Patent Publication Number: US-2012037202-A1

Title: Cord plate for photovoltaic module

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Patent Application No. 61/373,703, filed Aug. 13, 2010, which is incorporated herein by reference in its entirety. 
    
    
     FIELD OF THE INVENTION 
     Embodiments of the present invention generally relate to cord plates for photovoltaic modules and methods for manufacturing photovoltaic modules. 
     BACKGROUND OF THE INVENTION 
     A cord plate attaches to a photovoltaic module and permits the module to be electrically connected to other modules in a photovoltaic array. The cord plate serves as a junction box and includes access holes for electrical connections. If these access holes are not adequately sealed, moisture may enter the module&#39;s electrical connections and reduce performance or cause failure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a bottom perspective view of a photovoltaic module. 
         FIG. 2  is an exploded view of a photovoltaic module. 
         FIG. 3  is a top perspective view of a cord plate. 
         FIG. 4  is a bottom perspective view of a cord plate. 
         FIG. 5A  is a perspective view of a cap for an inner cavity of a cord plate. 
         FIG. 5B  is a perspective view of a cap for an inner cavity of a cord plate. 
         FIG. 6  is a perspective view of a cord plate and an adhesive layer. 
         FIG. 7  is a cross sectional side view of a cord plate filling with sealant. 
         FIG. 8  is a cross sectional side view of a cord plate filling with sealant. 
         FIG. 9  is a cross sectional side view of a cord plate filling with sealant. 
         FIG. 10  is a cross sectional side view of a cord plate filling with sealant. 
         FIG. 11  is a cross sectional side view of a cord plate filling with sealant. 
         FIG. 12  is a flow chart of a method for filling a cord plate with sealant. 
         FIG. 13  is a flow chart of a method for filling a cord plate with sealant. 
         FIG. 14  is a perspective view of a cap for an inner cavity of a cord plate. 
         FIG. 15  is a cross sectional side view of a cord plate filling with sealant. 
         FIG. 16  is a cross sectional side view of a cord plate filling with sealant. 
         FIG. 17  is a cross sectional side view of a cord plate filling with sealant. 
         FIG. 18  is a cross sectional side view of a cord plate filling with sealant. 
         FIG. 19  is a flow chart of a method for filling a cord plate with a first sealant and a second sealant. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The problem of moisture entering a photovoltaic module through the cord plate is solved by creating an improved cord plate with an electrical connection compartment configured to receive a flowable sealant. Manufacturing a waterproof cord plate is critical to producing a saleable module. For example, to achieve Underwriters Laboratories&#39; (UL) certification, the module must pass a wet high potential (hipot) test where the module is submerged in water. The module must also pass a wet test where a jet of water is sprayed at the electrical connections and outer surfaces. Since the junction box houses several electrical connections, the junction box is often targeted by the water jet. To ensure passage of these certification tests, an improved cord plate has been invented and is described herein. 
     In one aspect, a cord plate for a photovoltaic module may include a bottom surface and an inner cavity. The inner cavity may include a first partition separating a first chamber from a second chamber, a second partition separating the second chamber from a third chamber, a first passage extending from the first chamber to the bottom surface, a second passage extending from the second chamber to the bottom surface, and a third passage extending from the third chamber to the bottom surface. The cord plate may also include first conductor housing connected to the first chamber and a second conductor housing connected to the second chamber. The first conductor housing may include a first filling hole. Similarly, the second conductor housing may include a second filling hole. The inner cavity may include a first access hole extending from the first chamber to the bottom surface and a second access hole extending from the third chamber to the bottom surface. The cord plate may further include a cap configured to attach atop the inner cavity, and the cap may have a vent hole. The cap may also include a first weep hole and a second weep hole. 
     In another aspect, a method for manufacturing a photovoltaic module may include providing a photovoltaic module including a cover plate and positioning a bottom surface of a cord plate proximate to a hole in the cover plate. The cord plate may include an inner cavity extending to the bottom surface. The method may include filling the inner cavity with a flowable sealant wherein the sealant flows from the inner cavity to the hole in the cover plate. The method may also include applying an adhesive layer between the cover plate and the cord plate, wherein the adhesive layer comprises an opening aligned with the hole in the cover plate. In addition, the method may include inserting a first conductor into the inner cavity through a first opening in the cord plate. Similarly, the method may include inserting a second conductor into the inner cavity through a second opening in the cord plate. The inner cavity may include a first filling hole. Similarly, the inner cavity may include a second filling hole. The inner cavity may include a vent hole. The inner cavity may include a plurality of chambers interconnected to form a filling pathway extending from the first filling hole to the vent hole. In particular, the inner cavity may include a first partition separating a first chamber from a second chamber, a second partition separating the second chamber from a third chamber, a first passage extending from the first chamber to the bottom surface, a second passage extending from the second chamber to the bottom surface, and a third passage extending from the third chamber to the bottom surface. The inner cavity may include a cap having a vent hole extending from the second chamber to an external surface of the cap. The cord plate may include a first conductor housing connected to the first chamber. The first conductor housing may include a first filling hole. The method may include injecting a first flowable sealant into the first filling hole. The first flowable sealant may flow from an inner surface of the first conductor housing into the first chamber. The first flowable sealant may flow from the first chamber through the first hole to the bottom surface of the cord plate. The first flowable sealant may flow from the bottom surface through the second hole to the second chamber. The first flowable sealant may flow from the second chamber through the vent hole in the cap. The cord plate may include a second conductor housing connected to the second chamber. The second conductor housing may include a second filling hole. The method may include injecting a second flowable sealant into the second filling hole. The second flowable sealant may flow from an inner surface of the second conductor housing into the third chamber. The second flowable sealant may flow from the third chamber through the third hole to the bottom surface of the cord plate. The second flowable sealant may flow from the bottom surface through the second hole to the second chamber. The second flowable sealant may flow from the second chamber through the vent hole in the cap. Alternately, a flowable sealant may be injected into the inner cavity through the vent hole. 
