This Babbage column from the Economist is full of interesting information about the air conditioning that we have enjoyed over the past 110 years. Invented 110 years ago in Brooklyn by Willis Carrier, air conditioning has made indoor climate control of temperature and humidity first possible and then ubiquitous. Such is the now-typical pattern of technological change — create a new idea in response to a pressing problem, start with its application in a targeted and valuable market, and then use the lessons from that process to improve both the idea and its production process in ways that reduce costs and thus make the idea more affordable and available to more people.
I was intrigued to read that the pressing problem at the time was not heat, but humidity. Heat had been addressed 60 years earlier, using air cooled by being blown over ice. But heat + water = humidity, and the air’s water concentration can counteract the cooling effects. Humidity is also a problem in and of itself, and Willis Carrier was working on this problem for his employer’s client, a printing company in Brooklyn. Interior humidity makes inks dry slowly and run, so if they could reduce the humidity inside their facility, they could print more quickly, increasing their throughput and productivity and reducing their costs (especially their average fixed costs). So the compressor-driven air conditioner in your home today derives from a technology designed for industrial use to reduce humidity, not residential use to reduce heat. As my building engineer friends tell me, keeping a balance of heat and humidity in a building is the challenge for which the technology is built (and is, incidentally, why so many commercial buildings feel so cold in the summer — they are in part setting an internal temperature that helps them manage internal humidity).
The other quite interesting fact from the Babbage column is that some early compressors used carbon dioxide (CO2) under pressure, but that it was phased out because of its tendency to explode (oops!). Then came the use of chlorofluorocarbons (CFCs), which have been phased out due to their negative effects on atmospheric ozone (double oops!). Now, with modern coil and compressor engineering and manufacturing techniques, the compressors are sturdy enough that some manufacturers are returning to using CO2:
The industry is in the process of rediscovering CO2. Nowadays, diesel engines and other piped systems are built to withstand pressures substantially higher than those which caused carbon dioxide to fall out of favour. Like CFCs and HCFCs the gas is non-toxic and non-flammable. It is also all too abundant. John Mandyck, a vice-president of modern-day Carrier, says the company has already begun rolling out its first CO2-based products. They extract the gas from the air, making them carbon-neutral and easy to replenish in the event of a leak. A sea-faring system was deployed commercially last November.
Note that combination: green and convenient. That’s a wonderful consequence of continued, relentless innovation.