AU608701B2 - Integral frame and junction box for a photovoltaic module - Google Patents

Description

S O O 2 7. To: Commissioner of Patents File: 89 1 039 AUST A.l PATENTS ACT 1952 COMPLETE SPECIFICATION

(ORIGINAL)

FOR OFFICE USE Short Title: Int. Cl: Application Number: Lodged: '01 P/00oo/o011 Form

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1I Complete Specification-Lodged: Accepted: Lapsed: Published: Priority: [ish cocuLnt contains t,, anindjn- ade unide r Section 49 and is CoITCLl for prnig3 Related Art: TO BE COMPLETED BY APPLICANT Name of Applicant: Address of Applicant: Actual Inventor: Address for Service: WESTINGHOUSE ELECTRIC CORPORATION 1310 BEULAH ROAD,

CHURCHILL,

PITTSBURGH, PA. 15235, UNITED STATES OF AMERICA.

ROBERT BRUCE CAMPBELL RICHARD WILLIAM RUPNIK PETER MAXWELL ASSOCIATES, BLAXLAND HOUSE, 5-7 ROSS STREET, NORTH PARRAMATTA. N.S.W. 2151.

Complete Specification for the invention entitled: INTEGRAL FRAME AND JUNCTION BOX FOR A PHOTOVOLTAIC MODULE The following statement is a full description of this invention, including the best method of performing it known to me:-* SNote: The description is to be typed in double spacing, pica type face, in an area not exceeding 250 mm in depth and 160 mm in width, on tough white paper of good quality and it is to be inserted inside this form.

14599/78-L Printed by C. J. THOMPSON, Commonwealth Government Printer, Canberra in. uuMnMlsbiUNEK OF PATENTS, COMMONWEALTH OF AUSTRALIA. -la- The present invention relates to a photovoltaic module and more specifically to a junction box which is r ro formed integrally with the frame of the photovoltaic module.

5 A photovoltaic module is a device which is used to generate electrical power from sunlight. An example of a photovoltaic module is a solar panel. Typically, a °photovoltaic module utilizes a plurality of solar cells 'i mounted in a frame to convert the sun's light energy directly into usable electricity. The solar cells can be 0o 00 connected to each other in a variety of configuratio.., depending upon the needs of the system and the desigi of the solar panel and the solar cells themselves.

0: Each photovoltaic module typically has one or 15 two junction boxes for connecting it to the electrical system. These junction boxes are located on the back isurface of the photovoltaic module and cover a portion of the back surface. An example of this arrangement is found in the Model No. M55 solar panel made by Arco Solar, Inc.

In this arrangement, these junction boxes must be permanently attached to the back surface of the solar panel and environmentally sealed to maintain the electrical integrity of the solar panel. This can be a time consuming and expensive process. For example, in a module design that uses two pieces of glass, one for the superstrate and one for the substrate, a hole must be cut or drilled through the back substrate so that an electrical connection can be made. Another problem with 2 locating the junction box on the back of the panel is its vulnerability during handling and assembling. Because of its location on the back panel, the junction box serves as a convenient handle when moving the solar panel. This, however, increases the likelihood that the adhesive seal holding the junction box to the back of the panel could be accidentally broken and in turn cause the environmental and electrical integrity of the panel to be destroyed.

Another problem with locating the junction box 1 0 on the back surface of the photovoltaic module is that the Ct junction box covers a portion of the back surface. This r is particularly importa.t in a solar panel, where bifacial solar cells are used. A bifacial solar cell is one which is activated produces direct electric voltage and C, CO 15 current) by light striking either its front surface or its back surface. When bifacial solar cells are used in a photovoltaic module it is very important that the back surface of the solar cells not be covered.

t ~It is the object of this invention, to develop a photovoltaic module and junction .box having improved CV structural, electrical and environmental integrity and wherein any shading of the back surface of the module is minimized or eliminated.

*r The present invention relates to a photovoltaic module comprising a solar cell laminate for generating electricity, a plurality of frame members which support the solar cell laminate and a junction box for electrically connecting the solar cell laminate to a system, the junction box being formed integrally with at least one frame member. The frame formed by the frame members can be of any shape or size, but preferably it is rectangular.

Similarly, the frame member with which the junction box is formed integrally can be any of the frame members, but preferably it is one of the shorter frame members.

The present invention is particularly useful with photovoltaic modules utilizing bifacial solar cells where coverage of the back surface of the module must be minimized or, preferably, eliminated. By forming the

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i i 3 junction box integrally with the frame, none of the back surface of the photovoltaic mddule is covered and therefore none of the solar cells are covered. This results in an increase in the efficiency of the photovoltaic module.

The present invention is not limited to only those photovoltaic modules having bifacial solar cells, since it also improves the structural, electrical and environmental integrity of any photovoltaic module.

Another advantage of the integral junction box and frame of the present invention is the reduction in the total S°cost of the photovoltaic module since only one junction r box is used instead of two.

The removal of the junction box from the back of 9 15 the phQtovoltaic module also increases the structural, electrical and environmental integrity of the module.

