Urban heat island effects depend on a city’s layout

Image credit: metlink.org

One finding was ‘that in the state of Florida alone urban heat island effects cause an estimated $400 million in excess costs for air conditioning’. Of course in somewhere cold like Alaska such effects would likely be beneficial.

The way streets and buildings are arranged makes a big difference in how heat builds up, study shows.

The arrangement of a city’s streets and buildings plays a crucial role in the local urban heat island effect, which causes cities to be hotter than their surroundings, researchers have found.

The new finding could provide city planners and officials with new ways to influence those effects, says MIT News.

Some cities, such as New York and Chicago, are laid out on a precise grid, like the atoms in a crystal, while others such as Boston or London are arranged more chaotically, like the disordered atoms in a liquid or glass. The researchers found that the “crystalline” cities had a far greater buildup of heat compared to their surroundings than did the “glass-like” ones.

The study, published today in the journal Physical Review Letters, found these differences in city patterns, which they call “texture,” was the most important determinant of a city’s heat island effect.

The research was carried out by MIT and National Center for Scientific Research senior research scientist Roland Pellenq, who is also director of a joint MIT/ CNRS/Aix-Marseille University laboratory called MSE² (MultiScale Material Science for Energy and Environment); professor of civil and environmental engineering Franz-Josef Ulm; research assistant Jacob Sobstyl; MSE² senior research scientist T. Emig; and M.J. Abdolhosseini Qomi, assistant professor of civil and environmental engineering at the University of California at Irvine.

The heat island effect has been known for decades. It essentially results from the fact that urban building materials, such as concrete and asphalt, can absorb heat during the day and radiate it back at night, much more than areas covered with vegetation do.

The effect can be quite dramatic, adding as much as 10 degrees Fahrenheit to night-time temperatures in places such as Phoenix, Arizona. In such places this effect can significantly increase health problems and energy use during hot weather, so a better understanding of what produces it will be important in an era when ever more people are living in cities.

The team found that using mathematical models that were developed to analyze atomic structures in materials provides a useful tool, leading to a straightforward formula to describe the way a city’s design would influence its heat-island effect, Pellenq says.

Continued here.

via Tallbloke’s Talkshop

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February 22, 2018 at 03:46AM

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