Hohhot Pumped Storage Power Station

When energy demand is high, water from the upper reservoir supplies the power station with four 306 MW reversible Francis pump turbine-generators to generate electricity. After the power is generated, the water is discharged into a lower reservoir in the valley. When energy demand is low and the upper reservoir needs to be replenished, the water can be pumped back up when the pump-generators reverse into pumps. The upper reservoir is situated at an elevation of 1,940 metres (6,360 ft) and was formed by the construction of a 62.5 metres (205 ft) tall concrete-face rock-fill dam. It has a storage capacity of 6,660,000 cubic metres (5,400 acre⋅ft), of which 6,290,000 cubic metres (5,100 acre⋅ft) can be used for power generation. The lower reservoir is formed by two gravity dams constructed of roller-compacted concrete. The upstream dam at a height of 57 metres (187 ft) and serves to trap sediment in the river which is the source of water for the power plant. The second gravity dam, located downstream, is 69 metres (226 ft) tall and withholds the lower reservoir with a capacity of 7,170,000 cubic metres (5,810 acre⋅ft) of which 6,360,000 cubic metres (5,160 acre⋅ft) can be used for pumped-storage. The lower reservoir is located at an altitude of 1,400 metres (4,600 ft). The difference in elevation between the two reservoirs affords a hydraulic head (drop in water) of 521 metres (1,709 ft). It is estimated that the plant will generate 2.007 billion kWh annually but consume 2.677 billion kWh pumping. Because pumping occurs during periods of low energy demand when there is a surplus and electricity is cheap, the plant is economical.^[5][6][7]

• List of pumped-storage hydroelectric power stations