Long-term performance evaluation for deep borehole heat exchanger array under different soil thermal properties and system layouts. (15th February 2022)

• Record Type: Journal Article
• Authors: Cai, Wanlong; Wang, Fenghao; Chen, Chaofan; Chen, Shuang; Liu, Jun; Ren, Zhanli; Shao, Haibing
• Is Part Of: Energy. Volume 241(2022)
• Publication Date: 2022-02-15
• Subjects: Deep borehole heat exchanger array -- Heating system -- Soil thermal property -- System layout -- Long-term sustainability; Power resources -- Periodicals; Power (Mechanics) -- Periodicals; Energy consumption -- Periodicals; 333.7905
• DOI: 10.1016/j.energy.2021.122937
• Languages: English
• ISSNs: 0360-5442

Abstract

Abstract: To meet the prospect of carbon neutrality, Deep borehole heat exchanger (DBHE) shows good potentiality in extracting deep geothermal energy for building heating, especially in densely populated urban areas of northern China. To investigate the influence on different soil thermal properties and system layouts of the DBHE array, a comprehensive numerical model has been established by OpenGeoSys software coupled TESPy toolkit and a series of scenarios are simulated. Results show that thermal conductivity lay a more important influence on heat extraction performance for DBHE array, rather than volumetric heat capacity. The thermal plume of DBHE array will grow larger along with higher thermal diffusivity. For typical geological parameters in Xi'an, the inter-borehole spacing should not be set below 15 m or it will bring a risk of freeze in circulation. The heat extraction performance and long-term sustainability of single-line layout are obviously better than other layout patterns, also with a smaller ground area needed to deploy the boreholes. This study implies that soil thermal conductivity is the core factor in determining the heat extraction performance of DBHE array and also gives suggestions for the system design of DBHE array in the aspect of borehole spacing and system arrangement. Highlights: Long-term performance evaluation under different soil thermal properties for DBHE array. The level of soil thermal conductivity has a crucial impact on the heat extraction of DBHE array. Radius of thermal plume after long-term operation increases with soil thermal diffusivity. Proper inter-borehole spacing and arrangement geometry are suggested for DBHE array.