Thermal response testing of precast pile heat exchangers: Fieldwork report

Centrum Pæle A/S, Aalborg University, VIA University College and INSERO Horsens are partners in an industrial PhD project dealing with quadratic cross section pile heat exchangers. This document presents the fieldwork undertaken in the project at two test sites in Denmark: one in Horsens and another in Vejle. The tasks have been carried out between January 2014 and February 2016. The fieldwork consists mainly of several thermal response tests (TRT) of precast pile heat exchangers. Pile heat exchangers, also known as energy piles, are thermo-active ground structures that utilize reinforced concrete foundation piles as vertical closed-loop heat exchangers. The interpretation of the in-situ TRT yields the effective thermal conductivity of the ground λs [W/m/K] and the borehole or pile thermal resistance Rb [K·m/W]. These estimated thermal parameters form the basis for dimensioning a planned ground source heat pump installation based on closed loop vertical ground heat exchangers. However, this report does not cover topics related to the interpretation of TRT data.
The report is organized as follows: first, the concept of TRT is explained. Second, the test sites are described. Third, the field work is presented and a summary of the future work regarding the methodology to treat the data from the tests is provided. Finally, further documentation of the fieldwork, the pile heat exchangers and the TRT equipment is extended in diverse appendices.