The sun as reinforcement for a geothermal installation
[Annecy (Haute-Savoie) 130 700 hab.] When the results are not good, it is better to question yourself. Probably repeated many times to the students of the Vallin-Fier school in Annecy, this moral now applies to the building itself. The geothermal heating system in place has been a concern for several years. The mass of land that hosts eighteen probes has seen its temperature decrease, which has been affected by the performance of the heat pumps responsible for drawing calories from it, then raising the temperature.
“This is undoubtedly linked to a problem of sizing consumption at the time of design”, underlines Fabrice Buzio, coordinator of energy issues for the city. Annecy, for a time, applied a pure and simple shutdown of the installation. But in education, nothing is ever lost. Adding a solar roof will ultimately save the day. From now on, 78 square meters of panels will produce the sanitary hot water that the building needs. When the students are not there and the demand is low, especially during the summer break, they will mainly be called upon to warm the ground in anticipation of winter.
Experimental coupling
This concept of inter-seasonal storage is beginning to emerge (by relying on solar power or by recovering the heat provided by the bitumen of certain roads, for example). But he has to prove himself. In Annecy, the city has partnered with the Storengy company. The Engie subsidiary was looking for a site to ensure the power of this solar-geothermal coupling. It needs to assess in situ the buffering capacity of the soil and to learn how to optimize the management of such a system.
This technological development could, in the future, be used on other facilities that are losing momentum, such as on urban sites lacking space. To eradicate fuel oil from its territory without favoring the gas solution, the city of Annecy says it is attentive to this possibility of undersizing certain geothermal installations by betting directly on a solar supplement. While this coupling is of interest at building level, it also has a future in urban heating networks where solar thermal is underused.
Beyond the technical
In the meantime, this project will have to prove itself technically. It will also make it possible to perfect some administrative and financial practices. In theory, the Vallin-Fier facility had already provided aid to which it was entitled (at the time of its creation). It was therefore necessary to find solutions to pay for the panels, the modification of the hydraulic system and the two additional fodders made to measure the temperature of the basement. “We were able to work with theAdeme so that this demonstrator is compatible with its grant criteria,” says Sandra Moro, geothermal expert at Storengy.
Contact : Fabrice Buzio, coordinator of energy issues, [email protected]
Governance to be redesigned
“We understood the technical aspect of the demonstrator, but there was also a lot of work on the question of governance”, underlines Benjamin Marias, first deputy mayor of Annecy. Among the partners, the city and Storengy therefore, but also the Savoie Mont-Blanc University, “at the forefront of solar thermal” and which has been responsible for modeling the thermal properties of the site, because the challenge is to develop solutions adapted to the needs of each project and each territory. “On one too often cooperation problems, he continues. With this demonstrator, we managed to lift them. »