Nant de Drance

A European gigabattery in the heart of the Swiss Alps

A country with a reputation as a major player in hydropower, Switzerland has stepped up the role it plays in helping to balance Europe’s electricity grids. The Nant de Drance pumped-storage plant, which has a storage capacity equal to 400,000 electric car batteries, began operating in 2022.

Colossal. With a capacity of 900 MW, the Nant de Drance pumped-storage hydropower plant is one of the most powerful in Europe. Following a monumental 14-year construction project which won the Major Tunnelling Project of the Year award in London in 2014, the plant was commissioned in the summer of 2022. “Put simply, this is an enormous environmentally friendly water battery,” explains plant director Alain Sauthier. By providing a short-term solution for storing excess electricity produced mainly by solar and wind farms, the plant is set to play a key role in regulating the power grids of Switzerland and Europe.

The upper reservoir, Lac du Vieux Émosson, has a storage capacity of 20 million kWh. “That’s the equivalent of 400,000 electric car batteries,” says Alain Sauthier. This facility has really come into its own since the large-scale adoption of renewable energy all over Europe – which by its nature is not always reliable. “This plant’s capacity covers more than just Switzerland’s needs,” adds Alain Sauthier. “It was designed for the European markets, and geographically we are right in the middle.” Pumped-storage power plants like this are used to balance electricity supply and demand, guaranteeing the stability of the power grids and contributing to security of supply. At the heart of the plant, 600 metres underground, are its six reversible pump turbines. “This installation is very flexible and highly reactive,” claims Alain Sauthier. “We can switch from pumping at full speed to turning the turbines at full speed, a differential of 1800 MW, in less than five minutes.” The yield of a complete pump-turbine cycle is 80%.

Nant de Drance’s shareholders – Alpiq, Swiss Federal Railways, Forces Motrices Valaisannes and IWB Industrielle Werke Basel – have invested CHF 2 billion in the project. Each shareholder is entitled to a share of the plant’s production and pumping capacity commensurate with its investment, managing the energy as it sees fit. The project partners also pool their resources to operate the plant, which does not employ a workforce of its own. Its environmental impact is being offset by 14 projects worth a combined CHF 22 million, most of which work with environmental protection associations to recreate specific biotopes or rewild sites.