Solar energy absorbing coatings and methods of fabrication
Methods, systems, and devices are disclosed for fabricating and implementing optically absorbing coatings. In one aspect, an optically selective coating includes a substrate formed of a solar energy absorbing material, and a nanostructure material formed over the substrate as a coating capable of absorbing solar energy in a selected spectrum and reflecting the solar energy in another selected spectrum. A concentrating solar power (CSP) system includes heat transfer fluids (HTFs); thermal energy storage system (TES); and solar receivers in communication with HTFs and including a light absorbing coating layer based on cobalt oxide nanoparticles.
1. An optically selective coating, comprising:
a substrate including a solar energy absorbing material; and
a nanostructure material formed over the substrate to absorb solar energy in a selected spectrum and reflect the solar energy in another selected spectrum, wherein the nanostructure material includes a double layer structure, wherein a top layer of the double layer structure includes metal oxide nanoparticles of a first type, and wherein a bottom layer of the double layer structure includes metal oxide nanoparticles of a second type different from the first type, wherein a metal oxide nanoparticle of the first type is CuFeMnO 4 , and wherein a metal oxide nanoparticle of the second type is CuCr 2 O 4 .
2. The coating of claim 1 , wherein the top layer includes metal oxide nanoparticles of the first type embedded in a dielectric matrix material.
3. The coating of claim 2 , wherein the dielectric matrix material includes ceramic, glass, or silica.
4. The coating of claim 1 , wherein the nanostructure material includes nanorods or a core-shell structure coated with nanoparticles.
5. The coating of claim 4 , wherein the core-shell structure includes yttrium oxide (Y 2 O 3 ).
6. The coating of claim 1 , wherein the nanostructure material includes thermally resistant core-shell particles having semiconductor, metal and metal oxide as cores, wherein thermally resistant comprises remaining stable at high temperature operation which is from 400° C. to 750° C.
7. The coating of claim 1 , further comprising:
an antireflection layer disposed over the nanostructure material.
8. The coating of claim 1 , wherein the nanostructure material includes embedded hole patterns or polymer beads.
9. The coating of claim 1 , wherein at least one of the top layer or the bottom layer is a nonporous layer.
10. An optically selective coating, comprising:
a substrate including a solar energy absorbing material; and
a nanostructure material formed over the substrate, wherein the nanostructure material includes a double layer structure, wherein a top layer of the double layer structure includes CuFeMnO 4 nanoparticles embedded in a dielectric matrix material, wherein a bottom layer of the double layer structure includes CuCr 2 O 4 nanoparticles embedded in the dielectric matrix material, and wherein the top layer has a porosity of at least 20%.
11. The coating of claim 10 , further comprising:
an antireflection layer disposed over the nanostructure material.
12. The coating of claim 11 , wherein the antireflection layer includes MgF 2 .
13. The coating of claim 10 , the dielectric matrix material includes ceramic, glass, or silica.
14. The coating of claim 10 , wherein a size of the CuFeMnO 4 nanoparticles and a size of the CuCr 2 O 4 nanoparticles is less than 500 nm (nanometers).