Thermo-environmental investigation of solar parabolic dish-assisted multi-generation plant using different working fluids

The present study investigates the performance of a multi-generation plant by integrating a parabolic dish solar collector to a steam turbine and absorption chiller producing electricity and process heat and cooling. Thermodynamic modeling of the proposed solar dish integrated multi-generation plant is conducted using engineering equation solver to investigate the effect of certain operating parameters on the performance of the integrated system. The performance of the solar integrated plant is evaluated and compared using three different heat transfer fluids, namely, supercritical carbon dioxide, pressurized water, and Therminol-VPI. The useful heat gain by collector is utilized to drive a Rankine cycle to evaluate the network output, rate of process heat, cooling capacity, overall energetic, and exergetic efficiencies as well as coefficient of performance. The results show that water is an efficient working fluid up to a temperature of 550 K, while Therminol-VPI performs better at elevated temperatures (630 K and above). Higher integrated efficiencies are linked with the lower inlet temperature and higher mass flow rates. The integrated system using pressurized water as a heat transfer fluid is capable of producing 1278 and 832 kW of power output and process heat, respectively, from input source of almost 6121 kW indicating overall energy and exergy efficiencies of 34.5% and 37.10%, respectively. Furthermore, multi-generation plant is evaluated to assess the exergy destruction rate and steam boiler is witnessed to have the major contribution of this loss followed by the turbine. The exergo-environmental analysis is carried out to evaluate the impact of the system on its surroundings. Exergo-environmental impact index, impact factor, impact coefficient, and impact improvement are evaluated against increase in the inlet temperature of the collector. The single-effect absorption cycle is observed to have the energetic and exergetic coefficient of performances of 0.86 and 0.422, for sCO₂ operating system, respectively, with a cooling load of 228 kW.     

Development and performance assessment of a novel solar-assisted multigenerational system using high temperature phase change material

Solar-assisted multi-generation systems are eco-friendly with exceptional thermal performance. In the present study, a novel solar-assisted multi-generational system is proposed and investigated for multiple outputs. The proposed system consists of solar tower with heliostat, combined cycle (topping is Brayton cycle, while bottoming is Rankine cycle with reheat and regeneration processes), single effect Lithium-Bromide/water absorption chiller, heat pump, water-based thermal energy storage system and an electrolyzer. The system is integrated with high temperature phase change material (PCM) based thermal storage system for the continuous system operation. The salt PCM KF-MgF₂ is selected from the literature having melting temperature of 1280 K with high density and latent heat of fusion. The storage system ensures the stable and continuous working of the system during off sun hours. The aim of the present study is to thermodynamically and exergo-environmentally investigate the performance of PCM based solar driven multi-generation system.The results of the study depict that energy efficiency of single and multi-generation system is approximately 20.93% and 51.62%, while exergy efficiency is almost 22.51% and 53.45%, respectively. Hydrogen production rate and exergetic sustainability index of the proposed system is approximately 0.00742 kg/s and 0.078, respectively. Energy efficiency of multigeneration system is approximately 15.9% and 61% higher than tri-generation and co-generation systems at concentration ratio of 1000. Exergo-environmental impact index decreases to almost 5% by increasing direct normal irradiation, while exergetic sustainability index and exergy stability factor are increased to 125% and 54.2%, accordingly. Finally, energy efficiency of the single generation and multi generation systems are optimized at 23.56% and 56.83%, respectively.     

Development of some exergetic parameters for PEM fuel cells for measuring environmental impact and sustainability

This paper presents some new exergy-based parameters for PEM fuel cells to study how some of their operating aspects and system characteristics affect the environment and sustainability, based on some actual and literature data. The exergetic parameters of a PEM fuel cell developed here, in conjunction with environmental impact and sustainable development, are exergy efficiency, exergetic stability factor, environmental benign index and exergetic sustainability index. Any increase in efficiency improves exergetic sustainability. However, any increase in waste exergy ratio, exergy destruction factor, environmental destruction coefficient and environmental destruction index results in an increasing environmental impact of the PEM fuel cell and hence, a decreasing sustainability. Such parameters are expected to quantify how PEM fuel cells become more environmentally benign and sustainable.     

