干旱区生态环境知识资源中心

Passive radiative cooling dissipates heat from Earth into outer space through the atmospheric transparency window (8-13 mu m). This technique can be useful for applications in passive building cooling, thermal photovoltaic energy conversion, renewable energy harvesting and passive refrigeration in arid regions. Here we propose a novel design of thermal radiative structure based on one-dimensional (1-D) photonic films which reflects 98.28% of solar radiation while emitting remarkably and selectively in the atmospheric transparency window, where the peak emission reaches 99.5%. Samples are characterized experimentally by using a Fourier transform infrared spectrometer and the experimental results match well with the theoretical ones. The structure can theoretically achieve a temperature reduction of about 50.3 degrees C from the ambient air temperature without solar radiation and non-radiative heat transfer. Under dry air conditions and assuming non-radiative heat transfer coefficient hc=6.9 Wm(-2)K(-1), it can theoretically achieve a temperature reduction of about 6 degrees C under direct solar radiation (AM1.5). Without the presence of non-radiative heat transfer, it can cool down 36.3 degrees C below the ambient air temperature at daytime radiative cooling.