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[APD] LEDs and color temperature

On Sat, 3 Jan 2004 18:14:35 -0500, Ivo Busko <busko at stsci_edu> wrote:

"S. Hieber" <shieber at yahoo_com> wrote: <snip>
plants? I'd like to hear about that lamp, energy
efficiency, light dispersion, spectral output, etc.

Long time ago I posted something about LEDs (see http://fins.actwin.com/aquaticplants/month.200108/msg00601.htm l)

As far as I can tell, LEDs are not more efficient than
regular incandescent bulbs. And won't become better than
fluorescents are nowadays (about 30% efficiency). IMHO,
not good enough to justify the expense.

That link didn't work for me, but I have another one (that probably won't work soon?).


I'm not suggesting the 'organic LED's' of the article are worth waiting for, but there was some interesting information. Specifically, it said that normal (non-white) LED's produced light at only one wavelength. I assume, it would therefore be expensive to make a white LED, and so it would be better to use a large array of primarily red and blue LED's whose wavelengths are in the absorbtion range of photosynthesis (does photosynthesis occur over a wide range or a few discrete wavelengths?). I'm not sure if the plants would appear well 'illuminated' if you just used red and blue, though, because there would be no green light for you to see them by! (Incidentally the organic LED described would be an excellent all-round light source as it would produce a wide spectrum like an incandescent but be more efficient?)

This link has a comparison of lumen/watt efficiency.
It also states that LED's are a horrendously inefficient way to light larger objects (although it also says a 100W light bulb would still be marginally less efficient than LED's?).

Happy Self-Confessed Armchair Aquarist (until I get my own room), Andrew McLeod
thefish at theabyssalplain_freeserve.co.uk
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