Heat Extraction Distributed Thermal Response Test: A Methodological Approach and In-situ Experiment

Abstract

The Thermal Response Test (TRT) is a worldwide adopted in-situ thermal behaviour of the borehole can differ from the result obtained by means of a heat injection TRT. This issue is of peculiar interest for water-filled boreholes, where the BHE thermal resistance is related to the water temperature and density gradient in the borehole filling-space. In this operating mode a heat pump is usually employed and the constant heat transfer rate condition required by the models can be difficult to be respected since the efficiency of the cooling-machine is dependent on the inlet carrier-fluid temperature to the evaporator.In this paper a methodology to perform a heat extraction DTRT with constant heat transfer rate to the ground is presented. The approach described has been applied in a real water-filled borehole installed in Stockholm, Sweden. Data analysis results are presented and the outcomes regarding the evaluation of the local borehole thermal resistance are discussed and compared with those from an erlier heat injection test performed in the same borehole.

Colloquium 2016: Assessment of subsurface thermal conductivity for geothermal applications

“…The electric heating elements in a TRT unit can be replaced by a heat pump to run the test in heat extraction mode (Witte et al 2002;Rolando et al 2017). An air source heat pump is used, but the heat extraction rate can be subject to fluctuations, which can be minimized by installing a water reservoir and proper control valves in the TRT unit.…”

Calibration and Uncertainty Quantification for Single-Ended Raman-Based Distributed Temperature Sensing: Case Study in a 800 m Deep Coaxial Borehole Heat Exchanger

“…In the reviewed literature, application of the DTS technique to GSHP research first appears in the context of Distributed Thermal Response Testing (DTRT) [18][19][20][21]. DTRTs based on DTS is still a current topic of research and even seems to have regained interest in recent years [22][23][24][25][26][27][28].…”

Newton-Raphson method applied to the time-superposed ILS for parameter estimation in Thermal Response Tests

“…TRTs are now performed worldwide for both commercial and research purposes (IEA ECES Annex 21, 2013;Spitler & Gehlin, 2015;Witte, 2016;Zhang et al, 2014). Several developments of the TRT method have been undertaken since Mogensen's initial proposal, including:  Distributed Thermal Response Tests (DTRTs) through the use of fiber optic cables (Acuña, 2013;Fujii et al, 2009;Radioti et al, 2018;Sakata et al, 2018), wireless sensors (Martos et al, 2010) or wired sensors (Acuña, 2008;Aranzabal et al, 2016;Yu et al, 2013)  accounting for groundwater flow on the thermal response (Molina-Giraldo et al, 2011;Raymond et al, 2011;Rivera et al, 2015;Witte, 2007)  using different methods to calculate the average fluid temperature (Beier, 2011;Beier et al, 2012;Beier & Spitler, 2016;Lamarche et al, 2017;Marcotte & Pasquier, 2008)  modified control strategies or methodologies (Choi & Ooka, 2017;Raymond et al, 2015;Rolando, 2015;Rolando et al, 2017;Witte et al, 2002)  estimation of uncertainties (Witte, 2013)  definition of a criterion for the test duration (Poulsen & Alberdi-Pagola, 2015).…”

“…The method requires knowledge of the temperature change from time zero to infinity, thus extrapolation for large times must be performed since TRTs are finite in duration. Other authors have proposed experimental methods to keep the power as constant as possible, see for instance Witte et al (2002), Rolando (2015) and Rolando et al (2017). The ASHRAE guidelines for TRTs recommend power variations with a standard deviation lower than 1.5% of the average value (ASHRAE, 2011).…”