Patent Publication Number: US-9413287-B2

Title: Photovoltaic module support system

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a divisional of U.S. patent application Ser. No. 14/470,151, filed Aug. 27, 2014, which is a divisional of U.S. patent application Ser. No. 13/784,374, filed Mar. 4, 2013, now U.S. Pat. No. 8,844,214, issued Sep. 30, 2014, which is a divisional of U.S. patent application Ser. No. 13/011,185, filed Jan. 21, 2011, now U.S. Pat. No. 8,407,950, issued Apr. 2, 2013, the entirety of which are incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The invention relates generally to photovoltaic systems, and more specifically to a photovoltaic module support system. 
     BACKGROUND OF THE INVENTION 
     Solar energy produced by the sun can be captured by photovoltaic (PV) modules. Mounting systems for PV modules can be fixed or can track the sun&#39;s diurnal motion. Typical single axis tracking systems include a torque tube (roughly five feet above grade) capable of rotating a group of PV modules, which is installed on support posts (driven piles, drilled concrete piles or ballasted foundation). The torque tube supports one or more PV module support structures and PV modules on the support structure (or framed PV modules affixed directly to the torque tube). PV module power plants typically have hundreds or even thousands of rows of PV modules that are fixed in place and must be rotated to track the sun&#39;s diurnal motion. 
       FIGS. 1 a -1 c    illustrate one example of a typical single axis tracking system for PV modules. Multiple PV modules  100  are arranged in parallel rows  400 ,  500 , and  600 . The rows  400 ,  500 ,  600  generally run in the north-south direction, so that PV modules  100  in the rows can be tilted east and west to track the sun&#39;s rotation. The PV modules  100  are mounted onto a torque tube  115  elevated above the ground by support posts  104  that may be driven into the ground  110 . 
     At gaps  150  between PV modules  100  in a row  400 ,  500 ,  600 , a gearbox  101  or other rotation point is affixed to the torque tube  115  on either side of a PV module  100 . The gearbox  101  may be driven by independent motors at each support post  104 , or more commonly may be connected by an cantilevered lever arm  102  to a linkage  105  that connects all of the assemblies in a column of the PV array, as illustrated in  FIGS. 1 a   - 1   c.    
       FIGS. 1 b  and 1 c    illustrate the rotation of PV modules  100  when the linkage  105  is driven in a horizontal direction (for example, by a motorized screw mounted to a concrete base at one end of a column), the movement of the linkage  105  and the cantilevered lever arms  102  connected to gearboxes  101  causes the PV modules  100  to tilt to track the path of the sun. The PV modules may be tilted east or west in accordance with the movement of the sun. Typically, the rotation point, for example at gearbox  101 , is roughly five feet above the ground, and the linkage  105 , when employed, is 2-3 feet above the ground. 
     There are numerous problems with existing mounting systems such as the one illustrated in  FIGS. 1 a -1 c   . First, these mounting systems have a high center of gravity, due to the rotation point being at the very top of the mounting system. This can be a problem, as solar tracker systems must withstand high wind conditions. Second, using independent motors at each foundation is costly and inefficient. If the rotation points are instead connected by the linkage  105  illustrated in  FIGS. 1 a  and 1 b   , the linkage  105  impedes on construction, commissioning, and maintenance traffic flow through the PV array rows. Third, the gearbox  101  used to rotate the PV modules  101  and the support posts  104  both require space between the PV modules  100 , as illustrated in  FIG. 1 a   , preventing the PV modules  100  from being placed directly adjacent one another. This reduces the effective surface area of the array and is an inefficient use of real estate. Accordingly, there is a need in the art for a tracker system support structure that mitigates these and other problems. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1 a -1 c    illustrate an example support system for a conventional single axis solar tracker array. 
         FIGS. 2 a -2 c    illustrate top down and side views of a support system for a single axis solar tracker array using a truss and cradle assembly in accordance with an embodiment described herein. 
         FIGS. 3 a -3 f    illustrate top down, side, and perspective views of a support system for a single axis solar tracker array using a truss and butterfly cradle assembly in accordance with another embodiment described herein. 
