This post is taken from the newsletter ” Human warmth “, sent every Tuesday at 12 p.m. Every week, journalist Nabil Wakim, who hosts the Chaleur Humaine podcast, answers questions from Internet users on the climate challenge. You can register for free here:
“Thank you very much for Human Warmth. I just listened to the podcast on renewable energy. But why don’t you mention geothermal energy? » Question asked by Jean-Alain at chaud [email protected]
“Hello, you talk a lot in your podcasts about electricity but very little about heat, which is nevertheless very important. Can geothermal energy represent a serious alternative to gas or fuel oil? » Question asked by Nathalie to the address chaud [email protected]
My answer : Yes, geothermal energy – the use of heat present underground – can play a role in the transition. In France, it is developing, and the potential is there, but concrete obstacles mean that its development is slow. On the other hand, in several countries, it already occupies a large part of the energy mix.
1) Why geothermal energy can be useful
Geothermal energy consists of exploiting the heat naturally present in the subsoil. We speak of surface geothermal energy (between 0 and 200 meters underground) or deep geothermal energy (beyond 200 meters underground). The idea is that this energy can be used permanently, with very few greenhouse gas emissions, and can usefully replace the use of gas or fuel oil for heating. (If you want to know how it really works, this video presented by Fred, from “It’s not rocket science”, may be useful to you!)
It can be used for several purposes: the most common in France is the geothermal heat pump, to heat an individual house. But we can also drill deep holes to heat an entire neighborhood, through a heating network. This is, for example, the case in Cachan (Val-de-Marne). At a depth of 2,000 meters, the water is at a temperature between 55°C and 80°C, and a pump allows it to rise and then circulate throughout the city to heat housing and public services.
Last possible use: it can produce electricity, as is the case in a power plant in Guadeloupe, in the aptly named town of Bouillante.
2) Why don’t we do more
Geothermal energy therefore seems to be a solution to many problems, but it encounters a certain number of obstacles. First, it requires a larger investment: a geothermal heat pump is expensive, and assistance measures exist, but do not cover all of the costs. Then, as recalled a report from the High Commission for Planning, France is seriously lacking in driller labor: the country today has around a hundred, whereas to switch half of individual houses to surface geothermal energy within 15 or 20 years, it would take more than 2,000 specialists. Furthermore, the mapping of possible drilling is currently insufficient, notes the Geological and Mining Research Bureau (BRGM), particularly in regions where geothermal energy is little present (in the south-east of France, in particular). Finally, the construction of heat networks in a city is a slow and expensive process, which requires strong support from public authorities to carry out large-scale work in a city.
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