The 900 MW Nant de Drance pumped storage hydro power plant in Valais, Switzerland, will be put into operation on July 1, 2022, according to Alpiq.
This is the culmination of 14 years of work and intensive testing. Nant de Drance SA and its shareholders Alpiq (39%), SFR (36%), IWB (15%) and FMV (10%) will inaugurate the power plant in September.
Nant de Drance power plant will play a key role in stabilizing the Swiss and European electricity grids, Alpiq said. It will also contribute toward the security of supply of electricity in Switzerland.
Federal Councillor Simonetta Sommaruga and President of the Cantonal Council of Valais, Roberto Schmidt, inspected the power plant on June 18.
Located 600 m below ground in a cavern between the Emosson and Vieux Emosson reservoirs in the Finhaut municipality, the Nant de Drance power plant will feature six pump-turbine units with a capacity of 150 MW each. The highly flexible machines make it possible to switch from pumping at full power to turbining at full power in less than 5 minutes. The upper reservoir of Vieux Emosson holds 25 million m3 of water, which represents a storage capacity of 20 million kWh.
The construction of the Nant de Drance pumped storage power plant has involved some extraordinary work, Alpiq said. At the peak of construction, up to 650 people worked on the construction site and some 60 companies came together to realize this structure at a cost of around CHF2 billion ($2.1 billion). Situated at the heart of the mountain, the powerhouse cavern measures 194 m long, 52 m high and 32 m wide and required the excavation of 400,000 m3 of rock and the drilling of 17 km of tunnels. The Vieux Emosson dam located at 2,200 m altitude was raised by 21.5 m in order to double capacity of the reservoir and provide adequate storage capacity for the facility.
To minimize its environmental impact, Nant de Drance SA worked with environmental organizations from the earliest stages of the project. Fourteen projects at a total cost of CHF22 million Swiss francs ($23 million) have been, are or will soon be completed to offset the environmental impact of the construction of the pumped storage power plant and the very high-voltage line connecting it to the power grid.
