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Bert

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Reply with quote  #1 
My cousin is thinking about building a thermosyphon collector. He doesn't want to use fans or  electric. Something like this;
http://www.builditsolar.com/Projects/SpaceHeating/ShopThermosyphon/ShopThermosyphon.htm

but on a smaller scale. Maybe 8' tall by 12' wide.

I see that the one in the link uses the slanted dual screens. Would that work better at the slow air speeds or would a zero pass design?
Has anyone compared the two?



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Bert K.
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KevinH

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Reply with quote  #2 
Be sure to refer him to Gary's info here:  http://www.builditsolar.com/Projects/SpaceHeating/solar_barn_project.htm , especially the "Potential changes and refinements" and "Recent Testing" links.

Thermosyphon collectors can actually achieve good flow rates if designed properly.  Gary measured 3.9 cfm / sq foot on his (more than many people get with a fan).  To get good flow, however, takes large in/out vent openings that are sized properly relative to the depth of the collector (info in the above link).  Is this going to be on an out building like a garage or barn?  The large vents make it less practical for home use.  If the vents are too small it will get too hot.

One of the requirements of a thermosyphon collector is low air flow resistance.  That is one of the benefits of zero pass when using a fan, but I don't know what would happen with passive flow.  The gap might have to be widened or more layers used to widen the total gap.  I don't know of any one that has tried it.

Another interesting passive design that has been discussed here before is this one: http://www.iedu.com/Solar/Panels/

Kevin H
MN


Bert

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Reply with quote  #3 
This will be on a barn shaped building that he uses for his workshop and he even has a pool table upstairs. He has some form of heat in there but I'm not sure what. It was cool when I was there.
He has a weird door that closes over the stairway opening. It reminds me of a cellar door. This keeps it warm up there.
He wants to add some heat downstairs without spending too much.
I will show him those links.






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Bert K.
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gbwillson

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Reply with quote  #4 
I remember when I first tested my prototype ZP I ran a quick experiment by making the ZP passive. The results were NOT impressive compared to the 2-screen. My thought at the time was with my both my test collectors tilted back at a 60˚ angle the air entering either collector will stay against the glazing until it reaches the top of the collector. At that point with the 2-screen, the air must pass through the 2 screen layers and out the exit. This isn't much different from how a 2-screen normally works. But with the ZP, air enters, rises to the top of the collector against the cold glazing and only passes through a single layer of screen. But if the two collectors were vertical, I think the ZP might have the advantage, as the air will not only be heated by the screens on either side of the air flow, but the ZP has better air flow characteristics.

Greg in MN
Bert

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Reply with quote  #5 
If he decides to go forward we could probably built 2/3rds of it with 1/3rd a zero pass and one slanted. Wouldn't be too hard to switch one of those around after comparing.
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Bert K.
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mclark999

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Reply with quote  #6 
Why does he not want to use fans/electricity?  Is it to save cost or is there no electricity to the building. Or maybe to keep it simple?

It's really nice to be able to direct the heat through ducting to exactly where you want the heat.


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Double screen hot air collector
gbwillson

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Reply with quote  #7 
Another issue is he wants the unit to be horizontal. While it will work, 8'H x 12'W is not the best configuration for passive. Thermosiphoning works best with a long vertical flow. I think I remember a 2:1 ratio is the minimum required for good siphoning. A 12v fan hooked up to a small solar panel would greatly increase flow, while being free from any needed power for remote locations.

Greg in MN
KevinH

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Reply with quote  #8 
Gary's is wider (8 high x 20 wide) but it was set up in five 4x8 vertical sections.  Don't know if it is really necessary to do that or if it was just done that way to support the glazing.

Kevin H
MN
Bert

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Reply with quote  #9 
 My power  supply went on my computer yesterday. I should have it fix tomorrow. 
Using the other computer that I use for TV. It's a pain to type with.

He is cheap even though he makes more money than me. So probably no electric.
We could just make three panels in a row if they work better that way. Would be easier to put the glazing on anyhow. May need the support also being 8' tall.

if he wants my help he will have to wait until spring now. Getting cold. [smile]                              











i

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Bert K.
Michigan

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GOM

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Reply with quote  #10 
If the building in question has a south facing wall, a full trombe setup on that wall might also be a solution. My garage and workshop share a south facing adobe wall with no openings in it.  Wall is about 10 feet high by 20 long, hence 200 square feet.   Every time I walk by it, I get closer to building a large wood frame probably 8 by 18 feet and painting the white adobe within the frame flat black, then covering the whole works with plastic glazing.  The wall is shaded in summer so no problem there.  Lots of info on the web re trombe walls for completely passive heating.  Only disadvantage I see so far is the length of time the wall takes to heat up and for the heat to transfer through approximately 18 inches of adobe to the inside in my situation. Yeah, I could cut holes in the wall top and bottom for a thermosiphon but adobe walls are like flat roofs (which I also have).  You do NOT cut holes unless absolutely necessary!

I do have a kiva fireplace in the workshop side of this part of the house and have been tinkering with ways to mount a drainpipe heater on the roof and use an inline fan to take the 'product' down the chimney and into the shop/garage.  Question there is where to obtain interior 'cool' air to feed the input side of the heater. I've even thought of trying to input ambient outside air, usually in the 20s in mid winter and see just how much I can heat that through a lengthy drainpipe setup to then feed into the shop/garage. I currently use a 4 by 14 foot drainpiper for much of the main house but it is a closed loop system. Does a tremendous job and cuts both my heating and cooling cost by nearly 50% thanks to dry air here in summer and average 40 to 50 degree differences between noon and midnight.

Oh well, maybe I'll try to put both input and output for the drainpiper up/down the fireplace chimney. BTW, bless the guy who conceived of the drainpipers!  I love them!    
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