This study details the construction and performance testing of a mixed mode solar dryer using a combination of direct and indirect solar energy to dry food. One major benefit of this dryer design is its construction. It was simple to construct and was made with low cost materials, to make it feasible for use in developing countries. Previous research has identified several design factors that affect performance and efficiency: product loading density, number of trays, position of the absorber, and chimney type. Performance testing showed that chimney air speeds were not affected greatly by modifying the design aspects of the dryer, with only a small increase occurring when using a box-type chimney. Overall the temperatures were mostly dependent on irradiance, but using a collector-type chimney generally resulted in higher temperatures throughout the dryer. The RH change across the dehydrator was most affected by the number of trays, but the chimney type did have an effect on the RH right at the chimney exit. Efficiency testing showed that product loading density on the trays was tested at 40% and 60% capacity; there was no statistical difference observed for efficiency between the two levels. Our results show that the dryer was more efficient when using the maximum number of trays. The lowest position of the absorber (5 cm from the ground) was found to be most efficient. A box-type chimney was significantly more efficient than the collector-type chimney in this full factorial study.



College and Department

Life Sciences; Nutrition, Dietetics, and Food Science



Date Submitted


Document Type





solar dryer, efficiency, performance testing, dehydration, solar collector