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Green light to increase the power of the pumped storage power station Nant de Drance

While the construction work on the pumped storage power station Nant de Drance is in progress, the Board of Directors of the company Nant de Drance SA has definitively given the green light for the extension of the facility. Its power will thus be increased from 600 MW to 900 MW with the addition of two further turbine sets and the raising of the Vieux-Emosson dam by about 20 metres in order to double its capacity. This decision will allow the flexibility of the facility to be increased significantly and thus future electricity supply to be improved.

While the total cost of the initial project amounts to CHF 1.3 bn, the cost of its extension totals CHF 500 million, taking the overall cost of the facility to CHF 1.8 bn. The Board of Directors of Nant de Drance SA - the shareholders of which are Alpiq (54%), the Swiss Federal Railways (SBB, 36%) and FMV (10%) - considered this additional cost to be reasonable given the significant increase in power of the pumped storage plant, which in future should play an increased role in contributing to a secure electricity supply in Switzerland.

An indispensable resource for Switzerland's new energy policy The Nant de Drance project provides for a 600 MW underground pumped storage power station to be built between the Emosson and Vieux-Emosson dams. With the Nant de Drance Plus project, the installed capacity will be increased to 900 MW by adding two further sets of turbines 150 MW each. The volume of water held by the Vieux-Emosson dam will be increased from 13.5 million m3 to 25 million m3 by raising the wall of the dam by 20 metres. Because the small environmental impact will be fully offset by practical measures, only a minor modification to the present concession and a building permit for the raising of the dam and the re-sizing of the underground chambers and the hydraulics system have been required.

Owing to the new energy policy laid down by the Federal Council, the peak energy supplied by the hydroelectric facilities will have to be expanded in order to ensure a secure supply for the Swiss electricity grid, the SBB rail network and the private railway networks that take their supply from the SBB. As the Federal Council pointed out, pumped storage facilities will in future be one of the key resources for meeting the growing demand for balancing energy ensuring that the energy consumed through the grid is balanced at all times by the energy generated. The main reason for this increased demand in Switzerland and Europe is the expansion of new renewable energies, such as wind and solar power. Since these facilities are directly dependent on weather conditions, they have an irregular generating pattern that has to be topped up by balancing energy. Since pumped storage hydroelectric power stations represent a real stock of renewable energy that can be injected into the grid at any time, they offer an ideal complement to these new, more irregular energy forms, production of which is more irregular.

In order to allow the energy that will be produced at Nant de Drance to be transported and to secure the country’s electricity supply, the Swiss high-voltage grid and particularly the Valais grid will have to be upgraded. The Federal Council has in fact described the extension of the grid as being “imperative for Switzerland’s future production infrastructure”.

Progress of Nant de Drance construction work The work currently in progress concerns the boring of the various access routes between Châtelard and the chambers situated at an altitude of 1700 m and Vieux Emosson. This afternoon the boring of the access tunnel between Vieux-Emosson and the western collector on the shore of Lake Emosson will be completed. The last drill-and-blast operation on this underground link is scheduled to take place at about 2.00 p.m.

The immersion of the first water intake in Lake Emosson is scheduled for this autumn and work on the raising of the wall of the Vieux-Emosson dam will start in 2012. The power station will be gradually brought into service as scheduled from 2017.

For further information:

Alpiq Management Ltd., Corporate Communications Christel Varone, T +41 (0) 21 341 22 77

CFF SA, Central media service T +41 (0) 51 220 41 11,

FMV SA, Paul Michellod, Manager T +41 (0) 27 327 45 00

Remarks: Further information about the project is available on, or on be obtained via