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Solar Panel
By Frank Lussier, Section Remote Living Posted on Mon Sep 29, 2003 at 11:30:52 AM MST
None

Hi
I just finished building a warm air solar panel for my house.
I used 2x6 treated lumber for the box with 2- 2" holes on the bottom and the top, 1/4" plywood for the back, 2" Styrofoam insulation, 230 pop cans cut off the top and the bottom, 4'x7' thermal glass (patio door), I have 11 of them in my barn and a computer fan 5 inch square.
My first test was on a cloudy day, the temperature outside was 66°F and the temperature of the panel was 158°F not bad, this afternoon the temperature outside is 68°F and sunny and the temperature of the panel is 254°F. The panel is so hot the insulation is melting.
What can I put on the isolation to prevent melting?
Here are some pix

This website is amazing a lot of info a lot to learn.
Thanks
Frank

Solar Panel | 28 comments (28 topical)

Re: Solar Panel (none / 0) (#1)
by Budgreen on Mon Sep 29, 2003 at 11:59:42 AM MST

have you tried a more powerfull fan to circulate out the hot air faster? sounds like a safe bet to me. maybe also some larger holes > 2.5"

Re: Solar Panel (none / 0) (#3)
by Mike Wolak on Mon Sep 29, 2003 at 12:50:28 PM MST

Just wondering, the cans ends are removed and lined up to be a tube? The cans are mounted how? The bottom and top of the unit have a gap a can length this is where the in out holes are? The fan is sucking out or pressurizing in? Please more details on construction.

[ Parent ]

Re: Solar Panel (none / 0) (#5)
by Frank Lussier on Mon Sep 29, 2003 at 01:20:40 PM MST

Just wondering, the cans ends are removed and lined up to be a tube?
yes

-The cans are mounted how?
the cans are mounted in place with 1 inch shingle nails - pushed by hand-it's quite easy

The bottom and top of the unit have a gap a can length this is where the in out holes are?

-approx 1 1/2 can lenght and yes that is where the inlet and outlet are.

The fan is sucking out or pressurizing in?
-it is pressurizing in

Please more details on construction.

first i made a 3 sided rectangular box out of 2 x 6 lumber. i added a 1/4 plywood as the backing. i then added two inch stryrofoam insulation on the top, bottom and two sides ( i nailed them in place)

I caulked all joints

I then added my cans - 260 of them! lol

for the gap i added a piece of aluminium to cover the insulation.

i then painted everything black with high temperature matt paint.

then i added my thermal window - which was already in an aluminium frame. I screwed it on top of the 2 x 6

I drilled two holes of 2" side by side on the top and bottom (next time i will cut out one rectangular hole istead)

This is my first test panel.
Thanks
Frank

[ Parent ]

Re: Solar Panel (none / 0) (#2)
by Frank Lussier on Mon Sep 29, 2003 at 12:24:39 PM MST

have you tried a more powerful fan to circulate out the hot air faster? sounds like a safe bet to me. maybe also some larger holes > 2.5"

yes I just installed a 300 cfm fan and it brought down the temperature to 100 °F
but now i have to replace all the styrofoam because it's all melted lol!
boohoo. I was expecting a moderate to good temperature not 254 °F i got..i could bake a cake in it.

Thanks for your suggestion - it works

Re: Solar Panel (none / 0) (#4)
by troy on Mon Sep 29, 2003 at 12:57:41 PM MST

Styrofoam can't take the heat, as you know first hand. There is another kind of foam that is widely available and can stand heat in the 250+ range. One brand is Thermax. You can recognize it at the lumber yard because it is a dirty brown or yellow foam with a much finer "grain" than beaded styrofoam. It also typically has some kind of foil on both faces. I want to say it is isocyanurate foam, but I'm not totally sure on that.

I used it on a solar oven that routinely hits 300F no problem and the foam's still fine.

Don't depend on high air flow alone to solve the foam problem, because invariably, the fan will get unplugged or you'll have a brief power outage at just the wrong time and poof, melted foam.

Good luck and have fun!

troy

[ Parent ]

Re: Solar Panel (none / 0) (#6)
by Frank Lussier on Mon Sep 29, 2003 at 01:23:38 PM MST

Thanks for the info...i will be looking for that stryfoam. I tried first with all the scraps i had around the house and now i know the household styrofoam doesn't work lol.

