Development and Testing of a Multipurpose Solar Dryer for Smallholder Farmers – Corn (Zea mays) Drying

Ravindra Shrestha, Purdue University


The world population is expected to reach 10.5 billion by 2050 and it is estimated that food supplies would need to increase by 60% to meet the food demand. In densely populated tropical regions of Africa, Asia and the Americas, spoilage due to inadequate drying of crops and aflatoxin contamination results in high postharvest losses (PHL). A preliminary study of maize postharvest practices of smallholder farmers in Kenya and Senegal was conducted in order to determine smallholder post-harvest practices, and the causes and remedies for postharvest losses in Sub-Saharan Africa (SSA). Samples of shelled maize being dried had an average moisture content of 18% in Kakamega and 25–26% in Velingara. Aflatoxin in maize was found above the action level (20 ppb) in 14% of the samples in Velingara, while 20% of samples in Kakamega showed 1-6 ppb of aflatoxin. 72% of surveyed farmers in Kakamega and 26% in Velingara mentioned rain as the biggest challenge during drying of maize. Other major problems faced by the farmers during crop drying were birds and livestock eating grain, spillage, contamination from dust and rodents. Analyses from the surveys provided insight on technical approaches for drying that would be most likely to be adopted in both the communities. This work further involved the design, development and testing of solar dryer prototypes. FLUENT analysis of the first dryer prototype as well as lack of uniform drying of maize indicated need for improvement in airflow inside the dryer. Addition of six exhaust fans on the floor and two inlet fans in the back, along with two fans in the front, showed better and consistent airflow. The second dryer prototypes were fabricated accordingly and tested with field drying experiments of maize in different geographical locations - West Lafayette, Kenya and Senegal. The field test was a comparative analysis of maize drying using the multipurpose solar dryer with open-air sun drying on the drying trays and a tarp, respectively. The bottom trays inside the dryer and open-air trays dried maize at significantly faster rates compared to upper dryer trays and tarp in almost every experiment. The thermal efficiency of the solar dryer on first days of drying in the three locations ranged from 23–65%, 31–50% and 33–65%, respectively, depending on the loads and initial moisture content of grain. An average rise of 5–7°C (maximum up to 11°C) above the ambient temperature was observed during the experiments.




Ileleji, Purdue University.

Subject Area

Alternative Energy|Agriculture|Agricultural engineering

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