Self-adaptive heat management of solid oxide electrolyzer cell under fluctuating power supply

•A 2D SOEC model coupled with thermochemical energy storage is developed.•Self-adaptive heat management of SOEC is realized under fluctuating power supply.•The maximum temperature fluctuation range is reduced from 119.2 K to 31.7 K.•The maximum temperature gradient is reduced by 65 % at 1.5 V operating voltage. Solid oxide electrolyzer cell (SOEC) can efficiently reduce CO2/H2O into CO/H2 using renewable powers. But the fluctuating nature of renewable energy can significantly change the temperature field and cause thermal fatigue even mechanical failure. Herein, we propose a self-adaptive heat management method of SOEC by coupling SOEC with an in-situ thermochemical energy storage (TES) section. Co3O4/CoO redox pair is selected as the TES material for heat management during the exothermic and endothermic operating conditions. 2D dynamic models are developed to study the effects of TES section on the SOEC performances with a special attention on the temperature fluctuation. Results show that the addition of TES section can reduce temperature fluctuation by 73 %, from 119.2 K to 31.7 K. Besides, the maximum temperature gradient and the surface maximum temperature difference at 1.5 V are reduced to 2.62 K/mm and 30 K, respectively, which are 65 % and 82 % lower than those without TES section. An inlet temperature of 1123 K is found to be the best operating condition for the Co3O4/CoO pair in inhibiting the temperature fluctuation of the cell, where the standard deviation is 8.51. This study provides a novel strategy for efficient heat management and safe operation of SOEC under fluctuating working conditions.