International Journal of Exergy (48 papers in press)
Energy, exergy and environment analyses of a hybrid PV-system district heating system for a new household settlement in Germany
by Khaoula Daghsen, Dorra Lounissi, Bouaziz Nahla, Kallert Anna, Young Jae Yu
Abstract: This work presents an exergetic and environmental assessment of a hybrid district heating system(HDHS)analysed within two supply temperature levels. Energetic, exergetic and environmental performances are investigated. Results indicate that different scenarios have a lower degree of exergy efficiency in comparison to energy efficiency. The HDHS has a higher exergy efficiency (around 2%) and lower primary exergy demand (around 3%) compared to the normal district heating system (NDHS).Moreover, the combination of photovoltaic (PV) modules and low supply temperature reduces around 90 % of the exergy losses. Results of the environmental study confirm that the lower supply temperature added to the PV modules reduce CO2 emissions. In general, exergy analyses of the district heating systems should be conducted to make the exergo-environmental model, the matching of the quality level of demand and supply and the environmental impact, more known to the public and decision-makers in the context of multi-grid energy systems.
Keywords: CO2 emission; District heating; Exergy; Hybrid energetic systems,PV-modules.
Exergy cost analysis of Soil- Plant system
by Masoumeh BararzadehLedari, Yadollah Saboohi, Antonio Valero, Sara Azamian
Abstract: In this paper, inspired by a gas turbine power plant, the interaction between plant-soil processes has been simulated. This study indicates that solar energy in the photosynthesis process is equivalent to the fuel in combustion chambers. \r\nIn the glucose production process, when solar exergy is considered as a fuel, 99.4 percent of total exergy cost is supplied with solar exergy and only 0.6 percent of the exergy cost is provided by nutrients content. In general, 30% of the total exergy entering the Calvin cycle is consumed in glucose production and the remaining 70% is related to biomass generation. Moreover, 98% of the total exergy cost of the soil box is related to nutrient supply (due to the decomposition process), and only 2% percent is due to soil\'s nutrition. This happens because the decomposing processes include numerous energy-intensive chemical reactions and therefore, a high level of exergy cost.\r\n\r\n
Keywords: plant-soil process; exergy; Thermoeconomic analysis; exergy cost.
Exergy versus Labor in Aggregate Production Functions: Estimates for Ten Large Economies
by Robert U. Ayres, Ivan Savin, Jeroen Van Den Bergh, Lu Hao
Abstract: One can distinguish active (machines) from inactive (infrastructure) capital. Active capital consumes useful energy (or exergy) to do thermodynamic work that muscles and brains usually do. We use data for ten large economies and find that exergy performs just as well as, and hence can replace, labour in a Cobb-Douglas production function. This result is robust for each country separately and for all countries estimated together. Furthermore, when estimating a three-factor model (capital, labour and exergy), the coefficients of all three factors are positive and significant when all countries estimated together. When testing for each country separately the coefficient of exergy, unlike that of labour, is significant for China and Japan, while the opposite holds for the USA and the UK. Our findings underpin the essential role of energy behind GDP growth, and the relevance of exergy as either a substitute or complement for labour in aggregate production functions.
Keywords: GDP; Cobb-Douglas function; energy; capital.
Effects of the dissimilarity of water depth on energy and exergy efficiencies and productivity of solar energy
by R.K. Yadav, Mukesh Kumar, Jay Singh, Desh Bandhu Singh, Navneet Kumar
Abstract: This research work investigates the effect of dissimilarity of water depth on energy and exergy efficiencies and productivity of solar still of double slope type coupled to N alike evacuated tubular collectors. The analysis has been done for archetypal days of June and January for complex climatic situation of New Delhi using computer codes inscribed in MATLAB-2015a. It has been concluded that values of average daily efficiencies and productivity increase first and then become almost constant beyond water depth of 0.56 m.
Keywords: Exergy; Efficiency; productivity; ETC; double slope solar still.
Greenhouse gas emissions within the exergoenvironmental assessment of a compact combined cooling, heating and power system
by Monica Carvalho, Adriano Marques, Raphael Abrahao
Abstract: Because of the significant public concern regarding climate change (and global warming), greenhouse gas (GHG) emissions have been successfully employed to communicate environmental impacts. This study develops a Life Cycle Assessment of the equipment and energy flows of a combined cooling, heating and power system system, expressing the environmental impacts as GHG emissions. Environmental data was used as input to an exergoenvironmental assessment, based on the SPECO methodology. The GHG emissions associated with the consumption of natural gas and grid electricity are 0.258 and 0.227 kg CO2-eq/kWh, respectively. The internal combustion engine is responsible for the highest share of GHG emissions (15.95 kg CO2-eq/h), of which 15.80 kg CO2-eq/h is due to the formation of pollutants and the remainder refers to equipment. From the combined analysis of exergoenvironmental parameters, strategies that increase energy use and decrease irreversibilities should focus on the absorber heat exchanger, the steam generator, and heat recovery unit. Some of the recent energy policy responses to the COVID-19 crisis include the deployment of energy solutions such as combined energy systems, and exergoenvironmental assessments can promote the adoption of these more efficient systems.
Keywords: Thermoeconomics; SPECO; Carbon footprint; Absorption refrigeration; Allocation of emissions.
Sensitivity investigation of N similar evacuated tubular collectors having series connection by incorporating exergy analysis
by Desh Bandhu Singh
Abstract: This research work deals with the sensitivity investigation of N similar evacuated tubular collectors (N-ETCs) having series connection taking computer codes inscribed in Matlab-2015a considering a normal day of May for New Delhi complex climate. The sensitivity with respect to N for N-ETCs from exergy as well as heat gain viewpoints is maximum with mean sensitivity figure values as 0.92 and 2.11 respectively. This analysis will help the designer to focus on particular input parameter as per the requirement of user.
Keywords: sensitivity analysis; sensitivity figure; N; evacuated tubular collector; OAT; efficacy.
