Most efficient grow lights with most PPFD/PAR output are full spectrum based around CREE CXB-3590 or Samsung LM301B or some Luminus white COB LEDs. I don't believe there is any blue-red grow light with comparable efficiency, no matter how expensive. But of course it is OK if you don't agree.
I accept you may not want your room light with hot pink light and respect your preference in that regard, but as far as efficiency is concerned, there's no opinion involved. I'm talking about fact.
What's important here is, radiometric efficiency in the parts of the spectrum most important for photosynthesis. Radiometric efficiency is a measure of electrical power in vs optical power out in a certain bandwidth. A UV light might have a luminous efficacy of near zero Lumens per Watt, as most of the light is invisible, yet a radiometric efficiency of 30%.
Lumens is a measure of intensity scaled to the response of the human eye and is therefore irrelevant to this discussion. A green LED will be brighter than a blue or red one, given the same optical power output, purely because the eye has greater sensitivity in that region of the spectrum. Radiometrically speaking, green LEDs have appalling efficiency, compared to blue or red ones, they just look brighter. Perhaps one day better green LEDs will be developed.
As mentioned above, white LEDs are just blue ones with a phosphor to convert some of the blue to longer parts of the visible spectrum. They are radiometrically less efficient, than the equivalent blue LED because a lot of energy is lost in the phosphor: again, look up Stoke's shift. A white LED will appear brighter, than a blue one of the same power level, but that's only because the inefficiency is more than compensated for by the fact that the human eyes are more responsive to the phosphor emission, than the blue light. The white LEDs you've mentioned above are very good, but they have inferior radiometric efficiency, compared to equivalent red and blue ones.
I like the Luminus devices products because they specify both radiometric power output as well as luminous flux. Refer to the data sheet linked below. Note how the green LED is 2000lm, yet it only has a power output of 4.1W and the blue LED is only 400lm, yet it has a much higher power output of 7.2W! Do the calculations and you'll find the green LED is poorest in terms of power in vs power out, even though it's the brightest.
http://www.mouser.com/ds/2/245/Luminus_CBT120_Datasheet-472561.pdfIn summary: a white LED is pretty inefficient, as a grow light. Not only is lots of light lost in the phosphor, but most of the light is emitted in the middle of the visible spectrum which isn't used by plants.
Home
Help
Search
Login
Register
