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This solar refrigerator, invented by Emily Cummins, is a brilliantly simple solution for keeping food cool in a hot, dry environment. It's basically a metal cylinder surrounded by wet material, surrounded by a mesh sleeve to hold it all together.
Between the outer cylinder and the inner cylinder is an open compartment where any medium capable of holding water can be placed. The medium would usually be sand, wool or soil and is packed into the gap and then water is added.
When the fridge is placed in a warm environment, the sun's energy causes the water to evaporate from the medium. As the water/medium mix is held against the inner cylinder, heat is removed in the form of energy. Due to heat transfer the inner cylinder becomes cooler. The reduced temperature and completely dry environment of the inner chamber makes it perfect for the storage of perishables as it will allow items to be kept fresh for longer.
It's encouraging to think that important, real-world problems are still out there to be solved with a bit of ingenuity and the sort of materials that are taking up space in the corner of your garage.
Emily Cummins' Site (flash)
Amazing solar-powered fridge invented by British student in a potting shed helps poverty-stricken Africans [via MashupMark]
Just wanted to point out that this isn't exactly a new invention. See http://en.wikipedia.org/wiki/Pot-in-pot_refrigerator.
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there's a much longer write-up on TreeHugger, with good technical data and pictures of the original invention that came out of africa (and won the 2001 Time Magazine invention of the year)...
http://www.treehugger.com/files/2009/01/student-invents-solar-fridge.php
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I can remember my grandparents having an evaporation fridge when I was small, about 50 years ago. It was a Plaster of Paris box about 18" a side. There was a bowl shaped indentation in the top surface to pour water into.
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There's a much better idea around called the Solar Powered Icemaker. It uses ammonia for the "coolant", a solar reflector, a condenser and a few other parts. Apparently a $300 unit will produce 10 lbs of ice in under 3 hours. My deep freeze will barely do that. You can find a PDF describing it and how to put it together online.
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http://en.wikipedia.org/wiki/Zeer_pot I'm not sure how that counts as an invention in any sense of the word. The "third world" has been using these for years.
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http://en.wikipedia.org/wiki/Coolgardie_safe
Coolgardie was the site of a gold rush in the early 1890s, prior to the Kalgoorlie-Boulder gold rush.
For the prospectors who had rushed here to find their fortune, the harsh desert climate created great challenges. One such challenge was to extend the life of their perishable foods — hence the invention of the
Coolgardie safe.
The safe was invented in the late 1890s by Arthur Patrick McCormick, who used the same principle as explorers and travellers in the Outback used to cool their canvas water bags: when the canvas bag is wet the fibres expand and it holds water. Some water seeps out and evaporates, especially if it is in a breeze, and this keeps the stored water cool.
This technology in turn is commonly thought to have been adopted by explorer and scientist Sir Thomas Livingstone Mitchell, who had observed the way some Aborigines used kangaroo skins to carry water. [1]
http://en.wikipedia.org/wiki/Coolgardie_safe
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I have an old metal canteen that is disk shaped and the two round sides are covered in felt. You splash a little water on the felt and it cools as it evaporates.
Having said that - it *is* a good thing that people are looking for simple solutions to everyday problems that don't cost an arm and a leg. I'm sure there aren't a bunch of people in third world Africa with $300 + to buy an ice-maker.
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