Abstract:
An electrically conductive mounting/grounding clip, for use with a PV assembly of the type having an electrically conductive frame, comprises an electrically conductive body. The body has a central portion and first and second spaced-apart arms extending generally perpendicular to the central portion. Each arm has an outer portion with each outer portion having an outer end. At least one frame surface-disrupting element is at each outer end. The central portion defines a plane with the frame surface-disrupting elements pointing towards the plane. In some examples each arm extends from the central portion at an acute angle to the plane.

Description:
CROSS-REFERENCE TO OTHER APPLICATIONS 
       [0001]    This application claims the benefit of provisional patent application No. 60/780,819 filed on 9 Mar. 2006, attorney docket number PWRL 1044-1 and provisional patent application No. 60/821,869 filed on 9 Aug. 2006, attorney docket number PWRL 1045-1, the disclosures of which are incorporated by reference. 
     
    
     STATE SPONSORED RESEARCH OR DEVELOPMENT 
       [0002]    This invention was made with State of California support under California Commission Agreement Number 500-04-022. The Energy Commission has certain rights to this invention. 
     
    
     BACKGROUND OF THE INVENTION 
       [0003]    This invention generally relates to the mounting of framed photovoltaic (PV) modules atop roofs and other support structures, where positive mechanical securement of the modules to the supporting base or structure is desirable and electrical grounding of accessible metal components, such as the PV module frame and ancillary mounting components, is required. Known combined mounting/grounding devices require a special flange on the outside of the photovoltaic module frame and a specially designed clip or other attachment device. Therefore, conventional combined mounting/grounding devices are limited to use with specific module frame geometries. 
       BRIEF SUMMARY OF THE INVENTION 
       [0004]    A first example of an electrically conductive mounting/grounding clip, for use with PV assemblies of the type having electrically conductive frames separated by gaps, comprises an electrically conductive body having a central portion and first and second spaced-apart arms extending generally perpendicular to the central portion. Each arm has an outer portion, each outer portion having first and second outer ends. The clip also has a frame surface-disrupting element at each outer end. The central portion defines a plane. The frame surface-disrupting elements point towards the plane. In some examples the frame surface-disrupting elements comprise frame-surface-penetrating teeth. In some examples each arm extends from the central portion at an acute angle to the plane, such as 80-88°. 
         [0005]    A second example of an electrically conductive mounting/grounding clip, for use with an array of PV assemblies of the type having electrically conductive frames separated by gaps, includes an electrically conductive body. The body comprises a central portion and first and second spaced-apart, generally T-shaped arms extending from the central portion. Each arm extends from the central portion at an acute angle to the plane. Each arm has an outer portion, each outer portion having first and second outer ends. A plurality of frame surface-disrupting elements are at each outer end. The frame surface-disrupting elements of each arm are oriented in a direction generally parallel to a line connecting the outer ends of said arm. The central portion defines a plane and the frame surface-disrupting elements point towards the plane. 
         [0006]    An example of an electrically conductive mounting/grounding clip assembly, for use with an array of PV assemblies of the type having electrically conductive frames separated by gaps, includes an electrically conductive clip and a second member. The clip includes a central portion and first and second spaced-apart arms extending generally perpendicular to the central portion. Each arm has an outer portion and each outer portion has first and second outer ends. A frame surface-disrupting element is it each outer end. The central portion defines a plane and the frame surface-disrupting elements point towards the plane. The clip assembly also includes means for (1) biasing the frame surface-disrupting elements of the clip against electrically conductive frames of adjacent PV assemblies thereby electrically connecting the frames to one another through the clip, and (2) securing the clip to the second member. 
         [0007]    An example of a PV installation includes a support, first and second PV assemblies and an electrically conductive mounting/grounding clip assembly for use with the first and second PV assemblies. The first and second PV assemblies are of the type having electrically conductive frames separated by a gap, the frames each having an upper surface. The clip assembly comprises an electrically conductive clip. The clip includes a central portion and first and second spaced-apart, generally T-shaped arms extending generally perpendicular to the central portion. The central portion and arms define an access region accessible from above. Each arm has an outer portion, each outer portion having first and second outer ends. At least one frame surface-disrupting element is at each outer end. The central portion defines a plane. The clip assembly also includes a second member, positioned generally beneath the first and second PV assemblies and supported by the support, and an elongated connection member. The elongated connection member secures the clip to the second member and is extendable within the gap between the electrically conductive frames so that the frame-disrupting element can be forced against the electrically conductive frames thereby electrically connecting the frames to one another through the clip. The central portion comprises a hole and the elongated connection member comprises a connection element passing through the hole. The connection element has an upper end located completely within the access region and below the upper surface. In some examples the frame comprises an electrically non-conductive surface and the frame surface-disrupting portion comprises surface-penetrating teeth. In some examples the clip assembly further comprises means for preventing the clip from tipping away from the frame as the clip is biased against the frame by the elongated connection member. In some examples the connection element may include a threaded member, such as a bolt or a stud. 
