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Herein, thermochromic superhydrophobic coatings (TSCs) with different colors are prepared, and their surface wettabilities and optical properties are studied. The TSC coating maintains its surface superhydrophobicity even after a series of mechanical damage (sandpaper abrasion, gravel impact, and knife scratching), chemical corrosion, ultraviolet aging, and environmental temperature changes. Contaminants on the surface of the coating sre easily washed by water droplets. The TSC has a reversible color function with a critical discoloration temperature (Tc) approximately in the range 28–31 °C. In winter, the ambient temperature (Ta) is lower than Tc, and the TSC is dark and absorbs more solar energy. Although in summer, Ta > Ta, the TSC is light and reflects more solar energy. The sunlight exposure test shows that the surface temperature of the thermochromic pigment/polydimethylsiloxane (TP/PDMS) coating in winter is only 0.9 °C lower than that of the carbon black/PDMS (CB/PDMS) coating, whereas in summer, the surface temperature of the TP/PDMS coating is only 6.2 °C higher than that of TiO2/PDMS coating. Energy consumption simulation results show that the TP/PDMS coating decreases the total annual energy consumption in North China by 13.74% compared with the traditional white cooling coating. [ABSTRACT FROM AUTHOR]

Passive daytime radiative cooling (PDRC) coatings for building exteriors are important for building energy efficiency. The development of inexpensive and environmentally friendly radiative cooling (RC) coatings with high adhesion, waterproofing and UV-ageing resistance for building facades remains a highly challenging task. In this work, kaolin/polyacrylate (K/P) paints with excellent overall performance were prepared by spraying method using green waterborne acrylate as binder, cheap and easily available K as filler, and polymethylhydrosiloxane (PMHS) as hydrophobic modifier. The K/P coating has excellent optical properties with a solar reflectivity (SR) of 86.6% and an infrared thermal emissivity (ITE) of 96.8%. RC temperatures of 13.2 °C (under shielded condition) and 3.1 °C (under open condition) were achieved under direct outdoor daylight with an average irradiance of 778 W/m2. In addition, building energy simulations show that the K/P coating improves heating energy consumption while reducing building cooling energy consumption. However, for most cities in China, the energy savings of the K/P coating on annual building energy consumption is still as high as 6.6%. In particular, the K/P paint used as an exterior wall coating has high adhesion, excellent water resistance, and strong UV ageing resistance, and its optical properties (solar reflectance and infrared thermal emittance) remain unchanged after 10 accelerated ageing cycles. Therefore, the K/P coatings have excellent comprehensive performance and have a wide range of application prospects in the field of green and energy-saving buildings. [Display omitted] • The kaolin/polyacrylate (K/P) coatings can be produced on a large scale. • The K/P coating uses water as a solvent and do not pollute the environment. • The K/P coating achieved a sub-ambient temperature drop of 13.2 °C under direct sunlight. • The K/P coating exhibits high adhesion strength, excellent water resistance and strong ageing resistance. • Building energy consumption simulation shows that the CK/P coating can save about 6.6% of energy. [ABSTRACT FROM AUTHOR]

Passive daytime radiative cooling (PDRC) is a cooling technology with no energy consumption and no pollution generation. It emits self-generated heat to outer space using thermal radiation, thus reducing its temperature. Radiative cooling technology aims to the energy consumption problem of buildings and environmental pollution caused by the use of Freon in compressor air conditioners. Many kinds of radiative cooling coatings have been attempted, but the cost and large-scale practical application have been challenging. This work prepared a composite coating with a radiative cooling function using calcined kaolin (CK) powder and waterborne fluorocarbon (WF). The inexpensive CK has a wide particle size distribution and exhibits high solar reflectivity (RS) and infrared emissivity (EIR). The excellent adhesion and chemical stability of waterborne fluorocarbon (WF) provides a good guarantee for the practical use of the coating. As a result, the CK/WF coating achieves an RS of 91% and an EIR of 95% in the transparent atmospheric window (ATW) of 8–13 µm. The coating demonstrated a temperature decline of 3.8 °C under direct sunlight in the field. The coating meets the conditions for large-scale applications. When used as a roofing material for simulation, it can save up to 30% of energy consumption throughout the year. Overall, the CK/WF coating has outstanding energy saving and pollution reduction performance, which will further advance the radiant cooling material into real-world applications. [Display omitted] • The RS and EIR of Calcined kaolin/ water-based fluoro olefin vinyl ether copolymer (CK/WF) coating reached 91% and 95%. • The low powder content of the CK/WF coating provides high adhesion force. • Cheap CK powder provides a new idea to reduce the cost of radiation-cooling coating. • Under direct sunlight, the CK/WF coating can achieve a cooling effect of − 3.8 °C. • EnergyPlus simulations show that the coating could save 10% of energy consumption in most areas of China. [ABSTRACT FROM AUTHOR]