         FIGS. 4 a -4 c    illustrate top down and side views of a support system for a single axis solar tracker array using a truss and cradle assembly in accordance with another embodiment described herein. 
         FIGS. 5 a -5 c    illustrate top down and side views of a support system for a solar panel array using a truss and cradle assembly in accordance with another embodiment described herein. 
         FIGS. 6 a -6 c    illustrate top down and side views of a support system for a fixed axis solar panel array using a truss and cradle assembly in accordance with another embodiment described herein. 
         FIGS. 7 a -7 k    illustrate top down, side, front, and detail views of a folding truss in accordance with an embodiment described herein. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In the following detailed description, reference is made to the accompanying drawings which form a part hereof, and which illustrate specific embodiments of the invention. These embodiments are described in sufficient detail to enable those of ordinary skill in the art to make and use them. It is also understood that structural, logical, or procedural changes may be made to the specific embodiments discussed herein, without departing from the spirit or scope of the invention. 
     Described herein is support system for photovoltaic (PV) modules in a solar panel array. The support system utilizing a truss and cradle assembly described herein has beneficial structural properties that enable an increase in the distance between support posts and allows PV modules to be placed directly adjacent one another in a row, resulting in more efficient usage of real estate. The system also enables unobstructed passage between array rows during construction, commissioning, and maintenance. Embodiments of the system described herein enable rotation of multiple rows of PV modules in unison with a low center of gravity rotation point. 
       FIGS. 2 a -2 c    illustrate an embodiment of a PV module support system utilizing a truss and cradle assembly. Photovoltaic (PV) modules  100  are arranged in parallel rows  700 ,  800 ,  900  in a photovoltaic array. Photovoltaic modules  100  in a row  700 ,  800 ,  900  are affixed to and supported by a truss and cradle assembly  202 . The truss and cradle assembly  202  supports a manually installed frame and PV module system, or an automated install (cartridge) module support system such as described in U.S. patent application Ser. No. 12/846,621 entitled “A Mounting System Supporting Slidable Installation of a Plurality of Solar Panels as a Unit” (filed Jul. 29, 2010), U.S. patent application Ser. No. 12/846,365 entitled “Slider Clip and Photovoltaic Structure Mounting System” (filed Jul. 29, 2010), U.S. patent application Ser. No. 12/846,686 entitled “Apparatus Facilitating Mounting of Solar Panels to a Rail Assembly” (filed Jul. 29, 2010), and U.S. patent application Ser. No. 12/957,808 entitled “Method and Apparatus Providing Simplified Installation of a Plurality of Solar Panels” (filed Dec. 1, 2010), which are each incorporated by reference herein in their entirety. The truss and cradle assembly  202  is rotatably fixed by a rotary axis  201  to a foundation support  204 , which may be driven piles, drilled concrete piles, ballasted foundation, or other suitable support structure. 
     The truss and cradle assembly  202  at each row  700 ,  800 ,  900  of the array is driven by an electric motor and gearbox or a hydraulic system that is installed on opposite ends of a group of array columns, generally the east and west ends, as described in more detail below. An underground linkage  220  connected to the drive motors facilitates rotating PV modules  100  in multiple rows  700 ,  800 , and  900  in unison to track the sun&#39;s diurnal motion. Rotation of the truss and cradle assembly  202  at axis  201  is illustrated in  FIGS. 2 b -2 c    and is discussed in more detail below. 
