SINGLE AXIS SOLAR TRACKER WITH A TORSIONAL VIBRATION DAMPING DEVICE

Abstract

The solar tracker includes a pivoting assembly (2) having solar panels (3) fixed to a rotating shaft (1), a fixed structure with support elements (4, 5, 6) rotationally supporting the rotating shaft (1), a motor-reducer assembly (7) having an irreversible reducer (24) connected to the rotating shaft (1) at a motor connection point (12), and a torsional vibration damping device (8) having a moving member (9) rigidly connected to the rotating shaft (1) at a damper connection point (13) spaced apart from the motor connection point (12) and a stationary member (10) rigidly attached to the fixed structure. Both the moving member (9) and the stationary member (10) comprises elements capable to generate a magnetic field when a movement of the moving member (9) relative to the stationary member (10) occurs, resulting in a damping torque on the rotating shaft (1).

Claims

1. A solar tracker with a torsional vibration damping device, comprising: a rotating shaft having a longitudinal axis; a pivoting assembly fixedly connected to the rotating shaft, the pivoting assembly having solar panels arranged to receive solar radiation; a fixed structure comprising a plurality of support elements rotationally supporting the rotating shaft at a plurality of support points distributed there along; a motor-reducer assembly operatively connected to rotate the rotating shaft about the longitudinal axis so as to track the sun, the motor-reducer assembly being cinematically connected to the rotating shaft at a motor connection point and having an irreversible reducer configured to provide retention against torsional vibration of the rotating shaft at the motor connection point; and a torsional vibration damping device having one moving member rigidly connected to the rotating shaft to move therewith; wherein: the torsional vibration damping device further comprises a stationary member which is rigidly attached to the fixed structure; the moving member of the torsional vibration damping device is rigidly connected to the rotating shaft at a damper connection point spaced apart from the motor connection point and arranged to move close to the stationary member without contact; and both the moving member and the stationary member comprises elements capable to generate a magnetic field when a movement of the moving member relative to the stationary member occurs, resulting in a damping torque on the rotating shaft.

2. The solar tracker according to claim 1, wherein the moving member and the stationary member comprises permanent magnets and the other member selected between the moving member and the stationary member comprises electromagnets, so that a relative movement between permanent magnets and electromagnets in one or in the other member produces the damping torque on the rotating shaft.

3. The solar tracker according to claim 2, wherein said electromagnets are feed from an external source.

4. The solar tracker according to claim 2, wherein said electromagnets operate in a bidirectional mode charging an electrical power storage system connected to said electromagnets when a torsional galloping occurs at the solar tracker and said electromagnets being electrically feed by a discharge of said electrical power storage system when said torsional galloping is higher than a given threshold value.

5. The solar tracker according to claim 1, wherein one of the moving member and the stationary member comprises magnetic field-generating elements and the other member selected between the moving member and the stationary member comprises a section made of an electrically conductive, non-ferromagnetic material, relative movement between the magnetic field-generating elements and the section made of an electrically conductive, non-ferromagnetic material producing the damping torque by Foucault currents effect and subsequent magnetic field.

6. The solar tracker according to claim 5, wherein the magnetic field-generating elements are attached to a stationary damper section comprised in the stationary member and the section made of an electrically conductive, non-ferromagnetic material is a moving damper section comprised in the moving member.

7. The solar tracker according to claim 5, wherein the magnetic field-generating elements are attached to a moving damper section comprised in the moving member and the section made of an electrically conductive, non-ferromagnetic material is a stationary damper section comprised in the stationary member.

8. The solar tracker according to claim 2, wherein the electromagnets are placed at the stationary damper section comprised in stationary member and a moving damper section comprised in the moving member further includes permanent magnets.

9. The solar tracker according to claim 1, wherein the rotating shaft has opposite ends and an intermediate middle region, the motor connection point is located at or near to one of the opposite ends of the rotary shaft, and the damper connection point is located at or near to the other end of the rotary shaft.

10. The solar tracker according to claim 1, wherein the rotating shaft has opposite ends and an intermediate middle region, wherein and the motor connection point is located in the intermediate middle region, the damper connection point is located at or near to one of the opposite ends of the rotary shaft, and a second torsional vibration damping device is provided having a stationary member rigidly attached to the fixed structure and a moving member rigidly connected to the rotating shaft at a second damper connection point located at or near to the other end of the rotating shaft and arranged to move close to the corresponding stationary member without contact.

