SEOUL -- Passive daytime radiative cooling has been developed to enhance solar reflectivity and emissivity in the long-wavelength infrared region, but sustainable materials for radiative cooling have not been sufficiently investigated.
A team of researchers from the state-run Korea Research Institute of Chemical Technology (KRICT), Chung-Ang University in Seoul, and the University of California, Irvine, has developed an eco-friendly polymer structure for effective radiative cooling via thermally induced phase separation, using polylactic acid (PLA), a biodegradable thermoplastic polyester.
The hierarchically porous PLA realized high-performance passive radiative cooling without a silver coating for solar reflection, cooling as much as 9 degrees Celsius below the ambient temperature, the team said in a paper published on the website of ACS Sustainable Chemistry & Engineering, a peer-reviewed scientific journal.
"This cooling effect is the highest among all organic-based passive radiation cooling emitters reported so far," the team said. "The present work provides an ideal passive radiative cooling strategy for creating environmentally friendly buildings with reduced energy consumption."
KRICT described the porous PLA as an eco-friendly zero-energy cooling material that can be cooled like an air conditioner without using additional energy, reflect more than 95 percent of sunlight, and cool the surface of an object by heat radiation even under direct sunlight.
The cooling material can contribute to efficient heat management without energy use and can be applied to buildings, automobiles, and solar cells, the state research body said. "With this technology development, we will be able to preoccupy core technologies for energy reduction and efficient thermal management through active cooperation with companies related to materials and energy devices," KRICT head Yi Mi-hye said in a statement on July 14.
A subsequent study on scale-up techniques for mass synthesis and large-area coating is needed for commercialization that could create an economic ripple effect by replacing white paint, KRICT said.
Materials that introduced structures for heat dissipation on aluminum or silver substrates were expensive, vulnerable to impact, and difficult to apply to actual buildings. KRICT said that researchers have designed a hierarchical pore structure in PLA without a separate reflective layer substrate to develop an excellent radiation cooling material. The material applied to a building with an area of about 100 square meters for simulation was able to reduce power consumption by up to 8.6 percent per year.
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