Thermoeconomic analysis of SOFC-GT-VARS-ORC combined power and cooling system

The integration of the gas turbine cycle and organic Rankine cycle with the solid oxide fuel cell for power generation is quite prevalent. However, the need is also felt for systems capable of providing power with cooling. Therefore, it is proposed to integrate solid oxide fuel cell with gas turbine cycle, vapour absorption refrigeration system and organic Rankine cycle through the heat available with fluid in the cycle. Here intercooled and reheat gas turbine cycle is integrated with solid oxide fuel cell. Heat rejected in intercooling is used in vapour absorption refrigeration system for cooling. This paper presents thermoeconomic analysis. Results show that the combination of solid oxide fuel cell-gas turbine-vapour absorption refrigeration system-organic Rankine cycle yields increase in efficiency to 68.79% as compared to 58.88% from combined solid oxide fuel cell-gas turbine cycle. The cost of electricity per unit power output is found as 1939.93 $/kW.     

Design and modeling of a multigeneration system driven by waste heat of a marine diesel engine

In this study, a novel marine diesel engine waste heat recovery layout is designed and thermodynamically analyzed for hydrogen production, electricity generation, water desalination, space heating, and cooling purposes. The integrated system proposed in this study utilizes waste heat from a marine diesel engine to charge an organic Rankine and an absorption refrigeration cycle. The condenser of the Organic Rankine Cycle (ORC) provides the heat for the single stage flash distillation unit (FDU) process, which uses seawater as the feedwater. A portion of the produced freshwater is used to supply the Polymer Electrolyte Membrane (PEM) electrolyzer array. This study aims to store the excess desalinated water in ballast tanks after an Ultraviolet (UV) treatment. Therefore it is expected to preclude the damage of ballast water discharge on marine fauna. The integrated system's thermodynamic analysis is performed using the Engineering Equation Solver software package. All system components are subjected to performance assessments based on their energy and exergy efficiencies. Additionally, the capacities for power generation, freshwater production, hydrogen production, and cooling are determined. A parametric study is conducted to evaluate the impacts of operating conditions on the overall system. The system's overall energy and exergy efficiencies are calculated as 25% and 13%, respectively, where the hydrogen production, power generation, and freshwater production capacities are 306.8 kg/day, 659 kW, and 0.536 kg/s, respectively. Coefficient of Performance (COP) of the absorption refrigeration cycle is calculated as 0.41.     

Development and exergoeconomic evaluation of a SOFC-GT driven multi-generation system to supply residential demands: Electricity,fresh water and hydrogen

In this study, a novel multi-generation system is proposed by integrating a solid oxide fuel cell (SOFC)-gas turbine (GT) with multi-effect desalination (MED), organic flash cycle (OFC) and polymer electrolyte membrane electrolyzer (PEME) for simultaneous production of electricity, fresh water and hydrogen. A comprehensive exergoeconomic analysis and optimization are conducted to find the best design parameters considering exergy efficiency and total unit cost of products as objective functions. The results show that the exergy efficiency and the total unit cost of products in the optimal condition are 59.4% and 23.6 $/GJ, respectively, which offers an increase of 2% compared to exergy efficiency of SOFC-GT system. Moreover, the system is capable of producing 2.5 MW of electricity by the SOFC-GT system, 5.6 m³/h of fresh water by MED unit, and 1.8 kg/h of hydrogen by the PEME. The associated cost for producing electricity, fresh water and hydrogen are 3.4 cent/kWh, 37.8 cent/m³, and 1.7 $/kg, respectively. A comparison between the results of the proposed system and those reported in other related papers are presented. The diagram of the exergy flow is also plotted for the exact determination of the exergy flow rate in each component, and also, location and value of exergy destruction. Finally, the capability of the proposed system for a case study of Iran is examined.     

