In Issoire (Puy-de-Dôme), the factory heats the city (almost) for free

Mid-October. The sun beats down on the fifty hectares of land of the barracks located south of Issoire, commune of Puy-de-Dôme. Under the clock on the facade of the building facing the Place d’Armes is written “Act quickly and well”, the motto of the 28th Army Signal Regiment. A light breeze lifts the blue-white-red flag. The temperature shows 30°C. However, the inhabitants of the region are not fooled. They know that in Auvergne a bitter cold can strike overnight.

This is why the military unit, which houses up to nearly 1,000 people simultaneously, abandoned coal at the end of 2022 to connect to a new urban heat network. Revolutionary, this hybrid system recovers the heat produced by the furnaces of the Constellium aluminum foundry, the city’s largest employer, and uses wood residue from local forests in addition. “It is 90% renewable energy,” explains Tristan Thomazet, project manager at Dalkia, a subsidiary of the EDF group. To cope with possible peaks in consumption, two gas boilers complete the system.

Virtuous recycling

“Since commissioning, we have gained in comfort and efficiency,” says Nathalie Robert, second lieutenant. Between residential buildings, administrative services, armory, swimming pool, gymnasiums, restaurant, the military base has approximately 104,000 m2 of surface area to be heated. ” It is enormous ! » she blurted. In addition to this site, around forty buildings among the most energy-intensive in the municipality benefit from this system: fire station, schools, town hall, nautical center, hospital, etc.

A real boon for the municipality in a context of rising energy costs – fuel, electricity and heating – for local authorities (27.3% in 2022 according to the local finance and public management observatory ). Also connected are housing from the social landlord Auvergne Habitat and some private co-ownerships. “We wanted to find a way to recycle waste heat,” assures Stéphane Corre, director of the Constellium Issoire site. But our vocation is not to become an energy supplier. This is why we joined forces with the community and the operator to set up one of the most virtuous projects in France. »

Gains for the community

The management of maintenance and operation of the boiler room are left to Energ’Iss, a company under public service delegation (DSP) under contract with Dalkia for a period of twenty years. At the heart of it, David Faure, site manager, takes care of the gleaming pipes. “Wood makes it possible to supplement when the irregular activity of the factory decreases. And in case of great need, the hospital and the barracks each have an independent gas boiler. » Thus, the system aims to use fossil energy as little as possible. Bertrand Barraud, mayor of Issoire, confirms the exceptional environmental interest. “Not only does this system present no danger, but it also avoids the emission of nearly 5,000 tonnes of CO each year, the equivalent of the emissions of nearly 2,700 vehicles. » Initially, the project launched between 2019 and 2021 raised reluctance. The residents were not really against it but many were wary of possible power shortages. This was without taking into account the energy crisis and the boom in gas prices.

Since then, users have praised the technique as much as the stability of prices not indexed to fossil fuels. “With the explosion in costs, the gains are calculated in hundreds of thousands of euros for the community,” says Bertrand Barraud. This solution really sets an example! » Including in the eyes of the employees of the Issoire aluminum giant. “Most came to visit the installation,” concludes Tristan Thomazet. Knowing the interest of the project, they even find it pleasing to be able to contribute to it. Some of them live in homes served by the urban heating network and therefore benefit from the hot air coming from their company’s ovens. ” The circle is complete.