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Old 10-02-08, 02:09 PM   #1
Daox
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Default $150 4'x8' Solar Panel

I was browsing over on BuildItSolar.com and found this. It is an awesome and simple design using PEX tubing and aluminum heat transfer plates. Simply unbeatable price!

Solar Collector using PEX Tubing

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Old 10-03-08, 12:34 PM   #2
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that thing is awesome! and you're right, you can't beat that price. do you plan on building one?
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Old 10-03-08, 12:39 PM   #3
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You betcha! I don't know when I'll get around to it though. Hopefully next summer.

My sunroom already has hydronic heat which is currently run off the hot water heater. I will be installing hydronic heat into my living room in the future as well. So, I really hope to build an array large enough to satisfy a descent amount of space heating needs.
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Old 10-10-08, 02:06 AM   #4
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Pex is not designed for outdoor use. It shouldn't be exposed to sunlight for significant amounts of time. It's simply not designed for it, it will degrade as most plastics do from exposure from sunlight. Look at:

PEX Products - FAQ

If your really looking for a cheaper way than say new cooper tubing might I suggest the grills from the back of broken refrigerators welded or brazed together, plus your water heater is then recycled instead of using a new oil based product.
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Old 10-10-08, 07:12 AM   #5
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This is the quote from the FAQ.

Quote:
Can PEX be used for aboveground outdoor applications?

No. PEX is currently designed for indoor and buried applications only and is not recommended for outdoor, aboveground use. Short exposures to sunlight during construction are permissible, but should not exceed the manufacturer’s recommendations. PEX should be stored under cover, shielded from direct sunlight or in the original packaging. In the future, PEX products rated for outdoor use may be developed.

The thing is, in the design, the PEX is covered with either aluminum sheet or paint. The aluminum for sure is going to block any sunlight from degrading the PEX. The paint may not be the best blocker for sunlight, but its still not in direct light. That, or it could be covered up with something else (more aluminum perhaps).

I'm not saying the design is perfect. But, I do think you could make it totally workable and reliable.
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Old 10-10-08, 09:43 AM   #6
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Quote:
Originally Posted by Daox View Post
This is the quote from the FAQ.




The thing is, in the design, the PEX is covered with either aluminum sheet or paint. The aluminum for sure is going to block any sunlight from degrading the PEX. The paint may not be the best blocker for sunlight, but its still not in direct light. That, or it could be covered up with something else (more aluminum perhaps).

I'm not saying the design is perfect. But, I do think you could make it totally workable and reliable.

Yeah, but if you look on at one of the links the same guys builds the same one with copper pipe for $190.00. So for $60 dollars more you get.

1. 15% more heating capability.
2. a lot less fuss (since copper is more durable and can withstand the heat and exposure).
3. A heater that we know will last a lifetime.
4. Uses a highly recyclable product vs. a one use product that isn't recyclable.

Seems like a no brainer to me, it's just $60.00, and with the increase in efficiency will pay it's self off just as fast if not faster. Really copper pipe isn't that difficult to work with. Solder is a pretty easy thing to get the hang of, and it's a very good skill to obtain for DIY's.
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Old 11-14-08, 08:38 PM   #7
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Quote:
Originally Posted by Daox View Post
This is the quote from the FAQ.




The thing is, in the design, the PEX is covered with either aluminum sheet or paint. The aluminum for sure is going to block any sunlight from degrading the PEX. The paint may not be the best blocker for sunlight, but its still not in direct light. That, or it could be covered up with something else (more aluminum perhaps).

I'm not saying the design is perfect. But, I do think you could make it totally workable and reliable.
Hi,
Right -- The PEX is all protected from exposure to UV.
The first layer of protection is the SunTuf polycarbonate glazing -- it has a very aggressive UV cut off built into the outer layer. They add this coating to protect the glazing itself, but it also protects the PEX.
The 2nd layer is the aluminum sheet that covers all of the PEX except the bends at the ends of the serpentine runs. The tubing at the bends is protected a couple coats of the same black paint that I paint the absorber with, but you could use a more bombproof protection if you are concerned about it.

On the PEX crimp tool.
I tried to make the thing so as not to require any special tools. Within the collector, there are not joints at all -- its just one continuous run of PEX. To make the connections for the supply and return, I used SharkBite push on fittings. These are really easy to use -- they literally just push on. They are approved for for residential water supply plumbing, even if hidden walls -- so, they should stand up to the almost zero pressure in a drain back system with no problem. The Home Depot in our area sells a good selection of them -- the only down side is that they run about $6 per fitting.
A 2nd small problem is that they don't fit all PEX -- I found that I had to take out the inside bushing in the SharkBite to make them work with the PEX-AL-PEX I was using.

The thing to read very carefully on the PEX collector is the cautions on avoiding high stagnation temperatures. I don't think that it should see temperatures higher than about 230F. I avoid these high temps on mine at stagnation by using a high tilt angle (about 70 degrees) -- this keeps the stagnation temps down in the summer because the sun is so high that the incidence angle is very large. This works out well for me in that it also increases winter collection (when the sun is low), and gets more benefit from reflection off the snow. But, if you can't live with the stagnation temp limitation, the copper alternative (that still uses alum fins) is only a few bucks more, and (as mentioned above) is more efficient. All in all, I think the copper collector is probably better for most people.

The solar heated water storage tank and plastic pipe coil heat exchanger actually end up saving even more money than the cheap collector, and they can be used with (just about) any collector.

Gary
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Old 10-10-08, 09:47 AM   #8
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Very good point. I didn't think about the recyclability of it!

I think for the average DIYer, the attraction of the incredibly simple PEX collector is very nice. For someone who is willing to go a bit further, the copper/aluminum collector is probably the better choice.
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Last edited by Daox; 10-10-08 at 10:04 AM..
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Old 10-10-08, 07:30 PM   #9
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oh and I didn't read the whole Pex write up, but last time I used Pex I had to rent a specialized crimping tool for $20.00, because to buy it would have been expensive (it was 2 years ago but I want to say $100 plus. I know it was more than $60 because I'll just buy the tool if it costs 3x or less the daily rental fee or less if I know I'm going to use it again later. And I've only replaced about 20% of my indoor plumbing in my 80 year old house.
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Old 11-01-08, 07:36 PM   #10
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This looks like a good idea if you use the copper pipe instead. It has me thinking about an oil or water closed system for the bedroom and back bath in my house (thermal storage.) A small pump to encourage flow based on temp differential and a valve to shut it off in the summer.
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