Access to Water and Water Demand
With Gravity Storage, the water is pumped underneath a large rock mass. Depending on the size of the storage, the water demand is variable. The table below shows a rough estimate.
|Water discharge 8h [m³/s]||27||213||1.704|
|Water discharge 168h [m³/s](week)||1,3||10,1||81|
|Water discharge 720h [m³/s](month)||0,3||2,4||19|
The water required for the Gravity Storage is significantly lower than with a pumped storage power plant of comparable capacity. In particular, with greater construction depths of Gravity Storage, the relative water demand decreases significantly.
Ultimately however, a significant amount of water is still required. Therefore it is expedient to build the Gravity Storage in the vicinity of a water reservoir, like old pumped storage power plants or at substantial rivers or lakes where the minimal change in the water level due to the storage would be of no significance.
A water conveyance tunnel can be built to these water bodies. This tunnel does not necessarily need to be pressurized. Such tunnels cost approximately 5 million Euros per kilometer.
In isolated cases, like in the Middle East, the construction of an additional water reservoir or an underground basin in a cavern could also be reasonable.
Because the Gravity Storage is completely sealed with respect to its surroundings, the water used is not "contaminated" by inflows or mixing, and can therefore be returned to the water source with the same quality as when it was taken.
With Gravity Storage, the water is pumped underneath a large rock mass. Depending on the size of the storage, the water demand is variable.
Gravity Storage plants should be located in areas with solid bedrock. The most favorable sites have stable, little-faulted rock such as granite or compact layers of otherwise solid rock material.