Electricity has been traditionally produced and consumed at the same time because the available systems to store energy were not practical, expensive and bulky in most applications except emergency systems. The appearance of new battery technologies and the optimization of existing technologies as fuel cells and flywheel systems is changing this paradigm. Electrical Energy can be now stored cost-effectively and this will have a strong impact in the electrical system (smoothing the intermittency of renewable energies, storing excess of production, shifting peaks of consumption, increasing the efficiency, etc…) and in transportation (cars, trucks, buses, aircraft, ships, etc…).

ESS are normally three-way systems connected to (1) an electrical grid, which can be used to import and export energy, to (2) a storage system in DC and to (3) loads or a microgrid that can combine loads with generation.