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Daytime radiative cooler using porous TiO2: new approach
Applied Optics
|October 26, 2020
Summary
Researchers developed an inexpensive, scalable double-layer coating for passive daytime radiative cooling. This innovative material achieves significant sub-ambient temperatures and cooling power, ideal for solar cells and thermal management.
Area of Science:
- Materials Science
- Nanotechnology
- Thermal Engineering
Background:
- Passive daytime radiative cooling (PDRC) is crucial for thermal management, with applications in electronics and solar energy.
- Achieving PDRC requires materials with low solar absorptivity and high atmospheric transparency window emissivity.
- Current PDRC technologies face challenges in scalability and cost-effectiveness.
Purpose of the Study:
- To design and analyze a novel, inexpensive, and scalable double-layer coating for efficient passive daytime radiative cooling.
- To evaluate the optical properties and cooling performance of the proposed coating under various conditions.
- To demonstrate the potential for large-scale application in solar cells and related systems.
Main Methods:
- Fabrication of a double-layer coating comprising a porous titanium dioxide (TiO2) adsorbent layer and a borosilicate-crown glass (BK7) substrate.
- Characterization of optical properties, including solar absorptivity and thermal emissivity, across relevant spectral ranges.
- Experimental measurement of sub-ambient temperature drops and diurnal cooling power output under simulated solar irradiance and humidity.
Main Results:
- The proposed double-layer coating exhibits average absorptivity below 7% in the solar spectrum (0.3-2.5 µm).
- Achieved high emissivity of nearly 95% within the atmospheric transparency windows (8-13 µm and 16-26 µm).
- Demonstrated a sub-ambient temperature drop of 45°C and a cooling power of 133 W/m² under 1000 W/m² solar irradiance, maintaining performance in high humidity.
Conclusions:
- The developed double-layer coating offers an efficient and cost-effective solution for passive daytime radiative cooling.
- The design's scalability and robust performance under diverse conditions pave the way for practical applications.
- This advancement represents a significant step towards integrating PDRC technology into solar cells and other thermal management systems.
