Switzerland puts ‘water battery’ with a capacity of 20GWh into operation

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

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. When electricity is needed, the water can then flow to the lower reservoir through one of six turbines, together producing 900MW of power.

The Vieux Emosson reservoir, located higher up, contains about 25 million cubic meters of water, which, according to manager Nant de Drance, is equivalent to the energy capacity of 400,000 batteries in electric cars. The pump turbines can switch from pumping water to letting water flow through within five minutes. In other words, according to Nant de Drance the installation can switch between storing and discharging 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 together via a large underground tunnel network, up to 600 meters below the Swiss Alps. 18 kilometers of tunnels had to be dug, partly 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 / Sébastien Moret