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Heating using solar?

Discussion in 'Greenhouse - Shade house.' started by Diablo, Apr 15, 2012.

  1. Diablo

    Diablo New Member

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    I see a lot of talk regarding heating greenhouses, but never seen solar mentioned. Obviously the down side is that the sun has to be out and you would need alternative when it's not. But after you recoup initial costs, it's free heat.

    You can build a panel like the one in the following link for around $400 US. http://cansolair.com/products/cansolair-solar-max-240

    Specs say that you get an increase of 50-100 F above ambient temp. I believe, but don't quote me that it's for 1000 sqft.

    Lots of info on youtube about them. Just type in soda can solar heater, soda can solar panel, etc... There also a dvd that exists that show you in depth how to build one step by step.

    Anyway, just thought I would toss that out and see what others though, I plan on building some at some point to test.
     
  2. Murray

    Murray Site Admin Staff Member

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    Looking through he web site there is not a lot of detail on the internal structure. Do you know about that ?
     
  3. trebel

    trebel Member

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  4. Murray

    Murray Site Admin Staff Member

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    Thanks for that Trebel. Interesting.
     
  5. RupertofOZ

    RupertofOZ New Member

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  6. Castaway

    Castaway Senior Member

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    What is the point of the soda cans and the way they are cut at the ends? Is it to trap the heat slowly because of the way they cut the holes slows the flow of air?

    Its not made clear how that part works...
     
  7. Diablo

    Diablo New Member

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    The point of the cans is that they heat up and heat the air inside them as it flows from one end to the other.

    When you say the way they cut the ends, I'm not sure what you mean. But I have seen videos where they will instead of cutting a hole, they will cut slits into it, in order to try and slow the flow and churn the air.

    I talked to a guy who made some and did some testing and tried it both ways and he said there was little improvement in the increase in heat by making the slits and didn't feel they were worth the extra work. Also said that you could end up slowing the flow to the point that you may needed a bigger fan to circulate it.
     
  8. adamkenn

    adamkenn Member

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    Has Anyone ia Oz actually tried this ?
     
  9. Robert Phegan

    Robert Phegan New Member

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  10. Click

    Click New Member

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    I have made both the beer can air heater and a solar water heater. I'm currently using the water heater to heat my 1000 gallon fish tank. It raises the temp by 5 degrees on a day of sun. Heres a video I made when building it.

    http://youtu.be/9F_sPd9sQJM

    prt 2

    http://youtu.be/7W4TbrdWPTw
     
  11. Click

    Click New Member

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    I use my beer can air heater to heat a room in my house. I'll make a video of it soon and post it. It works quite well. What I have found is that just as much heat comes off the outside of the cans as goes through the centers of them. No need to seal the cans and collect the heat from both inside the cans as well as outside.
     
  12. davidl

    davidl Member

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    Click those 2 videos are marked as private view only....

    As someone who has studied a fair amount of physics, and specifically thermodynamics...
    I believe the selection, and shape of the cans and the way they are cut, I feel changes it's heating capabilities very little. As I see it the only losses contributing to inefficiency are
    - heat lost due to the surface emitting the heat back out as infra-red light, due to being very hot.
    - the amount of reflecting the heating surface (black surface) does. ie, how black can you make it. and how non-reflective, so no gloss paint.
    This is assuming the black surface is separated from the exterior by an air gap and uses insulating supports.
    However these losses would only be very minor at the temperatures you are likely to encounter in a home system.

    Having turbulent air flow contacting both the hot surface and the exterior casing will only serve to heat the casing and loosing heat through convection. However turbulent air flow inside the cans will make very little change, apart from how hard you have to pump the air.

    Having better thermal transfer between the air/water flowing through the device and the heating surface(s) means the operating temperature of the heating surface will change, but the amount of energy captured will not. ie, either you heat a little bit of air/water a lot, or you heat a lot of air/water a little.

    Possibly the best shape heating surface I could think of would be the simplest heat sink shape of straight fins running along a back plate, like the one picture on http://qualitekengineers.tradeindia.com/customised-aluminium-heat-sink-374112.html
    With the air/water flow running along the length of the fins, and the fins on the sunny side. You could if you wanted have fins on the other side too. The purpose of this shape is so that much reflected or re-radiated energy is likely to hit another one of the black surfaces in your heater for a 2nd chance at being absorbed / re-absorbed. Also it provides additional surface area for the air/water to collect the heat from the black surface to keep the temperature down and the infra-red re-radiation emissions down.

    All this being said, if you circulate your aquaponics water through this device it may be better having the hotter surface from a flat plate, to prevent anything not black in colour from growing on the surface.
     
  13. Click

    Click New Member

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    I have made the videos public. Sorry about that. I was having a little beef with youtube a while back and made all my vids private.

    I'll make a video soon of the air heater. At the base on the inside of the room I put two small desktop fans to force the air through it.

    The aluminum fins in the link you posted would probably work like a charm but the beer cans are much cheaper and because they are so thin, they make great heat sinks. I painted them and the rest of the inside of the box flat black.
     
  14. Click

    Click New Member

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  15. Sideshow

    Sideshow New Member

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    Why Not Solar Heating Similar to a pool? Run coils of black uv stabilised poly hose, even better over black background with a sheet of glass to trap heat. In 40c heat, it would be burning before coming out though, so you'd need a thermostat to switch on and of to that piping pump. Also in cold and low sun, coiled through a compost, I've seen that used to heat a wall panel heater with great results
     

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