Building a Better Air Conditioner with Passive Radiative Cooling

The new film works by a process called radiative cooling. This takes advantage of that fact that Earth’s atmosphere allows certain wavelengths of heat-carrying infrared radiation to escape into space unimpeded. Convert unwanted heat into infrared of the correct wavelength, then, and you can dump it into the cosmos with no come back.

— “How to keep cool without costing the Earth,” The Economist

The Economist article explains the materials science in greater depth, and layperson-friendly vocab. But if you don’t have time to geek out (maybe skip getting dressed to free up a few minutes, geeking out is the best), the short version is, Ronggui Yang and Xiaobo Yin of the University of Colorado have figured out how to make rolls of 50-micron-thick polymethylpentene with 8-micron glass beads in it, and the way they interact with infared can not only reflect heat away from a building but can suck interior heat out, and turn it into a wavelength that can pass through the atmosphere and back into space.

“The team estimates that 20 square metres of their film, placed atop an average American house, would be enough to keep the internal temperature at 20°C [68°F] on a day when it was 37°C [98.6°F] outside.”

It requires no electricity. It’s passive. The manufacturing cost is 50 cents a cubic meter. That means that if you buy $10 worth of this film, you might be able to throw out your air conditioner. The Economist estimates that 6% of U.S. electricity generation goes directly to cooling systems.

They need to do more in-the-wild tests. But this could be huge.