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Energy and power plant technology, piping construction

Piping systems for the Nant de Drance pumped storage power plant

In October 2015, the Kraftanlagen München GmbH was commissioned with an order for the engineering, procurement and construction of the primary and secondary cooling water system and pipelines of the KMA pump system in the Swiss Nant de Drance pumped storage power plant, which is located at the height of the Col de la Forclaz pass directly on the French border.

The power plant is designed for seven pump turbines, each with a generator output of 150 MW. Six pump turbines will be installed immediately, while an additional turbine can be equipped if required. Therefore, the total output of the pumped storage power plant is 900 MW in its current development stage, with an estimated annual capacity of 2,500 million kWh/year.

The pumped storage power plant can draw power from the power supply system in order to pump water from the lower lake to the upper lake – a difference in altitude of up to 400 m. If the energy is required in the grid, the power plant can supply 900 MW over the course of around 20 hours. The switch between generation and energy intake is possible in less than ten minutes. This great flexibility makes it possible to react quickly in the event of a peak energy requirement or a fast switch to energy storage – one of the key advantages of the Nant de Drance project.

Included in the contract for Kraftanlagen München are the detailed engineering and calculation of the cooling water systems and KMA pump system, the procurement of the pipeline material as well as the prefabrication and on-site installation. The lines with a nominal pipe diameter of up to DN 450 were produced exclusively with austenite. The installation of the cooling water system pipelines was carried out in the so-called cavern, the 190 m long, approximately 30 m wide and between 45 and 52 m high machine hall that houses the six machine groups at 150 MWel.

The material was transported to the cavern right when it was needed via a 5.7 km long access tunnel. The installation had to take place within precisely defined periods of time so as not to impede other installations. In total, approximately 17 km of tunnels were dug into the mountain for the power plant.

Fact Sheet

Alstom Renewable (Switzerland) GmbH

Project duration:
12/2015 – 01/2019

Installation duration

03/2016 – 09/2017

Technical data:

  • Laid pipelines in metres: 3,000
  • Materials: 1.4541
  • Nominal pipe diameters: DN 25 - DN 450
  • Pressure stages:
    - KMA pump system: PN 63
    - Cooling water/primary circuit PN 40
    - Cooling water/secondary circuit PN 16

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