Solid Oxide Fuel Cell Power System Research Articles

(Invited) The SOFC Program at the DOE’s Office of Fossil Energy and Carbon Management (FECM) and National Energy Technology Laboratory (NETL)

The Solid Oxide Fuel Cell (SOFC) Program, managed by the U.S. Department of Energy (DOE) Office of Fossil Energy (FE) and administered by the FE’s National Energy Technology Laboratory (NETL) is currently developing low-cost SOFC power generation systems. SOFC power systems have the potential to achieve greater than 60 percent efficiency. The SOFC’s operating temperature is lower than combustion-based processes and precludes NOx formation. In addition, there are near-zero emissions of CO2, criteria pollutants, and particulates. Furthermore, SOFC power systems require approximately one-third the amount of water relative to conventional combustion-based power systems. The Program includes the testing of SOFC with natural gas in distributed applications, including data centers. In addition to SOFC, there are several projects on various aspects of high temperature solid oxide electrolysis cell (SOEC) for electrolysis of water. The development of efficient systems for hydrogen production is very interesting, especially when supplementary heat is provided from solar or other waste heat sources such as nuclear or coal power plants.

Waste2Watts: Techno-Economic Feasibility of Biogas-Fed SOFC Power System Integrated with Biogas Cleaning Unit and Carbon Capture Technologies

As a promising power generation technology, the solid oxide fuel cell (SOFC) system demonstrates high electrical efficiency and overall efficiency in cogeneration mode. Operating at high temperatures (> 680 ˚C), SOFCs cogenerate high-quality heat and can be integrated with different industry facilities. Furthermore, SOFC technology demonstrates high fuel tolerance, including hydrogen, natural gas, ammonia, LPG, etc. Unlike other fuel cell technologies, SOFC systems can also tolerate impurities in the fuel, e.g., CO2, N2 or even a small amount of O2. Besides, the compact system configuration makes SOFC system of great potential in the decentralized application.In the context of the Paris Agreement, more and more solutions to replace fossil fuels have been proposed, where biogas is considered as one promising alternative. Biogas generally contains several impurities, making its application limited in the fuel cell technology field. Removing all the impurities and making it compatible for all the fuel cell technologies would be expensive. Whereas, since SOFC has high tolerance in fuel impurities, keeping certain harmful impurities under safe thresholds with a biogas cleaning unit and injecting the purified biogas into the SOFC system will be less costly. In this case, a biogas-fed SOFC system integrated with a biogas cleaning unit can be considered as a promising renewable technology by avoiding fossil fuel use and converting biowaste into electricity and heat.Although biogas is produced from a renewable source, its use in SOFCs still generates CO2 emissions when it is fed with biogas. To realize carbon neutrality or even being carbon negative in a biogas-fed SOFC system, carbon capture (CC) technology is introduced to meet the net-zero carbon emission target in 2050. One conventional carbon capture storage (CCS) technology is the calcium looping system, which uses CaO/CaCO3 in a carbonation-calcination loop to separate and capture the CO2 from the exhaust gas. This type of technology is quite mature for large-scale applications and has been widely used in thermal power plants for the desulfurization and denitrification of exhaust. Novel technology based on sodium carbonate solution is capable of not only carbon capture, but also biogas cleaning. For the carbon capture utilization (CCU) technology, the Fischer-Tropsch (FT) synthesis can convert CO2 with hydrogen into syngas via electrochemical or thermochemical catalytically driven processes.Focusing on the decentralized power system, small-scale biogas-fed SOFC system integrated with a biogas cleaning unit and CC system should be considered with capacity ranging from 20 kW to 200 kW. As a cogeneration system, the integration should not be limited to mass exchange. The electricity consumed by the biogas cleaning unit and CC system can be fulfilled via the SOFC system. Based on the system temperature pattern, a bigger heat exchange network can be formulated between three parts, which can avoid extra heat input. In this case, the optimality of overall system efficiency and revenue can be achieved.In this study, one biogas-fed SOFC power system is proposed with capacity ranging from 20 kW to 200 kW. The techno-economic evaluation is carried out in two cases, with or without heat and electrical integration. Meanwhile, in different cases, the techno-economic analysis of different biogas cleaning technologies and CC technologies will be performed as well. Two operation modes of the SOFC system are considered: (1) hot recirculation mixed before the reformer, (2) cold recirculation mixed before the reformer. Without the biogas cleaning unit and the CC technology, the biogas-fed SOFC system's electrical efficiency can exceed 65% as is demonstrated in Figure 1. Furthermore, Detailed techno-economic analysis has been carried out by three indicators: capital expenditure (CAPEX), operating expenditure (OPEX) and levelized cost of electricity (LCOE). Integrated with biogas cleaning unit via only mass exchange, the LCOE of the biogas-fed system without CC technology ranges from around 0.11 EUR/kWh (20 kW) to 0.085 EUR/kWh (200 kW). The cost breakdown is shown in Figure 2(a). Based on the SOFC system techno-economic analysis, different CC technologies are added and compared. When the conventional CC technologies like Calcium looping (CaL) and Fischer-Tropsch (FT) synthesis are scaled down to 20-200 kW and applied, unaffordable LCOE prices (0.65 EUR/kWh for CaL and 5 EUR/kWh for FT) indicate that these large-scale conventional technologies are not feasible for our cases. However, a novel technology based on Sodium carbonate looping with 97% CC efficiency is rather promising and shows much lower cost. As is indicated in Figure 2(b), the LCOE cost of the whole system is only around 0.151 EUR/kWh at 200 kW system capacity, indicating that it is a techno-economically feasible solution for a carbon-neutral biogas-fed SOFC system. Figure 1

