Underground power station

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Inside the Robert-Bourassa generating station, in northern Quebec, the largest underground power station in the world with an installed capacity of 5,616 MW.

An underground power station is a type of hydroelectric power station constructed by excavating the major components (e.g. machine hall, penstocks, and tailrace) from rock, rather than the more common surface-based construction methods.

Often underground power stations form part of pumped storage hydroelectricity schemes, whose basic function is to level load: they use cheap or surplus off-peak power to pump water from a lower lake to an upper lake, then, during peak periods (when electricity prices are often high), the power station generates power from the water held in the upper lake.

Notable examples[edit]

Some notable underground power stations are:

  • Chaira Hydroelectric power plant, Bulgaria, is the largest underground power station in the Balkans, built in 1980-1998. It generates 864 MW from 4 Toshiba turbines with a net rated head of 2,300 feet (701 m), and maximal speed of 600 rpm.
  • Churchill Falls Power Station, Newfoundland and Labrador, Canada is the second largest underground power station in the world. It generates 5,428 MW from 11 turbines. The powerhouse is 761 feet (232 m) long, 148 feet (45 m) high, 62 feet (19 m) wide and located 1,080 feet (330 m) underground. The two tailrace tunnels are 1691.64 m long. The net head is 312.42 m.
  • Edward Hyatt Power Plant inside the Oroville Dam, United States, is in a cavern carved into the bedrock of the Feather River canyon. It houses 3 Generator and 3 Pump/Generator units and their respective Transformers 650 feet (200 m) below the crest of the dam.
  • Goldisthal Pumped Storage Station, in Thuringia, Germany, built in 1991-2004, generates 1,060 MW from 4 turbines. It is unique (for its scale) in Europe, in that two of the four motor generators are designed as variable speed asynchronous machines. The machine hall is 482 feet (147 m) long, 161 feet (49 m)high, 52 feet (16 m) wide, with a separate transformer cavern (390 feet (120 m) long, 49 feet (15 m)high, 52 feet (16 m) wide).
  • Kannagawa Hydropower Plant is under construction in Japan. When completed, it will be the world's largest pumped storage plant, generating 2,700 MW. The power house is 709 feet (216 m) long, 108 feet (33 m) wide, 171 feet (52 m) high. The effective head is 2,343 feet (714 m) The first unit commenced operations in 2005, the second in 2012.
  • Kazunogawa Power Plant is a 1,600 MW underground pumped storage plant in Japan. Kazunogawa consists of four 400 MW generation units. The cavern for the underground power station is 1,600 feet (500 m) below the surface. It is 690 feet (210 m) long by 177 feet (54 m) high and 112 feet (34 m) wide. The head is 2,343 feet (714 m).
  • Manapouri Power Station, Fiordland, New Zealand, built 1963-1972, generates 850 MW from 7 turbines. It is built 660 feet (200 m) underground, and has two 10 km tailrace tunnels. The net head is 560 feet (170 m). The most notable feature of this station is that the lake and power station are located on the eastern side of the Southern Alps, with the tailrace tunnels traveling under a major mountain range, discharging in Doubtful Sound on the west coast.
  • IV. stage of Turček water main complex, built in 1917-1921, was first power station in Europe of its type. Generating station is housed in Main hereditary adit (also called Ferdinand hereditary adit). Water is brought through mineshaft above power plant in 2 ø 70 cm steel pipes. Power plant has 245m head and it has 3 Pelton trubines (built 1920) with 2,02 MW installed capacity. Energy is provided to nearby Kremnica town. In 1937 Turček cascade has undergone renconstruction and IV. stage power plant is still in use today with many of its original parts.