Patent Publication Number: US-8991065-B1

Title: Spacing gauge with thermal indicia for solar panel mounting systems

Description:
CROSS REFERENCE 
     This application is a divisional of U.S. patent application Ser. No. 13/872,759 filed on Apr. 29, 2013. The entire contents of U.S. patent application Ser. No. 13/872,759 are hereby incorporated by reference. 
    
    
     BACKGROUND 
     The present disclosure relates to solar photovoltaic (PV) panels systems and solar hot water systems, herein collectively referred to as solar panel systems. Specifically, the disclosure relates to an apparatus and system that compensates for thermal expansion and contraction of components in a solar panel system. 
     Solar panel systems, and in particular, rooftop mounted solar panel systems are generally susceptible to the weather. This includes seasonal and daily temperature changes. For example, in a dry or desert climate, temperatures may vary between day and night by as much as 60° F. (33.3° C.). In some regions of the United States, temperatures can vary seasonally by over 150° F. (83.3° C.). These temperature variations can cause significant expansion and contraction to solar PV panels or solar hot thermal panels, collectively referred to herein as solar panels, and to their mounting rails. This is particularly apparent when the solar panels are mounted in a continuous run of 100 ft. (30.48 m) to 300 ft. (91.44 m) or more. For example, a solar panel installation with a 100 ft. (30.48 m) run of aluminum mounting rail can expand or contract approximately 1.5 in (0.038 m) over a seasonal variation of 100° F. (54.5° C.) typical in many regions of the world. For a 300 ft. (91.44 m) run of solar panels that expansion and contraction would be approximately 4.5 in (0.114 m) over the same seasonal 100° F. (54.5° C.) temperature variation. 
     This expansion and contraction of solar panel system components can be challenging for concrete, and steel roof mounted solar panel system and can be particularly challenging for solar panel installations on wood sheathed roofs. For example, wood thermally expands 17%-22% of what aluminum would expand over the same given change in temperature. For the above mentioned 100° F. (54.5° C.) seasonal variation, a 100 ft. (30.48 m) length of wooden roof can expand as little as 0.25 in (0.0196 m) compared with 1.5 inches (0.038 m) for same length of the aluminum rail or back-to-back aluminum framed solar panels. This difference is enough to cause significant stress and possible buckling of components, including detachment of the mounting bolts, within the solar mounting system. 
     Attempts to solve this problem include creating thermal breaks or gaps between the a set length of rail, typically every 40 ft. (12.19 m) or 100 ft. (30.48 m) where there is a preset gap between both rail and solar panels on either side of the thermal break. This arrangement can be undesirable. For example, this arrangement dictates the structurally layout of the solar panels within the system making system planning challenging. It can also create gaps across solar panel arrays that may be aesthetically undesirable. 
     SUMMARY 
     This Summary introduces a selection of concepts in simplified form that are described the Description. The Summary is not intended to identify essential features or limit the scope of the claimed subject matter. 
     Disclosed are devices and a system for compensating for thermal expansion and contraction of rail mounted solar panel rooftop systems. The solar panel rooftop system includes mounting rails for securing the solar panels to the roof. The solar panels are secured to the mounting rails by end clamps and mid-clamps. In one aspect, a floating end clamp assembly secures a solar panel in slidable captive cooperation with a mounting rail. The floating end clamp assembly includes a floating end clamp base with a portion slidable and captive to the mounting rail and an end clamp that secures the solar panel to the floating end clamp base by a threaded fastener. 
     In another aspect, a rail splice bridges two mounting rails with a gap between the rails for thermal expansion and contraction. The rail splice can be non-movably secured to one of the rails and secured to the other rail in slidable captive cooperation. The rail secured in slidable captive cooperation has one degree of freedom to expand and contract relative to the rail splice and other mounting rail. 
     The rail splice includes indicia for setting the gap distance between rails based on ambient temperature at the time of installation. The indicia are calibrated for specific mounting rail material, ambient temperature extremes, and rail length between gaps. For example, the indicia can be calibrated for an aluminum, steel, or fiberglass mounting rails. The rail splice indicia can be calibrated for any mounting rail length. For example, the rail splice indicia can be calibrated for 40 ft. (12.19 m), 100 ft. (30.48 m), 200 ft. (61 m), or 300 ft. (91.4 m) lengths between gaps. These rail lengths are typical for solar panel installations. 
     Rail mounted solar panel installations with thermal expansion gaps generally do not allow solar panels to bridge the gap because this would create a rigid connection between the rails defeating the purpose of the gap. However, a solar panel installation utilizing a floating end clamp assembly to secure a solar panel that bridges the mounting rails creates a floating connection between the mounting rails. This affords the possibility for much more flexible installations than rail mounted solar panel systems with only rigidly mounted clamps. 
     In another aspect, a spacing gauge includes indicia for setting the gap distance between rails based on ambient temperature at the time of installation. The indicia are calibrated for a specific length between rail gaps, ambient temperature extremes, and rail material. For example, the indicia can be calibrated for an aluminum, steel, fiberglass, or other suitable material for rooftop mounted solar panel mounting rails. The rail splice indicia can be calibrated for any mounting rail length. The indicia can be printed, hot stamped, silkscreened, or otherwise applied along a wedge portion of the spacing gauge. The spacing gauge can include an optional handle portion or the wedge portion can include an integral handle. 
    
