Techno-economic evaluation of forced convection solar photovoltaic dryer for drying date palm (Phoenix dactylifera L.) fruit

Abstract

The drying experiment for dehydrating date palm (Phoenix dactylifera L.) fruits was carried out in this dryer (developed by CAZRI, Jodhpur) in the month of June, 2020. During the testing, the maximum average stagnation temperature in the drying chamber was found as 70°C and when loaded with 20 kg date palm it reduced to 64°C, when outside ambient temperature was observed as 39.5°C on a clear day (from 08:00 hr to 18:00 hr). During the drying trial, moisture content of date palm fruits got reduced from 65% (wet basis) to about 26% in 6 days by dryer, whereas in the open sun drying it is taken 8 days. The temperature gradient of the drying chamber got reduced from 6-8°C to 2-3°C in the system provided with pre-heater, which resulted in uniform drying. The effective moisture diffusivity was 4.34  10-9 m2.s-1, and the efficiency of the dryer was 16.1 per cent. The developed hybrid forced convection drying system produced better quality products in shorter time by the efficient use of solar energy. The economic evaluation of the hybrid forced convection solar dryer indicated high value of IRR (57.4 percent) and low value of payback period (2.10 years), suggesting the dryer to be cost efficient. The winnower was used for winnowing the 200-300 kg grains from threshed material in a day in the absence of natural wind. The winnower was also used for separating grains from straw to enhance the utility throughout the year.