Selective black for absorption of solar energy
First Claim
1. A black particle suitable for absorption of solar energy which comprises a reflective metal particle having an emissivity less than about 0.1 coated with a thin film of a semiconductor material which transmits wavelengths longer than 2 microns and which has an absorptivity of at least about 0.90, and a reflectivity of less than about 0.1.
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Abstract
Improved selective black particles for use in solar receivers are described. The improved selective blacks comprise small particles of a metal having a low emissivity which are coated with a thin layer of an optically dark material having high absorptivity and low reflectivity for solar wavelengths and which is transparent for higher wavelengths in the thermal range. The improved selective black particles can be applied, e.g., as a paint, to any surface suitable for a solar heat receiver.
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Citations
17 Claims
- 1. A black particle suitable for absorption of solar energy which comprises a reflective metal particle having an emissivity less than about 0.1 coated with a thin film of a semiconductor material which transmits wavelengths longer than 2 microns and which has an absorptivity of at least about 0.90, and a reflectivity of less than about 0.1.
- 9. A black surface for absorption of solar energy comprising a substrate coated with black particles in a binder transparent to wavelengths longer than about three microns, said black particle being a reflective metal particle having an emissivity less than about 0.1 covered with a thin film of a semiconductor material which transmits wavelengths longer than 2 microns and which has an absorptivity of at least about 0.90 and a reflectivity of less than about 0.1.
- 13. A paint comprising a solvent, a binder transparent to wavelengths longer than about 3 microns, and a pigment, said pigment being a reflective metal particle having an emissivity less than about 0.1 covered with a thin film of a semiconductor material which transmits wavelengths longer than 2 microns and which has an absorptivity of at least about 0.90 and a reflectivity of less than about 0.1.
Specification