Inauguration of an innovative geothermal power plant at Fort de L’Est in Saint-Denis, France

The Fort de L'Est in Saint-Denis welcomes a major advancement in energy transition with the inauguration of an innovative geothermal power plant. This facility strengthens the urban heating network by providing renewable and clean energy to supply about 7,500 households. At the heart of this local dynamic driven by Plaine Commune Énergie and SMIREC, this project concretely illustrates efforts in favor of sustainable development in the Ile-de-France region. The ingenious mix of biomass and deep geothermal energy, supported by an extensive nine-kilometer network, heralds a new era where efficiency and environmental respect go hand in hand.

A geothermal power plant at Fort de L'Est: a lever for local energy transition

At Fort de L'Est, the commissioning of this geothermal power plant provides Saint-Denis with a renewable energy source with a thermal capacity of 18 MWth. Managed by Plaine Commune Énergie, a subsidiary of Engie Solutions, it is part of the continuity of the power plants already present in Pleyel and Villetaneuse, making the municipality one of the most advanced areas in the Ile-de-France in terms of clean energy.

The choice to exploit the geological formation known as the Dogger, located 1,800 meters deep, illustrates the technical complexity of the installation. This pair of deep boreholes allows for the recovery of heat naturally present in the subsoil, thus providing a reliable and constant energy source throughout the year. Deep geothermal energy is particularly interesting because it does not suffer from intermittency, unlike other renewable sources such as solar or wind. Thus, it offers networks a stable base for heat supply.

The impact on local energy consumption is significant. According to the data provided, approximately 66% of the heating network in Saint-Denis is now supplied by renewable energies—a remarkable performance resulting from this synergy between geothermal energy and biomass. Gas, used solely as a backup, illustrates the city's desire to minimize its carbon footprint.

• Total capacity: 18 MWth (geothermal + heat pumps)

• Number of serviced housing units: 7,500 equivalents

• Length of the heating network: 9 km

• Drilling depth: 1,800 meters

• Sustainable combination: biomass and geothermal

This inauguration in Saint-Denis represents an example of successful implementation, adopting an innovative approach that combines technical performance with respect for environmental challenges. Residents can thus benefit from clean and stable heating in an urban context where energy needs are significant and must be controlled.

Construction and technical innovation: a project mobilizing a wide range of local expertise

The realization of the geothermal power plant at Fort de L'Est involved nearly 50 local and regional companies for over two years between 2023 and 2025. This collaboration highlights the importance of rigorous organization and extensive expertise in deep drilling, thermal installation, and networking. This project has created an impressive heating network of 9 kilometers, connecting several urban areas to ensure optimal distribution of the produced heat.

The techniques used for drilling have employed cutting-edge technology capable of extracting heat at a depth of about 1,800 meters in the Dogger rock formation. This formation is known for its favorable constant temperature for geothermal energy. The geothermal doublet installed allows for optimizing resource capture and ensuring a sustainable operation of the system.

In plumbing and sanitary installations, particular care has been taken to ensure the tightness of the pipes and the robustness of infrastructures against thermal constraints. The heat pumps, perfectly integrated into the system, enhance energy efficiency by maximizing the extracted heat while minimizing losses.

• Mobilization of around fifty companies between 2023 and 2025

• Technical drilling up to 1,800 meters deep

• Installation of a geothermal doublet in the Dogger formation

• Heating network of 9 km in the territory of Saint-Denis

• Advanced use of heat pumps coupled with the network

Particular attention has been paid to the rigorous management of hydraulic and thermal constraints, limiting the risks of leaks and failures. These elements are essential to ensure the sustainability of the system and the satisfaction of users. The Fort de L'Est power plant thus illustrates a perfect balance between technological innovation and reliable industrial plumbing practices.

Energy transition and sustainable development: geothermal energy as a lasting solution

In an era where energy transition is an absolute necessity, deep geothermal energy is increasingly established as a key renewable energy source. The Saint-Denis project fully aligns with this logic, illustrating how a city can significantly reduce its greenhouse gas emissions while ensuring reliable and sustainable energy service.

Fort de L'Est showcases a clever combination of renewable energies: biomass in addition to geothermal energy to diversify the sources, with gas as a backup solution only. This diversification secures the heat supply while reducing dependence on fossil fuels.

Mayor Mathieu Hanotin also emphasized the importance of this achievement by stating that it fits perfectly into the Territorial Climate Air Energy Plan, aimed at strengthening local energy autonomy and improving the quality of life for the residents of Saint-Denis. This project is a concrete example of public commitment and industrial ambition reconciled to address climate challenges.

• Reduction of carbon emissions through geothermal energy

• Biomass-geothermal coupling for more resilience

• Gas used only as backup

• Support for the objectives of the Territorial Climate Air Energy Plan

• Improvement of comfort and quality of life for residents

Geothermal energy also appears as an economic solution when the initial investment is considered over the long term, thanks to the stability of operating costs and the absence of dependence on fluctuations in fossil fuel prices. This stability also improves budget planning for local authorities and users.

The economic and social stakes linked to the establishment of a geothermal power plant

Beyond technical and environmental aspects, this power plant serves as a local economic engine and job creator. By mobilizing around fifty companies for nearly two years, it has contributed to revitalizing the economic fabric of the region, particularly in the construction, industrial plumbing, and renewable energy service sectors.

The work has promoted knowledge transfer and local innovation, consolidating valuable expertise in geothermal drilling and thermal installation. This experience now benefits companies and professionals in the sector, particularly specialists in sanitary plumbing and thermal network installation.

• Mobilization of 50 local companies

• Creation and maintenance of skilled jobs

• Reinforcement of regional expertise in geothermal energy

• Improvement of skills in industrial and thermal plumbing

• Creation of prospects for sustainable development in Seine-Saint-Denis

The development of geothermal power plants like that of Fort de L'Est contributes to structuring a sustainable energy sector, led by public and private actors, with positive outcomes for local life, in terms of both employment and technical expertise.

Future perspectives and deployment of geothermal energy in France

The geothermal power plant inaugurated at Fort de L'Est fits into a national context favorable to geothermal energy as a clean energy source. The French government has recently published a plan with seven concrete measures to support the sustainable development of geothermal drilling across the country.

As Saint-Denis becomes a concrete success example, other projects in Ile-de-France and beyond follow this dynamic. France’s geothermal potential still holds significant expansion margin, especially in regions where geology is conducive, such as Alsace or Burgundy. Utilizing these innovative technologies not only reduces dependence on hydrocarbons but also optimizes the energy management of local authorities.

On a technical level, the experiences gained at Fort de L'Est enrich the database and best practices regarding drilling, installation, and maintenance, facilitating the deployment of future large-scale geothermal projects.

• Government support plan for geothermal energy

• Increase in projects across French regions

• Optimization of drilling and maintenance techniques

• Increased contribution to carbon neutrality

• Strengthening urban heating networks with renewable energy

In summary, the inauguration of the geothermal power plant at Fort de L'Est is not merely a local investment. It is an essential link in the rise of renewable energies in France, reinforcing the model of clean and sustainable energy, accessible to citizens. For more information, you can visit the official page of the city of Saint-Denis at https://www.saintdenis.fr/actualites/nouvelle-centrale-geothermale.