Rising temperatures due to climate change, increasing demands for comfort, modern architecture with its emphasis on glass, etc., have a strong influence on our need for cooling. At the same time, the need for warmth during the winter season remains at a high level.

In order to make the best use of the natural “reserves” of heat and cold, heat pumps can be used which can, depending on the case, extract heat or cold from the natural environment. In the context of this challenge, it is proposed to look at the potential of the Rhone for the use case of the Ronquoz district in Sion, which will develop considerably over the next 10 to 30 years and will require a considerable supply of cold and heat.

The advantage of this area is its location close to the Rhone River, which could act as a natural source of cold in the summer, and perhaps a little warmth in the winter. The main challenge is to define how and where to optimise the extraction of this energy.


The profile and course of the river has already been defined as part of the Rhone correction project “Rhone 3”. This data cannot be changed and therefore provides a starting point that must be taken into account. This being said, there is still room for innovation in order to make the best use of all available energy. How can cold (and possibly heat) transfers be optimised?

  • Should we proceed in the traditional way with a “simple” interchange in the river bed? In this case, how can we avoid the river bed being too quickly invaded by the sediments carried along, taking into account the fact that the river gauge is fixed?
  • Should sheet piling be installed on the riverbed and the interchanges be built directly into it? If so, what about the cost? How can it be reduced?
  • To limit costs, could the water from the Rhône be pumped and used directly outside? What about the sediment with this option?
  • What other innovative solutions could be put in place?

In addition to all these technical considerations, cantonal standards must also be taken into account, for example a limit on heat discharges into the river that increases its temperature by a maximum of 5°. How can we be sure that this limit will not be exceeded despite the enormous projected needs?

Finally, another factor to be taken into account is the variability of the flow rate, which can be enormous and rapid depending on various external parameters such as turbines, which can have a major influence on this point (with, for example, differences of up to 100m3 per second for the Bieudron plant)

Heat recovery is also a problem in itself: at the time of greatest need, in winter, the temperature of the Rhône is quite low. Is it too low to be used sensibly with a heat pump? Are there alternatives that would still make sense? And if it makes sense, how can the use of this resource be industrialised?

This challenge consists of proposing innovative and optimised solutions to make the most of the fantastic resource that is the Rhône in the years to come.

In order to do this, you will have at your disposal the figures of the projected needs for the Ronquoz district project as well as the specification of the route and the gauge of the river planned within the framework of Rhône 3.


  • The solution should be industrialisable and take into account the huge projected needs
  • The solution should be economically efficient in order to maximise the cold (and heat) potential of the river
  • The solution should allow the potential of the Rhone to be used progressively and to accompany the development of the new district over the next few decades.
  •  The solution should take into account the different standards and limitations intrinsic to the use of the Rhône


  • Cantonal standard on waste heat
  • Projected needs for the Ronquoz neighbourhood project
  • Specification of the route and gauge of the river planned in the framework of Rhône 3
  • Other data?


Michel Barras

Energy Transition Manager

+41 27 617 33 02

+41 79 217 25 45

Rue de l’Industrie 43

1951 Sion

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OIKEN was created by the merger of Energie de Sion-Région SA (esr) and Sierre Energie SA (Siesa) at the end of 2019. As a distributor of energy and water as well as multimedia, heat and gas, OIKEN supplies the 26 municipalities in the Sierre and Sion regions.