Design of a solar hybrid dryer for copra drying

Abstract

A small scale, forced convection, solar-biomass hybrid dryer for drying copra has been designed, fabricated and tested for drying copra. The dryer is consisted with a solar air heater, a biomass-stove heat exchanger and a drying chamber. The biomass consumption of the dryer was found to be reduced by more than 60% when the solar air heater was in operation. The reduction of moisture content of copra from 50% to 7% was recorded after 32, 35 and 37 hours at drying temperatures of 72°C, 60°C and 55°C, respectively. The highest percentages of brown copra (13.33%) and low grade copra (1.67%) were recorded at 72°C and the remaining copra was either white or light brown. More than 75% of white copra could be produced by maintaining the drying temperatures below 60°C. Colorless coconut oil with good quality could be extracted mechanically by using both white copra and light brown copra obtained from hybrid drying.