For those of us living in hot climates, the air conditioner has become such an indispensable appliance that we can scarcely imagine how people lived in these places without them. We think about our ancestors who inhabited some of the hottest parts of Earth without the benefit of modern climate control, and we both pity and admire them.
Surprisingly though, air conditioning has been around since the dawn of civilization. For nearly as long as people have been building houses in hot places, we’ve been inventing ways to actively cool them down. Modern air conditioners are much more efficient and effective than the methods used in antiquity, but they’re actually based on the same basic principles.
Even when modern air conditioners were invented, they faced an uphill battle. Many people believed that cooling the air somehow went against the will of God and considered the whole idea of air conditioning sinful. They had forgotten, apparently, that people have been cooling the air inside their homes for thousands of years.
Most early forms of air conditioning relied on evaporative cooling. This makes sense; evaporative cooling is the mechanism that our bodies use to cool themselves down when hot, so it’s only natural that people would observe this and figure out a way to apply it to a whole house or building.
In ancient Egypt, people cooled down their homes by hanging wet reeds in their windows. As the air from outside blew through the window, the evaporation of the water in the reeds cooled it down, leading to more comfortable temperatures inside the home. This would have also had the effect of increasing the humidity inside the house, a nice bonus in a dry desert climate.
The ancient Persians were even more sophisticated in their cooling technology. They built special towers called windcatchers that captured the cool breezes and redirected them into the house. Sometimes they would force air to flow past an underground cistern filled with cool mountain water, chilling the air even more. Other times, all of the cool air would be forced into a cellar to keep perishable foods from spoiling.
In some places, underground water reservoirs were built with windcatchers and were capable of storing water at near-freezing temperatures, even in the hot summer months. This system was so effective that it eventually spread across the Middle East, through Arabia, and into Egypt.
In other places, people discovered ways to store snow and ice harvested in the winter until summer and used them to provide a cooling effect either by adding them to drinks or using fans to blow air over them.
Evaporative cooling is a simple technique, but it’s effective and easy to use. There are still cities in Iran where ancient windcatchers are the primary form of the air conditioning today.
Mechanical cooling was the next major step in the development of air conditioning, but it didn’t happen until the mid-18th century. Benjamin Franklin and John Hadley discovered that using volatile liquids such as alcohol or ammonia could drastically improve the efficiency of evaporative cooling, especially when aided with a bellows. Michael Faraday, building on their work, discovered that compressing ammonia and then letting it evaporate could chill the air. These were the first major steps toward developing mechanical cooling systems. For thousands of years, all we had was evaporative cooling. It worked fine, but it couldn’t necessarily work everywhere.
Desert climates are great places to use wet reeds and windcatchers to cool the air. Hot and dry weather lends itself well to evaporative cooling. Hot and humid weather is less ideal. It will still work, but not nearly as well.
It should come as no surprise, then, that a Floridian developed one of the first mechanical cooling machines (and ice makers). In 1842, a doctor in Florida named John Gorrie used compressed air to create ice. It worked by compressing the air and then forcing it through a series of pipes. As the air expanded, it cooled. This early compressor worked so well that ice formed on the pipes, turning into the world’s first ice maker.
Gorrie used the ice to cool the air in his hospital, in the hopes that the cool air would help his malaria patients with their fevers. By suspending the ice in a large basin near the ceiling, cool air would sink down and flow over the patients. It was an effective system, but it required enormous amounts of ice. Gorrie’s invention never took off like he thought it would, and although he had hoped to develop large, centralized air conditioning systems, he died before he could achieve that dream, and the idea of centralized AC died with him. For a time, at least.
Electrical Air Conditioning
The first modern air conditioner was designed and built by Willis Carrier, and began operating in Buffalo, New York in 1902.
Surprisingly, Carrier didn’t develop his air conditioner with comfort in mind. Instead, he was trying to improve the printing process for newspapers. Humidity levels in the air affected the paper and the ink, leading to inconsistencies in the print.
What Carrier did was, essentially, reverse the steam-heating process with which he was very familiar. His design forced air through cold coils, instead of hot ones, which condensed the water vapor in the air and allowed him to precisely control the humidity. The cooling effect was actually secondary.
By 1933, he’d improved the system drastically. He invented a belt-driven condensing unit along with a blower and evaporator coil that made the system much more efficient and effective.
Businesses were quick to realize that cooling the air and controlling humidity could also help improve productivity by making their workers more comfortable, and Carrier eventually formed the Carrier Air Conditioning Company of America, which is still in operation today. By the 1950s, he had expanded to residential and automobile sales, adding his air conditioning units to homes and cars at ever-increasing rates.
Before that, though, the 1904 World’s Fair in Saint Louis introduced the American public to comfort cooling. Large mechanical refrigerators cooled the Missouri State Building by pumping 35,000 cubic feet of air through the auditorium per minute.
By the 1920s, movie theaters were doing something similar. They used refrigeration technology to chill the air, and they forced it into the theater through vents in the floor. This drove hot air toward the ceiling and meant the upper levels in the theater would get uncomfortably hot, while the lower levels got so cold that people often resorted to wrapping their feet in newspaper to stay warm.
