Waste Glass-Derived Hierarchically Porous All-Inorganic Coatings for Sustainable Daytime Radiative Cooling

Area of Science:

• Materials Science
• Nanotechnology
• Sustainable Energy

Background:

• Passive daytime radiative cooling (PDRC) offers a sustainable thermal management solution.
• Current PDRC materials face challenges in cost and durability, limiting widespread adoption.
• Organic-based PDRC materials often exhibit poor performance under harsh environmental conditions.

Purpose of the Study:

• To develop a cost-effective and durable all-inorganic PDRC coating.
• To utilize industrial waste materials for sustainable PDRC applications.
• To investigate the relationship between material structure and radiative cooling performance.

Main Methods:

• Synthesized a hierarchically porous coating using industrial waste glass and alumina microparticles.
• Employed low-temperature processing (600 °C) with natural fluxes from waste glass.
• Engineered a random photonic network through controlled densification via alumina's steric hindrance.

Main Results:

• Achieved 96% solar reflectance and 95% atmospheric window emittance with an optimized 50 wt.% waste glass/50 wt.% alumina composite.
• Demonstrated sub-ambient cooling of ~4.0 °C (day) and ~4.5 °C (night) in field tests.
• Recorded a peak net cooling power of 108.1 W/m² and confirmed sustained optical stability after extreme thermal and weathering tests.

Conclusions:

• The developed all-inorganic PDRC coating offers a sustainable and high-performance alternative to traditional materials.
• Low-temperature processing of waste materials can yield advanced photonic structures for efficient radiative cooling.
• The material exhibits excellent durability and optical stability, suitable for practical thermal management applications.