[APD] Re: lighting efficiency coefficient

["Steve Pushak" <teban at powersonic_bc.ca>]

I wrote:
> We can define a dimensionless constant, call it the
> lighting efficiency coefficient, or LEC to coin a new
> acronym, which measures
> the percentage of rated lamp lumens which reaches the
> bottom of an aquarium. This is a gross measure of
> reflector efficiency.

Scott wrote:
> We can but why would we?
>
> There are lots of measurement techniques out there already.
> The lux from a lamp (bulb and reflector assembly) is
> already one of them. The problem is not a shortage of
> measurement techniques, but a shortage of actual
> measurements, a paucity of readily available data.

I agree that the currently available data for typical configurations
lacks measurements with water in the tanks. In my post I suggest that
the difference would be about 5% loss which will be offset by internal
reflection.

The LEC for a typical configuration is useful because it gives a method
to predict the illumination intensity if you know either the rated
lumens of your lamps or the wattage of the lamps & their type (T12 w tar
ballast, T8, CF, MH, etc).

The LEC estimate because even though it is conservatively low at 0.4, it
still indicates that 2 watts per gallon of lighting in a common
configuration gives 6 times the illumination for optimal nutrient
utilization. I suggest that working with plants & lights at the optimal
nutrient utilization level gives you the best advantage of plants over
algae for light utilization. Perhaps I should have stated this
explicitly.

For those people who wish to grow primarily Crypts & Anubias this
information should be highly useful! With the insight from the numbers
that I cranked out for y'all, it should be obvious that ideal Crypt
illumination is around 0.3 watts/gallon. I should think that this might
come as something of an epiphany. At 2 wpg, 2/3 or more of the light is
not being utilized by the Crypts however Cyanobacteria can make use of
all of it.

For most aquarium plants, the ideal illumination for algae competition
is between 1500 to 2000 lux. With a typical LEC of 0.4 to achieve 2000
lux you would need 0.74 WPG -not- 2 to 3 WPG! With a better reflector,
you would need even less!

George, do Allgayer & Teton describe how they measured & determined the
lux values in their table?

Steve

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