Patent Document

CROSS-REFERENCES TO RELATED APPLICATIONS 
       [0001]    This application claims the priority of German Patent Application, Serial No. 10 2009 037 720.4, filed Aug. 17, 2009, pursuant to 35 U.S.C. 119(a)-(d), the content of which is incorporated herein by reference in its entirety as if fully set forth herein. 
       BACKGROUND OF THE INVENTION 
       [0002]    The present invention relates to a mounting support for mounting a photovoltaic module having a glass pane on the top side of an, in particular, uneven roof panel. 
         [0003]    The following discussion of related art is provided to assist the reader in understanding the advantages of the invention, and is not to be construed as an admission that this related art is prior art to this invention. 
         [0004]    Presently, two approaches are used for installing a solar collector system on a flat roof or an inclined roof, as described with reference to  FIGS. 1 and 2 . As illustrated in  FIG. 1 , concrete blocks  1  are placed on the roof and a corresponding support structure  3 , on which conventional photovoltaic modules made of glass are mounted, is connected with the concrete blocks  1 . Disadvantageously, this structure is heavy and must be taken into consideration in the static design. Moreover, large quantities of material are required. Conversely, this approach has advantageously a high efficiency, because photovoltaic modules with one or two glass panes can be installed at a favorable angle. 
         [0005]    According to the second approach, a mounting foil  7  is glued onto the flat roof and is subsequently joined with a module foil  9 . This embodiment has a small roof load and low material costs; however, the efficiency of module foils is low. Installation is simple and advantageous, because the foil  7 ,  9  needs only to be installed in a single roll-up/unrolling direction  11  and joined with the roof panel by gluing or welding. 
         [0006]    For example, EP-A-08 018 443 discloses a support having the shape of an elongated strip. The bottom side of the support has a substantially planar structure and can therefore be readily joined with the roof panel. The top side of the support is interrupted by openings which extend transversely to a roll-up/unrolling direction from one edge to the other, thereby forming segments delimited by the openings. In one part of the segments, a respective attachment means for the photovoltaic modules is integrated, wherein the photovoltaic modules are arranged with respect to one another in the roll-up/unrolling direction in a predetermined grid pattern. The support is only suitable for roofs with a flat, smooth roof panel made of, for example, foil, copper sheets or galvanized sheets, because the support is glued or welded to the roof panel. In addition, the support must extend across a large area, because the support must be able to absorb the load of the photovoltaic modules, as well as snow and wind forces. 
         [0007]    It would be desirable to address this problem and to obviate other prior art shortcomings by providing a support for PV modules which is used only to orient and adjust the individual PV modules, which is capable of absorbing forces, provided that the roof construction can sustain the forces. It would furthermore be desirable to provide a support that can be rolled up and unrolled, which can be readily transported and handled due to its low weight, thereby allowing a precise orientation of the PV modules with respect to one another. The support should also be usable on uneven and rough surfaces. This additional characteristic property is advantageous in particular with roofs having roof panels made of shingles which are uneven at their overlaps, for example have a step or a shoulder, making gluing or welding impossible. This applies particularly to roofs widely used in the USA which are made of sand-coated roofing felt shingles, but also to domestic roofs covered with wooden shingles. 
       SUMMARY OF THE INVENTION 
       [0008]    According to one aspect of the present invention, a mounting support for mounting at least one photovoltaic module having a glass pane on a top side of a roof panel, includes an elongated strip constructed to be rolled up or unrolled, or both, in a roll-up/unroll direction, at least two attachment means disposed on the strip a having a modular dimension for attachment of the at least one photovoltaic module, a supporting location for an edge of the photovoltaic module disposed on a top side of the attachment means, and a padding protruding from a bottom side of the support disposed in a region of the attachment means to compensate for uneven areas of the roof panel. 
