Located high in the Swiss Alps in the canton of Valais, the plant is equipped with agile, reversible turbines that offer new levels of flexibility, says Robert Gleitz, a delegate of the board of directors of Nant de Drance: with the flick of a switch , the plant can go from storing energy to providing electricity.
The massive project took 14 years to complete. Around 17 kilometers (10.5 miles) of subterranean tunnels were excavated through the Alps while the six turbines are stored 600 meters (1970 feet) below ground, in a giant cavern the length of two football fields.
Nant de Drance repurposed two existing reservoirs, raising the upper one by 21.5 meters (71 feet) to double its capacity — it now holds more water than 6,500 Olympic-sized swimming pools.
As one of the largest facilities of its kind, the $2 billion project could play a vital role in stabilizing Europe’s electricity grid as the continent transitions to renewable energy, says Gleitz.
Making a splash
Pumped storage hydropower plants, which have been around for over a century, are particularly important for renewable energy because wind and solar rely heavily on the weather and don’t provide a consistent power supply.
“We can take energy (from the grid) when there is too much, and generate it again when it’s needed,” says Gleitz.
Unlike many of the plants that preceded it, Nant de Drance uses variable speed pump-turbines, says Pascal Radue, CEO of GE Renewable Energy Hydro which supplied equipment for the facility.
The turbines help to stabilize the electricity grid, says Radue.
“With a fixed speed turbine, you have to wait until the power plant is running at exactly the right speed to be synchronized to the grid,” says Radue, adding that this wastes time and energy. Variable speed turbines supply electricity to the grid immediately so there’s less risk of blackouts.
A big impact
That’s why modern projects favor closed-loop systems, like Nant de Drance, which don’t impact river systems, says Andrew Blakers, a professor of engineering at the Australian National University.
“The era of dam building is nearly over,” Blakers says, adding that these loop power plants take up a relatively small space given the energy security they provide. He estimates that to power a city with one million inhabitants for 24 hours would require around two square kilometers of flooded land, adding that pumped storage hydropower offers one of the highest efficiency energy storage solutions currently available.
Nant de Drance returns around 80% of the electricity it takes in back to the grid, and stores around 20 hours of backup energy, says Gleitz.
Transitioning to renewables
That’s why Nant de Drance is so significant. Located at the geographical heart of Europe, Switzerland could offer stability to the grid across the continent, says Rebecca Ellis, energy policy manager at the non-profit International Hydropower Association. Nant de Drance has increased Switzerland’s installed energy capacity by 33%, says Ellis, adding that it “shows the leadership of Switzerland” in the transition to renewables.
However, as the nation is not a member of the European Union, regulations are currently a barrier, says Gleitz. “The market rules are not easy,” he says. “We still need to have closer agreements with the EU.”
As the climate crisis intensifies, Gleitz hopes that Europe embraces the potential of the “clean energy storage” provided by pumped storage hydropower plants. “If we want to go in the direction of having clean power, Nant de Drance is one of the stepping stones on this path,” he says.