Technical Evaluation and Efficiency of two Solar Collector Types for Paddy Drying in Khuzestan Province

Khuzestan province produces 120,000 tones rice every year and possesses the forth rank in rice production in Iran. Paddy rice must be dried before milling. In some regions in Khuzestan, paddy is dried in traditional bed driers, resulting high costs and high losses from the point of quantity and quality. An indirect cabinet solar dryer with three trays and grooved collector was constructed to use solar energy, a project that could help farmers to increase their income and to reduce paddy losses. To measure and to record drying air temperature and humidity at different places (collector air incoming and outgoing and the drying chamber), a Digital Data Logger was designed, fabricated and mounted on the solar dryer. The dryer performance was evaluated by drying two paddy varieties (Shafagh and Anboori) in three levels of mass density of 1, 2, and 3 trays at two different solar dryer types of collectors: simple grooved collector (collector A) and grooved filled by turnery iron chaff collector (collector B). The results showed that maximum and minimum drying period required in different solar dryer treatments were 4 and 6.1 hours for Shafagh with 1 tray and for Anboori with 3 trays respectively. Longer time required for drying paddy rice in upper trays as the air flowing decreased due to increase in mass density. Mean time required for drying Shafagh variety was 12.8% shorter than that of Anboori variety. Increasing in number of trays in the solar dryer resulted in less rice losses. Results showed that utilizing solar energy, as a clean renewable energy source and appropriate method for reducing costs of  drying paddy rice, could be  recommended to use in Khuzestan province condition.