Abstract:
Disclosed herein are photovoltaic building materials and related methods of manufacturing and installing such materials. In one embodiment, a modular roofing structure comprises a photovoltaic shingle panel having a planar lower surface and an upper surface, and a rigid back member having a length the same as or greater than the length of the shingle panel and attached to the planar lower surface of the shingle panel. The roofing structure also includes at least one electrical contact pad on a lower surface of the back member, and at least one electrical conductor electrically coupled to the shingle panel via the lower surface and passing through the back member and out the lower surface. In such embodiments, the electrical conductor is electrically coupled to the at least one contact pad and extends past a front end of the back member sufficient to electrically contact a contact pad on another back member of a separate modular roofing structure couplable to the first.

Description:
PRIORITY TO APPLICATION 
     This Application claims the benefit of U.S. Provisional Application Ser. No. 60/523,417, filed on Nov. 19, 2003, and entitled “Photovoltaic Building Materials and Related Methods of Installation,” which is commonly assigned with the present application and incorporated herein by reference for all purposes. 
    
    
     TECHNICAL FIELD 
     Disclosed embodiments herein relate generally to building materials for covering the hip, ridge, rake, or other portion of a roof, and more particularly to materials disposed above a hip, ridge, rake, or other roof portion incorporating or comprising a solar panel(s) having a self-aligning mechanism for the rapid and uniform installation and electrical interconnection of a number of such materials. 
     BACKGROUND 
     The presence and use of electricity is an everyday necessity that every modem home and business enjoys. Equally enduring is the periodic cost of that electricity, based on the amount, typically in kilo-watt/hours (kwh), used at the specific location. Efforts to combat the ever-present high-cost of electricity in homes and businesses have explored a number of different avenues. For example, in the general consumer market (e.g., residences) solar power as a replacement for electricity provided by typical utility companies has been attempted relatively unsuccessfully in so-called “off-grid” connections. Such off-grid connections embody the use of solar power in lieu of conventional in-home electricity. 
     Whether it be the initial costs associated with such off-grid systems or the relatively difficult and costly maintenance required, off-grid systems have typically not been accepted by the consumer market. As a result, the use of solar power to supplement, rather than replace, conventional electricity has continued to gain acceptance. These so-called “on-grid” systems typically work in conjunction with conventional electrical connections to supplement that electrical power, for example, during times of peak use. By supplementing conventionally available electricity, the overall annual cost of residential (or commercial) electricity may be substantially reduced. 
     Conventional residential solar-powered on-grid systems are typically incorporated into the roof of a house, due to its orientation towards the sky. Earlier systems employed large, flat crystal solar panels dispersed across the surface of the roof to collect the solar energy. However, the fragility and high cost of the crystal materials, as well as the clearly distinguishable appearance of the panels from ordinary roofing shingles, has resulted in essentially a rejection of such system by the market place. 
     Modem systems have developed strips of solar shingles that are more durable and predominantly resemble ordinary roofing shingles, thus substantially concealing the system from plain view. Unfortunately, even such modem system suffer from deficiencies, such as the need to form multiple holes through the roof and into the attic area for each shingle strip in order to electrically connect all of the shingle strips to create a functional system. As the number of holes formed through the roof increase, so too do the chances of leakage through the roof during inclement weather. Moreover, making the electrical connections from one shingle strip to the next, and then to the circuit breaker box of the home, is typically quite tedious and exhausting. In addition, because the shingle strips replace the ordinary shingles typically used on roofs, an experienced or specifically skilled installer is typically needed to properly align the solar shingle strips during installation, just as with ordinary shingles, so that the aesthetics of the entire roof are preserved. Even so, panels located in the middle of a roofing section tend to be aesthetically unpleasing as they detract from the section&#39;s homogeneous and symmetrical appearance. As a result, a relatively inexpensive and residentially available solar-powered system is needed that does not suffer from these deficiencies. 
     BRIEF SUMMARY 
     Disclosed herein are solar powered photovoltaic (PV) building materials, such as roofing shingles, and related PV systems employing such materials. Methods of installing such materials are also disclosed. The disclosed PV systems and methods beneficially provide solar power to structures in either off-grid or on-grid connections. In one exemplary embodiment, interconnected PV modular roofing structures are for use on a hip, ridge, or rake of a roof as replacement for typical asphalt shingles. In some embodiments, the PV modular roofing structure includes a rigid back member and a PV solar panel mounted on the back member. In addition, the back member is sized substantially the same as the size of the solar panel, and is attached to an underside surface of the solar panel. In other embodiments, the PV modular roofing structure is a single piece of building material incorporating PV solar panel and a supporting back member. 
