A Comprehensive Review on Solar Drying Systems: Designs, Performance, Applications, and Future Perspectives

Abstract

Solar drying is an energy-efficient and sustainable technology for moisture removal from agricultural, food, and selected industrial products. This review synthesizes developments in solar drying systems reported up to 2020, focusing on system classification, design strategies, performance evaluation, applications, and future prospects. Solar dryers are categorized into direct, indirect, and mixed-mode configurations, with further distinctions based on natural or forced air circulation and hybrid integration. Key design parameters influencing performance including collector configuration, absorber characteristics, glazing, insulation, and airflow management are critically analyzed. Comparative assessment of thermal and drying performance indicators highlights the variability in efficiency across configurations and operating conditions. Applications spanning fruits, vegetables, grains, fish, medicinal plants, and other materials are examined with emphasis on product quality and process reliability. The review also summarizes prevailing modeling approaches used to predict drying kinetics and optimize system design. Economic feasibility and environmental advantages are discussed in terms of energy savings and emission mitigation potential. Current limitations related to intermittency, process control, and scalability are identified, and future research directions are outlined, including hybridization, thermal energy storage, and intelligent control strategies