Patent Publication Number: US-2011048504-A1

Title: Photovoltaic array, framework, and methods of installation and use

Description:
Priority is claimed to U.S. Provisional Application No. 61/015,829 filed on Dec. 21, 2007, to U.S. Provisional Application No. 61/104,834 filed on Oct. 13, 2008, to U.S. Provisional Application No. 61/104,838 filed on Oct. 13, 2008, and to U.S. Provisional Application No. 61/104,841 filed on Oct. 13, 2008, which are all herein incorporated by reference. 
    
    
     FIELD OF INVENTION 
     The present invention is directed to a photovoltaic array having an interconnected electrically non-conductive framework, the method for assembling the photovoltaic array, and a method for use thereof. The array does not have to be electrically grounded. 
     BACKGROUND 
     Commercially available solar energy photovoltaic arrays involve a large number of electrically conducting metallic structural components that need to be grounded. Some examples are included in the following, 
     Erling et al., U.S. Pat. No. 7,012,188, discloses a system for roof-mounting plastic enclosed photovoltaic modules in residential settings. 
     Mapes et al., U.S. Pat. No. 6,617,507, discloses a system of elongated rails of an extruded resin construction having grooves for holding photovoltaic modules. 
     Metten et al., U.S. Patent Publication 2007/0157963, discloses a modular system that includes a composite tile made by molding and extrusion processes, a track system for connecting the tiles to a roof, and a wiring system for integrating photovoltaic modules into the track and tile system. 
     Garvison et al., U.S. Pat. No. 6,465,724, discloses a multipurpose photovoltaic module framing system which combines and integrates the framing system with the photovoltaic electrical system. Some components of the system can be made of plastic. Ground clips can be directly connected to the framing system. 
     SUMMARY OF THE INVENTION 
     In one aspect, the present invention provides a framework comprising a plurality of interconnected electrically non-conductive framework elements disposed to supportingly receive and mutually interconnect a plurality of photovoltaic modules, each the framework element comprising
         a pair of generally parallel rails and a pair of generally parallel stiles interconnected therewith, wherein at least one rail and/or stile is an electrically non-conductive hollow member having an interior, the interior defining a fully enclosed guideway;   one or more longitudinally extended electrically conductive member disposed in at least one the guideway;   one or more electrical connector disposed interior to the at least one hollow member;   wherein a combination of the electrically conductive member and the at least one connector is disposed to electrically interconnect the frame element to another frame element or to one or more photovoltaic module upon installation thereof into the frame elements, thereby forming a photovoltaic array.       

     In another aspect, the present invention provides a photovoltaic array comprising
         a framework comprising a plurality of interconnected electrically non-conductive framework elements disposed to supportingly receive and mutually interconnect a plurality of photovoltaic modules;   a plurality of photovoltaic modules supportingly disposed upon the plurality of framework elements and interconnected therewith, each photovoltaic module having one or more edges that define a periphery;    and,   an electrical connection between the photovoltaic array and an external electrical load; and,    wherein each the framework element comprises
           a pair of generally parallel rails and a pair of generally parallel stiles interconnected therewith, wherein at least one rail and/or stile is an electrically non-conductive hollow member having an interior, the interior defining a fully enclosed guideway;   a longitudinally extended electrically conductive member disposed in at least one the guideway;   one or more electrical connectors disposed interior to the at least one hollow member; and,   wherein a combination of the longitudinally extended electrically conductive member and the at least one connector electrically interconnect the frame elements and the photovoltaic modules to one another, and to an electrical output connection disposed to permit electrical connection of the array to an external electrical load   
               

     The invention is further directed to a method comprising
         supportively disposing a plurality of photovoltaic modules, each having one or more edges that define a periphery, in a supported framework comprising a plurality of interconnected electrically non-conductive framework elements;   forming electrical interconnections between each the photovoltaic module and the framework or another photovoltaic module, thereby forming an array of interconnected photovoltaic modules; and,   providing the framework with an electrical output connection to connect the array to an external electrical load;    wherein each framework element comprises
           a pair of generally parallel rails and a pair of generally parallel stiles interconnected therewith, wherein at least one rail and/or stile is an electrically non-conductive hollow member having an interior, the interior defining a fully enclosed guideway;   a longitudinally extended electrically conductive member disposed in at least one the guideway;   one or more electrical connectors disposed interior to the at least one hollow member; and,   wherein a combination of the longitudinally extended electrically conductive member and the at least one connector electrically interconnect the frame elements and the photovoltaic modules to one another, and to the electrical output connection disposed to permit electrical connection of the array to an external electrical load.   
               

     In a further aspect, the present invention provides a method comprising illuminating a photovoltaic array with sunlight thereby generating an electrical current from the photovoltaic array, the photovoltaic array comprising
         a framework comprising a plurality of interconnected electrically non-conductive framework elements disposed to supportingly receive and mutually interconnect a plurality of photovoltaic modules;   a plurality of photovoltaic modules supportingly disposed upon the plurality of framework elements and interconnected therewith, each photovoltaic module having one or more edges that define a periphery;    and,   an electrical connection between the photovoltaic array and an external electrical load; and,    wherein each the framework element comprises
           a pair of generally parallel rails and a pair of generally parallel stiles interconnected therewith, wherein at least one rail and/or stile is an electrically non-conductive hollow member having an interior, the interior defining a fully enclosed guideway;   a longitudinally extended electrically conductive member disposed in at least one the guideway;   one or more electrical connectors disposed interior to the at least one hollow member; and,   wherein a combination of the longitudinally extended electrically conductive member and the at least one connector electrically interconnect the frame elements and the photovoltaic modules to one another, and to an electrical output connection disposed to permit electrical connection of the array to an external electrical load
 
and,
 
providing electrical power to the external electrical load.
   
               

    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  illustrates a residential rooftop upon which is disposed a photovoltaic array. 
         FIG. 1B  illustrates the basic components that make up a photovoltaic panel. 
         FIGS. 1C-1E  illustrate embodiments of structurally supported photovoltaic panels. 
         FIG. 3A  illustrates an embodiment of a wiring harness and connections found within a framework design. 
         FIGS. 3B-3D  illustrate embodiments of internally enclosed jumper wires and connectors built into the framework design. 
