Relative Exergy Research Articles

Exergetic analysis of a domestic refrigerator with an innovative mini-channel flat tube condenser

In this study, the energetic and exergetic performance of a household refrigerator with a unique compact heat exchanger composed of a mini-channel flat tube condenser and offset strip fins (OSF) is investigated experimentally by considering varying amounts of R600a (48–64 g) and capillary tube lengths (2800, 3300, and 3800 mm). The experiments have been performed for two refrigerators involving two different innovative condensers composed of mini-channel flat tube and offset strip fins which have varying orientations instead of conventional wire-on-tube condensers. The experiments were conducted in a climatic chamber at a temperature of 25 ± 0.5°C. According to the standard of IEC 62552:2015, the target temperatures of the fresh food and freezer compartments are set at 4°C and −18°C, respectively. Specific and relative exergy destructions of each component, total exergy destruction, the coefficient of performance, and second-law efficiency of the overall system with two different mini-channel condensers are reported for varying amounts of refrigerant and capillary tube lengths. The major concern of the investigation is to reveal the key components contributing to the degradation of the overall performance of the unique design. It is observed that the evaporator, which has a ratio of 52–69% in total exergy destruction within all investigated cases, is the most exergy destructive component and the exergy destruction of the evaporator decreases when the amount of R600a increases. The mini-channel condensers are the second exergy destructive components with a ratio of 19–22%. As an important outcome of this unique design’s investigation, exergy destruction of the condenser and compressor does not show a monotonic change with respect to the refrigerant amount and capillary length. Besides, the highest coefficient of performance and second-law efficiency are obtained when the amount of R600a is 48–50 g in all three capillary tube lengths.

Thermoeconomic analysis of the IWERS system for steam heat recovery from bakery ovens

AbstractThe integrated waste energy recovery system (IWERS) recovers heat from bakery ovens in supermarkets and other commercial facilities to heat domestic hot water, resulting in energy savings. This article presents a thermoeconomic analysis of the system's operation in a supermarket over the course of 1 year. The study shows that exergy destruction in IWERS is directly proportional to ambient temperature. During the hottest months of the year, IWERS experiences a 4% decrease in exergy performance, while the exergy unit cost of the product increases by up to 4.2%. Additionally, the steam condenser is responsible for the highest relative exergy destruction, reaching almost 45%. Moreover, the addition of equipment upstream of the process increases the exergy cost of production due to the destruction of exergy in the equipment. These results provide valuable information with important implications for energy efficiency, economic savings, and sustainability. Improving system efficiency would generate substantial benefits in energy savings, economic savings, and environmental impact for all commercial and industrial establishments that use bakery ovens.

Performance Analysis of Waste Biomass Gasification and Renewable Hydrogen Production by Neural Network Algorithm

Abstract This study assesses renewable hydrogen production via gasification of residual biomass, using artificial neural networks (ANNs) for predictive modeling. The process uses residues from sugarcane and orange harvests, sewage sludge, corn byproducts, coffee remnants, eucalyptus remains, and urban waste. Simulation data from aspen plus® software predict hydrogen conversion from each biomass type, with a three-layer feedforward neural network algorithm used for model construction. The model showed high accuracy, with R2 values exceeding 0.9941 and 0.9931 in training and testing datasets, respectively. Performance metrics revealed a maximum higher heating value (HHV) of 18.1 MJ/kg for sewage sludge, the highest cold gas efficiency for urban and orange waste (82.2% and 80.6%), and the highest carbon conversion efficiency for sugarcane bagasse and orange residue (92.8% and 91.2%). Corn waste and sewage sludge yielded the highest hydrogen mole fractions (0.55 and 0.52). The system can reach relative exergy efficiencies from 24.4% for sugarcane straw residues to 42.6% for sugarcane bagasse. Rational exergy efficiencies reached from 23.7% (coffee waste) to 39.0% (sugarcane bagasse). This research highlights the potential of ANNs in forecasting hydrogen conversion and assessing the performance of gasification-based renewable hydrogen procedures using biomass wastes.