     Comparing the system in  FIGS. 2 a -2 c    to the one in  FIGS. 1 a -1 c   , it is apparent that the truss and cradle assembly  202  facilitates the formation of rows of PV modules  100  that do not have gaps  150  between PV modules  100  needed in the  FIGS. 1 a -1 c    embodiment to provide space for the gearbox  101 . Since the  FIGS. 2 a -2 c    embodiment does not require this gap, longer spans of directly adjacent PV modules, or PV modules of a longer length than in other systems, can be used, resulting in a more efficient PV system. Also, the underground linkage  220  enables unobstructed passage between array rows  700 ,  800 ,  900  during construction, commissioning, and maintenance. Further, the system in  FIGS. 2 a -2 c    has a rotation point that is lower to the ground than the system in  FIGS. 1 a -1 c   . The  FIGS. 1 a -1 c    system requires a rotation point at the very top of the foundation support (about 5 feet above the ground), and, when the rows are connected to one another by linkages  105 , the cantilevered lever arm  102  and linkage  105  hang below this rotation point. In the  FIGS. 2 a -2 c    embodiment, however, the same rotation is achieved with a rotation point well below the top of the foundation structure (the rotation point can be about half as high as that in the  FIGS. 1 a -1 c    embodiment, or about 2-3 feet above the ground), and with a less obstructive linkage  220 . This improves stability and allows the spacing between foundation supports  204  to be increased. 
       FIGS. 3 a -3 f    further illustrate aspects of the embodiment of  FIGS. 2 a -2 c   . As illustrated in  FIG. 3 a   , there are multiple PV modules  100  in each row  700 ,  800 ,  900 ,  1000 ,  1100 . While one PV module is shown above each foundation support  204  in  FIGS. 3 a -3 c   , the system can include many PV modules  100  on the truss  202  between each foundation support, or one PV module  100  may span multiple foundation supports  204 . All of the rows  700 ,  800 ,  900 ,  1000 ,  1100  of PV modules  100  are driven by two electric motor and gearbox structures  225  installed at each end of the column. Alternatively, a hydraulic system or other motive system can also be used, as described below. 
       FIG. 3 c    provides a more detailed view of the truss and cradle assembly  202 . The PV module  100  is attached to a triangular truss  222  by installation rails  300  which enable a sliding connection with a recess in the PV modules  100  or a carrier for a plurality of modules in the manner illustrated in U.S. patent application Ser. No. 12/846,621. The PV modules  100  of this or any other embodiment described herein can also be attached to the triangular truss  222  using conventional clips, fasteners, screws, glue or any other suitable mechanism for attaching PV modules  100  to the triangular truss  222 . 
     The truss  222  is affixed to a cradle  223 , which in this embodiment is a butterfly cradle  222  having movable butterfly drive wings  323  and non-moving (fixed) butterfly drive arms  324 . The butterfly drive wings  323  are affixed to and support the truss  222 , and can be rotated about the axis  201  in either direction. The axis  201  may be a rotation bearing assembly, a gear drive, or any other suitable rotating connection. The axis  201  may be biased, for example, by a spring  325  inside a rotation bearing of the axis  201 , so that, when not acted upon by another force, the axis will return to a position holding the PV module  100  parallel to the ground  110  (the orientation illustrated in  FIG. 3 c   ). Other forces may be used to bias the axis  201 , such as external springs connected between butterfly drive wings  323  and the non-moving butterfly drive aims  324 , a programmable microprocessor that returns a gear drive axis to an upright position, or any other mechanism suitable for returning the PV module  100  to a parallel position when in not being acted upon by another force. The cradle structure  223  is attached to the foundation  204 . 
     Linkages  205  pass through holes in the non-moving (fixed) butterfly drive arms  324 , and are connected to the movable butterfly drive wings  323 . Thus, when a linkage  205  is pulled in a downward direction, it will pull down the respective connected movable butterfly drive wing  323  of the cradle  223 , which causes the movable butterfly drive wing  323  to rotate about axis  201 , thus tilting the PV module  100 . Linkages  205  may be a braided metal wire or other moveable connection. A sheath  206  around the linkages  205  allows free movement under ground  110 , and can be used to protect the linkages (and as a safety measure) above ground. 
     In  FIG. 3 c   , the example support system facilitates rotation of the PV module  100  to an orientation of about 45 degrees to either side. The rotation would generally be in the East-West direction, following the orientation of the sun. Greater rotation angles can be achieved by using a triangle truss  222  and cradle  223  with an acute angle A, providing greater rotation before reaching the butterfly drive arm  324  of the cradle  223 . Similarly, a more restricted rotation can be obtained by using a triangle truss  222  and cradle  223  with an obtuse angle A. 