The exergoeconomic optimization and economic sensitive analysis for flash-binary and double flash geothermal power systems
by Chao Luo
Abstract: The flash-binary and double flash power technologies are proposed to exploit the geothermal resources in Tibet and western Sichuan, China. The exergoeconomic optimization and economic sensitive are simulated by genetic algorithm. The results show that the levelized cost of electricity for flash-binary and double systems are 0.07052 US$/kWh and 0.0838 US$/kWh respectively before exergoeconomic optimization, and 0.06803 US$/kWh and 0.07331 US$/kWh respectively after exergoeconomic optimization. When the geofluid mass flow rate and power plant capacity are more than 50 kg/s and 1100 kW respectively, the plant cost per unit capacity maintains between 2000 US$/kW and 3500 US$/kW.
Keywords: Geothermal power generation; Flash-binary system; Double flash system; Exergoeconomic; Sensitivity.
Examination and thermodynamic modeling of a geothermal energy power plant for sustainable development; a case study
by Oguzhan Akbay, Fatih YILMAZ
Abstract: The new design article aims to assess the thermodynamic performance modeling of the geothermal power generation plant using real process data. This advised model comprises a steam turbine, high and low-pressure organic Rankine cycles, and also these plants are working by n-butane refrigerant. Moreover, with energy and exergy efficiencies, this proposed study is compared with different refrigerants. Looking at the consequences, the ORC-1's energy and exergy efficiencies are 14.49% and 19.03%, while the ORC-2's energetic and exergetic efficiencies are 10.75 %and 14.69%, respectively. Analysis results specified that the energy and exergy performances of the investigated power plant are 10.33% and 39.03%, respectively.
Keywords: Energy; exergy; geothermal power plant; thermodynamic; Organic Rankine cycle.
Exergetic assessment of a concentrated photovoltaic-thermoelectric system with consideration of contact resistance
by Aminu Yusuf
Abstract: Despite extensive studies on concentrated photovoltaic-thermoelectric systems, exergy analysis has not been given much attention. Herein, a comprehensive exergy analysis of a concentrated photovoltaic-thermoelectric system is presented. The results showed that increasing the number of thermoelectric modules in the system reduces the exergy destruction in the system, thereby improves the exergy efficiency. Likewise, performance of an individual thermoelectric module reduces with increase in the number of thermoelectric modules in the system. While increasing the contact resistance from 0% to 100% of internal resistance of the thermoelectric modules reduces the exergy efficiency of the thermoelectric modules by 50%.
Keywords: Contact resistance; performance evaluation; exergy efficiency; thermoelectric modules; concentrated photovoltaic; thermodynamic system; exergy destruction; solar energy; electrical energy; heat transfer; water cooled-system; one-dimensional model.
Exergy study of co-firing processes of low-grade coal with oil palm kernel shell (as received, torrefied, pyrolyzed), in a brick furnace, using aspen plus.
by Edward Siza Antolinez, Carlos Alirio Diaz Gonzalez, Nidia Juliana Caceres Garcia, Angie Karina Castro Jerez
Abstract: Exergy analysis of substitution of low-grade coal by raw, pyrolyzed or torrefied oil palm kernel shell (PKS) was developed using simulation software. Different cases were carried out, comparing coal combustion base-case with co-firing cases with raw and pre-treated PKS. Exergy efficiencies values of pyrolysis and torrefaction processes agree with the reported data. An increase in the energy density of PKS after these processes leads to a decrease in fuel consumption compared to the base coal combustion case. Furthermore, an increase in air requirements for co-firing cases with pyrolyzed and torrefied PKS shows that using a high air excess, compared to the base case, high thermal power values can be obtained with lower flame temperatures, decreasing irreversibilities in combustion and burning bricks processes. However, considering pretreatment processes, total irreversibilities in pyrolysis cases are average 30% greater than the case base, contrasting with torrefied cases, where total irreversibilities are about 20% greater than the case base. Finally, the lower specific fuel consumption of torrefied cases, added to a lower increase in irreversibilities, suggests that torrefaction of PKS may be an option to replace low-grade coal in this type of furnace. An extension with environmental analysis is recommended to obtain a more comprehensive decision criterion.
Keywords: Exergy study; coal substitution; biomass; cofiring; pyrolysis; torrefaction; Aspen plus.
Energy, exergy, and economic analyses of an innovative hydrogen liquefaction process utilizing liquefied natural gas regasification system
by Saman Faramarzi, Seyed Mojtaba Mousavi Nainiyan, Mostafa Mafi, Ramin Ghasemiasl
Abstract: A novel hydrogen liquefaction cycle integrated with the liquefied natural gas (LNG) regasification system is proposed. The novelty of this study is based on two parts: first, the proposed cycle is a process integration of LNG regasification, steam methane reforming (SMR), and hydrogen liquefaction systems, and second, the proposed model is more efficient in terms of energy consumption than other similar cycles mentioned in the literature. The specific energy consumption (SEC) and the capacity of the optimized proposed model are 6.59 kWh/kg_LH2 and 371 tones per day, respectively. The sales price of liquid hydrogen as the product of the proposed cycle is $ 2/kg in 3 years payback period, making it economically viable. Energy, exergy, and economic analyses are implemented to analyze the proposed hydrogen liquefaction cycle. The optimized case undergoes 30% better performance by the genetic algorithm (GA) optimization method in terms of SEC than the base case.
Keywords: Exergy analysis; Hydrogen liquefaction; Economic analysis; Genetic algorithm; LNG regasification; Mixed refrigerant.
Analysis of a Kalina Cycle Integrated with a Reheat Furnace
by Sevgi Aslan, Cuma Karakus, Yildiz Koc, Huseyin Yagli, Ali Koc
Abstract: In the present paper, parametric optimisation, energy and exergy analyses of KC was performed together with economic and environmental analyses. After parametric, energy and exergy analyses of KC, maximum net power production, thermal efficiency and exergy efficiency of KC were calculated as 389.44 kW, 33.86% and 68.96% at 430
Keywords: Reheat furnace; Kalina cycle; waste heat recovery; economic analyses; environmental analyses; energy; exergy.
