Metaheuristic optimization of borehole layouts for cost-effective ground-source heat pump systems

The economic viability of ground source heat pump (GSHP) systems is strongly influenced by the design of vertical ground heat exchangers (GHEs), as borehole drilling constitutes a major portion of the initial installation cost. Although GSHP systems provide efficient and sustainable heating and cooling by exploiting the thermal stability of the ground, reducing the total borehole field (often called borefield) drilling length remains a key challenge, particularly for large-scale applications. In this study, an optimization-based design framework is proposed using ground heat conduction analysis to reduce the total required borehole length while maintaining long-term heat pump performance. A reference design is first established using a conventional regularly spaced borehole arrangement in accordance with standard design practice to determine the required number of boreholes. Then, a genetic algorithm is employed to optimize the spatial distribution of boreholes with the objective of minimizing the total design length which directly impacts drilling-related cost. To ensure applicability of this framework under limited computational power available among designers, measures to improve the computation time of an optimized borefield layout such as modeling symmetrical layouts are assessed and those that are employed are validated. The results show a 14% reduction in total borefield length relative to the base-case design. These results are validated against pygfunction, a more advanced borefield simulation tool.