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  • solar hot air heater

    Something thats not been discussed here ..well i don'tdon't think it has.

    http://www.youtube.com/watch?v=n7SGz...eature=related

    plenty more info and designs on youtube

    cheap project ..maybe

    and will help to heat workshops ...will add to what you already have, or stand alone to take the chill off.

    i have a huge pile of double glazing units

    i have the fan .. fan is 6 inch from brand new faulty power supply

    i have the wood
    all i need now is the aluminium and a thermostat

    don't quite know how it would perform in the British cloud coverd winter ..but i have noticed that the coldest days are usually cloud free ..

    and my workshop always retains the night temperatures in it ..and is slow to warm up, even in summer its mostly cold in there....i would imagine it would make working in the shop a lot more pleasant.

    will have a go at it this summer.

    unless you guys talk me out of it ..but for the outlay ..ive nothing to loose but a bit of time....and a few watts to power the fan.

    btw these glazing panels are coated on the inside to ratain heat ..im really not sure which way around to use them in this project ..or if they would be benificial or a hinderance

    all the best...markj
    Last edited by aboard_epsilon; 01-01-2012, 04:40 PM.

  • #2
    Seems like a good proposition. Air to air heaters are simple. Leaks don't cause major headaches. I saw one years ago using steel shavings for the heat collection in place of the tubes in the video, which would fit right in with this forum. Another modification used beer cans with one end cut off and set (swaged maybe) into a flat plate and painted completely black to try to minimize reflectance from the surfaces. Air was passed along the back for the heat transfer. Since automobile radiators were once made by stacking short tubes side by side and soldering the ends (again probably slightly flared on the ends) I wondered whether cans couldn't be stretched on the open end into a hex to stack together without the plate. Had some cans saved up once to try but never quite got to it.
    .
    "People will occasionally stumble over the truth, but most of the time they will pick themselves up and carry on" : Winston Churchill

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    • #3
      Way back in the 70's I made a small collector like the one TGTool mentions using cut off beer cans. I used a small wood box and an old double pane window I had for the cover, a small fan with a stack switch out of an old furnace. The darn thing got so hot that if cracked the inner pane of glass. I also had to redo the beer cans and paint them with high temperature paint. Even with 10° outside temperatures, it would produce 110° discharge air. I never followed up on perfecting it. I think I got the idea from a Mother Earth Magazine. I know they work.
      _____________________________________________

      I would rather have tools that I never use, than not have a tool I need.
      Oregon Coast

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      • #4
        As already mentioned, beer or soda cans can be used for the tubing. One plan I saw the maker was cutting the ends in kind of pie shaped sections and then turning and twisting the cut sections to provide"swirl" of the air as it move up the tube. I don't know how much that would improve the efficiency. I f you search youtube for beer can solar heaters I think you will get some hits. I do wonder what you do with those sort of things in the summer though. Even with fans shut off and vents/ports closed off, there would still a lot heat made that would have to go somewhere.

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        • #5
          Originally posted by Gazz
          As already mentioned, beer or soda cans can be used for the tubing. One plan I saw the maker was cutting the ends in kind of pie shaped sections and then turning and twisting the cut sections to provide"swirl" of the air as it move up the tube. I don't know how much that would improve the efficiency. I f you search youtube for beer can solar heaters I think you will get some hits. I do wonder what you do with those sort of things in the summer though. Even with fans shut off and vents/ports closed off, there would still a lot heat made that would have to go somewhere.
          i suppose you could just Chuck a blanket over it ..when it gets so hot that it may damage itself

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          • #6
            I am just finishing up my design for an air to air heat exchanger for an electric dryer. It uses pop cans and I figured out a slick way to cut off the ends so they snap together. I will explain when I post the project.
            Free software for calculating bolt circles and similar: Click Here

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            • #7
              Does it have to be metal? Why not black plastic piping? I know when you lay it down in the sun it gets hot, already black, cheap, and stuff.
              Andy

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              • #8
                In warm weather it will get got enough to melt PVC or ABS.
                Free software for calculating bolt circles and similar: Click Here

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                • #9
                  I saw a version of that long ago that used aluminum flashing folded up into an accordian shape, painted flat black, and placed inside the box in similar fashion. That gives a very large surface area to exchange heat with the air. There were designs that would track the sun, while others were passive.
                  I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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                  • #10
                    I done a little searching for the Solar heater that I posted about earlier and Found it! it wasn't a Mother Earth thing, but Popular Mechanics. Google Books have all the old PM Magazines from the beginning. Here is a link to it if your interested.
                    http://books.google.com/books?id=OOI...lector&f=false
                    _____________________________________________

                    I would rather have tools that I never use, than not have a tool I need.
                    Oregon Coast

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                    • #11
                      Great idea,Thank you!

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                      • #12
                        Many years ago I made a solar heater for my pool that worked on the same idea only instead of air flowing through the tubes it was recirculated pool water. It was a 4' x 8' box mounted on my garage roof made out of 2 x 10's, inside the frame were several copper alum. coils that were originally air conditioner coils and I painted them black. The top of the box was covered with that wavy translucent fiberglass panel stuff (can't remember what it's called) When the sun was shining the water temp was around 120 degrees but I had to really throttle down the flow rate of the water or it would just come out luke warm and in a 35 k gallon pool it didn't make much difference. I later scrapped the idea. I cool rain would drop the water temp 10 times faster than a hot sunny day would warm it.

                        JL..................

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                        • #13
                          When you are heating something like a pool with direct heating of the pool water the temperature differential of the water going out of the heater and into the pool is irrelevant. You want the water to flow as fast as possible consistent with not wasting too much energy pumping it.

                          Even if the water going back to the pool doesn't feel warmed at all, it is. The larger the the differential between the incoming water and the entire length of the solar heater the more energy it absorbs. Slowing it down so the water in the heater becomes warm reduces the heat differential and therefor the heat transfer. The solar heater should feel cold, not warm. If it is warm it is rejecting and re-radiating incoming heat with subsequent lower efficiency.
                          Free software for calculating bolt circles and similar: Click Here

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                          • #14
                            I used flexible dryer duct coiled and sprayed black coiled in my collector box with a bathroom fan to move the air from shop and back.

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                            • #15
                              Solar heater up north

                              I built a solar air heater similar to www.cansolair.com style. I had my doughts at first untill I saw one running at -20c outside putting out 35c temp. Due to short hours and low angle of sun during winter the performance goes down. Edmonton's mean average temperature/year is 3c. winter to spring and spring to summer, (also summer to fall and fall to winter) it cuts about 30% of heating my single car garage. Output when running is about 10000 to 12000 btu average. I used the solar pop can style, mounted at 70deg to catch the winter sun angle. that makes it a little self regulating spring/summer/fall as output falls off as the sun goes higher. If I did it again I would set them at 50degrees to improve spring/fall performance. The biggest issue was getting enough cfm airflow thru the cans. I tried 6"/8" duct fans but the restriction was too much for the fans to overcome. I ended up using a furnace squirrel cage, variable speed fan assembly with a fan motor speed controler. (like a dimmer but made for cieling fans). Yesterday the unit ran for about 3 hours steady pumping 38c air into the garage. By itself it won't keep the temp up but it holds back the chill. I can come in after a sunny day with -20c temps and it is around 10c at bench level. It helps keep the air statified by lifting the cold air off the floor. I would run it with my propane tanktop heater and the temp at the floor would closely match the rest of the garage.
                              I like them and they do work.
                              Darcy

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