Optimal operating strategy and revenue estimates for the arbitrage of a vanadium redox flow battery considering dynamic efficiencies and capacity loss

Abstract

Vanadium redox flow batteries (VRBs) are a promising solution to facilitate the expansion of intermittent renewables. The efficiency of VRBs is dynamically dependent on the instantaneous operating states, including the output power level and state of charge (SOC). In addition, VRB capacity fades over long-term cycling and thus might limit the market revenue. Modelling these two factors would assist deciding better operating strategy, enhance and more precisely evaluate the economics of VRBs. This study establishes an operation optimisation model that integrates the characteristics of the dynamic efficiency performance and the capacity loss of VRBs. First, the dynamic efficiency functions of the operating states are transformed into VRB power functions using a fitting technique to be compatible with the operation optimisation model and reduce the computational complexity. The VRB power functions are then embedded into the operation optimisation model, which decides the optimal charge-discharge schedule of VRBs to maximise the revenue. The capacity loss model is also implemented to estimate the revenue decrease caused by capacity loss, which could help decide the preventive measures and capacity restoration from an economic perspective. The validity of the proposed model is demonstrated by case study results based on the market prices of ERCOT in 2014.