Solid Oxide Fuel Cell System Research Articles

A comparative analysis and optimization of two supersonic hybrid SOFC and turbine-less jet engine propulsion system for UAV

In this study, we compared two different types of propulsion systems for a supersonic unmanned aerial vehicle (UAV) flying at Mach 1.8, which are using two different types of fuel to determine their characteristics and advantages. Also, investigate the effect of various factors such as altitudes and key design parameters of the propulsion system on efficiency and flight duration. These proposed propulsion systems are using a solid oxide fuel cell (SOFC) to generate the heat required for the operation of the turbine and generate thrust. The hydrogen for SOFC is either stored in the tank or generated by the internal reformation of methane inside the fuel cell. We studied the effects of several key design parameters for these engines in different flight conditions and altitudes; carrying out a multi-objective optimization for each proposed propulsion system to maximize the thrust of the engine while keeping the fuel consumption at a minimum rate to achieve the longest flight duration. Then we determined the best conditions where the acceptable thrust is accompanied by reasonable flight duration. Results indicated that the efficiency and generated power of the propulsion system will increase by higher flight altitude or compressor pressure ratio. Also, due to the recirculation of fuel in the SOFC’s anode, we observed higher efficiency in comparison when hydrogen is used; since anode-recirculation causes higher fuel utilization. The optimization result shows that the efficiency and fuel consumption for the hydrogen-fueled system is 48.7% and 0.0024 kg/s, respectively, and 67.9% and 0.0066 kg/s. for the methane-fueled engine.

Design and energy analysis of solid oxide fuel cell and gas turbine hybrid systems with membrane reactor

ABSTRACT The methanol-reforming solid oxide fuel cell (SOFC) emits high concentration of CO2 from the anode outlet. To achieve the goal of clean and low-carbon power generation, a CO2 capture unit is integrated with SOFC. In this work, the CO2 capture unit were set at different places in the conventional SOFC and gas turbine (GT) hybrid system. One was to place the water-gas-shift membrane reactor (WGSMR) at the anode inlet (SOFC-MRpre) and the other at the anode outlet (SOFC-MRpost). The key parameters, including the anode off-gas recycling ratio (RR), steam-to-carbon ratio (S/C), and operating pressure, have been investigated. Besides, the effects of the parameters on the power production, electrical efficiency, system efficiency, and CO2 capture capacity of the two processes were analyzed. It was found that the electrical and system efficiencies reached 53.3% and 41.8% for the SOFC-MRpre process, while 62.0% and 60.4% for the SOFC-MRpost process, respectively. The results show that placing the membrane reactor at the anode outlet can significantly reduce the energy consumption of the vacuum and blower, thus increasing the system efficiency. Besides, near-zero carbon emissions with only a 7.3% energy penalty can be achieved by the SOFC-MRpost process. These results reveal that the SOFC-MRpost process has more advantages than the SOFC-MRpre process.

Modeling Analysis of SOFC System Oriented to Working Condition Identification

Solid oxide fuel cell (SOFC) generation system is an important equipment to realize “carbon neutralization”. In SOFC system, a fault will cause changes in working conditions, which is difficult to detect early and find the reason due to the high temperature and seal environment. Therefore, the mechanistic model is a feasible way to find the reasons for the change of system working conditions. In this paper, based on the first law of thermodynamics, the system model of SOFC is built under multiple working conditions, and the influence of stack, afterburner, heat exchanger, and reformer fault is studied on the thermoelectric characteristics and efficiency of the system. The results show that with the introduction of these fault mechanistic models, the dynamic response characteristics of SOFC system under multiple working conditions can be obtained by tracking the key performance parameters qualitatively. The work of this paper is helpful for the guidance of the fault diagnosis of SOFC system in the future.

