Experimental study on energy pile thermal-structure response during high temperature heat storage

Abstract

The combination of energy pile and underground heat storage is expected to be an effective way of clean urban heat supply in the future. High-temperature underground heat storage (circulation fluid temperature >50 °C) can further enhance heat transfer efficiency. However, this mode increases thermal-structural safety risks in energy pile. The novelty of this study is the exploration on the mode of “energy pile + high-temperature heat storage” and the feasibility of a short-term cooling method to mitigate pile thermal-structural response. In this study, an experimental system for high-temperature heat storage of energy pile (end-bearing pile) was built. The thermal-structural responses of energy pile under intermittent heat storage were investigated. The results showed that, during the process of five intermittent heat storage cycles, the pile top extended upward, the additional compressive axial force was exerted on each part of the pile, and the pressure between pile and soil increased. The rest period in the cycle could alleviate the thermal-structural responses. However, the alleviating effect was gradually weakened. The addition of active cooling could bring a beneficial effect on the thermal-structure responses of the pile in at least two subsequent cycles. A small amount of heat storage loss could reduce more thermal-structural safety risks for energy pile.