Abstract
Solar trackers that may be advantageously employed on sloped and/or variable terrain to rotate solar panels to track motion of the sun across the sky include bearing assemblies and other mechanical features configured to address mechanical challenges posed by the sloped and/or variable terrain that might otherwise prevent or complicate use of solar trackers on such terrain.
Claims
1. A bearing assembly comprising: a shaft configured to rotate around a rotation axis and comprising a first end and a second end opposite the first end; at least one bearing coupled to the shaft; a first solar module mounting structure coupler coupled to the first end of the shaft and configured to support a first solar module mounting structure comprising a first axis; and a second solar module mounting structure coupler coupled to the second end of the shaft and configured to support a second solar module mounting structure comprising a second axis, the second axis not aligned with the first axis.
2. The bearing assembly of claim 1, wherein the first axis is below the rotation axis.
3. The bearing assembly of claim 1, wherein the first axis is above the rotation axis.
4. The bearing assembly of claim 1, wherein the first axis is aligned with the rotation axis.
5. The bearing assembly of claim 1, wherein the first axis is above the second axis.
6. The bearing assembly of claim 1, wherein the first axis is below the second axis.
7. The bearing assembly of claim 1, wherein the first solar module mounting structure coupler has a first surface directly attached to the shaft, second solar module mounting structure coupler has a second surface directly attached to the shaft, the first surface having a lesser area than the second surface.
8. The bearing assembly of claim 1, wherein the first solar module mounting structure supports a first solar module having a center of gravity disposed above the rotation axis.
9. The bearing assembly of claim 1, wherein the first solar module mounting structure supports a first solar module having a center of gravity aligned with the rotation axis.
10. The bearing assembly of claim 1, wherein the first solar module mounting structure supports a first solar module having a center of gravity below the rotation axis.
11. The bearing assembly of claim 1, wherein the first and second solar module mounting structure coupler are each a cradle.
12. The bearing assembly of claim 1, further comprising first and second cradle clamps attached to the first and second solar module mounting structure couplers.
13. The bearing assembly of claim 12, wherein a top of first cradle clamp is disposed above or flush with a top of the first cradle.
14. The bearing assembly of claim 12, wherein a top of second cradle clamp is disposed below a top of the second cradle.
15. The bearing assembly of claim 1, wherein the first and second solar module mounting structure have a height and length, the height of the first and second solar module mounting structure being substantially identical and the length of the first and second solar module mounting structure being substantially identical, the height and length being perpendicular to each other and the height being perpendicular to the rotation axis and the length being parallel to the rotation axis.
16. A bearing assembly comprising: a shaft configured to rotate around a rotation axis and comprising a first end and a second end opposite the first end; at least one bearing coupled to the shaft; a first solar module mounting structure coupler coupled to the first end of the shaft and configured to support a first solar module mounting structure comprising a first axis; and a second solar module mounting structure coupler coupled to the second end of the shaft and configured to support a second solar module mounting structure comprising a second axis, the second axis aligned with the first axis and the rotation axis.
17. The bearing assembly of claim 1, wherein the first mounting structure axis and the second mounting structure axis are aligned with the rotation axis.
18. A tracker comprising: a plurality of foundations; a plurality of solar module mounting structures each comprising a first end and a second end between the plurality of foundations; a plurality of bearing assemblies on the plurality of foundations and comprising a transition bearing assembly configured to rotate around a rotation axis and comprising: a shaft; a first solar module mounting structure coupler coupled to the first end of the shaft and configured to support a first solar module mounting structure of the solar module mounting structures comprising a first axis; and a second solar module mounting structure coupler coupled to the second end of the shaft and configured to support a second solar module mounting structure of the solar module mounting structures comprising a second axis, the second axis not aligned with the first axis.
19. The tracker of claim 18, further comprising a slew drive coupled to a first solar module mounting structure of the solar module mounting structures and configured to rotate the first solar module mounting structure around the rotation axis of the first solar module mounting structure coupler of the solar module mounting structures.
20. The tracker of claim 19, wherein the first solar module mounting structure is adjacent to the slew drive, and the first solar module mounting structure comprises the first axis and is coupled to the transition bearing assembly.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0230] FIG. 1 shows an example of an all-terrain solar tracker arranged on sloped and rolling terrain with angle changes along its length to follow the natural terrain.
[0231] FIG. 2 shows an example of a mechanical stop assembly integrated with a straight bearing assembly. The mechanical stop assembly has two impact brackets that will contact the foundation at a certain tilt angle to resist further rotation of the tracker.
[0232] FIGS. 3A and 3B show a perspective view and a plan view of an example of a mechanical stop assembly integrated with a straight bearing assembly. The mechanical stop assembly has one impact bracket that will contact the foundation at a certain tilt angle to resist further rotation of the tracker.
[0233] FIG. 4 shows a perspective view of a straight bearing assembly with two cradles and cradle clamps. The straight bearing assembly has a mounting structure that integrates both sides of the assembly with the two bearing supports.
[0234] FIG. 5 shows a row-end cantilevered beam module support. This example shows the cantilevered beam bolted on to a mechanical stop assembly. Other bearing designs may be used to support the cantilevered beam assembly.
[0235] FIG. 6 shows an integrated articulated bearing assembly. Both side supports are integrated with one bearing support while the other bearing support is a separate piece that can swivel independently. The swiveling bearing support includes radius arms for positioning with relation to the structure and the flexible shaft, and are pivoted about a portion of the sides that rise up higher than the integrated bearing support to provide an axis about which to pivot.
[0236] FIGS. 7A, 7B, and 7C show a perspective view, an exploded view, and a side section of a center flex plate bearing assembly.
[0237] FIGS. 8A, 8B, and 8C show a perspective view, an exploded view, and a side section of the bearing assembly that includes thrust bearing surfaces and a device for frictional damping.
[0238] FIG. 9 is an alternative variation of the example of FIGS. 8A-8C and shows a bearing assembly that includes thrust bearing surfaces as part of the shaft itself rather than as part of the cradles.