Without the junction box on the back surface of the °module, it is unlikely a person handling the photovoltaic module will accidentally break the environmental seal and thereby impair the module's electrica. integrity.

.The integral frame and junction box of the present invention allows the parallel/series connections of the photovoltaic modules and their connection to the a *electrical system to be made more easily. In addition, a 25 hole no longer needs to be drilled in the back substrate 9 9 of the solar cell laminate. Instead, the electrical connection to the solar cells can be made at the edge of the solar cell laminate. It is also anticipated that the integral frame member and junction box of the present invention can reduce the overall cost of a photovoltaic module through the use of uniform standardized frame parts for all modules.

Other details, objects and advantages of the present invention will become more readily apparent from the following description of a presently preferred embodiment thereof.

In the accompanying drawings, a preferred embodiment of the present invention is illustrated, by way

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i 4 of example only, wherein: Figure 1 shows a photovoltaic module of the present invention wherein the junction box is formed integrally with the frame.

Figure 2 is a side view of a portion of the photovoltaic module of Figure 1 taken along line AA'.

Generally, the present invention provides a photovoltaic module 1 comprising a solar cell laminate 2, a frame 3 and a junction box 4 being formed integrally with frame 3 as shown in Figure 1. Preferably frame 3 is rectangular in shape and is comprised of four frame members 5. Typically frame 3 is made from a strong, lightweight material such as anodized, 204 etched aluminum, but it can be made of any material which would function as EL frame.

As shown in Figure 1, one is looking at the front side of photovoltaic module 1. There is no junction ,box located on the back surface of photovoltaic module 1.

Instead, junction box 4 is formed integrally with one 4tt frame member 5, preferably located at the top or bottom of I photovoltaic module i. By forming junction box 4 integrally with a shorter frame member, the amount of material needed for the junction box is decreased.

Soro However, junction box 4 could be formed integrally as a *44* 25 unit with any of the frame members. Junction box 4, preferably extends the entire width of photovoltaic module 1, although this is not necessary.

There is at least one first opening 6 in junction box 4 for a system connecting means to enable photovoltaic module 1 to be connected to the electrical system. Preferably, the system connecting means is a wire or cable 7 which is fed through a first opening 6 in the bottom of junction box 4 and is connected to a terminal strip 8 on terminal block 9. The wire or cable 7 may or may not be enclosed in a pipe or conduit. Preferably, first openings 6 are sized to receive cable or conduit couplings with a threaded sleeve and nut thereby forming an environmental seal at first openings 6. Usually two i i first openings 6 are activated, one for the positive connection to the system and one for the negative connection to the system. Any unused first openings 6 can be plugged, preferably with plastic plugs, to seal junction box 4 from the environment. Preferably, first openings 6 are located on the bottom of the integral junction box to prevent any covering of the front surface of the module and to provide easier access when the module is installed in a solar array.

Terminal block 9 may extend the entire length of junction box 4 but preferably it only extends partially S2 along that length. Terminal block 9 is made of a nonconducting material such as bakelite and is attached to the inside walls of integral frame member 5 and junction 15 box 4 with an adhesive.

Preferably, a portion of junction box 4 has been removed and replaced by a transparent cover 10 which is located beneath terminal strips 8 and terminal block 9.

r, Transparent cover 10 enables one to visually inspect the electrical connections on terminal block 9 from beneath the module without removing the cover. Preferably a captive rubber gasket 11 is used to environmentally seal transparent cover 10 to junction box 4 and thereby prevent entry of water and other foreign material which could harm the electrical connection. Due to its position, transparent cover 10 also has captive screws to avoid accidental loss during field installation and inspection.

Figure 2 shows a side view of a portion of photovoltaic module 1 taken along line AA' of Figure 1.

Preferably, integral frame member 5 and junction box 4 is rectangular in shape with four sides. The four sides of junction box 4 are preferably extruded as one unit or they can be assembled from four separately extruded pieces as long as they create an environmentally sealed chamber. A corner key locking arrangement shoul.d be sufficient if separately extruded pieces are used.

Preferably, terminal block 9 is shaped as shown in Figure 2. As a result, termainal strips 8 are i 6 angularly shaped to enable easier access from beneath once transparent cover 10 is removed. This configuration also enables terminal block 9 to fit snugly within the integral frame member and junction box. As shown in Figure 2, terminal block 9 has a plurality of holes 12 drilled in it just above terminal strips 8. Holes 12 permit an electrical connection to be made with solar cells 18.

Preferably an insulating insert 13, such as a high density rubber insert is placed in hole 12 to form an environmental seal and to prevent the solar cell laminate connecting means, such as conductor 14, from contacting terminal block 9. This is necessary since conductor 14 is typically not insulated and must be electrically isolated from frame 3. One end of conductor 14 is connected to a terminal strip 8 and the other end to solar cells 18.

At least one second opening 15 is provided in frame member 5 to permit an electrical connection to be made to solar cells 18. Preferably, second opening 15 is ,not in the same wall of frame member 5 as first opening 6.