         FIG. 4A  illustrates an embodiment of a method of installation of a photovoltaic panel onto a framework element, and electrical connection alternatives. 
         FIG. 4B  illustrates an embodiment of mechanical connectors on the framework element. 
         FIG. 4C  illustrates an embodiment wherein standard, generally weather-proof connectors are employed for effecting the electrical connections between the cables leading from the junction box of a photovoltaic panel to the framework element. 
         FIG. 4D  illustrates a recessed connecting element that is built into the structural member of the frame element that is suitable for use when the photovoltaic panel comprises internally disposed connecting elements that align with the connecting element shown in the figure. 
         FIG. 4E  illustrates an embodiment of the method for installing photovoltaic panels into the frame element, and two alternative embodiments for effecting the electrical connection. On the left of the figure can be seen a junction box with cables, and on the right a junction box with bulkhead mounted connectors lined up with connectors on the framework element. 
         FIGS. 4F and 4G  illustrate an embodiment of the method of installing photovoltaic panels into the frame element wherein the electrical connection elements are built into the frame of the photovoltaic panel and corresponding connection elements are built into the framework element. 
         FIG. 5A  illustrates an embodiment of a photovoltaic array wired in series. 
         FIG. 5B  illustrates an embodiment of a photovoltaic array wired in the combination of parallel and series. 
         FIGS. 5C-5E  illustrates wiring harness and links. 
     
    
    
     DETAILED DESCRIPTION 
     The present invention provides a framework having a plurality of interconnected electrically non-conductive framework elements disposed to supportingly receive and mutually interconnect a plurality of photovoltaic modules, each the framework element comprising a pair of generally parallel rails and a pair of generally parallel stiles interconnected therewith, wherein at least one rail and/or stile is an electrically non-conductive hollow member having an interior, the interior defining a fully enclosed guideway; one or more longitudinally extended electrically conductive member disposed in at least one the guideway; one or more electrical connector disposed interior to the at least one hollow member; and, wherein a combination of the electrically conductive member and the at least one connector is disposed to electrically interconnect the frame element to another frame element or to one or more photovoltaic module upon installation thereof into the frame elements, thereby forming a photovoltaic array. 
     In another aspect, the present invention provides a photovoltaic array having a framework comprising a plurality of interconnected electrically non-conductive framework elements disposed to supportingly receive and mutually interconnect a plurality of photovoltaic modules; a plurality of photovoltaic modules supportingly disposed upon the plurality of framework elements and interconnected therewith, each photovoltaic module having one or more edges that define a periphery; and, an electrical connection between the photovoltaic array and an external electrical load; and, wherein each the framework element having a pair of generally parallel rails and a pair of generally parallel stiles interconnected therewith, wherein at least one rail and/or stile is an electrically non-conductive hollow member having an interior, the interior defining a fully enclosed guideway; a longitudinally extended electrically conductive member disposed in at least one the guideway; one or more electrical connectors disposed interior to the at least one hollow member; and, wherein a combination of the longitudinally extended electrically conductive member and the at least one connector electrically interconnect the frame elements and the photovoltaic modules to one another, and to the external electrical load. 
     The invention is further directed to a method having supportively disposing a plurality of photovoltaic modules, each having one or more edges that define a periphery, in a supported framework comprising a plurality of interconnected electrically non-conductive framework elements; forming electrical interconnections between each the photovoltaic module and the framework or another photovoltaic module, thereby forming an array of interconnected photovoltaic modules; and, providing the framework with an electrical output connection disposed to permit electrical connection of the array to an external electrical load; wherein each the framework element comprises a pair of generally parallel rails and a pair of generally parallel stiles interconnected therewith, wherein at least one rail and/or stile is an electrically non-conductive hollow member having an interior, the interior defining a fully enclosed guideway; a longitudinally extended electrically conductive member disposed in at least one the guideway; one or more electrical connectors disposed interior to the at least one hollow member; and, wherein a combination of the longitudinally extended electrically conductive member and the at least one connector electrically interconnect the frame elements and the photovoltaic modules to one another, and to the electrical output connection disposed to permit electrical connection of the array to an external electrical load. 
     In a further aspect, the present invention provides a method for illuminating a photovoltaic array with sunlight thereby generating an electrical current from the photovoltaic array, the photovoltaic array having a framework comprising a plurality of interconnected electrically non-conductive framework elements disposed to supportingly receive and mutually interconnect a plurality of photovoltaic modules; 
     a plurality of photovoltaic modules supportingly disposed upon the plurality of framework elements and interconnected therewith, each photovoltaic module having one or more edges that define a periphery; and, an electrical connection between the photovoltaic array and an external electrical load; and, wherein each the framework element comprises a pair of generally parallel rails and a pair of generally parallel stiles interconnected therewith, wherein at least one rail and/or stile is an electrically non-conductive hollow member having an interior, the interior defining a fully enclosed guideway; a longitudinally extended electrically conductive member disposed in at least one the guideway; one or more electrical connectors disposed interior to the at least one hollow member; and, wherein a combination of the longitudinally extended electrically conductive member and the at least one connector electrically interconnect the frame elements and the photovoltaic modules to one another, and to an electrical output connection disposed to permit electrical connection of the array to an external electrical load and, providing electrical power to the external electrical load. 
     As used herein the term “photovoltaic module” refers to a prefabricated array of photovoltaic cells, the associated wiring and connections, and the associated supporting and enclosing structures thereof in the form of a unitary structure—typically a flat, rigid panel—suitable for direct installation in and interconnection with the framework, and thereby with other photovoltaic modules to form a photovoltaic array. Any photovoltaic cell known in the art is suitable for use in the present invention. The term “wiring” in the context of this invention encompasses all forms of interconnecting conductors whether printed conductive pathways, buss bars, single or multi-strand wires, and any other configurations of conductors that are used to conduct electricity from one point to another. 
     A pair of rails and a pair of stiles that are “generally parallel” shall be understood to mean that the rails and stiles combine to define a quadrilateral of which opposite sides do not intersect with one another. In most embodiments, the rails and stiles will be interconnected to form a rectangle disposed to supportingly receive a rectangular photovoltaic module. In another embodiment the rails and stiles will be interconnected to form a square. In addition, should the photovoltaic module depart from rectangular shape—for example, be fabricated in a trapezoidal shape—the rails and stiles may be disposed to form a quadrilateral wherein opposite sides do not intersect but also are not truly parallel. For descriptive purposes herein the term rail will denote the longer of the rail or stile used during assembly of the array, but the terms may be interchanged. 
