New Mass Transport Correlation for Vanadium Redox-Flow Batteries Based on a Model-Assisted Parameter Estimation

Abstract

In this work, a two-dimensional mathematical model is applied to develop a new mass transport correlation for an SGL GFD4.6A carbon felt applied in a 100 cm2 single cell vanadium redox-flow battery under realistic flow conditions. Already published mass transport equations for carbon felt electrodes show a large variation for the resulting Sherwood numbers and are summarized in this work to narrow the probable range of mass transport parameters. A detailed investigation of electrolyte properties, impedance spectroscopic characterization for evaluation of kinetic properties, and the use of potential probe signals to identify the overpotential of positive and negative electrodes are carried out before mass transport parameter estimation by a comparison of model and experimental data. The model validation yields a good agreement between predicted and experimental data with the following new and reliable mass transport equation: Sh = 0.07 Re 0.66 Sc0.45 (0.0018 < Re < 0.11). The characteristic length applied for the Sherwood and Reynolds number is the diameter of the carbon felt fibers.