         [0008]    A third example of an electrically conductive mounting/grounding clip, for use with a PV assembly of the type having an electrically conductive frame, comprises an electrically conductive body. The body has a central portion and first and second spaced-apart arms extending generally perpendicular to the central portion. Each arm has an outer portion with each outer portion having an outer end. A plurality of frame surface-disrupting elements are at each outer end. The central portion defines a plane with the frame surface-disrupting elements pointing towards the plane. In some examples each arm extends from the central portion at an acute angle to the plane. 
         [0009]    A second example of an electrically conductive mounting/grounding clip assembly, for use with a PV assembly of the type having electrically conductive frame, includes an electrically conductive clip and a second member. The clip comprises a central portion and first and second spaced-apart arms extending from the central portion. Each arm has an outer portion with each outer portion having an outer end. A frame surface-disrupting element is it each outer end. The central portion defines a plane and the frame surface-disrupting elements point towards the plane. The clip assembly also includes means for (1) biasing the frame surface-disrupting elements of the clip against the electrically conductive frame of an adjacent PV assembly thereby electrically connecting the frame to the clip, and (2) securing the clip to the second member. The clip assembly further includes means for preventing the clip from tipping away from the frame as the clip is biased against the frame by the biasing and securing means. 
         [0010]    A second example of a PV installation comprises a support, a PV assembly and an electrically conductive mounting/grounding clip assembly for use with the PV assembly. The PV assembly is of the type having an electrically conductive frame, the frame having an upper surface. The clip assembly comprises an electrically conductive clip. The clip comprises a central portion and first and second spaced-apart arms extending generally perpendicular to the central portion. The central portion and arms define an access region accessible from above. Each arm has an outer portion with each outer portion having an outer end. At least one frame surface-disrupting element is at each outer end. The central portion defines a plane. The frame surface-disrupting element points towards the plane. The clip assembly also includes a second member positioned generally beneath the PV assembly and supported by the support. The clip assembly further includes an elongated connection member securing the clip to the second member so that the frame-disrupting element can be forced against the electrically conductive frame thereby electrically connecting the frame to the clip. The central portion has a hole and the elongated connection member comprises a connection element passing through the hole. The connection element has an upper end located completely within the access region and below the upper surface. The clip assembly further includes means for preventing the clip from tipping away from the frame as the clip is biased against the frame by the elongated connection member. 
         [0011]    Various advantages, discussed below, accrue through the use of different examples of the invention. The clip assemblies can provide both a mounting and electrical grounding function. This saves considerable material and labor costs as compared to the conventional approach of running a grounding wire between all PV modules. The clips are can also be less expensive than typical tinned copper grounding lugs. The clips can be easily secured to the modules from above, unlike approaches which require the use of mounting and grounding holes in the module frame; such holes have limited accessibility, especially after installation. This reduces installation and maintenance costs. The clip assembly can be module neutral; that is, it can be used on any framed PV module in which at least portions of the frame are electrically conductive for grounding the PV module. Examples of the invention also do not require any special construction of the module frame, such as external flanges specific to a particular module manufacturer. The geometry of the clip assembly can comprise a direct connection for grounding as required by Underwriters Laboratories (UL) as opposed to some other approaches, where the grounding points are not directly connected to the module frame by the mounting bolt or stud. Some examples of the clip assembly are amenable to use as a grounding device independently from its function as a mounting device, if desired. 
