Solid Oxide Fuel Cell System Research Articles

Design and performance analysis of a coupled burner for the Solid Oxide Fuel Cell system

The Solid Oxide Fuel Cell (SOFC) system is characterized by high energy conversion efficiency and low emissions. The energy supply and recovery of the SOFC system are facilitated through the ignition burner and the off-gas burner, respectively. This study proposes a coupled design of the ignition burner and the off-gas burner to reduce the burner volume, thereby enhancing the power density of the SOFC system. The ignition burner employs radially opposed jet combustion with fully premixed natural gas, while the off-gas burner uses swirl diffusion combustion with the anode off gas. When the premixed gas and lean anode off gas are unable to sustain the flame, catalytic combustion is initiated. Simulation and experiment methods are utilized to analyze the performance of the coupled burner in this paper. The results indicate that uniform mixing is achieved with a high swirl number (s1 = 2.6) for the premixed gas, and the maximum excess air coefficient for stable flame combustion at 400 °C is 2.47. As the temperature of the cathode off gas increases, the flameout boundary for the premixed gas gradually increases; conversely, with increasing burner power, the flameout boundary gradually decreases. The intersection cooling effect of mixed air and circumferential high-temperature flue gas is effective, and the flame does not exceed the tolerance temperature of the catalytic carrier. The diffusion combustion of anode off gas with a swirl number (s2 = 0.5) exhibits great gas mixing uniformity without a high-temperature core region. When transitioning from flame to catalytic combustion with premixed natural gas and anode off gas, there is a temperature lag of approximately 60 s. The isotropic cylindrical cordierite catalytic carrier with a 400 mesh and a coating of 60 g/ft3 Pt0.1Pd0.5 achieves stable catalytic combustion in an environment with preheated air temperatures ranging from 400 to 600 °C and H2 concentrations of 0.25–2.91 %.

Thermodynamic and economic analysis of a novel solid oxide fuel cell, two level thermoelectric generator and double effect parallel absorption chiller integrated system

This study presents a comprehensive thermodynamic and economic analysis of a novel hybrid energy system integrating a Solid Oxide Fuel Cell (SOFC) with a Two-Level Thermoelectric Generator (TTEG) and a Double-Effect Parallel Absorption Chiller (DEPAC) for enhanced waste heat recovery. The primary objective is to maximize energy utilization and overall efficiency by leveraging the synergetic effects of these components. Unlike previous studies, this research uniquely evaluates the effectiveness of the integrated system and examines the impact of different Absorption Chiller configurations and the number of TTEG elements, filling a critical gap in the literature. The proposed system achieves a net electrical efficiency of 42.88 %, an energy efficiency of 44.61 %, and an exergy efficiency of 57.16 % under optimal conditions. This marks a significant improvement compared to standalone SOFC systems, with the TTEG effectively harnessing waste heat and contributing an additional 0.680 kW/m2 to the overall power output. The integration of the DEPAC system further enhances performance by providing cooling with a Coefficient of Performance (COP) of 1.351. The economic analysis reveals a positive Net Present Value (NPV) of $1,993,136, a Dynamic Payback Period (DPP) of 6.7 years, and a Levelized Cost of Electricity (LCOE) of $59/MWh, underscoring the system's financial viability. These findings demonstrate that the hybrid system offers a sustainable and efficient solution for power generation and waste heat recovery, aligning with the broader goals of advancing renewable energy technologies and setting a new benchmark in hybrid energy system design and optimization.

A Technical Study on an Integrated Closed-Loop Solid Oxide Fuel Cell and Ammonia Decomposition System for Marine Application

A Technical Study on an Integrated Closed-Loop Solid Oxide Fuel Cell and Ammonia Decomposition System for Marine Application

Internal temperature prediction and control strategy design of anode-supported solid oxide fuel cell for hot start-up process

