This wonderful thing is already used now in third world countries and was invented by a Nigerian teacher, Mohammed Bah Abba. You just need two clay pots, sand, a towel and a little of water to build this electric-free refrigerator. The pots are placed one inside another, and the space between them is filled with sand. Then you pour water to make the sand damp. Finally, the small pot will be covered by the damp towel. The system should be kept in dry, shady and well-ventilated location because evaporating water effect will cool the inner pot and keep the food inside fresh.
With this simple technology, fruits like tomatoes and peppers stay fresh for about 20 days, spinach can be kept for 12 days instead of spoiling after one day.
This is amazing! I was excited and immediately told to my colleagues. I thought they would be excited, too. But they weren't. I don't know why, maybe they don't have enough information, and didn't think that is for real. A guy told me that this is just for some where else having very high temperature, not for us. But I find no reasons why this can not be used widely in Vietnam. The system have had a widespread impact in the third world for food preservation in high temperature, dry climate. And Vietnam is also a hot climate country, with the maximum of 40 Celsius degree in summer. In that circumstance, using pot-in-pot cooler would save a lot of energy bills and improve life expectancy of poor working class.
The system also inspired someone to invent another type of electric-free fridge using different materials. Instead of sand, this system uses glass-foam, a waste product of glass recycling process. All recyclable materials are using in this cooler: glass foam, clay and bio-plastic, making it a light, green product.
That is called thermodynamic cooler and is a "transfer and optimization of basic technology". Take a look at this very beautiful and modern and useful thing.
