Study of the effect of flow frames on the performance of a 10 kW/40 kWh vanadium redox flow battery using a multi-scale model

The cell structure in vanadium redox flow batteries (VRFBs) critically impacts battery efficiency. Therefore, in this study, we evaluate the effect of different flow frames on VRFB cell performance and system efficiency. This is accomplished through a multi-scale model combining a 3D model of the cell and an equivalent circuit model (ECM) of the stack. The results reveal that during the discharge process, increasing the flow rate can boost the discharge voltage, but also leads to higher pumping power consumption. Moreover, the pressure drop of the cell decreases as the number of flow frame channels increases. Due to improved reactant concentration distribution, the five-channel flow frame has a higher discharge voltage than other configurations at low reactant concentrations, even exceeding that of the 20-channel flow frame. The flow frame and flow rate were optimized for a 10 kW/40 kWh VRFB with a genetic algorithm approach. Using a five-channel flow frame, a peak discharge efficiency of 93.70% was obtained at a flow rate of 960 mL/min. The results of this study may aid future design of kilowatt-scale VRFBs.