Persians engineered refrigerators

Persians engineered refrigerators in 400BC.

Persians created a manner of refrigeration by building large, cone-like structures with underground storage. These were called Yakhchāl (یخچال‎ ) in the Persian language, which means ice pit. They were used both for the storage of ice and the storage of food. These “refrigerators” meant that Persians could store ice during a desert summer.
Many had windtowers, in order to harness the wind to aid the cooling of ice and products in the Yakhchāl. Often there was a wall on one side of the Yakhchāl in which water would be channeled during the winter. The shade from the Yakhchāl would cause the water to freeze more, allowing more ice to be collected for storage for the summer.
The Yakhchāl had insulation made of sand, clay, egg whites, lime, goat hair, and ash. It also had a trench system that collected melted water from the ice and allowed it to refreeze at night and be recollected. The ice was generally used to serve royalties.