The Energy Storage Report 2024

Now available to download, covering deployments, technology, policy and finance in the energy storage market

20GWh pumped hydro energy storage plant starting operations in Switzerland


A pumped hydro energy storage (PHES) plant with a capacity of 20GWh in Valais, Switzerland will begin operations on Friday 1 July.

The launch of the Nant de Drance plant, which sits 600m below ground in a cavern between the Emosson and Vieux Emosson reservoirs, marks the conclusion of 14 years of construction. It will be officially inaugurated in September and its shareholders have invested CHF2.2 billion (US$2.3 billion) in the project.

This article requires Premium SubscriptionBasic (FREE) Subscription

Enjoy 12 months of exclusive analysis

  • Regular insight and analysis of the industry’s biggest developments
  • In-depth interviews with the industry’s leading figures
  • Annual digital subscription to the PV Tech Power journal
  • Discounts on Solar Media’s portfolio of events, in-person and virtual

Or continue reading this article for free

It features six turbines with a nameplate capacity of 150MW each meaning a maximum power of 900MW. The upper Vieux Emosson reservoir, which sits at an altitude of 2,200m, holds 25 million cubic meters of water which represents an energy storage capacity of 20GWh. That means a maximum duration of dispatch of 20 hours.

Utility Alpiq, the main shareholder in the project with a 39% stake, says the plant will play a crucial role in stabilising the electricity grid as more renewables come online. Swiss national railway company SFR is the next biggest with 36%, followed by utilities Industrielle Werke Basel (IWB) with 15% and Canton-owned FMV with 10% of a total share capital of CHF350 million.

The development involved 60 companies and at the peak of construction, 650 workers on-site. The power house cavern measures 194m long, 52m high and 32m wide and required the excavation of 400,000 cubed meters of rock and the drilling of 17km of tunnels. The Vieux Emosson dam, pictured, was raised by 21.5m which doubled the capacity of the reservoir.

Utility Alpiq said the plant has a ‘yield’ or ‘energy efficiency’ (rendement énergétique) of over 80% which it said was one of the highest for a PHES plant, presumably referring to round-trip efficiency. For comparison, a 250MW plant in Dubai, which recently approached the halfway point of construction, is slated to have a round-trip efficiency of 78.9%.

Some CHF22 million was spent on 14 projects to offset the environmental impact of the plant, mainly to recreate specific biotopes locally to encourage recolonisation of the area by displaced animals and plants.

PHES makes up the vast majority of operational energy storage capacity today, but newly operational facilities have been few and far between in recent years due the time taken for projects.

Read Next

May 31, 2024
Global investment group Brookfield intends to acquire French renewables and energy storage developer and independent power producer (IPP) Neoen.
May 30, 2024
The government of Mauritius has welcomed the commissioning of a 20MW battery storage project which will provide frequency regulation to the East African island nation’s grid.
May 29, 2024
Denmark-headquartered independent power producer (IPP) Ørsted and investment bank JP Morgan have closed a tax equity financing of US$680 million for solar and storage projects in the US.
May 29, 2024
Utility EWS AG and developer MW Storage have completed the expansion of a battery energy storage system (BESS) project in Switzerland from 20MW to 28MW, making it the country’s largest.
May 23, 2024
The Kern County, California hybrid facility will have the capability to generate up to 2GW of solar power co-located with up to 2GW of battery energy storage system (BESS) capacity, spanning approximately 12,875 acres of privately owned land.

Most Popular

Email Newsletter