Pumped storage hydroelectric power ––– Dinorwig Power Station, North Wales Dinorwig Power Station, located adjacent to the Snowdonia National Park in Gwynedd, North Wales, is Europe’s largest pumped storage hydroelectric power station. It is also one of the fastest, most dynamic power plants in the world, capable of delivering its full station output of 1800 MW in only 16 seconds. This rapid response is strategically important to the GB electricity system in helping National Grid maintain the balance of supply and demand on a second-by- second basis across the network. The An overhead view of Dinorwig’s lower reservoir, system enables 9100 MWh of energy to be Llyn Peris. stored when the electric demand is low, providing about 5hours of full-load extra production capability for peak demand hours. The power station complex was built deep underground, inside the Elidir Mountain, and beneath the old Dinorwig slate quarry. It sits between an upper reservoir at the top of the mountain, and a lower reservoir, 530m below in the valley. Water falling from the upper reservoir is used to drive One of the six massive reversible generators turbo-generators that supply power to the grid. Up to 60 cubic m/s of water are discharged into the lower reservoir. During off-peak periods, water is pumped back into the upper reservoir for future use. The station's six powerful generating units - reversible pump/turbines - stand in Europe's largest man-made cavern. Using off-peak electricity the six 288 MW units are reversed as pumps to transport water from the lower reservoir, back to the upper reservoir in Marchlyn Mawr. Dinorwig is comprised of 16km of underground tunnels, deep below Elidir mountain. Its construction required 1 million tonnes of concrete, 200,000 tonnes of cement and 4,500 tonnes of steel. When it was fully commissioned in 1984, Dinorwig Power Station was regarded as one of the world's most imaginative engineering and environmental project. It took nearly 10 years to plan and construct. Today, Dinorwig's A view of the penstock operational characteristics and dynamic response capability are still acknowledged the world over. Dinorwig is the largest scheme of its kind in Europe. It is now owned by a joint venture of International Power plc (part of the GDF Suez group) and Mitsui & Co., Ltd. This joint venture also owns a second, smaller pumped storage station at Ffestiniog, some 30 miles from Dinorwig. Source : GDF SUEZ / First Hydro Company http://www.fhc.co.uk/dinorwig.htm .