The pilot site Savica is located in the capital of Croatia, Zagreb. The pilot site is focused on the existing well Savica-1 that was drilled in 1981. The well was drilled to give insight into geological conditions and development of the Zagreb geothermal aquifer in its southeast part.
The depth of the well is 2202 m, and the drilling stopped in the targeted lithotamnian limestones and brecciaconglomerates. The targeted layers were tested in 1982 and production of geothermal brine was achieved. Afterwards, the well was left for further testing that did not occur to this day. Due to very low production capacity of the brine and the fact that the well is located in the industrial zone of the city near a cogeneration power plant, the Savica-1 well was selected as a pilot site for the repurposing into borehole thermal energy storage (BTES) technology. Heat storage would be performed during summer months from the power plant when only electricity and DHW is distributed to district heating system system of Zagreb.