Colored selective absorber coating with excellent durability

The colored solar-thermal collectors can provide advantages of architectural integration over energy performance. The colour appearance of the solar-thermal collectors can be achieved by increasing the number of layers. W/WAlN/WAlON/Al2O3 coating, fabricated by DC and RF magnetron sputtering showed a high solar absorptance of 0.948 and the low thermal emittance of 0.08 with a sky blue color appearance. The tandem absorber exhibited excellent long-term thermal stability at 500 °C in air for 150 h. The absorber deposited on SS substrates showed high solar selectivity (α/ε) of 0.918/0.11, even after heat treatment in air up to 500 °C for 100 h. The selective performance of the coating can be stable more than 25 years. The humidity test confirms the significant moisture resistant of the coating. In summary, the new W/WAlN/WAlON/Al2O3 -based coating with its colourful appearance is appropriate to be used in solar thermal collectors.