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Scientific Approach to Heating and Cooling


We were fascinated by this article from “Inside Science”. It gives an interesting overview of heating and cooling nature’s way and how heat and cooling can be manipulated using certain processes and models to regulate air temperature. This in itself could contribute to the global climate change issues and reduce the amount of air conditioning usage. The author is Joel N. Shurkin and this is a summary of his article.

(ISNS) — Cities are “islands” that raise temperatures by absorbing sunlight during the day, storing it, and releasing it back out at night, adding heat to an already changing climate. Painting roofs white relieves the so-called island effect, lowering temperatures in urban areas and it has become popular in many cities.

But scientists at Arizona State University report that the practice can make things worse in some places.

Reflecting sunlight to keep world temperatures cool is common in nature. Snow and ice, for instance, have a high albedo (reflective) effect and help keep temperatures from rising. Scientists believe one of the reasons the world’s climate is warming is that there is less ice now. Cities, which are generally paved over and covered with buildings, absorb heat from the sun, driving up the temperature.

Studies show that white roofs, which reflect sunlight instead of absorbing it, will cool temperatures in heavily developed places, like the Eastern Seaboard between Washington, D.C. and Boston. However, the ASU scientists project that lowering the temperature with reflective roofs can reduce much-needed rainfall part of the year, at least in their part of the world.

“Most of the work has been focused on temperatures,” said Matei Georgescu, an assistant professor at ASU’s School of Geographical Sciences and Urban Planning. “Do light roofs cool an area? The answer is, they do. We don’t find any contradiction.”

The researchers focused on the projected urban expansion of what is known as the Sun Corridor, the fastest-growing metropolitan area in the U.S., which includes metropolitan Phoenix, Tucson, Prescott and Nogales. The area is expected to have a population of 9 million by 2040.

They found that the growth would decrease annual rainfall by 12 percent. Painting all the rooftops white could reduce annual rainfall by another 4 percent.

Painting roofs white — or sometimes, planting gardens on rooftops — has become popular on in places like New York City and Chicago. Research by the National Center for Atmospheric Research shows that black asphalt roofs raise temperatures 2-4 degrees Farenheit and in theory, painting roofs white could mitigate that.
 
Computer models indicate that if every roof in every city were painted white the demand for air conditioning would be reduced, and temperatures in the cities would be reduced by an average of 0.7 degrees F.

Posted in: Latest News - On: 21st of November, 2012