Solar drying is still practiced in many countries where the wheat and lentil grain stocks are exposed to the sun so that they are sufficiently dried for storage. The disadvantage of this process is that there is a great chance of contamination and spoilage.
Solar drying used in agriculture or industrial drying process prove to be very useful in energy conservation. They not only save energy but also save time, improve quality, make the process efficient and protect the environment. The use of a solar dryer (which is different from classical drying) is useful across various industries for different purpose viz.
- In agriculture for crop drying
- In food processing for dehydration of fruits, potatoes, onions and vegetables
- In dairy industry for producing milk powder and casein
- In lumber industry for seasoning of wood and timber
- In textile industries for drying of textile material
There are two types of solar drying devices namely direct and indirect solar dryer
- The direct ones or cabinet dryers are enclosed, insulated structures inside which solar collection and drying takes place. Radiation is collected through a transparent cover (glass or plastic) in the drying chamber which is ventilated for improved airflow. Trays carrying the products to be dried are placed inside the chamber.
- The indirect solar dryer or thermo-siphon dryers have a collector and a separate drying chamber. They operate more efficiently and allow more control over drying. The collector heats up the air which rises and forces its way through the racks containing the products in the drying chamber. Such dryers may be without flow enhancement and they are best suited for high value commercial scale drying.
There are many websites that offer help with the construction of such dryers for home use. You can dry your food at home and without the contamination and spoilage endured during classical drying. The solar dryer is also a very good way to start saving energy. Most of the industrial dryers work on electricity and fossil fuels. Solar energy helps to provide industrial and agricultural drying with a non-conventional and economical way to dry foodstuffs.