Energy-Efficient, Uniform, Supplemental Plant Lighting for Research Greenhouses

Teaching and research greenhouses at universities and research stations typically require supplemental plant lighting. Lighting for research greenhouses is unlike lighting for commercial greenhouses. Aisles are often wider to permit group access, only parts of the greenhouse may contain plants, and light requirements may differ from place to place throughout the growing space. This paper describes how an innovative luminaire reflector design can provide rectangles of light, uniformly, where and when required. With the luminaires housing Philips Elite AGRO (R) 315 W ceramic metal halide lamps, mounted vertically, as an example, 280 mu mol m(-2) s(-1) can be provided 1.07 m below the luminaire, with no light falling outside the boundary of the lighted area and providing a 0.91x1.83 m lighted area with a uniformity coefficient of variation (CV) of 0.05 over the entire pattern. Luminaires can be mounted to provide larger or smaller lighted rectangles, or spaced to create adjoining or overlapping rectangles, creating lighting patterns with greater or less quantum flux, greater or less vertical uniformity, and different lighted areas, all with comparable CV values. Sections of benches can be controlled individually to provide different daily light integrals, or other control protocols may be used. The luminaire was designed using commercial computer software and this paper presents light values from those simulations to demonstrate the flexibility of the resulting luminaire. The paper discusses a multiplicity of ways to combine and overlap light patterns to produce a wide range of uniform quantum flux, while retaining the capability to light plants without wastefully spilling light onto the aisles, or lighting sections of benches temporarily empty of plants.