Design and development of an adequate ventilation system to preserve freshly harvested onions

Abstract

In many nations, onions are one of the significant economic crops that are farmed on a huge basis. The process of harvesting onion crops requires five to ten days for a big farm. Also, for better storage life onions should be gone through a field curing and drying process. So, daily harvested onions are temporarily stored on the farm with the help of a Tarpaulin. But heat and moisture emitted by onions do not get dissipated as conventional Tarpaulin, made up of Polyethylene, Nylon, Canvas, etc. are not breathable. Due to this improper ventilation, 30 to 60 % of onions get spoiled and their storage life decreases. Study shows that for the storage of the onion bulb the temperature should be 25 to 30 °C and relative humidity should be 65 to 75 %. This condition lowers the deterioration, rotting, and sprouting that occur as a result of physiological weight loss during storage. When we compare temperature and humidity variation for different onion storage systems, we found out that Polyethylene Tarpaulin cannot maintain the required temperature and humidity. Canvas can maintain humidity range but cannot maintain temperature. To achieve desired temperature and humidity range, we can use a forced ventilation storage system with the help of a duct system and spunbond fabric. To cool the onions, outside dry and cool air is circulated through the onions by using a blower and duct system. As spunbond fabric is breathable it is used to allow hot and humid air to pass. According to experimental results, a forced ventilated storage system is recommended to farmers which assures maximum marketable product, less cost, and simplicity in design.