Thermoelectrical comprehensive analysis and optimization of multi-stack solid oxide fuel cell system

•The multi-stack SOFC system mechanism model is constructed with system level validated two-dimensional SOFC stacks.•The themoelectrical performance of different stack module topologies are comprehensively analyzed and optimized.•The influence laws of stack topology on system electrical performance and thermal safety are revealed.•The optimal multi-stack SOFC system configuration is obtained and its operation characteristics are investigated. Solid oxide fuel cell (SOFC) is one of the most promising power generation technologies for its high efficiency, low emission, and fuel adaptability. The power of a single SOFC stack is usually limited to about 1 kW to guarantee its reliability, and stacks are therefore integrated in series or parallel to meet load power demand. However, the performance of a multi-stack SOFC system predominantly depends on the configuration (electrical and gas path structure) of the stack module. Consequently, it is important for the development of SOFC to explore the influence of stack integration structure on system performance and thermal safety, and to further grasp the multi-stack design principles by analyzing the input-output characteristics of the system. The existing studies mainly focus on the electric performance-related parameters analysis and optimization of multi-stack, without considering the thermal safety, the laws of the integration structure influence on system performance and comprehensive optimization on system level. In this work, general multi-stack SOFC systems with four gas distribution structures constructed by four validated stacks are considered and their thermoelectrical performance is systematically investigated and optimized under operational constraints based on a completed multi-SOFC system model. Moreover, the input-output characteristics, thermoelectrical performance and operation rules of the multi-stack SOFC system analysis are conducted, and finally, the stack module design principles and optimal stack topology are obtained. The results show that the parallel connection of two serial stack branches is preferred and can reach the maximum net system efficiency of 42.90 % and maintain the maximum temperature gradient within 6.04 K/cm at a low cost.