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Abstract Indian onion producers experience significant economic losses as a result of the unpredictable fluctuations in onion prices during the harvesting and postharvest stages. To address these difficulties and increase farmers' earnings, the transformation of onions into value-added goods such as onion paste, onion powder, onion sauce, and onion oil has emerged as a possible option. The objective of this project is to create a smart solar drying system based on Internet of Things (IoT) technique specifically designed for the dehydration of recently harvested red onions. In April 2023, a series of five experimental tests were carried out, examining the effects of different onion slice thicknesses ranging from 2 mm to 4 mm, with intervals of 0.5 mm. Each trial consisted of running the dryer for a duration of 9 h, specifically from 9:00 a.m. to 6:00 p.m., throughout the daylight hours for three consecutive days. The experiment involved evaluating different drying characteristics, such as moisture content on dry and wet bases, shrinkage ratio, and thermal efficiency. The drying time required to achieve a 10% moisture level (w.b.) was reduced by 30.19%, 16.98%, 11.32%, and 3.77% when comparing a 4-mm slice thickness to thinner alternatives of 2 mm, 2.5 mm, 3 mm, and 3.5 mm, respectively. The dryer had a superior thermal efficiency of 27.89% when the thickness was 2 mm, in contrast to 19.50% when the thickness was 4 mm. Significantly, onions that were dehydrated from slices measuring 2 mm and 2.5 mm in thickness showed exceptional suitability for the production of powdered onion.
Walke et al. (Wed,) studied this question.