Group effects in urban shallow geothermal energy

¹ Université Gustave Eiffel, IFSTTAR, GERS Department, F-77447 Marne-la-Vallée, France
² Università degli Studi di Perugia, DCEE, Italy

^* Corresponding author: jean.de-sauvage@ifsttar.fr

Abstract

Since the 1980’s, shallow geothermal solutions have been developed whose principle is to attach heat exchange pipes to the reinforcing cages of geotechnical structures. These low energy solutions combining a structural and a thermal role allow the fulfilling of the heating and cooling needs of buildings for a very low carbon cost. Energy geostructures are often placed in a groundwater flow. On one hand, it is a good way to avoid any multiyear thermal shift since the heat excess or default is tempered through the advection. This advection creates a thermal plume and heat waves in the soil can interact with downstream structures whose behaviour can be affected. The understanding of these interactions is essential for a smart management of the shallow geothermal development at the city scale. To study these interactions, a group of nine energy piles has been studied in Sense City, a mini city where a specific climate can be imposed and the underground water flow can be controlled. A numerical hydraulic-thermal coupled model was developed with the FEM software CESAR-LCPC to extrapolate the results. The combination of experimental and numerical models provides helpful results for the definition of guidelines concerning the prevention of interactions.