Collective behavior of boreholes and its optimization to maximize BTES performance

• Published in: Applied energy 2023-08, Vol.343, p.121208, Article 121208
• Main Authors: Ekmekci, Ece, Ozturk, Z. Fatih, Sisman, Altug
• Format: Article
• Language: English
• Subjects: Borehole thermal energy storage; Configurational effects; Ground source heat pumps; Thermal storage efficiency
• ISSN: 0306-2619; 1872-9118; 1872-9118
• DOI: 10.1016/j.apenergy.2023.121208

Borehole layout strongly affects the behavior of borehole heat exchangers (BHEs) and changes the performance of a borehole thermal energy storage (BTES). This study investigates the existence and importance of the optimum collective behavior of BHEs to maximize the performance of BTES. Charge benefit ratio, storage efficiency and configurational benefit factor are proposed as performance indicators for better and finer performance evaluations of BTES systems. A small-scale BTES consisting of ten boreholes arranged on a concentric double-ring layout is considered as an application. Performance variations with the inner and the outer radii of the borehole field are analyzed for the first five years of operation. The temperature fields of different configurations show the transition from collective to individual behavior of boreholes, which leads to an optimal radial configuration maximizing the performance indicators. It is seen that the indicators strongly depend on both inner and outer radii and they reach their maximums for the same distinct radial configuration. The optimum arrangement can almost double the thermal performance indicators. It is thus of great importance to optimize collective behavior to maximize the usage of stored thermal energy. The results are qualitatively general and represent the common behavioral patterns of BTES systems. •BHE layout affects the collective behavior and thermal performance of a BTES.•The transition from collective to individual behavior of BHE is analyzed.•The collective behavior is optimized for maximum thermal performance of a BTES.•The same optimum layout is obtained for all thermal performance indicators.