US20140150774A1

US20140150774A1 - Solar tracking apparatus and field arrangements thereof

Info

Publication number: US20140150774A1
Application number: US14/018,865
Authority: US
Inventors: Philip M. CHANG; Jayiesh Singh; Sandy Li; Eric Morgan; Asif Ansari; Trevor Vaughan; Stephen Caelers
Original assignee: Morgan Solar Inc
Current assignee: Morgan Innovation Inc
Priority date: 2012-11-30
Filing date: 2013-09-05
Publication date: 2014-06-05
Also published as: US20140150845A1

Abstract

A solar tracker assembly for mounting one or more solar tracking units, which can be adapted for use with various solar energy modules such as photovoltaic modules and heliostat mirrors, is provided. Each assembly comprises a frame of four sides connected at leg assemblies, each leg assembly being adapted for mounting a solar tracking unit. The frame may be configured as an oblique-angled, rhombus or diamond frame with a cross member extending between the closer-spaced leg assemblies. A set of frames may be arranged in the field with adjacent sides of adjacent frames being parallel, with spacing arms of predefined lengths interconnecting adjacent pairs of frames, to provide a desired hexagonal grid spacing.

Description

REFERENCE TO PRIOR APPLICATIONS

This application claims priority to U.S. Provisional Application No. 61/732,044 filed 30 Nov. 2012, the entirety of which is incorporated by reference. This application further incorporates the entireties of U.S. Provisional Applications Nos. 61/523,817 filed 15 Aug. 2011 and to 61/532,083 filed 7 Sep. 2011 and PC′I′ application PCT/IB2012/052723 filed 30 May 2012 by reference.

TECHNICAL FIELD

The present disclosure relates to the field of solar energy, and in particular to tracking solar tracking assemblies, and arrangements thereof.
Solar power is typically captured for the purpose of electrical power production by an interconnected assembly of photovoltaic (PV) cells arranged over a large surface area of one or more solar panels. Multiple solar panels may be arranged in arrays.
In addition to the difficulties inherent in developing efficient solar panels capable of optimum performance—including inconsistencies in manufacturing and inaccuracies in assembly—field conditions pose a further obstacle to cost-effective implementation of solar energy collection. Conventionally, solar tracker systems, which include a tracker controller to direct the positioning of the solar panels, benefit from mounting on a flat surface permitting accurate mounting of the system and ensuring stability by anchoring the system to a secure foundation, for example by pouring a concrete foundation. These requirements, however, add to the cost of field installation because of the additional equipment and manpower requirements.

BRIEF DESCRIPTION OF THE DRAWINGS

In drawings which illustrate by way of example only select embodiments that are described herein,

FIG. 1 is a perspective view of a ground-based tracking solar panel assembly;

FIG. 2 is a perspective, partially exploded view of a box frame portion of the assembly of FIG. 1 in a deployed state;

FIG. 3 is a perspective view of a portion of the box frame of FIG. 2 in a collapsed state;

FIG. 4 is a perspective view of a leg assembly for mounting to a truss of the box frame of FIG. 2;

FIGS. 5, 6 and 7 are perspective views of alternate frame configurations;

FIG. 8 is a perspective view of an armature assembly for use with the assembly of FIG. 1;

FIGS. 9 and 10 are side elevations of example solar panels for use with the assembly of FIG. 1;

FIGS. 11 and 12 are perspective views of a mounted photovoltaic tracker module from the assembly of FIG. 1;

FIG. 13 is an illustration of an example of a plurality of interconnected frames;

FIG. 14 is a schematic showing electrical and communication interconnections among a plurality of tracking solar panel assemblies of FIG. 1;

FIG. 15 is a flowchart illustrating a process for auto-calibration;

FIG. 16 is a further schematic showing electrical and communication interconnections among a plurality of tracking solar panel assemblies in a solar farm;

FIG. 17 is a perspective view of a ground-based tracking solar panel assembly;

FIG. 18 is a perspective view of a ground-based tracking assembly including a frame and armatures;

FIG. 19A is a perspective view of a leg assembly of the solar panel assembly of FIG. 17;

FIGS. 19B and 19C are detail views of the leg assembly of FIG. 19A;

FIG. 20 is a perspective view of the frame of FIG. 17 in a collapsed state;

FIG. 21 is a perspective view of the frame of FIG. 17 partially disassembled;

FIG. 22A is a side view of the frame and armatures of FIG. 18;

FIG. 22B is another side view of the frame and armatures of FIG. 18;

FIG. 23 is a perspective of an example of a plurality of interconnected frames;

FIG. 24A is a perspective view of an example of a ground-based tracking solar panel assembly;

FIG. 24B is a side view of an example of a ground-based tracking solar panel assembly;

FIG. 24C is a top view of an example of a plurality of interconnected frames;

FIG. 25A is a top view of an example of a field of interconnected frames in a first arrangement and orientation;

FIG. 25B is a top view of the field of FIG. 25B in a second orientation;

FIGS. 25C to 25E are top views of the field of FIG. 25B overlaid by diamond and hexagonal grids;

FIG. 26A is a top view of an example of a field of interconnected frames in a second arrangement;

FIGS. 26B and 26C are top views of the field of FIG. 26A overlaid by rectangular and hexagonal grids, respectively;

FIG. 27A is a top view of an example of a field of interconnected frames in a third arrangement;

FIGS. 27B and 27C are top views of the field of FIG. 27A overlaid by a hexagonal grid;

FIG. 28 is a perspective view of an armature assembly for use with the assembly of FIGS. 17 and 18;

FIG. 29A is a perspective view of a frame of a ground-based tracking assembly with a length-adjustable cross member;

FIG. 29B is a detail view of the cross member of the tracking assembly of FIG. 29A; and

FIG. 29C is a detail view of a leg assembly of the tracking assembly of FIG. 29A.

