Solargeotherm is a 3-years research project focused on the study of solar thermal energy storage into dry rock. Through a real-scale experimental device and heat transfer models, the project aims at evaluating the energetic potential of such a system. The experimental device includes 42 m² of thermal solar panels, three subvertical 180m deep boreholes equipped with double-U geothermal probes, and a 6 kW dry cooler. The probes are instrumented with an optical fiber that enables temperature monitoring all along the boreholes. The energy injection has begun in March 2010. Observations show that hardly 5% of the energy injected during the day is stored in the BTES, the major part being dissipated during the night. A detailed model of the double-U geothermal probe was developed under Comsol Multiphysics. Validated against the experimental data collected during the distributed thermal response test, it shows that, due to the thermal resistivity of the sealing grout, the rock thermal conductivity plays a minor role in the heat transfers between the hot circulating water and the surrounding bedrock. The development of a 3D-multilayer model is also in progress under the Finite Volumes hydrogeological code MARTHE. Simulating the system at a larger scale and pluri-annual periods of time, it will be used to explore different scenarios of energy storage/recovery cycles.