Switzerland starts using ‘water battery’ with a capacity of 20GWh

Switzerland is starting to use a huge ‘water battery’ to store energy in water reservoirs. The so-called battery has a capacity equivalent to 20GWh and should be able to power about 900,000 households.

A water battery is a way of storing energy by means of two water reservoirs at different heights, explains Euronews. Excess electricity, for example generated by windmills or solar panels, is used to pump water to the higher reservoir. If electricity is needed, the water can then flow to the lower reservoir through one of six turbines, generating 900MW of power in total.

The higher Vieux Emosson reservoir contains about 25 million cubic meters of water, which according to operator Nant de Drance is equivalent to the energy capacity of 400,000 electric car batteries. The pump turbines can switch from pumping water to allowing water to flow through within five minutes. In other words, according to Nant de Drance the installation can switch between storing and delivering energy within minutes.

The construction of the Nant de Drance battery cost about 2 billion euros and took fourteen years. At that time, the Emosson and Vieux Emosson reservoirs in Valais were linked by a large underground tunnel network, reaching as much as 600 meters under the Swiss Alps. 18 kilometers of tunnels had to be dug, among other things to be able to transport the necessary building materials and pre-assembled parts through the Alps.

The two water reservoirs in the Swiss Alps. Image via Nant de Drance / Sebastien Moret