05 March 2021

Geothermal installations

Various type of geothermal installations can be used to extract the calories from the subsurface. The technical choice is made according to the geothermal resource, characterized mainly by geology: water occurrence, temperature, flowrate, the rocks constituting the reservoir, but also by the end-users needs.

Groundsource heat pumps

When the heat of the geothermal resource is below 30°C, a heat pump is required.

It allows both the production of heat and cold. Thus, heating of installations in winter and refreshing in summer.

It can also be used as a base heat production, completed by another source of energy, if the energetical need is very high.

When the heat of the geothermal resource is below 30°C, a heat pump is required.
It allows both the production of heat and cold.

Temperature : < 30°C
Depth : <200m

Geothermal heat plants on Aquifer

The geothermal installation on open aquifer provides heat for direct uses: district heating, agrifood and industrial processes that need heat between 30 and 90°C.

Geothermal water usually provides from sedimentary rocks naturally porous and/or fractured (sand, sandstones, limestones, chalk).

Roches sédimentaires naturellement poreuses et/ou fracturées (sables, grès, calcaire, craie). L’eau géothermale provient de nappes phréatiques ou réservoirs aquifères.

Temperature: 30-90°C
Depth : 500-2500m

Geothermal heat plants on fractured reservoirs

Fractured reservoirs are usually tight rocks (granite, sandstones) highly fractured: the natural faults and fractures network allows the circulation of geothermal water, driven by convection loops.

Geothermal heat plants on fractured reservoirs provides heat for district heating, for heat or industrial or agrifood processes with high heat needs up to 140°C.

Roches naturellement fracturées (granite, grès) dont le réseau de failles permet la circulation de l’eau géothermale grâce à des boucles de convection.
Eau géothermale / Saumure en circulation 

Temperature: 110-140°C
Depth : 2500-3000m

Geothermal plants: volcanic systems

Volcanic regions have a very high geothermal gradient. The geothermal resource, made of rain or sea water, is accessible at low depth (500-1000m) for temperature higher than 250°C. This geothermal energy, usually called ‘High enthalpy’, that can be found in very specific geological contexts (volcanoes) allows electricity production.

Roches volcaniques fracturées (basalte) dans lesquelles s’infiltre l’eau. 
Eau de pluie et eau de mer

Temperature : + 250°C
Depth : 500-1000m

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