Refrigerator with the door open
How to build an air conditioner look at ogeneral ac !
But all’s not lost! Instead of letting the power of science defeat us, we just have to use it the right way.
At home, using the air conditioner will add plenty to your electricity bill; when physicist Tom Murphy tested his air conditioning scientifically, he found he used “more electrical energy in two days than we normally expend in a month.” You could try other strategies like opening your windows all night but shutting them tight first thing in the morning and throughout the daytime to keep hot air out of your home. In really hot climates, you might find you simply cannot do without the AC; even so, you can dramatically reduce how much it’s costing you (and how much energy you’re using) simply by turning the thermostat to a slightly higher setting.
Air conditioning units used to have another very harmful effect on the environment as well. Until the late 20th century, most used coolant chemicals known as chlorofluorocarbons (CFCs) (so called because they are made from the chemicals chlorine, fluorine, and carbon), which were also used widely in refrigerators. When old air conditioners and refrigerators were broken apart for scrap at the end of their lives, the coolant chemicals escaped into the atmosphere. Floating up into the stratosphere (the upper atmosphere), they rapidly damaged Earth’s ozone layer: the natural sunscreen that helps to protect us from the Sun’s harmful ultra-violet rays. Most modern air conditioners avoid CFCs (now banned in many countries under a global agreement called the Montreal Protocol) and use alternative coolant chemicals instead (typically halogenated chlorofluorocarbons or HCFCs). If you look closely at our top photo, you can see that the fan has a green “Ozone friendly” label on it, which means there are no CFC coolants inside.
Here to stay?
Love it or loathe it, we won’t be getting rid of our air conditioners anytime soon; in the United States, for example, all the trends are pointing the other way. According to a 2009 survey by the US Energy Information Administration (EIA), 87 percent of US households now have air conditioning, with a dramatic increase in every region of the country since 1980. Changing expectations have helped to drive that trend: around 90 percent of new homes are now fitted with AC. Affluent homes are more likely to use centralized air conditioning systems that cool the entire building; poorer homes rely on smaller, room-based air conditioning units fitted to windows or walls. Although centralized systems are overwhelmingly the most popular in the South, Midwest, and West of the country, room-based units are still significantly more popular in the colder Northeast. Not surprisingly, a 2017 study by the EIA found that residential air conditioning consumes 18 percent of US household electricity and causes a dramatic increase in consumption during the summer months.
Who invented air conditioners?
Drawing of Willis Carrier’s air conditioner patent from 1934, reissued 1941.
Photo: One of Willis Carrier’s air conditioner designs. This diagram is part of Carrier’s US patent #675,144, filed in 1933 and reissued in 1941, which you’ll find among the references below. Picture courtesy of US Patent and Trademark Office.
If you couldn’t live without your air-con, thank Willis Carrier (1876–1950). He was the man who pioneered this “cool stuff” in the early decades of the 20th century. Here’s one of his early designs—and note how closely it resembles my quick sketch up above. How does it work? Warm air is pulled in from a room (1), mixed with fresh air (2), conditioned, and blown back into the room by a fan (3). Heat is removed by the refrigerator chiller pipes in the center of the duct (4), which are fed and controlled by a system of pumps, compressors, valves, and thermostats (5).
Evaporative air coolers