Using a ray-tracing model to design a greenhouse with maximized transmission during winter

During winter, natural light limits crop growth, and it is therefore important to use all the available sunlight for crop production. Important factors that influence light transmission are the structure of the greenhouse (construction elements, orientation, roof slope, symmetrical or asymmetrical design) and the greenhouse roof material (base material, coating(s), diffuse or clear). A project was started to maximize light transmission during winter by optimizing these factors. In the first phase of the project, a simulation model was used to analyze a number of promising new concepts. To validate the simulation model, a practical experiment with scale models in the open field was carried out. During winter, the transmission of these scale models was measured. Despite a number of factors that could not be controlled or modelled, such as rain and condensation, in general there was a good match between measured and calculated values. As an overall conclusion, the simulation model showed no consistent differences from the measurements. An asymmetric cover (saw tooth) in combination with diffuse glass did not contribute significantly to light transmission in comparison with a Venlo type cover. This supported the decisions made during the design of the final full-scale demonstration greenhouse in the follow-up project.