Relative exergy and energy analysis of DI‐CI engine fueled with higher blend of Azadirachta indica biofuel with n‐butanol and NiO as fuel additives

AbstractAlternate fuels are in high demand for current engines and such fuels are studied both property‐wise and tested as fuel in the current engines. In current work, diesel engines are studied for higher blend Neem (Azadirachta indica) biodiesel (NB) as fuel, and fuel additives such as n‐butanol and NiO nano additives are chosen. Experimentation was performed on the experimental stationary engine which is coupled to eddy current dynamometer for four test fuels under varying fuel injection timings. Four test fuels were chosen for experimental studies which are Diesel 90% (vol %) + n‐butanol (10%), pure Neem biodiesel, NB 90% (vol %) + n‐butanol (10%), and Neem Biodiesel 90% + 25 ppm of nickel oxide dissolved in solvent. The synthesis of nickel oxide nano additives was done using a homogenous grinding method and XRD, FESEM, and EDS characterization signifies the presence of NiO. The Neem biodiesel was derived from base catalytic process and was studied using Gas Chromatography and Mass Spectroscopy apparatus for its chemical composition. The experimentation results which were focused were on the energy, exergy derived, and expenditure at varying fuel injection timings. The exergy and energy usage were almost similar in nature and entropy produced during the chemical‐to‐mechanical energy transfer reduced with the advancement in fuel injection timing to 27° bTDC for Diesel 90% + Bt.10%, NB90 + Bt.10% and NB100 + 25 ppm of NiO by 2.2%, 2.9%, and 4.6% respectively. Also, the exergy destruction retarded when with advancement in fuel inlet timing to 27° bTDC by 2.1%, 3%, 6.2%, and 6.8% for the same fuels, respectively.

High-efficiency utilization of biomass and seawater resources based on a distributed system with SOFC-assisted CO2 capture: Feasibility analysis and optimization

This paper develops a distributed system with SOFC-assisted carbon capture (SACC) by integrating the Rankine cycle, double-effect absorption chiller and multi-effect distillation unit to produce electricity, cooling and freshwater. To study the feasibility of the developed system, thermodynamic, economic and carbon footprint analyses and optimization are conducted on six different cases for the system. The results reveal that regardless of the biomass sources used as fuel, the developed SACC system requires 5%-9% less power consumption for CO2 capture compared to traditional methods. Moreover, the system fueled by switch grass exhibits superior efficiencies, and the system thermal efficiency (ηth) with SACC achieves 56.35% with corresponding levelized cost of products (cp) and total global warming potential (GWPt) of 54.94 $/GJ and −0.129 kg/kWh. Exergy analysis demonstrates that the prime mover unit (PMU) deserves the greatest irreversibility for all cases with a relative exergy destruction rate (y*k) of over 65% of the whole system. Within the PMU, the gasifier and SOFC are responsible for the highest irreversibility, and the y*k of the gasifier is over 50% and the SOFC’s is close to 9%. The parameter study indicates that an increase in the gasification temperature is unfavorable to ηth, however, it is conducive to the improvement of net power output (Wnet) when the temperature exceeds a certain value (e.g., 914.3℃ and 885.7℃ for Case-5 and Case-6). An appropriate increase in current density improves ηth and Wnet, and reduces cp, albeit slightly detrimental to environment. The optimization results demonstrate that Case-2 and Case-6 have superior thermodynamics and economics but are detrimental to the environment. In contrast, Case-1 and Case-5 are the most environmentally friendly, but their economics and thermodynamics are degraded to some extent.

