Switzerland launched its "water battery" with 20 million kWh of capacity

The underground "water battery" in Switzerland has cost the country €2 billion and 14 years to finish, but it is now operational. Because construction workers had to tunnel through more than 11 miles of Swiss Alps, the project took so long to complete.

The Emosson and Vieux Emosson dams in Valais are home to a hydro battery, which is made up of two separate bodies of water at varying elevations — in this case, they're almost 2,000 feet underground between the Emosson and Vieux Emosson dams.

Excess energy may be utilized to pump water from the lower basin to the higher pool. Water in the upper pool is allowed to flow back into the lower reservoir when power demand rises. When water flows, turbines are created that generate hydroelectric electricity as it spins.

The plant's name comes from the six pump turbines that can produce 900 MW of electricity. Nant de Drance built it and it is able to store 20 million kWh of energy, which should assist maintain Switzerland's power grid stable. It takes around 20 hours to empty the Vieux Emosson reservoir, according to sources. In recent months, a lot of outside-the-box thinking has been done by renewable energy enthusiasts.