Optimization of photovoltaic supplementary lighting system in strawberry greenhouse

Greenhouse planting can effectively control indoor environmental parameters, thereby improving the quality of greenhouse crops. Photovoltaic (PV) greenhouses not only provide clean energy, but also control the lighting environment. In order to improve the quality of strawberries, the off-grid PV supplementary lighting system was designed. The monocrystalline silicon PV module and the LED lights were used to supplement light for 2 hours every night on the ‘Miaoxiang 7’ strawberries on a 5-layer cultivation shelf, then their fruit quality was measured. The results showed that the maximum single fruit weight of strawberries without supplementary light was 19.3 g, the maximum soluble solid content of strawberries was 13.0%, while the maximum weight of strawberries optimized with supplementary light was 33.7 g, the optimized soluble solid content of strawberries was 15.5%. The PV module had been tested to generate 10.08 kW·h per day. In order to improve the operating speed of the supplementary light control system, particle swarm optimization (PSO) algorithm was used to optimize the control parameters, and the adjustment parameters Kp, Ki, and Kd in Proportional-Integral-Derivative (PID) controller were obtained to be 0.36,0.35, and 0.3, respectively. The average intensity of LED lamps was 19530 Lux at night. In this study, PSO algorithm was used to optimize the parameters of the supplemental lighting system to ensure that the system control output had no oscillation or overshoot. Thereby reducing the theoretical power consumption of 40 LED lamps running for 2 hours from 1.2 kW·h to the actual power consumption of 0.97 kW·h. This paper provides optimization ideas for light control in photovoltaic greenhouses, while also optimizing the quality parameters of strawberries.