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

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

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 1st 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.