Design, Development and Performance Evolution of a Low-Cost Solar Dryer

Abstract

Considerable amount of fruits and vegetables have been wasted due to non-availability of appropriate processing facilities in farmers field, in spite of high production in India with second rank in the world. A little of total fruit and vegetable productions in the country have been processed in industries. It has been noted that food crisis in most parts of the world is due to non-availability of processing and preserving facility rather than due to low production. Spoilage of fruits and vegetables can be reduced by drying and preserving them by suitable solar devices. Keeping in mind this requirement, a simple solar dryer has been fabricated at ICAR-CAZRI, Jodhpur. The dryer comprises a drying tray (0.75 m 0.53 m) made of wooden frame and SS wire mesh and a glass sheet (4 mm thick) fitted on a wooden frame and a couple of hinges with opening and closing arrangements. Suitable openings for entry of ambient air and exit of water vapour have also been provided. The cost of the dryer is about Rs. 800. The drying tray serves dual purpose of solar collector and drying chamber. The maximum stagnation temperature observed inside the drying chamber was 63 °C on loading of 3 kg ber (Ziziphus sp.). It was 49 °C, when the outside ambient temperature was 27 °C on a clear sunny day (from 10 am to 4 pm) in the month of December–January. For drying of 3 kg ber fruits to a final weight of 1 kg using the developed dryer, it took about 7–8 days. It has been observed that the drying time for Ziziphus (ber) decreased by 50% in comparison to open sun drying. The developed dryer was also successfully tested to dry spinach (Spinacia oleracea), grated aonla (Phyllanthus emblica) and beetroot (Beta vulgaris). This solar dryer would be very useful for small and marginal farmers.