     The term “longitudinally extended electrically conductive member” refers to a metallic wire having conductive thread-like elements, a metallic wire having a rigid rod element, a metallic buss-bar, a printed conductive pathway, or any other extended electrically conductive member that can be disposed within the guideway defined by the interior of the hollow member in the frame element, and provides electrical connection between one point of the hollow interior space and another point therein, as illustrated infra. 
     In one embodiment, the longitudinally extended electrically conductive member is a metallic wire. In another embodiment the longitudinally extended electrically conductive member is a metallic buss bar. 
     Further the term “electrical connector” refers to a localized device disposed to effect an electrical connection between the longitudinally extended electrically conductive member and some other electrical device or member, including a corresponding longitudinally extended electrically conductive member disposed within the interior of a different hollow member disposed within the framework. 
     In one embodiment, the electrical connector is a terminal post. In another embodiment, the electrical connector is a male or female receptacle disposed to interconnect with its respective female or male connector on a different corresponding frame element or photovoltaic module. Combinations of both types, as well as other types not specifically recited here, can be employed within the framework. 
     In one embodiment, all the rails and stiles are electrically non-conductive hollow members. The rails and stiles may be fabricated from any desired electrically non-conductive materials, including but not limited to ceramics, wood, silicate glasses, and plastic. In one embodiment the rails and stiles are fabricated from plastic. 
     The term “plastic” encompasses thermoplastic or thermoset organic polymers. All organic polymers suitable for use herein are rigid solids up to 90° C. or above. The term “plastic” shall be understood to encompass unreinforced polymers, particle-filled polymers, short fiber reinforced polymers, long-fiber reinforced polymers, and continuous-fiber reinforced polymers (composite materials). Any electrically non-conductive reinforcing fiber is suitable for use in forming the fiber reinforced polymers suitable for use herein. Suitable fibers include but are not limited to glass, polyaramid, and ceramic. 
     The term “short fiber reinforced polymer” is a term found in the art referring to a blend of a polymer and a reinforcing fiber characterized by a length of less than about 5 mm, wherein the fiber is dispersed with a continuous matrix of the polymer. The term “long fiber reinforced polymer” is a term of art referring to a blend of a polymer and a reinforcing fiber characterized by a length of about &gt;5 mm-50 mm, wherein the fiber is dispersed with a continuous matrix of the polymer. Continuous fiber reinforced polymers are also known as composite materials. Continuous fiber reinforced polymers generally involve fibers that are comparable in length to the article into which they have been incorporated. 
     Short and long fiber reinforced polymers may be prepared by extrusion blending, and fabricated by injection molding. Continuous fiber reinforced polymers must be prepared by yarn coating, polymer infusion into yarn bundles and the like. Fabrication may involve vacuum molding, pultrusion and such other methods that have been developed in the art for shaping of composite materials. 
     Suitable reinforcing fibers include glass fibers, polyaramid fibers, ceramic fibers, and other non-electrically conductive fibers that retain their distinctive fiber properties during processing and fabrication. Fiber reinforced polymers are extremely well-known in the art. Detailed descriptions of compositions, preparation, fabrication, and properties may be found in Garbassi et al. J. Poly. Sci. and Tech., DOI 10.1002/0471440264.pst406, and Goldsworthy et al., J. Poly. Sci. and Tech., DOI 10.1002/0471440264.pst074. 
     Any of the plastic compositions suitable for use herein may further comprise such additives as are commonly employed in the art of Engineering Polymers, including inorganic fillers, ultra-violet absorbers, plasticizers, anti oxidants, flame retardants, pigmentation and so forth. 
     Suitable plastics need to exhibit dimensional stability and good retention of mechanical properties when subject to continuous desert temperatures as high as 90-120° C., on surfaces exposed to the sun. Many plastics soften at temperatures below that temperature. Softening is unacceptable both from the standpoint of maintaining coplanarity of the photovoltaic modules and the solar cells of which they are composed, and of flexural, shear, and torsional resistance. Suitable plastics include but are not limited to polyamides, such as nylons, polyesters such as polyethylene terephthalate, polycarbonate, poly ether ketones, including PEK, PEEK, PEKK and the like; polyamideimides, epoxies, and polyimides. 
     Particular choice of a plastic resin from which to fabricate the framework will depend upon the specific environment in which it will be used, as well as cost. In a bone dry climate such as a desert, nylon polyamide may offer a desirable combination of properties. In a temperate climate, periods of rain and high humidity, will render nylon subject to dimensional instability and hydrolysis. For many purposes long-fiber reinforced polyethylene terephthalate resin is highly satisfactory and cost effective. In one embodiment, Rynite® PET polyester resin, available from the DuPont Company, is employed to fabricate the rails and stiles. 
     The term “photovoltaic array” refers to an arrangement of one or more photovoltaic modules, defined supra, positioned to convert sunlight (or other illumination) to electrical power. In a present typical photovoltaic array, a plurality of photovoltaic modules is arranged in coplanar array. In a typical commercial installation, a single photovoltaic module receiving full solar illumination outputs 4-5 amperes of current at 24 volts, and a photovoltaic array can output 30 amperes at about 500 to 1000 volts. 
     Safely handling the electrical power levels and voltage levels of a solar array in outdoor commercial and residential settings requires the grounding of all exposed metal parts; and the protection of electrical connections from corrosion. In the present invention, such connections are partially contained or completely contained within the interior defined by the non-electrically conductive hollow members of the framework element, or are isolated in their own non-conductive housing. No exposure of connectors to corrosive conditions occurs. 
     The photovoltaic array is characterized in that all of its internal electrical components: including photovoltaic cells, by-pass diodes, electrical conductors and interconnections are encased in and supported by non-conductive frame elements, non-conductive frame segments on the module, or other non-conductive housing. The photovoltaic array allows the output voltage to be electrically referenced to any arbitrary voltage without compromising safety or system integrity. No electrical grounding is required. In addition to the benefits in installation cost and safety associated with the photovoltaic array, there is also a benefit in increased electrical design flexibility over present-day photovoltaic arrays because the system may be installed under conditions where the reference voltage is well above ground potential—something not possible with present-day systems. However, setting the reference potential to ground is not precluded. 
