Portable Solar-Energy Drying System with Mechanical Stirring Device for Cereals under Egyptian Conditions

Document Type : Original Article


1 Department of agricultural engineering, faculty of agriculture, Damietta university, Egypt

2 Agricultural Engineering Department, Faculty of Agriculture Kafrelsheikh University, Egypt


The main goal of this present study is utilizing the available solar energy to dry main cereals under Egyptian conditions using a portable drying system (PDS) with mechanical stirring. The developed multi-commodity portable drying system has a dimensions of 5.5 x 2 x 2.8 m (length, width and height, respectively), and the height is 2.8 m. The dimension of air heating room was 2.4 x 2.4 x 1.3 m (length x width x height, respectively). A transparent 4 mm polycarbonate sheet used to cover both drying chamber and heating room. A movable transitionally stirring system powered by electric motor was attached to the dryer and it consisted of a stirring arms made from a rectangular plates of stainless steel that had 1900 mm long 20 mm thickness and 70 mm height and fixed in the steering shaft that moves by chains at both ends. The power which required for stirring and rotational moving have been calculated and analyzed their arms motion to define the suitable horsepower motor to be used. Three solar modules (300 W each) as solar panels was used to produce 900 watts was used to produce 900 watts (with considering the solar panel efficiency) go run the electric motor. The drying time and drying temperature were employed as a scientific base to compare between the dryer development and the open air sun drying. The harvested rice grain was used in 30 mm thick of layers in both dryers. The overall area used to install the dryer was 14 x 6 m. The new drying system was evaluated based on the drying time to achieve the target crop moisture content for storage and the difference in crop layers during the drying process. Also, rice milling was conducted after drying to record the milling indicators for both the PDS an open air solar drying. The average difference in temperature was 0.16 C for the PDS, while it was 2.77 C for the open air sun drying for two different measuring time, 10 am and 2 pm. The less differences in layers’ temperature are due to the stirring operation that is undertaken mechanically and on the desired base. The PDS takes less time than conventional sun drying to dry the rice grains as the rice grains reached to 12 % MC after 10 hours of drying process. PDS gave better milling quality in term of head rice than the traditional open air solar drying method.