[0239] FIG. 10 is an alternative variation of the example of FIGS. 7A-7C and shows two flex plates outboard of the bearing assembly. This variation may also be modified to only include one flex plate outboard of the bearing assembly.
[0240] FIGS. 11A-11B is an alternative variation of the example of FIG. 10, without a middle flex plate in the outboard flexures of the bearing assembly.
[0241] FIGS. 12A and 12B show an exploded view and a side view of a stepped module clip assembly.
[0242] FIG. 13 is an alternative variation of the example of FIGS. 12A-12B, and shows a side view of a module clip assembly that does not have steps.
[0243] FIGS. 14A, 14B, and 14C shows side views of the bearing assemblies. FIGS. 14A and 14B are transition bearing assemblies with their cradles offset from one another. FIG. 14C is a bearing assembly with cradles aligned with one another.
[0244] FIGS. 15A, 15B, and 15C show a perspective view of the bearing assemblies shown in FIGS. 14A, 14B, and 14C.
[0245] FIGS. 16A, 16B, and 16C show side views of the bearing assemblies with torque tubes disposed in the cradles. FIGS. 16A and 16B are transition bearing assemblies with their cradles offset from one another. FIG. 16C is a bearing assembly with cradles aligned with one another.
[0246] FIGS. 17A, 17B and 17C show perspective views of the bearing assemblies with torque tubes shown in FIGS. 14A, 14B, and 14C.
[0247] FIGS. 18A and 18B show side views of bearing assemblies in a tracker. FIG. 18A shows a bearing assembly with offset cradles aligned with each other but not the slew drive axis. FIG. 18B shows a transition bearing assembly with one cradle aligned with the slew drive axis and one cradle offset.
[0248] FIGS. 19A and 19B show side views of trackers extending along the north-south axis on substantially flat and sloped land, respectively.
DETAILED DESCRIPTION
[0249] The following detailed description should be read with reference to the drawings, in which identical reference numbers refer to like elements throughout the different figures. The drawings, which are not necessarily to scale, depict selective embodiments and are not intended to limit the scope of the invention. The detailed description illustrates by way of example, not by way of limitation, the principles of the invention. This description will clearly enable one skilled in the art to make and use the invention, and describes several embodiments, adaptations, variations, alternatives and uses of the invention.
[0250] As used in this specification and the appended claims, the singular forms a, an, and the include plural referents unless the context clearly indicates otherwise. Also, the term parallel is intended to mean substantially parallel and to encompass minor deviations from parallel geometries. The term vertical refers to a direction parallel to the force of the earth's gravity. The term horizontal refers to a direction perpendicular to vertical.
[0251] FIG. 1 shows an example all-terrain solar tracker arranged on varying terrain with angle changes along its length to follow the natural terrain. This tracker employs examples of many of the components described above in the summary and described in more detail below. These components include a cantilevered beam supporting a plus one module at one end of the tracker row, articulated bearings supporting significant changes in angular orientation between adjacent segments of the torque tube, flexure bearings supporting smaller changes in angular orientation between adjacent segments of the torque tube without requiring an articulated bearing, straight through bearings, mechanical stops limiting rotation of the tracker, and a row end bearing. The tracker in addition includes a slew drive configured to drive rotation of the torque tube around its long axes. Although the example of FIG. 1 and other figures shows a particular arrangement of certain components, other variations may employ any suitable combination and arrangement of the components described in this disclosure. Some elements illustrated in certain figures may be unlabelled in those figures and only be labelled in other figures, for convenience and clarity of illustration and to avoid repetition.
[0252] Instead of or in addition to torque tubes, any other solar module mounting structures may be used in the trackers and/or devices described in this specification. These solar module mounting structures may be or comprise z-purlins, spaceframes, and other like structures.
[0253] FIG. 2 shows an example of a mechanical stop for a single-axis tracker that incorporates two torque tube cradles 100, one integrated straight bearing assembly 101, two impact brackets 102 on one impact bracket assembly 105, one foundation 103, and one torque tube 104. Torque tubes may be inserted into the cradles on either side of the mechanical stop assembly, and one or the other cradle may be left off if the tracker does not continue in that direction. Torque tubes may be tubes having a cross-section of four or more flat sides, such as a rectangle, square, pentagon, hexagon, and octagon, for example. Torque tubes may have cross sections that are round instead of having flat sides, such as circles or ovals. As mentioned above, since other solar module mounting structures may be used instead of torque tubes, the torque tube cradle may be any attachment structure capable of securing solar modules other than torque tubes specifically. Solar modules may be mounted on the one or more torque tubes and rotated. A mechanical stop assembly may be mounted onto an integrated straight bearing assembly, or other type of bearing assembly (e.g., compact straight bearing assembly, a flexure bearing assembly, articulated bearing assembly, etc.), or provided as a separate and standalone assembly. At some angle, the impact bracket may contact an impact surface structure resulting in a physical blockage to further rotation of the torque tube. The impact surface structure may be the post of the foundation itself or a horizontal bar on the foundation that contacts the impact bracket assembly. The impact bracket assembly might have two parallel plates extending outward without an impact bracket between them so that the plates contact a bar on the foundation, or the plates may include the impact bracket extending between them to contact the foundation to result in the physical blockage. This physical blockage allows rotational loads applied to the torque tube to be resisted at this foundation when tilted to an angle that contact is made. Zero, one, or more mechanical stop assemblies may be incorporated in a tracker row to provide zero, one, or more physical blockages to rotation. If one mechanical stop assembly contacts a foundation before one or more other mechanical stop assemblies contact the foundation, then the one or more other mechanical stop assemblies may still contact the foundation in wind conditions that create sufficient flexing in the torque tube and bearing assemblies in the rest of the tracker system to allow the non-contacting mechanical stops to come into contact with their respective foundation. The mechanical stop assembly illustrated in FIG. 2 has two sides to stop both of a clockwise rotation of the bearing assembly 101 at a first maximum angle of rotation and stop a counterclockwise rotation of the bearing assembly 101 at a second maximum angle of rotation.
