Group Thermal Response Testing for Energy Piles


Thermal response testing is an in situ technique for characterising the thermal conductivity of the ground around a borehole heat exchanger. The test has seen renewed interest in recent years as an increasing number of ground heat exchangers are being constructed to provide renewable heating and cooling energy as part of ground source heat pump systems. The thermal response test involves applying a constant heating power to the ground via a circulating heat transfer fluid. Most test rigs are set up to cater for deep boreholes, with available heat transfer lengths typically more than 100m, and therefore have electrical heater capacities of a corresponding size. Pile heat exchangers are generally much shorter and the heat exchange length can be a little as 10m. This means that many standard thermal response test rigs cannot provide a low enough heating power and there is a risk of excessive temperature changes developing, especially during longer duration tests which can be recommended for larger diameter piles. One solution is to carry out the thermal response test on a group of piles, thereby increasing the effective heated length. This has the added advantage of testing a larger volume of soil. This paper examines the principles behind group thermal response testing for energy piles and considers the advantages and limitations of the approach with reference to a case study.

Meeting Name

16th European Conference on Soil Mechanics and Geotechnical Engineering, ECSMGE 2015 (2015: Sep. 15-17, Edinburgh, United Kingdom)


Civil, Architectural and Environmental Engineering

Keywords and Phrases

Boreholes; Cooling Systems; Geotechnical Engineering; Heat Exchangers; Heat Pump Systems; Heat Transfer; Piles; Soil Mechanics; Soil Testing; Soils; Thermal Conductivity, Borehole Heat Exchangers; Electrical Heater; Ground Heat Exchangers; In-Situ Techniques; Renewable Heating; Temperature Changes; Thermal Response; Thermal Response Test, Geothermal Heat Pumps

International Standard Book Number (ISBN)


Document Type

Article - Conference proceedings

Document Version


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© 2015 The authors and ICE Publishing, All rights reserved.

Publication Date

01 Sep 2015

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