平板状固体氧化物燃料电池的数值模拟

利用流体力学计算软件FLUENT建立平板状固体氧化物燃料电池（SOFC）三维数值模型，研究在不同操作条件和支撑形式下，活化极化、欧姆极化、浓度极化对SOFC性能的影响。在多孔电极中的气体流动符合达西定律的前提下，为满足不同的多孔电极设计，综合考虑了摩尔扩散和Knudsen扩散。另外还考虑了电池电化学反应热对欧姆极化的影响。分析结果表明，阴极和阳极支撑固体氧化物燃料电池具有较低的操作温度和较好的输出特性。     

耦合氨水吸收式制冷液化回收CO2的SOFC/GT/ST/ORC系统研究

为提高固体氧化物燃料电池(SOFC)的联供系统效率、降低碳捕集能耗,提出了一种基于SOFC/透平(GT)/蒸汽轮机(ST)、有机朗肯循环(ORC)和氨水吸收式制冷循环液化回收CO₂的联供系统。利用Aspen Plus软件搭建了SOFC本体模型,并对其进行验证。通过输入设计工况下的热力学参数,探究了电流密度、燃料利用率、汽碳比对SOFC本体及联供系统性能的影响。结果表明：在设计工况下,SOFC发电效率为55.5%、联供系统发电效率为76.5%、功冷联供效率为92.6%,与现有系统相比,各效率均有提升;当电流密度增加至极限电流密度时,浓差极化损失迅速增大,对系统性能产生负面影响;随着燃料利用率的提高,功冷比不断下降,各效率呈先增后减的趋势;当汽碳比为2时,联供系统的发电效率及功冷联供效率最大,分别为78.04%和93.2%。     

新型平板式固体氧化物燃料电池的开发和性能分析

利用商业数值分析软件和试验获得的电池各部件材料性能数据,改进了用于分析固体氧化物燃料电池(SOFC)单电池内部复杂物理过程的软件包.应用该软件包,得到了设计的新型高效平板式SOFC单电池内部各气体组分浓度、温度、电势、电流及电流密度等参数的分布规律.分析结果表明:在高燃料利用率情况下,阳极内组分扩散引起的浓度极化损失是影响电池性能的重要因素之一.该新型结构电池可有效改善电池的密封性,但其电解质需要较高的最大离子传导率.     

基于镧锶锰氧化物基阴极的中温固体氧化物燃料电池的性能优化研究

为了提高基于镧锶锰氧化物(LaxSr1-xMnO3,LSM)阴极的中温固体氧化物燃料电池(Solid Oxide Fuel Cell,SOFC)的电化学性能,文章利用CuO清扫Ce0.85Sm0.15O2-δ(SDC)晶界的SiO2杂质以提高SDC的离子电导率,制备了复合电解质材料SDC-CuO,并将SDC-CuO和LSM结合成复合阴极材料,随后分别制备了以LSM和LSM/SDC-CuO作为阴极的SOFC,并研究了这两种SOFC的电化学性能。研究结果表明:在开路电压和工作温度为800℃的条件下,LSM/SDC-CuO基阴极的SOFC的极化电阻为0.14Ω·cm2,明显低于LSM基阴极SOFC的极化电阻(0.36Ω·cm2);LSM/SDC-CuO基阴极的SOFC的最大输出功率密度为237 mW/cm2,显著高于LSM基阴极的SOFC的最大输出功率密度(132 mW/cm2)。     

管式固体氧化物燃料电池的数值模拟

通过耦合速度场、温度场、电势场和组分浓度场，建立了以纯氢气为燃料的管式固体氧化物燃料电池（SOFC）数学模型，并对西门子．西屋公司阴极支撑型（AES）管式SOFC进行了轴向二维模拟。模拟结果表明，组分浓度和电流密度的分布与SOFC的运行工况密切相关。在所模拟的电压范围内，欧姆极化起主要作用，提高固体氧化物燃料电池的平均工作温度、改善多孔电极的微观结构、使用纯氧代替空气作为氧化剂可改善电池性能。图8参10     

板式固体氧化物燃料电池积碳特性的数值研究

固体氧化物燃料电池(SOFC)阳极积碳的发生是制约其高效稳定运行的瓶颈问题,文中介绍了阳极积碳对SOFC的影响,回顾了国内外研究此问题的三个典型方向及其进展;在此基础上,利用用户自定义子程序(UDF)与流体动力学计算软件Fluent建立的SOFC完整极化数值模型,对一板式SOFC的反应特性与积碳特性进行数值模拟与分析....     

