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Hydrogen as an energy vector is seen as a key for the energy transition. Recently, more than 30 countries have launched their hydrogen strategies and roadmaps. Hydrogen storage and transportation are challenging steps of the hydrogen economy since all available options have significant drawbacks. This paper evaluates a power-to-liquid hydrogen process; the system is “charged” with electricity from renewable sources to produce hydrogen via water electrolysis; the produced hydrogen gas is liquefied and stored at ambient pressure and cryogenic temperature. The purpose of this paper is to report the first evaluation results of a system including a polymer electrolyte membrane electrolyser and a hydrogen liquefier. The evaluation was conducted using exergy-based methods, i.e. exergetic, exergoeconomic and exergoenvironmental analyses. The process of hydrogen liquefaction was simulated with the aid of the Aspen Plus software. The exergetic efficiencies for the liquefaction process and for the electrolyser are 42% and 47%, respectively. While the total exergetic efficiency of the power-to-liquid hydrogen system amounts to 44%. The total exergy destruction for the liquefier amounts to 9.3 MW and for the polymer electrolyser membrane electrolyser amounts to 19.3 MW. The electrolyser followed by the hydrogen compressors were identified as the components with the highest exergy destruction values and investment costs, while the compressors and the recuperators account for the highest exergoenvironmental impact. The sensitivity analysis shows that the specific liquefaction cost of hydrogen strongly varies with the electricity price and the cost of green hydrogen.

The design of solid oxide fuel cells (SOFC) using biogas for distributed power generation is a promising alternative to reduce greenhouse gas emissions in the energy and waste management sectors. Furthermore, the high efficiency of SOFCs in conjunction with the possibility to produce hydrogen may be a financially attractive option for biogas plants. However, the influence of design variables in the optimization of revenues and efficiency has seldom been studied for these novel cogeneration systems. Thus, in order to fulfill this knowledge gap, a multi-objective optimization problem using the NSGA-II algorithm is proposed to evaluate optimal solutions for systems producing hydrogen and electricity from biogas. Moreover, a mixed-integer linear optimization routine is used to ensure an efficient heat recovery system with minimal number of heat exchanger units. The results indicate that hydrogen production with a fuel cell downstream is able to achieve high exergy efficiencies (65–66%) and a drastic improvement in net present value (1346%) compared with sole power generation. Despite the additional equipment, the investment costs are estimated to be quite similar (12% increase) to conventional steam reforming systems and the levelized cost of hydrogen is very competitive (2.27 USD/kgH2).

In this study, parametric cycle analysis of a conceptual turbojet engine with an afterburner (TJEAB) was conducted at sea level conditions-zero Mach. Based on this analysis, exergetic sustainability parameters of TJEAB were scrutinized for military mode (MM) and afterburner mode (ABM). Constitutively, several design parameters of TJEAB were chosen so as to optimize performance and exergetic parameters which consist of specific fuel consumption (SFC), overall efficiency, exergy efficiency, environmental effect factor (EEF) and exergetic sustainability index (ESI). In this context, compressor pressure ratio (CPR), turbine inlet temperature (TIT) were preferred due to high effect of these variables on engine performance. CPR ranges from 4 to 11 whereas TIT varies from 1150 K to 1550 K. According to optimization of performance parameters, minimum SFC was achieved as 28.59 g/kN.s at MM and 43.95 g/kN.s at ABM. On the other hand, maximum overall efficiency is determined as to be 13.07 % at MM and to be 8.5 % at ABM. As for exergetic parameters, exergy efficiency was calculated as maximum with 30.85 % at MM and 23.2 %at ABM. Finally, maximum exergetic sustainability index of TJEAB was computed as 0.446 at MM and 0.269 at ABM. It is thought that energetic and exergetic parameters analyzed in this analysis could guide in designing turbojet engines in terms of lower fuel consumption thereby environmental-benign.

Water scarcity threatens human life and it is likely to be a main concern in the next century. In this work, a novel multigeneration system (MGS) is introduced and assessed with energy, exergy, and economic analyses. This MGS includes a gas cycle, multieffect distillation, an absorption refrigeration cycle, a heat recovery steam generator, and electrodialysis. Electrodialysis is integrated into this configuration to produce sodium hydroxide and hydrogen chloride from brine to prevent its release to the environment with harmful impacts. The other products are electricity, cooling, and demineralized water. For the evaluation of the proposed system, one computer code is provided in engineering equation solver software. For physical properties calculation, the library of this software is used. The MGS produces 614.7 GWh of electrical energy, 87.44 GWh of cooling, 12.47 million m3 of demineralized water, and 0.092 and 0.084 billion kg of sodium hydroxide and hydrogen chloride over a year. Energy and exergy evaluations demonstrate that the MGS energy and exergy efficiencies are 31.3% and 18.7%, respectively. The highest and lowest value of exergy destruction rate is associated with the combustion chamber and pump, respectively. The economic evaluation indicates that the net present value of this proposed system is 3.8 billion US$, while the internal rate of return and payback period, respectively, are 0.49 and 2.1 years.

Current study deals with performance evaluation of the solar power tower driven recompression with main compressor intercooling (RMCIC) supercritical CO2 cycle incorporating the parallel double evaporator organic Rankine cycle (PDORC) as bottoming cycle using low global warming potential fluids to reduce the global warming and ozone depletion. Using the PDORC instead of the basic organic Rankine cycle, waste heat from the intercooler and cycle exhaust were recovered simultaneously to enhance performance of the standalone RMCIC cycle. Exergy, thermal efficiency, efficiency improvement and waste recovery ratio were considered as performance parameters. A computer program was made in engineering equation solver to simulate the model. It was concluded that by the incorporation of the PDORC thermal efficiency was improved by 7–8% at reference conditions. Maximum combined cycle's thermal and exergy efficiency were found 54.42% and 80.39% respectively of 0.95 kW/m2 of solar irradiation based on R1243zf working fluid. Among the results it was also found that maximum waste heat was recovered by the R1243zf about 54.22 % at 0.95 effectiveness of low temperature recuperator.

The importance of renewable energy compared to fossil fuels is increasing due to growing energy demand and environmental challenges. Multi-generation systems use one or more energy sources and produce several useful outputs. The present study aims at investigating and comparing solar energy based multi-generation systems with and without once -through MSF desalination unit from the thermodynamic point of view. Firstly, hydrogen, electricity, and hot water for space heating and domestic usage are produced using the system, which consists of a parabolic trough collector, an organic Rankine cycle (ORC) and a PEM electrolyzer and heat exchanger as sub-systems. The performance of the entire system is evaluated from the energetic and exergetic points of view. Various parameters affecting hydrogen production rate and efficiency values are also investigated with the thermodynamic model implemented in the Engineering Equation Solver (EES) package. The system can produce hydrogen at a mass flow rate of 20.39 kg/day. The results of the study show that the energy and exergy efficiency values of the ORC are calculated to be 16.80% and 40% while those for the overall system are determined to be 78% and 25.50%, respectively. Secondly, once-through MSF desalination unit is integrated to the system between ORC evaporator and heat exchanger producing domestic hot water in the solar cycle in order not to affect hydrogen production rate while thermodynamic values are compared. Fresh water production capacity of the system is calculated to be at a volumetric flow rate of 5.74 m(3)/day with 10 stages. (C) 2022 Published by Elsevier Ltd on behalf of Hydrogen Energy Publications LLC.