11. The solar tracker according to claim 1, wherein the motor-reducer assembly is supported on a motor support element of the plurality of support elements, the motor connection point is located adjacent to the motor support element, the stationary member of the or each torsional vibration damping device is supported on a damper support element of the plurality of support elements.

12. The solar tracker according to claim 11, wherein one or more simple support elements of the plurality of support elements are located between the motor support element and the or each damper support element.

13. The solar tracker according to claim 6, wherein the stationary damper section comprises two opposite walls perpendicular to the longitudinal axis connected to one another by a bottom wall, a damping gap being provided between the opposite walls, wherein the opposite walls of the stationary damper section have respective arched top and bottom edges, and wherein the moving damper section has arched top and bottom edges.

14. The solar tracker according to claim 13, wherein the moving damper section is connected by an arm to a shaft fastening element fastened to the rotating shaft and the stationary damper section is connected by a base support to a post fastening element fastened to the damper support element.

15. The solar tracker according to claim 4, wherein said electrical power storage system is a capacitor bank.

16. The solar tracker according to claim 7, wherein the stationary damper section comprises two opposite walls perpendicular to the longitudinal axis connected to one another by a bottom wall, a damping gap being provided between the opposite walls, wherein the opposite walls of the stationary damper section have respective arched top and bottom edges, and wherein the moving damper section has arched top and bottom edges.

17. The solar tracker according to claim 16, wherein the moving damper section is connected by an arm to a shaft fastening element fastened to the rotating shaft and the stationary damper section is connected by a base support to a post fastening element fastened to the damper support element.

18. The solar tracker according to claim 8, wherein the stationary damper section comprises two opposite walls perpendicular to the longitudinal axis connected to one another by a bottom wall, a damping gap being provided between the opposite walls, wherein the opposite walls of the stationary damper section have respective arched top and bottom edges, and wherein the moving damper section has arched top and bottom edges.

19. The solar tracker according to claim 18 wherein the moving damper section is connected by an arm to a shaft fastening element fastened to the rotating shaft and the stationary damper section is connected by a base support to a post fastening element fastened to the damper support element.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The above and other features and advantages will be more fully understood from the following detailed description of merely illustrative and non-limiting embodiments with reference to the accompanying drawings, in which:

[0028] FIG. 1 is a diagrammatic elevation view of a solar tracker with a torsional vibration damping device according to an embodiment of the present invention;

[0029] FIG. 2 is a diagrammatic elevation partial view of the torsional vibration damping device included in the solar tracker of FIG. 1;

[0030] FIG. 3 is a cross-sectional view taken along the plane III-III of FIG. 2;

[0031] FIG. 4 is a diagrammatic elevation partial view of a torsional vibration damping device according to an alternative embodiment;

[0032] FIG. 5 is a cross-sectional view taken along the plane V-V of FIG. 4;

[0033] FIG. 6 is a diagrammatic elevation partial view of a torsional vibration damping device according to another alternative embodiment;

[0034] FIG. 7 is a cross-sectional view taken along the plane VII-VII of FIG. 6;

[0035] FIG. 8 is a diagrammatic elevation partial view of a torsional vibration damping device according to still another alternative embodiment;

[0036] FIG. 9 is a cross-sectional view taken along the plane IX-IX of FIG. 8;

[0037] FIG. 10 is a diagrammatic elevation view of a solar tracker with a torsional vibration damping device according to an alternative embodiment of the present invention;

[0038] FIG. 11 is a diagrammatic elevation partial view of a torsional vibration damping device according to another alternative embodiment; and

[0039] FIG. 12 is a cross-sectional view taken along the plane XI-XI of FIG. 11.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

[0040] Referring first to FIG. 1, reference sign 50 generally designates a solar tracker with a torsional vibration damping device according to an embodiment of the present invention. The solar tracker 50 is a single axis solar tracker comprising a rotating shaft 1 which has a longitudinal axis X. The rotating shaft 1 is rotationally supported at a plurality of support points distributed there along by a plurality of support elements 4, 5, 6 constituting a fixed structure. A pivoting assembly 2 is fixedly connected to the rotating shaft 1. The pivoting assembly 2 has one or more pivoting frames 25 attached to the rotating shaft 1 and a plurality of solar panels 3 arranged on the one or more pivoting frames 25 to receive solar radiation.