         [0012]    Other features, aspects and advantages of the present invention can be seen on review of the figures, the detailed description, and the claims which follow. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]      FIG. 1  is an exploded isometric view of a clip assembly; 
           [0014]      FIG. 1A  is an enlarged partial side view of the clip of  FIG. 1 ; 
           [0015]      FIG. 2  is an assembled isometric view of the clip assembly of  FIG. 1 ; 
           [0016]      FIG. 3  is an enlarged cross-sectional view of the clip assembly of  FIG. 2  shown secured to adjacent PV assemblies; 
           [0017]      FIG. 4  is a simplified overall view of two adjacent PV assemblies secured to one another using the clip assembly  FIGS. 1-3 ; 
           [0018]      FIGS. 5-8  illustrate different types of clip assemblies used with different types of support structures; 
           [0019]      FIG. 9  is an overall view of a peripheral clip assembly; 
           [0020]      FIG. 10  is a cross-sectional view of the clip assembly of  FIG. 9 ; 
           [0021]      FIG. 11  shows a clip assembly of  FIGS. 1 and 2  used at the periphery of a PV array with a spacer; 
           [0022]      FIGS. 12 and 13  are exploded isometric and isometric views of an internal clip assembly; and 
           [0023]      FIG. 14  is a cross-sectional view showing the clip assembly of  FIG. 13  secured to the internal lip of the frame of a PV assembly. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0024]    The following description will typically be with reference to specific structural embodiments and methods. It is to be understood that there is no intention to limit the invention to the specifically disclosed embodiments and methods but that the invention may be practiced using other features, elements, methods and embodiments. Preferred embodiments are described to illustrate the present invention, not to limit its scope, which is defined by the claims. Those of ordinary skill in the art will recognize a variety of equivalent variations on the description that follows. Like elements in various embodiments are commonly referred to with like reference numerals. 
         [0025]      FIG. 1  is an exploded isometric view of one example of a clip assembly  10  made according to the invention. Assembly  10  includes a clip  12  secured to a second member  14  by a bolt  16 . Second member  14  includes a base  18 , typically of extruded aluminum or some other appropriate material, and a sealant  20  secured to the lower surface  22  of base  18 . Sealant  20  is typically in the form of a butyl tape about 3 mm thick. Base  18  has a pair of raised portions  24  defining a gap  26  therebetween. Gap  26  extends down to a central region  28  of base  18 , central region  28  having a number of threaded holes  30  formed therein for receipt of bolt  16 . Base  18  also has a pair of flanges  32  having a number of mounting holes  34  used to secure second member  14  to a mounting surface, such as a roof. Bolt  16  passes through a central opening  36  in clip  12 , through a hole  38  formed in a spacer  40 , through gap  26 , and into a threaded hole  30 . Other types and configurations for base  18 , such as that shown in provisional patent application No. 60/821,869, may also be used. 
         [0026]      FIG. 2  shows clip assembly  10  in an assembled form while  FIG. 3  illustrates clip assembly  10  of  FIG. 2  securing adjacent PV assemblies to second member  14 .  FIG. 4  is a simplified overall view illustrating two clip assemblies  10  engaging adjacent PV assemblies  50  in the gap  58  between the PV assemblies. Clip assemblies  10  are commonly referred to as interior clip assemblies when used between adjacent PV assemblies. 
         [0027]    Clip  12  is a generally U-shaped structure having a central portion  42 , through which central opening  36  is formed, and a pair of upstanding arms  44 . Arms  44  and central portion  42  define an access region  45 . Access region  45  is accessible from above to provide clear access to bolt  16  thus facilitating the use of clip assembly  10 . Arms  44  include extensions  46  having downwardly extending teeth  48 . As shown in  FIG. 3 , clip assembly  10  is used with PV assemblies  50  of the type having electrically conductive frames  52  surrounding PV panels  54 . As can be seen in  FIGS. 2 and 3 , the head of bolt  16  is located completely within access region  45  and is located below the top surface of frame  52  of PV assembly  50 . In addition, the generally T-shaped configuration of arms  44  with downwardly facing teeth  48  provide for a low profile structure. This low profile structure creates a cleaner, less cluttered appearance and also minimizes shading of PV panel  54 . 
         [0028]    Frames  52  have an upper, circumferentially extending edge  56  which are engaged by teeth  48  of clip  12 . Frame  52  is typically anodized aluminum and thus has a non-conductive outer surface. Frame  52  may also have other types of non-conductive outer surfaces, such as a painted outer surface. To ensure good electrical contact between clip  12  and frame  52 , teeth  48  act as surface-disrupting elements. The serrated teeth or other structure cuts through any nonconductive material on frame  52  thereby creating a positive electrical connection with clip  12 , and via bolt  16 , to second member  14 . This helps to ensure good grounding between frames  52  of adjacent PV assemblies  50  through clip  12 . Other surface-disrupting methods could also be used, such as causing clip  12  to slide against and score a portion of frame  52  or through the use of other types of surface-disrupting structures or procedures. 
