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Podcast transcript
One of the biggest problems facing humanity for thousands of years has been heat.
The extreme heat makes it difficult to work at noon. Heat is particularly problematic in tropical areas because of the large populations that live there.
As cities grow, the perennially hot weather has become a factor restricting the construction of high-rise buildings.
All these problems were solved by one invention.
In this episode of Everything Everywhere Daily, you’ll learn more about air conditioning and how it helped start the modern world.
Heating and cooling are two sides of the same coin, but they operate very differently.
Heating is relatively simple. Take something and burn it, and you’ll generate heat. If that’s not possible, then we generate our own heat, and we can keep warm by trapping it in insulation.
Cooling, however, is a completely different matter. Cooling, or releasing energy, is much more difficult.
Traditionally, options for staying cool have been limited.
People often choose to avoid direct sunlight. They may wear long, loose-fitting clothing to keep warm air away from their bodies or wear a wide-brimmed hat to block out the sun.
Their buildings probably consisted of thick walls to keep the inside cool and block out the outside heat.
Many cultures also get around this by avoiding the hottest times of the day. In Spain and other cultures, people stop working around noon to avoid the heat. People leave their fields and businesses, go home, have a big lunch, and wait for the sun to set.
Most of these methods simply involve avoiding high temperatures and staying out of direct sunlight. That’s not a bad strategy, but it’s not quite the same as burning wood for heat.
However, there is a physical process that can remove heat from a system and cool it down: evaporation.
You may have experienced this yourself. If you get wet, the water on your skin cools you down. That’s why you can cool down by swimming in water, even if the water is warm.
For thousands of years, people around the world have used evaporation to cool themselves.
In ancient Egypt, people would hang wet reeds over their windows. The evaporation of water from the reeds cooled the air passing through the windows.
In Persia, they used a different system but based on the same basic principle. They built tall towers with openings, called wind catchers, facing the prevailing winds, capturing the airflow and directing it into the building. The air would then pass over a pool of water or a moist surface, cooling it as it entered the living space.
This technique is actually seeing a resurgence in modern buildings, which use passive cooling to lower temperatures without requiring any electricity.
During the Islamic Golden Age, many buildings had central courtyards with fountains or pools. These water features cooled the surrounding air through evaporation, while the courtyards provided shaded spaces.
Before discussing air conditioning further, I should explain why evaporation lowers temperatures, as this ancient technology is crucial to understanding how modern air conditioning works.
As we all know, matter can be in different states, specifically solid, liquid or gas. Heating or cooling something causes it to undergo a phase change, causing it to melt, freeze or boil.
However, a gas can have the same temperature as a liquid or solid. This is because when you measure the temperature of a substance, you are actually measuring the average kinetic energy of the molecules that make up the system. For example, the molecules in a glass of water do not all have the same energy.
When a water molecule evaporates, it absorbs heat energy from its surroundings. This energy breaks the molecular bonds between the liquid water molecules, causing them to escape into the air as vapor.
As it absorbs energy from the air, the air becomes cooler.
This principle of cooling by evaporation was used in the 18th and 19th centuries to experiment with, for example, liquefying gases. To achieve extremely low temperatures, they often used cascade cooling, cooling one gas first, then another, and so on.
This physical phenomenon was used to create the first refrigeration system. The first mechanical refrigeration system was created in 1834 by Jacob Perkins, an American inventor living in England.
His refrigeration system and all subsequent systems used a liquid called a refrigerant, which had a low boiling point. Early refrigerants used liquids such as ammonia, sulfur dioxide, methyl chloride, or propane. When these liquids changed phases in a closed loop, they carried heat out of the system, as if by evaporation.
This was not the first air conditioner, because air conditioning is not just about cooling. It is also about the regulation part of air conditioning, which regulates humidity, not temperature.
Hot weather is one thing, but hot weather with high humidity is especially annoying.
The invention of the first air conditioner is often attributed to Willis Carrier.
In 1902, while Carrier was working at Buffalo Forge, one of their customers had a problem. Sackett-Williams Lithographic Printing and Publishing Company in Brooklyn, New York, had a problem. When they were doing a four-color print, they had to run the paper through the press four times, and the paper had to be perfectly aligned.
The problem is that humidity can cause the paper width to change, disrupting the printing process.
Carrier developed a system that blows air over coils filled with cooling water. The moisture in the air condenses on the cooled coils, creating dehumidified, cooled air.