Anode-supported solid oxide fuel cell (SOFC) has a high energy efficiency while suffering from a poor transient performance such as start-up. In this study, a model-based design method is proposed to develop a suitable strategy for the rapid hot start-up of anode-supported SOFC (AS-SOFC). First, a mathematical model is established for a 25-kW SOFC system and the internal temperature is predicted. Subsequently, three different strategies are compared during hot start-up process. The results indicate that the positive-electrolyte-negative (PEN) temperature variation magnitude is 50 K and the response time is 1300 s when the hydrogen and the air flow rates are fixed for the afterburner and the cathode. If a PID controller is employed to regulate the flow rate of H2 to the afterburner, the PEN temperature variation magnitude decreases to 16 K with a shorter response time of 158 s. When increasing the air flow rate synchronously, the PEN temperature variation magnitude is merely 8 K, reduced by 84 % and 50 % compared with the previous strategies. Additionally, the gas temperature exiting from the afterburner declines significantly for the third control strategy. Thus, the lifetime and reliability of AS-SOFC is enhanced. The results provide a reference for the SOFC systems control such as domestic combined heat and power (CHP) and mobile applications.

Emulation tests of dynamics and control for a turbocharged SOFC system

This work regards experimental emulation activities for a Solid Oxide Fuel Cell (SOFC) pressurized by a turbocharger, focusing attention on the control system validation. The SOFC-based plant considered here was developed to couple high efficiency (due to pressurization) with reasonable capital costs. In detail, significant cost decrease (against SOFC hybrid plants including a microturbine) can be obtained with a turbocharger, due to large mass manufacturing process for these machines. Moreover, to pursue the zero emission target, the system was sized to operate with a renewable source fuel (biogas).Since this system has integration problems due to critical dynamic and control aspects, the University of Genoa designed and installed an experimental facility based on the coupling between a pressure vessel with a commercial turbocharger. The fuel cell is emulated equipping the vessel with a burner (to obtain the SOFC temperature range) and with inert ceramic material (to generate the same dynamic response).The tests presented in this work were obtained with this emulation rig operated in cyber-physical mode: the hardware interacted in real-time mode with previously validated software for components not physically included in the rig. The results demonstrated the system feasibility for load changes and validated the proposed control system, showing robustness and good prevention of critical conditions, such as SOFC thermal stress.

Technoeconomic and environmental performance assessment of solid oxide fuel cell-based cogeneration system configurations

In this study, an innovative energy solution to fulfil the electricity and heating needs of a mixed community, including residences, a commercial building, and a small brewery has been investigated. The primary objective is to comprehensively analyse the technoeconomic, and environmental aspects of a UK-based solid oxide fuel cell (SOFC) energy hub designed for local-scale electricity and heating demands. This present study investigates two different configurations: (a) SOFC-based cogeneration and (b) SOFC-heat pump cogeneration configuration. These configurations are modelled to provide year-round electricity and heating for a local scale application and are evaluated using hydrogen and natural gas as fuels. A thorough environmental assessment is also conducted for SOFC and SOFC-heat pump system configurations fuelled by natural gas. The hydrogen fuelled SOFC-heat pump configuration outperforms other system configuration with energy efficiency of 96 %. Meanwhile, the hydrogen-fuelled SOFC cogeneration system yields maximum exergy efficiency at 61.51 %. The natural gas-powered SOFC-heat pump cogeneration system yields the lowest levelized cost of energy (LCOE) at 0.1603 £/kWh, in comparison to the higher LCOE of 0.213 £/kWh for the alkaline hydrogen-fuelled system. The natural gas-fuelled SOFC system emits 0.3352 kg/kWh of CO2, with even lower emissions of 0.275 kg/kWh for the SOFC-heat pump system configuration.

Techno-economic evaluation of biogas-fed SOFC systems with novel biogas purification and carbon capture technologies

Small-scale biogas-fed solid oxide fuel cell (SOFC) systems, integrated with carbon capture storage (CCS) technologies, offer a sustainable solution for European farms’ heat and power demands with minimal carbon emissions. This study investigates different system configurations ranging from 20 to 200 kW, incorporating heat integration, fuel recirculation, biogas purification and CCS. Two scenarios are evaluated: an SOFC subsystem (1) with cryogenic biogas purification and a sodium carbonate loop for CCS, and (2) with dual sodium carbonate loops for biogas purification and CCS. Key performance metrics, such as system efficiency and levelized cost of electricity (LCOE), were assessed. At 60% recirculation ratio, 650 °C reforming temperature, and 85% fuel utilization, SOFC system electrical achieved the highest efficiency of 65%, with overall system efficiency of 53.6% (first configuration) and 57.4% (second configuration). Scaling effect reduced the LCOE of the first scenario from 0.165 €/kWh (20 kW) to 0.123 (200 kW), and the second scenario from 0.150 €/kWh (20 kW) to 0.116 €/kWh (200 kW). The cost breakdown reveals a significant investment cost from stack replacements. The study suggests that the optimized small-scale biogas-fed SOFC systems with CCS are viable for decentralized heat and power generation.

