Vol. 10, Issue 4 (2021)

Author(s):
Sivamma P, Mounika E, Carolin Rathina Kumari K, Senthil Kumaran G and Bindu B

Abstract:
Solar greenhouse drying is a method of removing moisture from the food material in which drying medium is solar energy which is easily available and low in cost for farmers. The solar energy is decreases in the monsoon months in comparison to non-monsoon months. The decrease in the solar energy results in lower temperatures in the solar greenhouse dryer. The aluminium foil which has 88% reflectivity and black mulch sheet which is best absorber and emitter of heat radiation were used in the solar greenhouse dryer to heat the air and maintains heat for longer time. Combination of alternate strips of aluminium foil on two sides, aluminium foil on south wall and black mulch sheet on the floor of the dryer were used to modify the dryer for conducting experiments and the parameters viz; temperature and relative humidity were recorded in both modified solar greenhouse dryer, solar greenhouse dryer and ambient conditions. Assessment of temperature in ambient condition, solar greenhouse dryer with and without modification showed the maximum temperature difference between solar greenhouse dryer without modification and ambient condition was about 11.5 °C whereas 19.5 °C maximum temperature difference between modified solar greenhouse dryer and ambient condition. The dryer was able to reduce moisture content of onion from initial moisture content of 669.23 per cent dry basis to 4.2 per cent in 31 h of drying whereas the traditional sun drying was able to reduce moisture content of onion from initial moisture content of 669.23 per cent dry basis to 26 per cent in 31 h of drying time. The results showed a considerable advantage of solar dryer over the traditional open sun drying method in term of drying rate and less risk for spoilage.