GNGTS 2019 - Atti del 38° Convegno Nazionale

172 GNGTS 2019 S essione 1.3 The idea principally starts from the needing of data networking useful for the optimization of low enthalpy geothermal systems. Indeed, the creation of detailed geothermal mapping based on petrological (lithotypes, mineralogical structures and textures), geochemical (fluid) and petrophysical (thermal conductivity) characterization is the only way for obtaining reliable information on thermal characteristics of the subsoil (Viccaro et al., 2016). These maps have the advantage to provide immediate information on the most suitable depths for the installation of geothermal probe systems (Claessonj and Eskilson, 1987). Results furnished for several lithologies investigated in this work have been also used for evaluations of the physical properties useful for the direct use of low-grade geothermal energy, emphasizing the fundamental role played by the lithology, structural and textural characteristics of the rocks on the final thermal conductivity of a layer. Geological and structural field work combined with thermal data of the subsoil have been established to be fundamental for the optimization of a direct use power system for a specific building in Santa Marina Salina. Understanding of the lithological characteristics of the subsurface, along with petrographic characteristics of rocks, revealed to be essential for the correct planning of the probe (geo-exchanger) field and the associated ground source heat pump (Tab. 1). Fig. 2 - Map of the geothermal potential (W/mK) for the studied area from 0 to 150 m depth (1:2000). a) 0-50 m in depth; b) 50-100 m in depth; c) 100-150 m in depth. Tab. 1 - Low enthalpy power plant dimensioning. Geothermal Heat Exchanger Maximum extraction per GHE [kW] 6 Maximum insertion per GHE [kW] 7 Appropriate number of GHE 5 GHE Depth [m] 125 Drilling meter [m] 625 This innovative approaches to the evaluation of low-grade geothermal resources could be certainly applied to other geological contexts and could increase the penetration degree into still reluctant markets - like in Italy - towards this type of renewable energy. References Claessonj Eskilson P 1987 Conductive heat extration to a deep borehole: Thermal analyses and dimensioning rules (University of Lund, Sweden). De Astis G Ventura G Vilardo G 2003 Geodynamic significance of the Aeolian volcanism (Southern Tyrrhenian Sea, Italy) in light of structural, seismological, and geochemical data Tectonics vol 22 issue 4.