Geothermal energy in France, an inexhaustible low-carbon energy source, but with a high investment cost

Local and inexhaustible energy, available without interruption almost everywhere in France on a small land area, its investment cost nevertheless remains high.

How does geothermal energy work?

There are three techniques: the so-called "surface" technique allows you to heat and cool using the temperature of the subsoil at a depth of less than 200 meters. Beyond the first five meters, it is around ten degrees and stable in all seasons. Cool enough for the summer, in winter a heat pump allows you to use the calories from the subsoil.

So-called "deep" geothermal energy involves extracting hot water from a depth of 1.000 to 2.000 meters, where the water temperature varies from 80 to 150 degrees. It is pumped into the water table and then reinjected into the subsoil.

Finally, high-energy geothermal energy involves extracting steam at temperatures above 150°C in areas with active volcanism. It can produce electricity but is not present in metropolitan France. In Guadeloupe, the Bouillante geothermal power plant has a capacity of 15,5 megawatts (MW). It can be found in Iceland, Kenya and Japan.

What is the share of geothermal energy in France?

Geothermal energy only represents 1% of heat consumption.

However, heat represents 43% of final energy consumption, of which only a quarter is of renewable origin, according to the Ministry of Energy Transition.

In February 2023, the government launched an "action plan" aimed at quadrupling the rate of deployment of deep geothermal projects by 2035, with production of 8 to 10 terawatt hours (TWh) in 2035 compared to 2,3 in 2021.

He increased the heat fund of the Agency for Ecological Transition (Ademe), intended to support the production of renewable heat in France, to 820 million euros in 2024.

Deep geothermal energy is particularly present in the Ile-de-France region, where the Dogger aquifer is one of the most exploited in the world with 58 power plants. It is also found in Alsace and near Bordeaux.

What is the energy performance of geothermal energy?

It is high. The coefficient of performance (COP), the ratio between the energy produced and that consumed to operate geothermal heat pumps, is at least three: they produce three times more energy than they consume.

So, for one kilowatt-hour (kWh) of electricity, we have three kWh of heat, compared to one for one with a classic electric radiator, explains David Coutelle, from the environmental research office Ginger Burgeap, also president of the geothermal commission of the Syndicat des énergies renouvelables (SER).

What are the obstacles to the development of geothermal energy?

"The main obstacle is its investment cost," says David Coutelle. "On the other hand, it is an economically controlled solution in operation."

According to him, the cost of deep geothermal drilling runs "in the tens of millions of euros" and that of prospecting campaigns in "hundreds of thousands of euros, even millions of euros".

For prospecting, a guarantee fund was created in 1982 but it mainly concerns the Ile-de-France region.

Finally, the availability of drillers is "a real issue but not the major sticking point", according to David Coutelle.

Who uses geothermal energy?

In total, one million French people are heated or cooled using surface geothermal energy.

In addition to communities and businesses, geothermal energy is also of interest to social landlords because it helps combat energy insecurity.

"The effect of climate change means that we will need to cool homes, schools, and nursing homes if we want people to continue living there," adds David Coutelle. "Geothermal energy allows us to do this naturally." Action Logement, France's leading landlord, has launched an operation to deploy geothermal energy in its housing stock.

La Samaritaine, the Louis Vuitton Foundation in Paris, Nanterre Coeur Université, Issy-Coeur de ville, the Confluence district in Lyon and the Airbus headquarters in Toulouse all use geothermal energy.