Conventional and enhanced exergy analyses of a parallel integrated thermal management system for pure electric vehicles
by Meijie Gao, Moran Wang, Kunfeng Liang, Chunyan Gao, Bin Dong, Lin Wang
Abstract: To improve the efficiency of the integrated thermal management system (ITMS) of pure electric vehicles, an enhanced exergetic analysis method was proposed. According to enhanced exergetic analysis, the exergy destruction distribution of main components of ITMS was detected in-depth, the internal factors arousing the exergy destruction of each component and the priority of component optimization can be recognized. The results indicate that the priority order of improving components of ITMS is the condenser, the battery evaporator, and then the cabin evaporator. The exergy destruction within the evaporator is entirely belonged to the endogenous part, and the exergy destruction of the condenser is mainly caused by the condenser itself, its endogenous exergy destruction (78.8%) is greater than the exogenous exergy destruction (21.2%). Meanwhile, the enhanced exergetic analysis suggested that the avoidable exergy destruction of the system accounts for about 68.7% of the total exergy destruction of the system, the potential for improvement of the system is huge. The interaction among the components is not strong, due to the 72.38% of exergy destruction in the system is endogenous.
Keywords: thermodynamics; ITMS; enhanced exergetic analysis; exergy destruction; pure electric vehicles.
Determining the effect of the turbocharger in a heavy-duty diesel engine using energy, exergy, sustainability and economic analysis
by Erdem Özyurt, Halil Ibrahim Topal, Mehmet Kopaç
Abstract: The experiments of the 16-cylinder turbocharged heavy-duty diesel engine operating with two different turbochargers were conducted at a constant speed and variable load conditions. Energy, exergy, sustainability and thermoeconomic analyses were performed at various operating loads to determine the best operating load of each turbocharger. Energy analysis indicated that the most heat loss occurred at exhaust gases in higher load. Exergy analysis pointed out that the most exergy destruction appeared in the engine block in all tests conducted. In addition, thermoeconomic and exergoeconomic parameters increased in higher load.
Keywords: Turbocharged diesel engine; energy-exergy analysis; thermoeconomics; sustainability.
Exergy diagnosis and performance analysis of a typical bagasse boiler
by Qianci Mo
Abstract: In this work, a model which derived from an equilibrium model was developed for the exergy analysis of a bagasse boiler. By comparison of model and experimental results, the reliability of model was proved. Based on the model, the effect of the process irresponsibility, exergy efficiency, and exergy improvement potential of the boiler were analyzed, and improvement measures were put forward.
Keywords: Exergy analysis; Bagasse; Boiler; Exergy destruction.
Parametric exergy analysis of a Two-Stage vapour compression cycle for freeze desalination comparing eco-friendly refrigerants
by S. Pavitran, Shrikant Jadhav, Suresh Gosavi
Abstract: The current work aims to analyse a two-stage vapour compression refrigeration(TSVCR) cycle for freeze desalination. In this system, a low-pressure reversible subsystem(LPS) performs simultaneous freezing-thawing. The high-pressure subsystem(HPS) ensures cycle thermal stability. A mathematical model is developed to evaluate energy and exergy performance. Three eco-friendly refrigerants(R1234ze(E), R1234yf and R1243zf) are considered and compared with R22. The results show COP ranging from 6.5 to 12.7, with a specific energy consumption of 8.2 to 14.8 kWh/m3 of freshwater. The highest exergy efficiency of 38.4% is reported for R1243zf, which is higher by 1-3%, compared to R22 and R1234ze(E). However, R1234yf exhibits 11.14% and 7.8% lower energy and exergy performance. The maximum exergy destruction arises from the low pressure compressor(29%) followed by the latent heat condenser(23%). The uncondensed refrigerant significantly affects the performance and thermal stability. The study shows R1243zf and R1234ze are good alternatives to R22 due to their better energy and exergy performance.
Keywords: Two-stage vapour compression; Freeze desalination; Exergy analysis; Eco-friendly refrigerants; Specific energy consumption.
EXERGOECONOMIC AND EXERGOENVIRONMENTAL ANALYSES OF THE PISTON AERO ENGINE: IN-CYLINDER APPLICATION
by Onder Altuntas, Elif Koruyucu
Abstract: In order to assess the amount of heat flow and losses in an energy system, it is essential to determine the shape and the direction of this flow. Thermodynamic analysis (combine with economical and environmental approaches) is an effective tool for this aim. To accurately determine the energy losses of a piston aero engine, such an energy system, the same calculation should be applied to each cylinder. Thus, the points that can be improved during the design and development phase can be clearly defined. This paper aims to show the energy-related economic and environmental parameters for each cylinder of a piston aero engine. This work was carried out in two phases of taxi (taxi-in and taxi-out). The maximum energy and exergy efficiencies of a piston aero engine were found to be 18.70% and 8.16%, respectively, during the taxi-in phase. The highest energy and exergy losses were observed in cylinder 2 the lowest exhaust temperature. The highest relative cost difference and the highest exergoeconomic factor were calculated as 385.62% (in cylinder 3) and 79.34% (in cylinder 4) in the taxi-in phase. The highest relative environmental difference and the highest exergoenvironmental factor were calculated as 147.27% (in cylinder 3) and 35.48% (in cylinder 4) in the taxi-in phase. As shown in exergoeconomic and exergoenvironmental analysis, the first parts to be improved are cylinder 3 and cylinder 4.
Keywords: piston-prop engine; exergoeconomic analysis; exergoenvironmental analysis; in-cylinder analysis.
