The Nant de Drance power plant has a capacity of 900 MW, making it one of the most powerful pumped storage plants in Europe. It is located 600 meters underground, between the Emosson and Vieux Emosson reservoirs, and has a storage capacity of 20 million kWh. The plant offers flexible power generation, playing a key role in stabilising the electricity grid throughout Europe and in safeguarding Switzerland’s power supply.
900
MWthe capacity of the Nant de Drance plant, which is equivalent to that of the Gösgen nuclear power plant
6
the number of Francis turbines, each with a capacity of 150 MW
20
million kWhthe plant's storage capacity corresponding to the capacity of 400,000 electric car batteries
No. 2
Emosson Lake is currently the second-largest reservoir in Switzerland, after Grande Dixence, and its 180-metre-high dam is the country’s fifth tallest
5
minutesthe time needed for the power plant to stop pumping at full speed and start turning the turbines at full speed; and less than 10 minutes to switch from turbine mode to pump mode.
80%
the plant's yield, which is currently one of the highest for a pumped storage power plant
25
million m3the capacity of the Vieux Emosson, which is more than 6,500 Olympic-sized swimming pools
2
countriesthe water in the Emosson reservoir comes from both Switzerland and France
425
mthe height of the two vertical penstocks that connect the Vieux Emosson and Emosson reservoirs – that's 100 m higher than the Eiffel Tower (324 m)
7
mthe diameter of the two penstocks
194
mthe length of the underground turbine chamber, which is equivalent to two football fields
20
hoursthe time needed to empty out the Vieux Emosson reservoir
18
kmthe total length of the underground galleries within the Nant de Drance plant
Protecting the environment
One of the priorities of Nant de Drance and the licensing authorities is to reduce environmental impact as much as possible. Fifteen projects at a total cost of twenty-two million Swiss francs have been, or will soon be, completed to offset the environmental impact of the following constructions: pumped storage power plant and very high-voltage line connecting the power plant to the power grid.
The work is managed by Nant de Drance SA and monitored by an advisory group represented by WWF, Pro Natura, the public authorities concerned, the canton of Valais as well as the Swiss Federal Office of Energy.