ABSTRACT

An indirect type solar dryer integrated with a sawdust stove that can be used for drying agricultural products was designed, constructed and evaluated. The research was aimed at enabling continuous drying of products during the cloudy period and off-sunshine hours. Hence, an additional means of supplying heat was included so that drying can be made continuous during the night time and in rainy seasons. The dryer mainly consists of a solar collector, drying chamber, and sawdust stove. The solar collector is made up of 4 mm thickness single layer glass, 2 mm black aluminum absorber plate, which is enclosed in a casing made from wood. The drying chamber houses the drying tray, is made from plywood with 2 cm thickness. The backup heater uses sawdust as the biomass feedstock and supplies heat to the drying chamber, when burnt. Different tests were carried out in order to evaluate the performance of the dryer. Solar hybrid test gave a better result when compared to the solar drying test and open sun drying. The average dryer temperature obtained during the hybrid solar drying was 39.5°C, whereas the solar dryer was 36.04°C.The dryer was also evaluated using plantain. Moisture content, drying rate, as well as drying efficiency were used in the performance evaluation .Moisture content was reduced from 51% to 15% fewer than fifteen sunshine hours during the solar hybrid drying test, while it took nineteen sunshine hours to dry the same quantity of product, during the solar drying test. Drying rate were 27.lg/hr. and 21.4glhr. for the solar hybrid dryer and solar dryer respectively. Drying efficiency was found to be 43.5% and 39.25%, for the solar hybrid dryer and solar dryer respectively. The solar hybrid dryer gave a better finished dried product compared to sun dried and solar dryer product