Pot-in-pot refrigerator

The pot-in-pot refrigerator, also known as a Zeer الزير in Arabic, is a food cooling device. It works by using the evaporation of water. It needs no electricity.

Functioning of a clay pot cooler

A clay pot cooler filled with vegetables

Vegetable sellers with clay pot cooler in the market at Ouahigouya, Burkina Faso

It is made by putting a clay pot inside a larger clay pot with wet sand in between the pots and a wet cloth on top. As the water evaporates it cools the inside, letting food stored in the inner pot to be kept fresh for some time. It must be placed in a dry, ventilated place for the water to evaporate to the outside.

Evaporative coolers perform poorly or not at all in climates with high humidity.

Mohammed Bah Abba of Nigeria patented the device in 1995 and was awarded a Rolex prize in 2000 for developing the “pot-in-pot preservation/cooling system”. However, the device was known at least as early as the Middle Kingdom of Egypt, as seen by the hieroglyphic kbb, "to cool".

Wine coolers

Earthenware wine coolers work on the same principle. They are soaked in cold water for a while, then emptied and put on the table. The pores of the earthenware are now full of water. Evaporation from the earthenware keeps white wine cool enough for several hours.

Other websites

• Rolex awards page on Mohammed Bah Abba
• The Zeer Pot Archived 2014-02-22 at the Wayback Machine - a Nigerian invention keeps food fresh without electricity
• Passive Cooling and Zeer Pots
• The Shell Award for Sustainable Development Archived 2016-04-13 at the Wayback Machine
• Zeer Pot - introduction and downloadable manual on manufacturing zeer pot refrigerators