         [0009]    According to another aspect of the invention, a method for mounting a photovoltaic system having a plurality of photovoltaic modules on an uneven roof panel applied on a wooden structure with a mounting support with the mounting support described above includes the steps of attaching a first part of the attachment means with screws to the wooden structure, placing an edge of a first photovoltaic module on the supporting surfaces of the first part of the attachment means, placing a second part of the attachment means on the roof panel such that the edge of the first photovoltaic module is arranged on the supporting location or a supporting surface of the second part of the attachment means, and attaching the second part of the attachment means with screws to the wooden structure. The padding seals damage to the roof panel caused by the screw-attachment to the wooden structure. 
         [0010]    According to yet another aspect of the invention, a method for mounting a photovoltaic system having a plurality of photovoltaic modules on an uneven roof panel applied on a wooden structure with the mounting support described above includes the steps of attaching a first part of the attachment means with screws to the wooden structure, placing a second part of the attachment means on the roof panel in such a manner that the at least one strip is under tension, attaching the second part of the attachment means with screws to the wooden structure, and placing and clamping the photovoltaic modules on the supporting location or supporting surface of the attachment means. The padding hereby also seals damage to the roof panel caused by the screw-attachment to the wooden structure. 
         [0011]    In the simplest embodiment, the aforementioned support includes a strip having along its length or at its ends respective attachment means, which are spaced by a distance determined by the modular pattern or the modular dimension. The spacing corresponds essentially to the height of the PV modules to be mounted plus one-time the gap between adjacent modules. Depending on the employed module, a different modular dimension can be selected. It is important that the modular dimension is always adapted to the dimensions of the module. In other words, when the PV module is mounted on the edge, the aforementioned width defines the modular dimension. A potentially different (i.e., shorter) modular dimension may be selected when the module is attached on the bottom side of the PV module. The padding protrudes a certain height from the bottom side of the support, wherein the height is selected so that the thickness is at least twice the thickness of conventional roof shingles, in addition to an upsetting distance which is required for pressing the padding form-fittingly and moisture-tight onto the uneven, sand-coated roof shingle. In the subsequently described installation of the support, the padding is, depending on its relative position to the shingle, pressed against the shingle or into the step or gap formed by an overlap. The top side of the support facing the sky is provided with one or more supporting surfaces, which serve as placement or supporting surface for the PV module to be installed. With the invention, photovoltaic modules based on glass technology can advantageously be used without the need for a heavy substructure. 
         [0012]    According to a modified embodiment of this basic pattern, a plurality of attachment means is attached on a strip having a length exceeding one meter, and the modular dimension forms a spacing of between 60 cm and 125 cm between the attachment means. The term “exceeding one meter” is intended to indicate that at least two PV modules can be attached on top of one another on the same strip. In practice, the strip may have a length of several meters, e.g., 20 to 50 meters, and may be cut to the desired length at the installation site. For example, several strips having a length of 7 meters, which then extend parallel to one another, can be cut for a roof having a length between roof ridge and gutter of 8 meters, with the plurality of attachment means forming respective rectangles. Likewise, in a modified embodiment having this arrangement of parallel strips, more than two mutually parallel strips may be provided which form a grid pattern where the attachment means are located at the nodes of rectangles arranged in a checkerboard pattern. 
         [0013]    In particular, with this grid shape of the support, transverse rails are advantageously provided which connect the opposing attachment means with each other. The strips themselves should, compared to the dimensions of the attachment means, form a relatively wide longitudinal rail connecting pairs of respective attachment means with each other. This width is required so that the position of the attachment means is maintained during the screw-down operation without rotating the attachment means. However, the strip should not protrude over the width of the attachment means. If the attachment means forms, in a top view, a rectangle with edges having lengths in a range between 5 cm and 12 cm, then a width of the strips (referred above also as longitudinal rail) should be between 8 cm 12 cm and the width of the transverse rails between 1 cm and 3 cm. A different, i.e. wider, width of the transverse rail may be selected if due to the employed material a rotation lock of the attachment means during screw-down can only be attained by stiffening the grid in a second direction. A small thickness of the strips and of the transverse rails should be selected, so that they are flexible and can be easily rolled up or unrolled. A thickness between 0.5 mm to 2 mm is sufficient because the thickness is required only for adjusting the attachment means. This takes into consideration that the support should be easy and comfortable to handle, facilitating a correct orientation and positioning of the attachment means, which are only subsequently joined with the roof panel and the structure underneath. 