[0254] FIGS. 3A and 3B shows a mechanical stop assembly with an impact bracket 102 on only one side of the bearing assembly 101 (rather than the two illustrated in FIG. 2), to stop only one of clockwise or counterclockwise rotation of the bearing assembly 101 at a first maximum angle of rotation. Also illustrated in this figure are two plates 144. The two plates 144 are parallel to each other and have the impact bar 140 between them and perpendicular to their direction of extension. The two plates 144 are attached at an attachment region to the bearing assembly. They can be removed from the bearing assembly and/or mounted at the opposing side of the bearing assembly. The two plates may have a hole 148 that either accommodates cables or accommodates hooks that supports cables in the tracker.
[0255] The bearing assembly may comprise a bearing support having bearing support slots 152 that allow pivoting and/or rotation of the bearing about an axis perpendicular to the bearing, e.g. an axis parallel to the long axis of the foundation. For example, the bearing support slots 152 may allow East-West rotation.
[0256] FIG. 4 shows an integrated straight bearing assembly. The integrated bearing assembly includes coupling devices that are typically used on single-axis trackers between foundations to connect the ends of torque tubes together. However, in this application, the coupling devices are integrated to the integrated straight bearing assembly cradles 100. In this application, the cradles 100 are fastened to the straight bearing shaft, which is supported by bearings 117 and restrained by bearing straps 116. There may be one or more bearings 117, e.g., two, and they may be plastic or any other material. The cradles 100 may allow coupling of the integrated bearing assembly with any type of solar module mounting structure, e.g., a torque tube. An integrated bearing assembly may have only one cradle 100 instead of two cradles disposed on opposite sides of the straight bearing shaft. Bearing support slots 152 in the top panel(s) of the integrated bearing assembly may be fastened to the bearings in a way that allows the bearings to swivel. For example, if the straight bearing shaft extends along a first axis, the bearing support slots may allow the bearings to move or swivel in a way that the straight bearing shaft pivots around a second axis coplanar with and non-parallel with the first axis, e.g., perpendicular with the first axis. For example, a solar tracker may have a first and second bearing assembly spaced apart from each other, with a first solar panel module in between them supported by a torque tube, and a second solar panel module extending on the opposite side of the second bearing assembly from the first solar panel module. In this example, the first solar panel module extends in a first direction and the second bearing assembly can extend in a second direction due to the swiveling allowed by the bearing support slots. The second solar panel module fastened to the second bearing assembly can extend in the first direction, in the second direction, or a third direction different from the first and second direction.
[0257] Adjustment slot 120 allows the integrated straight bearing assembly to tilt on top of a foundation to best accommodate the incoming and outgoing angles of the torque tubes supported by the cradles 100 on either end of the integrated straight bearing assembly. Each side panel may have any number of adjustment slots 120, e.g., two for each side, for a total of four. The adjustment slots may be any shape, such as the long slit with rounded corners illustrated, or circles or rectangles. The adjustment slots on each side panel may be horizontally disposed from each other as depicted, or may be vertically disposed from each other on the same side panel. For example, one side panel may have a circle adjustment slot vertically disposed over a long slit with rounded corners. Alternate methods could be imagined where the cradle is continuous along the top of the integrated straight bearing assembly with bearings and bearing straps designed to support the profile of the cradle 100, to further eliminate components in the design.
[0258] FIG. 4 shows an integrated straight bearing assembly with cradles 100 on either end. In this configuration a cradle clamp 106 is installed on each cradle assembly and captured by a retention hook 107 and two fasteners 108. A torque tube 104, as shown in FIG. 2, can be dropped into the cradles in FIG. 3 so that one end of the torque tube is supported by the cradle 100. A cradle clamp 106 can then be installed to secure the torque tube within the cradle so that it cannot come free by lifting, sliding, or falling out of the vertical opening. Other options may be used to secure the cradle clamp 106 and other cradle clamp designs may be used. The other end of the torque tube may then be supported by a cradle on a succeeding or preceding bearing assembly, or other mounting option. Various bearing assemblies may be used including articulating or flexure bearing assemblies. One or more sight holes 109 may be incorporated in the side of the cradle to allow visual verification of the location of the torque tube. The sight hole may also be located on other parts of the bearing assembly as deemed fit for visual verification of the location of the torque tube within the cradle. Alternatively, the shaft may be directly welded to and integral with the cradle, with part of the shaft protruding through the back of the cradle, such that no retention hook 107 and fasteners 108 are needed. The shaft protruding from the back of the cradle may space apart the torque tube inserted in the cradle from a vertically extending back corner of the cradle, preventing the torque tube from being crushed by the back corner. In other words, the protruding shaft acts as a spacer for the torque tube.
[0259] In the example of FIG. 4, both sides 110 of the integrated bearing assembly and both bearing supports 111 are integrated into one single piece of bent metal plate as opposed to being individual and separate components held together by fasteners, welding, or other joining processes. The metal plate may be bent to have two bearing support panels and two side panels extending perpendicular from the two bearing support panels and disposed on opposite sides of the two bearing support panels from each other. One bearing may be disposed on each of the two bearing support panels. Alternatively, the metal plate may have only one bearing support panel and one side panel, or two bearing support panels and one side panel. This assembly has multiple components that can provide flexure and movement to allow the angles of incoming and outgoing torque tubes to differ from each other. The body of the cradle 100 can be designed to flex, as can the cradle clamp 106. Further, the straight bearing shaft 112 can be designed to flex, as can the bearing supports 111 and the side of the integrated bearing assembly 110. For example, if the straight bearing shaft 112 extends along a first axis, the straight bearing shaft 112 can flex about one or multiple axes coplanar and non-parallel with the first axis, e.g., perpendicular with the first axis. The curved slots in the bearing support 111 allow the bearing 117 to rotate around the center of the integrated bearing assembly to accommodate misalignment of the foundation that the integrated bearing assembly is fastened to and the incoming and outgoing torque tubes that are supported by the cradles 100. The bearing 117 may be plastic, or any other suitable material. Movement of a torque tube in the cradle 100 can be designed into the cradle through a variety of methods including tighter fit on the top of the cradle than the bottom, or vice versa, through play allowed in the vertical direction, through sliding allowed in the axial direction, and through play allowed in the horizontal direction. This play allows the torque tubes to move in relation to the cradle 100 and cradle clamp 106 to accommodate differing incoming and outgoing angles of the torque tube. This play also allows natural attenuation of harmonics being transferred through the structure such as with oscillations brought on by blowing wind that causes the structure to shake. A bearing assembly that appears to be rigid can now allow slope changes purely through designing flexibility and play into the design.
