Zero emissions air conditioning? In Iran they have been using it for millennia

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There are days when heat melts even ideas. But the summer cannula has never gripped Iranian ingenuity. In the hottest country on the globe - the Lut desert in 2005 recorded the whopping? from 70'7ºC - in the city of Yazd, dozens of underground canals, the qanat, and pierced towers called badgir - which literally means windbreaker - profile a unique skyline , while refreshing its neighbors at zero cost. Local researchers believe that this jewel of the past is a promising instrument for the future .

It is five o'clock in the afternoon and Lorenzo - or Mithras, if we attend to the Zoroastrian divinity worshiped here for millennia - does not give truce to Yazd. Its rays cause the same effect as a nuclear bomb: nothing more absolute reigns, look where you look. Not a Yazdite shows the nose. Only small flocks of foreigners walk in a daze and this journalist, provided with much love for his work and a digital thermometer, dares to venture, with which he is falling, through the labyrinthine lanes of the old city.

The device marks 37.5ºC and 10% humidity at street level. A few meters away, a steep brick staircase leads inland. We penetrate her. As we descend the hair bristles from the taste. Seconds later we have reached the bottom and discovered the old mouth of one of the many reservoirs in which the neighborhood, in the past, was supplied with water. The thermometer records pleasant 25'4ºC and 73% humidity. Magic? Do not! Architectural excellence

" The people of Yazd learned to live at the rate imposed by nature, " summarizes Seyed Mohamed Husein Ayatolahí, a research associate at the International Center for Windbreak Research at the University of Yazd. The historic city sits in an oasis, at the crossroads between two large deserts. Therefore, fueled by the arid climate and water scarcity, its citizens went ahead of the great Roman engineers by establishing a complex hydraulic system at least 3,000 years ago. The coast of the Persian Gulf and Egypt dispute being pioneers of this system, but the Iranians perfected it.

Yazd drank thanks to qanat open on skirts of mountains like Sir Ku, which imposes its 4,075 meters high 70 kilometers to the southwest. The canals moved the water underground tens of kilometers to the city, where it was stored in warehouses or channeled to the basement of the wealthiest houses. It was its inhabitants who could enjoy the ideal arrangement of this zero-emission air conditioning system: which allows the wind captured in the towers to be combined with the water of the qanat.

"There are two types of natural ventilation," explains Seyedé Zeinab Imadian Razavi, head of the University Center for Windbreak Research. "The first occurs when the wind blows. An internal wall, inside the tower, captures the wind and channels it into the house; in the second type, the heat of the building leaves the house going up the badgir ." The effect of the pressure differential allows circulation through the air stays that, in contact with the water of the qanat , also cools.

"In this way, when the temperature outside reaches 40 degrees, in the basement it remains above 18 or 20 degrees . It is really nice, and the reason why Yazd's basements are profusely decorated. This is where it is done life during daylight hours in summer, "recalls the researcher. In the large traditional houses of Yazd, many converted into hotels, this effect can still be enjoyed. The inner courtyard, usually a garden embellished with a pond, receives the wind provided by a windbreak installed at one end, providing an opportunity for a delicious nap. If the heat is excessive, it is still possible to loiter more comfortably in the underground rooms. At night, Yazd's life moves to the rooftops. In the end, an open-air museum under the stars.

The jewels of the crown of Yazd are the badgir , which is complemented with adobe buildings always built inland, or a level above the ground to avoid the heat that the firm gives off. Razaví estimates that there are still about five hundred windbreakers left: "They are made of adobe and wooden bars, which act as structural and tensile elements. Due to its composition, adobe, with a high heat capacity, absorbs heat and does not release it until night, cold in arid areas. "

The wind trap, an art form

Ayatolahí highlights other functions of these peculiar towers. "They allow to lodge pigeons, important animals in Yazd because they allowed to beautify the gardens and obtain fertilizer for agriculture, closing another circle of sustainability". "The windbreaker," the architect emphasizes, "is also art. Each windbreaker has a form adapted to the wind it wants to capture. But there is also an aesthetic and social sense. They revealed the power of the families that built them. wealth".

Among all the slender and beautiful windbreakers of Yazd, the one in the garden of Dolat Abad stands out, with its 33 meters high. Built in 1857 and declared a World Heritage Site by Unesco, the jet of air that provides the lower rooms realizes the efficiency with which the badgir came to work in the past. "Today the lower badgir does not work as well as in the past, since Yazd's climate has changed. Now it is hotter and there is more dust in the air," Razaví laments.

With the pressing urgencies to reduce fossil energy consumption and generate less waste, the Yazd University Research Center team tries to update this millenary system , so that it can be used in new constructions. "We experiment with tall and humid columns, capable of opening and closing air channels at specific times of the day and adding, inside, facilities that improve efficiency," she details. For Mohamed Husein Ayatolahí, the necessary step is to open up to other international centers: "We want to collaborate with other universities to expand our research and develop the system beyond borders. We believe that the Iranian system can help improve the world."

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