Introduction: Solar Cooler in a Can

Picture of Solar Cooler in a Can

It's been getting really hot up in the Northern Hemisphere lately, so here's a way to combat the heat by making a cooler that stays cool. Just add water!

This project is based on the recent invention of Emily Cummins, originally designed for impoverished families in Africa to keep meat and milk from going bad. The beauty of the cooler is its simplicity. It can be made from scrap materials that can be found in almost any home, sometimes in the trash. The Evaporation Fridge consists of an inner and outer tube, with a wet material in between the two layers. Perishable items are kept in the inner tube in a sealed container. As the water in the wet material evaporates, it removes heat from the inner tube and lowers the temperature. The whole process can be compared to the human perspiration system. Think of the fridge as a cooler that sweats, except less gross.

UPDATE: Check out the new version here:

Step 1: Tools and Materials

Picture of Tools and Materials

I found all of my materials in my garage. If you can't find something, feel free to substitute similar object. My materials are as follows:

1 empty paint bucket
1 empty lantern propane tank(small)
2 plastic tank caps(from full or empty propane tanks)
4-6 rags/washcloths(anything that holds water: sand, sponge, wool, ShamWOW)
2 mesh gutter covers
1 can of spray paint
steel wool

The tools that I used are also very common:
drill press
1" hole saw drill bit
small drill bit
hacksaw with blade for metal
tin snips
hot glue gun

Step 2: Prepare Your Bucket

Picture of Prepare Your Bucket

I wanted my cooler to be portable, so I used a paint bucket with a convenient handle. A larger five gallon bucket would also work. I chose a plastic one because it won't rust. The first thing to do is remove all of the paint from the bucket. Just get the sludge out and rinse it off. Mine was latex so after it dried it just peeled off. If the bucket has rust on the rim, use some steel wool to scrub it off. Lastly, mark drilling points for 12 holes in the side of the can.

Step 3: Drill Your Bucket

Picture of Drill Your Bucket

Use the hole saw to drill the twelve 1" holes in the wall of your bucket. Try to make them even and consistent. These will be the "pores" of the system, letting water evaporate from them.

Step 4: Add a Screen

Picture of Add a Screen

You'll want to add a screen behind the pores so that the towels don't stick out and collect dirt. Simply roll up one of the gutter guards and stick it in the bucket. Then maybe make sure it sits flush against the edges.

Step 5: Make the Inner Screen

Picture of Make the Inner Screen

The inner screen helps keep the absorbent medium in place. It's made from a smaller section of the same gutter guard. If you bend the exposed barbs, you can lock them into the opposite end of the screen and create a tube shape.

Step 6: Create an Absorbent Bucket

Picture of Create an Absorbent Bucket

Now it's time to finish the bucket part of the bucket. Wrap 4 to 6 towels around the inner screen that you just created and insert the sushi roll into the bucket. Stuff the edges of the towels below the surface of the bucket. Your cooler is now ready to accept a food capsule.

Step 7: Prepare the Propane Tank

Picture of Prepare the Propane Tank

DO NOT PERFORM THIS STEP WITHOUT ADULT SUPERVISION! This step is NOT safe and I am not responsible if you blow yourself up. Proceed at your own risk.

Now, the propane tank must be completely empty. Make sure you release all of the propane from the tank by attaching a blowtorch attachment,  opening the valve, igniting any gas, and leaving the torch open after the flame goes out. Then carefully drill a small hole in the top dome of the tank. Next, use a hacksaw to cut the top off of the tank, making sure you rotate the tank as you go. There are two valves that protrude below the top of the tank and they make cutting more difficult.

Now sand down all of the sharp edges you just made and give the whole thing a nice new coat of paint.

Step 8: Finish the Capsule

Picture of Finish the Capsule

The only thing it's missing is a lid. It turns out that some propane tanks come with plastic bottoms that fit perfectly. You might also want to plug up any holes with hot glue to prevent rust.

Step 9: Assemble Your Solar Cooler

Picture of Assemble Your Solar Cooler

This solar cooler is just about ready to go for a test drive. To use it, simply put your food/drink into the capsule, close it up, and put it into the bucket. Then pour water over the capsule until the absorbent medium is full, and take the cooler outside with you. After enough water evaporates, your capsule will be sufficiently cool and ready to eat out of!

Please rate!


Sabata (author)2010-08-19

Coleman made a plastic bit called the Green Key that they included with their propane cylinders. Once the tank was "empty" you inserted the Green Key into the cylinder's valve. This allowed the last of the propane to slowly escape out of the cylinder so it was safe to recycle.

