LEDS ONLY EMIT LIGHT IN A VERY NARROW BANDWIDTH
SUPPLEMENTAL LIGHTING I GARDEN CULTURE
LED Pros: • Blue LEDs are relatively efficient compared to MH and have a good light maintenance • LEDs do not emit a lot of heat to the plant (but in total they do add the same amount of heat to a room). • Very long life. Cons: • LEDS only emit light in a very narrow bandwidth. To create a good spectrum you need many different colors, or white LEDs which are not as efficient. Green LEDs are the worst in efficiency, but you do need green light too. • LEDs are expensive compared to HPS and MH (up to 10 times the price). • LEDs are not good in generating UV. UV LEDs exist, but are very expensive, and/or have a short life. Many manufacturers refer to 380 nm LEDs as UV, specifically in aquatics applications, but that is just limited long wave UVA and visible light.
Typical LED red/blue spectrum for supplemental greenhouse lighting (Source: Illumitex)
Plasma spectrum (full spectrum version) The ideal supplemental light should add all the colors that HPS lacks in sufficient quantity, including UVA and UVB. I should note though that adding quality light at lower intensities than HPS creates dramatic quality improvement. It should not add any more heat to the crop, HPS already takes care of that. It should have a long life, and need no, or very few expensive lamp changes.
Plasma lamp with supplemental spectrum for HPS (all the colors that HPS lacks)
Plasma Light Pros: • Very high quality spectrum, including UVA and UVB • Good color stability over time. • Available as a full supplemental spectrum to HPS (so mostly all the colors that HPS lacks). • Very long life (30,000 – 50,000 hours, depending on used spectrum 6-10 years flowering!) • Very low infrared heat emitted to the plants, though the electronics and emitter add heat to the room. Cons: • Relatively inefficient (about the same as Metal Halide). • Higher investment cost (though relatively cheap over time compared to MH as you never have to change the lamp). • More expensive than LED.
So if you look at all the pros and cons, and if you want to add quality light to HPS in indoor facilities, you automatically come to LED and plasma lights as the best choices. The only question you now need to answer is: which one will give you the best quality, and the best return on investment? LED is cheaper than plasma, and has a better efficiency. However, LED lacks UVA and UVB in its spectrum, and it is hard to create an efficient, full continuous supplemental spectrum. Producing green light with LED is not efficient.
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