Cooling Without Power SkyCool Systems’ Radiative Cooling Panels That Reject Heat Directly to Space

Conventional air conditioning consumes enormous amounts of electricity and generates heat that exacerbates urban heat islands. SkyCool Systems has developed a radiative cooling material that can reject heat from buildings, vehicles, and refrigeration systems by emitting thermal radiation through the atmospheric window directly into the coldness of space – with no electricity required for the cooling effect itself. A divisional patent describes the layered material structure and UV-protection design that makes this technology durable enough for real-world outdoor deployment.

The Problem

Radiative cooling is a natural phenomenon: any object on Earth’s surface emits thermal radiation in the 8-13 micrometre wavelength range, which passes through the atmospheric window with minimal absorption and escapes to the cold of outer space. In principle, a surface with very high thermal emissivity in this range can shed heat passively even during the day, providing cooling that costs no electrical energy. Research has demonstrated that specially engineered surfaces can achieve net cooling below ambient air temperature even under direct sunlight by combining strong infrared emission with high solar reflectance.

The challenge for practical deployment is durability. Radiative cooling materials must be installed outdoors, where they face continuous exposure to ultraviolet radiation from sunlight, which degrades most polymers and coatings. If the cooling panel’s optical properties change over time due to UV damage, the cooling performance degrades. Creating a material with both the right spectral properties for effective radiative cooling and sufficient UV resistance to last for years in outdoor conditions is the core engineering problem.

What This Invention Does

The patent describes a cooling material with a two-layer architecture. The first layer is a thermally emissive layer with an average thermal emissivity greater than 0.85 in the spectral range of 5 micrometres to 15 micrometres – the range that includes the 8-13 micrometre atmospheric window through which thermal radiation escapes to space. This layer is responsible for the radiative cooling effect.

The second layer contains a plurality of particles configured for reflecting ultraviolet radiation. By positioning a UV-reflective particle layer to protect the thermally emissive layer from solar UV, the material maintains its optical properties over extended outdoor exposure without degrading.

In practice, the material is capable of reflecting greater than 93% of the weighted solar spectrum from 300 nm to 4 micrometres (preventing solar heating), while simultaneously emitting thermally in the 7-15 micrometre range (enabling radiative cooling). This dual spectral performance allows the material to achieve net cooling of at least 10 W/m2 at 300 K ambient air temperature, even during daytime exposure.

The cooling material is described for use as a panel affixed to building roofs, connected via a heat exchanger and pump to the building’s cooling load, effectively pre-cooling a fluid (such as water or refrigerant) before it enters a conventional air conditioning or refrigeration system. Applications also include vehicles, greenhouses, electrical cabinets, containerised living units, vending machines, and swimming pools.

Key Features

UV-protective particle layer. A second layer containing UV-reflecting particles (including ZnO, Si, HfO2, or ZnO2) shields the thermally emissive layer from solar UV radiation that would otherwise degrade the material’s long-term performance.

High thermal emissivity in the atmospheric window. The thermally emissive layer achieves average emissivity greater than 0.85 across the 5-15 micrometre range, ensuring strong radiative heat rejection through the atmospheric transparency window.

Solar reflectance above 93%. The material reflects more than 93% of the solar spectrum from 300 nm to 4 micrometres, preventing solar heat gain that would negate the radiative cooling effect during daytime operation.

10 W/m2 net cooling capacity. The system is capable of achieving a net cooling rate greater than 10 W/m2 at ambient conditions, sufficient to provide meaningful pre-cooling contributions to building HVAC systems.

Fluid loop integration. Cooling panels are configured with heat exchangers and pumps to transfer heat from a building or refrigeration system fluid to the radiative cooling surface, enabling integration with existing HVAC infrastructure.

Colour-capable design. By absorbing selected portions of the visible spectrum (400-900 nm), the material can display a visual colour while retaining its solar reflective and thermal emissive properties – an important aesthetic consideration for building rooftop installations.

Who Is Behind It?

The applicant is SkyCool Systems, Inc. of the United States. The named inventors are Aaswath Raman, Eli A. Goldstein, and Shanhui Fan – researchers who pioneered radiative cooling technology at Stanford University. This divisional was filed on 26 February 2026, derived from parent application AU 2020257428. Spruson and Ferguson in Sydney are the Australian patent attorneys.

Why It Matters

Global cooling demand is projected to triple by 2050, driven by economic development in hot climates and worsening heat stress from climate change. Conventional vapour-compression air conditioning accounts for roughly 10% of global electricity consumption and is a significant contributor to peak electrical grid loads on hot days. A passive radiative cooling technology that reduces the heat load on conventional air conditioning systems – or provides supplemental cooling with no electricity consumption – addresses both the energy cost and the grid reliability problems associated with cooling.

By combining effective radiative cooling performance with sufficient UV durability for multi-year outdoor deployment, the material described in this patent bridges the gap between laboratory demonstrations and commercially viable cooling products. Integration with standard fluid-loop heat exchange systems makes it compatible with existing building infrastructure without requiring wholesale replacement of HVAC equipment.

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AU 2026201465 was published in the Australian Official Journal of Patents on 19 March 2026 and is open for public inspection. Patent applications represent inventions that are sought to be protected and do not necessarily reflect commercially available products.

Related Concepts

Radiative cooling exploits the atmospheric transparency window in the 8–13 micrometre infrared range, through which surfaces on Earth can shed heat directly to the cold of outer space. Unlike conventional vapour-compression cooling, the cooling effect requires no electricity. Engineered materials combining high infrared emissivity with strong solar reflectance can achieve net sub-ambient cooling even in direct sunlight, offering a passive approach to reducing building energy demand and mitigating urban heat island effects.