Cool cities with Smart Surface technology

Drone photo of a truck painted in light gray paint on a city street (courtesy of the Phoenix Metropolitan Transportation Authority)
This cool pavement installation in Phoenix is ​​part of a 2021 pilot program. (Provided by Phoenix Market Traffic Bureau)

Asphalt, concrete, and a lack of tree cover raise urban temperatures. Roads, roofs and other surfaces absorb the sun’s UV rays and dissipate heat during the day and even late at night.

This trapped heat creates urban heat islands, areas where the natural land cover is replaced by pavements, buildings and other surfaces that collect more heat than other areas.

Smart surface technology could help reduce the impact of the climate crisis by reducing urban temperatures.

Smart surfaces are being used on streets, parking lots, and rooftops across the U.S. and soon around the world.

What is a smart surface?

Large solar panels lined up under the parking lot (© Mike Blake/Reuters)
UC San Diego’s parking lot structure, shown in February 2011, uses solar trees to provide shade and generate renewable energy. (© Mike Black/Reuters)

The Smart Surfaces Coalition, a group of 40 national and international organisations seeking to make urban centres more climate resilient, said these surface technologies could mitigate rising temperatures caused by the climate crisis, while enhancing urban resilience and saving funds.

These include:

  • Reflective coating on the road.
  • Solar panel outdoor shading structure.
  • Cool roofs reflect the building’s heat.
  • Green roofs and walls are covered with vegetation.
  • Porous pavement that absorbs rainfall and replenishes aquifers.

When extreme heat and urban heat islands meet, parts of the city are nearly impossible to reach cooler temperatures at night, leading to a buildup of heat during the day.

Smart surfaces can help reduce nighttime temperatures. Roads absorb heat during daylight hours, so if reflective surfaces absorb less heat during the day, roads will not retain and radiate heat at night.

“Because black asphalt absorbs 95 percent of the heat, the city’s heat island is felt at night, when they slowly release heat,” said Davis Collis, CoolSeal sustainability director at GuardTop, a company that makes smart surfaces. . “But cool road surfaces reflect 35-40 percent of the sun’s heat.”

Two different 2021 analyses—one in Stockton, Calif., and one in Baltimore—show that “citywide adoption of 12 smart surface strategies over 20 years would reduce peak summer downtown temperatures by nearly 3 degrees Celsius. , reducing urban CO2 emissions by 10 percent and a benefit-to-cost ratio of more than 5 to 1,” said Jackson Becce of Smart Surfaces Coalition.

A similar analysis is being conducted in Bhopal, India, to test the effectiveness of smart surfaces, he said.

Workers paint the sidewalk light gray in the parking lot next to the trees (Photo courtesy of Phoenix Metropolitan Transportation Authority)
Crews install cool pavement at Esteban Park in Phoenix. (Provided by Phoenix Market Traffic Bureau)

A recent pilot program by Arizona State University and the Phoenix Street Department of Transportation and Sustainability Office found that reflective road coatings can reduce road surface temperatures by 10 to 15 degrees Fahrenheit. Coatings can also reduce ambient air temperature, but this is more difficult to measure.

“We’ve had great results,” said Phoenix engineering manager Ryan Stevens, who is involved in planning for the Cool Roadways Partnership across the city. “Even a slight drop in temperatures across urbanized areas can have a very positive impact.”

Smart surfaces are one technology that may help mitigate the negative impacts of the climate crisis. Others include greenery measures such as tree canopies, urban farms and public gardens.

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