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Radiative cooling to deep sub-freezing temperatures through a 24-h day-night cycle
Zhen Chen1, Linxiao Zhu2, Aaswath Raman1
1Ginzton Laboratory, Department of Electrical Engineering, Stanford University, Stanford, California 94305, USA.
Nature Communications
|December 14, 2016
Summary
Radiative cooling technology achieves significant temperature reduction by using selective thermal emitters to dissipate heat into space. This passive cooling method demonstrated an average 37°C drop, exceeding previous modest results.
Area of Science:
- Thermodynamics
- Optics
- Materials Science
Background:
- Radiative cooling leverages the 8-13 μm atmospheric transparency window for passive heat dissipation into space.
- Current applications include passive building cooling, energy harvesting, and refrigeration, but demonstrated temperature reductions are modest.
Purpose of the Study:
- To theoretically and experimentally demonstrate ultra-large temperature reductions using radiative cooling.
- To overcome limitations of previous radiative cooling experiments.
Main Methods:
- Utilizing a selective thermal emitter designed for optimal infrared radiation.
- Minimizing parasitic thermal loads to enhance cooling efficiency.
- Conducting experiments in a populated, sea-level area over a 24-hour cycle.
Main Results:
- Theoretically achievable temperature reduction of up to 60°C.
- Experimentally demonstrated average temperature reduction of 37°C from ambient.
- Maximal temperature reduction of 42°C recorded under peak solar irradiance.
Conclusions:
- Selective thermal emitters and parasitic load elimination enable significant advancements in radiative cooling.
- Achieved temperature reductions far exceed previous experimental results.
- This technology holds promise for passive cooling applications, especially in arid regions.
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