Engineers at Stanford University have developed panels made from nanophotonic materials that will keep buildings cool when the sun shines, drastically reducing the energy needed for air conditioning. As a bonus, the panels, which have no moving parts and require no energy input, do not contribute to the greenhouse effect and warm the Earth. In fact, they would cool it.

The panels would be made of nanosized particles of quartz and carbide, both weak absorbers of sunlight. The panels would act as broadband sunlight mirrors, reflecting most solar energy away from the building. The particles on the panels have also been engineered to reflect sunlight as a narrow band of thermal radiation at a wavelength that does not interact with the atmosphere. This means the radiated heat ignores the atmosphere, sails through it, and gets dumped into outer space.

Researchers estimate that a square-meter panel would provide 100 W of cooling, about the same amount of power provided by a square-meter of 10%-efficient solar panels. So the reflective panels could replace solar panels used to generate electricity for air conditioning. And a typical one-story house with 10% of its roof covered with these no-maintenance panels could offset 35% of its air-conditioning needs during the hottest hours of the day. Researcher still don’t know what the commercial costs will be.

Resources: Stanford University, news.stanford.edu