Shanhui Fan’s radiative cooling could help reduce heat-related deaths
Using wavelengths of light, the surrounding air can be cooled without any external power source.
Professor Shanhui Fan and EE alum, Professor Aaswath Raman (UCLA) are using their technology to potentially reduce heat-related deaths. As higher temperatures become more frequent, the use of air conditioning increases, resulting in a cycle of baking the planet in an attempt to keep people cool.
Pictured are Aaswath Raman as a graduate student (on the left) with Professor Shanhui Fan in 2011.
Shanhui and Aaswath developed a film that was both highly reflective of visible light—so it wouldn't warm up in the sun—and an excellent emitter of infrared radiation at just the right wavelengths to pass through the atmosphere unimpeded. If the film covered the hood of a car, it would conduct heat away from the hood, cooling it without using any electricity.
Since they published their findings in 2014, other researchers have designed paints, gels, and wood that can remain cool in daylight. In 2020, their film was installed on a supermarket roof, resulting in energy savings of 15-20 percent.
The film is currently being tested on a few bus shelters in Tempe, Arizona. Preliminary results show that the roofs can be 30 degrees cooler than the surrounding air.
Today, Professor Aaswath Raman is involved in a UCLA project called Heat Resistant Los Angeles. "The idea is, can we go beyond shade?" he says. Historically, cities have focused on providing shade trees, parks, and green belts to help cool urban environments, but such projects often bypass low-income communities and take years to establish. Raman envisions using canopies coated with his film to cool large outdoor spaces; these could be set up quickly at a relatively low cost.
"It's very early days for the project," he says, "so it's still kind of speculative. But I'm hoping in a year or two we'll have some cool results and demos to share."
The World Health Organization estimates that between 1998 and 2017, heat waves killed at least 166,000 people around the world. If we continue to emit greenhouse gases at the current rate, deadly heat will put more than a billion people at risk by the end of the century.
The technology may ultimately help cool our cities, and it may be able to prevent tens or hundreds of thousands of deaths from the brutal heat waves to come, which would be no small feat. But to cool the whole world, we've known for decades what needs to be done: Leave fossil fuels in the ground.
Excerpted from "This new technology could help cool people down—without electricity"