Optimization of the operating point of a vanadium redox flow battery

Modeling a vanadium redox flow battery (VRB) is intrinsically a multiphysics task based on electrochemistry and fluid mechanics. The electrochemical model predicts the stack voltage and determines the internal losses and the vanadium concentrations within the battery whereas the mechanical model determines the power required to flow the electrolyte: this power represents also a system loss. This paper propose a new control strategy that enhance the overall performance of the battery by taking advantage of the knowledge of the VRB operating principles provided by the multiphysics model. The battery is either controlled by a reference current or a reference power; both cases are examined in detail and a method to determine the optimal operating point is proposed. The optimal control strategies are then compared to other strategies through a series of charge and discharge cycles. The energy efficiency is increased by 10%.