Flow battery storage is a type of energy storage power station that uses a group of batteries to store electrical energy. In rechargeable flow batteries, the liquid electrodes are composed of transition metals in water at room temperature. Charging and discharging of batteries occur by ion transferring from one component to another component through the membrane. The biggest advantages of flow batteries are the capability of pack in large volumes. Interest in flow batteries has increased considerably with increasing storage needs of renewable energy sources. They can be used as a rapid-response storage medium. Vanadium redox batteries are a type of flow battery. However, the biggest issue to use flow batteries is the high cost of the materials used in them, such as vanadium.
Flow batteries have relatively low energy densities and have long life cycles, which makes them well-suited for supplying continuous power. A 200 MW (800 MWh) flow battery is currently being constructed in Dalian, China. Battery storage is the fastest responding dispatchable source of power on grids, and it is used to stabilise grids, as battery storage can transition from standby to full power within milliseconds to deal with grid failures. At full rated power, battery storage power stations are generally designed to output for up to a few hours. Battery systems connected to large solid-state converters have been used to stabilize power distribution networks. Some grid batteries are co-located with renewable energy plants, either to smooth the power supplied by the intermittent wind or solar output, or to shift the power output into other hours of the day when the renewable plant cannot produce power directly. Battery storage technology is typically around 80% to more than 90% efficient for newer lithium-ion devices. Battery systems connected to large solid-state converters have been used to stabilize power distribution networks.