Control system development for energy-efficient lighting in greenhouses

This thesis focuses on the development and implementation of feedback control with application to an energy-efficient lighting system for potential application in a greenhouse environment. The proposed control system was developed and implemented in four stages. First, the lighting model for the red and blue lights was identified separately to ensure uniform light distribution at plant canopies. Subsequently, a daylight environment was constructed using the MATLAB/Simulink environment. The performance of the system was evaluated on a proof of concept system through a series of simulations to verify the control performance. In the second stage, the proposed concept was implemented to regulate the intensity of dimmable multi-spectrum LED fixtures for achieving desired spectral irradiance levels and color ratios while utilizing daylight harvesting to enhance energy-efficiency. To ensure the stability and performance, a Smith predictor was utilized to compensate for the delay introduced into the system by the communication hardware. Implementation of the proposed system with a smooth transient response ensured lower energy consumption for the LED panels. In the third stage, a testbed with environment monitoring and intelligent LED lighting control system was implemented with potential utilization in an Internet of Things (IoT) smart greenhouse environment. The performance of the LED control system was verified through conducting plant experiments in the proposed testbed. It was shown that the proposed testbed is capable of achieving the desired light requirement for the tested plant while maintaining satisfactory plant growth results. Finally, in the fourth stage, the proposed concept was extended to a small-scale plant growth and implemented on a Raspbian operating system with the IoT technology. The system was utilized to implement lighting control and environmental monitoring applications for greenhouses in remote areas. Results show potential for prominent energy savings when the proposed lighting system is utilized to grow kale microgreens, which further resulted in improved plant quality due to uniform lighting conditions achieved through feedback control.