Investigation of a new integrated system for multiple outputs with hydrogen and methanol

In this study, an integrated multigeneration system that can produce hydrogen, electricity, heat, and methanol simultaneously is thermodynamically investigated. This integrated multigeneration system consists of three subsystems, namely: (i) electrolyzer, (ii) thermal power plant; and (iii) methanol production reactor. Energy and exergy analyses of all system components, as well as the sustainability analysis of the whole system, is performed thoroughly. The integrated system's thermodynamic performance is thoroughly investigated by changing some critical operational and environmental parameters in parametric studies. Based on the results of this study, recommendations for better energetic, exergetic, and environmental performance are presented for better sustainability. The results of this study show that the integrated multigeneration system is capable of producing hydrogen, heat, electricity, and methanol with overall energetic and exergetic efficiencies about 68% and 47%, respectively.     

A study on sustainability analysis of solid oxide fuel cell and proton exchange membrane electrolyzer integrated hybrid multi-generation system

The main objective of this study is to perform the sustainability analysis of a proton exchange membrane electrolyzer (PEME) and solid oxide fuel cell (SOFC) integrated hybrid multi-generation system that is designed to operate in four modes. In this regard, the effects of performance parameters of PEME and SOFC systems on the sustainability of hybrid multi-generation system are parametrically investigated. Accordingly, in terms of hydrogen production, the best value of hydrogen production is estimated to be 33.09 kg/h for both M1 and M2 operating modes. Moreover, in terms of the sustainability indicators, the maximum power generation of the system is calculated to be 13.9 MW while maximum energy and exergy efficiencies and exergetic sustainability index are respectively obtained to be 89%, 47% and 0.85 in M3 operating mode. However, minimum total product cost per unit energy generation is estimated to be 15.64 $/GJ in M1 operating mode. Furthermore, in terms of the exergetic sustainability index, the maximum effect ratios of the SOFC and PEME on the hybrid multi-generation system are respectively determined to be 5.076 and 16.124 in M1 operating mode.     

A comprehensive review on hydrogen production from coal gasification: Challenges and Opportunities

This paper comparatively discusses hydrogen production options through coal gasification, including plasma methods, and evaluate them for practical applications. In this regard, it focuses on numerous aspects of hydrogen production from coal gasification, including (i) state of the art and comparative evaluation, (ii) environmental and economic dimensions, (iii) energetic and exergetic aspects, (iv) challenges, opportunities and future directions. Furthermore, this review paper outlines what differences it brings in and what contributions it makes to the current literature about such a significant domain of potential hydrogen production which can be used as clean fuel, energy carrier and feedstock. Accordingly, this comprehensive review offers some results as follows: (i) plasma gasification system produces higher amount of hydrogen from other gasification processes, (ii) less amounts of solid wastes (slag, ash, tar, etc.) are released during plasma gasification process compared to other gasification processes, and (iii) it is overall more sustainable Thus, plasma gasification is proposed as a potential option for hydrogen fuel production from coals and for practical application in energy sector. As a case study, some plasma gasifiers in the literature are analyzed in terms of the exergetic sustainability. Furthermore, the case study results show that the exergetic sustainability index decreases from 0.642 to 0.186, and the exergetic efficiency drops from 0.342 to 0.156, while the environmental impact factor increases from 1.556 to 5.372 with an increase of waste exergy ratio from 0.839 to 0.532, respectively.     

Global warming,environmental and sustainability aspects of a geothermal energy based biodigester integrated SOFC system

In this study, global warming, environmental and sustainability aspects of a geothermal energy based biodigester integrated SOFC system are parametrically analyzed. In this regard, a system is designed, consisting of three main subsystems such as Solid Oxide Fuel Cell, Anaerobic Digester, and a Heat Recovery Steam Generator. In order to investigate the global warming, environmental and sustainability aspects of the system, the energy and exergy analyses are performed, and the following indicators are taken into consideration, which are i) unit CO₂ emission, ii) environmental effect factor, iii) waste exergy ratio, iv) exergy destruction ratio, v) exergy recovery ratio, vi) exergetic sustainability index. Accordingly, the maximum exergetic sustainability index and exergy efficiency of the integrated system are calculated to be 0.486 and 0.367, respectively, in case the SOFC inlet temperature is equal to 633.3 °C while electric current density is 5500 A/m². On the other hand, the minimum exergy destruction ratio and the minimum environmental effect factor are obtained to be 0.74 and 2.33 while SOFC inlet temperature is 633.3 °C and SOFC current density is 8000 A/m². The minimum unit CO₂ emission of the whole system is determined to be 368.4 kg/MWh at 5500 A/m² of SOFC current density and 727 °C of SOFC inlet temperature while determined as 258.3 kg/MWh at 8000 A/m² of SOFC current density and 680 °C of SOFC inlet temperature. Thus, it can be said that such a system may be applied for reducing the CO₂ based global warming effects and improving the environmental sustainability.     

