Solar tracking device

• US 4,304,221 A
• Filed: 10/19/1978
• Issued: 12/08/1981
• 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:
  US05/953,771
• Time in Patent Office: 1,146 Days
• Field of Search: 126/438, 126/439, 126/424, 126/425, 126/450, 350/289, 250/203 R
• US Class Current: 126/581
• CPC Class Codes: F24S 2023/831 corrugated
• CPC Class Codes: F24S 2023/876 Reflectors formed by assemblies of adjacent reflective elements having different orientation or different features
• CPC Class Codes: F24S 23/70 with reflectors
• CPC Class Codes: F24S 23/745 flexible
• CPC Class Codes: F24S 23/80 having discontinuous faces
• CPC Class Codes: F24S 30/425 Horizontal axis
• CPC Class Codes: F24S 40/52 by modifying the heat collection, e.g. by defocusing or by changing the position of heat-receiving elements
• CPC Class Codes: F24S 50/20 for tracking
• CPC Class Codes: Y02E 10/47 Mountings or tracking

Abstract

Solar tracking apparatus is disclosed which utilizes received solar energy to effect tracking movements, the apparatus comprising focussing means, mounting means mounting the focussing means for tracking movements of the sun, drive means including heat expansible members movable with the focussing means, the heat expansible members being disposed relative to the focussing means so as to receive different amounts of solar radiation from the focussing means when the focussing means is misaligned with the sun so as to produce a differential expansion therein, the drive means being operable on differential expansion of said heat expansible members to cause movement of the focussing means in a direction towards realignment with the sun.

Claims

1. Solar energy conversion apparatus comprising concentrating means carried in a support structure for concentrating solar energy onto at least one surface, tracking means including first and second elongate metallic members which are disposed relative to the concentrating means to be differentially heated by the concentrated 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, one end of each of said members being resiliently connected to said support structure.

5. Solar energy conversion apparatus as in any one of claims 4, 1, 2 or 3 wherein said first and second elongate metallic members are straight rods arranged in spaced-apart, coextensive parallel relationship.

2. Solar energy conversion apparatus comprising a framework, a support structure rotatably mounted by hollow bearing members in said framework for rotation about an axis, a heat transfer conduit located along said axis and passing through said hollow members, concentrating means carried by the support structure and operable to concentrate solar energy onto at least part of said conduit, tracking means including first and second elongate metallic members which are disposed relative to the concentrating means to be differentially heated by the concentrated 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.

3. Solar energy conversion apparatus comprising concentrating means for concentrating solar energy onto at least one surface, tracking means including first and second elongate metallic members which are disposed relative to the concentrating means to be differentially heated by the concentrated solar energy when the concentrating means is misaligned with the sun, the differential heating of said metallic members producing differential thermal linear expansions thereof, one end of each of said members being connected to a rotatable body which is rotated in accordance with the differential expansions of said members, and drive means for producing tracking movements of said concentrating means in response to rotation of said body.

4. Solar energy conversion apparatus comprising concentrating means for concentrating solar energy onto at least one surface, tracking means including first and second elongate metallic members which are disposed relative to the concentrating means to be differentially heated by the concentrated 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, and radiation shielding means located between said first and second members for preventing unwanted radiation from striking said members.

6. Solar tracking apparatus comprising focussing means, mounting means mounting the focussing means for tracking movements of the sun, drive means including heat expansible members movable with the focussing means, said heat expansible members being disposed relative to the focussing means so as to receive different amounts of solar radiation from the focussing means when the focussing means is misaligned with the sun so as to produce a differential expansion therein, the drive means being operable on differential expansion of said heat expansible members to cause movement of the focussing means in a direction towards realignment with the sun and wherein said mounting means includes bearings supporting the focussing means at opposite ends thereof for rotation about an axis, said bearings permitting axial movement of the focussing means, tension means being provided between the focussing means and mounting means and operable to limit said axial movement at least in one direction relative to the mounting means, and wherein said tension means comprises an elongate member extending lengthwise at a location at least adjacent said axis and between opposed ends of the focussing means adjacent said bearing, said elongate member being secured at one end against lengthwise movement relative to the mounting means and at the other end against lengthwise movement relative to the focussing means, whereby when the mounting means is positioned with the said axis non-horizontal with the said one end of the elongate member uppermost, tendency of the focussing means to move downwardly along said axis by gravitational force is resisted by the said elongate member.

7. Apparatus as claimed in claim 6 wherein said elongate member is a wire.

8. Apparatus as claimed in claim 7 wherein said mounting means includes;

a pair of spaced upwardly extending support portions which respectively receive said bearings;

a tube being provided extending generally coaxially along said axis for flow of fluid to be heated by the apparatus, the said bearings being hollow and the said tube extending at either end therethrough, a central portion of the tube being mounted for rotation with the focusing means and end portions thereof being mounted to respective ones of the support portions of said mounting means said end portions being interconnected with the central portion by fluid tight couplings, the said wire extending through the central portion of the said tube and thence through one said end portion of the tube to the said one end of the wire which is secured, against lengthwise movement, to one of said support portions, the wire also extending at the said other end thereof to a coupling member within said central portion of the tube and to which the other wire end is secured against lengthwise movement.

9. Apparatus as claimed in claim 8 wherein the said bearings comprise ball bearings having outer annular races carried by the respective ones of said support portions of the mounting means and inner annular races carried by the said focusing means, balls of each said ball bearing being restrained against lengthwise movement relative to one of the races of that bearing, but the other race of that bearing presenting an annular surface which is flat and parallel to the bearing axis, when viewed in axial section, and against which the balls of that bearing engage in a manner such that they can move in the axial direction, along that annular surface.

