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Nant de Drance: First pump turbine connected to the grid

Finhaut – Yesterday one of the pump turbines at the Nant de Drance power plant was connected to the extra-high-voltage grid for the first time. This process went smoothly and marks a major step in the current test phase. Once the power plant is fully operational at the end of 2021, it will make an important contribution to the security of supply, providing flexible power generation and a total capacity of 900 MW.

The Nant de Drance teams have been testing some of the machines since March 2020, and yesterday they synchronised one of the pump turbine with the extra-high-voltage grid for the first time. These grid connection tests, which were a success, are a major step in getting the power plant up and running, a process that began in November 2019 when the intake valves were opened. Numerous tests are being carried out on the pump turbines and other installations during this period to ensure that every component meets the safety, quality and reliability requirements needed for the Nant de Drance power plant.

Flawless teamwork

There are currently close to 150 people working on site. Around 50 of them are involved in getting the power plant up and running, while the others are working on building the groups in the machine cavern and completing the finishing works. Commissioning is progressively carried out on several machines in parallel, which requires perfect coordination of these complex operations. The machine cavern holds a total of six pump turbines, each with a capacity of 150 MW. Work will continue until the end of 2021, when the Nant de Drance plant will be fully operational.

A cutting-edge power plant

Nant de Drance SA shareholders have invested about CHF 2.2 billion in the construction of the pumped storage power plant. This investment demonstrates a long-term vision and a willingness to meet the challenges of future electricity supply. Depending on demand, the 900 MW plant will be able to produce or store large quantities of energy in a very short period of time. This exceptional flexibility will play a decisive role, as electricity production becomes increasingly volatile due to the expansion of new renewable energies and the growing demand for flexibility. The balancing energy provided by Nant de Drance can balance short-term differences between electricity production and consumption. The plant will make a decisive contribution to the stability of the European electricity grid and the security of supply within Switzerland.

Construction timeline:

  • September 2008: construction work begins

  • July 2011: the project is modified, with the capacity increased from 600 to 900 MW and the upper dam raised

  • March 2014: the machine cavern is fully dug out

  • September 2014: work to raise the Vieux Emosson dam is completed

  • December 2018: the major construction work is completed

  • November 2019: the intake valves are opened for the first time

  • May 2020: the turbines are turned for the first time

  • August 2020: the first turbine is synchronised with the grid


For more information about the Nant de Drance power plant:


About Nant de Drance

The aim of the Nant de Drance project is to build a pumped storage power plant in a cavern between the Emosson and Vieux Emosson reservoirs in Valais Canton. With a total capacity of 900 MW, the power plant will play a key role in keeping the electricity grid stable both in Switzerland and across Europe. Nant de Drance SA, which is owned by Alpiq (39%), SBB (36%), IWB (15%) and FMV (10%), is responsible for building the power plant, bringing it online and operating it.

Nant de Drance SA

Aline Elzingre-Pittet

T: +41 21 341 22 77