Abstract—A direct-type natural convection solar dryer and a simple biomass burner have been combined to
demonstrate a drying technology suitable for small-scale processors of dried fruits and vegetables in
non-electrified areas of developing countries. From a series of evaluation trials of the system, the capacity of
the dryer was found to be 20–22 kg of fresh pineapple arranged in a single layer of 0.01-m-thick slices. The
overall drying efficiency of the unit was calculated to be | 9%. During the same trial, the drying efficiency of
the solar component alone was found to be 22%. Other trials estimated the efficiency of the burner in
producing useful heat for drying to be 27%. Key features of the biomass burner were found to be the addition
of thermal mass on the upper surface, an internal baffle plate to lengthen the exhaust gas exit path and a
variable air inlet valve. Further modifications to further improve the performance of both the solar and biomass
components of the dryer are suggested