Frank

[ Parent ]

Re: Solar Panel (none / 0) (#11)
by Norm on Mon Sep 29, 2003 at 06:24:17 PM MST

Why any kind of plastic foam at all? why not crumbled up newspapers? Thats what I've seen them use on solar cookers that boil water, funny isn't it we're so used to associating boiling water with fire or red hot heating elements and that the paper would catch on fire. Norm.
( :>) Norm
[ Parent ]

Re: Solar Panel (none / 0) (#14)
by troy on Mon Sep 29, 2003 at 09:40:05 PM MST

I would be cautious about the use of paper as an insulator that is used in a solar collector hooked to your house. As paper is exposed to routine high temperatures, a process of pyrolysis changes the structure of the paper so that the spontaneous ignition temperature drops to 200-300 degrees F. We do want to make heat, but not by burning the collector, or worse still, the house. Some claim that even wood can develop dangerously low ingnition temperatures upon prolonged exposure to solar collector heat. I think that is why you never see a commercial collector made from wood. I did see a recommendation to bake a sample of your wood at 300 for a week and see if there are any significant changes, smells, color, etc just to be safe.

Food for thought anyway.

Best regards,

troy

[ Parent ]

Re: Solar Panel (none / 0) (#15)
by Norm on Tue Sep 30, 2003 at 07:05:13 AM MST

Hey Troy: Thanks for the information I never realized something like that could possibly happen...once again I went typin' away and forgot to fully engage my brain...but even so someone might have tried it...now they'll know better, but I guess newspaper does work okay in an outdoor solar cooker. Sure do learn a lot from this board....don't we! Do you happen to have any good links about solar heating in this regard? Might be beneficial to all of us. (:>) Norm.
( :>) Norm
[ Parent ]

Re: Solar Panel (none / 0) (#20)
by troy on Tue Sep 30, 2003 at 05:58:03 PM MST

Hey Norm!

I built a flat plate aluminum collector with pretty good results. My dad built one that used recycled aluminum beer cans with just the top cut off, with the opening facing the sun. His idea was more surface area = more heat. I was not overly impressed with Dad's design. And I ran across this design, which is intriquing because it uses furnace filter for the absorber:

http://ww2.green-trust.org:8383/2000/solar/Homebuilt%20Collector%20Instructions.pdf

"The collector design was tested using the ASHRAE 93-77 procedure, at Western Michigan University's Energy Learning Center (no longer operating). The result: greater than 72% maximum efficiency. This was the highest efficiency air collector they ever tested. It bettered all liquid collectors but one, which it virtually equaled. I know of no non-concentrating air collector, Conserval's SolarWall included, with higher efficiency."

Best regards,

troy

[ Parent ]

Re: Solar Panel (none / 0) (#26)
by Gordy on Sat Oct 04, 2003 at 07:44:39 AM MST

For a good article on the furnace filter idea click on "more diaries" and go back to #52 Black paint on solar hot air experiment.

Speaking of filters don't forget to use one on the inlet side of your collector. Otherwise dust will start collecting on the black paint and start blocking the sun from your collector.

Gordy

[ Parent ]

Re: Solar Panel (none / 0) (#7)
by JackS on Mon Sep 29, 2003 at 02:05:06 PM MST

I would be most interested in seeing how this is built, a drawing or a pic of how its put together would be of help.

I have spent most of the summer experimenting with solar heat and have 2 panels installed, but neither have developed such great results

JackS

Re: Solar Panel (none / 0) (#8)
by Frank Lussier on Mon Sep 29, 2003 at 04:50:34 PM MST

This ia a sketch of the solar panel .
I hope this will be useful.

Frank

[ Parent ]

Re: Solar Panel (none / 0) (#9)
by Frank Lussier on Mon Sep 29, 2003 at 04:54:19 PM MST

sorry I forgot the sketch.

[ Parent ]

Re: Solar Panel (none / 0) (#12)
by pexring on Mon Sep 29, 2003 at 07:58:55 PM MST

Frank,

I too have made a solar panel this summer, although not as big as yours. Mine is 4'x5'. I'm getting temps in the mid to lower 100's on 50 degree days. Instead of aluminum cans, I simply lined the back of the panel with aluminum sheeting and painted it black with the high-heat paint. A couple questions for you:

I assume the air simply blows over the cans? Or can it blow through them too? I then assume the air comes in contact with the glass? Did you use a single or double glass?

At first I built mine with single glass, then made it double. Got much better results with double glass. Plus I would think double glass would be crucial to help shield against the cold in the winter. I'm about ready to make another panel or two as I know where I can get some big double-glass doors.

I'm basically wondering if tin cans are really better than aluminum sheets? Except for when the sun is straight on, you'd throw a lot of shadows too, which I avoided with the flat aluminum sheeting. Maybe I should try pressurizing mine and see if I can also get the temps to build-up. That would prove whether or not cans are worth all the work.

Thanks for posting. Always great to hear other ideas.

Mark

[ Parent ]

Re: Solar Panel (none / 0) (#13)
by Reno on Mon Sep 29, 2003 at 08:26:30 PM MST

Can I suggest bending the sheet in a zig zag pattern
45 degrees at the bends. This will dramatically increase
the surface area of the collector face while not increasing
the size of the apparatus.

