Registered: 1390979196 Posts: 6
Reply with quote #71
I've just checked the outside temperature. it is 13 degrees C at 20.00 hours.
I would also appreciate advice in the options for the collector. fins seem to be good, around 10CM is recommended. so would alum down pipes be good they can be around 5-6 cm so would increase the surface area exposed as the collector rob
Registered: 1352981942 Posts: 2,223
Reply with quote #72
Do you have a sketch of your latest backpass design using the solar cloth? I looked at the photos in post #57, and I couldn't clearly tell how the air was flowing. Is the air expected to stay behind the cloth, away from the glazing or flow on both sides, in which case it's not a backpass, but perhaps a Zero Pass? Actually, I'd be curious of the performance difference between air flowing behind only versus air flowing on both sides. Greg in MN
Registered: 1353153771 Posts: 1,845
Reply with quote #73
Greg, post #57 is the best photo, first is was one solid sheet and the air flowed behind it. And it did pretty good but I unstapled about 2 inches on each end and folded the screen over tight. I then took some more screen an just made a deflector behind it. This was primarily for looks and to keep the sun off the back and so the air does not flow right out to the front. Definitely not a zero pass as there is only one screen. Scott used Dual pass once but to me a dual pass is more like the ones shown earlier in the thread and in you earlier PDF where the air flows down the front or back and then back up the other side. But that is close enough and there is not a category for that type.
As I mentioned earlier I do think I would benefit from inputs and outputs more like your zero pass to equalize flow down both sides. Right now I am not sure how much air is flowing up the front but at least it is not stagnate there like a real backpass or downspout. I think with a fan I would get plenty of flow and it is screen so I think some air gets through even when in a full backpass layout. Dan Greg, This photo shows the backpass cartridge, you can see the thin gap at the top and bottom, I have a screen flap/deflector behind the gap.
Registered: 1359070732 Posts: 2,240
Reply with quote #74
OK, Rob @ #71, I get you !
In this case, effectively, to avoid excessive ducting, I agree you could use external "roof" air. I think the best idea would be to get the incoming air dragged as far down to the bottom of the house as possible, and even into a rock store or a water storage etc. You might find this article off the BIS interesting... http://www.builditsolar.com/Projects/SpaceHeating/SolAirHtSysBook/Chap02.pdf You might even be able to use your free solar air in your existing duct system from your CH boiler etc. Today I was pulling in external air through my roof slates - 10°C outside temp, and 20°C in the mezzanine, lowest feasible limit... I am currently working on a basement heat storage system - details of my project here... simplysolar.supporttopics.com/post/garagehermits-projects-6221962?&trail=41 Best of luck ! G_H
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(1) "Heat goes from hot to cold, there is no directional bias" (2) It's wrote, "voilà" unless talking musical instruments...
Registered: 1408185925 Posts: 7
Reply with quote #75
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Registered: 1383840458 Posts: 173
Reply with quote #76
Yay - what she said!!!