Table 1 Description of the TRT case studies

Hydro-geology

Dolostones with shallow clayish interpositions (0–150 m), compact crystalline limestone (150–170 m), aquifers levels at 2, 22, and 150 m

Dry gravel, saturated gravel, sand, and silt with saturated gravel (0–71.5 m), calcareous bedrock (71.5–115 m), aquifer level at 30 ÷ 32 m

Test BHE

Double U pipe, Φ_ext = 40 mm, D = 152 mm, H = 170 m, Termoplast Plus grouting (λ_gr = 2.0 W/(m K))

Double U pipe, Φ_ext = 32 mm, D = 130 mm, H = 115 m, Termoplast Plus grouting (λ_gr = 2.0 W/(m K))

Undisturbed ground temperature T₀

9.8 °C

13.1 °C

Expected ground properties

λ = 2.7 W/(m K)

λ = 2.23 W/(m K)

α = 1.17·10⁻⁶ m²/s

α = 9.37·10⁻⁷ m²/s