Solar Space Heater Using Old Pop Cans

I haven't yet tried this system but it seems very promising. Heres a video on how to make them. The guy in this video can get temps of 160 degrees ferenheit on a fall day

http://www.youtube.com/watch?v=XsF9RvVxFc4

For those who can't view the video here's the basics

materials: a window, enough popcans to cover the area of the window when placed sideways against it, 1-2 inch thick styrofoam insulation, two sections of dryer ducting with the length depending on the site, duct tape, an electric fan, cage wire

Steps

-measure and cut styrofoam to make a three sided box to attach to the frame of the window you have and let it dry. Duct tape the walls together along all edges to seal it. Make it deep enough to fit the diameter of the cans in

-cut an intake and outtake hole on each end of the back piece of foam that is wide enough to put the dryer ducting through

-place cage wire into the holes so that it sticks out 2-4 inches on either side of the styrofoam

-cut or drill out the bottom of the cans

-place them in the styrofoam box and cover with more cage wire after cutting a section of cage wire to fit snug inside the box

-spraypaint everything black

-add four more pieces of styrofoam to line the inside of the box, over top of the cage wire. then place screws into the narrow sides of the box every few inches to further ensure keeping the cage wire in place

-cut or drill the bottom of all of the cans

-place them inside and spraypaint the whole contraptions black

-apply high heat mortar around the edges of the box that will come in contact with the window in order to keep it in place

-put the window in place, seal with duct tape, and leave to dry

-now you're ready to position your unit in the sunniest spot possible

-attach the dryer ducting to the intake and outtake holes and seal with duct tape

-place fan at the end of the outtake ducting to move hot air from the unit and into the building you are heating

We built these in the 70's.... the problem we ran into is that there is a paint smell that comes off in the hot exhaust... I'm not sure what would happen if you used high temp paint and ran it a while before ducting into your living area.   

Also don't use pressed wood for permanent sides as it also puts off gas.

A little demo like this can be moved into position to catch a lot of sun. A larger one to heat your life pod (living area) would not be aimed directly into the sun except for a short while each day...unless you want to spend all yer time turning and repositioning it.  But, hey, if you want to do that to heat and save fuel it is a way to do it.

It could be a way to burn less wood in yer RMH to keep yer life pod warm.

Ahh the paint smell...why didn't I think of that. There's gotta be a less toxic way to darken the cans...

I'd love to have a rocket mass heater but the local government is very strict on fireplace code here and I doubt one would pass inspection.

Why is it that something (the RMH) that is new, saves energy, pollutes less than any other heater, is safer, is better for the planet...will save you money, and is comfortable, is always frowned on by the authorities?

Is it their Stocks and ties to wasteful systems that are affected or is it their blind ignorance to look at a system and say "WOW great idea?"

Questions don't need answers... That is why i bought land  that has no zoning... The RMH is more cost effective than anything else for me. I have an abundant supply of wood.

Passive solar is the best answer - especially for new construction... solar space heaters can be made, but they do have problems and limitations.

I would like to think that their strictness is in the best interest of the public health and safety. I could see the point that if you allowed everyone to go on making their own heating contraptions that more deaths will occur and/or houses burnt down. But if a system like the RMH is proven safe then it should be allowed. I would like to think this but I dunno, I could see corruption playing a part too.

I think the problem is that it is new and doesn't have the track record of the conventional wood stove.

One can hope that they are careful and have the best interest of protecting us at heart... But somethings they will not understand nor even try.. 

Maybe you can get a special permit for something else -  experimental or something..  If they have an engineer to look at it maybe they will approve...

I dunno...this municipal planning and building department is notoriously conservative and hard lined.

What is the farthest that you could run the dryer ducting without losing significant heat? My south side has no windows because a garage will be going in on that side. In the meantime I'd like to make a number of these to create the solar heat I would have gained with windows.
This means that I would be running the ducting around the corner into the slightly cracked open windows because I'm not cutting holes into the siding. It will be sealed at the window. I'm planning to wrap fiberglass batting around the ducting and topping off with black plastic to waterproof, unless there is a better idea.
The ducting would run approximately 4'. Would I be losing all my heat gain in that distance?

