This giant ‘hydro battery’ under the Alps could be a game changer for renewable energy in Europe

Starting operations last month, the water battery, called Nant de Drance, is a pump-storage hydropower plant that delivers the same energy storage capacity as 400,000 electric car batteries.

Located high in the Swiss Alps in the canton of Valais, the plant is equipped with agile and reversible turbines that offer new levels of flexibility, says Robert Glitz, a delegate to the Nantes-de-Drans board of directors: With the push of a button the plant can go from storing energy to providing electricity.

The massive project took 14 years to complete. About 17 kilometers (10.5 mi) of subterranean tunnels were dug through the Alps while the six turbines were stored 600 meters (1,970 ft) underground, in a giant cave the length of two football fields.

Nant de Drance has reused two existing tanks, raising the upper tank by 21.5 meters (71 ft) to double its capacity – it now contains water from more than 6,500 Olympic swimming pools.

As one of the largest facilities of its kind, the $2 billion project could play a vital role in stabilizing Europe’s power grid as the continent transitions to Renewable energy, says Glitz.

make a splash

Pumped storage hydroelectric power stations, which have been around for more than a century, are of particular interest to renewable energy because wind and solar are highly weather-dependent and do not provide a constant supply of energy.

“We can take power (from the grid) when there is a lot of it, and generate it again when needed,” says Gilts.

Unlike many plants that preceded it, Nant de Drance uses variable-speed pump turbines, says Pascal Radio, CEO of GE Renewable Energy Hydro, which provided the equipment for the facility.

Radio says the turbines help stabilize the power grid.

“With a constant-speed turbine, you have to wait for the power plant to run at just the right speed to be synchronized with the grid,” Radio says, adding that this wastes time and energy. The variable speed turbines supply electricity to the grid instantly so there is less risk of a blackout.

Significant impact

Historically, pumped “open-flow” hydroelectric storage stations, which are built on river systems and require dam construction, disrupt wildlife and damaged ecosystems. In Switzerland, where the first pumped storage hydropower station was built in 1890, nearly half of all river lengths have been altered artificially, with very few alpine rivers in a natural state.

That’s why recent projects favor closed-loop systems, such as Nant de Drance, that don’t affect river systems, says Andrew Blakers, professor of engineering at the Australian National University.

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“The era of dam construction is almost over,” Bleeckers says, adding that closed-loop power plants take up relatively little space due to the energy security they provide. He estimates that powering a city of one million people for 24 hours would require about two square kilometers of flooded land, adding that pumped storage hydropower provides one of the The most efficient energy storage solutions currently available.

Nant de Drance returns about 80% of the electricity it consumes to the grid, storing about 20 hours of standby power, says Gleitz.

Switching to renewable energy sources

Hoping to become the “first climate-neutral continent”, Europe has big ambitions for renewable energy: in 2020, just over a fifth of the continent’s total energy came from renewable sources, but in May this year the European Commission increased renewables For 2030 the target is from 40% to 45%.
To achieve this, new, high-capacity storage facilities are necessary, Blakers says. The European Energy Storage Association estimates that the continent will need 200 gigawatts of storage by 2030 More than four times its current storage capacity. In the decade between 2010 and 2020, only 8 gigawatts of storage was added to the grid.
The turbines are stored in an underground cave the length of two football fields.

That’s why Nantes de Drances very important. Switzerland, located in the geographic heart of Europe, can provide stability to the grid across the continent, says Rebecca Ellis, director of energy policy at the non-profit International Hydropower Association. Nantes de Drances has increased Switzerland’s installed capacity by 33%, Ellis says, adding that it “demonstrates Switzerland’s leadership” in the transition to renewables.

However, since the nation is not a member of the European Union, regulations are currently a roadblock, says Gilts. “The rules of the market are not easy,” he says. “We still need closer agreements with the European Union.”

Pumped stored hydropower could provide energy security outside of Europe, too: Blakers and his team identified about 600,000 potential sites for closed-loop systems — although only 1% of these sites would be required to meet total global energy storage needs, he adds.

As the climate crisis worsens, Glitz hopes Europe will embrace the “clean energy storage” potential offered by pumped hydropower plants. “If we are to go in the direction of clean energy, Nantes-des-Drans is one of the starting points on that path,” he says.

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