     Further, such PV modular roofing structures include conductive rods extending from the top surface of the back member to its bottom surface. At one end, the conductive rods make electrical contact with the underside of the PV solar panel, while the opposing ends extend away from the back member at one end of the PV modular roofing structure and are configured to make electrical contact with contact traces on the underside of the back member of an adjoining PV modular roofing structure partially overlapping the end of the first PV modular roofing structure. By employing the conductive rods, a series of PV modular roofing structures may be easily installed without the need to individually wire the modular roofing structures together, or to form holes through the roof for passing wires. In a specific embodiment, the PV solar panel further comprises photoelectric silica spheres across its upper surface, which in addition to generating the solar electricity also appear similar to the granules typically found on the exterior of asphalt-based shingles. 
     In one embodiment, the back member includes a step in thickness in a cross-sectional plane perpendicular to the substantially planar lower surface and parallel to the longitudinal axis of the back member. In addition, the thickness of the back member at the high level of the step is greater than the thickness of the back member at one of its ends. In a specific embodiment, the back member is composed of an injection-molded thermoplastic. Alternatively, the back member may be composed of any rigid material suitable for outdoor exposure, such as molded recycled tire rubber, metal, or even wood. In yet another embodiment, the back member includes a trapezoid-shaped base. The step in thickness of the back member is provided by a step in the height of the walls in a cross-sectional plane perpendicular to the base and parallel to the longitudinal axis of the back member. 
     For installation with “ridge vent” systems (to be discussed below), the back member preferably includes a plurality of channel walls extending from the base and communicating between a sidewall of the back member and an area near the longitudinal center axis of the PV solar panel. Preferably, the channels are formed in a herringbone pattern. Through the channels, the PV modular roofing structure is able to vent air escaping through a ridge opening formed at the apex of the ridge in a structure of the roof to the outside environment. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Reference is now made to the following detailed description of the preferred embodiments, taken in conjunction with the accompanying drawings. It is emphasized that various features may not be drawn to scale. In fact, the dimensions of various features may be arbitrarily increased or reduced for clarity of discussion. In addition, it is emphasized that some components may not be illustrated for clarity of discussion. Reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  illustrates an isometric view of an exemplary embodiment of a PV modular roofing structure for use in a solar-powered electrical system constructed according to the principles disclosed herein; 
         FIG. 2  illustrates a bottom view of the PV modular roofing structure of  FIG. 1 ; 
         FIG. 3  illustrates a side view of the PV modular roofing structure illustrated in  FIGS. 1-2 , viewed along an axis perpendicular to the longitudinal center axis of the solar panel; 
         FIG. 4  illustrates a top view of the back member before attachment of the PV solar panel; 
         FIG. 5  illustrates a front view of the back member, viewed from the trailing edge of the PV modular roofing structure of  FIGS. 1-2 ; 
         FIG. 6  illustrates a side view of a pair of interconnected PV modular roofing structures coupled together and employing the conductive rods described above; and 
         FIG. 7  is an isometric view of a group of interconnected PV modular roofing structures after installation on a hip, ridge, or rake portion of a roof. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Referring initially to  FIG. 1 , illustrated is an isometric view of a building material  5  for use in a photovoltaic (PV) solar-power electrical system constructed according to the principles disclosed herein. The material  5  is a PV modular roofing structure  5  and includes a PV solar panel  10  and a back member  20 . The photovoltaic panel  10  may be in the form of any symmetrical shape, such as a rectangle or a trapezoid. As shown in  FIG. 1 , however, the PV solar panel  10  is preferably trapezoid shaped because a trapezoid shape has been found to yield the best general appearance when the PV modular roofing structure  5  is installed in certain types of roofing layouts, as discussed in greater detail below. 
