The latest coating can effectively reduce any surf

New paint can effectively reduce any surface temperature

new paint can effectively reduce any surface temperature

October 1, 2018, let alone other performance 0

houses in Greece and other sunny countries are often painted white to reflect as much sunlight as possible. Now, researchers are using a new "passive radiation cooling" material to reinterpret this ancient strategy in order to reduce sunlight and heat. Most of these technologies cannot make use of existing roofs and walls, but a research team in the United States has now produced a cooling coating that can cover any surface, reducing the temperature by about 6 degrees Celsius. The new paint can be directly applied to the surface of any texture object, and can also be combined with different pigments to show different colors

this progress highlights "great progress in this field", said Xiaobo Yin, a materials scientist at the University of Colorado at Boulder. His team developed a passive radiation cooled plastic film and set up a start-up called radio cool to commercialize it. Yin said that these new materials may reduce the cooling cost by 15% under certain climatic conditions. "This is a big number." He said. In the United States, 17% of residential electricity is used for air conditioning, so the savings may be huge

white paint usually reflects only about 80% of visible light, and they still absorb ultraviolet and near-infrared rays, which can heat buildings. In order to do better, new materials must first be combined with materials or structures that can reflect almost all the sunlight, including near-infrared rays and, in some cases, even ultraviolet rays. In addition, they also need to contain polymers or other substances to use their chemical composition to dissipate additional heat at a wavelength of 8 to 13 microns. The atmosphere will not block the radiation of these wavelengths, so that the material can effectively release excess heat into space without heating the surrounding air

in 2014, the research team led by Shanhui fan, an electrical engineer at Stanford University in Palo Alto, California, reported in the journal Nature that through an alternating layer containing silica and hafnium dioxide, they created a highly reflective surface that could be 5 degrees Celsius lower than the surrounding air temperature. Last year, fan and his colleagues used another material - a combination of polymer and silver film - to cool water used in air conditioners. The team said that this technology could save 21% of the cost of air conditioning in summer. Since then, fan's team has set up its own startup skycool systems

Yin and his colleague Ronggui Yang made new progress last year: a plastic film embedded with tiny glass beads can reduce the surface temperature by 10 degrees Celsius. In Australia, applied physicist Angus gentle and Geoff Smith of Sydney University of Technology reported in 2015 that a cool roof material made of two polymers can make the roof 3 degrees Celsius and 6 degrees Celsius lower than the surrounding air temperature at noon and night, respectively

however, there is still a problem in applying these coatings to roof and siding materials. Highly reflective compounds can be integrated into traditional wooden and clay tiles for new buildings or renovations. But for the existing buildings, it is difficult to have more choices

and this is where the new passive cooling coating can be used

the Yuan Yang and Nanfang Yu teams of the Department of Applied Physics and applied mathematics of Columbia University published a paper in the new issue of the American journal Science, saying that the new material they developed is a "polyvinylidene fluoride hexafluoropropylene copolymer" with multi-scale micro nano pore structure. The film made of this material has 96% to 99.6% high reflectivity in the sunlight band and 97% high emissivity in the infrared radiation window, Refrigeration can be achieved without electricity during the day

the test results show that in the dry environment with sufficient light, the surface temperature of the film can be about 5.9 ℃ lower than the ambient temperature; In a humid environment, the film temperature can be about 2.9 degrees Celsius lower than the ambient temperature

according to the introduction, in this porous film, the refractive index of polyvinylidene fluoride is very different from that of air, which can effectively scatter sunlight, including ultraviolet light, visible light and near-infrared light. The tensile value is calculated to achieve high reflectivity and will not be heated by sunlight; The micron porous structure improves the emissivity of the material and increases the outward thermal radiation

it is understood that previously, the preparation of similar functional materials mostly required complex vacuum deposition equipment, and it was difficult to directly cover the surface of objects with arbitrary shape and texture. New materials have the advantages of low cost and strong applicability, and can be directly coated on any surface such as plastic, metal and wood

yang said that the surface of buildings often has color requirements. This material can be combined with pigments to show different colors. At the same time, the above in the sunlight is the detailed introduction of the use precautions and functional characteristics of horizontal tension machine. Near infrared light is reflected off, which can significantly reduce the temperature of buildings compared with traditional coatings

"it looks very suitable for wide application." Gentle said. Ronnen Levinson, a roof cooling expert at Lawrence Berkeley National Laboratory in California, said that the price of the new paint is about five times that of the traditional paint. But the increased cost brings benefits. Gentle said, "all these" very cool coatings make noon as cool as night. "