DETAILED DESCRIPTION

A self-ballasted solar tracker assembly is provided for concentrated or non-concentrated photovoltaic solar panels to maintain stability and alignment of the panels without requiring ground preparation. A modular, collapsible truss structure is provided as a frame to support a plurality of solar tracking units on which solar panels may be mounted. These individual panels are mounted at or near their center of gravity and positioned at corners or junctions of the frame. These structures are physically interconnectible in the field for enhanced stability, thus reducing or eliminating the need for external ballast (such as concrete blocks), and also for the purpose of facilitating electrical connection and data communication. Arrangement of a plurality of these interconnected structures in a solar farm or sub-farm provides for efficiency in grounding the supporting structures of the solar tracking units.
Turning to FIG. 1, a perspective view of a solar tracker assembly or unit 100 is shown. The assembly 100 generally includes a ground-mounted frame 10 for supporting one or more solar tracking units 200, such as the photovoltaic (PV) tracker modules illustrated in FIG. 1. In the example illustrated in FIG. 1, the solar tracking units 200 are shown supporting solar panels 205. The frame 10 includes a plurality of trusses 12, 22. In the example of FIG. 1, the frame 10 has a first pair of trusses 12, 12 of substantially equal length defining first opposing sides of the frame 10, joined to a second pair of trusses 22, 22 also of substantially equal length defining the remaining opposing sides via leg assemblies 30. The assembly of the trusses thus yields an overall parallelogrammatic, and in this specific example, a box or rectangular frame 10. The sides of the frame 10 need not employ trusses specifically, although the benefits of the structural stability of a truss design will be appreciated by those skilled in the art.
As shown in FIG. 2, each individual truss 12 includes an upper chord member 14 and lower chord member 16, and each individual truss 22 includes an upper chord member 24 and lower chord member 26. The chord members 14, 16 and 24, 26 are joined by a set of truss members 17, 27 respectively. Trusses 12, 22 in this example each include a set of four truss members 17, 27. The selection and arrangement of the truss members 17, 27 need not be limited to the example shown; depending on the selected dimensions and materials of the frame 10, more or fewer truss members 17, 27 may be employed. In addition, one or more struts 18, 28 may be mounted between the upper and lower chord members 14, 16 or 24, 26 to provide additional vertical support between the chord members. In the example of FIG. 2, some struts 18, 28 are provided near the ends of the trusses 12, 22, i.e., near the joints between adjacent trusses. The number (which may be zero or more) and arrangement of struts, as well as the number and arrangement of truss members, can be selected according to the specific requirements for the solar tracker assembly 100 installation, as well as inherent characteristics of the frame 10 and the tracker modules 200, including the weight of the tracker modules 200 to be supported, material used to fabricate the trusses 12, 22 and the geometry of the trusses 12, 22.
The trusses 12, 22 are joined at or near their respective ends at leg assemblies 30, shown in further detail in FIGS. 3 and 4. Each leg assembly 30 includes a shaft 31, and can include an adjustable foot member 37, as shown in one example of the leg assembly as illustrated in FIG. 2. The foot member 37 in this example is detachable and includes a plate member 39 extending from a stem 38. The stem 38 is attached to the shaft 31 of the leg assembly 30, and in some examples the attachment point of the stem 38 to the shaft 31 may be varied so as to permit adjustment of the overall height of the leg assembly 30, and thus of the solar tracking units 200 when mounted thereon. The stem 38 and plate member 39 may have alternate configurations than that described herein. In some examples, a spike member or other attachment component, not shown, for anchoring the leg assembly in the ground and/or electrically grounding the frame 10 can be provided in addition to or instead of plate member 39. A distal end of the leg assembly 30 provides a mounting end 35 for mounting an armature assembly bearing the solar tracking module 200.
The trusses 12, 22 and leg assemblies 30, and their respective components, may be manufactured from any suitable material. For example, the trusses and leg assemblies may be manufactured from galvanized steel or aluminum, and may be manufactured from extruded or drawn metal tubing, whether open or seamed. Further, in some examples, at least the upper chord members 14, 24 may be provided with an axial borehole or otherwise formed with an interior channel running the length of the chord member, open at either end (not shown), which is conveniently provided when the chord members are manufactured from tubing. Cables, wires and hoses, such as electrical cables and the like, as well as air or water hoses, may be threaded through the upper chord members 14, 24 and/or lower chord members 16, 26. Similarly, the leg assembly 30 may be provided with a similar axial borehole or interior channel. In the examples illustrated herein, the leg assembly 30 is a tubular member.
FIG. 3 illustrates three trusses 22, 12, 12 of the frame 10 joined to the four leg assemblies 30 illustrated in FIG. 2. In this example, the three trusses are assembled with the leg assemblies 30 in a collapsed state suitable for transportation. In this configuration, the trusses remain joined, but more easily transportable than when the frame 10 is completely assembled. The remaining fourth truss 22 may be provided separately. It will be appreciated, however, that even with the fourth truss connected in the frame 10, the frame 10 may still be collapsed to a substantially flat, folded structure suitable for transport. This view illustrates flange units 32, 33, 34 on the leg assemblies 30, which are provided for mounting the trusses 12, 22. It can be seen from the collapsed state that the fastening means used to join the trusses 12, 22 to the leg assemblies 30, shown in FIG. 4, are advantageously adapted to provide a hinged connection between each truss 12, 22 and the leg assembly 30 to permit the frame 10 to be shipped in a partially assembled state. Further, since the trusses 12, 22 may carry cables, wires or hoses in their respective upper or lower chords 14, 16, 24, 26, these components may be pre-threaded through the chords prior to shipping to minimize assembly time in the field, as well as shield the wiring, etc. from the elements, and reducing the need for expensive connectors.
Turning to FIG. 4, a further view of the leg assembly 30 is shown. A first, lower flange unit 32 is provided near a first end (i.e., near the end joined to the foot member 37) of the leg assembly. The flange unit 32 in this example comprises a set of four flanges 32 a, 32 b, 32 c, 32 d extending from the leg assembly. In this example of a box frame 10, the flanges 32 a, 32 b, 32 c, 32 d extend radially and are substantially equally spaced around the leg assembly 30, i.e., at right angles to one another. In this example, the individual flanges 32 a, 32 b, 32 c, 32 d and the lower chord members 16, 26 are provided with corresponding boreholes for receiving fasteners 42. The lower chord member 16, 26 is placed on the corresponding flange 32 c, 32 b such that the boreholes provided in each component are substantially aligned, and the fasteners 42 are used to join the chord member to its respective flange. The fasteners 42 may also facilitate an electrical connection between the chord member and the leg assembly 30 via its respective flange for electrical grounding purposes. Suitable fasteners 42 may be selected for joining and/or electrically connecting the chord members and flanges, such as the illustrated threaded bolts and washers. The fasteners mentioned herein may, for example, be self-tapping screws or split pins; thus the boreholes in the flange unit 32 and trusses 12, 22 need not be threaded.
It will be appreciated that other means of attaching a truss 12, 22 to the leg assembly 30 may be used; for example, the leg assembly 30 need not be provided with the flange units 32, 33, 34, but instead the upper and lower chords 14, 24, 16, 26 may be directly mounted onto the shaft. The individual flanges 32 b, 32 c, however, also provide support to the lower chord member 26, 16 of the truss 22, 12 mounted thereon. Although as illustrated in FIG. 4, the flange units 32, 33, 34 are shown fixed in predetermined positions on the shaft 31 of the leg assembly 30, in some examples the flange units 32, 33, 34 may be mounted on the shaft 31 at different heights of the shaft 31. The flange unit 32, for example, may comprise a tubular body with the flanges 32 a, 32 b, 32 c, 32 d extending therefrom, the tubular body having inner dimensions greater than the outer dimensions of the shaft 31. If the shaft 31 and tubular body of the flange unit 32 are circular, the flange unit 32 may be rotated to the desired orientation. The flange unit 32 may be slid along the length of the shaft 31 then fixed in position using appropriate fasteners. To simplify field installation, however, the flange units are fixed at predetermined positions.
Once the frame 10 is assembled, two of the flanges 32 a, 32 d in this example are not used to join any truss 12 or 22. However, it will be appreciated that providing the additional flanges 32 a, 32 d permits the leg assembly 30 to be joined to additional trusses (not shown), and to spacing arms, described below with reference to FIG. 13.
The upper flange units 33, 34 may be configured in a manner similar to the lower flange unit 32 described above. The upper flange units 33, 34 are spaced from the lower flange unit 32 on the shaft 31 to receive the upper chord members 14, 24 of the trusses 12, 22, again, in a similar manner to the lower flange unit 32. In this example, the upper chord members 14, 24 are disposed between the first flange unit 33, which supports the chord member, and the second flange unit 34. Fasteners 44 are then used to secure the chord member 14, 24 between the two flanges.
One or more of the leg assemblies 30 can include one or more ports 40 positioned at or near a level of the upper chord member 14, 24 when the latter is mounted to the leg assembly. A single such port 40 is shown in FIG. 4. Cables, wires or hoses threaded through the chord member 14, 24 may extend into a first port 40 corresponding to the open end of a first upper chord member 14, and pass through the leg assembly 30 to emerge from a second port corresponding to the open end of the second upper chord member 24, through which the cable, wire or hose continues. Alternatively, some cables and wires can be threaded through the chord member 14, 24 while others are attached to the exterior of the chord member 14, 24. For example, where the chord member 24 is electrically grounded, low voltage controls cables can be threaded through the chord member 14, 24, while high voltage power and controls cables can be run along the exterior of the chord member 14, 24 in order to electrically isolate them. In another example, some cables and wires can be attached to one side of the chord member 14, 24 while others are attached to the other side of the chord member 14, 24 such that the chord member 14, 24 acts as an electrical isolator. In yet another example, cables and wires may be threaded through the leg assembly 30 and run underground where they can be electrically isolated. The leg assembly 30 may also include a separator to isolate high and low voltage cables within the leg assembly 30.
The box shape of the example frame 10 provides a sufficiently stable configuration for mounting of solar tracking units 200. However, those skilled in the art will appreciate that alternative frame configurations are possible. An example of a triangular frame 50 is shown in FIG. 5, in which three trusses 52 are mounted to leg assemblies 54. In this particular configuration, the trusses 52 are substantially the same length, thus yielding a substantially equilateral triangle configuration; however, the trusses 52 may include two or three different lengths. The trusses 52 and leg assemblies 54 may be joined in a manner similar to that described in relation to FIG. 4, although unlike the example of FIG. 4, the flanges extending from the leg assemblies 54 will be arranged at angles suitable for joining the trusses in the desired triangular configuration.
Two other possible configurations are shown in FIGS. 6 and 7. FIG. 6 is a schematic representation of an X-configuration for a frame 60, with four trusses 62 mounted to a central support post 66 at a central point, and four leg assemblies 64 joined to a distal end of each truss 62. Solar tracking units, not shown, would then be mounted at least on one of the leg assemblies 64. The arrangement of the solar tracking units is thus similar to the arrangement of the solar tracking units 200 on the box frame 10 of FIG. 1. FIG. 7 shows a further X-configuration in which the trusses 72 again are mounted to a central support post 76, and extend in a similar arrangement to that shown in FIG. 6; however, the distal end of each truss 72 is mounted at a distal support post 74, and two leg assemblies 78 are joined to each of the distal support posts 74 by means of support beams 77 or a further truss. As in the example of FIG. 6, the frame 70 can support at least four solar tracking units (not shown), which can be mounted on the distal support posts 74. The examples shown in FIGS. 6 and 7 can be collapsed to facilitate transportation. The central support posts 66, 76 are provided with hinged connections, such that the trusses 62, 72 can be rotated. The distal support posts 74 of FIG. 7 are also provided with hinges, such that the leg assemblies 78 can be collapsed.
In the example illustrated in FIG. 1, the solar tracking units 200 are mounted on a mounting end 35 of the leg assemblies 30. The solar tracking unit 200 includes an armature assembly 80, shown in FIG. 8. A solar panel, such as those described in further detail below with reference to FIGS. 9 and 10, may be mounted on each of the armature assemblies 80. Each solar tracking unit 200 can also be provided with a sun position sensor (not shown) for use in computerized calibration to ensure that sunlight is normally incident on the surface of the solar panel, and to compensate for the vagaries of the field installation such as uneven terrain affecting the pitch of a given unit 200, and other issues such as manufacturing errors in the manufacture of the solar panel 210, 220 or its components, differences between the actual sun position and expected sun position, and the like.
The armature assembly 80 includes a shaft 82 having an external diameter sized to fit within the mounting end 35 of the leg assembly 30. The orientation of the shaft 82 within the leg assembly 30 may be determined during field installation, but generally the orientation will be determined by the desired north-south alignment of the frame 10 and the solar tracking units 200. Alignment of the solar tracking unit 200 on the frame 10 can be set by one or more notches or embrasures 93 at the first end of the shaft 82′, which receive one or more corresponding protrusions or pins (not shown) within the mounting end 35 of the leg assembly 30. In the example of FIG. 8, a first collar 98 and a second collar 99 are provided on the shaft 82 set back from the first end 82′. Each of the first and second collar 98, 99 have an external diameter greater than the shaft 82 or first end 82′, with the first collar 98 being sized to fit within the mounting end 35 of the leg assembly 30 (not shown in FIG. 8) with minimal or no clearance. The second collar 99 can have substantially the same external diameter as the first collar 98 so as to similarly fit within mounting end 35, with an upper lip 81 of greater diameter, which rests on the top edge of the mounting end 35 of the leg assembly 30 when mounted. Thus, the position of the lip 81 on the shaft 82, and in some examples the depth of the notches 93, determine the height of the armature assembly 80 once mounted on the leg assembly 30. In other examples, the entirety of the second collar 99 can have an external diameter greater than at least the internal diameter of the mounting end 35 of the leg assembly 30, and the lip 81 may be eliminated. The second collar 99 in that case would rest on the top edge of the mounting end 35. When mounted, the shaft 82 can be further secured to the mounting end 35 with flats 94 or other receptacles (for example, bores or other apertures) adapted to receive fasteners (for example, set screws, not shown) provided in the mounting end 35. In some examples, bores 36 (shown in FIG. 4) are provided in the mounting end 35 for receiving the fasteners.
