Recent advances in solar drying technologies: A Comprehensive review

Abstract

Preservation of food and vegetable products is an age-old practice for the retention of flavor, appearance, and quality. From ancient times, driers for drying food grains work on direct sun rays, firewood, fossil fuels, and coals causing carbon release. These available methods are expensive, unreliable, and unhygienic; thereby the use of a solar dryer working on free and clean energy is better for higher value addition to food preservation. The objective of this exploration is to study the recent developments in the use of different types of solar dryers for drying foods, vegetables, seafood, etc. There exist many studies on the effects of the parameters such as temperature, relative humidity, and speed of air, turbulence effect, sun irradiation, and the latitude of the location in the solar drying process. The findings show that the climate conditions such as solar radiation and atmospheric air play an important role in the drying efficiency of the solar dryer. A phase change material stores thermal energy during the daytime and releases heat during the nighttime. This process improves thermal efficiency and reduces heat loss during the drying period. On the one hand, a hybrid dryer integrated with a solar panel produces electricity for the operation of a DC blower circulating hot air inside the drying chamber for better drying. In addition, a critical review has been performed on the usage of different absorbing plates increasing heat transfer rate, use of various phase change materials for heat storage, and analysis of CFD simulation.