Materials for radiative cooling: a review

Abstract

Buildings use more than one-third of the total energy consumed in counties within the Mediterranean climate zones like in Turkey. During the summer months, the absorption of solar energy by the buildings increases the required cooling load significantly. One unconventional solution to this problem is the radiative cooling of the building surfaces and façades. If a surface benefits from daytime radiative cooling, its equilibrium temperature will be lower. This can be achieved only if 88% of solar radiation within the visible and near-infrared spectrum is reflected. For this purpose, paints and coatings may have an obvious advantage because of their low cost, simplicity and ease of application;however, strong solar reflectors may significantly mutate the color. On the other hand, the use of spectrally selective surfaces isof great value in practical applications such as collection of solar energy and spacecraft temperature control. In addition, the development of novel nano-patterning techniques and new designer materials for various applications are likely to surface. These developments may help to develop a wider data base for spectral and directional radiative properties of different materials. This review is to provide an overview of mainstream and such as cermets, paints and coatings, and metal oxides that can be used for radiative cooling of buildings. Also, a summary is provided for the theories, fabrication methods, usual design and possible future research opportunities to optimize these materials for spectral selectivity for specific applications.