I just checked Coleman's site and it says that the idea didn't catch on so they aren't including the Green Key with their cylinders anymore. That doesn't mean a person couldn't locate one or two if they wanted to try this project without fear of fire/explosion.


DIY-Guy (author)Sabata2011-10-25

As an alternative method of "safeing" a propane can before cutting it, someone here at Instructables suggested filling it with water to displace and absorb any traces of gas. Maybe the author or someone else will recognize which -ible talks about using water to make an empty propane tank safe for cutting.

Alpha2904 (author)2011-06-03

I wouldn't say evaporator based coolers are new, for they have been around for sometime using wicker baskets and such.

JamesRPatrick (author)Alpha29042011-06-03

Yeah they've been around at least since Egyptian times but this is a new design with more modern materials.

DIY-Guy (author)JamesRPatrick2011-10-24

James R Patrick-
Yeah I'll say evaporative cooling has been around since Egyptian times, even thin sheets of ice were made at night using the method! (Sorry I have no URL reference for that factoid, but I did read it in a book many years ago.)

Nice -ible, keep going with these.   :)


skitz (author)2011-07-11

I'd like to share my experiences with evaporative coolers hoping someone may improve on this design.

I think it could spur some ideas with all the brilliant people on this site

pohair (author)2011-07-06

Does it need to be painted lack? You didn't say so...

JamesRPatrick (author)pohair2011-07-06

This can is black plastic by default(no paint). If yours is metallic, keep it shiny. Otherwise paint it white as in this updated version.

ankitgarg2005 (author)2011-07-06

boss here is mine

Lectric Wizard (author)2010-07-30

Nice instructable but wouldn't it be easier to use a coffee can or similar to make the food capsule ? Then you wouldn't have the possibility of your food tasting like propane odorant . It is a great idea though !!

My original plan called for a coffee can and I spent about an hour looking for one, but nobody in my house drinks coffee. It would probably work better though. As for the propane odorant, there was no scent left in the tank after it was fully drained.

danneauxs (author)JamesRPatrick2011-02-25

yes, i was thinking this while reading. Great inst. & I think I'll try it with a coffee can. I always by metal ones just to keep for storage.

JamesRPatrick (author)danneauxs2011-02-25

By the way, this instructable has been updated with this new version for drinks.

chuckr44 (author)2010-07-30

I've been seeing this concept for 10+ years but no web site ever provides hard info on how well it works. Like, if it's the ambient (air) temperature is 90F, how cool is the inside of the pot? Does it cool more in shade or sun? Inquiring minds want to know. If it's 90F in the outside sun, and the inside of the pot is 80F, 80F is not conducive to food preservation.

jeanicrowe (author)chuckr442011-02-20

I'm sorry I can't give you the hard facts that you want, but as you probably already suspect, there are a lot of variables. Yes, it definitely works better in the shade. The cooling varies with the materials used for both the inner and outer containers and what you use for the packing material. This idea has been around since the 1800's at least, probably longer. My Grandma used a big crock that she kept filled with lemonade or water for the field hands. She kept it in the barn and the heat caused the crock to sweat which pulled the heat from the liquid inside the jar. It was quite a bit colder than the outside temperature, but if it was 100 degrees out, the liquid could not be called cold. Whatever you put inside the container should already be cold for the best results.
A filling of damp sand or crushed charcoal works very well for a filling between the two containers. You could also use sawdust, moss, straw or leaves, as long as you have water to dampen them. Using a porous container for the outer layer increases the cooling (for example a large unglazed flower pot) or sink your container into the ground with pebbles around it and keep them damp. In the old days, people often dug out a hole and put a wooden keg into the ground with a wooden box sitting on top. They back filled around the keg with small stones, wet them down and filled in around the barrel with dirt, which was mounded up around the box to allow rain to run away from the keg. The box was the 'lid' of this under ground cooler. A stick was fastened to the box and containers of food were tied to the stick and hung in the keg below. This kept food from spoiling for several days.
Just a little note of interest: In the middle east they made ice by pouring water in shallow trays and placing them where the wind would blow over them. The water would develop a thin layer of ice which would be collected before sunup and stored in tall jars, kept in a cool corner. Their houses were cooled naturally by woven mats hung across the small windows on the windward side of the house. These mats were kept damp by ladeling water across them. Natural swamp coolers!

ironsmiter (author)chuckr442010-07-30

This is a variation of a Zeer pot. when working at optimum efficiency, 80 degree dry day, you may get 60F inside the cooler. never tried it at 90, but should still work there. The design is not so much to refrigerate, as to cool. As for sun vs shade, it doesn't matter much, but the sun will add heat to the whole setup, so shade is better. What makes a bigger difference is local humidity. In the desert, these things work GREAT. In a rain forest, it wouldn't work at all. All depends on how well water is evaporating in your exact location. To that end, wind helps. I've used the clay pot/sand version, and was able to keep lunch meat edible for several days during the summer. Without the cooler, it would have lasted several HOURS. For me though, this style cooler works best to take HOT water, and give you COOL drinking water. You can fill the interior container with half your water, dump the other half onto the sponge/towel pad, and in an hour or two, have cool drinking water. To do this tho9ugh, I'd advise a stainless steel inner container. Used propane tanks tend toward not being food safe.

