Solar tracking device

• US 4,324,225 A
• Filed: 03/03/1978
• Issued: 04/13/1982
• Est. Priority Date: 07/11/1975
• Status: Expired due to Term

• Current Assignee: Vulcan Australia Limited
• Original Assignee: Vulcan Australia Limited
• Inventors: Trihey, John M.
• Primary Examiner(s): Jones, Larry
• Application Number:
  US05/883,313
• Time in Patent Office: 1,502 Days
• Field of Search: 126/425, 126/438, 126/439, 126/424, 126/417, 353/3
• US Class Current: 126/581
• CPC Class Codes: F24S 23/70 with reflectors
• CPC Class Codes: F24S 23/745 flexible
• CPC Class Codes: F24S 30/425 Horizontal axis
• CPC Class Codes: G01S 3/7861 Solar tracking systems
• CPC Class Codes: Y02E 10/47 Mountings or tracking

Abstract

Solar energy conversion apparatus comprises a solar energy utilization surface, a reflective solar energy concentrator, a tracking device operable to cause the concentrator to track the sun and thereby concentrate solar energy on the utilization surface, a structure defining a shaded zone between the concentrator and the utilization surface such that solar rays reflected from the concentrator toward the utilization surface do not enter the shaded zone when the concentrator is aligned with the sun, wherein the tracking device includes solar energy sensitive elements located within the shaded zone and producing tracking control signals when struck by solar rays when the concentrator is not aligned with the sun.

Claims

1. Solar tracking apparatus for tracking the sun comprising focusing means having first and second portions on opposite sides of a tracking plane to be directed at the sun, mounting means mounting the focusing means for tracking movements of the sun, drive means including first and second solar radiation sensitive elements movable with said focusing means, said first and second elements being disposed on opposite sides of said tracking plane but on the same sides as said first and second portions of the focusing means respectively, the disposition of the elements relative to the focusing means being such that (a) when the tracking plane is misaligned with the sun in a first sense, the first element receives solar radiation from the first portion of the focusing means and (b) when the focusing means is misaligned with the sun in a second sense opposite to the first sense, the second element receives solar radiation from the second portion of the focusing means, the drive means including actuating means responsive to differential exposure of said elements to solar radiation to control movement of the focusing means in a direction towards realignment of its tracking plane with the sun.

2. Apparatus as claimed in claim 1 wherein the focusing means comprises a reflective parabolic trough.

3. Apparatus as claimed in claim 1 or 2 wherein said first and second elements are elongate and parallel to one another.

4. Apparatus as claimed in claim 1 or claim 2 wherein said first and second portions have first and second focal lines respectively.

5. Apparatus as claimed in claim 4 wherein the said focal planes are parallel and each spaced by a distance d from the tracking plane on opposite sides thereof.

6. Apparatus as claimed in claim 5 wherein said first and second elements are each spaced by said distance d from said tracking plane on opposite sides thereof.

7. Apparatus as claimed in claim 5 wherein the mounting means mounts the focusing means for rotation about a rotation axis which is parallel to, between and equidistant from the first and second focal lines.

8. Apparatus as claimed in claim 4 wherein said elements comprise metallic members which are generally parallel to the said focal lines when the trough is viewed in plan but extend diagonally relative to said focal lines when viewed in side elevation.

9. Apparatus as claimed in claim 8 wherein the drive means includes a body which is mounted for rotation relative to the trough about a second axis which intersects and is perpendicular to said focal lines, one end of each of said members being coupled to said body at points on opposite sides of said second axis whereby expansion of one or other of the rods causes rotation of the body about said second axis.

10. Apparatus as claimed in claim 9 wherein said parabolic portions are formed as a single trough which is carried by a trough support structure mounted for rotation about said rotation axis in a framework, said drive means including a drum fixedly carried by the framework, an arm extending from said body and a line extending from the arm about said drum whereby rotation of said body causes relative movement between the line and the drum to thus cause rotation of the trough support structure relative to the framework.