Also, second opening 15 is preferably smaller than hole 12. Two perpendicular projections 16 and 17 extend from the wall of frame member 5 above and below second opening These projections along with the wall of frame member 5 form a C-shaped groove for receiving the edge of solar 25 cell laminate 2. As shown in Figure 2, solar cell laminate 2 is that portion of photovoltaic module 1 comprising solar cells 18 sandwiched between two layers of glass 19. Preferably, the layers are glass but other transparent media can be used.

The edge of solar cell laminate 2 abuts the wall of frame member 5 such that conductor 14 is located over a second opening 15. The advantage with this construction is that conductor 14 can easily emerge from the end of solar cell laminate 2 without having to drill a hole through glass 19. Preferably, there are two conductors 14, one for the positive connection to solar cells 18 and one for the negative connection to solar cells 18.

Similarly, there ere two second openings 15, one for the i i 7 positive connection and one for the negative connection.

A gasket 20, located between solar cell laminate 2 and projections 16 and 17, helps to environmentally seal solar cell laminate 2 and second opening 15. It also can serve as a cushion for solar cell laminate 2. Preferably, gasket 20 is an EPDM gasket.

Conductor 14 can be attached to terminal strip 8 by a variety of known means such as soldering, as long as a good electrical connection is made. Similarly, cable 7 can be attached to terminal strip 8 by a vari-ty of known means including screw 21. Additional terminal strips 8 can be provided on terminal block 9 to allow for additional electrical connections and circuitry, if necessary.

For example, it may be necessary due to the system 15 configuration to have a neutral terminal or some kind of protective circuitry such as a diode connected to solar cells 18. These additional terminal strips 8 provide this flexibility.

In one embodiment of the present invention, integral frame member 5 and junction box 4 is 43.18 cm x S3.175 cm x 5.08 cm (17" x 1.25" x Terminal block 9 is 12.7 cm x 2.69 cm x 4.60 cm x 1.06" x 1.81") with the top portion only being .97 cm wide. Trans- (t parent cover 10 in this embodiment is only 15.24 cm x 2.54 cm x These dimensions are provided solely as an example of the size of the integral frame member 5 and junction box 4 used with a photovoltaic module which is 43.18 cm x 101.6.cm.

While a bifacial photovoltaic module of the present invention does have an increase in the subtended area of 4% and a corresponding efficiency decrease (based on subtended area) of it has a net increase in efficiency due to eliminating the coverage of the back surface of the module by the junction box. In existing photovoltaic modules, two junction boxes and the assoriated bus connections are mounted on the back surface of the photovoltaic module, covering the backs of several of the solar cells. Typically, the sum of the areas of ii 8 these items is about 150 cm or about a 3.5% of the subtended area of the module. Covering these areas results in a decrease in the power output and efficiency.

This decrease in efficiency, however, will be greater than the area covered. A conservative estimate suggests a decrease by a factor of 1.5. For the 3.5% area covered, this results in an efficiency decrease of which is greater than the 4% loss due to the increase in the subtended area of the photovoltaic module of the present t 1 0 invention. The resulting increase in efficiency due to the uncovering of this back surface area is particularly ct r important since in many applications, the area subtended e, by a photovoltaic module is not as important as its power output. As a result, a module that produces 5.3% more ra 15 power with the same number of solar cells would be preferred to a smaller module with a lower power output.

While a presently preferred embodiment of practicing the invention has been shown and described with particularity in connection with the accompanying drawings, the invention may otherwise be embodied within ,the scope of the following claims.

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Claims (5)

1. A photovoltaic module having a solar cell laminate for generating electricity, a plurality of frame members which support the solar cell laminate and a junction box, characterized by the junction box being made integral with one of the frame members and having a terminal block made of an insulating material with an opening disposed therein aligned with an opening in the one frame member; a conductive c terminal strip disposed on said terminal block adjacent said oV opening izn the terminal block; a conductor electrically C c t connected to said solar cell laminate and said terminal strip; and an electrical insulating sealing material filling C said openings to form a seal and insulating said conductor C from said frame and a cable electrically connecting said terminal strip to a system that uses the electricity generated by said photovoltaic module.

2. The photovoltaic module of claim 1 characterized in c that the junction box has an opening in the one frame member for the cable and a seal is formed between the opening and the cable.

3. The photovoltaic module of claim 1 characterized in that the junction box has a sealed transparent cover plate to permit viewing of the terminal strip at all times without disturbing the sealed junction box.

4. The photovoltaic module of claim 1 characterized in that the cell laminate is bifacial for generating electricity from sunlight striking both surfaces of the solar cell laminate and the junction box does not cover either surface. ti SI i^- I i :11 The photovoltaic module of claim 1 characterized in that the frame members form a rectangular frame and the junction box is made integral with one of the shorter frame members.

6. A photovoltaic module substantially as hereinbefore described with-reference to the accompanying drawings. S DATED this 10th day of January, 1991. WESTINGHOUSE ELECTRIC CORPORATION t Patent Attorneys for the Applicant: C" PETER MAXWELL ASSOCIATES. r S i t 1A