Energy and environmental performance from field operation of commercial-scale SOFC systems

Solid Oxide Fuel Cells (SOFCs) are capable of generating electrical and thermal power with very high conversion efficiency and almost no pollutant emissions into the atmosphere. Despite extensive literature on SOFC-based energy system models and experimental testing at the cell and short-stack level, there is currently a lack of performance data for SOFC modules under actual field conditions. To fill this gap, the present work investigates the energy and environmental performance of six SOFC modules, ranging in size from 10 to 60 kW, over thousands of hours of operation. These systems, supplied by the three leading SOFC manufacturers in Europe, have been installed and operated in different non-residential buildings worldwide, as part of the European Comsos project. The aim of this study is to establish a comprehensive set of field operation data to characterise commercial-scale SOFC systems. Specifically, raw data are processed to derived electrical and thermal efficiency maps, degradation rates and pollutant emissions, including particulate matter (PM), nitrogen oxides (NOx) and carbon monoxide (CO). A comparison with competing technologies is also provided to better highlight the potential benefits of adopting SOFC-based cogeneration systems. Values in the range of 51–61% were found for the system-level electrical efficiency under rated conditions. The electrical efficiency also remained consistently high across a wide modulation range (between 50% and 100% of rated power), with peak values reaching 65%. In addition, promising results were obtained for the average percentage loss in electrical efficiency, with a minimum value of 0.7%/1000 h. Regarding the environmental analysis, NOx and CO emissions were analysed at both constant and variable power output, proving to be impressively low across the entire modulation range. The same applies to PM concentrations, which were below ambient level. Overall, SOFCs demonstrated to be one of the best cogeneration solutions for commercial-scale systems (tens to hundreds of kW in size), from both an energy and environmental perspective. However, further reductions in costs and dedicated financial schemes are necessary for a widespread market penetration.

A High-Speed, High-Temperature, Micro-Cantilever Steam Turbine for Hot Syngas Compression in Small-Scale Combined Heat and Power

Abstract Coupling a biomass gasifier with a solid oxide fuel cell system through a high-temperature syngas compressor holds great promise to achieve low-emission, small-scale combined heat and power, since it reduces the number of heat exchangers and increases the system efficiency. However, due to the demanding operating conditions (high temperatures, toxic and explosive gases), electrical motors are not suitable to drive the syngas compressor. Therefore, a high-speed, small-scale cantilever steam turbine that can valorize the system?s waste heat to power the compression is designed and developed. An iterative process involving preliminary design, meanline analysis, commercial tools, and in-house codes is used for the design. The design is then numerically analyzed using computational fluid dynamics. The 2.8 kW cantilever steam turbine with a tip diameter of 21 mm runs up to 210 krpm at temperatures of 525°C while being supported on dynamic steam-lubricated bearings. A low-reaction, full-admission design has been chosen to lower the steam consumption, the axial forces, and the turbine backface leakage. The turbine rotor is made of Ti6Al4V and coated for structural integrity and to withstand high temperatures. Despite the small scale of this design, the results obtained from the established correlations based on large-scale turbines yield a remarkable concordance with the results from the numerical analysis, in particular for the isentropic expansion efficiency prediction.