These systems were much too large and expensive to use in private homes, but home cooling was already catching on.
Charles Gates’ home in Minneapolis was the first private home to have air conditioning, in 1914.
In 1929, Frigidaire made a home split system cooling unit that, while small enough for home use, was still very heavy and more expensive than most could afford. General Electric managed to improve on that design and built a self-contained room cooler, but only produced 32 prototypes by 1931, without a production model in the marketplace.
Meanwhile, Robert Sherman invented the portable window-unit air conditioner in 1945 in Massachusetts. His unit could cool, heat, humidify, dehumidify, and filter the air. By 1947, Henry Galson had developed a more compact version that had sold over 43,000 units. This was the first time that the average American could afford to have a home air conditioning unit.
By the 1960s, most new homes had central air conditioning units. In addition, window units were even cheaper than they’d been in the 1940s.
Now, over 80% of the homes in the US use air conditioning. Most of those using central heating and cooling instead of window units. In addition to home cooling, it’s almost unimaginable now that cars used to have no air conditioning at one point. Just about every car in the US now has air conditioning. Ones that don’t are likely decades-old cars.
Both air conditioners and refrigerators require coolant. For the coolant to be effective, it has to be something more volatile than water.
Originally, the substances used as coolants were toxic and quite hazardous, often flammable. Early air conditioners often used ammonia, propane, or methyl chloride. All of these could cause fatal accidents in the event of a leak.
Thomas Midgley Jr. invented Freon, a trademark of DuPont, in 1928. It was the first non-flammable, non-toxic chlorofluorocarbon gas ever made. Since then, scientists have invented dozens of CFCs and HCFCs (hydrochlorofluorocarbons), all referred to as Freon. Each different iteration of Freon is assigned a letter and number value (R-11, R-22, etc.) to indicate its molecular structure.
R-22 is the Freon that’s currently in use in most AC systems in homes and workplaces. Automobile companies used to use R-12 in-car air conditioning. Then they discovered that R-12 had a negative effect on the ozone layer and switched to R-134a in 1994. R-12 and R-11 are no longer made in the US. However, they can still be imported and do see limited use.
CFCs and HCFCs are being phased out in favor of hydrofluorocarbons (HFCs), which lack chlorine. This is largely due to environmental concerns, but HFCs are still not especially environmentally friendly.
During the 1990s, a German refrigeration company developed an ozone-safe refrigerant from isopentane and isobutane. Major companies like Coca-Cola, General Electric, Ben and Jerry’s, and Unilever have begun switching to that refrigerant and supporting its manufacture and use in the United States.
Non-Vapor Compression Cooling
The next big thing in air conditioning technology might just be non-vapor compression. Several research projects are underway to determine the best approach to cooling or heating without the use of chemical refrigerants.
One approach is to use a specially designed polymer membrane to manipulate water molecules in the air and condition it that way. Another approach is thermoelastic cooling, which stretches and releases metal rods to create a cooling effect. This method currently requires a huge mechanical loading system. The hope is to reduce the size of the system by a factor of 10.
Another system uses a series of copper rods and a magnetic field to remove heat. Another uses an electrocaloric heat pump. The fifth and final project examines using fuel cells to allow the use of water as a refrigerant.
These projects are all still in the development stage. However, they all show promise as methods to improve the energy efficiency of air conditioners.
There are other projects investigating the use of different compressor designs, with the same refrigerants currently in use, to improve efficiency. These could lead to much smaller units than the ones currently in use.
Humans have used some form of air conditioning for as long as we’ve lived in hot places. It’s one of the great hallmarks of civilization: using our ingenuity to make our environment more comfortable for us.
Our modern air conditioners work very differently from the windcatchers of ancient Persia, but they retain the same principle. They replace hot air with cooler air and make the home a more pleasant place to be.
When you switch on your air conditioner, you aren’t just cooling your home; you’re taking part in a grand tradition. We’ve been finding ways to keep our homes cooler than the world outside for thousands of years. We’ll continue working to find new and innovative ways to cool them in the future.
For more information, see: What is the Difference Between a Heat Pump and an Air Conditioner?
ECM Air Conditioning, with its headquarters located in Boynton Beach, FL, provides air conditioning services within Palm Beach County, Broward County, Martin County, and St. Lucie County. If you’re having issues with your HVAC system, we’re on-call and ready to assist you with your air conditioning needs. So if you’re in need of AC service, don’t hesitate to contact us today to schedule an air conditioning service call diagnostic! Our AC service experts will diagnose any issues that may be occurring with your HVAC system and help to repair your AC issue on the spot.
Best of all because ECM is the largest AC company in South Florida our local warehouse facility that is 69,000 SQFT houses over $1 million in inventory and fully stocks our 127 vehicles on the road, making us one of the very few AC service companies capable of repairing most issues right on the spot. That means no waiting and no downtime without air conditioning for you & your family in the blistering Florida heat!
Call us at 561-295-1763 or contact our AC service team online by clicking here.