Control-Oriented Model of a Vanadium Redox Flow Battery With Crossover Effects

The vanadium redox flow battery (VRFB) is an attractive grid scale energy storage option, but high operating cost impedes widespread commercialization. One way of mitigating cost is to optimize system performance, which requires an accurate model capable of predicting cell voltage under different operating conditions such as current, temperature, flow rate, and state of charge. This paper presents an isothermal VRFB model based on principles of mass transfer and electrochemical kinetics that can predict transient performance with respect to the aforementioned operating conditions. The model captures two important physical phenomena that occur at significantly different time scales as a result of vanadium crossover: (1) rapid self discharge reactions and (2) capacity loss after long term cycling. A gap metric analysis showed that a linear controller for the flow rate may be suitable near the 50% SOC range.