An anonymous reader quotes a report from IEEE Spectrum: Researchers at the Center for Translational Atomaterials (CTAM) at Swinburne University of Technology in Melbourne, Australia, have developed a new graphene-based film that can absorb sunlight with an efficiency of over 90 percent, while simultaneously eliminating most IR thermal emission loss — the first time such a feat has been reported. The result is an efficient solar heating metamaterial that can heat up rapidly to 83 degrees C (181 degrees F) in an open environment with minimal heat loss. Proposed applications for the film include thermal energy harvesting and storage, thermoelectricity generation, and seawater desalination.
The 3D structured graphene metamaterial (SGM) is composed of a 30-nanometer-thick film of alternating graphene and dielectric layers deposited on a trench-like nanostructure that does double duty as a copper substrate to enhance absorption. More importantly, the substrate is patterned in a matrix arrangement to enable flexible tunability of wavelength-selective absorption. The graphene film is designed to absorb light between 0.28- to 2.5-micrometer wavelengths. And the copper substrate is structured so that it can act as a selective bandpass filter that suppresses the normal emission of internally generated blackbody energy. This retained heat then serves to further raise the metamaterial’s temperature. Hence, the SGM can rapidly heat up to 83 degrees C. Should a different temperature be required for a particular application, a new trench nanostructure can be fabricated and tuned to match that specific blackbody wavelength. “The new material also uses less graphene by significantly reducing the film thickness to one third, and its thinness aids in transferring the absorbed heat more efficiently to other media such as water,” the report adds. “Additionally, the film is hydrophobic, which fosters self-cleaning, while the graphene layer effectively protects the copper layer from corrosion, helping to extend the metamaterial’s lifetime.”
The research is published in the journal Nature Communications.
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Source: Slashdot – Graphene Solar Thermal Film Could Be a New Way To Harvest Renewable Energy