Abstract

Solar dryers have not been widely used in rural areas due to their high cost and relatively poor performance compared to traditional open air drying. The first phase of this project produced design criteria and a computer model for indirect natural convection dryers which have given satisfactory performance. This second phase will use the results and the experience gained during the first phase to develop natural convection solar dryers suitable for on-farm use and to encourage their use in West Africa. Six institutions, five in West Africa and one in Canada, will collaborate on the project. The Canadian institution will develop design procedures for direct and mixed-mode dryers, and the West African institutions will use the available information to develop various natural convection dryers, utilizing local and low-cost materials. On-farm tests will be carried out in the West African countries to determine the technical and socioeconomic viability of the dryers and to encourage their use.

Post-Project Summary

A simple but accurate model of an indirect passive solar crop dryer was developed and experimentally validated at Queen's University, Canada. A procedure for using the model to design a dryer to meet a particular need was also developed. The effect of fitting a small fan to an indirect passive solar crop dryer was evaluated both numerically and experimentally. The fan produced a considerable improvement in dryer performance while drawing a small amount of electrical power. An indirect passive solar crop dryer fitted with an unglazed collector gave satisfactory performance, provided the collector was properly sized. Studies of dryers using heated chimneys were also completed. A database on natural convection dryers was compiled. Specifically designed dryers were field tested in participating West African countries. The dryer tested in Nigeria showed satisfactory performance. The dryer tested in Togo performed well but its cost needed to be reduced. The dryer tested in Senegal demonstrated its superiority over the traditional method of drying and its acceptance by users was established. Field testing was not fully achieved, however, due to working conditions within certain countries, and issues concerning adoption and cost were not completely addressed. Research results were disseminated by means of publications in journals and conference proceedings.

Recipient Institution(s)