This new biodegradable film could save 20 per cent on energy bills
The material is made from polylactic acid – a bioplastic derived from plants – and passively reflects nearly all solar radiation while allowing heat from inside buildings to escape into the sky.
Researchers from Zhengzhou University and the University of South Australia say the metafilm can be an alternative to air conditioning systems, which contribute significantly to greenhouse gas emissions in cities.
'Our metafilm offers an environmentally friendly alternative to air-conditioning,' Yangzhe Hou, lead author of the study and a PhD candidate at the University of South Australia and Zhengzhou University.
'The material reflects nearly all solar radiation but also allows internal building heat to escape directly into outer space. This enables the building to stay cooler than the surrounding air, even under direct sunlight.'
In testing, the film passively reduced temperatures by as much as 9.2C during peak sunlight hours, according to the study published in Cell Reports Physical Science on Wednesday. On an average, it kept surfaces 4.9C cooler during daytime and 5.1C cooler at night.
Unlike conventional cooling systems, the film requires no electricity or mechanical components.
The metafilm also withstood harsh weather conditions, maintaining its cooling performance even after 120 hours of exposure to strong acid and the equivalent of eight months of ultraviolet exposure outdoors, according to the study.
It continued to cool surfaces by up to 6.5C under those conditions.
'Most existing passive radiative cooling systems rely on petrochemical-based polymers or ceramics that raise environmental concerns,' Dr Xianhu Liu from Zhengzhou University said.
'By using biodegradable PLA, we are presenting a green alternative that offers high solar reflectance, strong thermal emission, sustainability and durability.'
Computer simulations showed using the metafilm on buildings in hot cities such as Lhasa in China 's Tibet region could reduce annual energy consumption by over 20 per cent.
'This isn't just a lab-scale success,' Professor Jun Ma from the University of South Australia claimed. 'Our film is scalable, durable and completely degradable. This research aims to contribute to sustainable development by reducing reliance on fossil fuels and exploring feasible pathways to improve human comfort while minimising environmental impact.'
The team is now looking into large-scale manufacturing and possible applications in transportation, agriculture, electronics and biomedical products, including cooling wound dressings.
Passive cooling technologies have gained traction in recent years, with various teams experimenting with ceramic coatings, reflective paints, and polymer-based films. However, many such innovations have faced limitations around cost, fragility, or environmental impact. Other recent breakthroughs include an ultrawhite starch-based film that passively cools surfaces by reflecting 96 per cent of sunlight and a ceramic roof coating that withstands extreme temperatures while reducing cooling loads by 20 per cent.
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