Investigating electric heater failure scenarios in solid oxide electrolysis cell systems with a novel three-dimensional dynamic SOEC stack model

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Green hydrogen, produced from electrolysis systems powered by zero-emissions renewable energy sources, has the potential to significantly contribute to a sustainable energy future. Performing electrolysis at high temperatures using solid oxide electrolysis cells (SOECs) offers advantages compared to low temperature electrolysis because of significantly higher electrical efficiency, co-electrolysis, and heat integration features. Since the early 2000s, significant efforts have been made to develop SOEC models to investigate the performance characteristics under various operating conditions. This study presents a novel 3-dimensional dynamic SOEC stack model to evaluate system dynamics and control during heater failure scenarios. The study demonstrates that with the implemented control strategies, the changes in the stack temperature gradient are negligible under inlet steam heater failure since the stack heaters are positioned on the same side as the steam entering the stack. On the other hand, when the inlet air heater fails, the temperature gradient increases from 13 °C to 36 °C because the air inlet heater is located on the opposite side of the stack heaters. To overcome stack heater failure scenarios, two potential strategies are investigated: 1) increasing the inlet air temperature and 2) manipulating operating current. Both control strategies are effective. Increasing inlet air temperature does not impact the system efficiency, but increasing the operating current requires an additional 0.67 kWh per kg of H2 produced.