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Energy from the Earth

When boring down into the earth, the temperature increases by an average of 1°C every 30 metres. The principle of geothermic energy consists of drawing on the energy contained in the Earth’s crust for use as heating or electricity.

Increasing the use of geothermal power is an energy policy priority in Geneva. Our local geology means that there is excellent potential for this energy source. Underground resources could cover a significant two-thirds of the canton’s heating needs and part of its electricity consumption.

Shallow, medium or deep geothermal

At shallow depths (50m to 400m), rocks in the earth have a constant, year-round temperature of 12°C to 25°C. Installing geothermic probes or pumping water into underground groundwater systems, together with heat pumps, represent significant potential for generating heating solutions.

At medium depths (from approximately 400m to 3,000m), the underground temperature is between 25°C and 100°C. Water that circulates in these geological layers or in fault lines can be pumped and used directly in thermal installations, for urban heating or heating greenhouses.

At much deeper levels (between 3,000m and 6,000m), rocks can reach temperatures of almost 200°C. This energy, when captured, can produce heat and also electricity. Deep geothermal heating presents enormous energy potential, but considerable investment is required to develop this sector and improve our knowledge of what lies this deep underground.


Benefits


Innovative projects

SIG supports the use of geothermal energy by offering customers special conditions to supply electricity to a heat pump, but also by initiating and piloting innovative geothermal schemes across the canton.

2011 saw the inauguration of the Laurana Parc in Thonex. This is a group of buildings now largely heated by a shallow geothermal source (approximately 300m deep), and other installations of this kind may follow suit.

Many individual homes can also run like this. Homeowners use heat pumps, which enable them to take advantage of ground temperatures by transmitting them their home heating network.

GEothermie 2020

The State and SIG signed a convention on 11th February 2014 to launch GEothermie 2020, a prospection and exploratory programme that will research the resources available in local subsoil.

The programme is run by the State and SIG is responsible for undertaking prospection.

SIG started geophysical surveys on 18th August 2014, along the Chancy road between Chancy and Bernex. Two methods are used depending on the layout of the land: ground-penetrating radar and resistivity. No drilling is carried out during this phase, as only radio waves are used to map under the surface. Further surveys will be carried out across the Geneva canton.

Find out more about the programme


Cooled by lake water

The thermal Genève Lac Nation (GLN) project, which supplies heat and cooling facilities to numerous companies in the Sécheron district, has helped near-surface geothermal energy to really take off.
The GLN project works on the principal of piping deep lake water (which acts as a heat sink) to the climate control systems in participating buildings. This system also provides heating in newly-constructed buildings via the installation of high-performance heat pumps.
This technique, which works particularly well for cooling systems, will feature in many new building schemes such as the GéniLac project. Lake Geneva is an ideal reservoir for near-surface geothermal energy.

Key figures