engleski

Hydrogeological research for water-source heat pump utilization in Babin kuk peninsula (Dubrovnik, Croatia)

The study was conducted in order to determine optimal locations for the positioning and design/development of extraction and injection wells with total capacity of 50 l/s which will be used in a water-source heat pump system of a hotel. Since the location is in vicinity of the sea, the idea was to extract sea water. The research was carried out in three phases. (1) Initial hydrogeological prospection was done by mapping structural elements and determining the positions of tension fractures in the rock mass, representing the most promising structural element to ensure favorable hydraulic properties of the future wells. The main obstacle in positioning the boreholes was the size of the available terrain. Drilling of the first piezometer had demonstrated the assumption about the favourability of tensional fractures as a target. (2) Borehole cores of the two drilled piezometers were analyzed and main hydrogeological and engineering geological properties were determined (3) Locations of two abstraction wells and two reinjection wells were determined. Abstraction wells were positioned on the same discontinuity further from the coastline, while two reinjection wells were placed on another discontinuity recognized at the ground surface closer to the coastline. Pumping tests were conducted on all wells. Maximum wells capacity was 170-420 L/s, depending on the well. However, constant pumping of such high quantities would cause capacity reduction of all wells. It can be concluded that the positioning of the wells was adequate since every single well has high enough yield to supply water for projected heat pump system by itself. Wells further from the coastline are more favourable to serve as abstraction wells since water temperature is more constant. Although water temperature will certainly experience some seasonal variations, it will be far less pronounced than in the case of direct intake from the sea, increasing the seasonal performance factor of entire heat pump system.

water-source heat pump, borehole positioning, structural features, hydraulic parameters

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