Performance Evaluation and Cost Economics of a Low Cost Solar Dryer for Ber (Zizyphus mauritiana) Fruit

Abstract

Increasing population and high cost of fuels have created opportunities for using alternate energies for post-harvest processing of foods. Solar food processing is an emerging technology that provides good quality foods at low or no additional fuel cost. A number of solar dryers, collectors and concentrators are currently being used for various steps in food processing and value addition. Keeping in mind this future requirement, a reliable, efficient and low cost box type solar dryer was designed and developed at ICAR-Central Arid Zone Research Institute, Jodhpur to dry perishable arid agricultural produce. In this paper, the performance of box type solar dryer was evaluated with ber (Zizyphus mauritiana) fruit because it is one of the popular seasonal fruit in India but highly perishable in nature. During the performance evaluation, the maximum stagnation temperature inside the drying chamber was observed to be 63°C and on loading with 3 kg ber it reduced to 49°C, while outside ambient temperature was 27°C on a clear sky condition (from 10:00 h to 17:00 h) in the month of January, 2016. During the drying process, moisture content of ber fruits reduced from 80% (wet basis) to about 26% within 7 days. As compared with open sun drying, the duration of drying was reduced by about more than 50% of the time.The efficieny of this dryer was found to be 12.1%. The cost-benefit ratio was 3.84, which shows the potential of using solar dryers in place of conventional dryers. The developed dryer was also used to dry spinach and grated aonla and beetroot. Appearance, taste and flavour of ber in this dryer was superior to that of open sun drying. The use of solar dryer will be a great boon for farmers of arid region of Rajasthan.