Thermal plume dispersion induced by shallow geothermal applications: the case study of Villaverla (Italy)

Abstract

Among the shallow geothermal applications, the opportunity to detect the thermal plume dispersion induced by a borehole heat exchanger (BHE) coupled with a ground source heat pump in an unconfined aquifer can provide crucial data for environmental purposes. The interpretation of these data could lead to useful information to (1) accurately simulate transport model; (2) to acquire aquifer properties data and (3) to evaluate the environmental impact at local scale.
This paper aims to provide the results of a geophysical methodology developed in order to characterize and to detect the spatial and temporal distribution of the temperature on the ground. Moreover, the presented heat transfer test could be applied also in other applications instead of classical aquifer tracers tests, in order to (1) minimize the environmental impact of tracers, (2) reduce overall costs and (3) improve the aquifer properties evaluation.
With the aim of identify the ground thermal footprint dispersion over time, in the described test the authors combined a fiber optic Distributed Temperature Sensing device, an Electrical Resistivity Tomography, a temperature logs and a thermal properties device. A modified Thermal Response Test device (TRT) trigged the underground heat transfer. The test site area is located in the Villaverla area, in the North Eastern Venetian Plain (Italy). The experimental measurements have been then compared with FEM modelling simulation outcomes, in order to verify the coupling of thermo-geophysical model and simulation output. Finally, the FEM model can be used for aquifer pollution/contamination prediction and management.