The Evolution of Air Conditioning Technology

By Steve Brachmann
June 20, 2014

As the sweltering heat of summer begins to set in across the country during the summer months, people all over the country are running to their thermostats or single-unit air conditioners to stay cool. Just by pressing a few buttons, a typical American homeowner has the capability to completely control the temperature and humidity in a space. This innovation has revolutionized the demographics of our entire country, allowing many people to live comfortably in southern climates which would otherwise be oppressively hot.

Air conditioners work on the essential premise of removing heat from forced air, often by blowing that air across cooling coils filled with refrigerants. Air conditioning has taken root in the psychology of middle class America, evidenced by the large number of homeowners who have at least one air conditioning unit in their homes. The incredible amounts of energy used to power these units have incited a large number of critics who speak out against the widespread use of air conditioning technologies. However, others are quick to point out that the number of British thermal units (BTUs) used by air conditioners pales in comparison to the amount of energy consumed by Americans for heating.

IPWatchdog is returning once again to our Evolution of Technology series to take an in-depth look at how AC technologies have developed over the years. Modern air conditioning goes back more than one century in America, although the evidence showing human attempts at cooling the air goes back millennia. Today, we’re sharing a quick timeline of heating, ventilation and air conditioning (HVAC) technologies, with a special focus on beating the heat. We also take a closer look at the current state of air conditioning technologies, including a trio of patents related to air conditioning within automobiles..


Precursors to Modern Air-Conditioning Technology

Evidence about man’s attempts to provide some sort of cooling technology to beat the heat in warmer climates extends back almost 2,000 years. Early air conditioning systems from 2nd century China, for example, involved a manually-powered rotary fan designed to force air through a room. In 3rd century Rome, a system was developed for the importing of ice from the mountain regions via donkey train to cool the garden of Emperor Elagabalus. Roman citizens had already attempted ways of cooling their abodes by circulating cool water from the aqueducts through channels within the walls of their homes.

During medieval times, there’s a notable lack of advancement of any type of innovation related to air conditioning, especially for systems that cool the air. For the most part, people relied on architecture, building rooms with large openings to the outdoors for breezes to pass through and positioning windows so that minimal sunlight entered a room. Most documenters of the early days of air conditioning technology point back to experiments performed in the mid-18th century by famed American patriot and inventor Benjamin Franklin. In 1758, he and Cambridge University professor John Hadley discovered how to freeze water by evaporating alcohols and other volatile liquids at the water’s surface. A few decades later in 1820, English inventor Michael Faraday achieves similar results by compressing and liquefying ammonia.

Efforts that involved cooling the air to increase patient comfort in hospitals and other medical facilities launched the next wave of advances in air conditioning technology, although the story of the technology in this time period is tinged with a great bit of misfortune. During the 1830s, John Gorrie was a Florida physician who decided to study the effect of climate on humans, and especially why there seemed to be a higher number of American cases of yellow fever in the south and nearly none in the northeast. He created a system that forced air by fan through a bucket of ice created by an ice making machine, receiving a patent for the invention in May 1851 from the U.S. Patent and Trademark Office. Not only was he unable to find financial backing for his invention, however, he had to contend with political pressure from the ice industry interests in the north that felt threatened by the invention. There are many people, though, especially Floridians, who credit him not only as an early father of air conditioning but also refrigerators and the ice machine.

Another attempt at improving air conditioning technology arose in response to one of the sadder days in the history of the United States. On July 2nd, 1881, U.S. President James Garfield was shot by an assassin and passed away more than two months later, on September 19th of that year. In order to provide comfort to the commander in chief during his final weeks, engineers from the U.S. Navy constructed a cooling unit that blows hot air over a water-soaked cloth, forcing cool air to travel underneath the hot air. During a Washington D.C. summer which regularly reached temperatures of 90 degrees Fahrenheit, this system was able to cool a room’s temperature by 20 degrees. The system couldn’t be called efficient, however; in the course of two months, one-half million pounds of ice was used to keep the President comfortable.


Willis Haviland Carrier and the Modern Air Conditioner

Although cooling the air was a major focus of development for early air conditioners, there was another major factor in air quality which had not been addressed until the early 1900s: humidity. Coupled with high temperatures, excessive levels of water vapor in the atmosphere was not only a major cause of human discomfort, but also served to hamper a number of industrial processes, such as paper printing operations.

