Thermal performance enhancement of borehole heat exchangers by thermally induced groundwater convection in aquifers

Jin Luo, Yanting Shao, Zezhou Yan, Xuesong Han and Qinghai Guo

Renewable Energy, 2025, vol. 243, issue C

Abstract: The groundwater flow can significantly influence the thermal performance of Borehole Heat Exchangers (BHEs). However, natural groundwater flows are often extremely slow. Therefore, stimulating groundwater convection in an aquifer becomes an important alternative. This paper presents a novel approach that refills BHEs with high-permeable materials to induce groundwater convection in aquifers. Testing the BHE operation in cooling mode revealed that the fluid outlet temperature of the novel BHE was 10.7–16.1 °C lower than that of a conventional BHE, indicating a significant improvement in thermal performance. To better understand the underlying mechanism, a physical model test demonstrated that the gravel-filled BHE formed a convective-flow circuit in the aquifer, transferring heat with greater efficiency than relying solely on heat conduction. Temperature monitoring further confirms that thermal stagnation near the pipe was significantly alleviated by the high content of free water. In conclusion, the reduction of heat accumulation in boreholes can be attributed to two factors: the increased heat capacity of the backfills and the induced convective flow that dissipates heat into the ground.

Keywords: Ground source heat pump (GSHP); Borehole heat exchanger (BHE); Thermal performance enhancement; Induced groundwater convection (search for similar items in EconPapers)
Date: 2025
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Persistent link: https://EconPapers.repec.org/RePEc:eee:renene:v:243:y:2025:i:c:s0960148125002010

DOI: 10.1016/j.renene.2025.122539

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