    
     
       DRAWINGS 
         FIGS. 1A-1D  each show, in side view, sections of a solar panel and rail system. 
         FIG. 2  shows a detailed view of a section of  FIG. 1B  illustrating the sliding end clamp and rail splice in combination. 
         FIG. 3  shows a top perspective view of  FIG. 1B . 
         FIG. 4  shows the solar panel and rail system of  FIG. 3  with one of the solar panels removed for clarity. 
         FIG. 5  shows a partially exploded view of a portion of  FIG. 4 . 
         FIG. 6  shows a detailed view of the sliding end clamp portion of  FIG. 5 . 
         FIG. 7  shows a side detail view of a sliding end clamp securing a solar panel to the rail. 
         FIG. 8  shows an end view of sliding end clamp and mounting rail. 
         FIG. 9  shows a front perspective view of the sliding end clamp. 
         FIG. 10  shows a side view of the sliding end clamp. 
         FIG. 11  shows a rear perspective view of the sliding end clamp. 
         FIG. 12  shows an exploded front perspective view of the sliding end clamp. 
         FIG. 13  shows a top view of the sliding end clamp. 
         FIG. 14  shows a sectional view of  FIG. 13 , of the sliding end clamp. 
         FIG. 15  shows, in a partially exploded view, an alternative floating end clamp base, end clamp, and nut. 
         FIG. 16  shows an end view of the alternative floating end clamp base secured in slidable captive cooperation to the mounting rail. 
         FIG. 17  shows a perspective view of the alternative end clamp base. 
         FIG. 18  shows the rail splice bridging two mounting rails, the rail splice including gap-setting indicia based on ambient temperature. 
         FIG. 19  shows a detailed view of a section of  FIG. 18  showing the gap-setting indicia of the rail splice. 
         FIG. 20  shows a perspective view of the rail splice of  FIG. 18 . 
         FIG. 21  shows an exploded view of the rail splice and associated fasteners of  FIG. 18 . 
         FIG. 22  shows an alternative rail splice bridging two rails, the rail splice including gap-setting indicia based on ambient temperature. 
         FIG. 23  shows a detailed view of a section of  FIG. 22  showing the gap-setting indicia of the rail splice. 
         FIG. 24  shows a sectional view of  FIG. 22 . 
         FIG. 25  shows a front view of a slidable mounting plate. 
         FIG. 26  shows a side view of screws and the slidable mounting plate in combination. 
         FIG. 27  shows mounting rails being spaced in accordance with ambient temperature by a spacing gauge with gap setting indicia. 
         FIG. 28  shows the spacing gauge of  FIG. 27 . 
         FIG. 29  shows a detailed section of  FIG. 28  showing the gap-setting indicia. 
         FIG. 30  shows the spacing gauge with alternatively positioned gap-setting indicia. 
         FIG. 31  shows a detailed section of  FIG. 30  showing the gap-setting indicia of  FIG. 30 . 
     
    
    
