Design, Development, and Performance Evaluation of an Improved Indirect Solar Mango Dryer for Sustainable Post-Harvest Preservation in The Gambia

Post-harvest losses of fresh mangoes remain a significant challenge to food security, rural livelihoods, and agro-industrial development in The Gambia. During the annual mango harvesting season, substantial quantities of fruit are lost because of rapid deterioration, inadequate preservation technologies, limited access to reliable electricity, and dependence on traditional open-sun drying methods. Although solar drying offers an environmentally sustainable alternative, many existing cabinet dryers exhibit poor airflow distribution, excessive humidity retention, uneven drying, and mould formation, reducing product quality and limiting adoption by rural processors. This study presents the design, development, and engineering evaluation of an improved indirect natural-convection solar mango dryer specifically adapted to the climatic conditions of The Gambia. The proposed system integrates a high-efficiency solar air collector, an insulated drying chamber, food-grade removable trays, a balanced natural ventilation system, and a vertical chimney with an adjustable damper to improve airflow and moisture removal. The dryer is designed to process 20–50 kg of fresh mango slices per batch, operating within an optimal drying temperature range of 50–65°C while maintaining continuous natural airflow. Engineering analyses include airflow modelling, chimney design, solar collector optimization, tray configuration, and material selection using locally available resources. The design emphasizes improved drying uniformity, reduced drying time, enhanced product quality, and effective prevention of mould development through controlled ventilation and moisture extraction. The proposed dryer provides a low-cost, energy-efficient solution suitable for smallholder farmers, cooperatives, and rural agro-processing enterprises. Beyond reducing post-harvest losses, the system contributes to renewable energy utilization, food security, rural income generation, and climate-resilient agricultural development in The Gambia. The study establishes a practical engineering framework for future prototype validation, performance testing, and commercialization of sustainable solar drying technologies for tropical fruit preservation across West Africa. The engineering design parameters and construction principles presented in this paper are derived from the prototype developed for research and field testing in The Gambia.