Thermodynamic analysis of a novel integrated system operating with gas turbine,s-CO2 and t-CO2 power systems for hydrogen production and storage

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

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 of a sustainable multi-generation system with re-compression sCO2 Brayton cycle for hydrogen generation

Current research aims to develop, design, and analyze a novel solar-assisted multi-purpose energy generation system for hydrogen production, electricity generation, refrigeration, and hot water preparation. The suggested system comprises a solar dish for supplying the necessary heat demand, a re-compression carbon dioxide-based Brayton cycle, a PEM electrolyzer for hydrogen generation, an ejector refrigeration system working with ammonia, and a hot water preparation system. The first law and exergy analyses are implemented to determine the performance of the multi-generation plant with various outputs. Besides, the exergo-environmental evaluation of the plant is conducted for the environmental impacts of the plant. Furthermore, parametric analyses are executed for investigating the system outputs, exergy destruction rate, and system efficiencies. According to the results, the rate of hydrogen generated by means of the multi-generation power plant is determined to be 0.062 g/s which corresponds to an hourly production of 0.223 kg. Besides, with the utilization of the supercritical closed Brayton cycle, a power generation rate of 74.86 kW is achieved. Furthermore, the irreversibility of the overall plant is estimated as 535.7 kW in which the primary contributor of this amount is the solar system with a destruction rate of 365.5 kW.     

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.     

Geothermal and solar based mutligenerational system: A comparative analysis

The current study focuses on the comparative analyses of multigeneration systems integrated with an electrolyzer for the production of hydrogen, for work rate a regenerative Rankine Cycle and finally for the cooling effect vapor absorption cycle was used. The power produced by both proposed systems was observed to yield some difference based on their positioning in the system and similarly, the rate of hydrogen production from the electrolyzer was also observed. Energetic and exergetic analyses of both the systems are done including all the concerned components. Certain parameters are varied to observe the overall changes in the system along with their effect on the overall efficiencies. A comparative analysis between the two proposed systems was carried out in the present study and eventually providing an efficient system, adding up to the novelty of this publication. At the similar ambient working conditions one of the systems was observed to yield an approximately 0.45% power efficiency difference but when the working parameters were varied, the difference was observed to be abrupt. The electrolyzer has a generation rate of 0.296 g/s and 0.2648 g/s respectively for both systems at base working conditions. At 800 W/m² of solar irradiance, the Rankine-Trough-Vapour (RTV) cycle produced 11.77% more net power as compared with Vapour-Trough-Rankine (VTR) cycle. Hydrogen production is considered to be one of the most valuable asset of this analysis because of its immense use in multiple processes. Furthermore, this study suggests the most efficient system for different atmospheric conditions.     

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.     

Performance analysis of a novel heat recovery system with hydrogen production designed for the improvement of boiler effectiveness

In this study, a multi-generation system is designed for the waste recovery of a 150 MW coal-fired power plant. The waste heat from the boiler system of the power plant is recycled in the power block with supercritical organic Rankine Cycle to obtain the required energy for the proton exchange membrane electrolyzer block. Then, two different cases are handled to utilize the products of the proton exchange membrane electrolyzer block. In the first case, H₂ is stored as an energy carrier to be used for external operations where O₂ was used for the enrichment of the combustion air. In the second case, H₂ is used for the enrichment of the fuel where O₂ is used for the enrichment of the combustion air as in the first case. It is determined that it is available to produce H₂ in an amount of 0.0417–0.0433 kmol/s. The energy efficiency of the overall system is determined as 25.37% and 24.05% where the exergy efficiency of the overall system is determined as 31.56% and 29.80% for the first and second cases, respectively.     

Performance assessment of a biogas fuelled molten carbonate fuel cell-thermophotovoltaic cell-thermally regenerative electrochemical cycle-absorption refrigerator-alkaline electrolyzer for multigenerational applications

In recent years, there has been increasing interest in fuel cell hybrid systems. In this paper, a novel multi-generation combined energy system is proposed. The system consists of a molten carbonate fuel cell (MCFC), a thermally regenerative electro-chemical cycle (TREC), a thermo photovoltaic cell (TPV), an alkaline electrolyzer (AE) and an absorption refrigerator (AR). It has four useful outputs, namely electricity, hydrogen, cooling and heating. The overall system is thermodynamically modeled in a detailed manner while its simulation and modeling are done through the TRNSYS software tool. Power output, cooling-heating and produced hydrogen rates are determined using energetic and exergetic analysis methods. Results are obtained numerically and plotted. The maximum power output from the system is 16.14 kW while maximum energy efficiency and exergy efficiency are 86.8% and 80.4%,. The largest exergy destruction is due to the MCFC.     

