Aluminum Can Solar Heater

This is how I made an aluminum can solar heater!

Step 1: Save Cans

Pop cans, beer cans, sparkling water cans, any aluminum cans you can save, save them!

Step 2: Gather Supplies

Once you have a bunch of aluminum cans saved, gather these supplies:

Black spray paint (high heat) mine was for grills.

High heat caulk/glue

wood ( I used 1x4's), and a piece of 1/4" thick plywood for the back

foam board insulation, or other foam/insulation

drill

Wood screws

Glass panel, plexiglass, or tempered glass panel

Step 3: Drill Holes in Cans

Please be very careful with this step!!!

Take all of the pop tabs off of the cans, rinse any leftover soda or liquid out of the cans and let them dry.

CAREFULLY drill holes (I drilled 3 holes in the bottom of each can, with the largest drill bit I had). This is to let air pass through the cans.

I just tried to hold the can steady and drilled with a bit of pressure to prevent the can from going flying.

Step 4: Assembly

Once you have holes drilled in all of your cans, you can begin stacking them on top of each other and securing with high heat caulk or glue.

*You can add as many rows of cans as you like, as long as they fit in the "box" you will be building.

I determined my "box" size by a piece of tempered glass that I had left over from an old T.v. stand. It was 24" x 42".

I had a scrap piece of plywood about 1/4" thick that I used for the back of the box. I then just cut my 1x4's to fit around the edge of the plywood making a frame, slightly larger than the piece of glass.

Note: * You can use regular glass, tempered glass, or even plexiglass as long as the sun is able to shine through it and it is thick enough to keep the heat in.

Take a piece of foam board insulation ( I had mine laying around from the previous owners of our house, I also used some parts of a pool noodle), and cut to size to fit around the back and sides of your box. Use your high heat caulk to seal all holes and edges. When dry use your high heat matte black spray paint to spray the foam insulation.

Next I took another 1x4 board and using a large hole drill bit, mine was 1.5inches, drill holes in the middle of the board for as many rows of cans that you have. For example, if you have 5 rows of cans, you would drill 5 holes in the middle of your board. Attach this board (I used wood screws) horizontally about 3 inches from the bottom of your box. Caulk all edges and/or gaps. We want this to be air-tight!

Then, I used the same drill bit to make a larger hole in the middle of the bottom board of my box ( see photos). I did this by overlapping the holes made by my 1.5 inch drill bit. This is to let more air in. I repeated the process for the top board of my box. This is to let the air out. (More on this in a minute!)

Now you can add your rows of cans. Simply line them up matching the holes in your board that you just drilled holes in and use high heat caulk or glue to secure in place. I added some extra caulk to the backs of the cans to help them stay stable. Now you can spray paint everything in your box with the high heat matte black spray paint. Try to get around all the corners and nooks and crannies.

Once dry you can use your high heat glue to attach your glass to the top of the box. Make sure to make a good seal. Again, we want this to be air-tight!

* Since the tempered glass was so heavy, I had to reinforce it by tying a fitness band around it to keep it in place. If I were to do it again, I would use plexiglass or make a recessed box to hold the glass in place better. It did end up working very well though!

Step 5: How It Works & Try It Out!

*How it works:

When you set the solar heater out in the sun, even on a cool day it can heat up to 160 degrees or so. My solar heater was only out in the sun for a few minutes before it started to really heat up. It was fun to watch and measure the heat as well. I used a meat thermometer to measure the temperature of mine. It was only about 50 degrees outside as well.

When cool air enters the hole in the bottom of the box it is warmed by the black cans and glass, that have been absorbing the sun's heat. The matte black paint is dark so it attracts the sun's rays. The holes in the cans create a turbine effect that spins the air around in the cans as it passes through each can. Warm air rises naturally, so as the air passes through each can, it gets a little bit warner. Finally as air exits out the top hole of the box, and you can feel the warmth!

*Note: Make sure the box is tilted a bit (I leaned mine on a chair), so that the cool air can enter from the bottom of the box.

Also, make sure your box is facing the sun ; )

Comments

[crazypj]

I think a couple of people missed the point. As far as I can tell the main expense was the black paint? Everything else recycled so I guess main reason for Instructable is to show what can be done without spending ton of cash? You also get some practical stuff out of it. From experience I can tell you, using a 'step drill' (the 'Christmas tree' shaped cutters) makes drilling very thin material much easier than a regular drill and for aluminium cans, the cheapest one you can get hold of will work fine.

