Dynamic behavior analysis of solid oxide fuel cell system with auxiliary components under variable operating conditions

Solid oxide fuel cell (SOFC) system offers the benefits of high efficiency, low emissions, and quiet operation. However, complex interactions among components and the closed-loop nature of operating parameters present challenges for system control. This study investigates the dynamic responses of a standalone SOFC stack and a SOFC system integrated with auxiliary components under step changes of key operating parameters. Results demonstrate that auxiliary components play a critical role in shaping transient responses. A step increase in current reduces the fuel flow into the burner, ultimately causing stack temperature fluctuations due to increased current and decreased inlet temperature. The greater the current increase step magnitude, the larger the stack temperature fluctuation amplitude. A step increase in fuel and air flow respectively leads to an increase in the fuel and air entering the burner. The step increase of fuel flow causes the stack temperature to fluctuate, first dropping rapidly and then rising slowly. The step increase of air further lowers the stack temperature, as the burner and heat exchangers reduce the inlet gas temperature. Under +15 % step change in current, inlet fuel flow, and air flow, the changes in output power and response time are +512.3 W/330.3s, +667.7 W/836.8s, and −573.8 W/412.8s. Based on these findings, the prioritization of current regulation is recommended to achieve faster responses, improved efficiency, and enhanced thermal safety. Fuel and air flow adjustments are suggested as secondary measures for thermal and efficiency optimization.