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

Figure 4

Calculated difference in temperature (black line) between scenario 1 (with heat recharge) and scenario 2 (without heat recharge) at end of the heat extraction period ( days), together with best-fit polynomial approximation to the curve (red dashed line). The total difference in stored heat is calculated by integrating the polynomial with respect to radial volume between 0.06 and 20 m and is estimated as almost 9000 kWh (which it should theoretically be). The distribution of this stored heat with radial distance is shown in the background histogram bars by 1 m radial slices. The histogram suggests that the bulk of the stored heat is at radial distances of 3 to 10 m from the borehole (peak at 6-7 m). The polynomial best fit curve has an equation .