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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.

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.

This study investigates the hidden thermal losses of glass plate, collector plate, water pipe and storage tank of solar water heater in the process of energy conversion. The present non-conventional energy methods are insufficient, whereas the exergy analysis provides a remarkable solution. Thus, employing the exergy analysis, entropy generation, exergy destruction and exergy efficiency of each subsystem of solar water heater are computed. The obtained results showed that the entropy generation and exergy destruction are high during the heat transfer in each subsystem. Henceforth, the existing solar water heater design is modified placing hexagonal honeycomb structure between the glass plate and the collector plate and also water pipe is insulated to trap huge amount of solar energy. The proposed design exhibits improved exergy efficiency when compared with the existing model, which enhances the performance of the system.

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.

A novel solid oxide fuel cell (SOFC) multigeneration system fueled by biogas derived from agricultural waste (maize silage) is designed and analyzed from the view point of energy and exergy analysis. The system is proposed in order to limit the greenhouse gas emissions as it uses a renewable energy source as a fuel. Electricity, domestic hot water, hydrogen and cooling load are produced simultaneously by the system. The system includes a solid oxide fuel cell; which is the primary mover, a biogas digester subsystem, a cascaded closed loop organic Rankine cycle, a single effect LiBr-water absorption refrigeration cycle, and a proton exchange membrane electrolyzer subsystem. The proposed cascaded closed-loop ORC cycle is considered as one of the advanced heat recovery technologies that significantly improve thermal efficiency of integrated systems. The thermal performance of the proposed system is observed to be higher in comparison to the simple ORC and the recuperated ORC cycles. The integration of a splitter to govern the flue gas separation ratio is also introduced in this study to cater for particular needs/demands. The separation ratio can be used to vary the cooling load or the additional power supplied by the ORC to the system. It is deduced that net electrical power, cooling load, heating capacity of the domestic hot water and total energy and exergy efficiency are 789.7 kW, 317.3 kW, 65.75 kW, 69.86% and 47.4% respectively under integral design conditions. Using a parametric approach, the effects of main parameters on the output of the device are analyzed. Current density is an important parameter for system performance. Increasing the current density leads to increased power produced by the system, decreased exergy efficiency in the system and increased energy efficiency. After-burner, air and fuel heat exchangers are observed to have the highest exergy destruction rates. Lower current density values are desirable for better exergy-based sustainability from the exergetic environmental impact assessment. Higher current density values have negative effect on the environment.

This study measures the resource efficiency of a basic oxygen steelmaking plant and develops visual maps of its resource use using raw energy and material data extracted directly from the control system. Resource efficiency is measured in units of exergy and resource flows are visualised in Sankey diagrams. Both the metric and the visuals are computed in close-to-real time scales, and are presented on a daily basis over a period of two weeks. Results show the highest level of resource efficiency (73.8%, Day 11) occurs not when energy intensity is greatest (Day 14) but instead when both energy intensity and material yields are high. Combining energy and materials into a single metric – resource efficiency – is shown to provide plant managers with a clearer picture of where interventions might deliver the greatest efficiency gains and redefines the concept of best practice.

Sorption thermal battery has revealed vast potential of heat utilization to address the issue of long-term energy storage. A hybrid compression-assisted sorption thermal battery is presented for solar energy utilization, which aims to solve the mismatch of heat storage and supply in cold region. Thermodynamic performance of the hybrid sorption thermal battery in cold region is analyzed by using MnCl2–SrCl2 and MnCl2–CaCl2 working pairs and then compared with that of basic sorption type with internal heat recovery. It is demonstrated that when ambient temperature in winter ranges from −30 °C to -5 °C, energy and exergy efficiencies of hybrid thermal battery using different working pairs increase from 0.74 to 0.865 and 0.25 to 0.43, respectively. Energy efficiency of hybrid thermal battery is almost twice higher than that of basic type with internal heat recovery. For different operating parameters, mass ratio and global conversion rate have a larger influence on thermal performance than isentropic efficiency of compressor. Although energy storage density per salt of basic sorption thermal battery is a bit higher than that of hybrid type, the density per reactor of hybrid compression-assisted thermal battery could be improved by 50%, which indicates a good system compactness in real application.

To enhance the performance of the thermodynamic systems, reduce the pollutants emission to the environment, and decline the fuel utilization, waste heat recovery methods are in high interest. In this paper, a new configuration of an integrated solid oxide fuel cell and gas turbine combined with a biogas reforming cycle is presented for the cogeneration of power and hydrogen. The thermal energy discharged from the SOFC-GT system is used to supply the energy required for the reforming reaction in the biogas reforming cycle for hydrogen production. Comprehensive thermodynamic and thermoeconomic modeling has been performed using EES software. Also, a parametric study has been performed to demonstrate the effect of different parameters on the main performance metrics of the devised system. The results revealed that the energy efficiency and exergy efficiency of the proposed combined system have increased compared to the SOFC-GT system by 23.31 % and 28.19 % , respectively. The net output power and hydrogen production rate are obtained by 2726 kW and 0.07453 kg / s , respectively. From the exergy viewpoint, the afterburner causes a considerable amount of exergy destruction for the system by approximately 26 % of the total exergy destruction rate. Besides, the sensitivity analysis revealed that by increasing the inlet temperature of the fuel cell, the cell voltage reaches a maximum value at a temperature of 679 K and then decreases. Moreover, the total exergy destruction rate and SUCP of the cogeneration system is calculated by 1532 kW and 9400 $ / GJ , respectively.

Two schemes of power and refrigeration cogeneration Kalina cycle with adjustable refrigeration temperature (PPRAT-KC) based on the efficient cogeneration cycle PPR-KC are proposed and studied. In the PPRAT-KC, the refrigerant vapor is absorbed in a pressure adjustment absorber with dilute solution either from the separator or the low-pressure pump, and by altering the flow rate of the dilute solution, the refrigeration temperature is able to be adjusted with nearly no effect on the amounts of energy outputs. The amount of net power or refrigeration capacity in the PPRAT-KC can be also adjusted by changing the flow rate of solutions fed to the power and refrigeration sub-cycles. Under temperatures of heat source and cooling water of 400℃ and 30℃, respectively, the change range of refrigeration temperature for the two schemes of the PPRAT-KC are about from -22℃ to 7.5℃, and the performances of the two schemes are similar. With the same work concentration of 0.5 and refrigeration temperature of -15℃, the effective exergy of PPRAT-KC is 0.5653, which is 4.145% and 10.97% higher than those of the PPR-KC and the triple pressure Kalina cycle, respectively.