Performance analysis and optimization of a hydrogen liquefaction system assisted by geothermal absorption precooling refrigeration cycle

The present paper deals with the hydrogen liquefaction with absorption precooling cycle assisted by geothermal water is modeled and analyzed. Uses geothermal heat in an absorption refrigeration process to precool the hydrogen gas is liquefied in a liquefaction cycle. High-temperature geothermal water using the absorption refrigeration cycle is used to decrease electricity work consumption in the gas liquefaction cycle. The thermoeconomic optimization procedure is applied using the genetic algorithm method to the hydrogen liquefaction system. The objective is to minimize the unit cost of hydrogen liquefaction of the composed system. Based on optimization calculations, hydrogen gas can be cooled down to ?30 °C in the precooling cycle. This allows the exergetic cost of hydrogen gas to be reduced to be 20.16 $/GJ (2.42 $/kg LH₂). The optimized exergetic cost of liquefied hydrogen is 4.905 $/GJ (1.349 $/kg LH₂), respectively.     

Thermodynamic analysis and assessment of an integrated hydrogen fuel cell system for ships

In this thermodynamic investigation, an integrated energy system based on hydrogen fuel is developed and studied energetically and exergetically. The liquefied hydrogen fueled solid oxide fuel cell (SOFC) based system is then integrated with a steam producing cycle to supply electricity and potable water to ships. The first heat recovery system, after the fuel cells provide thrust for the ship, is by means of a turbine while the second heat recovery system drives the ship's refrigeration cycle. This study includes energy and exergy performance evaluations of SOFC, refrigeration cycle and ship thrust engine systems. Furthermore, the effectiveness of SOFCs and a hydrogen fueled engine in reducing greenhouse gas emissions are assessed parametrically through a case study. The main propulsion, power generation from the solid oxide fuel cells, absorption chiller, and steam bottoming cycle systems together have the overall energy and exergy efficiencies of 41.53% and 37.13%, respectively.     

Design and energy evaluation of a stand‐alone copper‐chlorine (Cu‐Cl) thermochemical cycle system for trigeneration of electricity,hydrogen, and oxygen

In this article, a new stand‐alone Cu‐Cl cycle system (SACuCl) for trigeneration of electricity, hydrogen, and oxygen using a combination of a specific combined heat and power (CHP) unit and a 2‐step Cu‐Cl cycle using a CuCl/HCl electrolyzer is presented. Based on the self‐heat recuperation technology for the CHP unit and the heat integration of the Cu‐Cl cycle unit, the power efficiency of the SACuCl for 5 prescribed scenarios (case studies) is predicted to achieve about 48% at least. The SACuCl uses the technologies of the dry reforming of methane and the oxy‐fuel combustion to achieve a relatively high CO₂ concentration in the flue gas, and CO₂ emissions for power generation could be almost restricted by 0.418 kg/kWh. From the aspect of the electricity required for hydrogen production, it is verified that the 2‐step Cu‐Cl cycle system is superior to the conventional water electrolyzer because the CHP process supplies the heat/electricity for Cu‐Cl thermochemical reactions and a thermoelectric generator is connected to the exhaust gas for recovering the power consumption from the compressor and the CuCl/HCl electrolyzer. Finally, the heat exchanger network and the pinch technology are employed to determine the optimum heat recovery of the Cu‐Cl cycle. In case 5 analyzed for the SACuCl, the electricity required for the heat‐integrated 2‐step Cu‐Cl cycle is predicted to dramatically decrease from 4.39 to 0.452 kWh/m³ H₂ and the cycle energy efficiency could be obviously increased from 23.77 to 31.97%.     

Electrolyzer-fuel cell combination for grid peak load management in a geothermal power plant: Power to hydrogen and hydrogen to power conversion

This study provides comprehensive energy, exergy, and economic evaluations and optimizations of a novel integrated fuel cell/geothermal-based energy system simultaneously generating cooling and electricity. The system is empowered by geothermal energy and the electricity is mainly produced by a dual organic cycle. A proton exchange membrane electrolyzer is employed to generate the oxygen and hydrogen consumed by a proton exchange membrane fuel cell utilized to support the network during consumption peak periods. This fuel cell can be also used for supplying the electricity demanded by the network to satisfy the loads at different times. All the simulations are conducted using Engineering Equation Solver software. To optimize the system, a multi-objective optimization method based on genetic algorithm is applied in MATLAB software. The objective functions are minimized cost rate and maximized exergy efficiency. The optimum values of exergy efficiency and cost rate are found to be 62.19% and 18.55$/h, respectively. Additionally, the results reveal that combining a fuel cell and an electrolyzer can be an effective solution when it comes to electricity consumption management during peak load and low load periods.     