In this study, ten different blends were prepared with binary and ternary combinations of diesel, palm oil biodiesel (0 vol%, 15 vol%, 20 vol% and 30 vol%), and diethyl ether (0 vol%, 5 vol% and 10 vol%) and were tested in a diesel engine. The experiments were performed on various engine loads (500 W, 750 W, 1000 W and 1250 W) and various injection timings (25 degrees CA bTDC, 30 degrees CA bTDC and 35 degrees CA bTDC) at a fixed crankshaft speed of 3000 rpm. The prepared blends were compared in terms of exergy and exergoeconomics. It may be said that exergy efficiency and specific exergy cost of work for blends improved with increasing injection timings at high engine loads. However, at low engine loads, these parameters worsened with increasing injection timings. As a result, at 500 W, relative exergy efficiency of D70PO20DE10 was 0.57 for 25 degrees CA bTDC and 0.54 for 35 degrees CA bTDC. However, at 1250 W, this value was 0.59 for 25 degrees CA bTDC and 1.16 for 35 degrees CA bTDC. Similarly, at 500 W, relative specific exergy cost of work for D70PO20DE10 was 5.29 for 25 degrees CA bTDC and 5.94 for 35 degrees CA bTDC. However, at 1250 W, this value was 5.31 for 25 degrees CA bTDC and 2.66 for 35 degrees CA bTDC. Finally, it can be concluded that neat diesel had the best results compared to all blends considered in this study in terms of exergy and exergoeconomics.

In this present research study a multi-generation energy system which is coupled with CO2 capture unit which is based on Rankine cycle, organic Rankine cycle, ejector cooling system and absorption chiller has been analyzed via energy, exergy, exergy-economic aspects by developing MATLAB, also to achieve the optimum operating condition genetic algorithm has been applied for system optimization. The objective of this study is to propose an optimized efficient integrated energy system to recycle the energy waste of a typical industrial factory. The optimization has been illustrated on a Pareto frontier to achieve the optimum scheme of the multi-generation system regarding technical and economic viewpoints. Results indicate the optimal condition of this system has occurred at 0.37 exergy efficiency with 0.03 $/s. Furthermore, by surging the mass flow rate of waste gases up to 70 kg/s, net power output augmented up to 7500 kW. Besides, hydrogen production and produced desalinated water rise up to 8.5 g/s and 16 kg/s, respectively.

The principal aim of the current research is the design and optimization of a multi-generation unit capable of generating electricity and potable water and hydrogen. The system comprises a gas turbine unit, a high-temperature solid-oxide fuel cell (SOFC), a combustion chamber, and a multi-effect desalination (MED) system. The pressurized steam and fuel enter the anode side of high-temperature SOFC and the air goes to the cathode side. Due to reactions inside the SOFC, a high amount of electricity produces, and excess H 2 enters the combustion chamber. Hot flue gases can run a gas turbine and a MED unit to generate more electrical power and desalinated water. The study illustrated the impact of current density on voltage losses and output power and output voltage of SOFC. A parametric examination is also conducted to demonstrate the influence of primary design variables on the system performance. Exergo-economic multi-criteria optimization is used to determine the optimized parameters to obtain the higher efficiency and lower cost of fuel and equipment. Calculations represented that the suggested arrangement is able to generate 53.46 kg/s desalinated water, and 54.8 MW electricity and 7.43 kg/h hydrogen energy. The system exergy efficiency under this condition is about 36.45% but the results of optimization showed that this value could rise up between 50.8% and 61.17% with the lowest system cost.

In this research paper, comprehensive thermodynamic modeling of an integrated energy system consisting of a multi-effect desalination system, geothermal energy system, and hydrogen production unit is considered and the system performance is investigated. The system's primary fuel is a geothermal two-phase flow. The system consists of a single flash steam-based power system, ORC, double effect water–lithium bromide absorption cooling system, PEM electrolyzer, and MED with six effects. The effect of numerous design parameters such as geothermal temperature and pressure on the net power of steam turbine and ORC cycle, the cooling capacity of an absorption chiller, the amount of produced hydrogen in PEM electrolyzer, the mass flow rate of distillate water from MED and the total cost rate of the system are studied. The simulation is carried out by both EES and Matlab software. The results indicate the key role of geothermal temperature and show that both total exergy efficiency and total cost rate of the system elevate with increasing geothermal temperature. Also, the impact of changing absorption chiller parameters like evaporator and absorber temperatures on the COP and GOR of the system is investigated. Since some of these parameters have various effects on cost and efficiency as objective functions, a multi-objective optimization is applied based on a Genetic algorithm for this system and a Pareto-Frontier diagram is presented. The results show that geothermal main temperature has a significant effect on both system exergy efficiency and cost of the system. An increase in this temperature from 260 C to 300 C can increase the exergy efficiency of the system for an average of 12% at various working pressure and also increase the cost of the system by 13%.

This article is a careful examination of an energy poly-generation unit integrated with an evacuated solar thermal tube collector. A proton exchange membrane (PEM) electrolysis unit is used for hydrogen production, an ejector refrigeration system (ERS) is utilized for cooling demand, and a heater unit is used for heating demand. All sub-systems are validated by considering recent articles. Cooling and heating demand, as well as the net output power are calculated. The modeled poly-generation system's exergy and energy efficiency are maximized by considering the inlet temperature of the heat exchanger and primary pressure of the ejector with the parametric evaluation of the system. The proposed poly-generation set-up can produce cooling load, heating load, and hydrogen with amounts of 5.34 kW, 5.152 kW, and 63 kg/year, respectively. Based on these values, the energy efficiency, and exergy efficiency are computed to be 64.14%, and 49.62%, respectively. Higher energy and exergy efficiencies are obtained by reducing high pressure of the refrigeration cycle or decreasing the temperature outlet of an auxiliary heater. The heat exchanger and thermal energy storage unit have the highest cost rate among all system components with 73,463 $ and 46,357, respectively. Parametric study indicates that the main determinative elements in the total cost rate of the system are the heater, and the solar collector.

