Analysis of Geo-Temperature Restoration Performance under Intermittent Operation of Borehole Heat Exchanger Fields

Chaofeng Li, Jinfeng Mao, Zheli Xing, Jin Zhou and Yong Li
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Chaofeng Li: Institute of Military Environmental Teaching and Research, PLA University of Science and Technology, Nanjing 210007, China
Jinfeng Mao: Institute of Military Environmental Teaching and Research, PLA University of Science and Technology, Nanjing 210007, China
Zheli Xing: Institute of Military Environmental Teaching and Research, PLA University of Science and Technology, Nanjing 210007, China
Jin Zhou: Institute of Military Environmental Teaching and Research, PLA University of Science and Technology, Nanjing 210007, China
Yong Li: Institute of Military Environmental Teaching and Research, PLA University of Science and Technology, Nanjing 210007, China

Sustainability, 2015, vol. 8, issue 1, 1-14

Abstract: Intermittent operation can improve the coefficient of performance (COP) of a ground source heat pump (GSHP) system. In this paper, an analytical solution to analyze the geo-temperature restoration performance under intermittent operation of borehole heat exchanger (BHE) fields is established. For this purpose, the moving finite line source model is combined with the g-function and the superposition principle. The model takes into account the heat transfer along the borehole, thermal interference between BHEs, and the influence of groundwater flow. The accuracy of the model is validated through comparison with an experiment carried out under intermittent operation. The model makes it possible to analyze the geo-temperature restoration performance and its influencing factors, such as BHE spacing, heat flow rate, operation mode, and groundwater flow. The main conclusions of this work are as follows. The heat transfer along the borehole should be considered when analyzing the geo-temperature restoration performance. When the BHE spacing increases, the soil temperature change decreases and the heat recovery improves. Therefore, adequate borehole separation distance is essential in the case of a multiple BHE system with unbalanced load. The presence of groundwater flow is associated with interference between the BHEs, which should not be ignored. In the case of long-term operation, the groundwater flow is beneficial to the geo-temperature recovery process, even for downstream BHEs. Finally, a greater groundwater flux leads to a better geo-temperature recovery.

Keywords: soil temperature recovery; intermittent operation; borehole heat exchanger fields; influence factors (search for similar items in EconPapers)
JEL-codes: O13 Q Q0 Q2 Q3 Q5 Q56 (search for similar items in EconPapers)
Date: 2015
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (2)

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