Persians Already Invented Air Conditioning Thousands of Years Ago: This Is How Their 'Wind Catchers' Worked

  • Millennia ago, the Persians knew the secret of modern technology.

  • They designed huge chimneys to catch the cool breeze.

Persian windcheaters
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The history of air conditioning is quite interesting. Heat has always existed, and not only do our bodies react to it in a certain way, but some materials don’t take to it well and make some tasks more complicated. Over the years, civilizations have supported elevated temperatures as best they could. The Chinese used fans, the Romans ate snow, and the Arabs installed underwater channels inside their villas.

However, a few hundred years ago, the Persians already had “wind catchers,” which allowed rooms to be cooled efficiently and with differences of up to 60 degrees Fahrenheit from the outside temperature. They're truly fascinating structures.

A chimney, more or less. It’s complicated to trace the origin of wind towers, but they’re estimated to be about 1,500 years old. Although there were vestiges in ancient Egypt it seems it was in Mesopotamia, now Iran, where inhabitants refined and popularized these structures.

These towers had a series of vents to catch the wind. Depending on the openings, the towers could be unidirectional—which means they had a single opening in the prevailing wind direction—bidirectional, or multidirectional, with multiple slots perpendicular to the wind direction.

Early air conditioning. These towers were a highly optimized passive cooling system. Engineers knew that acute angles favored airflow separation and were a more optimal form than rounded shapes. In some cases, it was possible to completely or partially close the air duct to prevent the spread of disease or the infiltration of during storms.

Simplicity was key. The tower’s height was essential to capturing the clean air and creating a chimney effect inside the structure. The tower’s vents captured the clean, cold air and directed it into the interior of the house or room. Due to thermal buoyancy, cold air weighs more than hot air. As such, the hot air inside moved upward and exited through one of the output holes, which didn't catch the wind because of the chimney effect.

Graphic of how the Persian wind catchers work

Adding groundwater. In addition to separating the airflow, the architects added eaves that act as ailerons to reduce turbulence when the wind was too strong. While this system effectively let the hot air escape and left clean, cool air in its place, Persian engineers knew they could improve it. And so they did.

About 3,000 years ago, the Persians also developed qanats, an irrigation system based on underground channels under their villas. Between the qanat and the dwelling was a space through which air circulated at a comfortable temperature because of convection. The Persians discovered that they could create vents on the house floor so that cold air could enter from above through wind catchers and from below.

Past and... future? Ultimately, it’s a system that creates natural ventilation by intelligently directing fresh air inside and ejecting hot air. The temperature differences between the inside and outside help vary the pressure, which is why officials are currently considering applying this method in their cities.

In addition to the historic buildings that still use this system in some parts of Iran and Egypt, we have examples like Qatar University in Doha and Saint-Étienne Métropole in France, with multi-purpose spaces that use aluminum panels that work with any wind direction. And in the United Kingdom, buildings with towers provide this chimney effect, among other buildings in different regions worldwide.

Climate change. The exciting thing is that when we’re looking for ways to reduce our carbon footprint, solutions from the past can be relevant in new construction. With this wind-catching system, the temperature can be reduced by 46 to 60 degrees Fahrenheit compared to the outside temperature, resulting in significant energy savings.

Studies have also shown that incorporating wind catching systems can reduce the cost of a building’s energy consumption by 23.3%. Considering that conventional mechanical ventilation accounts for one-fifth of the world’s electricity consumption, it's important to evaluate these alternatives.

As mentioned earlier, several architects worldwide have included these passive cooling solutions in their buildings in recent decades. Now, when you see one, you’ll know it isn’t a marvel of modern architecture, but an invention with a few millennia under its belt.

Images | Rαge | Bernard Gagnon | Sky2105

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