Compound reflects 98.1% of sunlight
The most effective air conditioning in the world might just be a can of paint. As long it’s the whitest paint in the world, which scientists at Purdue University have perfected after seven years of work. It’s so white that it reflects 98.1% of sunlight and outputs infrared heat, meaning it could save about 10 kilowatts of air conditioning energy per 1,000 square feet when applied to the rooftops of buildings.
“When we started this project about seven years ago, we had saving energy and fighting climate change in mind,” Xiulin Ruan, a professor of mechanical engineering said on the “This Is Purdue” podcast.
Most commercial white paints reflect between 80 and 90% of sunlight, so Ruan and his graduate students’ invention steps things up significantly. It’s already made the “Guinness World Records” book for 2022 as the world’s whitest paint.
Ruan considered more than 100 different materials to include in the world’s whitest paint, whittling that number to 10 then testing about 50 formulations for each before settling on a compound featuring varying sizes of barium sulfate particles at a high concentration. The different sizes allow the paint to scatter more sunlight. As a result, the paint has a more powerful cooling effect than most household air conditioners.
Once Ruan secures patents on the whitest paint, work will turn to scaling it for widespread use on commercial building rooftops. The resultant energy savings could make for a huge savings in cost and greenhouse gas emissions.
This radiative cooling is a “passive cooling technology that offers great promises to reduce space cooling cost, combat the urban island effect, and alleviate the global warming,” Ruan’s team said in a paper accompanying the announcement.