     The PV solar panel  10  is comprised of any type of photoelectric material capable of use in a solar-powered electrical system. For example, the PV solar panel  10  may be a solar panel based on thin films, or even conventional crystal/silica solar panels. In another exemplary embodiment, the PV solar panel  10  may be a solar panel constructed from photoelectric silica spheres  17  formed on an aluminum base or frame. Examples of such spherical photoelectric systems are produced by Spheral Solar Power, Inc. of Cambridge, Ontario in Canada. Of course, a PV system constructed as described herein is not limited to the use of spherical solar panels, and may employ any type of solar panel either now existing or later developed. 
     One advantage to the use of spherical solar panels is the aesthetic value provided by this relatively new technology. For example, as shown in  FIG. 1 , the spheres  17  in such systems are randomly dispersed across the exposed face of the PV solar panel  10 . As such, the spheres  17  may closely resemble the granules typically employed with asphalt-based shingles, when the disclosed modular roofing structures are used as replacements for conventional shingles. As a result, passersby viewing an installed system as taught herein will have a difficult time distinguishing a system of the present disclosure and a conventional asphalt-based roof. In addition, current technology allows such photovoltaic spheres to be formed in a variety of colors. Thus, an even more aesthetically pleasing result may be achieved by selecting or customizing specific colors for the spheres comprising the PV solar panel  10 . 
     When manufactured, the PV roofing structures  5  may have any shape and may be constructed to any desired size. However, since the PV structures  5  are photovoltaic devices, the needed exposed surface area of each structure (for generating the desired amount of energy) should be taken into consideration. In an exemplary embodiment of the PV roofing structure  5 , the exposed surface area of the structure  5  may provide 1 to 2 square feet of photovoltaic capabilities. In one specific example, the width of the PV structure  5  may be about 26 inches, while the length may be about 14 inches. In such an embodiment, the PV structure  5  may provide approximately one to two square feet of photovoltaic surface area. Of course, no limitation to any particular size for the PV structure  5  is intended. 
     Turning now to  FIG. 2 , illustrated is a bottom view of the PV modular roofing structure  5  illustrated in  FIG. 1 . As shown in  FIG. 2 , the back member  20  extends substantially the width of the PV modular roofing structure  5  and is attached to the PV solar panel  10  by any suitable adhesive or by another affixing means. In addition, the back member  20  includes a base  25  having a predominately trapezoid shape for mounting the PV solar panel  10 , and has substantially the same length as the PV solar panel  10 . For example, in an exemplary embodiment, if the PV solar panel  10  has a length of 13¼ inches, the back member  20  may be 13 inches long. 
     The back member  20  is attached to the PV solar panel  10  such that a longitudinal center axis  11  of the PV solar panel  10  and a longitudinal center axis  21  of the back member  20  are aligned. In addition, in the illustrated embodiment, a short edge  13  of the PV solar panel  10  and a short edge  23  of the back member  20  are also aligned. For the purposes of this specification, the end of the PV modular roofing structure  5  having the short edges  13 ,  23  of the PV solar panel  10  and back member  20  will be referred to as the “back end,” and the opposite end of the PV modular roofing structure  5  will be referred to as the “front end.” 
     Also, the back member  20  has two sidewalls  22   a  and  22   b  extending from the base  25 . The back member  20  also has multiple channel walls  24  spreading across the base  25 , and in this embodiment are arranged in a “herringbone” pattern to provide support for the back member  20 , and thus the overall PV modular roofing structure  5 . To facilitate the folding of the PV modular roofing structure  5 , the back member  20  preferably has a slit  27  along its longitudinal center axis  21 . The base  25  also has rectangular holes  28  in areas proximate the channel walls  24 . Advantageously, the holes  28  may be employed so as to limit twisting and deforming of the base  25  under elevated temperatures that are commonly experienced on the roofs of buildings. This feature is especially beneficial with PV modular roofing structures as disclosed herein are employed as building materials on the roofs of structures to provide solar power thereto. 
     In an exemplary embodiment, the back member  20  is manufactured from an injection-molded thermoplastic material, such as injected-molded polystyrene, polypropylene, or polyethylene. The polystyrene, polypropylene, or polyethylene materials may be low, medium, or high density and may be used with 40% to 70% filler by weight. Such filler may include limestone, gypsum, aluminum trihydrate (ATH), cellulose fiber, and plastic polymer fiber. Other thermoplastic materials that may be used include ethylene-vinyl-acetate (EVA) polymer materials, ethylene-mythylene-acrylate (EMAC) materials, neoprene materials, and polychlorosulfonated polymer (Hypalon) materials. Although an injection-molded thermoplastic material is described herein, any rigid material suitable for outdoor exposure is also suitable for manufacturing the back member  20 . F or example, molded recycled tire rubber, metal, or wood may also be used. 
