On a mission to lessen the impact of global warming, engineers from Purdue University have created the whitest paint ever. So white, that if you painted an entire building with their paint, it may be able to cool them enough to reduce the need for air conditioning.
It all started last year when the team created an ultra-white paint that pushed the boundaries on just how white paint could be. Evolving from this, their newer paint is not only whiter, but can help keep surfaces cooler than paint ever has before.
“If you were to use this paint to cover a roof area of about 1,000 square feet, we estimate that you could get a cooling power of 10 kilowatts. That’s more powerful than the central air conditioners used by most houses,” said Xiulin Ruan, a Purdue professor of mechanical engineering.
Comparatively, your standard commercial white paint actually gets warmer rather than cooler.
Two features give this new white paint its extreme whiteness. One is the paint’s very high concentration of a chemical compound called barium sulfate, which is also used to make photo paper and cosmetics white.
“We looked at various commercial products, basically anything that’s white,” said Xiangyu Li, a postdoctoral researcher at the Massachusetts Institute of Technology, who worked on this project as a Purdue Ph.D. student in Ruan’s lab. “We found that using barium sulfate, you can theoretically make things really, really reflective, which means that they’re really, really white.”
The second is that the barium sulfate particles are all different sizes in the paint. The extent of light scattered by each particle depends on its size, which means that a wider range of particle size allows the paint to scatter more of the light it gets from the sun.
“A high concentration of particles that are also different sizes gives the paint the broadest spectral scattering, which contributes to the highest reflectance,” said Joseph Peoples, a Purdue Ph.D. student in mechanical engineering.
Because of the paint’s extreme whiteness, it’s also the coolest on record. The researchers were able to demonstrate that outdoors the pain can keep surfaces 19 degrees Fahrenheit cooler than ambient surroundings. It can also cool surfaces 8 degrees Fahrenheit below their surroundings under strong sunlight during noon hours.
The solar reflectance of this paint is so effective, it’s even been shown to work in the middle of winter. During an outdoor test with a temperature of 43 degrees Fahrenheit, the paint still managed to lower the sample temperature by 18 degrees Fahrenheit.
You may only be hearing about this incredible discovery now, but the coolest white paint is actually a result of six years of research, building on attempts dating back to the ’70s to develop radiative cooling paint. The fact that this could truly be an alternative for having an air-con is actually amazing, and would do our environment immeasurable good.
The technique that the researchers used to create the paint is compatible with the commercial paint fabrication process, really just leaving it up to logistics to make this paint an actual thing you can purchase.
Patent applications for this paint formulation have been filed through the Purdue Research Foundation Office of Technology Commercialization.