A quantitative analysis for radiative cooling of a novel window composed of nanoparticles film in hot seasonal region

Abstract

Spectrally selective design offers a promising strategy to block solar heat gain, further improving windows’ energy efficiency. This study proposes a spectrally selective CWO/PVA nanocomposites for glazing coating. The proposed coating material combining the advantages of visible transparency (T<inf>VIS</inf> = 31.28 %), high NIR blocking (T<inf>NIR</inf> = 0.5 %) and high emissivity (0.92) in atmospheric window (8–13 µm), holds great promise for efficient window applications. To demonstrate the energy-saving ability of the coating material, chamber tests were conducted in Hong Kong, which demonstrated that the coating can decrease the highest indoor temperature at noon by 13.45 ℃. To further evaluate the annual energy-saving performance of the coating material, a transient model was developed, and annual energy-saving simulation was implemented in Hong Kong. Simulation results showed that the proposed CWO glazing can reduce building indoor solar heat gain by 53.6 % and 62.6 % in summer and winter, with annual energy saving of 1763.64 MJ/(m2·year) and annual average SHGC of 0.33. In particular, the coating enhanced the radiative heat dissipation of glazing window which accounts for total solar heat gain by 28 % and 33 % respectively in summer and winter. These results show that the proposed spectrally selective coating has a significant application potential in reducing energy consumption of buildings, especially for hot regions and summer season. Considering the little concentration on enhancing radiative cooling, this paper focus on broad spectral range (0.3–2.5 µm) and find the great benefit of high IR emissivity on energy saving.