Design Considerations for Borehole Thermal Energy Storage (BTES): A Review with Emphasis on Convective Heat Transfer

Figure 9

(a) A groundwater-filled BHE in unfractured rock, where heat transfer from the two warm shanks (upflow and downflow) of a U-shaped heat exchange pipe to the borehole wall is facilitated by thermally driven convection; (b) a BHE backfilled with grout and where conduction is the main heat transfer mechanism; a coaxial open borehole heat exchange arrangement.