PEM Electrolysis Simulation and Validation

Abstract

To meet the ever-growing demand for polymer electrolyte membrane (PEM) electrolyzers to operate at higher current densities, higher pressures and higher temperatures, a zero dimensional simulation was developed to optimize operating conditions and cell geometries. The model presented was focused on capturing the performance of an electrolyzer operating at higher current densities ranging from 2-6 A/cm 2 . This entails focusing more on the mass transport and ohmic losses (both proton and electron transport) that dominate under these conditions. Removing a gas from the catalyst layer can be much easier than removing a liquid due to the lower densities and higher diffusivities, thus reducing the onset of mass transport losses. This is what allows the PEM electrolyzer to operate at high current densities when compared to PEM fuel cells, however, it prompts changes in how the mass transport losses should be accounted for. A design tool was developed to optimize operational and geometrical parameters of a PEM electrolyzer. Models with a strong focus on ohmic losses and prediction of membrane proton transport were combined to improve the prediction of the ohmic losses. These are particularly important when operating at high current densities due to the linear dependence ohmic losses have with current density. This model is then validated under various operating conditions. A separator plate/flow field design optimization was performed and conducted with the goal of maximizing the conductive contact areas.