The concern for environmental devastation due to high dependency on fossil fuel sources is shifting focus towards efficient utilization of energy by integrating renewable energy and integrated energy system. Efficient energy deployment can be attained by alleviating the actual losses, costs and environmental impact of the energy sources. This paper aims to address the above issues by reviewing the 4E analysis known as energy, exergy, exergoeconomic and exergoenvironment analysis of thermal power plants, intermittent renewable energy and integrated energy system. Amongst other noteworthy aspects outlined in this paper, it has been found out that extensive work has been done on TPP energy and exergy analysis but exergoeconomic and exergoenvironment analysis are still considered as emerging fields. Moreover, most of the analysis conducted for intermittent renewable energy and integrated energy system is based on energy analysis. Some vital conclusions have been drawn from literature survey like boiler, PV surface module and wind rotor are the major sources of exergy destruction/losses in thermal power plants and intermittent renewable energy system. Decreasing the above components losses will significantly increase the energy quality, thereby will achieve a cost-efficient, sustainable and eco-friendly energy system.

Horticultural products are an important source of carbohydrates, proteins, organic acids, vitamins and minerals for human nutrition. The objective of this study is to evaluate energy use pattern, environmental impacts and cumulative exergy demand analysis under different cropping systems including pistachio, nectarine, peach and apple in Qazvin province of Iran. Results showed the total energy consumption of pistachios, nectarines, peaches and apples were 24100 MJ ha −1, 25150 MJ ha −1, 30100 MJ ha −1 and 26800 MJ ha −1, respectively. The life cycle assessment method is considered as an appropriate assessment tool for ecosystem analysis through identification, quantification and evaluation of discharged and released resources in the environment. Analysis used ReCiPe2016 method, three environmental categories including (human health, ecosystems and resources) in this study were selected to cover different environmental impacts. On-Orchard emissions and chemical fertilizers are two important factors in the environmental emissions of horticultural products. The share of On-Orchard publications in pistachio, nectarine and peach crops is more than 75% related to human damage category. In addition, the amount of nitrogen in the ecosystem category has a significant effect. The results related to the resource damage category show that the rate of nitrogen release in pistachios, nectarines, peaches and apples is about 45%, 40%, 35% and 30%, respectively. Cumulative exergy demand analysis shows that pistachio and nectarine products have the highest and lowest energy release in all forms, respectively. In general, it can be concluded that the use of organic fertilizers and replacement of worn equipment can help to produce more sustainable horticultural products. Also, it is recommended for future studies use of modeling methods to predict the products under study as well as fuzzy optimization methods to save energy and reduce environmental impact.

Series and parallel two-stage evaporative strategy for vapor compression refrigeration cycles characterized by temperature and humidity independent control were presented. The theoretical model was established to analyze the performance of parallel two-stage evaporative strategy regarding the coefficient of performance (COP), exergy loss, exergy efficiency in comparisons with series system. And refrigerants R290 and R600 with low global warming potential (GWP) and no ozone depletion potential (ODP) are proposed as alternative refrigerants for R134a in two systems. The results show that compared with R134a, the proposed R600 has better performance with higher specific refrigerating capacity and coefficient of performance, of which specific refrigerating capacity increase 102.72% than that of R134a on average. Series two-stage evaporative strategy for vapor compression refrigeration cycle with R600 had the optimal techno-economic performance, which COP and exergy efficiency are 7.8% and 11% higher than that of parallel two-stage evaporative strategy, respectively.

The liquid desiccant air conditioning system is amongst the promising technologies for the provision of efficient air conditioning, particularly in hot humid climate conditions. By their benefits, membrane-based dehumidification systems have drawn large attention. Various techniques are used to enhance the performance of different dehumidification system types. The effect of using calcium chloride nanofluid solution with the added silicate nanoparticles as a desiccant solution in a hollow fiber membrane contactor system investigated experimentally. The airflow rate through the fibers is 11.2 m3/h with inlet relative humidity and temperature of 60 % and 35 °C, respectively. The sensitivity analysis was made to reveal the effect of desiccant temperatures, nanoparticle concentrations, and solution flow rates on sensible, latent, and total effectiveness and 2nd law efficiency of the system. The results indicate that using nanofluid instead of a pure desiccant solution, the values of sensible and latent effectiveness improved at the condition of high inlet solution temperature. The effect of employing nanofluid on exergy performance is the highest for the highest concentration of nanoparticles and inlet solution temperature. The maximum change of exergy destruction rate resulted by using nanofluid solution took place at a maximum flow rate of 244 ml/min for 1% nanofluid concentration. Using 1 % nanofluid instead of a pure solution, the rate of exergy destruction increased by 82 % and 160 % for 20 °C and 26 °C solution temperatures, respectively.

Solar energy based power generation systems can reduce pollutants emissions by reducing fossil fuel consumption. A new option for this idea is the Organic Rankine cycle coupled with a concentrating solar collector. The present study provides the Organic Rankine cycle performance using energy, exergy and economic approaches, selecting the appropriate operating fluid for the cycle consisting of Organic Rankine cycle and Linear Fresnel solar reflector. The effect of different organic fluid as well as different nanofluids on the overall performance of the cycle is investigated. Sensitivity analysis is discussed to evaluate the effect of various factors such as solar radiation, inlet temperature of solar system, mass flow rate, and inlet temperature and pressure of turbine on energy system performance. It was found that, the results provided in the present study do not correspond to any of the findings of previous similar studies. In addition, about 170 collectors of Linear Fresnel reflectors are needed to supply the thermal power required by the Organic Rankine cycle system. Under design conditions, the Levelized Cost of Energy and Simple payback time for the proposed hybrid system are obtained 0.0446 Euro/kWh and 7.74 years, respectively. Furthermore, the investment cost of the Linear Fresnel reflector system plays a key role in the economic justification of the proposed hybrid energy system.

In this study, the energy, exergy and yield is calculated for two cultivars of quinoa (Sajama and Titicaca) production. The result shows that the energy consumption, exergy consumption, energy efficiency, and exergy efficiency for producing quinoa are calculated to be 10,932.34 MJ/ton, 14,6940 MJ/ton, 141.32% and 15.9% in Sajama cultivar and 6,442.42 MJ/ton, 98,243.6 MJ/ton, 215.3% and 20.6% in Titicaca cultivar, respectively. The grain yield of Titicaca cultivar is higher, although its growth duration is less as compared to Sajama cultivar. The combined application of bio-fertilizer with chemical fertilizers give the highest growth duration, grain yield, 1000-seed weight, biological yield and harvest index, when compared with the sole application of fertilizer and no fertilizer. Nitrogen fertilizer consumes the highest amount of total energy inputs followed by irrigation water and diesel fuel for quinoa production. About 97.5% of total input exergy consumed in quinoa production is water irrigation. Thus, it is clear that decrease in the use of irrigation water decreases the environmental impact and increases sustainability and vice versa. In pursuit of sustainable agriculture goals, Titicaca cultivar could be introduced as advanced cultivar in saline and drought stressed fields as a crop with high potential yield and nutritional value.

