International. Researchers have developed a biodegradable film made of cellulose acetate that, thanks to its radiative cooling properties, effectively protects from the melting of ice subjected to solar radiation, with possible applications for icy foods and glaciers.
Ice plays an important role in many aspects of life, from food preservation to sports to ice ecosystems, providing an incentive to protect ice from melting under solar radiation. Fundamentally, ice melts under sunlight due to the imbalance in the energy flow of incoming sunlight and outgoing thermal radiation.
The development of bioengineering in daytime radiative cooling offers an interesting strategy for balancing energy flows. Scientists have used a variety of materials and structures in these promising works, including stamped or multi-layer photonic structures, nanoparticle-based porous polyethylene film, cooling wood, and super-white paints with solar reflectivity greater than 0.95.
Therefore, radiative cooling can balance energy flows without energy consumption to protect ice sustainably.
To preserve ice in sunlight, several strict requirements must be met. For example, an increase in net radiation power from 70 to 110 Wm-2 can prevent ice or frozen food from melting without additional refrigeration.
In a study published in Science Advances (1), a team of scientists presents a hierarchically designed radiative cooling film developed using abundant and biodegradable cellulose acetate (CA) molecules. The film uses connected nanofibers to form multiple pores of different sizes to ideally scatter and reflect sunlight.
They monitored the evolution of the temperature of frozen foods wrapped in different materials under natural sunlight outdoors. This results in longer shelf life of iced foods covered with THE AC film below 0 degrees Celsius for 5.5 hours due to the optical properties of the packaging materials. The material provided very effective passive preservation with 98% integrity after 80 minutes of exposure to sunlight.
Using experiments with climate models, the scientists also demonstrated how THE CA film effectively protected ice systems, such as glaciers at high latitudes. Its design and excellent radiative cooling capacity made it possible to reduce the surface temperature by 4°C at high latitudes.