| Okuyahagi Pumped Storage Power Station | |
| Coordinates: | 35.2322°N 137.4286°W |
| Country: | Japan |
| Location: | Toyota, Aichi Prefecture Ena, Gifu Prefecture |
| Status: | O |
| Operator: | Chubu Electric Power Company |
| Res Capacity Total: | 9900000m2 (Kuroda Dam lake, effective) |
| Lower Res Name: | 80000000m2 (Yahagi Dam reservoir) |
| Plant Pumpgenerators: | 3 x 116 MW reversible Francis turbines (Okuyahagi 1) 3 x 260 MW reversible Francis turbines (Okuyahagi 2) 2 x 31 MW Francis turbines (Yahagi 1) 1 x 32 MW Francis turbine (Yahagi 2) |
| Plant Hydraulic Head: | Okuyahagi 1: 161m (528feet) Okuyahagi 2: 404m (1,325feet) |
| Plant Capacity: | 1160MW |
The is a group of large pumped-storage hydroelectric power plants and smaller conventional plants located in Toyota, Aichi Prefecture, and Ena, Gifu Prefecture, Japan. With a combined installed capacity of, it is among the largest pumped-storage power stations in Japan.
The facilities are run by the Chubu Electric Power Company.The station includes 4 distinct power plants. The first two power plants, Yahagi 1 and 2 are conventional power plants.[1] [2] The other two plants, Okuyahagi 1 and 2 are pumped-storage plants. Yahagi 1 uses water from the Yahagi Dam (矢作ダム)[3] and has a capacity of 60 MW. Yahagi 2 uses water from the Second Yahagi Dam (矢作第二ダム),[4] a smaller dam downstream of the main one, and has a capacity of 31.2 MW.
The pumped-storage station has an unconventional configuration, with three reservoirs at different heights.[5] The lower reservoir is created by Yahagi Dam on the Yahagi river. The upper reservoir is the Kuroda Dam lake, an artificial lake created by the Kuroda Dam. A third reservoir, in between the two at an intermediate elevation is formed by the Tominaga Dam. The two Okuyahagi power stations work in tandem between the three reservoirs.[6] [7] This configuration was necessary because of the geological conditions in the area, with a fault that prevented the safe construction of a single connection between upper and lower reservoirs.Okuyahagi 1 is the upper power plant, operating between the upper and the intermediate reservoir using 3 units with a combined capacity of 323 MW.[8] The first unit started operation in September 1980, while the second and third units became operational in February 1981.The Okuyahagi 2 is the lower power plant operating between the intermediate reservoir and the lower reservoir employing 3 units with a combined capacity of 780 MW. Okuyahagi 2 became operational together with the first plant, with the first unit online in September 1980 and the other 2 in February 1981. The two plants operate as a single power station. Both station have a maximum water flow rate of 234 cubic meter per second.