The Zeer pot

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?