This Ultra-White Paint May Someday Replace Air Conditioning
https://www.smithsonianmag.com/innovation/ultra-white-paint-may-someday-replace-air-conditioning-180977560/...n tests conducted during sunny, midday hours on the roof of a campus building in West Lafayette, Indiana, the paint kept outdoor surfaces 8 degrees cooler than the ambient surrounding temperatures. At night, the paint kept surfaces 19 degrees cooler than their surroundings.
“Our paint can lose heat by its own emission—it emits heat to deep space,” Ruan says. “With such little absorption from the sun, our paint loses more heat than it absorbs. This is really exciting for us. Under the sun, it cools below the ambient temperature and that’s hard to achieve.”
Heat-rejecting white paints on the market now are typically made with titanium dioxide, which reflects certain wavelengths of sunlight—mainly, the visible light and near-infrared wavelengths—but absorbs the sun’s ultraviolet rays, causing the surface to heat up, Ruan says.
“Commercial white paints are cooler than the other, darker-colored paints, but they are still warmer than the ambient or surrounding temperature,” Ruan says....