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The Zeer pot is an African cooling gadget which, for less than $2US in local materials and without electricity, can extend the storage lifetime of fresh produce by as much as 18 days. It is of staggeringly simple design: Two clay pots are nested with a relatively thin layer of sand between them. The sand is watered twice daily, and the inner pot, which is lidded, is cooled by evaporation. It's interesting to note that, although the technology to manufacture the zeer pot has existed literally since the dawn of civilization, it is not known to have been produced until recently. Who would have thought there was a profound invention remaining to be discovered using only clay and sand?
Look up "botijo" ob6dz9yn eHow. It is an unglazed pottery jug used in Spain to keep drinking water cool. It has been used in Spain since the time of the Moors.
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Interesting. But I get the feeling you are trying to suggest that a botijo is basically the same thing as a Zeer pot. Which it really isn't. A botijo, like a Zeer pot, cools by evaporation, but evaporation cooling in itself is certainly older than the time of the Moors. The Zeer pot is a rather sophisticated scientific design executed in accessible materials, and it includes a number of features that, I believe, make it unique: It's double-walled for insulation, has separate coolant and storage volumes, and incorporates a layer of sand in order to maximize surface area across which useful heat and phase transfers occur.
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Anyone found a solid set of #'s on how much cooling the Zeer pot actually provides? I see lots of generalities, expressed in terms of how many days a tomato stays fresh, and one experiment that showed essentially no cooling, but admittedly a poor experimental design.
I'd love to see "a Zeer pot of x size in t temperature and h humidity lowers temperature b d degrees".
Oh but I am too lazy to do it myself!
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Ha!
Welcome to the Spanish "botijo".
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The principle was known and used. There was an article in the "Boy Mechanic" about an almost identical cooler.
http://chestofbooks.com/crafts/popular-mechanics/The-Boy-Mechanic-1000-Things-for-Boys-to-Do/Cooler-for-Milk-and-Butter.html
But i think that the outer clay pot does cool better than a simple box as in the above article, and the two pots make it simple and cheap.
Evaporative coolers based on a box covered with wet canvas where used in australia. The moisture was automatically provided by a container on top of the box so no manual wetting was necessary during the day.
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