The system worked, and many people reported feeling more comfortable around the machines. Carrier combined the two to create Carrier Corporation, which is today one of the largest air conditioning companies in the world.
The term air conditioning was coined in 1906 by Stuart Cramer, a North Carolina textile mill operator, who wanted to increase the humidity in the factory air to make it easier to handle textiles.
Khalil liked the name and chose it as the name of his company.
Air conditioning didn’t catch on right away. Early systems were expensive, bulky, and required electricity, which wasn’t widely available in the early 20th century.
The first home with air conditioning was built in Minneapolis in 1914, 12 years after air conditioning was invented. The system was so large that it required a separate room in the house to house the equipment. It is not even known if the system was ever used, as the owner died a year before the system was completed.
In 1922, Carrier developed the centrifugal refrigeration compressor. It made air conditioning systems smaller and cheaper, with fewer moving parts.
The first place to adopt the new system was the Rivoli Theater in New York City in May 1922.
It turns out that movie theaters were early adopters of air conditioning. They could easily convert the ductwork of their heating systems into air conditioning systems, and air conditioning could attract customers. On hot summer days, many people would buy movie tickets not because they were interested in the movie, but because they wanted to spend an hour or two away from the hot and humid weather.
The first window air conditioner suitable for installation was invented in 1931. This system is very similar to the window air conditioners used by many people around the world today.
These first window air conditioning systems were very expensive. In 1932 dollars, one air conditioner cost between $10,000 and $50,000. If converted to modern dollars, the price would be between
As late as the 1930s, home air conditioning was still only available to the wealthy.
The first automotive air conditioning system was introduced in 1933, and Chrysler became the first major automaker to equip its cars with it in 1935. However, the system was extremely expensive.
It wasn’t until after World War II that home air conditioning became commonplace. In 1945, Life magazine ran a four-page feature on air conditioning titled “Air conditioning/after the war will become cheap enough to be installed in private houses.”
Their predictions will come true.
In 1947, sales of the inexpensive window air conditioner reached 43,000 units, and over the next decade sales exploded.
By the early 1960s, central air conditioning systems were being used in homes, allowing them to cool entire buildings without the need for bulky units hanging out of windows.
As air conditioning became affordable and available in all public places, it began to change major social and cultural patterns.
Communities in deserts or extremely hot climates usually don’t have many people. Suddenly, people could live in such areas without having to endure the scorching heat. Communities like Phoenix, Arizona, and Las Vegas, Nevada, saw population booms after the advent of air conditioning.
Air conditioning also enabled the development of skyscrapers. In a recent episode, I covered the history of skyscrapers and the technological innovations that made them possible. One important development I didn’t mention in that episode was air conditioning.
For a variety of reasons, very tall buildings cannot allow windows on the upper floors to be open. This means that all the heat generated on the lower floors will be trapped in the building as it rises. Not to mention the problem of an entire wall of windows being heated by the sun.
Without air conditioning, such a building would be extremely uncomfortable or uninhabitable.
Or maybe it was air conditioning that made the whole country feasible. In 2010, Lee Kuan Yew, the founder of modern Singapore, was asked in an interview, “Besides multicultural tolerance, what else has driven Singapore’s success?”
His answer was direct and surprising. He said:
Air conditioning. Air conditioning is the most important invention we have ever had, perhaps one of the greatest inventions in history. It has changed the nature of civilization by allowing civilization to develop in tropical regions.
Without air conditioning, you can only work in the cool early morning or evening hours. The first thing I did when I took office was to install air conditioning in the civil service office buildings. This is the key to improving public efficiency.
Air conditioning has become so important across the world that it is one of the largest consumers of electricity.
For example, India consumes 91 TWh of electricity per year for air conditioning alone, while the United States consumes more than 600 TWh.
The largest number of U.S. casualties in the second Iraq war came from roadside IEDs that exploded near trucks carrying fuel. What was all that fuel used for? The biggest use was for air conditioning.
The importance of air conditioning can be seen in what happens when it goes away. During heat wave power outages, thousands of people may die without air conditioning.
In the past 20 years, 3,142 people have died from heat-related causes in the United States. Most of them were caused by malfunctioning air conditioners in their homes. In 2003, a heat wave in France killed about 15,000 people, most of whom were over 75 years old.
Air conditioning has become an integral part of modern society. It makes people live and work more comfortable, and it has made cities and countries that were previously uninhabitable more livable.
Although many people don’t realize it, air conditioning has become one of the mainstays of the modern world.