     A photovoltaic module suitable for use in the photovoltaic array comprises a structural component, a plurality of electrically interconnected photovoltaic cells typically arranged in a parallel coplanar array with an optically clear protective cover, and a protective backing; the photovoltaic cells being sandwiched and sealed between the cover layer and the backing layer. In one embodiment the structural component is a peripheral frame. In an alternative embodiment the structural component is an underlying supporting structure. 
     In one embodiment, the photovoltaic module further comprises an electrical junction box to which the output wires of the photocells are connected, and from which high voltage cables from the junction box are connected to weather resistant connectors bulkhead mounted on one or more the hollow members, with electrical connections between photovoltaic modules effected by electrical conductors internal to at least a portion of the hollow members. 
     In a further embodiment, the photovoltaic module has high voltage connecting cables with weather-resistant plugs. In an alternative embodiment, the photovoltaic module is provided with integrated electrical connections within the structure of the module, as described below. 
     In another embodiment, each rail and stile is fabricated from plastic, each photovoltaic module further comprises a frame segment member enclosing at least a portion of the periphery, the frame segment member housing electrical power output connections; and, wherein all of the electrical conductors and connections that interconnect the photovoltaic modules one to another are internal to at least a portion of the hollow members and the frame segment members. 
     Photovoltaic modules in present commercial use are coplanar arrays of photovoltaic cells that make up a flat panel. Similarly, photovoltaic arrays in present commercial use are typically in the form of flat coplanar arrays of flat panel photovoltaic modules. However, the present invention is operable in embodiments wherein the photocells in a module, or the modules themselves describe a curved surface rather than a plane. 
     Any photovoltaic cell that converts sunlight into electrical power is suitable. A typical photovoltaic cell in widespread commercial use comprises layers of doped and undoped silicon, sandwiched between two layers of metal conductors. There are many types of photovoltaic cells in the art, single layer, double layer, triple layer, etc., any of which could be used with this invention, if formed together and electrically interconnected to form a power producing photovoltaic module. Photovoltaic cells are connected in series and/or parallel to obtain the required values of current and voltage for electric power generation in the photovoltaic array. 
     Several semiconductor compositions have been developed for use as photovoltaic cells in solar modules. Both amorphous and crystalline silicon and crystalline gallium arsenide are typical choices of materials for solar cells. Using means well-known in the art, dopants are introduced into the pure compounds, and metallic conductors are deposited onto each surface: a thin grid on the sun-facing side and usually a flat sheet on the other. Typically, solar cells are made from silicon boules, polycrystalline structures that have the atomic structure of a single crystal. The pure silicon is then doped with phosphorous and boron to produce an excess of electrons in one region and a deficiency of electrons in another region to make a semiconductor capable of conducting electricity. Photovoltaic modules suitable for the practice of the present invention are available commercially from a number of manufacturers, including Evergreen Solar, Inc, Marlboro, Mass.; Solarworld California, Camarillo, Calif., and Mitsubishi Electric Co., New York, N.Y. 
     Any electrically non-conductive, engineered, structural material including ceramics, wood, and polymers, could be used to form the structural members of the photovoltaic modules and the framework elements. If the material is classified as a non-conductor according to appropriate regional Standards Organizations, such as UL (Underwriters Laboratories), CUL, or TUV, it is appropriate for use in this invention. To be UL certified, materials must meet UL 1703 (Standard for Safety for Flat-Plate Photovoltaic Modules and Modules); UL 498 (Attachment Plugs and Receptacles); and/or UL 1977 (Component Connectors Used for Data, Signal and Power Equipment Applications), as appropriate. Additional information on UL certification can be found at http://www.ul.com/dge/photovoltaics/ and http://www.ul.com/dge/photovoltaics/tests.html 
     In one embodiment, the photovoltaic module is provided with plastic structural members. In another embodiment, the photovoltaic module has metallic structural members, necessitating that the metallic members that would otherwise be exposed be subject to encapsulation in plastic. Any means for encapsulating in plastic is satisfactory, for example, coatings, extrusions, laminations, bonding, cladding, with the proviso that the encapsulation be weather-resistant. 
     In one embodiment mechanical connections between framework elements are made of plastic, and are of the snap-together variety. Mechanical connections may be reversible to make replacement of damaged parts easy. Suitable mechanical connections include, but are not limited to: snap-together, spring-loaded, quarter-turn, bayonette, interlocking, and quick connect—disconnect assemblies such as those used in the discrete-part manufacturing industry. 
     Electrical connections between framework elements may conveniently be effected using conventional high voltage connectors wherein the male connector is located on one component, disposed to mate with the female component disposed on the component to which it is to be connected. Suitable connectors are preferably approved for photovoltaic applications by organizations such as UL and TUV. 
     In one embodiment, each photovoltaic module is disposed in and connected electrically and mechanically to a framework element made up of rails and stiles. The photovoltaic module is provided with both mechanical and electrical connectors compatible with complementary connectors provided in the framework element to which it is connected. Suitable mechanical connections provided in the photovoltaic module include but are not limited to a frame that snaps into a receiving track on the framework element, and pass-through holes in a frame on the photovoltaic module for mounting to the framework element. In the case where pass-through holes are employed, the mounting screws and mating fasteners, such as threaded standoffs, rivets, inserts or nuts, are either insulated or isolated from the framework elements made of plastic, coated with an insulating surface, capped with an insulating cover or combinations. Electrical connectors should be certified for outdoor use in wet locations with exposure to sunlight (i.e., UV exposure resistance). Power connectors for use with photovoltaic modules and framework should be designed robustly enough to withstand use as a DC circuit interrupt device, under overload conditions, as outlined in UL 498 and UL 1977. 
     In one embodiment, the photovoltaic module is of a design currently in widespread commercial use, characterized by output conductors that are connected to a junction box mounted on the back of the photovoltaic module with high voltage output wires having weather-tight connectors at the end, as illustrated in  FIG. 3D  ( 308  and  307 ). The output high voltage wires are connected into the framework wiring. 
