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The Pot-in-Pot Refrigerator: Zeer

By: Elizabeth Hinds - Updated: 9 Mar 2014 | comments*Discuss
Water Food Cooling Environment

For most of us a fridge in the kitchen is an essential: how else can you keep your food fresh? Or cool your drinking water on hot summer days? But a fridge is one of the biggest electricity-devouring devices in your home, and that's not good for the environment.

Per minute, it doesn’t need much electricity to run a fridge, especially if you compare it to an electric kettle, which can use 10 times as much, but remember that your fridge is on for 24 hours, 7 days a week. Even today's more efficient fridges that claim to be environmentally friendly still need a constant supply of electricity.

Wouldn’t it be wonderful for the environment – and your electricity bills – if there were a way of keeping food cool that didn’t entail such a drain on the national grid? Well, now there is!

The History of the Zeer

Unsurprisingly perhaps it’s in a hot third world country that such a method has been invented. The scorching 40 degree heat of a summer day in Africa is not conducive to keeping food cool and fresh. Farmers have to dispose of their crops quickly or eat rotten food, and a lot of the harvested produce is wasted.

In the 1990s, Muhammed Bah Abba was working for aid agencies in Nigeria, trying to find ways to help small communities, when he recalled his childhood experience growing up in a family of pot-makers.

He worked out that by putting one earthenware pot inside another and creating an insulating layer in-between, it would be possible to create an effective cooling system. He spent two years experimenting before coming up with the prototype for the award-winning desert cooler, which is now being marketed throughout Nigeria and other parts of Africa.

The desert cooler does not require electricity or any other power source, making it ideal for third world rural villages - or people trying to live their lives in a more environmentally friendly way. According to Science in Africa magazine a zeer will keep tomatoes fresh – or edible - for up to 20 days; even meat can be kept in good condition for a week or two.

And all it takes is some sand, water and two pots.

Here’s What You Do

  • Find two large flowerpots – earthenware not plastic! One should be about 2-3 cm's larger in diameter than the other. If they have holes at the bottom plug with a piece of clay or cork.
  • Put a layer of sand in the bottom of the larger pot.
  • Place the smaller pot inside the larger. The layer of sand needs to be thick enough for the two pots to end up about the same height.
  • Carefully fill between the pots with sand.
  • Pour water on the sand until it can’t absorb any more.
  • Cover with a damp cloth.
  • Check the water and the cloth regularly: you’ll need to refill about twice a day.
  • Keep in a dry, well-ventilated space.

How it Works

The water in the sand evaporates in the heat. This in turn draws heat out from the inner pot, thus keeping cool food stored inside. By keeping the sand wet, it becomes an ongoing process.

At the moment, the zeer, or pot-to-pot fridge, is only suitable for keeping food cool on a small scale, but has been proved to be so effective, that it may only be a matter of time before this environmentally friendly food and water cooler is developed further.

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PS. Inner bag should be a waterproof one of course.
LoftyDave - 9-Mar-14 @ 6:34 PM
This is like re-inventing the wheel! The cooling by evaporation system has been in use forhundreds of years. only you use goatskins (canvass bag is a good substitute). Place food inside a small skin/bagsecure top and place inside a larger skin/bag. fill the gap with water and hang it up. When it starts to clog turn it inside out and scrub it.
LoftyDave - 9-Mar-14 @ 6:29 PM
Do these work regardless of external temperature or do you need a certain temperature gradient?
Jenny - 9-Oct-12 @ 9:30 PM
I should imagine that minerals in the water are the reason for the lack of wicking thru the clay pot.
zoek - 16-Aug-12 @ 10:52 PM
A scrub with vinegar should do the job. I am using a strap to tie the inner pot down rather than sand to prevent it from floating. This makes it easier to replace the water as mineral deposits build up and to clean the pots. If you can collect rain water from the roof it should be much closer to distilled water.
John - 30-Jun-12 @ 3:35 PM
The zeer I made using a terra cotta pot seems to be plugging up, which is understandable unless you are using ultrapure water. How do you get around this? At first water came out of the pores pretty well, now only at the bottom, soon nothing.
steve - 8-Aug-11 @ 4:17 PM
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