       FIGS. 3 d -3 f    provide perspective views of components in the  FIGS. 3 a -3 c    embodiment.  FIG. 3 d    illustrates two support structures  555  that include foundations  204  and cradle structures  223 . The support structures  555  have been installed in a row  1000 . These support structures  555  can support a truss  222 , such as the truss illustrated in  FIG. 3 e   . Multiple support structures  555  in a row may support a single truss  222 . 
       FIG. 3 e    illustrates a perspective view of the truss  222 . The truss  222  includes top rails  706  connected to side supports  701  and top supports  702 . Though shown here as a triangular support structure with rail side supports  701  and open sides, the truss  222  could also have planar side supports  701  that create a continuous side wall on the sides of the truss  222 . The truss  222  may be any length suitable for transport and on-site installation. The truss  222  may be a fixed structure or may be a folding truss (described in more detail below). The top rails  706  may be configured with parallel installation rails  300  that enable PV modules  100  to be mounted by sliding multiple PV modules  100  onto the installation rails  300 . Alternatively, a cartridge that holds a plurality of PV modules  100  may be slidably mounted onto the installation rails  300  of top rails  706 . Though shown here configured with installation rails  300  for mounting PV modules  100 , any suitable mounting method may be used to affix PV modules  100  to the top rails  706 , as discussed above.  FIG. 3 f    illustrates the support structure  555  with the truss  222  and PV modules  100  installed. 
     The tilting of multiple rows of PV modules  100  in unison is now described with reference to  FIGS. 3 a -3 b   . In  FIGS. 3 a -3 b   , the connection of each row  700 ,  800 ,  900 ,  1000 ,  1100  by linkages  205  enables rotation of several rows in unison. In this embodiment, electric motors and gearboxes  225  at each end of the column provide the necessary force to move the linkages  205 . Multiple electric motors and gearboxes  225  at each end of the column may be used for long-spanning rows, to provide sufficient power to tilt the entire row. 
     To tilt the PV modules  100 , the motor and gearbox  225  at one end of the column retracts the linkage  205 , for example by winding the connected linkage  205  around a spool  245 . When the linkage  205  is retracted, it pulls downward on the movable butterfly drive wing  323  of the connected cradle  202 , and this causes the butterfly drive wing  323  to rotate about its axis, tilting the PV modules  100  in one direction. Since all of the cradles  202  in the rows  700 ,  800 ,  900 ,  1000 ,  1100  are connected by linkages  205 , all of the PV modules  100  in the column are tilted in the respective direction by the tension of the linkages  205  between the cradles  222 . To tilt the assemblies  202  back in the opposite direction, the motor and gearbox  225  at the other end of the column retracts the connected linkage  205 , and the PV modules  100  are tilted back in the opposite direction. 
     The truss and cradle assemblies  202  may be biased into a neutral position (orienting PV modules parallel to the ground  110 ) by a spring  325  in a rotation bearing of axis  201 , or any other suitable biasing structure. This way, if the electric motors and gearbox  225  fails (due to power outage or other reasons), the system will maintain this neutral position. This avoids damage by winds, and inefficiencies that can be caused by a static tilted position. 
     Retracting linkages  205  using an electric motor and gearbox  225  is one way to move the rows in unison, but those of skill in the art will recognize that there are other acceptable ways to tilt these assemblies in unison. For example, if the linkage  220  is sufficiently rigid, motors and gearboxes  225  are only necessary on one end of the column, as they could both push and pull the linkages  220  (as opposed to only pulling, as described above). A hydraulic system could also be used at one end of the column to both push and pull the linkages  220  to tilt the PV modules  100 . 