     In another embodiment the output high voltage wires such as are present in current commercial offerings are replaced by high voltage connectors mounted right on the junction box, and inserted directly into complementary connectors mounted on the framework element, as illustrated in  FIG. 4E  right side. 
     In another embodiment, the photovoltaic module has no external wires. Instead the output wires are run within the module frame to connectors that are coincident with through-holes in the frame that match up to mounting posts on the framework element, thereby achieving both mechanical securing and electrical connection at the same time, as shown in  FIGS. 4F and 4G . 
     In most applications, the photovoltaic array requires some sort of supporting surface on which the framework is constructed. Suitable supporting surfaces include a roof-top, a concrete pad, and the ground. Using known methods currently employed in the art, the framework can be mounted on a moveable sub-structure that enables the array to “follow the sun” across the sky. 
     In one embodiment, all the rails and stiles are electrically non-conductive hollow members. 
     In one embodiment, the rails and stiles are fabricated from plastic. 
     In one embodiment, the plastic is glass-reinforced polyethylene terephthalate. 
     In one embodiment, the longitudinally extended electrically conductive member is a metallic wire. 
     In one embodiment, the longitudinally extended electrically conductive member is a metallic buss bar. 
     In one embodiment, the electrical connections between the photovoltaic modules comprise output wires from the photovoltaic module connected to an electrical junction box, and high voltage output cables from the junction box connected to weather-resistant connectors bulkhead-mounted on one or more the hollow members, with electrical connections between photovoltaic modules effected by electrical conductors internal to at least a portion of the hollow members. 
     In one embodiment, each rail and stile is fabricated from plastic, each photovoltaic module further comprises a frame segment member enclosing at least a portion of the periphery, the frame segment member housing electrical power output connections; and, wherein all of the electrical conductors and connections that interconnect the photovoltaic modules one to another are internal to at least a portion of the hollow members and the frame segment members. 
     In one embodiment, the output of the photovoltaic array is connected directly to an electrical load. In an alternative embodiment, the output is processed or conditioned in a step that precedes connection to an external load. In one embodiment, the direct current (DC) output of the photoarray will be directed to a power inverter that converts the DC output to AC, and then to a transformer either for conditioning for long distance high voltage power transmission, or for low voltage local power use. 
     In one embodiment, the output of the photovoltaic array is delivered by hardwiring to an external electric component such as a power inverter, to convert the high voltage DC generated by the solar cells to the applicable utility grid voltage, frequency and cycles (120 vAC-60 hz-1 phase or 480 vAC-60 hz-3 phase in the US). In an alternative embodiment, the array is provided with a high voltage output disconnect that connects to an external cable. In a further embodiment, the output of the photovoltaic array is used to charge electrical storage devices, such as lead acid batteries, to store electrical power. 
     In one embodiment, the array is positioned to receive the maximum amount of sunlight. At temperate latitudes, the array is maintained at an angle in the range of 15 to 40° with respect to the horizontal. In a further embodiment the angle is adjusted to maintain maximum exposure to sunlight over the course of the year as the angle of the sun in the sky changes with the seasons. 
     In one embodiment of the invention, all electrical connections and wiring for the entire array are buried in the structure either within the frame segment of the photovoltaic module or the hollow member of the frame element. In an alternative embodiment, all electrical connections and wiring for the entire array are buried in the structure with the exception of weather-tight high voltage connections between the photovoltaic module and the framework element with which it is associated. In both embodiments, electrical grounding connections are unnecessary. 
     In the embodiment wherein all electrical connections and wiring for the entire array are buried in the structure either within a frame segment member of the photovoltaic module or the hollow member of the frame element, electrical connections are made as the array is mechanically assembled. In the case where junction boxes and weather-tight high voltage cables are employed, some wiring in-the-field continues to be necessary. 
     These and other embodiments are depicted in  FIGS. 1-5 . Throughout the following detailed description similar reference numerals refer to similar elements in all figures of the drawings. It should be understood that various details of the structure and operation of the present invention as shown in various Figures have been stylized in form, with some portions enlarged or exaggerated, all for convenience of illustration and ease of understanding. 
       FIGS. 1-5  show schematically several closely related embodiments of the device and the method for assembling a photovoltaic array. In the embodiments, the photovoltaic array is installed on a residential, slanted rooftop, common in many parts of the United States. The figures represent only a few of many framework/photovoltaic module geometries possible by this invention. 
     Numerous other embodiments are envisioned to fall within the invention. These include but are not limited to installations on flat roofs and on the ground. Additional embodiments include but are not limited to those wherein each framework element is individually constructed, and then snapped together in the field to form the array. 
     One embodiment that can be constructed from those depicted in the figures is an embodiment in which all electrical conductors and connections are fully contained within the framework. 
       FIG. 1A  illustrates one embodiment of a photovoltaic array  101  installed on residential rooftop  100 . The photovoltaic array,  101 , comprises a framework,  102 , each framework element,  103 , mechanically and, in some embodiments, electrically connected to another framework element with internal electrical Interconnects. Each framework element,  103 , holds a photovoltaic module  104 . 
       FIG. 1B  shows the basic sandwich structure,  105 , that depicts a general photovoltaic module wherein a photocell array  105   pv  is located between a clear, protective top layer  105   tc , and the protective bottom layer  105   pb . Also, shown  FIG. 1C through 1E  are various types of photovoltaic modules,  116 ,  110 , and  114 . Each type of photovoltaic module comprises one or more structural members such as a frame  106  shown in  FIG. 1C , in other embodiments support beams in  FIG. 1D  shown as  113 , and in  FIG. 1E  shown as  115 . In one embodiment the structural members of the photovoltaic module are plastic such as a fiber reinforced plastic. Structural members of the photovoltaic module include but are not limited to framing, backing, beams, or other such elements as are required to hold the multi-layer photovoltaic module together, and to resist flexure. In one embodiment the photovoltaic module  116  has a peripheral supporting structural frame  106  that achieves adequate rigidity through a thick, rigid, extrusion surrounding the photovoltaic module. Alternatively, the same degree of structural support can be achieved with a light-weight supporting frame and structural stiffeners  113  bonded to the backside of the photovoltaic module,  110 . Alternatively, module  114  has an integrated backside supporting structure  115  In all cases, the brittle, easily damaged photovoltaic cells should be adequately supported and protected to prevent micro-cracking during violent weather if the output of the photovoltaic module is to remain intact for its desired lifetime. 
