Cool the environment with a non-powered metal film

Scientists at the University of Colorado Boulder (USA) have invented a type of metal film that works to cool the surrounding environment without using electricity.

Compiled from transparent microspheres with polimer and silver, this material applies passive radiation cooling to dissipate the heat from the object it covers. The membrane is capable of removing energy like infrared radiation as well as reflecting sunlight.

While night-radiation cooling materials, including pigment paint, have proven successful, day-to-day applications are challenging. The problem arises that such materials absorb sunlight, quickly exceed cooling energy and burn the surface of the subject.

This has prompted researchers to create a material that reflects sunlight while allowing infrared emission.

The cooling film sheet can be pressed in rolls, allowing large quantities of production.(Photo: colorado.edu).

They created a flexible, two-layer thin film: A transparent polymer layer containing 8 micrometer diameter silicon-dioxide (SiO ₂ ) dispersions and a 200 nanometer thick silver coating.

Ronggui Yang, the author of the work, said this randomly dispersed polymer film is transparent to the sun's spectrum but can release infrared rays. Collective resonance of microspheres will ensure effective film in infrared radiation. At the same time, sunlight can penetrate the above material and reflect through the silver coating, preventing warming.

During the test sessions, the result of the energy released through the average cooling process of this film was more than 110 W / m ² during 72 hours, the average midday energy was 93 W / m ² . This is equivalent to the amount of electricity synthesized from a typical solar cell of the same area. This transparent polymer film can also be used to coat the surface of solar cells, not only cooling but also increasing the efficiency of batteries.

Yang researcher commented that the main advantage of this technology is that it can operate 24/7 without using electricity or water. This is also an opportunity to discover potential applications in the energy, aerospace and agriculture industries .

However, the disadvantage of this study is that wrapping the film into a layer around buildings will not be as simple as covering a layer on the roof. The film can cool the building in the hot summer, but if it is at night or winter, the film will continue the process of lowering its temperature.