Solar Air Heater - Pop can heater

[Perry]

I thought this might be of interest to a few of you here.  Not much to say.

240 popcans, painted black, outlet temp over 80C(off the scale of my thermometer)

Well worth the effort.  Cheers, Perry

[offgirdonhydro]

I do like it but it need beer cans.  

[Capt Slog]

That's a really neat job and looks good on the side of your house.

The last time I saw a post about one of these, it was mounted vertically and so the heat just came out the top through a vent into the building (cold air went into the bottom from the building too, but you probably assumed that!)  

I'm guessing then that yours is fed by forced air, from a blower or fan?

I'm thinking that one of these could be a good addition to the tumble drying that Mrs Slog insists on baking all our clothes in (I have shorts that no longer fit due to this, and NO, I haven't put on weight).

[snowcrow]

Looks great Perry!!! What are you using to circulate the air? I've been having friends save they non-returnables for this very reason!! Hope to get my collector do this fall.

Blessings, Snow Crow

[Perry]

I had initially planned on mounting the unit vertically. The neighbors house throws a good shawdow during the winter with the low sun angle. So I moved it up as high as I could and it was worth it.

I push the air thru with a 250 CFM squirrel cage fan controlled by a snap disk thermostatic switch.

I need  more air flow. The fan does not cut out from the time the sun hits the panel. (The panel makes heat faster then I can pull it out.) Even with an outside air temperature below 30C I still get +80C out.

When I get some time I'm planning on converting some of this hot air into hot water.

Now if I could only convert some of my own hot air into hot water.....I'd be able to heat my neighbors house too.  

[luckeydog]

Great job on your project. it looks good to.

another throw away material you can use is old

burnt out fluorescent tubes.

Using a stainless steel wire and a 12v car battery you

can cut the ends of the fluorescent tubs off.

use the fluorescent tubes in the same way you used the pop cans.

[DamonHD]

I'd be cautious of the Mercury remaining in the tubes (and the phosphor coating) if I was then going to blow air through the tubes and into my house!

Rgds

Damon

[TomW]

Damon;

Good point and you beat me to it.

I see lots of crazy and dangerous advice here but don't always comment cuz folks think I am picking on people. Illegal to just toss them in a landfill now, too, I think so thats a clue they are not exactly "safe".

Cheers.

TomW

[Ungrounded Lightning Rod]

Mercury is easy to bake out.  The phosphors are another matter.  (I'm pretty sure they're water-soluble going in, but I don't know if they get changed once in place.  Try soaking the tubes in soapy water, and add a bit of vinegar if they don't start soaking off right away.)

I understand really old fluorescent tubes (like in the '50s) also had some very toxic "phosphor" coatings.)

[luckeydog]

Damond.

you bring up a valid point that I did not think of.

I had gotten the idea from a old Mother Earth News article.

I do know the tubes wash out very easily with just water.

there is a white power coating inside the tube and what

you end up with is a clear glass tube.

I have no Idea how hazardous fluorescent tubes really are.

heck next year they will probably say mercury is good for you...lol

If anyone knows the level of hazard that fluorescent tubes pose please

chime in I would really like to know.

I was considering  building a solar hot air heater using fluorescent tubes.

Thanks

Luckeydog

.

[luckeydog]

OK I did some looking around the net

and found this http://www.epa.gov/mercury/spills/index.htm#flourescent

It looks like the largest hazard of fluorescent tubes

are the mercury in them. I found in another article

talking about the power may be an eye irritant.

the hazard of mercury seems to be more of a hazard

to the environment , pregnant or nursing mothers and small children.

so I still want to know will the mercury stay in the glass and pose a threat

after the tube has been cleaned out?

Lukeydog

.

[Phil Timmons]

Do these things work well with "tin" (steel) cans, as well?  I started saving ours from canned veggies, soups, etc., to sort small parts into, but it seems our collective appetite and consumption far over-produces my sorting ambitions.  I now have a couple of barrels full extra tin cans, with more piling up daily.  I know Al has better heat transfer characteristics, but free is free.

I guess this is built by vertically stacking the cans with some size hole drilled (hole saw?) in the bottom of each can in the stack?  I suppose with your soda/pop cans you need to line up the drinking hole in the top with hole you drill in the bottom of each can beneath?  