A High-Temperature, High-Speed, Oil-Free Syngas Compressor for Small-Scale Combined Heat and Power

Abstract For low-emission, small-scale combined heat and power generation, integrating a biomass gasifier with a downstream solid oxide fuel cell system is very promising due to their similar operating conditions in terms of temperatures and pressures. This match avoids intermediate high-temperature heat exchangers and improves system efficiency. However, to couple both systems, a high-temperature and oil-free compressor is required to compress and push the low-density, high-temperature bio-syngas from the gasifier to the solid oxide fuel cell stack. The design and development of this high-temperature, high-speed, and gas-bearing supported compressor is presented in this work. An iterative process involving preliminary design, meanline analysis using commercial tools and in-house models is used for the design, which is then numerically analyzed using computational fluid dynamics. The goal is to achieve a design with a wide operating range and high robustness that withstands extreme working conditions. The 727 W machine is designed to run up to 210 krpm to compress 18.23kg/h of syngas at 350°C and 0.81bar. The centrifugal compressor has a tip diameter of 38 mm and consists of 9 backswept main and splitter blades. The impeller is made of Ti6Al4V and coated to prevent hydrogen embrittlement from the hot and highly reactive bio-syngas. The results obtained from the established models suggest a good concordance with the results from numerical analyses, despite the high temperatures and small scale of this design.

Thermodynamic analysis and multi-objective optimization of different gas turbine configuration strategies for an atmospheric SOFC system

Solid oxide fuel cells (SOFCs) play a critical role as a key technological component in the utilization of hydrogen energy. Extensive research has been conducted on pressurized SOFC hybrid systems, focusing on performance enhancement and novel system configurations, etc. However, the planar SOFC suitable for commercial application exists limitations that confine its operation solely to atmospheric pressure. Moreover, SOFC exhaust contained considerable potential for energy recovery. In light of these limitations, two hybrid power generation systems of SOFC and GT have been proposed: direct and indirect utilization of SOFC cycle exhaust. Parameter and exergy analysis has been conducted to investigate the characteristic of SOFC-GT system. Multi-objective optimization is performed by setting exergy efficiency and output power as objective. The results reveal that the combustion process contributes significantly to system losses, with exergy efficiency reaching a maximum of 49.48% and 41.61%, respectively. Additionally, the system's maximum output power reaches 92 kW. Notably, the indirect SOFC-GT system demonstrates an 8% increase in exergy efficiency compared to the direct SOFC-GT system at the same output power. To improve the overall system fire efficiency, it is recommended to develop planar SOFCs suitable for high pressure and slow down the reaction process inside the combustion chamber.

Stack performance classification and fault diagnosis optimization of solid oxide fuel cell system based on bayesian artificial neural network and feature selection

Solid oxide fuel cell (SOFC) has attracted much attention because of its high efficiency and silent power generation, and can be applied to the field of fuel cell-powered unmanned boats. However, a fuel deficit failure in the system can lead to reduced stack performance, reducing the reliability of SOFC applications in the field of unmanned boats. Therefore, this paper proposes an efficient breakdown diagnosis model for SOFC system fault diagnosis. Firstly, Bayesian artificial neural network is constructed by using the best feature data subset after Relief-F combined with minimum Redundancy Maximum Relevance algorithm feature selecting. Secondly, the correct diagnosis rate under different number of optimal features is calculated, and the best feature combinations are combined to verify. Finally, the particle swarm algorithm selects the optimal hidden neuron count to optimization model. Experimental findings suggest that for correct diagnosis rate, the breakdown diagnosis model based on the optimal number of 3 features can reduce the training time and maintain high accuracy compared with the use of all 34 features. This research result provides a feasible way for the fault diagnosis application of SOFC system power generation in the field of unmanned boats.

Numerical analysis and parametric optimization of a direct ammonia solid oxide fuel cell system integrated with organic Rankine cycle

In this study, to maximize the electrical efficiency of the direct ammonia solid oxide fuel cell (SOFC) system, anode-off gas is recirculated for enhancing the system fuel utility and the system exhaust heat is utilized for the organic Rankine cycle (ORC) generating additional electricity. To confirm the superiority of the anode-off gas recirculation (AOGR) SOFC–ORC hybrid system, its electrical efficiency has been compared with two reference systems such as the stand-alone SOFC system without AOGR and the stand-alone AOGR SOFC system. A numerical model on three systems has been developed using Aspen Plus® and validated. Parametric analysis of the three systems has been conducted by varying the operating parameters such as the pump pressure, current density, AOGR ratio, condensation ratio, and fuel utilization. The AOGR SOFC-ORC hybrid system has the highest electrical efficiency among the three types of systems, 70.92 % under nominal conditions. The optimal operational range for the AOGR SOFC-ORC hybrid system has been revealed. As an ammonia-fueled distributed power generation, the proposed system can contribute to achieving net zero in countries where renewable energy is not abundant. This study can provide fundamental insights for establishing an optimization of direct ammonia SOFC systems.

