Australian scientists have unveiled a groundbreaking roof coating that can cool surfaces up to 6°C below ambient temperatures while also extracting water from the atmosphere. This innovative development, led by researchers at the University of Sydney, offers a potential solution to mitigate the effects of extreme heat events, which are becoming increasingly common due to climate change.
The new coating, made from a porous film, can be applied to existing roofs and works by reflecting 96% of incoming solar radiation. It also boasts high thermal emittance, effectively dissipating heat into outer space when the sky is clear. This phenomenon, known as passive radiative cooling, allows the paint to remain cooler than the surrounding air, even during the hottest parts of the day.
How the Technology Works
According to Prof. Chiara Neto, the study’s lead author, the coolness of the painted surface facilitates the condensation of atmospheric vapor, similar to dew forming on a car overnight. “This material is able to extend the period over which dew can form by at least a couple of hours,” Neto explained. “Instead of having dew forming only for four to six hours on a good night, you can extend that to eight or 10 hours.”
The research, published in the journal Advanced Functional Materials, involved testing a prototype for six months at the Sydney Nanoscience Hub. The cool paint was paired with a UV-resistant topcoat that encouraged dew droplets to roll into a receptacle. The study found that up to 390 milliliters per square meter per day could be collected for about a third of the year. For an average Australian roof of 200 square meters, this could yield up to 70 liters of water on days favorable for dew collection.
Potential Impact and Applications
Prof. Neto emphasized the dual benefits of the coating, stating, “The cooling aspect and the water go hand in hand when we talk about impact.” She suggested that the system could be particularly beneficial for buildings in remote areas or locations with limited access to groundwater. While the cooling effect might be less pronounced in well-insulated buildings, most Australian homes, which often lack adequate insulation, could see significant temperature reductions.
Beyond individual buildings, the coating could help mitigate the urban heat island effect, where urban areas become significantly warmer than their rural surroundings due to heat absorption by hard surfaces. However, the initial prototype used poly(vinylidene fluoride-co-hexafluoropropene), a material not suitable for large-scale use due to environmental concerns with perfluorinated materials. The researchers are now working on commercializing a water-based paint with similar cooling properties, expected to be priced comparably to standard premium paints.
Expert Opinions and Future Prospects
Sebastian Pfautsch, a professor of urban management and planning at Western Sydney University, noted that cool coatings have been under development for a decade but have yet to achieve widespread commercial availability. “I expect that this will happen before 2030,” he said, highlighting the potential for retrofitting existing buildings with the new technology. Pfautsch also praised the dew collection feature, stating, “Three or four watering cans that you get for free from your roof – that’s fantastic as a principle.”
However, Pfautsch cautioned that the effectiveness of water collection could be challenged during drought conditions, when relative humidity is low, resulting in less water being collected. Despite these challenges, the promise of this technology is significant, offering a sustainable approach to cooling and water collection in the face of intensifying climate change.
As the world grapples with the impacts of global warming, innovations like this roof coating represent a step forward in adapting to and mitigating the effects of extreme weather. The ongoing development and eventual commercialization of such technologies could play a crucial role in building resilience against future climate challenges.
