Spectral and angular emission control based temperature sensitive radiative cooling device
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Solution Overview
Problem
Conventional radiative cooling devices exhibit inefficient cooling performance due to fixed emissivity in specific wavelength ranges and angles, failing to adapt to ambient temperature changes, leading to degradation in cooling efficiency under varying environmental conditions.
Innovation Solution
A radiative cooling device with an angle-dependent emissivity spectrum that adjusts based on temperature changes, utilizing a polymer layer with a multilayer thin film, nanopattern, and dispersed nanoparticles, or metamaterials, to maximize radiative heat emission and efficiently cool objects without energy consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a radiative cooling device uses fixed emissivity in specific wavelength ranges and angles, then the device structure is simple and easy to manufacture, but the cooling performance degrades when ambient temperature changes
Solution Approach 1:
The patent applies the dynamics principle by making the emissivity spectrum angle-dependent rather than fixed. The device structure includes specific geometric configurations that cause the emissivity to dynamically adjust based on the viewing angle, allowing the device to adapt to different ambient temperature conditions without changing its physical structure. This resolves the contradiction by enabling temperature adaptability through angular dependency while maintaining manufacturing simplicity.
Solution Approach 2:
The patent applies parameter changes by modifying the emissivity spectrum characteristics through geometric design parameters. By controlling the shape, size, and arrangement of the device components, the emissivity spectrum is tuned to be angle-dependent, which allows the device to maintain effective cooling performance across varying ambient temperatures. This resolves the contradiction by achieving temperature adaptability through parameter optimization rather than structural complexity.
2Productivity
If a radiative cooling device has high emissivity in the entire mid-IR range or from 8 μm to 13 μm at any angle, then the device covers broad wavelength range, but the cooling rate is inefficient and cannot sufficiently lower the temperature
Solution Approach 1:
The patent applies local quality by creating angle-dependent emissivity distribution rather than uniform high emissivity across all angles. The device is designed to have enhanced emissivity in specific angular ranges that correspond to optimal cooling conditions, while maintaining appropriate emissivity in other angles. This localized optimization of emissivity quality achieves both high cooling rate and reliable cooling performance by directing radiative heat transfer more effectively.
3Device complexity
If a radiative cooling device uses isotropic emissivity, then the device design is simple, but the cooling performance is only effective at normal temperature and degrades when temperature changes
Solution Approach 1:
The patent applies asymmetry by transitioning from isotropic (uniform in all directions) emissivity to anisotropic (direction-dependent) emissivity. The device structure incorporates asymmetric geometric features that cause the emissivity to vary with angle, enabling the device to adapt to different ambient temperature conditions. This asymmetric design achieves temperature range adaptability while maintaining relatively simple device complexity through geometric rather than material complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The device achieves rapid and effective cooling by dynamically adjusting its emissivity spectrum in response to temperature changes, outperforming conventional devices by maintaining a lower temperature than the ambient environment, with a cooling performance enhancement of at least 5°C and up to 20°C below conventional limits.
Implementation Method 1
A radiative cooling device refers to a device capable of cooling an object lower than the ambient temperature by itself without external energy even under sunlight
Implementation Method 2
an angle-dependent emissivity spectrum in the infrared range changes depending on the relative high and low of the temperature
Data Source
AI summary
The present disclosure relates to a radiative cooling device which is sensitive to the ambient temperature and in which the emissivity changes depending on the infrared wavelength range and emission angle, and a method of cooling an object using the radiative cooling device.