I don't think you would lose the heat, but you might create the need for a fan or two.

tel wrote:
I don't think you would lose the heat, but you might create the need for a fan or two.

Thanks tel- I think you're right about the fans. I'll look around and see what I've got.

Do you think using black construction paper or britol board instead of spraypaint would work just as well to attract heat, yet not produce toxic fumes like the spraypaint?

I don't think those would work just as well because they wouldn't be so tightly adhered to the metal, but I'm sure they would still work to some degree.  what about blackening the cans with soot?  there are low odor, no VOC paints available, too, though they might be expensive and not as quick as spray paint unless you have access to a paint gun.

Thanks for the ideas. If by soot you mean wood ash then I have lots of that to try out.

I plan on trying this as soon as I have enough cans, got 40 coming my way today Since I am not pumping the air into a living space the fumes won't bother me. Just curious if you could get away with everything being siliver so it reflects back to the glass and it will still keep it trapped. Just trying to think of a way around the whole black paint issue.

blitz1976 wrote:
I plan on trying this as soon as I have enough cans, got 40 coming my way today Since I am not pumping the air into a living space the fumes won't bother me. Just curious if you could get away with everything being siliver so it reflects back to the glass and it will still keep it trapped. Just trying to think of a way around the whole black paint issue.

Everything inside the solar air heater, that is converting light to heat, needs to be FLAT Black.

Ok well I tried a real cheap simple version of this. I took about 12 cans and put them into the lid of a cardboard box. Made a hole at the top and bottom for air flow and just taped the cans to the box since it doesn’t have a glass front to keep it held back. I then spraypainted and taped it to my south facing garage window with a thermometer. I didn’t seal or insulate it, I simply taped the box to the window. My garage is 40  F, and within an hour the air temperature coming out was 120F with mostly sunny conditions. I suspect it didn’t go much higher than that because of the lack of insulation and sealing. I am now building a bigger one that is sealed better and Im going to hook up fans to it. Ill post my findings 

Very cool mini project.  What was the final temp raised to in the space.  You mentioned it started out at 40 degrees

in stead of op cans add another piece of glass and fill it with black beauty

http://www.badboyblasters.com/id80.html

i fill clear glass bottles with it and set them in solar windows in the winter

My garage is pretty big so the heat didn’t really put a dent in the entire space. It was closer to mid 60’s to 70 closer to the heater though, and the internal temperature of the unit was only 120 max. Now im going to focus on larger air volume and see how it goes.

I also thought about the idea of glass and some kind of thermal mass behind the actual cans to absorb the heat and release it, once those cans cool it can go down pretty quick. I was pretty amazed though that without the sun the internal temperature was still above 70. 

blitz1976 wrote:
My garage is pretty big so the heat didn’t really put a dent in the entire space. It was closer to mid 60’s to 70 closer to the heater though, and the internal temperature of the unit was only 120 max. Now im going to focus on larger air volume and see how it goes.

I also thought about the idea of glass and some kind of thermal mass behind the actual cans to absorb the heat and release it, once those cans cool it can go down pretty quick. I was pretty amazed though that without the sun the internal temperature was still above 70. 

I believe that you want the thermal mass inside (the space you want heated). Blow the hot air over the thermal mass, and then when the sun sets... isolate  the solar collector (so it wont draw in cool air). Then the thermal mass just radiates its stored heat.

Ill give that a shot

charles johnson "carbonout" wrote:
in stead of op cans add another piece of glass and fill it with black beauty

http://www.badboyblasters.com/id80.html

i fill clear glass bottles with it and set them in solar windows in the winter

I looked at your link for black beauty. I will have at least one fan, so would you recommend this product be isolated from the fan-drawn area within the heater unit? 

Amadou wrote:
I looked at your link for black beauty. I will have at least one fan, so would you recommend this product be isolated from the fan-drawn area within the heater unit? 

It looks to me that Charles is putting the black beauty inside his south facing window... I have not figured out how it would work inside an active air unit.

yes i put it in clear bottles on my window sills. so i don't need paint.

what i was suggesting was another layer of glass on top of pop cans then use the black beauty to cover the
unpainted cans       


                                      like this pic

blue = glass
black= Black beauty
grey =cans

charles johnson "carbonout" wrote:
yes i put it in clear bottles on my window sills. so i don't need paint.

what i was suggesting was another layer of glass on top of pop cans then use the black beauty to cover the
unpainted cans       


                                      like this pic

blue = glass
black= Black beauty
grey =cans

I completely understand now and the illustration really helped!

