Development and Performance Evaluation of a Dual Heat Dryer; a Renewable Energy Technology for Sustainable Processing of Agro-Produce

Rural agricultural sector in developing countries such as Sri Lanka is still lacking efficient and cost effective devices for processing of agricultural produce. A dual heat dryer which utilises rice husk and solar energy for thermal energy generation required for the drying process was designed and developed at the Institute of Post Harvest Technology (IPHT), Sri Lanka for dehydration of agricultural produce. Performance evaluation of the dual heat dryer gave promising results for adoption by the farming community. The dryer is able to generate drying air temperatures ranging from 40 to 110°C thus, facilitating a variety of crop produce to be dried, such as drumsticks, bitter gourd, papaya, mango, lemon grass, mushroom and many more, with natural convection airflow. In most instances drying using solar energy alone is insufficient to accomplish the drying operation because the drying process has to be continued up to 10-15 hrs extending into the night. The incorporation of biomass energy into solar drying enables the drying process to be continued even in the absence of sun shine and thereby ensuring product quality. The benefit/cost ratio is 10:1 in the dryer and hence adoption by the farming community or in rural areas is extremely feasible. Furthermore, the renewable energy technology discussed in this paper would help to enhance the socio-economic development of the rural community in developing countries like Sri Lanka.