On the performance of energy walls by monitoring assessment and numerical modelling: a case in Italy

Thermoactive diaphragm walls have proved their efficiency for near-surface geothermal energy use. To get insights into the heat transfer process occurring between the heat exchanger pipes and the surrounding boundaries, an instrumented real case located in Northern Italy was taken as reference. Combining on-site monitoring data with computational simulations, the role of the basement space in governing the heat fluxes in the different seasons, and the energy performance of the diaphragm wall and of the ground source heat pump system, is highlighted. The numerical analysis represents an effective predictive tool, but is also highly sensitive with respect to parameters of uncertain or complex definition, such as the boundary thermal conditions and the thermal input at the pipe inlet. Intermittent operation and idle periods require a refined simulation, discretising the time dependency of the input variables in appropriate short time steps.