Carbonaceous selective absorber for solar thermal energy collection and process for its formation

• US 4,594,995 A
• Filed: 12/10/1984
• Issued: 06/17/1986
• Est. Priority Date: 12/14/1982
• Status: Expired due to Fees

• Current Assignee: John D. Garrison
• Original Assignee: John D. Garrison
• Inventors: Garrison, John D.
• Primary Examiner(s): Jones, Larry
• Application Number:
  US06/680,273
• Time in Patent Office: 554 Days
• Field of Search: 126/417, 126/901, 428/634, 427/160, 427/166, 427/223, 427/224, 427/225, 427/226, 427/227, 427/248.1, 427/251, 427/255
• US Class Current: 126/569
• CPC Class Codes: C23C 28/00 Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D
• CPC Class Codes: F24S 70/225 for spectrally selective absorption
• CPC Class Codes: F24S 70/30 Auxiliary coatings, e.g. anti-reflective coatings
• CPC Class Codes: Y02E 10/40 Solar thermal energy, e.g. solar towers
• CPC Class Codes: Y10S 126/908 Particular chemical

Abstract

A selective absorber consisting of a number of thin layers on a supporting substrate, including (1) a carbonaceous layer, (2) a catalyst layer, and (3) a metallic infrared reflecting layer. The catalyst layer serving to catalyze the pyrolysis of a carbon containing gaseous compound or compounds to form the carbonaceous layer. Methods of production are described.

Claims

1. A method of constructing a solar selective absorber, comprising the steps of:

(a) depositing an infrared reflecting layer on a substrate;

(b) depositing a catalyst layer on said infrared reflecting layer; and

(c) depositing a carbonaceous layer on said catalyst layer by exposing said catalyst layer to a carbon containing gas compound at temperatures in the range of from 250°

to 550°

C.

2. The method recited in claim 1, wherein said infrared reflecting layer is a metal selected from the group consisting of copper, silver and aluminum.

3. The method recited in claim 1, wherein said catalyst layer is a metal selected from the group consisting of nickel, cobalt, copper, palladium and platinum.

4. The method of claim 1, wherein said substrate is a material selected from the group consisting of metal, glass and ceramic.

5. The method of claim 1, wherein said carbon containing gas is a gas selected from the group consisting of acetylene, ethylene, Mapp gas, butane and propane.

6. The method of claim 1, wherein the depositing of said catalyst layer comprising electroplating, using solutions having a metal salt concentration in the range of 3 to 350 grams per liter.

7. The method of claim 6, wherein the plating solution temperature is in the range of 0°

to 100°

C., and the plating current density is in the range of 0.50 to 10 milliamperes per square centimeter.

8. The method of claim 1, wherein said substrate is glass.

9. A method of constructing a solar selective absorber, comprising the steps of:

(a) depositing a catalyst layer on an infrared reflecting substrate; and

(b) depositing a carbonaceous layer on said catalyst layer by exposing said catalyst layer to a carbon containing gas compound at temperatures in the range of from 250°

to 500°

C.

10. The method recited in claim 9, wherein said catalyst layer is a metal selected from the group consisting of nickel, cobalt, copper, palladium and platinum.

11. The method of claim 9, wherein said carbon containing gas is a hydrocarbon.

12. The method of claim 9, wherein said carbon containing gas is selected from the group consisting of acetylene, ethylene, Mapp gas, butane and propane.

13. A solar selective absorber of the type having a normal solar air-mass-two absorptance of greater than about 0.75 and hemispherical emittance at 100°

C. of less than about 0.25 for selectively absorbing solar radiation in the range of about 0.3 to 2.0 microns while substantially reflecting infrared radiation and thus having low infrared emittance so that the heat loss after collection is minimized, comprising;

(a) a substrate;

(b) an infrared reflecting layer deposited on said substrate, said infrared reflecting layer having sufficient thickness to substantially prevent the transmission of light having wavelengths greater than 0.4 microns, and having a reflectance greater than 90 percent for infrared wavelengths greater than 1.0 micron;

(c) a catalyst layer deposited on said infrared reflecting layer said catalyst layer having a thickness of the order of 0.01 to 0.1 micron, and being a metal selected from the group consisting of group VIII metals and copper, for catalyzing the formation of carbon; and

(d) a carbonaceous layer pyrolytically deposited on said catalyst layer, said carbonaceous layer having a thickness of the order of 0.01 to 0.10 microns.

