Development of Pico Solar Crop Dryer (POD) for Farm Level Grain Drying by Small Holder Farmers in Africa

2019-08-13T16:43:58Z (GMT) by Mingyuan Chen
For African farmers, proper drying is considered to be the biggest single factor in determining whether grain can be effectively stored without deterioration. The primary goal of the project is to develop and test the Pico solar crOp Dryer (POD). The overall goal is to improve the POD’s performance, making it acceptable to small holder farmers in Kenya and other developing countries, and positioning it for commercialization. In the POD tests shelled maize was placed in wooden or plastic trays and that were covered with plastic sheets. In the final design, seven small fans of the type used for cooling electronics moved air through the dryer. Power was supplied by a 12 volt, 30 Watt Solar Panel and a 12 volt 7 ampere hour lead acid battery. A charge controller allowed the fans to draw energy from both the solar panel and the battery. The POD was tested at Purdue from 2017 to 2019. The most recent Purdue test on freshly harvested maize was conducted in September 2018. The POD was able to dry 142 kg of 30.1% mc maize to 13.3% in 24.5 hours of drying over 3 calendar days giving an overall drying rate of 0.68 percentage points per hour. The POD dried the maize in 0.84 of the time required to dry maize on a tarp. In the summer of 2018, the components for assembling 5 POD’s were prepared and sent to Kenya for testing. The tests were conducted in Nakuru county in November 2018, and in Trans-Nzoia, Uasin Gishu, and Nandi counties in March 2019. Overall average drying rates for the tests varied, depending on weather conditions, from 0.58 to 0.97 percentage points per hour. A thin layer drying equation was adapted for use in investigating the effects of weather conditions and the airflow rate on the POD drying rate. Adoption of the POD by small holder farmers in Kenya and other developing countries should lead to a reduction in post-harvest losses caused by improper drying. Although testing has been primarily focused on drying maize, it could be adapted for drying other crops.