In the current work, a solar-based energy plant that includes an organic Rankine cycle, an NH 3 − LiNO 3 operated refrigeration system, reverse osmosis desalination, and hydrogen production device are integrated, modeled, and optimized. A parametric examination is designed with Matlab software to show the impact of varying primary system variables on outputs like system total energy, exergy efficiency, and total exergy output. All processes have been carried out for different working fluids, namely iso-butane, Propane, n-octane, and the results are compared. Parametric analysis reveals that at solar radiation of 800 W/m2, which is reasonable for the sun in most of the Middle East, selecting n-Octane as a working media results in an increase in the hydrogen production rate of about 150%. This also confirms the importance of selecting the right working fluid for the ORC unit. Moreover, the influence of substantial decision variables on the hydrogen production, net out pout power, exergy efficiency indicated that multi-criteria optimization is necessary. The multi-objective optimization strategy suggests the TIP = 1753 kPa, Toil = 99 °C , η i s t u r = 0.9, η i s p u m p = 0.87, and AHeliostat = 2800 m2, for the optimum state of the studied system. Additionally, the scatter distribution and sensitivity analysis for optimum point introduced by multi-criteria optimization utilized for better understanding the optimization process.

In the present work, the performance improvement of a waste heat recovery system is investigated by applying a fuel cell and thermoelectric generator. With the use of energy, exergy, exergo-economic, and environmental analyses (4E analysis), the performance of the improved system is evaluated. A mathematical simulation in the Engineering Equation Solver (EES) is developed for basic and modified systems. Comparative analysis is carried out to demonstrate the benefit of the suggested system. The logical and correct combination of appropriate subsystems can lead to the maximum exploitation of an energy source, which is the innovation of the present work. The comparison of suggested system (PR/FC-TEG) with the CHP system indicates that the net output power of the PR/FC-TEG system is 3881 kW compared with 958.4 kW for the CHP system. However adding fuel cell to the PR/FC-TEG system increase output power by about 2162 kW, and it imposes 4823 kW exergy destruction rate to the system. The exergy destruction rate of the PEM FC, regenerator, and vapor generator are about 88.96% of the total exergy destruction rate, which infers the importance of these components in the PR/FC-TEG system improvement. Parametric analysis on the PR/FC-TEG performance with changing four influencing parameters is performed. Results indicate that increasing the turbine 1 inlet temperature by about 1.1% increases the cost of generated electricity from 72.92 to 73.88 $/GJ and decreases the sustainability index from 1.68 to 1.65. The multi-objective optimization of the developed system can be a promising option for future study.

The main purpose of the current research work is to suggest a novel integrated multi-generation energy system and scrutinize 4E evaluation. This system consists of a solid oxide fuel cell, a PEM electrolyzer for hydrogen production, and an ejector-based absorption chiller for the coefficient of performance improvement. All parts of this system are verified with existing reports and papers. Effect of fuel cell current density, SOFC fuel cell temperature, absorption chiller evaporator temperature, and condenser temperature, and outlet turbine pressure has been investigated and reported. The effect of mentioned parameters on the exergy and cost rate has been considered. Data illustrate that the maximum exergy destruction rate belongs to the SOFC contributing 60% of the total exergy destruction rate of the system. Under the given condition of the system, the net produced power is about 200 kW with an exergy efficiency of 30.2% and thermal efficiency of 60.4%. At the considered condition the total cost rate of the system is estimated about 22.29 $/hr. The results of the present work provide a scientific base for designing poly-generation systems with high efficiency and reasonable cost rate.

This study focuses on the heat transfer characteristics of the evaporation terminal, the cool distribute unit (CDU) and refrigerant flow distribution of a water cooled multi-spilit heat pipe system (MSHPS) used in data center. The finite time thermodynamic analysis, the exergy method and the software SIMULINK was employed to build the simulation model of the combined system. The results show that the IT servers should concentrate on arranging at the location below 1.3 m. The CDU has a heat transfer of about 74 J in a period of 6 s. And the optimum flow rate of the CDU is 0.82 kg/s. The flow distribution characteristic of a CDU which connect 2 heat pipe evaporator terminals of 6 kW was calculated, and the working fluid is R22. Then the free cooling time,part time free cooling and energy saving potential in major cities of China were analysised. The energy saving potential is from 61% to 25%. The results are of great significance for the operational control and practical application of a MSHPS and other pipe-net systems.

The performance of a wind turbine depends on its first law efficiency and second law efficiency. This study focuses on the second law of efficiency, that is, the exergy efficiency of a wind turbine. This study introduces a novel technique for determining the optimum performance conditions of a wind turbine. Jhimpir City, Pakistan, was selected for the case study. The wind speed distribution in the selected area was analyzed using different probability density functions. The three-parameter Weibull distribution is the best probability density function for fitting wind speed variation. The probability distribution of the total wind exergy is performed, and a one-year variation of the wind exergy is plotted, showing the maximum exergy around the middle of the year. The exergy efficiency of the turbine using a power curve and wind exergy was determined at different wind speeds. The probabilities of the various exergy efficiencies were also determined. The results show that a high exergy efficiency has a high probability but so does low exergy efficiency owing to seasonal variations. The proposed method can be extended to any wind farm to determine the geographical and meteorological parameters of the site.

In the last decade, the search for cleaner fuels like biodiesels is gaining wide popularity, and exergy analysis are widely used in design and performance evaluation to identify the various losses. In this study, three neat biodiesels are tested for energy and exergetic performance in a single-cylinder, four-stroke IDI diesel engine. The experiments are conducted for waste poultry fat biodiesel (WPFBD), palm oil biodiesel (POBD), and waste cooking oil biodiesel (WCOBD) at various loads by maintaining a fixed rpm of 1500. Parameters like exergetic efficiency, exergy destruction, and various heat loss factors are computed from the thermodynamic models. The in-cylinder combustion pressures, heat release rate, and fuel consumption are also measured. Results show that WCOBD dominates the other two biodiesels by achieving high exergetic efficiency (52.74%) and low exergetic destruction (3.74 kJ). The in-cylinder combustion pressures and net heat release for WCOBD show smoother combustion with better torque conversion. In contrast, POBD shows high fuel consumption and more unaccounted heat losses. Better utilization of heat input by converting it into useful work was achieved for WCOBD at 75 and 100% loads. Similarly, the exhaust emissions from WCOBD compared with diesel fuel at all the loads reveal that except for NOx, there is a drastic reduction of CO, UHC, and exhaust smoke.

The use of lower global warming potential refrigerants as an alternative to hydrochlorofluorocarbons and hydrofluorocarbons from an environmental perspective is the need of an hour. The feasibility and possibility of alternative refrigerants in the existing refrigeration system can be recognized using exergy assessment. This will lead to improving the thermal performance of the refrigeration systems. In this paper, exergy assessment of a multistage multi-evaporator vapor compression refrigeration system is performed using the Simulink model. A total of eighteen refrigerants are considered for the analysis from the environmental perspective, safety considerations, etc. The evaporator-1, evaporator-2, and condenser temperatures are varied from 0 °C to 15 °C, −15 °C to −5 °C, and 25 °C to 33 °C respectively. The highest exergy destruction among all the components is found for both the compressors, followed by the condenser, evaporators, expansion devices, and internal heat exchanger. Refrigerants R141b, R123, R245ca, R245fa, and R152a showed better thermal performance than hydrofluoroolefins refrigerants, but have high GWP values. R1234ze(E), and R1234yf are environmentally friendly and achieved similar performance to conventional refrigerants.

