LED Grow Lights
LED grow lights are designed to provide artificial light in photosynthesis process for plant growth. Plants make use of photosynthesis to convert water and carbon dioxide to make organic compounds such as cellulose or glucose. Artificial light has long been employed both experimentally and commercially to produce supplemental or total light for plants. These include the demand for year round cultivation of small potted flowering plants, exotic flowers, fresh fruits, vegetables, herbs, growth of plant cuttings, bulbs, seeds and other propagules, and early start of bedding plants. The light has in general been of a spectrum which is most fitted to plant growth produced by relatively efficient lamps that have a relatively high lumen per watt ratio. These grow lights can be electrically powered lights that give off a spectrum of lights used for photosynthesis. An absorption spectrum of a photosynthetic pigment associated with photosynthesis of a plant is primarily in a blue color region and a red color region, and light in such regions is recognized as essential for growing a plant. Generally, plants subjected to more blue light tend to grow stouter and with broader leads. Plants exposed to more red light are likely to grow faster and taller though with thinner stems and smaller leaves. Hence, a light source that generates light in the blue color region and the red color region is widely acknowledged as a light source for growing a plant.
Lighting conditions including illumination uniformity and proximity of the radiation source to plants related to such cultivation are considered to have powerful effects on the quality and abundance of plants. Accordingly, attempts have been made to provide for the homogeneous illumination of growing plants in greenhouses. Examples of different light sources include metal halide (MH) light, fluorescent light, high-pressure sodium (HPS) light, incandescent light. These broad-spectrum light sources are not efficient in generating light energy when it comes to plant growth. With fluorescent grow lights, the conversion of electrical energy into light energy is moderately efficient, however the spectral content of the light energy is such that much of it is effectively wasted, and doesn't help with plant growth. MH lights have a blue tint and therefore are typically used during vegetative growth. HPS lights emit a yellowish/red tint suitable for the flowering portion of the grow process. Metal halide and high pressure sodium bulbs can provide an extremely bright, intense light, yet are also inefficient, both regarding their conversion of electrical energy to light energy, and also concerning spectral content. Besides that, MH and HPS lights may generate wavelengths that are potentially detrimental to plants. In particular, they product considerable amounts of radiated infrared (IR) energy, which can lead to heat damage to plants.
The field of light emitting diodes (LED) is a rapidly developing technology that has the promise to substantially cut down energy consumption for general lighting as well as for indoor horticulture. The best AlInGaP red and AlInGaN green and blue HB-LEDs is capable of having internal quantum efficiencies better than 50%. LEDs can be focused entirely on the photo-synthetically active regions of the light spectrum, specifically blue and red (400-500 nm and 600-700 nm respectively) without wasting energy on the green (500-600 nm) region which is not invaluable to plants during the vegetative phase. LED-based light sources support full controllability of both the direction and intensity of the emitted radiation, making it feasible to avoid most of the losses involving traditional grow lights. LEDs produce light in a uni-directional fashion, eradicating the necessity of reflectors, further improving efficiency. Because LED lighting is significantly cooler than conventional plant lighting sources, an LED-based plant light may be located much closer to a plant than a conventional plant light, with a resulting increase in light intensity falling on the leaves of a plant. Furthermore, the narrow spectral bandwidth characteristic of colored LEDs makes it possible for selection of the peak wavelength emission that most closely satisfies the absorption peak of a selected plant pigment. When used for indoor growing, the conversion of electrical energy to light energy by LEDs is usually efficient, particularly when compared to incandescent bulbs such as MH and HPS bulbs.