(Invited) The SOFC Program at the DOE’s Office of Fossil Energy and Carbon Management (FECM) and National Energy Technology Laboratory (NETL)

The Solid Oxide Fuel Cell (SOFC) Program, managed by the U.S. Department of Energy (DOE) Office of Fossil Energy and Carbon Management (FECM) and administered by the FECM’s National Energy Technology Laboratory (NETL) is currently developing low-cost SOFC’s and reversible SOFC systems (rSOCFs). SOFC power systems have the potential to achieve greater than 60 percent efficiency. The SOFC’s operating temperature is lower than combustion-based processes and precludes NOx formation. In addition, there are near-zero emissions of CO2, criteria pollutants, and particulates. Furthermore, SOFC power systems require approximately one-third the amount of water relative to conventional combustion-based power systems. The Program includes the testing of SOFC with natural gas in distributed applications, including data centers. In addition to SOFC, there are several projects on various aspects of high-temperature solid oxide electrolysis cell (SOEC) for electrolysis of water. Development of reversible SOFC systems, rSOCFs, is the new central focus of FECM. The development of efficient systems for hydrogen production is very interesting, especially when supplementary heat is provided from solar or other waste heat sources such as nuclear power plants.

Waste2Watts: Techno-Economic Feasibility of Biogas-Fed SOFC Power System Integrated with Biogas Cleaning Unit and Carbon Capture Technologies

Solid oxide fuel cell (SOFC) systems show immense potential for efficient biogas utilization, which can significantly reduce carbon emissions by integrating with biogas cleaning units and carbon capture technologies. Despite the significant benefits, the high cost of the integrated system presents a challenge. Therefore, a techno-economic assessment is necessary to evaluate the feasibility of the integrated system and provide guidelines for cost reduction. The ideal capacity for an integrated biogas-fed SOFC power system ranges between 20 kW to 200 kW. Firstly, a comparison of different biogas types and stack technologies is conducted to evaluate the system performance. Secondly, a techno-economic investigation of the feasibility of different system designs is performed by comparing different carbon capture technologies with various biogas cleaning units. The study results can facilitate the optimization of the integrated system's design and operation and pave the way for large-scale implementation of SOFC technology in the energy industry.