Enhanced exergy analysis and optimization of a trigeneration system
by Sina Zandi, Atabak Fazeli, Kamyar Golbaten Mofrad, Gholamreza Salehi, Mohammad Hasan Khoshgoftar Manesh
Abstract: In this paper, an integrated trigeneration system including Brayton, organic Rankine, and ejector refrigeration cycles has been analyzed and optimized from energy, exergy, exergoeconomic, exergoenvironmental (4E) perspectives in summer and winter for decreasing destruction cost and environmental impact. The remarkable novelty of this work is environmental considerations, along with analyzing systems thermodynamically and economically. The results show that the amount of product in summer is higher than in winter while destruction of environmental impacts is lower. Exergy efficiency has been obtained at 24.3% and 23.6% in summer and winter, respectively.
Keywords: Trigeneration system; ejector refrigeration cycle; exergoeconomic analysis; exergoenvironmental analysis; waste heat recovery; advanced exergy analysis.
Exergy analysis of a novel concentrated photovoltaic - thermoelectric system
by Aminu Yusuf, Sedat Ballikaya
Abstract: Exergy analysis of a thermodynamic system is carried out to identify sources, causes and magnitude of both reversible and irreversible losses, and it is a useful tool used in improving the performance of a system. Herein, an exergy analysis of a novel concentrated photovoltaicthermoelectric system is presented. Results showed that losses increase with increase in the optical concentration ratio and at high optical concentration ratio, it is more beneficial to lower the efficiency temperature coefficient than to increase the energy conversion efficiency of the photovoltaic.
Keywords: concentrator; copper plate; exergy efficiency; hybrid system; irreversibilities; microchannel heat sink; optical concentration ratio; reference efficiency; photovoltaic; temperature coefficient; thermal resistance; thermoelectric module.
Effect of Edge Curvature on the Entropy Generation Rate in Micro/Nano Scale Flakes of Equal Area
by Saad Bin Mansoor, Bekir Sami Yilbas, Hussain Al-Qahtani
Abstract: Micro/nanoscale heat transport in low dimensional films remains vital in the design and sustainable operation of microelectronic devices. Heat conduction in 2D, microscale flakes of diamond with curvilinear geometry is investigated utilizing the phonon radiative transport model. The form of the equation for radiative phonon transport (EPRT) is arranged such that it applies to non-orthogonal coordinate systems. The entropy generation rate in a low dimensional film is formulated incorporating the phonon intensity distribution. Numerically-generated, body-fitted grids are used in the solution of the EPRT. In the procedure adopted, the phonon intensity distribution is predicted first and later used to compute the entropy generation rate. This procedure is repeated for various edge curvatures and the effect of changing curvature on the entropy generation rate is studied. It is found that increasing edge curvature results in a decrease of the total entropy generation rate per unit depth.
Keywords: Low dimensional films; phonons; microscale transfer; entropy; body fitted coordinates; metric tensor; radiative transport; EPRT; discrete ordinates method; numerical.
Energy and exergy analysis of a novel ejector-absorption combined refrigeration cycle using natural refrigerants
by Abhishek Verma, S.C. Kaushik, S.K. Tyagi
Abstract: This article presents the theoretical analysis of a unique ejector-absorption combined refrigeration system for producing low-temperature refrigeration at -25
Keywords: Transcritical CO2; ejector; waste heat; absorption refrigeration; exergy.
Thermal-hydraulic performance of constructal Y-shaped and X-shaped tube heat sinks in laminar flow
by Murat Aydin, Antonio F. Miguel, Devaneyan Solomon Nitesh, Eda Aydin
Abstract: The ability and efficiency to dissipate heat is strongly dependent on the design of heat exchanger. Bifurcating systems are the solutions to fundamental access-maximization problems. The performance of a forced-air heat sink with single Y-shaped, double Y-shaped and X-shaped configurations of tubes is investigated in this work. A 3-D numerical study is performed at Reynolds numbers (Re) ranging from 5 to 1500, under a constant heat source. The study mainly focuses effect of the design of tube configurations on both the thermal and hydraulic performances. Among these configurations the optimal thermo-hydraulic performance against Re is determined. The deposition of particles from flowing air on wall of tubes may be detrimental for both thermal and hydraulic performances. The effect of particle size and Re number on deposition rates is also investigated.
Keywords: cooling; heat dissipation; airflow resistance; thermo-hydraulic performance; bifurcating tubes; deposition of particles.
Energy and exergy analyses of skipped cycle mode in a single-cylinder engine fueled with diesel and natural gas
by Erdal Tuncer, Battal Dogan, Tarkan Sandalci, Dervis Erol
Abstract: In this study, performance and exhaust emissions were examined experimentally at different engine loads (25%, 50%, and 75%) at a constant speed of 1500 rpm using pure diesel before modifications and pure natural gas (NG100) after modifications. Furthermore, experimental studies were conducted under 2 Normal-1 Skipped cycle (2N1S) and 3 Normal-1 Skipped cycle (3N1S) conditions using pure natural gas as a fuel in a converted spark-ignition engine. In the present study, energy and exergy analyses were performed using the performance and exhaust emission values obtained from experiments. As a result of the energy analysis, effective thermal efficiency values of 39.46% and 34.37% were found in diesel and natural gas fuels, respectively, at an engine load of 75% without cycle skipping. It was observed that the effective thermal efficiency value reached the maximum value of 35.99% in case of cycle skipping in natural gas and at an engine load of 50%.
Keywords: natural gas; skipped cycle; pollutant emissions; energy analysis; exergy analysis.
Exergy and exergoeconomic analyses of an ORC-assisted vapor compression refrigeration cycle
by Nurettin Yamankaradeniz
Abstract: In this study, the thermodynamic performance of a vapor compression refrigeration cycle (VCRC) in which an organic Rankine cycle (ORC) has integrated and that generates electricity by utilizing a geothermal source is investigated. The systems energy and exergy performance has evaluated by using various refrigerants used in the ORC system, depending on the evaporator (ORC) temperature (70-120
Keywords: organic rankine cycle (ORC); vapor compression refrigeration cycle (VCRC); energy performance; exergy; exergoeconomic analysis.