         [0029]    In the example of  FIGS. 1-3 , three teeth  48  are used at each extension  46  of arms  44 . The use of a number of points  44  at each extension  46  allows some adjustment in the position of clip  12  relative to frame  52 , thus facilitating installation. Teeth  48  are oriented to be generally parallel to a line connecting extensions  46  of each arm  44  and thus generally perpendicular to the adjacent frame  52 . 
         [0030]    Arms  44  are preferably not perpendicular to central portion  42 . In the disclosed example, arms  44  extend inwardly over central portion  42  to define an included angle  53 , see  FIG. 1A . Included angle  53  is an acute angle and typically ranges from 80-88°, and is about 83° in the disclosed example. This helps to strengthen clip  12  because arms  44  will tend to straighten out under load. Another advantage with the angulation of arms  44  is that doing so results in more of a point contact by teeth  48  with frame  52 . This can be for two primary reasons. The first reason is that teeth  48 , for practical purposes, do not narrow down to a true point but rather to a line or edge, the length of which is as long as clip  12  is thick. Therefore, by angling arms  44 , the ends of teeth  48  first engage frame  52  to provide more of a point contact than a line contact. The second reason is based upon the fact that manufacturing constraints limit how sharp of an edge teeth  48  will exhibit. In some examples, teeth  48  will exhibit a rounded edge so that if arms  44  were perpendicular to central portion  42 , teeth  48  would provide a generally cylindrical surface against frame  52 . 
         [0031]    Clip  12  also secures frame  52  to second member  14  by capturing the frame between arms  44  of clip  12  and raised portions  24  of base  18 . Spacer  40 , as suggested in  FIG. 3 , helps to ensure adjacent PV assemblies  50  are located in a proper distance from one another. Spacer  40  is typically made of rubber or some other material including, for example, metal or cardboard, sized to be larger than the width of central portion  42 , illustrated in  FIG. 3 . The size of spacer  40  is chosen so that when PV assemblies  50  expand during hot weather, or otherwise, PV assemblies  50  have room to expand before contacting clip  12 . This helps to prevent damage to PV panels  54 , which could occur if PV assemblies  50  were to press directly against clip  12  during such thermal expansion. The use of spacer  40  simplifies installation and by eliminating the need to use a special tool to ensure proper spacing of PV assemblies during installation. Although the primary grounding created by clip  12  is from frame  52  of one PV assembly  50  to frame  52  of an adjacent PV assembly, clip assembly  10  can also be used to provide grounding between PV assembly frames  52  and second member  14 . 
         [0032]    Clip assembly  10  provides a low profile mounting/grounding clip assembly usable with a wide variety of PV assemblies of the type having an electrically conductive circumferential frame having an exposed upper peripheral surface. 
         [0033]      FIG. 5  illustrates a clip assembly  62  that uses a clip  64  similar to clip  12  but turned upside down with teeth  48  facing the opposite direction so that they also pointed downwardly to engage frame  52  of PV assemblies  50 . In addition, instead of using a central bolt  16 , clip assembly  62  has a pair of L-shaped legs  66  extending downwardly from the arms  68  of clip  64 . Second member  70  in this example has an upwardly extending stud  72  passing through a hole, not shown, formed in the bent end  74  of each leg  66  with a nut  76  securing leg  66  to second member  70 . 
         [0034]      FIGS. 6 and 7  disclose further alternative embodiments similar to the embodiment of  FIGS. 1-4 , with a stud-type mount in  FIG. 6  including a stud  78  and a nut  80  and a bolt type mount in  FIG. 7 , and a different type of second member  82  supporting PV assemblies  50 . The second members supporting PV assemblies  50  in  FIGS. 5-7  are used to support sloped PV assemblies. This type of structure is shown in more detail in U.S. patent application Ser. No. 11/616,575, filed 27 Dec. 2006, entitled Supported PV Module Assembly, attorney docket number PWRL 1041-2, the disclosure of which is incorporated by reference. 
         [0035]      FIG. 8  shows a still further embodiment in which clip assembly  84  includes a clip  64  connected to a pair of wind deflectors  86 . Wind deflectors  86  may be of the type shown in the above referenced U.S. patent application Ser. No. 11/616,575. Clip assembly  84  also includes an L-shaped leg, not shown but similar to L-shaped leg  66  of  FIG. 5 , to provide an electrical ground connection and a hold down or support function for PV assemblies  50 . A clip assembly can also be constructed to provide securement point(s) for other photovoltaic array components, such as a ballast pan, a visual shield, a fire shield, a wire tray or wire securement device, or a structural member. The securement points(s) may consist of a mounting hole, a threaded stud, or a snap fit device. A clip assembly can also provide an attachment point for a conventional grounding lug or grounding wire. A particular securement point may also act as both a structural point and grounding point. Unlike clip assembly  10 , clip assembly  62 ,  84  of  FIGS. 5 and 8  are most useful for use with PV assemblies  50  having frames  52  of a chosen height. 