         [0014]    If the grid it is not too wide, i.e., for example, the width is adapted for a single PV module up to a maximum of three PV modules (corresponding to two to four attachment means positioned side by side), then the strips, the transverse rails and the attachment means may form an integral injection-molded plastic part. Assuming a module width of 120 cm and a position of each of the attachment means of 30 cm from the edge of the narrow side of the module for a spacing between modules of 5 cm, then the grid width will be about 70 cm for a single PV module installed width-wise (distance 60 cm plus twice half the width of the attachment means itself which has a width of 10 cm), and of 195 cm for two PV modules installed side-by-side, and additionally 125 cm for each additional adjacently installed PV module. With a 50 m long rolled-up grid for a single module width, adjustment and attachment supports for 77 PV modules can be provided with a height of the PV module of 60 cm. With a 195 cm wide grid for two adjacent PV modules already for 150 for PV modules, with a 220 cm wide grid for three adjacent PV modules for 231 PV modules, etc. Advantageously, the support, in particular when implemented as an injection molded part, is provided with means for routing an electric cable. This may be accomplished either with clamps or clips, in which the conventional wiring cables for the PV modules are snapped in, or the electrical cables themselves are connected with the injection molded part, for example integrated therein, so that only their terminals are routed to the outside, or the cables are permanently mechanically attached, for example glued or welded, to the top side of the strips and rails. 
         [0015]    PV modules with metallic frames may not require attachment means with a rubber support. However, for grounding, the attachment means or at least parts of the strip should be made of metal. 
         [0016]    The padding on the bottom side of the mounting support should have at least one of the following characteristic properties: it is made of an elastic material, it is made of a hydrophobic material, it has a structure exerting a spring force, it has a chamber that is open towards the bottom and filled with a material capable of flowing under pressure, and/or it is made of a sealing mass, for example cellular rubber impregnated with bitumen. Because the padding comes into contact with rainwater, the material must be insoluble in water. It may be, for example, a swelling material which swells when exposed to moisture. In this way, the sealing action of the padding increases over time. A structure exerting a spring force provides, for example, that the padding is made of an elastic material and provided with cavities. During compression, the cavities have the tendency to return to their original shape and therefore provide a sealing effect. Advantageously, the cavities or chambers are provided with a lower opening oriented towards the roof panel. A material which becomes liquid under pressure and is squeezed out of the opening may be introduced into this chamber. This is particularly advantageous when a gap is encountered accidentally. In this case, the sealing compound contained in the pockets or pores enters the gap in a liquid state. 
         [0017]    For attaining a defined height of the PV module on the attachment means, the top side of the attachment means is provided with one or two supporting locations for the edge of the PV module, for example for the two edges of adjacent PV modules. To prevent point loads on the glass of the installed PV module, the supporting locations may advantageously be configured as supporting surfaces which are separated from each other by a separation wall operating as a stop. The separation wall prevents the two edges of adjacent PV modules, which are clamped using the same attachment means, from striking each other. The separation wall may also be formed in two parts, with one part for one photovoltaic module and another part for the other adjacent photovoltaic module. The gap between the separation parts, which can also be viewed as forming separate stops, should be as large as possible to reduce material use and weight. To facilitate the attachment means to be screwed to the wooden roof structure, the material is thinned, preferably in the central region of the attachment means, and can be easily penetrated by a self-threading screw. 
