Cooling polymer coating enables energy-free rooftop water collection

Researchers from the University of Sydney and Dewpoint Innovations have engineered a nano-porous polymer coating that passively cools building surfaces and enables atmospheric water collection without energy input. The material, composed of PVDF-HFP, reflects up to 97 percent of sunlight, radiates heat, and lowers coated surface temperatures by as much as six degrees Celsius compared to ambient air. This cooling allows water vapor in the air to condense on the coating and form droplets.

Outdoor tests conducted on the Sydney Nanoscience Hub rooftop demonstrated dew capture on 32 percent of days over six months, with each square meter of coated surface able to collect up to 390 milliliters of water daily under optimal conditions. A 12-square-meter rooftop could thus meet the drinking water needs of one person per day. The technology is suited to applications in horticulture, livestock care, cooling, and hydrogen production, which requires nine liters of water per kilogram produced. Scaling up collection areas could provide water resources to remote or industrial locations.

Unlike traditional white paints that rely on titanium dioxide, the porous PVDF-HFP coating achieves high reflectivity through its structure rather than UV pigments. According to Dewpoint Innovations CTO Dr Ming Chiu, the material avoids glare by diffusing light and remains robust under prolonged direct sunlight. Durability tests showed no evidence of degradation.

The technology also offers potential benefits in reducing urban heat island impacts and lowering air-conditioning energy demands. Dew formation was detected in arid regions as well, provided that night-time humidity increased above a threshold, and the method is intended to supplement, not replace, rainwater. Dewpoint Innovations is developing a water-based formulation to enable simple rooftop application using rollers or sprayers. With rainwater systems present in more than two million Australian homes, the dew-coating could add supplementary water supply.

The innovation was licensed by Dewpoint Innovations in 2022 from the University of Sydney and is now moving into commercial development aimed at broader use in housing, agriculture, and infrastructure designed for climate resilience.

Research Report:Passively cooled paint-like coatings for atmospheric water capture