       FIGS. 4 a -4 c    illustrate another embodiment of a PV module support system utilizing a truss and cradle assembly. This embodiment uses a similar truss and cradle assembly  302 , but the cradle is configured with only one set of drive arms, and instead of being driven by linkages  205  connected to an electric motor and gearbox  225  or hydraulics, it is driven by individual electric actuators  210  located at each foundation support. The electric actuators  210  push or pull one side of the truss and cradle assembly  302  to tilt the PV modules  100  in one direction or another. The electric actuators  210  are connected by an electrical connection  240  such as a shielded electrically conductive wire. The electrical connection  240  is connected, at one end of the PV array, to a power supply  230 . As in the other embodiments, the truss and cradle assembly  302  may be biased in a neutral position, so that if there is a failure of the electric actuators  210  or the electrical connection  240 , the truss and cradle assembly  202  will return to a neutral position. 
       FIG. 4 c    illustrates a detail view of one of the support structures in the  FIGS. 4 a -4 b    embodiment. As illustrated in  FIG. 4 c   , the PV module  100  is connected to the truss and cradle assembly  302  by installation rails  300 , but could also be connected using conventional clips, fasteners, screws, glue or any other suitable mechanism for attaching PV modules  100  to the triangular truss  222 . The cradle  423  in this embodiment has a single set of drive arms  224 , unlike the butterfly-style cradle in  FIG. 3 c    (which has two sets of arms  323 ,  324 ). The cradle  423  is rotatably connected to an electric actuator  210  which can be a motor-driven or hydraulic actuator. The other end of the actuator  210  is rotatably connected to the foundation  204 . When the actuator  210  pushes or pulls on the drive arm  224  of the cradle  423 , the PV module  100  is rotated one direction or another. The axis  201  may allow any desired range of motion, including motion past 45 degrees in either direction. The actuator  210  can be electrically connected to actuators  210  of other support structures by an electrical connection  240 , which may be under ground (as illustrated in  FIG. 4 c   ). The electrical connections  240  may also be run through the foundation  204  so that the wires are entirely protected from outside elements. 
     As with the  FIG. 3 a -3 f    embodiment, the truss and cradle assembly  302  of this embodiment facilitates the use of PV modules  100  which are mounted adjacent one another and without the presence of the PV module gaps  150  required due to the presence of the gearbox  101  in  FIG. 1 a   . For this reason, longer PV modules can be used, resulting in a more efficient array and tracker system. Also, the underground electrical connection  240  enables unobstructed passage between array rows during construction, commissioning, and maintenance. Further, the system in  FIGS. 4 a -4 c    has the rotation point that is lower to the ground than the system in  FIGS. 1 a -1 c   , which improves stability and allows the spacing between foundation supports to be increased. 
       FIGS. 5 a -5 c    illustrate yet another embodiment of a PV module support system utilizing a truss and cradle assembly. The  FIGS. 5 a -5 c    embodiment is essentially the same as the  FIGS. 4 a -4 c    embodiment (with like parts identified using like reference numbers), except this embodiment does not include the attached actuators  210 . In this embodiment, the truss and cradle assembly  302  is not configured with any structure that would rotate the assembly  302  around the axis  201 . The axis  201  can be biased using a spring  325  in the axis  201  assembly to maintain the PV module in the neutral position shown in  FIGS. 5 b    and  5   c.    
     The  FIGS. 5 a -5 c    embodiment provides several advantageous features of the other embodiments, including a low center of gravity, improved structural support, and the ability to use long-spanning PV modules. Additionally, the  FIGS. 5 a -5 c    embodiment can be upgraded in the future by adding actuators  210  to provide solar tracking functionality. Though illustrated in  FIGS. 5 a -5 c    with a single drive aim cradle  224  similar to the one in the  FIGS. 4 a -4 c    embodiment, the  FIG. 5 a -5 c    embodiment may also be configured to use the butterfly cradle  223  illustrated in  FIGS. 3 a -3 c   . If this embodiment is configured with the butterfly cradle, a linkage  220  and motor  225  can be added to the structure (as shown in  FIGS. 3 a -3 c   ) as a future upgrade to provide solar tracking functionality. In yet another alternative embodiment, the axis  201  of the cradle  223  may be removed altogether and the  FIGS. 5 a -5 c    embodiment may be configured with a fixed (nonmovable) cradle structure  224  connected to the foundation  204 . Though this embodiment would not be upgradable to a solar tracker system, it would still provide the other advantageous structural features described herein. 
