Dynamic performance of soil thermal energy storage with internal and external boreholes control strategy for space heating

This study dynamically assesses the performance of a borehole thermal energy storage (BTES) system using a residential vertical U-shaped buried pipe configuration for space heating. Compared with traditional BTES full-switching pipeline control strategies, this study proposes a novel strategy that emphasizes dynamic operating characteristics and focuses on internal and external operating strategies to address heating demand profiles. A numerical model is built to evaluate the impact of zoned pipeline activation sequences, inlet flow rate, and insulation layer thickness on soil thermal energy storage and heating efficiency. Results reveal that initiating the internal pipeline zone first enhances total thermal energy storage capacity by 14.89 MJ and the thermal storage efficiency by 14 %. Increasing both the flow rate and the thickness of the insulation layer enhances the thermal energy storage efficiency. The total thermal energy storage can be increased by 2.3 MJ when the flow rate is increased by 1 m/s and by 1.8 MJ when the thickness of the insulation layer is increased by 20 mm. During heating phases, short-term heating demand benefits from prioritizing internal pipelines, whereas prolonged heating requires prioritizing external zones to maintain high thermal efficiency. The research results provide guidelines for the dynamic management of BTES, emphasizing that strategies should be selected based on demand patterns and operational flexibility.