The Nant de Drance power plant near Finhaut in Valais will be the second-largest pumped storage power plant in Switzerland. Construction started in 2008 and Nant de Drance will be commissioned in 2018. It will help to balance the energy from alternative sources in order to ensure an equilibrium between consumption and production in the Swiss electricity grid.
When electricity consumption is high, the water stored in the Vieux-Emosson reservoir falls through two 425-metre-high vertical shafts into the underground power plant. From there, it is fed through a turbine before being pumped into the Emosson reservoir. Conversely, during periods of low electricity demand, the water is pumped from the Emosson reservoir to the Vieux-Emosson reservoir. The Nant de Drance power plant is therefore able to store energy from excess production.
Swissgrid is tasked with transporting electricity from power plants to the major consumption centres. The construction of Nant de Drance, one of Switzerland’s largest pumped storage power plants, also represents a challenge for Swissgrid: it must ensure the transportation of the produced energy volume. To do so, a new 380kV line will be constructed between Nant de Drance and Martigny. The approximately 20-kilometre-long line will also require new switching substations and substations.
The Swiss transmission grid already has a number of structural bottlenecks. In particular, in Valais, the lines between St. Triphon and Riddes as well as between Chamoson and Chippis are extremely stressed. The Valais grid construction projects are essential to connect the Valais hydroelectric power to the Swiss 380kV grid and thus transport the energy across Switzerland.
A total of 130 km of lines will be constructed along new routes in Valais. This will significantly improve the situation: it will allow a total of 220 kilometres of line to be dismantled. Numerous lines, such as on the plateau of Salvan, will disappear entirely.
Flyer on the grid construction projects in Valais
At the end of April, Swissgrid presented the report on the Strategic Grid 2025. It shows the grid construction projects that Swissgrid believes will be necessary in the next ten years in order to ensure security of supply and prepare the grid for the energy future.
The investments required in the coming ten years will amount to about CHF 2.5 billion. This is significantly less than previously estimated. CHF 1 billion relates to the replacement and maintenance of existing infrastructure and CHF 1.5 billion is for expansions and new constructions.