Correlating Mid-Infrared Absorption With Radiative Efficiency in Passive Daytime Radiative Cooling Systems

Area of Science:

• Materials Science
• Optics
• Thermodynamics

Background:

• Passive daytime radiative coolers (PDRCs) enable cooling by reflecting sunlight and emitting thermal radiation to space.
• Optimizing PDRCs requires specific optical properties across UV to mid-infrared wavelengths.
• Key requirements include high solar reflectivity and selective mid-infrared emittance.

Purpose of the Study:

• To fabricate PDRCs using silica-loaded poly(4-methyl-1-pentene) thin films.
• To correlate the photonic properties of PDRCs with their radiative cooling efficiency.
• To establish a quantitative criterion for assessing PDRC performance.

Main Methods:

• Fabrication of PDRCs via hot-pressing silica-loaded poly(4-methyl-1-pentene) films onto silver-coated stainless-steel slabs.
• Characterization of the photonic response (reflectivity and emittance) of the fabricated PDRCs.
• Measurement and correlation of thermodynamic radiative efficiency with optical properties.

Main Results:

• Demonstrated fabrication of PDRCs with tailored photonic properties.
• Established a direct correlation between mid-infrared emittance and radiative power.
• Showcased that strong mid-IR emittance leads to higher radiative efficiency at room temperature.

Conclusions:

• The study provides a clear quantitative criterion for evaluating PDRC performance based on mid-infrared emittance.
• Optimized photonic properties, particularly in the mid-IR, are crucial for effective passive cooling.
• This research advances the development and assessment of efficient passive daytime radiative cooling technologies.