Nice pic thanks. Would water in the soda cans work as long as they were sealed?

Has anyone ever used a fresnal lens on this setup?

Carbonout, I don't understand if you are talking about an outside active unit or an inside passive unit.

Active = a fan blows cool air through the heater that heats and actively comes out warm into the area you want heated.

Passive = open the curtain in a south facing window and have the sun come in and heat an object or objects.



Water in an outside unit is bad. (Can freeze) Once again.. your thermal mass should be inside or under the area you want heated.

The fresnal lens needs to be constantly turned to follow the sun and could easily cause a fire... Use the fresnal lens to cook or run a Sterline or steam generator... The fresnal lens needs constant monitoring without an elaborate set up.


I've been down all these roads and i can tell you that the Rocket Mass Heater is the way to go...unless you have zero ways to get free sticks or pallet wood to burn.

The exception is passive solar heat...always is the best way to heat.

Your active units will take lots of work, will have moisture problems, will take years to break even on cost of construction. The RMH can be built with little cost and will most likely pay for itself in a month or the first season.

i use bottles filled with black sand in my windows in the winter. In the summer i dump the sand and use the bottles for wine. Someones else complained about paint fumes so i suggested covering pop cans with black sand.

Does that help clear things up ??

The water idea would be for an inside unit only. I tried a better cheap version in my sunroom this past weekend, the temps got to 140 F, I put a little fan on it and it maintained about 100-100 F with the exhaust being around 80F. I basically use this room to “supercharge” the heat that gets fed into the rest of my house which is about 2600 square feet. Yesterday it was in the high 30’s and my heat stayed off from 7am until well after midnight when it finally reached 67F. Most of the day I had temps from 70 to 72F in the main part of the house. Im repeating the process today without the heater to see if there is much of a difference, I don’t suspect there will be a huge difference. My house is just really well insulated.

A RMH isn’t really an option for us for a couple of reasons, but I agree it is a super cool efficient heat source.

You don't need any mass storage inside unless you are getting so much energy from the sun that you have too much heat. Usually this don't happen, but if it does, then look into some mass storage. Your sealed up home and good insulation is the right way to go before looking into solar.  Most people skip this step and go straight into solar before they seal up and insulate.

Water takes a great deal of time and energy to heat up - so you would need a lot of extra solar energy streaming in to consider water as a storage medium. 

If you have a small amount of extra solar energy just use dark colored items to absorb solar energy and it will re-radiate the stored energy later.  Simple passive storage...dark rocks, tile, even furniture will work...Carbonout's bottles filled with black sand is a great example.


 

Thanks Ronie...My ultimate goal is to put this on top of my insulated box for my tropicals ...see my thread on overwintering tropicals. I figure that this will heat up providing a heat blanket around the insulated area. I will put big rocks in the pit with the tropicals to absorb that heat and then use electric (evil as it is as backup. Right now im just testing these things to see what kind of results I get.

Travis Philp wrote:
I would like to think that their strictness is in the best interest of the public health and safety. I could see the point that if you allowed everyone to go on making their own heating contraptions that more deaths will occur and/or houses burnt down. But if a system like the RMH is proven safe then it should be allowed. I would like to think this but I dunno, I could see corruption playing a part too.

I think the problem is that it is new and doesn't have the track record of the conventional wood stove.

Conventional woodstove design has a track record of killing people with severe burns and respiratory problems, so I'm not sure how it could be worse. 

It's not corruption exactly, just the social realities of manufactured vs. site-built devices, and the logistics of educating officials who will quite reasonably suppose you're biased.

We're working with a very eco-friendly planning dept. on establishing a process for permitting RMH's here in Portland, OR.

One of the complications is that your local stove inspector is just about trained to read a UL sticker on a manufactured woodstove, and make sure you haven't used baby squirrels to prop it up against the shower curtain. 
(Clearances, installed according to instructions, stickers still in place, and nothing obviously wrong.) 
To build something unique on site requires a whole other department, pre-engineered drawings, etc.  I think it's partly because the insurance industry uses regulatory approval to determine whether they'll insure your building, and any given civil servant doesn't want to stick their neck out to say it's OK unless an expert has already OK'd it. 