Thermodynamic and exergetic analysis of a novel multi-generation system based on SOFC, micro-gas turbine, s-CO2 and lithium bromide absorption refrigerator

To improve the utilization of waste heat from a solid oxide fuel cell (SOFC), a novel multi-generation energy system is proposed and analyzed from the viewpoints of energy and exergy. It consists of a SOFC, a micro-gas turbine (MGT), a supercritical carbon dioxide (S-CO2) Brayton cycle and a lithium bromide absorption refrigerator. The main part of the SOFC-MGT waste heat is recovered by a S-CO2 Brayton cycle to generate excessive electric power. The residual exhaust heat of MGT is respectively recovered by a domestic heating device and a lithium bromide absorption refrigerator to produce heating and cooling. In this study, a mathematical model of the proposed system is developed to evaluate the system thermodynamic characteristics and determine the influences of input parameters like ambient temperature, fuel flow rate, current density and air flow rate. The results reveal that the multi-generation energy system obtains the electric power of 696.9 kW, heating capacity of 24.98 kW and cooling capacity of 88.81 kW under design condition, and the energetic round trip efficiency and electrical efficiency of the system are 70.49% and 60.59%, respectively. According to sensitivity analysis, the current density has the greatest influence on the system round trip efficiency and electrical efficiency and the reformer intake fuel flow rate shows the most influential effect on SOFC voltage. The burner accounts for the maximum exergy destruction among all components. Overall, the multi-generation energy system based on SOFC is superior to the standalone SOFC power system in the respect of energy and exergy.

A multi-objective energy coordinative and management policy for solid oxide fuel cell using triune brain large-scale multi-agent deep deterministic policy gradient

In this paper, a data-driven multi-objective energy coordinative management policy is proposed in order to enhance the net output power and efficiency of a solid oxide fuel cell (SOFC) and prevent constraint violations. This study focuses on the optimization agent and controller design for a SOFC power system to maintain stable oxygen excess ratio (OER) and fuel utilization (FU) ratio as well as meet the load demand simultaneously. The optimization agent is responsible for output the reference OER and FU, aiming to achieve maximum net output power and operational efficiency as well as dynamic constraint satisfaction times in terms of OER and FU in real time. By applying reference OER and FU settings, the air and hydrogen flow within the SOFC can be effectively controlled by coordination of the air control agent and hydrogen control agent, respectively. In addition, a triune brain large-scale multi-agent deep deterministic policy gradient algorithm (TBL-MADDPG) is proposed. In order to improve the robustness of the proposed policy, the design of TBL-MADDPG entails curriculum learning, imitation learning and a large-scale multi-agent training framework. The performance of this proposed method is verified by the experiment.

An Optimized Strategy for Fuel Cell Degradation Control in SOFC Power Systems

Solid Oxide Fuel Cell (SOFC) is an attractive energy conversion device due to its high efficiency and fuel flexibility. Key operation parameters such as current, temperature and fuel utilization are critical variables in SOFC systems that directly impact efficiency and longevity. The degradation of the SOFC performance not only limits the operating temperature range of the SOFC stack in the system, but also simultaneously generates Joule heat, which further causes the stack to deviate from its initial thermal balance.In this paper, a semi-empirical SOFC dynamic model with degradation is proposed and validated by experiment data. The degradation in the above model is developed based on current density, temperature and fuel utilization to simulate cell performance decay over time due to ohmic loss growth and the heat generation by cell resistance. The coupling between key parameters, stack performance and degradation during long-term load following and the impact of stack degradation on the entire system long-term performance is discussed and investigated. An optimized strategy uses both feedback and feed-forward control law is designed to track the desired power demand with the aim of mitigating the degradation and compensating the time differences between dynamics at different time-scale.

