Comparative Analysis and Performance of Solar Dryers with Backup Incinerators for Nsukka Sub-tropical and Makurdi Humid Locations Using Selected Farm Produce

A solar dryer and hybrids incorporating back up incinerators were designed and constructed for performance evaluation and analysis of efficiencies for selected farm produce of cassava grates, okra and chilli pepper in two climatic locations (sub-tropical of Nsukka and humid of Makurdi in Nigeria) at the University of Nigeria, Nsukka and Federal University of Agriculture, Makurdi, Nigeria. It consists of a solar collector, drying chamber, and incinerator. The dryer was used for drying at night; sunshine days and cloudy days. They were used for test drying, termed ‘no-load’ test (without any farm produce) and ‘on-load’ (cassava grates, okra and chilli pepper) as selected farm produce. Their respective weight losses were used to determine the reduction in moisture content. Drying was assumed to have taken place in the falling rate periods, which enabled the use of only one drying rate constant. Graphs of drying rates against time were plotted in each case and used to obtain the drying rate constant, K for the various conditions and locations. Comparison was made for the drying rate at the two locations. The efficiencies of the equipment at various locations were calculated and the drying rate efficiencies were also obtained. Results obtained showed that drying was fastest during the solar drying and least during the incinerator drying and the control drying respectively. The drying rate was also faster at Nsukka tropical location than Makurdi humid location. The mean location drying rate efficiencies obtained were 98.8%, 94.7%, and 87.4% for solar dryer, solar-incinerator dryer and incinerator dryer respectively. The computed efficiencies for the equipment were 56%, 13% and 16% for solar dryer, solar incinerator dryer and incinerator dryer respectively. The dryers can be used to substitute garri dehydration and drying of other farm produce in rural and semi-urban areas for improved quality.