Spectrally Selective Daytime Radiative Cooling Coating

Area of Science:

• Materials Science
• Sustainable Energy
• Environmental Engineering

Background:

• Passive daytime radiative cooling (PDRC) is a promising carbon-free technology for urban heat island mitigation and building energy reduction.
• Conventional PDRC emitters struggle in urban settings due to parasitic absorption of ambient thermal radiation, limiting their effectiveness.

Purpose of the Study:

• To develop a scalable, spectrally selective radiative cooling coating that overcomes the urban penalty.
• To demonstrate enhanced cooling performance in simulated urban environments.

Main Methods:

• Fabrication of a micro-nano porous poly(vinyl fluoride) (PVF) layer via phase inversion, combined with a silver substrate.
• Characterization of spectral selectivity, solar reflectance, and mid-infrared emittance within the atmospheric window (8-13 µm).
• Testing in simulated urban canyon conditions to evaluate cooling performance against broadband emitters.

Main Results:

• Achieved record spectral selectivity of 1.37.
• Demonstrated 97.5% solar reflectance and 94.4% mid-infrared emittance confined to the atmospheric window.
• The selective emitter performed 1.9°C cooler than a broadband emitter in urban canyon simulations, neutralizing heat gain.

Conclusions:

• The developed spectrally selective coating effectively mitigates urban heat gain, outperforming broadband emitters.
• The coating exhibits excellent scalability, adhesion, self-cleaning, and durability, making it suitable for practical applications.
• This technology presents a viable pathway for integrating radiative cooling into sustainable urban development.