WeatherImpact Earth


Technology being tested in Phoenix could make cities cooler

Phoenix skyline
Posted at 5:17 AM, Jun 10, 2021
and last updated 2021-06-11 08:20:30-04

PHOENIX — Warmer is the new normal in Phoenix.

According to the recently updated average temperatures, we have seen a warming trend in both our daytime and nighttime temperatures.

At night, we know it’s a combination of climate change and urban development that is influencing overnight low temperatures.

Along with reducing greenhouse gases, mitigating the urban heat island could help slow the trend of rising temperatures and there is research happening right here in the Valley to test new technologies that could make a difference in how we cool our cities in the future.

That is the idea behind a stretch of roadway in the Garfield District, south of downtown Phoenix.

It is one of eight neighborhoods in the Valley where an asphalt sealant product called CoolSeal by manufacturer GuardTop is being tested as a method to mitigate the heat island effect.

Jennifer Vanos is an assistant professor at Arizona State University. She says the goal of the CoolSeal is to reflect the sun’s energy back into space so that the heat is not absorbed by the asphalt as would typically happen with traditional sealants.

“No city has tried this before the way Phoenix is trying this and so we’re really leading in that space globally,” says Vanos.

This research is looking at the benefits and potential effects of this product. So far, they have found that the surface temperature of the asphalt coated by the CoolSeal is 16 degrees Fahrenheit lower than the asphalt covered by traditional seals.

The air temperature above the asphalt is cooler too, by about 0.44 degrees Fahrenheit.

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“Now that doesn’t sound like a lot, and it’s not necessarily something our body would be able to feel but one of the goals we have over the coming year is to be able to take those numbers for each neighborhood and do calculations on what that means for energy use, and what that means for water use, and what that does potentially mean for human health,” explains Vanos.

David Sailor is the Director of Urban Climate Research at ASU. He says the CoolSeal can help reduce how much of the sun’s energy is absorbed, but there is also new technology that could actually cool the surrounding air even further.

It’s known as “passive radiative cooling material” and it reflects and radiates energy, so the surface is actually cooler than the air temperature at all times, explains Sailor.

“It’s a game-changer of sorts in the ability to cool our cities because even a white surface on a rooftop like we’re overlooking right here, those white surfaces still remain a little bit hotter than the air temperature during the day, so you’re adding heat to the environment, not as much as a dark surface but they are adding heat. If we replace that white surface with a passive radiative cooling surface, it would actually be below air temperature at all times and that would allow us to further cool the environment,” says Sailor.

Innovations such as this could also allow for heat island mitigation strategies to be implemented on a wider scale, even in our own homes. These technologies come in darker colors, so it would mean that you could benefit from the cooling effects without necessarily having to have a white or light-colored roof.

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While not all of these technologies are on the market yet, Sailor says now is the time to start considering them as part of the future of infrastructure.

“We have our fate in our own hands let's take advantage of that and the more that we can make our cities livable, thriving communities, the better we sort of guard against the risk of flight away from our cities,” says Sailor.

Sailor also adds that while these technologies could really make a difference in how we experience and mitigate the heat here in the Valley, it’s important to always look at not just the benefits but also any adverse consequences they could bring so that we make informed decisions as our city continues to grow and develop.