If you have ever redone a room in your home and gone to the hardware store to look for fresh paint, you know that there is a very of different shades of white on the market. It seems that there is a new white shade in the city – and this may have some (or literal) climate implications.
In a study published Thursday in ACS Applied Materials & Interfaces, researchers at Purdue University say they have now made the whitest paint on the planet. The Purdue researchers surpass their own record, which was set just last fall when they ever created a white paint, which, according to researchers, reflects up to 98.1% of the light. paint that reflects 95.5% of sunlight.
It seems useless to rush to get the whitest paint of all with just a few percentage points, while many of us cannot see the difference between most white sample chips at Home Depot. However, in terms of the cooling effects of white paint, those small percentages matter.
Anyone who goes outside on a hot summer day knows that he is wearing white clothes; white reflects light, while black absorbs. But white paint currently on the market with labels such as “ultra-reflective” or “high-reflective” reflects only about 80% to 90% of light, said Xiulin Ruan, a lead author of the study. It may be enough to make your kitchen look dazzling on a daily basis – but speaking of cooling features, it’s less effective.
“We consider 90% to 98% not very different, but we need to think about recording sunlight,” Ruan said. “Our paint absorbs 1.9% of the sunlight, but the commercial paint, even with reflectors, absorbs 10% of the sunlight – five times as much as our paint absorbs. They look white, they are pretty white, but they are not white enough – they cannot cool outside the ambient temperature. ”
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Ruan said that efforts to develop the whitest paint possible that could also serve as refrigerants until the 1970s. Ruan’s team alone has been working for about seven years to make white paint even whiter, and is making methods to add reflective materials to the paint so that it can reflect the sun. This successful white paint contains high concentrations of barium sulphate – a chemical compound used to make white cosmetics and photo paper – with particles of different sizes spread over the paint.
“The sunlight has different colors because it has different wavelengths,” Ruan explained. “We need different particle sizes to scatter each wavelength.”
The development of this kind of ultra-reflective paint can be a game changer for how we design buildings as our world gets hotter and hotter. There is a growing amount of work around the choice of urban design: to replace super-warm and super-absorbent asphalt roofs for reflective surfaces, or to build in parks or other buildings green spots in cities to literally cool the area – can help us reduce the heat in cities and other built-up areas without using more energy to power air conditioners.
Ruan and his team have big visions for the paint’s potential; they estimate that using super-reflective white paint on a large scale in cities like Reno or Phoenix can save up to 80% on air conditioning costs. “If you have very hot days, our paint alone may not do the job, but on other days it may not turn on your air conditioner,” he said.
These kinds of climate hacks sound like the solution to all our problems – but there are still many real considerations to hammer out if you’re thinking of designing cities to beat the heat. “To make cities more reflective, one has to be very, very, very practical,” said Hashem Akbari, a professor of civil engineering at the University of Concordia.
Akbari pointed out that frequent wear and tear on reflective roofs or walls can affect the reflectance percentages measured in a laboratory environment. “Soot and dust tend to reduce surface reflection,” he said. “If they start with a super-duper 95% reflectivity, the pollutants from the air, the droplets, can collect soot on the surface and reduce the reflectance.”
Akbari said the beginnings of replacing roofs, which need to be updated every few decades or so, are frequently replaced with more reflective materials – regardless of the whiteness of the paint you use or the percentage it actually reflects – for the most cities be a good start. .
‘If every roof that had to be replaced could be replaced with a very reflective roof, all the roofs would be very reflective within ten to thirty years. You don’t have to drive a specific technology like a coating, ‘he said. “We need to encourage marketing and insulation of reflective materials as the roofs are changed.”