Solar tubes for "natural" lighting ?!?!??!

[munchieiam]

A very interesting thread over at reef central discussing this topic. Sounds like it might be worth looking into.

http://www.reefcentral.com/vbulletin/showthread.php?s=&threadid=56125

munch

[ March 08, 2002: Message edited by: munchieiam ]</p>

 

[jamesw]

We've discussed these tubes over here on reefs.org a few times, so this is not new ground.

Richard Harker uses natural sunlight as the predominant light source for his aquarium. Perhaps he will chime in here. FWIW, natural sunlight (direct) is about FOUR TIMES as powerful as a 400w metal halide lamp.

Cheers
James

 

[Anonymous]

hi.
So far, it has been just talks, and no show...

From solatube website:
http://www.solatube.com/faqs_general_compare2electric.htm
<blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr> A standard 100 watt incandescent bulb produces 1200 lumens.
A 40-watt, 48-inch fluorescent tubes produces 2300 lumens.
The 10-inch Solatube produces up to 3750 lumens
The 14-inch Solatube produces up to 6500 lumens <hr></blockquote>

So a 400MH is brighter than 3 large solatubes at mid-day.

Compare to James' statement, the difference is the attenuation of light due to reflection down the tube (not direct sunlight).

[ March 08, 2002: Message edited by: seven ephors ]</p>

 

[rharker]

We've discussed these tubes over here on reefs.org a few times, so this is not new ground.

Solar tubes look bright to our eyes, but actually produce very little light. The light has to be reflected quite a few times to get from the roof to the tank and each reflection reduces the remaining light. As I recall, at the tank typical light levels were reduced to 1-2% of sunlight outside.

Richard Harker uses natural sunlight as the predominant light source for his aquarium. Perhaps he will chime in here. FWIW, natural sunlight (direct) is about FOUR TIMES as powerful as a 400w metal halide lamp.

I'll be happy to. I use industrial size pendants that generate about 700 uE/m^2/sec at the bottom of the tank directly under the fixture tapering off to about 200 uE two feet away, but when the sun hits the tank, it is hard to tell the lights are on. Interestly, indirect sunlight has no value whatsoever. Even during the summer, indirect sourthern exposure windows produce 10-15 uE, about what a solar tube might provide. Before spending money on a solar tube, someone contemplating the expense ought to borrow an inexpensive light meter and check one out. Everyone who has, has been quite disappointed.

Richard Harker

 

[rharker]

<blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr>Originally posted by seven ephors:
<strong>
From solatube website:
http://www.solatube.com/faqs_general_compare2electric.htm
</strong><hr></blockquote>

I think the operative phrase is "up to" meaning that most of the time it isn't. For an idea how sunlight varies through the day, go to:

http://www.animalnetwork.com/fish2/aqfm/1999/july/features/2/default.asp

To put their comparison into perspective, a 100 watt incadescent bulb in a desk lamp type reflector puts out about 50 uE/m^2/sec at 18 inches. If a solar tube produces four times the light at some point in the day, it matches a double ended AB 10,000 K bulb in an AB fixture which puts out about 170 uE.

The problem is that the solar tube is producing this briefly at the peak of the day whereas the metal halide is generating this light all day.

Richard Harker

 

[jamesw]

I'll link directly to the picture on Fancy Publications website. Note that I have not "stolen" the picture, only linked to it using the bulletin board's "Image" feature:

Cheers
James

 

[Minh Nguyen]

How much light the tube collect (area and angle of collecting area), and the efficiency in reflecting the light, are the important factors here. If the collecting area of the tube is small like a circle two feet in diameter that is oblique angle from the sun, then the amount of light is not too much. How ever, if the collecting area is large and the angle is direct perpendicular to the sunray, I am sure the tube can be useful.
I think large skylight like what light Richard?s tank works best.

 

[Jeff Hood]

I guess you could always use it as a supplement to 20000K bulbs and as natural moon lighting. No computer program just the real thing.

Jeff