Biomass gasification technology is a promising process to produce a stable gas with a wide range of applications, from direct use to the synthesis of value-added biochemicals and biofuels. Due to the high capital/operating costs of the technology and the necessity for prudent management of thermal energy exchanges in the biomass gasification process, it is important to use advanced sustainability metrics to ensure that environmental and other sustainability factors are addressed beneficially. Consequently, various engineering techniques are being used to make decisions on endogenous and exogenous parameters of biomass gasification processes to find the most efficient, viable, and sustainable operations and conditions. Among available approaches, exergy methods have attracted much attention due to their scientific rigor in accounting for the performance, cost, and environmental impact of biomass gasification systems. Therefore, this review is devoted to critically reviewing and numerically scrutinizing the use of exergy methods in analyzing biomass gasification systems. First, a bibliometric analysis is conducted to systematically identify research themes and trends in exergy-based sustainability assessments of biomass gasification systems. Then, the effects of biomass composition, reactor type, gasifying agent, and operating parameters on the exergy efficiency of the process are thoroughly investigated and mechanistically discussed. Unlike oxygen, nitrogen, and ash contents of biomass, the exergy efficiency of the gasification process is positively correlated with the carbon and hydrogen contents of biomass. A mixed gasifying medium (CO2 and steam) provides higher exergy efficiency values. The downdraft fixed-bed gasifier exhibits the highest exergy efficiency among biomass gasification systems. Finally, opportunities and limitations of exergy methods for analyzing sustainability aspects of biomass gasification systems are outlined to guide future research in this domain.

Reactivity-controlled compression ignition (RCCI) combustion involves in-cylinder fuels blending of varying reaction rates to enhance the combustion magnitude by stratification. Nitrogen oxides (NOx) and soot control techniques increase carbon monoxide (CO) and unburned-hydrocarbon (UHC) emissions in RCCI at low loads. A modified injection and proper Biogas mixing may reduce further CO, UHC, and trade-off with other emissions. The effects of loads (5.5 and 6.5 bar IMEP), port mixing distances (0–100%), swirl ratios (0–80%), and biogas pressures (1–4 bar) on the mixture distribution and emissions were evaluated experimentally, at 1600 rpm. Exergy analysis and combustion kinetics were applied for more understanding of emissions attributes. The process at 5.5 bar IMEP improves mixture homogeneity, uniform fuel stratification and reduces emissions across the mixing intervals. Injection at valve reduces CO, UHC, and NOx emissions by 11.54%, 9.38%, and 33.75% at 5.5 bar IMEP. Operating at the valve, 80% swirl ratio and 1 bar pressure further reduce the UHC (115.77 ppm), NOx (3.89 ppm), and PM (5.29 ppm) emissions by 1.94%, 49.94%, and 77.42%, than normal airflow. Thus, injecting biogas of low pressure at the valve amidst a stream of swirling air contributes to trade-off reduction techniques at low load.

Based on the “three box” exergy analysis model, a black box-gray box hierarchical exergy analysis and evaluation method is put forward in this paper, which is applied to evaluate the power generation technology of differential pressure produced by natural gas expansion. By using the exergy analysis theory, the black box - gray box hierarchical exergy analysis models of three differential pressure power generation technologies are established respectively. Firstly, the “black box” analysis models of main energy consuming equipment are established, and then the “gray box” analysis model of the total system is established. Based on the calculation results of exergy analysis indexes, the weak energy consumption equipment in the whole power generation process is accurately located. Taking a gas field in southwest China as an example, the comprehensive energy consumption evaluation of the three power generation technologies is carried out, and the technology with the best energy consumption condition among the three technologies is determined. Finally, the rationalization improvement measures are put forward from improving the air tightness, replacing the deflector and reducing the flow loss.

In high-temperature and high-humidity environments, a large amount of energy is consumed to cool and dehumidify outdoor air by dedicated outdoor air systems in nearly zero energy buildings. Desiccant wheels have the advantages of large moisture removal capacities and continuous regeneration. However, the application of desiccant wheels in nearly zero energy buildings is limited by their large regeneration heat capacity and high temperature after dehumidification. A dedicated desiccant wheel outdoor air cooling system is thus proposed. An experimental setup is built and used to test the performances of three modes for dedicated desiccant wheel outdoor air cooling systems. The results show that mode Ⅰ (wet membrane humidifier downstream evaporation section of heat pipe heat exchanger) has a higher performance coefficient and higher exergy efficiency compared to other modes. The thermodynamic and exergy performances of the proposed mode Ⅰ system are determined. The results show that the thermodynamic coefficient decreases from 1.3 to 0.52 and the exergy efficiency decreases from 0.76 to 0.18 when the regeneration temperature increases from 60°C to 110°C.

This is the first study to apply a combination of two thermoeconomic approaches (UFS and H&S) with Life Cycle Assessment (LCA) to a chilled water system installed in a shopping mall. The objective is to obtain monetary and environmental costs for the thermal energy stored by developing both thermoeconomic and thermoenvironmental assessments. The thermoeconomic study determined internal flows, defined inputs and products, and described the productive structure to obtain exergy and monetary costs. The LCA methodology quantified the greenhouse gas emissions associated with equipment operation and energy flows. The results indicated efficient thermoeconomic behavior for the heat exchangers. The monetary and environmental costs of chilled water are, respectively, US$ 0.2267/MJ and 0.8186 kg CO2-eq/MJ.

In this study, a novel expander rocket engine cycle that uses a third fluid as the combustor coolant and the turbine driver was discussed. A detailed system scheme with two stage cryogenic heat exchangers of the third fluid cooled (TFC) liquid rocket engine was improved. The design highlighted the phase-change heat transfer model of the regenerative cooling channels (RCC) on the basis of previous experiments. Subsequently, the state parameters distribution for the system was first proposed. In addition, the exergy analysis of cooled Rankine cycle (CRC) loop was investigated. The effects of the third fluid methane mass flow rate ( m ˙ t f ) on the exergy efficiency of CRC loop were further analyzed. The results demonstrated that the m ˙ t f and the design geometric dimension of the RCC can well meet the thermal protection requirements of the thrust chamber. In the exergy analysis process, the exergy loss of the RCC was the largest. The exergy loss ratio of cryogenic heat exchanger Ⅰ and Ⅱ vary greatly due to the difference of the heat transfer performance. With the increase of the m ˙ t f , the exergy efficiency of CRC loop decreased slightly, while the maximum output power from the heat transferred through the thrust chamber wall ( W m a x ) increased. The results will be benefit for a better thermal performance of the TFC engine through the optimization of the m ˙ t f and subassemblies.

