Development of flexible radiative cooling film and its application system analysis

Abstract

In this dissertation, radiative cooling(RC) film development and performance analysis are conducted. Radiative cooling is one of the next-generation cooling technologies that has the advantage of creating a cold surface without power consumption and can effectively respond to the increasing cooling demand. In order to realize radiative cooling technology, it is necessary to implement wavelength-selective optical properties. That is, it is essential to maximize the reflection in the solar spectrum (i.e., 0.3-2.5 um) and the emissivity in the atmospheric transmission window (i.e., 8-13 um). The existing inorganic multilayer structures use a silver(Ag) reflective layer to reflect sunlight, which is not only an expensive but also has low scalability issue. In the case of the previous radiative cooling materials based on particle dispersion showed advantageous in scalability, however, detachment or cracks are frequently occurred due to the hardness or stiffness of the base material, leading to performance degradation. In order to overcome these weaknesses, it is intended to derive a structure with polymer-based base material with high concentration of micro-nano size particles, having flexible and high durability features. We developed a process using a low-viscosity intermediate solvent in order to create a high-performance flexible radiative cooling material. Using the method, we fabricated several RC film and measure its optical properties. We showed that deriving the optimal structure of a particle-dispersed polymer by changing the particle type, particle size, and film thickness is important. In addition, the RC film structure was optimized using a genetic algorithm based on Mie scattering. The ideal configuration of multi-particles, such as particle size and volume fraction, is determined by optimization. In addition, an outdoor test apparatus, which simulates buildings, was developed, and the energy-saving benefit of radiative cooling was experimentally demonstrated. Last but not least, the application systems of radiative cooling film were proposed and studied. Through system-level analysis, the amount of energy savings in the building and the increase in the efficiency of photovoltaic power generation were determined.