# Solar Air Heater



## justgreenhomes (Nov 8, 2009)

Just finished this a week ago. It kicks out 95 deg air when the sun is shining! A 34"x48" solar air heater made from a salvaged window sash.


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## Scuba_Dave (Jan 16, 2009)

Nice, is it Alum siding painted black?

I'm working on a couple larger ones
To the left of the ladder will be a ~6x6 unit w/Alum cans inside


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## wwpro (Nov 24, 2009)

Good timing 

I've been reading about this all week, I'll keep an eye on this thread .

Looking great by the way :thumbup:


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## Yoyizit (Jul 11, 2008)

~3000 BTU/hr when the sun shines. . .?


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## justgreenhomes (Nov 8, 2009)

Scuba_Dave: Most of the black surface is 3/4" polyiso insulation that separates the cool side from the hot side. The fins are just drywall corner bead. I've seen the ones with aluminum cans and I wondered if all of the work was worth it. Maybe I'll try it on my next one. My heater sits in the window so it can be removed in the spring.

I've got plans for a larger one, but I needed to warm my wife up to the idea. I'm llokin gforward to updates on yours.

I just posted an article on my blog about how I made mine.

Yoyizit: I'll have to do a test on the CFM to verify, but I think 3,000 BTU/hr is close.


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## Yoyizit (Jul 11, 2008)

justgreenhomes said:


> Yoyizit: I'll have to do a test on the CFM to verify, but I think 3,000 BTU/hr is close.


The Solar Constant is 1 kw per sq. meter and 34"x48" is about one sq. meter.


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## Red Squirrel (Jun 29, 2009)

That's pretty cool. Just read up on the concept, think I'll look into trying this. Not sure where I'd set it up though but I'm sure I can find a place.


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## Scuba_Dave (Jan 16, 2009)

So my system should put out about 9,000 BTU...nice
Once I get one going I'm going to build a few more
Yeah.....Wife's OK with one....more if she can see some heat from the 1st one :laughing:


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## justgreenhomes (Nov 8, 2009)

Yoyizit: I was using the equation:
Q=4.5 x CFM x (delta h) so 
CFM = Q/(4.5 (delta h))
CFM = 3000/4.5*30
CFM = 22.2

Here's a section drawing:


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## Yoyizit (Jul 11, 2008)

justgreenhomes said:


> Yoyizit: I was using the equation:
> Q=4.5 x CFM x (delta h) so
> CFM = Q/(4.5 (delta h))
> CFM = 3000/4.5*30
> ...


It must be a stack effect formula.

You could save some bucks with these things.
The cost of maintenance is ~$0 and the MTBF is probably very high.

But, treated wood is poisonous; I hope the moving air doesn't drag toxins out of the wood.


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## tpolk (Nov 7, 2009)

I have six windows facing winter sun all day. I have ribbed commercial grade metal roofing I can use to build several. Is there a clearer design I can use or is this just a common sense build. Looks like air is circulating from house over face and back in. carpenter by trade so have some working knowledge. I'm guessing you need to be able to shut the window sash at nite or you have a reverse value thanks timothy


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## justgreenhomes (Nov 8, 2009)

Yoyizit: I thought the toxins from treated wood were only a problem if they leach into the ground or if you have prolonged contact with your skin. I've never heard of a concern that they coudl become airborn. Just to be safe, I'll prime the rest of the exposed wood.








tpolk: how's this? There are more photos in my photo gallery. The ribbed metal roofing should work just fine. No the window closes on the top of the air heater. You should put foam insulation (air conditioner weatherstripping) between the glass of the bottom sash and the bottom rail for the top sach. I took the extra measure of installing insulating window film to help stop any air infiltration.


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## Red Squirrel (Jun 29, 2009)

I'm really interested in trying this for my house, I'll have to pay more attention where the sun shines the most and see if that location is viable. Do you think this would work in -30 weather? Ironicly when it's that cold out it tends to be very sunny out.


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## Scuba_Dave (Jan 16, 2009)

Here are some pics of one someone built
They just used Alum screening
Anything to soak up the heat from the sun will work
Alum works best I think....and cans are inexpensive



















85+ degree air coming out


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## justgreenhomes (Nov 8, 2009)

I'm betting that it will. Maybe not quite the 30 deg delta but I'll let you know when it gets that cold here.


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## tpolk (Nov 7, 2009)

thanks justgreen much easier to see and thanks dave. it appears to me the one in daves is equipped to close at nite to stop warm air from leaving house and unless you have thermal mass in the heater I'm thinking thats needed thats why I was asking about being able to close house window sash which I did'nt see in your design. thanks timothy


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## justgreenhomes (Nov 8, 2009)

Well, its 30 degrees and sunny today. The solar air heater is kicking out 85 degree air.


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## Yoyizit (Jul 11, 2008)

Anybody make one of these disguised to look like dark window shutters, for a retrofit? 

One on each side of each southern-facing window would have the necessary sq. footage, and with the slats at a 30° angle, depending on your latitude, they might do quite well. You'd then need interior vents.


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## justgreenhomes (Nov 8, 2009)

Yoyizit - Interesting idea. I'll have to put that on my todo list.


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## Ron6519 (Mar 28, 2007)

I wonder if you can do that(solar heating) to a brick house. Cut through the interior wall to the 1" space between the sheathing and the brick and use the upward convection in the space to draw heat from the brick. Maybe add a fan to pull the heat out of the space.
The brick is like a heat sponge in the summer so it might work. I need to drill a few small holes and insert a thermometer to see how warm it is.
Ron


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## Yoyizit (Jul 11, 2008)

Ron6519 said:


> I wonder if you can do that(solar heating) to a brick house. Cut through the interior wall to the 1" space between the sheathing and the brick and use the upward convection in the space to draw heat from the brick. Maybe add a fan to pull the heat out of the space.
> The brick is like a heat sponge in the summer so it might work. I need to drill a few small holes and insert a thermometer to see how warm it is.
> Ron


Heat Capacity brick = 900 Jkg-1K-1 Heat capacity stone = 800-900 Jkg-1K-1
You'd also need to know how well the surface of the brick absorbs sunlight; an emissivity hopefully close to 1.0.


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## Scuba_Dave (Jan 16, 2009)

They actually use walls of stone etc as a thermal mass to capture & store heat behind a glass wall

Called a trombe wall:


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## justgreenhomes (Nov 8, 2009)

Trombe walls work even better if there is no insulation between the thermal mass and the inside of the house, and if insulation can be placed on the outside of the glass at night.


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## DIYtestdummy (Jan 16, 2008)

I've been kicking this idea around for 2 years now (our home anniversary was 12/17). The only obstacles are:

1. I have side-opening windows

2. Wife would rather crank up the heater than have anything "ugly" in the windows.

:whistling2:

The trombe wall or a water wall would be great for my south wall made entirely of brick and no windows, but the summers here are blistering hot! I would have planted a green wall or built an "adjustible" pergola, but still have to match the sun's patterns and wait for the neighbor to decide on our party wall.


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