In this research, the thermodynamic (energy and exergy) analysis of a single slope solar still using graphite plates and block magnets (GPBMSS) was investigated during summer and winter climatic conditions of Coimbatore city (latitude: 11°01′68′′N and longitude: 76°95′58′′E), in India, 2019. The results observed in GPBMSS were compared with a conventional solar still (CSS) under the same climatic conditions. The outcomes observed that the hourly productivity in GPBMSS was 19.6% and 22.8% higher in summer and winter days, respectively, when compared to CSS. The cumulative productivity in GPBMSS was found to be about 3.93 kg/m2 and 3.56 kg/m2 respectively, for 12 h observations during summer and winter days. Furthermore, the energy and exergy efficiencies of GPBMSS were substantially improved by 20.6% and 18.1% when compared to CSS during summer days. Similarly, the energy and exergy efficiencies of GPBMSS were increased by 18 and 19% compared to CSS in winter days. In addition, the maximum basin exergy destruction was observed in CSS compared to other solar still components. The results observed that the heat storage ability of the graphite plates and water magnetization in GPBMSS greatly decreased the exergy destructions. Finally, the water quality analysis proved that the distillate collected from both GPBMSS and CSS satisfied the requirements recommended by the Bureau of Indian Standards. HIGHLIGHTS Graphite plates and block magnets are attached in a solar still basin (GPBMSS) and improved the productivity by 3.93 kg/m2 and 3.56 kg/m2 respectively, in summer and winter climatic days.; The energy efficiency of GPBMSS was substantially improved by 20.6 and 18%, respectively, compared to CSS during summer and winter days.; The exergy efficiency in GPBMSS was enhanced by 18.1 and 19%, respectively compared to CSS in summer and winter days.

This study presents a simple approach for the exergy analysis of heat exchanger networks (HENs). This approach is based on approximating the irreversibility distribution ratio ( φ ) and the exergy destruction of a HEN in a large natural gas refinery, without needing to design the individual heat exchangers. Only the thermodynamics properties and the temperatures of the hot and cold streams at the inlets and outlets of the heat exchangers, as well as a model assuming for temperature distributions along the exchangers, are required. The exergy efficiencies and destructions were calculated for the individual heat exchangers and therefore for the HEN by superposing them. Also, φ and Bejan number were obtained by approximating irreversibilities arising from the heat transfer and pressure drop due to fluid friction. The total φ ( φ tot ) in the whole network was 0.188, with a Bejan number of 0.842. The results showed that the main source of the exergy destruction in the whole heat exchanger network of the plant is the irreversibility arising from heat transfer and the heat transfer irreversibility contribution to the total irreversibility in all the HENs was 84.2%. Moreover, the overall exergetic efficiency was 63.34%, which shows a great potential for improvement in the network system under consideration.

The roller kiln is characterized by significant heat losses mainly caused by flue gas and cooling gas accounting for 70%. In this study, four novel power cycles including a basic organic Rankine cycle (BORC), a regenerative organic Rankine cycle (RORC), a Kalina cycle11 (KC11) and a Kalina cycle 34 (KC34) with the parallel double-evaporator (PD) configuration are proposed for dual-level waste heat recovery for a roller kiln. To identify the superiority system, the recommended power cycles are assessed and compared from an integrated thermodynamic and economic perspective. The impacts of the basic operating parameters on net power output, exergy efficiency, electricity production cost and savings to investment ratio are discussed. Meanwhile, the single-, bi- and three-objective optimizations are conducted and the optimal solutions are compared. The results indicated that for the considered optimization models, PDKC34 achieved the highest net power output of 211.06–224.45​ kW and thermal efficiency of 20.02–21.20%, PDBORC had the best economic performance on electricity production cost of 0.0875–0.0932 $/kWh, payback period of 5.709–6.210 year and savings to investment ratio of 2.191–2.335 while PDRORC with R-141b possessed the best exergy efficiency of 45.11–49.17%. On the whole, the four thermodynamic cycles contributed to the best thermodynamic performance in the maximizing net power output model while these had the best economic performance in the minimum EPC model. Besides, the evaporation unit had the highest impact on exergy destruction and total investment cost among all components for the studied optimization models.

In recent years, attentions are focused on the application of cutting-edge reactors to utilize the remarkable virtues such as safety and also higher thermal efficiency. Sodium-cooled fast reactors (SFRs) are midst the promising types of fourth generation reactors for their non-reacting behavior and packed configurations, which are considered as heat source of various thermodynamic systems. Accordingly, nitrogen Brayton cycle could be devised as power conversion system (PCS) of the mentioned sodium cooled reactors, due to its simple arrangement. In present study, proposing the topping system of nitrogen Brayton cycle as a power generation system which is driven by the sodium reactor system, Kalina and heat pump cycles, as bottoming cycles, were designed to increase the performance of the overall system by integration with topping system. Subsequently, energy, exergy and exergoeconomic analyses were carried out to examine the reliability of the proposed system. The results displayed that under operating conditions, thermal efficiency, exergetic efficiency of the proposed system are 34% and 62%, respectively. Furthermore, using the exergy point of view, it was revealed that steam generator heat exchanger, SGHX, is the foremost cause of exergy destruction. Also, in order to attain an inclusive insight over the system, a parametric analysis was conducted. Therefore, investigating the influence of alterations in key features of the overall cycle, several optimum working conditions, such as optimal basic concentration of ammonia in Kalina cycle, optimal turbines (I&II) expansion ratio and low-pressure compressor pressure ratio etc., were derived.

This paper proposes a modified dual-ejector and dual-evaporator transcritical CO2 refrigeration cycle for supermarket application. Based on the conventional dual-evaporator transcritical CO2 refrigeration cycle, the modified cycle introduces two ejectors and a flash tank. The first liquid-vapor ejector sucks partial throttling flash vapor flowing to the low-temperature evaporator into the high-temperature evaporator; the second vapor-vapor ejector takes the vapor from the high-temperature evaporator as the primary flow to entrain the vapor from the low-temperature evaporator, and then the compressor suction pressure is lifted. Furthermore, the introduction of the first ejector increases the primary flow of the second ejector, and then improves the ability of the second ejector to lift the suction pressure of the compressor. The performance comparison between the two cycles is conducted by adopting energy and exergy analysis methods, and the efficiencies of the two ejectors are also analyzed. The comparison results demonstrate that the use of dual-ejector reduces the compressor pressure ratio by up to 19.1% under a typical working condition, and the improvements of the COP and exergy efficiency could reach up to 15.9%∼27.1% and 15.5%∼27.5% under all given working conditions. In addition, the modified cycle has an optimal gas cooler pressure of around 8.15 MPa, which is lower than the 8.3 MPa of the conventional cycle. The performance comparison results state clearly the energy-saving potential of the modified cycle and its application prospect in supermarket refrigeration.