Effective use of hydrogen sulfide and natural gas resources available in the Black Sea for hydrogen economy

In this article, we propose a novel system to effectively deploy an integrated fuel processing system for hydrogen sulfide and natural gas resources available in the Black Sea to be used for a quick transition to the hydrogen economy. In this regard, the proposed system utilizes offshore wind and offshore photovoltaic power plants to meet the electricity demand of the electrolyzer. A PEM electrolyzer unit generates hydrogen from hydrogen sulfide that is available in the Black Sea deep water. The generated hydrogen and sulfur gas from hydrogen sulfide are stored in high-pressure tanks for later use. Hydrogen is blended with natural gas, and the blend is utilized for industrial and residential applications. The investigated system is modeled with the Aspen Plus software, and hydrogen production, blending, and combustion processes are analyzed accordingly. With the hydrogen addition up to 20% in the blend, the carbon dioxide emissions of combustion decrease from 14.7 kmol/h to 11.7 kmol/h, when the annual cost of natural gas is reduced from 9 billion $ to 8.3 billion $. The energy and exergy efficiencies for the combustion process are increased from 84% to 97% and from 62% to 72%, respectively by a 20% by volume hydrogen addition into natural gas.     

Technico-economic analysis of off grid solar PV/Fuel cell energy system for residential community in desert region

A technico-economic analysis based on integrated modeling, simulation, and optimization approach is used in this study to design an off grid hybrid solar PV/Fuel Cell power system. The main objective is to optimize the design and develop dispatch control strategies of the standalone hybrid renewable power system to meet the desired electric load of a residential community located in a desert region. The effects of temperature and dust accumulation on the solar PV panels on the design and performance of the hybrid power system in a desert region is investigated. The goal of the proposed off-grid hybrid renewable energy system is to increase the penetration of renewable energy in the energy mix, reduce the greenhouse gas emissions from fossil fuel combustion, and lower the cost of energy from the power systems. Simulation, modeling, optimization and dispatch control strategies were used in this study to determine the performance and the cost of the proposed hybrid renewable power system. The simulation results show that the distributed power generation using solar PV and Fuel Cell energy systems integrated with an electrolyzer for hydrogen production and using cycle charging dispatch control strategy (the fuel cell will operate to meet the AC primary load and the surplus of electrical power is used to run the electrolyzer) offers the best performance. The hybrid power system was designed to meet the energy demand of 4500 kWh/day of the residential community (150 houses). The total power production from the distributed hybrid energy system was 52% from the solar PV, and 48% from the fuel cell. From the total electricity generated from the photovoltaic hydrogen fuel cell hybrid system, 80.70% is used to meet all the AC load of the residential community with negligible unmet AC primary load (0.08%), 14.08% is the input DC power for the electrolyzer for hydrogen production, 3.30% are the losses in the DC/AC inverter, and 1.84% is the excess power (dumped energy). The proposed off-grid hybrid renewable power system has 40.2% renewable fraction, is economically viable with a levelized cost of energy of 145 $/MWh and is environmentally friendly (zero carbon dioxide emissions during the electricity generation from the solar PV and Fuel Cell hybrid power system).     

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.     

Design and analysis of a combined floating photovoltaic system for electricity and hydrogen production

The current study deals with a potential solution for the replacement of fossil fuel based energy resources with a sustainable solar energy resource. Electrical energy demand of a small community is investigated where a floating photovoltaic system and integrated hydrogen production unit are employed. Data are taken from Mumcular Dam located in Aegean Region of Turkey. PvSyst software is used for the simulation purposes. Furthermore, the obtained results are analyzed in the HOMER Pro Software. Photovoltaic (PV) electricity provides the required load and excess electricity to be used in the electrolyzer and to produce hydrogen. Saving lands by preventing their usage in conventional PV farms, saving the water due to reducing evaporation, and compensating the intermittent availability of solar energy are among the obtained results of the study for the considered scenario. Stored hydrogen is used to compensate the electric load through generating electricity by fuel cell. Floating PV (FPV) system decreases the water evaporation of water resources due to 3010 m² shading area. FPV and Hydrogen Systems provides %99.43 of the electricity demand without any grid connection or fossil fuel usage, where 60.30 MWh/year of 211.94 MWh/year produced electricity is consumed by electric load at $0.6124/kWh levelized cost of electricity (LCOE).     

