Smart windows – Transmittance tuned thermochromic coatings for dynamic control of building performance

Abstract

Thermochromic window technologies promise energy-saving capabilities through intelligent regulation of solar irradiation indoor penetration. Although improvements have been made, nanoparticle thermochromic coated glazing technology has not yet achieved optimal balance between luminous transmittance and solar modulating capability. While luminous transmittance can be increased, this generally comes at the cost of reduced solar modulation, and this trade-off requires exploration. Thermochromic glazing with varying luminous transmittance and corresponding solar modulation has hence been developed through coating VO2 nanoparticles directly onto glazing by adjusting thicknesses of the coatings. The advantages of this method are simplicity of process, high purity of starting materials, compatibility with a wide range of substrates, and reproducibility in switching properties. The effects of the thermochromic glazings on building performance were then explored using building simulation for desert, Mediterranean, and temperate climates. It was found that 7.1–46.4% annual energy-saving can be achieved in comparison to using an uncoated clear double-glazed window. Trade-off between energy-saving capability and UDI500-2000 lx within the space was also explored and results showed that the designed thermochromic glazing reduced visual discomfort 1.2–3.2 m into the space. Overall, responding to external conditions, thermochromic technological advancements can help make buildings more resilient to future weather changes.