Research On Broadband Passive Infrared Radiation Cooler Based On Micro-nano Structure Metamaterial

Radiation cooling,as a passive,efficient,and renewable cooling method,has received widespread attention in the field of energy conservation.Historically,radiative cooling has been limited at nighttime because diffusers with intense thermal radiation lack high reflectivity in the solar radiation band.With the development of radiant material technology in recent years,such as the development of photonic radiators and metamaterials,the advantages of the daytime radiant cooling have been fully tested and theoretically verified.This thesis first describes the current status of passive radiant cooling technology,and introduces the materials and advanced structures used in various coolers,and the current research focus in the field of radiant cooling.At the same time,the basic principle of radiant cooling technology is introduced and analyzed in detail,including different mathematical and physical descriptions,which laid a solid theoretical foundation for the design of the cooler.Then we design and numerically simulate a three-dimensional pyramid multilayer ultra-broadband thermal emitter based on all-dielectric materials working at ambient temperature(300 K)for cooling purpose,and finally achieve broadband high radiation in the infrared atmospheric window and extremely low overall solar spectrum absorption.A net cooling power of more than 156 W/m~2 has been obtained under direct sunlight during the day,which has a cooling potential of 42.4°C;while during the nighttime,the net cooling power exceeds 199 W/m~2,which has a cooling potential of 58.5°C.Even under non-radiative heat transfer conditions,ch(28)12 W(m~2K),the cooler can still lower the temperature to 9.6?and 12.3?below ambient temperature during the day and night respectively.The multilayer all-dielectric three-dimensional pyramid structure designed in this thesis not only solves the shortcomings of poor infrared absorption selectivity in planar photonics devices,but also overcomes the shortcomings of metal/dielectric materials with the high absorption of sunlight.The research work in this thesis has further promoted the development of all-dielectric material-based passive radiative cooling.Experimentally,we design and fabricate a polymer metamaterial cooler with a micro-nano structure.Randomized microstructured polymer materials and simple manufacturing methods,better cooling performance can be achieved during the daytime.The polymer cooler proposed in this thesis has flexible characteristics and can be easily combined with common substrate materials,such as silicon wafers or metal reflectors,to achieve outdoor cooling.In addition,the application of this polymer radiation cooler to solar panels can significantly reduce the temperature or required cooling power of solar cells.It provides a better solution for solar cell thermal management.Finally,in the summary section of this thesis,the future of radiative cooling technology is discussed and prospected.The photonic radiant cooler and polymer metamaterial radiant cooler designed in this thesis provides important references for promoting the development of radiant cooling technology and have important energy saving and emission reduction significance.