Thermodynamic and economic analysis of a novel multi-generation system integrating solid oxide electrolysis cell and compressed air energy storage with SOFC-GT

Traditional gas-fired power plants are characterized by low efficiency and challenges in peak regulation. Even with the incorporation of compressed air energy storage, they still exhibit deficiencies in flexibility during peak load regulation. In this paper, we propose a novel hybrid power system based on gas-fired power plants, capable of producing electricity, heat, and hydrogen, while achieving flexible peak load regulation. The system is comprehensively evaluated using energy analysis, exergy analysis, and economic analysis. Results show that the total energy efficiency and exergy efficiency of this hybrid power system perform well, surpassing existing research on fuel cell-gas turbine systems. Among the subsystems, the fuel cell contributes the most to the total energy output of the hybrid system but also incurs the highest exergy losses, while the relative exergy losses of the water electrolysis and compressed air energy storage systems are relatively small. The configuration of dual energy storage systems enhances the flexibility in peak load regulation. Additionally, the proposed hybrid system exhibits low carbon emissions of 0.08 to 0.12 t/GJ. Considering factors such as discount rate, the initial investment cost can be recovered in 5.81 years, and the calculated net present value is 492,275.82 k$. Thus, the proposed scheme also possesses certain advantages in terms of economic feasibility.

Comparison of an absorption-compression hybrid refrigeration system and the conventional absorption refrigeration system: Exergy analysis

This paper presents an exergy analysis considering different operating conditions of an alternative configuration of an ammonia-water hybrid absorption refrigeration system, where part of condensation heat is recovered and supplied to generator (RCHG-ARS). In order to identify and quantify the irreversibilities in each component of the cycle and its variations, the exergy efficiency and the relative exergy loss of the system were evaluated. Moreover, the results obtained were compared with those obtained by the conventional ARS cycle. Furthermore, the effect of the internal heat exchanger effectiveness on the exergy efficiency and relative exergy loss was analyzed. The results indicate that the generation temperature and the exergy efficiency of the RCHG-ARS cycle decrease in 24 °C and 30%, respectively, it in comparison to ARS cycle at the conventional generation pressure (11.67 bar). However, to decrease the generator pressure at 5.94 bar, the evaporation temperature for the RCHG-ARS decreases in 19.3 °C and the exergy efficiency can be 0.20% higher than the obtained with the ARS cycle. It is also revealed that the exergy efficiency for the RCHG-ARS cycle become more significant at lower condensing and evaporating temperatures as well as lower generator pressures and higher internal heat exchanger effectiveness respect to ARS cycle. Moreover, the minimum values of relative exergy losses are obtained at higher generator temperatures or lower evaporating and condensing temperatures in the RCHG-ARS cycle. Finally, it can be concluded that the main components that increase the relative exergy destruction in the RCHG-ARS cycle are the generator, absorber and the compressors.

Dealing with Aspects of Performance and Environmental Impact of Aircraft Engine with Thermodynamic Metrics

The limited energy source indicates the necessity of efficient energy consumption in every field of life. Especially, the prompt growth in aviation sector makes this issue more important. In this study, effects of power settings on several thermodynamic indicators regarding low by-pass turbofan engine (LBP-TFE) are investigated. For this aim, the energy and exergy analyses are implemented to the system of turbofan engine for eighteen operating points. According to performance analysis, thrust value of the LBP-TFE changes from 10.77 kN to 71.8 kN throughout RPM values. According to exergetic findings, relative exergy losses from Fan outlet decreases from 52.34 % to 30.58 % whereas exergy efficiency of the LBP-TFE increases from 10.9 % to 30.1 %. Considering improved exergy efficiency, it changes 25.03 % and 41.03 % at the same RPM intervals. As for environmental assessments, environmental effect factor (EEF) of LBP-TFE diminishes from 5.8 to 1.32 while ecological effect factor decreases from 9.16 to 3.31. Finally, specific irreversibility production of LBP-TFE decreases from 0.4811 MW/kN and 0.2716 MW/kN. Considering these outcomes, behaviour of the investigated metrics regarding main components is different from each other. Therefore, the results of these parameters calculated for the whole engine could help understanding optimum running point in terms of exergetic and environmental sustainability.

