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Nant de Drance power plant: intake valves to be opened for the first time

The construction of the Nant de Drance pumped storage power plant is progressing as planned. A major milestone will be achieved in mid to late November, when the plant's two penstocks, which are central to the production of energy, will be filled with water for the first time. The Nant de Drance plant will be fully operational in 2021.

After passing the final round of dry safety tests, the two 425-metre vertical penstocks that connect the upper Vieux Emosson and lower Emosson reservoirs will be opened in stages starting at the end of November. They will first be filled to the same level as the lower Emosson reservoir. During this initial phase, tests will be run to ensure the pipes and the main valves are watertight and working properly.
The penstocks will then both be filled up to the upper level – that of the Vieux Emosson lake. The water will be kept at that level for several weeks to ensure that the rock around the penstocks is stable.
The next step will be to conduct mechanical and electrical tests on the six pump turbines; the first tests with water will be carried out in early 2020 and will continue over several months to be sure that the turbines are working optimally. The six 150 MW turbines will then gradually be brought into operation, and the power plant will be fully up and running by the third quarter of 2021.

A future-oriented power plant

Nant de Drance SA shareholders have invested more than CHF 2 billion in the construction of the pumped storage power plant. This investment is part of a long-term vision and is aimed at meeting the challenges of supplying electricity going forward. Depending on demand, the 900 MW plant will be able to generate or store large quantities of power in a very short space of time. This kind of flexibility will be crucial, as the growing use of renewable energies will create more volatility in energy production. The energy reserve at the Nant de Drance plant will help to balance energy production and consumption. The plant will therefore play a key role in stabilising the electricity grid throughout Europe and in safeguarding Switzerland’s power supply.

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