The use of fossil fuels leads to depletion of fuel reserves and environmental pollution. One way to achieve a sustainable future in urban areas and remote communities is to use the independent renewable energy systems. Meanwhile, solar energy is one of the most common sources of energy generation that has attracted of the world. The present study provides the comprehensive examine the performance of two parabolic dish collector and flat-plate collector from energy, exergy, Enviroeconomic and Exergoenviroeconomic view of points. To examine the performance of solar systems, the climatic conditions of two different cities in Asia (Beijing and Tehran) have been used. In addition, the performance of the systems is investigated under different parameters and using different working fluids and MWCNT nanoparticle. It was found that the both solar systems have better overall performance in Tehran than in Beijing. Moreover, in the months when the solar collector has lower exergy efficiency, its use in Tehran compared to that Beijing has a better exergy performance than other months. In addition, the lowest and highest Levelized Cost of Energy are belong to dish collector (in Tehran with water) and flat plate collector (in Beijing with Dowtherm Q), respectively. For Tehran, LCOE of dish collector increases more than 5.5-fold when using water/MWCNT nanofluid instead of water.

The purpose of this paper is to propose a novel combined cooling, heating, and power generation system driven by evacuated tube solar collectors for residential applications. Accordingly, evacuated tube collectors are employed to provide sufficient heat for cooling and power generation purposes, while the waste heat of the evacuated tube collectors is then exploited for heating. The proposed system is comprehensively analyzed from various standpoints i.e., energy, exergy, and exergoeconomic. Afterward, the multi-objective genetic algorithm optimization – as a suitable tool – is applied to the system to extract a trade-off between the competing objective functions. The results showed that R124 results in better exergetic efficiency compared to other refrigerants. The parametric study outcomes indicate that with increasing the collector area, total product cost reduces but the total cost rate increases dramatically. The results also show that input parameters can directly affect the exergetic sustainability index to be cautiously designed. The optimization results show that the system’s maximum exergy efficiency is 10.06% while the minimum total cost rate is obtained as 0.4835 $/h. Further, the decision factors’ scatter plots show that LiBr mass fraction should be around 25% for optimal operation. Overall, the proposed system can be employed for cooling, heating, and power generation as a potential cycle.

Solar desalination is a promising technology to reduce the costs and environmental impact associated with the use of fossil fuel resources. Currently, almost all reverse osmosis (RO) desalination technologies powered by solar thermal energy are based on organic Rankine cycle (ORC) systems. Considering the significant advantages of the Stirling cycle in the utilization of solar energy, in this paper we present a RO desalination system powered by a solar dish-Stirling (DS) engine; a detailed parametric analysis based on finite-time thermodynamics is carried out to evaluate the water productivity as well as the energy and exergy efficiency of the system. The water productivity monotonically increases with increasing absorber temperature, while the optimal absorber temperature for maximum energy and exergy efficiency ranges from 1100 to 1300 K. Linear correlations are found between the optimal working fluid temperature of the source side and the maximized water productivity, energy/exergy efficiency, and average absorber temperature. The water productivity and energy/exergy efficiencies show an initial increase followed by a decrease with increasing sink side temperature. Among these properties, the stagnation point for maximum water productivity is found at a higher sink side temperature.

Three novel geothermal-based organic Rankine cycle (ORC) systems are proposed to enhance the efficiency and for waste heat recovery purpose. The proposed systems are modeled based on a basic ORC system (concept 1), an ORC system with an internal heat exchanger (concept 2), and a regenerative ORC system (concept 3). Accordingly, two thermoelectric generators (TEG) are introduced into the systems to exploit the waste heat of the system. The condenser is replaced with a TEG unit while the other TEG unit is used to recover the waste heat of the reinjected geothermal fluid. A comprehensive numerical investigation is conducted to compare the proposed systems from the thermodynamic and thermo-economic points of view. Furthermore, the most favorable proposed system is considered for optimization purposes and multi-objective optimization using the genetic algorithm is performed. Accordingly, a Pareto frontier is extracted consisting of the optimal solutions along with the scatter distribution of the critical parameters. The results indicate that the third proposed concept holds the highest exergy and energy efficiency among the studied systems. Also, the concept concludes the highest power output from the employed TEG units. The results further show that the first concept has the lowest associated cost with the system and the smallest payback period and at the same time higher net power generation. At the baseline of the systems, the exergy efficiencies are 59.39%, 57.92%, and 60.27%, and the total product costs are 25.8 $/GJ, 28.79 $/GJ, and 31.27 $/GJ for the first, the second, and the third proposed concepts, respectively. Results of the multi-objective optimization of the third concept reveal that the superheater temperature difference should be kept at higher values while the optimal range of the figure of merit is between 0.9 to 1.6. The proposed systems can be designed practically to exploit the geothermal heat source and recover the waste heat of the system.

Excessive consumption of fossil fuels has led to depletion of reserves and environmental crises. Therefore, turning to clean energy sources is essential. However, these energy sources are intermittent in nature and have problems meeting long-term energy demand. The option suggested by the researchers is to use hybrid energy systems. The aim of this paper is provide the conceptual configuration of a novel energy cycle based on clean energy resources. The novel energy cycle is composed of a wind turbine, solar photovoltaic field (PV), an alkaline fuel cell (AFC), a Stirling engine and an electrolyzer. Solar PV and wind turbine convert solar light energy and wind kinetic energy into electricity, respectively. Then, the generated electricity is fed to water electrolyzer. The electrolyzer decomposes water into oxygen and hydrogen gases by receiving electrical power. So the fuel cell inlets are provided. Next, the AFC converts the chemical energy contained in hydrogen into electricity during electrochemical reactions with by-product (heat). The purpose of the introduced cycle is to generate electricity and hydrogen fuel. The relationships defined for the components of the proposed cycle are novel and is examined for the first time. Results showed that the output of the introduced cycle is 10.5 kW of electricity and its electrical efficiency is 56.9%. In addition, the electrolyzer uses 9.9 kW of electricity to produce 221.3 grams per hour of hydrogen fuel. The share of the Stirling engine in the output power of the cycle is 9.85% (1033.7 W) which is obtained from the dissipated heat of the fuel cell. In addition, wind turbine is capable of generating an average of 4.1 kW of electricity. However, 238.6 kW of cycle exergy is destroyed. Two different scenarios are presented for solar field design.

This paper assesses the exergetic performance inside transcritical CO2 ejector refrigeration system integrated with thermoelectric subcooler (EJE + TES) through conventional and advanced exergy analyses. The results point out that 89.44% of the total exergy destruction is endogenous, which clearly demonstrates that it is not close in the interrelations among the system components. In addition, increasing the efficiency of the different components can decrease the exergy destruction by about 53.36%. The avoidable exergy destructions induced by the compressor is the highest, which indicates that priority should be given to the improvement of the compressor, followed by the thermoelectric subcooler, evaporator, ejector and gas cooler, while the expansion valve has almost no potential for improvement. This conclusion differs from that obtained by the conventional exergy method. The effects of the pinch temperature difference in each heat exchanger, as well as the compressor and ejector efficiencies on cycle theoretically exergetic performance are considered. When the compressor and ejector efficiencies increase from 0.5 to 0.9, the avoidable endogenous exergy destruction taking place in the corresponding system component are reduced by 93.61% and 82.33%, respectively. The performance of the EJE + TES system can be enhanced through reducing the pinch temperature difference.

