Ffestiniog Power Station
| Ffestiniog Power Station | |
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The upper reservoir, Llyn Stwlan, and dam.
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 Location of Ffestiniog Power Station in Wales
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| Country | Wales |
| Location | Ffestiniog, Gwynedd |
| Coordinates | 52°58′51″N 03°58′08″W / 52.98083°N 3.96889°WCoordinates: 52°58′51″N 03°58′08″W / 52.98083°N 3.96889°W |
| Commission date | 1963 |
| Owner(s) | First Hydro |
| Pumped-storage power station | |
| Upper reservoir | Llyn Stwlan |
| Lower reservoir | Tanygrisiau Reservoir |
| Pump-generators | 4 |
| Power generation | |
| Nameplate capacity | 360 MW (480,000 hp) |
The Ffestiniog Power Station is a 360-megawatt (480,000 hp) pumped-storage hydroelectricity scheme near Ffestiniog, in Gwynedd, north-west Wales, United Kingdom. The power station at the lower reservoir has four water turbines, which can generate 360 megawatts of electricity within 60 seconds of the need arising. The station, commissioned in 1963, was the first major pumped storage system in the UK. The upper reservoir is Llyn Stwlan which discharges 27 cubic metres per second (950 cu ft/s) of water to the turbine generators at the power station on the bank of Tan-y-Grisiau reservoir. The building of the lower reservoir flooded the route of the Ffestiniog Railway which had to build a deviation around the reservoir and power station.
The plant is operated by First Hydro, a UK company owned by a joint venture of International Power and Mitsui & Co., and has an average efficiency of 72–73% i.e. it uses 39% more electricity (when pumping the water back up to the Llyn Stwlan) than it actually produces.
The idea of using pumped storage as a way of coping with rapid, short-term changes in the demand for electricity in England and Wales was first considered in 1948, and having found a suitable site, the Ffestiniog station was authorised by Act of Parliament, specifically the North Wales Hydro Electric Power Act 1955. The first task facing engineers was to provide access roads to the sites, and work on constructing these started in 1957. This enabled work to commence on the two dams and the power station shortly afterwards. A pumped storage scheme requires two reservoirs at different levels, and the upper reservoir was created by enlarging Llyn Stwlan, high up on Moelwyn Mawr. Llyn Stwlan was located in a cirque basin, formed by glacial erosion.
The lake had previously been enlarged in 1898 by the Yale Electricity Company, who built a dam and used the water to generate power at Dolwen, located near Tanygrisiau, below the lower reservoir. The company was formed by the Votty Quarry company, and direct current was transmitted by overhead line to Dolgarregddu, near the centre of Blaenau Ffestiniog, where there was a 100 hp (75 kW) gas engine and two semi-diesel engines, which generated an additional 240 kW. This was used to supply power to the town when it was not required by the quarry. Because of the voltage drop in the system, a final 48 kW booster set was needed at the quarry. The Dolwen station continued to operate after the new scheme was finished, although it was subsequently decommissioned and the building was converted into two semi-detached houses, and then an 8-bedroom detached house.
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Wikipedia