The 900 megawatt (MW) Nant de France pumped storage power plant in Valais, Switzerland, came online in July after 14 years of challenging construction and testing. The gigantic “water battery” is capable of storing enough hydroelectric energy to power as many as 900,000 homes.

Gigantic Swiss ‘water battery’

The Nant de Drance “water battery” has a storage capacity of 20 million kWh of electricity. It will help stabilize Switzerland’s and Europe’s electrical grids by both reducing the chances of a grid overload when demand is high, and providing more power when it’s needed.

It took up to 650 construction workers working on the site at once, and around 60 companies working together to complete the project.

Six underground turbines are located 600 meters (1,968 feet) underground in a cavern between the Emosson and Vieux Emosson reservoirs in Valais, southern Switzerland.

Emosson, the lower reservoir, is the second-largest reservoir in Switzerland, and its 180-meter-high (590-feet-high) dam is the fifth tallest in the country.

The upper reservoir of Vieux Emosson holds 25 million cubic meters of water, which represents a storage capacity of 20 million kWh. It was raised by 21.5 m (70.5 feet) in order to double its capacity.

Each underground turbine has a capacity of 150 MW. The turbines can switch from pumping at full power to turbining at full power in less than five minutes, and it takes them less than 10 minutes to switch from turbine mode to pump mode. Three hundred sixty cubic meters of water per second passes through the turbines.

When there’s too much electricity in the grid, water is pumped from the lower reservoir to the higher reservoir, and the surplus energy is stored in the upper reservoir.

When power is needed, water flows from the upper reservoir and through the six underground turbines into the lower reservoir in order to generate electricity.

This animation illustrates how it works:

Nant de Drance SA and its shareholders Alpiq, SFR , IWB, and FMV will inaugurate the power plant in September.

Read more: Eco Wave Power will construct Spain’s first wave-energy power plant

Photos: Nant de France

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