11. Apparatus as claimed in claim 10 wherein the arm is generally T-shaped and has one leg extending generally parallel to the rotation axis and a cross-leg generally perpendicular thereto, the ends of said line being connected to ends of said cross-leg and said line convoluting at least once about said drum.

12. Apparatus as claimed in claim 9 wherein the focusing means is carried by a support structure which is mounted for rotation about said rotation axis in a framework, the centre of gravity of the support structure and focusing means being at or near said rotation axis, said body having a weight connected thereto, which, when said body is rotated by expansion of one of said metallic members, causes the support structure and focussing means to become unbalanced and thus rotates under gravity about said rotation axis.

13. Apparatus as claimed in claim 10 wherein the metallic members extend from a point near the surface of the trough and project from the top of the trough when viewed in side elevation, the parts of said rods above said focal lines being thermally shielded.

14. Apparatus as claimed in claim 13 wherein the metallic members have slots at locations adjacent said focal lines, said slots being parallel thereto.

15. Solar energy collecting apparatus comprising tracking apparatus as claimed in claim 11 or claim 13 or claim 14 and energy collecting means located to receive reflected energy at said first and second focal lines.

16. Apparatus as claimed in claim 15 wherein the collecting means comprises a tube through which heat transfer fluid is passed.

17. Apparatus as claimed in claim 16 wherein said tube is stationary relative to the trough.

18. Apparatus as claimed in claim 15 including photo electric elements mounted upon the tube.

19. Solar energy collecting apparatus comprising solar tracking apparatus as claimed in claim 1 and arranged to focus solar energy on energy collecting means, said tracking means being mounted in a housing which is substantially transparent and a plate-type solar energy absorber, located generally beneath said tracking apparatus and within said housing.

20. Apparatus as claimed in claim 19 wherein said energy collecting means comprises a tube for transmitting heat transfer fluid, said absorber being coupled to said tube and acting as a preheater for said heat transfer fluid.

21. Apparatus as claimed in claims 19 or 20 wherein there is provided reflectors for reflecting solar energy towards said absorber.

22. Apparatus as claimed in claim 21 wherein the reflectors are within the housing.

23. Apparatus as claimed in claim 22 wherein the reflectors are coupled to the tracking apparatus and are arranged to be moved thereby.

24. Apparatus as claimed in claim 23 wherein the reflectors are arranged to rotate in the same sense but at approximately half the rate of rotation as the trough.

25. Solar conversion apparatus comprising:

concentrating means, including a reflective surface, for concentrating solar energy onto at least one surface,

tracking means for causing the concentrating means to track the sun,

said tracking means including first and second elongate metallic members which are dispose relative to the concentrating means to receive solar energy from said reflective surface to be differentially heated by solar energy when the concentrating means is misaligned with the sun, the differential heating of said metallic members producing differential thermal linear expansions thereof and drive means for producing tracking movements of said concentrating means in response to said differential linear expansions of said metallic members.

26. Solar conversion apparatus as claimed in claim 25 wherein said elements are shaded from direct incident solar radiation when the concentrating means is correctly aligned with the sun and receive solar energy reflected from the concentrating means when the concentrating means is mis-aligned with the sun.

27. Solar conversion apparatus as claimed in claim 26 wherein the tracking means further includes further a heat or light sensitive element or elements whch are operable to cause rotation of the concentrating means when said concentrating means is grossly mis-aligned with the sun, said further element or elements being arranged to receive and be responsive to direct solar radiation when said concentrating means is grossly misaligned with the sun.

28. Solar conversion apparatus as claimed in claim 26 or 27 wherein said elements extend from said reflective surface to said surface onto which solar energy is concentrated.

29. Solar conversion apparatus as claimed in claim 25 or 26 wherein said reflective surface comprises a trough of generally parabolic configuration.

