Advancements in solar greenhouse dryers for crop drying

Current developments in solar greenhouse dryers for drying agricultural crops are presented in this paper, with an emphasis on design improvements and thermal performance enhancement. This review explores the integration of greenhouse dryers with solar photovoltaic systems, solar thermal collectors, and photovoltaic-thermal and thermal energy storage units to enhance drying performance. For the purpose of optimizing the drying process, design innovations such as passive and active solar heating systems, size and shape, heat storage, and air circulation mechanisms are investigated using numerical and experimental approaches. The prospect of improving the thermal performance, energy efficiency, and quality of crop dried, resulted through the integration of various solar technologies with greenhouse dryers is exceedingly promising. Such hybridization of indirect solar greenhouse dryers was found to be one of the latest developments with improved drying efficiency to preserve crops. The economic viability, environmental sustainability, and future prospects of solar greenhouse dryers are also discussed, along with potential research and development areas. Moreover, basic thin layer drying models, performance evaluation parameters, and validation tools are discussed.