Infrared-Transparent Aerogel Enhances Subambient Passive Cooling by 5.2°C
Researchers at the City University of Hong Kong have engineered a white infrared-transparent aerogel that improves the efficiency of passive cooling systems. According to TechXplore Engineering, the material decouples solar reflection from thermal insulation, allowing buildings to achieve significant temperature reductions below the ambient environment without consuming electricity or emitting greenhouse gases.
Context from Industry Pulse
The development of the white infrared-transparent aerogel by the City University of Hong Kong team addresses the thermal efficiency gap in passive cooling. By using ultra-high-molecular-weight polyethylene, the researchers solved structural stability issues common in porous cooling materials. Their multiscale optical-thermal model allows for precise performance predictions based on material thickness and local weather, bridging the gap between lab-scale material science and building-scale energy applications. The technology’s success in both humid Hong Kong and arid Abu Dhabi suggests a versatile solution for urban heat islands. Furthermore, the inclusion of fire resistance and aesthetic color options targets practical barriers to adopting sustainable building materials in residential construction.
"This research presents a highly efficient radiative cooling material, as well as a prediction framework from material design to building energy efficiency."
Engineers led by Professor Edwin Tso Chi-yan developed a white infrared-transparent aerogel to address a critical limitation in current subambient daytime radiative cooling technology. Standard cooling materials often struggle with parasitic heat gain because they rely on a single surface to reflect sunlight and emit heat. As TechXplore Engineering reports, this new aerogel separates these functions to achieve deeper cooling levels.
The team utilized ultra-high-molecular-weight polyethylene as a substrate for the aerogel. This specific material choice provides a higher entanglement density than standard high-density polyethylene, which helps the aerogel maintain a stable three-dimensional porous structure. The resulting material achieves an atmospheric-window transmittance of 94.5% and a solar reflectance of 96.6% through a simplified one-step solvent-exchange process.
Field tests conducted in diverse climates demonstrated the practical benefits of the technology. In Hong Kong, applying the aerogel over existing radiative cooling coatings resulted in an additional temperature drop of 5.2°C. Testing in the arid environment of Abu Dhabi showed that the aerogel-enhanced roofs could reduce annual apartment building energy consumption by 14.6 GJ, representing a 55% improvement over standard radiative cooling savings.
Durability tests suggest the material is suited for long-term outdoor use. TechXplore Engineering notes that the aerogel maintained its optical properties after 75 days of accelerated ultraviolet exposure, simulating two years of natural sunlight. The material also features hydrophobic properties for self-cleaning and demonstrated superior fire resistance compared to existing organic cooling materials. The researchers even produced colored variants in red, yellow, and blue to meet different architectural aesthetic requirements.
The Industry Pulse Bottom Line
This new aerogel offers a scalable, electricity-free method to boost building cooling performance by over 5°C, potentially reducing annual HVAC energy demands by 55% through superior solar decoupling.