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Start date: 2020Subject: search.filters.subject.Alternative energy

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    Item type:Publication,
    Repeated disordered structure for radiative cooling application via scalable stamping method from designed CaCO3 templates
    (2026-07-01)
    Kaewmanee, Taweesak
    ;
    Sakata, Patawee
    ;
    Gridtayawong, Pharit
    ;
    Rueangsawang, Worawut
    ;
    Ponghiransmith, Chattrarat
    Radiative cooling via micro-patterned surfaces provides energy-efficient solution for thermal regulation by enhancing selective thermal emission within the atmospheric transparency window (8–13 μm). This study investigates the effects of microstructural patterning through a low-cost and scalable stamping technique. The patterning templates were uniquely produced by the removal of randomly-distributed CaCO<inf>3</inf> polymorphs—calcite and vaterite with specific sizes. The novel calcite-imprinted structures exhibit superior mid-infrared emissivity (>0.96) and maintain consistent temperature reduction across varying weather conditions, outperforming vaterite-based films. However, the cooling performance of unmodified patterns is limited by solar absorption. To address this, TiO<inf>2</inf> (rutile phase) is incorporated into a polymer matrix before being stamped to enhance solar reflectivity. Moreover, hydrophobic aerogels could be inserted between micropattern gaps to facilitate self-cleaning functionality. A composite film containing 3 wt% TiO<inf>2</inf> with the calcite micro-patterning and hydrophobic aerogel achieves a temperature drop of 4.8 °C, compared to 1.2 °C of pristine patterns relative to that of a clear film. For real-world applicability, the optimized patterning strategies were further validated on fiber cement rooftile surfaces, yielding best temperature reductions of 2.5 °C compared to pattern-free coating under a tropical climate. The calculated net cooling power of 3 wt% TiO<inf>2</inf> patterned film with aerogel is 26.9 W/m<sup>2</sup>. This novel passive-cooling stamping strategy is low-cost, scalable, and suitable for large-area deployment, reducing the energy burden of active cooling technologies.