Thermo-electrochemical modeling of oxygen ion-conducting solid oxide fuel cells with internal steam reforming in the water-energy nexus

The precise estimation of chemical equilibrium state is highly crucial when simulating electrochemical and thermodynamic aspects of oxygen ion-conducting solid oxide fuel cells (SOFC). One way to determine the equilibrium state of an internal reforming solid oxide fuel cell system is to compute the total Gibbs free energy of the system (G) and then, adjust the molar amounts of each substance, subject to element balances, so as to minimize G. Multi-dimensional optimization algorithms can be used for this purpose. In this paper, a powerful analytical solution method called Lagrange's method of undetermined multipliers is used for estimating the chemical equilibrium state. The effects of each current density, reaction temperature and pressure of the stack, and fuel and carbon dioxide utilization ratios on the voltage losses and output voltage and power of the stack, efficiency, and molar portions of the exhaust chemical species in anode and cathode, are investigated. The solid oxide fuel cell stack simulations by Lagrange's method at a definite state shows an efficiency of 54.6% and output power of 158.3 kW.

Modeling of a Grid-Independent Set-Up of a PV/SOFC Micro-CHP System Combined with a Seasonal Energy Storage for Residential Applications

Renewable energy sources based on solar and wind energy provide clean and efficient energy. The intermittent behaviour of these sources is challenging. At the same time, the needs for efficient, continuous and clean energy sources are increased for serving both electricity and thermal demands for residential buildings. Consequently, complimentary systems are essential in order to ensure a continuous power generation. One of the promising energy sources that helps in reducing CO2 emissions, in addition to providing electrical and thermal energy efficiently, is a Solid Oxide Fuel Cell (SOFC) system operated in a combined heat and power (CHP) mode, due to high electrical efficiencies (in full and part load) and the fuel flexibility. Currently, most studies tend to focus on fuel cell model details with basic information about the building’s energy requirements. Nevertheless, a deep understanding of integrating fuel cell micro-CHP systems with renewable energy systems for the residential sector is required. Moreover, it is important to define an operating strategy for the system with a specific controlling method. This helps in evaluating the performance and the efficiency of the building energy system. In this study, an investigation of different configurations of a hybrid power system (HPS) was carried out. The intended aim of this investigation was to optimize a HPS with minimal CO2 emissions, serving the energy demands for a single-family house efficiently and continuously. As a result of this study, a photovoltaic (PV)/SOFC micro-CHP system has satisfied the intended goal, where the CO2 emissions are significantly reduced by 88.6% compared to conventional systems. The SOFC micro-CHP plant operated as a complimentary back-up generator that serves the energy demands during the absence of the solar energy. Integrating the Power to Gas (PtG) technology leads to a similar emission reduction, while the PtG plant provided a seasonal energy storage. The excess energy produced during summer by the PV system is stored in the fuel storage for a later use (during winter). This SOFC micro-CHP configuration is recommended from an energy and environmental perspective. In terms of feasibility, the costs of SOFC based micro-CHP systems are significantly higher than traditional technologies. However, further technology developments and the effect of economy of scale may cause a substantial drop in costs and the micro-CHP shall become economically competitive and available for residential users; thus, enabling a self-sufficient and efficient energy production on site.

Sorption-enhanced propane partial oxidation hydrogen production for solid oxide fuel cell (SOFC) applications

Solid oxide fuel cells (SOFC), as high-temperature fuel supply systems, are regarded as one of the most adaptable technologies in terms of efficiency, flexibility, and environmental friendliness. Catalytic propane partial oxidation is recognized as an efficient gas supply method for SOFC applications. However, incombustible by-product CO2 would decrease the purity of hydrogen, thereby reducing the power of fuel cells. Sorption-enhanced propane partial oxidation is an efficient way to adapt to SOFC operating conditions while improving hydrogen production and reducing carbon dioxide emissions. This paper introduces a cage-like porous Ce1-xCaxMO3-λ (M = Co, Fe and Cu) sorbent for providing high carbon dioxide sorption capacity and improving hydrogen purity over the Ni/Al2O3 catalyst. As obtained, Ce1-xCaxFeO3-λ and Ni/Al2O3 sorbent-catalyst performed the best, with the highest hydrogen yield up to 1654 μmol/gcat·s which was 1055 μmol/gcat·s higher than that of pure Ni/Al2O3. The produced reforming gas is served as a fuel in the proposed SOFC system. A maximum output power density of 581 mW/cm2 was reached. This work offered a simple and viable way of combining inexpensive and robust catalyst-sorbent for sorption-enhanced propane partial oxidation in terms of efficient indirect hydrogen supply toward SOFC power generation.

