Enhanced solar spectral reflectance of thermal coatings through inorganic additives

Space cooling of buildings is responsible for a substantial portion of energy consumption and greenhouse gas emission. In order to reduce the building energy consumption, reflective coatings have been adopted extensively since they can effectively minimize undesirable solar energy absorption. In this paper, functional additives (i.e. titanium dioxide and hollow glass beads) are used to improve the reflective and insulation properties of thermal coating materials. The thermal impact upon the application of different reflective coatings on concrete panels is experimentally examined. The experimental results have shown that the coating containing titanium dioxide and hollow glass beads leads to a drop in interior surface temperature, up to 3.5 °C, implying that such coating can effectively reduce heat absorption and cooling load for buildings. The finite-difference time-domain simulation (FDTD) which can simulate the propagation of electromagnetic waves is used here to investigate the reflection of electromagnetic waves and to explore the working principles of additives. The numerical simulations demonstrate the reflective behavior in the coating material, showing that embedded TiO₂ nanoparticles can significantly improve the reflective performance of coating films. It is envisioned that a nontoxic coating with high level of reflectance and insulation can be characterized and the working principles of different additives can be revealed.