Advances in Renewable Energy-Based Drying Systems for Food Materials: A Comprehensive Review of Innovations, Smart Integration, and Sustainability

Drying is a fundamental unit operation in food processing, essential for extending shelf-life, ensuring microbial safety, and preserving nutritional quality. However, conventional drying techniques such as open sun drying and fossil-fuel-powered systems are often energy-intensive, environmentally unsustainable, and inconsistent in product quality. In response, renewable energy-based drying systems have emerged as viable, eco-efficient alternatives that align with global decarbonization goals and sustainable development objectives. This comprehensive review presents recent advancements in renewable drying technologies powered by solar, wind, biomass, and hybrid energy sources. It systematically explores system classifications, engineering configurations, and the integration of intelligent control mechanisms such as the Internet of Things (IoT), artificial intelligence (AI), and computational fluid dynamics (CFD) for real-time monitoring and optimization. The incorporation of thermal energy storage, particularly phase change materials (PCMs), is highlighted for improving energy reliability and drying performance. Material-specific drying strategies for fruits, vegetables, grains, fish, meat, and herbs are analyzed with emphasis on nutrient retention, microbial safety, and uniformity. Additionally, the review evaluates the techno-economic and environmental performance of renewable drying systems, supported by real-world case studies and lifecycle assessments. Barriers to widespread adoption such as high initial costs, intermittency of energy sources, and policy gaps are critically discussed, along with pathways for scaling through modular designs, financial incentives, and capacity building. By bridging technological innovation with sustainability imperatives, this review offers a multidisciplinary framework for researchers, engineers, and policymakers to accelerate the deployment of renewable energy-based drying technologies in food processing systems worldwide.