In the past decade, compressed air vehicles have attracted much attention because of their zero pollution, high efficiency, environmental friendliness and relative maturity. To further explore the potential of compressed air technology in vehicles, three-stage and four-stage compressed air engine systems are optimized in present study by analyzing the energy and exergy distribution from a technological viewpoint. Their characteristics are compared in terms of shaft work, coolth, overall efficiency, and exergy distribution. Stage expansion ratios differ under maximum work output. The shaft work and coolth of both systems are increased with the increase of working pressure, turbine inlet temperature, or stage efficiency. Three-stage compressed air engine systems have a lower work output and coolth than four-stage compressed air engine systems at given operation condition. The overall efficiencies of these two systems are comparable to those of conventional diesel engines and fuel cell vehicles. Exergy losses of the two systems are composed by the exergy loss in the turbines, heat exchangers, and exits. The analyses suggest that increasing the number of stages, improving stage efficiency, and utilizing coolth to reduce the exergy loss in heat exchangers are effective ways to decrease the total exergy loss and improve the work output and overall efficiency of the compressed air engine systems.

Molten salts are typically used as energy storage media in concentrating solar power systems for their lower costs and environmental impact. This study aims to map and optimize the performance of parabolic trough concentrators (PTCs) working with molten salt-based nanofluids (MSNFs) as heat transfer media at high temperatures. The thermal, hydraulic, energetic, and exergetic performances were analyzed and optimized using a unique framework of Monte Carlo optical simulations, computational fluid dynamics, data-drive support vector regression, particle swarm optimization, and decision-making techniques. Three molten salts (Solar Salt, Hitec, and Hitec XL) and three nanoparticle types (Al2O3, CuO, and SiO2) were investigated in a broad range of volumetric concentrations (0.0–4.0%), operating Reynolds numbers (4 × 103 to 40 × 103), and temperatures (535–805 K). The results showed a maximum energy efficiency of 69.1%, achieved when using SiO2-Hitec nanofluid (1.0%) at a Reynolds number of 40 × 104 and temperature of 535 K. The maximum achieved exergy efficiency was 70.48%, obtained using pure Hitec at a Reynolds number of 40 × 104 and temperature of 535 K. The maximum possible enhancements in energy and exergy efficiencies in the covered range are 17.0 and 42.0%, respectively. The optimal combination of energy and exergy efficiencies are ∼73.1 and 69.0%, obtained using CuO-Hitec nanofluid at temperature, Reynolds number, and concentration of 535 K, 39912.98, and 0.019%, respectively. The optimum combination of percentage enhancements in energy and exergy efficiencies are 0.465 and 7.182%, respectively, which corresponds to CuO-Hitec nanofluid operating at 805 K, 32025.4, and 0.092%, respectively.

Currently, the air source heat pump is widely used for space heating. Although the CO2 has great potential in the refrigeration system, the basic transcritical CO2 heat pump performance is restricted by the huge throttling irreversibility caused by the higher gas cooler outlet temperature. The internal heat exchanger has been investigated extensively from the energetic perspective. However, little information is available about the exergy analysis, let alone the exergoeconomic analysis. In this paper, the transcritical CO2 heat pump with/without the internal heat exchanger is studied with the energy, exergy, and exergoeconomic analysis. Results show that the optimal coefficient of performance can be increased to 2.96 and 2.17 in the different heating terminals. The enlarged internal heat exchanger effectiveness is also beneficial to reduce the optimal discharge pressure and increased the system coefficient of performance. The throttling valve irreversibility is decreased from 0.067 to 0.145 kW·kW−1 to 0.040–0.071 kW·kW−1. With total irreversibility decrement, the exergy efficiency can be effectively improved, resulting in the 55.65%-73.42% reduction of the throttle valve cost rate. Considering the CO2 compressor investment, its total exergy cost rate increment is reached up to 34.06%-50.21%, leading to the higher exergoeconomic factor. However, the sensitivity analysis results show that the cost per unit of exergy production is more sensitive to the electricity price. Moreover, the optimal cost per unit of exergy production reduction is declined by 58.71% with the return water temperature of 30 °C.

This communication presents the implementation of a central receiver where helically coiled tubes are employed in order to enhance the rate of solar to heat conversion, which is the energy source that drives a cogeneration cycle which consists of organic Rankine cycle and the ejector-absorption refrigeration cycle. A numerical simulation with the application of computational fluid dynamics using the ANSYS-FLUENT package was conducted to examine the effect of the coil diameter and inlet oil (Duratherm 600) temperature on the pressure and temperature of solar heat transfer fluid (SHTF) which leaves the receiver. It is found that for inlet temperature of 92°C and direct normal irradiations of 850 W/m2, the outlet temperature of solar heat transfer fluid is raised by 9% when the coil diameter increased from 150 to 400 mm. Further, cogeneration cycle response to altering operating parameters is also investigated. From 100% radiative solar energy supplied to cogeneration cycle, it is revealed that fluids of organic Rankine cycle; R141b, R600a, and R143a produce the energetic output as 20.64%, 15.04%, and 8.33%, respectively, and the remaining solar input energy is lost to environment through temperature difference. The exergy distribution shows that for R141b operated cycle out of 100% solar exergy, 16.79% is produced as exergetic output, 81.94% is the exergy destroyed, and the remaining 1.27% is the exergy loss.

The cooling of the motor is one of key factors of keeping higher running efficiency of the refrigeration compressor. Suction refrigerant gas cooling motor is a widely used cooling method but it has poor cooling effect. A novel method of directly cooling screw compressor motor by thermosyphon refrigerant was proposed by authors. In this paper, the refrigeration system with thermosyphon refrigerant cooling motor (RSTRCM) and its basic principle were introduced firstly, then the mathematical model of energy and exergy of the system was built, and the test loop of an NH3/CO2 cascade refrigeration system was set up. Finally, compared with the refrigeration system with compressor suction gas cooling motor (RSCSCM), numerical analysis results showed that as condensation temperature of LTL is 5°C, RSTRCM can get higher exergy efficiency by up to 23.53%, and if condensing temperature of LTL increases from -5°C to 5°C, the power consumption of CO2 compressor and NH3 compressor in RSTRCM were reduced by 4.26% and 5.46% on average, separately. The test results showed that as the condensing temperature of the system is 40°C and the evaporation temperature is -45°C, -35°C, and -30°C, the coefficient of performance (COP) of RSTRCM were higher than that of RSCSCM by 10.42%, 6.61%, and 6.25%, respectively, which verify that the method of thermosyphon refrigerant cooling compressor motors can significantly improve the performance of the NH3/CO2 cascade refrigeration system.