Energetic and Exergetic Analysis of Optimum Insulation Thickness for Cold Storages
by Nuri Alpay Kürekci, Özlem Emanet
Abstract: In this study, the optimum insulation thickness of cold storage walls was calculated energetically and exergetically for five selected insulation materials, whose payback periods were calculated and compared. The effect of each materials unit volume price on the optimum insulation thickness and payback period was also examined. The values of the optimum insulation thickness for polyurethane, extruded polystyrene, rock wool, glass wool, and expanded polystyrene are 2.358.43 cm, 5.0116 cm, 5.8118.76 cm, 8.1024.40 cm, and 9.2828.08 cm, respectively, based on energetic analysis, and 0.087.73 cm, 0.9114.74 cm, 0.9717.26 cm, 2.0122.52 cm, and 2.2625.91 cm, respectively, based on exergetic analysis.
Keywords: Optimum Insulation Thickness; Cold Storage; Energy Saving; Thermo-Economic Analysis; Exergetic Analysis; Cooling Degree-Day Value.
Practical method for measuring exergy
by Ekaterina Yushkova, Vladimir Lebedev
Abstract: Today, the enthalpy method is most often used to study technological installations for energy efficiency. Exergy analysis gives the most complete and objective assessment of various types of energy. Study presents an experimental setup that simulates a heating system to which an exergy meter is connected. As a result of the experiment, it turned out that the amount of heat remains constant if the temperature difference between the inlet and outlet is constant. However, the exergy method showed that exergy increases with an increase in the inlet temperature (even with a constant temperature difference); therefore, fuel consumption also increases with an increase in the initial temperature. The heat meter was invented a long time ago, but the device for measuring exergy did not yet exist. The device will give an impetus for a more active development of exergy analysis.
Keywords: exergy; exergy measuring device; account of exergy in the heat supply system; exergoeconomic.
Thermodynamic analysis of a coal fired supercritical thermal power plant integrated with Molten Carbonate Fuel Cell powered by coal gasification.
by A.PRUTHVI DEEP, SUJIT KARMAKAR
Abstract: A detailed thermodynamic analysis is carried out to study the outcomes from a 500MWe steam power plant upon integrating Molten Carbonate Fuel Cell (MCFC). The modeling and analysis of the power plants are performed using a computer software program, Cycle Tempo. The proposed plant with Carbon dioxide (CO2) utilization factor, ? ??_f= 90%, has improved the steam power plants net energy efficiency by 17.87%. The integrated plant produces 724.11 MWe net power output with energy and exergy efficiencies of 37.91% (Higher Heating Value basis) and 34.69%, respectively.
Keywords: Energy; Exergy; High ash coal; Gasification; MCFC; CO2 utilization factor.
Exergy analysis of a coal-fired thermal power plant in Kangal district of Turkey
by Sevgi ERZEN, Halil Ibrahim ACAR, Oguzhan PEKTEZEL
Abstract: In this study, thermodynamic analysis of Kangal thermal power plant operating in Turkey was performed. Energy and exergy values of 35 points in the power plant were calculated. Energy and exergy equations of all components were derived to analyze the system performance. Exergy destruction, the second law efficiency and the efficiency defect were calculated for the system components. Also, the effect of ambient temperature on exergetic performance of the turbines and the condenser was analyzed. Results were presented in graphs. The boiler was determined as the equipment that caused the greatest exergy destruction with 91.7%. The second high pressure feed water heater showed the greatest second law efficiency with 94.39. Thermal and the second law efficiency of the power plant were found to be 32.8% and 52.6%, respectively. It was found that increase in ambient temperature had a positive effect on condenser while had a negative effect on turbines.
Keywords: Exergy analysis; Thermal power plant; Ambient temperature; Efficiency defect.
DETERMINATION OF OPTIMUM PV/T CONFIGURATION ON HORIZONTAL PLANE FOR MAXIMUM EXERGY OUTPUT
by Halit Bas, Atilla Biyikoglu, Birol Kilkis
Abstract: The optimization of PV/T flat-plate water collector groups depending on the variable values of mass flow rate, tube diameter, tube spacing and number of collectors was made based on exergy efficiency. Two different hydronic configurations, namely, series and series-parallel connection arrangements were investigated. A analytical model was developed to obtain exergy efficiencies. The results showed that when all other parameters were kept constant, the total exergy gain for any operating condition was higher at the series connected collector arrangement than at the series-parallel one.
Keywords: PV/T collector; collector configuration; exergy efficiency; exergy-based optimization.
Exergy evaluation of integrated liquefier-cryocondensation and cryosorption helium purification systems based on experimental data
by TRIJIT KUMAR MAITI, Sandip Pal, Balaram Kundu, Parthasarathi Ghosh
Abstract: The present investigation conducts on two different methods of cryogenic helium purification processes with the identical input (1.50%v/v N2 impurity) and output (grade 4.5). Accordingly, exergy analysis has been performed with experimental data on two kinds of commercial purifiers, viz. an integrated liquefier-purifier (cryocondensation) and a cryosorption purifier. The current study evaluates quantitatively the superiority of cryosorption purifier and assesses the exergy performance of helium liquefier on being integrated with different methods of purification systems. The key findings are useful for selecting, augmenting, and developing an efficient purification process.
Keywords: Helium; Purifier; Liquefier; Exergy; Energy; Cryo-condensation; Cryosorption; Specific Power Consumption; Figure of Merit.
ENERGY AND EXERGY ANALYSES OF AN AIR SOURCE HEAT PUMP OPERATING IN COOLING MODE
by Hayati Tore, Ali KILICARSLAN
Abstract: The energy and exergy analyses of a heat pump were experimentally carried out for refrigerants R134A, R404A, R407C. The effect of the environmental temperature (outdoor air temperature) between 25
Keywords: Heat pump; Coefficient of performance; Exergy destruction; Exergy efficiency; R134A; R404A; R407C.
