Influence of spatial variability of ground conditions on energy pile thermal yield
Influence of spatial variability of ground conditions on energy pile thermal yield
Energy piles are a cost-effective alternative to conventional boreholes in shallow geothermal systems as they can lower capital investment while maintaining efficient heat exchanging capability when properly designed. Among a range of parameters that affect the thermal yield of energy piles, ground thermal and hydraulic properties have a decisive influence. Studies on energy pile thermal yield usually consider homogeneous ground conditions, or, to a lesser extent, horizontally layered ground conditions. However, spatial geological heterogeneity exists not only between the soil-stratified layers in the vertical direction but also within each horizontal layer. This study investigates the impact of spatial hydro-geological heterogeneity on heat transfer within the ground. A three-dimensional numerical model is developed to solve for heat transport considering several numerically generated lognormal autocorrelated random fields of ground thermal conductivity and permeability values, transformed from geostatistical random Gaussian distributions based on their statistical distributions. Results show that the assumption of homogeneous ground characteristics has a marginal effect, up to ~6% in energy provision, when the variations in thermal and hydraulic properties are small, making it a pragmatic assumption in such cases. However, the uncertainty in energy yield prediction becomes considerable, in between ~13% to ~25%, for significant ground variability. Moreover, accounting for the variability in hydraulic properties such as the permeability is more detrimental than the thermal conductivity.
Q. I. Alqawasmeh; Guillermo A. Narsilio; M. J. Kreitmair
18th European Conference on Soil Mechanics and Geotechnical Engineering (ECSMGE2024)
E - Environment, water and energy
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