Solar-based power and desalination system using super-critical carbon dioxide (S–CO2) Brayton cycle can be considered as one of the most promising development directions of future energy. This study presents the design and behaviour estimate of a novel concentrated solar-driven power and desalination (CSPD) system using S–CO2 Brayton cycle and multi-stage flash (MSF) desalination technology. Operation simulations and exergic analysis of the CSPD system are conducted by utilizing the Ebsilon software. Operation behaviour estimate results of the CSPD system show that the efficiency of S–CO2 Brayton cycle is 36.6%. The electric power and freshwater daily output of the CSPD system are 50.1 MW and 4050.8 t. The CSPD system can perform the solar-driven electricity production and solar-driven desalination simultaneously according to the pre-set operation strategy. The exergic analysis results indicate that the solar tower receiver and heat exchanger of desalination system have the two maximum energy destructions as well as the two lowest exergy efficiencies. The economic analysis results reveal that the CSPD system has an equivalent LCOE (levelized cost of electricity) of 0.059 $∙kWh−1 and an LCOW (levelized cost of water) of 1.15 $∙t−1, which means the CSPD system is economically feasible.

Solar energy is a widely used green energy resource that is used for drying processes. Through this assessment, the performance of an Indirect Solar Dryer (ISD) with three different cases, namely solar collector - without Thermal Energy Storage (TES), with TES unit having Phase Change Material (PCM) and with TES having fins inserted PCM have been experimentally analyzed during spring and summer seasons for drying Momordica charantia. Totally six experiments were undertaken to compare temperature, drying kinetics, and energy analyses. The initial moisture level of 2 kg of specimen decreased from 1.84 kg of water (92% w. b) to 0.24 kg of water (12% w. b) in 10.5 h utilizing ISD with TES having fins inserted PCM (Test 6). The maximum thermal efficiency achieved about 19.41% on Test 6. Exergy efficiency increased from 8.66% to 79.02% at Test 6. Environmental impacts assessment has revealed that the Energy Payback Time for the ISD was 1.42 years. The CO2 emission, mitigation, and carbon credit gained (Test 6) are 23.88 kg/year, 20.13 tons, and $100.642 to $402.569 for the 35 years’ intended lifespan. The assessment report showed that the device established was a potentially effective commercial drying technique, both in energy utilization and environmental sustainability.

A CO2 cryogenic separation process is proposed and designed for the new liquefied natural gas (LNG) purification cold box. This process is based on the liquefaction process using brazed plate heat exchanger (BPHE) and two separators are embedded between the liquefaction and subcooling heat exchangers to remove frozen CO2. The separator adopts one-use one-standby mode to ensure uninterrupted operation. The main parameters are first obtained through the phase diagram and solubility curve, and then verified by HYSYS simulation. The simulation results show that the preset values are in good agreement with the simulation. LNG enters the separator at 163 K and then is cooled down to 132.5 K to freeze and separate the CO2, so that the CO2 solids will not block the heat exchanger when they are further subcooled. When the mole fraction of CO2 inside the separator accumulates to 10%, the process will switch to another separator to work. The mixed refrigerants (MRs) heat the frozen separator to above 189 K, and the mixtures (solid CO2 and LNG) become liquid and flow out. The change of the process does not cause the temperature crossover inside the heat exchanger. Furthermore, the exergy losses of the proposed process are slightly increased by 1.3% compared to the original process.

Energy and exergy analyses were performed on a glass furnace regenerator and hydrogen production via thermal catalytic ammonia decomposition. A novel integration between energy and exergy analyses was suggested to predict the performance of thermodynamic and hydrogen production systems. It was found that the heat recovered by the combustion air of the south side regenerator was higher than that on the north side because of the fouling effect of the deposit materials and the heat lost through the regenerator walls. The maximum energy and exergy efficiencies of the south side regenerator were 98% and 93%, respectively, while those of the north regenerator side were 96.3% and 80%, respectively. The integration between energy and exergy analyses was also applied to investigate the performance of H2 production from the catalytic NH3 decomposition system. The conversion rate results proved that an increase in the ammonia feeding pressure was unfavorable. Moreover, the maximum energy and exergy efficiencies of the NH3 thermal decomposition system were 73.5% and 13.34% at a feeding pressure of 100 kPa, respectively. Furthermore, the non-equilibrium of the system is identified from the integrated effectiveness and entropy generation number.

Solar energy as a clean energy source is widely investigated to find out the effective mechanisms to meet a large part of energy demand in the near future. In the present research, a square-spiral finned quadruple-flow solar collector assisted dryer has been designed, and numerically compared with finless collector. Main aim of the current work is to develop and analyze a sustainable solar drying system. In this study, different from similar works, heat transfer surface area has been enhanced by using square spiral geometry which is an unconventional fin type. According to the numerical findings, a finned quadruple-flow collector which found more efficient has been manufactured, integrated with a drying chamber and performance experiments have been conducted. In the manufactured solar dryer, a PV panel has been used to run utilized fan. CFD simulation and empirical outcomes of this research exhibited the successful design of finned quadruple-flow collector. Experimentally obtained average efficiency of quadruple-flow collector varied in the range of 73.27-78.19%. Also, mean exergy efficiency of drying chamber was found between 44.16 and 58.38%. Sustainability index and waste exergy ratio values as important factors were attained between the ranges of 1.93-2.73 and 0.52-0.56, respectively. (c) 2021 Elsevier Ltd. All rights reserved.

The present investigation presents a novel hybrid solar-biomass system for electric power generation in remote areas. The proposed system integrates a Supercritical Brayton Cycle (SBC) to an Organic Rankine Cycle (ORC) as a bottoming cycle, driven by a Concentrated Solar Tower (CST) system and biomass furnace (coconut shell). The thermal energy generation potential of the biomass was determined from the fiber content, lignin, density, calorific value, and ash content, and the level of pollutant emissions at different combustion rates. Energy and exergy analyses were carried out considering three scenarios: hybrid solar-biomass SBC-ORC, SBC-ORC/solar, and SBC-ORC/biomass. The results revealed that coconut shells feature a low content of inorganic matter with a calorific value of 25.29 MJ/kg, and the best combustion efficiency (CO2/CO) was given at a speed of 0.0895 °C·min−1 (43.16%). The hybrid solar-biomass SBC-ORC system showed an exergetic efficiency of 26.60%, an increase of 17.28% with respect to the SBC-ORC/solar system in its base condition. The turbine inlet temperature was the variable with the greatest influence on the exergetic efficiency of the SBC-ORC/solar system, which reached a maximum of 23.8% at 700 °C. In conclusion, the integration of coconut shell biomass as an alternative and supplementary thermal source is a promising solution for the intermittence of solar-driven systems. This study demonstrated that the novel hybrid system ensures stability, good combustion efficiency, and enhanced performance compare to the standalone solar operation.

