Nant De Drance Hydropower Plant

FinhautSwitzerland 46° N · 6° E

Nestled deep within the breathtaking Swiss Alps near the village of Finhaut in the Valais region, the Nant de Drance Hydropower Plant stands as a monumental…

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Introduction

The Nant de Drance Hydropower Plant, tucked deep within the Swiss Alps near Finhaut in the Valais region, stands as a monumental symbol of Switzerland’s commitment to renewable energy and innovative alpine engineering. As one of Europe’s largest pumped-storage facilities, it plays a vital role in stabilizing the national grid, supporting the integration of wind and solar power, and ensuring a reliable energy future. With its impressive 900 MW capacity and cutting-edge, low-impact underground design, Nant de Drance exemplifies the fusion of sustainability, technology, and environmental responsibility (Nant de Drance SA; AFRY; Power Technology; Finhaut Municipality).

This guide delivers in-depth information on the plant’s history, technical marvels, visiting options, ticketing, accessibility, and practical travel advice for exploring both Nant de Drance and the broader Valais region.

Nant de Drance is a cornerstone of Switzerland’s energy strategy. It enables large-scale energy storage and helps balance the grid as intermittent renewables rise, by rapidly switching from pumping to generation within five minutes. Its location—between the Vieux Emosson (upper) and Emosson (lower) reservoirs—uses the natural elevation to efficiently store and generate power, while its entirely underground design minimizes environmental and visual impact.

Historical Background & Construction

Vision and Planning

The project was initiated in the early 2000s to address Switzerland’s growing need for flexible, large-scale energy storage. In 2002, AFRY (then Pöyry) conducted early feasibility studies, leading to approval by the Swiss federal authorities in 2007 and the formation of Nant de Drance SA in 2008. Ownership is shared among Alpiq Suisse SA, Swiss Federal Railways, Industrielle Werke Basel, and Canton of Valais (Nant de Drance SA).

Major Construction Phases

  • 2008–2011 Excavation of 1.7 million m³ of rock, creation of 18 km of tunnels, and the main access tunnel (5.6 km) using a TBM with a 9.45 m diameter (Sika; AFRY).
  • 2011–2014 Construction of the underground machine hall (194 × 52 × 32 m) and transformer cavern, and raising of the Vieux Emosson dam wall by 20 m to double storage capacity (Sika).
  • 2014–2020 Installation of six 157 MW reversible Francis pump-turbine units and two 425 m deep vertical shafts for high flexibility (Power Technology; AFRY).
  • 2020–2022 Extensive testing, culminating in official commissioning in July 2022 and inauguration in September 2022 (Nant de Drance SA).

Technical & Engineering Highlights

  • Underground Design Entirely subterranean, the plant’s construction minimizes visual and ecological disturbance, using recycled excavated material for concrete (Sika).
  • Reservoir System Utilizes the Emosson and Vieux Emosson reservoirs (up to 395 m hydraulic head), with the upper dam expanded to 25 million m³, supporting a total hydro reservoir capacity of 227 million m³ (Power Technology).
  • Power & Flexibility 900 MW installed capacity, 2.5 billion kWh annual production, and capability to shift between pumping and generating in under five minutes (Hydropower.org).

Environmental & Societal Impact

Environmental Stewardship

  • Minimal Footprint Underground placement preserves the alpine landscape (Powertage).
  • Reservoir Expansion By increasing the size of an existing reservoir rather than building a new one, further ecosystem disruption was avoided.
  • Compensation Projects Fourteen habitat restoration and biodiversity initiatives, including alpine meadows restoration, reforestation, wildlife corridors, and aquatic ecosystem management (Nant de Drance).
  • Efficiency Over 80% energy storage yield, supporting decarbonization of the Swiss and European grids.

Societal Benefits

  • Grid Stability Key asset for energy security as renewables grow (Nant de Drance).
  • Economic Boost CHF 2 billion investment, thousands of jobs during construction, and ongoing skilled employment (Powertage).
  • Regional Development Enhances Valais’s reputation for innovation and attracts tourism and research.

Visitor Information: Hours, Tickets & Tours

Visiting Hours

  • Season Guided tours typically run from June to September, with occasional spring and autumn dates.
  • Times Most tours start between 9:00 AM and 3:00 PM. Always confirm current schedules on the official website.

Tickets & Booking

  • Prices Adult tickets usually CHF 25–35; discounts for children, students, and seniors.
  • Advance Booking Mandatory due to safety and capacity limits. Book via the official website or phone.
  • Group Tours Free for groups of 10+ (by arrangement); special requests for smaller groups may be considered (Alpiq).

Guided Tours

  • Languages French, German, and English.
  • Duration 2–3 hours, including a descent 600 m underground to the machine hall and interactive exhibits.
  • Age Limit Minimum age generally 12 years for safety reasons.
  • Group Size 10–20 people per tour.

Accessibility

  • Mobility Underground areas are not fully accessible; inquire about accommodations in advance.
  • Facilities Visitor center at Emosson Dam offers educational exhibits, café, restrooms, and restaurant.

Safety Guidelines

  • Clothing Warm layers and sturdy shoes recommended (underground temperature ~12°C).
  • Safety Gear Helmets and vests provided and required.
  • Photography Permitted in designated areas only.

Travel Tips & Nearby Attractions

Getting There

  • By Car Accessible via mountain roads from Martigny (Switzerland) or Chamonix (France), with parking by Emosson Dam.
  • Public Transport The Mont-Blanc Express train connects Martigny and Chamonix, stopping at Finhaut. Shuttle or taxi connects Finhaut to Emosson Dam (Finhaut Municipality).
  • Hiking Scenic trails link Finhaut, Emosson Dam, and area viewpoints.

Local Highlights

  • Emosson Dam Panoramic views, walking trails, and a miniature railway.
  • Finhaut Village Traditional alpine atmosphere and access to nature.
  • Alpine Hiking Numerous routes for all skill levels.
  • Mont Blanc & Trient Valley Ideal for combining technical tours with natural and cultural excursions.

Tips

  • Plan Ahead Tours must be reserved in advance.
  • Combine Activities Pair your plant visit with local hikes or cultural stops.
  • Seasonal Events Check for local festivals or educational workshops.

Frequently Asked Questions (FAQ)

Q: How do I book a tour?
A: Reserve in advance via the official Nant de Drance website or by phone.

Q: Are children allowed?
A: The minimum age is typically 12 years.

Q: Is the plant accessible for those with reduced mobility?
A: Underground areas are not fully accessible; contact the visitor center for options.

Q: What should I bring?
A: Warm clothing, sturdy shoes, and a camera for scenic views.

Q: Are there group discounts?
A: Group tours (10+) are often free; individual ticket discounts available for students, seniors, and children.

Q: Can I visit alone or in a small group?
A: Standard tours are for groups of 10+, but contact the visitor center for special arrangements.

Q: What else can I see nearby?
A: Explore the Emosson Dam, Finhaut village, hiking trails, and the scenic Valais region.

Essential Facts & Figures

  • Installed Capacity 900 MW (comparable to a large nuclear power plant)
  • Energy Storage 20 GWh (equal to 400,000 electric car batteries)
  • Switching Time <5 minutes from pumping to generating
  • Infrastructure 18 km of tunnels, machine hall 600 m underground
  • Altitude Vieux Emosson reservoir at 2,225 meters

Contact & Further Information

Next stop

15 min walk Lac Du Vieux Émosson Read on →