Development of solar tunnel dryer for drying of seasonal fruits in rural areas

Abstract:

Can rural fruit growers protect their seasonal produce from the 30-40% post-harvest losses that open-sun drying fails to prevent? This research set out to design, fabricate and evaluate a low-cost solar tunnel dryer suited to small farm holdings, using mango, banana and guava as test commodities. The dryer used a 4.2 m × 1.6 m semi-circular frame covered by UV-stabilised polyethylene and a 12 W DC exhaust fan powered by a 20 W solar panel. Trials ran between March 2023 and June 2024 at Rift Valley College of Food Technology. Mango slices (5 mm) reached a safe moisture level of 11.4% (wb) in 18 hours against 28.6% in open-sun drying. Banana chips and guava pieces showed similar trends, with drying times cut by 38-46% relative to the open method. Product quality was considerably better: ascorbic acid retention ranged from 67.3% to 81.2%, colour (L* value) stayed closer to fresh samples, and microbial counts remained within the 10³ CFU/g safety limit. The average thermal efficiency was 31.8% and the benefit-cost ratio was 1.87. Findings point to the solar tunnel dryer as an affordable, field-ready option for reducing seasonal fruit wastage in villages without reliable grid supply.