Abstract
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•The energy performance of a D/M/D film in hot weather is elucidated.•The long-wave regulation of a D/M/D film proved to be important.•Suitable application mode of a D/M/D film is demonstrated.•A clear relationship between the Ag thickness and optical properties is presented.•Samples with highest Tvis and Tvis + Rsi are prepared for energy-efficient windows.
A dielectric/metal/dielectric (D/M/D) film with a high visible (0.38–0.78 μm) transmittance and a high solar infrared (0.78–2.5 μm) reflectance can be applied on the outdoor surface of a window for energy saving in hot weather. However, in this kind of application with a D/M/D film, the regulation of long-wave (>3 μm) radiation is often neglected but proved to be significant in energy saving according to our previous work. For a ZnO/Ag/ZnO structure on flexible PET applied as a visible transparent solar infrared reflecting film with a low long-wave emittance, based on matrix formulation and a ray-tracing method, the influence of Ag layer thickness on visible transmittance (Tvis), solar infrared reflectance (Rsi) and long-wave emittance (εlw) are investigated. Two samples with the highest Tvis and Tvis + Rsi are prepared, respectively, with high visible transmittance, high solar infrared reflectance and low long-wave emittance, simultaneously. In hot weather, compared with a traditional silica glass, the exterior applied film consumes more energy, while the interior applied film saves 9.6% energy consumption for cooling.