INV-21040
Compressor-based cooling systems that provide comfortable interior environments for infrastructure, accounts for about 20% of the total electricity consumption around the world. The resultant heating effects and greenhouse gas emissions accelerate global warming and climate change.
Emerging passive radiative cooling (PRC) techniques are a solution that can achieve sub-ambient cooling effects under direct sunlight without any energy consumption. This would simultaneously reflect sunlight and radiate excessive heat as infrared thermal radiation to outer space through the Earth’s atmospheric window. However, for practical applications, state-of-the-art PRC materials face challenges such as complicated and expensive fabrication approaches and performance degradation arising from surface contamination.
This invention addresses critical global and the United States market needs for green energy techniques and sustainable, recycling approaches for interior energy usage. Northeastern University inventors designed, fabricated, and demonstrated the self-cooling and self-cleaning capabilities of recyclable, scalable-manufactured PTFE-microparticle coated cellulose-fiber composites, named “Cooling Papers”.
Cooling Papers are functional composites that are an attractive candidate for improving energy efficiencies because they eliminate the need for coolants, electricity, and compressor required by traditional mechanical cooling systems. In addition, the novel recipe of Cooling Papers enables an ease of manufacturing, installing, wrapping, coating, peeling, and recycling. This reduces the costs of large-scale manufacturing. The self-cleaning and anti-scratch properties of Cooling Papers is designed to provide labor-free maintenance and extends the products’ life under environmental conditions including relative humidity, UV exposure, and temperature range from -30°C to 80°C for operation.
Through a four-season outdoor test, Cooling Papers provides radiative cooling performance, strong mechanical strength, anti-fatigue, and anti-scratch properties. The passive cooling effect is better than that of the commonly used building materials such as brick, wood, and concrete. Cooling Papers can scatters sunlight with a high reflectance of about 0.96 meanwhile, exhibiting an infrared emissivity of 0.92. The PTFE based super-hydrophobic coating protects Cooling Papers from water wetting and dust contamination for outdoor applications but also reinforces its solar reflectance.
Recycling of the used material and the use of wood chips contribute to its green energy functionality and sustainability for passive cooling.