Surface geothermal energy is emerging as a sustainable heating solution, exemplified by Olivier Roy’s home installation in Rueil-Malmaison, where he drills to access stable underground temperatures. This method significantly reduces energy costs while minimizing carbon emissions. Geothermal systems are gaining traction in France, heating neighborhoods and providing summer cooling in public buildings. Despite challenges such as installation space, the government aims to significantly increase geothermal energy production in the coming years, highlighting its potential as a renewable resource.
Exploring the Future of Energy Beneath Our Feet
Could the key to sustainable energy lie underground? Olivier Roy, a resident of Rueil-Malmaison in Hauts-de-Seine, showcases the potential of surface geothermal energy as he reveals his first drilling well located in his garden. “We had to reach a depth of 18 meters to tap into the limestone layer,” he explains. This innovative heating solution is set to warm his home throughout the winter months by utilizing the stable temperatures found between 10 and 200 meters below the surface, typically ranging from 12°C to 15°C. The warm water stored underground is extracted and directed to a heat pump, which then heats the living space.
The cooled water is subsequently returned underground, where it is naturally reheated. “We extract ten liters and return ten liters. Our method ensures we do not exhaust this resource,” Olivier notes, highlighting his significant savings on electricity — five times less than traditional heating methods. Despite investing 20,000 euros to transition from his old oil heating system, he estimates that he will recover this cost within ten years. “Previously, our annual energy expenses averaged around 3,500 euros for oil and electricity. Now, we spend approximately 1,500 euros on electricity. This transition is both cost-effective and environmentally friendly, helping us lower our carbon footprint,” he elaborates.
The Expanding Role of Geothermal Energy
This geothermal system results in emissions of carbon dioxide (CO2) that are ten times lower than those from oil. In France, around 200,000 installations currently utilize surface geothermal energy. While their prevalence has surged in the past five years, they still account for only 1% of total heat consumption, as per government statistics. This resource is inexhaustible and can be harnessed throughout the country, even in densely populated urban settings.
In Nice, geothermal energy is effectively employed to heat an entire neighborhood. Eduard Maldonado, who oversees southern infrastructure development, shares, “We have twelve drill sites that extend to 40 meters deep to harness geothermal energy. The heat pumps efficiently meet the heating demands of the neighborhood, covering a total area of 550,000 square meters across approximately 50 buildings.”
During the summer months, surface geothermal energy also provides ‘geocooling’ for public buildings. “In this classroom, the temperature is maintained at a comfortable 21 degrees. The heat is evenly distributed through the floor and walls,” explains Yann Rozier, a climate transition project manager. In warmer weather, the cooler underground temperature can be utilized to cool the building without the need for a heat pump, leveraging the concept of ‘geocooling.’ “When outside temperatures soar to 35 degrees, the temperature difference is substantial,” adds the expert.
However, this technology does come with challenges, such as the space required for installation. In Clamart, Hauts-de-Seine, the Optic 2000 company faced limitations in heating its expansive 11,000 square meters solely with this system. “The necessary connections would have been too extensive and costly, which was not feasible within our budget,” lamented Florence Jobic-Bouchard, the head of general services at the optician’s office.
Nonetheless, an investment of 1,300,000 euros has been made to ensure that geothermal energy covers two-thirds of the heating requirements for the eyewear manufacturer. Looking ahead, the government has ambitious plans to quadruple the production of this renewable energy source within the next decade.