Laminar forced convection in a tube with a nano-encapsulated phase change materials: Minimizing exergy losses and maximizing the heat transfer rate

The present work investigates the potential of NEPCM mixtures via analyses of convective heat transfer and exergy losses, and trade-offs between them inside a tube with a constant wall temperature. Experimental data for viscosity and thermal conductivity of the mixture was used within numerical simulations over a broad range of dimensionless parameters, including Reynolds number, mass fraction, melting strength, phase change zone thickness, and location of phase change zone. The effect of these parameters on the melting process, convective heat transfer and exergy loss is evaluated. The findings indicate that, although employing a NEPCM can boost the Nusselt number and heat transfer rate by 9.3 % and 16.1 %, as compared to the water, the exergy losses were enhanced up to 17 %. Additionally, in some circumstances, the Nusselt number and heat transfer rate both increased by 5.9 % and 2.5 %, respectively, whereas the exergy losses were zero. An optimal value of ω=0.02 was found to provide reasonable improvement in heat transfer rate increase with no exergy losses. Importantly, the present study shows that although higher NEPCM mass fractions can continue to increase the heat transfer performance, their benefit is rapidly offset above ω=0.02 due to heat transfer related exergy losses. Additionally, it was concluded that, in comparison to other parameters, the location of the phase change and the mass concentration of NEPCMS substantially affected the percentage of molten NEPCM and the latent heat efficacy.

Exergoenvironmental evaluation of kalina power generation system

ABSTRACT The basic needs of man are food, clothing, and shelter besides air and water. In providing these needs, power generation systems play a crucial role. Day by day, for various reasons such as explosion of population, the demand for power is increasing tremendously. Power generation systems need to generate more power. A novel power generation system suitable for recovering waste heat at a medium temperature range is examined in the present work. To assess the performance of a power generation system, energy and exergy measures are necessary. Energy measures provide enough details about the performance of the system. To know the systematic performance analysis, detailed exergy analysis alternatively profound as advanced exergy analysis and environmental impact are to be investigated. Exergoenvironmental analysis on the proposed Kalina power generation system has been carried out under hot sink conditions. Considering the proposed decision variables relative exergy destruction (ĖD/ĖP), relative environmental impact (Ẏ/ĖP), and relative investment cost (Ż/ĖP), the performance of the system has been assessed. The exergy destruction and the destruction cost rate of 29.23 kW and 0.478 $/hr at turbine inlet conditions of 185°C and 45 bar have been achieved. The exergoenvironmental factor fb and the relative difference rb have revealed that the components with high environmental impact have to be minimized. Turbine and HE4 are the components that contribute to higher total exergy and devise related impact on the environment.

Energy and Exergy Analysis of Vapor Compression Refrigeration System with Low-GWP Refrigerants

In this paper, a first- and second-law analysis of vapor compression refrigeration is presented to estimate and propose the replacement of R134 with working fluids having less global warming potential (GWP) and less exergy destruction and irreversibilities. Six different refrigerants were studied, namely, R717, R1234yf, R290, R134a, R600a, and R152a. A thermodynamic model was designed on Engineering Equation Solver (EES) software, and performance parameters were calculated. The model was deployed on all six refrigerants, while the used output parameters of performance were cooling capacity, coefficient of performance, discharge temperature, total exergy destruction, relative exergy destruction rates of different components, second-law efficiency, and efficiency defect of each component. The performance parameters were estimated at different speeds of the compressor (1000, 2000, and 3000 rpm) and fixed condenser and evaporator temperatures of 50 °C and 5 °C, respectively. The isentropic efficiency of the compressor was the same as the volumetric efficiency, and it was taken as 75%, 65%, and 55% at the compressor speeds of 1000 rpm, 2000 rpm, and 3000 rpm, respectively. A comparison of the performance parameters was presented by importing the results in MATLAB. It was found that the compressor had the highest exergy destruction compared to the other components. It was found that R152 was the refrigerant with zero ozone depletion potential (ODP) and a GWP value of 140 with less exergy destruction and irreversibilities. Moreover, it was easy to use R152a with good thermodynamic characteristics. It is estimated that R152a is a suitable replacement for R134a, as it can be used with few modifications.