[0260] FIG. 5 shows a cantilevered beam module support 114 to be used at the end of a tracker row to add one or more modules 113 without the need for an additional foundation 103 and bearing assembly 101, particularly when only one or very few solar modules needs to be added to the end of the tracker. The cantilevered beam module support 114 comprises a short section of torque tube with a square plate attached to the end that is then attached to the bearing assembly 101. In this application, a straight bearing assembly 101 with an impact bracket assembly 105 is shown, but other bearing assemblies may also be used such as, but not limited to, straight bearing assembly, articulating bearing assembly, and flexure bearing assembly. Additionally, the impact bracket assembly 105 may have only one impact bracket 102 on one side as described above, rather than the two as illustrated.
[0261] The torque tube used at the end of the tracker at the cantilevered beam module support 114 may be shorter than torque tubes used in the rest of the tracker, such as 1/8th or less the length of other torque tubes. If so, the torque tube at the end supports only one solar module rather than, for example, eight solar modules per torque tube. This torque tube may also be large enough to support other numbers of modules, such as from two to seven solar modules.
[0262] FIG. 6 shows an integrated articulated bearing comprising one bracket with two sides 110 integrated with a bearing support 111, a pivoting bearing support 118, two cradles 100, two cradle clamps 106, an articulating joint assembly 119, two bearings 117, and two bearing straps 116. Adjustment slots 120 in the two sides 110 allow the integrated bearing support to tilt on the foundation to achieve the angle of the torque tube that will be clamped in the cradle 100 on that side of the integrated articulated bearing. The pivoting bearing support 118 on the other side can still articulate by pivoting around the pivot point 121 that is coincident with the center of the articulating joint to allow a change in the incoming and outgoing angles in the vertical direction. The bearing support slots 152 on top of both the bearing support 111 and pivoting bearing support 118 allow the articulated joint to be installed at an angle to the integrated bearing assembly and to allow a change in incoming and outgoing angle in the plane of the torque tubes supported by either cradle 100. Both torque tube cradles 100, and the flexibility built into the rest of the bearing assembly, can allow further articulation to accommodate differences in incoming and outgoing angles of the associated torque tubes through flexure of the components or gaps between the torque tubes and the cradles 100.
[0263] The angle ? between rotation axes of the torque tubes may be, for example, ?0 degrees, ?5 degrees, ?10 degrees, ?15 degrees, ?20 degrees, ?25 degrees, ?30 degrees, ?35 degrees, ?40 degrees, ?45 degrees, ?50 degrees, ?55 degrees, ?60 degrees, ?65 degrees, ?70 degrees, ?75 degrees, ?80 degrees, ?85 degrees, or up to 90 degrees. The angle between a rotation axis of a torque tube and the horizontal may be, for example, ?0 degrees, ?5 degrees, >10 degrees, ?15 degrees, ?20 degrees, ?25 degrees, ?30 degrees, ?35 degrees, ?40 degrees, ?45 degrees, ?50 degrees, ?55 degrees, ?60 degrees, ?65 degrees, ?70 degrees, ?75 degrees, ?80 degrees, >85 degrees, or up to 90 degrees. These examples refer to the magnitude of the angle between the rotation axes. The angles may be positive or negative with respect to the horizontal. These rotation axes may intersect at the articulating joint.
[0264] FIG. 7A, 7B, and 7C show a flexure bearing assembly that uses a flex plate 122 in the center of the assembly to allow differing incoming and outgoing angles for the torque tubes supported by the cradles 100. A stub shaft 123 with a mating plate 124 is used to attach the cradle 100 to the flex plate 122. The stub shaft 123 may have a square plate welded and/or fastened to the cradle. Alternatively, the stub shaft 123 may be directly welded to the cradle without the square plate in between. The stub shaft 123 may protrude out the back of the cradle to space the torque tube inserted in the cradle from the curved corner of the cradle, and prevent crushing or cracking of the torque tube by the curved corner. Each of the associated components can provide flexure to allow changes in the incoming and outgoing angles of the torque tubes supported by the cradles 100. In this method, the unconstrained bearing supports 125 are not located with respect to the center of the flexure plate, but could be with the addition of a pivot point 121 feature as shown in FIG. 6. The mating plate 124 may incorporate various features to reduce stress points along its surface such as radiused contact plates, overload springs 133, force distributing washers for the fasteners, a combination of these items, and other items obvious to one skilled in the art of material stress analysis, reduction, and optimization. For example, the overload spring 133 may prevent a bolthead from cracking the flex plate 122. Additionally, a spacer 154 may help the mating plate contact the flex plate 122. The spacer 154 may have its corners that are in contact with the flex plate 122 grinded down into a taper or rounded corner so that the edges contacting the flex plate 122 don't crack the flex plate 122. Alternatively, the mating plate may be bent to contact the flex plate (with similar rounded edges) without a spacer 154 in between. This design may also include an integrated bearing assembly as shown in FIG. 5 on one side of the bearing assembly to reduce the overall cost and complexity of the product.
