engleski

Determination of subsurface thermal properties for heat pump utilization in Croatia

Project GeoMapping was conducted in order to commence the process of mapping shallow geothermal potential in different regions of Croatia. Heat pumps coupled to closed-loop borehole heat exchangers (BHE) have been widely utilized and investigated theoretically and experimentally in the past few decades. Theoretical models are based on the assumption of a homogeneous and isotropic medium, which does not correspond to real subsurface conditions. Long-term performance of BHEs depends on the balance between heat extraction during the heating period and heat injection into the surrounding ground during the cooling period. This balance depends on climate of the region and ground thermal properties, which is why it is necessary to investigate the potential corresponding to local conditions. Subsurface conditions vary between the Pannonian part in the NE and the Dinaridic part in the SW of Croatia. Eight pilot sites have been chosen for exploratory core drilling, four in each of the regions. As a part of this project different approaches for determination of ground thermal properties were applied: direct measurement of rock/sediment thermal properties at laboratory scale and conventional and distributed thermal response tests (TRT and DTRT) in natural scale. Thermal properties of the most frequent subsurface materials in Croatia have been determined, and it was found that properties in the Dinaridic part are more favourable for BHE installation, but also harder to predict.

ground thermal conductivity; direct measurement of thermal conductivity; distributed thermal response test; heat pumps; Croatia

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