[ Parent ]

Re: Solar Panel (none / 0) (#17)
by pexring on Tue Sep 30, 2003 at 07:43:32 AM MST

In my original design I tried a corrugated sheet of metal. The shadows became a problem, and it seemed to take forever to heat-up. Once it heated, it worked OK. I'm trying to create a solar heating panel that starts heating with the first morning sun! So far the flat black aluminum seems to work best for that.

Mark

[ Parent ]

Re: Solar Panel (none / 0) (#16)
by Frank Lussier on Tue Sep 30, 2003 at 07:39:06 AM MST

Hi
Yes the air go through and over them, you can get those double glass door at any windows manufacturer, usually the are $45 - $75 with small defect.

[ Parent ]

Re: Solar Panel (none / 0) (#10)
by Budgreen on Mon Sep 29, 2003 at 05:41:46 PM MST

quite impressive!

I was thinking of making a solar water heater to use for my garage but a design similar to this would save the trouble of making a pump and heat exchanger setup

Re: Solar Panel (none / 0) (#18)
by Frank Lussier on Tue Sep 30, 2003 at 07:57:28 AM MST

I was concerned with the wood when I made this solar panel but I am going to try finding some 2x6 aluminium tracks, I bought some 2x4 aluminium studs and track for my office I hope they make the in 2x6.

Frank

Re: Solar Panel (none / 0) (#19)
by troy on Tue Sep 30, 2003 at 05:15:22 PM MST

If the wooden framing members were well insulated from the hot part of the collector and none of the wood was exposed, I would take the chance on my house. I'm just not sure I would take that chance for someone else if I were a manufacturer.

Good luck and have fun!

troy

[ Parent ]

Re: Solar Panel (none / 0) (#21)
by John D on Tue Sep 30, 2003 at 09:54:03 PM MST

You mentioned you were using treated 2x6. I think if you do some checking you will find there are extremely deadly chemicals used in the preservation process. When the wood is heated these chemicals can easily vaporize, mix with the air and I won't go there. Just some food for thought.

Re: Solar Panel (none / 0) (#22)
by Frank Lussier on Wed Oct 01, 2003 at 03:36:47 PM MST

Hi guys

I just bought some 2x6 channels for steel stud framing and the only insulation I found was from ROXUL - it is made from nonflammable material, the max temperature is 1200°F.

I am putting the new solar panel together today, when I'm finished I will post the new pictures. They are annoucing rain for the next few days. I can't wait to see how high a temperature I will get with this new panel. As soon as I get the data, I will post it.

Frank

Re: Solar Panel (none / 0) (#23)
by JackS on Wed Oct 01, 2003 at 04:13:50 PM MST

Hi Frank
i have been busy testing solar heat too, today
i put up my old satellite dish after modifyng it and saw 370 degrees out of it, i am trying to figure out how much heat it will make while not tracking the sun and will begin testing tomorrow,
i saw 120 degees off of it while it was on the ground not pointed directly at the sun, but a couple of these position just right will provide some hot water

JackS

[ Parent ]

Re: Solar Panel (none / 0) (#25)
by richard on Thu Oct 02, 2003 at 04:06:25 PM MST

Try a ( C ) band dish. 6 or 8 ft. size.

[ Parent ]

Re: Solar Panel (none / 0) (#27)
by veewee77 on Mon Oct 06, 2003 at 08:47:05 PM MST

I have a c-band, 6ft spun aluminum dish that I an going to try to use like this.

How would be the best way to shine the aluminum?

DS

[ Parent ]

Re: Solar Panel (none / 0) (#24)
by Frank Lussier on Wed Oct 01, 2003 at 04:26:28 PM MST

cool, keep me posted.
Frank

Re: Solar Panel (none / 0) (#28)
by Homebrewed12vdc on Thu Oct 09, 2003 at 11:36:27 AM MST

I have 4 of these that heat a 700 square foot building, they work well but i well give you a few pointers on better constuction. First of all I found that 2 inch copper tubes instead of cans works better, I also made my frame out of alunuim. The computer case fans work well, I have a 8 inch by 2 in slot in the bottome and top of mine, with four fans in it, this way if one fails it still has three to run on. Another thing I did which works good was a set the exterior of the top at a 70degree angle and mounted a VW solar panel wired to the fans, this way the brighter the sun, and the hotter the heater gets the more speed the fans turn on. This setup took me from 5 cords of wood 2 years ago to heat my building down to little over a cord of wood last winter. Hope this helps youout and everybody else out there who is trying to use the natural resources.

Solar Panel | 28 comments (28 topical)

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