Dynamic life cycle assessment of solid oxide fuel cell system considering long-term degradation effects

In this work, we conduct a detailed cradle-to-product life cycle analysis in order to quantify the environmental impact of generating electricity using a conventional natural gas-fueled solid oxide fuel cell (SOFC). In contrast to previous studies, we account for SOFC degradation using a model previously developed by the authors to simulate deterioration in performance of SOFC over operating time. Midpoint environmental impacts were quantified using the ReCiPe 2016 and TRACI 2.1 US-Canada 2008 characterization methodologies in SimaPro. The resulting global warming potential was higher than those reported for SOFCs, which are underestimated because they neglect degradation. The results were compared with the environmental burdens associated with power generation using two conventional combined heat and power systems (i.e., gas turbines and internal combustion engines of various capacities), showing that even when accounting for long-term SOFC degradation impacts, the environmental performance of SOFCs is superior. This is true even though the analysis used a conservative approach in which SOFC system waste heat was not utilized. This means that if waste heat was utilized, the next environmental impact per unit energy produced would be even lower.

A review on mathematical modelling of Direct Internal Reforming- Solid Oxide Fuel Cells

The Solid Oxide Fuel Cells (SOFCs) anode materials are catalytically active for Direct Internal Reforming (DIR) thus avoiding the need of external reformer. However, practical application of DIR in SOFCs requires careful system design and selection of operating conditions to avoid cell degradation due to carbon depositions and other impurities. In recent years, numerous simulation studies, besides experimental investigations, have been carried out to understand the physical and electrochemical complexities of DIR-based SOFC systems in order to develop viable designs and optimize the operating conditions before conducting costly experiments. The objective of this work is to review the present status of DIR-SOFC modeling efforts and consolidate their findings in order to highlight the unresolved problems for future research in this field. A specific focus of this review has been given to the multiscale mathematical modeling. Pre-reforming techniques, influences of the chemical and electrochemical reaction kinetics and operational variables along with future prospects of the DIR-SOFC have been also reviewed and discussed.

Application of NixCo1-x catalyst on solid oxide fuel cell anode for biogas dry reforming

Based on commercial solid oxide fuel cell (SOFC), an effective dry reforming catalyst Ni 0.7 Co 0.3 /Al 2 O 3 +(10% La 2 O 3 ) was prepared and applied for cell performance test under internal reforming conditions. The CH 4 /CO 2 ratio of 2:1 corresponds to a power density of 651 mW cm −2 at 850 °C, an increase of 384 mW cm −2 compared with the test without catalyst under the same atmosphere. It is found that catalyst can greatly alleviate the carbon deposition on Ni-based anode when hydrocarbon serves as fuel. Since CO 2 can act as a reforming reactant, no water vapor is required; there is no side-effect of water vapor (diluting the fuel). This internal DRM technology can help to convert part of the exhaust heat into chemical energy; it is crucial for improving the efficiency of SOFC system fueled with biogas. • Dry reforming of methane is studied in combination with SOFC test. • Catalysts of Ni x Co 1-x /Al 2 O 3 with or without La 2 O 3 are examined systematically. • Ni 0.7 Co 0.3 /Al 2 O 3 +10%La 2 O 3 is selected as the optimized catalyst. • Internal reforming of CH 4 :CO 2 = 2:1 results in 651 mW cm −2 of SOFC output at 850 °C.

