Solar and thermal dual-band electrochromic windows for energy-efficient buildings

Area of Science:

• Materials Science
• Sustainable Energy
• Building Physics

Background:

• Windows are major contributors to building heat gain and loss.
• Traditional electrochromic (EC) windows only manage visible and near-infrared light, neglecting long-wave infrared (LWIR) thermal radiation.

Purpose of the Study:

• To develop a dual-band electrochromic window capable of independently modulating solar transmission and LWIR emissivity.
• To enhance energy efficiency and reduce carbon emissions in buildings.

Main Methods:

• Integration of a dynamic copper-bismuth (Cu-Bi) based reversible metal electrodeposition system.
• Implementation of a spatial rotation architecture for independent control of solar and thermal properties.
• Outdoor thermal performance tests and building energy simulations.

Main Results:

• Achieved 52.2% modulation in solar transmission (ΔTsol) and 0.87 modulation in LWIR emissivity (ΔɛLWIR).
• Demonstrated significant temperature reductions (up to 22.2°C) in summer and increases (up to 1.5°C) in winter.
• Projected higher year-round energy savings and CO2 emission reduction compared to conventional windows.

Conclusions:

• The developed solar and thermal dual-band EC (STDEC) window offers a sustainable solution for energy-efficient buildings.
• Independent control over solar gain and thermal radiation is key to optimizing building energy performance.
• This technology presents a promising pathway for reducing the carbon footprint of the built environment.