Thermoeconomic analysis of a power/water cogeneration plant

Cogeneration plants for simultaneous production of water and electricity are widely used in the Arabian Gulf region. They have proven to be more thermodynamically efficient and economically feasible than single purpose power generation and water production plants. Yet, there is no standard or universally applied methodology for determining unit cost of electric power generation and desalinated water production by dual purpose plants.A comprehensive literature survey to critically assess and evaluate different methods for cost application in power/water cogeneration plants is reported in this paper. Based on this analysis, an in-depth thermoeconomic study is carried out on a selected power/water cogeneration plant that employs a regenerative Rankine cycle. The system incorporates a boiler, back pressure turbine (supplying steam to two MSF distillers), a deaerator and two feed water heaters. The turbine generation is rated at 118 MW, while MSF distiller is rated at 7.7 MIGD at a top brine temperature of 105 °C. An appropriate costing procedure based on the available energy accounting method which divides benefits of the cogeneration configuration equitably between electricity generation and water production is used to determine the unit costs of electricity and water. Capital charges of common equipment such as the boiler, deaerator and feed water heaters as well as boiler fuel costs are distributed between power generated and desalinated water according to available energy consumption of the major subsystems. A detailed sensitivity analysis was performed to examine the impact of the variation of fuel cost, load and availability factors in addition to capital recovery factor on electricity and water production costs.     

PEM electrolysis for production of hydrogen from renewable energy sources

PEM electrolysis is a viable alternative for generation of hydrogen from renewable energy sources. Several possible applications are discussed, including grid independent and grid assisted hydrogen generation, use of an electrolyzer for peak shaving, and integrated systems both grid connected and grid independent where electrolytically generated hydrogen is stored and then via fuel cell converted back to electricity when needed. Specific issues regarding the use of PEM electrolyzer in the renewable energy systems are addressed, such as sizing of electrolyzer, intermittent operation, output pressure, oxygen generation, water consumption and efficiency.     

Development of a novel combined energy plant for multigeneration with hydrogen and ammonia production

In order to meet the energy and fuel needs of societies in a sustainable way and hence preserve the environment, there is a strong need for clean, efficient and low-emission energy systems. In this regard, it is aimed to generate cleaner energy outputs, such as electricity, hydrogen and ammonia as well as some additional useful commodities by utilizing both methane gas and the waste heat of an integrated unit to the whole system. In this paper, a novel multi-generation plant is proposed to generate power, hydrogen and ammonia as a chemical fuel, drying, freshwater, heating, and cooling. For this reason, the Brayton cycle as prime unit using methane gas is integrated into the s-CO₂ power cycle, organic Rankine cycle, PEM electrolyzer, freshwater production unit, cooling cycle and dryer unit. In order then to evaluate the designed integrated multigeneration system, thermodynamic analyses and parametric studies are performed, revealing that the energy and exergy efficiencies of the whole plant are found to be 69.08% and 65.42%. In addition, ammonia and hydrogen production rates have been found to be 0.2462 kg/s and 0.0631 kg/s for the methane fuel mass flow rate of 1.51 kg/s. Also, the effects of the reference temperature, pinch point temperature of superheater, combustion chamber temperature, gas turbine input pressure, and mass flow rate of fuel on numerous parameters and performance of the plant are investigated.     

