When, at the turn of the 2010s, the idea of reconnecting with Nancy’s thermal history germinated in the mind of André Rossinot, then mayor, the question of energy and that of water, a resource that has become so precious, were not yet the focus. Three decades later, a vast urban thermal center that plays the card of environmental sobriety, created on the site of an unfinished project dating from the beginning of the 20the century, will open its doors in Nancy. The operation of the place, which should be operational in a few months, has been entrusted to ValVital, the French number two in the thermal industry.
“You can’t imagine the number of people who challenge me to play the guinea pigs during the four months of the blank march which will begin in mid-December”, launched, Tuesday, Mathieu Klein, mayor (PS) of Nancy. Between the idea of a mayor who wanted to boost the attractiveness of his city and the realization of a 100 million euro project, a lot of water has flowed under the bridge! It is a challenge, today, to open a thermal complex, at a time when the requirements of sustainable development, the management of resources and energy constraints are more and more pressing!
Not so much, after all, since the water that will supply the 3,230 square meters of pools offering 18 aquatic activity points, from baby swimmers to spa guests coming for rheumatology treatment, comes out of the hot ground, drawn from the site itself, at a depth of 800 meters, without any withdrawal from the drinking water network.
“A lot of advantages”
“This project has many advantages, notes Nicolas Chabanne, one of the architects in charge of the project’s fluid engineering. It is located in the city center, and not in the countryside or the outskirts, so it limits travel. But the big chance is that we don’t need to heat the water. With this water at 34.5°C, we are between 25°C and 30°C for the aquatic and recreational part and for the thermal treatment part, we are between 34°C and 40°C. » Nancy Thermal will therefore not have to know the difficulties encountered by certain municipal swimming pools, forced to close their doors due to the explosion in the cost of gas heating.
When all pools are full, the center uses 4,500 cubic meters instantly
There remains the amount of water necessary for the operation of the complex. Thermal water under close surveillance, used for all pools, whether recreational or curative. When all the pools are full, the center uses 4,500 cubic meters instantly! The well is located within the perimeter of the centre. It pumps in a very large groundwater table that goes as far as Germany, and even in times of drought the level remains constant. No heat loss, the circuit is extremely short. Once used, the water is discharged into the city’s rainwater network.
As for the heating of the ambient air, the project avoids any consumption of fossil energy. The center is connected to the urban heating network of the metropolis, from renewable energies (biomass, waste recovery, cogeneration). Anne Démians, who led the architectural project, was part of the continuation of the original Art Nouveau construction signed by the architect Louis Lanternier, to which she juxtaposed contemporary architecture, while rehabilitating some remarkable elements, a round swimming pool surrounded blue-green mosaics of the most beautiful effect, or joinery by Jean Prouvé replaced in the gallery.
“The building is passiveexplains M.me Demians. It is closed, with concrete walls for thermal inertia, with very few facades compared to the developed surface. Water, the basis of activity, which arrives hot is free energy. And it is even used several times, recycled for showers after passing through the treatment area”. Virtuous to the end, the site even endeavored to preserve the presence of a small frog of 2 centimeters, the midwife Alyte, of which 385 individuals were captured and released in the neighboring park. They will be under surveillance for the next ten years.