Nant de Drance

Nant de Drance - Ventilation

Client / Owner

Nant de Drance SA (Alpiq 39% - CFF 36% - IWB 15% - FMV 10%)


2013 - 2018


Nunatak Architects for the services corresponding to the secondary works. 

Project description

The concerned infrastructure is the Nant de Drance 900 MW pumped storage power station located in Valais – Switzerland.

The project includes:

  • A main machine cavern (194m x 52m x 32m LHW) containing 6 Francis reversible groups (150 MW each).
  • Secondary caverns (transformers, valves).
  • 17 km of underground tunnels / galleries.
  • 8 electrical substations. 


  • Determination of ventilation objectives as current regulations and different modes (comfort, fire , etc.)
  • Developing the operating principle diagrams of ventilation flow
  • Predimensioning ventilation equipment and optimization of electrical power
  • Quotation and quantitative estimation of equipment
  • Detailed definitions of modes / ventilation scenarios
  • Sizing fans / piece and ductwork
  • Design of ventilation facilities ( power plants, wells , etc.)
  • Plans, quantitative , etc.
  • Studying the formation of fog gallery
  • 3D fire simulation to verify / validate the sizing of the fire ventilation

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