JamesRPatrick (author)ironsmiter2010-08-15

That's really interesting considering my new test results, from Virginia.

gossumx (author)chuckr442010-07-30


tylerpienta (author)2010-10-26

make shur u clean out the inside bc there would be gas residue and u put food in ther soo yea....

oldhacker (author)2010-09-16

Great idea. I am looking into adapting this concept to make a portable cooler for keeping perishable foods in while camping. Basically using evaporation cooling to enhance a traditional cooler / icebox. Does anyone have any thoughts on materials? For eample is the outer shell best made of metal (ie a good onductor) or plastic? Also, could it be finned to increase surface area?

Then the inner liner. If the food is put in chilled plus some ice blocks would it be best to use an insulated inner to keep the heat out or would that be counterproductive in that colling would not be efficient?

Doc Holliday (author)2010-07-30

I had a '57 MGA Roadster, while in Virginia in 1969-1972. I used to take ladies on tours/picnics, with a straw hamper lashed to the back deck. In front of this was a bottle or two of wine, wrapped in whetted towels. The airflow over these ensured a nice chilled beverage at the end of a drive in 90 degree plus weather. Despite the humidity, the car speed solved that.

That's really interesting considering my new test results, from Virginia.

nutsandbolts_64 (author)2010-07-31

I think I read something like this somewhere else... but as I remember it, yeah it works like that

Oh, and one more thing. IT'S PERFECT I TELL YOU, PERFECT!!!!! lol. I'll make another version.

I appreciate your enthusiasm. You might like the new version more though, check my page.

Culturespy (author)2010-07-31

It would be great if you would find out what the average internal temperature is and post it along with the humidity and temp where you tested it.

JamesRPatrick (author)Culturespy2010-08-15

I don't have a way to measure humidity(other than my own discomfort), but I got some data for the updated version here. The new cooler was tested in Virginia, USA.

ziggiau (author)2010-08-01

This looks like the perfect use for old nappies.

Kiteman (author)ziggiau2010-08-02

Ewww - old *clean* nappies, please!

JamesRPatrick (author)Kiteman2010-08-04

Haha I used brand new bulk washcloths, but old, washed rags would be better and more "eco-friendly." Not sure what a nappie is though...

ziggiau (author)JamesRPatrick2010-08-04

You know those toweling squares you fold into clever triangles to put on babies bottoms to collect everything that comes out from the bottom end? Once you're done using them for that purpose (a couple of years down the track) you're left with perfectly good squares of toweling.

JamesRPatrick (author)ziggiau2010-08-15

Ah, diapers. We've always used disposables, which are super absorbent and have lots of other uses.

Kiteman (author)JamesRPatrick2010-08-05

Nappies = daipers. See Ziggiau's description for more.

Kiteman (author)2010-07-30

I would seriously question Emily Cummins' claim to have invented this cooling system.

Evaporative cooling have been used in developing nations for some time - Cummins has only changed the materials, as the originals used two clay pots, with water-soaked sand in between. The water evaporated straight through the porous clay.


Having said that, this is a good Make. Well done.

bruc33ef (author)Kiteman2010-07-30

Yes, this is an old bushcraft idea. It was redesigned by a guy in Africa (who also claimed he invented it) and won a Rolex Award for it several years ago. He called it a Zeer Pot, or pot-in-pot refrigerator. Here are some links: That said, making it from a paint can and some common western domestic items is a nice adaptation and worthy of an Attaboy.

JamesRPatrick (author)bruc33ef2010-07-30

I know it's not an original idea, but this inventor had the easiest, most recent version of it. I also got the idea after reading about her on MAKE:

Kiteman (author)JamesRPatrick2010-07-30

We're not having a go at you. You credited sources and everything. She's the one claiming to have invented the device.

Calorie (author)Kiteman2010-07-30

Thanks for clarifying that to James. I sometimes feel the board becomes a bit esoteric, particularly about what is authentic or not.

James, nice job. But in the future do not tempt the safety gods. It doesn't take a lot of gas to make a very solid burst. You can loose your hearing, etc. There are other substitutes. But other than that, rock on.

