Experimental and numerical studies on an energy piled wall: The effect of thermally activated pile spacing

Abstract

Over the last decades, converting foundation elements such as piles, retaining walls and tunnel linings into energy geo-structures has gained popularity around the world. These geo-structures form part of ground source heat pump (GSHP) systems to constitute a clean, renewable, and economical solution for space heating and cooling. This work utilises experimental investigations in combination with numerical simulations to study the thermal performance of energy piled walls, specifically regarding the effect of thermo-active pile spacing. This knowledge can aid towards better design guidelines and the determination of the number of piles to be thermally activated in the wall system. The experimental results from a section of a pilot energy soldier piled wall in Melbourne (Australia) and the numerical results from a validated finite element model suggest that the thermal performance of piled walls can be significantly affected by close pile spacing. In addition, parametric analyses were performed to understand the role of some other key design parameters. The results indicate that the depth of the wall impacts the thermal performance of the GSHP system more significantly than the thermal conductivity of the ground. Considering a real-world scenario where a fixed number of piles are constructed for a typical building at relatively close spacings, one may increase the “thermal” pile spacing by activating less piles overall. It is found that activating every other pile (1/2 of the total number of piles) or every other second pile (1/3 of them) can still provide over 70% or 50%, respectively, of the maximum thermal energy compared to activating every pile.