Yangyang Pumped Storage Power Station

The Yangyang Pumped Storage Power Station uses the water of the Namdae-Chun River to operate a 1000 MW pumped storage hydroelectric power scheme, about 10 km west of Yangyang in Gangwon Province, South Korea. The lower reservoir is created by the Yangyang Dam on the Namdae and the upper reservoir by the Inje Dam is located 937 m above the power plant. Construction on the power plant began in 1996 and it was completed and dedicated on September 13, 2006. It is operated by Korean Midland Power Co., a subsidiary of Korea Electric Power Company and was completed at a cost of ₩1.1 trillion won (US$1.4 billion). The first generator was operational on February 23, 2006 and the last August 10, 2006.

Design and operation
The operation of the power plant begins on the Namdae-Chun River where it is dammed by the Yangsang (Sangbu) Dam at 38.02083°N, 128.55417°W, creating the lower reservoir. This dam is 61.5 m tall and 275 m long concrete gravity dam. Water from a 124.9 km2 catchment area collects into the lower reservoir which has a 19982000 m3 capacity, of which 4200000 m3 is active (or "useful") capacity for the power station. The lower reservoir has a surface area of 1.1 km2 and operates at storage levels between 127 and 131 m above sea level.

During low electricity demand periods, such as the night time, water from the lower reservoir is pumped 937 m above the valley to the upper reservoir in the mountains. The upper reservoir is created by the Inje Dam, located 5.3 km2 west of the Yangyang Dam at 38.01889°N, 128.49639°W. The Inje is a 84 m tall and 415 m long rock-fill embankment dam. The capacity of the upper reservoir is 4200000 m3 and it has a surface area of 190 m2. When electricity demand rises and the power plant begins to operate, water is released from the upper reservoir back towards the underground power plant, at the western edge of the lower reservoir. Water fluctuations in the upper reservoir range from 900 m and 936 m above sea level. The power plant contains four 250 MW reversible Francis turbine-generators for an installed capacity of 1,000 MW. The drop in elevation affords a maximum hydraulic head (drop) of 817 m and effective head of 776 m.

Additionally, there are 2 x 1.5 MW Wind turbines installed at the upper reservoir and a 1.5 MW small hydro turbine on the Yangsang Dam.