Pumped Hydro
Pumped storage is method of storing electrical energy as potential energy by pumping water from a reservoir or lake to another reservoir at a higher elevation and storing it for use in generating electricity when required. Base-load power is used to pump water at off-peak times, which is then released through turbines to provide electrical power at times of peak demand. The plants are very flexible and can be used to allow a greater integration of intermittent energy sources, eg., wind, into the grid system. They also provides other important services to the grid operator which help balance the transmission system.
Turlough Hill pumped storage plant in Wicklow was built in 1974 by the ESB. The concept is widely used throughout the world and has proven to be very successful for peak shaving and the provision of a range of additional ancillary services.
As with all hydro schemes, pumped storage systems can respond very rapidly to surges in demand. The Dinorwig PHES in Wales can achieve its full output of 1,800MW in 16 seconds.