基于模型的5 kW SOFC系统操作参数寻优

为延长固体氧化物燃料电池（SOFC）的寿命、提高系统性能，以5 kW平板式SOFC系统为研究对象，在满足功率需求和温度约束的条件下，探究其通过寻优最佳的操作参数组合以实现最高的系统效率。首先采用模块化建模方法，基于工作机理建立SOFC独立发电系统的模型。其次，基于所建立的系统模型，通过定义4个操作参数，并结合系统的热电约束，形成SOFC系统效率优化问题。针对该优化问题，提出一种结合元启发式优化算法的两级优化方案，即将操作参数按照对SOFC系统的影响分为两级，对第一级操作参数进行离散取值，对第二级操作参数采用麻雀搜索算法进行优化。结果表明，所提优化方案可获得全局最优操作点，使SOFC系统满足功率需求和温度约束条件且系统效率达到最优。     

连接体结构对固体氧化物燃料电池性能影响的数值分析

固体氧化物燃料电池（SOFC）中连接体结构对电池性能有重要影响。为探究连接体结构对固体氧化物燃料电池性能的影响，建立了传统直通、圆柱形、矩形和凹形4种不同连接体结构SOFC的三维数值模型，并对其流体流动、组分传递、电化学反应和固体流体传热的多物理场耦合过程进行了数值模拟。结果表明，在一定条件下，圆柱形、矩形和凹形连接体结构有利于电池中气体的传输，使电池的电流密度和输出功率均有所提升，其中凹形连接体结构的提升效果最明显，圆柱形、矩形连接体结构的次之。不同孔隙率下圆柱形、矩形和凹形连接体结构均优于传统直通连接体结构，在阴极孔隙率较小时其优势更加明显。     

SOFC阳极气体循环中气流引射器的设计及仿真分析

SOFC阳极气体循环对SOFC系统的性能有着很大的影响,气流引射器是实现该系统的关键设备.介绍了SOFC阳极气体循环的气流引射器的设计思路,建立了适用于多组分气体的气流引射器模型,并对该气流引射器在变工况下的性能进行了仿真.仿真结果表明,该气流引射器有着良好的变工况性能,适用于SOFC阳极气体循环系统.     

考虑电气转换及储能一体化的SOFC热电联供技术优化

当前热电联供技术优化方法,仅分析储能和发电装置的关系,导致优化后的热电联供技术,在环境温度和负荷率影响下,热电联供热力性能较低,为此提出考虑电气转换及储能一体化的SOFC热电联供技术优化。分析电堆电化学反应,确定SOFC产生的能源指标;依据SOFC电堆电化学反应计算结果,建立电气转换及储能一体化的SOFC热电联供系统模型结构,根据SOFC热电联供系统运行流程,分析SOFC发电装置、储能设备、热能处理设备之间的工作互通关系;基于分析结果,确定OFC热电联供技术优化目标,设计目标函数和最大装机容量约束并求解,实现SOFC热电联供技术优化。实验结果表明：在环境温度和负荷率影响下,考虑电气转换及储能一体化的SOFC热电联供技术优化方法,优化后的热电联供热力性能更高。     

Numerical characterization of a microscale solid-oxide fuel cell

In this study, a single unit of planar micro-solid-oxide fuel cell (μSOFC) is investigated numerically to evaluate the influences of flow channel design, oxygen composition, and thermal operating conditions on cell performance. Four flow channel designs are examined under the co-flow configuration: serpentine, double serpentine, rod bundle, and oblique rib. For all designs, the contacts areas of interconnect to electrodes are kept consistent to maintain the ohmic losses at the same level. To characterize the mass transport effects, there are three different compositions, 100% O₂, 50% O₂/50% N₂ and air, fed to the cathode inlet. Different thermal conditions, adiabatic and isothermal, are applied to the outer boundary of the μSOFC and the results are compared. The outcomes suggest that both thermal conditions and oxidant composition show remarkable influences on μSOFC performance. Under adiabatic conditions, the rise of cell temperature causes a decrease in reversible voltage, deteriorating the overall cell competence. When oxygen is diluted with nitrogen, local gas diffusion becomes dominant to the cathode reaction. Bulk flow, on the other hand, plays a minor role in cell performance since there is little deviation in the polarization curves for all flow channel designs, even at high current densities. For comparison, the flow visualization technique is employed to observe the transport phenomena in various flow channel designs. The flow patterns are found to resemble the concentration distribution, providing a useful tool to design μSOFCs.     