(Plenary) Update on the SOFC Program at the DOE’s National Energy Technology Laboratory

The Solid Oxide Fuel Cell (SOFC) Program, managed by the U.S. Department of Energy (DOE) Office of Fossil Energy (FE) and administered by the FE’s National Energy Technology Laboratory (NETL) is currently developing low-cost SOFC power generation systems. SOFC power systems have the potential to achieve greater than 60 percent efficiency. The SOFC’s operating temperature is lower than combustion-based processes and precludes NOx formation; there are near-zero emissions of CO2, criteria pollutants, and particulates. Furthermore, SOFC power systems require approximately one-third the amount of water relative to conventional combustion-based power systems. The Program includes the testing of SOFC with natural gas in distributed applications, including data centers. In addition to SOFC, there are several projects on various aspects of high temperature solid oxide electrolysis cell (SOEC) for electrolysis of water. The development of efficient systems for hydrogen production is very interesting, especially when supplementary heat is provided from solar or other waste heat sources such as nuclear or coal power plants.

An Optimized Strategy for Fuel Cell Degradation Control in SOFC Power Systems

Solid Oxide Fuel Cell (SOFC) is an attractive energy conversion device due to its high efficiency and fuel flexibility. Key operation parameters such as current, temperature, and fuel utilization are critical variables in SOFC systems that directly impact efficiency and longevity. The degradation of the SOFC performance not only limits the operating temperature range of the SOFC stack in the system, but also simultaneously generates Joule heat, which further causes the stack to deviate from its initial thermal balance.In this paper, a semi-empirical SOFC dynamic model with degradation is proposed and validated by experiment data. The degradation in the above model is developed based on current density, temperature, and fuel utilization to simulate cell performance decay over time due to ohmic loss growth and the heat generation by cell resistance. The coupling between key parameters, stack performance, and degradation during long-term load following and the impact of stack degradation on the entire system long-term performance is discussed and investigated. An optimized strategy uses both feedback and feed-forward control law is designed to track the desired power demand with the aim of mitigating the degradation and compensating the time differences between dynamics at different time-scale.

(Plenary) Update on the SOFC Program at the DOE’s National Energy Technology Laboratory

The Solid Oxide Fuel Cell (SOFC) Program, managed by the U.S. Department of Energy (DOE) Office of Fossil Energy (FE) and administered by the FE’s National Energy Technology Laboratory (NETL), is currently developing low-cost SOFC power generation systems. SOFC power systems have the potential to achieve greater than 60 percent efficiency. The SOFC’s operating temperature is lower than combustion-based processes and precludes NOx formation; there are near-zero emissions of CO2, criteria pollutants, and particulates. Furthermore, SOFC power systems require approximately one-third the amount of water relative to conventional combustion-based power systems. The Program includes the testing of SOFC with natural gas in distributed applications, including data centers. In addition to SOFC, there are several new projects on various aspects of high temperature solid oxide electrolysis cell (SOEC) for electrolysis of water. The development of efficient systems for hydrogen production is very interesting, especially when supplementary heat is provided from solar or other waste heat sources such as nuclear or coal power plants.

Analysis of a biogas-fed SOFC CHP system based on multi-scale hierarchical modeling

Biogas is an abundant renewable energy source which can be produced by anaerobic treatment of biological waste such as sewage sludge, agro-industrial waste, and industrial animal waste. The utilization of biogas instead of fossil fuels in a solid oxide fuel cell (SOFC)-based system is a promising choice to achieve a fossil-free and sustainable energy future. A biogas-fed decentralized SOFC combined heat and power (CHP) system model is proposed and analyzed. The system consists of a pre-reformer, an SOFC stack, an afterburner and a heat-recovery boiler. The system model integrates a multi-scale hierarchical three-dimensional SOFC stack model with zero-dimensional balance of power component models, which enables simultaneous investigations of both the overall system performance and the stack-internal distributed properties down to the electrode scale. The effects of steam/carbon ratio, biogas composition and operation voltage of the SOFC stack on the electrical and CHP efficiencies of the system, as well as the temperature gradient within the SOFC stack were studied. The proposed system model is demonstrated as an insightful and powerful tool for designing hybrid SOFC combined heat and power systems.

