Ground Source Energy

A thermo-active pile with a single U-loop is analysed using a 2D thermal analysis, which provides the correct distribution of temperature in a section far from any of the boundaries. The temperature along the circle that contains the pipes is subsequently averaged and converted into a time-series that can be used in 2D coupled THM analysis to determine forces and displacements arising from thermo-active pile operation. The integral of the temperature distribution in the full 2D section can also be used to establish the thermal performance of the pile in W/m, enabling more accurate thermal design of these heat exchangers.

When a larger number of U-loops is used, heat transfer from the pipes to the pile and the surrounding ground accelerates and overall larger temperatures are obtained. This indicates a considerably larger thermal performance in W/m and explains that current designs maximise the number of pipes within the cross-section of the thermo-active pile. However, with greater heat transfer, mechanical forces within the structure increase and need to be acknowledged in its design, as seen in the work by Liu et al. (2020) [accepted version] for thermo-active piles and Sailer et al. (2022) [accepted version] for thermo-active retaining walls. There are also implications in terms of thermal interference when thermo-active piles are arranged in pile groups - read more about this in Liu & Taborda (2023) and Liu & Taborda (2024).