INNOVATIVE COATINGS FOR EFFICIENT BUILDING THERMAL MANAGEMENT

The first part of this work proposes a solution for the challenge discussed section 1.2.1 by designing and validating a radiative cooling paint that is durable when attached to a substrate, and biodegradable when dispersed into the environment. Said paint also features high solar spectrum reflectivity and high sky window (8-13 microns) emissivity which enables it to achieve sub-ambient surface temperature throughout the day, even under direct sunlight. Full-biodegradation is observed in lab-based biodegradability testing using a comparison test between a biodegradable sample and a non-biodegradable sample.

The second part of this work demonstrates an innovative dual-layer design featuring a thin layer of leuco dye based thermochromic paint applied on top of a thick layer of BaSO4-based ultra-white daytime radiative cooling paint. This design utilizes thermochromism, a temperature-activated reversible chemical reaction that drastically changes the absorptivity of the affected media. In this work, the leuco dye-based thermochromic top layer effectively works as an autonomous thermal switch that, when temperatures are high and cooling is required, it switches to a "colorless state," enabling the radiative cooling basecoat to reflect incoming sunlight and emit radiatively, effectively cooling the surface. Conversely, when temperatures are low and heating is needed, the thermochromic top layer activates and transforms into an absorbing surface. This activation blocks the reflective and emitting bottom layer from radiatively cooling the surface, and instead absorbs incoming radiation to heats up the surface.