The UL sticker is required by EPA for woodstoves, furnaces, and in fact almost all manufactured appliances.  So the inspectors naturally look for it.

BUT
Any wood-burning device over 900 kilos (about 1800 lbs) is not a woodstove, and is exempt from EPA (includes site-built masonry heaters which are categorically more efficient and clean; fireplaces which are categorically worse; and certain large industrial devices.)

Try getting a building inspector to personally authorize a unit without the sticker he's trained to look for. 
Try getting an engineer to stake his license on the characteristics of local soils, mixed according to obscure cultural traditions, as a heat-resistant monolithic masonry material.
Try getting the EPA to write you a letter saying something's exempt from their requirements (not their business = not a priority, do you suppose?). 
Our city department wasn't even sure who the person at EPA would be, who is authorized to write such a letter.  There are a handful on a national website for specific commercial device models.

I agree passive solar is the most efficient - good passive design can save literally centuries of energy inputs for very minimal investment.

Probably the most useful thing we've learned in our permit process is that local codes make exceptions for certain situations: antique devices, or the only option for cooking, or the only way to heat a building.  If you're off the grid, researching those exemptions could save you a ton of hassles.

On the original topic

ronie wrote:
Everything inside the solar air heater, that is converting light to heat, needs to be FLAT Black.

Actually, sealed plastic containers of water, with a little colorant if you like, work great.  So does a brick floor or a lovely tinted cement slab with insulation underneath.  Passive solar absorbers don't need to be black; most thermal mass absorbs heat quite effectively when located inside a sunny window. 

Black does help maximize temperatures, though, which you need if you're going to use really inefficient fans and hot air instead of just directly heating some thermal mass.

If you want flat black without fumes, I'd suggest a direct carbon deposit  by sooting up the metal like campfire cookware, or by "curing" it the way you do with cast iron.  A more high-tech version for solar hot water setups is "infrablack," a black copper oxide produced by treating a copper surface with certain acids.

The other option is to, you know, put the garage somewhere else.
Does your car / storage unit really need all that the sunlight?

Or, you could buy SolaTube Directional Light Collectors! (tm, etc)

I'm actually kinda excited about them, but in general I favor elegant simplicity over Rube Goldberg gadgetry.

-Erica Wisner
http://www.ErnieAndErica.info

Thanks for all the great info Erika..

Erica Wisner wrote:


On the original topic
Actually, sealed plastic containers of water, with a little colorant if you like, work great.  So does a brick floor or a lovely tinted cement slab with insulation underneath.  Passive solar absorbers don't need to be black; most thermal mass absorbs heat quite effectively when located inside a sunny window. 

Black does help maximize temperatures, though, which you need if you're going to use really inefficient fans and hot air instead of just directly heating some thermal mass.

Here's the thing Erika...the original link to the pop can space heater was not a passive unit... it is an outside active unit that had black painted cans and a fan that blew air across the cans and into a living space...
It became very hard to distinguish whether people were talking about the active outside unit or passive solar heat..

Water outside just don't seem a good idea.. Inside with passive you are right, many things could be used for heat storage.

I actually have one of these pop can beasties in the wilds of Northeastern Ontario, been working for the last 3 heating seasons.  My average use of natural gas has gone from $112 Canadian /month to $69/mo equal billing over 10 months, no bills in July and August.  At 39.9 cents per cubic metre delivered this equates to saving 1077.69 cubic meters or 1002255.64 BTU's.   No smell problems as I used a flat black motorcycle exhaust paint and cured it in the summer sun for over a month before needing heat.  My intake/exhaust is a little more complicated to open only when there is heat above 25 celsius and close an insulated trap door when temperatures are low preventing backflow of cold air.  As I have used a programmable thermostat for the last 5 years on thr natural gas furnace and only done some minor caulking and draft stoppage most of the difference can be attributed to the passive solar heater, 4'x8'.  I would also note last year was one of the coldest and darkest ever, we had 9' snow banks and I could hardly throw the snow over the  edges of the driveway.  I will confess to having shaped the snow in the back yard into a reflector to increase the effect of the heater, it seemed to help.  What's a bloke to do when the snow is that deep.

