Porous Polymer Composite for Passive Daytime Radiative Cooling
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Solution Overview
Problem
Traditional space cooling technologies consume significant electricity and have a net heating effect on the global climate, while vapor-compression-based systems use refrigerants with a strong greenhouse effect, necessitating an energy-efficient and environmentally friendly alternative for daytime radiative cooling.
Innovation Solution
A porous polymer composite with a thermoplastic polymer matrix and selectively emitting particles is developed, achieving high solar reflectivity and infrared emissivity through a scalable manufacturing process, eliminating the need for reflective metal layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If vapor-compression-based cooling systems are used to achieve space cooling, then cooling effect is provided, but electricity consumption increases and greenhouse effect is intensified
Solution Approach 1:
The cooling system uses passive radiative cooling that operates autonomously without external energy input. The selective emitting particles and porous polymer matrix automatically emit thermal radiation in the atmospheric transparency window (8-13 μm) to achieve subambient cooling, eliminating the need for electricity-consuming vapor-compression systems
Solution Approach 2:
The patent replaces the mechanical vapor-compression cooling system with a passive radiative cooling system based on thermal radiation physics. Instead of using mechanical compressors and refrigerants, the system utilizes the natural thermal radiation properties of selectively emitting particles to achieve cooling through the atmospheric transparency window
2Temperature
If vapor-compression-based cooling systems are used, then cooling effect is achieved, but refrigerants with strong greenhouse effect are required
Solution Approach 1:
The patent converts the harmful greenhouse effect into a beneficial cooling mechanism by utilizing the atmospheric transparency window (8-13 μm). The selectively emitting particles are designed to emit thermal radiation precisely in this wavelength range, allowing heat to escape to outer space (3K) while avoiding absorption by greenhouse gases, thus achieving cooling without harmful refrigerants
3Object-affected harmful factors
If reflective metal layers are used to achieve high solar reflectivity, then solar energy reflection is improved, but manufacturing complexity and cost increase
Solution Approach 1:
The patent uses a composite material system consisting of selectively emitting particles dispersed in a porous polymer matrix. This composite achieves both high solar reflectivity (≥80%) and high infrared emissivity (≥80%) in the atmospheric transparency window, eliminating the need for complex reflective metal layer structures while maintaining excellent radiative cooling performance
Solution Approach 2:
The porous polymer matrix provides inherent solar reflection through its porous structure, eliminating the need for additional reflective metal layers. The pores scatter and reflect solar radiation effectively, while the selectively emitting particles embedded in the matrix provide high infrared emissivity, achieving both requirements with a single integrated material system
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 composite achieves a subambient temperature drop of up to 6.1°C and a cooling power of 85 W/m² under direct sunlight, with potential applications in building and apparel cooling via reflection of sunlight and thermal radiation into outer space.
Implementation Method 1
reflect solar energy away from irradiated surfaces
Implementation Method 2
emit thermal radiation into the cold outer space (having a temperature of about 3K) through what is referred to as the atmospheric transparency window (e.g., wavelengths in a range from 8-13 μm)
Implementation Method 3
The porous polymer composite for daytime radiative cooling includes a porous polymer matrix comprising a thermoplastic polymer and including a plurality of pores
Data Source
AI summary
A porous polymer composite for daytime radiative cooling includes a porous polymer matrix comprising a thermoplastic polymer and including a plurality of pores, and selectively emitting particles dispersed in the porous polymer matrix. When exposed to solar radiation, the porous polymer composite comprises an infrared emissivity of at least about 80% in a wavelength range of 8-13 μm and/or a solar reflectivity of at least about 80% in a wavelength range of 0.3-2 μm.