Numerical and Experimental Study of the Flow-by Cell for Vanadium Redox Batteries

A mathematical model for vanadium redox batteries (VRBs) is considered. The model has been tuned using experimental data obtained for a single cell with flow-by design. Mass transfer limitations have been determined from experimental data, and a new correlation for mass transfer constant is proposed. Self-discharge of the battery resulting from crossover of vanadium ions through membrane is taken into account by the model as well. It is shown that Fick’s law for diffusion describes crossover rather well. The crossover has a large impact on the battery voltage during discharge, but can be neglected during charge due to mutual compensation of diffusion and migration fluxes. Good agreement (with average error less than 7 %) between the experimental and modelled polarization and charge-discharge curves is observed in the whole current density region.