Transparent Polymer Coatings for Energy-Efficient Daytime Windows Cooling

Abstract

Sunlight management of transparent windows is important for buildings or vehicle cooling. Functional layers that block near-infrared solar radiation also absorb sunlight and aggravate the interior heat loads. Here, we introduce a daytime radiative cooling strategy that promotes window cooling without affecting the aesthetics or functionalities. This strategy relies on selecting suitable bond vibrations using the typical transparent silicone polydimethylsiloxane (PDMS). The PDMS coating with solar absorption of 0.004 and infrared emissivity of 0.93 across the atmospheric window, achieves a record theoretical cooling power of 103 W/m2. Outdoor experiments show the temperature drop can reach 8.7 °C for a PDMS-coated near-infrared reflective glass. Model evaluation of the annual cooling energy consumption in 12 cities worldwide shows that the PDMS-coated window can save energy between 0.62 and 30.52 kWh/m2, which is most prominent in warm cities. This window cooling strategy provide a different path to simultaneously optimize the daylighting and thermal management of buildings.