Technical review on coaxial deep borehole heat exchanger

Abstract This review paper summarizes recent developments regarding geothermal exploitation using coaxial deep borehole heat exchangers (DBHE). Specifically, this study focuses on field tests, analytical and semi-analytical approaches, numerical simulations. First, tests applications of DBHE are summarized future work for the is suggested. Then, ongoing modeling approaches evaluated capability incapability describing physical behaviors. Lastly, key factors design discussed based collected results. Regarding should focus more (1) long-term performance; (2) effect groundwater flow within formation fractures; (3) technology larger diameter boreholes; (4) new cheap materials insulated inner pipe; (5) treatment fluid, pipe wall, different working fluid; (6) economic analysis DBHE-based power plant. As methods simulations, it important to consider dependence fluid properties pressure temperature. Besides, verification calibration empirical models fluids other than water such as CO 2 be performed laboratory tests. Different pump parameters optimized obtain maximum thermal a DBHE, an recommended by many researchers. An intermittent pattern could realistic when DBHE. To further improve performance continuous research enhance transfer still important.