The armature assembly includes a yoke 84 provided with a yoke mount 79, a crosspiece 85 extending from the yoke mount 79, and first and second arms 86 extending from the crosspiece 85. In the configuration shown in FIG. 8, the arms 86 extend substantially perpendicularly from the crosspiece 85 and are substantially parallel to the yoke mount 79 and to each other, although in other configurations their relative position with respect to the crosspiece 85 and the yoke mount 79 may vary according to the design of the solar panel mounted on the armature assembly 80. A gusset 83 for added rigidity is mounted on the crosspiece 85 and arms 86. The yoke mount 79 extends through and is fixed to the center of crosspiece 85. The yoke mount 79, the crosspiece 85, the arms 86 and the gusset 83 may be manufactured as individual components welded together to form the yoke 84. Alternatively, the yoke 84 may be integrally formed as a single part by die casting.
A bearing or bushing, not shown in FIG. 8, may be provided within the yoke mount 79 to facilitate rotation of the yoke 84 about shaft 82. A first drive system for controlling yaw movement of the solar tracking unit 200 includes a first gear wheel 90 fixed to the shaft 82, and therefore stationary relative to the frame 10. A second gear wheel 91 in engagement with the first gear wheel 90 is also provided on the crosspiece 85, extending from the same face of the crosspiece 85 as the first gear wheel 90. The second gear wheel 91 is fixed relative to the yoke 84. In the example of FIG. 8, the first and second gear wheels 90, 91 are disposed on the inside of the yoke 84, i.e., between the arms 86. A first drive assembly including a motor and gearbox 92 is provided for the second gear wheel 91 for controlling rotation of the second gear wheel 91 to cause the yoke 84 to rotate around the fixed first gear wheel 90 and the shaft 82. An example of a suitable drive assembly includes a weatherproof and durable stepper motor having an output shaft connected to a sealed gearbox that has an output shaft with a pinion gear (the second gear wheel 91). The pinion gear (the second gear wheel 91) can therefore provide higher torque than the stepper motor, the increase in torque depending on the gear ratios of the gears contained inside the sealed gearbox. The pinion gear connected to the output shaft of the sealed gearbox engages the first gear wheel 90 and can operate in an unsealed environment. The first drive system thus provides for rotation of the yoke 84 up to 360 degrees (or greater) in a clockwise or counter-clockwise direction. In use, the armature assembly 80 may be enclosed in a weatherproof cover (not shown) to protect the drive systems from ice, rain, sand, etc.
An axle 88 is mounted through holes 87 provided near the ends of the two arms 86. Again, appropriate bearings or bushings may be provided, not shown. Each end of the axle 88 terminates in a plate 89 for mounting to an underside of a solar panel, shown in the following figures. The precise configuration of the plates 89 will depend on the attachment means used to mount the solar panel to the armature assembly 80; in this case, grooves are provided in the perimeter of the plate 89 to receive fasteners to join the armature assembly 80 to the solar panel. A second drive system controlling pitch of the solar tracking unit 200 is provided on the yoke 84 and axle 88; a first gear wheel 95 is mounted on the axle 88, and a second gear wheel 96 in engagement with the first gear wheel 95 is mounted on the yoke 84. In this example, the first gear wheel 95 is a circular sector wheel rather than a full circle like the gear wheel 90. Since yaw over a wider range (i.e., over 180 degrees) may be provided by the first drive assembly comprising the gear wheels 90, 91, pitch adjustment of the solar tracking unit 200 over a range of 90 degrees is likely sufficient. In other examples, the gear wheel 95 may be a semicircular shape rather than a quarter-wheel; depending on the proximity of the solar panel to the axle 88, it may not be possible to provide a full-circular gear wheel on the axle 88. The second gear wheel 96 is controlled by a further drive system including a motor and gearbox 97, also mounted on the yoke 84. An example of a suitable drive assembly includes a weatherproof and durable stepper motor having an output shaft connected to a sealed gearbox that has an output shaft with a pinion gear (the second gear wheel 96). The pinion gear (the second gear wheel 96) can therefore provide higher torque than the stepper motor, the increase in torque depending on the gear ratios of the gears contained inside the sealed gearbox. The pinion gear connected to the output shaft of the sealed gearbox engages the first gear wheel 95 and can operate in an unsealed environment. In the example of FIG. 8, the motor 97 and second gear wheel 96 are mounted on the arm 86 proximate to the gear wheel 95.
In FIG. 8, spur gears are illustrated; however, other types of gears may be employed as well to provide motion in the two substantially orthogonal planes perpendicular to the shaft 82 and axle 88. Tension springs, not shown, may be provided to ensure engagement between the teeth of the gears 91, 96 and 90, 95. Home switches, not shown, may be provided on each of the two drive assemblies for use in returning the solar panels to a default position. Both the motors 92 and 97 are controllable using a local control unit described below.
The solar panel mounted to the armature assembly 80 may take any suitable shape. For example, the solar panel can include one or more flat plate solar panel modules made of semiconductors such as silicon, gallium arsenide, cadmium telluride, or copper indium gallium arsenide or can be a concentrated solar panel employing concentrating optics. In the case of concentrated solar panels, the solar panels include individual optical modules comprising PV cells. The optical modules may or may not include integrated electronics such as power efficiency optimizers and the like. Optics provided with the individual optical modules may include multiple-component optics. Embodiments of multiple-optic assemblies are described in United States Patent Application Publication Nos. 2011/0011449 filed 12 Feb. 2010 and 2008/0271776 filed 1 May 2008. An integrated concentrating PV module is described in United States Patent Application Publication No. 2011/0273020 filed 1 Apr. 2011. The entireties of the documents mentioned herein are incorporated herein by reference. The individual optical modules may be combined in series in strings of optical modules, which in turn may be connected in parallel with other strings to yield an array of optical modules. One or more strings of optical modules can be arranged in a plane to form a solar panel module.
FIG. 9 illustrates a first solar panel 210 in a “podium” configuration, in which solar panel modules of optical modules are arranged in a staggered formation to define a two-level panel. Strings of optical modules are mounted on one or more crosspieces 212 to form the solar panel modules. The crosspieces 212 may be manufactured from aluminum or any suitable material providing the weather resistance, rigidity and stability required for field use. The crosspiece 212 defines at least one recessed level 213 and at least one raised level 214, each bearing a plurality of optical modules 218. The crosspiece 212 in FIG. 9 comprises a single raised level 214 between two recessed levels 213; however, multiple raised levels 214 may be interleaved between multiple recessed levels. In this example, the optical modules 218 are mounted on heat sinks 216 which space the optical modules 218 from the crosspiece 212. Heat sinks may be manufactured from any suitable material; in FIG. 9, the heat sinks 216 are manufactured from extruded aluminum, and have an “I” beam configuration including a support 216 a, which is mounted to the crosspiece 212 such that the optical modules 218 are substantially parallel to the level 213, 214, and the set of optical modules on a given level 213, 214 are substantially flush with one another. A series of fins 216 b are provided to dissipate heat. Multiple crosspieces 212 to which the optical module strings are fixed are themselves connected by beams 215, shown in FIGS. 11 and 12, to which the armature assembly 80 can be attached.
An alternative “delta” solar panel configuration 220 is shown in FIG. 10. In this example, the crosspiece 222 comprises two arms 224 angled and meeting at a central apex 226. Again, the optical modules 230 are mounted to heat sinks 228, which in turn are mounted to the arms 224 at supports 228 a. While, as mentioned above with respect to FIG. 9, the heat sinks may take a different form, the modified “I” beam form shown in FIG. 10 permits the individual optical modules 230 to be mounted parallel to each other in a terraced arrangement. Again, the armature assembly 80 can be mounted to beams, not shown in FIG. 10. Both these staggered and delta configurations 210, 220 thus offset adjacent strings of optical modules at different heights and consequently improve air flow around the panel, thus assisting in reducing wind loading and promoting thermal transfer from the heat sinks, and may allow the panels 210, 220 to operate at a somewhat higher efficiency than otherwise. A solar panel comprising a plurality of flat plate solar panel modules can likewise have a staggered or a delta configuration. In some examples, solar panel modules can be attached directly onto the at least one recessed level 213 and the at least one raised level 214 or onto the angled arms 224, without the need for heat sinks 216, 228.
FIG. 11 illustrates the connection of the crosspieces 212 and beams 215 mentioned above. The plates 89 provided on the axle 88 of the armature assembly 80 may be fixed to the beams 215 using appropriate fastening means. The individual solar tracking units 200 and panels are usefully mounted with their center of gravity aligned with the position of the leg assembly 30 to enhance stability of the unit overall. The staggered and delta configurations of the solar panels 210 and 220 also enhance stability once installed; when the panels are mounted on the armature assembly 80, the axis of rotation (the pitch rotation, as defined by the axle 88) is substantially aligned with the center of gravity of the panel 210, 220 due to the arrangement of the offset adjacent strings of optical modules. This can be seen in FIGS. 9 and 10 by the position of the axle 88 with respect to the panel 210, 220. The panel design thus reduces the amount of energy required to drive the panel between different orientations, and assists in maintaining tracking accuracy.
Alternatively, the solar panel, whether a flat plate solar panel or a solar panel comprising concentrating optics, may have a “planar” solar panel configuration where all the receivers lie in one plane (not shown). If the center of gravity of the solar panel and panel frame used to mount the solar panel to the armature assembly is not at the center of the axle 88, then when the axle 88 is rotated, the center of gravity will be moved vertically against gravity requiring the system to do work. Therefore it can be advantageous to maintain the center of gravity of the solar panel and panel frame at the center of the axle 88. To maintain the center of gravity of the solar panel and panel frame at the center of the axle 88 a counterweight may be attached to the solar panel or panel frame to shift the center of gravity to the desired location (not shown).
FIG. 11 also illustrates a possible conduction path for grounding the supporting structures of the solar tracking units 200. A conductor 1100 is fixed at or near one end by a fastener 1101 to the beam 215, and extends to the fastener 1103 affixing the conductor 1100 to the gusset 83. A second end of the conductor 1100 is then fixed to the mounting end 35 of the leg assembly 30, for example at a further fastener 1105 joining the armature assembly 80 to the leg assembly 30. The conductor 1100 is fastened to the armature assembly 80 allowing enough slack to permit movement of the solar tracking unit 200 using the yaw and pitch drive assemblies. The conductor 1100 may be any suitable grounding wire or cable, such as insulated 10-gauge wire, and the fasteners any suitable type, and are advantageously self-tapping ground screws that are corrosive-resistant and paint-coated to resist degradation in field conditions.
FIG. 12 illustrates an alternate wiring for grounding the supporting structures of the solar tracking unit 200. In this example, a first length of conductor 1201 is fixed between the fastener 1101 and a further fastener 1102 provided on the yoke arm 86. A second length of conductor 1202 is fastened to the gusset 83 using fastener 1103, and to the leg assembly 30 by the fastener 1105 on. In this manner, the yoke 84 and the gusset 83 provide part of the conductive grounding path, rather than relying on a longer length of cabling to provide the conductive path. In this manner, the amount of torsion and/or bending of the cable may be reduced, compared to the wiring of FIG. 11, since the conductor 1201, 1202 is subjected to less movement as the yaw and pitch drive assemblies move the solar tracking unit 200 along multiple axes.
When deployed in the field, box frames 10 are advantageously positioned so that one truss of the frame 10 is aligned in a north-south direction. An example of alignment and positioning is shown in FIG. 13, which depicts three box frames 10 as they may be arranged in the field with shorter trusses oriented in a north-south direction. To maintain spacing between the frames 10, spacing arms 1302, 1304 of predetermined length are fixed to trusses or leg assemblies of adjacent frames 10. Spacing arms 1302, 1304 may be aligned with upper chord members 14, 24 or along the ground. For example, as illustrated in FIG. 13, spacing arms 1302 oriented in the north-south direction can be aligned with upper chord members 14, 24 and spacing arms 1304 oriented in the east-west direction can be at or near ground level which can allow for people to move more easily between the frames 10 and, where spacing permits, for vehicles to be driven between the frames 10 in the east-west direction. The interconnection enhances the structural solidity of the frames 10 overall, and reduces the need for external ballasting of the frames 10. The lengths of the spacing arms 1302, 1304 and the dimensions of the frames 10 themselves are selected according to the desired spacing of individual solar tracking units 200, which can be based at least in part on the size of the solar panels and/or environmental considerations such as shading and wind speeds, and on manufacturing considerations, for example based on an analysis of the relative component, shipping and land use costs and optimal power production. For example, the distance between leg assemblies in the north-south direction may be approximately 3.44 m and the distance between leg assemblies in the east-west direction may be approximately 4.98 m where panels of the type shown in FIGS. 11 and 12 are used.
In addition to physical interconnection of frames 10 of the solar tracker assemblies 100 for the purpose of enhancing stability, the individual solar tracking units 200 are interconnected within a single solar tracker assembly 100. A local control unit 1402 (LCU), shown in FIG. 14, can be provided on each assembly 100 to control all solar units 200 provided on a single frame 10. Alternatively, a single LCU 1402 can be used to control the solar tracking units 200 on several frames (not shown). For example, a cluster of frames 10 could be positioned and arranged such that an LCU 1402 is mounted only to a single frame 10 of the cluster and the other frames 10 do not have local control units mounted thereto. Wires can be run from the single LCU 1402 to each of the solar tracking units 200 on the frames of the cluster. Within a given frame 10 having four solar tracking units 200, pairs of the units 200 may be connected in series with one another, and these pairs connected in parallel with one another, thus permitting increased voltage to reduce power losses in interconnecting wires. Each pair of units 200 can be provided with a current and/or voltage sensor (not shown) in communication with the LCU 1402. In some examples, individual solar tracking units 200 on a single frame are independently controllable and each solar tracking unit 200 can be provided with a current and/or voltage sensor.
The LCU 1402 can receive input including astronomical data (which may be pre-programmed in the LCU or alternatively received over a network), readings from the current or power sensors, and readings from the sun position sensors on each solar tracking unit 200. The LCU uses the input data to determine the solar panel position for each unit 200 and outputs signals to control the motor and to communicate with other components in the field or over a network. The LCU 1402 may also be provided with a temperature sensor to measure the ambient temperature at the assembly 100 site. If the temperature is detected to rise above a predetermined threshold, the LCU 1402 can stop tracking the sun until the temperature returns to an operational range (e.g., −20 to +50 degrees Celsius). If wind speed exceeds a predetermined threshold (e.g., over 35 mph), the LCU 1402 can output a signal to the motors 92, 97 to move the solar tracking units 200 into a horizontal “stowed” position. If no temperature (or wind speed) sensor is provided on the individual assembly 100, weather data may be provided to the LCU 1402 over a communication line from a central location in a solar farm in which the assembly 100 is located, or alternatively from another network source.