Thermoeconomic analysis and artificial neural network based genetic algorithm optimization of geothermal and solar energy assisted hydrogen and power generation

The study aims to optimize the geothermal and solar-assisted sustainable energy and hydrogen production system by considering the genetic algorithm. The study will be useful by integrating hydrogen as an energy storage unit to bring sustainability to smart grid systems. Using the Artificial Neural Network (ANN) based Genetic Algorithm (GA) optimization technique in the study will ensure that the system is constantly studied in the most suitable under different climatic and operating conditions, including unit product cost and the plant's power output. The water temperature of the Afyon Geothermal Power Plant varies between 70 and 130 °C, and its mass flow rate varies between 70 and 150 kg/s. In addition, the solar radiation varies between 300 and 1000 W/m² for different periods. The net power generated from the region's geothermal and solar energy-supported system is calculated as 2900 kW. If all of this produced power is used for hydrogen production in the electrolysis unit, 0.0185 kg/s hydrogen can be produced. The results indicated that the overall energy and exergy efficiencies of the integrated system are 4.97% and 16.0%, respectively. The cost of electricity generated in the combined geothermal and solar power plant is 0.027 $/kWh if the electricity is directly supplied to the grid and used. The optimized cost of hydrogen produced using the electricity produced in geothermal and solar power plants in the electrolysis unit is calculated as 1.576 $/kg H₂. The optimized unit cost of electricity produced due to hydrogen in the fuel cell is calculated as 0.091 $/kWh.     

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.     

Performance assessment of a solar hydrogen and electricity production plant using high temperature PEM electrolyzer and energy storage

This paper investigates the performance of a high temperature Polymer Electrolyte Membrane (PEM) electrolyzer integrated with concentrating solar power (CSP) plant and thermal energy storage (TES) to produce hydrogen and electricity, concurrently. A finite-time-thermodynamic analysis is conducted to evaluate the performance of a PEM system integrated with a Rankine cycle based on the concept of exergy. The effects of solar intensity, electrolyzer current density and working temperature on the performance of the overall system are identified. A TES subsystem is utilized to facilitate continuous generation of hydrogen and electricity. The hydrogen and electricity generation efficiency and the exergy efficiency of the integrated system are 20.1% and 41.25%, respectively. When TES system supplies the required energy, the overall energy and exergy efficiencies decrease to 23.1% and 45%, respectively. The integration of PEM electrolyzer enhances the exergy efficiency of the Rankine cycle, considerably. However, it causes almost 5% exergy destruction in the integrated system due to conversion of electrical energy to hydrogen energy. Also, it is concluded that increase of working pressure and membrane thickness leads to higher cell voltage and lower electrolyzer efficiency. The results indicate that the integrated system is a promising technology to enhance the performance of concentrating solar power plants.     

Performance investigation of an integrated wind energy system for co-generation of power and hydrogen

In this paper, a wind turbine energy system is integrated with a hydrogen fuel cell and proton exchange membrane electrolyzer to provide electricity and heat to a community of households. Different cases for varying wind speeds are taken into consideration. Wind turbines meet the electricity demand when there is sufficient wind speed available. During high wind speeds, the excess electricity generated is supplied to the electrolyzer to produce hydrogen which is stored in a storage tank. It is later utilized in the fuel cell to provide electricity during periods of low wind speeds to overcome the shortage of electricity supply. The fuel cell operates during high demand conditions and provides electricity and heat for the residential application. The overall efficiency of the system is calculated at different wind speeds. The overall energy and exergy efficiencies at a wind speed 5 m/s are then found to be 20.2% and 21.2% 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.     

Development of hybrid photovoltaic-fuel cell system for stand-alone application

In this paper we present firstly the different hybrid systems with fuel cell. Then, the study is given with a hybrid fuel cell–photovoltaic generator. The role of this system is the production of electricity without interruption in remote areas. It consists generally of a photovoltaic generator (PV), an alkaline water electrolyzer, a storage gas tank, a proton exchange membrane fuel cell (PEMFC), and power conditioning units (PCU) to manage the system operation of the hybrid system. Different topologies are competing for an optimal design of the hybrid photovoltaic–electrolyzer–fuel cell system. The studied system is proposed. PV subsystem work as a primary source, converting solar irradiation into electricity that is given to a DC bus. The second working subsystem is the electrolyzer which produces hydrogen and oxygen from water as a result of an electrochemical process. When there is an excess of solar generation available, the electrolyzer is turned on to begin producing hydrogen which is sent to a storage tank. The produced hydrogen is used by the third working subsystem (the fuel cell stack) which produces electrical energy to supply the DC bus. The modelisation of the global system is given and the obtained results are presented and discussed.