| Imaichi Pumped Storage Power Station | |
| Coordinates: | 36.8319°N 139.6678°W |
| Country: | Japan |
| Location: | Nikkō, Tochigi Prefecture |
| Status: | O |
| Construction Began: | 1979 |
| Opening: | 1988[1] |
| Operator: | TEPCO |
| Res Name: | Kuriyama |
| Lower Res Name: | Imaichi |
| Plant Pumpgenerators: | 3 x 350 MW reversible Francis turbines[2] |
| Plant Hydraulic Head: | 524m (1,719feet) |
| Plant Capacity: | 1050MW |
| Plant Storage Hours: | 7,350 MW·h |
The is a large pumped-storage hydroelectric power station in Tochigi Prefecture, Japan. With a total installed capacity of, it is one of the largest pumped-storage power stations in Japan.[3] The facility is run by the Tokyo Electric Power Company (TEPCO).[3] The power plant started operation in July 1988 with a capacity of 350 MW (one unit operational). The other two units entered operation in December 1991.[4] The plant is one of the many large scale pure pumped-storage plants built in Japan since the 1970s to compensate for the increased penetration of base-load nuclear power and peak load from cooling and air-conditioning.[5]
Like most pumped-storage facilities, the power station uses two reservoirs, releasing and pumping as the demand rises and falls. The upper reservoir is contained by the Imaichi Dam, a concrete gravity dam, at an altitude of 512 m. The reservoir is fed by the Togawa river.[4] The lower reservoir is contained by the Kuriyama Dam, a rock-fill embankment dam at an altitude of 1054 m.[4] The reservoirs can store 9100000m2 of water. Of that storage volume, 6200000m2 can be used for power generation.This is enough for about 7 hours of operation at full generation capacity,[1] giving a total energy storage capacity of about 7.35 GWh.
The power plant is housed in a large cavern 400 m underground and includes three 350 MW Francis reversible pump-turbines.The cavern dimensions are 33.5 m width, 51 m height, and 160 m length.[6] The power station work on a daily or weekly storage cycle.[4] The plant is connected to the high voltage transmission system with a 500 kV power line. These power lines constituted the world's first practical applications of 500 kV XLPE (cross-linked polyethylene) cables, together with the power connection at the Shimogo Pumped Storage Power Station.[7]