System Simulation and Analysis of an LNG-Fueled SOFC System Using Additively Manufactured High Temperature Heat Exchangers

A laboratory-scale solid oxide fuel cell (SOFC) system using liquefied natural gas (LNG) as a fuel is designed to be used as an energy converter on seagoing vessels (MultiSchIBZ project). The presented system design phase is supported by thermodynamic system simulation. As heat integration plays a crucial role with regard to fuel recirculation and endothermic pre-reforming, the heat exchanger and pre-reforming component models need to exhibit a high degree of accuracy throughout the entire operating range. Compact additively manufactured tube-bundle and plate-fin heat exchangers are designed to achieve high heat exchange efficiencies at low pressure losses. Their heat transfer correlations are derived from experimental component tests under operating conditions. A simulation study utilizing these heat exchanger characteristics is carried out for four configuration variants of pre-reforming and heat integration. Their system behaviour is analyzed with regard to the degree of pre-reforming and the outlet temperature of the fuel processing module. The combination of allothermal pre-reforming with additively manufactured plate-fin heat exchangers exhibits the best heat integration performance at nominal full load and yields a partial load capability to up to 60% electrical load at net electrical efficiencies of 58 to 60% (LHV).

Thermodynamic design, evaluation, and optimization of a novel quadruple generation system combined of a fuel cell, an absorption refrigeration cycle, and an electrolyzer

In this article, a solid oxide fuel cell system is combined with a generator absorber heat exchanger absorption refrigeration cycle and a proton exchange membrane electrolyzer unit to use most of the fuel energy and recover waste heat and material. This quadruple-generation system produces electric power, refrigeration, heating, and hydrogen from natural gas as the primary energy source for the system. The thermodynamic and environmental performances of the system are studied comprehensively to identify the effects of the key operating parameters on the system operation. The results show that as fuel cell current density increases from 2000 to 8000 A/m2; the system energy and exergy efficiencies decrease by nearly 20%, but the unit carbon dioxide emission increases by 30.38%. Also, the energy and exergy efficiencies are maximized, and the unit carbon dioxide emission is minimized at a specified value of fuel utilization factor. Additionally, increasing the steam to carbon ratio has a damaging effect on the system efficiencies but leads to higher unit carbon dioxide emission. Then, the genetic algorithm is applied to optimize the condition, so the highest exergy efficiency is attainable. The optimization results demonstrate that an exergy efficiency as high as 0.6443 is achievable.

Optimization of Operating Conditions of a Solid Oxide Fuel Cell System with Anode Off-Gas Recirculation Using the Model-Based Sensitivity Analysis

Designing a configuration of an efficient solid oxide fuel cell (SOFC) system and operating it under appropriate conditions are important for achieving a highly efficient SOFC system. In our previous research, the system layout of a SOFC system with anode off-gas recirculation was suggested, and the system performance was examined using a numerical model. In the present study, the system operating conditions were optimized based on the system configuration and numerical model developed in the previous paper. First, a parametric sensitivity analysis of the system performance was investigated to demonstrate the main operating parameters. Consequently, the fuel flow rate and recirculation ratio were selected. Then, the available operating conditions, which keep the system below the operating limits and satisfy the desired system performance (Ufuel > 0.7 and ηelec > 45%) were discovered. Finally, optimized operating conditions were suggested for three operating modes: optimized electrical efficiency, peak power, and heat generation. Depending on the situation, the demand for electricity and heat can be different, so different proper operating points are suggested for each mode. Additionally, using the developed model and the conducted process of this study, various optimized operating conditions can be derived for diverse cases.

Thermal partial oxidation of n-butane in a micro-flow reactor and solid oxide fuel cell stability assessment

The direct use of n-butane in solid oxide fuel cell (SOFC) systems has been challenging due to high performance degradation and/or failure due to carbon deposition on the anode. Previous works have explored SOFCs with expensive integrated catalysts to promote the longevity of the SOFC, but few have achieved significant operating hours. In this work, a SOFC with no integrated catalyst is fed n-butane for 288 h utilizing a novel micro fuel reformer. The impact of temperature (800–900 °C), total flow rate (10–50 mL.min−1), and equivalence ratio (1–5) on the thermal partial oxidation of n-butane in the micro-flow reactor are characterized. A literature review of n-butane fueled SOFC systems confirms that the 288-hour long term stability test achieved in this study is among the longest conducted with a low voltage degradation of 0.00034 V.h−1. Scanning electron microscope (SEM) images of the SOFC anode confirm no carbon deposition occurred on the surface. Microscale partial oxidation with light internal reforming provides an alternative to traditional catalytic oxidation and internal reforming SOFC systems.

