The idea of a greenhouse dryer is to replace the function of the solar collector by a green
house system. The roof and wall of this solar dryer can be made of transparent materials
such as glass, fibre glass, UV stabilized plastic or polycarbonate sheets. The transparent
materials are fixed on a steel frame support or pillars with bolts and nuts and rubber packing
to prevent humid air or rain water leaking into the chamber other than those introduced from
the inlet opening. To enhance solar radiation absorption, black surfaces should be provided
within the structure. Inlet and exhaust fans are placed at proper position within the structure
to ensure even distribution of the drying air.
Designed properly, greenhouse dryers allow a greater degree of control over the drying
process than the cabinet dryers [17] and they are more appropriate for large scale drying.