Energy and Exergy Analyses of Passive Solar Still Augmented with Nanoparticles
by Vikas Kumar Thakur, Manoj Kumar Gaur
Abstract: The paper presents the comparative energy and exergy analysis of passive solar still (SS) with two different nanoparticles and without nanoparticles. The analytical expressions of condensing cover, base fluid, and basin liner temperature are developed for both the cases. The daily yield of the SS with plain water, ZnO and CuO nanofluid is 1620, 2305, and 3365 mL/m2 respectively. The diurnal energy efficiency with CuO nanofluid is 26.56% and 39.14% higher than the ZnO nanofluid and plain water respectively. Moreover, the diurnal exergy efficiency with CuO nanofluid is 42.67% and 107.76% more than SS with ZnO and without nanofluid respectively.
Keywords: Solar Still; Distillation; Energy efficiency; Exergy efficiency; Nanoparticles.
Energetic and exergetic investigation on a solar powered integrated system of ejector refrigeration cycle and Kalina cycle
by Ayman J. Alazazmeh, Abdul Khaliq, Shiv Lal
Abstract: Energetic and exergetic investigation of a solar powered system which simultaneously produce power and refrigeration is reported. Solar field is applied to drive the Kalina cycle bottoming with the ejector refrigeration cycle. Performance was analyzed after altering influencing operating parameters to investigate their effect on expander power, refrigeration load, exergy of refrigeration, energy efficiency, and exergy efficiency of the system. Results shows power output, energy efficiency, and the exergy efficiency of system increases while the energy and exergy of refrigeration are declined as the hot oil outlet temperature rises. Increase in concentration of ammonia-water basic solution results in the significant increase of expander power and increase in systems energy and exergy efficiency. From 100% energy supplied 25.4% appears as power and 10.52% produces as refrigeration, and rest 65.08% is lost. From 100% solar exergy supplied to system, 26.63% produced exergy, 1.85% is the exergy loss, and remaining 71.52% is destroyed.
Keywords: Solar power tower; Kalina Cycle; ERC; Energy; Exergy.
New Optimum Multi-Generation System Configuration for Cooling, Heating, Power, Natural Gas and Hydrogen Production
by Mojtaba Babaelahi
Abstract: One of the vital problems is access to energy systems that produce multiple products simultaneously. This paper aims to provide an optimal power plant that simultaneously generates cooling and heating loads, power, natural gas, and hydrogen. The proposed cycle includes various thermodynamic processes. The proposed system was evaluated using thermodynamics's first and second laws. In this research, Thermoflex software was used for system evaluation. Finally, multi-objective optimization is performed to achieve maximum efficiency.
Keywords: Cooling; Heating; Power; Hydrogen; Optimization.
Performance comparison of solar powered cogeneration and trigeneration systems via energy and exergy analyses
by Shadab Ahmad, Mohd Parvez, Tasmeem Ahmad Khan, Suhail Ahmad Siddiqui, Osama Khan
Abstract: The study focuses on the comparison of solar-operated cogeneration and trigeneration energy systems. The prime objective of the system is to develop a novel solar thermal driven combined heat and power system at the first stage and then to extend the concept for the simultaneous production of electric power, process heating, and cooling at the second stage. The computed results present the energetic output which increased from 58% to 63% while shifting the mode of operation from cogeneration to trigeneration. The combined setup for the trigeneration exhibited higher efficiency of 66.63% in comparison to the cogeneration setup of 34.5%.
Keywords: cogeneration; trigeneration; absorption refrigeration; exergy analysis; exergy destruction.
Exergy Analysis of a Hybrid Thermoelectric Generator/Two-Stage Double-Lift Aqua-Ammonia Absorption Cooling System
by Hamza Tahaineh
Abstract: Nowadays, absorption refrigeration cycles using renewable energy or waste heat are very attractive. A hybrid thermoelectric generator/two-stage double-lift ammonia-water absorption refrigeration cycle powered by an evacuated tube solar collector was examined. A detailed thermal analysis was carried out by means of the Engineering Equation Solver. The typical location to install a thermoelectric generator was found to be after the evaporator and desorber 2. The coefficient of performance improves from 0.2 to 0.5 when the temperature difference after desorber 2 is raised from 5
Keywords: Thermoelectric generator (TEG); Absorption Refrigeration System (ARS); Exergy; Coefficient of Performance (COP); Power.
Exergy Analysis of Purified Water Plant in a Pharmaceutical Industry
by Yigit Kupcu, Mahir Ince, Mahmut Bayramoglu
Abstract: Thermodynamic optimization of manufacturing plants at design or operation stages is known to be a complex process, resulting from the consideration of various design and operation parameters. Exergy analysis is an appropriate tool to implement the thermo-economical optimization of processes in a convenient way. In this study, exergy analysis was applied to a purified water plant in the pharmaceutical industry composed of various units such as ultrafiltration (UF), activated carbon columns, softener columns, reverse osmosis (RO), degasser, and continuous electro deionization unit (CEDI) process, and the exergetic efficiencies were found to be 75.47, 84.70, 64.78, 37.67, 96.88, and 85.50%, respectively. Considering the exergetic efficiency of the entire plant of 4.35%, significant opportunities are available to increase the energy and exergy efficiencies of this purified water plant by means of structural as well as parametric optimization tasks. By considering that most of the energy destruction in this plant stems from pump motors, especially in the RO unit, energy recovery devices such as pressure ex-changers and Pelton wheels may be used to increase the energy efficiency of the plant.
Keywords: desalination; exergy; pharmaceutical industry; plant performance.