         [0018]    The support for PV modules having a metal frame can be completely prepared in the factory, because the clamping part is narrower than the module spacing, because the module frames can also withstand point loads. An opening for penetration of the screw is also advantageous, in particular if the opening is sized so that the tip of the screw can be easily screwed in and securely held in place. With this approach, a clamping part which after installation exerts on the photovoltaic module a force directed towards the supporting surface should be added to the attachment part before. The clamping part should be somewhat narrower than the spacing between two adjacent PV modules. In this way, the clamping part can already be installed in the factory together with the screw inserted into the opening. When the PV module is placed onto the supporting surfaces of the attachment means, the clamping parts are initially rotated in a longitudinal direction parallel to the module edge and are then rotated perpendicular to the module edge after the placement of the PV module, before the screw is screwed into the wooden structure, in particular the wooden covering boards of a shingled roof, and tightened, whereby the PV module is clamped down. 
         [0019]    According to a variant of the aforedescribed solution using a screw, several screws may be used, wherein the attachment means is provided in the central region with a blind hole, which alone or an inserted sleeve have an interior thread, and wherein in addition to the blind hole two spaced-apart thinned regions or recesses are provided in the material which are arranged mirror-symmetrically in relation to the blind hole. With this variant, the force required to clamp the PV module is advantageously not transferred to the roof panel and its substructure, but remains entirely inside the attachment means and is absorbed by the machine screw which tightens the clamping part in the direction towards the attachment means. 
         [0020]    Regarding the method for installing the photovoltaic module, the object is solved according to a first embodiment of the invention in that in a first method step a first part of the attachment means is screwed down on the wooden structure, that in a second method step one edge of the photovoltaic module is placed on the supporting surfaces of the first part of the attachment means, that in a third method step a second part of the attachment means is placed on the roof panel such that the edge of the previously placed photovoltaic module facing the one edge is placed on the supporting surfaces of the second part of the attachment means, and that in a fourth method step the second part of the attachment means is screwed down on the wooden structure, wherein the padding seals any damage to the roof panel caused when the screws are screwed into the wooden structure. With this installation method, the strips or longitudinal rails of the mounting support can be dimensioned to be somewhat longer than required for the exact spacing. The attachment means is then no longer used to set the spacing at the same time: because one edge of the PV module already makes contact with the stop of one attachment means, whereas the stop of the other attachment means only needs to be moved to the other edge of the module, where it is fixed in place. 
         [0021]    The second embodiment of the invention is different in that the object is solved in that in a first method step a first part of the attachment means is screwed down to the wooden structure, that in a second method step a second part of the attachment means is placed on the roof panel in such a manner that the strip(s) and optionally the transverse rails is/are under tension, that in a third method step the second part of the attachment means is screwed down to the wooden structure, and that in a fourth method step the photovoltaic modules are placed on the supporting surfaces of the attachment means where they are clamped, wherein the padding seals any damage to the roof panel caused when the screws are screwed into the wooden structure. With this installation method, the complete substructure for the PV modules can be finished first, before subsequently all PV modules are placed sequentially or, when using several installers, concurrently onto the support in a single operation and fixed with the associated clamping part. 
