1. A pot-in-pot refrigerator
Suppose you are in a developing country with a hot climate. You lack reliable electricity, and a generator is too expensive. Suppose you sell fruits and vegetables. How do you keep your produce from rotting in the heat; how do you prevent it from being swarmed by flies?
The answer: a refrigerator, under $2, made only of earthen pots.
(Figure from here)
The idea seems similar to the earthen pots I used to have wonderfully cool water from in India. Still, this is different. There are two pots involved – it’s a pot-in-pot system – and the apparatus is a lot more versatile. It can store peppers, eggplant, spinach, and they can stay edible for up to twelve days; sometimes even longer. The Nigerian Mohammed Bah Abba, from a family of pot-makers, is credited with the invention. Details:
To the surprise of many, the world’s cheapest refrigerator costs less than $2 dollars to make, uses minimal resources to produce and runs completely without electricity. It’s called a zeer pot, or the pot-in-pot and was developed by Mohammed Bah Abba, who realized that he could put the second law of thermodynamics and transpiration to work for him. The zeer pot, is actually two earthenware pots (I’m assuming they are both unglazed), one pot smaller than the other. The smaller pot is put inside the bigger pot, and the space in-between them is filled with sand. The sand is made wet with water (twice a day) and a wet towel is put on top of the two pots to keep warm air from entering the interior. As water in the sand evaporates through the surface of the outer pot, it carries heat, drawing it away from the inner core, thus cooling the inside of the inner pot which can be filled with soft-drinks, water, fresh fruit, vegetables or even meat. A damp cloth placed on top keeps the inside pot away from hot air. In this way, fresh produce can be kept for long periods of time without the need for electricity, or camping coolers made high embodied energy. Tomatoes and peppers will last for up to three weeks, and African spinach, or rocket, which normally would spoil after just a day in the intense African heat, can and will remain edible for up to twelve days. Eggplants will keep for up to 27 days instead of three. It can even be used for storing sorghum and millets for a long time since it protects from humidity, thus preventing fungi from developing. The zeer will keep water (and other liquid beverages) at about 15 degrees Celsius, and even meat can be kept fresh for long periods.
The new technology is now being used by farmers at the market. Fresh produce is kept inside, with just a couple fresh items displayed on the damp towel resting on top. In this way, most of the produce is kept hidden away from both warm air and insects. In the past, all produce was displayed in the open air, attracting flies resulting in stomach disease such as dysentery. Now food can be kept fresh for longer and kept away from flies...even miles away from electricity or ice.
(Figure from here)___
2. Pedal-powering a knife-sharpener
The pot-in-pot cooler is something new, designed and produced from readily available local materials. Now consider how something as simple and commonplace as a bicycle can be used, yes, for getting from one place to another, but also for a very different trade: knife sharpening.
Bikes are, as Zuckerman says,
“a platform that’s seen perhaps the most innovation in Africa. With a little bit of hacking, you can turn a bicycle into a cargo vehicle, loading it down with frightening quantities of bananas. Add a wheeled cart behind and a bicycle is an ambulance. Add a tiny one-stroke engine and it’s a motorbike, capable of propelling the rider over long distances… and she can start pedaling when she runs out of gas. In Uganda, bicycles become phone booths, with wireless phones attached to metal boxes mounted on the handlebars.”But using a bike for knife sharpening has an altogether different appeal. It is remarkably simple and intuitive, as most improvisations often are. And it reminded me of something from my school days in India, in Ahmadabad and Nagpur.
My parents bought me a large, rather cumbersome black bicycle; I believe it was one of those hardy Hero bicycles. Others – I envied them – used colorful, pink and red ones, the BSA SLRs, with a side stand. This last detail about side stands is important. Mine didn’t have a side stand: the stand went symmetrically over the back wheel; you had to pull the weight of bicycle backwards to park it. The delightful thing about this feature was that you could sit and pedal in parked position, and the wheel would spin without the bicycle moving. It was always a pleasure to pedal like this, just for timepass.
But the power generated by the pedaling can be put to good use. And so it has been:
Bikes get really interesting when you let them change function. In my single favorite video on Afrigadget, Peter Kahugu shows off his knife-sharpening bicycle in Nairobi. I love the video because I owned the same damned bicycle when I lived in Ghana in 1993. It’s a heavy, Indian-made beast, but it’s indestructible, and has some cool features. One useful feature is a huge kickstand that surrounds the back wheel. This lets you park the bike with the rear wheel off the ground… which allows you to ride the bike and spin the rear wheel without the bike going anywhere.
That’s the key to Peter’s business, as he uses the power of that back wheel to turn a belt which turns a grindstone mounted on the handlebar… which lets Peter sharpen knives and scissors, a trade that pays him a solid wage, roughly $10 a day. His business is entirely portable, which lets him bring his services to his clients. And he can take his tools home at the end of the day. The bicycle is still a transport tool, but it’s also a power generation tool.
(Figure from here.)
Interesting, isn’t it? In India, I remember the knife-sharpener coming once in six months or so, checking if we had any work for him. I remember him riding a bicycle; I remember also the steady hum of his sharpener. But did he use the same system described above for generating power? I don’t seem to recall very clearly.
But Indian readers - maybe you have a better recollection?