Patent Application
20110048504
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.
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.
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
In another aspect, the present invention provides a photovoltaic array comprising
The invention is further directed to a method comprising
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
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 >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
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
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
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
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.
Referring to
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. 3B2, 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
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
Referring to
In the embodiment depicted in
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
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
The magnified section illustrated in
Magnified sections found in
In the embodiment depicted in
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
Numerous wiring configurations can be employed in forming the photovoltaic array.
In an alternative embodiment,
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.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/US08/87893 | 12/22/2008 | WO | 00 | 10/6/2010 |
| Number | Date | Country | |
|---|---|---|---|
| 61015829 | Dec 2007 | US | |
| 61104834 | Oct 2008 | US | |
| 61104838 | Oct 2008 | US | |
| 61104841 | Oct 2008 | US |
