Performance Testing of a Solar Thermal Fruit Dryer – a Case Study to Reduce Food Waste in Mozambique
Abstract
The purpose of this project is to investigate an innovative technology for sustainable preservation of juicy fruits in developing countries with the aid of simple solar thermal drying technology. Approximately five million tonnes of citrus fruit produced in Mozambique is annually wasted (FAOSTAT, 2015). A large solar energy potential and large fruit spoilage in Mozambique present the opportunity to implement a simple method for fruit preservation, combining solar thermal drying with a semipermeable membrane bag containing fruit juice. A small-scale indirect passive solar air dryer for drying the membrane bags was constructed and evaluated in terms of drying flux as a function of temperature, relative humidity and air flow rate. Measurements were initially carried out in the laboratory and later complemented with a field study in Mozambique. The dryer achieved a temperature interval that was required for high quality fruit drying and lowered the relative humidity. However, it was further found that air flow passing over the bags acted as an important parameter in the drying meaning that an increased air flow rate increased the drying flux to a larger extent than first assumed. The findings provide insight on the drying process and on how to improve the design of the solar air dryer.
Keywords
Solar thermal, Indirect solar dryer, Semipermeable membrane, Fruit drying, Food waste, Development project.