High temperature spectral selective coatings for solar thermal systems by laser sintering

• Laser sintered tungsten spectral selective coating for high temperature application.
• Thermal stability up to 650 °C in air for at least 36 h.
• Application of laser sintered coating for central tower systems.
• High figure of merit for laser sintered coating.
• High solar absorptance ~87% after heat treatment at 650 °C in air for 36 h.

Spectral selective coatings for solar thermal receivers have been fabricated by laser sintering of tungsten micro and nano particles on stainless steel substrate and show solar absorptance of ~90% at room temperature. The coatings remain stable after heat treatment at 650 °C in air for at least 36 h. A high figure of merit of ~50 has been achieved for laser sintered coatings. Two laser scans were performed at different energy densities, one to sinter nanoparticles and other to control surface morphology, so that high solar absorptance and low thermal emittance can be achieved. Laser sintering was carried out under atmospheric pressure that enabled the formation of a protective oxide layer that provided thermal stability to 650 °C. Solar thermal receivers in tower systems operate at high temperatures in air and laser sintering is a promising approach to fabricate spectral selective receiver coatings for this application.