The solar crop dryers used in these experiments were built from a
design commonly found in Tanzania (Fig. 1—obtained from Bertha
Mjawa, Ministry of Agriculture Food Security and Cooperatives, Republic
of Tanzania government). The dryer consists of a lightweight wooden
frame that is 1.5 m tall, 1.8 m wide, and 1 m deep wrapped in a 4 mm
thick clear plastic sheet supported on four 0.3 m legs. There is a corrugated
piece of aluminum painted black on the floor of the dryer which
is called the absorber plate (for absorbing solar radiation). There are
four removable drying racks (of 0.8 m × 0.8 m), two of which are near
the top of the dryer and two near the absorber plate on the bottom.
Each rack has a square frame filled with mesh onto which sliced tomatoes
are placed. Cooler, dry air enters the dryer near the absorber plate
through a screened window and rises across the drying racks and tomatoes.
Warm, moist air is removed at the top of the dryer through another
screened window.