Besançon. Geothermal energy blows heat and cold on three buildings on Place Granvelle
Decarbonizing municipal public services and reducing the city's impact on climate change: this is one of the challenges of the energy transition implemented by the municipal majority. After biomass and solar power, it's time for geothermal energy . This Friday, June 20, 2025, the community inaugurated the installation of a new system designed to heat or cool three buildings on Place Granvelle in Besançon: the Musée du Temps, the Kursaal, and the Ledoux Theater .
"An investment in the future, in equipment that is among the municipality's major energy consumers," recalls Mayor Anne Vignot . Geothermal energy will make it possible to replace more than 50% of this consumption with renewable energy. In Besançon, the elected official and her services intend to combine two approaches: "Continue to work on the most energy-intensive buildings and on schools, which are increasingly impacted by high temperatures."
Two wells located in Place Granvelle pump water from a groundwater table located about ten meters underground. This water, measured between 13°C and 16°C, is then transported via a network of pipes to a heat pump located in the basement of the Petit Kursaal. The borehole collectors converge on this room, where the water is then sent to other facilities, including an exchanger made of honeycomb plates to produce heat and cold. Important detail: the groundwater circulates in a closed circuit. It is pumped, circulates through the facilities, and is then discharged further down, without being mixed with other water. In short, this separation guarantees the absence of pollution of the water tables. Only calories (thermal energy) are transferred from the groundwater to the heating water.
Depending on needs, the system can provide heat or cold, in "Geocooling" mode. Only the natural cold of the water tables is used to cool the premises, without the use of machines, only with pumps. For the distribution of heat, the heat pump is used to recover calories and raise the water temperature, from 10° to 50°. With several uses at stake: preheating air blown into the premises and supplying the radiator circuit.
The challenges of geothermal energy in figures
The facility, located in Place Granvelle, Besançon, will produce 500 megawatt hours per year. This will provide 50% of the heating for the three municipal buildings and halve their gas consumption. The total cost of the geothermal project: €900,000 including tax.
Across the entire municipal building stock, the City congratulates itself in a press release, "this is a 3.2% reduction in total fossil gas consumption which may seem modest but which, combined with other projects, particularly wood-fired boilers, has made it possible to double the amount of renewable energy produced in municipal buildings, increasing from 18% to almost 39% in just 6 years." The gas energy bill is reduced by €43,000 per year.
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