The LCU 1402 may self-calibrate its expected sun position determined from received astrological data by comparing feedback from the sun sensors or power sensor (i.e., current and/or voltage sensors) on each tracking unit 200 in the iterative process shown in FIG. 15. At 1510, an initial sun position is calculated by the LCU 1402. At 1520, feedback is received from the sun sensors, and at 1530 an offset is computed between the received sun sensor data and the calculated position. An orientation difference between the feedback position and the calculated position is determined at 1540, and at 1550 a coordinate transformation based on that determined difference is applied to the calculated position. As the LCU 1402 continues to receive feedback from the sensors at 1520, the transformation may be further adjusted. The transformation is then applied to other sun position calculations made by the LCU 1402 to control the position of the solar panels 210, 220 on the various solar tracking units 200. While the sun sensors on each solar tracking unit 200 thus may be used to compensate for factors such as uneven terrain or imperfect installation, misalignment of the sun sensor with respect to the individual panel 210, 220 in the unit 200 may result in continuous degraded performance. Accordingly, the LCU 1402 may additionally or alternatively track the mechanical maximum power point (MPP) for each panel or plurality of panels using the current and/or voltage sensors, and carry out calibration of the panels by incrementally adjusting the alignment of individual panels along each axis to determine an optimal position.
Multiple LCUs 1402 can be interconnected in the field by field wiring 1400, as shown in FIG. 14. The field wiring 1400 may include a power bus for the assemblies 100 as well as communication wiring for each of the LCUs 1402. In one example, power line communication is used to effect communication between the LCUs 1402 and a global control or supervisory unit, not shown, which receives data from each of the plurality of LCUs 1402 within a farm or sub-farm of assemblies 100. The global control unit may receive data such as sun sensor data, power or current readings for each individual tracking unit 200 pair or for the entire assembly 100, and may transmit data to the LCUs 1402 including motor control instructions and other operational data, such as astrological data. Control of individual solar tracking units 200 may also be effected from the global control unit, thus overriding the associated LCU 1402. For example, maintenance personnel may use the global control unit to force the solar tracking units 200 the stowed position or to another position for maintenance and repair, or to deactivate single solar tracking units 200. In other examples, wireless (RF) communication or wired serial communications may be used between the LCUs 1402 and the global control unit. The global control unit may also optionally be accessible by operators over a public or private network, such as the Internet, for remote control of the global control unit and of individual LCUs 1402. There is thus provided a network of independently operable solar tracking units 200, each of which may be controlled using a central control system.
Some or all of the LCUs 1402 can also be made so that they do not require field wiring. This can be achieved by using wireless (e.g., radio frequency) communication between the LCUs 1402 and the global control unit and by powering the LCUs 1402 either off the solar panels that the LCU is tracking or by powering each of the LCUs 1402 with one or more secondary solar panels that are connected directly to the LCU 1402 and do not contribute to the power conducted by the main power bus of the solar farm which conducts the power produced by the solar tracking units 200. The secondary solar panels can be integrated directly into the casing of the LCU 1402 (not shown).
The global control or supervisory unit can be integrated into one of the LCUs 1402 in a solar farm. Alternatively a smaller solar farm might need only a single LCU controlling multiple trackers and serving simultaneously as the LCU and the global control unit.
FIG. 16 illustrates an example layout of a solar sub-farm or assembly array 1600 using solar tracking assemblies 100 a-100 i as described herein. The array 1600 in FIG. 16 includes nine assemblies 100 set out in a grid formation, with columns of assemblies 100 connected by spacing arms 1602, 1604 and field wiring, which may follow the path of the spacing arms 1602, 1604. It can be seen that assemblies 100 e and 100 f do not include a full complement of solar tracking units 200.
Typically, when assemblies 100 are installed, the supporting structures of each solar tracking unit 200 is grounded using the conductive paths described above with respect to FIGS. 11 and 12. An earthing electrode such as a grounding rod or spike may be connected to each of the leg assemblies 30 to prevent the accumulation of undesired voltage on the frames 10 and the supporting structures (e.g. the crosspieces, beams and armature assembly) of the solar tracking units 200. To reduce cost of installation, since the spacing arms 1602, 1604 provide a conductive path between the units 200, a central grounding location for a grounding rod or spike 1650 connected to one of the frames 10 of the assembly array 1600 is selected in a position that provides the minimum possible path between the furthest individual solar tracking unit 200 within the array 1600 and the grounding spike 1650.
With the foregoing frame 10 and units 200, the solar tracker assemblies 100 are easily installed in the field. As mentioned above, various features of the assemblies 100 can compensate for uneven terrain; advantageously rough grading of the site is carried out to roughly level the ground, and to create paths for maintenance access. On unstable ground or fertile soil, a thin layer of crushed concrete aggregate may be distributed to assist in stabilizing the ground and/or prohibiting plant grown. The pre-wired, collapsed frame 10 having three trusses 12, 22 is unfolded, and the fourth truss 22, 12 fixed in place. The foot member 37 on each leg assembly 30 is adjusted, if necessary, to compensate for uneven terrain; however, this adjustment need not be completely accurate since variations in the terrain can also be compensated for by auto-calibration of the tracker modules. Armature assemblies 80 are then distributed to each leg assembly 30, and dropped into place on the mounting end 35 of the leg assembly 30, and fixed in place with a fastener. The solar panel 210, 220 is then fixed to the armature assembly 80 via the plates 89 and fasteners. The overall height of the frame 10 and armature assembly 80 is such that cranes or similar equipment are not necessary for installation of the panels 210, 220. In a further embodiment, the panels 210, 220 are shipped with removable handles that permit the installation personnel to lift the solar panel 210, 220 and to place it on the armature assembly 80.
Grounding wires are then attached as necessary, and the motors 92, 97 connected to wiring within the frame 10 leading to the local control unit 1402. The motor wiring may pass, in part, through the leg assemblies 30 and/or truss assemblies. The local control unit 1402 is mounted on the frame 10 and connected to the wiring already provided on the frame 10. The local control unit 1402 is then connected to the power bus interconnecting the other assemblies 100. Field wiring is provided by pre-cut and terminated bundles of PV-rated cabling containing the PV power bus and the local control unit power/communication bus. The field wiring may lie directly on the ground between solar tracker assemblies 100, although in those regions where it may interfere with maintenance paths between assemblies 100 it may be desirable to bury the cabling or otherwise protect it.
If air or water hosing is provided within the frame 10, this hosing is connected to a source. The hosing may be connected to cleaning implements (e.g., a spray gun) and used to clean the tracking solar module 200 or other components of the assembly 100.
Another configuration of a solar tracker assembly or unit 2100 is shown FIG. 17. The assembly 2100 generally includes a ground-mounted frame 2010 for supporting one or more solar tracking units 2200, which can include PV tracker modules as described above, or heliostat mirrors. In the example illustrated in FIG. 17, the solar tracking units 2200 are shown supporting a solar panel module 2210 with several solar panels 2205. The frame 2010 includes a plurality of trusses 2012 of substantially equal length. The assembly of the trusses 2012 yields an overall parallelogrammatic, and in this specific example, a rhombus (or diamond) frame 2010. The sides of the frame 2010 need not employ trusses specifically, although the benefits of the structural stability of a truss design will be appreciated by those skilled in the art.
Each individual truss 2012 includes an upper chord member 2014 and lower chord member 2016. The chord members 2014 and 2016 are joined by a set of truss members 2017. Trusses 2012 in this example each include a set of four truss members 2017. The selection and arrangement of the truss members 2017 need not be limited to the example shown; depending on the selected dimensions and materials of the frame 2010, more or fewer truss members 2017 may be employed. In addition, one or more struts 2018 may be mounted between the upper and lower chord members 2014 and 2016 to provide additional vertical support between the chord members. In the example of FIG. 18 two struts 2018 are provided between adjacent trusses and these can be used to support the LCU 2402.
The trusses 2012 are joined at or near their respective ends at leg assemblies 2030 shown in further detail in FIG. 19A. A cross member 2046 attaches the two leg assemblies 2030 a, 2030 c that are positioned closest to one another, and adds structural support and rigidity. Additional truss members 2048 extending from the trusses 2012 to the cross member 2046, which here is depicted as a chord member that can be manufactured in a similar manner to the chord members and leg assemblies of the frame, and can also be a truss, also add structural support. Each leg assembly 2030 includes a shaft 2031, and can include an adjustable foot member 2037. The foot member 2037 in this example is detachable and includes a plate member 2039 extending from a stem 2038. The stem 2038 is attached to the shaft 2031 of the leg assembly 2030, and in some examples the attachment point of the stem 2038 to the shaft 2031 may be varied so as to permit adjustment of the overall height of the leg assembly 2030, and thus of the solar tracking units 2200 when mounted thereon. The stem 2038 and plate member 2039 may have alternate configurations than that described herein. In some examples, a spike member or other attachment component, not shown, for anchoring the leg assembly in the ground and/or electrically grounding the frame 2010 can be provided in addition to or instead of plate member 2039. A distal end of the leg assembly 2030 provides a mounting end 2035 for mounting an armature assembly 2080 for bearing the solar tracking module 2200.
The trusses 2012 and leg assemblies 2030, and their respective components, may be manufactured from any suitable material. For example, the trusses and leg assemblies may be manufactured from galvanized steel or aluminum, and may be manufactured from extruded or drawn metal tubing, whether open or seamed. Further, in some examples, at least the upper chord members 2014 may be provided with an axial borehole or otherwise formed with an interior channel running the length of the chord member, open at either end (not shown), which is conveniently provided when the chord members are manufactured from tubing. Cables, wires and hoses, such as electrical cables and the like, as well as air or water hoses, may be threaded through the upper chord members 2014 and/or lower chord members 2016. Similarly, the leg assembly 2030 may be provided with a similar axial borehole or interior channel. In the examples illustrated herein, the leg assembly 2030 is a tubular member.
Six brackets 2049 extend from the leg assembly 2030 shown in the example of FIG. 19A. Each of the brackets 2049 are provided with boreholes for receiving fasteners 2042. The lower chord members 2016 are placed on the corresponding brackets 2049 e and 2049 f such that the boreholes provided in each component are substantially aligned, and the fasteners 2042 are used to join the chord member to its respective bracket. The upper chord members 2014 are sandwiched between two brackets 2049 a, 2049 c and 2049 b, 2049 d respectively, the extra brackets provide additional support. The fasteners 2042 may also facilitate an electrical connection between the chord member and the leg assembly 2030 via its respective bracket for electrical grounding purposes. Suitable fasteners 2042 may be selected for joining and/or electrically connecting the chord members and brackets, such as the illustrated threaded bolts and washers. The fasteners mentioned herein may, for example, be self-tapping screws or split pins; thus the boreholes in the brackets 2049 and trusses 2012 need not be threaded.
It will be appreciated that other means of attaching a truss 2012 to the leg assembly 2030 may be used; for example, the leg assembly 2030 need not be provided with the brackets 2049, but instead the upper and lower chords 2014, 2016 may be directly mounted onto the shaft. The individual brackets 2049, however, also provide support to the chord member 2014, 2016 mounted thereon.
Although as illustrated in FIG. 19A, the brackets 2049 are shown fixed in predetermined positions on the shaft 2031 of the leg assembly 2030, in some examples the brackets 2049 may be mounted on the shaft 2031 at different heights of the shaft 2031.
The shaft 2031 and the plate member 2039 are provided with additional boreholes. It will be appreciated that providing the additional boreholes permits the leg assembly 2030 to be joined to additional trusses (not shown), and to spacing arms. With reference to FIG. 19B, it is shown that a spacing arm 2304 can be mounted to the leg assembly 2030 by means of mounting features in the spacing arm 2304 provided with boreholes, such as the illustrated fork 2343, fixed to the leg assembly 2030 by fasteners (not shown). With reference to FIG. 19C, it is shown that a spacing arm 2302 can be assembled onto the plate 2039 by means of boreholes and fasteners. One or more of the leg assemblies 2030 can include one or more ports 2040 positioned at or near a level of the upper chord member 2014 when the latter is mounted to the leg assembly. A single such port 2040 is shown in FIG. 19A. Cables 2054, wires or hoses threaded through the chord member 2014 may extend into a first port 2040 corresponding to the open end of a first upper chord member 2014, and pass through the leg assembly 2030 to emerge from a second port corresponding to the open end of the second upper chord member 2014, through which the cable, wire or hose continues. Alternatively, some cables and wires can be threaded through the chord member 2014 while others are attached to the exterior of the chord member 2014. For example, where the chord member 2014 is electrically grounded, low voltage controls cables can be threaded through the chord member 2014 while high voltage power and controls cables can be run along the exterior of the chord member 2014 in order to electrically isolate them.
In another example, some cables and wires can be attached to one side of the chord member 2014 while others are attached to the other side of the chord member 2014 such that the chord member 2014 acts as an electrical isolator. In yet another example, cables and wires may be threaded through the leg assembly 2030 and run underground where they can be electrically isolated. The leg assembly 2030 may also include a separator to isolate high and low voltage cables within the leg assembly 2030. The mounting end 2035 of the leg assembly includes an upper lip 2043 provided with fasteners 2045 for coupling and fastening an armature assembly thereto. In this particular example the fasteners 2045 can be, but are not limited to press fitted wheel studs for fastening an armature by means of nuts.
