Passive radiative cooling provides an energy-saving method for heat management in buildings. Solar reflective paints are versatile and scalable formats that can be readily applied for this cooling technology. We investigate solar reflective paints consisting of hollow silica (SiO2) and hollow titanium dioxide (TiO2) microparticles as pigments and methyltrimethoxysilane as a binder. The hollow microparticles are synthesized via sol-gel and etching methods to control their diameter. Paint formulation is optimized for high total solar reflectance, measured by a UV-visible-near infrared photospectrometer, without exceeding the critical particle volume content. By introducing air volume into the particles and selecting optimal particle size, solar reflectance of the dry paints is significantly improved. Compared to TiO2 microparticle samples, paints with hollow SiO2 microparticles are more effective at rejecting solar irradiation on average while also requiring less particle volume content. Thermal and spectral emissivity measurement also indicates that the hollow SiO2 microparticle paint has the highest broadband infrared emission, followed by a commercial paint and a TiO2 sample. Outdoor experiment in a tropical climate demonstrates that the paint with hollow SiO2 microparticles has better cooling performance than a commercial cooling paint product. The results suggest the potential of hollow SiO2 microparticles for improving radiative cooling paints.

中文翻译：

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中空二氧化硅和二氧化钛微粒在太阳能反射涂料中的使用，用于热带地区的日间辐射冷却应用

被动辐射冷却为建筑物的热量管理提供了一种节能方法。太阳光反射涂料是通用且可扩展的格式，可以很容易地应用于这种冷却技术。我们研究了由中空二氧化硅（SiO2）和中空二氧化钛（TiO2）微粒作为颜料以及甲基三甲氧基硅烷作为粘合剂组成的太阳光反射涂料。中空微粒通过溶胶-凝胶和蚀刻方法合成以控制其直径。涂料配方经过优化，可通过紫外可见近红外分光光度计测得的高总太阳反射率，而不会超出临界颗粒体积含量。通过将空气量引入颗粒中并选择最佳颗粒尺寸，可大大改善干漆的太阳光反射率。与TiO2微粒样品相比，具有中空SiO2微粒的油漆在平均拒绝日光照射方面更有效，同时还需要较少的颗粒体积含量。热和光谱发射率测量还表明，中空的SiO2微粒涂料具有最高的宽带红外发射，其次是商业涂料和TiO2样品。在热带气候下的户外实验表明，具有空心SiO2微粒的涂料具有比商业冷却涂料产品更好的冷却性能。结果表明中空SiO2微粒具有改善辐射冷却涂料的潜力。热和光谱发射率测量还表明，中空的SiO2微粒涂料具有最高的宽带红外发射，其次是商业涂料和TiO2样品。在热带气候下的户外实验表明，具有空心SiO2微粒的涂料具有比商业冷却涂料产品更好的冷却性能。结果表明中空SiO2微粒具有改善辐射冷却涂料的潜力。热和光谱发射率测量还表明，中空的SiO2微粒涂料具有最高的宽带红外发射，其次是商业涂料和TiO2样品。在热带气候下的户外实验表明，具有空心SiO2微粒的涂料具有比商业冷却涂料产品更好的冷却性能。结果表明中空SiO2微粒具有改善辐射冷却涂料的潜力。