Efficient Passive Cooling Over a Novel Bifunctional Polymer Bilayer Composite Simultaneously Possessing Radiative and Evaporative Cooling Properties
Qingxi Xin, Benchi Ma, J.-P. Le Ru, Yu Zhou, Dengwei Jing
Abstract
Abstract Passive cooling technologies being free from additional energy consumption, offer significant advantages in reducing carbon emissions and mitigating global warming. However, radiative cooling has a thermodynamic limit, and evaporative cooling requires additional components, which restricts their large‐scale application, respectively. Herein, a radiative/evaporative bifunctional cooling bilayer is presented, featuring an upper layer composed of poly(vinylidene fluoride‐cohexafluoropropene) [P(VdF‐HFP)] integrated with a hygroscopic hydrogel lower layer [polyacrylamide (PAAm)/alginate‐CaCl 2 ]. High solar reflectance (0.916) and long‐wave infrared emittance (0.900) of the P(VdF‐HFP) combined with hydrogel evaporation enable a notable 15.4 °C temperature drop under 706.3 W·m −2 solar radiation. The bilayer is demonstrated to be effective under outdoor conditions for continuous three cloudy days, achieving an average temperature reduction ranging from 6.3 to 15.7 °C. Considering the low cost and simplicity of the preparation method, ease of large‐scale fabrication, and good cooling performance, this bilayer structure provides a promising strategy for the application of passive cooling.