FIG. 20 illustrates four trusses 2012 of the frame 2010 joined to the four leg assemblies 2030. In this example, the four trusses are assembled with the leg assemblies 2030 in a collapsed state suitable for transportation. In this configuration, the trusses remain joined, but more easily transportable than when the frame 2010 is completely assembled. This view illustrates brackets 2049 on the leg assemblies 2030, which are provided for mounting the trusses 2012. The brackets 2049 can be welded onto the leg assembly 2330, or attached by any other means. It can be seen from the collapsed state that the fastening means used to join the trusses 2012 to the leg assemblies 2030, are advantageously adapted to provide a hinged connection between each truss 2012 and the leg assembly 2030 to permit the frame 2010 to be shipped in a partially assembled state. Further, since the trusses 2012 may carry cables, wires or hoses in their respective upper or lower chords 2014, 2016 these components may be pre-threaded through the chords prior to shipping to minimize assembly time in the field, as well as shield the wiring, etc. from the elements, and reducing the need for expensive connectors.
As shown in FIG. 21 a frame 2010 can be collapsed by detaching truss 2012 b from leg assembly 2030 c and detaching truss 2012 d from leg assembly 2030 d. This can be done by removing the fasteners that fasten said trusses to the respective brackets of said leg assemblies. In the cases where the fasteners are screws and bolts, these can simply be removed for shipping and reattached during assembly. As described by the arrows, truss 2012 b rotates towards truss 2012 a. Then both trusses 2012 a and 2012 b are rotated together towards the cross bar 2046. Further, trusses 2012 c and 2012 d rotate individually towards the cross member. The result is a collapsed frame as shown in FIG. 20.
As described previously a rhombus-shaped tracker assembly 2100 has two leg assemblies 2030 a, 2030 c that are closer together and two leg assemblies that are further apart 2030 b, 2030 c, as shown in FIGS. 22A and 22B. FIGS. 22A and 22B are two different side views of the frame 2010. Rhombus-shaped tracker assemblies 2100 stagger the position of the solar tracking units mounted thereto to minimize shading-related losses.
Trackers can be interconnected with pre-measured spacing arms to minimize installation time, as well as optimize field layout for minimal tracker-to-tracker shading. A field of interconnected tracker assemblies 2100 can thus mutually ballast each other. In one example, a field of interconnected tracker assemblies may enable operation in winds up to 35 mph. An example of alignment and positioning is shown in FIG. 23, which depicts nine frames 2010 in rows as they may be arranged in the field. When deployed in the field, tracker assemblies 2100 are advantageously positioned so that the cross members 2046 are aligned in a north-south direction. It can be seen from FIG. 23, and from FIG. 24C discussed below, that a consequence of such positioning is that adjacent sides of adjacent frames are substantially parallel, taking into account possible variations in terrain. The resultant geometry of the solar tracking units and frames of these examples will be readily appreciated by those skilled in the art. To maintain spacing between the frames 2010, spacing arms 2302, 2304 of predetermined length are fixed to trusses or leg assemblies of adjacent frames 10. Spacing arms 2302, 2304 may be aligned with upper chord members 2012 or along the ground. For example, as illustrated in FIG. 23, spacing arms 2304 can be aligned with upper chord members 2012 and spacing arms 2302 oriented in the north-south direction can be at or near ground level which can allow for people to move more easily between the frames 2010 and, where spacing permits, for vehicles to be driven between the frames 2010.
The interconnection enhances the structural solidity of the frames 2010 overall, and reduces the need for external ballasting of the frames 2010. The lengths of the spacing arms 2302, 2304 and the dimensions of the frames 2010 themselves are selected according to the desired spacing of individual solar tracking units 2200, which can be based at least in part on the size of the solar panels and/or environmental considerations such as shading and wind speeds, and on manufacturing considerations, for example based on an analysis of the relative component, shipping and land use costs and optimal power production.
FIGS. 24A-24C further illustrate a possible implementation of a field or farm of rhombus-shaped tracker assemblies 2100. FIG. 24A is an isometric view of an example tracker assembly 2100 similar to that of FIG. 17. FIG. 24B is a side view, of the example tracker assembly 2100. FIG. 24C is a top view of an example solar farm similar to that shown in FIG. 23.
As can be seen in FIG. 24A, in the example shown here, the solar tracking units 2200 mounted on the frames can accommodate modules 2205 of standard-sized silicon PV solar panels 2210. The solar panel modules 2205 can be positioned on-sun throughout the day within 2 degrees of precision by a field-proven drive train. FIG. 24C illustrates the relative position of solar tracking units (here, with solar panels mounted on armatures, the latter not being not shown) with respect to one another in an example field of four solar tracker assemblies 2100 a-2100 d. Circumference c indicates the range of the panel turning radius on an axis of the solar tracking unit. As already described above, structural support and rigidity of each solar tracker assembly 2100 a-2100 d can be enhanced by corresponding cross members 2046, indicated in FIG. 24C as 20146 a, 20146 b, and 2046 c in solar tracker assemblies 2100 a, 2100 b, and 2100 c. Also as described above, alignment and positioning can be maintained between the frames by spacing arms 2302, 2304 of predetermined lengths, which are fixed to trusses or leg assemblies of adjacent frames. FIG. 24C illustrates that frames 2010 a, 2010 b, and 2010 c are interconnected with each other and with other solar tracker assemblies (not shown) with spacing arms 2302 and 2304. As can be seen in FIG. 24C, one spacing arm 2302 can be parallel to the cross members 2046 of the frames 2010, while the other spacing arm 2304 can be parallel with a side of the frames 2010. These spacing arms of predetermined length thus assist in maintaining regular spacing between adjacent frames 2010 and accordingly between adjacent solar tracking units 2100.
In this example, the distance in the north-south direction between leg assemblies, and consequently solar tracking units, is indicated by d₁in FIG. 24C and is approximately 4.8 m. The distance between leg assemblies in the east-west direction, as indicated by d₂, is approximately 8.083 m. It can also be seen in FIG. 24C that the arrangement of these rhombus-shaped frames 2010 a-2010 d results in corresponding pairs of leg assemblies (not shown in FIG. 24C) spaced by substantially the same distance, taking into account possible variations due to uneven terrain, although as discussed herein the configuration of the solar tracker assemblies can mitigate such variations. For example, the pair of solar tracking units 2201 a and 2203 a, which is the pair of solar tracking units that are closest together in solar tracking assembly 2100 a, are spaced by distance d₁along the north-south direction; likewise, the corresponding pair of solar tracking units 2201 b and 2203 b in adjacent solar tracking assembly 2100 b is spaced by the same distance d₁. In addition, it can be seen in the example of FIG. 24C that the distance in the same direction between corresponding leg assemblies or solar tracking units 2201 a, 2201 b in two adjacent solar tracking assemblies 2100 a, 2100 b is also d₁. Similarly, FIG. 24C further illustrates that the distance between the remaining pair of solar tracking units or leg assemblies in a given solar tracking assembly (e.g., solar tracking units 2204 a and 2202 a of assembly 2500 a), indicated as d₂, is the same as the distance between corresponding solar tracking units or leg assemblies in adjacent solar tracking assemblies, as can be seen by the distance d₂in the east-west direction between solar tracking unit 2202 a of solar tracking assembly 2100 a and corresponding solar tracking unit 2202 b of solar tracking assembly 2100 b.
FIG. 24B shows that this example of a tracker assembly can be 1.554 m in height h₁from the ground to the top of the armature (not shown in FIG. 24B), and 0.678 m in height h₂from the ground to the upper chord member 2014. In the examples of FIGS. 24A-24C, the tracking units each hold solar panels 2210 comprising three solar panel modules 2205; therefore, in this particular example, twelve solar panel modules 2205 are supported by each tracker assembly 2100. Additional specifications for this example implementation of a tracker assembly are as follows: the maximum solar panel area per tracker assembly is 21 m²; the tracker weight is 195 kg; the maximum wind speed in stow position is 120 mph; the maximum operational wind speed is 35 mph; the tracking accuracy is less than 2 degrees; the azimuth control angle is 360 degrees; the elevation control angle is 20-95 degrees; the electrical power requirements are 85-265 V AC, 50 hz or 60 hz for single and split phase respectively; the theoretical nominal power consumption is 35.0 kWh/year; the operational temperature is −20 to 50° C. and the storage temperature is −40 to 85° C. Those skilled in the art will understand that these dimensions are not mandatory; other dimensions and configurations can be used depending on the specific application and may be dependent on the solar panel dimensions or other constraints and conditions. In addition, communication to the individual solar tracking assemblies or units mounted on each leg assembly may be achieved via a power line or USB. As mentioned above, the operator may control the assemblies and units by issuing commands over a network. This can include wireless transmission to the global control unit as well as wireless transmission from the global control unit to the LPUs. Communication between the LPUs and individual solar tracking units may be wireline (e.g. the power line or USB connection mentioned above) rather than wireless.
It can be appreciated from FIGS. 23 and 24C in particular that a rhombus frame such as that of FIG. 17 and the following figures, discussed above, makes possible a particular configuration of solar tracker assemblies 2100 in the field unlike the rectangular grid arrangement of FIG. 14 or 16. As can be seen in the example of FIGS. 23 and 24C, the field comprises a set of solar tracker assemblies 2100 arranged such that adjacent sides of adjacent solar tracker assemblies 2100 are parallel. However, as most clearly seen in FIG. 24C, the result is that the individual solar tracking units, the positions of which are determined by the position of leg assemblies on which the individual solar tracking units are mounted, are arranged in a staggered formation with in substantially equally-spaced rows and columns.
This is further illustrated in FIG. 25A, which depicts another example of a field of interconnected solar tracker assemblies having an oblique-angled (i.e., non-square) rhombus or diamond frame as generally described above. In this figure the spacing arms 2302, 2304 have been omitted to reduce clutter in the drawings, but it will be understood by those skilled in the art that the physical spacing and interconnection can be accomplished using the spacing arms 2302, 2304 as described above. In this example field, eight solar tracker assemblies 2500 a to 2500 h are illustrated with in a similar arrangement to the nine solar tracker assemblies 2100 of FIG. 23 or 2100 a to 2100 d of FIG. 24C; in other words, with all solar tracker assemblies oriented in the same direction, with adjacent sides of each solar tracker assembly (as defined by the sides of that assembly's rhombus frame) being parallel to the immediately adjacent (i.e., nearest neighbour) solar tracker assembly. There may, of course, be more or fewer solar tracker assemblies and solar tracking units than illustrated in these examples. As illustrated, each solar tracker assembly 2500 a to 2500 h is provided with four solar tracking units a, b, c, and d. However, it will be understood by those skilled in the art that each assembly need not be provided with a full complement of solar tracking units; a single solar tracking assembly may be provided with between zero and four solar tracking units. The solar tracking units are generally presumed to be collocated with a corresponding leg assembly (not shown in FIG. 25A), the leg assembly thus defining the position of the solar tracking unit with respect to the other solar tracking units in a single assembly 2500 a, as well as with respect to other assemblies 2500 b to 2500 h in the field. In the discussion of spacing, orientation and arrangement of solar tracker assemblies herein, references to the position of the leg assembly and the position of the solar tracking unit may be used interchangeably.
As in the case of FIGS. 23 and 24C, the cross member of each solar tracker assembly may be substantially aligned with the north-south direction indicated as direction D₁(the east-west direction is therefore D₂), but as will be discussed below, the physical interrelationship among the set of tracker assemblies does not require orientation in a cardinal direction. FIG. 25A shows an overlay of part of a rectangular grid having rows 2502 a to 2502 d, aligned to be substantially collinear or parallel with the major diagonals of a set of the solar tracker assemblies, and columns 2504 a to 2504 d, which are substantially collinear or parallel with the minor diagonals of a set of the solar tracker assemblies (i.e., substantially collinear with a set of cross members within the entire group of assemblies). Each of these rows and columns contains a set of one or more solar tracking units. Thus, for example, row 2502 b is collinear with the major diagonal (not marked) of solar tracker assemblies 2500 a and 2500 b, and contains four solar tracking units (units d and b of both assemblies 2500 a and 2500 b). Row 2502 d is collinear with the major diagonals of solar tracker assemblies 2500 c and 2500 d and contains four solar tracking units as well (units d and b of assemblies 2500 c and 2500 d). Rows 2502 a and 2502 b are each parallel to the remaining rows, and are consequently parallel to the major diagonals of the solar tracker assemblies 2500 a to 2500 h. Row 2502 a contains two solar tracking units, unit a of both assemblies 2500 a and 2500 b. Row 2502 c contains four solar tracking units, unit c of assemblies 2500 a and 2500 b, and unit a of assemblies 2500 c and 2500 d. Column 2504 a contains four solar tracking units, unit d of assemblies 2500 b and 2500 f, and unit b of assemblies 2500 c and 2500 g. Columns 2504 b, 2504 c, and 2504 d similarly contain four solar assemblies from different sets of solar tracking assemblies. As small height variations may exist between adjacent frames or leg assemblies due to variations in the terrain, “collinear” includes those cases where there is no true collinearity but the sides, cross members, or spacing arms in question are substantially collinear for practical purposes, for instance where both members lie in planes that are substantially coincident.
As an aside, it will be appreciated by those skilled in the art that the geometry of a rhombus or diamond shape generally comprises two diagonals, extending between opposing vertices of the rhombus. The lesser diagonal extends between the two closer vertices, while the greater diagonal extends between remaining vertices, which are further apart. Of course, in a square rhombus where the angles defined at each vertex is 90°, the diagonals will be of equal length; however, as illustrated in the accompanying figures and as discussed above, the rhombus frames in these examples are non-square or oblique-angled. As explained above, the cross members 2046 of each frame connect the leg assemblies that are closer to each other, and are thus substantially aligned with the lesser diagonal. The cross members and lesser diagonals of the solar tracker assemblies 2500 a to 2500 h (or in a field of any number of similarly positioned assemblies) may thus be considered to be more or less collinear or parallel. The length of the cross member may not be the exact length of the lesser diagonal, allowing for the dimensions of the leg assemblies to which the cross member is attached, and any fastening means provided on the cross member or leg assemblies.
Returning to FIG. 25A, it can be seen that, by virtue of the physical spacing between the frames of adjacent solar tracker assemblies 2500 a to 2500 h and the rhombus (diamond) configuration of the solar tracker assembly frames, adjacent rows and columns of solar tracking units are alternately staggered; thus, assuming that the field is aligned with the cardinal directions as indicated in FIG. 25A, nearest neighbour (by distance between leg assemblies) of a given solar tracking unit is not directly to the north or south; for example, compare unit b of assembly 2500 a, with nearest neighbours a and c of assembly 2500 a and unit a of assembly 2500 c. The next solar tracking unit directly to the south (i.e., in a line substantially parallel with D₁and with a row as defined above) is not the nearest neighbour.
