Evaluation of ground source heat exchangers system feasibility to contribute at the ecological transition of the Marche Region in the 2016 earthquakes reconstruction areas: numerical models and maps of the shallow geothermal energy potential

In 2016 central Italy was hit by a seismic sequence (Mmax 6.5) that caused human victims, damages, and collapses of buildings, changing hopelessly the urban landscape of many towns. After these events, the Marche Region started an economic program which involved measures for the restoration and reconstruction of damaged or destroyed buildings. In this context, the exploitation of shallow geothermal energy (SGE), through the installation of ground source heat exchangers (GSHEs) coupled with heat pumps, could be a useful tool for heating and cooling these new, or renovated, buildings, being SGE a renewable, clean and without surface impact technology solution for high efficiency space heating and cooling needs covering. This would strongly contribute to preserve the Central Apennine environment. To identify the most suitable areas for ground source heat exchangers, a map of the geothermal potential of the southern sectors of the Marche Region (upper-middle portion of the Potenza River) was developed. By consulting the third level seismic microzonation data made available by the National Civil Protection database, it was possible to reconstruct the stratigraphy of the area. In order to estimate the geothermal potential of the study area, the main parameters (thermal conductivity, volumetric heat capacity) were averaged over the first 100 meters of the subsoil, which is the most common depth of GSHEs. After this, all the investigated points were interpolated by means of dedicated algorithms to give a visualization of the spatial distribution of the geothermal potential throughout the study area. Further study has also involved numerical modelling approach in order to verify the thermal impact induced in the subsoil, during the time, by the system operation and detect the best solution to improve the sustainability of the geothermal solution. Indeed it was possible to reproduce, in detail, the undisturbed thermal assessment of the ground and the induced effects over time by the geothermal system operation. Starting from the 3D numerical modelling of closed loop heat exchangers field, by using the local geological and hydrogeological available features and, possibly, data produced by Ground Response Tests performed in the surrounding area, a calibration session of the modelling process was made. Several scenarios have been performed by means of the modelling analyses in order to simulate the thermal effects of GSHP running into the subsoil and detect the best countermeasures finalized to balance the heat seasonal exchange processes with the ground. A map representing the feasibility and potential of the GSHP solutions adoption is also achieved. Various graphs and images, describing the efficiency of the system and the thermal plume development in the subsoil, have been obtained.