Two Swiss Reservoirs Turned into World’s Largest ‘Water Battery’ to Power Europe–Time-Lapse Video Will Blow Your Mind

Next week a revolutionary new form of energy storage will debut in Switzerland after 14 years of engineering and installation.

With a storage capacity of 20 million kilowatt hours, enough to store the energy from wind, solar, nuclear or hydro and channel it to nearly 1 million homes, the Nant de Drance hydro-electric plant is ready to change the energy picture for Southern Europe.

The logistics of the Nant de Drance 900 megawatt “water battery” will blow one’s mind to read about, and involves the carving of 14 miles of tunnels under the Swiss alps in order to assemble massive prefabricated turbines and pumps around a pair of water reservoirs 1,800 feet underground.

Located under the Emosson and Vieux Emosson in the Swiss Canton of Valais, it’s Europe’s largest water battery, consists of six 150-megawatt Francis turbine-generators, and cost nearly $2 billion to complete.

But how does a water battery work, and what exactly is it? Electricity can be generated through heat, but also through kinetic energy. In considering the latter, rewenable energy storage devices take advantage of the fact that electricity can be “stored” by using its excess to move an object—in this case water.

Water from one large pool is pumped into another large pool in an underground chamber above. In this way electricity is “stored” in the sense that when power is needed in the homes of Switzerland, the water is then pumped through hydroelectric turbines to the chamber below with nothing other than the force of gravity.

The electricity generated from the kinetic energy of the falling water into the turbines is like the discharging of a battery—400,000 car batteries in the case of Nant de Drance.

“The Russian invasion of Ukraine has shaken the energy markets to their very core, [and] the effects this is having on the market are unprecedented in scale,” said Antje Kanngiesser, CEO of Alpiq Group, lead shareholder of Nant de Drance.

“From today’s perspective, the pumped storage power plant is an essential cog in the wheel for ensuring security of supply and grid stability in Switzerland and in the surrounding countries.”

While renewable energy storage often takes the form of large battery banks, the use of gravity or kinetic force is also growing.

A Scottish firm called Gravitricity is utilizing a similar principal, only with a 25-ton weight that is lifted up a tunnel—perhaps an old mineshaft—with the excess renewable energy, before its release channels those kilowatts back into the grid.