System-level analysis of switching strategies in reversible solid oxide cells under controlled thermal gradients

Thermal dynamics of reversible Solid Oxide Cells (rSOC) raise concerns about materials integrity when dealing with rapid power fluctuations. Previous studies investigating rSOC dynamics limited their scope to the cell or stack, overlooking system-level behavior. This work integrates a 1D dynamic rSOC cell model with a system model in Aspen Dynamics, including balance of plant (BoP) and control loops. The integrated models allow a joint analysis of cell's temperature gradients, switch duration, and BoP consumption. Results show that a complete switch duration ranging from 44 to 138 min can be achieved, while respecting temporal gradients constraint of 5 to 1 K/min. A variable air flow lowers BoP energy consumption by 31-33%, but requires a longer transition (+30-37%). Two case studies – sudden electrolysis-to-fuel cell switch and night-to-day transition – are then analyzed, suggesting that auxiliary power supply is essential to sustain BoP operation during switch while respecting safe thermal gradients.