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The joint research of Croatian, Swiss and Slovenian researchers will focus on the development of modelling approaches (different scales) for the use of medium and deep borehole heat exchangers and subsurface energy storage concepts. Different hydraulic and thermal conditions and the effects of groundwater flow will be considered. The proposed project will address the utilisation of geothermal energy in two specific environments. In the border area between north-western Croatia and north-eastern Slovenia (western part of the Pannonian Basin), the potential of revitalising abandoned deep oil and gas wells for the use of geothermal energy will be investigated. The revitalisation of wells with closed systems (by circulating brine in a closed circuit) for direct heating purposes or as heat storage is being considered. 

In the pilot areas of Zagreb and Ljubljana, the utilisation of geothermal energy competes with other uses of the subsurface. The project will develop a new geothermal probe concept suitable for the utilisation of geothermal energy in urban areas. The collection and interpretation of geological data in the pilot areas will form the basis for the development of geological, hydrogeological and thermal 3D models, which will be used for modelling the heat transfer in the boreholes. The models will be linked through optimisation procedures to a decision support system that will enable better planning for efficient and sustainable use of geothermal energy in the pilot areas and areas with similar geological characteristics.