Thermal Response Testing of Large Diameter Energy Piles

Linden Jensen-Page, Fleur Loveridge and Guillermo A. Narsilio
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Linden Jensen-Page: Department of Infrastructure Engineering, University of Melbourne, Parkville, VIC 3010, Australia
Fleur Loveridge: School of Civil Engineering, University of Leeds, Woodhouse Lane, Leeds LS2 9JT, UK
Guillermo A. Narsilio: Department of Infrastructure Engineering, University of Melbourne, Parkville, VIC 3010, Australia

Energies, 2019, vol. 12, issue 14, 1-25

Abstract: Energy piles are a novel form of ground heat exchanger (GHE) used in ground source heat pump systems. However, characterizing the pile and ground thermal properties is more challenging than for traditional GHEs. Routine in-situ thermal response testing (TRT) methods assume that steady state conditions in the GHE are achieved within a few hours, whereas larger diameter energy piles may take days or even weeks, thereby incurring significant costs. Previous work on pile TRTs has focused on small diameters up to 450 mm. This paper makes the first rigorous assessment of TRT methods for larger diameter piles using field and laboratory datasets, the application of numerical and analytical modelling, and detailed consideration of costs and program. Three-dimensional numerical simulation is shown to be effective for assessing the data gathered but is too computationally expensive for routine practice. Simpler fast run time steady state analytical models are shown to be a theoretically viable tool where sufficient duration test data is available. However, a new assessment of signal to noise ratio (SNR) in real field data shows how power fluctuations cause increased uncertainty in long duration tests. It is therefore recommended to apply transient models or instead to carry out faster and more cost-effective borehole in-situ tests for ground characterization with analytical approaches for pile characterization.

Keywords: shallow geothermal; ground source heat pump; energy piles; foundations; thermal response test; numerical analysis (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2019
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (8)

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