The physical spacing and frame shape is preserved even when the field as a whole is oriented in a different direction. FIG. 25B illustrates the same field of interconnected solar tracker assemblies 2500 a to 2500 h, with solar tracking units a, b, c, and d labelled as in FIG. 25A. All assemblies are again in the same orientation with respect to each other and spaced as described above, although in this example the entire field of solar tracker assemblies has been rotated such that a side of each frame is substantially parallel with the direction D₁(which as noted above may be a cardinal direction). Given the parallelogrammatic shape of the frames, each frame of the assemblies 2500 a to 2500 h accordingly has a pair of sides substantially parallel with this direction. Rotation of the field in this manner gives rise to an advantageous field layout, discussed below. The rectangular modules (e.g., solar panels) carried by each solar tracking unit have been rotated in FIG. 25B to have the same alignment with respect to D₁as those modules in FIG. 25A. Once again, it can be seen that in a set of rows 2506 a to 2506 d and columns 2508 a to 2508 d aligned with orthogonal directions D₁and D₂, respectively, the field of assemblies 2500 a to 2500 d yields sets of staggered rows or columns of solar tracking units. Thus, the solar tracking units in row 2506 a (unit a of assembly 2500 a, unit d of assembly 2500 c, and unit a of assembly 2500 g) are evenly spaced with respect to each other, and staggered with respect to the solar tracking units in row 2506 b (unit c of assembly 2500 a, unit b of assembly 2500 e, and unit c of assembly 2500 g), which themselves are evenly spaced in their own row. Similarly, the solar tracking units in a given column such as 2508 a (consisting of six a and d units from three different tracker assemblies 2500 d, 2500 f and 2500 g) are staggered in relation to the solar tracking units in an adjacent column, such as 2508 b (consisting of six b and c units from the same three tracker assemblies). It can be seen that a given row or column need not have the same number of solar tracking units as its neighbouring rows or columns, or indeed as any other row or column.
It can further be recognized that the layout of solar tracking units in a field arranged as in FIGS. 23, 24C, 25A and 25B can be defined according to other schemas. For instance, the staggered spacing of the solar tracking units may be expressed in the form of a diamond grid as illustrated in FIG. 25C, with each solar tracking unit of a given solar tracking assembly occupying a distinct diamond cell within the grid. Thus, as indicated in FIG. 25C, in solar tracker assembly 2500 a, solar tracking units a to d occupy corresponding diamond cells 2512 a to 2512 d, and in solar tracker assembly 2500 b, solar tracking units a to d occupy corresponding diamond cells 2514 a to 2514 d. It can be seen that the diamond cells in this configuration tile the area covered by the field of solar tracker assemblies 2500 a to 2500 h.
An alternate expression is shown in FIGS. 25D and 25E. These figures illustrate that the same layout of the solar tracking units may be defined by a hexagonal grid layout, where each solar tracking unit occupies a corresponding hexagonal cell, the hexagonal cells tiling the area covered by the field. Thus, the solar tracking units a to d of solar assembly 2500 a occupy corresponding hexagonal cells 2522 a to 2522 d, and solar tracking units a to d of solar assembly 2500 b occupy corresponding hexagonal cells 2524 a to 2524 d. Each solar tracking unit in the hexagonal grid can have between two and six immediate neighbours (i.e., separated by the shortest distance). Unit b of solar tracker assembly 2500 d has only two neighbours, units a and c of the same assembly 2500 d; unit a of assembly 2500 f has six neighbours, including b, c, and d of its own assembly 2500 f, as well as unit b of assembly 2500 c, unit c of assembly 2500 b, and unit d of assembly 2500 d.
The hexagonal grid schema gives rise to a further definition of the layout, illustrated in FIG. 25E. It can be seen that the hexagonal grid can be subdivided into sets of adjacent, contiguous cells or clusters, each comprising a central cell (e.g., the cell containing unit d of assembly 2500 c) and six immediately adjacent cells (e.g., units b and c of assembly 2500 a, units a and c of assembly 2500 c, and units a and b of assembly 2500 e). Some such clusters may be complete clusters of seven cells, as in the case of clusters 2526 a and 2526 b; other clusters may be partial due to the layout of the solar tracker assemblies, as in the case of clusters 2526 c and 2526 d. As mentioned earlier, control of each solar tracking unit in a given assembly may be provided by an LCU, not shown; in each cluster of the cellular arrangement, the solar tracking units may be controlled by up to four different LCUs.
As mentioned above, rotation of the field of solar tracker assemblies from the orientation shown in FIG. 25A can result in an advantageous field layout. One such layout is illustrated in FIG. 26A. This figure illustrates an example field of eight solar tracker assemblies 2600 a to 2600 h, each having the same orientation, in this case each frame having a pair of sides substantially parallel to a first direction D₁. This pair of sides includes side 2612 b on each frame. The remaining sides of each frame, which include sides 2612 a, are of course parallel to one another within each frame, and are also parallel to the corresponding sides of each other frame in the field. Again, D₁may be a cardinal direction, such as north or south, and the other direction D₂, perpendicular to D₁, can be east or west. The tracker assemblies are notionally arranged into a set of parallel columns or rows: here, four columns ( assemblies 2600 a, 2600 e; assemblies 2600 b, 2600 f; assemblies 2600 c, 2600 g; and assemblies 2600 d, 2600 h) and two rows (assemblies 2600 a to 2600 d, and assemblies 2600 e to 2600 h). These columns are thus parallel with the sides of the frames that are substantially parallel with D₁.
Because the tracker assemblies 2600 a to 2600 h are arranged with a side parallel to the first direction D₁, the entire field of tracking units and tracker assemblies defines a generally rectangular area, with sides parallel to D₁and D₂. Arranging the field in this manner provides for efficient usage of the land available for erecting a farm of solar tracking assemblies, which is often divided into parcels having boundary lines and access roads running north-south.
As set out earlier, the individual frames may be interconnected with spacing arms. In the example of FIG. 26A, spacing arms 2602 connect adjacent frames within a given column and are substantially collinear (and consequently substantially parallel) with a first side of each frame in the column. The spacing arms 2602 in other columns are likewise collinear and parallel with the corresponding side of their respective frames, here marked as side 2612 b. These spacing arms define the spacing between the frames, and consequently between the solar tracking units of adjacent frames, within a given column, in the first direction D₁.
The spacing of adjacent columns is controlled by a second set of spacing arms 2604, which here are shown as substantially collinear and parallel with the cross members 2646 of each assembly 2600 a to 2600 h. These cross members 2646, as discussed above, may be aligned with the lesser diagonal of each rhombus frame. The second set of spacing arms is accordingly not parallel with a side of the frames.
The arrangement of FIG. 26A differs from that of FIG. 25A in that not only are the solar tracker assemblies 2500 a to 2500 h of FIG. 25A staggered, but the solar tracking units a, b, c, d are, likewise; but in FIG. 26A, the solar tracker assemblies 2600 a to 2600 h are not staggered, but the solar tracking units a, b, c, d are still staggered. The arrangement of FIG. 26A thus yields the staggered layout of solar tracking units, but accomplishes this with aligned columns and rows of solar tracking assemblies, rather than with a staggered arrangement. The staggered arrangement of solar tracking units is illustrated in FIG. 26B in a manner similar to that of FIGS. 25A and 25B, with rows of solar tracking units 2562 a, 2562 b, 2562 c, and 2562 d parallel to direction D₂, and columns of solar tracking units 2654 a to 2654 d parallel to direction D₁. It will be easily appreciated from the drawing that the arrangement of solar tracking units remains staggered, by comparing the arrangement of units in adjacent rows or columns to one another.
The staggered arrangement of solar tracking units can, again, be defined in terms of the hexagonal grid and the cellular clusters discussed in connection with FIGS. 25D and 25F. As shown in FIG. 26C, a first cluster of hexagonal cells 2626 a contains solar tracking unit c of solar tracker assembly 2600 a at its center, surrounded by adjacent cells containing units b and d of solar tracker assembly 2600 a, unit d of assembly 2600 b, units a and b of assembly 2600 e, and unit a of assembly 2600 f. This first cluster accordingly comprises solar tracking units from four different solar tracker assemblies and four different adjacent frames; consequently, this first cluster includes solar tracking units controlled by four different LCUs. Solar tracking unit c of solar tracker assembly 2600 a has six neighbouring solar tracking units; other units may have fewer neighbouring units, such as unit a of solar tracker assembly 2600 a, which has only two. FIG. 26C includes another complete cellular cluster 2626 b; other clusters 2626 c, 2626 d are incomplete due to the arrangement of solar tracker assemblies.
An alternative layout of solar tracking units and solar tracker assemblies, which also provides the substantially rectangular field, is shown in FIG. 27A. Like the arrangement of FIG. 26A, all frames of the solar tracking assemblies 2700 a to 2700 h have a pair of sides, including sides 2712 a indicated in the drawing, that is substantially parallel to the first direction D₁. The remaining pair of sides in each frame remains parallel to each other, within each frame; however, alternating columns of frames comprise sets of solar tracker assemblies of opposite orientations, so these sides are not all parallel to each other within the entire field. Sides 2712 b, indicated in FIG. 27A for each solar tracker assembly, has different orientations according to the column in which the assembly is located.
Again, the tracker assemblies are notionally arranged into sets of parallel columns. In this example, there are four columns ( solar tracker assemblies 2700 a and 2700 e; assemblies 2700 b and 2700 f; assemblies 2700 c and 2700 g; and assemblies 2700 d and 2700 h). In each of these columns, pairs of sides are substantially parallel with D₁. Of the remaining sides, the adjacent sides of adjacent solar tracker assemblies (e.g. 2700 a, 2700 e) are parallel. Adjacent columns of solar tracker assemblies, on the other hand, are arranged in opposing (effectively mirror image) orientations, such that the lesser diagonals (and cross members 2746) are arranged in opposing directions. If D₁is north, then the cross member 2746 of solar tracker assembly 2700 a is aligned along a west-northwest to east-southeast direction, while the cross member 2746 of solar tracker assembly 2700 b, in an adjacent column, is assigned in an east-northeast to west-southwest direction. The precise heading of these directions will depend on the specific frame geometry employed in the field. The effect is that not every cross member 2746, or every side 2712 b of all frames in the field, will be parallel.
The individual frames of each assembly may be interconnected with spacing arms. As with the example of FIG. 26A, spacing arms 2702 a, 2702 b connect adjacent frames within a given column, and are substantially collinear or parallel with a corresponding side of each frame in the column. Thus, in the first and third columns of assemblies ( assemblies 2700 a, 2700 e; and 2700 c, 2700 g), the spacing arms 2702 a are substantially collinear with sides 2712 a, and are consequently parallel with direction D₁. However, in the example of FIG. 27A, for the remaining columns of assemblies (2700 b, 2700 f; 2700 d, 2700 h) spacing arms 2702 b, which are parallel with direction D₁as well, are not collinear with the corresponding sides 2712 a of the frames to which they are attached, but are rather collinear with the opposite side to 2712 a. Spacing arms 2702 b could alternatively be attached to the frames of those columns so as to be collinear with sides 2712 a.
The spacing of adjacent columns is controlled by a second set of spacing arms 2704 a and 2704 b. Because of the opposing orientations of adjacent columns, the position of these spacing arms will vary by column. Spacing arms 2704 a are collinear with sides 2712 b of the solar tracker assemblies of the first and third columns; spacing arms 2704 b are collinear with the cross members 2746 of the solar tracker assemblies of the second and fourth columns. In this example, the result is that all spacing arms 2704 a, 2704 b are parallel to each other. In an alternate embodiment, spacing arms 2704 b may be aligned in an opposing direction (e.g., between unit b of assembly 2700 b, and unit d of assembly 2700 c).
As with the example of FIG. 26A, the solar tracking units a, b, c, d of all of the solar tracker assemblies in the field are staggered, while still providing aligned columns of solar tracker assemblies and generally aligned rows of solar tracker assemblies, that fit within a generally rectangular area. The staggered arrangement of solar tracking units can, as before, be defined in terms of a hexagonal grid and cellular clusters. FIG. 27B illustrates a parceling of hexagonal cells into clusters 2726 a to 2726 d. Complete clusters 2726 a and 2726 b thus include seven contiguous cells, and their central solar tracking units (unit c of solar tracker assembly 2700 a, and unit d of solar tracker assembly 2700 c) have six neighbours, while others, such as unit d of assembly 2700 f has only four. Clusters 2726 a and 2726 b contain solar tracking units associated with three different solar tracker assemblies, and thus three different LCUs. This is not the only subdivision of the hexagonal grid possible. FIG. 27C illustrates an alternate set of clusters 2728 a to 2728 d, where cluster 2728 a includes solar tracking units from four different solar tracker assemblies.
As those skilled in the art will appreciate, shading from adjacent solar panels is a concern when multiple solar tracking units are erected in proximity to one another. Particularly at the beginning and end of daylight, the angle of incident sunlight on a PV panel may cause the PV panel to cast a shadow on one or more adjacent panels, thus reducing the adjacent panels' performance. In some solutions, a backtracking algorithm is employed to compute optimum angles—which may be different—for each PV panel within a field in order to minimize shading. Backtracking, and other optimization solutions, are used to remedy the defects that arise in solar farms after deployment, whether these defects arise due to issues such as shading, environmental conditions, installation errors, or manufacturing defects within the PV modules themselves. The shading issue, in particular, is one that arises due to the physical arrangement and spacing of solar tracking units in the field. On the one hand, one might consider that an increase in the number of solar tracking units in the field will improve the yield of the entire field; on the other hand, when available space for erecting the field of solar tracking units is constrained, extra solar tracking units may only be accommodated by moving the existing units closer together, which increases the potential for a loss of efficiency and overall performance due to shading.
The hexagonal grid arrangement of solar tracking units illustrated in the foregoing drawings has been found to provide improved performance over the rectangular or square grid arrangement otherwise possible using the same sets of frame sides or trusses, by reducing the incidence of shading between adjacent solar panels. Table 1, below, sets out modelled data on a month-by-month basis for a hexagonal grid and rectangular grid system comprising an identical number of solar tracking units, each equipped with a 2.99×1.67 meter PV panel with 15.48% efficiency at a latitude of 34.73° N. The rectangular model was based on an arrangement of sixteen solar tracker assemblies with four solar tracking units apiece in a 4×4 rectangular grid, with solar tracking units separated by 4.1 meters in the east-west direction, and 4.7 m in the north-south direction. The hexagonal model was based on an arrangement of the sixteen solar tracking assemblies arranged as in FIG. 26A, again with separation of units by 4.1 meters in the east-west direction and 4.7 m in the north-south direction. Table 1 provides the calculated yield in kWh for the hexagonal and rectangular grid models, based on the average output of the solar panel mounted at or near the center of the entire grid, and taking into account shading effects due to other panels in the grid. As can be seen in Table 1, the hexagonal grid arrangement yielded improved performance during most months of the year, and overall about a 3% improvement over the rectangular grid arrangement.