The present paper introduces a novel latent heat storage system applicable to hot water systems equipped with a Phase Change Material (PCM) and a Novel set of Blossom-Shaped Fins (BSFs). The water supplied by the collector is injected into the heat exchanger as a Heat Transfer Fluid (HTF). The PCM is charged during the daytime and will be reused as a primary system to supply the building's heating load at nighttime. The system's performance is investigated for various geometrical parameters, including the fin-number, fin's degree of compactness, fin-height, and the combined-fin heights/pin. Moreover, thermodynamic optimization through exergy analysis is applied to give better insights into the system's performance and efficiency. Results imply that both the variations of the fin-number and the fin's degree of compactness improve the charging time by 17% and 2%, respectively. Moreover, the fin-number variations positively affect the exergy efficiency by 6%, while compactness of fins shows a converse behavior with an 8% reduction in the exergy efficiency. On the other hand, the fin height/pin parameter variations improve the melting performance by 15% while having fewer exergy efficiencies. In addition, reducing the fin-height parameter improves the exergy efficiency of the case with the least melting time by 25% while associated with the most prolonged melting duration. Hence, considering the different impacts of geometric parameters on the exergy efficiency and the storage time, one should pay attention to the designer's view and climate conditions to choose the suitable heat exchanger based on the desired application. If the storage time is limited, the combined fin height/pin is preferred. Otherwise, the fin-height might be a better candidate to achieve higher exergy efficiencies and system performance.

Despite its shortcomings, fossil-based fuels are still utilized as the main energy source, accounting for about 80% of the world's total energy supply with about one-third of which comes from coal. However, conventional coal-fired power plants emit relatively higher amounts of greenhouse gases, and the derivatives of air pollutants, which necessitates the integration of environmentally benign technologies into the conventional power plants. In the current study, a H2–CO synthesis gas fueled solid oxide fuel cell (SOFC) is integrated to the coal-fired combined cycle along with a concentrated solar energy system for the purpose of promoting the cleaner energy applications in the fossil fuel-based power plants. The underlying motivation of the present study is to propose a novel design for a conventional coal-fired combined cycle without altering its main infrastructure to make its environmentally hazardous nature more ecofriendly. The proposed SOFC integrated coal-fired combined cycle is modeled thermodynamically for different types of coals, namely pet coke, Powder River Basin (PRB) coal, lignite and anthracite using the Engineering Equation Solver (EES) and the Ebsilon software packages. The current results show that the designed hybrid energy system provide higher performance with higher energy and exergy efficiencies ranging from 70.6% to 72.7% energetically and from 35.5% to 43.8% exergetically. In addition, carbon dioxide emissions are reduced varying between 18.31 kg/s and 30.09 kg/s depending on the selected coal type, under the assumption of 10 kg per second fuel inlet.

Cooling towers are important components within recirculating cooling water systems. Due to a shortage of freshwater resources, seawater cooling towers are widely used both in manufacturing and everyday life. This paper researches the mechanical draft counterflow wet seawater cooling tower (MDCWSCT), and establishes and verifies a detailed thermal performance calculation model. Referring to the second law of thermodynamics, the heat and mass transfer performance and exergy performance of the seawater cooling tower were studied. The effects of salinity, inlet air speed, and air wet-bulb temperature on the cooling efficiency, thermal efficiency, and exergy efficiency were analyzed. The results show that compared to the air wet-bulb temperature, changes in air speed have more influence on cooling and thermal efficiency under the study conditions. Moreover, the air wet-bulb temperature is the significant parameter affecting exergy efficiency. With an increase in salinity, the cooling, thermal, and exergy efficiency are about 2.40-8.25 %, 1.06-3.09 %, and 2.47-7.73 % lower than that of freshwater, respectively, within an air speed of 3.1-3.6 m/s. With an increase in salinity, the cooling, thermal, and exergy efficiency are about 2.28-8.47 %, 1.03-3.37 %, and 2.44-7.99 % lower than that of freshwater, respectively, within an air wet-bulb temperature of 25-27 ℃. Through the exergy analysis of the seawater cooling tower, it is obvious that the heat and mass transfer performance and exergy performance can be improved by selecting the optimum operating conditions and appropriate packing specifications.

Indirect injection of Diesel fuel using swirl chambers is an interesting research option ever since the concept was coined by the researchers across the globe. In this typical concept, fuel is sprayed into the swirl chamber incorporated in the cylinder head of engine for primary combustion for the obvious benefit of getting lower NOx emissions keeping a low injection pressure. Typical systems use a single swirl chamber for this purpose. In this study, a novel design of swirl chamber which can produce dual swirl leading to higher turbulence, better mixing of compressed air and fuel is proposed and tested. Comparative performance and exergy analysis are done with a single swirl chamber and the newly developed dual swirl chamber. Performance testing on both the single and novel dual swirl chamber IDI engine showed that at higher loads both designs have equally good. At a load of 10kgf the BSFC and Brake thermal efficiency is identical and experimental results showed that dual swirl has lower NOx emissions, CO emission but, at the penalty of slightly higher SFC (as compared to single swirl chamber) respectively by 11.18%, is 4.47% and 0.36%. The exergy analysis of the novel dual swirl chamber and the single swirl chamber shows that the destroyed exergy of DSC is 5.65% higher compared to SSC, though input availability is more in DSC. This is the area where further research work must be done, to minimize it.

Renewable energy-based hydrogen production plants can offer potential solutions to both ensuring sustainability in energy generation systems and designing environmentally friendly systems. In this combined work, a novel solar energy supported plant is proposed that can generate hydrogen, electricity, heating, cooling and hot water. With the suggested integrated plant, the potential of solar energy usage is increased for energy generation systems. The modeled integrated system generally consists of the solar power cycle, solid oxide fuel cell plant, gas turbine process, supercritical power plant, organic Rankine cycle, cooling cycle, hydrogen production and liquefaction plant, and hot water production sub-system. To conduct a comprehensive thermodynamic performance analysis of the suggested plant, the combined plant is modeled according to thermodynamic equilibrium equations. A performance assessment is also conducted to evaluate the impact of several plant indicators on performance characteristics of integrated system and its sub-parts. Hydrogen production rate in the suggested plant according to the performance analysis performed is realized as 0.0642 kg/s. While maximum exergy destruction rate is seen in the solar power plant with 8279 kW, the cooling plant has the lowest exergy destruction rate as 1098 kW. Also, the highest power generation is obtained from gas turbine cycle with 7053 kW. In addition, energetic and exergetic efficiencies of solar power based combined cycle are found as 56.48% and 54.06%, respectively.

