV) based ejector absorption refrigeration cycle (EARC) is evaluated using thermodynamic and thermoeconomic tools for a house requiring ~3.4 kW peak cooling in Libya. The solar data of Al-Jofra city is utilized to operate the CSPV system that produce enough heating and electricity for the refrigeration cycle generator and the thermal energy storage, as well as the system circulation pumps. The thermal energy storage medium uses Therminol as the heat storage fluid to utilize the system when there is no solar energy input. The overall COP and exergy efficiencies of the system at peak times are 0.82 and 32%, respectively. Cooling cost flow rate of the overall system is found to be around $0.22 per hour at generator temperatures above 100⁰C without thermal energy storage, while it is determined to be as high as $0.29 per hour with storage. Even though the system present high cooling costs due to high investment costs for the CSPV equipment, almost 6.58 tons of annual CO2 emissions can be prevented with this renewable based cooling system when replaced with conventional vapor compression refrigeration systems.
Keywords: Clean Cooling; Absorption Refrigeration; Ejector; Concentrated Solar Photovoltaics; Thermoeconomics.
Energetic and Exegetic Analysis of A Novel Multi-Generation System Using Solar Power Tower
by Muhammad ABID, Victor Adebayo, Victor Adebayo, Ugur Atikol, Ugur Atikol
Abstract: In this study, energy and exergy analyses are conducted on a multi-generation system driven by renewable energy source. The system produces power, domestic hot water and cooling as output by means of a gas cycle, a steam cycle, a double-effect absorption chiller and two domestic hot water heaters. The parametric study is carried out so as to examine the result of varying some operating conditions such as ambient temperature and irradiation from the sun on the effectiveness of the system. The solar multi-generation system is seen to have an energetic efficiency of 55.94% and an exergetic efficiency of 29.23%, while the COP (en) of the double-effect absorption chiller is determined to be 1.253 and the exegetic efficiency of the absorption chiller is 0.3762. The exergy destruction assessment for some components of the system shows that the receiver of the solar power tower is the component with the highest exergy destruction rate. Increasing the evaporator temperature of the absorption chiller is seen to raise the COP (en) of the chiller.
Keywords: Energetic; exergetic; multi-generation; double-effect absorption chiller; solar energy.
Conventional and advanced exergy analyses of an air-conditioning system in a subway station
by Hua Yin, Huafang Guo, Zhihua Tang, Junyan Yu, Haiyang Lu
Abstract: Air-conditioning systems in subway stations consume a large amount of energy. In this study, conventional and advanced exergy analyses were carried out to determine the energy-saving potential of an air-conditioning system in a subway station. Results show that air handling unit (AHU) should be improved for the highest values of relative irreversibility (RI) with conventional exergy analysis, whereas the compressor should have the highest improvement priority for the largest avoidable exergy destruction with advanced exergy analysis. Moreover, influences of compressor efficiency, condensation temperature, and evaporation temperature on avoidable exergy destruction of the air-conditioning system were also investigated. According to the findings, compressor efficiency significantly influences the systems total avoidable exergy destruction. The lower the compressor efficiency, the more rapidly the avoidable exergy destruction of the compressor increases. Furthermore, the avoidable exergy destruction of condenser, compressor, cooling tower (CT), and cooling water pump (CWP) increases with the rise of the condensation temperature, whereas that of the evaporator, throttling valve (TV), condenser, compressor, CT, and CWP decreases with the rise of the evaporation temperature.
Keywords: conventional and advanced exergy analyses; air-conditioning system; subway station.
Increasing exergy efficiency of a coal-fired thermal power plant via feedwater-heating repowering application
by Mustafa Zeki Yilmazoglu, Altug Alp Erdogan
Abstract: This study presents an exergetic comparison when feedwater-heating repowering method is used in a coal fired thermal power plant. Design data for Soma A thermal power plant was used to calculate the exergetic efficiency before repowering. Secondly, the exergetic efficiency calculations were repeated for thermal power plant after feedwater-heating repowering method. It was found that exergy destruction in combustion chamber (boiler) decreased from 84% to 66%. However, exergy destruction for the combustion chamber of gas turbine was found to be 15%. Total exergy destruction increased from 54.4 MW to 69 MW. However, total exergy destruction per installed capacity decreased from 2.3 MW/MWel to 1.99 MW/MWel. In addition, exergetic efficiencies for the designed and repowered cycles were found to be 31% and 34%, respectively. In conclusion, the feedwater-heating repowering method can increase the exergetic efficiency of the coal fired thermal power plants.
Keywords: Repowering; exergy; feedwater heating; thermal power plant; exergetic efficiency.
Exergetic Performance of Building Attached Photovoltaic Power Plant: A Case Study for an Olive Oil Production Corporation
by Elif Bozoglan, Mete Cubukcu, Eylem SAGLAM, A. Evren Ogutcen
Abstract: It is known that solar energy is among the most available and sustainable renewable sources of energy. Nowadays, there has been a gradual increase in the use of solar energy in the generation of electricity for industrial purposes. This study utilized energy and exergy analyses to assess the performance of a building attached photovoltaic plant (BAPV), installed on the roof of an olive oil manufacturing company situated in Izmir, Turkey. The plant has been reported to have a capacity of 701.2 kWp, and was designed as a grid connected model. Strings having a total of 21 monocrystalline solar modules constitute the BAPV system. These monocrystalline solar modules are more efficient in electricity production, compared to the polycrystalline ones. Prior to conducting analysis on exergetic performance, data were collected from Sunny Portal. These included data on total insolation of solar energy, panel surface temperature, ambient temperature, electricity production, etc. In 2017, energy and exergy efficiencies, exergy destructions and sustainability indexes were determined as a function of ambient temperature. The plant was found to have an exergy efficiency around 12.49-15.76%. Also, it was discovered that the sustainability indexes of the BAPV plant were in the region of 1.14-1.19. The module plane and the electricity produced, recorded annual solar irradiation of 1561.32 kWh/ (m2y) and 878.29 MWh/y, respectively. As a result of the values, this study recorded a mean annual electricity specific yield of 1252.55 kWh/kWp and performance ratio of 81.86 %.
