Three-dimensional analysis of multiple inclined borehole heat exchangers

This research develops and applies a numerical modelling method for inclined borehole heat exchangers (BHE) in ground-source heat pump systems. Inclined BHEs have the advantage of reducing the ground-level footprint of the overall BHE field. Computational modelling of the ground heat transfer using the commercial code COMSOL Multiphysics has revealed that inclined BHEs offer additional performance benefits compared to vertical BHE fields. When heat is injected constantly, both types of fields perform similarly at first, but over a longer period of time, the inclined BHE fields show significant benefits due to the increased ground volume in the deeper portion of the field. Similar conclusions are reached when transient loading conditions are considered. Notably, when cooling dominates, inclined BHE fields outperform vertical ones for a simulated period of 10 years. This indicates that inclined BHE fields are better equipped to handle imbalanced energy loads. To summarize, inclined BHE fields offer advantages in ground-volume utilization and resilience to energy load imbalances compared to vertical fields.