Design,fabrication and energy-saving evaluation of five-layer structure based transparent heat mirror coatings for windows application

Transparent heat mirror which allows the transmission of visible sunlight while reflects the infrared thermal energy is an effective building energy efficiency technology for hot climatic regions.In this work,a five-layer dielectric/metal/dielectric/metal/dielectric(DMDMD)coating of Si_(3)N_(4)/Ag/Si_(3)N_(4)/Ag/Si_(3)N_(4)structure is proposed.The radiative properties of the five-layer coatings are theoretically investigated by transfer matrix method.The thicknesses of the layers are optimized by using particle swarm optimization method.The sample of the designed Si_(3)N_(4)/Ag/Si_(3)N_(4)/Ag/Si_(3)N_(4)coating is prepared and the building energy performance when applying the DMDMD coating in a simple office room is also investigated,taking the hot weather condition of Guangzhou,China as an example.The simulated results show that the Tave+Rave value of the five-layer coating is 8%higher than that of the three-layer coating,and the long-wave emittance of the five-layer coating is 24.8%lower than that of the three-layer coating.And the application of the five-layer coatings on the glazed window could provide the highest energy saving rate of 8.9%when compared with the traditional low-e coatings.