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Algae Scrubber Basics 10 of 14

Posted 02/19/2012 at 09:35 AM by Floyd R Turbo

LEDs – Why they are different

LEDs are a completely different source of light. Fluorescent, metal halide, HPS, and other HID lighting are all mercury based, and the light is shifted from the ultraviolet range into the visible range with phosphors. LEDs emit certain colors of light depending on the compounds used in the diode itself, so it is initially visible light; phosphors are then sometimes used to shift wavelength to achieve various colors.

LEDs, very recently, have proven to be highly efficient, and as more people build LED Algae Scrubbers, more information is being confirmed. There are still a few unanswered questions, but LED Algae Scrubbers so far have been shown to have a few major advantages over CFL and T5HO.

The most obvious one is lamp life - they never actually burn out (unless you drive them too hard). LEDs have what is called an L70 (or L80) rating, which is the number of hours, running at rated junction temperature, at which the total lumen output will have dropped to 70% of its original output. At this point in time, that is usually about 50,000 hours. If they are on 18 hours/day, that's about 7.6 years to L70.

However, as has been predicted, there is a big difference with LEDs when it comes to Algae Scrubbers. Since LED Algae Scrubbers ‘waste’ very little (if any) bandwidth, they are, in effect, double or better the intensity of CFL or T5HO for comparable PAR output. What this means is that you generally only need to run them half as long, or 9 hours a day (just like the double-light CFL/T5HO Algae Scrubber). Couple that with the fact that the intensity of a well built LED Algae Scrubber fixture is, on average, 1.5x the PAR of a comparable T5HO fixture (I have verified this on a Nova 1126/7 vs 50W e-Shine), LEDs are somewhere between 3 and 5 times as effective. Some DIY LED users have claimed that they have found that you can get away with 1/5 the total LEDs wattage vs. CFL or T5HO and get [i]better results[i/]. Not only that, 50,000 hours at 9 hours/day is over 15 years to the L70 date. Some manufacturers are claiming L70 dates into the 100,000 hour range, and while that may not be proven, it’s actually highly probable the LEDs themselves will last that long (the rest of the fixture? I doubt it.)

Some possible negative factors for LEDs are the up-front initial cost, long-term phase shift, and the effect of steadily decreasing output. Phase shift is the reason that most small municipal airports are avoiding LED lighting; white LEDs are actually blue with phosphors added, and they ‘fade’ over time, and shift to blue. Runway lights are white, taxiway lights are blue, and getting them confused is bad. The LED industry is rapidly evolving, so the L70 numbers will continue to increase, cost will decrease, and issues like phase shifting will likely be improved upon. The flipside to the L70 and phase shift issues is that most people who are DIYing LED Algae Scrubber lighting will likely replace their fixture with the next best thing before this ever becomes an issue, if it even becomes an issue at all. With a stock fixture, at least those currently available at an affordable price, will probably fail for some other issue before the LEDs go bad (driver, power supply, fan, moisture problem, etc), prompting the user to replace the fixture with a better one.

LED Grow Lights for Algae Scrubbers

The LEDs that you want to use for growing algae on an Algae Scrubber are the exact fixtures that are used to grow plants. There are different plant-growth fixtures available, and some are not what you want. ‘Flowering’ lamps have a lot of variety of lamp types that you do not need.

Here’s the bottom line: you only need RED. Nothing else is really necessary. White LEDs of any kind have not proven to be highly effective, and neither are Blues (with the exception that they accompany reds in a low ratio).

The best results so far have utilized 660nm “Deep Red” LEDs; there have been far fewer attempts using 630nm Red LEDs. These wavelengths roughly correspond with the Chlorophyll A and B red peaks. Optionally, some 455nm Royal Blue LEDs can be thrown in; according to horticulturalists, and one study by NASA, this ratio is approximately 7:1 red: blue.

One Algae Scrubber user, who has made multiple LED Algae Scrubbers over the past couple years, commented that the use of only 660nm produced great growth, but with the addition of a single blue LED, that growth got ‘stronger’. The algae was more difficult to scrape from the screen, and the strands were more stringy or ribbon-like, and less hair-like. This anecdotal evidence suggests that the blue component is used supplementally in some fashion. So a little blue can’t hurt; add too many and you’re probably just wasting power.

To my knowledge, no one has tried 660s in combination with 435s (which are the corresponding “A” peaks) or 630s with 455s (“B” peaks); however I have a couple of fixtures that I had custom made just for the purpose of testing this. Eventually. Sigh.

Recently, someone told me chlorophyll utilizes the “A” band during midday sunlight, while the “B” band is utilized more in the morning and evening, when the “A” band is mostly reflected and/or absorbed by earth’s atmosphere. Anecdotal evidence seems to support this.

Here are some examples of LED fixtures people have made, and a few growth pics as well.

^^ That was how it looked at first, and below is how it looks more recently (9 days growth)

He stated that “due to the reduction of parameters, now my net grows quite thin, on the other hand not increased my biological load, so I assume that growth is normal”. Thin? Yes. Green? Yes. With CFL or T5HO, you would tend to get yellow growth.

^^ notice mostly shades of green. Only green.
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