EKSERJİ ANALİZİ İLE BİR AKIŞKAN YATAKLI KAZANIN İYİLEŞTİRME OLANAKLARININ TESPİT EDİLMESİ

In this study, a circulation-type fluidized bed boiler's exergy performance in a power generation plant was investigated. The boiler was examined not as a whole but by dividing it into its sub-systems. In the analysis, the sub-systems' exergy performance was evaluated in terms of criteria such as exergy efficiency, exergy destruction, fuel depletion ratio, relative exergy destruction ratio, exergetic improvement potential, and productivity lack ratio. In addition, the effect of different dead state temperatures on these exergy performance criteria is compared and discussed. As a result of the analysis, the highest exergy efficiency was achieved in the furnace with 80.2% at 6℃, while the highest exergy destruction occurred in the furnace as 18,118.9 kW at 27℃. The highest exergetic improvement potential was realized in Economizer-II with 11,593.82 kW at 6℃, and the lowest in Economizer-I at 27℃ with 631,9 kW. The effect of the increase in the dead state temperature on the exergy performance criteria applied to boiler sub-systems was variable. It showed its effect as an increase in some sub-systems and a decrease in others.

Energy-exergy analysis of an integrated small-scale LT-PEMFC based on steam methane reforming process

This study reports a novel integrated system for power generation with on-site produced hydrogen and heat recovery. The main equipment of the integrated system includes a steam methane reforming (SMR) reactor for hydrogen production, a palladium membrane (Pd-M) unit for hydrogen purification, a waste heat collector (HC) unit for heat recovery, and a low-temperature proton exchange membrane fuel cell (LT-PEMFC) for power generation. ASPEN Plus and MATLAB/Simulink jointed simulation model is used to establish an accurate model for the whole integrated system. Moreover, for the SMR reactor, it is found that the RPlug reactor simulation module is more appropriate compared with the RGibb module. Then a detailed parametric analysis is carried out to estimate the effects of hydrogen utilization, the SMR reactor operating temperature, and the current density of the PEMFC stack on the overall energy and exergy efficiency of the integrated system. Finally, thermodynamic analysis is performed on the integrated system with S/C of 3.0, SMR reaction temperature of 700 °C, PEMFC hydrogen utilization rate of 0.8, and power generation of 520 W, delivering energy and exergy efficiencies as high as 47.4% and 45.7% under these operating parameters. The thermodynamic analysis shows that the PEMFC stack is the primary source of the system exergy destruction (326.27 W) with 34.33% of the relative exergy destruction ratio.

Impact of different fuel usages on thermodynamic performances of a high bypass turbofan engine used in commercial aircraft

In this study, energy, exergy, and sustainability analyses are performed for the PW4056 engine to observe the different fuel effects on the thermodynamic performance of a turbofan engine. For this purpose, energy and exergy analyses are performed at the same dead state conditions, and then sustainability analyses are conducted for kerosene and hydrogen-powered engine and its main components. Also, nineteen thermodynamic performance metrics are adapted for the purpose of the study and used to compare the fuel performances. It is found that the fuel mass flow of the hydrogen fuel (1.03 kg/s) is lower than the kerosene fuel (2.85 kg/s), the exhaust gases mass flow of the hydrogen fuel (117.14 kg/s) is lower than the kerosene fuel (118.96 kg/s). The minimum exergy efficient component is determined as the combustion chamber in both cases, which are 64.24 % for kerosene case and 58.20 % for hydrogen case. The lowest relative exergy loss ratio is calculated to be 28.28 % for Fan outlet loss for hydrogen case, while the maximum relative exergy consumption ratio is calculated to be 51.93 % for combustion chamber for hydrogen case. The maximum productivity lack ratio is computed as 161.65 % for combustion chamber for hydrogen case, whereas the minimum relative fuel exergy waste ratio is computed as 0.02 % for high pressure turbine for hydrogen case, The highest exergetic improvement potential rate is obtained to be 24231.48 kW for combustion chamber for hydrogen case, while the lowest product ratio indicator is found to be 17.03 % for low pressure compressor for kerosene case. Furthermore, the minimum exergetic sustainability index is obtained to be 1.39 for the combustion chamber for the hydrogen case, whereas the maximum environmental effect factor is obtained to be 0.72 for combustion chamber for hydrogen case. On the other hand, with the usage of hydrogen fuel; it is observed that the exergy efficiency of the overall engine decreases from 26.9 % to 24.3 %, the ecological effect factor of the overall engine goes up from 3.712 to 4.113, the exergetic sustainability index of the overall engine rises from 0.321 to 0.369, and the waste exergy cost flow of the overall engine increases from 17.41 × 10 −3 US$/kW to 19.09 × 10 −3 US$/kW.

