Mapping the low-enthalpy geothermal potential of Quaternary alluvial aquifers in Slovakia

The study proposes a methodology for the construction of a thematic map of the suitability of the Quaternary shallow alluvial sediments for heat pumps. This map was compiled on the basis of the minimum groundwater temperature, specific capacity of a well, the aquifer thickness, the groundwater temperature range (amplitude), and ranking of the months according to the lowest groundwater temperature. A second methodology allows the creation of a thematic map of the groundwater energy potential. This map is based on two criteria: 1. the specific capacity (l s−1 m−1) of the borehole and 2. the temperature change due to the consumption of heat energy. The calculated energy in kW was classified into one of seven usability categories. The highest rated categories in both maps coincided with areas with the largest sediment volumes (the widest alluvia and the highest sediment thickness) coinciding with the highest river flows. Suitability decreases considerably at higher elevations (mountainous) river catchments with a small volume of sediment as characterized by narrow valleys and low sediment thicknesses. There is a logical link between these factors in relation to the potential for heat pumps exploitation.