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solardan1959

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Reply with quote  #21 
Jeff,
absolutely not!
A couple of post earlier I talked about the same collectors in a horizontal mode, Scott ask about vertical and I was already interested so....

I did this again today and am amazed at how much this long screen puts out with no fan, the picture you refered to is with no fan.  at 20 degrees in, the screen was putting out 124 degrees at 2.4 MPH with no fan through natural thermosyphoning action.  That's over 20 degrees higher than I was getting with a fan in the horizontal position with 2.8 MPH and uses no power!  I tried hard to get a photo of the air coming out as you could see the heat wave from thirty feet away but could not get a good photo.

The fans are a way to compensate for this natural action in a horizontal configuration since the air can not rise naturally.  Fans are also used to compensate for small vents, or as in this case, the heat is at a higher level than you want then you can use a fan and adjust the output to a more comfortable and safe level.  Because of the higher flow you get with a fan and the lower temp, your panel will run more efficiently.

Now I wish I went with my original ideal of a long horizontal vertical collector, I would have saved a lot a juice and maybe got a lot more heat, (though I can't complain, I got about 5 hours today of 80-95 degree heat free with 20 degrees outside).
Dan

Jp27300

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Reply with quote  #22 
"Now I wish I went with my original ideal of a long horizontal vertical collector, I would have saved a lot a juice and maybe got a lot more heat,"

 I wasn't sure what you meant.

Also have you found the reflective insulation is better than painting it black for the screens?

NH Jeff
solardan1959

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Reply with quote  #23 
Woops,  long horizontal vertical collector, can't have it both ways.  I built a long horizontal screen collector 3X20 feet.  I wanted to run it straight up but my roof was not high enough for the 20 foot collector so I went horizontal.

If you went with something that blocked 90 or better of the sunlight does it really matter what's behind it?
When I went reflective I felt more layers were required to "capture" all the light.  With two layer the black box worked slightly better.  Right now my reflective does seem to perform better but it has one more layer of screen.  Someday I'll get that third layer on my standard and see how they both compare then.  Not enough sun due to trees and low sun to do any testing now on those collectors.
Dan

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Scott Davis

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Reply with quote  #24 
Hi Dan,

Actually, what I was getting at is to run one double layer screen collector horizontal and an identically sized double layer screen collector vertical in a side by side test to see what, if any difference the orientation makes.

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solardan1959

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Reply with quote  #25 
Scott,
  I know that's what you were getting at but I'll flip it back and forth a few times and get a trend.  But while it works great horizontally it's amazing what it's doing in a vertical position.  Check out how the numbers come out on the efficiency calculator.  I made an error yesterday talking about my garage heater, I somehow got the cfm too high by a lot), but these numbers are are all right using 2X3 for the input and output vents but 91%.  Something is weird.
Dan

 
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Scott Davis

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Reply with quote  #26 
Wouldn't that be nice! 

For those following along.  A hot air collector with 50% - 60% efficiency is typical.  It's unlikely that much above 70% is attainable, though you never know what we might come up with!

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solardan1959

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Reply with quote  #27 
I did do some more testing today but saw something odd, I never could get the flow I got
yesterday, only about 1.5 MPH max, until I put it next to the house again. Then
the 2.5 MPH came back. Not sure if some other effect is taking place but since
the 8.8 flow seems high I'll have to throw that out.

with a 1.5 MPH or 5.5 cfm flow the efficiency works out to 52%, that's a little easier to sell.

Scott,  laying down at noon, the best fan flow I gould get was 1.8 and the temp maxed out at 97 degrees.
I stood it upright and the temp ran right up to 126 but the flow was only about 1.1 MPH.  When I ran the flow to 1.8 MPH with a fan the temp settled at about 104 degrees.  A little better than horizontal but not much. 
Dan

netttech

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Reply with quote  #28 
Impressive comparison along with good heat numbers.

The more screen is used in different configuration it seems to perform!

Jeff
Central IL
Scott Davis

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Reply with quote  #29 

It is great to hear that screen is working well in both horizontally and vertically oriented collectors!  I suspected it would, but your testing is building a lot more confidence!

Horizontal collectors are a great, low profile, neighborhood friendly option for a lot of folks.

Dan, thanks so much for all the testing you are doing.  You are definitely moving the DIY solar art forward and we really appreciate it!  I hope that others will jump in and do some side by side testing as well!


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markrunning

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Reply with quote  #30 
Hi, I've been following your discussion on vertical vs horizontal collectors. I recently built two 3x8 vertical screen collectors and a pleased with the results. To further size up a collector that would really make a difference at heating my shop I would need to go to a 4x24 horzontal to use my last available south wall. I was just about to start building a 4x24 downspout collector but find myself wondering if a screen model may prove more efficient after reading your results. Has anyone tried a screened collector including a plenum in a larger horizontal orientation?
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