Design and performance evaluation of a fruit solar dryer for smallholder farmers.

Abstract

Uganda experiences post-harvest fruit losses of up to 50% due to inadequate storage facilities, poor handling practices, and limited access to affordable preservation technologies, resulting in economic losses, reduced household incomes, and food insecurity. While many try to dry fruit in the open sun, the process is frustratingly slow and often leaves the food contaminated by dust and insects, although commercially available dryers are often too expensive and energy-intensive for smallholder farmers. To address this, I designed and fabricated a forced -convectional solar dryer that uses low-cost automation to create a controlled drying environment. I built the system specifically to handle 2 kg batches of pineapple focusing on reducing moisture content from 85% (wet basis) to 12% or less. Unlike conventional solar dryers, the proposed design integrates sensor-based automation using an Arduino Uno microcontroller, DHT22 temperature and humidity sensor, PWM-controlled DC fans and a standalone solar photovoltaic power supply enabling automatic regulation of drying conditions without reliance on grid electricity. The dryer was designed using Computer Aided Design modelling and thermal-airflow simulations and fabricated from locally available materials to enhance affordability and replicability. Performance evaluation under Ugandan climatic conditions demonstrated that the system reduced pineapple moisture content from 85% to 12% within 16 hours, representing a 50% reduction in drying time compared to open-sun drying. The dryer maintained an average chamber temperature of 50°C and relative humidity below 60%, achieving a mean thermal efficiency mean thermal efficiency 7.8 ± 2.6%, mean SMER 0.109 ± 0.036 kg/kWh; and water activity 0.52 ± 0.02 (< 0.60 shelf-stability threshold), while producing cleaner, more uniformly dried fruit with improved colour retention and texture. These results demonstrate the potential of the proposed automated forced-convection solar dryer as an affordable, sustainable, and scalable solution for reducing post-harvest fruit losses among smallholder farmers.