[0265] FIG. 8A, 8B, and 8C show a compact bearing assembly with integrated thrust bearing and frictional damping. The bearing shaft 128 may be integral with the cradles, and welded to the back of the cradles to protrude out of the cradle back with a protrusion 160 that spaces the torque tubes from the curved corners of the cradle. A cross section of the bearing shaft 128 may be circular. The shaft 128 may have a same diameter throughout its entirety. A bearing strap 116 may strap the bearing shaft 128 to the bearing 117 and the bearing support below with the aid of fasteners, for example four fasteners with two fasteners on each side. The bearing strap 116 and bearing 117 may both overlap and extend in both directions from the vertical center of the bearing shaft 128. The bearing 117 may be longer than the bearing strap 116 and extend up to the or substantially up to the entire length of the bearing shaft 128. The bearing strap 116 itself may be longer than half of the bearing shaft 128. The compact bearing assembly may have only one bearing 117 as well as only one bearing strap 116. The bearing 117 has two or more bearing thrust surfaces 126 that each directly contacts one the cradle thrust surface 158 of opposing cradles 100 to provide frictional load on the bearing shaft 128 that can dampen dynamic responses arising in the tracker during operation such as during wind events. The bearing thrust surfaces 126 may be on opposing sides of the bearing 117, may be planar, and may have a non-rectangular shape. The cradle thrust surface 158 may be planar and may have a rectangular or square shape, and the bearing shaft 128 may be disposed through the center of the cradle thrust surface 158 to protrude out of the other side. The cradle thrust surface 158 may have edges in contact with curved corners of the cradle 100. The frictional load may be achieved by the bearing strap 116 and/or the bearing 117 directly contacting the shaft 128 and transferring the force from the cradle thrust surface 158.
[0266] FIG. 9 shows a bearing assembly with integrated thrust bearing and frictional damping, including two bearings instead of just one. The plastic bearing 117 can provide a thrust surface 126 against which the shaft thrust surface 127, or face of a cradle 100 as shown in FIG. 3, can contact to maintain the position of the bearing shaft 128 in the center of the bearing. Other methods may use an articulating joint, flexure device, or other device, instead of a bearing shaft 128. In addition, the plastic bearing 117 and the bearing strap 116 can provide frictional load on the bearing shaft 128 that can be useful for damping dynamic responses that may arise in the tracker during operation such as during wind events. The bearing shaft 128 may have square plates between it and the cradles rather than being directly welded onto the cradles itself. The bearing shaft here may be smaller diameter than the one shown in FIGS. 8A-8C, and may have a varying diameter, where the diameter is smaller at the thrust surfaces than, for example, at the vertical center of the bearing shaft or in the regions closest to the cradles.
[0267] FIG. 10 shows a flexure bearing with the flexure plates 122 located outboard of the plastic bearings 117 and bearing straps 116. A mating plate 124 can be installed on one or both ends of the bearing shaft 128 to allow the cradles 100 to flex to accommodate differing incoming and outgoing angles of the torque tubes supported by the cradles 100. The longest dimension of the mating plate 124 may be perpendicular to the longest dimension of the cradle back. A flex plate 122 is between the mating plate 124 and the cradle 100 to allow differing incoming and outgoing angles for the torque tubes supported by the cradles 100. The flex plate 122 may be octagonal. An overload spring may also be in contact with the flex plate 122 to prevent cracking caused by boltheads. A spacer 154 may help the mating plate contact the flex plate 122.
[0268] FIGS. 11A and 11B show a flexure bearing with mating plates 124 located outboard of the plastic bearings 117 and bearing straps 116. In this embodiment the two mating p124 do not have a flex plate in between. Even so, they have flexibility to allow differing incoming and outgoing angles for the torque tubes supported by the cradles 100. For example, they can flex around two perpendicular axes that sit within a plane in between them (e.g., in the midpoint between them), the normal of the plane being the same direction that the bearing shaft 128 extends along. The mating plates 124 are not illustrated here in direct contact with each other, being in direct contact with spacers 123 between them. Alternatively, they may have bent edges so that they are in direct contact with each other. One of the mating plates 124 may be in direct contact with or integral with the bearing shaft 128. The other of the mating plates 124 may be in direct contact with or welded and integral with the cradle 100. For example, it may extend from the rectangular back of the cradle 100 to form wings. The two mating plates 124 here may have their longest dimensions extending in the same direction and/or have their overall shapes to be matching with each other in orientation. Each of the mating plates 124 may be rectangular or non-rectangular. Of course, the devices shown in FIGS. 10 and 11A-11B may use a compact bearing assembly as shown in FIGS. 8A-8C rather than a bearing assembly having two bearings.
[0269] FIGS. 12A and 12B show a stepped module clip. A module clip clamps a solar module 113 to a torque tube 104. The stepped module clip may comprise an upper stepped module clip 129, a lower stepped module clip 130, a tube strap 131, and module clip fasteners 132. Both the lower and upper stepped module clips have multiple levels on which the edge of the module can be placed, for example, two or more steps, e.g., three steps each. Using the upper edge of a lower module clip on one side of a solar module, and the lower edge of another module clip on the other side of a solar module, will result in the solar module being installed in a non-parallel manner with the torque tube. They may be installed on the torque tube facing the same direction, with the solar module being clipped at one end on one side of the module clip and clipped on the other end of the at the opposing side of the module clip. Because the module clip is asymmetric and facing the same side this results in the non-parallel orientation of the solar module. The upper stepped module clip 129 and lower stepped module clip 130 may have a length on their longest sides in a direction perpendicular to the torque tube and parallel to longest side of the solar module. The upper stepped module clip 129 may be shorter than the lower stepped module clip 130, or they may have the same length. The stepped module clip may comprise one, two, or more fasteners fastening the upper stepped module clip 129 to the lower stepped module clip 130, and fastening both to the tube strap 131 which secures the module clip to the torque tube. The tube strap 131 may have a rectangular or square shape.
[0270] As FIG. 13 shows, in an embodiment the module clip may have smooth or flat surfaces on all sides and have no steps. The angled upper portion 168 and lower portion 172 still allows the clipping of solar module to be non-parallel to the torque tube.
