Advancements in solar assisted drying technologies: A comprehensive review post 2017

Solar drying has gained significant popularity for drying agricultural and food products in recent years. This review presents a comprehensive overview of the state-of-the-art in solar drying, focusing on developments post 2017. By incorporating theoretical, experimental, and numerical analyses, this study examines various aspects of the technology, including design evolution, operating modes, drying products, load/no-load conditions, heat transfer augmentation, and heating systems. In design modifications, various changes in its north wall designs, drying tray arrangements, painting for enhancing absorption, implementing thermal energy storage systems, etc. Are reviewed exploring important designs for improved thermal and economic performance. Under operating modes, the performances of different combinations, such as direct, indirect, and mixed-mode operations under load/no-load conditions are explored. To augment heat transfer within solar dryers, different techniques such as use of phase change materials for thermal energy storage, sensible heat storage using metal plates, pebbles, and sand are examined. Moreover, modifications involving integration of finned structures with dryer interiors, trays, additional solar collectors, storing energy using geothermal mode and earth contact heat exchangers for augmenting heat transfer are explored too. After reviewing a handful of past works, it is found that for loaded condition, maximum temperature of 73.6 °C was achieved by using the combination of indirect and mixed mode. Along with some important outcomes, a series of recommendations have also been put forward at the end for future implementation of the dryer which may serve as a valuable guide for further advancements and real-life applications. [Display omitted] •A comprehensive review by classifying solar dryers in direct, indirect and mixed mode is presented.•Design modifications of dryer and quality aspects of dried products presented.•Economic and environmental impact analysis of dryers done.•Comparative study of dryers done with future recommendations.