Energy tunnels allow the harvesting of untapped heat at shallow depths in the underground to meet the thermal energy requirements of buildings and infrastructures over large areas. Such heat can derive from two sources: the ground surrounding energy tunnels and the air circulating in the environment internal to these tunnels. To date, various investigations have addressed the role of ground characteristics on the heat exchange potential of energy tunnels, as they significantly influence the amount of geothermal energy that these geostructures can harvest. Despite the comparable role of airflow characteristics on the amount of aerothermal energy that energy tunnels can harvest, no extensive analysis of this problem has been reported before this study. To fill in this knowledge gap, this paper investigates the heat exchange potential of energy tunnels for a broad range of internal airflow characteristics. From this perspective, the work specifically provides: (i) the first charts, validated against representative experimental evidence, summarizing the thermal power that energy tunnels can harvest per unit surface for different convection heat transfer coefficients and temperatures associated with internal airflows, as well as undisturbed temperatures and effective thermal conductivities of the ground; and (ii) the analysis of an energy tunnel at the regional scale, based on the application of the developed charts and the use of a large hydrogeological dataset. Based on the results of this study, it is concluded that the internal airflow characteristics significantly influence the harvesting of aerothermal energy through energy tunnels. Together with the ground characteristics, which can markedly vary along energy tunnel applications at the regional scale, internal airflow characteristics rule the thermal power that can be harvested through such heat exchangers, deserving thorough quantifications for any adequate energy performance assessment.

能量隧道允许在地下的浅层收集未开发的热量，以满足大面积建筑物和基础设施的热能需求。这种热量可以来自两个来源：能量隧道周围的地面和在这些隧道内部环境中循环的空气。迄今为止，各种研究已经解决了地面特征对能量隧道热交换潜力的作用，因为它们显着影响了这些地质结构可以收集的地热能量。尽管气流特性对能量隧道可以收集的空气热能的量具有相当的作用，但在本研究之前没有报道过对这个问题的广泛分析。为了填补这个知识空白，本文针对各种内部气流特性研究了能量隧道的热交换潜力。从这个角度来看，这项工作具体提供了：（i）第一张图表，根据代表性实验证据进行了验证，总结了能量隧道在不同对流传热系数和与内部气流相关的温度下每单位表面可以收集的热功率，以及不受干扰的温度和地面的有效热导率；(ii) 在应用开发的图表和使用大型水文地质数据集的基础上，对区域尺度的能源隧道进行分析。根据这项研究的结果，得出的结论是，内部气流特性显着影响通过能量隧道收集空气热能。连同在区域尺度上沿能源隧道应用可能显着变化的地面特性，内部气流特性决定了可以通过此类热交换器收集的热功率，值得对任何适当的能源性能评估进行彻底的量化。