Fused filament fabrication for anode supported SOFC development: Towards advanced,scalable and cost-competitive energetic systems

Solid Oxide Fuel Cells (SOFC) are electrochemical devices that efficiently convert hydrogen or other fuels into energy and heat and are considered a promising and environmentally friendly alternative to mitigate the effects of climate change. The difficulties found for the SOFC devices implementation into the market have triggered an enhanced need of research on the manufacturing strategy, since the cells and stack fabrication remain a complicated procedure. In this work, the capabilities of an additive manufacturing (AM) process, as it is Fused Filament Fabrication (FFF), applied to anode supported SOFC were explored for the first time, due to the strengths this technology offers in terms of materials versatility and cost-competitive process. Moreover, the ability of tuning the support porosity during the printing process was demonstrated, minimizing the pore former concentration required and avoiding reformulation of the feedstock to achieve higher porosity in the anode. In the cell fabrication, low-cost techniques for thin film deposition were employed. The preliminary geometry investigated represents a novel SOFC device that shows an electrochemical performance comparable to that found in the conventional SOFC fabrication and it opens the possibility of potential single-cell and stack designs in which the use of ceramic sealing could be avoided and the system durability increased.     

Evaluation of system configurations for solid oxide fuel cell-based micro-combined heat and power generators in residential applications

The evaluation of solid oxide fuel cell (SOFC) combined heat and power (CHP) system configurations for application in residential dwellings is explored through modeling and simulation of cell-stacks including the balance-of-plant equipment. Five different SOFC system designs are evaluated in terms of their energetic performance and suitability for meeting residential thermal-to-electric ratios. Effective system concepts and key performance parameters are identified. The SOFC stack performance is based on anode-supported planar geometry. A cell model is scaled-up to predict voltage–current performance characteristics when served with either hydrogen or methane fuel gas sources. System comparisons for both fuel types are made in terms of first and second law efficiencies. The results indicate that maximum efficiency is achieved when cathode and anode gas recirculation is used along with internal reforming of methane. System electric efficiencies of 40% HHV (45% LHV) and combined heat and power efficiencies of 79% (88% LHV) are described. The amount of heat loss from small-scale SOFC systems is included in the analyses and can have an adverse impact on CHP efficiency. Performance comparisons of hydrogen-fueled versus methane-fueled SOFC systems are also given. The comparisons indicate that hydrogen-based SOFC systems do not offer efficiency performance advantages over methane-fueled SOFC systems. Sensitivity of this result to fuel cell operating parameter selection demonstrates that the magnitude of the efficiency advantage of methane-fueled SOFC systems over hydrogen-fueled ones can be as high as 6%.     

Modeling design and analysis of multi-layer solid oxide fuel cells

The thermo-mechanical analytical model proposed for different solid oxide fuel cell (SOFC) designs addresses the deformation behavior and mechanical stability of SOFCs at various thermal stresses, specifically the creep resistance and the long-term endurance beyond the elastic limit.The model considers the deformation of multi-layer SOFC in the temperature range of 600-800 °C and presents the combination of the correlated parameters for SOFC performance evaluation, stability and long-term endurance under realistic operating conditions and temperature gradients. The numerical analysis of the thermo-mechanical properties of the SOFC materials is presented in terms of mechanical behavior at failure conditions and the influence of rheological and structural properties on SOFC long-term endurance. The SOFC thermal behavior, creep parameters of the SOFC materials and long-term stability are analyzed in terms of stresses, deformations and displacements.In terms of broader impact, the algorithms for Maurice-Levi and Voltaire theorems and their validity for non-elastic, e.g. viscous-elastic, viscous-plastic, and elastic-plastic deformations were confirmed. This result allowed us to apply the stress condition of non-elastic body to the stress condition of the elastic body which is relevant to the SOFC operation at elevated temperatures.     

Numerical study of a flat-tube high power density solid oxide fuel cell: Part II: Cell performance and stack optimization

The flat-tube high power density (HPD) solid oxide fuel cell (SOFC) is a geometry based on a tubular type SOFC, and is being developed by Siemens Westinghouse and other international companies in Japan and Korea. It has increased power density, but still maintains the beneficial feature of secure sealing for a tubular SOFC. In this paper, the electric performance of a flat-tube HPD SOFC is studied. This paper also investigates the effects of the stack chamber number, stack shape, and other stack geometry features on the performance of the flat-tube HPD SOFC. The results show that the performance of a flat-tube HPD SOFC is better than a tubular SOFC with the same active cell surface, and that increasing the number of chambers number can improve the overall performance of a flat-tube HPD SOFC. The height of a flat-tube HPD SOFC and the thickness of the ribs do not have much effect on the performance of the cell as is expected. This study will help to design and optimize the flat-tube HPD SOFC.     

A CFD-based model of a planar SOFC for anode flow field design

This study presents a 3D CFD model of a planar SOFC with internal reforming for anode flow field design. The developed model reflects the influence of various factors on fuel cell performance including flow field design and kinetics of chemical and electrochemical reactions. The case study illustrates applications of the CFD model for planar SOFC with different anode flow field designs. Simulation results indicate the importance of the anode flow field design for planar SOFCs. The model is useful for optimization of fuel cell design and operating conditions.     

