Experimental study on thermal behavior of energy piles in sand with different temperature levels subjected to heating cycles

With the increasing global demand for sustainable energy sources, the utilization of shallow geothermal energy has emerged as an effective solution for heating and cooling buildings, roads, and bridges. Among various active geothermal structures, energy piles not only serve structural functions but also operate as ground heat exchangers, offering considerable environmental and economic advantages over conventional heating and cooling technologies. Despite their growing use in both developed and developing countries, challenges in the design and uncertainties in the performance of energy piles under different loading conditions remain key obstacles to the development of precise implementation standards. Extensive research including field tests, numerical modeling, and physical modeling has been conducted to better understand the thermo-mechanical behavior of energy piles. However, formulating a comprehensive scientific framework and design code still requires further investigations that consider geological and climatic influences. While this technology helps reduce energy consumption and environmental pollution, it introduces specific design challenges due to thermal and mechanical loading. Numerical and experimental studies have shown that seasonal thermal loads can cause stress and displacement changes in energy piles, though such changes are generally within acceptable limits under standard operating conditions. In this study, the ۱-g physical modeling approach was used to thoroughly investigate the behavior of an energy pile. The tests were conducted in a small-scale laboratory setting using Firoozkooh sand No. ۱۶۱ and a closed-end aluminum pile as a heat exchanger with water as the circulating fluid. Two experiments were carried out to study the effect of applied temperature change on the pile. In the first test, a ۱۰°C temperature rise was applied, while in the second test, the pile was subjected to a ۲۰°C increase. The axial thermal displacements showed almost linear and reversible paths during the heating and cooling cycles, indicating that the pile could return to its original state after thermal fluctuations.

کلیدواژه ها:

Energy pile ، Renewable energy ، Thermal loading ، Heat exchanger