Do you seal or tape the cans together, or glue (caulk / silicone) them to the back?  I see you have stacked them and built this on a nominal 4 x 8 foot foam board sheet.  Looks good.  Do folks ever stack these type arrays together (series, as it were), or just draw the air off in parallel if they are using more than one?

Thanks.

[richhagen]

The collector looks great.  

The last one I saw posted here was FrankG of theworkshop.ca who made a vertical one.  His story on his is here:

http://www.theworkshop.ca/energy/collector/collector.htm

He also got good results with his.  Rich

[Perry]

Hi Phil,

I think the steel cans would rust from any mositure in the air. At night the cans would get cold and the warm moist air inside would condense and I'm sure there would be some corrosion.

I do notice the first bit of air out of it on start up appears humid.  It dries out real fast.

High temp silicon the cans together.  I used a piece of angle iron to make a little jig. Elevated one end and let them set up. Keeps them nice and straight. then I silicon the cans onto the insulation. Then painted. Make sure to use an insulation that is UV rated so it does not break down.   The R-Max has an aluminum foil which solves this. The cut ends need to be protected. Some planning in your cuts and overlaps solves this problem. Seal the seams with silicon.  My box is airtight. Try to seal it all up on a low humidity day. (No moisture inside to condense on the lens.)

As for the holes in the end, I don't recommend a hole saw. It grabs the thin material too fast and the can becomes a dangerous spinning weapon.  Try a wood bit in your drill press. Go slow and careful. The point of the bit scrapes thru the aluminum nice and clean. My bit did 240 cans and doesn't appear worn at all.

I don't see a need to run these in series.  The air out is very hot.

Ok, I think I got all your questions.  If I missed something feel free to ask.

Cheers,  Perry

[TomW]

Perry;

Sorry I drifted off topic on my previous comment.

I like that idea and it looks like a good project. A small PV panel driving a fan would make it stand alone solar powered. I use a little makeshift unit like that in my office window. A PC fan a small 12 volt PV panel and an aluminum dryer vent flex tube painted black. Works pretty well for its size.

Cheers.

TomW

[ghurd]

Very Nice Project!

TomW,

You beat me to that.  More sun, more heat, more CFM, while less radiated/conducted BTUs to the outside.

Wondering if the efficiency would be better if the cans were mounted vertically?  Like the solar fan, but without the solar fan.

G-

[Perry]

I thought about the solar panel as well.  I found it kinda hard to actually find a nice DC fan that would move a decent amount of air.  

Before I mounted the unit I sat it up vertically in the back yard without a fan on it, just to try it out. You can feel movement of air, but not the volume of air you need to keep the temps down (to take advantage of the full effect of the heating unit).  As it stands now I would like an axial inline fan with even more volume.  I would like to see the thermostatic switch cut out from the panel being cooled down below the 40C cutout.

Perry

 

[coldspot]

Perry-

Nice, very "Hot" or cool!!!

LOL,:)

What did you use to cover the cans with?

240 cans?, is it about 4'x8'?

Anyway, I've been saving cans, (Boo+Koo Energy, Wild Berry, 24 Oz size, about totally black), My girlfriends brother drinks a lot of them and I can just about keep up with washing them out and storage of them till I have enough for a 10'x10' wall, (640 cans total)!

next year maybe or a smaller one this late fall.

(want to test try a window size unit using "RedBull" little cans, have enough for a couple feet by same now most drilled).

 

[biffster]

The holes do not need to line up.  In fact, you require turbulence for optimal heat transfer.  Heat energy transfers more quickly with a bigger thermal gradient. If you had laminar flow, the boundary layer air that's up against the tube would warm up, but not move away from the tube, creating a weaker thermal gradient.

Having small holes or leaving the tops on the cans is also a problem because you will end up with eddies in the air flow, that stay hot, once again reducing your gradient.

So these are the tweaks I would make to this design for maximum heat transfer:

• Cut X's into the can bottoms, and turn the triangular flaps into little fins to mix up the air as it flows through the tubes.
  
• Remove the tops of the cans so you don't get eddies behind the flat surface.
  
  

Of course, the builder already has great results, so maybe its just better to build it as easily as possible!

Regards, Biff.

[Becky]

Perry, where can I get more info on how to build the Pop Cna heater PLEASE1!!

[luckeydog]

I built a pop can heater and you can see how I did it.

