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US 5,523,132 AGranted
Thin film solar selective surface coating
AssigneeThe University of Sydney
InventorsQi-Chu Zhang, David Mills, Anthony Monger
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AssigneeThe University of Sydney
InventorsQi-Chu Zhang, David Mills, Anthony Monger
Estimating the term…
Solar energy absorptive coatings that comprise single cermet layers with a homogeneous metal volume fraction exhibit an absorptance of about 0.8, which is not high enough for practical solar applications. To achieve absorptance greater than 0.9, graded composite films have been developed, but they give rise to higher thermal emittance due to the absorption edge not being sharp enough. This leads to increased thermal emittance at high operating temperatures, in the range of 300.degree. C. to 500.degree. C. There is now disclosed a novel solar selective surface coating which is composed of two cermet layers, with different metal volume fractions in each layer. The two cermet layers have different thicknesses, and the layers have thicknesses and volume fractions such that solar radiation is absorbed by internal absorbing and phase cancellation interference, but the cermet layers are substantially transparent in the thermal infrared region.
A solar selective surface coating which comprises a solar energy absorptive cermet coating deposited directly on at least one layer of infrared reflective metal, the absorptive cermet coating comprising at least two layers of cermet, each layer of cermet being substantially homogeneous and having a refractive index which is different from the or each adjacent layer, and each layer of cermet having a thickness which is substantially transparent to infrared radiation and which provides for absorption of solar radiation by internal absorption and phase cancellation interference.
A solar selective surface coating which comprises a solar energy absorptive cermet coating deposited directly on at least one layer of infrared reflective metal, the absorptive cermet coating comprising two layers of cermet, each layer of cermet being substantially homogeneous and having a refractive index which is different from the adjacent layer, and each layer of cermet having a thickness which is substantially transparent to infrared radiation and which provides for absorption of solar radiation by internal absorption and phase cancellation interference.
The surface coating as claimed in 2 wherein the reflective metal layer has a thickness in the range 100 to 400 nm and comprises a metal selected from the group consisting of Au, Cu, Mo, Pt and Ag.
A solar collector element which comprises a tube through which a heat exchange material is passed, a glass envelope surrounding the tube, an evacuated space defined by the tube and the envelope, and a solar selective surface coating deposited on an outer surface of the tube;
A solar selective surface coating which comprises at least one layer of infrared reflective metal, an anti-diffusion layer deposited on the refractive metal layer and a solar energy absorptive cermet coating deposited directly on the anti-diffusion layer, whereby the anti-diffusion layer is positioned between the refractive metal layer and the absorptive cermet coating, the absorptive cermet coating comprising two layers of cermet, each layer of cermet being substantially homogenous and having a refractive index which is different from the adjacent layer, and each layer of cermet having a thickness which is substantially transparent to infrared radiation and which provides for absorption of solar radiation by internal absorption and phase cancellation interference.
Dependencies are inferred from the claim text.