Advances in solar drying technologies: A comprehensive review of designs, applications, and sustainability perspectives
Abdul-Hamid Mohammed, Clement A. Komolafe, Anthony Simons
Abstract
A lack of adequate postharvest equipment has been a significant cause of food shortages in many developing countries. In terms of cost, traditional open sun drying appears economical; however, it faces limitations such as being highly labour intensive, exposing products to direct sunlight, and risking quality loss due to pests and animal invasion. Using solar energy to dry these food products is a promising approach that does not compromise their nutritional value. Despite significant advances in solar energy drying systems, the adoption of solar drying remains limited due to low energy efficiency, inconsistent performance under varying weather conditions, and the absence of scalable design frameworks. This review critically examines developments in solar drying technologies from 2020 to 2025, addressing the increasing need for sustainable postharvest processing solutions. It combines technical, environmental, and socioeconomic perspectives to provide a comprehensive overview of current solar drying systems. The analysis reveals a notable shift from traditional dryers to advanced hybrid configurations that incorporate energy storage materials, nanomaterials, ejector heat pumps, and smart control systems. These innovations have greatly improved thermal efficiency, reduced drying times, and preserved product quality. Application-specific customization, guided by computational tools such as CFD, artificial neural networks (ANN), etc. This review serves as a valuable resource for researchers, engineers, and policymakers aiming to scale up solar drying as a climate-resilient, energy-efficient, and economically sustainable solution. It also highlights emerging research trends, identifies key performance indicators, and underscores the importance of integrating computational modeling with sustainability metrics as future directions.