How to cool your home with hi-tech mirrors

A team of engineers at Stanford University has designed hi-tech mirrors that cool buildings by beaming heat away from them and into space.

A team of experts at Stanford University led by electrical engineering Professor Shanhui Fan invented a new energy-saving way of cooling buildings. The system uses particular mirrors covered with an ultrathin, multilayered material that reflects the incoming sunlight and beams it into space, keeping buildings cool during the day and night.

How the mirrors work

Thanks to the material they’re coated with, the mirrors capture the heat and send it into space in the form of infrared light, at a frequency that allows it to pass through the atmosphere without warming the air. So, these mirrors insulate buildings from heat without having an impact on the environment.

The result obtained with these mirrors is what the Stanford team calls “photonic radiative cooling”, an effective method that offloads heat from buildings, reducing the demand for air conditioning.

hi-tech mirrors air conditioning
This technology was conceived to be accessible to everyone ©

The coating material

The mirrors work for the particular material they’re coated with. The material, according to researchers, won’t have a prohibitive cost, so, it will be available on large scale. The researchers believe that the coating might be sprayed on common mirrors, which would drastically reduce production costs.
The coating material is 1.8 microns thick (thinner than an aluminium foil) and is formed by 7 layers of silicon dioxide and hafnium oxide, on top of a thin layer of silver.

photonic radiative cooling
The photonic radiative cooling is possible thanks to the special material with which the mirrors are covered ©

Some figures

Hi-tech mirrors can catch about 97% of the sunlight that strikes a building, cooling it by about 9 ° F (-12 ° C) compared to the external temperature. In the United States this technology would reduce the electricity demand by 15%, because this is the percentage of energy used to power air conditioning systems.

“I am personally very excited about their results,” said Marin Soljacic, a physics professor at the Massachusetts Institute of Technology. “This is a great example of the power of nanophotonics.”


Cover image ©

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