SolaTubes for reef tanks

[pvtschultz]

The only thing that would set a Solar-Tube apart from a skylight would be the ability to concentrate the light to the top surface of the aquarium. I have natural sunlight coming through a south window that strikes my tank from about 10-2, especially during the winter months up here in WI, but when the light isn't coming from the top of the tank, it becomes very hard to see inside the tank. And for those of us up North, we usually don't have vaulted ceilings at all unless it was called for during construction. Most older homes up here, and the new ones, have 14-24 inches of insulation in the attic for those beautiful winter days that never hit zero. But for overall lighting purposes, you can't beat a skylight, but for concentration of light, the solar-tube should be the ticket...a tracking system would be the cat's milk.

 

[Herpervet]

The tubular skylight gives better intensity during low light periods because it bounces the light down the light shaft.

A conventional skylight is very inefficient.

We FINALLY started construction on our new facility and the tank project has changed.

I am still using two 4 X 4 skylights with active tracking but now the lens will be about 42 inches from the water surface to give me head room when standing over the tank.


Added three thin rails underneath to suspend 250 watt metal halide pendants to supplement some 20K spectrum which should help the overall appearance substantially.

Hopefully I will have pics up soon of the skylights etc.

 

[jayo]

Kind of off topic, but another reason to prefer the tube skylights to conventional (in addition to ease of install/seal) is that regular skylights will gain/lose a lot more heat - you end up with a large area with terrible insulation. This can be something to consider based on your climate.

jayo

 

[H20ENG]

I really think that if you build / install them right, regular skylights are the best route for natural lighting. You can get dual-paned skylights for insulation.
Herp, I forgot about your tracking panels- those things look awesome! Cant wait to se them.

 

[chask]

Herpervet,

I too am interested in those tracking panels. This is for a skylight??? Somehow I must have missed it before. Could you provide more information please?

Thanks
Charles

 

[salty joe]

The Velux brand skylight has an outstanding flashing kit. Normally they have a double coating of low E, which helps prevent heat loss but also cuts down UV. Hopefully, they are available in clear glass.

Would a 40" x 40" skylight with a polished aluminum plenum down to the tank provide less light than 4 21 inch tubes? If this is so, can someone please explain why.

I was thinking that maybe the solar panel industry would have the answer as to the exact orientation for a skylight in a given location to maximize light.

I am also very interested in the tracking panel. Any info would be much appreciated.

 

[Shoestring Reefer]

I would think that, everything else being the same, the amount of light would be proportional to the area of the opening. So I think that a 40" X 40" skylight would provide more than (4) 21" tubes. But I guess actual area would have something to do with it, and those might be nominal dimensions.

But, keep in mind: with a wider tube, the light has to bounce off the sides fewer times before it reaches the bottom. Fewer bounces = more light. So, if the reflectivity of the solar tubes and the aluminum duct were the same, you would get more light transmitted through the duct.

 

[Ehydo]

Actually that is not true. In a rectantular area there is less light transmitted because of the angles the light has to bounce. In a tube there are no corners or dead spots for the light to get diffused. Also in a tube when light hits a small spot the light reflected reflected is wider than the original beam and transfers to a bigger area allowing the light to concentrate.

It is called total internal reflection.

 

[Shoestring Reefer]

Ok, th ecorners make a bit of sense--I guess someone could try to fabricate rounded courners, that migh be a PITA. But I don't get what you mean by rounded surfaces reflecting more light, if that was what you were getting at.

 

[Ehydo]

It reflects in wider patterns, But there are limitations to the light travel.

 

[Ehydo]

In a tube it is easier to control how the light is coming into it. That allows you to control the direction of the reflected rays and the refracted rays. That allows you to get a higher useful percentage of the light entering the tube.

look here and do some theorizing

http://www.tulane.edu/~sanelson/geol211/proplight.htm

 

[Shoestring Reefer]

Was the link for general discussion? I couldn't figure out what it has to do with round vs square tubes; maybe that's not why you posted it?