       FIGS. 2A and 2B  ( FIG. 2B  is a break-out illustration of  FIG. 2A  as designated in  FIG. 2A ) illustrate an embodiment of the method for directly assembling an array of framework elements  103  into the photovoltaic array  101 . A first end member,  201 , made from 5 cm×5 cm (2×2) cross-section, hollow, fiber-reinforced plastic (FRP) tubing, forms one side of a framework, and a second end member,  204 , forms the opposite side of the framework  200 . The first end member  201  interconnects with a plurality of rectangular cross section hollow FRP tubing cross-members,  205 . Each cross-member  205  is further connected at the opposite end with an intermediate member,  203 , of rectangular cross-section hollow FRP tubing provided with plastic interconnects,  202 . Unlike the end-members above the intermediate members,  203 , are provided with plastic interconnects facing in opposite directions so that the intermediate members  203  can interconnect to cross pieces  205  on both sides of the intermediate member. 
       FIGS. 2C through 2E  illustrate embodiments comprising a matrix of mounting shoes,  207 , which attach to the roof,  100 , at premeasured locations  209 - 214 , in order to secure the framework members  201 ,  203 ,  204  and  205 , via mounting feet,  208 , affixed beneath some or all of the plastic interconnects,  202 . In an embodiment the feet can be plastic. In an embodiment shown in  FIG. 2E , the mounting feet,  208 , are U shaped pieces, with an open channel  230  in the bottom, which engages the roof-mounted, mating tongue  220  on each corresponding mounting shoe,  207 . 
     Referring to  FIG. 3A , each member  201 ,  203  or  204  (not shown), can contain an internal electrical interconnect wiring harness,  301 . In an embodiment shows a fully enclosed hollow interior  327  which accommodates the wiring. This wiring harness replaces the need for field wiring to interconnect the photovoltaic modules into an electrical array. Because the present invention has no exposed metal parts, there is no need for grounding at any point in the array. For purposes of clarity, the wiring harness  301  is broken out separately in FIG.  3 B 1  and FIG.  3 B 2 , and shown as parts  303 ,  304 ,  305 , and  306 . The components of the wiring harness shown in the figures can be combined if desired into the wiring harness at a remote location such as a factory, away from the in-the-field installation site of the photovoltaic array. As shown in the figures, the wiring harness depicted comprises a return electrical conductor wire  303 , a circular perforated reinforcing tube,  304 , jumper wires  305  between adjacent framework elements, all of which are snapped onto non-conductive spacers,  306 . In one embodiment, the jumper wires are terminated with high voltage connectors such as are currently employed in the art of photovoltaic arrays. In an alternative embodiment, the jumper wires are formed into coils  305   a , see  FIG. 3C , that are incorporated into an integrated electro-mechanical connection, as discussed below. 
     In one embodiment, the internal wiring harnesses employed herein can be formed as follows, although the invention is not limited to any particular method for forming the structural members: The spacers  306 , as shown in FIG.  3 B 2 , are slid onto a 15-20 foot length of a preferably circular cross-section, preferably perforated, non-conductive rigid tube  304 , preferably plastic, to predetermined points along the tubing, to be prepositioned where the electrical connections are to be made to the photovoltaic modules The spacers are then permanently affixed by any suitable means including but not limited to thermal, solvent, or adhesive bonding. Next, the electrically conductive interconnect wires,  303  and  305  are formed to shape dictated by the specific wiring scheme for each specific application. Shaping may be, but need not be, effected by bending over tooling on a bench before snapping them into place on the prepositioned spacers  306 . 
     As shown in  FIG. 3A  the assembled wiring harness is then inserted into the appropriate end or intermediate member,  201 , 203 , and  204 . In one embodiment, the interior of the end and intermediate members after insertion of the wiring harness is sealed with foam, or sealed otherwise to retard the ingress of moisture, oxygen, insects, and debris. 
     This internal wiring harness eliminates the need for interconnect wiring between photovoltaic modules in the field, if photovoltaic modules with an internal connector design are installed. One embodiment is shown in  FIG. 3D . 
     Referring to  FIG. 3D , in some embodiments, the framework cross members  205  contain an internal, electrical interconnect wiring harness  309 . This wiring harness replaces the need for some of the field wiring required in other embodiments. 
     In the embodiment depicted in  FIG. 3D , the wiring harness ( 309 ) is assembled from one or two electrical jumper wires  310  disposed to connect framework members,  201  and  203 , having weather-tight high voltage connectors,  307  (bulkhead) or  308  (plug), all of which are fastened onto non-conductive spacers/holders,  306 . Corresponding weather-tight connectors  307  (bulkhead) are installed in each framework interconnect member  202  and electrically connected to the internal wiring harness  301  depicted in FIGS.  3 B 1  and  3 B 2 . The corresponding plugs in the ends of the framework cross members  205  make a continuous electrical connection with the wiring harness in the members  201 ,  203 , or  204  upon assembly on the roof. 
     The internal wiring harness in cross member  205  eliminates the need for some of the interconnect wiring between photovoltaic modules during installation on a rooftop. Since the wiring is present in the cross members  205 , all that is necessary during installation is to connect the framework elements mechanically and the wiring is concomitantly connected. 
     In the embodiment shown in  FIG. 3A-3D , the plastic interconnect,  202 , is in the form of a hollow rectangular shaped tube that is sized to fit into the hollow rectangular aperture of the cross-member. In the practice of the present invention, there is no particular form required for the plastic interconnect. It may, for example, be conical in shape, it may be a truncated square pyramid in shape, prismatic or any shape that will permit the ready interconnection of the end or intermediate members with the cross-members. 
     The plastic interconnects,  202  can for example be manufactured from appropriately sized tubing in the form of a hollow rectangular prism, cut to length and bonded to the end or intermediate members. Alternatively, the plastic interconnects can be injection molded. Any method of bonding known in the art is satisfactory including mechanical fastening, gluing; thermal bonding; dielectrical bonding; or ultrasonical bonding. The end and intermediate members can also be manufactured with integral interconnects by injection molding or compression molding. 