Development and performance analysis of a new solar tower and high temperature steam electrolyzer hybrid integrated plant

In this article, an extensive thermodynamic performance assessment for the useful products from the solar tower and high-temperature steam electrolyzer assisted multigeneration system is performed, and also its sustainability index is also investigated. The system under study is considered for multi-purposes such as power, heating, cooling, drying productions, and also hydrogen generation and liquefaction. In this combined plant occurs of seven sub-systems; the solar tower, gas turbine cycle, high temperature steam electrolyzer, dryer process, heat pump, and absorption cooling system with single effect. In addition, the energy and exergy performance, irreversibility and sustainability index of multigeneration system are examined according to several factors, such as environment temperature, gas turbine input pressure, solar radiation and pinch point temperature of HRSG. Results of thermodynamic and sustainability assessments show that the total energetic and exergetic efficiency of suggested paper are calculated as 60.14%, 58.37%, respectively. The solar tower sub-system has the highest irreversibility with 18775 kW among the multigeneration system constituents. Solar radiation and pinch point temperature of HRSG are the most critical determinants affecting the system energetic and exergetic performances, and also hydrogen production rate. In addition, it has been concluded that, the sustainability index of multigeneration suggested study has changed between 2.2 and 3.05.     

Comparative energetic and exergetic performance analyses for coal-fired thermal power plants in Turkey

The purpose of this study is to analyze comparatively the performance of nine thermal power plants under control governmental bodies in Turkey, from energetic and exergetic viewpoint. The considered power plants are mostly conventional reheat steam power plant fed by low quality coal. Firstly, thermodynamic models of the plants are developed based on first and second law of thermodynamics. Secondly, some energetic simulation results of the developed models are compared with the design values of the power plants in order to demonstrate the reliability. Thirdly, design point performance analyses based on energetic and exergetic performance criteria such as thermal efficiency, exergy efficiency, exergy loss, exergetic performance coefficient are performed for all considered plants in order to make comprehensive evaluations. Finally, by means of these analyses, the main sources of thermodynamic inefficiencies as well as reasonable comparison of each plant to others are identified and discussed. As a result, the outcomes of this study can provide a basis used for plant performance improvement for the considered coal-fired thermal power plants.     

Exergetic sustainability indicators for a high pressure hydrogen production and storage system

This study examines the exergetic sustainability effect of PEM electrolyzer (PEME) integrated high pressure hydrogen gas storage system whose capacity is 3 kg/h. For this purpose, the indicators, previously used in the literature, are taken into account and their variations are parametrically studied as a function of the PEME operating pressure and storage pressure by considering i) PEME operating temperature at 70 °C, ii) PEME operating pressures at 10, 30, 50 and 100 bar, iii) hydrogen gas flow rate at 3 kg/h and iv) storage pressure between 200 and 900 bar. Consequently, the results from the parametric investigation indicate that, with the ascent of storage pressure from 200 to 900 bar at a constant PEME operating pressure (=50 bar), exergetic efficiency changes decreasingly between 0.612 and 0.607 while exergetic sustainability between 1.575 and 1.545. However, it is estimated that waste exergy ratio changes increasingly between 0.388 and 0.393 while environmental effect factor between 0.635 and 0.647. Additionally, it is said that the higher PEME outlet pressure causes the higher exergetic sustainability index, the lower environmental effect factor, the lower waste exergy output, the higher exergetic efficiency. However, the higher storage pressure causes the lower exergetic efficiency, the higher waste exergy output, the higher environmental effect factor and the lower exergetic sustainability index. Thus, it is recommended that this type of the system should be operated at higher PEME outlet pressure, and at an optimum hydrogen storage pressure.     

Energy,exergy, exergo-economic and exergo-environmental analyses of solar based hydrogen generation system

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.     

Energetic and exergetic performance evaluations of a geothermal power plant based integrated system for hydrogen production

In this paper, we propose an integrated system aiming for hydrogen production with by-products using geothermal power as a renewable energy source. In analyzing the system, an extensive thermodynamic model of the proposed system is developed and presented accordingly. In addition, the energetic and exergetic efficiencies and exergy destruction rates for the whole system and its parts are defined. Due to the significance of some parameters, the impacts of varying working conditions are also investigated. The results of the energetic and exergetic analyses of the integrated system show that the energy and exergy efficiencies are 39.46% and 44.27%, respectively. Furthermore, the system performance increases with the increasing geothermal source temperature and reference temperature while it decreases with the increasing pinch point temperature and turbine inlet pressure.     

