An isomorphic multi-energy circuit analysis method for multi-stack SOFC systems considering nonlinear electrochemical reaction and gas transport

Solid Oxide Fuel Cell (SOFC) is a promising technology for hydrogen energy utilization. Whereas, the current multi-stack system analysis faces the challenge of computational efficiency improvement without sacrificing accuracy. This work proposes a multi-energy circuit (MEC) model for SOFC stacks, consisting of an electrical circuit and a thermal circuit. The electrical circuit simultaneously describes the chemical energy transport along the flow direction as well as its transport and conversion at the vertical direction. Meanwhile, a local resistance model is established to describe the components in the electrical circuit, which divides each electrode into transport layer and reaction layer with interfaces determined by the operation condition dynamically. Besides, by using electro-thermal analogy, the thermal circuit model is constructed to describe the thermal energy conservation along the flow direction and heat transfer vertical to the flow direction. Consequently, an accurate and efficient solution algorithm of the MEC model is proposed based on the separation of the linear matrix topology from the nonlinear component characteristics. Compared to the existing quasi-2D model and iterative solution method, the MEC analysis method is 30 times faster for an individual stack with prescribed output current. For a four-stack system with prescribed total output voltage, the MEC analysis method costs only 552 s, while the existing method fails to converge. Besides, the MEC analysis method has great potential in the topology and operation optimization of multi-stack structures as demonstrated finally.