Mohammed stays cool

With summers getting steadily hotter, food storage is an issue. Pictured is Mohammed Bah Abba’s Pot-in-pot invention, which won a Rolex Award of $100,000 –a refrigerator than runs without electricity.

Here’s how it works. You take a smaller pot and put it inside a larger pot. Fill the space in between them with wet sand, and cover the top with a wet cloth. When the water evaporates, it pulls the heat out with it, making the inside cold. It’s a natural, cheap, easy-to-make refrigerator.

Evaporative fridges are a relatively well-tested, proven, low-tech approach to cooling. They can cool produce, food and beverages at about 15-20°C below ambient temperatures. They are most appropriate in hot, dry (not humid) climates where there are no other alternatives (and cannot be used for critical purposes such as vaccine storage).

Absorption Refrigerator: These operate on heat cycle, which is normally powered by a kerosene or gas (LPG) burner. A flame or heat element powers the heating cycle, which creates the cooling affect via a heat exchanger.

In gas fridges the flame is powered by LPG.

In kerosene/paraffin fridges the flame is powered by kerosene or paraffin. These fridges emit particulates (and/or gases).

Vaccine Refrigerators: the World Health Organisation (WHO) has approved a number of low voltage DC PV vaccine refrigerators for vaccine storage and medical uses. These can be powered by PV systems.