Energy Storage

Technologies built specifically to hold energy for later release rather than to convert a primary source into usable power at the moment of generation, including compressed-air energy storage, flywheel energy storage, the lithium-ion battery and pumped storage hydropower. Belongs here: any technology whose primary function is storing energy across time, whatever the storage medium, mechanical, electrochemical or gravitational. Does not belong here: the hydropower turbines that generate electricity from a natural head of water, grouped under Hydropower Turbine, distinct from pumped storage use of hydropower machinery to store rather than merely generate.