Numerical analysis of heat transfer in thermo-active diaphragm walls

In the frame of the exploitation of low enthalpy geothermal energy the thermo-active ground structures represent an effective engineering solution for the thermal energy production for heating and/or cooling of buildings and infrastructures. In this paper, the behaviour of thermo-active diaphragm walls is studied, from the perspective of both the geothermal energy exploitation and the influence of the heat transfer process on the soil temperature field. Finite element thermal analyses have been performed on a diaphragm single segment equipped with heat exchangers, to evaluate the relevant parameters and optimise the pipe layout. Then, the effects of the thermo-active diaphragm on the soil temperature field have been investigated to evaluate the performance of the geothermal system, in the short and long term and for heating/cooling working conditions. The numerical results highlight that the soil represents an effective heat storage mass and a proper balance between the two working conditions over the year is necessary to avoid thermal drifts and maintain the performance of the system.