Dynamic Behavior of an SOEC System With a Schedule-Based Start-Up and Operating Process

Abstract

The solid oxide electrolysis cell (SOEC) is recognized as a promising method for hydrogen production, attributed to its high efficiency. Steam is split into hydrogen and oxygen by electrolysis at high temperatures. Electrolysis is inherently an endothermic process; however, it can be transformed into an exothermic process depending on the operating voltage. During the start-up process, the heat reaction is observed to change from endothermic to exothermic around a thermoneutral voltage. In this study, a dynamic model of the solid oxide electrolyzer system was developed, and the behavior of the system during the start-up process was analyzed. A dynamic model of the stack was developed to investigate the behavior of cell temperature and current density. Furthermore, 1D models of heat exchangers and 0D models of blowers were developed and verified against experimental results. These components were systematically organized and simulated. The temperatures of the stack and components during a schedule-based start-up process were investigated. Additionally, the behavior during the load change process, shifting from an endothermic reaction to an exothermic reaction, was examined. It was found that to reach an operating condition above the thermoneutral voltage, additional heat is required for the stack due to its endothermic reaction. The effect of air on the stack was also found to be dependent on the operating voltage of the stack.