1kW家用SOFC-CHP系统建模及性能分析

构建一个以天然气为燃料的SOFC-CHP系统,推导SOFC传热传质及电化学方程,建立各个组件的数学模型,编写计算程序,对发电功率为1kW的家用SOFC-CHP系统在设计工况下进行性能模拟并探讨不同系统参数对性能的影响。计算结果表明:在设计工况下,系统热电联供效率远高于电池单独发电的效率;此外,随着燃料入口流量的增大,系统发电功率存在一个最大值,燃料利用率与发电效率不断减小,系统热电联供效率不断增大,SOFC的温度梯度分布则越来越平缓;同时发现降低过量空气系数可以提高该CHP系统的性能。     

A numerical study on the heat and mass transfer characteristics of metal-supported solid oxide fuel cells

The heat and mass transfer characteristics of solid oxide fuel cells (SOFCs) need to be considered when designing SOFCs because they heavily influence the performance and durability of the cells. The physical property models, the governing equations (mass, momentum, energy and species balance equations) and the electrochemical reaction models were calculated simultaneously in a 3-dimensional SOFC simulation. The current density-voltage (I-V) curves measured experimentally from a single SOFC were compared with the simulation data for code validation purposes. The error between the experimental data and the numerical results was less than 5% at operating temperatures from 700 °C to 850 °C. The current density and the mass transfer rate of an anode-supported SOFC were compared with those of a metal-supported SOFC. The metal-supported SOFC had a 17% lower average current density than the anode-supported SOFC because of the bonding layer, but it showed better thermal stability than the anode-supported SOFC because of its more uniform current density distribution. The current density, temperature and pressure drop of the metal-supported SOFC were investigated for several channel designs. A high current density was observed near the hydrogen inlet and at the intersection of the hydrogen and air channels. However, there was a low current density under the rib and at the cell edge because of an insufficient reactant diffusion flux. When the proper channel design was applied to the metal-supported SOFC, the average current density was increased by 45%.     

Three-dimensional computational fluid dynamics modeling of anode-supported planar SOFC

Modeling plays a very important role in the development of fuel cells and fuel cell systems. The aim of this work is to investigate the electrochemical processes of a Solid Oxide Fuel Cell (SOFC) and to evaluate the performance of the proposed SOFC design. For this aim a three-dimensional Computational Fluid Dynamics (CFD) model has been developed for an anode-supported planar SOFC with corrugated bipolar plates serving as gas channels and current collector. The conservation of mass, momentum, energy and species is solved by using the commercial CFD code FLUENT in the developed model. The add-on FLUENT SOFC module is implemented for modeling the electrochemical reactions, loss mechanisms and related electric parameters throughout the cell. The distributions of temperature, flow velocity, pressure and gaseous (fuel and air) concentrations through the cell structure and gas channels is investigated. The relevant fuel cell variables such as the potential and current distribution over the cell and fuel utilization are calculated and studied. The modeling results indicate that, for the proposed SOFC design, reasonably uniform distributions of current density over the active cell area can be achieved. The geometry of the cathode gas channel has a substantial effect on the oxygen distribution and thus the overall cell performance. Methods for arriving at improved cell designs are discussed.     

Numerical modelling and comparative analysis of direct ammonia fuelled protonic and oxygen- ion conducting tubular solid oxide fuel cell

The main emphasis of this work is developing a 3D numerical model and investigating the performance characteristic of a direct ammonia fuelled protonic-conducting tubular solid oxide fuel cell (NH₃-T–SOFC–H) in comparison with the corresponding hydrogen-fuelled one and direct ammonia feed oxygen -ion conducting tubular solid oxide fuel cell (NH₃-T–SOFC–O) under the same operating parameters and geometrical shape. The findings revealed that NH₃-T–SOFC–H has outstanding performance over T–SOFC–O counterparts at intermediate temperature (973 K) when operated under similar working conditions and geometrical designs. On the other hand the NH₃-T–SOFC–O is promising for higher operating temperatures. The outcomes of the study are also confirmed that the power performance of NH₃-AS-T–SOFC–O is better than the other supports of both electrolytes when the anode electrode is constructed at the outside portion of the tubular cell. Yet, the other remarkable result found in this study is that NH₃– CS- T–SOFC–O has outstanding performance compared to all supports of both electrolytes when the fuel electrode is built in the inner portion of the tube. In addition, the finding indicates that the power performance of ammonia-fuelled tubular cells is strongly influenced by the anode position, operating temperatures, and pressures in both electrolytes yet the effect of cell temperature is more influential in the protonic-conducting cell. It is also observed that the performance of ES-T-SOFC is lower than AS- and CS-T-SOFC in both electrolytes and anode positions.