Effective, angle-independent radiative cooler based on one-dimensional photonic crystal

Area of Science:

• Materials Science
• Optics
• Thermodynamics

Background:

• Passive radiative cooling offers a sustainable alternative to conventional cooling methods.
• Achieving high emissivity within the atmospheric transparency window is crucial for effective radiative cooling.
• Minimizing solar heat gain is essential for daytime radiative cooling performance.

Purpose of the Study:

• To propose and demonstrate a simple, low-cost radiative cooler based on a one-dimensional photonic crystal.
• To achieve ultra-broadband emissivity within the 8-13μm atmospheric transparency window.
• To evaluate the cooling performance under both nighttime and daytime (solar) conditions.

Main Methods:

• Fabrication of a one-dimensional photonic crystal structure.
• Utilizing a tandem structure of lossy and lossless materials to optimize optical resonances and reduce reflection.
• Characterization of average emissivity within the 8-13μm wavelength range.
• Measurement of cooling power density under nighttime conditions and theoretical evaluation under solar irradiance.

Main Results:

• The radiative cooler exhibits an average emissivity of 96% within the 8-13μm atmospheric transparency window.
• A maximum cooling power density of 113.0 W/m² was achieved at night.
• Theoretical maximum cooling power density of 83.0 W/m² was predicted for daytime operation with a 97% solar reflector under 1000 W/m² solar irradiance.

Conclusions:

• The proposed one-dimensional photonic crystal radiative cooler is a simple and effective solution for passive cooling.
• The device demonstrates high emissivity and significant cooling power, suitable for both day and night operation.
• This technology holds promise for energy-efficient cooling applications.