Vanadium: a Transition Metal for Sustainable Energy Storing in Redox Flow Batteries

Energy storage systems (ESS) are devices able to maintain energy over time before it is transformed into useful work. The availability features of energy stored (say, amount, readability, etc.) is always a matter of available technology and available materials: vanadium is now turning to be one of the best element for storing energy. Different systems can be used for this purpose, as a function of the nature of the energy vector, such as water, air, electricity, and fossil fuels. Water reservoirs, compressed air tanks, lead acid batteries, and fuel tanks are a few common examples of potential energy storage systems. The main performances of energy storage are availability in time and space, storage volume, energy concentration, and energy transportability. All these features have dramatically determined the past two centuries, as fossil fuels have won the game because of their ready-to-use and transportability. The present shift toward renewable sources has its main drawbacks in managing their storage. Apart from biomass and hydro power, most of these cannot be stored and/or transported to the place of use: they must first be converted into electricity.