How to Air Condition a Whole Town

If you think your cooling bills are expensive, imagine if you had to air condition a space big enough to fit thousands of people. The world’s largest cooling units move massive amounts of thermal energy to chill vast spaces.

The new World Trade Center site has one of the largest air conditioning units in the United States. The massive machine cools the PATH hub and 9/11 memorial by pumping water through a series of steel pipes. The system relies on water from the cool depths of the Hudson River. Approximately 30,000 gallons every minute will pour into one of five centrifugal cooling towers. Each tower weighs over 85 tons and collectively they can cool the equivalent of 700 homes worth of space. By using already chilled water from the frigid river, the cooling unit is also one of the most environmentally friendly HVAC units for its size.

In the Arab world, massive projects to air condition have long been essential to maintain regular business in the sweltering summer. Qatari developers have taken things to the extreme with an AC big enough for a city. Qatar’s massive oil and gas wealth and relatively small population help make it the richest state per capita in the world. Off the coast of Doha in the Persian Gulf, the Pearl of Qatar sits as a high watermark of opulence and extravagance in the emirate. The Pearl sits on over 1,000 acres of man-made real estate and currently has nearly 12,000 residents, a few dozen restaurants, and twice as many retail stores. The whole thing is cooled by the world’s largest air conditioner. It uses 28 centrifugal chillers to cool water that is then pumped through pipes all across the development. Running that much water places a strain on the desert’s resources, so the Pearl’s designers built a desalination plant to help feed the city’s water needs.

Qatar’s neighbor, Saudi Arabia has a system to air condition that’s only slightly smaller: Johnson Controls’ 1.2 million square foot cooling plant. In figurative terms, it is the grandest cooling plant because it cools what Muslims believe to be the House of God. The Holy Mosque, or Al-Masjd-al-Haram, in Mecca is a massive complex with original portions of the site dating to the seventh century A.D. The current structure houses the Ka’aba Stone, which Muslims revere as the dwelling place of the Lord. A pilgrimage to the holy ground is a requirement of the faith, and over one million people make the trip every year during Ramadan. Some years, the scorching Arabian sun can turn the temperature up to 140 degrees. That’s enough heat to smoke a roast. Thankfully for the health and safety of the pilgrims, it is cool enough to visit the site even in the heat of summer.

Donna J. Seymour