     One alternative for achieving firm, positive connection that is also reversible is to employ spring fingers  250  (shown in  FIG. 3A ) that are molded to or otherwise attached to the exterior surface of the tubing, that are pushed inward when cross member  205  is slid over the open face of interconnect  202  to a pre-determined position at which point the compressed fingers spring out into corresponding holes  251  in cross member  205  to lock the two framework members together. In another embodiment the holes do not penetrate the surface of the cross member. If it is desired to disassemble the framework, the spring fingers  251  can be depressed so that corresponding cross member  205  can be slid off the corresponding plastic interconnect  202 . This eliminates all of the drilling and mechanical fastening required in conventional metallic frames, greatly reducing the assembly and installation time on the roof. 
       FIG. 4A  illustrates an embodiment of a single framework element set up to hold one photovoltaic module. Shown in  FIG. 4A  are two alternative electrical connections, magnified in sections  4 C and  4 D, and the framework details of the electro-mechanical interconnection between the photovoltaic module and framing elements. Also shown are internally threaded electrically conductive standoffs  FIG. 4B ,  401  which are bonded to the plastic structural member  205  making up the framework element to affix the intended photovoltaic module atop the framework element. Details of the internally threaded standoffs  401  which hold the photovoltaic module are shown in magnified section of  FIG. 4B . The standoffs can be attached to the framework element by installing them into mounting holes drilled into the plastic structural member by heating them with a heated threaded tip, bonding them with adhesive, solvent bonding, or ultrasonically bonding. 
     The magnified section illustrated in  FIG. 4C  shows high voltage cables  108  leading from the junction box  107  (shown in  FIG. 4A ) found on the back of a photovoltaic module (module not shown in  FIG. 4C ) are plugged into the bulkhead connectors  307  to complete the electrical circuit with the wiring harness,  301  (shown in  FIG. 4A ), via bulkhead connectors mounted on the member  201  of the framework element. In an embodiment, high-voltage bulkhead connectors are hardwired to the end of wiring elements  305  in the wiring harness, at a remote location, before being transported to the installation site and fastened to the corresponding framework elements  201 ,  203  or  204  (not shown), followed by placing of the photovoltaic module onto the framework element and securing. 
     Magnified sections found in  FIGS. 4D and 4G  illustrate embodiments wherein a coil  305   a  is wound on the end of a jumper wire  305  or return electrical conductor wire  303  that has the internal diameter of the internally threaded electrically conductive standoffs with insulating caps  401 . By positioning the coil  305   a  beneath the appropriate conductive standoff  401 , and inserting an appropriate-length conductive set screw  405  through  401  and into the coil the mechanical standoff doubles as an electrical connection to the photovoltaic module  104  (see  FIG. 4F ) from the internal wiring harness  301  when the photovoltaic module has an internally wired frame segment member as described above. 
       FIGS. 4E and 4F  each illustrates a single framework element holding one photovoltaic module,  104 , via the electro-mechanical standoffs,  401 . 
       FIG. 4E  depicts an embodiment in which the photovoltaic module has a junction box  107 , interconnect wiring  108  and weather-tight connectors  109 . The framework element has mating weather-tight bulkhead fittings  307 . In this embodiment, prior to affixing the photovoltaic module to the framework element, the plug connectors  109  are connected to the corresponding bulkhead connectors  308 . Following the electrical connection, the panel is positioned on the framework element and connected thereto using the pre-positioned mechanical standoffs  401 , and attachment screws. 
       FIG. 4E  also depicts, on the right, the case where the photovoltaic module junction box  107  is mounted close enough to the framework element  203  that only weathertight connectors  109  are needed to connect the junction box  107  to the mating weathertight bulkhead fittings  307 , eliminating the cost of the interconnect wiring  108 . 
       FIG. 4G  illustrates details of an embodiment in which connectorless connections are made to the wiring harness  301 . This connectorless electrical connection invention eliminates the photovoltaic module interconnect wiring  108 , having the water-tight connectors  307  and  109 , and the junction box  107 , all shown in  FIG. 4E . These are expensive items which are subject to high failure rates when directly exposed to severe outdoor environments for long periods of time. 
     In the embodiment depicted in  FIGS. 4F and 4G , all conductors and connectors are fully enclosed within the structural members of the photovoltaic array. The junction box is eliminated. In  FIG. 4F , a photovoltaic module,  104 , is installed onto a frame element defined by structural members  201 ,  203 , and  205 , formed by snapping the ends of cross-members  205  onto the appendages  202  disposed on members  201  and  203 . The photovoltaic module is provided with a peripheral frame,  106 , which houses the wiring,  409 , including the isolation diodes (not shown) commonly employed in the art, and connectors,  409   a , associated with the module. In the case depicted in  FIG. 4G , the connector is just a coil formed at the end of wire  409   a . Referring to  FIG. 4F , the frame is provided with a series of mounting holes along its surface,  450 , which are located to align with the mounting standoffs  401  disposed on the upper surface of the framework element. The mounting standoffs are insulating caps disposed upon a threaded metal element,  405 , disposed to receive the mounting screws,  405   a . Referring to  FIG. 4G , electrical connection is effected by inserting an electrically conductive mounting screw  405   a  through mounting hole  450  in the frame  106  of the photovoltaic module  104  where the metallic screw  405   a  comes into electrical contact with connection  409   a  within the frame, and screws into the threaded metal element  405  which in turn is in electrical contact with connector  305   a , thereby forming an electrical connection between  409   a  and  305   a . This method of electrical termination replaces the junction box  107 , interconnect wiring  108  and connectors  109 , at a significant cost savings, as well as long term reliability. 
     In the practice of the invention, the framework elements are both electrically and mechanically connected to form an integrated photovoltaic array. All the array wiring and interconnections can be performed at a remote location prior to installation on site. In the embodiment depicted in  FIG. 4E , there is a need for making cable connections from the photovoltaic panel to the framework members. In the embodiment depicted in  FIG. 4F-4G , there are no cable connections to be made, and the electrical and mechanical connections are made simultaneously, without the necessity of in the field wiring. Because there is no exposed wiring, and no chance of short circuits to exposed metal parts since there aren&#39;t any, there is no need for the extensive grounding of the framework such as is commonly done. 
