Lighting for a Greenhouse
Ideally, plants in a greenhouse would get all of the light they require from the sun, but that’s rarely the case. Supplementary greenhouse lighting can be used to modify the effective day span to influence the plant life cycle or to boost plant growth when natural light levels are reduced. A less-demanding purpose of greenhouse lighting is to supply work lighting when it is dark outside.
Incandescent lamps are the traditional kind of light bulbs that were once most commonly employed for home lighting. Incandescent bulbs are inefficient in contrast to most other kinds of lighting because they release more of the energy as heat than as mild. These lights can be used to artificially manipulate the period of the daytime period to inhibit or support flowering, and they function adequately as work lights, however they do not work well as grow lights.
Fluorescent bulbs are more efficient than incandescent bulbs, and they produce a spectrum of light that is more useful to plants, making them a better alternative for grow lights. Fluorescent bulbs generally generate a low-intensity lighting, so they work best when you’re able to place them close to the plants, such as on germination benches. Fluorescent fixtures also have a tendency to be bulky and large, so hanging them high in the greenhouse can produce shade and protect against natural lighting from reaching plants.
Quartz-halogen lights are more efficient than incandescent bulbs, however, like incandescent bulbs, the light they make tends to be narrowly focused. In contrast, fluorescent bulbs produce light that spreads out over a broader area, allowing one bulb to uniformly illuminate a bigger space and be more efficient than quartz-halogen bulbs.
High-Intensity Discharge Lighting
High-intensity discharge lighting, either metal halide or high-pressure sodium lamps, combines high efficiency with high light quality, making it the ideal choice for greenhouse grow lighting. Metal halide lighting closely mimics natural light and functions nicely when natural lighting is limited, while high-pressure sodium lamps work better as a supplement to natural lighting. Sodium lamps are more efficient and are more often used in commercial greenhouse operations. HID lighting is cheaper initially than other illumination options and is usually more expensive to run.