Another stage in Nant de Drance power station construction completed

An important milestone has been reached in the construction of the Nant de Drance pumped storage power station: the unveiling of the machine cavern, one of the largest in Europe, in the presence of Federal Councillor Doris Leuthard, Head of the Federal Department of the Environment, Transport, Energy and Communications (DETEC). The plant is scheduled to become operational by late 2018 and will make a significant contribution to the new energy strategy of Switzerland.

Nearly 200 guests gathered this morning at the Nant de Drance worksite in Châtelard (Canton of Valais) to celebrate the completion of drilling work on the machine cavern. Among them were Federal Councillor Doris Leuthard and representatives of federal, cantonal and communal authorities together with the project partners - Alpiq, Swiss Federal Railways, IWB, and FMV (Forces Motrices Valaisannes). "In the long term, storage options and balancing reserves are required for the growing volatile production of renewable energy. This is the only way in which the much-emphasised image of the Alps as the battery of Europe can become reality," explained Federal Councillor Leuthard, adding that this power station shows how important it is to have a link with Europe and how essential our access to the European market is. "But Nant de Drance is also an important part of the National Energy Strategy 2050. Nant de Drance shows that investments should be made despite the currently critical situation on the electricity market," continued Federal Councillor Leuthard.

With its impressive dimensions – 194 metres long, 32 metres wide and 52 metres high – the machine cavern is one of the largest underground works in Europe. It is located 600 metres beneath rock between the Emosson and Vieux-Emosson dam reservoirs. To get there, a 5.6 km long access tunnel was bored from Châtelard. Excavation of the cavern began in September 2011 and was completed two and a half years after the initial mining work. In total, 400,000 m3 of material weighing nearly 630,000 tonnes was excavated with explosives and transported to the Châtelard storage site.

Production and storage of large quantities of energy

The machine cavern will be the core component of the future plant since it will house the six groups of pump turbines with a total capacity of 900 MW that will enable the production or storage of large quantities of energy at very short notice, according to needs. When electricity demand is high, water stored in the Vieux-Emosson dam upper reservoir will be turbined in the machinery cavern to produce energy. Conversely, when the grid has an excess electricity supply, water from the Emosson reservoir will be pumped to the Vieux-Emosson reservoir for storage of the energy.

The power station will become operational in stages starting in 2018. The shareholder partners – Alpiq (39%), SBB (36%), IWB (15%) and FMV (10%) – are investing nearly 1.9 billion Swiss francs in its construction. Michael Wider, Chairman of the Board of Directors of Nant de Drance SA, recalled that “Nant de Drance shareholders are proud to have undertaken this project. The future plant will be a concentrate of high technology. It will be capable of switching from full power turbine operations to full power pumping operations in less than 10 minutes. This great flexibility will be a major asset in future on the Swiss and international electricity markets, although today the basic conditions are not yet in place to fully benefit economically from the value of pumped storage facilities in their key market.”

The next stage in 2014 will see the arrival of the first steel pipes, completion of drilling on the second vertical shaft, and pursuit of work to raise the height of the Vieux-Emosson dam. The installation of equipment in the machinery cavern can now begin.

An essential tool for security of supply

The future Nant de Drance power station is very well suited to the Swiss Federal Council's energy strategy, as this plant can balance electricity production and electricity consumption by providing balancing energy. This is particularly important, considering the growing, irregular production of electricity from new renewable energies. Nant de Drance will be able to make an important contribution to the stability of the European electricity grid and to Switzerland's security of supply. This power station will also cover the electricity requirements of the Swiss Federal Railways during peak demand periods on the rail network.

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