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
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
The tools that I used are also very common:
1" hole saw drill bit
small drill bit
hacksaw with blade for metal
hot glue gun
Step 2: 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
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
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
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
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
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
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
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!