         [0022]    As described above, with both approaches, the clamping means associated with the attachment means for clamping and affixing the photovoltaic modules can be installed at the same time the attachment means are screwed down on the wooden structure. In addition, with both variants, the grid can advantageously already be cut to size according to the available roof shape and roof size before installation, possibly already at the manufacturing site of the mounting support, before the grid is installed, thereby forestalling any inconvenience during the actual installation. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         [0023]    Other features and advantages of the present invention will be more readily apparent upon reading the following description of currently preferred exemplified embodiments of the invention with reference to the accompanying drawing, in which: 
           [0024]      FIG. 1  a conventional installation method for photovoltaic modules on a flat roof; 
           [0025]      FIG. 2  conventional installation method for a photovoltaic foil on a flat roof; 
           [0026]      FIG. 3  a cross-section through a detail of a mounting support according to the invention with two installed attachment means; 
           [0027]      FIG. 3   a  a detailed view of  FIG. 3  with a single-screw embodiment; 
           [0028]      FIG. 3   b  a detailed view of  FIG. 3  with a three-screw embodiment; 
           [0029]      FIG. 4  a basic arrangement of the mounting support according to the invention; 
           [0030]      FIG. 5  a modification of the basic arrangement enlarged to an elongated strip; 
           [0031]      FIG. 6  a modification of the basic arrangement enlarged to a rectangle; 
           [0032]      FIG. 7  a modification of the basic arrangement enlarged to the shape of a rope ladder; 
           [0033]      FIG. 8  a modification of the basic arrangement enlarged to a grid. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0034]    Throughout all the figures, same or corresponding elements may generally be indicated by same reference numerals. These depicted embodiments are to be understood as illustrative of the invention and not as limiting in any way. It should also be understood that the figures are not necessarily to scale and that the embodiments are sometimes illustrated by graphic symbols, phantom lines, diagrammatic representations and fragmentary views. In certain instances, details which are not necessary for an understanding of the present invention or which render other details difficult to perceive may have been omitted. 
         [0035]    Turning now to the drawing, and in particular to  FIGS. 3 ,  3   a  and  3   b , there is shown with the reference symbol  11   a  mounting support for mounting rigid photovoltaic modules  13  on an uneven roof panel. The roof panel is composed of a plurality of shingles  15  which are nailed in overlapping relationship onto a wooden substructure  17 , typically with roofing nails (not shown). The shingles  15  may be made of sand-coated roofing felt, wood, or other suitable materials. Due to the overlap, a step  19  is formed in the overlap region, which for an installation of the shingles  15  with an offset is maximally twice the shingle thickness. 
         [0036]    The photovoltaic modules  13  are to be installed on this type of roof panel. To this end, the mounting support  11  is composed of a strip  21  having attachment means  23  arranged in regular intervals, the so-called modular dimension. Each attachment means  23  has on its top side two supporting surfaces  25 , which each support an edge of adjacent PV modules  13 . The two supporting surfaces  25  are separated from each other by a separation wall  27  which prevents adjacent modules  13  from striking each other and also operates as a stop during installation of the PV modules  13 . The attachment means  23  has on its bottom side a padding  29  made of an elastic material, operating as a seal when compressed. In the illustrated exemplary embodiment, the padding  29  extends across the entire underside of the attachment means  23 . It would also be sufficient to use a round or rectangular padding  29  with a diameter or edge length between 5 mm and 20 mm, as described below when discussing its functionality. 
         [0037]    Each of two attachment means  23  are connected with one another by way of the longitudinal rail or strip  21 . To illustrate the two variants shown in  FIGS. 3   a  and  3   b ,  FIG. 3  shows on the right side a single-screw variant and on the left side the three-screw variant. It should be noted that in reality the support is always equipped with only a single type of attachment means  23 . In the illustrated embodiment, the strip  21  and the attachment means  23  are manufactured as a single part, for example, by an injection molding process. 
         [0038]    The variant illustrated on the light side in  FIG. 3   a  includes a bore  31  located in the central region of the attachment means  23 . The bore  31  extends perpendicular to the supporting surfaces  25  and is preferably implemented so as to terminate before the padding  29  or to slightly penetrate into the padding. A screw  33  is inserted through the bore  31 , and the thread of the screw  33  is screwed into the wooden structure  17  located underneath the shingles  15 . A clamping part  35 , which has at its bottom side a rubber part  37  to prevent sliding and scratching of the PV modules  13 , is provided as an accessory to the attachment means  23 . A protective foil (not shown) similar to the rubber part  37  can be applied on the supporting surfaces  25  of the attachment means  23  before installation of the PV module  13 . 
         [0039]    The diameter of the bore  31  may be larger than the outside diameter of the screw  33 , allowing the screw  33  to move freely inside the bore  31 . To prepare the mounting support  11  for installation ahead of time, the diameter of the bore  31  should be slightly smaller than the diameter of the exterior thread of the screw  33 . In this case, the clamping part  35  can already be positioned during manufacture of the support  11  and can be rolled up together with the mounting support  11 , held in place by the screw  33 . 
         [0040]    As seen clearly in  FIG. 3   a , the padding  29  is compressed after the clamping part is pressed against the PV module  13  and protects the region where the screw  33  penetrates the shingles  15  from incursion of moisture. 
         [0041]    The complementing  FIG. 3   b  shows the three-screw variant, where the central bore  31  is replaced with a blind hole  38 , with the bottom of the blind hole  38  terminating a safe distance from the underside of the attachment means  23 . If the material from which the attachment means  23  is made has a sufficiently high firmness, then the inside of the blind hole  38  can be directly provided with an interior thread. The clamping forces are then directly introduced into the attachment means  23 . Conversely, if the attachment means  23  is made of a softer plastic, then a metal sleeve should be anchored therein during manufacture of the attachment means  23 , whereby the clamping forces are then transmitted indirectly via the sleeve to the attachment part  23 . 
         [0042]      FIG. 4  shows a top view onto the basic component of the mounting support  11  in the smallest unit of the strip  21 , which forms only a single longitudinal rail, having only one respective attachment means at each of its ends. The PV module  13  is installed on the roof panel by installing two of these basic components next to each other. 
         [0043]      FIG. 5  shows the next larger structure, wherein the strip  21  has the length of several meters and includes several attachment means  23 . The attachment means  23  are spaced from one another with an identical distance A, thereby forming a modular dimension A. The strip  21  then includes a plurality of longitudinal rails  21   a  to  21   e  which each connect two corresponding adjacent attachment means  23  with one another. 
         [0044]      FIG. 6  shows two adjacent basic components according to  FIG. 4 , wherein two strips  21  and  21 ′ are arranged next to each other and the opposing attachment means  23  and  23 ′ are connected in pairs by way of a transverse rail  39 . 
         [0045]    A still more complex structure of the mounting support  11  which is prefabricated as a single piece is shown in  FIG. 7 . The row structure of  FIG. 5  is combined with the rectangular structure of  FIG. 6 , forming a structure similar to a rope ladder. In other words: all attachment means  23  and  23 ′ located along the strips  21  and  21 ′ at the same position in the strip  21 ,  21 ′ are connected in pairs via a respective transverse rail  39 . 
         [0046]    The largest possible type of mounting support  11  is obtained when several of the ladder-shaped arrangements of strips  21 ,  21 ′ and attachment means  23 ,  23 ′ shown in  FIG. 7  are combined next to one another into a grid  41 , as illustrated in  FIG. 8 . This Figure also shows the connection scheme of the involved 16 PV modules. The positive terminals of the PV modules are indicated by a plus-sign and the negative terminals with a minus-sign. The cable connections are indicated by continuous thick lines, which need only be connected from one module  13  to the next module  13 ; a longer connection is sometimes required which can be implemented via external cables with clamps formed on the rails or with electric cables integrated in the rails. 
         [0047]      FIG. 4  shows another electric cable  43  which is integrated inside the longitudinal rails  21  and the transverse rail  39 . Alternatively, attachment with an adhesive to the bottom or top side of the rail  31 : 39  may be selected. The ends of the electric cable could either be provided with a first component of a plug connection, or with a contact pad  45  which provides electrical contact to the PV module by way of pressure. 
         [0048]    While the invention has been illustrated and described in connection with currently preferred embodiments shown and described in detail, it is not intended to be limited to the details shown since various modifications and structural changes may be made without departing in any way from the spirit and scope of the present invention. The embodiments were chosen and described in order to explain the principles of the invention and practical application to thereby enable a person skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated.

Technology Category: f