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Thread: Testing Solar Heater (aluminum cans) set up

  1. #1 Testing Solar Heater (aluminum cans) set up 
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    I'm going to build a solar heater to heat air and direct the heated air into a room. I want to test variations of builds including number of cans in a length needed on the low sun days as well as setting up fins inside the tube of cans to slow the airflow down and create a turbulence, verses just leaving the tubing wide open. Anyone have any suggestions about how I should properly set up my experiment? Basically I've decided to do it like this..

    Use a mini fan such as a computer cooling fan to produce airflow. I plan to regulate the air flow speed by variation of the voltage.

    Measure the air temp coming out versus ambient air temp of cans in a series...
    - 8 cans, 92cm
    - 12 cans, 138cm
    - 16 cans, 184cm

    One can is approximately 11.5cm long.

    Initial testing will house the cans in a long cardboard box covered with plastic-wrap to help prevent heat loss from the wind. (probably made from 1qt milk cartons and tapped together to expedite the testing and keep costs low.

    If anyone has any experience with this or suggestions about my setup or what I should test or how to test it, my ears are open. Thanks.

    Dustin


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  3. #2  
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    Think you have a good start.

    If I understand you right you're test question is "will adding fins transfer more heat to the air?"


    You biggest problem might be adjusting your air flow so it's all the same in your control (collector with fins) and your collector with fins. I suggest a low tech way to measure flow such as one of those cheap anemometers that uses a swinging arm of course set at the same position from your air output; there might be simpler ways. Than adjust your 12V fan using a variable resistor until your control and the finned air output is the same.


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  4. #3  
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    What is the function of the cans?

    A heat collector the size of 16 pop cans will produce a trivial amount of heat.

    Why do you want to create turbulence? I don't think your problem will be transferring heat. The problem will be having enough heat to transfer.
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  5. #4  
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    It should be a couple hundred watts of solar...not sure how efficient this set up with be, but it should be enough to get a measurable rise in temperature. Similar can designs of a meter sq show output temps near 200 F.

    Never been crazy about the can idea though---think the simple metal gutter, or mesh-in-conduit collectors are at least as good and don't have the problems of air leakage.
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  6. #5  
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    I agree, not crazy about the can idea. I think the simplest heat collector would be an insulation, sheet of black corugated metal, top sheet of glass sandwich in a frame. Air in at lower corner and out at upper opposit corner. That's your basic passive solar setup.
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  7. #6  
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    Sounds good. I've tested 6 cans (as 2 of them were destroyed in the making process) and i got an air output of 125F on a day with cool winds and 80F ambient temperature. I ended up using a battery operated 3V personal cooling fan for the job. It put out a nice warm consistent air. I'll have to check into those anemometers Lynn_Fox. Thanks for the input.
    I'll be going with more cans later, as I drink more stuff, ha ha.

    One main reason I'm using cans is because they are free. And I've eliminated the air leakage problem by simply enclosing the box/housing airtight.
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  8. #7  
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    One main reason I'm using cans is because they are free. And I've eliminated the air leakage problem by simply enclosing the box/housing airtight
    My concern wasn't so much loosing air into the box, but between each can. Most of the air lost into the box will not be available at your output.

    I do understand though, if sealed properly, you'll probably get performance similar to down spouts collectors.
    Here's a DIY test of several types. Comparing the Best DIY Solar Hot Air Collector Construction Designs
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  9. #8  
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    Thanks for the link to the comparison. Perhaps I should jump onto their testing train and join forces with them. They've sparked some new ideas for me.

    I'm sorry Lynx_Fox, but I don't understand what a down spout collector is. Perhaps it's the tubing connected to a housing rain gutter used in a box and painted black?

    My thinking about sealing the box would be that, once the pressure in the box equalized with the fan's air input, the leakage in the cans would stop. But then as I've thought about this, I wonder if increasing the air pressure in the box would have an adverse effect on letting some of my free heat escape through the air and out of the glass/framework of my box. I'm not sure if that would be radiation heat or conduction heat. I'm not very scientific.
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