Current Drying Methods

A traditional storage and drying method for corn that is still on the cob. The cribs are made from wood and have mesh-like sides to allow air flow through the corn. They vary in size and shape, though most are significantly longer than they are wide. The rate at which the corn dries is heavily dependent on the humidity, wind speed, and how easily the air can flow through the crib (Food and Agriculture Organization of the United States, 1994).

Sun drying method that utilizes a raised, ventilated platform to increase airflow around the grain. This method is similar to roadside drying, but the rate of moisture taken out of the grain is increased due to the rate at which the air is replaced around the grain (Chua & Chou, 2003).

Active solar drying utilizes the same principles as passive drying, but includes a pump or fan to increase airflow over the grains. The increased airflow can make a significant difference in drying times because the air that has absorbed moisture from the grains is being replaced at a higher rate (Chua & Chou, 2003). The pump or fan require some form of power, which most farmers in developing countries do not have easy access to. Alternative forms of power like solar and wind could be viable options given they are not too expensive. If the farmer is located near a body of flowing water, he could potentially use a water wheel to power a turbine or a fan directly.

According to The Principles, Classification and Selection of Solar Dryers, indirect-type dryers use natural convection of air for drying. The dryers are able to generate additional resistance for the air movement through the use of vertically placed trays on racks with some space in between the consecutive trays. This arrangement of trays works to achieve the “chimney effect,” which increases the vertical flow of air resulting from the difference in density of the air in the cabinet and atmosphere. Designs are typically comprised of an air-heating solar-energy collector, an insulated ducting, a drying chamber and a chimney.