Dutch industrial designer Jo Szczepanskaha has come up with the Outback refrigerator. It is basically a food refrigerator that does not require any electrical system.
According to the designer, the mechanism of this contraption uses natural evaporation to produce refrigeration. This natural system is based on the famous “Zeer” pot, which has zero electrical consumption.
Known as Zeer, it was used in Ancient Egypt (2500 BC). Professor Mohammed Bah Abba produced its more modernist version, and made it available on a large scale to the general public.
The system consists of a clay pot inside a larger clay pot. A layer of damp sand is inserted between the two pots, while a damp cloth covers the pots. Passive heating of this container occurs when it is placed in the sun. Due to this solar energy, the inner container (with the food) heats up, and therefore the evaporation process takes place. With evaporation, hot air from the pots is transmitted to the sand layer, while cold air (or at least fresh air) from the sand enters the inner container, to fill the void. Thus, the inner pot with the food is kept cold by natural evaporation.