Application of Multiple Linear Regression and Artificial Neural Networks in Analyses and Predictions of the Thermoelectric Performance of Solid Oxide Fuel Cell Systems

Application of Multiple Linear Regression and Artificial Neural Networks in Analyses and Predictions of the Thermoelectric Performance of Solid Oxide Fuel Cell Systems

Emergoenvironmental analysis and sustainable flexible peaking of a novel solar-assisted solid oxide fuel cell cogeneration system

The development of green and sustainable conversion technologies is imperative to alleviate the current severe energy and environmental crises and to achieve the goal of carbon neutrality. This project presents a novel cogeneration system that integrates a solid oxide fuel cell afterburning system, an energy recovery system, and a parallel heating system equipped with multistage utilization, solar-assisted, and flexible peaking technologies. Following the establishment and validation of the system, power source analysis, parameter sensitivity studies, three-objective optimization, and internal exergy flow investigation are carried out. Subsequently, the positive impacts of multistage utilization, solar-assisted, and flexible peaking technologies, as well as the thermoeconomic and emergoenvironmental operating characteristics of the system, are discussed. The numerical results demonstrate that the emergoenvironmental factor and emergy environmental impact difference of the system are 70.15 % and 82.52 %, and the energy efficiency is improved by 1.41 %∼19.09 %, respectively, compared with similar solid oxide fuel cell systems, confirming its favorable thermodynamic performance and emergoenvironmental impact. The system achieves daily heating savings of 3302 kWh and life cycle economic benefits of $19,310,524, with a repayment of the investment cost in 4.17 years, reflecting considerable economic benefits. This project also demonstrates exergy flow, module defects, and improvement mechanisms from the perspective of emergoenvironmental, providing a valuable reference for the promotion of green energy.

Research on large-signal stability of SOFC-lithium battery ship DC microgrid

Aiming at the solid oxide fuel cell (SOFC) applied to the ship DC microgrid in the face of pulse load disturbance is prone to make the SOFC voltage drop too large leading to the DC grid oscillation problem. In this paper, a stability criterion method for SOFC-Li battery DC system based on hybrid potential function is proposed. Firstly, a mathematical model of shipboard DC microgrid with SOFC-Li battery is established and the accuracy of the model is verified. Then, the stability criterion of the system based on the hybrid potential function under large disturbances is constructed. Subsequently, the effects of system stability under impulse load conditions were analysed under different parameters. Based on the constructed criterion, simulation verification of the stability boundary conditions of the SOFC system operating independently or jointly with a lithium battery system is carried out. The experimental results show that the proposed stability criterion and control strategy are effective in accurately predicting the system stability boundary. The experimental results verify the effectiveness of the proposed method in improving the stability of the system and provide a theoretical basis for further research on the dynamic characteristics of SOFC systems under complex load conditions.

An Indirect Ammonia Fuelled Solid-Oxide Fuel Cell System with free cracking from Waste Heat

An Indirect Ammonia Fuelled Solid-Oxide Fuel Cell System with free cracking from Waste Heat

Efficiency and longevity trade-off analysis and real-time dynamic health state estimation of solid oxide fuel cell system

Solid oxide fuel cell (SOFC) is a promising energy conversion technology due to its advantages of high efficiency, low emissions, and fuel adaptability. Addressing the balance between efficiency and longevity is crucial for their application on a large scale. Accurate estimation and prediction of the health state of SOFC systems is essential for the study of optimization between system efficiency and degradation. In this work, the influence law of degradation, the relationship between efficiency and longevity, and their joint optimization, alongside the state of health (SOH) estimation of the SOFC system have been deeply investigated, based on a rigorously validated model of a degraded SOFC system. First, the influential variables that predominantly influence system degradation are identified and analyzed via principal component analysis, including stack average temperature, stack temperature gradient, and fuel utilization. Then, the exploration of the trade-off relationship between system efficiency and longevity under all operating conditions is conducted, and the influence laws of influential variables on system degradation are revealed. In light of the lack of accuracy during load changes and the high time cost for existing SOH estimation methodologies, a novel improved SOH estimation strategy, considering both stack voltage and current-related states, is proposed for real-time estimation of system SOH under varying fuel compositions and dynamic power scenarios. The performance of the proposed method is demonstrated by comparing with existing methodologies. This comprehensive study lays the groundwork for the effective and sustainable health management of SOFC systems, ensuring their efficiency and longevity are maintained at an optimal balance.

