In a forward-looking initiative, the communes of Lilas, Pantin, Pré-Saint-Gervais, and soon Romainville in Seine-Saint-Denis, located in the greater Paris area, are gearing up to be heated by geothermal energy by 2025. The ambitious project, spearheaded by the local public company (SPL) Unigeo, was established in February 2022 through collaboration among the three communes and Sipperec, the intermunicipal syndicate for energy and communication networks in the outskirts of Paris.
The groundwork for this groundbreaking endeavor was laid as early as 2017, with the first doublet of wells for the geothermal network already drilled, and plans for a second doublet underway, slated for completion by the first quarter of 2024. Subsequently, construction of a geothermal heating plant will commence.
A substantial investment of approximately EUR 80 million has been poured into the project to date, with support from the Île-de-France regional council contributing EUR 8 million in subsidies and an additional EUR 15 million from the French Environment and Energy Management Agency (ADEME).
The heart of this innovative heating solution lies in the Dogger aquifer, a layer of limestone approximately 2 kilometers deep in the Île-de-France region. Geothermal fluids within this aquifer boast temperatures ranging from 55 to 85 °C. The first doublet, drilled at Lilas with a 40-degree deviation to a depth of around 1700 meters, has undergone a testing phase, revealing a promising flow rate of up to 100 cubic meters per hour. During the operational phase, a pump will enhance this capacity to 320 cubic meters per hour.
To harness the geothermal energy, a heat exchanger comprising titanium plates will transfer heat from the geothermal fluids to a fresh water network. The cooled geothermal fluids will then be returned to the Dogger.
The future heating network is projected to serve approximately 20,000 housing equivalents, including over 4,500 in Lilas. This encompasses a variety of dwellings, from social housing complexes and condominiums to public buildings and the Marie Curie College. According to Sipperec, the adoption of geothermal heating is anticipated to prevent the production of 28,000 tonnes of CO2 annually.
Inès Gelu, Director of Unigeo, emphasizes that the use of geothermal energy will ensure a stable cost of heating throughout the proposed 15-year contract. Although the heating network won't be entirely reliant on geothermal power, requiring a portion to be supplemented by gas, Gelu notes that the anticipated savings in comparison to fluctuating gas prices are significant, with ADEME stipulating a minimum of 5% below gas prices.