This instructable is being entered in the Green Tech Contest so please vote.
This solar fridge is a simple and quick diy project. The reason I decided to build it was because the fridge in your house takes up a ton of energy. This fridge is so cheap and reliable that it can be used in 3rd world countries. It takes about 15 to 30 minutes to complete and it only cost around $15 dollars.
Here is what you need
1 large clay flower pot
1 small clay flower pot
sand (I used about 1/4 of a bag)
clay or plumbers putty (only needed if there is a whole in the bottom of the pot)
Step 1: Filling up the holes
The first step is to see if you have a hole at the bottom of your pot. If there is not a hole then you can skip this step. If there is a hole then take your clay or putty and firmly press it into the hole and cover it. Make sure there is no gaps for water to leak out.
Step 2: Even the pots
Fill the larger pot with a layer of sand. Then put the smaller pot inside the larger one and level the sand until both pots are at even height.
Step 3: Finishing with the sand
Fill the remaining area between the pots with sand.
Step 4: Time to put the water in
Pour water into sand to saturate it completely. Once the water begins welling up instead of soaking in, you can stop.
Step 5: Stock the fridge
put any items you want into the fridge.
Step 6: Almost done
Now you have to soak the towel and place it over the top of the pots.
Step 7: Usage of your fridge
Make sure you put your fridge in a shaded place. Also return once or twice a day and refill the sand with water and dampen the towel.
Step 8: How it works
The action that allows it to stay cool is the evaporation of the water surrounding the smaller pot. As the water evaporates, heat draws out from the smaller pot, keeping the contents inside much cooler the the surrounding environment.