Energy storage devices are “charged” when they absorb energy, either directly from renewable generation devices or indirectly from the electricity grid. They “discharge” when they deliver the stored energy back into the grid. Charge and discharge normally require power conversion devices, to transform electrical energy (AC or DC) into a different form of chemical, electrochemical, electrical, mechanical, and thermal.
Energy storage can store surplus energy from intermittent renewable sources, such as solar PV and wind power, until it is required – allowing therefore for the integration of additional renewable energy into the system.
Different energy storage systems – centralised and decentralised – consider different technological possibilities, which EASE organises in 5 energy storage classes: chemical, electrochemical, electrical, mechanical and thermal.