TABLE 1

Month	Hexagonal	Rectangular	% Difference

January	107.9	102.4	5.37
February	121.6	113.2	7.42
March	162.7	154.2	5.51
April	181.9	178.4	1.96
May	203.1	203.8	−0.34
June	202.7	205.7	−1.46
July	207	208.3	−0.62
August	194.5	192.8	0.88
September	167.4	161.1	3.91
October	145.9	135.9	7.36
November	111.6	105.4	5.88
December	101.1	96.3	4.98

Table 2, below, compares the performance of the hexagonal and rectangular grid arrangements by latitude over a year. The hexagonal arrangement resulted in an increase in power output of about 2-4% per year over the rectangular arrangement, depending on the latitude of the field.

TABLE 2

Latitude	Hexagonal	Rectangular	% Difference

0	2145.8	2091.4	2.60
10	2128.7	2059.7	3.35
20	2075.8	2014	3.07
30	1976.6	1917.4	3.09
34.7	1907.7	1857.1	2.72
40	1816	1776	2.25
50	1589.7	1558.5	2.00
60	1332.5	1303.4	2.23
70	1135.2	1094.2	3.75

The arrangement of solar tracking units in a hexagonal arrangement as described above thus provides some relief from the effect of interfering shading from nearby units. In cases where a prefabricated system such as the frame assembly described herein is employed and/or where available land for erecting a solar farm is available, the ability to arrange the assemblies as described herein provides an advantage over the prior art. As can be seen from the examples described above, a rhombus frame configuration can be obtained from the same trusses or sides used to construct a square frame, and the predetermined lengths of the frame sides, cross members, and spacing arms provides for efficient and relatively quick assembly in the field. In a further variation, discussed in greater detail below, the cross member of the solar tracker assembly can be adjustable in length, providing for flexibility in layout when the solar tracker assembly is deployed in the field.
In addition to physical interconnection of frames 2010 of the solar tracker assemblies 2100 for the purpose of enhancing stability, the individual solar tracking units 2200 are interconnected within a single solar tracker assembly 2100. This is illustrated in relation to the rhombus frame of FIG. 18. A local control unit 2402 (LCU) can be provided on each assembly 2100 to control all solar units 2200 provided on a single frame 2010. Alternatively, a single LCU 2402 can be used to control the solar tracking units 2200 on several frames (not shown). For example, a cluster of frames 2010 could be positioned and arranged such that an LCU 2402 is mounted only to a single frame 2010 of the cluster and the other frames 2010 do not have local control units mounted thereto. Wires can be run from the single LCU 2402 to each of the solar tracking units 2200 on the frames of the cluster. Within a given frame 2010 having four solar tracking units 2200, pairs of the units 2200 may be connected in series with one another, and these pairs connected in parallel with one another, thus permitting increased voltage to reduce power losses in interconnecting wires. Each pair of units 2200 can be provided with a current and/or voltage sensor (not shown) in communication with the LCU 2402. In some examples, individual solar tracking units 2200 on a single frame are independently controllable and each solar tracking unit 2200 can be provided with a current and/or voltage sensor. The LCU 2402 can use a die cast aluminium enclosure that serves as a heat sink. The electrical system and communication of tracker assembly 2100 is generally similar to the diagram of FIG. 15, and any elements not described in relation to this embodiment can be found in the description of the embodiments above.
In the example illustrated in FIGS. 17 and 18, armatures 2080 and the solar tracking units 2200 are mounted on a mounting end 2035 of the leg assemblies 2030. The solar tracking unit 2200 includes an armature assembly 2080, shown in FIG. 28. A solar panel may be mounted on each of the armature assemblies 2080. Each solar tracking unit 2200 can also be provided with a sun position sensor (not shown) for use in computerized calibration to ensure that sunlight is normally incident on the surface of the solar panel, and to compensate for the vagaries of the field installation such as uneven terrain affecting the pitch of a given unit 2200, and other issues such as manufacturing errors in the manufacture of the solar panel 2210 or its components, differences between the actual sun position and expected sun position, and the like.
The armature assembly 2080 includes a shaft 2082 including a lip 2098 provided with boreholes that match the fasteners (for example press fitted studs) 2045 described in FIG. 19A. The orientation of the shaft 2082 with regards to the leg assembly 2030 can be determined by the fasteners 2054 and boreholes, as these can only be matched in a predetermined orientation, such that the solar tracking units 2200 are always properly aligned. During assembly, cables 2099 running through the shaft 2080 are connected to cables in the leg assembly 2030, before fixing the armature 2080 on the leg assembly. Once the cables have been properly connected, the boreholes of the lip 2098 can be matched to fasteners 2045 of the upper lip 2043 and then they can be secured by means of a bolt or any other fastening means.
The armature assembly includes a yoke 2084 provided with a yoke mount 2079, a crosspiece 2085 extending from the yoke mount 2079, and first and second arms 2086 extending from the crosspiece 2085. In the configuration shown in FIG. 28, the arms 2086 extend substantially perpendicularly from the crosspiece 2085 and are substantially parallel to the yoke mount 2079 and to each other, although in other configurations their relative position with respect to the crosspiece 2085 and the yoke mount 2079 may vary according to the design of the solar panel mounted on the armature assembly 2080. In this embodiment no gusset is required. The yoke mount 2079 extends through and is fixed to the center of crosspiece 2085. The yoke mount 2079, the crosspiece 2085 and the arms 2086 may be manufactured as individual components welded together to form the yoke 2084. Alternatively, the yoke 2084 may be integrally formed as a single part by die casting.
A bearing or bushing, may be provided within the yoke mount 2079 to facilitate rotation of the yoke 2084 about shaft 2082. A first drive system for controlling yaw movement of the solar tracking unit 2200 includes a first gear wheel 2090 fixed to the shaft 2082, and therefore stationary relative to the frame 2010. A second gear wheel 2091 in engagement with the first gear wheel 2090 is also provided on the crosspiece 2085, extending from the same face of the crosspiece 2085 as the first gear wheel 2090. The second gear wheel 2091 is fixed relative to the yoke 2084. In the example of FIG. 28, the first and second gear wheels 2090, 2091 are disposed on the inside of the yoke 2084, i.e., between the arms 2086. A first drive assembly including a motor and gearbox 2092 is provided for the second gear wheel 2091 for controlling rotation of the second gear wheel 2091 to cause the yoke 2084 to rotate around the fixed first gear wheel 2090 and the shaft 2082. An example of a suitable drive assembly includes a weatherproof and durable stepper motor having an output shaft connected to a sealed gearbox that has an output shaft with a pinion gear (the second gear wheel 2091). The pinion gear (the second gear wheel 2091) can therefore provide higher torque than the stepper motor, the increase in torque depending on the gear ratios of the gears contained inside the sealed gearbox. The pinion gear connected to the output shaft of the sealed gearbox engages the first gear wheel 2090 and can operate in an unsealed environment. The first drive system thus provides for rotation of the yoke 2084 up to 360 degrees (or greater) in a clockwise or counter-clockwise direction. In use, the armature assembly 2080 may be enclosed in a weatherproof cover (not shown) to protect the drive systems from ice, rain, sand, etc.
An axle 2088 is mounted on concave portions 2087 provided near the ends of the two arms 2086. Again, appropriate bearings or bushings 2081 may be provided, for example bushings manufactured by Igus GmbH. Each end of the axle 2088 terminates in a plate 2089 for mounting to an underside of a solar panel. The precise configuration of the plates 2089 will depend on the attachment means used to mount the solar panel to the armature assembly 2080; in this case, grooves are provided in the perimeter of the plate 2089 to receive fasteners to join the armature assembly 2080 to the solar panel. A second drive system controlling pitch of the solar tracking unit 2200 is provided on the yoke 2084 and axle 2088; a first gear wheel 2095 is mounted on the axle 2088, and a second gear wheel 2096 in engagement with the first gear wheel 2095 is mounted on the yoke 2084. In this example, the first gear wheel 2095 is a circular sector wheel rather than a full circle like the gear wheel 2090. Since yaw over a wider range (i.e., over 180 degrees) may be provided by the first drive assembly comprising the gear wheels 2090, 2091, pitch adjustment of the solar tracking unit 2200 over a range of 95-150 degrees is likely sufficient. In other examples, the gear wheel 2095 may be a semicircular shape rather than a quarter-wheel; depending on the proximity of the solar panel to the axle 2088, it may not be possible to provide a full-circular gear wheel on the axle 2088. The second gear wheel 2096 is controlled by a further drive system including a motor and gearbox 2097, also mounted on the yoke 2084. An example of a suitable drive assembly includes a weatherproof and durable stepper motor having an output shaft connected to a sealed gearbox that has an output shaft with a pinion gear (the second gear wheel 2096). The pinion gear (the second gear wheel 2096) can therefore provide higher torque than the stepper motor, the increase in torque depending on the gear ratios of the gears contained inside the sealed gearbox. The pinion gear connected to the output shaft of the sealed gearbox engages the first gear wheel 2095 and can operate in an unsealed environment. In the example of FIG. 28, the motor 2097 and second gear wheel 2096 are mounted on the arm 2086 proximate to the gear wheel 2095.
In FIG. 28, spur gears are illustrated; however, other types of gears may be employed as well to provide motion in the two substantially orthogonal planes perpendicular to the shaft 2082 and axle 2088. Tension springs, not shown, may be provided to ensure engagement between the teeth of the gears 2091, 2096 and 2090, 2095. Home switches, not shown, may be provided on each of the two drive assemblies for use in returning the solar panels to a default position. Both the motors 2092 and 2097 are controllable using a local control unit described below.
The solar panel mounted to the armature assembly 2080 may take any suitable shape. For example, the solar panel can include one or more flat plate solar panel modules made of semiconductors such as silicon, gallium arsenide, cadmium telluride, or copper indium gallium arsenide or can be a concentrated solar panel employing concentrating optics, or heliostat mirrors. In the case of concentrated solar panels, the solar panels include individual optical modules comprising PV cells. The optical modules may or may not include integrated electronics such as power efficiency optimizers and the like. Optics provided with the individual optical modules may include multiple-component optics. The individual optical modules may be combined in series in strings of optical modules, which in turn may be connected in parallel with other strings to yield an array of optical modules. One or more strings of optical modules can be arranged in a plane to form a solar panel module.
As mentioned above, the cross members 2046 of the solar tracking assemblies may be adjustable in length. This permits the frames of the solar tracker assemblies to be deployed with different spacing between the leg assemblies. An example implementation of an adjustable-length cross member 2946 is illustrated in FIGS. 29A to 29C. FIG. 29A shows the cross member 2946 mounted in a frame assembly similar to that shown in FIGS. 18, 18 and 21. In this example, the cross member 2946 is a simple chord assembly formed of suitable material, such as extruded or drawn metal. The length adjustability of the cross member 2946 in this example is provided by a telescoping configuration from two nesting chord members 2950, 2960. As can be seen in FIGS. 29A and 29B, the first chord member 2950 in this example is conveniently shaped as a channel beam or C-bar having two sidewalls 2952 depending from a plate 2953, thus defining a channel with an open end 2954 for receiving the second chord member 2960. The channel is sized to receive the second chord member 2960, which in this example is a rectangular beam. The combined length of the first and second chord members 2950, 2960 is greater than the greatest required length for the cross member 2946.
The first chord member 2950 is provided with boreholes 2955 nearer the receiving (open) end 2954. These bore holes can be spaced by increments which can be used to define different finished lengths for the cross member 2954, e.g., every 10 or 15 cm. The second chord member 2960 is provided with corresponding boreholes 2965 nearer an engagement end 2964, which engages the receiving end 2954 of the first chord member 2950. The engagement end 2964 of the second chord member 2960 is accordingly inserted into the receiving end 2954 of the first chord member 2950 until the total length of the two members 2950, 2960 is at a desirable length, and at least one set of corresponding boreholes 2955, 2965 is aligned. Suitable fasteners, such as screws, are engaged in the corresponding boreholes to fix the members 2950, 2960 together. The boreholes 2965 are advantageously spaced by the same increments as the boreholes 2955 so that when the two members 2950, 2960 are engaged, a plurality of boreholes of both members 2950, 2960 are aligned and can receive fasteners. Other profiles and fastening means for the first and second chord members 2950, 2960 may of course be employed; for instance, the chord members may be telescoping tubular members (channel or closed) that can also comprise the boreholes described above, or may comprise flat plates or other members with substantially flat contact surfaces where fasteners are applied.
The cross member 2946 can be fixed to opposing leg assemblies 2030 much in the same manner described with reference to FIGS. 19A to 19C. However, since the overall length of the cross member may vary, the angles of the rhombus frame 2010 will likewise vary. The brackets or other means used to attach the trusses 2012 forming the sides of the frame 2010 are therefore adapted to accommodate changes in the attachment angle. FIG. 29C illustrates brackets 2970 which are similar to those brackets 2049 described above with reference to FIG. 19A, but are wider to accommodate different positions of the truss 2012. As can be seen in FIG. 29C, an upper bracket 2970 a is provided with at least one curved slot 2972, sized to receive the bolt or other fastener used to attach the truss 2012 to the leg assembly 2030. The truss 2012 can therefore be inserted between the upper bracket 2970 a and a lower bracket 2970 b at the desired angle, and positioned so that a borehole on the truss 2012 registers with the slot 2972. The fastener 2974 can then be inserted in the aligned slot and borehole. Alternatively, a number of boreholes, rather than a single slot, may be provided in the upper bracket 2970 a, or else a number of straight slots extending radially along the bracket, to allow for flexibility in positioning the truss 2012 at the leg assembly 2010.
Various embodiments of the present invention having been thus described in detail by way of example, it will be apparent to those skilled in the art that variations and modifications may be made without departing from the invention. The invention includes all such variations and modifications as fall within the scope of the appended claims.

