Mathematical Modeling of a Proton-Conducting Solid Oxide Electrolyzer Cell Using Computational Fluid Dynamics Simulation

Abstract

The proton-conducting solid oxide electrolyzer cell (H-SOEC) is a novel electrolysis technology, which operates in the intermediate temperature range (500-700°C), as opposed to the high temperature (800-1000°C) operating range of oxygen ion conducting solid oxide electrolysis cells (O-SOECs), or the low temperature (70-80°C) operating range of proton-exchange membrane (PEM) electrolyzers [1]. Proton-conducting electrolyte has high ionic conductivity in this intermediate temperature range, which is not exhibited in O-SOECs; this means that there are fewer material challenges for the development of these devices because they do not need to withstand temperatures up to 1000°C [1,2]. Additionally, this temperature ranges yields the benefits of improved thermodynamics at increased temperature, meaning they require less electrical energy input as compared to PEM electrolyzers [1]. H-SOECs are a promising technology because they retain the thermodynamic benefits of operation at high temperature, without the material complications seen in O-SOECs. The purpose of this work is to model the 2D current density distribution of an H-SOEC at a applied electrolysis voltage. The model considers overpotential losses that occur due to kinetics of the electrochemical reaction, resistance in the cell components, and mass transport. The mathematical model uses electrochemical parameters fit with experimental data from [3] and is incorporated into the solving routine of computational fluid dynamics (CFD) software, Fluent. Figure 1 shows an example of the current density distribution in a planar H-SOEC cell that was obtained from the model simulation. Such parametric distribution is difficult to be measured, and the outcomes of this work would help the experimental development of this novel electrolyzer technology through optimization of operating conditions like temperature and gas feed compositions. The modeling approach also helps understand the thermal-flow management needs of this device as it is scaled up to the stack level. It will also provide a baseline understanding for more complex models that consider the internal transport phenomena in 3D, as only limited modeling papers on H-SOEC are available now.