Growth and Agronomic Traits of Green Onion under the Agrovoltaic System with Red Supplemental LED Lighting

Abstract

Background and objective: An agrovoltaic system is a power generation method applying photovoltaics (PV) to crops cultivated on a farm. Usually, the PV system covers less than 30% of the upper surface of crops on the ground. If the PV system covers the upper layer of the crops, the yield will decrease by 15-20% due to the shading of the PV module. This study was carried out to investigate the effects of red supplemental light-emitting diode (LED) lighting under the PV system on growth and agronomic traits of green onions.Methods: To resolve the issue about decreasing yield, we constructed a 50 kW agrovoltaic system with the red (660 nm peak) LED dimming facility on the farm with 3 different plots for comparison. The 1^st was PV + LED (two parts of dimming area: 3 hours and 6 hours). The second was only PV, and the last was a reference for comparison of yield (control plot). We transplanted uniform seedlings of green onions on three areas of the farm on June 23, 2020. We used red LED lighting for 3 hours and 6 hours after sunset and harvested green onions on October 25, 2020. We used less than 1% of electricity of total power generated by the agrovoltaic system for supplemental LED lighting.Results: The result of harvesting under the agrovoltaic system with 3 hours of lighting showed that there was 38% more yield than the control plot. We also discovered the optimal amount of supplemental LED lighting because even 6 hours of lighting were not better than 3 hours.Conclusion: Applying supplemental LED lighting after sunset can compensate for the yield decrease. The LED supplemental lighting for 3 hours is optimal for crop harvest. We expect that this system can be helpful to farmers who want to construct an agrovoltaic system.