Experimental investigation and analyses of CI engine fueled with different blends of waste plastic oil and diesel
by Amar Kumar Das, Sudhansu Sekhar Sahoo, Achyut Kumar Panda
Abstract: The present work focuses on the energy, exergy, and economic study of a compression ignition engine working with waste plastic oil (WPO). Blends like 10% to 30% by volume of WPO with diesel are prepared and investigated experimentally to evaluate the performance parameters. The thermal efficiency and exergetic efficiency are found to be increased by 3.38% and 6.92 % with an increase in WPO blend up to 20% compared to the neat diesel case. The cost rate of inlet fuel for WPO20 is found to be decreased substantially from that of diesel. Moreover, the Sustainability Index of WPO20 by 1.38% higher than diesel ensured the extended durability of the engine and lesser damage to ecological factors.
Keywords: Waste plastic oil; Compression ignition engine; Exergy analysis; Economic analysis; Sustainability index.
Special Issue on: CPOTE2020 The Energy System Beyond 2020 - Exergy Application in Assessment and Optimisation
Characterization of the Effect of Water Content on the Methanol Spray Combustion
by Chih-Yung Wu, Bo-Yi Hu
Abstract: The methanol spray combustion in the laboratory-scale combustor was experimentally studied in the present study, especially for the effect of the water content in methanol on the flame phenomena. The results showed that as the water content in the fuel mixture was less than 10%, and the flames can be sustained stably. The appearance of the flames was not significantly different for various water contents in the fuel mixture. However, the flame length was reduced by increasing water contents, but there was no apparent change in the flame lift-off height. The exergy efficiency was in the range of 18-21%. In addition, near flame extinction, the increase of specific exergy destruction can be found. As the water content in the fuel mixtures was increased by 10%, the exergy efficiency reasonably decreased by 9.98%, but the thermal efficiency reduced by 26.61%.
Keywords: spray combustion; methanol economy; exergy analysis.
Simultaneous thermodynamic and economic enhancement of heat pumps based on a new method for avoidable irreversibility assessment
by Volodymyr Voloshchuk, Paride Gullo, Olena Nekrashevych
Abstract: The paper presents a new method aimed at the simultaneous thermodynamic and economic enhancement of air-source and water-source heat pumps. The novel approach allows estimating the avoidable parts of the exergy destruction and investment expenditures by avoiding the need for ideal process introduction, being the most critical issue associated with the application of the existing advanced exergy-based methodology. In fact, within the proposed new method the values of the avoidable parts of investment expenditures of the k-th component belonging to the considered heat pumps are determined assuming a greatly efficient component rather than not an extremely inefficient one. The proposed approach was applied to domestic hot water heat pumps using R410A and R134a to evaluate its potential. The results obtained suggested that at the investigated operation conditions the condenser and the evaporator are components for which minimizing irreversibilities can provide simultaneous thermodynamic and economic enhancement.
Keywords: exergy analysis; avoidable exergy destruction; Heat pumps; component interactions; thermodynamic improvement; economic improvment; exergoeconomic analysis.
Energy and exergy analyzes of a cogeneration unit in an oil refinery: a case study
by Luiz Fernando Ferreira, Waldyr Gallo
Abstract: This case study performed energy and exergy analyses of a cogeneration plant in an oil refinery, generating 97.8 MW of electrical power and 885 t/h of steam at 485
Keywords: Energy Analysis; Exergy Analysis; Cogeneration Operation; Industrial Indicators.
Improving the operation of heat exchanger networks through exergy analysis
by Bahar Saeb Gilani, Tatiana Morosuk
Abstract: In this paper a procedure is introduced to compare alternative control configurations for the optimal operation of heat exchanger networks. The novelty of the proposed method lies on the exergy-based formulation of the optimization problem. The method uses the advantage of exergy analysis in quantifying the thermodynamic inefficiencies of heat exchangers and mixers as the fundamental elements of heat exchanger networks. Two different bypass placements are compared for an example heat exchanger network at steady state to illustrate the advantage of exergy analysis in understanding and improving the performance of the system. It is shown that in some cases solving the optimization problem based on energy does not indicate any differences between alternative design configurations. Whereas solving the optimization problem aiming at the minimum exergy destruction provides the missing information. For the studied heat exchanger network, while both designs require the same amount of heat utility, one design demonstrates around 25% less exergy destruction. It is also shown for the first time in this paper that applying exergy-based optimization reveals further room for the improvement of the heat exchange network operation. By readjusting the manipulated variables of the control system, the total exergy destruction of the heat exchanger network can be reduced by over 6% for both studied design configurations.
Keywords: Heat Integration; Heat Exchanger Network; Exergy Analysis; Optimal Operation; Control Configuration; On-line Optimization.
Exergy and economic assessment of renewable electricity generation from sugarcane straw for improved efficiency of sugarcane biorefineries
by Pablo Silva Ortiz, Daniel Flórez-Orrego, Adriano Pinto Mariano, Vyacheslav Kafarov, Silvio De Oliveira Junior, Rubens Maciel Filho
Abstract: The share of renewable resources in the Brazilian domestic energy consumption achieved 46% in 2019, out of which 18% corresponds to sugarcane-derived energy, whereas 11% is specifically related to sugarcane bagasse. Sugarcane and straw (i.e., sugarcane tops, dry and green leaves) represent useful energy inputs to the Brazilian electricity mix, often used as supplementary fuels in the cogeneration systems of sugarcane mills of first-generation (1G), autonomous (AUT, only ethanol) and annexed (ANX, both sugar and ethanol production). However, the collection and conversion of these energy resources are typically performed using inefficient conversion systems (< 30%), which impacts the overall performance of the production process. Hence, this work focuses on the revamp of existing sugarcane biorefineries and cogeneration units by using those byproducts, aiming to increase the selling of surplus electricity. Simulation processes are employed to denote incremental modifications related to sugarcane straw recovery achieved in the harvesting systems. In this regard, a techno-economic comparison is performed based on various indicators, namely, the exergy efficiency, unit exergy cost, and the irreversibility rate as thermodynamic performance criteria. This analysis allows identifying potential improvements in the sugarcane cogeneration plants. A sensitivity analysis is also carried out considering the main parameters related to the industrial plant scale, the operating period, the fraction of sugarcane straw consumed in the cogeneration plant, as well as other economic indicators. The results show that the straw recovery through harvesting systems may increase the surplus electricity by up to 30% when sugarcane biorefineries consider the maximum straw recovery fraction. Moreover, the increment in the exergy cost of the straw gathering influences the extended exergy efficiency of the cogeneration unit and, consequently, the entire sugarcane biorefinery. For example, when all of the recovery straw fractions are used the overall process efficiency could achieve a reduction in the AUEC of 13% (ANX) and 16% (AUX). Similarly, it was determined that using the straw fraction improves performance in the cogeneration system, resulting in AUEC reductions of 29% (ANX) and 25% (AUT), respectively. In conclusion, the capitalization on sugarcane residues may increase the contribution of this industry to the decarbonization of the Brazilian electricity mix and increment of profits/ incomes resulting from the negotiation of decarbonization credits (CBios) in the Brazilian sugarcane market.