Right at the start of the 20th century, a young engineer from the region of Buffalo, NY, Willis H. Carrier, was tasked with a problem to solve for a Brooklyn-based printing press, the Sackett-Wilhelms Lithographing & Publishing Company. The company had been having problems with improperly drying inks and wrinkling paper, and it was believed that conditioning the air could somehow solve the issue. In 1902, Carrier had a breakthrough revelation while standing on a misty train platform in Pittsburgh. He had an idea that he could control the humidity of air by passing it through water to create fog, essentially drying excess water from the air.

From U.S. Patent No. 808897, entitled “Apparatus for Treating Air.”

Carrier applied this theory to create a system which could increase or decrease the air humidity within a room for commercial purposes. U.S. Patent No. 808897, entitled Apparatus for Treating Air and assigned to Carrier and the Buffalo Forge Company, protected a system of spray-treating air with a heated liquid spray to increase humidity or a cooled spray to decrease humidity. The air was conditioned by forcing it through a series of separator plates arranged in a zigzag fashion; liquid could be leached from the air by the inertial force of the air forced by fans against a film deposited on the separator plates.

In 1915, Carrier was part of a group of engineers who left the Buffalo Forge Company, which shifted operations from research and development to solely manufacturing, who founded the Carrier Engineering Company. The company devoted itself to increasing the applications for Carrier’s air conditioning technologies, which ranged from industrial manufacturing facilities to cooling air for movie patrons at indoor theaters. In fact, Carrier’s technology may have led to the rise of the summer movie blockbuster when it was installed in the Rivoli Theater in New York City’s Times Square in 1925, the first of many theaters to install air conditioning units to satisfy summer crowds.

From U.S. Patent No. 1085971, titled “Method of Humidifying Air and Controlling the Humidity and Temperature Thereof.”

Carrier was responsible for a great deal of innovation in the world of air conditioning. By 1911, he had developed what would become known as the Rational Psychrometric Formulae, which he disclosed that year to the American Society of American Engineers. The formula has been used as a fundamental standard for air conditioning calculations by technology developers. In February 1914, he was issued U.S. Patent No. 1085971, titled Method of Humidifying Air and Controlling the Humidity and Temperature Thereof. This patent protected a system of treating air by saturating it with a water spray at a certain temperature to regulate the humidity and air temperature of a room. His 1922 invention of a centrifugal refrigeration unit was also revolutionary for its central compressor, which reduced the size of the entire unit. This “centrifugal chiller” also replaced the use of previously toxic and flammable refrigerants, like ammonia, for a safer air conditioning unit to be used in homes and buildings.

Carrier’s invention benefitted an incredible array of manufacturing operations within the United States and the greater world beyond, including textiles, meat processing and medical capsules. It also led to the ability for artificial climate control within residential and office facilities, creating a major shift in demographic and architectural trends in America. Although only 10 percent of U.S. homes had an air conditioner by 1965, fifteen years after Carrier’s death, an amazing 86 percent of American homes had at least one unit by the year 2007.

The history of air conditioning technology isn’t completely intertwined with that of heating and ventilation, although HVAC systems for indoor air quality control typically encompass all of these technologies. In the 1920s, another engineer who would be inducted into the National Inventors Hall of Fame, David Crosthwait, began working on a number of innovations related to heating and ventilation technologies. The first of 39 U.S. patent grants issued to Crosthwait was U.S. Patent No. 1727965, which is titled Vacuum Heating System. Issued in September 1929, it protected a steam heating apparatus that could provide heat to various portions of a single building through a ventilation system. Other inventions patented by Crosthwait include a window thermostat to determine heating requirements in a room as well as a single-unit heater and air conditioner.


Current Innovations in Air Conditioning Technologies 

The statistics show that air conditioning has certainly taken a hold in our world and many people in developed nations have grown accustomed to the ability of controlling the temperature of their environment. In the United States, energy consumed by residential air conditioning units doubled between the years 1993 and 2005, and increased another 20 percent by 2010. Air conditioning technologies are also quickly making their presence felt in developing nations, although the links between the cooling agents in air conditioners and global warming are becoming more pronounced and worrisome. The amount of energy that Americans use on their HVAC systems is mind-boggling; studies on the subject report that Americans use about as much electricity on air conditioning as the entire continent of Africa uses for all purposes.

