Study On Materials And Structures Based On Radiative Cooling Coatings In Buildings

With the development of science and technology and the improvement of human production level,people’s demand for consumption of energy are growing rapidly,and the energy consumption for heating and cooling in buildings accounts for about 15% of the world’s total energy consumption.In views of the current world energy structure,it is not difficult to find that non-renewable energy such as coal,oil and natural gas still dominates.The large consumption of these resources will not only lead to energy crisis,but also bring serious harm to the earth’s environment in the future.Therefore,energy conservation and emission reduction has become one of the most effective ways to alleviate the above difficulties.Radiation cooling,a passive cooling method,which can emit the heat of the earth surface objects through the atmosphere window into the cold outer space without energy input,attracts more and more researchers’ attention.In this paper,we propose to prepare low-cost and high-efficiency coating for building refrigeration above ambient temperature by adding particles to polymer(APTP)system.In this study,polydimethylsiloxane(PDMS)was selected as the ideal medium for the study because of its stable chemical properties and high selective emissivity in the atmospheric window band.For the scattering particles,we studied three kinds of metal oxides: Zn O,Ti O2 and Zr O2.Through comparison,Zr O2 was selected as the final target material,and the research was carried out from two aspects.For the theory part of the APTP system,we utilize Mie theory combined with Monte Carlo simulation to analyze Zr O2,Ti O2 and Zn O particles,optimize the particle size,volume fraction and film thickness,and obtain the optimal structure.The results show that the Zr O2 / PDMS coating with particle size of 500 nm,volume fraction of 10% and film thickness of 500μm has the best radiative cooling performance,which can achieve a theoretical temperature drop of 5K lower than the ambient temperature.According to the above calculation results,we have carried out the corresponding experimental preparation and performance characterizations.Through the optical properties test,the Zr O2/PDMS samples show 93.55%(300-1350nm)and 92.25%(3-25 μ m)reflectivity and emissivity.The Zr O2/PDMS samples and commercial white paint were tested outdoors for three days.The results show that the samples can achieve sub-environment temperature drop in the whole day.The maximum average temperature drop during the day is 9.8K,which is 4.4K lower than that of commercial white paint,and the average temperature drop at night is 2.9K.Finally,we established the House Model to verify the actual performance.Compared with commercial white paint,the average temperature drop of 4.2K is obtained for the prepared samples.In conclusion,the APTP film was successfully obtained by calculation and experimental characterizations.The radiative cooling performance of the Zr O2/PDMS coating was verified by the House Model.This work provides reference for the future application of radiative cooling in buildings.