COOLING WITHOUT ENERGY

APPLYING a coating to the material a component is made from can alter its thermal properties.

Nano coatings are under development that variously increase surface area, reduce trapped vapour that causes critical heat flux, prevent the build-up of impurities, inhibit corrosion and restrict ice formation.

Earlier this year, a team engineers at the of University of Colorado Boulder in the United States announced a breakthrough “metamaterial” coating that has the ability to cool objects even under direct sunlight without consuming energy or water.

At just 50 micrometers thick (slightly thicker than the aluminium kitchen foil), this glass-polymer hybrid material can be economically manufactured on rolls, meaning it could be adopted on a large scale for numerous applications.

By reflecting incoming solar rays back into the atmosphere while helping infrared (heat) radiation escape from the surface to which it is applied, this metamaterial could provide an effective barrier for vehicle exteriors that reduces the thermal load for air-conditioning systems to deal with.

It works by embedding microscopic infrared-radiant glass spheres into a polymer film, with a thin silver layer beneath to reflect as much heat as possible.

Other obvious applications include residential, commercial and industrial buildings, while the researchers are also looking at how the metamaterial can be used in the power generation, aerospace and agriculture industries.

The researchers claim that “just 10 to 20 square meters of this material on the rooftop could nicely cool down a single-family house in summer”.

Another use for the metamaterial could be to improve the efficiency and lifespan of solar panels, which start to lose their ability to generate electricity when they reach high temperatures.

Whether the metamaterial can be applied to heat exchangers to boost their efficiency remains to be seen.

By the end of this year, the researchers hope to have a  200 square metre “cooling farm” prototype operating near their university campus in Boulder, Colorado.