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https://www.sciencenews.org/article/this-paint-sweats-keep-your-house-cool>
"A cool house without air conditioning may soon be possible.
Scientists in Singapore have developed a new type of paint that reflects
sunlight and cools surfaces by slowly evaporating water. Unlike other
commercially available cooling paints, which are designed to repel water to
protect the underlying material, the new one even works in hot, humid places,
offering a low-energy way to stay cool, researchers report June 5 in
Science.
“The key is passive cooling,” which requires no energy input, says material
scientist Li Hong In other words, it works without using electricity or
mechanical systems. Right now, radiative cooling is the most common type of
passive cooling used in materials, including certain paints. It works by
reflecting sunlight and radiating heat from a surface such as walls or roofs,
into the sky. But in humid places like Singapore, water vapor in the air traps
heat near the surface, which prevents it from escaping into the atmosphere and
keeps the surfaces warm.
In response, Hong and two other material scientists from Nanyang Technological
University developed a cement-based paint that combines three cooling
strategies: radiative cooling, evaporative cooling, which our skin uses, and
solar reflection. In the study, the scientists painted three small houses: one
with regular white paint, one with commercial cooling paint that uses only
radiative cooling and one with their new formula. After two years of sun and
rain in Singapore, the first two paints had turned yellow. But “our paint was
still white,” says coauthor Jipeng Fei. Unlike other colors, white helps
materials maintain their high reflectivity and cooling performance.
The paint’s porous structure holds water and slowly releases it, like the body
does sweat. It reflects 88 to 92 percent of sunlight, even when wet, and emits
up to 95 percent of the heat it absorbs. Nanoparticles boost reflectivity and
strength, helping the paint maintain its white color over time. A small amount
of polymer and salt help retain moisture and prevent cracking. Tests showed the
house covered in the new paint used 30 to 40 percent less electricity for air
conditioning than the other houses."
Via
Climate for Change
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*** Xanni ***
--
mailto:xanni@xanadu.net Andrew Pam
http://xanadu.com.au/ Chief Scientist, Xanadu
https://glasswings.com.au/ Partner, Glass Wings
https://sericyb.com.au/ Manager, Serious Cybernetics
