Numerical analysis of a highly efficient cascade solid oxide fuel cell system with a fuel regenerator

One of the most effective ways to improve the electrical efficiency of a solid oxide fuel cell system is to maximize the fuel utilization of the system. As a method to increase fuel utilization, the anode off-gas from the first stack is supplied to the second stack. Because low fuel concentrations in the first stack could highly reduce the performance of the second stack, a fuel regenerator is installed after the first stack to remove the water and increase the fuel concentration. In this study, a numerical model of a cascade solid oxide fuel cell system was developed using Aspen Plus®. To capture the effects of the fuel regeneration rate on the electrical efficiency of the cascade solid oxide fuel cell system, the models were simulated at various operating parameters such as the fuel utilization, steam-to-carbon ratio, external reforming ratio, and current density. As a result, the electrical efficiency of the system increased with increasing fuel regeneration rate. However, when the fuel regeneration rate becomes 100%, the electrical efficiency of the cascade system is not the highest efficiency because of the power consumption of the electric heat pump.