Experimental performance of a passive greenhouse solar dryer for paddy

Abstract

Sun drying is a popular post-harvest operation to maintain the quality of rice during the storage period. Farmers use different treatments and thicknesses for sun drying of paddy in Ampara district, Sri Lanka. A study was conducted to evaluate the drying treatments' suitability and effectiveness as practiced by local paddy farmers during the drying process. The grain with an initial moisture content of 28% (dry basis) was sun-dried with three types of drying treatment and three levels of thickness of grain. This experiment was conducted between 8.30 am and 4.30 pm at the South Eastern University of Sri Lanka in August 2020. Two dryers were fabricated, and it was found that the duration of drying of paddy from 28% to 13% moisture content on a dry basis was 300 to 660 minutes depending upon the drying treatments and thickness. The thermal storage greenhouse dryer is reasonable at shallow thickness with less time to reach the necessary moisture level than other drying treatments. A thermal storage greenhouse can be utilized for drying paddy at 4 cm thickness for 420 minutes. It was found that with an increase in the thickness of paddy from 2 cm to 6 cm, the drying time increases. A statistically significant interaction was obtained between drying treatments and thickness level on moisture removal of paddy. Therefore, the moisture removal rate differs from the paddy's drying treatments and thickness under thermal storage passive type greenhouse.