       FIGS. 6 a -6 c    illustrate another embodiment of a PV module support system utilizing a truss and cradle assembly. In the  FIG. 6 a -6 c    embodiment, the truss and cradle assembly is fixed in an angled position. In one example configuration, the lowest point of the PV module may be 18″ above the ground or building structure such as a roof, and the PV module  100  may be angled at a 25 degree angle relative to the ground  111  or building structure. As with other embodiments, the use of a truss and cradle assembly  402  permits the use of long spans of adjacent PV modules  100 , or longer PV modules  100 , without requiring gaps  150  in the PV modules for supporting foundations  204 . Additionally, the configuration of the truss and cradle assembly  402  with the cradle  423  holding the truss  222  at an angle off-center provides a low center of gravity and improved structural properties as compared to a system with a high connection point to the PV module. This, combined with the structural rigidity offered by the truss  222 , allows the foundations  204  to be spaced further apart within a row of the PV module array. 
     The embodiments described herein each include a triangular truss can spans the length of a row in the PV array. The truss  222  may be a fixed truss that is pre-assembled or assembled on-site, or may be a folding truss design.  FIGS. 7 a -7 i    illustrate top, side, and front views of an embodiment of a folding truss design. In  FIGS. 7 a -7 c   , the truss  222  is in an unfolded state. The top rails  706  are connected to a bottom box beam  703  via side supports  701  attached with pins  710  that provide pivot points. Top supports  702  and diagonal supports  704  are attached to the top rails  706  for additional support. The front view ( FIG. 7 c   ) illustrates the triangular truss shape formed by the folding truss design. The triangle truss  222  shown has angles of 90 degrees at angle A and 45 degrees at angles B, though the triangle truss could be in other configurations, such as an equilateral triangle with 60 degree angles A and B. 
     Various mechanisms may be used to hold the truss  222  in the unfolded state. For example, the bottom box beam  703  may have indents  750  at the point where each side support  701  will come to rest in the unfolded state. This is illustrated in  FIGS. 7 j  and 7 k   , which show a top-down view of a segment of the bottom box beam  703  and side support  701 . When the structure is unfolded and the side supports  701  are within the indents  750 , the bottom box beam  703  will have a tendency not to move in either direction to fold, especially because the weight on the side supports  701  will generally be in a downward direction (towards the ground). When sufficient force is placed upon the bottom box beam  703  in a lateral direction, the side supports  701  will move out from the indents  750 , as illustrated in  FIG. 7 k   . Another way to fix the structure in the unfolded state is to add fixed cross beams to the unfolded structure that would prevent the folding action of the triangular truss  222 . These can be added between adjacent side supports  710 , between the top supports  702  and the bottom box rail  703 , or to any two points that would prevent the folding action described below and depicted in  FIGS. 7 d -7 i   . Any suitable method of fixing the truss in the open state can be used to prevent folding of the truss  222 . 
       FIGS. 7 d -7 f    illustrate the truss  222  as it is in the process of being folded. The bottom box beam  703  comes forward and up, and will fold in the indicated direction until it meets the top rails  702 . The pins  710  on side supports  701  provide a rotation point, and hinges  720  allow necessary articulation for the bottom box beam  703  to move up and forward, towards the top rails  702 . 
       FIGS. 7 g -7 i    illustrate the truss  222  in a folded position. Here, the bottom box beam  703  rests against the top rails  702  of the triangular truss structure. The hinges  720  of the side supports  701  have folded to allow articulation of the bottom box beam  703 , and the side supports  701  have fully pivoted about rotation points provided by pins  710 . The folding truss  222  enables easy transportation and storage of the truss until it is commissioned for use in an installation. The folding truss  222  can be used in fixed PV module arrays or in solar tracker systems. 
     While embodiments have been described in detail, it should be readily understood that the invention is not limited to the disclosed embodiments. Rather the embodiments can be modified to incorporate any number of variations, alterations, substitutions, or equivalent arrangements not heretofore described without departing from the spirit and scope of the invention.