By Mark Jones
The Science Desk at The Atlantic pulled together its 74 mind-blowing science stories of 2022. I finished the list with my mind unblown, but one observation did linger. Number 9, “beyond a certain temperature — as low as 95°, by some estimates — fans do more harm than good,” stuck in my head. Now, as unprecedented heat stifles parts of the U.S. and Europe, pausing to think of living without cooling is definitely mind-blowing.
Summer temperatures make me thankful for Carl von Linde, Willis Carrier, and Ralph Peo. Linde developed the first practical industrial refrigeration unit in 1876. He took the concepts of vapor compression cooling and made a practical device. It remains the technology used in refrigerators and air conditioners. Air conditioning, as we know it today, came on the scene about 120 years ago thanks to Willis Carrier. He intended to control humidity, only later to recognize that his patented “Apparatus for Treating Air” could control temperature, too. Ralph Peo patented the car AC. Today, there are no new models on the U.S. market without air conditioning. Whether in a car or a house, air conditioners rely on vapor compression cooling.
Vapor compression cooling is more than 150 years old. Improvements in compressors and control of electric motors have improved energy efficiency, yet vapor compression is still the best refrigeration technology we’ve got. Reports through the years have promised better. Thermoelectric coolers, thermoacoustic heat pumps, elastocaloric cooling, and more have been hyped — but haven’t yet displaced vapor compression. It seems we’re long overdue. Reports of an air conditioner that “left the industry blown away” gave me hope. The advance was one I admired on Kickstarter, now a commercial product. It is beautiful in its simplicity, a U-shaped window air conditioner where the window fills the U. It places the vapor compression equipment outside the window, reducing noise. Installation is easier. The biggest thing in window ACs in years is actually using the window. It is an innovative product, a big thing in the market, but, at its heart, it’s still vapor compression technology. It doesn’t offer the step-change in efficiency promised by the hyped technologies. It doesn’t obsolete 150-year-old technology.
It is a bit disheartening, but I shouldn’t be surprised. Technology replacement is hard. The centuries-old fan is still the world’s dominant technology for cooling, effective even above 95º F. It turns out, Fact 9 is wrong. Sweat is our defense against heat. Evaporative cooling is the mechanism. Increasing temperature speeds up evaporation; increasing humidity slows it down. It isn’t as simple as 95º F. A 2015 study found fans effective at well higher than 108º F, depending on the humidity. Newer studies are consistent in concluding that there is no one temperature. It depends on temperature and humidity. The conclusions are nuanced. Even the oft-quoted 95º F wet-bulb temperature is not accurate for everyone. Very high humidity can make temperatures below 90º F dangerous. Thankfully, for many of us, there is AC, which is only getting better with time. Innovations are happening with the potential for even bigger improvements to come. The shape of a window unit, innovative as it is, won’t be the end of the story.
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Filed Under: Commentaries • insights • Technical thinking