From U.S. Patent No. 8746584, entitled “Heater Interlock Control for Air Conditioning System.”

Development does continue in the world of air conditioning technologies and improvements to energy efficiency are one area where manufacturers are trying to make a dent. One recent patent issued by the USPTO in the area of energy-efficient air conditioning units is U.S. Patent No. 8744632, which is titled System and Method for Operating an Economizer Cycle of an Air Conditioner. This system improves the process for switching between refrigeration and economizer cycles by analyzing the outside atmosphere’s dew point as well as the outdoor temperature and humidity. This patent was issued to Airxcel, Inc., of Wichita, KS, in June 2013. Damage from excess heat building up in HVAC systems will likely be mitigated by the technology expressed in U.S. Patent No. 8746584, entitled Heater Interlock Control for Air Conditioning System. This patent, issued to Trance International Inc. of Piscataway, NJ, protects an air conditioner with a heating element control designed to prevent energization of the heating element in response to a faulty signal from the conditioner’s air blower.

Automobile applications for air conditioning technologies made up a large degree of the recently issued patents which caught our eye during our search of recent AC innovations. Methods for cooling the rechargeable energy storage system (RESS) in electric and hybrid electric vehicles responsive to outdoor temperatures are protected by U.S. Patent No. 8744658, titled Outside Air Temperature Correction for a Vehicle. This system, patented by GM Global Technology Operations LLC of Detroit, MI, also improves the outdoor temperature reading ability of temperature sensors installed on these vehicles, providing more accurate temperature readings which aren’t corrupted by heat discharged by the vehicle’s RESS.

From U.S. Patent No. 8744673, titled “Vehicle Air Conditioner and Control Method and Program for Vehicle Air Conditioner.”

Heating, ventilation and air conditioning systems within vehicles may be able to provide better temperature correction in response to solar radiation thanks to the technology expressed within U.S. Patent No. 8744673, issued under the title Vehicle Air Conditioner and Control Method and Program for Vehicle Air Conditioner. This patent, jointly issued to Mitsubishi Heavy Industries, Ltd. of Tokyo, Japan, and Suzuki Motor Corporation of Hamamatsu-shi, Japan, provides better temperature control of the right and left sides of a vehicle to correct for heat created by sunlight.

Finally, we were also intrigued by a patent for an invention that is designed to both condition and deodorize the air within a vehicle. U.S. Patent No. 8740420, entitled Air Conditioner That Enables Deodorizing Using a Photocatalyst, was issued in early June of this year to Denso Corporation of Kariya, Japan. This patent protects a system of air conditioning which utilizes a photocatalyst installed on a heat exchanger. An ultraviolet ray lamp operated periodically with the blower excites the photocatalyst, releasing a deodorizing agent into the conditioned air.

The Author

Steve Brachmann

Steve Brachmann is a writer located in Buffalo, New York. He has worked professionally as a freelancer for more than a decade. He has become a regular contributor to, writing about technology, innovation and is the primary author of the Companies We Follow series. His work has been published by The Buffalo News, The Hamburg Sun,,, Motley Fool and Steve also provides website copy and documents for various business clients.

Warning & Disclaimer: The pages, articles and comments on do not constitute legal advice, nor do they create any attorney-client relationship. The articles published express the personal opinion and views of the author and should not be attributed to the author’s employer, clients or the sponsors of Read more.

Discuss this

There are currently 3 Comments comments.

  1. Mark Nowotarski June 21, 2014 5:30 am


    Great article. Now that we have inventors using synthetic biology to make plants that glow in the dark (see, is anyone looking at an air conditioning plant (or more precisely, a plant based heat pump)?

  2. Milley Morgan June 25, 2014 7:08 am

    Very Informative . Thank you for sharing it.

  3. Gary Mathews July 2, 2014 8:33 am

    Hi Steve, thanks for sharing such a nice and informative post regarding air conditioners. Air conditioners are a great way to keep your home cool.

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