A material can cool surfaces by dissipating heat to outer space as infrared radiation, even when the Sun is at its peak. Similar materials developed previously worked only at night, or were not cost-effective enough to make on a large scale.

Xiaobo Yin and Ronggui Yang at the University of Colorado Boulder and their colleagues made a film by embedding glass microspheres in a transparent polymer matrix and coating the back of this with silver. The film reflected almost all sunlight, and the spheres interacted strongly with certain wavelengths of infrared radiation that are not absorbed by the atmosphere. The rate at which the film emitted this radiation into space was high enough to achieve a net cooling effect.

The material is relatively lightweight and easy to manufacture, potentially making it suitable as a low-cost cooling technology, say the authors.

Science http://doi.org/bzk2 (2017)