TEMPE, AZ — Keeping cool in the Valley can be a huge challenge, especially as climate change drives temperatures higher.
Arizona State University has teamed up with the company 3M to try to lower temperatures at Tempe bus shelters. They're using a specific film on top of the roof that reflects the sun's energy upward. It also radiates the heat from the roof's surface up into space, making it feel cooler underneath the stop.
David Sailor directs the Urban Climate Research Center at ASU. He explained that on top of hot desert temps, the Valley also has darker surfaces that absorb the energy of the sun and structures with materials that absorb heat, store it and release it.
"Those combined with a general lack of vegetation and moisture availability for evaporative cooling result in a city that is hotter than it would be otherwise," said Sailor, also a professor at the School of Geographical Sciences and Urban Planning.
Sailor's team is looking at cutting-edge technology to mitigate that urban heat island effect. At a few of the bus stops, they're studying the effectiveness of passive radiative cooling material on the roofs. This coating is lighter, compared to the copper-colored material on most bus stops in Tempe. The new material reflects the sun's energy and also radiates its own heat out of the urban environment and into space.
"What that gives us is the potential to have surfaces throughout the city of Phoenix that are actually cooler than the air temperature at all times," said Sailor.
Sailor said the results have been promising. Temps on the roof's surfaces and under the shelters are cooler.
"You can apply these same kinds of coatings on bus stop roofs, on rooftops of buildings and so forth," he said.
Sailor said they're working with Tempe leaders, who are currently developing new bus stops.
His team hopes to release findings from the study soon. This is one of several projects they're working on.