Independent operation of centrally located borehole heat exchangers coupled with PVT modules for ground thermal load balancing

초록

This paper presents an independent operation strategy for a centrally located borehole heat exchanger (BHE) connected to photovoltaic-thermal (PVT) modules, aimed at mitigating ground thermal imbalance and interference in hybrid ground source heat pump (HyGSHP) systems. The system targets buildings with high domestic hot water (DHW) demand, wherein outer BHEs operate in parallel to handle the load, while the central BHE is thermally recharged using heat from PVT modules. This selective thermal compensation enables localized ground recovery and spatially responsive operation. An analytical finite line source (FLS) model was developed to simulate individual BHE behavior and long-term ground responses. Over a 20-year simulation, the proposed strategy improved entering water temperature (EWT) by up to 2.5 degrees C and reduced life cycle cost (LCC) by up to 50 % compared to conventional parallel operation. Additionally, the load imbalance index decreased by up to 77.2 % through centralized heat injection and thermal interference. These results highlight the advantages of combining analytical modeling with independent BHE control for improving performance and cost efficiency in HyGSHP systems under highly unbalanced conditions.

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