[0271] FIGS. 14A and 15A illustrate a transition bearing assembly 180. The transition bearing assembly 180 may include a straight bearing assembly including a bearing shaft 128 going through at least one bearing strap 116. For example, the bearing strap 116 may be in direct contact with both the shaft 128 and the bearing support 111, and the bearing strap 116 may secure the shaft 128 to the bearing support 111. The bearing strap 116 may be curved in cross-section, or it may be rectilinear as illustrated in FIG. 15A, e.g., having a cross-sectional shape (viewed in the direction of the axis of the shaft 128) that is at least a part of a polygon. The rectilinear shape may allow better control of friction force and/or clamping from the bearing strap 116 on the shaft 128 compared to a curvilinear bearing strap.
[0272] The bearing shaft 128 may have a rotation axis RI such that the straight bearing assembly and the transition bearing assembly may rotate around this rotation axis, for example when driven by a slew drive 190 coupled to the transition bearing assembly. That is, the bearing shaft 128 may be secured and constrained by the bearing strap 116 to the bearing support 111, such that within the constraint of the bearing strap it may rotate around the rotation axis R1. The rotation axis R1 may, for example, be parallel to a length of the shaft 128 and/or run through a center of the circular cross-section of the shaft, a plane of the cross-section being perpendicular to the length of the shaft.
[0273] The transition bearing assembly 180 includes two solar mounting structure couplers, i.e., cradles 100, disposed on opposing sides of the assembly. Cradle clamps 106 may be secured to each of the cradle 100 in order to secure respective solar mounting structures, e.g., torque tubes 104, to the cradles. Each of the torque tubes 104 may have a torque tube axis. The torque tube axis may run through a center of a cross section of the torque tube, the cross section having a plane perpendicular to the length of the torque tube and/or perpendicular to the rotation axis of the straight bearing assembly. The torque tube axis may extend parallel to the rotation axis R1, or may be angled to be non-parallel with respect to the rotation axis R1.
[0274] A cradle 100 on one side of the bearing shaft 128 may be disposed so that respective torque tubes 104 secured in the cradles 100 may have axes that are offset from each other, i.e., not coaxial. Alternatively, the torque tubes 104 may have axes that are aligned with each other. FIGS. 16A, 16B, and 16C illustrate torque tubes disposed in transition bearing assemblies with different orientations of cradles resulting in coaxial or aligned torque tube axes. A first torque tube 104 may have a first torque tube axis T1, while a second torque tube 104 extending from the opposing side of the transition bearing assembly may have a second torque tube axis T2. As mentioned above, the transition bearing assembly, the straight bearing assembly, and/or the bearing shaft 128 may have a rotation axis R1. The first torque tube axis T1, the second torque tube axis T2, and the rotation axis R1 may be variably offset or aligned with each other in various configurations.
[0275] In embodiments of the invention as illustrated in FIG. 16A, rotation axis R1 is offset from both first torque tube axis T1 and second torque tube axis T2, while first torque tube axis T1 and second torque tube axis T2 are offset from each other. For example, first torque tube axis T1 may be below rotation axis R1 and above second torque tube axis T2. In FIG. 16B, rotation axis R1 is aligned with (i.e., coaxial with) first torque tube axis T1, and both rotation axis R1 and first torque tube axis T1 are offset from and not aligned with second torque tube axis T2. For example, second torque tube axis T2 may be below both rotation axis R1 and first torque tube axis T1. Even when offset from each other, axis T1, axis T2, and axis R1 may extend parallel or substantially parallel with each other; however, this is not a requirement, and two of the axes, or all three, may not be parallel with each other. On the other hand, FIG. 16C illustrates rotation axis R1 aligned with both first torque tube axis T1 and T2. This type of bearing assembly may be called a pass-through bearing or a concentric bearing. In this case, the solar modules disposed on the torque tubes 104 coming out of the concentric bearing may each have their center of masses be above the rotation axis R1. Alternatively to the above described orientations, the cradles may be disposed so that at least a first one of the torque tubes 104 has their axis T1 or T2 above the rotation axis R1. The second of the torque tubes 104 may have their axis T1 or T2 above, aligned with, or below the rotation axis R1. The second torque tube 104 may have its axis offset from the first torque tube 104 or aligned with it. In any case, the solar modules disposed on the at least one of the torque tubes 104 above the rotation axis may have their center of masses above the rotation axis R1.
[0276] The cradles 100 disposed on opposing sides of the bearing shaft 128 may differ from each other in shape, dimension, material, and/or weight, or they may be identical in any or all of those characteristics. For example, the height of cradle 100 supporting torque tube 104 with axis T2 may be greater than the height of cradle 100 supporting torque tube 104 with axis T1, where the height is measured from the bottom of the cradle to the top of the cradle and is perpendicular to the rotation axis R1. This differing height between cradles is depicted in FIGS. 14A and 14B. This may allow the cradle 100 to support a torque tube 104 with a lower axis T2 even when that cradle is directly attached to the bearing shaft 128 having a higher elevation than the axis T2. Additionally, the cradles 100 may be attached to opposing sides of the bearing shaft 128 so that their backs are in direct contact with the shaft 128. These backs may be flat surfaces that are, for example, rectangular, though they may be any shape. The area of the back of cradle 100 supporting torque tube with axis T2 may be greater than the area of the back of cradle 100 supporting torque tube with axis T1, in order to allow the offset to occur. Furthermore, as shown in FIGS. 14A and 14B, the left cradle may comprise less material than the right cradle, e.g., less metal, allowing savings on production costs.
[0277] The cradle clamps 106 used to secure the torque tubes to each cradle 100 may be identical to each other in shape, dimension, material, and/or weight, or the cradles clamps 106 for respective cradles 100 may differ in any of those characteristics. Even when the cradle clamps 106 for the cradles 100 are identical to each other in the above characteristics, they may be disposed at different elevations from each other, both in elevation with respect to the ground and elevation in to the bottom of their respective cradle 100 (elevation in this case means distance above a reference point, generally a fixed point on the ground unless specified). For example, cradle clamp 106 securing torque tube with axis T1 may be disposed at a greater elevation than cradle clamp 106 securing torque tube with axis T2. Additionally, at least one of the cradle clamps 106 securing a torque tube may be disposed so that the top of the cradle clamp is above or flush with a top of the cradle 100 to which it is secured, as shown in FIG. 14B with the left cradle clamp securing the torque tube T1. On the other hand, another one of the cradle clamps 106 may be disposed so that the top of the cradle clamp is below the top of the cradle 100 to which it is disposed, as shown in FIG. 14B in the right cradle clamp securing the torque tube T2.
