Transparent metafilms for enhanced thermal regulation in energy-efficient windows

Area of Science:

• Materials Science
• Optical Engineering
• Thermal Engineering

Background:

• Transparent metafilms offer spectrally selective properties for energy-efficient windows.
• Prior research optimized materials and thickness for visible transmittance and near-infrared reflectance.
• The impact of metafilm placement on optical and thermal performance, particularly in the mid-infrared (MIR) for radiative cooling, remains underexplored.

Purpose of the Study:

• To analyze a five-layer TiO2/Ag/TiO2/Ag/TiO2 metafilms structure.
• To evaluate the effect of interior versus exterior coating placement on window performance.
• To investigate the influence of metafilm position on mid-infrared (MIR) emissivity and radiative cooling.

Main Methods:

• Numerical simulations using the transfer matrix method.
• Systematic evaluation of two installation scenarios: interior and exterior coating.
• Analysis of optical properties (visible transmittance, NIR reflectance) and thermal performance (MIR emissivity, radiative cooling power).

Main Results:

• Both interior and exterior configurations achieved high visible transmittance (~0.88) and NIR reflectance (~0.98).
• The interior-coated configuration exhibited significantly higher emissivity (0.8) in the 8-14 μm atmospheric transparency window compared to the exterior-coated configuration (0.01).
• Interior placement resulted in superior passive radiative cooling capability and net radiative cooling power.

Conclusions:

• Metamaterial film placement critically impacts mid-infrared radiation and thermal performance.
• Interior coating placement optimizes solar modulation and enhances thermal dissipation for energy-efficient windows.
• This study provides insights for designing metafilms in energy-saving window systems, especially for hot climates.