When Rebecca Sunenshine moved to Phoenix, Arizona, she was shocked by her first electricity bill. She called the utility and told them they must’ve made a mistake.
It was a $400 or $500 bill, explained Sunenshine, a medical director for Disease Control with the Maricopa County Health Department.
They asked her if she had just moved here. This wasn’t a mistake. In fact, ACs in Arizona account for a quarter of the energy use or more than four times the nation’s average. And, it’s not a luxury because, without AC, the summer temperatures here can be fatal.
Unfortunately, in 2020, Maricopa County had 323 heat-related deaths, a record in the country. Sunenshine explained that the country is on track to exceed this number.
The Hottest June in North America
Scorching temperatures haven’t just been common in the Southwest. June was also the hottest month ever recorded in the north of America.
In July, a heatwave claimed some 200 lives in Oregon and Washington, as well as 600 more people who’re thought to have died in British Columbia due to the heat.
With global temperatures rising, the need for ACs soared and in 20 years, the electricity which will be needed to power the ACs in the world is expected to triple.
Sadly, the fossil fuels that are burned to run ACs already add 117 million metric tons of CO2 every year, in the US only. Ironically, these devices that help keep us cool are also baking the planet.
An Eco-Friendlier Option Is Crucial
Even aside from their carbon footprint, ACs directly influence our surroundings, explains Aaswath Raman, professor of engineering at the University of California, Los Angeles. These devices pump the hot air back into the environment and contribute to a hotter planet.
Raman has been focused on finding eco-friendlier alternatives to ACs for almost a decade. He’s part of a small global community of researchers that have been working on various materials like wood, thin films, and paints with one property.
With the use of light wavelengths, these materials help cool down the air without the need for a power source. In some cases, it can help drop down the temperature by 10 degrees F or more.
These new materials could help reduce some of the negative effects of climate change, particularly in cities where urban heat raises the temperature by more than 17 degrees.
A Smarter Way to Stay Cool in Summer
Raman is the founder of this nascent research field. The idea for a potentially better way to keep the temperatures down came to him in 2012 when he was prepping his Ph.D. at Stanford. He was looking through some older science articles and became attracted by a concept some scientists were researching decades before, but it had been dismissed later.
This idea is harnessing a natural phenomenon known as radiative cooling to make objects less hot. This is a process happening all around us. Namely, everything that has been warmed will eventually cool down if the heat source is eliminated.
Researchers wondered if there’s a way to make materials suitable to radiate heat even in daylight, but it didn’t bear any fruits. Raman found references claiming that this can’t be done in the daytime.
But, he decided to pursue it anyway. Being trained in the physics of optics, he studied how the light of different wavelengths affects different materials. He had tools and tech that researchers in the past didn’t.
He submitted a proposal to the ARPA-E that has an open funding call every three years. Although the energy secretary at the time Steve Chu didn’t think this was plausible, the agency gave him funding and a one-year deadline.
This was probably one of their smallest grants.
How Did Raman Create the New Cooling Tech
Together with his Stanford mentor Shanhui Fan, Raman made a film that consists of alternating layers of silica, glass, and hafnium dioxide, a compound that’s used in optics to coat mirrors and lenses.
The film reflected visible light and didn’t warm up in the sun. And, when it covered the hood of the car, it conducted the heat away from the hoot and it cooled it down without any electricity.
During the tests, the film showed to be warmer in the shade because its view of the sky was blocked; on the other hand, when they put it in the sunlight, it dropped down, around 10 degrees.
Raman, Fan, and Eli Goldstein, a Stanford colleague, launched SkyCool, a company through which they’re further developing the tech and will try to make it commercial. In spring last year, they installed the film-coated panels on the roof of one supermarket in California.
The water that passes through these panels is cooled down by the film and then goes into the ACs and refrigerators of the building and cools down their components and reduces the electricity used for their powering, resulting in 15 to 20 percent energy savings.