The No. 1 and No. 2 are two large

pumped-storage Pumped-storage hydroelectricity (PSH), or pumped hydroelectric energy storage (PHES), is a type of hydroelectric energy storage used by electric power systems for load balancing. The method stores energy in the form of gravitational potential ...

hydroelectric power plants in Yuzawa,

Minamiuonuma is a city located in Niigata Prefecture, Japan. , the city had an estimated population of 55,354 in 20,047 households, and a population density of 96.1 persons per km². The total area of the city was . Geography Minamiuonuma is situated in a ...

Niigata Prefecture is a Prefectures of Japan, prefecture in the Chūbu region of Honshu of Japan. Niigata Prefecture has a population of 2,227,496 (1 July 2019) and is the List of Japanese prefectures by area, fifth-largest prefecture of Japan by geographic area ...

Japan Japan ( ja, 日本, or , and formally , ''Nihonkoku'') is an island country in East Asia. It is situated in the northwest Pacific Ocean, and is bordered on the west by the Sea of Japan, while extending from the Sea of Okhotsk in the north ...

. With a combined installed capacity of , the system is the third largest pumped-storage power station in Japan. The facilities are run by

Electric Power Development Company The , operating under the brand name J-POWER, formerly , is an electric utility in Japan. It mainly produces electricity from coal and hydroelectric power stations. It also has a few wind farms and is currently building a nuclear plant in Ohma ...

(J-Power). Like most pumped-storage facilities, the power station uses two reservoirs, releasing and pumping as the demand rises and falls. Tashiro lake, formed by the

Kassa Dam is a dam in Yuzawa, Niigata Prefecture is a prefecture in the Chūbu region of Honshu of Japan. Niigata Prefecture has a population of 2,227,496 (1 July 2019) and is the fifth-largest prefecture of Japan by geographic area at . Niigata ...

, is the upper artificial reservoir, while

Futai Dam is a dam in Yuzawa, Niigata Prefecture, Japan, completed in 1978. is a dam constructed on the Kiyotsu River, Shinano River System, found in Yuzawa, Niigata Prefecture, Japan. The 87-meter high rock-fill dam forms the lower reservoir of J-P ...

on the Kiyotsu river forms the lower reservoir. Both dams are rockfill type dams, with a height of 90 m and 87 m, respectively. The reservoirs were built between 1972 and 1978. Okukiyotsu No. 1 is the first plant to be built on the site, and employs four 260 MW pump/generator units, for a total net capacity of 1000 MW. The maximum water flow is 260 cubic meters per second. Construction on the plant started in 1972 and it became operational between 1978 and 1982. Okukiyotsu No. 2 is a later addition to the site. The plant is composed of two adjustable speed pump/generator units for a combined power capacity of 600 MW and a maximum water flow of 154 cubic meters per second. Adjustable speed units allow for a rapid variation of power levels during both pumping and generation. These were the highest hydraulic head adjustable speed units in the world. Construction of the second plant started in 1992 and it became operational in 1996. Both plants have an effective head of 470 m. Some of the interior of the second power plant can be visited by the public. The Okky Museum, managed by J-Power, also provides models of the station and explicatory panels and media. File:Futai Dam lake.jpg, Futai Dam lake File:Okukiyotsu power station.jpg, Okukiyotsu power station File:Okky museum.jpg, Okky museum File:Okukiyotsu II power station B1.jpg, Okukiyotsu No. 2 power station interior, part of the Okky museum File:Kassa Dam under construction.jpg, Upper reservoir and Kassa Dam under construction

Notes

{{Dams in Niigata Prefecture Dams in Niigata Prefecture Pumped-storage hydroelectric power stations in Japan Energy infrastructure completed in 1978 Energy infrastructure completed in 1996 1978 establishments in Japan

See also

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