The influence of the ground coupled heat pump's labor on the ground temperature in the boreholes – Study based on experimental data

• Whole year monitoring of ground coupled heat pump boreholes has been conducted.
• During heating season the boreholes cooled down by 0.3 K–1.1 K on average.
• In the summer two among five boreholes have been actively regenerated.
• Temperature of borehole regenerated by solar collectors has risen by 0.2 K.
• Temperature of borehole regenerated by free-cooling has returned to prior state.

The paper presents the results of observations made during whole year monitoring of the temperature of the 78 m deep boreholes. The boreholes serve as lower heat source for ground coupled heat pump used as one of heating sources in Energy Technology Center in Świdnica (Poland). Two of those boreholes were regenerated during warm season by free-cooling system and heat from solar collectors. It has been observed that the boreholes temperature changes along with the outdoor temperature changes during heat pump labor. During the heating season the heat source has cooled down by 0.3–1.1 K in comparison to the starting point. The temperature of non-regenerated borehole was lower by 0.4 K in the beginning of the next heating season in comparison to the former one. The temperature of borehole regenerated by free-cooling (63% of returned energy) has been kept the same, and the temperature of borehole regenerated by solar collectors (99% of returned energy) has risen by 0.2 K in comparison to the point before former heating season.