Keywords: Solar energy; building attached photovoltaic power system; exergetic efficiency; exergetic destruction; sustainability index; electricity yield analysis.
Municipal solid waste based multigeneration system for different districts of Karachi
by Tahir Abdul Hussain RATLAMWALA
Abstract: In this study, a novel multi-generation system comprising of municipal solid waste powered Rankine cycle, solar parabolic trough collector, absorption chiller, electrolyzer and reverse osmosis, all integrated together to produce useful outputs namely electricity, drinkable water, cooling, warm water, heating, hydrogen and dry air, is proposed and thermodynamic assessment is carried out. Energy analysis and exergy analysis has been carried out by setting up multiple parameters. System performance for different districts in Karachi is then investigated by performing a parametric study by changing system parameters such as municipal solid waste input, calorific values, and ambient temperature, the corresponding changes in system outputs and efficiencies are then compared. The systems average energy and exergy efficiencies are found out to be 88.6% and 60.3% respectively.
Keywords: energy; exergy; efficiency; multi-generation; Karachi; solar; biomass; power; waste to energy.
GEOTHERMAL AND SOLAR ENERGY AMALGAMATED MULTIGENERATION SYSTEM ESCORTING DIVERSE NEEDS OF A DISTRICT
by Tahir Abdul Hussain RATLAMWALA
Abstract: Geothermal wells and their integration with other renewable resources have been in use since long and extensive research is being done, but in this study we are working on another aspect which is; geothermal wells whose pressure heads have been lowered with time and which are potentially considered as low head wells and called as Shallow-depth geothermal. Using a geothermal well with low temperature and pressure head alone is not suitable and economical but still they have potential and can contribute if designed in an intelligent manner. So,in this paper, a parabolic trough collector (PTC) with a meshed source of low temperature and pressure head accompanying dual flash is used with a Rankine cycle, an Electrolyzer and absorption cooling, and heating system. A pattern of PTCs is used for solar heating phenomena. Detailed energetic and exergetic analysis are done for the whole system including all the components individually. Different analysis and iterations are done and plotted against their different results. The parameters that are variegated to change the output of the system are ambient temperature, solar irradiance, mass flow rate of the fluid, temperature gradient of the geothermal well; temperature had an upshot on the net power produced by the Turbines HPT and LPT, outlet temperature of the solar collector all-inclusive energetic and exergetic efficiency. Variant utilitarian outputs of this domestic meshed diverse generation system are the heating of the domestic water, space heating in a favorable temperature range constraint and freshwater production. The effective difference in the temperature across the collector ranging from 70
Keywords: Solar; Geothermal; Dual flash; energy; exergy; hydrogen; cooling; power.
Thermodynamic analysis and assessment of a geothermal cooling system for a house
by Buket Ozcan, Ilkyaz Ekin Aykurt, Melisa Akpak, Tuna Tacer, Nurdan Yildirim, Arif Hepbasli, Huseyin Gunhan Ozcan
Abstract: In this study, a geothermal assisted cooling system with a vapor absorption chiller (VAC) was designed in order to meet the cooling demand of a 140 m2 detached single-family house in Izmir, Turkey. In the considered system, the geothermal fluid is transported to the VAC, where water and ammonia are used as an absorbent and a refrigerant, respectively. Energy and exergy analyses methods are utilized to assess the performance of the system while some operational properties of the VAC such as pressure, temperature, ammonia concentration and flow rate are determined. Based on the parametric studies undertaken, optimum operating conditions of the VAC are obtained to be 30
Keywords: vapor absorption chiller; geothermal energy; residential cooling; economic analysis; exergy analysis.
Special Issue on: IEEES-10 Exergetic Modelling of Advanced Energy Systems
Exergetic Approach to Determine Optimum Insulation Thickness for Cooling Applications with Life cycle Integrated Economic Analysis
by Emin Acikkalp, Süheyla Yerel Kandemir, Onder Altuntas, T. Hikmet Karakoc
Abstract: Optimum insulation thickness for building walls is investigated using a new method called as Combined economic and environmental methods (CEEM). In this method, environmental costs are integrated in the fuel and insulation material costs and in this way, it is possible to consider both of economic and environmental aspects. Environmental cost of carbon dioxide, fuel and insulation materials are added to their cost and total annual cost for the system is calculated and results are investigated according to insulation thickness. In this paper, optimum insulation thickness with life cycle integrated economic analysis in terms of exergy approach is defined. Rockwool and glasswool are chosen as insulation materials and calculations were made for Bilecik located in Marmara region in Turkey. Optimum points are found for CEEM, economic approach and environmental approach and they are compared with each other.
Keywords: Insulation thickness; life cycle integrated economic analysis; energy consumption.