Radiative Cooling Structure for Daytime Solar Heat Rejection
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Solution Overview
Problem
Existing radiative cooling technologies face challenges in efficiently cooling buildings during the daytime due to the absorption of solar radiation, which complicates the process and reduces effectiveness.
Innovation Solution
The development of a radiative cooling device that incorporates a solar spectrum reflecting structure and a thermally-emissive structure, integrated into a single constitution, to suppress the absorption of solar radiation and enhance thermal emission in mid-infrared wavelengths, thereby facilitating efficient daytime cooling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a radiative cooling device is used during daytime, then cooling effect is improved, but absorption of solar radiation increases
Solution Approach 1:
The cooling device applies different optical properties to different wavelength ranges: high reflectivity in the solar spectrum (0.3-2.5 μm) and high emissivity in the thermal infrared range (8-13 μm). This local differentiation of optical characteristics allows the surface to simultaneously reject solar heating and emit thermal radiation for cooling.
Solution Approach 2:
The device employs a composite structure combining a dielectric layer and a metallic layer, where each material contributes specific optical properties. The dielectric layer provides high emissivity in the infrared range, while the metallic layer enhances solar reflection. This composite approach enables simultaneous achievement of both cooling functions.
2Loss of energy
If solar spectrum reflecting structure is added, then solar radiation absorption is suppressed, but device complexity increases
Solution Approach 1:
The device merges the solar reflection function and thermal emission function into a single integrated coating structure. Rather than using separate components or systems, both functions are achieved through a unified multilayer coating applied directly to the building surface, simplifying the overall system.
Solution Approach 2:
The invention changes the optical parameters (reflectivity and emissivity) of the surface coating to achieve the desired performance. By adjusting the thickness, material composition, and optical properties of the coating layers, the device optimizes solar reflection and thermal emission without requiring complex mechanical or structural modifications.
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
This solution enables effective daytime radiative cooling, capable of offsetting up to 32% of a building's air conditioning needs during peak hours, leading to significant energy savings and reduced demand on rooftop solar systems.
Implementation Method 1
A solar spectrum reflecting structure configured and arranged to suppress light modes within the structure from coupling to sources that are externally located relative to the object being cooled
Implementation Method 2
A thermally-emissive structure configured and arranged to facilitate thermally-generated emissions from the object and in mid-infrared (IR) wavelengths
Implementation Method 3
radiative cooling techniques that exploit the natural transparency window for electromagnetic waves in the Earth's atmosphere to transport heat from terrestrial objects
Data Source
AI summary
Various aspects as described herein are directed to a radiative cooling device and method for cooling an object. As consistent with one or more embodiments, a radiative cooling device includes a solar spectrum reflecting structure configured and arranged to suppress light modes, and a thermally-emissive structure configured and arranged to facilitate thermally-generated electromagnetic emissions from the object and in mid-infrared (IR) wavelengths.