Keywords: Exergy analysis; Sugarcane straw; Irreversibilities; Biorefinery performance.
Energy, Exergy, Economic, and Environmental Analyses and Multi-objective Optimization of Using Turbo-expanders in Natural Gas Pressure Reduction Stations
by Hossein Haghjoo, Emad Aram, Gholamreza Ahmadi, Davood Toghraie
Abstract: In this paper, the utilization of turbo-expanders (TEs) in natural gas pressure reduction stations (NGPRSs) is evaluated and optimized multi-objectively. A 4E (energy, exergy, economic, and environmental) analyses is conducted. In this regard, NGPRS of the Montazeri Power Plant in Iran is considered and simulated in Cycle-Tempo and MATLAB. Then, the exergy efficiency (?exergy) and the costs of electricity generation (Zelec) are selected as the objective functions and the system is optimized using the genetic algorithm approach. Results of the simulations indicate that in case of not using the TEs, about 23MW exergy will be lost during the throttling process. However, using the two TEs saves 18MW of the referred exergy. Also, it leads to the generation of about 121650 MWh green electricity per year. It prevents the emission of 65756 tons of CO2 and makes it possible to sell an approximate value of 294640 million Rials of electricity.
Keywords: Turbo-expander; NG Pressure Reduction Station; 4E analysis; CO2 Reduction; Multi-objective Optimization.
Special Issue on: TUBA WCEST-2021 The Role of Exergy in Energy Science and Technology
Exergy analysis and multiobjective optimization of ORC using NSGA-II
by Ashwni Ashwni, Ahmad Faizan Sherwani
Abstract: A detailed analysis of the organic Rankine cycle is carried out using environmentally friendly working fluids such as butane, isobutane, hexane, etc. in this study. Moreover, its performance is optimized using the non-dominated sorting algorithm-II. The results indicate that evaporator temperature and the condenser temperature have a major influence on the ORCs exergetic performance. ORC has an optimal exergetic efficiency of 60.49%, 1.6 years payback period with a $7846 life cycle cost using hexane.
Keywords: Exergy; Sensitivity; Organic Rankine cycle; NSGA-II.
Exergy Analysis and Multiobjective Optimization of ORC Using NSGA-II
by Mohammad Ali Sabbaghi, Mohammad Sefid
Abstract: In this paper, thermodynamic analysis and optimization studies are investigated on an ORC for multigeneration using geothermal and biomass energies. Results indicated that the ORC is responsible for 65% of the total exergy destruction rate. The produced hydrogen and freshwater rates are 1.264 lit/s and 5.9 kg/s, respectively. By increasing the temperature of the geothermal source from 400 to 430 K, the hydrogen and freshwater production rates increase to 19.6 and 17.6 %. If all energy is supplied by biomass, the amount of emitted CO2 will increase to 60.3%.
Keywords: Organic Rankine Cycle; Exergy; Environmental; Hydrogen; Desalination; Optimization.
Special Issue on: GCGW-21 Exergetic Assessment of Systems for Better Sustainability
Exergy, can it be used to reflect the environmental issues of a fuel?
by Yaning Zhang, Tao Liu, Mengmeng Guang, Wenming Fu, Bingxi Li
Abstract: Can exergy be used to reflect the environmental issues of a fuel? This article elaborates if and how exergy can be used to reflect the environmental issues of a fuel, and details the processes for some typical fuels. The results show that the exergy method can be well used to reflect the environmental issues of a fuel. The case studies further show that coal samples (1324.99-1437.47 kJ/kg) have higher total environmental impacts than the biomass samples (381.02-1078.81 kJ/kg), and the environmental impacts are mainly contributed by CO2 (52.72%-99.37%), followed by ash (0.18%-35.93%), SO2 (0%-11.77%) and NO2 (0.16%-8.75%).
Keywords: exergy; fuel; environmental issue; coal; biomass.
Exergetic assessment and exergoeconomic diagnosis of a sugarcane plant in northeastern Brazil
by Edmilson Junior, Carlos Santos, Markus Porangaba, Rafael Oliveira, Adriano Marques
Abstract: The increase in industrial needs increased the demand for fuels, electricity and the growth of climatic effects. This study performs an exergoeconomic evaluation in a sugar, ethanol and electricity production plant located in the Northeast of Brazil. The objective is to identify thermoeconomic inefficiencies, exergy destruction and efficiencies, determine the costs of exergy flows and a step by step of exergoeconomic diagnosis using the SPECO method. The results show the greatest inefficiencies presented in boiler 1 (48 MW, 28%), boiler 2 (43 MW, 25%) and boiler 3 (31 MW, 18%). The production of steam costs R$ 63.88 for each GJ of energy. The total cost of exergy destruction in the boilers is R$ 3808 per hour of operation which means about 84% of all exergy destroyed in the plant. The exergoeconomic diagnosis concludes that the equipment that needs optimization primarily are the deaerator (5904% rk) and the condenser (1674% rk).
Keywords: Exergoeconomic; Exergy Destruction; Specific exergy cost; Sugar cane; Thermodynamic analysis.