Advanced technologies and performance investigations of solar dryers: A review. (December 2020) - Kumar, Pradeep
Highlights: Mixed mode solar dryer with PCM is the most efficient dryer among all kind of dryers. Thermal energy storage system can be used to enhance the working of the dryer after sunset. Daytime of drying can be reduced by using PCM. Abstract: Solar drying is the basic process to reduce the moisture content of the products to a certain level below which deterioration of product does not occur. There are mainly three types of solar dryers; direct solar dryer, indirect solar dryer, and mixed-mode solar dryer with various sizes, capacities, and designs. The main aim of this study is to review all these types of solar dryer based on characteristics of the product being dried and technical, economic and environmental aspects. It is found that the efficiency of the solar dryer and drying rate mainly depend upon air temperature and velocity, followed by solar radiation, type of product, initial moisture content, total mass of the product and thermal energy storage materials. There are so many options to dry the product in different ways like drying the product using fossil fuel and solar radiation, hybrid drying system, etc. There are several problems using fossil fuel such as limitation of resources, higher cost and its adverse effects in environment. Open sun drying also has so many drawbacks such as debris, rain, blowing wind, insect infestation, human and animal interference, etc. Mixed mode solar dryer with thermal energy storage materials is found to be one of the best solar dryers in all kind of dryers with respect to its efficiency and drying time.