Thermal charging of boreholes

This paper presents experimental study of thermal charging the boreholes that are used for inter-seasonal thermal storage of heat and coolth integrated with ground-coupled heat pump and unglazed solar collectors. After 180 days of thermal charging, it was observed that the temperature of the ground at 21 m depth and 1 m distance from the borehole had increased by 2.5 °C. The unglazed collectors are able to collect heat for charging the heat storage borehole at an average of 43.9 MJ day−1. The system is able to charge borehole at an average heat transfer rate of 57 W m−1. A comparison of the experimental results with the simulated results of a TRNSYS model of the system showed a good agreement. The mean efficiency of the unglazed solar collector during 180 days charging operation was found to be 30% and the mean efficiency of the system was found to be 38%.