     Also illustrated on the PV modular roofing structure  5  is a pair of conductive rods  29  (one of which is labeled  29 ). The conductive rods  29  extend from the back end of the PV modular roofing structure  5 , and extend parallel to the longitudinal axis  21  of the back member  20 . In an exemplary embodiment, the conductive rods  29  are comprised of copper, but any appropriate electrically conductive material may also be employed. Preferably, the conductive rods  29  are rigid and are permanently affixed to the back member  20 . In one embodiment, the conductive rods  29  are integrated into the process for forming the back member  20 , such that the conductive rods  29  pass from the top side of the back member  20  to its bottom side. In other embodiments, the conductive rods  29  are installed on the back member  20 , for example, with clips, after the member  20  has been formed. For example, holes are formed from the front to the back of the back member  20 , and the conductive rods  29  passed therethrough and secured to the back member  20 . Of course, other methods for manufacturing the back member  20  with the conductive rods  29  may also be employed. 
     By passing from one side of the back member  20  to the other, the conductive rods  29  provide an electrical connection between these two sides. As such, when the PV solar panel  10  is installed on the top of the back member  20 , the conductive rods  29  provide a conduit for transmitting the electricity generated by the solar panel  10  to the underside of the back member  10 . Once transferred to the underside of the back member  20  of one PV modular roofing structure  5 , the extension of the conductive rods  29  out from the PV modular roofing structure  5  provide an opportunity to contact conductive traces on the underside of an adjoining PV modular roofing structure (not illustrated), which are electrically connected to the conductive rods on this adjoining PV modular roofing structure, thus continuing the electrical circuit between PV modular roofing structures. Alternatively, if no further PV modular roofing structures are being employed, the conductive rods  29  provide an easily accessible connection point for electrically coupling the PV modular roofing structures in the PV system with a power converter or directly to the structure&#39;s electrical breaker box. As a result, the conductive rods  29  allow a quick and easy process for installing a plurality of PV modular roofing structures constructed as disclosed herein by allowing adjoining PV modular roofing structures to be overlapped a predetermined distance so that the conductive rods  29  make electrical contact with the next PV modular roofing structure. 
     Embodiments employing the disclosed PV modular roofing structure  5  may also incorporate a ventilation function for use in “ridge vent” systems. Presently, many homes and structures are constructed such that the peak of a roof has an opening of approximately two inches along its length. This opening is conventionally covered by a special ridge vent material that allows air to pass out of the home, but prevents insects and moisture from entering into the home. For a detail disclosure of ridge vent shingles and ridge vent systems, see U.S. Pat. Nos. 6,418,692 and 6,530,189, which are commonly owned by the Assignee of the present disclosure and are incorporated herein by reference for all purposes. When a PV modular roofing structure  5  with the back member  20  is used as roofing material and placed on a ridge vent roof, the air being vented from the ridge of the roof passes through the channels formed by the channel walls  24  to the outside environment. Advantageously, the herringbone pattern of the channel walls  230  prevents the entry of water into the ridge vent by forcing the water to take a difficult path through the back member  20 . 
     Accordingly, the installation of ridge vent material underneath the PV modular roofing structure  5  is not necessary, and only a one-step installation process is needed to install PV modular roofing structures according to this embodiment on a ridge vent roof. Moreover, when employing the PV modular roofing structures disclosed herein as part of a ridge vent system, the conductive rods  29  discussed above can easily pass through the opening at the ridge of the roof, thus removing the need to form multiples holes across the roof to provide an avenue for electrically connecting the PV modular roofing structures, as is commonly found conventional solar-power roof systems. The use of the PV modular roofing structures disclosed herein as building materials in ridge vent systems is described in greater detail with reference to  FIG. 7 . 
