Solar fruit drying technologies for smallholder farmers in Uganda, A review of design constraints and solutions

Abstract

Solar fruit drying is a technology that is successfully applied on both domestic and commercial scale among smallholder farmers in Uganda. However, existing solar drying technologies are marred with multiple deficiencies such as inefficient conversion of trapped solar radiation to meet required enthalpy, low throughput, long drying times, and inherent difficulty to achieve acceptable hygiene among others. This review critically examines existing solar drying technologies in Uganda, highlighting design constraints and plausible solutions for supporting the growing fruit drying industry. The common types of solar dryers in Uganda are the static-bed box type solar dryer model, the PPI tunnel solar dryer model, the NRI Kawanda cabinet solar dryer, the hybrid tunnel solar dryer and the UNIDO solar hybrid dryer model. Findings reveal that the challenges characterizing existing dryers in perspective of design are attributed to; poor material selection, poor mass and energy transfers, total dependence on solar energy, lack of capacity by local craftsmen to replicate new and improved models, difficulty to clean the dryers caused by inapt model configurations, and high cost of installation to mention a few. Therefore, a need exists to develop efficient and affordable designs using scientifically proven methods such as Computer Fluid Dynamics to pre-test and optimize the dryer and incorporating alternative energy sources in the design to ensure an all-weather dryer. Additionally, disseminate such innovations to farmers, retool local artisans with quality fabrication skill sets, and develop simple manual with standards and fabrication procedures for the fruit dryers.