[0041] In the shown embodiment, the support elements 4, 5, 6 are individual support posts anchored to the ground although alternatively they could be part of a base structure anchored to the ground.

[0042] The rotating shaft 1 extends along the one or more pivoting frames 25 and has opposite ends and an intermediate middle region. The plurality of support elements 4, 5, 6 comprises a motor support element 4 located at the intermediate middle region of the rotating shaft 1, two damper support elements located near the opposite ends of the rotating shaft 1, respectively, and one more simple support element 6 located between the motor support element 4 and each damper support element 5.

[0043] A motor-reducer assembly 7 is supported on the motor support element 4. The motor-reducer assembly 7 comprises an electric motor 23 connected to a reducer 24 which in turn is connected to the rotating shaft 1 at a motor connection point 12 located adjacent to the motor support element 4, so that the motor-reducer assembly 7 is operatively connected to rotate the rotating shaft 1 about the longitudinal axis X so as to track the sun. The reducer 24 is an irreversible reducer which provides retention against torsional vibration to the rotating shaft 1 at the motor connection point 12.

[0044] In the illustrated embodiment, the irreversible reducer 24 comprises a motor-driven worm screw meshed with a gear wheel which is coaxially fixed to the rotating shaft 1, wherein the worm screw can rotate the gear wheel, but the gear wheel cannot rotate the worm screw. However, other kinds of well-known irreversible reducers and/or other mechanical connections, including for example roller chains, belts, levers or connecting rods, between the reducer and the motor connection point 12 of the rotating shaft 1 will readily occur to one skilled in the art without departing from the scope of the invention.

[0045] Each damper support element 5 and each simple support element 6 is connected at the upper end thereof to a bearing support 16 carrying a bearing 26 mounted around the rotating shaft 1 for supporting the rotating shaft 1 and guiding rotation thereof.

[0046] In the embodiment shown in FIG. 1, two torsional vibration damping devices 8 are mounted on the damper support elements 5 and connected to the rotating shaft 1 at respective damper connection points 13 adjacent the corresponding damper support elements 5, so that the damper connection points 13 are located near the opposite ends of the rotating shaft 1 far away from the motor connection point 12. In an alternative embodiment (not shown) the motor support element 4 with the motor-reducer assembly 7 and the motor connection point 12 are located at or near one end of the rotating shaft 1 and one damper support element 5 with a single torsional vibration damping device 8 and a single damper connection point 13 are located at or near the other end of the rotating shaft 1.

[0047] As best shown in FIGS. 2 and 3, each torsional vibration damping device 8 comprises a moving member 9 rigidly connected to the rotating shaft 1 and a stationary member 10 rigidly attached to the corresponding damper support element 5. The moving member 9 has a moving damper section 14 connected by an arm 19 to a shaft fastening element 20, such as a shaft clamp, which is fastened to the rotating shaft 1 at a damper connection point 13 adjacent the damper support element 5 so that the moving damper section 14 moves with the rotating shaft 1. The stationary member 10 has a stationary damper section 15 connected to a base support 21 which in turn is connected to a post fastening element 22, such as a post clamp, fastened to the damper support element 5, so that stationary damper section 15 remains stationary together with the damper support element 5.

[0048] Alternatively, the arm 19 of the moving member 9 can be directly attached to the bearing 26, which is usually comprised of two complementary solid parts made of a low friction plastic material. The stationary damper section 15 can be alternatively connected to the bearing support 16.

[0049] The stationary damper section 15 comprises two opposite walls 17 perpendicular to the longitudinal axis X, which are made of a ferromagnetic material, for example, in a non-limitative way, iron, cobalt, nickel or alloys thereof. The opposite walls 17 have respective arched top and bottom edges and are connected to one another by an arched bottom wall 18. The moving damper section 14 of the moving member 9 is made of an electrically conductive, non-ferromagnetic material, for example aluminium, cooper, or alloys thereof. The moving damper section 14 is plate-shaped, has opposite surfaces perpendicular to the longitudinal axis X and arched top and bottom edges.

