High temperature radiation-selective coating and related apparatus

Abstract

A solar receiver includes a wavelength selective coating comprising a first diffusion barrier layer, a metallic IR reflective layer, a solar absorptive layer, an anti-reflective layer, and/or a hard coat protective layer. Selective absorber coatings, which are characterized by a high solar absorption coefficient and low thermal emission, can be used to convert captured solar radiation into usable heat. In embodiments, more efficient selective coatings are provided that combine relatively high solar absorbance (e.g., greater than about 0.96) with relatively low thermal emittance (e.g., less than about 0.07 at 700° C.), and that are thermally stable above 600° C., for example, in outdoor conditions. The use of such coatings in a solar field may allow for an increase in the operating efficiencies thereof at operating temperatures of about 600° C. or greater.

1 . A solar selective coating for use on a solar central tower, the coating comprising, in sequence:
 a first diffusion barrier layer;   a metallic IR reflective layer;   a solar absorptive layer; and   an anti-reflective layer;   wherein said first diffusion barrier layer comprises at least one diffusion barrier material, and   the solar selective coating has an absorptivity of at least 95% with respect to the AM 1.5 spectrum at long term operating temperatures of at least 600° C.   
     
     
         2 . The solar selective coating of  claim 1 , wherein the solar absorptive layer has a thickness of between approximately 80 nm and 120 nm. 
     
     
         3 . The solar selective coating of  claim 1 , wherein the diffusion barrier material includes at least one selected from SiOx, SiN, TiO 2 , TiOx, a metal/AlOx CERMET and a metal/SiOx CERMET. 
     
     
         4 . The solar selective coating of  claim 1 , further comprising a second diffusion barrier layer adjacent to the first diffusion barrier layer. 
     
     
         5 . The solar selective coating of  claim 4 , wherein one of the first and second diffusion barrier layers includes at least one selected from SiOx, SiN, TiO 2  and TiOx. 
     
     
         6 . The solar selective coating of  claim 5 , wherein the other of the first and second diffusion barrier layers includes at least one selected from a metal/AlOx CERMET and a metal/SiOx CERMET. 
     
     
         7 . The solar selective coating of  claim 1 , further comprising a natural oxide layer of a substrate on which the solar selective coating is disposed. 
     
     
         8 . The solar selective coating of  claim 7 , wherein the substrate includes at least one of a carbon steel, a low alloy steel, a high alloy steel, a stainless steel, and a superalloy. 
     
     
         9 . The solar selective coating of  claim 1 , wherein the IR reflective layer includes at least one of a noble metal and a refractory metal silicide. 
     
     
         10 . The solar selective coating of  claim 1 , wherein the solar absorptive layer is a CERMET layer. 
     
     
         11 . The solar selective coating of  claim 10 , wherein the ceramic portion of the CERMET includes at least one of an aluminum oxide or a silicon oxide and the metal portion of the CERMET includes at least one of Pt, Ni, Pd, W, Cr or Mo. 
     
     
         12 . The solar selective coating of  claim 4 , further comprising a third diffusion barrier layer between the IR reflective layer and the solar absorptive layer. 
     
     
         13 . The solar selective coating of  claim 12 , wherein the third diffusion barrier layer includes at least one selected from SiOx, SiN, TiO 2  and TiOx. 
     
     
         14 . The solar selective coating of  claim 1 , further comprising a hard coat protective layer. 
     
     
         15 . The solar selective coating of  claim 1 , wherein the solar absorptive layer is a thick hard coat protective layer. 
     
     
         16 . The solar selective coating of  claim 1 , wherein the solar absorptive layer has a thickness greater than 120 nm. 
     
     
         17 . A coated metal article for use in a solar central tower, the coated metal article comprising:
 a metal layer comprising carbon steel, low alloy steel, high alloy steel, stainless steel, or a superalloy; and   a solar selective coating provided over a surface of said metal layer, the solar selective coating comprising:
 a first diffusion barrier layer; 
 a metallic IR reflective layer; 
 a solar absorptive layer; 
 an anti-reflective layer; and 
 a hard coat protective layer, 
   wherein said diffusion barrier layer comprises at least one diffusion barrier material, and the solar selective coating has an absorptivity of at least 95% with respect to the AM 1.5 spectrum at long term operating temperatures of at least 600° C.   
     
     
         18 . The coated metal article of  claim 17 , wherein said metal layer forms a conduit and the solar selective coating is provided over an external surface of the conduit. 
     
     
         19 . The coated metal article of  claim 18 , wherein the external surface of the metal layer is a polished surface. 
     
     
         20 . The coated metal article of  claim 17 , wherein the coated metal article comprises a portion of a solar receiver of the solar central tower. 
     
     
         21 . The coated metal article of  claim 17 , wherein the solar selective coating has an emissivity of less than about 0.07 at 700° C. 
     
     
         22 . A solar thermal energy system comprising:
 a coated metal article; and   at least one heliostat that reflects insolation onto the coated metal article,   wherein the coated metal article comprises:
 a metal layer comprising carbon steel, low alloy steel, high alloy steel, stainless steel, or a superalloy; and 
 a solar selective coating provided over a surface of said metal layer, the solar selective coating comprising:
 a first diffusion barrier layer; 
 a metallic IR reflective layer; 
 a solar absorptive layer; 
 an anti-reflective layer; and 
 a hard coat protective layer, 
 
 wherein said diffusion barrier layer comprises at least one diffusion barrier material, and the solar selective coating has an absorptivity of at least 95% with respect to the AM 1.5 spectrum at long term operating temperatures of at least 600° C.