In an effort to curb global warming, Purdue University engineers have created the whitest paint to date.
Coating buildings with this paint can one day cool enough to reduce the need for air conditioning, the researchers say.
In October, the team created an ultra-white paint that expanded the boundaries of how white paint can be. Now they have overcome it. Newer paint is not only whiter, but can also keep surfaces colder than the formulation the researchers had previously demonstrated.
“If you used this paint to cover a ceiling area of approximately 1,000 square feet (333 meters), we estimate that you could get a cooling power of 10 kilowatts.. This is more powerful than the central air conditioners that most homes use, ”said Xiulin Ruan, a professor of mechanical engineering.
Researchers believe that this white may be the closest equivalent to the blackest black, “Vantablack,” which absorbs up to 99.9% of visible light. The new whiter paint formula reflects up to 98.1% of sunlight, Compared to 95.5% of sunlight reflected by the researchers’ previous ultra-white paint, and sends infrared heat away from a surface at the same time.
Typical commercial white paint becomes warmer rather than colder. Paintings on the market that are designed to repel heat reflect only 80% to 90% of sunlight and they cannot make surfaces colder than their surroundings.
The team’s research article showing how painting works is published on the cover of Applied Materials & Interfaces magazine.
Two characteristics give the paint its extreme whiteness. One is the very high concentration of paint in a chemical compound called barium sulfate that is also used to make photo paper and cosmetics white.
The second feature is that barium sulfate particles have different sizes in the paint. The amount of light that each particle scatters depends on its size, so a wider range of particle sizes allows the paint to disperse more of the light spectrum from the sun.
The whiteness of the paint also means that the paint is the coldest recorded. Using high-precision temperature reading equipment called thermocouples, researchers demonstrated outdoors that paint can keep surfaces at 10 degrees Celsius colder than its ambient environment at night. It can also cool surfaces to 4 degrees Celsius below its surroundings under intense sunlight during noon hours.
This white paint is the result of six years of research based on attempts dating back to the 1970s to develop radiant cooling paint as a viable alternative to traditional air conditioners.