Opportunity
Buildings consume over 34% of global energy, with cooling loads exceeding 50% in hot climates. Conventional cooling methods, such as air conditioners, rely on refrigerants that exacerbate climate change and ozone depletion. Existing radiative cooling paints often use single minerals like titanium oxide (TiO₂) to reflect sunlight, but they fail to cover the full spectrum of heat-causing wavelengths. This limitation reduces their effectiveness in passive cooling, leaving a gap for a solution that combines broad-spectrum solar reflectance with efficient heat dissipation through the infrared atmospheric window (8,000–13,000 nm).
Technology
The patent introduces a multi-layer coating comprising:
- A bottom reflective layer (e.g., TiO₂ or ZnO nanoparticles) to reflect visible and near-infrared light.
- A top reflective layer (e.g., Al₂O₃ nanoparticles) to reflect ultraviolet light, complementing the bottom layer’s spectrum.
- A polymer matrix (e.g., PDMS, PVDF, or PMMA) with high mid-infrared emissivity (8,000–13,000 nm) to dissipate absorbed heat into space.
The layers are stacked to avoid mixing nanoparticles, which would widen absorption rather than reflection. The coating also includes a hydrophobic outer layer for durability and self-cleaning.
Advantages
- High solar reflectivity (>93%) across UV, visible, and near-infrared wavelengths.
- Passive cooling: No energy input required; reduces reliance on air conditioning.
- Eco-friendly: Eliminates refrigerant use, lowering greenhouse gas emissions.
- Versatile: Applicable to buildings, vehicles, solar panels, and roads.
- Durable: Hydrophobic layer resists weathering and dust.
Applications
- Building coatings: Roofs and walls for energy-efficient temperature regulation.
- Transportation: Cooling surfaces of cars, ships, and cargo containers.
- Solar panels: Prevents efficiency loss due to overheating.
- Urban infrastructure: Reduces heat island effect on roads and pavements.
- Industrial use: Protects oil tanks and pipelines from overheating.
