Redox-flow batteries for high energy-to-power ratio storage: a preliminary experimental study

In conjunction with the worldwide interest in the safeguard of the environment, the possibility of storing electricity to allow larger renewable energy source penetration is increasingly getting ground. In this framework, among all the potential stationary energy storage systems, Redox Flow Batteries (RFBs) appear as one of the most promising solutions. This is because of their several advantages, such as the unique capability to decouple energy content from power, which makes them well adaptable at different network services and installation locations. This paper aims to display the RFBs scenario inside the global stationary storage situation. The principle of operation of these batteries is illustrated and the current landscape described. Some preliminary experimental results of an existing commercial solution of a vanadium RFB (VRFB) are presented, highlighting strengths and weaknesses points of this category. Charge and discharge experimental tests under realistic grid-interconnection scenario are performed, measuring the VRFB under study global efficiency, by an estimation of its internal losses: shunt currents, self-discharge rate and auxiliary system power consumption. Considering all these losses, the results display an overall VRFB efficiency around 50%, against the typical values taken from literature, that range between 70% to 90%.