[0050] The magnetic field-generating elements 11 are permanent magnets 27 attached to both opposite walls 17 of the stationary damper section 15 forming two respective arched rows facing each other and rows having a centre in the longitudinal axis X. Each permanent magnet of one arched row is directly facing a permanent magnet of the other arched row. In an alternative embodiment (not shown), the magnetic field-generating elements 11 are electromagnets 28 energized with electrical current that can be generated for example by the solar panels 3 instead of permanent magnets 27.

[0051] As best shown in FIG. 2, the permanent magnets 27 of the two arched rows have front surfaces laying in two respective planes parallel to the opposite walls 17 and therefore perpendicular to the longitudinal axis X. Between the front surfaces of the permanent magnets 27 of the two arched rows a damping gap is provided. The moving damper section 14 of the moving member 9 is inserted so that it can move in the damping gap close to the magnetic field-generating elements 11 without contact.

[0052] Relative movement between the permanent magnets 27 constituting the magnetic field-generating elements 11 and the moving damper section 14 made of an electrically conductive, non-ferromagnetic material produces a damping torque by Foucault currents effect which counteracts the effect of torsional vibration of the pivoting assembly 2 produced by the wind or by other causes.

[0053] FIGS. 4 and 5 show an alternative embodiment which is a variant of that described above in relation to FIGS. 2 and 3. The embodiment shown in FIGS. 4 and 5 differs from FIGS. 2 and 3 in that the permanent magnets 27 constituting the magnetic field-generating elements 11 are attached to only one of the opposite walls 17 forming one arched row rows having a centre in the longitudinal axis X. The permanent magnets 27 have front surfaces laying in a plane parallel to the opposite walls 17, and the damping gap is provided between the front surfaces of the permanent magnets 27 and the wall opposite thereto. The plate-shaped moving damper section 14 of the moving member 9 is inserted so that it can move in the damping gap close to the magnetic field-generating elements 11 without contact. Alternative embodiments shown in FIGS. 6-7 and 8-9 are inverse constructions to those described above with reference to FIGS. 2-3 and 4-5. In the embodiments shown in FIGS. 6-7 and 8-9 the magnetic field-generating elements 11 are attached to the moving damper section 14 of the moving member 9 and the stationary damper section 15 of the stationary member 10 is made of an electrically conductive, non-ferromagnetic material.

[0054] In FIGS. 6 and 7, the stationary damper section 15 of the stationary member 10 comprises two opposite walls 17 perpendicular to the longitudinal axis X. The opposite walls 17 are made of an electrically conductive, non-ferromagnetic material, such as aluminium, cooper, or alloys thereof. The opposite walls 17 have respective arched top and bottom edges and are connected to one another by an arched bottom wall 18. A damping gap is provided between the two opposite walls 17. The stationary damper section 15 is fixedly attached to the damper support element by a post fastening element, such as a post clamp.

[0055] The moving damper section 14 is plate-shaped and has opposite surfaces perpendicular to the longitudinal axis X and arched top and bottom edges. The moving damper section 14 is made of a ferromagnetic material, for example, iron, cobalt, nickel or alloys thereof. The magnetic field-generating elements 11 are permanent magnets 27 attached to both opposite surfaces of the moving damper section 14 forming two respective opposite arched rows having a centre in the longitudinal axis X. Each permanent magnet of one arched row is directly opposite to a permanent magnet of the other arched row. The permanent magnets 27 have opposite front surfaces laying in two respective planes parallel to the opposite surfaces of the moving damper section 14. The moving damper section 14 is connected by an arm 19 to a shaft fastening element 20, such as a shaft clamp, which is fastened to the rotating shaft 1. The moving damper section 14 with the permanent magnets 27 is inserted so that it can move in the damping gap without contact.

