Underground power station

An underground power station is a type of hydroelectric power station constructed by excavating the major components (e.g. machine hall, penstocks, and tailrace) from rock, rather than the more common surface-based construction methods.

One or more conditions impact whether a power station is constructed underground.

The terrain or geology around a dam is taken into consideration, as gorges or steep valleys may not accommodate a surface power station.

[1] After World War II, large hydroelectric power stations were placed underground more often in order to protect them from airstrikes.

[2] Often underground power stations form part of pumped storage hydroelectricity schemes, whose basic function is to level load: they use cheap or surplus off-peak power to pump water from a lower lake to an upper lake.

Inside the Robert-Bourassa generating station , in northern Quebec , the world's largest underground power station, with an installed capacity of 5,616 MW.