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Scientists have created a super white paint that is Vantablack’s yin to yang.
While ultra-black materials can absorb more than 99.96 percent of sunlight today, this new super white layer can reflect 95.5 percent of all photons that hit it.
Instead of being heated in direct light, objects painted with this new acrylic material can stay cooler than the surrounding temperature even in the sun, which could enable a new energy-efficient way to control the temperature inside buildings.
Other “heat-rejecting paints” we currently have can only reflect 80 to 90 percent of sunlight and cannot reach temperatures lower than ambient.
“It is a persistent task to develop a radiative cooling solution below ambient that offers a convenient form of single layer particle matrix paint and high reliability,” says mechanical engineer Xiulin Ruan of Purdue University in Indiana.
“This is essential for the broad application of radiative cooling and to alleviate the effect of global warming.”
In summer, many modern buildings rely on air conditioning units that push heat from the inside of a building to the outside. This, together with the excess heat generated by the intense energy required to achieve cooling, contributes to turning cities into “heat islands” and further exacerbates global warming.
Radiative cooling is a passive technology that reflects heat from a building back into space, but it is much more difficult to achieve than radiant heating.
Since the 1970s, scientists have been trying to figure out how to reflect enough sunlight so that passive cooling is more effective than an active air conditioner.
Some have recently even tried putting together ‘reverse solar panels’, which can capture some of that outgoing heat and convert it into energy, even overnight.
But at this time, these are still just concepts, and it’s unclear if such devices could actually work outside of a simple simulation.
Painting residential and commercial buildings in super white might be a more feasible approach, at least in the near future.
The new acrylic paint was made using high particle concentration calcium carbonate fillers of a wide range of sizes, which can efficiently disperse all wavelengths of the solar spectrum.
The paint matrix also has a vibratory resonance peak, which ensures that a large amount of heat is reflected outward, at a much higher rate than other cooling paints can achieve.
During two days of field tests at different locations and under various climatic conditions, the researchers tested the paint’s radiative cooling capabilities and found that it could scatter 95.5 percent of sunlight, remaining 10 degrees C below room temperature overnight and at least 1.7 degrees C below room temperature. at noon.
Compared to surfaces coated with the same thickness of commercial white paint, objects covered with the calcium carbonate paint maintained substantially lower temperatures in infrared images.
Additionally, this paint is brushed and dried in the same way, and is abrasion resistant, waterproof, and can withstand the weather for at least three weeks, although longer tests are currently underway.
“Our paint is compatible with the commercial paint manufacturing process and the cost can be comparable or even lower,” says Ruan.
“The key is to ensure the reliability of the paint so that it is viable in long-term exterior applications.”
The authors say their paint is “the best reported radiative cooling performance,” although they acknowledge that during the review of their results, another team published a paper arguing that the cooling paint should include high concentrations of broadband particles.
They also suggest incorporating fluorocarbon-based polymers, which show high resistance to weathering.
“Many conventional white paints, although designed to last, experience drops in solar reflectance over time,” explains the other recent article.
“Materials such as fluoropolymer-based binders could improve reflectance life and therefore reduce averaged costs per year.”
Creating a single-layer paint that can reflect heat directly into space without requiring an input of energy would be a huge advantage for the climate crisis, as cooling generally runs on fossil fuels and has a large overall impact on the environment. global warming.
The new paint has yet to undergo some more testing, but patents have already been filed. The name has yet to be revealed.
The study was published in Cell Reports Physical Sciences.
