A review on indirect type solar dryers for agricultural crops – Dryer setup, its performance, energy storage and important highlights

• Published in: Applied energy 2020-01, Vol.258, p.114005, Article 114005
• Main Authors: Lingayat, Abhay Bhanudas, Chandramohan, V.P., Raju, V.R.K., Meda, Venkatesh
• Format: Article
• Language: English
• Subjects: Active and passive solar dryers; Drying; Indirect type solar dryer; Pay-back period; Solar drying; Thermal energy storage
• ISSN: 0306-2619; 1872-9118
• DOI: 10.1016/j.apenergy.2019.114005

•Literature data of different indirect type solar dryers (ITSD) were discussed.•ITSD with sensible and latent heat storage system was reviewed.•ITSD with roughened solar collector was extensively reviewed.•Chemical pre-treatment, payback period and economic analysis were discussed.•Important findings and summaries of ITSD were listed and tabulated. Inadequate preservation techniques and poor storage provisions lead to deterioration in the quality of agricultural products. Advanced processing techniques have been used to reduce postharvest losses of agricultural goods. Drying is a processing technique used for food product preservation. Drying by solar energy is an ancient food preservation technique. Solar dryers of various sizes, capacities and designs are available for drying applications in agricultural industries. Indirect type solar dryer (ITSD) is one of the prominent dryers used to dry food products and this type of dryer with its unique features, types, and different technique incorporated to improve its performance has not been investigated so far in any detail. The purpose of this work is to review the features and benefits of ITSD. A commonly used classification of different types of solar dryers is also presented. Heat transfer enhancement on ITSD and the influence of pre-treatment before drying are also effectively reviewed. Payback period and cost analysis of ITSD are discussed. Important findings on ITSD have been reviewed, discussed and tabulated. The most dominant parameters affecting the drying rate are air temperature and velocity, followed by solar radiation, type of product, initial moisture content and total mass of the product. Passive solar dyers were easy to fabricate compared to active dryers. The drying rate of pre-treated foods was high and the quality of the product remained intact after drying.