Higher heating value, exergy, pyrolysis kinetics and thermodynamic analysis of ultrasound-assisted deep eutectic solvent pretreated watermelon rind biomass

The higher heating value (HHV) and exergy of ultrasound-assisted deep eutectic solvent pretreated watermelon rind (WMR) biomass were investigated. Thereafter, the co-pyrolysis of the WMR biomass and coal blends was studied. The pyrolysis kinetics and thermodynamic parameters of the WMR-coal blends were determined using four isoconversional models (Flynn-Wall-Ozawa, Kissinger-Akahira-Sunose, Friedman and Starink). The HHVs of the pretreated WMR ranged between 12.73 and 19.28 MJ/kg, while the exergy value for the raw and pretreated WMR were 16.08 and 21.55 MJ/kg, respectively. The lower heating value related exergy had the greatest influence on the overall exergy of the WMR. The values of the pre-exponential factor showed variations in wide range, and the change in entropy of the system displayed both negative and positive entropies. The activation energy and enthalpy varied directly with the amount of coal in the blends. Amongst the isoconversional model methods, Friedman model was the best predictor of the kinetic parameters.

Combined biomass gasification, SOFC, IC engine, and waste heat recovery system for power and heat generation: Energy, exergy, exergoeconomic, environmental (4E) evaluations

A novel hybrid system using biomass as fuel for both power and heat generation, which consists of biomass gasification unit, solid oxide fuel cell, homogeneous charge compression ignition engine and waste heat recovery unit, is proposed in this work. Based on the modeling, the system is comprehensively evaluated by multiple approaches including energy, exergy, exergoeconomic and environmental analyses. It is found that the overall energy efficiency and exergy efficiency of the hybrid system could reach up to 68% and 51%, both of which are comparable to those of other reported hybrid fuel cell systems. The exergy destruction of the gasifier is the largest whose relative exergy destruction is up to 21.5%. The component of fuel cell contributes to 71% of the total power but with small relative exergy destruction. On the contrary, the HCCI engine contributes to less power but has larger exergy destruction compared to SOFC. The exergoeconomic analysis showed that the fuel cell component has a high exergoeconomic factor of 98.09% due to the large capital investment cost. By comparison, the component engine has much lower exergoeconomic factors of 5.41%. The cost of exergetic product of the hybrid system is 9.7 $/GJ. Besides, the proposed hybrid system presents a low carbon dioxide emission of about 0.119 to 0.139 t/GJ, which indicates few environmental impacts for the system. These results reveal that the proposed biomass-fueled hybrid system is high-efficiency, low-cost and clean for both power and heat generation, which could be promising candidate as advanced energy conversion technology in practical applications.