Thermodynamic performance analysis and environmental impact assessment of an integrated system for hydrogen and ammonia generation

A novel multigeneration plant that's using natural gas for power, hydrogen, ammonia, and hot water generation, is planned and analyzed, in the current paper. The suggested combined plant integrated with four sub-systems, which are the Brayton cycle, reheat Rankine cycle, the high-temperature steam electrolyzer for hydrogen production, and ammonia synthesis processes. Also, thermodynamic analysis and environmental impact assessment are conducted for the designed plant and sub-systems. Moreover, the sustainability index analysis of this proposed study is conducted. The effects of some important indicators on the performance and on the environmental impact of the modeled system and sub-processes are also studied. According to analyses results, it is noted that the energetic and exergetic efficiencies of the suggested system are 51.83% and 70.27%, respectively, and also the total CO₂ emission rate is 11.4 kg/kWh for the integrated plant. Furthermore, the total irreversibility rate is computed as 40007.68 kW, and furthermore, the combustion chamber has a maximum irreversibility rate with 20,033 kW, among the proposed plant components.     

The effects of hydrogen fuel usage on the exergetic performance of a turbojet engine

In this study, the hydrogen fuel effect on the exergetic performance of a turbojet engine used in a military trainer aircraft is investigated. For the first step, the performance assessments of the exergetic performance are conducted according to jet fuel usage and the actual test cell data of the engine. For the second step, an exergetic evaluation is parametrically estimated to use the hydrogen fuel in the engine. Finally, the performance results of the engine run by jet fuel are compared with the performance results of the engine run by hydrogen fuel. Regarding the results of this study, by using hydrogen fuel in the engine, the exergy efficiency of the engine decreases from 15.40% to 14.33%, while the waste exergy rate increases from 6196.51 kW to 6669.4 kW. At the same time, the exergy rate of the fuel rises from 7324.87 kW to 7785.25 kW, hence the specific fuel exergy of the hydrogen fuel is higher than that of the jet fuel. The waste exergy flow cost of the engine rises from 16.52 × 10^?3 US$/kW to 17.79 × 10^?3 US$/kW. The environmental effect factor of the engine escalates from 5.49 to 5.98 and the ecological effect factor increases from 6.49 to 6.98. On the other hand, the exergetic sustainability index of the engine reduces from 0.182 to 0.167 when the sustainable efficiency factor of the engine goes down from 1.182 to 1.167. Between the components, for both jet fuel and hydrogen fuel, the CC has the highest values of the fuel exergy waste ratio, the relative waste exergy ratio, the product exergy waste ratio, the fuel ratio indicator, the product ratio indicator, the waste exergy cost flow, the environmental effect factor, the ecological effect factor, and the exergetic improvement potential when the CC has the lowest values of the exergy efficiency, exergetic sustainability index, and sustainable efficiency factor, respectively. The reason for this result is that the combustion process contains high irreversibities. The obtained results indicate that the hydrogen fuel usage in the turbojet engine badly affects the exergetic performance of the engine and its components (especially the combustion chamber) hence the specific exergy of the hydrogen fuel is higher than the jet fuel's. On the other hand, the exhaust emissions emitted to the environment decrease from 0.509 kg/s to 0.0045 kg/s with the hydrogen fuel usage.     

Parametric analysis of a solar energy based multigeneration plant with SOFC for hydrogen generation

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.     

Energy and exergy performance assessment of a novel solar-based integrated system with hydrogen production

In this study, a new solar power assisted multigeneration system designed and thermodynamically analyzed. In this system, it is designed to perform heating, cooling, drying, hydrogen and power generation with a single energy input. The proposed study consists of seven sub-parts which are namely parabolic dish solar collector, Rankine cycle, organic Rankine cycle, PEM-electrolyzer, double effect absorption cooling, dryer and heat pump. The effects of varying reference temperature, solar irradiation, input and output pressure of high-pressure turbine and pinch point temperature heat recovery steam generator are investigated on the energetic and exergetic performance of integration system. Thermodynamic analysis result outputs show that the energy and exergy performance of overall study are computed as 48.19% and 43.57%, respectively. Moreover, the highest rate of irreversibility has the parabolic dish collector with 24,750 kW, while the lowest rate of irreversibility is calculated as 5745 kW in dryer. In addition, the main contribution of this study is that the solar-assisted multi-generation systems have good potential in terms of energy and exergy efficiency.     