     Turning now to  FIG. 3 , illustrated is a side view of the PV modular roofing structure  5  illustrated in  FIGS. 1-2 , viewed along an axis perpendicular to the longitudinal center axis  11  of the solar panel  10 . As shown in  FIG. 3 , the sidewall  22   a  of the back member  20  is composed of a wedge-shaped or triangular section that extends along a length of the PV modular roofing structure  5 . Sidewall  22   b  is substantially identical, yet opposite, to sidewall  22   a . In addition, at any point along the longitudinal axis  21  of the back member  20 , the height of each of the channel walls  24  (as well as any other support walls included on the back member  20 ) corresponds to the height of the sidewalls  22   a  and  22   b  at that longitudinal position. 
     Also shown in  FIG. 3  is one of the conductive rods  29  discussed above. As described above, the conductive rods  29  pass through the body of the back member  20  to provide an electrical connection from the top of the back member  20  to its bottom side. As the PV solar panel  10  is placed on the top of the back member  20 , if a two-piece structure for the PV modular roofing structure is used, electrical contact between the conductive rods  29  and the PV solar panel  10  is made. Specifically, the PV solar panel  10  may be designed with contact pads formed in particular locations on its underside. Thus, when the PV solar panel  10  is affixed to the back member  20 , those contact pads would come into contact with the conductive rods  29 . Then, electricity generated by the PV cells on the solar panel  10  may be transferred through the conductive rods  29  to the underside of the back member  20 . In addition, the extension of the conductive rods  29  away from the trailing edge of the PV modular roofing structure  5  and towards the next PV modular roofing structure to be installed in the PV system may be seen. 
     Looking now at  FIG. 4 , illustrated is a top view of the back member  20 , before attachment of the PV solar panel  10 . In one exemplary embodiment, the top surface of the back member  20  is corrugated, with the corrugations running longitudinally along the back member  20 . In such an embodiment, the corrugations facilitate the adherence of the PV solar panel  10  to the back member  20 , however this is not required. Also illustrated are the locations of the openings  28  over the channel walls  24  formed on the underside of the back member  20 . Moreover, contact pads  31  that are electrically coupled to the conductive rods  29  may be seen on the top of the back member  20 . While not required, employing contact pads  31  on the back member  20  facilitates an electrical connection from contact pads on the PV solar panel  10  (not illustrated) to the conductive rods  29 . 
     Referring now to  FIG. 5 , illustrated is a front view of the back member  20 , viewed from the trailing edge of the PV modular roofing structure  5 . The extension of the conductive rods  29  from the underside of the back member  20  may be seen from this front view. In addition, a folding point along the slit  27  described above can be more easily seen. More specifically, when employed in ridge vent systems, the back member  20  (and thus the solar panel  10  attached thereto) is bent along the longitudinal axis  21 , where the thickness of the back member  20  is the least. As a result, the sidewalls  22   a ,  22   b  are brought downwards and towards each other, giving the PV modular roofing structure  5  a fold angle, for example, of about 75° to 90°. With such a fold, the PV modular roofing structure  5  may then be placed over the ridge opening in the roof, which is illustrated and described with reference to  FIG. 7 . 
     Looking now at  FIG. 6 , illustrated is a side view of a pair of novel interconnected PV modular roofing structures  100   a ,  100   b  coupled together and employing conductive rods  129 , as described above. Each of the PV modular roofing structures  100   a ,  100   b  includes a PV solar panel  110  and a back member  120 , which are similar to the solar panel  10  and back member  20 , respectively, illustrated in the previous figures. As illustrated, after the first PV modular roofing structure  100   a  is installed on a roof, the second PV modular roofing structure  100   b  is installed by partially overlapping the first PV modular roofing structure  100   a.    
     In this exemplary embodiment, the back members  120  of the PV modular roofing structure  100   a ,  100   b  include a notch to help determine how much of the first PV modular roofing structure  100   a  is overlapped by the second PV modular roofing structure  10   b . In such embodiments, by predetermining the amount of overlap, the installer of the PV system can be certain that the conductive rods  129  are properly aligned with respect to the adjoining PV modular roofing structure. For example, the conductive rods  129  of the first PV modular roofing structure  100   a  may be seen extending towards the second PV modular roofing structure  10   b , and contacting underside contact pads  133  formed on the back members  120 . The conductive rods  129  are electrically connected to the contact pads  133  via conductive traces  139  to maintain the electrical connection from one PV modular roofing structure to the next. As a result, an electrical connection may be made from the tip of the conductive rods  129  of one PV modular roofing structure, through the conductive rods  129  to contact pads  131  on the top of the back members  120 , and then to contact pads  135  on the underside of the PV solar panels  110 , without the use of wires along the way. Such interconnections simply continue from PV modular roofing structure to PV modular roofing structure until the roofline, ridge, hip or rake is completely covered. 
