Civil engineers examine urban cooling strategies using reflective
surfaces

Date:
June 21, 2021
Source:
University of Pittsburgh
Summary:
Researchers used a Computational Fluid Dynamics model to find ways
to decrease cost and increase usage of cooler surfaces. The paper
examined the possibility of applying cooler surfaces to just half
the surfaces in a city.



FULL STORY ==========================================================================
If you've ever been in a city's central core in the middle of summer,
you know the heat can be brutal -- and much hotter than in the surrounding region.


========================================================================== Temperatures in cities tend to be several degrees warmer than in its
rural areas, a phenomenon called the Urban Heat Island (UHI) effect. Many cities have been observed to be 2-4-oC warmer than the countryside in
virtually every inhabited continent. This phenomenon occurs because urban infrastructure, especially pavements, absorbs a lot of heat as compared
to natural vegetated surfaces. This heat pollution causes higher air conditioning and water costs, while also posing a public health hazard.

One mitigation strategy called gray infrastructure involves the
modification of impermeable surfaces (walls, roofs, and pavements) to
counter their conventional heating effect. Typical urban surfaces have
a solar reflectance (albedo) of 0.20, which means they reflect just
20 percent of sunlight and absorb as much as 80 percent. By contrast, reflective concrete and coatings can be designed to reflect 30-50 percent
or more. Cities like Los Angeles have already used reflective coatings
on major streets to combat heat pollution, although the solution can be expensive to implement city-wide.

Researchers at the University of Pittsburgh Swanson School of Engineering
used a Computational Fluid Dynamics model to find ways to decrease
cost and increase usage of cooler surfaces. The paper, published in
the journal Nature Communications, examined the possibility of applying
cooler surfaces to just half the surfaces in a city.

"This could be an effective solution if the surfaces selected were
upstream of the dominant wind direction," said lead author Sushobhan
Sen, postdoctoral associate in the Department of Civil and Environmental Engineering. "A 'barrier' of cool surfaces preemptively cools the warm
air, which then cools the rest of the city at a fraction of the cost. On
the other hand, if the surfaces are not strategically selected, their effectiveness can decline substantially." This research gives urban
planners and civil engineers an additional way to build resilient and sustainable infrastructure using limited resources.

"It's important for the health of the planet and its
people that we find a way to mitigate the heat produced
by urban infrastructure," said coauthor Lev Khazanovich, the
department's Anthony Gill Chair Professor of Civil and Environmental Engineering. "Strategically placed reflective surfaces could maximize
the mitigation of heat pollution while using minimal resources." ========================================================================== Story Source: Materials provided by University_of_Pittsburgh. Original
written by Maggie Pavlick. Note: Content may be edited for style and
length.


========================================================================== Journal Reference:
1. Sushobhan Sen, Lev Khazanovich. Limited application of reflective
surfaces can mitigate urban heat pollution. Nature Communications,
2021; 12 (1) DOI: 10.1038/s41467-021-23634-7 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/06/210621174101.htm

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