LOCIE has two test platforms for studying heat transfer in the near subsurface in the presence of geothermal heat exchangers.
The test bench for geothermal baskets in real conditions consists of a set of five geothermal baskets with a diameter of 1 m, buried at a depth of between 1 and 3 m, equipped with temperature probes and connected to a 4 kW water-to-water heat pump. This device allows the influence of soil type and distance between baskets, soil freezing, and stress mode to be studied.
This bench has been equipped with electrodes in order to study changes in soil temperature and humidity disturbed by heat extraction or injection through a geothermal basket.
The test bench for geothermal baskets under controlled conditions consists of an insulated tank with thermal insulation on its side walls. The tank is filled with a model soil (calibrated silica sand). The upper and lower surfaces of the sand are subjected to imposed temperature conditions that reproduce the usual boundary conditions. This device reproduces the temperature and humidity conditions encountered underground on a1/10th scale. It also makes it possible to reproduce precipitation and the presence of a stagnant water table, the level of which can be fixed.
The sand is equipped with thermocouples and humidity sensors. Electrodes are also installed so that the thermal and hydrological evolution of the soil over time can be studied. Three thermostatic baths are used to thermally control the tank and the geothermal basket installed inside it.