     Beneficially, since the electrical connection across the disclosed PV system is carried directly from one PV modular roofing structure to the next, external wiring for the system need only be connected to the conductive rods  129  of the PV modular roofing structures at the ends of a string of interconnected PV modular roofing structures. Thus, holes for wiring each solar panel to the system need not be made through the roof of the structure. Of course, not only does such a system of interconnected PV modular roofing structures eliminate the risk of leaks through such holes, but the installation process for the entirety of PV modular roofing structures is substantially simplified. More specifically, an installer need simply install one PV modular roofing structure over the next, at the predetermined alignment, without the need to drill holes and electrically connect each PV modular roofing structure along the way. 
     Also illustrated along the outer faces of the solar panels  110  are pluralities of photoelectric spheres  137  of the type described above. By employing such spheres  137  in the disclosed system, rather than traditional crystal solar panels and the like, the look of the granules typically found on the outside of asphalt-based shingles may be readily imitated when the disclosed PV modular roofing structures are used as building materials for roofs. Such imitation allows PV systems of the type disclosed herein to more easily blend-in with surrounding conventional asphalt roofs, so as not to draw unwanted attention to the roof of the structure. Also as mentioned above, this look may be further enhanced in those embodiments where colored photoelectric spheres  137  are employed. Of course, a PV system of modular roofing structures constructed as disclosed herein is not limited to the use of photoelectric spheres  137  for the power-generating components on the PV solar panels  110 . 
     Turning finally to  FIG. 7 , illustrated is an isometric view of the placement of a series of interconnected PV modular roofing structures  5   a ,  5   b , and  5   c  after installation on a hip, ridge, or rake portion of a roof. Each of the PV modular roofing structures  5   a ,  5   b , and  5   c  is a PV solar-power modular roofing structure constructed according to the principles disclosed herein. In addition, as discussed above, each of the PV modular roofing structures  5   a ,  5   b ,  5   c  have been folded along its longitudinal center axis,(see above) to form an inverted V-shape with the rigid back members  20  inside of, and supporting, the solar panels  10 . Once folded, the PV modular roofing structures  5   a ,  5   b ,  5   c  may then be used on the cap of the hip, ridge, or rake portion of a structure&#39;s roof. 
     To begin the installation process for the disclosed PV system, a first PV modular roofing structure  5   a  is placed on the hip, ridge, or rake portion of a roof, and installed by nailing or other suitable means. A second PV modular roofing structure  5   b  is then placed partially over the top of the first PV modular roofing structure  5   a , with the front end of the second PV modular roofing structure  5   b  placed over the back end of the first PV modular roofing structure  5   a . The front end of the second PV modular roofing structure  5   b  is then slid toward the front end of first PV modular roofing structure  5   a  until the step of the back member  20  of the second PV modular roofing structure  5   b  engages the edges of the first PV modular roofing structure  5   a  at the back end. The second PV modular roofing structure  5   b  is then nailed or otherwise suitably fastened in place on the roof, in a manner similar to that of the first PV modular roofing structure  5   a . A third PV modular roofing structure  5   c  is then installed partially over the second PV modular roofing structure  5   b , in the same or similar manner. 
     As will be appreciated by those skilled in the art, PV modular roofing structures according to the embodiment of  FIG. 7  provide a number of benefits. First, the step of each back member  20  allows the next PV modular roofing structure to be easily aligned for a quick and uniform installation. Second, the thickness of the back member  20  enhances the appearance of the PV modular roofing structures and provides a wood-like look to the PV modular roofing structure when used as replacements for roofing shingles. Third, since the back member  20  is substantially the same length as the solar panel  10 , the thickness of each PV modular roofing structure is enhanced across its entire length, and the PV modular roofing structures thereby avoid an exaggerated “saw-tooth” appearance after installation. Also, since the back member  20  of each PV modular roofing structure is made of a rigid material, the PV modular roofing structures will not droop over time or after exposure to extreme temperatures. 
