Site investigation for energy geostructures

Abstract

Energy geostructures are structure or infrastructure foundations used as heat exchangers as part of a ground source heat pump system. While piles remain the most common type of energy geostructure, increasingly infrastructure projects are considering the use of other buried structures such as retaining walls and tunnels for heat exchange. To design and plan for construction of such systems, site investigations must provide appropriate information to derive analysis input parameters. This paper presents a review of what information regarding the ground, and also the structures themselves, would be required for the ground energy system design process. Appropriate site investigation methods for energy gesotructures are reviewed, from desk study stages through in situ testing to laboratory testing of samples recovered. Available methods are described and critically appraised and guidance for practical application is given.

Thermal Response Testing of Large Diameter Energy Piles

“…When applied to a borehole GHE, this minimum time criteria typically equates to less than ten hours [32]. However, when applied to larger diameter energy piles the minimum time becomes several days or even weeks [25,33], having significant implications for TRT durations and, hence, cost.…”

“…In the absence of in-situ characterization, the ground thermal properties are typically determined from databases of regional data or the results of laboratory scale tests on soil samples. These approaches are reviewed in terms of accuracy in [30,33]. Recent analysis by [40] also includes the cost benefit of field versus desktop and laboratory characterization and shows the benefits of the former only being realized in GSHP systems above about 50 kW capacity.…”

Investigation on the thermal response of steel pipe energy piles with different backfill materials

“…A parametric analysis was made to find the best pairs of ground thermal conductivity (λg) and the thermal conductivity of the backfill material (λc) values, which is related to the pile thermal resistance. More than one combination of values can provide best-fit thermal conductivity and thermal resistance from experimental results in terms of minimum RMSE [47,48]. However, as there are a good number of tests, it was possible to compare the results and check the validity of the values.…”

Évolution des paramètres pressiométriques d’un massif argileux non saturé soumis à des variations monotones et cycliques de la température

“…Les géostructures énergétiques sont des ouvrages géotechniques qui permettent un échange thermique entre une structure et le terrain via la circulation d'un fluide caloporteur dans un circuit intégré. Ces systèmes utilisent le sol comme une source de chauffage ou de refroidissement pour les bâtiments adjacents (Fromentin et al, 1999 ;Laloui et al, 2003 ;Brandl, 2006 ;Bourne-Webb et al, 2016 ;Loveridge et al, 2017 ;Antoinet et al, 2017). Il peut s'agir, par exemple, de murs de soutènement, de revêtements de tunnel (Zhang et al, 2013) ou de pieux énergétiques (Pahud et al, 1999 ;Moel et al, 2010).…”