Solar Tunnel Dryer is a tunnel type chamber, which is used for drying of various crops using Green House effect. It helps to preserve the food and also increase the shelf life of the product. It is covered with multi wall Polycarbonate sheet that traps solar energy and has an insulation effect, thereby maintaining high temperature for a longer period of time. Further solar dryer filters out the UV radiations, which helps products to retain the colour.
The temperature difference between the ambient and inside cabinet is 15°C–25°C on good sunny days. The dryer can protect from rain, insect, dust, and rodent. These dryers are modular, easily transportable/ portable, and constructed according to users requirement.
Minimal thermal losses due to direct penetration of solar radiation into the cabinet through the polycarbonate sheet, with maximum efficiency. The temperatures achieved in the cabinet are in the range of 45–65°C on a clear sunny day and is maintained uniformly.These driers provide guarantee of clean and hygienically processed products.
Drying time depends on several factors such as moisture content of the material to be dried, its porosity as well as size.
In any case, the solar drier makes use of free solar energy that is available for at least six hours during the day. In comparison to drying in the open, drying in the solar tunnel reduces drying time by about 60 percent. In addition, dried products retain their natural color and have a uniform look as well as texture that can help better market prices. Drying in the sun can turn agricultural products black but not when a solar tunnel is used. Tomatoes, onions, figs, sapota, mango, amla, chillies and grapes can easily be dried within the solar tunnel.