     Furthermore, by carrying the electrical connection directly from one PV modular roofing structure to the next, external wiring for the PV system need only be connected to the end PV modular roofing structures, and no holes for such wiring need to be made in the roof along the way. Moreover, in ridge (or similar) installations, the ridge opening provides access to the attic of the structure into which wires needed for the PV system are typically run.  FIG. 7  illustrates a ridge opening  50  formed at the cap of the ridge of the roof prior to installing the PV modular roofing structures  5   a ,  5   b ,  5   c . The opening  50  is made so that the underside of the roof (and attic) may be properly ventilated, thus increasing heating and cooling efficiency of the structure. As the vented air rises up through the opening  50 , it is funneled through the channel walls described above and out of the structure through vent holes along the sidewalls  22   a ,  22   b  of each of the structures  5   a ,  5   b ,  5   c.    
     Once all of the PV modular roofing structure  5   a ,  5   b ,  5   c  for the system have been installed, electrical wires  55  need only be attached to the end(s) of the string of interconnected PV modular roofing structures, and passed through the opening  50  and into the structure for connection to the PV system. As may be seen, since both the wires  55  and conductive rods  29  are covered beneath the folded PV modular roofing structures  5   a ,  5   b ,  5   c , these electrical components are sheltered from inclement weather after installation. In an advantageous embodiment, the wires  55  are electrically connected to an inverter (or similar circuitry) and then to the electrical breaker box for the structure, in order to provide an on-grid PV solar power system to supplement the traditional electricity provide by the local utility company. Of course, in other embodiments, the PV modular roofing structures  5   a ,  5   b ,  5   c  may be wired to a power converter for storage of the electricity generated by the PV solar panels  10  on the PV modular roofing structures  5   a ,  5   b ,  5   c  in electrical storage devices, such as batteries. In either embodiment, the series electrical interconnection of the PV modular roofing structures  5   a ,  5   b ,  5   c  provides for both simplified installation and simplified wiring of the PV system. 
     In yet another embodiment, the PV roofing structures  5   a ,  5   b ,  5   c  may still be placed end-to-end as illustrated, but all three structures formed together as a single elongated unit. In such embodiments, the complete structure would look basically the same as in the other embodiments discussed, however, the installation of longer units would be quicker and would have less modular connections to be concerned with. In one example of such an embodiment, only the first roofing structure  5   a  includes the electrical conductors  29  the extend out to contact the next PV structure. Thus, the second and third PV structures  5   b ,  5   c  may simply be electrically interconnected using any other means rather than employing the extending electrical conductors  29  that contact the adjacent PV structure when separate PV structures are individually installed. In addition, in such embodiments, the back member located at the back end of the overall elongated structure (a structure including  5   a ,  5   b , and  5   c  together) may still include contact pads  131 ,  133  (see  FIG. 6 ) to provide an electrical connection point for another large PV structure formed from multiple PV structures/rigid back members. When embodiments such as these are constructed and installed, an additional benefit provided is the speed and ease of installation given fewer electrical interconnections. More specifically, although such larger PV structures still connect to an adjacent PV structure in the same manner described above, the larger PV structures occupy more roof area per unit, thus decreasing the number of PV structures installed and decreasing overall installation times. While various embodiments of photovoltaic shingles constructed according to the principles disclosed herein, and PV system incorporating such PV modular roofing structures, have been described above, it should be understood that they have been presented by way of example only, and not limitation. The breadth and scope of the invention(s) should thus not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents. Moreover, the above advantages and features are provided in described embodiments, but shall not limit the application of the claims to processes and structures accomplishing any or all of the above advantages. 
     Additionally, the section headings herein are provided for consistency with the suggestions under 37 CFR 1.77 or otherwise to provide organizational cues. These headings shall not limit or characterize the invention(s) set out in any claims that may issue from this disclosure. Specifically and by way of example, although the headings refer to a “Technical Field,” the claims should not be limited by the language chosen under this heading to describe the so-called technical field. Further, a description of a technology in the “Background” is not to be construed as an admission that technology is prior art to any invention(s) in this disclosure. Neither is the “Brief Summary” to be considered as a characterization of the invention(s) set forth in the claims found herein. Multiple inventions are set forth according to the limitations of the multiple claims associated with this disclosure, and the claims accordingly define the invention(s), and their equivalents, that are protected thereby. In all instances, the scope of the claims should not be constrained by the headings set forth herein.