Degradation modeling in solid oxide electrolysis systems: A comparative analysis of operation modes

To fully realize the potential of solid oxide electrolysis (SOE) systems, improvements in long-term durability and scalability are required. Investigating and comparing different degradation mechanisms under different conditions is crucial. A multi-scale cell to system level time-dependent simulation framework for SOE systems including various degradation phenomena is presented. Galvanostatic, Potentiostatic, and Potentio-Galvanostatic operation, a combination of the two previous modes, are investigated. The time and space evolution of various performance and degradation parameters are compared. Potentio-Galvanostatic operation consistently maintains stable efficiency throughout its lifetime. Near thermoneutral condition is maintained in Potentiostatic and Potentio-Galvanostatic operations, while degradation eventually leads to exothermic operation in Galvanostatic mode. Cathode overpotential is higher in Galvanostatic operation, while in Potentio-Galvanostatic operation, it drops over time as the temperature increases. After 25,000 h of operation under specified conditions, the area-specific resistance (ASR) experiences a 51% and 62% increase in Galvanostatic and Potentiostatic operations, respectively, while Potentio-Galvanostatic operation results in only a 4% increase compared to the beginning of life. Interconnect oxidation is most pronounced in Potentio-Galvanostatic mode, highlighting the need for high-quality steels and coatings in this operation strategy. Over time, in Galvanostatic operation, the current density shifts from being highest at the inlet towards the outlet.