Solid oxide fuel cell (SOFC) technology offers a clean and efficient way to generate electricity from natural gas. Since various integration options with thermal cycles have been proposed to achieve ...even higher electrical efficiencies, it is interesting to see how these compare. In addition, the influence of the SOFC operating parameters on thermal cycles is not yet adequately addressed. In this study, a stand-alone SOFC system is thermodynamically analysed and compared to configurations combined with a gas turbine or steam turbine, as well as a novel SOFC-reciprocating engine combined cycle system. The results are mapped in contour plots for the entire SOFC operating envelope, revealing the influence of fuel utilisation, cell voltage, average stack temperature and gas turbine pressure ratio on different combined cycles. An exergy analysis is included to quantify notable losses in the systems and identify potential further improvements. The pressurised SOFC-gas turbine combined cycle achieves the highest electrical efficiencies for stack operation at moderate cell voltages and high temperatures, while the steam turbine combined cycle is more efficient at high cell voltages and low stack temperatures. The SOFC-reciprocating engine combined cycle shows similar behaviour to the steam turbine combined cycle, but achieves slightly lower efficiencies.
•Various SOFC-combined cycles are thermodynamically analysed and compared.•A novel SOFC-reciprocating engine combined cycle is included in the analysis.•The combined cycles are compared within an entire SOFC operating envelope.•Contour plots reveal differences in dependencies on stack operating parameters.•An exergy analysis provides guidance for potential further efficiency improvements.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
•Principal case study for retrofitting solid oxide fuel cells in large power plants.•Model development based on previously experimentally validated models.•Process is feasible to retrofit up to 40MWe ...SOFC modules and partial CO2 capture.•Full scale SOFC and CO2 capture requires major process redesign and modifications.•Exergy analysis indicates high efficiency improvement with SOFC integration.
This article presents a detailed thermodynamic case study based on the Willem-Alexander Centrale (WAC) power plant in the Netherlands towards retrofitting SOFCs in existing IGCC power plants with a focus on near future implementation. Two systems with high percentage (up to 70%) biomass co-gasification (based on previously validated steady state models) are discussed: (I) a SOFC retrofitted IGCC system with partial oxy-fuel combustion CO2 capture (II) a redesigned highly efficient integrated gasification fuel cell (IGFC) system with full oxy-fuel CO2 capture. It is concluded that existing IGCC power plants could be operated without major plant modifications and relatively high electrical efficiencies of more than 40% (LHV) by retrofitting SOFCs and partial oxy-combustion CO2 capture. In order to apply full scale CO2 capture, major process modification and redesign needs to be carried out, particularly in the gas turbine unit and heat recovery steam generator (HRSG). A detailed exergy analysis has also been presented for both the systems indicating significant efficiency improvement with the utilization of SOFCs. Additional discussions have also been presented on carbon deposition in SOFCs and biomass CO2 neutrality. It is suggested that scaling up of the SOFC stack module be carried out gradually, synchronous with latest technology development. The thermodynamic analysis and results presented in this article are also helpful to further evaluate design challenges in retrofitted IGCC power plant systems for near future implementation, gas turbine part load behaviour, to devise appropriate engineering solutions and for techno-economic evaluations.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
•A novel concept of a trigeneration plant using fuel cell vehicles is presented.•Energy and water production based on FCEVs studied.•Internal reforming SOFCs are compared with catalytic ...reformers.•Efficiency penalties with CCS are presented.
Delft University of Technology, under its “Green Village” programme, has an initiative to build a power plant (car parking lot) based on the fuel cells used in vehicles for motive power. It is a trigeneration system capable of producing electricity, heat, and hydrogen. It comprises three main zones: a hydrogen production zone, a parking zone, and a pump station zone. This study focuses mainly on the hydrogen production zone which assesses four different system designs in two different operation modes of the facility: Car as Power Plant (CaPP) mode, corresponding to the open period of the facility which uses fuel cell electric vehicles (FCEVs) as energy and water producers while parked; and Pump mode, corresponding to the closed period which compresses the hydrogen and pumps to the vehicle’s fuel tank. These system designs differ by the reforming technology: the existing catalytic reformer (CR) and a solid oxide fuel cell operating as reformer (SOFCR); and the option of integrating a carbon capture and storage (CCS).
Results reveal that the SOFCR unit significantly reduces the exergy destruction resulting in an improvement of efficiency over 20% in SOFCR-based system designs compared to CR-based system designs in both operation modes. It also mitigates the reduction in system efficiency by integration of a CCS unit, achieving a value of 2% whereas, in CR-based systems, is 7–8%. The SOFCR-based system running in Pump mode achieves a trigeneration efficiency of 60%.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The requirement of Unmanned Aerial Aircrafts (UAVs) is attracting R&D institutions to search for efficient alternative energy resources and energy conversion systems.
Fuel cell exhibits high second ...law efficiency and has the capability of converting electrochemically several fuels. Hydrogen is a promising fuel for aircrafts due to exhibit the highest specific energy and carbon free. This fuel is not available in its pure form and industries utilize diverse technologies to extract from other energy resources such as biomass. However, the feasibility of the fuel depends on both efficient extraction and usage in energy conversion systems. Consequently, the entire power chain of converting biomass into mechanical work should be analyzed 1.
