Modeling of single- and double-sided high-pressure operation of solid oxide electrolysis stacks

Abstract

This study concerns numerical investigation of a solid oxide electrolysis stack, in which the cells are pressurized on only the fuel side (single-sided mode) or both fuel and air sides (double-sided mode). A 90-cell stack model is used to study the effects of the operating pressure on the polarization curves, area-specific-resistance (ASR), temperature, and pressure. The model predicts higher open-circuit voltage (OCV), lower ASR, and lower pressure drops over the flow fields at higher operating pressures. The latter leads to flexibility in the flow field design. The results show that the single-sided mode hinders the OCV increase and reduces the ASR. Nonetheless, the ASR reduction under the double-sided mode is more significant than the single-sided mode. Therefore, the double-sided mode performs better at high current densities since its higher ASR reduction provides a lower increase in the stack voltage (/input power). Moreover, the results indicate a nonlinear relationship between the temperature distribution and the operating pressure under the double-sided mode due to its counteracting effects on the ohmic heat sources and reaction heat sink. It is illustrated that the temperature difference over the stack decreases under the double-sided mode at higher operating pressures and lower current densities.

Topics & Concepts