The pumped storage scheme consists of an upper and a lower dam, each capable of holding more than 20-million cubic metres of water.
generated by conventional coal and nuclear plants, is used to pump water to the upper reservoir.
The upper Bedford Dam, on Bedford stream— a tributary of the Wilge River— was completed in April 2011. It is a 39m tall concrete-face rock-fill dam. It has a 22.4-million cubic metre water storage capacity, of which 19.2-million cubic metres can be used for power generation.
The lower Braamhoek Dam, on Braamhoek stream— a tributary of the Klip River— was completed in November 2011. It is a 41m tall rollercompacted concrete gravity dam. It has a 26.3-million cubic metre water storage capacity, of which 21.9-million cubic metres can be pumped up to the upper reservoir.
A 2km long headrace tunnel connects the upper reservoir to the underground power station, which will house 4 × 333 megawatts( 447 000hp) reversible Francis pump-turbines. The elevation between the two reservoirs affords a hydraulic head( water drop) of 480m( 0.30mi). Water from the power station is discharged down a 2.5km( 1.6mi) long tailrace tunnel to the lower reservoir
To generate electricity during times of peak demand, water is released from the upper dam, passing through the pump / turbines, into the lower dam. During times of low energy demand, the pump / turbines are used to pump the water from the lower dam, back to the upper dam.
“ Water flows at high speed down to the turbines at around 60km / h, with enough water passing through each turbine to fill an Olympic-sized swimming pool in six seconds. Rotating at 428 revolutions per minute, each unit will produce 333MW, giving a total of 1 332MW for the station,” Eskom explains.
“ On completion of all four units, Ingula will be part of Eskom’ s peaking fleet of power stations. It can respond to demand increases on the national grid within two-and-a-half minutes. Upon completion, Ingula will be Africa’ s newest and largest pumped storage scheme and the nineteenth largest in the world.” u networking tech news environment industry infrastructure municipalities
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