Efficient Development and Utilization of Geothermal Energy: An Analysis of the Operational Strategy for Deep-Buried Pipe-Type Energy Piles Considering Seepage Effects

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.