In an effort to slow global warming, engineers at Purdue University have created the whitest paint yet.
Coating buildings with this paint could one day cool them enough to reduce the need for air conditioning, the researchers say.
In October, the team created an ultra-white paint that pushed the boundaries of what white paint can look like. Now they have gotten over it. The newer paint is not only whiter, but can also keep surfaces cooler than the formulation the researchers previously demonstrated.
If you were to use this paint to cover a ceiling area of about 333 square feet, we estimate that you could get a cooling capacity of 10 kilowatts.That’s more powerful than the central air conditioners most homes use, ”said Xiulin Ruan, a mechanical engineering professor.
Researchers believe this white is the best equivalent of the blackest black, “Vantablack”, which absorbs up to 99.9% of visible light. New whiter paint formula reflects up to 98.1% of sunlight, compared to 95.5% of the sunlight reflected by the researchers’ previous ultra-white paint, while simultaneously directing infrared heat away from a surface.
Typical commercially available white paint gets warmer rather than cooler. Paints on the market that are designed to reject heat reflect only 80% to 90% of sunlight and they cannot make surfaces colder than their surroundings.
The team’s research paper showing how paint works is on the cover of Applied Materials & Interfaces magazine.
Two characteristics give the painting its extreme whiteness. One of these is the paint’s very high concentration of a chemical compound called barium sulfate that is also used to whiten photo papers and cosmetics.
The second characteristic is that the barium sulfate particles have different sizes in the paint. The amount of light each particle scatters depends on its size, so a wider range of particle sizes allows paint to disperse more than the spectrum of sunlight.
The whiteness of the paint means that too the painting is the coldest ever recordedUsing highly accurate temperature measuring equipment called thermocouples, the researchers showed outdoors that paint can keep surfaces 10 degrees Celsius cooler than their surroundings at night. It can also cool surfaces to 4 degrees Celsius below its environment in strong sunlight during the midday hours.
This white paint is the result of six years of research based on efforts going back to the 1970s to develop radiant cooling paint as a viable alternative to traditional air conditioners.