One Dimensional Mathematical Modelling of the All-Vanadium and Vanadium/Oxygen Redox Flow Batteries

Abstract

The one-dimensional (1-D) model for both the all-vanadium redox flow battery (VRFB) and the vanadium/oxygen redox fuel cell (VORFC) incorporates species conservation equations along with an advection term to describe the concentration changes in the porous electrodes. Also, a complete Nernst equation, which accounts for proton concentrations in both systems, is included to improve the cell voltage prediction without using any arbitrary fitting contact voltage. The model is also coupled with the electrochemical reaction kinetics of the vanadium species and the gaseous oxygen (VORFC). Some results predicted by the model are validated against experimental data from the literature successfully such as charging and polarization characteristics. All the predicted trends as well as the cell voltages are consistent with those from higher-dimensional models, which indicate that both the surface overpotentials and transfer current densities vary primarily in the cross-flow (x-) direction.