mekennedy1313 wrote:
I actually have one of these pop can beasties in the wilds of Northeastern Ontario, been working for the last 3 heating seasons.  My average use of natural gas has gone from $112 Canadian /month to $69/mo equal billing over 10 months, no bills in July and August.  At 39.9 cents per cubic metre delivered this equates to saving 1077.69 cubic meters or 1002255.64 BTU's.   No smell problems as I used a flat black motorcycle exhaust paint and cured it in the summer sun for over a month before needing heat.  My intake/exhaust is a little more complicated to open only when there is heat above 25 celsius and close an insulated trap door when temperatures are low preventing backflow of cold air.  As I have used a programmable thermostat for the last 5 years on thr natural gas furnace and only done some minor caulking and draft stoppage most of the difference can be attributed to the passive solar heater, 4'x8'.  I would also note last year was one of the coldest and darkest ever, we had 9' snow banks and I could hardly throw the snow over the  edges of the driveway.  I will confess to having shaped the snow in the back yard into a reflector to increase the effect of the heater, it seemed to help.  What's a bloke to do when the snow is that deep.

Hey, very cool, sounds like the effort was worth it. 

Air is inefficient, but the nice thing is it won't freeze, or boil, like most liquids could.  Its inefficiency is arguably a safety factor, since it's harder to burn things with it. 

We put in a RMH and now use about 1/7 the natural gas - essentially, hot water only - compared to the previous tenants. 

We live in the milds of maritime Pacific NW, where sun is a scarce resource and wood is plentiful.  If somewhat soggy. 
We do supplement with electric space heat when we're too lazy to run the fire (or warming up after an away weekend), but too much of that costs alarming amounts.

We are currently located in the back "granny flat" apartment of a shared property, south of a south-facing carport, which means passive solar is almost the exact opposite of what we have.  So I fantasize about it.  There's nothing we do in the carport, that couldn't be done behind the house and leave some sun for our living room.  But it's a legacy structure.

The owners are friendly, though, so we may be able to put in something like Solatubes, reflectors, or a solarium to catch a little heat from the prime mover. 

Or (this is Ernie's latest) a solar-heated, fluid-circulating, radiant-heated earthen floor.  Prop. glycol or water with antifreeze (we rarely get much below freezing here). 
He's been reluctant to put pipes in earthen floors before due to the possibility of leaks (and passive solar works better anyway if you can get it), but for this situation he has spotted some continuous pipe for the floor section. 
We'll have to work out a place for the fluid to collect or recirc at night; I think a thermostat might be the way to go.

Sorry to twitter on about side topics.  I was looking for something new, and there were my old RMH's again.  And some remarkably civil people discussing them.  I'll let you carry on with the pop-can creativity.

Thanks,
Erica

Oh yes, forgot to mention.  If you have any significant snowfall keep the heater vertical!  The effort to clean off an inclined heater is a sure way to puncture it if you used plastic.  At my latitude, 48 deg N,  there is little difference in efficiency anyway.

I have zero mechanical aptitude but I loved this idea so much, I've started gathering cans for it ,  as I don't drink beer or pop.
One example on you tube ingeniously used salvaged aluminum rain gutter at the top and bottom of the unit.  I will use flat black stove paint as these can attain high heat levels.

I am toying with ideas , wondering in summer when we do not need heat , could you use the hot air vented from the top it to power a Stirling engine?

Synergy wrote:
I am toying with ideas , wondering in summer when we do not need heat , could you use the hot air vented from the top it to power a Stirling engine?

Yes but you cannot build a cost effective stirling to extract a useful amount of power.  High power stirlings exist but they cost many thousands of dollars!

Think otherwise then join
http://tech.groups.yahoo.com/group/HotAirEngineSociety/
and look at the many years of discussion there.

if you re-route the outlet to the outside, it will make a sort of solar chimney and circulate air through a room or building if you've got an inlet in a different part of the building.  if the incoming air is cooler, you've got yourself a heater and air-conditioner.  just a little bit of extra plumbing is all it should take.