Modeling and analysis of cross-flow solid oxide electrolysis cell with oxygen electrode/electrolyte interface oxygen pressure characteristics for hydrogen production

Abstract

Correctly estimating the spatial distribution of thermal, electrical and gas characteristics in solid oxide electrolysis cells (SOEC) improves its safety and operating life. This study proposes a 2-D cross-flow stack model with new gas characteristics of oxygen electrode/electrolyte interface oxygen pressure related to delamination of the oxygen electrode. It is validated by experimentally measured thermoelectric characteristics. The advantage of adding the new gas characteristics is discussed regarding to certain operating conditions. The analysis demonstrates that it can optimize the operating envelope in which the stack is not exposed to unsafe conditions, which lead to accelerated degradation. Furthermore, the sensitivities of the oxygen electrode/electrolyte interface oxygen pressure spatial distributions to the key operating variables are investigated, namely current density, sweep gas flow ratio, fuel utilization and the operating pressure. Increasing sweep gas flow ratio ranging from 1.0 to 14.0, fuel utilization and operating pressure decreases the oxygen electrode/electrolyte interface oxygen pressure and increases its uniformity. However, increasing the sweep gas flow ratio in the range of 0.4–1.0 increases the oxygen electrode/electrolyte interface oxygen pressure and decreases its uniformity. Increasing sweep gas flow ratio, fuel utilization and operating pressure greatly affects the position of its maximum value.