Determination of Optimal Distance Between Boreholes

Abstract

In Ground Source Heat Pump Systems (GSHPS), distance between boreholes is a very important parameter for reliability, long life time and performance of the whole system. In large scale applications of GSHPS, more than one borehole is needed and determination of the optimal distance between boreholes becomes an important issue. In this study, the effect of distance between boreholes on heat transfer rate per unit borehole length (unit HTR value) is computationally investigated. Four different configurations consisting of 2, 3, 5 and 9 boreholes are considered. 3 and 6 months averaged unit HTR value of the most critical borehole in each configuration is compared with that of single borehole to determine the performance loss. Variations of performance loss due to thermal interactions of boreholes with both time and distance are analyzed. Furthermore, the effects of thermal conductivity of ground on temperature distributions around borehole is also examined. Results can be used to determine the optimal borehole distance for various applications.