In warm places around the world, it is difficult to keep your house at a cool land pleasant temperature. Air conditioners are an option, but they use a lot of energy to work. A team of University of Colorado Boulder engineers, however, has developed a scalable manufactured metamaterial to act as a kind of air conditioning system for structures. It has the ability to cool objects even under direct sunlight with zero energy and water consumption.

When applied to a surface, the metamaterial film cools the object underneath by efficiently reflecting incoming solar energy back into space while simultaneously allowing the surface to shed its own heat in the form of infrared thermal radiation.

The material consists of visibly scattering but infrared-radiant glass microspheres into a polymer film, with a thin silver coating underneath in order to achieve maximum spectral reflectance. It measures just 50 micrometres thick — slightly thicker than the aluminum foil found in a kitchen — and can be manufactured economically on rolls, making it a potentially viable large-scale technology for both residential and commercial applications.

The material could provide, for instance, an eco-friendly and low-cost means of supplementary cooling for thermoelectric power plants, which currently require large amounts of water and electricity to maintain the operating temperatures of their machinery. In addition to being useful for cooling of buildings and power plants, the material could also help improve the efficiency and lifetime of solar panels. In direct sunlight, panels can overheat to temperatures that hamper their ability to convert solar rays into electricity.

For another self cooling material, see here.