10. Solar tracking apparatus for tracking the sun comprising focussing means, mounting means mounting the focussing means for tracking movements of the sun, drive means including heat expansible members movable with the focussing means, said heat expansible members being disposed relative to the focussing means so as to receive different amounts of solar radiation from the focussing means when the focussing means is misaligned with the sun so as to produce a differential expansion thereof, the drive means being operable on differential expansion of said heat expansible members to cause movement of the focussing means in a direction towards realignment with the sun, and wherein the focussing means includes first and second parabolic portions having first and second focal lines respectively and first and second planes respectively which include said first and second focal lines and in cross-section include the axis of the first and second parabolic portions respectively, and wherein said first and second planes are each spaced from a central tracking plane of the apparatus by a distance d and are each parallel thereto, and wherein the mounting means mounts the focussing means for rotation about a rotation axis which is parallel to, between and equidistant from the first and second focal lines, and wherein said heat expansible elements comprise at least two metallic members which are generally located in the first and second planes respectively but extend diagonally relative to said first and second focal lines, and wherein the mounting means includes a framework and a support structure being mounted in said framework for rotation about said rotation axis and wherein said metallic members are coupled between said support structure and said framework whereby differential thermal expansions therein effect rotation of the support structure relative to the framework, the first and second members having one end thereof resiliently connected to the support structure, and wherein the drive means further includes a body which is mounted on the support structure for rotation relative thereto about a second axis which is generally perpendicular to the members, the other 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.

11. Apparatus as claimed in claim 10 wherein the focussing means comprises a reflective parabolic trough.

12. Apparatus as claimed in claim 10 or 11 wherein said drive means further includes a drum carried by the framework, an arm extending from said body and a flexible line extending from the arm about said drum whereby rotation of said body about said second axis causes relative movement between the line and the drum to thus cause rotation of the support structure relative to the framework.

13. Apparatus as claimed in claim 12 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.

14. Apparatus as claimed in claim 12 wherein the members project above the first and second focal lines of the parabolic portions and the parts of said members above said focal lines being thermally shielded.

15. Apparatus as claimed in claim 10 wherein the centre of gravity of the support structure and focussing 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 or other of said members, causes the support structure and focussing means to become unbalanced and thus rotates under gravity about said rotation axis.

16. Apparatus as claimed in claim 10 wherein the first and second members have first and second slots which are located adjacent and parallel to said first and second focal lines respectively whereby when the tracking plane of the apparatus is near alignment with the sun, solar energy from the first parabolic portion is reflected onto the first member and solar energy reflected from the second parabolic portion passes through the slot in said second member and impinges upon the first member.

17. Apparatus as claimed in claim 16 wherein said members are of flat cross secton with longer cross-sectional dimensions parallel to the said tracking plane and arranged side-by-side;

said slot of each member extending between locations adjacent but spaced from opposite side edges of that member and at an angle to such side edges and from one major face of that member to the other.

18. Apparatus as claimed in claim 17 wherein portions of the members above the said slots are positioned further away from the said tracking plane than portions therebelow.

19. Apparatus as claimed in claim 18 wherein shielding of the parts of said members above said focal lines is effected by a housing having a reflective baffle for reflecting light onto one member which has passed through the slot in the other rod.

20. Apparatus as claimed in claim 18 or claim 19 wherein upper edges of the members, at the location of the said slots, are shielded by respective reflective elements to reflect radiation away therefrom.

21. Apparatus as claimed in claim 18 wherein a reflective shield is located between the members at locations along the members and below the focussing means to reduce unwanted radiation striking the members from opposed sides of the trough.

22. Apparatus as claimed in claim 21 wherein said focussing means comprises a plurality of ribs spaced from one another in the direction of extent of the focussing means and extending transversely to said direction, the said ribs having concave parabolic edges aligned when viewed in the direction of extent of the trough, the said parabolic portions being formed from respective sheets interconnected with the ribs so as to extend in the said lengthwise direction between the said ribs and resiliently deformed thereagainst to assume the same concave parabolic configuration of the said edges, when viewed in the direction of extent of the focussing means.

23. Apparatus as claimed in claim 22 wherein the said sheets have upturned flanges at opposed edges thereof the sheets being arranged with said flanges extending lengthwise of the said trough so that one said flange of each said sheet extends lengthwise along a respective outer lengthwise extending edge of the trough and the outer said flanges of the sheets extend in adjacent parallel relationship lengthwise of the trough in contact with a central lengthwise extending abutment interconnecting central portion of the said ribs, the said other flanges abutting the said abutment and means being provided resiliently biasing said further flanges in a direction towards the said ribs, the said one flange being provided with resilient means resiliently biasing these against outer ends of the ribs and biasing the said one flange inwardly.

24. Apparatus as claimed in claim 23 wherein the said resilient means comprises spring clips.

25. Apparatus as claimed in claim 10 further including energy collecting means located to receive reflected energy at said first and second focal lines.

26. Apparatus as claimed in claim 25 wherein the collecting means comprises a tube through which heat transfer fluid is passed.

27. Apparatus as claimed in claim 26 wherein said tube is stationary relative to the focussing means.

28. Apparatus as claimed in claim 25 or 26 including photo-electric elements mounted upon the tube.

29. Apparatus as claimed in claim 10 wherein the members are connected, at ends thereof remote from the said one ends thereof, to the said mounting means by means of a resilient connection maintaining said members in tension.

30. Apparatus as claimed in claim 29 wherein the said members are of flat cross-sectional configuration with longer cross-sectional dimensions parallel to the said tracking plane and extending in side-by-side relation, one to either side of said tracking plane, the said remote ends thereof having means interposed therebetween to constrain them against movement transverse to the said tracking plane and to constrain the members against rotation about lengthwise axes thereof.