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Old 01-09-20, 01:12 PM   #11
GaryGary
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Hi,

Here is an interesting solar air to water heater that goes a long ways back, but is very simple.
https://www.builditsolar.com/Project...aterHeater.pdf

The air to water heat exchanger they build by just attaching fins to the outside of the hot water storage tank makes it really simple, but probably not as efficient as a radiator style heat exchanger.

I think one challenge you face is that solar air heating collectors tend to be less efficient than solar water heating collectors. You can see this in the test results that the SRCC gets for air vs water heating collectors -- http://solar-rating.org/
Maybe this has to do with low specific heat and low density of air making it hard to get really efficient heat transfer from the absorber to the air flow?

For a drain-back copper collector, I like this one:
https://www.builditsolar.com/Experim...perAlumCol.htm
Its easy to build, uses only half inch copper pipe with no expensive fittings.
I think that for a single glazed collector with a steep tilt, it can be left in the summer stagnated without hurting the collector. About $6 per sqft.

This is the one I use mounted on the side of my house for water and space heating, and even with double glazing (which makes the collector run warmer when stagnated), it has been just fine for about 10 years.
https://www.builditsolar.com/Project...Space/Main.htm

But, if you go with the air to water design, it will be very interesting to see what you learn.

Gary

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Old 01-10-20, 10:42 PM   #12
gadget
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Quote:
Originally Posted by GaryGary View Post
Hi,

Here is an interesting solar air to water heater that goes a long ways back, but is very simple.
https://www.builditsolar.com/Project...aterHeater.pdf

The air to water heat exchanger they build by just attaching fins to the outside of the hot water storage tank makes it really simple, but probably not as efficient as a radiator style heat exchanger.

I think one challenge you face is that solar air heating collectors tend to be less efficient than solar water heating collectors. You can see this in the test results that the SRCC gets for air vs water heating collectors -- http://solar-rating.org/
Maybe this has to do with low specific heat and low density of air making it hard to get really efficient heat transfer from the absorber to the air flow?

For a drain-back copper collector, I like this one:
https://www.builditsolar.com/Experim...perAlumCol.htm
Its easy to build, uses only half inch copper pipe with no expensive fittings.
I think that for a single glazed collector with a steep tilt, it can be left in the summer stagnated without hurting the collector. About $6 per sqft.

This is the one I use mounted on the side of my house for water and space heating, and even with double glazing (which makes the collector run warmer when stagnated), it has been just fine for about 10 years.
https://www.builditsolar.com/Project...Space/Main.htm

But, if you go with the air to water design, it will be very interesting to see what you learn.

Gary
Great! Thanks Gary, i'm going to look this stuff over tonight.
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Old 12-28-20, 08:14 AM   #13
solarhotairpanels
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Originally Posted by gadget View Post
Thanks everyone.

I think I read through every build on that site. Screen absorber is definitely the way to go for heating air. Very simple and affective.

I was hoping to find someone that has tried heating water with solar heated air via a radiator style exchange. I checked online again to night and looks like I get to be the guinea pig. Any takers want to try it before I get to??
Just keep in mind..

anytime you do a great job building something to create heat then transfer it / then transfer it / then transfer it... you are going to have heat loss each step of the way.

hot air panels work great when the sun is out..
Can't stor hot air

Thinking about using hot air to heat water makes me go coo coo?
Don't think that's going to work out to good for you. Just my opinion.

I have 2 hot air collectors I built that have been kicking butt for many years now.
Time to change my poly carponate glazing though.. gets weathered and dull over time but that's about it.
They take 66 degree air from the pantry inside my house and raise that temp to 98 to 120 degrees which is pumped back in to 2 rooms in my house on the south side of the house.

and just for the record, it doesn't matter if it's 10 degrees outside... as long as the sun is on my collectors they heat up quickly and pump hot air back into my house like we the people.

Works kick butt! (when the sun is out)

Try not to get to tied up over thinking new ways to do something that others have already tested.

Make a delicious cup of coffee
Sit down at your computer and go to http://builditsolar.com Do some research, you'll find every kind of solar heating build you can imagine there and most systems have been tested and YES they concluded that the screen works best when building a hot air collector but my 2 hot air collectors are not made with screen.

I managed to come accross someone throwing out a piece of 4 ft high x 25 ft sheet aluminum that use to be there swimming pool wall on an above ground pool so I used aluminum for my absorber place and back panel of collector. Sandwiched the insulation between 2 pieces of aluminum. Worked out great during the build.

Just for the heck of it after reading about the screen.
I added screen to mine to test and the temps only rose 2 degrees hotter then what I was already generating so I removed the screen. Didn't need it.

My snap disc fan on/off controller is set to 98 degrees.
Once my fan kicks in it stays on constantly while sun is on collectors.
Couldn't be happier.

There are PDF files on this website of my collector build for your viewing if interested.

Take care and good luck with your ventures. I sincerely do hope you are successful.

Solarhotairpanels

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Pat from Warwick, RI

Please Note:
Comments and/or suggestions I make here at the forums on 'your' projects as well as my own have all been carefully and scientifically calculated by 'the seat of my pants'
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