# evacuated solar tubes



## Galroc (Jan 25, 2009)

Google didn't really help with this question.

I am looking at evacuated solar tubes, mainly sunmaxx tubes.

I have two roof sections that face south. The largest one (900sqft) faces south-east and is 73% efficient according to http://www.roofray.com/calculators

The smaller section (270sq ft)  faces south-west and is 80% efficient. 

Now, I have read that some people actually like to face their collectors towards the south-east to catch the morning sun to heat up their storage before showers.

I could tilt the tube rack but then that makes everything (plumbing) a bit more complicated. The collectors can also be turned within their mounts to face the sun more.

http://www.apricus.com/image/Misc/IAM-graph.gif

As seen in the above graph, the collectors get more efficient when the sun isn't overhead.

If I face the collectors SE, then I lose a bit of the early evening sun. But, my latitude is fairly north, so the sun should be still visible to the collectors even at the horizon. I should check tonight to see if that is the situation.

Any comments...


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## Dune (Jan 27, 2009)

I wouldn't worry about the plumbing getting more complicated. That is a one shot deal, but the output of the collectors is a lifetime afair. Don't compromise the angle to save a bit of initial labor.


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## velvetfoot (Jan 27, 2009)

That's a way cool link.
My roof is facing southeast so there is some hope for me, although there are a fair amount of tall trees around the place.
Of course, most of the trees don't have leaves at this time of year.
Depending on the roof angle, which I don't know, I could be at 83% potential.  I'm guessing that's not too bad.
In my case, two story house, I guess the snow could be a factor. 
A lot to think about.
Thanks again for the link.


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## TimCroft (Mar 4, 2009)

Evac tubes are not as sensitive to horizontal angle as flat plate.   Tilt is always better if you can change it summer to winter.  The plumbing needs some flexibility to tilt but that is a one time headache.  If you have enough storage, a hot shower in the morning is easy with yesterday's heat.

Tim


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## solarguy (Mar 6, 2009)

I would find out what you declination?? is for true south in your area than pick which roof to mount your system on that comes closest to true south providing that section of roof will not have any shade factor.....

Bob


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## sweetheat (Apr 3, 2009)

new house we are working on will have 48 feet of vieesman evacuated tube set on 45 degree angle roof directly south.  to view, see what's new section www.sweettimberframes.com sweetheat


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