Grid energy storage

Grid energy storage (also called large-scale energy storage) is a collection of methods used to store electrical energy on a large scale within an electrical power grid. Electrical energy is stored during times when production (especially from intermittent power plants such as renewable electricity sources such as wind power, tidal power, solar power) exceeds consumption, and returned to the grid when production falls below consumption. As of 2017, the largest form of grid energy storage is dammed hydroelectricity, with both conventional hydroelectric generation as well as pumped storage hydroelectricity. Alternatives include rail energy storage, where rail cars carrying large weights are moved up or down a section of inclined rail track, storing or releasing energy as a result; or disused oil-well potential energy storage, where weights are raised or lowered in a deep, decommissioned oil well.