Comparative Study between Solar Dryer and Open Sun dried Tomato under North Plateau Climatic Zone

Abstract

The solar dryer consists of transparent glass window, tray, solar photovoltaic fans and solar panel. The solar radiation passes through the transparent glass window, located on the top of the cabinet. The cabinet is made of anti-corrosive material and of modular nature to meet the varying sizes and loading capacities of food products, ranging from 7 to 8 kg. The ambient air enters from the bottom of the cabinet and gets heated up with solar radiation incident from the top window. The heat energy is trapped in the cabinet and heats up the air. The hot air passed through the trays, carries the moisture from the product to the space below the glass. Then it is exhausted by Solar Photovoltaic Fans. The forced circulation of air in the cabinet is achieved through this solar fan. Assessment of the dryer showed a raised temperature of about 470c attainable in the drying chamber. The dryer temperature and drying rate was found to be higher than the natural open sun drying method. The dryer was able to reduce moisture content of tomato from initial moisture content of 93 per cent wet basis to 4 per cent in three days with effective drying time of 24hr and drying rate of 0.03833 kg/hr, whereas the traditional sun drying was able to reduce moisture content of tomato from initial moisture content of 93 per cent wet basis to 4 per cent in five days with drying time of 34hr and drying rate of 0.0272 kg/hr. 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.