Since ancient times, people in areas with hot climates have opted for brightly colored roofs that reflect sunlight with a view to keeping their indoor spaces cool. White or bright-hued surfaces are naturally great at reflecting heat, but cooling rooms below is another story. Now, engineers at Stanford University have come up with a new twist to this basic premise. Instead of merely relying on roof color, they created a multilayer coating that simultaneously reflects most incoming sunlight and absorbs heat, which is then discharged away.
A group of Stanford University researchers set off to create a mirrored coating that also radiated energy at long wavelengths. The scientists, however, admit that no natural material exists that both reflects solar wavelengths and remains radiative in thermal wavelengths. The trick lies in structuring a surface that would reflect lower and upper ranges while discharging microwaves that can’t be absorbed by air.