[0278] Another way to describe the offset nature of the cradles 100 from each other is by describing the back of the cradles 100, which may be the attachment surface in direct contact with the bearing shaft 128. The attachment surfaces of opposing cradles in a transition bearing assembly 180 may have different areas from each other. Thus, even when the top of these attachment surfaces are horizontally aligned with each other as shown in, for example, FIG. 14A, the centers of the plane attachment surfaces (i.e., the intersection at the center of the width and center of the length of these surfaces) may be horizontally offset from one another due to the differing areas of the attachment surfaces. Even when the attachment surfaces of opposing cradles 100 have the same area as each other, their centers may still be offset, causing the torque tube axis of the respective torque tubes they support to be offset from each other. As a note, the centers of these attachment surfaces do not themselves have to be in direct contact with the bearing shaft 128, but may simply be on the same plane as other regions which are in direct contact.
[0279] Solar modules 113 may be disposed on the torque tubes 104. Solar modules 113 disposed on opposing torque tubes 104 extending out of the transition bearing assembly may be disposed at different elevations than each other. For example, solar modules disposed on torque tube 104 with axis T2 may have their center of gravity aligned with the rotation axis R1, while solar modules disposed on the torque tube 104 with axis Tl may have their center of gravity above the rotation axis R1. Alternatively, solar modules disposed on a torque tube 104 may have their center of gravity below the rotation axis RI if the cradle 100 offsets the torque tube enough.
[0280] The transition bearing assembly may include other bearing assemblies described in this specification rather than the particular straight bearing assembly depicted in FIGS. 14-16. For example, the transition bearing assembly may include an articulated bearing assembly (e.g., as shown in FIG. 6) or a flexure bearing assembly (e.g., as shown in FIG. 7A) rather than the straight bearing assembly. In these cases, the cradles 100 each be directly attached to one of two opposing shafts rather than just a single shaft, at least one of the two opposing shafts comprising the rotation axis R1. Since articulated bearing assemblies and flexure bearing assemblies may angle one of the cradles 100 relative to the other, the torque tube axes may be angled from one another particularly with these assemblies.
[0281] FIGS. 15A, 15B, and 15C illustrate perspective views of the bearing assemblies, while FIGS. 17A, 17B, and 17C illustrate perspective views of the bearing assemblies with the torque tubes 104 secured to the cradles. This may be a partial view of the bearing assemblies disposed in a tracker.
[0282] A solar module tracker may include a slew drive to rotate the torque tubes and the solar modules disposed on them. In such a tracker a slew drive axis S1 of a slew drive 190 may not be aligned with the torque tube axis (e.g., torque tube axis T1) of the torque tube 104 immediately adjacent to the slew drive. On the other hand, any solar modules disposed on that torque tube 104 and/or subsequent torque tubes down the tracker may have their center of masses aligned with the slew drive axis S1, so that the slew drive 190 may rotate these solar modules around their center of masses. This is shown in FIG. 18a.
[0283] However, it may be preferred that this first torque tube 104 directly adjacent to the slew drive 190 is at a different elevation than some or all of the other torque tubes in the tracker, for example the second torque tube sharing the same transition bearing assembly 180 as the first torque tube. This is achieved with the offset cradle in the transition bearing assembly 180 as shown in FIG. 18b and described above in FIGS. 16A and 16B.
[0284] In this case, a slew drive axis S1 of a slew drive 190 may be aligned with the torque tube axis (e.g., torque tube axis T1) of the torque tube 104 immediately adjacent to the slew drive. This torque tube 104 may extend to the transition bearing assembly 180 on an foundation adjacent to the slew drive foundation. This type of slew drive may be called a concentric slew drive, since it may have one or more cradles 100 whose attachment surface centers align with the center of the concentric slew drive and/or cradles 100 carrying torque tubes whose torque tube axis aligns with the center of the concentric slew drive. The slew drive may have a circular cross section along the axial direction of the tracker such that the slew drive center is the center of the circle. This center may also be the slew drive axis S1 around which the slew drive 190 rotates the torque tubes, solar modules and/or bearing assemblies to which it is coupled to. In FIG. 18b, the transition bearing assembly 180 has a first torque tube 104 having torque tube axis T1. Another torque tube may extend from the opposing side of the first torque tube and have an axis T2 (such as shown in FIG. 16B). This axis T2 is offset from axis T1. Consequently, axis T2 may be offset from slew drive axis SI and the center of slew drive 190. For example, it may be at a lower elevation, or it may be at a greater elevation.
[0285] Past the transition bearing assembly 180 next to the slew drive, the bearing assemblies on the subsequent foundations may have different configurations. For example, these other bearing assemblies may have the configuration shown in the right bearing assembly of FIG. 18A. Each of the cradles on this bearing assembly may be of the same configuration as shown in the right cradle of FIG. 14B. As a result, they may be referred to as offset bearing assemblies with the center of their cradles offset from the rotation axis of the bearing assembly. In other words, both of the torque tubes 104 supported by each of these offset bearing assemblies may have second torque tube axis T2 aligned with each other and offset from rotation axis R1. Alternatively or additionally, some or all of these subsequent bearing assemblies may have the configuration shown in FIG. 16C, where the cradles are not offset from rotation axis R1 but aligned with it instead. Either way, the transition bearing assembly 180 allows a concentric slew drive to transition easily into torque tubes with axes offset from the axis of the concentric slew drive.
