Thermal and Electrical Performance of a Cascade PV/T Solar Drying System and Drying Kinetics of Carrot Slices

Solar hot-air drying technology has developed rapidly in the field of low-temperature fruit and vegetable processing; however, fluctuations in solar irradiance affect the stability of system energy supply and energy utilization efficiency. In this study, a cascaded photovoltaic/thermal (PV/T) solar drying system was constructed, and drying experiments were conducted on slices of the “Hohhot Hongying No. 2” carrot cultivar at 40, 45, 50, 55, and 60 °C. A hierarchical normalization method was employed to reduce the effects of meteorological differences among the experimental days, and the thermal performance, energy consumption, and drying kinetic characteristics of the material were analyzed. The results showed that the quasi-steady-state thermal efficiency of the system ranged from 29.7% to 38.3%. At 50 °C, the electrical energy consumption per unit mass of water removed was the lowest, at 0.430 kWh/kg. The effective moisture diffusivity calculated based on Fick’s second law increased from 8.99 × 10−9 to 1.98 × 10−8 m2/s with increasing drying temperature, and the coefficients of determination under all operating conditions were greater than 0.9906. Arrhenius fitting yielded a pre-exponential factor of 4.37 × 10−3 m2/s and an activation energy of 34.09 kJ/mol. Under the present experimental conditions, 50 °C exhibited a relatively favorable balance between energy consumption and drying rate within the investigated temperature range. These findings may provide a reference for selecting the operating parameters of small-scale PV/T solar drying systems. Nevertheless, further repeated experiments and product-quality assessments are required to verify the broader applicability of the results.

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