Are construction errors in the placement of ground heat exchanging loops in energy piles important to consider?

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4. Are construction errors in the placement of ground heat exchanging loops in energy piles important to consider?

Shallow geothermal energy is considered as an efficient and sustainable green technology to heat and cool buildings. Incorporating the ground heat exchanging loops (GHEs) inside structural piles, known as energy piles, increases the economic viability of the technology by reducing the high capital cost associated with drilling traditional shallow geothermal boreholes. Despite the extensive literature on loops connected in series inside energy piles, optimal distribution or lack of thereof of loops connected in parallel remain mostly unexplored. For this purpose, a three-dimensional numerical model has been built to undertake parametric analyses on an energy pile equipped with GHEs connected in parallel considering different distributions around the pile perimeter to optimise the GHEs placement. The study covers different ranges of influencing parameters, including pile diameter, pile length, flow rate, pipe diameter, and ground thermal conductivity. Results show that the GHEs placement generally has a marginal effect on the total thermal yield of the energy pile. However, the heat transfer share between individual loops is highly dependent on its distribution, particularly for certain pile diameters. This may affect maintaining the thermal equilibrium performance. Moreover, in symmetrical loop distributions, an insignificant thermal performance penalisation was observed for a range of separation-to-shank distance ratios from 0.5 to 1.5. While installing the loops in symmetrical and evenly spaced distribution (i.e., separation-to-shank distance ratio equal to 1) is recommended, the latter result indicates that there is flexibility when installing the GHEs loops, with deviations from design during construction rendering low impacts on overall thermal performance.

18th European Conference on Soil Mechanics and Geotechnical Engineering (ECSMGE2024)

E - Environment, water and energy