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Revolutionary white paint could cool Greek island buildings better than AC

New white paint
Professor Xiulin Rouen, who developed a new revolutionary white paint that cools buildings. Credit: Facebook / Xiulin Ruan

A revolutionary new ultra-white paint that looks just like the brilliant screed used on so many buildings in the Cyclades and other Greek islands can replace the air conditioner one day, it reflects so much heat back into space.

Recently developed by researchers at Purdue University, the paint reflects a staggering 98.1% of the sunlight, much more than the average 10-20% of the sunlight that most commercial white paints make today.

Grecian Delight supports Greece

The new product is so effective that it cools buildings to an incredible 19 degrees Fahrenheit. Xiulin Ruan, a professor of mechanical engineering at Purdue University, co-authored a scientific paper on the findings.

He and his colleagues believe that the paint can help fight global warming and reduce our dependence on air conditioning and even electric air exchangers.

White paint
The Greek island of Mykonos and many other Cycladic islands are famous for their whitewashed buildings. New white paint can help keep them – and the planet – much cooler in the future. Credit: Cifo Buscemi / Wikimedia Commons / CC0

Once applied, the new paint can keep surfaces up to 19 degrees Fahrenheit colder than the environment, according to Purdue. The new paint, which researchers say may even be purchased next year or so.

The scientists responsible for the breakthrough are from Purdue’s engineering department. They recently published their groundbreaking findings in the journal ACS Application materials and interfaces.

The Greek island of Naxos. Credit: Sergio Alvarez image of a tank Creative Commons Attribution-Share Alike

The study was funded by both the Purdue Refrigeration Technology Research Center and the U.S. Air Force Research Office.

“Our paint absorbs only 1.9 percent of the sunlight, while commercial paint absorbs 10 to 20 percent of the sunlight,” explains Rouen.

Contrary to intuition, even white paint actually absorbs the sun’s rays and heat instead of reflecting most of them back into the sky. On sunny days, even white paint actually heats up, making it difficult to maintain cooler interiors.

Even the whitest white paint on the commercial market today reflects at most 80-90 percent of the light, according to Rouen.

Credit: The Church of the Taxiarches in the village of Vati on Sifnos. Photo: Here / Wikimedia Commons / CC BY-SA 4.0

The new Purdue paint not only reflects almost all of the sun’s rays back into space, but also sends infrared heat away from the building’s surface, equivalent to an average cooling capacity of 113 watts per square meter (10.7 square feet).

When paint is applied to the roof of a building, researchers say, it leads to significant savings.

The cooling effect exceeds that of the air conditioner

On the roof of a home of 1,000 square meters, this means that the cooling power of 10 kilowatts will be generated by the paint – which, according to Rouen, is more powerful than most residential central air conditioners.

When the Indiana heat burned, the researchers tested the new paint on the Purdue campus building at noon on sunny days, proving that the paint kept outside temperatures respectfully eight degrees lower than the ambient temperature at the time.

But at night, the revolutionary characteristics of the paint came to the fore when they discovered that the surfaces remained 19 degrees colder than their surroundings.

“Our paint can lose heat through its own radiation – it radiates heat into deep space,” Rouen explained. The Smithsonian magazine.

“With so little absorption from the sun, our paint loses more heat than it absorbs. This is really exciting for us. Under the sun it cools below ambient temperature and this is difficult to achieve. “

Barium sulphate particles are a player changer for ultra white paint

A video made by the team using an infrared camera shows exactly how much the paint cools the surfaces on which it is located, with the whitest of all white paints being represented by a dark purple square in the middle, showing its cold temperature.

Naturally, commercially available white paints, even those marketed as heat-repellent products, are colder than dark paints, but are still made with titanium dioxide, which absorbs the sun’s ultraviolet rays, which drives everyone heat the surface on which they are used.

“Commercial white paints are colder than other, darker colors, but still warmer than the ambient or ambient temperature,” notes Rouen.

Researchers have naturally refused to try to use materials that could reflect rather than absorb brutal UV rays. Testing more than 100 different materials over the past seven years, they finally hit barium sulphate after finding that calcium carbonate reflected a surprising 95.5% of the sun’s rays.

Barium sulfate is incredibly even more effective than calcium carbonate. Already used in cosmetics as well as in photographic papers, the substance is created by reaction
barium hydroxide and other sources of barium with sulfuric acid.

Ruan and other researchers also took two additional steps to improve the reflective nature of the paint, using a sixfold concentration of barium sulfate particles as the most heat-resistant paints on the market. They also used barium particles of different sizes in the mixture.

“We’ve found that if you put different particle sizes in your paint, then each particle size can scatter and reflect different wavelengths, and all of them together can reflect the full range of wavelengths of sunlight,” says Rouen.

The new paint is truly revolutionary, and not just because it will obviously reduce the need for air conditioning.

The paint would reduce heat convection in cities, the use of fossil fuels

When air conditioners are used, they simply remove heat and moisture from the indoor and transfer them outside, increasing the overall radiator effect of a city or town.

Also, of course, the use of paint would reduce the need for electricity and / or fossil fuels for air conditioning.

The types of electromagnetic waves emitted by the surface of ultra-white paint can pass through the atmosphere and back into deep space, according to researchers.

“Air conditioners can cool your house, but they transfer heat from the inside of the house to the outside – the heat is still in the city, still on Earth, in our air,” says Rouen.

“So even if you don’t care about the electricity bills you pay, the Earth will warm up anyway. Our paint does not use any power, but more importantly, it sends heat into space. The heat doesn’t stay on Earth, so it really helps the Earth cool down and can stop the warming trend. “

According to Purdue researchers, their ultra-white paint can reduce air conditioning to a staggering 70 percent in desert cities such as Reno, Nevada and Phoenix, Arizona.

Taking the experiment to the extreme, they extrapolated that if they could cover 0.5 to 1 percent of the earth’s surface – including buildings, roads, unused land, you would say – with ultra-white paint, it would be enough to stop global warming.

“It’s a large area, but if one day we have to use this approach to help reverse the warming trend, it’s still affordable – paint isn’t expensive,” Rouen said.

Purdue scientists have already applied for a patent for the ultra-white paint and are committed to determining how durable it will be for household and commercial purposes.

Price shouldn’t be an issue, Rouen says, and a gallon costs almost exactly as much as a gallon of plain paint at the moment, approximately $ 30 to $ 40 a gallon.

Elizabeth Thompson, vice president of the United States Green Building Council, is fascinated by the prospects the paint offers for the future.

“When I first heard about it, I imagined, ‘Wow, this can be used in all sorts of different urban settings in the United States and internationally,'” she said.

“It is precisely this potential that is so strong and captivating. It will be great to see how this develops and how researchers are able to develop its applications. “

The American Green Building Council is a non-profit group that has developed an Energy Leadership and Environmental Design (LEED) rating system for sustainable buildings. It now offers a “heat island reduction credit” for buildings whose owners work for LEED certification.

According to Thompson, the new ultra white paint is changing the game in this area.

Using materials that have an initial solar reflectivity of 33 percent during installation, or 28 percent in three years, is one of the ways homeowners are currently trying to make their buildings more energy-compatible, Thompson said. The 98.1 percent solar reflectivity of Purdue blows these requirements completely out of the water.

“It’s just a completely different cooling, which is very exciting,” Thompson said.

“We hope. This is something we all hope scientists and researchers will help us discover, opportunities we didn’t know existed for how to live more sustainably. “

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