Chromaticity and optical properties of colored and black solar–thermal absorbing coatings

Two important trends in solar–thermal utilization in buildings are building integration and color appearance. Coatings based on titanium alloy nitride show variety of different colors. These can be controlled by film thickness for a single layer stack, or by putting another layer on top of the first layer. Strong absorption around 500 nm is important to cause color appearance. Chromaticity and optical properties of colored coatings were studied and compared to black coatings. In the three-point gamut system, such colors show an additive mixture property. Solar absorptance of 0.80–0.95 can be obtained with thermal emittance of 0.04–0.09 (100 °C). These coatings provide a choice for solar–thermal integration in buildings where appearance is an important feature.