[0286] Each of the torque tubes in the tracker may have one or more solar modules disposed upon them. Alternatively, the torque tube between slew drive 190 and the transition bearing assembly 180 may not have any solar modules disposed upon it, or it may have fewer solar modules disposed upon it compared to the torque tube which it shares the transition bearing assembly 180 with (extending out of the opposing side of transition bearing assembly 180) and/or compared to subsequent torque tubes supported by other bearing assemblies down the tracker.
[0287] Other benefits are possible with the described bearing assemblies. FIG. 19A depicts a tracker and illustrates how the transition bearing assembly 180 may be used in a tracker to increase power generation. For example, the tracker may include the same transition bearing assembly 180 on every foundation 103 between torque tubes 104. That is, each transition bearing assembly may have a cradle 100 at the south end of the transition bearing assembly which raises the torque tube higher than the cradle 100 at the north end of the transition bearing assembly, in the same way as those shown in FIGS. 16A and 16B. These transition bearing assemblies may be oriented in the same way as each other along the tracker, so that each torque tube in the tracker is raised at one end and lowered at the opposite end, e.g., raised at their north end and lowered at their south end. In other words, one end of the torque tube may have a greater elevation than another end of the torque tube, the elevations being calculated with respect to a fixed reference point (such as the bottom of the first foundation in the tracker, or the lowest point on the ground which the tracker is installed on). As a result, each torque tube may be angled from the horizontal, for example from 1-30 degrees, for example from 1-15 degrees, for example from 1-5 degrees. The degree at which each torque tube is angled may be the same as other torque tubes, or may be different from each other as desired. In any case, this angling may result in a tilt of the modules placed on the torque tube towards the south. Often in an installed tracker, the sun is south relative to the trackers (e.g., in the northern hemisphere). Tilting the modules towards the south and orienting it even more towards the sun may result in increased power generation on the order of 1% or more. Of course, the orientation of the transition bearing assembly 180 may be reversed in the tracker such that the modules are tilted towards the north, if desired. Additionally, in embodiments of the invention, the modules may be tilted at different angles from the horizontal when compared to each other, instead of at a uniform angle from the horizontal throughout the tracker. The orientation illustrated in FIG. 19A may be referred to as a sawtooth arrangement by virtue of the shape it creates throughout the tracker.
[0288] The bearing assemblies used may all have the same configurations, e.g., they may all be of the type shown in FIG. 16A, or may all be of the one shown in FIG. 16B. Alternatively, some of them may be of the type shown in FIG. 16A, while others may be of the type shown in FIG. 16B, for example depending on the degree of the slope they are respectively disposed over.
[0289] As noted above, the transition bearing assemblies may have articulated bearing assemblies or flexure bearing assemblies. Articulated bearing assemblies and flexure bearing assemblies may have more flexibility, allowing the cradles 100 coupled to them to tilt. The backs and bottoms of cradles may be useful in describing this tilt. For example, FIG. 16A illustrating the straight bearing assembly shows the backs of cradles 100 directly attached to the bearing shaft 128. The backs are perpendicular to the rotation axis R1. The bottom of cradles 100 supporting the torque tubes 104 are perpendicular to the backs of the cradles, and parallel with the rotation axis R1.
[0290] This orientation is similar to the neutral position of transition bearing assemblies 180 having the flexure or articulated bearing assembly instead of the straight bearing assembly. The backs of the cradles 100 directly attached to (a shaft of) the flexure or articulated bearing assemblies is perpendicular to a rotation axis RI of the transition bearing assembly 180 when the flexure or articulated bearing is in a neutral position. The bottom of the cradles is parallel to the rotation axis RI in the neutral position and/or the horizontal line shown in FIG. 18. When the cradles 100 are allowed to tilt from the neutral position by the flexure or articulated bearing assemblies, the bottom of the cradle is tilted at an angle with respect to the rotation axis and/or the horizontal line and the back of the cradle is no longer perpendicular to the rotation axis R1. For example, the lower cradle (the north-facing cradles in FIG. 19A) may be tilted upwards away from the ground so the cradle is angled with respect to the horizontal. This allows the bottom of the lower cradle to be flush with the tilted torque tube it's supporting so that it provides better support and constraint on the torque tube. The higher cradle (the south-facing cradles in FIG. 19A) may be tilted downwards to face the ground so the cradle is angled with respect to the horizontal (which angle may be different from the that of the lower cradle). This tilt allows the bottom of the higher cradle to be flush with the tilted torque tube it's supporting. In this way the articulated bearing assembly or flexure bearing assembly may support torque tubes that are more secured in the cradles when they are tilted in the tracker.
[0291] FIG. 19A shows the tracker installed on flat land. The tracker may also be installed on south-facing slopes or north-facing slopes. The latter is illustrated in FIG. 19B. Particularly, many north-facing slopes are not economically feasible to install trackers on because they are oriented so far away from the sun that they would require expensive grading or other installation costs in order to produce any significant amount of energy. A tracker with the transition bearing assemblies 180 that allow an easy mechanical way to tilt the modules towards the south where the sun resides increases the viability of land that previously would not have been economically feasible, such as certain north-facing slopes.
[0292] In FIG. 19B, the foundations 103 may have different heights as each other as measured from their base to their top, i.e., the distance each foundation spans from the ground to the transition bearing assemblies 180. On the other hand, the transition bearing assemblies 180 may have south-facing cradles at a same elevation as each other, and north-facing cradles at a same elevation as each other, the elevation being measured vertically from a fixed reference point, such as for example the bottom of the first or last foundation 103 in the tracker. Likewise, the transition bearing assemblies 180 may be level with each other at the same elevation so that they do not form a slope angled with respect to the horizontal. However, this is not a requirement, and the transition bearing assemblies 180 may have different elevations from each other with respect to a fixed reference point. Alternatively, the foundations 103 may have equal height as each other measured from the ground to the transition bearing assemblies 180 even when installed on a slope.
[0293] This disclosure is illustrative and not limiting. Further modifications will be apparent to one skilled in the art in light of this disclosure and are intended to fall within the scope of the appended claims.
