Researchers in Australia have come up with a new type of outdoor paint that can reduce surface temperatures by up to 6C while extracting fresh water from the atmosphere.
The invention, devised by a team from the University of Sydney and the startup Dewpoint Innovations, could help cool buildings during extreme weather, as well as tackle water scarcity in arid areas.
A six month trial of the material revealed that the coating can harvest 390ml of water per square metre each day, meaning that the daily drinking needs of one person could be met with a 12-square-metre surface coated in the paint.
"This technology not only advances the science of cool roof coatings but also opens the door to sustainable, low-cost and decentralized sources of fresh water – a critical need in the face of climate change and growing water scarcity," said Professor Chiara Neto from the University of Sydney’s Nano Institute, who led the research team.
"While humid conditions are ideal, dew can form even in arid and semi-arid regions where night-time humidity rises. It's not about replacing rainfall but supplementing it – providing water where and when other sources become limited."
The paint works by reflecting up to 97 per cent of sunlight and radiating heat into the surrounding air.
The cooler surface then creates the necessary conditions for water vapour in the atmosphere to condense into droplets, similar to the way a bathroom mirror steams up during a hot shower.
Placed on an angled roof, the water droplets roll off the paint and are collected in a gutter.
“Our design achieves high reflectivity through its internal porous structure, delivering durability without the environmental drawbacks of pigment-based coatings," said Dr Ming Chiu, chief technology officer of Dewpoint Innovations.
“By removing UV-absorbing materials, we overcome the traditional limit in solar reflectivity while avoiding glare through diffuse reflection. This balance between performance and visual comfort makes it easier to integrate and is more appealing for real-world applications."
The breakthrough was detailed in a study, titled ‘Passively cooled paint-like coatings for atmospheric water capture’, published in the journal Advanced Functional Materials.
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