The material created in China that lowers the temperature of the buildings without consuming a single electricity watt

A world where buildings are not only well isolated from abroad, but cool them as much as an air conditioning, without consuming a single electricity watt. That is what a team of Chinese and Australian scientists promises with their new bioplastic material.

Short. Researchers at the University of Zhengzhou and the University of Australia del Sur presented a biodegradable film capable of cooling buildings without using electricity. According to a study published in Cell Reports Physical Sciencethis coating can reduce the temperature of a surface to 9.2 ° C in full sun.

9 degrees less. In the material field tests, carried out on a Zhengzhou roof, east of China, the results were overwhelming. In full sun, during noon, the material reached a cooling peak of 9.2 ° C below the ambient temperature. The average tests was -4.9 ° C during the day and -5.1 ° C during the night, which is equivalent to a cooling power of up to 136 watts per square meter.

The film takes advantage of a known phenomenon, “passive radiative cooling” (PRC). In a nutshell, it is a lining designed to do two things: reflect sunlight so as not to heat up, and emit internal heat outwards. But it does it in an extremely efficient way. According to the simulations presented by the researchers, apply this film on the roofs of a city like Lhasa, in the Tibet, would reduce annual cooling consumption up to 20.3%.

How it works. The “metaphilm” is made of polyactic acid, better known as Pla plastic; A material derived from plant sources such as corn or sugarcane, so it is biodegradable. The turn is how researchers managed to create a porous and continuous structure through a novel phase separation technique at low temperature.

This microstructure has an ultrabaja thermal conductivity (of 0.049 w/m · k) and reflects almost all the solar radiation that affects it (98.7%), avoiding the initial heating and heat transfer to the interior. It also emits heat abroad thanks to its porosity.

The manufacturing process is relatively simple: the PL is dissolved in chloroform, crystallizes at -20 ° C and then ethanol is used to induce phase separation before drying the film. This method is suitable for large -scale production, which paves the path for commercialization.

More resistant than other attempts. One of the great challenges of previous radiative cooling materialsespecially biodegradables, it was their durability. But this new coating has demonstrated exceptional durability. The researchers submerged him in acid for 120 hours and then exposed him to ultraviolet radiation equivalent to eight months of weathering exposure.

Surprisingly, the material not only survived, but maintained a cooling performance between 5 ° C and 6.5 ° C below the ambient temperature after the hard aging process. The team attributes it to its high crystallinity, which gives it a thermal and chemical stability much higher than that of its predecessors.

The applications go far beyond the roofs of the buildings. Researchers already explore their use in transport, to cool vehicles, agriculture, to protect crops, electronics and even the biomedical field, to apply to dressings that regulate the temperature.

Images | Yangzhe Hou et al.

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