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 2016 by far the largest form of grid energy storage on grids is dammed hydroelectricity, with both conventional hydroelectric generation as well as pumped storage.

An alternative to grid storage is the use of peaking power plants to fill in.

The stores are used - feeding power to the grids - at times when consumption that cannot be deferred or delayed exceeds production. In this way, electricity production need not be drastically scaled up and down to meet momentary consumption – instead, transmission from the combination of generators plus storage facilities is maintained at a more constant level.

An alternate and complementary approach to achieve the same effect as grid energy storage is to use a smart grid communication infrastructure to enable Demand response (DR). Both of these technologies shift energy usage and transmission of power on the grid from one time (when it's not useful) to another (when it's desperately immediately needed).

Any electrical power grid must adapt energy production to energy consumption, both of which vary drastically over time. Any combination of energy storage and demand response has these advantages:

Energy derived from photovoltaic, tidal and wind sources inherently varies  – the amount of electrical energy produced varies with time of day, moon phase, season, and random factors such as the weather. Thus, renewables present special challenges to electric utilities. While hooking up many separate wind sources can reduce the overall variability, solar is reliably not available at night, except when stored in molten salt, and tidal power shifts with the moon, so it is never reliably available on peak demand.

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