Review Paper/ A Review of Thermal Response Test Analysis Using Pumping Test Concepts by Jasmin Raymond 1 , Ren´ e Therrien 2 , Louis Gosselin 3 , and Ren´ e Lefebvre 4 Abstract The design of ground-coupled heat pump systems requires knowledge of the thermal properties of the subsurface and boreholes. These properties can be measured with in situ thermal response tests (TRT), where a heat transfer fluid flowing in a ground heat exchanger is heated with an electric element and the resulting temperature perturbation is monitored. These tests are analogous to standard pumping tests conducted in hydrogeology, because a system that is initially assumed at equilibrium is perturbed and the response is monitored in time, to assess the system’s properties with inverse modeling. Although pumping test analysis is a mature topic in hydrogeology, the current analysis of temperature measurements in the context of TRTs is comparatively a new topic and it could benefit from the application of concepts related to pumping tests. The purpose of this work is to review the methodology of TRTs and improve their analysis using pumping test concepts, such as the well function, the superposition principle, and the radius of influence. The improvements are demonstrated with three TRTs. The first test was conducted in unsaturated waste rock at an active mine and the other two tests aimed at evaluating the performance of thermally enhanced pipe installed in a fully saturated sedimentary rock formation. The concepts borrowed from pumping tests allowed the planning of the duration of the TRTs and the analysis of variable heat injection rate tests accounting for external heat transfer and temperature recovery, which reduces the uncertainty in the estimation of thermal properties. Introduction In situ thermal response tests (TRT), also referred to as borehole thermal conductivity tests, are used to estimate 1 Corresponding author: D´ epartement de G´ eologie et de G´ enie G´ eologique, Universit´ e Laval, 1065 Avenue de la M´ edecine, Qu´ ebec (Qu´ ebec), G1V 0A6, Canada; +1 418 656 2131; fax: +1 418 656 7339; jasmin.raymond.1@ulaval.ca 2 D´ epartement de G´ eologie et de G´ enie G´ eologique, Universit´ e Laval, 1065 Avenue de la M´ edecine, Qu´ ebec (Qu´ ebec), G1V 0A6, Canada. 3 D´ epartement de G´ enie M´ ecanique, Universit´ e Laval, 1065 Avenue de la M´ edecine, Qu´ ebec (Qu´ ebec), G1V 0A6, Canada. 4 Institut National de la Recherche Scientifique, Centre Eau Terre Environnement, 490 de la Couronne, Qu´ ebec (Qu´ ebec), G1K 9A9, Canada. Received March 2010, accepted December 2010.  2011, The Author(s) Ground Water  2011, National Ground Water Association. doi: 10.1111/j.1745-6584.2010.00791.x subsurface and borehole thermal properties, which are required for the design and sizing of ground-coupled heat pump systems. Estimated properties are the thermal con- ductivity of the subsurface and the thermal resistance of the borehole. These properties are needed to calcu- late the required length of ground heat exchangers in a given application, which is the main cost associated with a ground-coupled heat pump system. An accurate estima- tion of thermal properties from TRTs therefore has a direct impact on the efficiency and costs of heat pump systems (Marcotte and Pasquier 2008). During a standard TRT, water flowing in a closed loop installed in a ground heat exchanger is heated with an electric element to provide a heat source that perturbs sub- surface temperatures (Gehlin 2002). The typical depth of ground heat exchanger is between 100 and 150 m. Water temperatures at the inlet and the outlet of the ground heat exchanger and flow rates are measured during the test. 932 Vol. 49, No. 6 – GROUND WATER – November-December 2011 (pages 932 – 945) NGWA.org