Nanofluid offers remarkable thermal and optical properties favourable for direct solar absorption. The nanofluids prepared by the conventional two-step synthesis method have low colloidal stability, while that synthesized through the one-step method is costly. Hence the nanofluid synthesized using an economical one-step method has great significance. In the present study, a highly stable C-dot/water nanofluid was synthesized using an economical one-pot synthesis method. The optical characterisation, corrosion analysis and cost estimation of the nanofluid were conducted. The influence of C-dot/water nanofluid on the performance of direct absorption solar collector was analyzed. The direct absorption parabolic solar collector employed with C-dot/water nanofluid yielded a maximum thermal efficiency of 73.41% at Reynolds number of 2952, while that for water was 15.79%. Thermodynamic analysis of the system and cost estimation of the nanofluid was performed to establish its commercial suitability in various solar thermal devices. The maximum exergy destruction was found to be 924.3 W and was more or less constant at all flow rates. The main highlight of the new C-dot/water nanofluid is its significantly high colloidal stability and was found to be stable for more than six months. The corrosion rate of the new C-dot/water nanofluid was obtained as 0.094 mm/year, while that for the base fluid was 0.372 mm/year. With superior optical performance, corrosion resistance, and low production cost, the C-dot nanofluid has the potential to be a prospective working fluid in various direct absorption solar thermal systems.

Energy enhancement and utilization of renewable energy sources have become inevitable solutions for the concerns of fossil fuel depletion and global warming. Two different cogeneration systems are proposed for cooling and power generation. A gas turbine and an ejector refrigeration cycle are employed in the configurations, in which gas turbine cycle uses biogas as the required fuel. First, these two configurations are analyzed from energy and exergy perspectives. A comprehensive parametric study is also performed by decision variables for the optimization. Results reveal that both energy and exergy efficiencies of conventional combined gas turbine/ejector refrigeration cycle can be improved up to 44.6% and 33.54%, respectively. Besides, the outcomes of the parametric study point out that the combustion chamber has a significant effect on energy and exergy efficiencies and can increased them about 10%. Also, it is found that the vapor generator accounts for the highest exergy destruction among all components. Moreover, by using a genetic algorithm as an optimization method, the thermal and exergetic efficiencies of the base system improves. In the best operating condition, the thermal and exergetic efficiencies of the system reach 57.11% and 36.68%, respectively.

The present study investigates the advanced exergy assessment in a solar absorption power cycle to reveal the inefficiency of the system. Unlike simple exergy assessment, which only assesses exergy destruction, advanced exergy evaluates avoidable, unavoidable, exogenous, and endogenous exergy destructions. EES software is employed to model the proposed absorption power cycle, in which the power is generated using a low-temperature heat source driven by solar energy. The novelties of the present study are the use of solar energy in absorption power and applying the advanced exergy assessment. According to the results, the total energy and exergy efficiencies are 6.655% and 7.011% in the real state, 8.517% and 8.973% in the unavoidable state, and 9.433% and 9.938% in the ideal state, respectively. In other words, both efficiencies improve by 41.7% and 10.75% under ideal and unavoidable conditions compared to the real state, respectively. The outcomes reveal that the unavoidable exergy destruction is greater than the avoidable exergy destruction in the constituents, implying that no structural refinement can be effective in the system. Among the components, 73.69 kW exergy destruction occurs in the solar collector, of which 67.47 kW is endogenous destruction. Also, the unavoidable and avoidable exergy destructions equal 73.03 kW and 0.66 kW in the solar collector, respectively. Moreover, the unavoidable endogenous part accounts for the highest proportion of exergy destruction in the solar collector, while the avoidable exogenous destruction is less than zero. It means that by improving the component itself, it is possible to reduce the exergy destruction.

This work presents an energy, exergy, and environmental evaluation of a novel compound PV/T (photovoltaic thermal) waste heat driven ejector-heat pump system for simultaneous data center cooling and waste heat recovery for district heating networks. The system uses PV/T waste heat with an evaporative-condenser as a driving force for an ejector while exploiting the generated electric power to operate the heat pump compressor and pumps. The vapor compression system assessed several environmentally friendly strategies. The study compares eleven lower global warming potential (GWP) refrigerants from different ASHRAE safety groups (R450A, R513A, R515A, R515B, R516A, R152a, R444A, R1234ze(E), R1234yf, R290, and R1243zf) with the hydrofluorocarbon (HFC) R134a. The results prove that the system presents a remarkable overall performance enhancement for all investigated refrigerants in both modes. Regarding the energy analysis, the cooling coefficient of performance (COPC) enhancement ranges from 15% to 54% compared with a traditional R134a heat pump. The most pronounced COPC enhancement is caused by R515B (a 54% COPC enhancement and 49% heating COP enhancement), followed by R515A and R1234ze(E). Concerning the exergy analysis, R515B shows the lowest exergy destruction, with the highest exergy efficiency than all investigated refrigerants. Funding for open access charge: CRUE-Universitat Jaume I

In industrial engineering, hydrogen is usually transported and stored after being liquefied, which is an energy-intensive process. Aiming to liquefy hydrogen with high efficiency and low consumption, a novel hydrogen liquefaction process based on dual-path hydrogen refrigeration is proposed innovatively and simulated by Aspen HYSYS to determine the key parameters. Taking the specific energy consumption (SEC) as the objective function for the optimization by genetic algorithm (GA), optimum parameters could be obtained. Meanwhile, the single variable method is conducted to analyze the impact of key parameters on process characteristics. Under the premise of complete liquefaction, the SEC, coefficient of performance (COP) and exergy efficiencies (EXE) of the proposed system are 7.041 kWh/kg LH2, 0.1834, 0.5413, respectively. Compared with the other three hydrogen liquefaction systems simulated under the same conditions, they are decreased by 22.16% and increased by 33.58% and 42.37%, respectively. The results show that the proposed system shows better performance under lower consumption.

For energy systems, sustainability is a major concern that must be carefully considered when designed and established. Emergy analysis is an effective technique to scrutinize the sustainability of these systems. On the other hand, water shortage is seen to become a big problem in the close future; however, this problem can be effectively alleviated by combined electricity/water production plants, where waste heat is recovered to generate freshwater. This study applies emergy analysis to evaluate and improve the sustainability, renewability, environmental impacts, and economic aspect of such a plant, in which a multi-stage desalination (MSF) system is employed to recover the waste heat from a gas turbine (GT). The plant is fueled by biomass/natural gas (system I), natural gas (system II), and biomass (system III), and the above-mentioned features are compared for the different fuel types. To estimate chemical equilibrium state inside the gasifier, Lagrange's method of undetermined multipliers is applied. Also, considering exergy efficiency and emergy sustainability index as objective functions, biomass/natural gas-fueled system is optimized by adopting a multi-objective optimization approach based on the non-dominated sorting genetic algorithm II (NSGA II). To predict the optimized points' behavior, the Pareto optimal frontier of the system is utilized. The results reveal that using biomass as inlet fuel remarkably improves the sustainability index and reduces environmental impacts. The optimization results show that as sustainability index increases, exergy efficiency decreases. Also, the two optimized points of the system are found to have exergy efficiencies of 20.14% and 25.09% and sustainability indices of 24.67% and 13.60%.

