Tuesday, August 4, 2015

An AC with a 550-year warranty

Source: The Hindu  

The wind-catcher at the Takht Mahal in Bidar fort.— photo: gopichand t.

This natural cooling system is in existence in the old Bidar fort

What is the warranty period on your air-conditioning system — five, seven or at the most 12 years? How about a system that has a warranty of 550 years?

Bidar fort houses this system. The Gagan Mahal, or the grand palace that has the takht (throne), has just such a natural cooling structure.

Local guides call it the ‘Bahmani AC’. Built by the Bahmani kings in the 15th century, it still functions.

Cool air gushes out from the bottom of the twin tunnels that are connected to towers on the ceiling. However, the roof of the building has collapsed, depriving visitors of a real air-conditioned experience.

The technique involved is simple. Hot air, sucked in from the surroundings, moves up a quadrangular pillar. It gets cooled, gains weight and comes down. Air is thus cooled by convection and evaporation.

The walls of the tower, exposed to the sun, attract cool humid air towards them. This happens through multiple vents, providing ample supply of cool air. Two such pillars are fixed in each room, on opposite sides of the hall.

These structures, called Badgeer, Malqaf or Hawa Khamba (wind-catcher), are also found in other buildings, including the Rangeen Mahal, Turkash Mahal or Queen’s Palace, and the Diwan-e-Khas or VIP enclosure.

There are some such structures inside the city too. Havelis of zamindars and the rich had these structures. “I had saw them while growing up in the old city,” says historian Abdul Samad Bharati.

V. Govindan Kutty, groundwater expert who has worked on the Surang Bavi system of medieval era aqua ducts in Bidar, said the method of cooling buildings involved both wind tunnels and underground water canals.

“There were several wind-catchers along the Jamuna Mori or the Shukla Teertha channels originating in the old city and ending in the Bidar fort. Some houses had basements where people would collect water. The combination of wind-catchers and underground channels led to general cooling of these houses,” Mr. Kutty said. He points out that this system is used extensively in Iran, where multiple wind-catchers are built over cisterns to chill water.

“The government should take steps to conserve these structures” says Digambar Thakur, heritage enthusiast.

This natural cooling system is in existence in the old Bidar fort


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