 I don't think I would uses Styrofoam again it melted..lol the thing got dam hot.

 hear is the link

 http://www.coloradowindpower.com/page.php?26

 It was a fun and easy project.

 Luckeydog

.

[Perry]

Sorry Becky,

Haven't been on here for a bit.  Very busy.

I built it from scratch.  What did you need to know?

I'll try my best to share the details of the project.

Cheers, Perry

[Perry]

Very slow reply......sorry.

The lens is Lexan.  (Does not fade.)

I started with 4'X 8' sheet.  Trimed it to fit my can layout.

I like the window idea.  I thought of it myself.  I would not use a back board to it due to the cans being inside the house already. No lens required if placed inside behind your window.   Also...I would not use a manifold on the intake or exhaust.  I'd just let convection carry the air from the bottom of the can-tube assembly to the top.

My problem is the windows on the southside of my house fall in the shadow of my neighbors house during the winter.

Sorry for the slow reply.

Perry  

[zeno]

Hi Perry.  Nice work on this unit.  I'm curious about the manifold, if you're still around.    Did you use the Rmax insulation for that or is that wood with a foil covering on it?  A wee bit hard to figure out from these pictures.

[rsck]

Just a few quick questions. Is your collector 2' X 4' or 4' X 8'? Also why the curved surface? Does the curved plexiglass help capture the sun light? Planning on building one soon. Should I insulate all sides as well? Thanks.

[medicmike]

rsck,

I am currently building one of these heaters.  My design is 2'x 8'.  I am also using a curved surface as I read somewhere that it helps to catch maximum light.  I used silicone caulk to seal all the seams and insulated with a foam insulation panel covered with aluminum survival blankets I picked up at a dollar store.  I beleive this will help reflect light to the cans.  I used a CPU fan I found on clearance at Radio Shack and am using a 12 volt solar panel to run it.  The only thing giving me trouble is figuring out a thermostat to turn on the panel at a high temp and turn it off at around 90 f.  Any advise on this?  I will post a link to construction photos and how it performs when I finish.

[luckeydog]

let the solar panel be your thermostat. you could use a thermostat inside the area that you are heating.. just use a typical home heating thermostat with a mercury switch in line with the hot lead to the fan.

or you can do like i do and just let the solar panel run the fan. If its sunny it runs if it is not sunny the fan dose not run.

Luckeydog

.

[medicmike]

Thanks for the suggestions.  I think I will just let it run off the solar panel and not worry too much about a thermostat for now.  I found a thermostat design on motherearthnews that might work.  For now I have 140 more cans to prepare, silicone, and paint and then I will be done.....

[Mr Fahrenheit]

I know this is an old thread, but I have some questions.

1.  Are there and close up photo's of the Air In/Air Out?
   
2.  These stacks all have a cut out at the bottom and top (if it were going upawrds), but are otherwise in Parallel?
   
3. No fan is used to move the heat?
   
4. Is that just snipped tin at the ends to make the chambers top and bottom?
   
5. What are you lining the box with?
   
   

Thanks!

Jason

[inthecold]

Perry your pop-can-heater looks sweet.

Hope you have time to answer a few questions.

Any difference in your heating bill?

How many sq feet is it heating?

Do you have any plans that you can post?

What did you build your frame out of?  Is that white paint or some type of covering on the frame?  What did you use for the back of the frame?  What about fire hazard?

I notice that your covering is not flat are your cans also in an arch to match your cover?  Does it mater if it is flat or arched?

What did you make what appears to be a manifold out of?

Are each column of cans connected so that air enters in can #1 and works its way out at can #240 or does air enter each column at the bottom and exit at the top of the column?

What about toxic off-gassing from the glue, paint or other materials in the construction?

What do you do with the unit in the spring, summer months?

Thanks for your time.

[jeff260z]

I am also building one based on the cansolair design. Your heater is my inspiration. Nice work.

I've been playing with different fin designs on the bottom of the cans. I think cutting fins in the can bottoms will act as a heatsink, allowing the air to soak heat from the can. We know the sun heats the cans up and the most efficient designs should keep the heat collectors (cans) cool. This means that as much of the suns heat as possible is being absorbed by the air...

If your output air temp is well over 80 degrees then maybe you need more airflow?

[jodenmel]

how is the heat going into the house and where is the cold air return.

Finally what is the frame made of and is the cover plexiglas.

Thank You

Jodenmel