Science Advances · 2019 · 505 citations · 31 references
Natural SciencesMaterials EngineeringMaterials ScienceAir ConditioningHeat TransferPolymer ChemistryHigh-performance PolymersInfrared Optical MaterialsOptical PolymersPassive CoolingSolar RadiationThermal InsulationAir Conditioning EfficiencyAir Conditioning PerformanceHigh-reflectance MaterialsRadiative CoolingRadiative Cooling SurfacesRadiative Properties Of MaterialsThermal Infrared MaterialsThermal Insulation Systems
Recent advances in passive radiative cooling have improved performance, yet daytime demonstrations still fall short of theoretical limits because of high solar absorption and inadequate thermal insulation. The study aims to develop a polyethylene aerogel that can be integrated with existing emitters to mitigate these shortcomings. The authors fabricated a 6‑mm‑thick polyethylene aerogel exhibiting 92.2 % solar‑weighted reflectance, 79.9 % infrared transmittance (8–13 µm), and 28 mW m⁻¹ K⁻¹ thermal conductivity. The experimental setup achieved a daytime cooling power of 96 W m⁻² and a temperature drop of up to 13 °C below ambient, demonstrating that the material could markedly improve passive radiative coolers for air conditioning and portable refrigeration.
Recent progress in passive radiative cooling technologies has substantially improved cooling performance under direct sunlight. Yet, experimental demonstrations of daytime radiative cooling still severely underperform in comparison with the theoretical potential due to considerable solar absorption and poor thermal insulation at the emitter. In this work, we developed polyethylene aerogel (PEA)-a solar-reflecting (92.2% solar weighted reflectance at 6 mm thick), infrared-transparent (79.9% transmittance between 8 and 13 μm at 6 mm thick), and low-thermal-conductivity (kPEA = 28 mW/mK) material that can be integrated with existing emitters to address these challenges. Using an experimental setup that includes the custom-fabricated PEA, we demonstrate a daytime ambient temperature cooling power of 96 W/m2 and passive cooling up to 13°C below ambient temperature around solar noon. This work could greatly improve the performance of existing passive radiative coolers for air conditioning and portable refrigeration applications.
31
Solutions for a cultivated planet
Jonathan A. Foley, Navin Ramankutty, Kate A. Brauman et al. · Nature · 2011 · 8.3K citations · Full text
Passive radiative cooling below ambient air temperature under direct sunlight
Aaswath P. Raman, Marc Abou Anoma, Linxiao Zhu et al. · Nature · 2014 · 3.4K citations
Radiative human body cooling by nanoporous polyethylene textile
Po‐Chun Hsu, Yu Song, Peter B. Catrysse et al. · Science · 2016 · 1.2K citations · Full text