[sheila.wallace.737]

You are correct, some missed the point entirely 🥲
I built mine with cardboard, to fit the inside corner of my kitchen window . So I didn’t block all the light. It was 5’ tall and 2’ wide. I used a small solar charger and pc fan. It works well, my kitchen was 78’ but the time I made my coffee in the mornings

[Njturner84]

I'm not sure who would go through the hassle of bringing this in and out of their house 100 times a day to reheat it. I imagine all that extra opening of your front door would defeat the purpose too. And i especially have no plans of putting holes through my house to run ducting. For those in the same shoes... I have seen this done before where you just mount the box in a window in your home that gets a lot of sunlight during the day. Even build a couple and put them in different Windows on different sides of the house

[Yonatan24]

Build a base that tracks the sun, and moves it accordingly.

[sgbotsford]

Not worth it, unless you are really constrained for space. Just build more of them.

[sheila.wallace.737]

It is worth it. One small unit built to fit my kitchen window, warmed up my kitchen in winter to 78’ buy the time I was up making coffee

[bmurphy21]

The heat is usually piped in from the outside, they aren't supposed to store heat, just generate it. As for putting them inside a window, a simple piece of black metal or plastic inside the window would attract heat and the cans wouldn't be required. Homes can be designed with walls and floors of concrete or similar materials, often tiled or coloured in dark colours. If you search passive solar design you can find out more about this. I can't seem to paste the link into Wikipedia.

[sgbotsford]

You don't drag it in and out. Typically you mount them against the foundation, and run a pair of ducts into the house. See http://builditsolar.com/ for lots more info on this sort of project.

[sheila.wallace.737]

I made ours for a south facing window, “Out of cardboard”!! We also used a small solar charger and pc fan.. so once the morning sun hits the window and charger, I had a nice warm winter kitchen.
Oh. Please note, we built the cardboard solar heat exchanger to fit the inside of the window! So much Easier, makes sense too , now we didn’t need to find glass .. it works amazing well.

[Wapata]

Hi !
What do you heat with that ?

[msuzym]

Why can’t you just install this on the inside of a window. Wouldn’t it just heat the inside air?

[jtharp1]

Very nice. I built one but it took a long time to drill the cans (it was 4'X8"). when I rebuilt it, I used gutter downspout instead of cans. No drilling and just cut to length. It works very well to heat my garage.

[stad168]

Have you ever thought about using the same concept but running a hose through the cans to create a color hot water heater for a pool? Do you think it would work?

[justin.jackson]

Thats actually a method that has been around for years. Someone mentioned it in a comment above, but I also remember my dad talking about doing it in the 70's. Certainly, you could do it with cans but the go to method is to use black PVC pipe. You pretty much just divert the water leaving the pool pump and run it through the PVC which has been laid somewhere where it can get plenty of sun, usually the roof, then tie it back into the outflow from the pool pump. I've heard of it done with the regular white PVC spray painted black because the white is usually cheaper, the problem there is that the black PVC will hold up far longer in the sun due to its UV resistance

[Tacticalbaton12]

My understanding is black pvc is sewage pipe and treated with chemicals when made ???? Not for pool use...

[johnt011]

If you are worried about too much heat use CPVC which is designed for hot water but it is also a smaller inside diameter.

[johnt011]

Black PVC is also very large and is certainly Not conducive for the stated purpose. Schedule 40 PVC 3/4" or 1" painted black is a good choice as it will allow a good flow of water still allow it to have time to heat depending on the length of the pipe. Using multiple U shapes will allow the water the best amount of time to heat. Hope this helps.

[sgbotsford]

More likely polyethylene pipe -- available any farm store. PVC is expensive, rigid and environmentally evil. That said the water can get hot enough to melt poly, especially in summer when you don't actually need the heat for the pool. Using PEX pipe will reduce the chance of this happening,but it costs more.

If you are heating domestic hot water, the vacuum tubes with the high efficiency coatings do a better job -- at more money. Use a simple cheap system as a pre-heater.

[DavidS925]

Make an X out of 2x4s. You're going to spiral black PVC irrigation tubing through that X by drilling holes in the wood. It takes effort as the radius gets smaller, but you can get the whole 100 feet in there. Then enclose it in a box made from 5/4 deck boards. A back made from Styrofoam painted black and a front made from corregated roofing completes it. You need to make a bypass in your pool plumbing and allow only some of the water into the heater so it sends enough time in the coil to get warm.

[Lillyvilleky]

I haven't thought about that, however I have seen people use black tubing made into coiled circles to lay over their pool to heat it, and yes it works. As for running it through the cans, I'm guessing you would need some sort of a pump to pump the water through, but I think anything is possible (with sunshine and a little pink!)
-lillyvilleky ; )