The application is similar as was previously described, the system is an aquarium with a circulation system that takes water from the main tank out through a plumbing system, passes the water over an roughed-up clear plastic canvas screen (vertically oriented, and illuminated from both sides), and then the water is returned to the main tank. Algae grows on the screen and removes waste just as in any other waste-removal application, and the algae is harvested once a week. So far, the most success with this method is from using T5HO lamps in the 3000K red/bloom bulb spectrum.
I wish to mimic this as closely as possible with LED lighting. There appear to be several hurdles to overcome to make this happen. Here are some pictures:
Chlorophyll A & B absorb this:
Here's where some non-LED lights sit in the spectrum
Here's Warm White LEDs and Chlorophyll A & B
The issue here seems to be that WW hits the B pretty well, but according to this other thread on this site:
And specifically this response:
rlantis wrote:It can depend upon what species of algae you are growing, but generally speaking, the strongest absorption peak for chlorophyll 'a' is in the deep blue, followed by deep red. (BTW, don't let the misplaced color spread in the picture throw you off, despite what it shows, it's 430-460nm blue, and 660-700nm red).
For your purposes, you can practically ignore the chlorphyll 'b' line, since there are only about 1/3 as many 'b' receptors as 'a', and because the chlorophyll 'b' is (considered to be) an "accessory" pigment that transfers the light it absorbs to chlorophyll 'a'.
And DO ignore the wavelengths that are closer to the baseline between deep blue and deep red peaks, because they are so inefficiently absorbed that you'll waste most of the power used to develop the light. Good luck, and happy algae growing.
Which doesn't show the .png file so I can't quite tell 100% what is being referred to, what you really want is the Chlorophyll A. However, is that going to be the case for an aquarium application, and would it differ between freshwater and saltwater?
So far, the best I've been able to come up with is that to cover all the spectrum for A & B, there should be a ratio of 2 reds to 1 blue to 1 warm white (planning to use high-power CREEs). Does this sound right? The Warm White hits the B and the reds/blues hit the A?
The other issue I am wondering about it the unity of spread. The filters using this method and T5HO typically have the lamps (with reflectors) about 2-3" away from the screen upon which the algae is grown. It seems that no one has really been able to mimic successful growth using LEDs. My theory is that T5HO spreads the same light evenly (spectrum wise) over the whole length. LEDs are too focused to spread it evenly at close range (4 inches or less). Mix that in with the fact that you need multiple types of LEDs to get the proper spectral range for growing algae, and you end up with needing a fixture that must group 2:1:1 red:blue:WW at a distance far enough away to achieve a uniform spectral spread.
Theoretically, is is possible to get a uniform spread over a screen in such close proximity?
Also, there is the lumen factor. What I understand is that if you match LED lumen output with T5HO lumen output, you'll fry your algae, because lumens are adjusted for human perception. So is there another unit/form of measurement that should be used to try to mimic T5HO with LED?
I hope someone can answer, or point me in the right direction...