Test di risposta termica per la geotermia superficiale: un approccio geostatistico

Thermal Response Test (TRT) is an onsite test used to characterize the thermal properties of shallow underground and of the borehole used to extract / inject heat. The consolidated deterministic methodology based on the "Infinite Linear Source" (ILS) theory is reviewed and a nested probabilistic approach for TRT output interpretation is proposed. 5 key parameters (ground thermal conductivity, ground volumetric heat capacity, borehole thermal resistance, initial time, final tima) are required for applying the theory and must be deduced by the test records. Once chosen, through different methods, initial and final test time, based on geostatistical residual model in the time-logarithm, the drift analysis of temperature records allows for robust ground thermal conductivity identification, whose precision is measured by estimation variance. Afterwards a new monovariate regression on the original data allows for the identification of the theoretical relationship between ground capacity and borehole resistance. Once chosen the most appropriate probabilistic distribution functions, it is possible to find the joint probabilistic distribution function conditional to the relationship. Finally the conditional expectation allow for identifying the correct and optimal couple of the estimated values