A pressurized ammonia-fed planar anode-supported solid oxide fuel cell at 1–5 atm and 750–850°C and its loaded short stability test

Ammonia is a useful energy carrier for solid oxide fuel cell (SOFC) with advantages over hydrogen. Understanding of the performance and stability of ammonia-fed SOFC operated at elevated pressure (p) is an important step towards the development of high-efficiency hybrid SOFC power system with micro gas turbine (MGT). This paper reports cell performance, electrochemical impedance spectra (EIS), and stability measurements of a pressurized ammonia-fed anode-supported SOFC at p = 1–5 atm and T = 750–850°C using a planar (50 × 50 mm2) single-full-cell (400 μm Ni-YSZ anode/3 μm YSZ electrolyte/12 μm LSC-GDC cathode). The full cell together with metallic frames and current collectors are sandwiched by a pair of rib-channel flow distributors (interconnectors) in a high-pressure testing facility. Results show that pressurization and increasing temperature enhance the ammonia-fed SOFC performance significantly having almost the same power densities as those of hydrogen/nitrogen-fed SOFC, as substantiated and explained by EIS data and an equivalence circuit model where the effects of p and T on ohmic, gas diffusion, and gas conversion impedances are shown. Moreover, the loaded short (10 h) stability tests at 700°C and 0.8 V for 1 atm/3 atm cases reveal no/little power degradation, where the microstructures without any crack within the scale of SEM observation and nearly the same element atomic percentages of Ni-YSZ anode surfaces from EDX spectra are found. These results suggest that the pressurized ammonia-fed SOFC is a promising candidate for the hybrid SOFC-MGT power generation.

Economic viability of bitcoin mining using a renewable-based SOFC power system to supply the electrical power demand

One of Bitcoin’s most significant problems is its seemingly insatiable use of electricity. In the present research, along with providing the required power for Bitcoin (BTC) mining, a solid oxide fuel cell (SOFC) system fed either by natural gas or biogas as a renewable source of energy is used to supply the electricity demand. Thermodynamic modeling for the fuel cell system is applied to determine the required biogas or natural gas. For the proposed cases (grid-based, natural gas-fed SOFC and biogas fed SOFC), various scenarios depending on the Bitcoin price and mining difficulty are proposed. Also, the economic viability for each scenario in several countries is investigated and compared. Results indicate more profitability for grid-based mining in Bitcoin prices up to $20,000, but as the Bitcoin price increases SOFC based mining operations achieve reasonable profitability. It is shown that Iran, Russia, and China with cumulative cash flows of $87,300, $77,200 and $70,500 respectively, are the best countries to mine BTC using grid electricity while Iran, Canada and Russia are the best countries using a natural gas-fed SOFC system. While the profitability of SOFC-based mining is lower than grid-based mining, the latter method compensates with better sustainability and lower environmental costs.

Effect of blending hydrogen to biogas fuel driven from anaerobic digestion of wastewater on the performance of a solid oxide fuel cell system

Fuel composition is proved to have a significant influence on the performance of solid oxide fuel cell (SOFC) systems. In the present research, the effect of hydrogen injection to biogas-fed SOFC power systems is investigated. Hydrogen production is performed through implementing a Photovoltaic-based solar system to electrolyze water by means of a Proton Exchange Membrane (PEM) electrolyzer. In the present research, waste water as the primary source of energy is chosen to drive a novel integration of photovoltaic with SOFC systems. For comparison reasons, two cases depending on the hydrogen storage scenario or hydrogen utilization in the SOFC system are developed. Thermodynamics and exergoeconomic models have been developed to analyze the performance of proposed systems. Results indicate that increasing the molar ratio of hydrogen in the biofuel mixture up to 0.35 increases the SOFC cell voltage and the system net output power up to 4%. Also, due to the certain advantages of hydrogen, blending hydrogen with biogas results in a reduction of CO2 emission by 16%. The overall efficiency of the system, when the produced hydrogen is totally stored in the storage tank, would be higher than that of the system where the produced hydrogen is partially utilized in the SOFC system. The economic analysis revealed that the unit product cost of the system shows approximately a linear reduction with an increase in the hydrogen amount of the fuel.

