Simulation of a vanadium-cerium redox flow battery incorporating graphite felt electrodes

Abstract

• The reaction environment in a V-Ce redox flow battery is described by a 3D simulation. • Mass transport is calculated from known hydrodynamics in ‘flow-by’ porous electrodes. • Navier-Stokes and Brinkman models are coupled to consider two flow zones. • Mass transport is linked to electrochemical reaction rates and electrolyte potential. • The 3D simulation could predict experimental cell potential and state of charge. Computational fluid dynamics (CFD) simulations are used to predict the electrolyte dispersion, mass transport, current–potential distributions and state of charge in a vanadium-cerium redox flow battery (RFB) containing graphite felt electrodes, the half-cell flow compartments being separated by an anion exchange membrane. A polymeric mesh was placed between graphite felt and membrane; the anolyte and catholyte were pumped to separate stirred tanks in the batch recirculation mode. The simulation of single-phase flow was performed using the Brinkman and Navier-Stokes equations to describe flow dispersion within the graphite felt and polymeric mesh, respectively. At the same time, mass transport and current distribution were computed by solving mass and charge conservation equations. Fluid dynamics revealed a periodic velocity distribution within the porous electrode, which was influenced by the polymer mesh between electrode and membrane. A mean fractional conversion of 0.005 per pass was achieved. During a galvanostatic cycle, the state of charge fell from 36 to 10% over a 70 min discharge then rose from 10 to 30% during charge. A relatively uniform potential distribution was achieved along the length of the graphite felt in the presence of the low conversion per pass. The numerical model demonstrated a good agreement between the predicted and experimental cell potential and state of charge, with an average deviation below 0.12%. The unit cell RFB performance showed voltage, coulombic, and energy efficiencies of 85, 83, and 70%, respectively. A numerical model of the vanadium-cerium RFB served as the first approach to a more robust experimental study.