Design, Construction and Performance Evaluation of an Automated Mixed Mode Solar Tracking Cacao Dryer

Abstract

This study designed, developed, and undertook performance evaluation of a mixed-mode solar dryer with solar tracking collector, which is integrated with electric heaters as a backup heat source for drying fermented cacao beans. The drying mechanism was based on the combination of direct radiation and convective heating with the incorporation of electric backup heaters to address the intermittent effect of drying. The solar tracking collector maximized the
solar reception during daytime by providing sufficient heat inside the chamber. The electric heaters also provided reliable heat sources during night time, preventing the occurrence of moisture re-absorption by the beans. The developed system maintained a drying temperature range of 40-600C by automatically switching the drying modes depending on the weather conditions. At the average drying rate of 0.17kg/h in 48 hours of continuous drying, it dehydrated the cacao beans from an initial moisture content in wet basis of 57.49% to 0.65%, against the ambient temperature of 200C-360C. Drying time was shortened by 50% against traditional open or natural sun-drying, which takes 4-6 days, reducing it to two days or 48 hours. The integrated design of the mixed mode solar dyer provided the ability to carry out the drying process continuously by optimizing heat sources while maintaining the drying requirements for cacao beans. This study validated that the solar dryer is suitable for drying cacao beans.