Solid oxide electrolysis cell under real fluctuating power supply with a focus on thermal stress analysis

Solid oxide electrolysis cell (SOEC) can efficiently utilize electricity for fuel generation through high-temperature electrochemical reaction. When directly using renewable powers, SOEC will frequently deviate from the optimal operating conditions and generate severe thermal stress, leading to cracks or even thermomechanical failure. To investigate the thermomechanical behavior of SOEC with fluctuating power supply, we develop 2D dynamical models by fully considering the electrochemical reaction, electron/ion/molecular transport, heat/momentum transfer and thermal-mechanical interaction. The distribution of thermal stress is detailly analyzed and the inlet gas temperature is identified as a key factor, where the maximum thermal stress can be decreased from 305 to 135 MPa with the inlet gas temperature increasing from 973 to 1073 K. We also dynamically optimized the anode gas flow rate by following fluctuating applied voltages, where a power function of voltage V5 is found to be an optimum choice. Compared with a constant flow rate of 400 SCCM, the maximum temperature and thermal stress with dynamically controlled flow rate can be decreased by 98.7 K and 65.3 MPa, respectively. This paper presents an implementation approach for the peak temperature reduction and thermal stress optimization in SOECs. •A 2D dynamic model for tubular solid oxide electrolysis cell is developed.•The parametric studies on SOECs is conducted with fluctuating PV power supply.•Thermal stress distribution is detailly analyzed for thermomechanical optimization.•The inlet gas temperature has significant influence on thermomechanical behavior.•Thermal stress can be decreased by 65.3 MPa with dynamically controlled flow rate.