A comprehensive review of the solar dryer

Drying of agricultural products is an energy-demanding process. High costs, scarcities in fossil fuels and environmental threats attract the use of solar energy as an alternate source, especially in developing countries. Increasing environmental concerns led to the use of clean and green energy resources in the field of drying agricultural products. A solar dryer integrated with a thermal energy storage system is reasonably efficient for continuous and uniform drying of agricultural produce in the temperature range of 40-75 degrees C which is the requisite for drying most of the products. Such dryers have become a natural choice to replace drying systems based on fossil fuels. Many studies have been performed till date by a number of researchers for the last few decades for drying agriculture and food products by a solar dryer. This review paper primarily presents an appraisal of the significant contributions made so far in the field of solar drying systems, with the latest updates in drying technology. Solar dryers which offer drying during off-sunshine hours have been specially mentioned. Some novel ideas like use of phase change materials and desiccant materials which enhance the performance and effectiveness of the dryer have also been attempted.