This cassava dryer is the result of a team project in appropriate technology intended for farmers in Sub-Saharan Africa. Powered by a 12-volt battery, the dryer eliminates the need to travel long distances to a cassava plant or wait for sun-based drying. The battery is charged by farmers using a novel technology that harnesses energy from pre-existing sources, such as human-powered bicycles or spinning motorcycle wheels, and converts it into mechanical or electrical energy. This technology and the cassava dryer are both made from locally-available materials and skills so as to encourage a sustainable and local economy.

Initial dryer concepts ranged from tumblers to “salad spinners” to dehumidifiers. We ultimately chose a dehydrating concept that uses a fan to carry away moisture.

To validate this concept, we first ran experiments on a food dehydrator within a custom-built humidity chamber. The results were positive, and we moved forward with designing a prototype.

The crux of our design lies in the use of a “Kentank” – a commonly used water tank in Sub-Saharan Africa. While it blocks the sun, it protects the cassava from rain and vermin. Wooden slats slide through holes cut in the tank to hold trays made of wood and overlapping chicken wire.

We prototyped with a similarly-sized tank available in the United States. The cassava is dried by small, 12-volt computer fans at the top, which are similar to parts that might be found in a junkyard in Sub-Saharan Africa (such as the fan from a broken-down car).

A significant factor in drying times was the density and size of the cassava on the trays. In addition to designing the hardware, we ran experiments to determine the optimal arrangement and ensure that drying times made sense considering the cost of the dryer.

In order to mimic the hot and humid conditions of Sub-Saharan Africa in the middle of winter in Connecticut, we built a full-scale humidity chamber to test our prototype and different cassava densities.