The tube does not concentrate the light, it diffuses it--unless the sun is shining directly down the tube, in which case it still won't have any significant concentrating effects.

For example, imagine a skylight of a given area on a flat roof, and the sun hits it at a 45-degree angle. You end up with a bright, square patch the size of the skylight. But maybe not where you want the light. Next to it, place a verticle solar tube of the same area. Out of the solar tube, the light will spread at a 45-degree angle in all directions. So, you end up with a bigger but dimmer patch, but it's where you want it.

So, to sum it up, a solar tube won't concentrate the light more than a skylight (unless you taper it) it just puts it in a different location for you.

 

[Ehydo]

Are you comparing a standard skylight to a solar tube or a skylight with a reflective metal box on it like saltyjoe was saying?

Either way tou are going to get more light out of the solar tube because there is a parabolic lens on the end concentrating more light to start with.

So SaltyJoe if you have an equal circumference of a Skylight with a reflective plenum and a solar tube you will get more light our of a solar tube and you will not have to re-frame your roof.

 

[Shoestring Reefer]

Both. I was comparing the solar tube to the plain skylight to demonstrate the fact that it does not concentrate the light. About the "parabolic lenses": from what I've read here, those just use clear plastic domes, not parabolic lenses. Other manufacturers have similar information.

Out of curiosity-are you basing what you've been posting on manufacturer claims or some published data, or just what you thought up? An educated guess (which is what i 've been doing some of the time) is better than nothing when we don't have much else to go on, but it should be prefaced with something like "I think".

 

[Ehydo]

Mike, I totally agree with a plain plastic lens cap they would be no different. The concentrating of the light before it enters the tube is extremely important. Here is a link to the one that I was looking at. I looked at some others but this one is the most recent. http://www.toolbase.org/tertiary_printT.asp?TrackID=&CategoryID=1282&DocumentID=2024

 

[wazbot]

I'm having 4 solatubes put in my roof this coming wednesday if all goes to plan...

unfortunately my tank and stand are still being constructed, so it will be a while before I can post any real results or such.

I'm hoping I will get enough sunlight here in Perth, Western Australia, to not need MH, but we will see. I have a few spare kicking around so if i need to supplement, I will.

As soon as I have some happy snaps, I will post them

Wazbot

 

[Ehydo]

That sounds great wazbot. Get us some pictures. Most of this thread is talk and no pics.

 

[salty joe]

It's my understanding that you do not want UV protection when lighting a reef tank. Also, with a sun pipe I would think that the diffuser at the bottom of the pipe would be counterproductive.

 

[gatohoser]

Glass reduces UV (the kind u need to avoid) by a large percentage so unless this is a straight open tube, which i dont think it is although ive never seen it, i dont think that would be much of a problem.

 

[wazbot]

Okay, the day we have all been waiting for (well, me anyway)...

My 4 solatubes were installed today, no hitches at all.

The tubes themself are almost directly vertical, no significant bends (i'll try to get a photo of this), and the light was astonishing. :eek1:

The installers had a lux meter with them, so I managed to get some readings before, during and after installation. All the readings were taken at midday, but I will be getting a lux meter myself tomorrow so that I can take some proper readings over the next couple of months.

Before installation, at the proposed water level of the tank (about 24cm, 10inches? below the lowest point of one tube), the lux was 160, once the holes had been cut in the ceiling and roof it rose to about 700, and then with the completed installation it hit 60000! Keep in mind it is mid summer here, with super clear blue skies. For reference the lux in full sun outside was at 105000.

I still need to remove some dust from inside the tubes with a duster on a long pole, so this may raise the lux a bit. Also, there is no difuser of any sort on the tubes, other than the acrylic dome on the roof, I was initially worried about the heat, but after sitting under it for 30 minutes I decided it wouldn't be an issue. If I am wrong, I can easily put a clear acrylic disc inside the tube to create an insulating air pocket (there are small brackets inside for the normal diffusers).

Anyway, here are the pics, zipped for your convenience!