The Horticulture Innovation Lab's Pallet Dryer

Aware of the need for a simple and efficient dryer for grains and other bulk-handled commodities, we wondered if we could develop a modification of the UC Davis chimney dryer, which has proved to be so successful for drying of fruits, vegetables, and even fish.  The requirements that we felt should be met by such a dryer are that it needs to have relatively large capacity (100 kg minimum), provide protection from rain, birds, and rodents, be portable, inexpensive, and constructed, as much as possible, with locally-available materials and technologies.  To meet these requirements, we designed the UC Davis Pallet Dryer, a solar-heated bin dryer. 

Using the Pallet Dryer to Dry Coffee

As an example of the effectiveness of the dryer, the data in this report show temperatures, humidities and bean moisture content during experiments testing the dryer for drying green washed coffee beans.  The bin was loaded with ca. 50 kg of coffee beans with a moisture content of 48%.  The control comprised beans on a raised bed covered with a hoop greenhouse structure, mimicking what is commonly used in production areas. Following this trial, the bin was loaded using a serpentine method compared with control.

The pallet dryer was very effective in drying green washed coffee beans, and the direct bin system was probably faster, and certainly less complex than the ‘serpentine’ arrangement.  Both systems dried the beans considerably faster than the raised bed system that was used as a control.