Frequency Control of Low Inertia Power Grids With Fuel Cell Systems in Distribution Networks

High penetration of variable renewable energy resources to distribution networks brings new challenges to frequency control in transmission systems; notwithstanding, coordinated exploitation of some widely distributed resources in distribution networks could support overall system frequency control. We developed a centralized control scheme to utilize existing solid oxide fuel cell systems in distribution networks to mitigate frequency deviation in the transmission system. This novel control scheme minimizes curtailing renewable resources. It appropriately prioritizes adjusting active or reactive power of medium voltage connected fuel cell systems to efficiently provides frequency support, while keeping the renewable sources connected. A co-simulation platform was also developed to allow for analyzing the interactions between transmission and distribution networks. It enhances simulation capability through parallel distributed real-time simulations. This platform enables ex-ante analysis of the impact of control strategies of distribution system on transmission system. A set of experimental results on European transmission and distribution network benchmarks demonstrated the performance of the developed primary frequency control scheme using solid oxide fuel cell systems.

Development of a Sustainable Nitrogen-Doped Biochar Desulfurizer for Solid Oxide Fuel Cell Systems

Development of a Sustainable Nitrogen-Doped Biochar Desulfurizer for Solid Oxide Fuel Cell Systems

Remaining useful life prediction of a multi-stack solid oxide fuel cell system with degradation interactions

Remaining useful life prediction of a multi-stack solid oxide fuel cell system with degradation interactions

Soft-Sensor Based Operation of a Solid Oxide Fuel Cell System with Anode Exhaust Gas Reciculation

Soft-Sensor Based Operation of a Solid Oxide Fuel Cell System with Anode Exhaust Gas Reciculation

A Novel Application of Bypass Valve for Temperature Difference Mitigation between the Multi-Stack in a 5kw Solid Oxide Fuel Cell System

A Novel Application of Bypass Valve for Temperature Difference Mitigation between the Multi-Stack in a 5kw Solid Oxide Fuel Cell System

A High Activity Cathode of Sm0.2ce0.8o1.9 Decorated Mn1.5co1.5o4 Using Ion Impregnation Technique within a Solid Oxide Fuel Cell System

A High Activity Cathode of Sm0.2ce0.8o1.9 Decorated Mn1.5co1.5o4 Using Ion Impregnation Technique within a Solid Oxide Fuel Cell System

Preparation and characterization of RHA based ceramic membrane for gas leak testing in SOFC seals

Solid Oxide Fuel Cell (SOFC) systems show great potential in future power generation applications. SOFC has many advantages, including high efficiency, low emission, and flexible modular structure. SOFC is an electrochemical device that converts fuel into electricity directly. If hydrogen gas is used, it will produce electricity and waste products in the form of heat and water vapor. The complete SOFC module system consists of a furnace, cell stack, fuel and oxygen. Several parameters that affect SOFC performance are fuel flow rate, furnace temperature, cell material, and collector current. SOFC consists of anode, electrolyte, cathode, and current collector. These parameters have a correlation with each other in building a SOFC system, resulting in a good cell and optimal output voltage. SOFC based on electrolyte material yttria stabilized zirconia (YSZ) operates at working temperatures between 600 to 1,000°C, so all materials used must be able to withstand these temperatures. In the empirical case to separate each function of the components in the fuel cell, a sealant is needed. The sealant function prevents fuel and oxidant leakage in the stack and electrically isolates the cells in the stack. So the other sealant material requirements are to have thermal and chemical compatibility with other cell components, chemically and physically stable at high temperatures and have good mechanical strength. The composition of the material (RHA, CaO, Al2O3, MgO and BaO) with six formulations (F1-F6) which was determined as a gas leak test specimen through a synthesis process using the ball mill method for 12 hours resulted in a grain variation between 3.808 um – 19.631 um. The production of gas leak test specimens was successfully carried out by molding which was designed to be effective using a material weight of 1.5 grams with a 96% PVA binder as much as 20% by weight. The size of the specimen obtained in the form of a membrane with a thickness of 1-1.1mm. The preparation of the test material can be continued in the next gas leak test process.