The paper aims to solve drawbacks associated with Gas Turbine GT by integrating a novel cascaded system into a combined cycle simultaneously. Parabolic trough collectors preheat the air at the combustion chamber inlet, then drive an absorption inlet-air cooling cycle that controls the ambient-air temperature at the compressor's inlet. This study uses the 2nd law of thermodynamics to estimate the maximum available energy, calculate the electric exergy efficiency, and explore the maximum irreversible exergy destruction in the system's components. Artificial Neural Network was employed to develop a multi-objective optimization by linking data collected from equations in the Engineering Equation Solver software with Matlab. Spider diagrams investigated the effect of varying several key operating parameters on the performance of the system, identifying gas turbine as the highest irreversibility sub-unit and the solar field parabolic trough collectors as the second. Design improvement for the combustion chamber can reduce 303.6 MW, and for parabolic trough collectors field reduce 58.9 MW. Artificial neural networks with multi-objective optimization maximized the electric exergy destruction to 46.19% and minimized the exergy destruction to 489.4 MW, relative to the corresponding values from the simple design point.

In this study, an optimal scheme is proposed by utilizing waste streams at a plant-wide scale along with pressure retarded osmosis (PRO) membrane allocation in complex industrial networks for energy recovery. Chemical exergy pinch analysis (ChExPA) and process graph (P-graph) are used to address the problem. The ultimate goals of utilizing the tools are (1) determine the optimal external load consumption, (2) minimizing the waste discharge, and (3) sustainable energy production while utilizing high chemical exergy potential waste discharges. A reliability assessment assisted with Monte-Carlo simulation is further performed to evaluate the proposed solutions from P-graph considering uncertainties. The effectiveness of the proposed methodology is explained using three industrial case studies which covered both intra-plant and inter-plant networks. The results indicated that ChExPA and P-graph can effectively identify the optimal location of the PRO membrane in industrial networks. Upon analyzing the complex inter-plant industrial networks 7.795 MW net power output was harnessed, and significantly higher waste of 384.92 kg/s was recovered with a levelized cost of energy of 0.073 $/kWh. The inter-plant network shows the greatest net profit which accounted for approximately $1,191,000 (i.e., 5.84 times higher than stand-alone plants) with a reasonable payback-period of 4.5 years.

Energy quality in each country is one of the important indicators of economic development, Which affects the economic growth of that country. Exergy analysis, considering all flow properties including pressure, temperature, composition, is a powerful way to evaluate the energy consumption of equipment such as natural gas and liquefied gas plants. Inefficiency of a system can be defined by the conventional exergy analysis method, While, irreversible resources and real potentials for system improvement can only be identified by the advanced exergy analysis method. This analysis splits conventional exergy destruction into two exogenous and endogenous parts according to origin, and also unavoidable and avoidable parts according to the ability to remove and modifications. In this method, the exergy concept was separated by considering the ideal and avoidable condition assumptions. As a real case study, a natural gas liquid plant 800, from National Iranian South Oil Company located in southwest of Iran was considered to be investigated by conventional exergy analysis, advanced exergy analysis methods. The results of conventional exergy analysis illustrated that the highest amount of exergy destruction belonged to compressor and heat exchanger with 509.99 and 629.04 kW, respectively. However, in the case of heat exchanger, despite having the highest rate of exergy destruction, it is not considered in modification priorities due to its low avoidable exergy destruction value. Also, advanced exergy analysis suggested that the exergy destruction of the compressor and heat exchanger will be reduced by improving performance of these components.

In this study, two wind-solar-based polygeneration systems namely CES-1 and CES-2 are developed, modeled, and analyzed thermodynamically. CES-1 hybridizes a heliostat based CSP system with wind turbines while CES-2 integrates heliostat-based CPVT with wind turbines. This study aims to compare the production and thermodynamics performance of two heliostat based concentrated solar power technologies when hybridized with wind turbines. The systems have been modeled to produce, freshwater, hot water, electricity, hydrogen, and cooling with different cycles/subsystems. While the overall objective of the study is to model two polygeneration systems with improved energy and exergy performances, the performances of two solar technologies are compared. The wind turbine system integrated with the comprehensive energy systems will produce 1.14 MW of electricity and it has 72.2% energy and exergy efficiency. Also, based on the same solar energy input, the performance of the heliostat integrated CPVT system (CES-2) is found to be better than that of the CSP based system (CES-1). The polygeneration thermal and exergy efficiencies for the two systems respectively are 48.08% and 31.67% for CES-1; 59.7% and 43.91% for CES-2. Also, the electric power produced by CES-2 is 280 kW higher in comparison to CES-1.

The high-temperature heat pump steam system (HTHPS) is an effective way to replace the calcining boiler's steam. However, the large temperature span of the system leads to colossal exergy loss of refrigerant in expansion valves and other components. Therefore, it is hoped to adopt the dual-flash vaporization process to improve the system's steam production performance. In this paper, three thermodynamic models and exergy models of HTHPS with a double flash evaporation process are established. Furthermore, this paper uses the multivariate simulated annealing algorithm to calculate the optimal COP of the system. Then, by comparing the single-stage compression (SC) system and the quasi-two-stage compression (QTC) system, the influence of the dual-flash vaporization process on HTHPS is analyzed. The results show that under the same environment, the COP of the dual-flash vaporization process compression system is 23.8% 44.54% higher than that of the SC system. With the increase of the system temperature span, the flash steam supplemental process brings the system to improved thermodynamic performance. Moreover, the exergy model of the dual-flash system is closest to the reversed Carnot cycle, when the evaporation temperature is 50 °C and the condensing temperature is 110 °C.

The present study deals with the performance analysis of thermochemical energy storage system based on four different working pairs, namely LaNi4.85Sn0.15-MmNi4.6Al0.4, LaNi4.75Sn0.25-MmNi4.6Al0.4, LaNi4.65Sn0.35-MmNi4.6Al0.4 and LaNi4.55Sn0.45-MmNi4.6Al0.4. The first law and second law performance parameters are considered to evaluate the performance of the energy storage system. The temperature of heat storage and heat recovery for the four different working pairs are in the range of 93–140 °C and 105–165 °C respectively. Recovering the heat at higher temperature than that of storage is called heat upgradation. Highest degree of heat upgradation is 24 °C, and it is obtained for the working pair of LaNi4.55Sn0.45-MmNi4.6Al0.4. The theoretical highest energy storage density and COP are 129 kJ/kg and 0.54 respectively for the working pair of LaNi4.65Sn0.35-MmNi4.6Al0.4. From the second analysis, the lowest exergy loss and highest second law efficiency are 2.57 kJ and 96.4% respectively for the working pair of LaNi4.75Sn0.25-MmNi4.6Al0.4. Based on the first law analysis, the working pair, LaNi4.65Sn0.35-MmNi4.6Al0.4, is taken as best pair and based on the second law analysis, the working pair, LaNi4.75Sn0.25-MmNi4.6Al0.4, is taken as best pair. However, suitable working pair need to be selected based on the type of application.