     DESCRIPTION 
     Certain terms, for example, “horizontal”, “vertical”, “left-side”, and “right-side” are relative terms and refer to the relative relation of the elements as presented in the figures; they are not meant to limit the meaning or scope of the claims. 
     The following description is made with reference to figures, where like numerals refer to like elements throughout the several views,  FIGS. 1A-1D  each show, in side view, a section of a solar panel system  10 .  FIGS. 1A-1D  each show one or more solar panels  11  secured to mounting rails  13  by mid-clamps  15 . In  FIGS. 1A ,  1 B, and  1 D, end clamps  17  secure the solar panels  11  to the mounting rails  13 . In  FIGS. 1A-1D , mounting brackets  19  secure the mounting rails  13  to a roof surface.  FIG. 1A  shows the right most portion,  FIG. 1B  shows the right central portion,  FIG. 1C  shows the left central portion, and  FIG. 1D  shows the left most portion of the solar panel system  10 . 
     The solar panel system  10  of  FIGS. 1A-1D  include a floating end clamp assembly  21  and a rail splice  23 , both shown in  FIG. 1B , that in combination, allow the solar panels  11  and the mounting rails  13  to expand and contract with corresponding changes in temperature. One way to facilitate thermal expansion is to place a gap between the mounting rails  13  that joined by the rail splice  23  and similarly between the floating end clamp assembly  21  and the end clamp  17  adjacent to the floating end clamp assembly  21 . This disclosure will detail apparatus for setting the gap width based on current ambient temperature, material of the mounting rails  13 , and maximum expected ambient temperature. 
       FIG. 2  shows a detailed view of a section of  FIG. 1B  illustrating the floating end clamp assembly  21  and rail splice  23  in combination.  FIG. 3  shows a top perspective view of  FIG. 1B  showing the solar panels  11  in combination with the mid-clamps  15 , the end clamps  17 , and floating end clamp assembly  21 .  FIG. 4  shows the solar panel system  10  of  FIG. 3  with one of the solar panels  11  removed for clarity to show the mounting rail  13  and rail splice  23 .  FIG. 5  shows a partially exploded view of a portion of  FIG. 4  showing rail splice  23  separated from the mounting rails  13 .  FIG. 6  shows a detailed view of the floating end clamp assembly  21 , mounting rail  13 , and solar panel  11 .  FIG. 7  shows a side detail view of  FIG. 6 , but including the solar panel  11  on the left side to show the floating end clamp assembly  21  securing the solar panel  11  to the mounting rail  13 . 
     Referring to  FIGS. 1B and 2 ,  4 , and  7 , the end clamp  17  non-movably secures the solar panel  11  to the mounting rail  13 , both of the right-hand side of the figure. In  FIG. 7 , a threaded fastener  29  and nut  31  non-movably secure the end clamp  17 . The threaded fastener  29  shown securing the end clamp  17  on the right-hand side of  FIG. 7  is a t-bolt. Screws, bolts with washers, or any threaded fastener, either alone or in combination with the nut  31  that can non-movably secure the end clamp  17  to the mounting rail  13  can be used in place of the t-bolt. 
     In  FIGS. 1B and 2 , the floating end clamp assembly  21  secures, in slidable captive cooperation, the solar panel  11  of the left portion of the figure, to mounting rail  13  of the right portion of the figure. In  FIGS. 4-5 , the floating end clamp assembly  21  of  FIG. 4  is unobstructed by the solar panel  11  for clarity. In  FIG. 5 , the floating end clamp assembly  21  of  FIG. 4  is shown in exploded view and includes a floating end clamp base  33 , a threaded fastener  29 , and an end clamp  17 . The mounting rail  13  includes a top groove  35 . The floating end clamp base  33  engages the top groove  35  in slidable captive cooperation. The threaded fastener  29  of  FIGS. 5 and 7  for securing the solar panel  11  of  FIGS. 4 and 7  to the floating end clamp assembly  21  is a standard hex head bolt. Other suitable threaded fasteners capable of securing the solar panel  11  to the floating end clamp assembly  21 , can be used, for example, an Allen head bolt, or a threaded screw. 
     Referring to  FIG. 1B , the mid-clamp  15  non-movably secures the opposing side of the solar panel  11  to the mounting rail  13 . Referring to  FIG. 2 , fasteners  25  non-movably secure the mounting rail  13  on the left portion of the figure is to the rail splice  23 . Floating fasteners  27  secure, in slidable captive cooperation, the mounting rail  13  on the right portion of the figure to the rail splice  23 . This arrangement of mounting rail  13  and rail splice  23  allows the mounting rail  13  of the right hand portion of  FIG. 2  to expand and contract as the ambient temperature changes by sliding in captive cooperation along the rail. The described arrangement of the floating end clamp assembly  21 , solar panel  11 , and the mounting rail  13 , allows the solar panel  11  of the left portion of the figure and the mounting rail  13  of the right portion of the figure to move freely in slidable captive cooperation as various elements of the solar panel system  10  expand and contract with changes in ambient temperature. 
       FIG. 8  shows an end view of floating end clamp assembly  21  and mounting rail  13 . The floating end clamp assembly  21  includes the floating end clamp base  33  and the end clamp  17 . The end clamp  17  the threaded fastener  29  secures the floating end clamp base  33 . The threaded fastener  29  does not engage or bind the mounting rail  13  in order not to impede sliding of the floating end clamp base  33  along the mounting rail  13 . The head of the threaded fastener  29  is hidden but is represented by broken lines for clarity. 
       FIGS. 9-14  show, in several views, the floating end clamp assembly  21  including the end clamp  17  and floating end clamp base  33 .  FIGS. 9-10  and  12 - 14  include the threaded fastener  29 . The threaded fastener  29  is shown as a bolt, as previously described, but can be any suitable for securing a solar panel to the floating end clamp base  33  by the end clamp  17 .  FIG. 9  shows a front perspective view of the floating end clamp assembly  21 .  FIG. 10  shows a side view of the floating end clamp assembly  21 .  FIG. 11  shows a rear perspective view of the floating end clamp assembly  21 .  FIG. 12  shows an exploded perspective view of the floating end clamp assembly  21 .  FIG. 13  shows a top view of the floating end clamp assembly  21 .  FIG. 14  shows a sectional view of  FIG. 13 , of the floating end clamp assembly  21 . 
     Referring to  FIG. 12 , the floating end clamp base  33  includes a top  37 , sides  39 , and an inner portion  41 . The sides  39  are configured to slidably engage the vertical sides of the mounting rail  13  of  FIGS. 5 and 8 . The inner portion  41  is shaped to engage the top groove  35  of the mounting rail  13  of  FIG. 5  is slidable captive cooperation. The inner portion  41  projects downward from the top  37 . The shape of the inner portion  41  is shown complementary to the shape of the top groove  35  of  FIG. 8  and fills the cross section of the of the top groove  35  cavity of  FIG. 8 . This allows the inner portion  41  to hold the floating end clamp base  33  in slidable captive cooperation. The floating end clamp base  33  is free to move along the length of the top groove  35  but is also held captive to the top groove  35  of  FIG. 8 . While the inner portion  41  is shown complementary in shape to the top groove  35  of  FIGS. 5 and 8 , other shapes that hold the floating end clamp base  33  in slidable captive cooperation can be used. In  FIG. 12 , the inner portion  41  can be held in slidable captive cooperation with the top groove  35  of  FIG. 8 , if a section of the inner portion  41  distal to the top  37  is wider than the external opening of the top groove  35  but narrower than the inside cavity of the top groove  35  of  FIG. 8 . The section of the inner portion  41  proximal to the horizontal base  37  is narrower than the top groove  35  of  FIG. 8 . 
     Referring to  FIG. 8 , in this arrangement, the inner portion  41  is slid into the top groove  35  at the end of the mounting rail  13 . The top  37  in combination with the sides  39  straddle the rail. The sides  39  can provide stability as the floating end clamp assembly  21  slides along the rail. Referring to  FIG. 12 , a threaded aperture  43  engages the threaded fastener  29 , and secures the end clamp  17  to the floating end clamp base  33 . 
     In an alternative aspect,  FIG. 15  shows a partially exploded view with a floating end clamp base  45 , end clamp  17 , and nut  31 . The floating end clamp base  45  is engaged to the mounting rail  13  in slidable captive cooperation. The mounting rail  13  includes a plurality of side grooves  47 . 
       FIG. 16  shows an end view of the floating end clamp base  45  secured in slidable captive cooperation to the mounting rail  13 .  FIG. 17  shows a perspective view of the floating end clamp base  45 . Referring to  FIGS. 16-17 , the floating end clamp base  45  includes a top portion  49  and side portions  51 . Each side portion  51  projects downward from opposing edges of the top  49 . The floating end clamp base  45  forms a modified u-shape. Each side portion  51  includes a bent or hooked end  53 . The hooked end  53  is shaped to engage and hold the floating end clamp base  45  to the side groove  47  of  FIG. 16 .  FIG. 16  shows two examples of hooked ends  53  capable of engaging and holding the floating end clamp base  45  to the side groove  47 . In the illustrated example, one of the hooked ends  53  is u-shaped and the other of the hooked end  53  shown bent or formed with a slight inset. This combination allows hooked end  53  that is u-shaped to be pivoted into place first followed by snapping the hooked end  53  with the inset into place. 
     In  FIGS. 16-17 , the floating end clamp base  45  is shown with a threaded post  55  integral to the floating end clamp base  45 . The threaded post  55  can be permanently joined to the top portion  49  of the floating end clamp base  45 . Alternatively, the threaded post  55  can be screwed into threaded aperture, for example, a threaded insert. In  FIG. 16 , the nut  31  engages the threaded inserted. The nut  31  secures the end clamp  17  shown in  FIG. 15 , to the top of the top portion  49  of  FIG. 16 . 
     One of the problems recognized by the inventors is that leaving a gap of arbitrary distance between spliced mounting rails, may not be sufficient to allow for proper thermal expansion and contraction without taking into account the ambient temperature at the time of installation and the temperature variation for a given location. For example, a solar panel system installed in Wisconsin would have a very different temperature range than different temperature extremes than a moderate climate like Hawaii.  FIGS. 18-30  apparatus that assist the installer to set the proper gap distance based on the combination of total rail length between gaps and the ambient temperature at the time of installation. 
       FIG. 18  shows the rail splice  23  mounted between the mounting rails  13  where the rail splice  23  includes indicia  59  for setting the gap.  FIG. 19  shows the detailed section  57  of  FIG. 18  showing the indicia  59  in detail.  FIG. 20  shows a perspective view of  FIG. 18  showing the rail splice  23  joining the mounting rails  13 . The indicia  59  for setting the gap are also shown.  FIG. 21  shows an exploded view of the rail splice  23  of  FIG. 18 . 
     Referring to  FIG. 19 , a reference mark indicium  61  indicates the recommended position for the end of the mounting rail  13  on the left-hand side of  FIG. 18 . The indicia  59  includes a plurality of temperature indicating text and reference marks for setting the position to set the mounting rail  13  on the right-hand side of  FIG. 18  based on the ambient temperature at the time of installation. For example, if the ambient temperature was 0° F. (−17.8° C.) at the time of installation than end of the mounting rail  13  of the right side of  FIG. 15  would be aligned proximate to the indicium  59  of  FIG. 19  marked with “0 F”. In addition to the indicia  59  for indicating the ambient temperature,  FIG. 19  shows instruction indicia  62 . The instruction indicia  62  can include instructions of how to use the rail splice  23 . The instruction indicia  62  can include calibration information, as shown in  FIG. 19 , where the instruction indicia  62  indicates that the rail splice  23  was calibrated for 40 ft. (12.19 m) rail length and ambient temperatures from 20° F. (−6.7° C.)-100° F. (37.8° C.). 
     Referring to  FIGS. 18 and 20 , the fasteners  25  non-movably secure the mounting rail  13  on the left-hand side of the figure to rail splice  23 . The floating fasteners  27  slidably secure the mounting rail  13  on the right-hand side of the figure the rail splice  23 . The fastener  25  for non-movably securing the mounting rail  13  to the rail splice  23  can be a threaded bolt  63 , or a shoulder-bolt, in combination with a nut  31 , through an aperture  65  in the rail splice  23  as shown in  FIG. 21 . The floating fastener  27  of  FIGS. 18 and 20  can be a threaded bolt  63  in combination with a nut that does not allow the bolt to extend passed its end portion; for example, a nylon or polymer insert lock nut  67 , known in the trade as a nylock nut, as shown in  FIG. 21 . The threaded bolt  63 , the polymer insert lock nut  67 , and the aperture  65  combination of  FIG. 21 , allow the mounting rail  13  on the right-hand side of  FIGS. 18 and 20  to slide in captive cooperation with the rail splice  23  along the side groove  47  also shown in  FIGS. 18 and 20 . 
       FIG. 22  shows the rail splice  23  mounted between the mounting rails  13  where the rail splice  23  includes indicia  59  for setting the gap.  FIG. 23  shows the detailed section  69  of  FIG. 22  showing the indicia  59  in detail. The indicia  59  of  FIG. 19  are typical of what can be used in an environment with wide temperature variations, and are spaced and calibrated for a 40 ft. (12.19 m) rail length between gaps. The indicia  59  of  FIG. 23  are spaced, for a moderate climate, such as Hawaii, with moderate temperate variations, and calibrated for a 100 ft. (30.48 m) rail length between gaps. As previously described for  FIGS. 18 and 19 , the mounting rail  13  on the left-hand side of  FIG. 22  is lined up with the reference mark indicium  61  of  FIG. 23 . The mounting rail  13  on the right-hand side of  FIG. 22  is lined up in a position between indicia  59  that approximately represents the present ambient temperature. For example, if the ambient temperature is 75° F. (23.9° C.), then the mounting rail  13  on the right-hand side of  FIG. 22  would be lined up between the indicia  59  marked “70 F” and “80 F” as shown in  FIG. 23 . 
     In  FIG. 22 , the fasteners  25  non-movably secure the mounting rail  13  on the left-hand side of the figure to rail splice  23  as previously described. The mounting rail  13  on the right-hand side of the figure is slidably secured in captive cooperation to the rail splice  23 . In  FIGS. 22 and 24  the rail splice  23  is held in slidable captive cooperation with the side groove  47  of the mounting rail  13  by a combination of a screw  71 , polymer insert lock nuts  67 , and a mounting plate  73 .  FIG. 25  shows a front view of the mounting plate  73 .  FIG. 26 , in side view, shows the screw  71  secured to the mounting plate  73 . In  FIG. 25 , the mounting plate  73  includes apertures  65 . The apertures  65  are threaded to hold and secure the screws  71 . A shoulder-stud can be used in place of the screw  71 . It is also possible to replace the screws  71  with threaded standoffs that are integral to the mounting plate  73  if desired. 
     In  FIGS. 18-25  the indicia  59  are calibrated to set a specific gap distance for a given ambient temperature indicated under the indicium  59 . The calibrated distance is based on the material of the mounting rails  13  of  FIGS. 18 and 22 , and the distance between rail gaps. The gap distance can be calculated by the following formula:
 
 Dg=a·ΔT·L   (1)
 
where:
 
Dg=the gap distance
 
a=the coefficient of thermal expansion
 
ΔT=the change in temperature
 
L=the length of each of the mounting rails between gaps
 
     For determining the minimum gap distance, ΔT=Tmax−Ta. Where, Tmax is the maximum possible anticipated temperature and Ta is the ambient temperature indicated by the indicia  59 . For example, if the mounting rails  13  of  FIGS. 18 and 22  are made of aluminum, the coefficient of thermal expansion for aluminum is 12.3×10 −6  in./in. ° F. (22.23×10 −6  m/m ° K), the total length of the mounting rails  13  without a gap, L=40 ft. (12.19 m), and the maximum anticipated temperature Tmax=120° F. (48.9° C.), then the gap distance for an ambient temperature of 70° F. (21.1° C.) would be Dg=(12.3×10 −6  in./in. ° F.)(120° F.-70° F.)(40 ft.)(12 in./ft)=0.3 in. (0.0076 m). For a ambient temperature of 0° F. (−17.8° C.), the gap distance would be Dg=(12.3×10 −6  in./in. ° F.)(120° F.-0° F.)(40 ft.)(12 in./ft.)=0.7 in. (0.018 m). 
     The indicia  59  on the rail splice  23  can be engraved, etched, silkscreen, printed, hot stamped or otherwise applied to the rail splice  23  of  FIGS. 18 and 22  by a method appropriate for affixing the indicia  59  based on the material of the rail splice  23 . Alternatively the indicia  59  can be printed, stamped, or otherwise applied to a label that is affixed to the rail splice  23 . 
     The indicia  59  on the rail splice  23  can be calibrated for any desired length or mounting rail material or even solar panel frame material. For example, the spacing gauges can be calibrated for aluminum, steel, fiberglass, or carbon fiber rails. The spacing gauge  75  can be calibrated to any desired rail or solar panel frame material by changing the coefficient of linear expansion, “a,” in equation (1) to the appropriate value for the desired material. While the rail length in the examples where either 40 ft. (12.19 m) or 100 ft. (30.48 m), the indicia  59  on the rail splice  23  can be calibrated for any rail length by simply changing L in equation (1). 
     Referring to  FIG. 27 , a spacing gauge  75  can be used for setting the gap distance between mounting rails  13  based on ambient temperature as an alternative to indicia  59  on the rail splice  23 . The spacing gauge  75  can be made of plastic, metal, paper, laminated paper, or any desired material suitable for receiving indicia  59 . Referring to  FIGS. 27-28 , the spacing gauge  75  includes a wedge portion  77 . The wedge portion  77  includes indicia  59  for setting the gap distance between the rails of  FIG. 27 , in accordance with ambient temperature at the time of installation. The indicia  59  can be printed, engraved, stamped, silkscreened, or applied to spacing gauge  75  by any method appropriate for applying indicia  59  to the particular material of the spacing gauge  75 . Alternatively the indicia  59  can be applied to a die cut, printed or stamped label and the label can be affixed to the spacing gauge  75 . The spacing gauge  75  can optionally include a handle portion  79  for grasping the spacing gauge  75 . Alternately a handle or grasping portion can be integrated into the wedge portion  77 , if desired. Referring to  FIG. 28 , the spacing gauge  75  can include an aperture  81  for securing the spacing gauge  75  to a key ring. The spacing gauge  75  can also include instruction indicia  62  indicating how to use the spacing gauge  75 , calibration information, or both. The calibration information can indicate the type of material and rail length the spacing gauge  75  was calibrated for. 
     Referring to  FIG. 27 , the following process can be used to adjust the gap distance between the mounting rails  13 . The fasteners  25  associated with the mounting rail  13  on the left-hand side of the figure are tightened so rail splice  23  is immovably secured to that mounting rail  13 . For a typical aluminum rail and aluminum splice, 20 ft-lb (27.12 Nm) of torque is suitable. Those skilled in the art will readily recognize the appropriate torque required to immovably secure the mounting rail  13  on the left-hand side of  FIG. 27  to the rail splice  23 . The floating fasteners  27  are tightened so to secure, in slidable captive cooperation, the mounting rail  13  on the right-hand side of  FIG. 27  to the rail splice  23 . The mounting rail  13  on the right-hand side of  FIG. 27  is free to move with one degree of freedom longitudinally along the rail splice  23 . The wedge portion  77  is inserted into the gap between the mounting rails  13  as shown until the indicium  59  corresponding to the ambient temperature, at the time of installation, aligns with the top edge of one of the rails. 
     Referring to  FIG. 28 , the indicia  59  sets the rail gap of  FIG. 27  based on the width of the wedge portion  77  at the particular indicium  59 . For example, indicium  59  positioned to the far left of the figure is at a position where the wedge portion  77  has a width of “D1g.” When the spacing gauge  75  is inserted between the mounting rails  13  of  FIG. 27  so that the top of the mounting rail  13  lines up with the indicium  59  positioned to the far left of the figure in  FIG. 28 , then the spacing gauge  75  will push the mounting rail  13  that is in slidable captive cooperation to a position corresponding to a gap of width “D1g.” The indicium  59  positioned most right in the figure is positioned where the wedge portion  77  has a width of “D2g.” When the spacing gauge  75  is inserted between the mounting rails  13  of  FIG. 17  so that the top of the mounting rail  13  lines up with the indicium  59  positioned with the right most-position of the figure in  FIG. 28 , then the spacing gauge  75  will push the mounting rail  13  that is in slidable captive cooperation to a position corresponding to a gap of width “D2g.” 
       FIG. 29  shows a detailed section  85  of  FIG. 27  illustrating set of indicia  59 . The indicia  59  are calibrated to set a specific gap distance for an anticipated temperature range and a given ambient temperature; the given ambient temperature is indicated under the indicium  59 . The calibrated distance is based on the material of the mounting rails  13  of  FIG. 27  and the distance between rail gaps. The gap distance can be calculated by equation (1). Different spacing gauges can be produced based on desired material using the coefficient of thermal expansion “a,” temperature range using ΔT, and various total length of joined rails without a gap. 
     As previously described, ΔT=Tmax−Ta. Where, Tmax is the maximum possible anticipated temperature and Ta is the ambient temperature indicated by the indicia  59 . For example, if the mounting rails  13  of  FIG. 27  are made of aluminum, the coefficient of thermal expansion for aluminum is 12.3×10 −6  in./in. ° F. (22.23×10 −6  m/m ° K). If the total length of mounting rails  13  without a gap, L=40 ft. (12.19 m). The maximum anticipated temperature Tmax=120° F. (48.9° C.). The gap distance for an ambient temperature of 70° F. (21.1° C.) would be Dg=(12.3×10 −6  in./in. ° F.)(120° F.-70° F.)(40 ft.)(12 in./ft.)=0.3 in. (0.0076 m). For a ambient temperature of 0° F. (−17.8° C.), the gap distance would be Dg=(12.3×10 −6  in./in. ° F.)(120° F.-0° F.)(40 ft.)(12 in./ft.)=0.7 in. (0.018 m). 
     The following formula can be used to determine the placement of the indicia  59  along the wedge portion  77  of  FIG. 28 :
 
 Ip=Dg /sin(θ)  (2)
 
where:
 
Ip=the distance from the tip of the wedge to the location of the indicium  59 .
 
θ=the angle between the opposing wedge sides.
 
