Thermo-mechanical performance of a proposed energy pile system in cold regions

Abstract

Energy piles are bi-functional structural elements that are used to support the structural loads of a building and to operate as a geo-heat exchanger for shallow geothermal energy systems. In urban areas, energy piles can eventually be used to harvest the heat loss through the basement enclosure and re-inject the energy to the building for the heating and cooling purposes. In spite of a higher thermal profile beneath the buildings due to energy loss through the below-grade envelope, an underground thermal imbalance may still occur due to the application of energy piles in cold regions. This paper aims to study the structural performance of an energy pile in cold regions considering the potential occurrence of thermal imbalance in the foundation soil through a Thermo-Mechanical (TM) analysis. This will be the first step of adoption of such a technology in Canadian cold climate. Results showed a safe margin between the pile settlement and the allowable settlement. However, the axial stress applied to the pile increased by 9% due to thermal loads. In addition, a maximum decrease of 9% in mobilized shaft friction along the pile-soil interface was recorded due to the thermal loads. To consider the energy piles as an alternative for buildings energy supply in cold regions, further considerations should be made to keep the mechanical response of the energy piles in the admissible range.