Energy,exergy and economic analyses and multiobjective optimization of a novel solar multi-generation system for production of green hydrogen and other utilities

Renewable energy based multi-generation systems can help solving energy-related environmental problems. For this purpose, a novel solar tower-based multi-generation system is proposed for the green hydrogen production as the main product. A solar-driven open Brayton cycle with intercooling, regeneration and reheat is coupled with a regenerative Rankine cycle and a Kalina cycle-11 as a unique series of power cycles. Significant portion of the produced electricity is utilized to produce green hydrogen in an electrolyzer. A thermal energy storage, a single-effect absorption refrigeration cycle and two domestic hot water heaters are also integrated. Energy, exergy and economic analyses are performed to examine the performance of the proposed system, and a detailed parametric analysis is conducted. Multiobjective optimization is carried out to determine the optimum performance. Optimum energy and exergy efficiencies, unit exergy product cost and total cost rate are calculated as 39.81%, 34.44%, 0.0798 $/kWh and 182.16 $/h, respectively. Products are 22.48 kg/h hydrogen, 1478 kW power, 225.5 kW cooling and 7.63 kg/s domestic hot water. Electrolyzer power size is found as one of the most critical decision variables. Solar subsystem has the largest exergy destruction. Regenerative Rankine cycle operates at the highest energy and exergy efficiencies among power cycles.     

Thermodynamic performance assessment of ocean thermal energy conversion based hydrogen production and liquefaction process

In the proposed study, the thermodynamic performance assessment of ocean thermal energy conversion (OTEC) based hydrogen generation and liquefaction system are evaluated. In this context, the energetic and exergetic analyses of integrated system are conducted for multigeneration. This integrated process is consisted of the heat exchangers, turbine, condenser, pumps, solar collector system, hot storage tank, cold storage tank and proton exchange membrane (PEM) electrolyzer. In addition to that, the impacts of different design indicators and reference ambient parameters on the exergetic performance and exergy destruction rate of OTEC based hydrogen production system are analyzed. The energetic and exergetic efficiencies of integrated system are founded as 43.49% and 36.49%, respectively.     

Geothermal and solar energy–based multigeneration system for a district

In this study, parabolic trough collector with an integrated source of geothermal water is used with regenerative Rankine cycle with an open feedwater heater, an electrolyzer, and an absorption cooling system. The absorption fluids used in the solar collectors were Al₂O₃‐ and Fe₂O₃‐based nanofluids. Detailed energetic and exergetic analyses are done for the whole system including all the components. A comparative analysis of both the used working fluids is done and plotted against their different results. The parameters that are varied to change the output of the system are ambient temperature, solar irradiance, the percentage of nanofluids, the mass flow rate of the geothermal well, the temperature gradient of the geothermal well that had an effect on the net power produced, and the outlet temperature of the solar collector overall energetic and exergetic efficiencies. Other useful outputs by this domestic integrated multigeneration system are the heating of domestic water, space heating (maintaining the temperature at 40°C‐50°C), and desalination of seawater (flash distillation). The hydrogen production rate for both the fluids diverges with each other, both producing average from 0.00490 to 0.0567 g/s.     

Parametric study of exergetic efficiency of a small-scale cogeneration plant incorporating a heat pump

A comparative parametric analysis is carried out of a small-scale combined heat and power plant incorporating a heat pump and the conventional system in which heat is produced in a hot water boiler and electrical energy is drawn from the power grid. Relative exergetic efficiency is defined as the quotient of exergetic (rational) efficiencies of the cogeneration plant and the related conventional system. Dependence of this efficiency on the power-to-heat ratio for chosen values of parameters characterizing the compared systems is calculated and shown pictorially.     

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.     

Development and analysis of a novel biomass-based integrated system for multigeneration with hydrogen production

Energy and exergy analyses of an integrated system based on anaerobic digestion (AD) of sewage sludge from wastewater treatment plant (WWTP) for multi-generation are investigated in this study. The multigeneration system is operated by the biogas produced from digestion process. The useful outputs of this system are power, freshwater, heat, and hydrogen while there are some heat recoveries within the system for improving efficiency. An open-air Brayton cycle, as well as organic Rankine cycle (ORC) with R-245fa as working fluid, are employed for power generation. Also, desalination is performed using the waste heat of power generation unit through a parallel/cross multi-effect desalination (MED) system for water purification. Moreover, a proton exchange membrane (PEM) electrolyzer is used for electrochemical hydrogen production option in the case of excess electricity generation. The heating process is performed via the rejected heat of the ORC's working fluid. The production rates for products including the power, freshwater, hydrogen, and hot water are obtained as 1102 kW, 0.94 kg/s, 0.347 kg/h, and 1.82 kg/s, respectively, in the base case conditions. Besides, the overall energy and exergy efficiencies of 63.6% and 40% are obtained for the developed system, respectively.     

A novel combined biomass and solar energy conversion-based multigeneration system with hydrogen and ammonia generation

In the present study, an innovative multigeneration plant for hydrogen and ammonia generation based on solar and biomass power sources is suggested. The proposed integrated system is designed with the integration of different subsystems that enable different useful products such as power and hydrogen to be obtained. Performance evaluation of designed plant is carried out using different techniques. The energetic and exergetic analyses are applied to investigate and model the integrated plant. The plant consists of the parabolic dish collector, biomass gasifier, PEM electrolyzer and hydrogen compressor unit, ammonia reactor and ammonia storage tank unit, Rankine cycle, ORC cycle, ejector cooling unit, dryer unit and hot water production unit. The biomass gasifier unit is operated to convert biomass to synthesis gaseous, and the concentrating solar power plant is utilized to harness the free solar power. In the proposed plant, the electricity is obtained by using the gas, Rankine and ORC turbines. Additionally, the plant generates compressed hydrogen, ammonia, cooling effect and hot water with a PEM electrolyzer and compressed plant, ammonia reactor, ejector process and clean-water heater, respectively. The plant total electrical energy output is calculated as 20,125 kW, while the plant energetic and exergetic effectiveness are 58.76% and 55.64%. Furthermore, the hydrogen and ammonia generation are found to be 0.0855 kg/s and 0.3336 kg/s.     