Energy and exergy analyzing of a wind turbine in free stream and wind tunnel in CFD domain based on actuator disc technique

Abstract In this article, the effects of a wind tunnel on the MEXICO wind turbine experiment based on a generalized Actuator Disc model and the second law of thermodynamics are investigated. In this model, both Computational Fluid Dynamic (CFD) and a developed User Defined Function (UDF) code are used to simulate the wind turbine’s performance in both wind tunnel and free stream modeling. Metrological variables such as ambient pressure and temperature, velocity, and specific humidity are considered to analyze the wind turbine’s performance. The maximum relative exergy efficiency difference between the wind tunnel and free stream at the wind speed of 16 m s-1, is 7.01%. Also, pressure, temperature and relative humidity, which mainly are neglected in energy analysis, have a considerable effect on wind turbine performance in both wind tunnel and the free stream conditions. It is shown that the combination of the actuator disc and the second law of thermodynamics provides a better insight compared with the first law analysis; therefore, it provides an appropriate approach for wind power simulation.

Exergetic Analysis and Exergy Loss Reduction in the Milk Pasteurization for Italian Cheese Production

The cheese industry has high energy consumption, and improvements to plant efficiency may lead to a reduction of its environmental impact. A survey on a sample of small-medium Italian cheese factories was carried out in order to assess the efficiency of heat recovery of the milk pasteurization equipment for the cheese production. Then, an exergetic analysis to calculate the related exergy loss was carried out together with a cost-benefit analysis to identify the optimized value of the heat efficiency. The exergy loss reduction was determined throughout an exergy analysis that takes into account this last value and the comparison with the previous exergy losses. Finally, the feasibility and the consequent additional reduction of exergy losses were verified, if a cogeneration heat and power (CHP) combined to the pasteurization equipment is assumed. Results show a current heat recovery efficiency of 93.2% in the Italian cheese factories; a close connection between the exergetic losses and the efficiency of the heat recovery exchanger; the optimized recovery efficiency equal to 97.3% obtained from the cost-benefit analysis; a related important exergetic loss reduction of −45% in the heat exchangers, as a second result of the exergetic analysis; a similar reduction of the exergy loss (−42%) of the whole system, as a third result of the exergetic analysis; a total exergy loss reduction of 22.9 kJ kg−1milk, which corresponds to a lower environmental impact due to CO2 reduction; a further reduction of the exergy loss of −10% when the cogeneration heat and power CHP are used.

Thermodynamic performance assessment of solar-based combined power and absorption refrigeration cycle

Concentrated solar power technology has gained rapid pace in the area of sustainable energy. In recent years concentrated solar power is being appreciated worldwide as they effectively convert available solar energy to its true potential resultant energy. In this context, the principal objective of this research is to develop a model driven on solar thermal integrated with a cogeneration cycle. The effect on power generation was noted by varying parameters such as DNI, turbine inlet pressure, mass flow rate of molten salt and turbine entrance temperature was ascertained on energy and exergy efficiencies of cogenerated driven cycle. From the results it was observed, a gradual growth at turbine entry pressure ranging between 180 bar to 220 bar causes an eventual rise in first law related efficiency and exergy related efficiency of Rankine and cogeneration cycle from (31.115% to 31.44%; 42.05% to 42.56%) and (42.03% to 42.14%; 56.04% to 56.55%).

Exergy analysis for the multi-effect distillation - reverse electrodialysis heat engine

Reverse electrodialysis (RED) heat engine is a novel technology to convert low grade heat into electricity. Through combining the multi-effect distillation (MED) with RED, the so-called MED-RED heat engine has received increasing attention over the recent years. In this paper, a comprehensive theoretical exergy analysis for the MED-RED heat engine has been carried out based on a validated mathematical model. And the influences of relevant operation and design parameters on the exergetic performance of the heat engine were investigated. The results showed that the preheater, condenser and RED unit were main sources of exergy destruction in the heat engine. The total relative exergy destruction of these three components was 59.8% and the exergetic efficiency of the heat engine reached 4.7% under the design condition. Moreover, elevating the temperature of hot water had a negative effect on enhancing the exergetic performance of the heat engine. On the contrary, increasing the concentration of initial brackish solution or the number of effect evaporators in the MED was helpful for improving the exergetic performance of the heat engine. Finally, discussion in terms of improving the exergetic performance of the heat engine was carried out and relevant approaches were presented.