This idea has been used in the past. The ever frugal VW air cooled series had the same idea. You loaded ice into the gray container on the window and then airflow over the ice within the gray tube would be funneled into your car cabin.

RichardBronosky (author)Kiteman2010-08-01

Considering that a Nigerian man received an Invention of the Year award from Time Magazine for this very item in 2001,28804,1936165_1936254_1936632,00.html I'd have to call Emily a designer, not an inventer. Hers looks better, but Mohammed Bah Abba's can be produced for $0.20 and he has distrubuted more than 100,000 units! ( according to )

ac-dc (author)RichardBronosky2010-08-09

He invented that particular design, Emily invented her particular design, but evaporative solar coolers have been around for hundreds if not thousands of years.

RichardBronosky (author)ac-dc2010-08-10

I'm sorry, but you don't invent a design, you design a design and invent an invention. Sometimes a new use for an old idea is considered to be an invention because it is innovative. However using metal instead of clay isn't even innovation.

beehard44 (author)Kiteman2010-08-10

Emily Cummins just adapted this idea from the ones made of porous clay more of an "upgrade" than an Invention

johnny3h (author)Kiteman2010-08-01

Evaporative cooling has been around since the first sweaty, wet caveman discovered he could stand on a hilltop and the breeze would cool him. Of course, naturally, there is no recorded confirmation of this. My earliest knowledge of evaporative cooling was in the early 1950's when as a young boy, in the Cub Scouts, I read everything I could get my hands on regarding canping and woodsmanship. One of the first articles refered to cooling water stored at a campsite. It recommended using a "Lister Bag" which was a canvas water bag made of very tightly woven cotton fiber. The weave was tight enough that it did not leak, BUT... the water would "wet" all of the bag fiber, and the evaporation of the water from the bag surface would cool the bag and the water inside. I also read about the Indians of the US Southwest and Mexico storing their water in porus [unglazed] clay pots which resulted in the same seepage and cooling effect as the later to come Lister Bag [my earliest knowledge of its use was during World War One, but it may go back earlier in military history. Regardless, the concept of evaporative cooling, and a dual wall container with a water absorbent material in between very long "predates" Ms. Cummins so-called "invention" of her cooling device. All she did was to modify the materials used, not invented something new. As for the discusions regarding the ultimate minimum temperature obtainable, there are MANY FACTORS that determine that, including: the RATE of evaporation which hinges on ambient temperature, whether of not there is any wind blowing over the evaporative material, and the speed of that wind. Although I don't know the numbers, I also suspect that the barometric pressure mayhave an effect on the rate of evaporation also. Since it has been years since I read, contemplated, and used evaporative cooling, it probable that there are other factors effecting evaporative cooling. In hundreds of years of evaporative cooling being in use by mankind worldwide, I seriously doubt anyone could get a patent [which requires a "new" novelty] for a process which has been in the "public domain" for so long.

Tampaguy (author)Kiteman2010-08-01

"An invention is a new composition, device, or process. An invention may be derived from a pre-existing model or idea, or it could be independently conceived in which case it may be a radical breakthrough. In addition, there is cultural invention, which is an innovative set of useful social behaviors adopted by people and passed on to others.[1] Inventions often extend the boundaries of human knowledge or experience. An invention that is novel and not obvious to others skilled in the same field may be able to obtain the legal protection of a patent." - check if out on wiki. Yes, this IS an invention. You might also google her name, where this cooler is definitively referred to as an INVENTION. She invented a new system for 3rd world countries to move forward in the struggle to move to a more modern society. You are overly critical. check the facts.

Kiteman (author)Tampaguy2010-08-01

I did google her.

I did check my facts.

Shame that she didn't, really: Inventor's rule #1 - check nobody else thought of it first.

eulaliaaaa! (author)2010-08-11

If you look on the mini images, this step looks like Frankenstein!

eulaliaaaa! (author)2010-08-11


Omni DIY (author)2010-07-30

I think it would be awesome if someone (or perhaps myself) made a wind powered fridge with a similar principle. Have a wind turbine that is hooked to a gear box with a faster spinning fan. the fast fan blows air past the cooler which speeds up the evaporation process. No electronics!

Use a fan to power a fan? You are going to lose a lot of power unless you have a really high quality gearbox. Just have a funnel or a couple of bits of board to catch the wind and concentrate it on the cooler.

About This Instructable




Bio: Currently pursuing a degree in Mechanical Engineering. contact: jamesrpatrick(at)
More by JamesRPatrick:Solar Cooler in a CanAir Cooled Paintball MaskPortable Speaker System
Add instructable to: