Abstract:
A racking system for photovoltaic solar panels greatly reduces material, weight, labor and system profile as compared to previous mounting systems. Special pedestals are secured to a roof at far larger spacings and fewer number than required in previous systems. The pedestals are configured for efficient and dependable flashing for waterproofing the roof. In assembly the extruded aluminum components are fitted together quickly with efficient and strong connections, with the photovoltaic panels retained in a compact array and fully supported along the length of each panel. The fittings provide for field adjustment of the height of the uprights, helping accommodate uneven roof surfaces, such as flat roofs.

Description:
This application claims priority from provisional application No. 61/400,208, filed Jul. 23, 2010. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention concerns solar collection systems, and particularly a racking or mounting system especially for photovoltaic solar panels, typically roof-mounted but also ground-mounted, in a tilted-up array. 
     Many different arrangements have been suggested in the literature and used for supporting an array of solar collector panels, either on roof surfaces or ground mounted. Examples are shown in U.S. Pat. Nos. 7,531,741, 4,278,070, 6,105,317 and U.S. Pub. No. 2003/0094193. It is known to use aluminum extrusions for support members and joists or beams in a solar panel racking system. 
     Prior to this invention solar panel racking systems have employed roof-secured pedestals which are difficult to reliably waterproof, and these roof mountings have been positioned as closely as every four feet. Typically, the systems had a very large number of components to be assembled, as well as great weight in bracing, beams and panel supporting members such as to be difficult and time consuming to assemble, and far heavier than needed, often requiring engineering and roof structural modification to allow the installation, due to the weight of the systems. In addition, the roof connections, where the waterproof roofing was penetrated, were often not reliable or were costly because of the type of flashing that had to be installed. Further, on industrial or commercial flat roofs some variation in roof height is typical, and with past systems the roof elevations often had to be mapped out so that pedestals of appropriate height could be pre-cut before installation. 
     Conventional racking systems usually employ clips that grip over top edges of the solar panels, and the racking arrangements usually require spaces between adjacent panels in the array, reducing total area available for solar collection. 
     A principal object of the current invention is to overcome these problems of prior systems, to provide a lightweight but rugged and strong tilt-up solar panel mounting system that is simple, quick to install and with fewer roof penetrations, producing great savings in total weight and labor, as well as avoiding the need for engineering or structural modification on a roof and allowing field-modification of effective pedestal heights. 
     SUMMARY OF THE INVENTION 
     The solar panel racking system of the invention, particularly useful with photovoltaic panels, overcomes the problems of prior systems and greatly reduces the cost and weight of an installation. It is estimated that the system can save at least 15% on total installation cost, which includes the cost of the photovoltaic panels themselves, and can reduce cost of racking by up to 70%. The racking system greatly reduces material, labor and system profile as compared to previous mounting systems. Special pedestals are secured to a roof at far larger spacings and fewer number than required in previous systems. The pedestals are configured for efficient and dependable flashing for waterproofing the roof. These pedestals, in an assembly according to the invention, can be at least at five foot spacings and preferably about eight foot spacings or greater horizontally (laterally, parallel to the long dimension of the panels typically east-west direction) and about five foot or greater spacings in the perpendicular (typically north-south) direction. This greater spacing is due to the efficient structural framework above. 
     In assembly the extruded aluminum components are fitted together quickly with efficient, strong and versatile connections, with the photovoltaic panels retained in a compact array and fully supported along the long sides of each panel, with panel edges fitted into structural east-west oriented channel members. The fittings provide for field adjustment of the height of the uprights, helping accommodate uneven roof surfaces, such as flat roofs. 
     Structural channel members such as used in the invention have previously been used in Europe to support photovoltaic panels by their edges, but only on roof-plane installations where the panel array follows the roof plane, not in tilt-up arrays. Moreover, this previous use of the structural channels had only the narrow sides of panels supported in the channels, failing to support the photovoltaic panels by their long edges. 
     It is therefore among the objects of the invention to reduce weight and cost of racking for solar panel mounting, while providing for fast and efficient assembly, reliable roof flashing, fewer roof penetrations and field adjustability of height components. These and other objects, advantages and features of the invention will be apparent from the following description of a preferred embodiment, considered along with the accompanying drawings. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view showing an array of solar panels supported and retained in the racking system of the invention, the system being shown partially constructed. 
         FIGS. 2A ,  2 B and  2 C are schematic elevations showing installation of a panel between structural members. 
         FIG. 3  is a perspective view showing initial erection of components of the racking system. 
         FIG. 4  is a perspective view with the racking system further assembled. 
         FIG. 5  is a perspective view showing a connection detail whereby panel-engaging structural beam channel members are secured to main, sloping joists. 
         FIG. 5A  is an end view or section view showing one preferred configuration of an extruded joist member, as a box beam. 
         FIG. 6  is another perspective view showing main beams or joists, a panel-engaging structural channel member and a solar panel retained in the structural channel member. 
         FIG. 7  is a cross section view showing an example of the panel retaining structural channel member. 
         FIG. 8  is a side view showing a connector component. 
         FIG. 9  is a perspective view showing connection of a column or leg to main joists as typical at laterally interior positions in the racking assembly. 
         FIG. 10  is a perspective view showing a pedestal for securement down to a roof. 
         FIG. 11  is a cross section view showing a column or leg member. 
         FIG. 12  is a perspective view showing connection of the column member to a main beam and to a bracing member. 
         FIG. 13  is a view showing the erected racking system from a rear perspective. 
     
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     In the drawings,  FIG. 1  shows an example of a tilt-mounted array  10  of rectangular photovoltaic solar collectors  12 , in a setup of a racking system  14  comprised primarily of a series of extruded aluminum components in a structural framework. As illustrated, the panels  12  are in a substantially planar grid and arrayed in “landscape” orientation, that is, the long sides of the collector panels in the lateral horizontal direction, sometimes referred to herein as the east-west direction, with the high and low sides of the tilt-up array being north and south, respectively. The use of these directions herein and in the claims is approximate and only for reference, since the north-south directions will be reversed in the southern hemisphere. 
     Importantly, the panels are structurally supported along the length of their long sides, by horizontal structural frame members or channel members  16  which have channels into which the panels are assembled, which can be by sliding them into place or preferably by a drop-in assembly step, discussed below. This support at the long edges is important and is actually required by at least one major photovoltaic panel manufacturer. The framing channel members preferably are double-sided, although two channels could be used back-to-back if desired, to make the framing channel member  16 . Pedestals  18  and legs or uprights  21  are also seen in  FIG. 1 , but these are better illustrated in other views. 
       FIGS. 2 ,  3  and  4  are views indicating the assembly of the array of panels  12  in the racking system  14 .  FIG. 3  shows assembly of one of a series of main joists  20  onto a series of the legs or support columns  21 , each of which is secured to a pedestal  18  (together sometimes referred to as a leg). The pedestals  18  are configured to be secured to a roof, penetrating the waterproof roofing material and being capable of reliable waterproof flashing. They may be used on a flat roof or an inclined roof; in the latter case the pedestals and columns can extend up obliquely, at an angle generally perpendicular to the roof. The pedestals could have angled base plates if desired in some cases if it is important that the loading on the roof at each pedestal be applied generally vertically. 
       FIG. 4  shows a single solar panel  12  after assembling it into channels of the appropriately spaced panel-supporting framing beams or framing channel members  16 . The panels and framing channel members  16  define essentially a first, upper plane, while the series of supporting joists  20  below define essentially a second, lower plane. Note that in  FIGS. 1 ,  3  and  4  the main joists  20  are shown as used singly at outer (east-west) ends of the array, but preferably the main joists  20  are doubled into main joist pairs at all main support lines (north-south lines of support) of the system except the outer locations in the racking system, as shown. They preferably are doubled by connecting one joist to each side of a column  21  (see  FIG. 9 ). The pedestals/columns can thus be at wide spacings, at least about five feet and preferably eight feet or more widthwise, and code requirements will be met, with sufficient joist beam support per length of panels in the array. This minimizes structure in the structural framework and more importantly, greatly reduces the number of legs and roofing penetrations. Greater lateral spacings can be used depending on roof support structure beneath, since greater spans increase point loading. Prior systems typically used four feet spacings laterally. It is noted that reliable, warranted waterproof flashings can cost $100 per roofing penetration. 
       FIGS. 2A-2B  show schematically a preferred arrangement for support of the panels  12  between structural framing channel members  16 . Preferably these channel members  16  are on lateral lines spaced apart by a distance demonstrated in  FIG. 2A , such that when the upper or north side of a panel  12  is fully inserted into the open channel  22  at the south side of a first or north channel member  16  or line of channel members, the south or downhill side of the panel  12  will just clear the upper flange north side  16   b  of an opposed (south side) channel member  16  or line of channel members. For this purpose the upper flange north side  16   b  of each channel member is shallower than the upper flange south side  16   c , on each channel member. The lower flange north side  16   d  is deeper than the flange  16   b  immediately above, so that the side of the panel when lowered will rest on that lower flange  16   d . After the panel is lowered, it is moved into place by fully sliding it into the open channel  16   e  of the channel member, as shown in  FIG. 2B  and indicated by the arrow  23 . The north side of the panel rests on the lower flange south side  16   f  of the first channel member (north or left in the figures), as shown in  FIGS. 2B and 2C , and both the north and south edges of the panel  12  are covered by channel flanges. The panel will not escape, even in windy conditions.  FIGS. 2A-2C , as well as  FIGS. 4-6 , show that the open channels  16   e  are rectangular, three-sided open channels formed between upper and lower flanges ( 16   b ,  16   d ;  16   c ,  16   f ) between which a solid, single-wall web  16   q  extends, the channels receiving similarly and complementarily shaped rectangular edges of the solar panels. The rectangular panel edges are formed by an edge face and adjacent and perpendicular upper and lower panel surfaces. Panel edges substantially fill the height of the open channels, while allowing for the assembly shown in  FIG. 2A . 
       FIG. 2C  shows a preferred method and arrangement for retaining the framing channel members  16  down against the upper surfaces of the main joists  20 . This connection is also shown in  FIG. 5 , a perspective as viewed from the north side of the array. The framing beams  16  are oriented laterally, secured to the main joists  20 , which are tilted north-south.  FIGS. 2C and 5  also show solar panels  12  retained in channels  22  of the framing beam  16 . As noted above, in a preferred racking system the main joists will be doubled at interior positions of the main support lines, as shown in  FIG. 5 . The main joist  20  is here shown as a box beam, an aluminum extrusion with several nut-capturing channels in its sides, one of which is shown at  24 . These channels, which can be shaped generally as shown in  FIG. 5A , are locking channels for nuts or threaded plates to receive bolts in order to secure a bracket or clip such as the clip  26  shown in side view in  FIG. 8 . A machine bolt  28  is inserted through an opening in the clip  26 , to engage with a captured channel nut such as shown at  30  in  FIG. 5A . Such a channel nut is elongated in one direction and insertable through the slot of the channel  24 , then turned to a position where it is locked in place to receive the threaded bolt. It may have a compression spring on its bottom side (as well known) for temporary holding in place. The box beam  20  shown in  FIG. 5A  is available commercially, or it can be fabricated in a different configuration so long as appropriate connection means is available, such as shaped channels for channel nuts. 
     The clip  26  is shaped to engage with a fastening channel  32  of the framing beam  16 . This lower, fastening channel  32  is formed between a second or lower flange  16   d  of the beam  16  and a bottom flange  36 . This bottom flange  36  extends out more widely than the other flanges and preferably includes a locking lip  38 . Thus, it can be seen that the fastening clip or bracket  26 , which has a tail  40  with a step  42 , fits closely in the fastening channel  32  for locking the framing beam  16  in place against the main joist  20 . These clips are preferably used on the north sides of the framing channel members  16 , for aesthetics. The north, tilted-up side is less visible than the south side of the array, and, as seen in  FIGS. 5 and 7 , the south side of each channel member  16  can have a closed section or box  34  as shown in the drawings (see  FIGS. 5 and 7 ), for better aesthetics at the south, lower side of the array. Alternatively, the open fastening channel  22  can occur at both north and south sides if desired. The clips  26  could thus be used on either or both opposed sides of the channel beam  16 . 
       FIG. 6  is another view showing a solar panel  12  received in the main channel  22  of the framing channel beam  16 . The fastening channel  32  is also illustrated in this view. The main joists, the box beams  20 , are also shown. The assembly permits positioning of the solar panels in the channels  22  with clearance from the low profile of the clips  26  and bolts  28 ; the bolt is below the level of the channel  22 . 
     It should be understood that the box beam  20  could be configured differently if desired. What is important is that these main joists have adequate strength such that the pedestals or roof connections can be widely spaced, such as at least about five feet and preferably about eight feet or more in the lateral direction and at least about five feet in the perpendicular direction of the roof, as well as that the joist have some convenient and accessible form of connection for securing the panel framing channel beam  16  to the joist and for securing the joists to the leg columns and ultimately to the pedestals, as discussed below. 
     Note also that the doubled joist pairs could be replaced with heavier, equivalent single main joists of equal load capacity (this may require building code exceptions or changes in some jurisdictions). The joist pairs provide an advantage in securing joists such as at  35  in a line of channel members  16 ; joints are needed in large, wide arrays. The channel beams  16  can be abutted at adjacent ends with the joint  35  between joists  20  at a joist pair, and the joists provide for securement of each channel beam and individually to a joist as shown in  FIG. 5 . This could also be done with a specially formed single joist, wide enough to make the joint. 
       FIGS. 9-12  show the column  21  and its connection to the main joist or joists  20 . The column or leg  21  may be generally I-beam shaped (H-shaped) in cross section, basically a double “C” back-to-back as shown in  FIG. 11 . Although this member could be extruded aluminum, it is more preferably galvanized steel for strength and compactness.  FIG. 9  shows the preferred double joist ( 20 ) arrangement for interior, non-edge positions in the array. Both joists  20  are secured to the leg or column  21  in the manner shown, described below. This leg or upright  21  connects to a custom-formed pedestal  18  of the invention such as shown in  FIGS. 10 and 11 . The upright has connection channels  45  at its two opposed sides for receiving locking nuts as described above with reference to  FIG. 5A  (although typically of a larger size), and for connection to the pedestal  18 , the pedestal has a slotted upper end, i.e. a vertically extending slot  46  through its middle, as shown for an adequate depth to fully interlock with the column. A top portion  48  of the pedestal is square or rectangular, sized to fit within the confines of the upright leg member  21 , between flange ridges  50 , as indicated by dashed lines  52  in  FIG. 11 . The upper portion  48  of the pedestal has holes  54  for bolts to extend through the pedestal and through the central web  56  of the upright leg member  21 . In a preferred embodiment the pedestal is machined of aluminum or steel, with a lower portion  58  solid and preferably cylindrical as shown. The bottom end of this cylindrical portion can be connected with machine screws or welded or otherwise secured to a separately formed base plate  60 . Typically two aligned holes are used to secure the base plate down to a roof joist or rafter, and it is preferred that two sets of fastener holes  62  and  64  be provided, so that the pedestal can be oriented in either of two perpendicular directions for orienting the generally H-shaped leg or column member  21  as desired for further connections. 
     The pedestal  18  shown in  FIG. 10  is thus convenient and efficient for a connection to roof trusses or rafters, and it can also be used for carrying electrical cables from the array, or for ground mounting of solar panel racking. The same base plate  60 , or a base plate modified as desired, can be set on a concrete footing. For that application the bottom portion  58  of the pedestal can be shorter if desired, with no flashing required. Alternatively, a standard UNISTRUT ground mount, capable of receiving the upright  21 , could be used in lieu of the custom pedestal  18  of the invention. 
