Climate-based annual daylight modelling for greenhouses with supplemental electric lighting

Recent advances in LED-based luminaire design have enabled greenhouse operators to temporally control both the photon flux density (PFD) and spectral irradiance incident upon the plant canopy. However, it is difficult to predict the performance and benefits of these luminaires without knowledge of the time-varying PFD and spectral irradiance due to daylight. We have addressed this problem with the development of horticultural lighting design software that incorporates validated climate-based annual daylighting calculations, physically-based modelling of glazing and light diffusion materials, modelling of spectral reflectance from greenhouse crops and surrounding surfaces, and accurate simulation of optical radiation distribution within the greenhouses from direct sunlight, diffuse daylight, and supplemental electric light sources. These measurements can be used to determine daylight availability, monthly daily light integrals, automated shade and energy curtain deployment schedules, and projected electrical energy costs, all in advance of building the physical structures.