Here in Australia most people have heard of the Coolgardie Safe, designed in the 19th century as a farmhouse refrigeration device. I once owned an old-fashioned Coolgardie Safe and experimented with it for a while.
The Coolgardie Safe was simply a wire framed box with wheat sack strips hanging down the sides, which were kept wet by the process of osmosis from a dish or small tank of water.
The food inside the Safe was kept cool due to the principle that evaporation takes away heat; the wet hessian strips experience evaporation from the wind and the sun and thus you have a refrigerator. You can feel the same effect when you leave the water at the beach and stand in the sun for 5 minutes.
Sadly, I could never get my Coolgardie Safe to work very well, so I abandoned this invention but held onto the idea until something better should come along.
Two years ago I was researching alternative energy developments on the internet when I came across a story about an African version of the Coolgardie Safe which seemed to me to be more robust than the traditional Australian cooler, and probably more efficient........this story along with complete details on how to build the Birchip No-Power Fridge will be published in the Summer issue of Earth Garden Magazine, (it is possible that it might be published earlier, in the Spring issue) available from most newsagents.
The Mitticool Fridge
A potter has invented an innovative refrigerator that is made in clay and stays cool.
It can be called a Matka to store veggies, fruits and milk. Alternatively, it is also called Mitticool, a fridge made of clay.
The refrigerator has two large water tanks at the top and bottom that cool the sides.
The upper portion of the refrigerator can store about 20 litres of water, while the bottom cabinet has separate space for storing fruits, vegetables and milk.
The natural cooling process inside the refrigerator can keep vegetables and fruits fresh for around five days, while milk can be preserved for three days.
Mitticool can lower the temperature by about eight degrees Celsius in comparison to the room temperature.
Mitticool Web-Links
Video...A Fridge that does not need electricity
Mitticool Home Page
Absorption Refrigeration
This is another idea for unpowered refrigeration. It appears to have the potential to bring the refrigeration temperature down almost to zero.
Web Links
A New Vision for Refrigeration