Comparison of Geological and Shallow Geothermal Characteristics of some Adriatic Regions in the Circum–Adriatic Countries (LEGEND project)

none3The Adriatic Area shows one of the best climatic and geological conditions for fully exploiting the potentials of low temperature geothermal energy with ground-source heat pumps (GSHP) due to the presence of a medium temperature sedimentary basin across the Western Adriatic shore and the shallow geothermal conditions which characterize the entire Eastern Adriatic Countries. The participating regions in the LEGEND project (IPA Adriatic programme) provide benchmarking reports to be able to exchange experiences of shallow geothermal energy potential and to overcome barriers for faster development of GSHP for heating and cooling in the Adriatic region. The whole Adriatic territory has very diverse geological and hydrogeological characteristics. The Southern Alps, the External Dinarides and the Apennines are mostly represented by carbonate rocks, the latter two also by marl and sandstone (flysch rocks). Alluvial sediments (conglomerate, gravel, sand, silt, clay) are found along the narrow riverbeds and in wider groundwater basins, i.e. Po valley alluvial fan deposits (Italy). Thermal conductivity and volumetric heat capacity values are quite similar to the same rock types everywhere in the Adriatic region, in dry and wet conditions, typically in the range 2.4 to 3.0 W/(m·K) and 2.3 MJ/(m3K) respectively for limestones, 2.4 W/(m·K) and 2.2 MJ/(m3K) for flysch rocks, or for example, important for alluvial deposits as clay with 1.6 W/(m·K) and 2.4 MJ/(m3K), and as gravel including sand and silt with 2.1 W/(m·K) and 2.4 MJ/(m3K). Temperatures, geothermal gradients and heat flow density (HFD) are mostly below the world mean values for continents, i.e. geothermal gradient in the karstic areas of south west Slovenia and in Istria is in a range 10 to 25 mK/m, similar in Montenegro (Podgorica region) with up to 30 mK/m and HFD of 20 to 50 mW/m2. However, restricted areas with elevated values exist, e.g. in the upper 500 m of the Slovenian coastal area the geothermal gradient is up to 45 mK/m with a HFD same as the world mean value for continents (71 mW/m2). Average and elevated values are found also in Province of Ferrara with gradients from 20 to 65 mK/m.mixedDušan Rajver; Joerg Prestor; Francesco TintiDušan Rajver; Joerg Prestor; Francesco Tint