Analytical approach to groundwater-influenced thermal response tests of grouted borehole heat exchangers

► Determination of the Darcy velocity based on TRT measurements. ► Calibration of the moving line source theory for TRT evaluation. ► Simultaneous determination of the thermal conductivity and the Darcy velocity. ► Successful validation of the presented method based on three different test cases. ► Determination of the correlation between thermal conductivity and Darcy velocity. For ground-source heat pump (GSHP) systems, the thermal response test (TRT) is commonly used to determine the heat transport parameters of the subsurface. The main limitation of this approach is the assumption of pure conductive heat transport, which might result in significant deviations. Based on the moving line source theory, a parameter estimation approach is introduced, which is sensitive to conduction and advection. This approach is calibrated and successfully tested against three different test cases. The presented analytical approach therefore expands the field of application of the TRT to advection-influenced conditions beyond a Darcy velocity of 0.1mday−1.