Design and analysis of a new solar hydrogen plant for power,methane, ammonia and urea generation

In this paper, a solar power-based combined plant for power, hydrogen, methane, ammonia and urea production is proposed. A parabolic trough collector is utilized for the system prime mover. Moreover, steam Rankine cycle, organic Rankine cycle, hydrogen production and compression subsystem, ammonia, methane and urea production units, single-effect absorption cooling unit, and freshwater production plant are integrated together to develop the present system for better system performance and cost-effectiveness and reduced environmental impact. In order to analyze and evaluate the proposed multigeneration plant, thermodynamic, parametric and economic studies are performed. According to the assessment results, it is found that energetic and exergetic efficiencies of the present multigeneration plant are 66.12% and 61.56%, respectively. The comparisons of the subsystem and overall plant efficiencies show that the highest energetic and energetic efficiencies belong to freshwater production plant by 79.24% and 75.62%, respectively. In addition, the present parametric analysis indicates that an increase in the reference temperature, solar radiation intensity and working pressure of the solar process has a positive effect on the plant's performance. The cost analysis reveals that as the solar radiation intensity and the working pressure of the solar process increase, the hydrogen generation cost decreases. Furthermore, the hydrogen generation cost is achieved to be 1.94 $/kgH₂ at 650 W/m² of the solar radiation intensity, with other parameters remaining constant.     

Analysis and performance assessment of a combined geothermal power-based hydrogen production and liquefaction system

In this paper, the thermodynamic study of a combined geothermal power-based hydrogen generation and liquefaction system is investigated for performance assessment. Because hydrogen is the energy of future, the purpose of this study is to produce hydrogen in a clear way. The results of study can be helpful for decision makers in terms of the integrated system efficiency. The presented integrated hydrogen production and liquefaction system consists of a combined geothermal power system, a PEM electrolyzer, and a hydrogen liquefaction and storage system. The exergy destruction rates, exergy destruction ratios and exergetic performance values of presented integrated system and its subsystems are determined by using the balance equations for mass, energy, entropy, energy and exergy and evaluated their performances by means of energetic and exergetic efficiencies. In this regard, the impact of some design parameters and operating conditions on the hydrogen production and liquefaction and its exergy destruction rates and exergetic performances are investigated parametrically. According to these parametric analysis results, the most influential parameter affecting system exergy efficiency is found to be geothermal source temperature in such a way that as geothermal fluid temperature increases from 130 °C to 200 °C which results in an increase of exergy efficiency from 38% to 64%. Results also show that, PEM electrolyzer temperature is more effective than reference temperature. As PEM electrolyzer temperature increases from 60 °C to 85 °C, the hydrogen production efficiency increases from nearly 39% to 44%.     

Exergetic pollution potential: Estimating the revocability of chemical pollution

The waste exergy approach to quantitative comparison of environmental impacts is considerably improved by proposing a separate accounting of material and energetic waste exergy and the implications are discussed within the context of sustainability. The exergy of mixing of a waste stream is found to be particularly well suited to an exergetic definition of chemical pollution and a correlative relationship with environmental pollutant cost (EPC) is suggested. A comprehensive measure of chemical environmental impact called pollution potential is defined as temperature multiplied by the change in configurational entropy per mole of pollutant in the environment. The result is related to the ideal thermodynamic work of chemical separation per mole required to instantaneously revoke a chemical pollutant, thereby returning the environment to a pristine reference condition. The current pollution potentials and total exergy of revocation of several notable atmospheric pollutants are estimated. Carbon dioxide is found to have low pollution potential in comparison to most halogenated hydrocarbons, but the vast quantities of anthropogenic carbon dioxide in the atmosphere would require much more total exergy of separation to revoke.     

Exergy analysis of a thermal power plant with measured boiler and turbine losses

In this paper, a thermodynamic analysis of a subcritical boiler–turbine generator is performed for a 32 MW coal-fired power plant. Both energy and exergy formulations are developed for the system. A parametric study is conducted for the plant under various operating conditions, including different operating pressures, temperatures and flow rates, in order to determine the parameters that maximize plant performance. The exergy loss distribution indicates that boiler and turbine irreversibilities yield the highest exergy losses in the power plant. In addition, an environmental impact and sustainability analysis are performed and presented, with respect to exergy losses within the system.