A Preliminary Study on an Alternative Ship Propulsion System Fueled by Ammonia: Environmental and Economic Assessments

The shipping industry is becoming increasingly aware of its environmental responsibilities in the long-term. In 2018, the International Maritime Organization (IMO) pledged to reduce greenhouse gas (GHG) emissions by at least 50% by the year 2050 as compared with a baseline value from 2008. Ammonia has been regarded as one of the potential carbon-free fuels for ships based on these environmental issues. In this paper, we propose four propulsion systems for a 2500 Twenty-foot Equivalent Unit (TEU) container feeder ship. All of the proposed systems are fueled by ammonia; however, different power systems are used: main engine, generators, polymer electrolyte membrane fuel cell (PEMFC), and solid oxide fuel cell (SOFC). Further, these systems are compared to the conventional main engine propulsion system that is fueled by heavy fuel oil, with a focus on the economic and environmental perspectives. By comparing the conventional and proposed systems, it is shown that ammonia can be a carbon-free fuel for ships. Moreover, among the proposed systems, the SOFC power system is the most eco-friendly alternative (up to 92.1%), even though it requires a high lifecycle cost than the others. Although this study has some limitations and assumptions, the results indicate a meaningful approach toward solving GHG problems in the maritime industry.

Thermodynamic analysis of a solid oxide fuel cell jet hybrid engine for long-endurance unmanned air vehicles

The turbine-less jet engine is promising due to the compressor driven by a motor and the high combustor exit temperature. It is a key problem that how to provide electric power for the motor. In this paper, a novel solid oxide fuel cell (SOFC) jet hybrid engine with anode and cathode recirculation is proposed and investigated where the SOFC power system is instead of the turbine to provide power for the compressor. For the system, compressed air entering into SOFC cathode channel is preheated by cathode recirculation exhaust. The gases reform in the reformer, which are air, fuel and steam from the anode recirculation exhaust. Reformed gases are provided for the SOFC anode channel. SOFC produces electric power to drive the compressor by a motor. Then, SOFC exhaust enters the combustor. The combustor exhaust expands and produces propulsion power in the nozzle. In order to evaluate and improve the performance of the SOFC jet hybrid engine, the thermodynamic analysis model is built. The energy and exergy analysis are accomplished. The effect of pressure ratio and flight altitude on the performance of the hybrid engine are studied. In addition, sensitivity analysis is accomplished. The preliminary results are as follows: (1) The thermal efficiency, the specific thrust and the specific impulse of the engine could reach to 57.60%, 790.00 N/(kg⋅s−1) and 4132 s under design conditions. (2) The sum of the relative exergy destruction ratio of the SOFC, the combustor, the nozzle and the exhaust is over 85%. (3) The total pressure recovery coefficient of the SOFC has a strong influence on the performance of the SOFC jet hybrid engine.

A review of sorbents for high-temperature hydrogen sulfide removal from hot coal gas

Integrated gasification combined cycle (IGCC) and solid oxide fuel cell (SOFC) systems are considered as the most promising clean coal technologies. Syngas derived from coal gasification is the major fuel sources for IGCC and SOFC power systems; however, large amounts of sulfur compounds, mainly in the form of hydrogen sulfide, are produced during gasification. Hydrogen sulfide has to be removed prior to syngas utilization to protect downstream equipment from high-temperature corrosion. Therefore, hydrogen sulfide removal from raw syngas plays a key role in successful application of IGCC and SOFC systems. Hot coal gas desulfurization using solid sorbents is a more efficient technique for hydrogen sulfide removal, compared with conventional cold coal gas desulfurization with amine solution. This article reviews solid sorbents for high-temperature desulfurization, e.g., transition metal oxides, rare-earth oxides, spinel oxides, perovskite oxides, nanoelemental metals and mesoporous desulfurizers. Composite oxides that combine the properties of diverse metal oxides are promising candidates for hot coal gas desulfurization. The extensive background knowledge and the state of the art on high-temperature sorbents for hydrogen sulfide removal in this review provides inspiration and guidance to develop new cost-effective sorbents.

