Analytical Study, One Dimensional Computational Simulation, and Optimization of an Electrode Supported Solid Oxide Electrolysis Cell

Abstract

A one dimensional mass transfer analysis was performed for convective transport as well as mass transport within a porous media. This analysis was based on the analogous average heat transfer within a duct. Equations were developed to calculate the concentration of gas species at the triple phase boundary sites present at the interface of a porous electrode and a nonporous electrolyte. The mass transport analyzed on the steam side electrode of a solid oxide electrolysis cell was performed for a ternary gas mixture. In this analysis two gas species were actively diffusing in the presence of a third inert carrier gas. Multicomponent diffusion coefficients were determined for each species in the steam side electrode mixture. The mass transport analysis performed on the air side electrode utilized a binary gas mixture, namely air. At less than one percent of the total mixture of air, the combined effects of Argon and Carbon Dioxide were assumed to be negligible. This assumption allowed us to consider air a binary mixture. A comprehensive model was developed to determine cell performance under various operating condition and multiple cell geometries. The output of this model was used to optimize various physical features of the cell. Tests were performed on electrode supported solid oxide electrolysis cells at the Idaho National Laboratory. These cells were subjected to various operating temperatures and inlet steam mole fractions. Voltage vs. current density experimental data were collected and compared to computational data in order to validate the model.