Vanadium Redox Flow batteries (VRB) store electricity through a reversible chemical reaction. In contrast to conventional batteries, chemical energy is stored in external electrolyte tanks (Chen et al., 2009). The active material (i.e. an aqueous liquid electrolyte) is pumped from the tanks into the AC/DC converter where either chemical energy is converted to electrical energy (discharge) or electrical energy is converted to chemical energy (charge).
Installations range between 50 kW and 1 MW, with commercial units typically between 5 and 250 kW. VRB are well suited for multiple applications (JRC, 2014). This factsheet focuses on large VRB batteries (utility or distributed systems) for bulk electricity storage, capable of supplying power for longer periods (discharge times of >1h).