Geothermal Boreholes in Poland—Overview of the Current State of Knowledge

Geothermal energy can be useful after extraction from geothermal wells, borehole heat exchangers and/or natural sources. Types of geothermal boreholes are geothermal wells (for geothermal water production and injection) and borehole heat exchangers (for heat exchange with the ground without mass transfer). The purpose of geothermal production wells is to harvest the geothermal water present in the aquifer. They often involve a pumping chamber. Geothermal injection wells are used for injecting back the produced geothermal water into the aquifer, having harvested the energy contained within. The paper presents the parameters of geothermal boreholes in Poland (geothermal wells and borehole heat exchangers). The definitions of geothermal boreholes, geothermal wells and borehole heat exchangers were ordered. The dates of construction, depth, purposes, spatial orientation, materials used in the construction of geothermal boreholes for casing pipes, method of water production and type of closure for the boreholes are presented. Additionally, production boreholes are presented along with their efficiency and the temperature of produced water measured at the head. Borehole heat exchangers of different designs are presented in the paper. Only 19 boreholes were created at the Laboratory of Geoenergetics at the Faculty of Drilling, Oil and Gas, AGH University of Science and Technology in Krakow; however, it is a globally unique collection of borehole heat exchangers, each of which has a different design for identical geological conditions: heat exchanger pipe configuration, seal/filling and shank spacing are variable. Using these boreholes, the operating parameters for different designs are tested. The laboratory system is also used to provide heat and cold for two university buildings. Two coefficients, which separately characterize geothermal boreholes (wells and borehole heat exchangers) are described in the paper.