Assessment of performance and quality parameters for drying neem leaves in photovoltaic-thermal solar dryer

This research objective is to experimentally evaluate the performance of a photovoltaic-thermal indirect mode solar dryer for drying neem leaves under variable weather conditions of a year (winter and summer for sunny and cloudy days). The neem leaves moisture content findings indicated that the values decreased to 0.07 (d.b.) from 4.56 (d.b.) in 375 min for sunny winter, 465 min for cloudy winter, 315 min for sunny summer, and 405 min for cloudy summer weather conditions. The maximum drying parameters values were determined to be 6.15 kWh/kg for specific energy consumption, 0.23 kg/kWh for specific moisture extraction rate, and 18.54% for drying efficiency in cloudy winter weather conditions. The maximum thermal efficiency of 29.17% was achieved in sunny summer and the electrical efficiency was 10.14% in cloudy winter. The maximum heat transfer and mass transfer coefficients and Sherwood number were determined to be in sunny summer with ranges of 0.34-21.54 W/m2K, 0.35-22.18×10-3 m/s, and 0.50-30.47, respectively. The findings of quality parameters reveal that the drying product quality was not much affected by measuring total color change, antioxidant activity, total flavonoid content, and total phenolic content. In sunny summer, an ideal working environment was obtained after taking into account all performance characteristics.