The dynamic growth of renewables in national power systems is driving the development of energy storage technologies. Power and storage capacity should correspond to system-scale requirements in the field of power and capacity. One such technology is liquid air energy storage. As the main energy expenditures in this system are related to the liquefaction module, authors focused their research on analysis of the advanced liquefaction modules. The six most common liquefaction sections were considered. Depending on the regasification section pressure, various amounts of cold media can be obtained, stored, and used during liquid air energy storage system charging mode. Mathematical modelling results show that when the regasification section pressure is below 100 bar, the type of liquefaction system used has no significant influence on the unit energy expenditures of liquefaction section. Since additional air cooling is desired for higher pressure values, appropriate choice of liquefaction system type can minimise unit energy expenditures for air condensation. One of the main parameters from the efficiency point of view is the temperature before the throttling valve, as lower values contribute to a reduction in recirculated flow, leading to lower power demands for compressors. The highest efficiencies for almost all considered cases were reported for the Kapitza system: 57.72% for 100 bar regasification pressure. Importantly, the Kapitza and Heylandt systems retain good efficiency with higher regasification pressures, until 160 bar. For the other cases, the discrepancies between efficiencies for 100 bar and 160 bar are significant. The highest difference was observed for the simplest system – Linde-Hampson – where the efficiency drop exceeds 12%. For the best analysed system (Kapitza) exergy analysis were leaded. The main single component exergy destruction was reported for the Joule-Thompson valve (25.56%), which is related with isenthalpic throttling of air. In general, the highest share of exergy destruction in the system occurs in the heat exchangers (26.15% in total).

This paper reports on an energy/exergy analysis of a standalone solar-hydrogen system with a metal hydride (MH) system thermally managed using a phase change material (PCM). This is a self-contained thermal management arrangement that stores the heat released from the MH unit, when it is being charged and transfers it back to the MH while discharging hydrogen. The first and second laws of thermodynamics were used to develop a mathematical model in MATLAB to simulate this system and quality its performance from the energy and exergy viewpoints. The model was then applied on a passive standalone house, with ∼3.8 MWh/year electricity demand, located in southeast Australia. The exergy efficiencies of the solar PV, electrolyser, fuel cell and the whole solar hydrogen system were found to be 6.5%, 88%, 50.6%, and 3.74%, respectively. The paper also provides the detailed entropy generation and exergy analysis on the MH hydrogen storage unit together with its PCM-based thermal management arrangement. The results show that the annual entropy generation, exergy destruction and exergy efficiency of the MH hydrogen storage unit were 173 Wh/K, 51.5 kWh, and 98.8%, respectively.

In this paper, a proposal for a novel integrated Brayton cycle, supercritical plant, trans critical plant and organic Rankine cycle-based power systems for multi-generation applications are presented and analyzed thermodynamically. The plant can generate power, heating-cooling for residential applications, and hydrogen simultaneously from a single energy source. Both energetic and exergetic analyses are conducted on this multi-generation plant and its subsystems in order to evaluate and compare them thermodynamically, in terms of their useful product capabilities. The energetic and exergetic effectiveness of the multi-generation system are computed as 44.69% and 42.03%, respectively. After that, a parametric study on each of the subsystems of the proposed combined system is given in order to provide a deeper understanding of the working of these subsystems under different states. Lastly, environmental impact assessments are provided to raise environmental concerns for several operating conditions. For the base working condition, the results illustrate that the proposed plant has 0.5961, 0.0442, 0.6265 and 1.678 of exergo-environmental impact factor, exergy sustainability index, exergy stability factor and sustainability index, respectively.

This work considers an analysis using energy and exergy of turbines for a coal-based conventional steam power plant of 500 MW under the Damodar Valley Corporation (DVC), India to optimize its operating conditions. An effort has also been made to control the environmental emission of different gases from the plant. Hence, a control volume is assumed consisting of a high-pressure turbine (HPT), an intermediate turbine (IPT), and a low-pressure turbine (LPT) of the plant. A thermodynamic-based model is considered in determining the performance of turbines in the power cycle under various unit loads (60%, 80%, and 100%). This analysis includes a prediction of energy, then exergy, and related irreversibility of flow stream to and from said control volume under the unit load conditions. The improvement in heat rate of the turbine with an increase in load is also estimated. As found, the heat rate reaches a minimum when the plant operates at higher unit loads (80% and 100%), which is an economical condition of operation. With the basis of the improved heat rate, a reduction in coal consumption, plant ash generation, also SO2 and CO2 emissions by the plant are estimated.

Greenhouse drying systems are sustainable and clean applications for preserving agricultural crops. In this work, a single-slope greenhouse drying system has been modified with solar absorber and thermally insulated north wall. Also, the designed and manufactured north wall has been coated with graphene nanoplatelet-embedded black paint. Greenhouse dryers with north wall and nano-embedded north wall modifications have been experimentally compared with a conventional greenhouse dryer. Main goal of this research is to upgrade the performance of a greenhouse drying system without using any auxiliary heating device and complex structural components. According to the experimental outcomes, drying time was reduced as 75 and 90 min by utilizing north wall and nano-enhanced north wall, respectively. Furthermore, exergy efficiencies of greenhouse dryers with north wall and nano-enhanced north wall were attained as 4.67% and 5.38%, respectively while this value for conventional greenhouse dryer obtained between 2.61 and 2.70%. Moreover, utilizing graphene nanoplatelets in black paint improved the specific moisture extraction rate as 40% in comparison to conventional greenhouse dryer.

A 3D two-phase analysis is conducted to evaluate the second law features of a counter-flow four-layer microchannel heat exchanger (MCHE) operating with an Al2O3–water nanofluid. The coolant is considered water, while the hot fluid is the nanofluid. Three MCHEs with varied number of channels are examined. This investigation highlights the minimization of the exergy destruction to figure out the conditions in which the amount of degraded energy is lowest. Suspending more nanoparticles diminishes the thermal irreversibility of the nanofluid up to 61.6%, whereas the cold water experiences around 11.7% higher thermal irreversibility. At the small flow rates, increasing the volume fraction causes smaller exergy destruction, while at great flow rates, the trend becomes slightly ascending. The greater flow rate results in the greater thermal and frictional entropy generations. The second law efficiency firstly escalates via increasing the volume fraction but then remains almost constant or even descends somewhat.