Actively heated fiber optics based thermal response test: A field demonstration

Zhang, Bo; Gu, Kai; Shi, Bin; Liu, Chun; Bayer, Peter; Wei, Guangqing; Gong, Xülong; Yang, Lei

doi:10.1016/j.rser.2020.110336

Cited by 46 publications

(23 citation statements)

References 44 publications

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“…The test was performed with a heating cable unit and a cable length of 22.5 m [3]. The heating cable technique was used because it is an affordable, easy and sound technique to infer the underground thermal conductivity as already demonstrated in the literature [3][4][5]. Submersible temperature sensors (accuracy 0.1 • C, resolution 0.032 • C) were placed along the heating cable at depths of 2.5, 5, 10, 12.5, 15, 17.5, 20 and 22.5 m from the ground level.…”

Section: Field Tests 251 Trt With Constant Heat Injectionmentioning

confidence: 99%

“…On the other hand, borehole thermal resistance cannot be properly assessed with a heating cable test. Other than being very compact and needing only 120 V power, the heating cable unit can provide a TC profile of the ground with several temperature sensors at depth, or with a fiber-optic cable [4,5]. Moreover, it does not require a BHE since it can be performed in open wells, provided that water is present to ensure thermal contact with the subsurface.…”

Section: Introductionmentioning

confidence: 99%

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Evaluation of Subsurface Heat Capacity through Oscillatory Thermal Response Tests

2021

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Two methods are currently available to estimate in a relatively short time span the subsurface heat capacity: (1) laboratory analysis of rock/soil samples; (2) measure the heat diffusion with temperature sensors in an observation well. Since the first may not be representative of in-situ conditions, and the second imply economical and logistical issues, a third option might be possible by means of so-called oscillatory thermal response tests (OTRT). The aim of the study was to evaluate the effectiveness of an OTRT as a tool to infer the subsurface heat capacity without the need of an observation well. To achieve this goal, an OTRT was carried out in a borehole heat exchanger (BHE). The total duration of injection was 6 days, with oscillation period of 12 h and amplitude of 10 W m−1. The results of the proposed methodology were compared 3-D numerical simulations and to a TRT with a constant heat injection rate with temperature response monitored from a nearby observation well. Results show that the OTRT succeeded to infer the expected subsurface heat capacity, but uncertainty is about 15% and the radial depth of penetration is only 12 cm. The parameters having most impact on the results are the subsurface thermal conductivity and the borehole thermal resistance. The OTRT performed and analyzed in this study also allowed to evaluate the thermal conductivity with similar accuracy compared to conventional TRTs (3%). On the other hand, it returned borehole thermal resistance with high uncertainty (15%), in particular due to the duration of the test. The final range of heat capacity is wide, highlighting challenges to currently use OTRT in the scope of ground-coupled heat pump system design. OTRT appears a promising tool to evaluate the heat capacity, but more field testing and mathematical interpretation of the sinusoidal response is needed to better isolate the subsurface from the BHE contribution and reduce the uncertainty.

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Section: Field Tests 251 Trt With Constant Heat Injectionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Evaluation of Subsurface Heat Capacity through Oscillatory Thermal Response Tests

2021

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“…Active‐DTS experiments have thus been conducted in sealed boreholes (Coleman et al., 2015; Maldaner et al., 2019; Munn et al., 2020; F. Selker & J. S. Selker, 2018) and other promising studies proposed the direct deployment of FO cables vertically into unconsolidated sedimentary aquifers using direct‐push equipment (Bakker et al., 2015; des Tombe et al., 2019). Concurrently, active‐DTS methods were largely developed and applied in unsaturated soils, offering the possibility of estimating the soil water content and thermal properties (Benitez‐Buelga et al., 2014; He, Dyck, Horton, Li, et al., 2018; He, Dyck, Horton, Ren, et al., 2018; Sayde et al, 2010, 2014; Weiss, 2003; Wu et al., 2019) or conducting distributed thermal response test for geothermal energy applications (Vélez Márquez et al., 2018; Zhang et al., 2020).…”

Section: Introductionmentioning

confidence: 99%

Numerical and Experimental Validation of the Applicability of Active‐DTS Experiments to Estimate Thermal Conductivity and Groundwater Flux in Porous Media

Simon

Bour

Lavenant

et al. 2021

Water Resources Research

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In groundwater hydrology, the characterization of the distribution of groundwater flow within the critical zone received considerable attention in the last decades (Freeze & Cherry, 1979). Our ability to quantify groundwater flow greatly controls our ability to characterize aquifers, predict contaminant transport, and understand biogeochemical reactions and processes occurring in the subsurface (Kalbus et al., 2009; Poeter & Gaylord, 1990). Groundwater flow at interfaces such as recharge and discharge areas also plays a key role in the preservation of groundwater-dependent ecosystems (Kalbus et al., 2006; Sophocleous, 2002). The quantification of groundwater fluxes is also particularly relevant for geothermal energy since they control heat exchange and storage capacities (Diao et al., 2004). Similarly, the characterization of seepage through dams, dikes, and reservoirs is also critical for geotechnical engineering (Foster et al., 2000). The spatial distribution of groundwater fluxes is largely driven by subsurface heterogeneities. Thus, in past decades, the characterization of the distribution of groundwater fluxes and their quantification relied on the capacity of characterizing and modeling the spatial variability of hydraulic conductivities (de Marsily, 1976). Considering the challenge in characterizing the field variability of hydraulic properties, the use of heat as a tracer has been widely developed and applied to characterize flow in aquifers or at interfaces such as the hyporheic zone (

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“…In fact, one of the most recent works by Zhang et al. (2020) provides an alternative to the use of TRT by using active fiber‐optics, and discuss the topic at great length. Therefore, this paper will concentrate in discussing only the quantification of groundwater fluxes.…”

Section: Introductionmentioning

confidence: 99%

Heat Dissipation Test With Fiber‐Optic Distributed Temperature Sensing to Estimate Groundwater Flux

Val

Carrera

Pool

et al. 2021

Water Resources Research

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We measure groundwater flux and thermal parameters around a borehole performing a heat dissipation test by heating the armor of a single fiber‐optic cable and interpreting the resulting heating curves with a new analytical method. The procedure is similar to thermal response tests, but benefitting from the high spatial and temporal resolution of distributed temperature sensing and lasting longer, so as to measure advective dissipation. Field installation relies on an innovative method in hydrogeology, which is based on the installation of the FO cable in the annular space of the well, close to the aquifer matrix. The proposed new analytical method, expands the traditional Moving Infinitesimal Line Source Model to account for the effects of the field set up and cable materials. In fact, we show that the resulting temperature build‐up goes through four periods easy to identify using the log derivative of temperature (dT/d (ln(t))): Initial response, skin (cable insulation), conduction dominated and advection dominated. We test the proposed method in an unconsolidated shallow aquifer with controlled pumping. Results are of the same order of magnitude of independent estimates of groundwater velocity.

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Actively heated fiber optics based thermal response test: A field demonstration

Cited by 46 publications

References 44 publications

Evaluation of Subsurface Heat Capacity through Oscillatory Thermal Response Tests

Evaluation of Subsurface Heat Capacity through Oscillatory Thermal Response Tests

Numerical and Experimental Validation of the Applicability of Active‐DTS Experiments to Estimate Thermal Conductivity and Groundwater Flux in Porous Media

Heat Dissipation Test With Fiber‐Optic Distributed Temperature Sensing to Estimate Groundwater Flux

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