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Thread: soda can passive hot air panel, worth the hassle?

  1. #11
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    I saw where someone used a small drill press and a hole saw. They would use one of the polyurethane (or similar) beer can holders to grip the can by hand.

    They claimed it went real fast.

    I tore the tops out with a pair of side cutters and plan to knock the other end off with a disc grinder - no drill press available.

    Russ

  2. #12
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    Default Just Made one - Not Sure

    I'm just about finished making one of these soda can heaters and I don't think I'd do it the same way again. It takes a long time to deal with the cans and I don't see why you wouldn't get just as good results if you used a flat sheet of aluminum flashing.

  3. #13
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    Search downspouts here some have had some experience using downspouts instead of cans. certainly easier.
    Rich
    WWW.solarsaves.net

    NABCEP certified Technical Sales Professional

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    http://www.calculator.net/voltage-drop-calculator.html (Voltage drop Calculator among others)

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  4. #14
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    Agreed- the down spouts would be easier and one can rig a string of baffles to insert in the down pipe to provide turbulent flow for better heat transfer.

  5. #15
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    First post, forgive me if I maek a mess of it.

    Keep the task in mind. Sunlight hits an object and warms it, we need to get the heat out of the object into the air. Two things that help this are air turbulence and surface area.

    The cans have a big advantange over downspouts because if made with holes in the ends smaller than the can, the air passing through will become turbulent and strip the heat off the metal surface more effectively.

    Second advantage is the remaining end material of the can increases the area of metal exposed to the air flow. This is like having fins attached to the inside of the can to help heat the air. A bunch of baffles inside will increase turbulence, but unless they are firmly attached to the outside of the can they won't increase the heat transfer area.

    Smaller holes slow the air flow, but they should be worth it. Haven't made tests, my gut says holes about half the diameter of the can would be about right.
    Last edited by Pappio; 10-02-2011 at 09:22 AM. Reason: add content

  6. #16
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    Hi Pappio - Welcome to Solar Panel Talk!

    It just depends on how much time you want to spend on the unit.

    The downspout with baffles would be much quicker and easier - unless one is constrained on space the area can easily be taken care of.

  7. #17
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    Default can heater

    I made one and I like It a lot. Its gotten up to around 95 on 30 degree days. I think it would put out more if I could get more air flow. I just have a small 12 volt pc fan, ran off a small solar panel.

  8. #18
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    Default My obstacle is the mounting board

    I did a test 2 years ago with a 2 ft x 2 ft x 1 inch silver covered foam board and about 50 or so beer / pop cans painted black with holes punched in the bottoms. I wrapped the entire thing in window shrink wrap and cut air slits in the top and bottom for the air.

    On fairly cold days in Colorado, but with good sun, and calm wind, the panel put out air at the top at 180 degrees. For this prototype, there was no fan, but the hot air was definitely coming out. My concern and my obstacle was that I was concerned that under certain conditions that the foam board might catch on fire. I've been trying to find a fire resistant light foam board or Insulate http://www.energyboom.com/emerging/insulation-mushrooms become available in my area, but I haven't found anything. Any ideas?

    For my next prototype I have an 8 ft by approx 2 ft by 2 inch foam board and one clear 8 foot ridged roof panel. I think I'll get another one that is dark for the bottom. I don't think this will catch on fire, but how sure am I. I'm planning on a small fan (ideas?), but this could fail and the panel overheat. The south wall under the eaves, get's quite warm, even in the winter - not a good place for a fire.

    = = = = = =
    Also fire resistant foam panels that are not toxic when heated might be handy for insulating interior north walls.

  9. #19
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    Just use Dow XPS foam board - easy to find and cheap - won't burn when you put a match to it.

  10. #20
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    Here is the original one with patents and real testing. It is quite copyable, although they might complain

    http://www.cansolair.com/

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