Thermal response testing of a multiple borehole ground heat exchanger

This paper presents the methodology, results and a discussion of thermal response tests (TRTs) performed on a multiple borehole ground heat exchanger. The ground heat exchanger consisted of nine 80-m deep boreholes. TRTs with durations between 48 and 260 h were performed on individual boreholes. Tests were analysed using common evaluation methods, and ground conductivity and borehole resistance values were determined for all nine boreholes. In addition to these parameters, the undisturbed ground temperatures were also determined for individual boreholes using multiple approaches. A sensitivity analysis was performed to analyse the effects of various test and parameter uncertainties on the ground thermal conductivity and borehole thermal resistance estimations.