     For example, for a 40 ft. (12.19 m) length or rail between gaps, a rail material of aluminum, an angle between opposing wedge sides of 30° the indicium  59  for an ambient temperature of 0° F. (−17.8° C.) would be placed with respect to the tip of the wedge portion  77  at Ip=(0.7 in.)/sin(30°)=1.4 in. One of the advantages of placing the indicia  59  on the angled edge of the wedge portion  77  instead of the straight edge of the wedge portion  77  is that the distance between indicium  59  is greater than the actual gap distance and allows for easy placement of the gap. 
     Nonetheless, it may be desirable to place the indicia  59  on the straight edge of the wedge portion  77 .  FIG. 30  shows the spacing gauge  75  with the indicia  59  on the straight edge of the wedge portion  77 . The spacing gauge  75  can also include a handle portion  79 , an aperture  81 , and instruction indicia  62 , as previously described.  FIG. 31  shows a detailed section  85  of  FIG. 30  illustrating the indicia  59 . Referring to  FIG. 30 , the indicia  59  sets the rail gap of  FIG. 27  based on the width of the wedge portion  77  at the particular indicium  59  as previously described. For example, indicium  59  positioned to the far left of the figure is at a position where the wedge portion  77  has a width of “D3g.” When the spacing gauge  75  is inserted between the mounting rails  13  of  FIG. 27  so that the top of the mounting rail  13  lines up with the indicium  59  positioned to the far left of the figure in  FIG. 30 , then the spacing gauge  75  will push the mounting rail  13  that is in slidable captive cooperation to a position corresponding to a gap of width “D3g.” The indicium  59  positioned most right in the figure is positioned where the wedge portion  77  has a width of “D4g.” When the spacing gauge  75  is inserted between the mounting rails  13  of  FIG. 27  so that the top of the mounting rail  13  lines up with the indicium  59  positioned with the right most-position of the figure in  FIG. 30 , then the spacing gauge  75  will push the mounting rail  13  that is in slidable captive cooperation to a position corresponding to a gap of width “D4g.” 
     The following formula can be used to determine the placement of the indicia  59  along the wedge portion  77  of  FIG. 30 , with Ip, Dg, and θ, as previously defined for equation (2):
 
 Ip=Dg /tan(θ)  (3)
 
     For example, for a 100 ft. (30.48 m) length or rail between gaps, a rail material of aluminum, an angle between opposing wedge sides of 40° the indicium  59  for an ambient temperature of 0° F. (−17.8° C.) would be placed with respect to the tip of the wedge portion  77  at Ip=(0.7 in.)/tan(40°)=1.4 in. The gap distance is determined by equation (1), assuming Tmax=120° F.: Dg=(12.3×10 −6  in./in. ° F.)(120° F.-0° F.)(100 ft.)(12 in./ft.)=1.8 in. (0.046 m). 
     In  FIG. 27  showed a wedge portion  77  that included a straight edge parallel to the vertical side of the mounting rail  13  and an angled edge with respect to the vertical side of the mounting rail  13 . It may be desirable to make a wedge portion  77  where both edges are angled with respect to the vertical side of the mounting rail  13 . In that case, the placement of the indicia  59  can be determined by equation (2) except θ is the angle between the edge of the wedge portion  77  that includes the indicia  59  and a line originating at the vertex of the wedge that is parallel to the vertical edge of the mounting rail  13 . 
     The spacing gauge  75  can be manufactured with calibration for any desired length or mounting rail  13  material, range of anticipated temperature extremes, or even solar panel frame material. For example, the spacing gauges can be calibrated for aluminum, steel, fiberglass, or carbon fiber rails. The spacing gauge  75  can be calibrated to any desired rail or solar panel frame material by changing the coefficient of linear expansion, “a,” in equation (1) to the appropriate value for the desired material. While the rail length in the examples where either 40 ft. (12.19 m) or 100 ft. (30.48 m), the spacing gauge  75  can be calibrated for any rail length by simply changing L in equation (1). 
     Apparatus and methods for compensating for thermal expansion and contraction of solar panels rail mounted systems has been described. It is not the intent of this disclosure to limit the claimed invention to the examples, variations, and exemplary embodiments described in the specification. Those skilled in the art will recognize that variations will occur when embodying the claimed invention in specific implementations and environments. For example, it is possible to implement certain features described in separate embodiments in combination within a single embodiment. Similarly, it is possible to implement certain features described in single embodiments either separately or in combination in multiple embodiments. It is the intent of the inventor that these variations fall within the scope of the claimed invention. While the examples, exemplary embodiments, and variations are helpful to those skilled in the art in understanding the claimed invention, it should be understood that, the scope of the claimed invention is defined solely by the following claims and their equivalents.