Mohammed Bah Abba's Pot-in-Pot is one of my favourite design innovations ever. Without electrical refrigeration, until now Northern Nigeria's poor agricultural population has had no access to food preservation:
"The device owes its cooling powers to a simple law of thermodynamics. When moisture comes into contact with dry air, it evaporates, causing an immediate drop in temperature. When the water in the sand between the two pots evaporates, the inner pot is kept cool, preserving the goods inside."
Clearly 'high-tech' is a matter of perspective. Aside from the benefits to subsistence farmers, the Pot-in-Pot has initiated a cascade of positive effects:
"Abba's project has brought about major changes for many Nigerians: eggplants can last for 27 days rather than three, African spinach can be kept for 12 days instead of spoiling after one day, while tomatoes and peppers stay fresh for three weeks. Food hygiene standards and overall health are improving.
"The Pot-in-Pot's flow-on benefits for Northern Nigeria are widespread, helping to slow the rural exodus to the cities. Farmers no longer need to sell their produce in a hurry. Business is growing, and the revival of the local pottery industry is also helping to reduce the region's high unemployment.
"The Pot-in-Pot is also a step forward for women in the region, as young girls are free to attend school, instead of hawking food every day. Already, village primary schools report an increase in the number of girls enrolled."
Pretty cool. The same technique has been used for thousands of years to cool water by tribesmen all over the world. A big jar suspended under a roof, so that it's kept in the shade. The clay of such sort that it's semi-permieable by the water, so that it slowly passes through the shell of the vessel and then evaporates in the heated outer air, thus the water is kept cool. No one, afaik, has placed an inside vessel into the water, pretty smart.
And then there's a 19th-century Australian invention known as the Coolgardie Safe, which used some similar principle to keep its contents cool.
The town I live in was settled by Quakers, the museum has an example of a refrigerator that uses a similar technique but with a wood box. It claims to be the first such device in America although that could be local folklore. Certainly the Pot-in-Pot can't be the first such invention of that type, in fact the Amish currently use this one, in production since 1900:
what makes Pot-in-Pot special is the use of local materials and skills so that it can be accepted by the local culture. I suspect Africa has a lot to learn from the Amish and other modern low-tech cultures, maybe there should be an Amish technology transfer to Africa.
In Viktor Papanek's _Design for the Real World_ there is a picture of a hand-cranked refrigerator he designed for the UN but I have never been able to find anything else about it.
Even had the chance to ask Papanek once when he was lecturing at the Massachusetts College of Art on design and he didn't seem to remember it.
the pot-in-pot is indeed a great idea.
i saw something similar of quaker/amish type origin:
a box with material cloth walls whuich were dampened every so often.
considering how we cool off by sweating, i'm not surprised we came up with this.
Heck of a post - although I'm not sure that school enrollment is always a good thing.
fwiw, here's an ask slashdot on hand-powered hardware.
and sorta a related article on a 'cascade of positive effects!' (albeit diesel :)
Wo! Indigenous technology...Now you are talking!
Wine drinkers have been using this technology for decades. That's what those unglazed terra cotta wine holders are for: soak it in water, place wine bottle inside, as water evaporates, it cools the wine.