Greenhouse Artificial Lighting Control

Industrial scale greenhouses have, during the last decade, reached a high level of automation. However, lighting control is in general still controlled manually because of the type of lamps (High Pressure Sodium) that are used. With High Brightness LEDs about to reach the market today sufficiently high power for greenhouse grown crops can be achieved, and this opens up for advanced lighting control. Optimized control will, however, be a difficult task because the needs of the plants differ between individual plants, crops, time of the day, time of the growth cycle, temperature, and of course the natural ambient light. In this approach to this problem we distinguish four different control loops: growth control, ambient light compensation, light stress detection and recovery, and spectrum optimization, where the focus of this work is on the latter two. In particular it is shown here that light induced photoinhibition, decreasing photosynthetic yield and potentially damaging the plants, can be remotely detected in a light environment.