Whiter than the Whitest: This Paint is the Fairest of them all, and the Coolest

The Research

Purdue University is one of the top public research institutions developing innovative solutions to today’s toughest challenges. Discovery Park is a place where Purdue researchers are encouraged to push traditional boundaries, collaborate across disciplines with policymakers and business leaders to create solutions for a better world. The researchers showed in their study that like an external paint, their barium sulphate-based paint can potentially handle outdoor conditions. The technique that the researchers used to create this eco-friendly paint also is compatible with the commercial painting process. Furthermore, the paint stands out by efficiently deflecting harmful infrared radiation from the surfaces it covers. 

IN CONTRAST TO COMMERCIALLY AVAILABLE THERMALLY REFLECTIVE PAINTS THAT OFTEN CONTRIBUTE TO HEATING THEIR SURROUNDINGS AND TYPICALLY REFLECT ONLY 80-90% OF RADIATION, THIS INNOVATION OFFERS A CONSIDERABLE IMPROVEMENT IN ENERGY EFFICIENCY AND SUSTAINABILITY FOR INDUSTRIAL AND WAREHOUSING APPLICATIONS.

The Technology

Radiative cooling is a passive cooling technology that offers great promises to reduce space cooling cost, and address global warming. Continuous attempts have been made to achieve passive daytime radiative cooling with single-layer paints, but they often require a thick coating or show partial daytime cooling. This eco-friendly paint is developed to enhance the reliability in outdoor applications, achieving solar reflectance of 98.1% and sky window emissivity of 0.95. With barium sulphate, you can theoretically make things effectively reflective, which means that they are radiantly white. The new whitest paint formulation reflects up to 98.1% of sunlight and sends infrared heat away from a surface at the same time, making it the best paint for exterior surfaces.

The Benefits

Typically, a commercial white paint gets warmer rather than cooler. Paints in the market that are designed to rebound heat reflect only 80%-90% of sunlight and cannot make external surfaces cooler than their surroundings. Predominantly, two features give this paint its extreme whiteness. One is the paint’s very high concentration of a chemical compound called barium sulphate, and the second is the size of the particle, which contributes to the reflectance. The paint’s whiteness also means that the paint is the coolest. *Using high-accuracy temperature reading equipment called thermocouples, the researchers demonstrated outdoors that the paint can keep surfaces 4.5 degrees Celsius cooler than their ambient surroundings at night. It can also cool surfaces below their surroundings under strong sunlight during noon hours, representing a 58% reduction of heat gain from the sun. Commercial paints in this manner can offer an average cooling power of 117W/m2.

IF YOU WERE TO USE THIS PAINT TO COVER A ROOF AREA OF ABOUT 1,000 SQUARE FEET, YOU COULD GET A COOLING POWER OF 10 KILOWATTS. THAT’S MORE POWERFUL THAN THE CENTRAL AIR CONDITIONERS USED BY MOST WAREHOUSES.