Comparison of different solar dryers with and without heat storage for crop drying: A review

Solar drying systems have proven to be cost-effective and environmentally friendly for drying various products. An extensive investigation of solar dryers with different designs, applications, and operating principles is conducted. Compared to direct drying, solar drying improves product quality by lowering moisture content without compromising the original product's qualities. Solar dryers are of two types: passive solar dryers and active solar dryers. Passive-mode solar dryers circulate air through natural convection, whereas active ones circulate air through forced convection. Crop-affected design characteristics include crop sensitivity, cost and time available to dry the crop, crop moisture content, the level of drying required, and so on. A wide range of research has been carried out on the thermal modeling of the dryer, using different designs. This article also discussed and compared the drying performance of three basic solar dryers: direct solar dryer, dryer with PVT air collection, and phase change materials (PCM). Even though PCM dryers are more expensive and uncommon, their ability to speed up drying at night makes them impactful.