Solar Dryer, energy saving and food conservation

Using a solar dryer is a process that has been practiced since man learned to think for himself. This might sound like an exaggeration but it isn't. When man understood that food has to be preserved; the first thing that he thought of was drying it. As it is widely accepted that stone-age man didn't have microwaves or other heating devices, he used the sun's heat to dry roots, berries, tubers and meat.

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 agricultural 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; and 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.

Many vegetables and herbs can be dried and then stored for the rest of the year. Peas and beans should be dried with varieties of dried mint to enhance the flavor. Beans prefer a bay leaf in each jar. Garlic and onions need to be peeled and sliced to about 3-4 mm thickness. There are many other fruits and veggies that can be dried using a solar dryer. Some fruits like tomatoes, apples, figs, grapes require additional efforts.

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.