Natural convection solar crop-dryers of commercial scale in Ghana: design, construction and performance

SYNOPSIS Traditional open sun-drying, the predominant method of food preservation in Ghana, has serious drawbacks leading to significant post-harvest losses (between 20 and 30%). Mechanical dryers can provide high quality products with minimum losses but they require sources of electrical or chemical energy, which, in the case of Ghana, are costly or scarce. This makes the development of an effective natural convection solar dryer an attractive alternative. A mixed-mode natural convection solar crop-dryer (a dryer in which the crop is dried by a combination of the direct absorption of solar radiation and by natural convection where air, heated by solar energy, is passed over the crop) has been designed. Two commercial dryers, based on this design and capable of handling between 1,000 and 1,500 kg of various agricultural products (such as cassava, pepper, maize, okra, etc.) have been constructed and partially tested at Agona-Asafo in the central region of Ghana. The results of these preliminary tests indic...