Off-axis cassegrain solar collector

Patent metadata

Field	Value
Publication number	US-9335015-B2
Application number	US-201314373683-A
Country	US
Kind code	B2
Filing date	Jan 18, 2013
Priority date	Jan 23, 2012
Publication date	May 10, 2016
Grant date	May 10, 2016

Abstract

The disclosure generally relates to concentrating daylight collectors and in particular to concentrating daylight collectors useful for interior lighting of a building. The concentrating daylight collectors generally include a cassegrain-type concentrator section that provides for a full-tracking solar collector with one moving part and with a high efficiency of coupling of collected solar irradiation to a stationary duct. In some cases, the disclosed concentrating daylight collectors can be used more conventionally, such as for directing sunlight onto a photovoltaic cell for generation of electrical power, or an absorbing surface for extraction of thermal energy.

First claim

What is claimed is:

1. A solar collector, comprising:
a parabolic reflector having a vertex, a parabolic focal point, and a first axis therebetween; and
a hyperbolic reflector having a first focal point coincident with the parabolic focal point, a second focal point, and a second axis including the first and second focal points;
wherein the first axis can be aligned at an elevation angle and an azimuth angle without movement of the second axis, such that solar radiation incident upon the parabolic reflector and reflecting from the hyperbolic reflector, propagates within an output collimation angle of the second axis,
further comprising an exit aperture disposed in the parabolic reflector, along a line passing through the vertex of the parabolic reflector, wherein the exit aperture comprises a slot that extends to a rim of the parabolic reflector.

2. The solar collector of claim 1 , wherein the hyperbolic reflector is affixed to the parabolic reflector such that the hyperbolic reflector and the first axis collectively rotate around the second axis, as the first axis is aligned to the azimuth angle.

3. The solar collector of claim 1 , wherein the hyperbolic reflector remains stationary as the first axis is aligned to the azimuth angle.

4. The solar collector of claim 1 , wherein the exit aperture comprises a material that is transparent to solar radiation.

5. The solar collector of claim 1 , further comprising a light duct disposed along the second axis and capable of accepting solar radiation propagating within the output collimation angle of the second axis.

6. The solar collector of claim 5 , wherein the light duct is a hollow reflective light duct having an input aperture.

7. The solar collector of claim 5 , wherein the light duct includes an input aperture disposed proximate the second focal point.

8. A solar collector, comprising:
a parabolic reflector having a vertex, a parabolic focal point, and a first axis therebetween;
a hyperbolic reflector having a first focal point coincident with the parabolic focal point, a second focal point, and a second axis including the first and second focal points;
an exit aperture disposed in the parabolic reflector and on a plane defined by the first and second axis; and
a light duct disposed along the second axis;
wherein the first axis can be aligned at an elevation angle and an azimuth angle without movement of the hyperbolic reflector or the light duct,
wherein the exit aperture comprises a slot that extends to a rim of the parabolic reflector.

9. The solar collector of claim 8 , wherein the exit aperture comprises a material that is transparent to solar radiation.

10. The solar collector of claim 8 , wherein the second focal point is proximate an input aperture of the light duct.

11. The solar collector of claim 8 , wherein the second focal point is within the light duct.

12. The solar collector of claim 8 , wherein the light duct extends through the exit aperture.

13. The solar collector of claim 8 , wherein the hyperbolic reflector is affixed to the light duct.

14. The solar collector of claim 8 , wherein the first axis is aligned toward the sun.

15. The solar collector of claim 8 , wherein the light duct comprises a reflective hollow light duct.

16. The solar collector of claim 8 , wherein an input light ray within a first collimation half-angle of the first axis reflects from the parabolic reflector, reflects from the hyperbolic reflector, and is directed into the light duct within a second collimation half-angle of the second axis.

17. A solar collector, comprising:
a parabolic reflector having a vertex, a parabolic focal point, and a first axis therebetween;
a hyperbolic reflector having a first focal point coincident with the parabolic focal point, a second focal point, and a second axis including the first and second focal points;
an exit aperture disposed in the parabolic reflector and on a plane defined by the first and second axis; and
a light duct disposed along the second axis;
wherein the first axis can be aligned at an elevation angle and an azimuth angle, and at least one of the hyperbolic reflector and the light duct rotates around the second axis,
wherein the exit aperture comprises a slot that extends to a rim of the parabolic reflector.

18. The solar collector of claim 17 , wherein the exit aperture comprises a material that is transparent to solar radiation.

19. The solar collector of claim 17 , wherein the second focal point is proximate an input aperture of the light duct.

20. The solar collector of claim 17 , wherein the second focal point is within the light duct.

21. The solar collector of claim 17 , wherein the light duct extends through the exit aperture.

Assignees

• 3M Innovative Properties Co

Inventors

• Freier David G
• Quinn Timothy L
• Corrigan Thomas R
• Trotter Byron E

Classifications

• F24S23/79

  with spaced and opposed interacting reflective surfaces · CPC title

• Y02E10/47

  Mountings or tracking · CPC title

• F24S30/452

  Vertical primary axis · CPC title

• F24S23/12

  Light guides · CPC title

• Y02B10/20

  Solar thermal · CPC title