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 to the Nant de Drance board: at the flick of a switch. , the plant can switch from storing energy to supplying electricity.
The massive project took 14 years to complete. Around 17 kilometers (10.5 miles) of underground tunnels were excavated through the Alps while the six turbines are stored 600 meters (1[ads1],970 ft) underground, in a giant cave the length of two football pitches.
Nant de Drance reused two existing reservoirs, raising the upper one by 21.5 meters (71 ft) 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 an important role in stabilizing Europe’s electricity grid as the continent transitions to renewable energy, says Gleitz.
Make a splash
Pumped storage hydropower plants, which have been around for over a century, are particularly important for renewable energy because wind and solar are dependent on the weather and do not provide a steady supply of electricity.
“We can take energy (from the grid) when it’s 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 plant.
The turbines help to stabilize the power grid, says Radue.
– With a turbine with a fixed speed, you have to wait until the power plant runs at exactly the right speed to be synchronized to the grid, says Radue, adding that this wastes time and energy. Variable speed turbines deliver power to the grid immediately, so there is less risk of power outages.
A big impact
That is why modern projects favor closed loops, such as Nant de Drance, which do not affect river systems, says Andrew Blakers, professor of engineering at the Australian National University.
“The era of dam building is almost over,” says Blakers, adding that these closed power plants take up relatively little space given the energy security they provide. He estimates that to power a city of one million inhabitants for 24 hours would require about two square kilometers of flooded land, adding that pumped hydropower offers one of the most efficient energy storage solutions currently available.
Nant de Drance returns around 80% of the electricity it takes back to the grid, storing around 20 hours of reserve energy, says Gleitz.
Transition to renewable energy
That is why Nant de Drance is so important. Located in the geographical heart of Europe, Switzerland can offer stability to the grid across the continent, says Rebecca Ellis, energy policy director at the non-profit organization International Hydropower Association. Nant de Drance has increased Switzerland’s installed energy capacity by 33%, Ellis says, adding that it “shows the leadership of Switzerland” in the transition to renewable energy.
But since the nation is not a member of the EU, regulations are currently a barrier, says Gleitz. “The market rules are not simple,” he says. “We must still have closer agreements with the EU.”
As the climate crisis intensifies, Gleitz hopes that Europe embraces the potential of “the clean energy storage” that pumped hydropower provides. “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.