Solar collector

• US 4,339,484 A
• Filed: 03/03/1980
• Issued: 07/13/1982
• Est. Priority Date: 05/17/1977
• Status: Expired due to Term

• Current Assignee: University of Sydney
• Original Assignee: University of Sydney
• Inventors: Harding, Geoffrey L.
• Primary Examiner(s): MCCAMISH, MARION E
• Application Number:
  US06/126,918
• Time in Patent Office: 862 Days
• Field of Search: 126/443, 126/442, 126/438, 126/270, 126/271, 126/417, 428/36, 428/432, 428/433, 428/450, 428/469, 428/471, 428/539, 428/913, 428/35
• US Class Current: 428/34.6
• CPC Class Codes: F24S 10/45 the enclosure being cylindrical
• CPC Class Codes: F24S 60/00 Arrangements for storing heat collected by solar heat collectors working fluids forming pools or ponds F24S10/10
• CPC Class Codes: F24S 70/225 for spectrally selective absorption
• CPC Class Codes: F24S 70/25 Coatings made of metallic material
• CPC Class Codes: Y02E 10/44 Heat exchange systems
• CPC Class Codes: Y10S 428/913 Material designed to be responsive to temperature, light, moisture
• CPC Class Codes: Y10T 428/1317 Multilayer [continuous layer]

Abstract

A solar energy collector element which comprises a glass tube which is coated on its exterior surface with a solar selective coating, the coating comprising a metal substrate which has a relatively low infra-red emittance and a composite metal film. The composite metal film comprises a metal-carbide which is deposited on the substrate by a reactive sputtering process.

Claims

1. A solar energy collector element comprising a first glass tube into which a fluid to be heated can be directed, a second glass tube which has an internal diameter which is greater than the external diameter of the first tube and which is located about the first tube, an end-sealed evacuated space defined by the external and internal surfaces respectively of the first and second tubes, and a solar selective surface coating on the external surface of the first tube;

the solar selective surface coating comprising a substrate and a composite metal film, the substrate having a thickness of at least 0.05×

10^-6 m. and being composed of a metal which has a relatively low infra-red emittance, and the composite metal film comprising a metal-carbide which has a thickness between 0.04×

10^-6 m. and 0.20×

10^-6 m. and which is deposited on the substrate by a reactive sputtering process.

2. A solar energy collector element as claimed in claim 1 wherein the metal carbide film has an electrical resistance which is not greater than 100 k Ω

per square.

3. A solar energy collector element as claimed in claim 1 wherein the composite metal film comprises atoms of iron, chromium, nickel and carbon which are deposited to form a film thickness of about 0.10×

10^-6 m.

4. A solar energy collector element as claimed in claim 1 wherein the substrate comprises copper which is deposited on the surface of the first tube by a sputtering process.

5. A solar energy collector element comprising a first glass tube into which a fluid to be heated can be directed, a second glass tube which has an internal diameter which is greater than the external diameter of the first tube and which is located about the first tube, and end-sealed evacuated space defined by the external and internal surfaces respectively of the first and second tubes, and a solar selective surface coating on the external surface of the first tube;

the solar selective surface coating comprising a substrate and a composite metal film, the substrate having a thickness of at least 0.05×

10^-6 m. and being composed of a metal which has a relatively low infra-red emittance, and the composite metal film comprising a metal-carbide which has a thickness of at least 0.04×

10^-6 m. and which is deposited on the substrate by a reactive sputtering process.

6. A solar energy collector element as claimed in claim 5, wherein the metal-carbide film has a thickness of about 0.09×

10^-6 m.

7. A method of making a solar energy collector element and which comprises the steps of:

depositing onto the external surface of a first glass tube to a thickness of not less than 0.05×

10^-6 m. a substrate composed of a metal having a relatively low infra-red emittance,

depositing onto the substrate by a reactive sputtering process a metal-carbide film, the metal-carbide film being deposited to a thickness falling within the range 0.04×

10^-6 m. to 0.20×

10^-6 m,

locating about the first tube a second glass tube which has an internal diameter greater than the external diameter of the first tube,

interconnecting the first and second tubes whereby a space is defined therebetween, and

evacuating the space between the first and second tubes.

8. A method as claimed in claim 7 wherein the composite metal film is deposited as a mixture of iron, chromium, nickel and carbon atoms to a total thickness of about 0.10×

10^-6 m.

9. A method as claimed in claim 7 wherein the substrate is deposited in the form of copper by a sputtering process.

10. A method of making a solar energy collector element and which comprises the steps of:

depositing onto the external surface of a first glass tube to a thickness of not less than 0.05×

10³¹ 6 m. a substrate composed of a metal having a relatively low infra-red emittance,

depositing onto the substrate by a reactive sputtering process a metal-carbide film, the metal-carbide film being deposited to a thickness of at least 0.04×

10^-6 m,

locating about the first tube a second glass tube which has an internal diameter greater than the external diameter of the first tube,

interconnecting the first and second tubes whereby a space is defined therebetween, and

evacuating the space between the first and second tubes.

11. A method as claimed in claim 10, wherein the metal-carbide film is deposited to a thickness of about 0.09×

10^-6 m.