Enhancing Thermal Performance of Vertical Ground Heat Exchangers Through a Central Borehole Removal Design

The high initial cost of ground heat exchanger (GHE) systems, particularly in applications with significant annual building thermal load imbalances, remains a major barrier to their adoption. In traditional rectangular grid patterns of boreholes, thermal saturation in cooling-dominated buildings mainly affects the central zone, rendering central boreholes less effective. This study investigates an innovative approach to enhance the thermal performance of vertical GHEs by removing these central boreholes using the pygfunction Python package. The central borehole removal design (CBRD) was implemented across various building thermal loads and ground conditions, resulting in reduced borehole interaction and a substantial decrease in total GHE length. Specifically, the CBRD approach achieved up to 51% savings in total GHE length compared to traditional rectangular grid patterns, significantly lowering the initial cost without additional expenses. Although energy consumption savings over a 30-year period were modest (up to 2.2%), the initial cost savings were substantial. Further optimizations indicated that additional reductions in borehole length could be achieved by removing boreholes beyond the central ones, while still maintaining the maximum entering fluid temperature (EFT). Yet, additional optimizations are needed as achieving optimal configurations requires detailed information on factors such as available land area and drilling depth limits, which are site-specific.