Modeling and control-oriented thermal safety analysis for mode switching process of reversible solid oxide cell system

A reversible solid oxide cell (rSOC) system can balance the surplus and shortage of electricity generated from renewable energy grid by working either in energy conversion or in storage mode. A dynamic model of the rSOC system was developed and validated against experimental data. It can be used to determine the dynamic thermal characteristics during mode switching. This work focuses on the influence of different operating parameters on the temperature distribution in the rSOC stack along the gas flow direction in the system environment. The extremum of local temperature gradient in the dynamic process is proposed for the first time, and it hardly changes when adjusting air excess ratio (AR) and fuel utilization (FU). In addition, the results show that the maximum PEN temperature (MaxT_PEN) increases with the decrease of AR in the transients, but FU has little effect on the local MaxT_PEN. AR and FU affect the MaxT_PEN (Compared with FU, AR is more significant) and the maximum temperature gradient (MaxT_grad) in steady-state, but the control current does not. The proposed control currents significantly decrease the MaxT_PEN and MaxT_grad in the transient process, and the ramp current works better than the multi-step current. Overall, this work identified the effects of operating parameters on the thermal characteristics of the rSOC stack in switching from electrolysis to fuel cell mode under the system environment. It guides the development of the thermal management strategy of the rSOC system.