     Numerous wiring configurations can be employed in forming the photovoltaic array.  FIG. 5A  illustrates the photovoltaic modules  200  interconnected in series, with wiring harnesses in framework members  201  and  203 . In this wiring scheme, no wiring harness is required in framework element  204 . Interconnect wiring is located in the lower cross members  205 . 
     In an alternative embodiment,  FIG. 5B  illustrates the photovoltaic modules  200  interconnected in series left to right, and in parallel top to bottom. Wiring harnesses  501  are found in framework members  201  and  204 , while framework members  203  have short conductive links  502  (see  FIG. 5E ) between the electro-mechanical fasteners  401  immediately adjacent to each other. These linked standoffs,  502  are inserted inside the vertical framework elements  203  at the factory instead of inserting individual standoffs  401 , thereby eliminating altogether the wiring harness  301  or  501  from framework elements  203  for this embodiment. As shown in  FIG. 5D ,  503  indicates the regularly spaced standoff pairs that can be inserted as a single column into the framework member. This virtually eliminates all panel interconnect wiring and embodies the simplest embodiment. 
       FIGS. 5C and 5D  show an embodiment of a method for connecting adjacent photovoltaic modules together. In  FIG. 5C , a buss  501  replaces the wiring harness  301  depicted in FIG.  3 B 1 .  FIG. 5D  depicts the “jumper lugs”  502  indicated in  FIG. 5B ; the jumper lugs are mounted on each of the inboard vertical framework elements,  203 , greatly simplifying the internal wiring of the photovoltaic array and associated manufacturing costs. 
       FIG. 5E  illustrates the detail of the “jumper lugs”  502  shown in  FIG. 5D , consisting of two threaded standoffs,  401 , electrically connected by a conductive link,  507 . 
     LEGEND FOR DRAWINGS 
     
         
         
           
               100 —residential rooftop 
               101 —assembled photovoltaic (PV) array 
               102 —assembled framework mounted on roof 
               103 —individual framework elements that together make up the framework ( 102 ) 
               104 —generic photovoltaic (PV) modules 
               105 —the basic PV module layered structure including the photocell array,  105   pv ; sandwiched between the clear, protective top layer,  105   tc ; and the protective bottom layer,  105   pb.    
               106 —peripheral supporting structural frame surrounding layered PV structure  105   
               107 —electrical junction box on back of PV panel connecting wiring inside PV module to high voltage electrical leads  108   
               108 —high voltage electrical leads connecting junction box  107  to weather-tight plugs  109   
               109 —weather-tight plugs connecting high voltage electrical leads  108  to bulkhead connectors mounted on framework element 
               110 —One embodiment of a suitable PV module, structurally supported with a light-weight supporting frame,  111 , via mounting holes,  112 , and structural stiffeners  113  bonded to the backside of the photovoltaic module  105   
               111 —light weight peripheral supporting frame surrounding basic layered PV structure  105   
               112 —mounting holes in light weight peripheral supporting frame 
               113 —structural stiffeners bonded to backside of PV panel  110   
               114 —alternative PV panel, with integrated backside supporting structure, framing or backing  115  bonded to backside 
               115 —integral backside supporting structure for panel 
               116 —embodiment of PV panel with peripheral supporting frame 
               200 —framework 
             201—framework end member, forming one side of a framework 
               202 —framework mechanical interconnect member bonded to  201 ,  203 ,  204   
               203 —framework intermediate member 
               204 —framework end member, forming opposite side of framework 
               205 —framework cross-member 
               207 —mounting shoes, fastened to roof to support framework 
               208 —mounting feet, fastened to framework elements, which engage the roof-mounted, mating tongue on each corresponding mounting shoe,  207   
               209 —location of where left-most framework member  201  will be fastened to roof 
               210 —location where right-most framework member  204  will be fastened to roof 
               211 —location where upper-most foot of framework members  201 ,  203  and  204 , will be fastened to roof 
               212 —location where lower-most foot of framework members  201 ,  203  and  204 , will be fastened to roof 
               213 —location where feet of framework members  203  will be fastened to roof 
               214 —location where rows of framework elements  201 ,  203  and  204  will be fastened to roof 
             Point  209 , 211 —upper-left most mounting foot location for framework array 
             Point  210 , 211 —upper-right most mounting foot location for framework array 
             Point  209 , 212 —lower-left most mounting foot location for framework array 
             Point  210 , 212 —lower-right most mounting foot location for framework array 
               250 —spring finger 
               251 —spring finger hole 
               301 —framework element internal electrical interconnect wiring harness, both inside framework elements  201 ,  202  and  203   
               303 —a return electrical conductor wire 
               304 —a circular perforated reinforcing tube 
               305 —jumper wires between adjacent framework elements 
               305   a —coil of internal electrical wiring forming a connector. 
               306 —non-conductive spacers/wire holders 
               307 —high voltage bulkhead electrical connectors which mate with  308   
               308 —high voltage plug-type electrical connectors which mate with  307   
               309 —internal, electrical interconnect wiring harness in framework cross-pieces  205 , which connects wiring harness in framework elements  201 ,  203  or  204  and consists of components  306 ,  307 ,  308 , and/or  310   
               310 —jumper wire in wiring harness inside framework crosspiece  205  to connect two adjacent photovoltaic modules 
               327 —hollow enclosed interior 
               401 —insulated standoffs capping mechanical fasteners  405   b  located in framework element which, with mating fastener,  405   a , passing through mounting hole  450  hold module to framework element 
               405   a —conductive screw which connects the module to the framework element via conductive holes  450 , insulated standoffs  401 , and threaded element  405 . In the case of electrical connections  409   a  and  305   a , the screw  405   a  also effects the electrical connection. 
               405 —threaded conductive element disposed to receive screw  405   a    
               409 —electrical lead from the photovoltaic module  105  routed through the surrounding plastic frame  106 , to  2  of the mounting holes  450   
               409   a —coil formed at end of conductor  409   a  to served as electrical connector. 
               450 —mounting hole in module frame 
               501 —electrical buss bar replacing wiring harness  301   
               502 —jumper lugs short conductive link inside framework element  203  to create a series electrical connection of adjacent modules in each row of the photovoltaic array 
               503 —column of short conductive links  502  inside framework member  203   
               506 —magnified view illustrating details of an embodiment in which a short conductive link  507  connects two adjacent mechanical fasteners  401  inside a framework element  203   
               507 —short conductive link