If you thought refrigeration was new and ours for the claiming, think again. More than 2,400 years ago, they had refrigerators in the ancient kingdom of Persia. They were not portable and powered by electricity with an easy metal door, but they worked just fine enough to get some ice even in the hot summer and to preserve some food.
It was called the Yakhchāl (ice pit) and some of them built many hundred years ago before the birth of Jesus Christ, still stand in the Middle East. Today, the word Yakhchāl is used for the modern refrigerator in Iran and Afghanistan.
The Persians mostly used the Yakhchāl for making and storing ice, which then made it available to them throughout the year, even in the hot summer.
The huge dome-shaped structure was constructed with a special mortar made out of sand, clay, lime, ash, goat hair and egg shells. This mortar ensures that the wall is a strong insulator against heat and is also water-resistant.
Under the dome is a special large basement where the cooling occurs.
The ancient Persians had a thorough understanding of wind and ventilation systems and how to use it to control indoor temperature. Consequently, the basement where the ice was stored, could be made to have a temperature very much lower than the temperature outside.
The air entering the refrigeration basement was normal hot air drawn from ground level, but it was cooled before entering the refrigeration chamber by flowing underground through a qanat – a water canal deep in the ground, that was used to supply water to homes. Like their ancient refrigerator, many of the canals skilfully dug deep in the ground by the Persians, still work in present day Iran.
Some of the cooling also came from the top of the Yakhchal. Using special wind towers designed to draw cool air into homes and remove warm air, the Persians drew cool wind from the top and directed it down into the cooling basement, while warm air was also expelled upwards through the top.
The refrigeration process also accelerated by the Persians by introducing ice collected from the mountains, when it was available. Water coming in for refrigeration was also made to flow in the shade of a wall, to keep it more cool and reduce heat gain.
The Yakhchal gave way along with the demise of the ancient Persian kingdom, and also to modern electricity and the modern refrigerator. Today, some of them stand as relics of a glorious kingdom from history.