30. Solar conversion apparatus as claimed in claim 29 wherein said elements extend diagonally from the trough to said surface.

31. Solar conversion apparatus as claimed in claim 30 wherein said trough has first and second parabolic portions which have first and second focal lines which are parallel to one another the first and second portions being operable to concentrate solar energy on first and second surfaces at said first and second lines respectively when the concentrating means is correctly aligned with the sun.

32. Solar conversion apparatus as claimed in claim 31 wherein there are first and second of said diagonally extending metallic elements which extend in first and second planes respectively said first plane including the inner edge of said first parabolic portion and said first focal line and the second plane including the inner edge of the second parabolic portion and said second focal line.

33. Solar converting apparatus as claimed in claim 32 wherein said trough is mounted for rotation about a rotation axis which is parallel to and between said first and second focal lines.

34. Solar converting apparatus as claimed in claim 27 wherein said further heat or light sensitive elements or element comprise an extension of said first or second metallic element, said extension being located generally outside said trough.

35. Apparatus as claimed in claim 25 wherein said members are straight.

36. Apparatus as claimed in claim 25 or 35 including means to maintain said members in tension.

37. Apparatus as claimed in claim 25 or 35 wherein said members are of rectangular cross-section.

38. Solar energy conversion apparatus comprising concentrating means for concentrating solar energy onto a surface and tracking means for effecting tracking movements of the concentrating means wherein the concentrating means has first and second portions operable to concentrate the solar energy into first and second spaced, parallel focal lines which are located on said surface when the concentrating means is correctly aligned with the sun and wherein said tracking means includes first and second solar energy sensitive elements which are so located relative to the first and second portions such that when the concentrating means is misaligned with the sun either (a) solar energy from the first portion is concentrated onto said first element or (b) solar energy from second portion is concentrated onto said second element depending upon the sense of misalignment.

39. Apparatus as claimed in claim 38 wherein said first and second portions of said concentrating means are reflective parabolic portions.

40. Apparatus as claimed in claim 39 or 38 wherein said concentrating means is mounted for rotation about a rotation axis which is parallel to said focal lines and between said focal lines.

41. Apparatus as claimed in claim 39 or 38 wherein said first and second parabolic portions have first and second inner edges which are adjacent and parallel to one another, and wherein said first element is located in a first plane which includes said first edge and said first focal line and said second element is located in a second plane which includes said second edge and said second line.

42. Apparatus as claimed in claim 41 wherein said parabolic portions comprise a single trough structure having a flat region between said first and second inner edges.

43. Apparatus as claimed in claim 41 wherein said first element extends diagonally with respect to said rotation axis from adjacent to said first edge to said first line and said second element extends diagonally with respect to said rotation axis from adjacent to said rotation axis from adjacent to said second edge to said second line.

44. Apparatus as claimed in claim 43 wherein said elements are located side by side.

45. Apparatus as claimed in claim 42 wherein the first and second parabolic portions have first and second upper edges respectively which are located at a level which is between said rotation axis and said lower edges whereby upper portions of one or other of said first and second elements is exposed to direct solar radiation when said concentrating means is grossly misaligned with the sun.

46. Apparatus as claimed in claim 39 wherein said first and second parabolic portions are formed in a single trough and wherein there is a flat between said first and second parabolic portions.

47. Apparatus as claimed in claim 38, 39 or 46 wherein said focal lines are located on the outer surfaces of photovoltaic elements when the concentrating means is correctly aligned with the sun.

48. Apparatus as claimed in claim 47 wherein said photovoltaic elements are arranged in first and second parallel rows each element within said first and second row having its outer face transverse to the mean direction of radiation received from the first and second parabolic portion respectively.

49. Apparatus as claimed in claim 48 wherein said rows of photovoltaic elements are moved in unison with the concentrating means.

50. Apparatus as claimed in claim 49 including a heat transfer conduit in thermal contact with said photovoltaic elements.

