Dunkle’s equation was originally applied in SOLSTILL to calculate the convective heat transfer between the basin water and the cover. This is in accordance with the approach used by the majority of previous researchers. The predicted temperature of the water in the still and the measured values are shown in Figure 3 while the predicted and measured distillate produced is shown in Figure 4. As shown in Figure 3, the predicted water temperature closely follows the trends in the measured data. The maximum discrepancy is 8 0C in the

most overcast day (i. e., the second day of testing), while the differences recorded for the rest of the days were up to 5 0C. Similar results were obtained for the predicted distillate from the still. The simulation model over-predicted the experimental result every day with a maximum error of 34 % on the cloudiest day. With the use of Dunkle’s equation, the model overpredicted the cumulative distillate by 14.7% over the 7 day period of testing.

Figure 4. The predicted distillate using the Dunkle model and measured distillate from the

standard still.