This study presents the results of a “Well-to-Wing” efficiency analysis (WTW) of liquid hydrogen produced through biomass gasification for aviation. The power chain comprises 3 subsystems: a biomass gasification plant, a hydrogen liquefaction unit, and a Solid Oxide Fuel Cell/Gas Turbine (SOFC/GT) system.
Results reveal that the SOFC/GT system provides considerable higher exergy efficiency when compared to the competing propulsion systems whereas the conventional hydrogen liquefaction process induces significant exergy destruction, generating inefficiency in the entire power chain. Hence, conclusions also provide suggestions for increasing the overall efficiency.
•“Well-to-Wing” analysis of liquid hydrogen for an UAV is determined.•Hydrogen production technologies still require improvements to enhance efficiency.•Liquefaction of hydrogen negatively affects the efficiency of the power chain.•SOFC/GT systems can play an important role in aviation.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
This study deals with the thermodynamic modeling of biomass Gasifier–SOFC (Solid Oxide Fuel Cell)–GT (Gas Turbine) systems on a small scale (100 kWe). Evaluation of an existing biomass ...Gasifier–SOFC–GT system shows highest exergy losses in the gasifier, gas turbine and as waste heat. In order to reduce the exergy losses and increase the system's efficiency, improvements are suggested and the effects are analyzed. Changing the gasifying agent for air to anode gas gave the largest increase in the electrical efficiency. However, heat is required for an allothermal gasification to take place. A new and simple strategy for heat pipe integration is proposed, with heat pipes placed in between stacks in series, rather than the widely considered approach of integrating the heat pipes within the SOFC stacks. The developed system based on a Gasifier–SOFC–GT combination improved with heat pipes and anode gas recirculation, increases the electrical efficiency from approximately 55%–72%, mainly due to reduced exergy losses in the gasifier. Analysis of the improved system shows that operating the system at possibly higher operating pressures, yield higher efficiencies within the range of the operating pressures studied. Further the system was scaled up with an additional bottoming cycle achieved electrical efficiency of 73.61%.
•A new and simple strategy for heat pipe integration between SOFC and Gasifier is proposed.•Anode exhaust gas is used as a gasifying agent.•The new proposed Gasifier–SOFC–GT system achieves electrical efficiency of 72%.•Addition of steam rankine bottoming cycle to proposed system increases electrical efficiency to 73.61%.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Thermodynamic calculations were carried out to evaluate the performance of small-scale gasifier–SOFC–GT systems of the order of 100
kW. Solid Oxide Fuel Cells (SOFCs) with Nickel/Gadolinia Doped ...Ceria (Ni/GDC) anodes were considered. High system electrical efficiencies above 50% are achievable with these systems. The results obtained indicate that when gas cleaning is carried out at temperatures lower than gasification temperature, additional steam may have to be added to biosyngas in order to avoid carbon deposition. To analyze the influence of gas cleaning at lower temperatures and steam addition on system efficiency, additional system calculations were carried out. It is observed that steam addition does not have significant impact on system electrical efficiency. However, generation of additional steam using heat from gas turbine outlet decreases the thermal energy and exergy available at the system outlet thereby decreasing total system efficiency. With the gas cleaning at atmospheric temperature, there is a decrease in the electrical efficiency of the order of 4–5% when compared to the efficiency of the systems working with intermediate to high gas-cleaning temperatures.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Energy and exergy performance of ammonia fuelled solid oxide fuel cell (SOFC) integrated system in wastewater treatment plants (WWTPs) is evaluated in this study. Ammonia can be recovered through a ...struvite precipitation process in the form of an ammonia‐water mixture (with 14 mol.% ammonia) and used as a carbon‐free fuel. A series of experiments has been conducted for SOFC single cell to evaluate the performance with different ammonia‐water mixture ratios. An ammonia‐SOFC system was modeled in Cycle Tempo for detailed thermodynamic analysis. The heat from the electrochemical reaction in the SOFC and catalytic combustion in an afterburner is used in the struvite decomposition process. However, the generated heat is not sufficient to meet the heat demand of the struvite decomposition reactor. To improve the sustainability of the system in terms of heat demand, the system can be integrated into a heat pump assisted distillation tower, meanwhile, the ammonia concentration of the fuel stream increases. Increasing the ammonia concentration to 90 mol.% increases the energy and exergy efficiencies of the SOFC system. The net energy efficiency of the integrated system with a heat pump assisted distillation tower is 39%, based on the LHV of the ammonia‐water mixture.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Solid oxide fuel cell–gas turbine (SOFC‐GT) systems provide a thermodynamically high efficiency alternative for power generation from biofuels. In this study biofuels namely methane, ethanol, ...methanol, hydrogen, and ammonia are evaluated exergetically with respect to their performance at system level and in system components like heat exchangers, fuel cell, gas turbine, combustor, compressor, and the stack. Further, the fuel cell losses are investigated in detail with respect to their dependence on operating parameters such as fuel utilization, Nernst voltage, etc. as well as fuel specific parameters like heat effects. It is found that the heat effects play a major role in setting up the flows in the system and hence, power levels attained in individual components. The per pass fuel utilization dictates the efficiency of the fuel cell itself, but the system efficiency is not entirely dependent on fuel cell efficiency alone, but depends on the split between the fuel cell and gas turbine powers which in turn depends highly on the nature of the fuel and its chemistry. Counter intuitively it is found that with recycle, the fuel cell efficiency of methane is less than that of hydrogen but the system efficiency of methane is higher.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
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