51. Apparatus as claimed in claim 50 wherein the heat transfer conduit moves with said photovoltaic elements.

52. Apparatus as claimed in claim 38 wherein said portions of said first and second elements are located adjacent to said first and second lines respectively.

53. Apparatus as claimed in claim 38 wherein said surface comprises the outer surface of a heat transfer conduit.

54. Apparatus for tracking the sun, said apparatus comprising focusing means for concentrating solar energy into first and second spaced lines which are located on or near a solar energy utilization surface when said focusing means is correctly aligned with the sun, first and second solar energy sensitive elements operable on impingement of solar energy thereon to produce control signals for controlling tracking movements of the focusing means, said first and second elements being located relative to said surface such that when the focusing means is misaligned with the sun either (a) the first line impinges upon the first element or (b) the second line impinges upon the second element.

55. Apparatus as claimed in claim 54 including shading means to shade said first and second elements from direct solar radiation when the focusing means is correctly aligned with the sun.

56. Apparatus as claimed in claim 54 or 55 wherein portions of said first and second elements are located adjacent to said first and second lines respectively.

57. Apparatus as claimed in claim 56 wherein said first and second elements extend from adjacent the focusing means to adjacent the first and second lines respectively.

58. Apparatus as claimed in claim 55 including heat transfer means located relative to the focusing means such that said first and second lines impinge thereon when the focusing means is correctly aligned with the sun.

59. Apparatus as claimed in claim 58 wherein said heat transfer means comprises a single conduit.

60. Solar energy conversion apparatus comprising a solar energy utilization surface, reflective concentrating means, and tracking means, said tracking means being operable to cause the concentrating means to track the sun and thereby concentrate solar energy on said surface characterized in that the apparatus includes means defining a shaded zone between said concentrating means and said surface such that solar rays reflected from the concentrating means towards said surface do not enter said zone when the concentrating means is aligned with the sun and wherein said tracking means includes solar energy sensitive elements located within said zone, said elements producing tracking control signals when struck by solar rays when the concentrating means is not aligned with the sun.

61. Apparatus as claimed in claim 60 wherein said concentrating means comprises a reflective trough and wherein said means defining a shaded zone extends longitudinally of said trough and spaced therefrom.

62. Apparatus as claimed in claim 60 or 61 wherein said solar energy sensitive elements comprise first and second elongate elements which are parallel to one another.

63. Apparatus as claimed in claim 62 wherein said trough has first and second parabolic portions which concentrate solar energy on said surface in first and second lines.

64. Apparatus as claimed in claim 63 including mounting means for mounting said trough for rotation about a rotation axis which is parallel to, between and equidistant from said first and second lines.

65. Apparatus as claimed in claim 64 wherein said elements comprise metallic members which are generally parallel to the said first and second lines when the trough is viewed in plan but extend diagonally relative to said lines when viewed in side elevation.

66. Apparatus as claimed in claim 65 wherein the tracking means includes drive means responsive to said tracking control signals, said drive means including a body which is mounted for rotation relative to the trough about a second axis which intersects and is perpendicular to said first and second lines, one end of each of said members being coupled to said body at points on opposite sides of said second axis whereby expansion of one or other of the members causes rotation of the body about said second axis.

67. Apparatus as claimed in claim 66 wherein said parabolic portions are formed as a single trough which is carried by a trough support structure mounted for rotation about said rotation axis in a framework, said support structure including a counter-weight bar, the bar constituting said means defining a shaded zone.

68. Apparatus as claimed in claim 64 wherein said energy utilization surface moves in unison with said trough and includes first and second faces which are transverse to the mean direction of solar energy reflected from said first and second parabolic portions respectively.

69. Apparatus as claimed in claim 68 wherein said faces comprise energy responsive faces of photovoltaic cells.

70. Apparatus as claimed in claim 69 wherein said cells are mounted on a heat transfer conduit.