Novel solid oxide fuel cell system integrating adsorption cooling, heating, and carbon dioxide fertilization for greenhouse tomato production

Fuel cells have been widely used for power sources in the power plant, building, and transportation sectors, while few attempts have been made to use fuel cells for agriculture. Heating costs make up a high proportion of agricultural operating costs, and fossil fuels are the primary fuels used, which affects agricultural income according to changes in international oil prices. This study proposes a novel solid oxide fuel cell(SOFC) system integrates adsorption cooling, heating, and carbon dioxide fertilization for greenhouse tomato production. To confirm the superiority of the proposed system (Case 3) in terms of efficiency, its energy consumption is compared with that of the reference systems (cases 1 and 2). Case 1 uses only the air-cooled scroll chiller while Cases 2 and 3 utilize both the air-cooled scroll chiller and the adsorption chiller as a heating and cooling device for the horticulture. In order to reduce the energy consumption for the horticulture thermal management, electrical and thermal energy required for the adsorption chiller are supplied by the SOFC. Case 3 supplied SOFC exhaust gas to fertilize carbon dioxide in horticulture for photosynthesis of the tomato. To determine the heating and cooling loads for horticulture, horticulture energy modeling has been developed based on target temperature, weather data, and tomato evapotranspiration using TRNSYS®. The total power consumption in Case 3 is reduced by up to 12 % during the heating season compared to Case 1, but it increases by up to 6.2 % during the cooling season. For Case 2, there is a savings of 9.8 % during the heating season but an increase of up to 4.1 % during the cooling season compared to Case 1. The study contributes to reduction of the energy consumption for the greenhouse crops production. This finally results in the significant reduction of the carbon emission and the enhancement of the economics in agricultural field.

Comparative Study of Thermodynamic Performances: Ammonia vs. Methanol SOFC for Marine Vessels

AbstractIn response to escalating environmental concerns and the imperative to institute effective energy management strategies, the pursuit of alternative fuels has emerged as a pivotal endeavor for realizing sustainable energy solutions. Methanol and ammonia have surfaced as particularly promising and environmentally friendly liquid fuels, holding significant potential for aiding in the attainment of decarbonization objectives and addressing global energy requirements. This research proposes and scrutinizes a sophisticated cogeneration system integrating solid oxide fuel cells (SOFCs), gas turbine (GT), steam Rankine cycle, and organic Rankine cycle. Direct utilization of ammonia and methanol as fuel in this intricate system is examined, with the design and modeling facilitated through the utilization of Aspen HYSYS V.12.1. The thermodynamic performance of the proposed system is rigorously assessed by employing the foundational principles of the first and second laws of thermodynamics. The direct SOFCs fueled by ammonia and methanol exhibit notable energy efficiencies of 64.25 % and 58.42 %, respectively. Remarkably, the amalgamated systems showcase heightened energy efficiencies, witnessing a commendable increase of 12.64 % and 10.66 % when powered by ammonia and methanol, respectively, as compared to individual SOFC systems. Examination of exergy destruction reveals the SOFC as the principal contributor, with electrochemical and chemical processes constituting the primary sources of irreversibility. Additionally, explicit values for exergy destruction in the GT, afterburner, and heat exchanger components are provided. A comprehensive parametric study underscores the pivotal role of the fuel utilization factor (Uf), identifying a value of 0.85 as optimal and significantly augmenting the thermodynamic efficiency of the system. This analysis not only substantiates the potential of ammonia and methanol as effective carriers for hydrogen but also underscores the efficacy of waste heat recovery as a viable strategy for enhancing the overall thermodynamic performance of an SOFC system. The findings presented herein contribute valuable insights, paving the way for the strategic utilization of alternative fuels and cogeneration systems in the broader context of sustainable and environmentally conscious energy solutions.