In this study, a thermodynamic analysis of the hybrid heat source driven organic Rankine cycle integrated flash tank vapor compression refrigeration (ORC-FTVCR) system is conducted using five different hydrocarbon fluids such as hexane, heptane, octane, nonane, and decane. The hybrid heat source consists of a solar collector and a biomass burner system. The system coefficient of performance (COPs), overall exergetic efficiency (ηoex), are taken as the indices of the thermal performance of the system. The impact of the operating parameters such as the intensity of solar radiation, inlet temperatures of expander and VCR evaporator, isentropic efficiencies of the compressor and expander, and the condenser saturated vapor temperature on system performance is also investigated. The results indicate that the system performs better using heptane as the working fluid. The values of COPs, ηoex, for ORC-FTVCR system using heptane are 0.551 and 4.21%, respectively. The solar collector and the biomass burner system contribute 88% to the total exergy destruction of the system.

The present study develops a novel energy system comprising a double-flash based geothermal cycle, a solar-driven cycle, a polymer electrolyte membrane (PEM) system and a waste heat recovery system. The proposed system can be used to generate electricity, produce hydrogen, space heating and prepare domestic hot water, and the solar-driven cycle can be turned off as a double-flash geothermal system when there is no solar radiation and the storage is empty. The unique aspect of the proposed system lies in the coupling relationship between the three turbine units in clear weather. Energy and exergy analyses are carried out to determine the irreversibilities, show the performance of the system and compare it with sole geothermal system. The results show that the proposed system has satisfactory thermodynamic properties. Under the reference conditions, the proposed energy system has a 148.3% (from 6171 kW to 15321 kW) increase in power generation compared with a sole double-flash geothermal system; under the optimal working conditions, the energy efficiency and exergy efficiency of the system can reach 29.6% and 29.2%, respectively. Furthermore, the effect of changing various system parameters on the energy and exergy efficiencies of the entire system and its subsystems were also studied.

Solar hot water storage tanks with mantle heat exchangers are widely used in balcony wall-mounted solar heating system in China. The thermal behaviour of a novelty mantle solar water tank with vertical inlet and outlet water tubes has been investigated both experimentally and numerically. Dimensionless parameter can well characterize the stratification of water and thermocline dynamics in the water tank. In the discharging mode, as the dimensionless time increases, the thermocline thickness gradually increases, and the mixing in the water tank intensifies. The dimensionless exergy gradually decreases with the increase of the dimensionless time.

This paper proposes using sodium-cooled fast reactor technologies for use in hydrogen vapor methane (SMR) modification. Using three independent energy rings in the Russian BN-600 fast reactor, steam is generated in one of the steam-generating cycles with a pressure of 13.1 MPa and a temperature of 505 °C. The reactor's second energy cycles can increase the gas-steam mixture's temperature to the required amount for efficient correction. The 620 ton/hr 540 °C steam generated in this cycle is sufficient to supply a high-temperature synthesis current source (700 °C), which raises the steam-gas mixture's temperature in the reactor. The proposed technology provides a high rate of hydrogen production (approximately 144.5 ton/hr of standard H2), also up to 25% of the original natural gas, in line with existing SMR technology for preparing and heating steam and gas mixtures will be saved. Also, exergy analysis results show that the plant's efficiency reaches 78.5% using HTR heat for combined hydrogen and power generation.

This work provides a comparative technical assessment of three technologies for CO2 removal from air: two aqueous-scrubbing processes and one solid sorbent process. We compute productivity and exergy and energy consumption using process simulations and mathematical optimization. Moreover, we evaluate the cost range and discuss the challenges for large-scale deployment. We show that all technologies can provide high-purity CO2 and that the solid-based process has the potential to offer the best performance, owing to an exergy demand of 1.4–3.7 MJ.kgCO2−1 and a productivity of 3.8–10.6 kgCO2.m−3.h−1. Translating productivity and energy into cost of CO2 capture via a simple model, we show that the capital cost is the main cost driver. All technologies have the potential to operate below 200 $.tonCO2−1 under favorable, yet realistic, energy and reactor costs. The solid-sorbent process achieves this under a broader range of conditions and is less dependent on the installation cost when a high mass transfer is achieved.

In this work, a novel thermochemical cycle (Boron-based) to produce ammonia is coupled with chemical looping combustion (CLC) process to produce final primary products of ammonia, CO2, water, and electricity. Manganese oxide-based CLC provides high purity N2, water and thermal energy for the carbothermal reduction of liquefied natural gas (LNG) occurring at 1200 °C. Gaseous synthesis gas from the carbothermal reduction is used as a fuel in the CLC's fuel reactor. Ammonia is produced through the hydrolysis of boron nitride (BN) and liquefied at atmospheric pressure. Thermodynamic equilibrium computations are used to predict the conversions of reactions involved in this proposed system. The overall system is then evaluated from energetic and exergetic perspectives to reflect upon the efficiency of reactors and subsystems. The production of approximately 25 metric t/h of NH3 is achieved while power production reaches 232 MW. The exergetic efficiency of the overall system is calculated to be 53.8%. Moreover, life cycle assessments are performed to assess boron oxide environmental impacts and evaluated the exergy-based allocation of greenhouse gases emission to ammonia at 0.772 kg CO2 (eq.)/kg NH3. About 61% reduction in emissions relative to the global average of ammonia synthesis is estimated.

The amount of stored thermal energy and the stratification in the packed bed thermal energy storage systems decrease in the afternoon because of the reduction in the solar power and solar-air heater panel's collector outlet temperature, so the charging process must be ceased at a particular instant. The optimal charging period is determined by considering the degree of stratification, energy/exergy stored, and the energy discharged during the 6 h of space heating. The proposed packed bed is divided into three sections lengthwise. Different bed materials have been placed separately in these regions regarding their volumetric heat capacity to promote stratification and sensible heat storage during charging. The bed's stratification level is determined via an exergy analysis to evaluate the discharge efficiency of the bed. The particle diameter and discharge air velocity on the system's thermal and hydrodynamic performance are inspected. The fan energy consumption during the discharge process is evaluated in the analyses. Distinctively, the air velocity is varied to obtain a minimum heat load of 18 kW for 6 h discharge process. A transient, one-dimensional finite-difference model is developed and validated with an experimental study conducted in the literature. Thermal energy storage and the stratification level are improved thanks to segmented bed by 85% and 135%, respectively.

