Considering the fact that residential air-conditioners consume up to 15% of the total energy used in housing buildings across the United States, Stanford University engineers have come up with a paint coating solution that reflects sunlight, or rather directs heat away from the house into outer space, and as well cools the house and the planet at a go.

The team of researchers developed an ultrathin, multilayered, nanophotonic material that is capable of reflecting the sun’s heat away from buildings in order to cool it, while also directing internal heat from inside the building to the outside to effect a natural cooling system. Just like a mirror would reflect sunlight, the paint coating reflects away sunlight heat and draws a building’s interior heat outside. The building is cooled, and the planet is also cooled.

The researchers have called the system a “photonic radiative cooling”, and they achieved the breakthrough with a coating that is made up of silicon dioxide (SiO2) and hafnium dioxide (HfO2) – set on a thin layer of silver. These materials are then arranged into seven layers that is 1.8 microns thick which is actually thinner than aluminum foil – and with the ingenuity of the scientists, this material has the ability to reflect sunlight and also conduct infrared rays.

Professor Shanhui Fan, leader of the team, opines that “Every object that produces heat has to dump that heat into a heat sink. What we’ve done is to create a way that should allow us to use the coldness of the universe as a heat sink during the day.” Actual tests prove that the coating is capable of reflecting away 97% of incoming sunlight and when this is combined with the photonic radiative cooling system, then the material becomes cooler than the surrounding air by about 9oF or 5oC.

With tests carried out in the laboratory, the scientists face some little challenges before making this coating paint available for commercial use. They are still working to make it applicable for residential use, and as well as work out a cost effective way for its commercial production.

2 Responses

  1. David Horn

    A coating that reflects low wavelength sunlight and emits long wavelength heat is good, but the concept is not new. There are a lot of products on the market, but cost is high and durability is a problem.
    I would like to know the spectral properties of this new material. Please add to the article.

    To claim that this cools the planet is totally misleading. To make even the slightest difference, a significant proportion of the planet’s surface would need to be covered. It may cool a house or a car, but not the planet.
    I would love to see this coating used on cars, where, together with low E window glass, it would significantly reduce the need for air conditioning. I have always bought white or silver cars for this reason, though it is hard to tell how a white or silver paint will perform in the far IR spectrum.
    One way to tell is to feel the temperature of the surface of a row of cars in the sunlight.

  2. Zaphod

    Well, that about wraps it up for global warming.

    Especially with the fact one need only make 20 square miles of simple reflective coating to undo all supposed human caused global warming to date… This is just icing on the cake! Now people will want more CO2 to help the rainforest recover faster.


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