Air conditioning

Air conditioning, often abbreviated as A/C or air con, is the process of removing heat from an enclosed space. This process helps achieve a comfortable interior temperature. It can also control the humidity, which is the amount of moisture in the air. Air conditioning is a part of a larger group of systems known as HVAC, which stands for heating, ventilation, and air conditioning.

By maintaining a steady indoor environment, these systems allow buildings to remain comfortable regardless of external weather. This technology is vital for human health in hot climates. It can prevent heat stroke, dehydration, and kidney failure caused by hyperthermia. In fact, air conditioning is estimated to avert 190,000 heat-related deaths every year.

Most modern air conditioners use a process called vapor-compression refrigeration.

This mechanism works by moving heat from one area to another. In many systems, a compressor is used to manage a refrigerant. A heat pump is a similar device, but it includes a reversing valve. This valve allows the machine to change direction so it can both heat and cool a space.

While some units are small enough for vehicles or single rooms, others are massive enough to cool entire skyscrapers.

Air source heat pumps are also becoming more common in cooler climates.

Humans have used various methods to stay cool since prehistory. In the ancient city of Hamoukar in modern Syria, people used double-walled living quarters. These walls had a gap between them to encourage airflow. Ancient Egyptians also used many passive cooling techniques. These methods spread from the Iberian Peninsula through North Africa, the Middle East, and Northern India.

Passive cooling relies on natural elements rather than powered machines. Today, architects are reviving these traditional techniques to create sustainable 21st-century buildings.

Scientific discoveries paved the way for modern cooling. In 1558, Giambattista della Porta described how mixing ice with potassium nitrate could chill it below freezing. In 1620, Cornelis Drebbel demonstrated a way to chill the Great Hall of Westminster Abbey using troughs and vats. Later, in 1758, Benjamin Franklin and John Hadley studied evaporation. They used a bellows to speed up the evaporation of liquids like alcohol. This process drove down the temperature of a thermometer bulb significantly.

These early experiments proved that temperature could be manipulated through chemical and physical processes.

The 19th century brought major breakthroughs in compression technology. In 1820, Michael Faraday discovered that compressing and liquefying ammonia could chill air. In 1842, John Gorrie used compressor technology to create ice for his patients in Florida. He hoped to eventually use his machines to cool entire cities. In 1851, James Harrison created the first mechanical ice-making machine in Australia. He received a patent for an ether vapor-compression refrigeration system that produced three tons of ice per day. These developments moved cooling from a scientific curiosity to a mechanical reality.

Modern electrical air conditioning began to take shape in the late 1800s. In 1894, István Röck began making industrial ammonia compressors driven by electric motors. By 1896, his factory produced cooling apparatuses for hospitals and theaters.

In 1901, Willis H. Carrier built the first modern electrical air conditioning unit. He installed it at a printing company in Brooklyn, New York, to control temperature and humidity. This helped keep paper dimensions and ink alignment consistent. The term "air conditioning" was actually coined by Stuart W. Cramer in 1906. He compared the process to "water conditioning" used in textile mills.

Air conditioning became a staple of modern life throughout the 20th century. The first domestic units were installed in 1914. In 1931, H.H. Schultz and J.Q. Sherman developed the window unit, which went on sale in 1932. Car air conditioning followed, with Chrysler offering semi-portable units in 1935 and Packard in 1939. By 1945, Robert Sherman invented a portable unit that could also filter air. In 1954, Ned Cole even developed the "Austin Air-Conditioned Village," a suburb with built-in cooling. These innovations helped shape postwar metropolitan growth alongside highways and automobiles.

Despite its benefits, air conditioning has a significant environmental impact. In some years, air conditioning used about 7% of global electricity. It also emitted approximately 3% of greenhouse gases. Because of this, the United Nations has called for more sustainable technology. They suggest using alternatives like selective shading, windcatchers, and thermal insulation. As the world grows, finding ways to cool our spaces without harming the climate remains a major challenge.