Multi-objective analysis of evacuated tube solar-electric hybrid drying setup for drying lotus bee pollen

This work aims to develop an evacuated tube solar-electric hybrid drying setup and enhance its performance using evacuated collector and photovoltaic systems. The setup performance was evaluated by dehydration of lotus bee pollen using two different strategies inducing solar heating drying and mixed heating drying at three different temperatures (40, 50, and 60 °C). The system was also compared with open sun drying. Compared with open sun drying, about 45%, 23%, 30%, and 41% reduction in the process time was induced by solar heating drying and mixed heating drying (40, 50, and 60 °C), respectively. For both solar heating and mixed heating drying, the mechanical energy, thermal energy generated by electric heating tubes, and radiation thermal energy accounted for were in the range of 12.2–38.5%, 0.0–15.3%, and 60.5–87.8%, respectively. From the perspective of drying efficiency and energy consumption, the developed evacuated tube solar-electric hybrid drying setup was more beneficial under mixed heating drying at 40 and 50 °C. The dryer efficiencies under the cases of mixed heating drying at 40, 50 °C were 48% and 34% higher than that of solar heating drying, while mixed heating drying had lower total energy consumption, specific energy consumption and specific electric energy consumption. The developed equipment can effectively reduce greenhouse gas emissions and has a short payback period of 1.24 years. Based on the findings of this research, it could be concluded that, resulting in decreased drying time, GHG emissions and enhanced energy efficiency, the developed equipment is a promising drying technology.