         [0036]      FIGS. 9 and 10  illustrate what is sometimes called a peripheral clip assembly  88 . Unlike clip assemblies  10 ,  62  and  84 , a peripheral clip assembly  88  is used to securely mount PV assembly  50  and may be used to ground frame  52  to a support member. Similar types of installations are shown in U.S. Pat. Nos. 6,058,930 and 6,722,357, attorney docket numbers PWRL 1026-1 and 1027-1, the disclosures of which are incorporated by reference. In this embodiment perimeter clip  90  is secured to second member  92  using a bolt  16 , an optional washer  94 , and a standoff  96 . The length of standoff  96  is determined by the height of frame  52 . Standoff  96  helps to prevent perimeter clip  90  from tipping away from frame  52  when bolt  16  is tightened. Other types of spacers may also be used for this purpose. Bolt  16  grounds frame  52  to second member  92 , which in this embodiment is a laterally-extending support mounted to a torque tube  98  of a tilted, tracking solar collector assembly. In this case frames  52  of a row of PV assemblies  50  are grounded to one another through second member  92  and, optionally, to other rows of PV assemblies through torque tube  98  and other second members  92 . 
         [0037]    Clip assembly  10  of  FIGS. 1 and 2  can be used at the periphery by using, for example, a spacer  100  located between the otherwise unused extensions  46  of clip  12 , see  FIG. 11 , and the second member  14 . Spacer  100  has a periphery  102  configured to accommodate frames  52  having different heights. Other types of variable-height of spacers, including threaded, telescoping spacers and spacers consisting of stacks of individual spacer elements, can also be used. 
         [0038]      FIGS. 12-14  illustrate an internal clip assembly  106  designed as a modification of clip assembly  10  of  FIGS. 1 and 2 . Clip assembly  106  includes a clip  108  and pieces of electrically insulating adhesive-backed tape  110 ,  112 . Tape  110  is secured to raised portions  24  of base  18  to cover the end of upper surface  114  opposite clip  108 . Tape  112  is adhered to clip  108  as shown in  FIGS. 12 and 13  to lie above gap  26 . Bolt  16  is tightened onto base  18  and then PV assembly  50  is secured to clip assembly  106  by sliding an internal lip  116  of frame  52  between clip  108  and base  18  engaging insulating tape  110 ,  112 . In this example internal clip assembly  106  acts to secure PV assembly  50  in place but does not provide a grounding function. In other examples internal clip assembly  106  could be configured to provide a grounding function as well as a mounting function by, for example, causing a spike to pierce the surface of lip  116  when the lip is inserted between clip  108  and base  18 . Tape  110 ,  112  helps to ensure the snug engagement of lip  116  between clip  108  and base  18  and also helps to reduce marring of the surface of lip  116 . Although tape  110 ,  112  is in this example electrically insulating, it need not be. 
         [0039]    The above-described embodiments have a clip assembly supported by a support. The support is typically a commercial or residential roof or support frame member for a solar energy tracking system. The support can also include trellises, carports, shade structures, and so forth. The clip assembly can also be supported directly on the ground. 
         [0040]    The clip assembly is preferably designed to withstand uplift and lateral loads as appropriate for the application. The clip materials are chosen for required strength, corrosion resistance, and aesthetics. 
         [0041]    During installation the mounting bolt may be torqued such that the threaded member and the clip are pre-loaded above the maximum code wind load plus an appropriate safety factor. This ensures a secure mechanical and electrical connection in all field conditions and excludes moisture from the ground bond area at teeth  48  by creating a high pressure connection zone around each point. 
         [0042]    The use of threaded connections has been emphasized. However, other types of connections, such as a ratchet-type of connections and connections using spring fingers, may also be used. 
         [0043]    The above descriptions may have used terms such as above, below, top, bottom, over, under, et cetera. These terms are used to aid understanding of the invention are not used in a limiting sense. 
         [0044]    While the present invention is disclosed by reference to the preferred embodiments and examples detailed above, it is to be understood that these examples are intended in an illustrative rather than in a limiting sense. It is contemplated that modifications and combinations will occur to those skilled in the art, which modifications and combinations will be within the spirit of the invention and the scope of the following claims. Any and all patents, patent applications and printed publications referred to above are incorporated by reference.