OPERATION
The average solar insolation for all evaluations is shown in figure 4 over the 2-day assessment period. Temperatures within the dryer were generally elevated over ambient levels in all trials, particularly in the plenum. Temperatures measured in the thermal rock storage area were observed to be greater than ambient levels until 7:00 a.m. on the second day of each trial. Although data was not collected for trials without the thermal rock bed, these results indicate at least some heat dissipation into the drying cabinet through the night. This is further evidenced by overnight, average exhaust velocities of 0.011 m s-1. However, some heat loss was experienced farther in the cabinet as evidenced by slightly decreased temperatures recorded at each subsequent tray level as well as in the chimney. In fact, exhaust temperatures were reduced by approximately 16.7°C as compared with the incoming heated air delivered into the plenum.