     The cylindrical exterior of the upright pedestal portion  58  enables effective and reliable flashing in an inexpensive manner, using cone-shaped flashing devices which are available commercially. This portion  58  preferably is about six inches in height, or preferably at least about five inches in height for roof flashing application. This pedestal could take other forms if desired, such as a square or rectangular shape from the upper portion  48  continuing down to the connection with the base plate  60 . This will provide four faces for flashing, which can be reliably done but typically at greater expense as compared to the cylindrical version that is reliably flashed with an off-the-shelf flashing device. 
     Note that the invention enables some field-adjustability of the racking. For example, if a flat roof of a building has height variations, the connection shown in  FIG. 9  can be adjusted to accommodate for up to several inches in variation. This is done by selecting the height of the L-shaped bracket(s) ( FIG. 9 ) in its connection to the leg or column  21 . If needed a further L-shaped bracket could be available to the installer, with a longer vertical leg, as an alternative. In addition, some adjustment is possible at the bottom of the upright, where it connects to the pedestal  18 . This is accomplished by variation in the depth to which the H-shaped upright member is fitted over the top section  48  of the pedestal. Holes through the web  56  of the upright  21  can be drilled on site, then bolts installed. 
     A further important advantage of the invention is that the connections of the main joists to the legs afford the ability to swing the planar portion of the assembly upwardly (typically lifting the north side), to near-vertical plane arrangement, to enable re-roofing a building. The connections such as shown in  FIG. 9 , at the bolts  66 , can be loosened to slip the lower leg of the L-bracket  68  up and out of the upper end of the column. The lowermost line of connection to the pedestals (south side) can be left in place and the entire panel assembly swung upright away from the north columns, temporarily, for this purpose. 
       FIGS. 9 and 12  show connections to the upright or column  21 . As noted above, an oriented channel nut can be positioned in one of the channels  45  at one of the opposed sides of the upright leg  21 . A bolt  66  is shown connecting an L-shaped bracket  68  to the side of the leg  21 , the bolt  66  being connected with the locking nut, not shown. In the connection shown, the L-shaped bracket  68  is further connected to a box beam or main joist  20 , using a channel  24  in the joist and a bolt  70  ( FIG. 9 ) and a locking nut fitted therein. The joists can be separated by the width of the leg or column  21 , held closely against the leg, to afford more stability and reduce lateral load on the L-bracket.  FIG. 12  shows a column/main joist connection from a different angle, and this could be at a corner of an array. This view further shows an angled brace  72  (see also  FIG. 13 ) which can comprise a single C-shaped extrusion as shown. This drawing further reveals a locking channel nut  74  engaged inside the C-section brace, receiving a bolt  76 . A spring  75  is connected to the nut  74  for positioning. 
     As noted above, bracing  72  is shown in  FIG. 13 , and in a system such as shown, is used in both directions. The extrusions described above make convenient the connection of bracing to the uprights or other components where needed. The single C-shaped channels can have slots to receive bolts for this purpose. The cross bracing can be done in other arrangements, depending on wind and seismic loading requirements. For example, the system in  FIG. 13 , for many applications, could eliminate the braces  72  on the right in the drawing, and the rear braces could occur at some but not all inter-leg spaces. 
     Some of the off-the-shelf components of the above described assembly are as follows:
         Double-C shaped upright  21 : UNISTRUT No. P4101   Single-C shaped brace  72 : UNISTRUT No. P1000 (or P1000SL, with slots for mounting options, if needed)   L-brackets  68 : UNISTRUT P1068   Channel nuts: UNISTRUT P1010, P4010 (spring can be removed)       

     The invention is illustrated primarily with photovoltaic solar panels, but the described racking can be used for other solar collector panels as well. The term solar panels in the claims is intended to include such other forms of solar panels. 
     The above described preferred embodiments are intended to illustrate the principles of the invention, but not to limit its scope. Other embodiments and variations to these preferred embodiments will be apparent to those skilled in the art and may be made without departing from the spirit and scope of the invention as defined in the following claims.