As a shallow geothermal energy development technology, energy pile contributes to sustainable development. The seepage effect has a positive effect on the heat transfer performance of the energy pile, and the heat transfer efficiency of the energy pile can also be improved by optimizing the operation strategy. Combined with the structural characteristics of the deep-buried energy pile, the heat transfer characteristics of the deep-buried energy pile are analyzed under continuous and intermittent operation conditions, and the effect of seepage on the heat transfer performance is further investigated under the intermittent operation mode. The results show that the long-term operation of the deep-buried energy pile will reduce its heat exchange performance and aggravate the heat accumulation phenomenon inside the pile body, and the intermittent operation can maintain a higher instantaneous heat exchange rate (HER) in the long-term operation compared with the continuous operation. Considering the energy demand, when the intermittent ratio is 5, the average HER of the pile body only decreases by 68.93 W, and the overall energy efficiency of the pile body is improved by 7.7%. Combined with the operating effects of different intermittent ratios, the optimal range of the circulating medium flow rate for deep buried pipe energy piles should be selected from 1.0 m3/h to 1.2 m3/h. Groundwater seepage can weaken the degree of heat accumulation inside the DBP-EP piles and improve the overall heat exchange efficiency of DBP-EP, and combined with the intermittent operation mode will be able to further alleviate the DBP-EP heat buildup. The two factors promote each other and have a positive impact on the piles, positively affecting the soil’s long-term heat exchange.
This paper describes a study on the heat transfer properties of the deeply buried pipeline energy pile group, which is an efficient and convenient geothermal development technology. Through in situ experiments and a simulation algorithm, the research investigated the heat transmission characteristics of the deeply buried pipe energy pile group and optimized different intermittent operation schemes. The findings suggest that prolonged operation of the pile cluster intensifies heat buildup within the pile foundation, thereby adversely affecting the system’s overall heat exchange efficiency. Employing an intermittent operating mode can alleviate this heat accumulation phenomenon, thereby promoting sustained heat exchange performance of the piles over time. To evaluate the comprehensive thermal interaction and energy efficiency ratio of the energy pile heat exchange system, various intermittent operation strategies were compared in the study. Among them, the intermittent operational scheme with a ratio of n = 5 was found to be optimal, with the total average heat transfer rate of the pile set only 0.51% lower than that of the continuous operational mode, but the overall energy efficiency ratio improved by 19.6%. The intermittent operational mode proposed in this study can achieve the goal of saving energy and efficiently extracting geothermal resources, providing theoretical guidance for the extraction and utilization of subsurface geothermal power by energy piles.