Thermal Performance Analysis on the Seasonal Heat Storage by Deep Borehole Heat Exchanger with the Extended Finite Line Source Model

Deep borehole heat exchanger is promising and competitive for seasonal storage in the limited space underground with great efficiency. However, performance of essentially deep reaching kilometers was seldom studied. In addition, previous research rarely achieved comprehensive assessment its thermal due to storage. Insight into complicated transfer characteristics during whole process prior charging subsequent discharging urgent need be clarified. To this end, an extended finite line source model proposed investigate stages. It developed modifications classical consider spatio-temporally non-uniform distribution flux density anisotropic conductivity rock. general, simulation results demonstrate that deteriorates rapidly both stages, making it impossible sustain long-term efficient operation. Specifically, discovered low temperature utilized only upper section as effective section, enhancement extraction potential heating season not significant. While high by could enhance 30 40 days initial stage heating. Throughout discharging, maximum up 11.27 times efficiency evaluated at 2.86 based on average exchange rate. The findings study are intended provide a guidance decisionmakers determine most suitable strategy facilitate application engineering practice.