14. An improved solar selective absorber of the type in which

a thin absorptive layer, for absorbing solar radiation, is deposited on a base structure which includes a substrate for structural length and means for infrared reflectance,

wherein the improvement comprises

the upper surface of said base structure including a means for catalyzing the pyrolytic decomposition of a carbon containing gas, and a carbonaceous layer catalytically deposited thereon to serve as the thin absorptive layer for absorbing solar radiation,

said improved selective absorber having a solar air-mass-two absorptance of greater than about 0.75 and a hemispherical emittance at 100°

C. of less than about 0.25 for selectively absorbing solar radiation in the wavelength range of about 0.3 to 2.0 microns while substantially reflecting infrared radiation of wavelengths greater than about 2.0 microns and thus having low infrared emittance so that the heat loss after collection is reduced.

15. The invention of claim 14, wherein said carbon containing gas is a hydrocarbon.

16. The invention of claim 14, wherein said carbonaceous layer is formed in a conveyer oven at near atmospheric pressure.

17. The improved solar selective absorber of claim 14, wherein

(a) said infrared reflectance means includes an infrared reflecting layer deposited on said substrate;

(b) said catalyzing means includes a catalyst layer deposited on said infrared reflecting layer; and

(c) said carbonaceous layer is deposited on said catalyst layer.

18. The improved solar selective absorber of claim 14, wherein

(a) said infrared reflectance means is provided by said substrate material;

(b) said catalyzing means includes a catalyst layer deposited on said substrate; and

(c) said carbonaceous layer is deposited on said catalyst layer.

19. The improved solar selective absorber of claim 14, wherein

(a) said infrared reflectance means includes an infrared reflecting layer deposited on said substrate;

(b) said catalyzing means are provided by said infrared reflecting layer material; and

(c) said carbonaceous layer is deposited on said infrared reflecting layer.

20. The improved solar selective absorber of claim 14, wherein

(a) said infrared reflectance means and said catalyzing means are provided by said substrate material;

and

(b) said carbonaceous layer is deposited on said substrate.

21. The invention of claim 14, wherein said catalyzing means are provided by a metal selected from the group VIII metals.

22. The invention of claim 14, wherein said catalyzing means are provided by cobalt or nickel.

23. The invention of claim 14, wherein said catalyzing means are provided by copper.

24. The invention of claim 14, wherein said carbon containing gas is acetylene.

25. An improved solar selective absorber of the type having a normal solar air-mass-two absorptance of greater than about 0.75 and a hemispherical emittance at 100°

C. of less than about 0.25 for selectively absorbing solar radiation in the range of about 0.3 to 2.0 microns while substantially reflecting infrared radiation of wavelengths greater than about 2.0 microns and thus having low infrared emittance so that heat loss after collection is reduced, comprising;

(a) an infrared reflecting substrate, said infrared reflecting substrate having sufficient thickness for structural strength and to substantially prevent the transmission of light having wavelengths greater than 0.4 microns, and having a reflectance greater than 90% for infrared wavelengths greater than 1.0 micron;

(b) a catalyst layer deposited on said infrared reflecting substrate, said catalyst layer having a thickness of the order of 0.01 to 0.1 microns, and being of a metal selected from the group consisting of group VIII metals and copper, for catalyzing the formation of carbon; and

(c) a carbonaceous layer pyrolytically deposited on said catalyst layer.

26. An improved solar selective absorber of the type having a normal solar air-mass-two absorptance of greater than about 0.75 and a hemispherical emittance at 100°

C. of less than about 0.25 for selectively absorbing solar radiation in the wavelength range of about 0.3 to 2.0 microns while substantially reflecting infrared radiation of wavelengths greater than 2.0 microns and thus having low infrared emittance so that heat loss after collection is reduced, comprising;

(a) a substrate;

(b) an infrared reflecting catalyst layer deposited on said substrate, said infrared reflecting catalyst layer having sufficient thickness to substantially prevent the transmission of light having wavelengths greater than 0.4 microns, and having a reflectance greater than 90% for wavelengths greater than 1.0 micron, said infrared reflecting catalyst layer being a metal selected from the group consisting of group VIII metals and copper for catalyzing the formation of carbon; and

(c) A carbonaceous layer pyrolytically deposited on said infrared reflecting catalyst layer.

27. An improved solar selective absorber of the type having a normal solar air-mass-two absorptance of greater than about 0.75 and a hemispherical emittance at 100°

C. of less than about 0.25 for selectively absorbing solar radiation of wavelengths in the range of about 0.3 to 2.0 microns while substantially reflecting infrared radiation of wavelengths greater than 2.0 microns and thus having low infrared emittance so that heat loss after collection is reduced, comprising;

(a) an infrared reflecting catalyst substrate, said infrared reflecting catalyst substrate having sufficient thickness for structural strength and to substantially prevent the transmission of light having wavelengths greater than 0.4 microns, and having a reflectance greater than 90% for infrared wavelengths greater than 1.0 micron, said infrared catalyst substrate being a metal selected from the group consisting of group VIII metals and copper, for the formation of carbon; and

(b) a carbonaceous layer pyrolytically deposited on said infrared reflecting catalyst substrate.