Claims

1. A field of interconnected solar tracking units, the field comprising:

a plurality of solar tracking units arranged in a hexagonal grid arrangement, each solar tracking unit of the plurality of solar tracking units having between two and six neighboring solar tracking units,

wherein movement of each solar tracking unit of the plurality of solar tracking units in relation to at least one axis of said solar tracking unit is controlled by a local control unit, each local control unit controlling up to four solar tracking units of the plurality of solar tracking units, said up to four solar tracking units being mounted on a single oblique-angled, rhombus frame associated with said local control unit.

2. The field of interconnected solar tracking units of claim 2, the field thus comprising a plurality of frames, each frame comprising four leg assemblies connected by sides of substantially equal length, the leg assemblies being adapted for mounting a corresponding solar tracking unit, the frame comprising a greater diagonal defined by a distance between two of the four leg assemblies separated by a greater distance and a lesser diagonal defined by a distance between a remaining two of the four leg assemblies separated by a lesser distance.

3. The field of interconnected solar tracking units of claim 3, each frame of the plurality of frames being interconnected by at least one spacing arm of predetermined length to an adjacent frame, the at least one spacing arm thus maintaining a regular spacing among the plurality of solar tracking units to provide the hexagonal grid arrangement.

4. The field of interconnected solar tracking units of claim 3, wherein adjacent sides of adjacent pairs of frames are substantially parallel.

5. The field of interconnected solar tracking units of claim 4, each frame comprising a pair of sides substantially parallel to a cardinal direction.

6. The field of interconnected solar tracking units of claim 5, wherein at least some of the spacing arms are substantially parallel to the cardinal direction.

7. The field of interconnected solar tracking units of claim 6, wherein others of the spacing arms are substantially parallel to either the lesser diagonal of a frame to which the spacing arm is attached, or to a side of the frame to which the spacing arm is attached other than a side of the pair of sides substantially parallel to the cardinal direction.

8. The field of interconnected solar tracking units of claim 7, wherein each of the frames is in substantially a same orientation.

9. The field of interconnected solar tracking units of claim 7, wherein the plurality of frames is arranged in alternating parallel columns of frames in opposing orientations, the frames within each column being arranged in substantially a same orientation and having a pair of sides substantially parallel to the column.

10. The field of interconnected solar tracking units of claim 7, wherein the others of the spacing arms interconnected adjacent columns of frames, and comprise both spacing arms parallel to the lesser diagonal of the frame to which the spacing arm is attached, and spacing arms parallel to the side of the frame to which the spacing arm is attached other than a side of the pair of sides substantially parallel to the cardinal direction.

11. The field of interconnected solar tracking units of claim 1, wherein the one or more solar tracking units comprise either one or more heliostat mirrors or one or more photovoltaic modules.

12. The field of interconnected solar tracking units of claim 1, wherein the local control unit is configured to control movement of the up to four solar tracking units in relation to two axes.

13. The field of interconnected solar tracking units of claim 1, wherein each frame is associated with a distinct local control unit, the field of interconnected solar tracking units further comprising a global control unit in communication with each distinct local control unit, the global control unit being adapted to issue instructions controlling each local control unit.

14. The field of interconnected solar tracking units of claim 3, each frame further comprising a cross member of a defined length extending substantially along the lesser diagonal and being fixed to each of the two leg assemblies separated by the lesser distance.

15. The field of interconnected solar tracking units of claim 14, wherein the plurality of solar tracking units mounted on the plurality of frames thus interconnected are mutually ballasted.

16. A field of interconnected solar tracking assemblies, the field comprising:

a plurality of solar tracker assemblies with a plurality of solar tracking units mounted thereon, each solar tracker assembly comprising:

an oblique-angled, rhombus frame comprising four leg assemblies interconnected by sides of substantially equal length; and

one or more solar tracking units of the plurality of solar tracking units mounted on one or more of the four leg assemblies, movement of the one or more solar tracking units in relation to at least one axis being controlled by a local control unit associated with the solar tracker assembly,

the plurality of solar tracker assemblies being arranged such that the plurality of solar tracking units mounted thereon define a substantially hexagonal cellular arrangement comprising a plurality of at least two adjacent clusters of cells of the cellular arrangement, each cluster comprising a central cell surrounded by six immediately adjacent cells, each of said clusters comprising solar tracking units controlled by at least three different local control units.

17. The field of interconnected solar tracking assemblies of claim 16, wherein at least one of said clusters comprises six solar tracking units controlled by four different local control units.

18. The field of interconnected solar tracking assemblies of claim 17, wherein frames of adjacent solar tracker assemblies of the plurality of solar tracker assemblies are interconnected by spacing arms of predetermined length, the spacing arms thus maintaining spacing for the substantially hexagonal cellular arrangement;

all of the frames having substantially the same orientation and having a greater diagonal and a lesser diagonal, all of the frames being arranged in columns along a first direction, at least some of the spacing arms being substantially collinear with the lesser diagonal of a frame to which the spacing arm is connected, and others of the spacing arms being substantially collinear with a side of each frame to which the spacing arm is connected, said side extending substantially parallel to the first direction.

19. The field of interconnected solar tracking assemblies of claim 17, wherein frames of adjacent solar tracker assemblies of the plurality of solar tracker assemblies are interconnected by spacing arms of predetermined length, the spacing arms thus maintaining spacing for the substantially hexagonal cellular arrangement, all of the frames having a greater diagonal and a lesser diagonal;

the plurality of solar tracker assemblies being arranged in columns along a first direction, a first set of columns comprising a set of solar tracker assemblies arranged in a first orientation, the first set of columns being interleaved with a second set of columns comprising a set of solar tracker assemblies arranged in a second orientation different from the first orientation,

at least some of the spacing arms being substantially collinear with a side of a frame to which the spacing arm is connected, at least some of said sides extending substantially parallel to the first direction, and others of the spacing arms being substantially collinear with the lesser diagonal of a frame to which the spacing arm is connected.

20. The field of claim 18, wherein the first direction is a north-south direction.