[0056] The embodiment shown in FIGS. 8 and 9 is a variant of that described above in relation to FIGS. 6 and 7. The embodiment shown in FIGS. 8 and 9 differs from FIGS. 6 and 7 in that the permanent magnets 27 constituting the magnetic field-generating elements 11 are lodged in openings formed in the plate-shaped moving damper section 14. The openings and the permanent magnets 27 form an arched row having a centre in the longitudinal axis X. The permanent magnets 27 have opposite front surfaces laying in two respective planes parallel to the opposite surfaces of the moving damper section 14 at either side of the moving damper section 14. The moving damper section 14 with the permanent magnets 27 is inserted so that it can move in the damping gap.

[0057] FIG. 10 shows a solar tracker with a torsional vibration damping device according to an alternative embodiment of the present invention which differs from that described above with reference to FIG. 1 in that the solar tracker 50 includes one single torsional vibration damping device 8 in cooperation with the motor-reducer assembly 7. In this embodiment, the rotating shaft 1 has two opposite ends, a motor support element 4 is located at or near to one of the opposite ends of the rotary shaft 1, one damper support element 5 is located at or near to the other end of the rotary shaft 1, and two simple support elements 6 are located between the motor support element 4 and the damper support element 5.

[0058] The damper support element 5 and each simple support element 6 are connected at the upper end thereof to a bearing support 16 carrying a bearing 26 mounted around the rotating shaft 1. The motor support element 4 supports a motor-reducer assembly 7 comprising an electric motor 23 connected to an irreversible reducer 24 which in turn is connected to the rotating shaft 1 at a motor connection point 12 located adjacent to the motor support element 4. The damper support element 5 supports a torsional vibration damping device 8 which is connected to the rotating shaft 1 at a damper connection point 13 adjacent the damper support element 5. The torsional vibration damping device 8 may be, for example, according to any one of the embodiments described with reference to FIGS. 2-9.

[0059] With this construction, the motor connection point 12 is located at or near to one of the opposite ends of the rotary shaft 1 and the damper connection point 13 is located at or near to the other end of the rotary shaft 1.

[0060] It will be understood that in any of the embodiments of the solar tracker 50, the number of support elements 6 located between the motor support element 4 and the or each damper support element 5 is variable, and that additional torsional vibration damping devices 8 can be associated to one or more of the support elements 6 located between the motor support element 4 and the or each damper support element 5.

[0061] The embodiment shown in FIGS. 11 and 12 refer to an alternative embodiment of the torsional vibration damping device in which the moving member 9 has a moving damper section 14 connected by an arm 19 to the shaft 1 and the stationary member 10 has a stationary damper section 15 connected to a base support 21 which in turn is connected to a post fastening element 22, as in the previous embodiments of FIGS. 2 to 9.

[0062] As a differential characteristic of this of this embodiment the moving damper section 14 of the moving member 9 comprises permanent magnets 27 and the stationary damper section 15 of the stationary member 10 includes electromagnets 28, so that a movement of the arm 19 with the permanent magnets 27 as a consequence of the turns of the rotating shaft 1 with regard to the electromagnets 28 that are activated produces an interference between the magnetic fields (permanent magnets 27 and electromagnets 28) resulting in a damping torque on the rotating shaft 1, as the movement of the arm 9 is slowed down counteracting the torsional galloping effect on said rotating shaft 1.

[0063] The electromagnets 28 can be feed from an external source under control in a possible embodiment of a control unit which detects the torsional galloping effect on said rotating shaft 1 and proceed to activation of the electromagnets 28. In an alternative preferred embodiment the electromagnets 28 operate in a bidirectional mode charging an electrical power storage system implemented in a possible embodiment by a capacitor bank (not represented in the drawings) connected to said electromagnets 28 when a torsional galloping occurs at the solar tracker and said electromagnets 28 are later in an automatic way electrically feeded by a discharge of said electrical power storage system when said torsional galloping is higher than a given threshold value, under control for example of the cited control unit.

[0064] The control method to activate the cited electromagnets 28 can be very diverse, as for example: activation of a DIAC when there is a voltage in the electrical power storage system, a microcontroller with an accelerometer, a microswitch, optical, magnetic switches, inclination switches, etc.

[0065] In any of the embodiments of the torsional vibration damping device described above, the arched top and bottom edges of the plate-shaped moving damper section 14 as well as the arched top and bottom edges of the opposite walls and the arched bottom wall of the stationary damper section 15 preferably have a centre in the longitudinal axis X.

[0066] The scope of the invention is defined by the attached claims.