Exergetic analysis and economic evaluation of central tower receiver solar thermal power plant

This article presents the analytical evaluation of a central tower receiver solar thermal power plant with air‐cooled volumetric receiver using exergy analysis. The energetic and exergetic losses as well as the efficiencies of a typical central tower receiver‐based solar thermal power plant have been carried out under the specific operating conditions. The enhancement in efficiency of the plant from the variation in power input to constant power input achieved by thermal storage backup condition has been determined. It is found that the year round average energetic efficiency can be increased from 24.15% to 25.08% and year round average exergetic efficiency can be increased, from 26.10% to 27.10% for the selected location Jodhpur. The unit cost of electric energy generation (kWh_e) is found to be INR 10.09 considering 30‐year lifespan of the solar plant along with a 10% interest rate. The present study provides a base for the development of future solar thermal power plants in India. Copyright © 2013 John Wiley & Sons, Ltd.     

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.     

A medium-temperature solar thermal power system and its efficiency optimisation

This paper firstly expounds that the reheat-regenerative Rankine power cycle is a suitable cycle for the parabolic trough collector, a popular kind of collector in the power industry. In a thermal power cycle, the higher the temperature at which heat is supplied, the higher the efficiency of the cycle. On the other hand, for a given kind of collector at the same exiting temperature, the higher the temperature of the fluid entering the collector, the lower the efficiency of the collector. With the same exiting temperature of the solar field and the same temperature differences at the hottest end of the superheater/reheater and at the pinch points in the heat exchangers (e.g., the boiler) in the cycle, the efficiencies of the system are subject to the temperature of the fluid entering the collector or the saturation temperature at the boiler. This paper also investigates the optimal thermal and exergetic efficiencies for the combined system of the power cycle and collector. To make most advantage of the collector, the exiting fluid is supposed to be at the maximum temperature the collector can harvest. Hence, the thermal and exergetic efficiencies of the system are related to the saturation temperature at the boiler here.     

Evaluation of hybrid solar-wind-hydrogen energy system based on methanol electrolyzer

In this study, it is aimed to meet the annual electricity and heating needs of a house without interruption with the photovoltaic panel, wind turbine, methanol electrolyzer, and high temperature proton exchange membrane fuel cell system. The system results show that the use of the 2 WT with 18 PV was enough to provide the need of the methanol electrolyzer, which provides requirements of the high temperature proton exchange membrane fuel cell. The produced heat by the fuel cell was used to meet the heat requirement of the house with combined heat and power system. Electrical, thermal and total efficiencies of fuel cell system with combined heat and power were obtained as 38.54%, 51.77% and 90%, respectively. Additionally, the levelized cost of energy of the system was calculated as 0.295 $/kWh with combined heat and power application. The results of this study show that H₂ is useful for long-term energy storage in off-grid energy systems and that the proposed hybrid system may be the basis for future H₂-based alternative energy applications.     

Performance assessment of parabolic dish and parabolic trough solar thermal power plant using nanofluids and molten salts

The present study has been conducted using nanofluids and molten salts for energy and exergy analyses of two types of solar collectors incorporated with the steam power plant. Parabolic dish (PD) and parabolic trough (PT) solar collectors are used to harness solar energy using four different solar absorption fluids. The absorption fluids used are aluminum oxide (Al₂O₃) and ferric oxide (Fe₂O₃)‐based nanofluids and LiCl‐RbCl and NaNO₃‐KNO₃ molten salts. Parametric study is carried out to observe the effects of solar irradiation and ambient temperature on the parameters such as outlet temperature of the solar collector, heat rate produced, net power produced, energy efficiency, and exergy efficiency of the solar thermal power plant. The results obtained show that the outlet temperature of PD solar collector is higher in comparison to PT solar collector under identical operating conditions. The outlet temperature of PD and PT solar collectors is noticed to increase from 480.9 to 689.7 K and 468.9 to 624.7 K, respectively, with an increase in solar irradiation from\ 400 to 1000 W/m². The overall exergy efficiency of PD‐driven and PT‐driven solar thermal power plant varies between 20.33 to 23.25% and 19.29 to 23.09%, respectively, with rise in ambient temperature from 275 to 320 K. It is observed that the nanofluids have higher energetic and exergetic efficiencies in comparison to molten salts for the both operating parameters. The overall performance of PD solar collector is observed to be higher upon using nanofluids as the solar absorbers. Copyright © 2015 John Wiley & Sons, Ltd.