New Paint Provides Passive Cooling Potential
Researchers from independent nonprofit research institute SRI International have recently developed a new self-cooling, water-based paint to provide an energy-efficient solution to extreme heat.
The paint, which reportedly resembles standard white house paint, utilizes two different methods to cool down structures.
About the Paint
SRI explains that July 2023 was the hottest month globally in recorded human history, leading to a growing need for affordable, energy-efficient methods for cooling.
“The active cooling solutions we have today are not sustainable and will not be adequate going forward,” said Anish Thukral, research scientist and materials engineer at SRI, who is leading the development of this paint. “A passive cooling solution like this is particularly valuable because it is cheaper and more accessible than air conditioning.”
The paint formulation is water-based and can be sprayed, rolled or brushed on to surfaces. It also offers fewer potentially harmful volatile organic compounds compared to solvent-based formulas and is free of per- and polyfluoroalkyl substances.
The paint reportedly contains designed pigments to reflect 96% of the sunlight that hits it, according to reflectance data measured by SRI researchers.
Additionally, the second cooling method is based in the paint’s materials that radiate heat in the atmospheric transparent window, or a specific band of infrared wavelengths that are known to pass easily through Earth’s atmosphere.
Since these wavelengths don’t interact with anything in the atmosphere, the researchers explain that they are able to use the temperature difference between the paint and outer space to dissipate heat.
This has reportedly demonstrated the paint to cool a surface up to 10 degrees Fahrenheit below ambient air temperature, as well as 23 degrees F below its uncoated counterpart. These results were based on an internal test conducted on a rooftop in Palo Alto, California.
“That is the real magic of science,” said Thukral. “We’re using outer space as a direct heat sink, and space is always available and extremely cold. So, it’s a clean and sustainable solution for cooling.”
One application of focus is for outdoor electrical boxes to regulate internal temperatures to protect the sensitive and expensive electronic equipment inside.
“We have good adhesion on multiple surfaces; it works on rigid as well as flexible substrates; it has a similar resistance to abrasion as commercial paint would have; if it gets dirty, you can wash it with water,” Thukral said.
According to SRI, the researchers also hope to use the paint on rooftops to lower building temperatures, cool vehicle interiors or for application on playground structures.
“We’re trying to get this paint out into the world,” Thukral added. “It could have an impact on a very broad population.”
Recent Cooling Coating
Earlier this month, it was reported that a new “cooling glass” technology from the University of Maryland aims to combat rising global temperatures by turning down indoor heat without electricity.
The microporous glass coating, published in the journal Science, can reportedly lower the temperature of the material beneath it by 3.5 degrees Celsius at noon.
According to UMD’s news release, the coating reflects up to 99% of solar radiation to stop buildings from absorbing heat. Additionally, it emits heat in the form of longwave infrared radiation into space, where the temperature is generally around -270 C, or just a few degrees above absolute zero.
This phenomenon is known as “radiative cooling,” where space effectively acts as a heat sink for the buildings.
The new cooling glass design along with the “atmospheric transparency window,” or a part of the electromagnetic spectrum that passes through the atmosphere without boosting its temperature, can send large amounts of heat into the cold sky.
Professor in the Department of Materials Science and Engineering Liangbing Hu, who led the project, says that the coating has the potential to reduce a mid-rise apartment building’s yearly carbon emissions by 10%.
The new glass is reportedly able to withstand exposure to water, ultraviolet radiation, dirt and flames, enduring temperatures of up to 1,000 degrees C. The glass coating can be applied to a variety of surfaces such as tile, brick and metal.
Assistant Research Scientist Xinpeng Zhao, the first author of the study, explained that the team used finely ground glass particles as a binder, allowing them to avoid polymers and enhance its long-term durability outdoors. They reportedly chose the particle size to maximize emission of infrared heat while simultaneously reflecting sunlight.