Feedforward-feedback control of a solid oxide fuel cell power system

One of the main challenges for wide-spread utilization of the solid oxide fuel cell (SOFC) power systems is how to achieve high electrical efficiency without increasing the degradation rate of the fuel cells. To run the SOFC power system at high efficiency over a long period of time, properly designed controllers are indispensable.Although a number of various approaches to control SOFC have been proposed so far, it seems that the design of control system, along with simple tuning procedure, has not been treated in a consistent manner. This issue is addressed in the present paper resulting in a feedforward-feedback control structure. The feedforward part is based on the stoichiometry of electro-oxidation, reforming and combustion reactions, which allow immediate response to variable current demand. The feedback part performs additional fine adjustment of fuel and air supply in order to minimize the undesired system temperatures variations. The selection of pairings of manipulated and controlled variables for control is based on physical knowledge of the system. Input/output pairing for single-loop feedback control is assessed by the relative gain analysis. An efficient procedure for tuning the parameters of the feedback controllers is suggested, relying on simple open-loop step responses of the system.The proposed low-level control is assessed on a detailed physical model of a 2.5 kW SOFC power system by simulating two nonstationary load regimes. Simulations show that the control provides a robust operation under large load variations while meeting the operating constraints. Due to its simplicity, the control is feasible for implementation on a real SOFC system.

Recurrent Neuro-Fuzzy Control of Grid-Interfaced Solid Oxide Fuel Cell (SOFC) System

The paper presents controller design, modelling, and simulations of the solid oxide fuel cell (SOFC) system. The SOFC model is used for the development of the fuzzy control scheme to improve the system performance. The SOFC is widely acknowledged for the clean distributed power generation. However, dire process problems occur frequently when the stand-alone fuel cell is directly interfaced with the electricity grid. Moreover, sustaining the optimal power quality and load following is the huge challenge, during the peak power demand schedule from the utility grid and large load perturbations. Consequently, a suitable and highly efficient control system is required for controlling and following the power load demands for the complex grid interfaced SOFC power systems. Therefore, a novel nonlinear hybrid adaptive recurrent fuzzy neural network (ARFNN) is developed for the control of the grid interfaced SOFC. The rapid power load following and safe SOFC operation requirement is also considered in the design of the closed loop control system. Simulation results proved that the proposed hybrid ARFNN enhances the optimal power quality and load-following than the conventional PI control scheme.

A Simplificative Approach‐based Modeling of SOFC Power Systems Fed by Natural Gas

AbstractThe fuel cell system is modeled to investigate output factors including voltage, power, and system efficiency for various input elements including different fuel composition, the air and fuel temperature and their utilization ratios. The purpose of this study is to examine the proficiency of a tubular solid oxide fuel cell (SOFC) by simplification in modeling calculation which results in the minimum required data. An electrochemical model is defined at first, and different current losses types were calculated in the next step. In further papers the amount of air and fuel is known and in some of them operating temperature must be known. But in this study it is enough to know the current density and required generated power of the SOFC. Since the amount of reacted methane is almost equal to input value, after performing this calculation for several fuel cells and validating it, the most optimal value for methane output is evaluated and output parameters of SOFC are calculated, then results are validated. The effect of main factors, including system temperature, pressure, current density, air and fuel flow rates and air to fuel ratio on the SOFC efficiency, were studied. Modeling method of current study provides optimum air and fuel flow rate.