Solar Tunnel Drying System: A Literature Review

Abstract

Production, productivity, and area under production from fruits and spices are gradually increasing. Improper processes of freshly harvested spice and fruit products will make them undergo qualitative deterioration with each passing hour. This deterioration is more pronounced in high humid areas. Drying process in one or the other form is essential. Freshly harvested spices and fruit products in average contain more than 80% moisture. The commodities need to be dried to have a moisture content below 10% in the shortest possible time for safe storage. Drying process in most cases are accomplished by the open sun. Meanwhile, the environmental condition in solar tunnel drying is enclosure type and the product is protected from rains, dust, insects, and rodents. Solar tunnel drying, a widely used bulk dryer, facilitates faster drying than open drying by virtue of the greenhouse effect. Commercial cultivators by and large choose faster drying methods using wood and fossil fuel-fired heating sources. This study attempts to review recent advances of various designs and working of the greenhouse drying system in totality, like auxiliary drying during off-sun hours, bulk drying feasibility, ease in loading and unloading along with an analysis of key features and economics involved.