A ground source heat pump (GSHP) system provides efficient space heating and cooling and thus is regarded as a contributor to achieve net-zero emissions targets. This study focuses on an economical type of GSHP system – energy walls where earth retaining walls are equipped with pipes to act as geothermal heat exchangers in addition to being geotechnical structures. A detailed numerical investigation is performed to study the long-term heat exchange mechanism between the walls and the surrounding ground. The work highlights the significance of the existence and magnitude of groundwater flow on the temperature distribution of the ground and the thermal performance of energy walls. Compared to the case when there is no subsurface flow, the energy retaining wall can offer up to a 6 % better coefficient of performance (COP) or provide up to 1.3 times higher thermal yield for relatively slow groundwater flow velocities of 0.013 m/d. The COP can improve up to 93 % and thermal yield up to 23 times for high velocities of 2 m/d, even in extremely cooling-dominant thermal demand cases. The study also shows that the ground thermal conductivity plays a crucial role on performance when groundwater flow is minimal, however, as the convective heat transfer resulting from the groundwater flow becomes more dominant, the influence of thermal conductivity gradually diminishes. It is also found that the absorber pipe flow rate has a rather small effect on the system thermal performance, of less than a 10 % COP difference in all studied cases. This suggests that obtaining reliable hydrogeological information specifically on the groundwater flow velocity and direction are crucial for accurate predictions and optimal design for energy retaining walls and large scale GSHP installations. The insights from this study can improve the design and enhance the uptake of retaining walls for efficient heating and cooling of above/underground spaces - critical components in achieving a clean energy future.

地源热泵 (GSHP) 系统提供高效的空间加热和冷却，因此被视为实现净零排放目标的贡献者。本研究的重点是一种经济型地源热泵系统——能量墙，其中土质挡土墙除了作为岩土结构外，还配备了管道，作为地热热交换器。进行了详细的数值研究，以研究墙壁与周围地面之间的长期热交换机制。这项工作突出了地下水流的存在和大小对地面温度分布和能量墙热性能的重要性。与没有地下水流的情况相比，能量挡土墙可以提供高达 6% 的性能系数 (COP) 或高达 1。对于 0.013 m/d 的相对较慢的地下水流速，热产量高出 3 倍。对于 2 m/d 的高速，即使在以冷却为主的热需求情况下，COP 也可以提高高达 93%，热产量提高高达 23 倍。研究还表明，当地下水流量最小时，地面热导率对性能起着至关重要的作用，然而，随着地下水流产生的对流传热变得更加主导，热导率的影响逐渐减弱。还发现吸收器管道流量对系统热性能的影响相当小，在所有研究案例中 COP 差异小于 10%。这表明，获得可靠的水文地质信息，特别是关于地下水流速和方向的信息对于能量挡土墙和大型 GSHP 装置的准确预测和优化设计至关重要。这项研究的见解可以改进设计并加强挡土墙的吸收，以有效加热和冷却地上/地下空间——实现清洁能源未来的关键组成部分。