In the current study, the energy and exergy efficiencies of three hydrogen production systems from ammonia decomposition using dielectric barrier discharge plasma (DBD) were comparatively evaluated. The hydrogen gas was separated in a cylindrical plasma membrane reactor (PMR) using the Pd–Cu40% membrane with a thickness of 20 μm. The pre-catalytic reactor (CR) is added to the second system (CR-PMR), additionally, the CR is filled with the catalytic material type of 2%Ru/Al2O3 and the CR temperature is raised to 450 °C. Furthermore, the zeolite material type of SA-600 A was added to the PMR in the third H2 production system (PMR) to enhance the hydrogen permeation through the Pd–Cu membrane. The hydrogen production rate was enhanced by combining the plasma and zeolite material in the third system (CR-CPMR). Moreover, the maximum obtained hydrogen production rates were 2.66, 81.6, and 96.6% in PMR, CR-PMR, and CR-CPMR or catalytic PMR, respectively. Also, it was observed that the energy efficiency increased by adding the CR to the system, while, the exergy efficiency values of all ammonia decomposition systems were still low due to the effect of system irreversibility. Additionally, the maximum energy efficiencies values were 0.8, 16.1, 44.1%, while the maximum exergy efficiencies values were 0.156, 4.91, and 6.344% for PMR, CR-PMR, and CR-CPMR, respectively. The exergy destruction rate of all NH3 decomposition systems was still high although using the modified systems. The depletion factor is enhanced with the feeding ammonia flow rate increased while the sustainability index decreased at the same flow rates. Moreover, it was seen that the depletion factor results of PMR only were higher than other systems due to the exergy destruction rate was high.

The heat exchanger for air dehumidification using liquid desiccant is mainly composed of an air-solution heat exchanger (dehumidifier) and a solution-refrigerant heat exchanger, wherein there are three liquids, i.e., air, desiccant solution, and refrigerant. The same air dehumidification process can be achieved by different solution flow rates (ms). Limited studies have revealed which solution flow rate is optimal (ms,opt) for minimizing the exergy input of the heat exchanger (Excooler). Thus, the analytical solution for the effectiveness of the entire heat exchanger (e) is theoretically deduced in this study, by the virtue of which, the ms,opt can be determined by solving ∂e / ∂ms = 0. Results reveal that e can be improved from 0.50 to 0.56 and Excooler can be saved by 17.9% in the given case, when the flow rate ratio of solution to air increases from 0.7 to the optimal value 1.5. Moreover, the air-solution-refrigerant flow rate matching plays an important role in the heat exchanger effectiveness. As a media fluid between the variable-temperature fluid (air) and the constant-temperature fluid (refrigerant), there is no solution flow rate to make the air-solution flow rate matching and solution-refrigerant flow rate matching simultaneously achieved. A compromised ms,opt should be pursued to balance the air-solution mismatching and the solution-refrigerant mismatching. It is anticipated that the findings of this research can be used for achieving an efficient air dehumidification process in the heat exchanger using liquid desiccant.

The present study focuses on the energy, exergy, exergo-economic, and exergo-environmental analyses of the solar-assisted multi-generation system. The multi-generation system consists of parabolic trough solar collector, regenerative power plant, double-effect absorption chiller system, proton exchange membrane electrolyzer, and multi-stage flash desalination plant. In the regenerative power plant, liquid petroleum gas (LPG) based boiler is implemented. The propane (C3H8) is used as the fuel in the boiler combustion chamber. The thermal and exergetic efficiencies of the power cycle are observed to be 41.08% and 23.26%, respectively. The electrical power of 1.384 MW is produced by the low-pressure turbine. Whereas, the thermal COP and exergetic COP are observed and maintained in the range of 1.28 to 0.22, respectively. The liquid hydrogen is produced by the PEM electrolyzer with the thermal and exergetic efficiencies of 60.83% and 64.65%, respectively. Furthermore, the exergo-economics and exergo-environmental analyses have also been conducted and all the parameters have been analyzed and concluded through graphs and tables.

In this research, the performance of serial two-stage compression (STC) cycle and bypass two-stage compression (BTC) cycle on the household refrigerator-freezers is tested in the laboratory. Then, based on the results of the experiments, exergy, exergoeconomic analyses, and cycle optimization are carried out. Considering that replacing refrigerants in household refrigerator-freezers is one of the approaches to increase the performance and environmental impact of these systems, R436A refrigerant (46% Isobutene and 54% Propane mixture) is used and analyzed to replace previous refrigerants. Finally, the multi-objective optimization of the mentioned cycles is performed with both refrigerants. For analyses, two models of refrigerator-freezers with different cycles are used (STC cycle with R134a refrigerant and BTC cycle with R-600a refrigerant). In both models, two evaporators for refrigerator-freezer compartments are used. International standards (IEC 62552) are used to test refrigerator-freezers. MATLAB and REFPROP 9.1 software are used to model the systems. According to the results of the analyses, the STC cycle with R436A refrigerant has more total exergy destruction rate (0.727 kW) compared to R134a refrigerant. In the BTC cycle, in which the fresh food compartment (FFC) and freezer compartment (FZC) operate, the total exergy destruction rate with R-600a refrigerant (0.422 kW) is less than with R436A refrigerant. In the case of the BTC cycle in which only the FZC operates, the total exergy destruction rate with R-600a refrigerant (0.455 kW) is less than with R436A refrigerant. The most exergoeconomic factor among cycle equipment is related to the compressor (about 98%). The highest COP value between cycles is related to the STC cycle with R134a refrigerant.

In this paper, Energy, Entropy and Exergy (EEE) analysis of flat plate solar collector is studied through a mathematical model by considering the overall loss coefficient as a non-constant parameter. The overall loss coefficient is calculated by minimizing the top loss coefficient using Lagrange multiplier optimization technique and also by empirical formulas. Further, energy efficiency, entropy generation, exergy destruction and exergy efficiency of the flat plate solar collector are also determined for the both aforesaid overall loss coefficients. The exergy efficiency of the proposed model has been doubled, when compared with the experimental measurements in the earlier literature. Also, comparing the proposed methods, it is observed that exergy efficiency obtained by using the minimal top loss coefficient is reasonably high and it enhances the overall collector’s efficiency.

Abstract The carbon dioxide concentration in the atmosphere has reached extremely high levels, generating environmental concerns. Unfortunately, despite the climate change, CO2 is not included nowadays as a key environmental issue in Best Available Technique (BAT) reference documents (BREF). Industrially, the widespread industrial technology to capture CO2 is the chemical absorption using aqueous monoethanolamine (MEA) at 30%wt, which is the basis of comparison for novel alternative techniques in the literature and seems a suitable candidate to be proposed as Best Available Technique. Nevertheless, there is an intense research to find alternative solvents that decrease the energy consumption for carbon capture and many solvents are claimed in the literature to outperform MEA. A novel empirical surrogate model and exergy balances are used to confirm that MEA is still the best candidate to be proposed as Best Available Technique. The surrogate model proposed in this study properly regresses the CO2 gas liquid equilibrium data. The regressed parameters of the model are tabulated in this study for many aqueous alkanolamines and their mixtures, being the basis for computationally inexpensive chemical absorption column design. The surrogate model parameter considering the temperature is related with the chemical absorption energy and the consumed energy for solvent recovery. The obtained results show that none of the considered alkanolamine outperforms MEA in all the considered aspects, i.e. energy and solvent flowrate. MEA minimum flowrate is 15.62 mol solvent/mol gas and its heat of absorption regression parameter is − 27,745 J/mol. The proposed mathematical method is useful as a fast assessment for other novel alternatives that will be proposed in the future, providing energetically more efficient and cleaner technologies for CO2 capture. Graphic abstract