     As shown in  FIG. 1 , a photovoltaic module  100  may include a cord plate  105 . The cord plate  105  may serve as a junction box. The cord plate  105  may receive one or more electrical wires (e.g.  115 ,  120 ) and connect the module  100  to other electrical devices or modules. In particular, a first electrical wire  120  and a second electrical wire  115  may be connected to the module  100  through the cord plate  105 . The cord plate  105  may be constructed from polycarbonate, plastic, resin, rubber, or any other suitable material. During installation, the cord plate  105  may be affixed to a cover plate  110  of the module  100 , and an adhesive layer  210  may be inserted between the cord plate  105  and cover plate  110 . Once electrical connections have been made, a flowable sealant may be injected into voids within the cord plate  105  to restrict moisture from accessing the electrical connections and internal surfaces of the module  100 . 
     As shown in  FIG. 2 , an adhesive layer  210  may be inserted between the cord plate  105  and a cover plate  110  during installation. The adhesive layer  205  may be any suitable adhesive such as acrylic foam tape. In particular, 3M VHB Acrylic Foam Tape (product number 5952) or 3M FAST Acrylic Foam Tape may be used. Alternately, the adhesive layer  210  may be a liquid-based adhesive such as silicone, polyurethane, epoxy, or any other suitable liquid adhesive. Before the adhesive layer  210  is inserted between the cord plate  105  and cover plate  110 , one or more contacting surfaces may be primed or otherwise treated to improve adhesion. For example, isopropyl alcohol may be applied to the surfaces to remove contamination. Next, a bottom surface  430  of the cord plate  105  may be flame treated to improve adhesion. Alternately, a liquid primer may be employed to prepare the mating surfaces for joining. 
     The cover plate  110  serves as a protective cover for the rear side of the module  100 . The cover plate  110  may include a transparent protective material such as borosilicate glass, soda lime glass, or polycarbonate. Alternately, the cover plate  110  may be a non-transparent material such as Coveme&#39;s APYE or 3M&#39;s polymer back sheet. As shown in  FIG. 2 , the cover plate  110  may contain a hole  215  which allows a first lead  220  and a second lead  225  to reach an outer surface of the module  100 . The first lead  220  may be a positive lead and the second lead  225  may be a negative lead. During assembly of the module  100 , the first lead  220  may be attached to the first electrical wire  120 . Similarly, the, second lead  225  may be attached to the second electrical wire  115 . These electrical connections may be secured by soldering, brazing, spot welding, wire nuts, or any other suitable joining technique. 
     The cord plate  105  may include a top surface  365  and a bottom surface  430 . As shown in  FIG. 4 , the bottom surface  430  of the cord plate  105  may be substantially flat to improve mating with the adhesive layer  210  and cover plate  105 . The bottom surface  430  may include a first and a second access hole ( 420 ,  425 ). A first access hole  420  may permit access to the first lead  220  on the module  100 , thereby exposing the first lead  220  and permitting the first conductor  120  to be joined to the first lead  220 . Similarly, a second access  425  hole may expose a second lead  225  on the module  100 , thereby permitting it to be joined to the second conductor  115 . 
     As shown in  FIG. 3 , the top surface  365  of the cord plate  105  may include an inner cavity  350  positioned near the center of the cord plate  105 . The inner cavity  350  may include two partitions ( 355 ,  360 ) that effectively divide the inner cavity  350  into three chambers ( 305 ,  310 ,  315 ). For example, a first partition  355  may separate a first chamber  305  from a second chamber  310 , and a second partition  360  may separate a second chamber  310  from a third chamber  315 . The first and second partitions ( 355 ,  360 ) may be located within the inner cavity  350  as shown in  FIGS. 3 and 6 , or the partitions ( 355 ,  360 ) may be located within the cap as shown in  FIG. 5B . Although the inner cavity  350  is depicted as a long slender cavity, this is not limiting. For example, the inner cavity  350  may be square, round, or any other suitable shape. 
     The inner cavity  350  may accommodate a plurality of bypass diodes connected in parallel to solar cells. If reverse biasing of a cell occurs due to a mismatch in short-circuit current between series connected cells, the bypass diode may provide an alternate current path around the reverse biased cell. As a result, the bypass diode protects cells from being damaged when the module  100  is partially shaded, has a broken cell, or experiences a cell string failure. 
     The cord plate  105  may include a plurality of holes extending from the inner cavity  350  to a bottom surface  430 . For example, the cord plate  105  may have a first passage  405  extending from the first chamber  305  to the bottom surface  430 . Similarly, the cord plate  105  may have a second passage  410  extending from the second chamber  310  to the bottom surface  430  and a third passage  415  extending from the third chamber  315  to the bottom surface  430 . The first, second, and third passages may have any suitable shape or size that permits flowable sealant to pass through. To improve flow of sealant through the passages ( 405 ,  410 ,  415 ), and thereby decrease required injection pressure, the inlets and outlets of the passages may contain radial chamfers. 
     As shown in  FIG. 3 , the cord plate  105  may include one or more conductor housings protruding from the top surface  365 . The conductor housings ( 330 ,  335 ) may be configured to receive and secure conductors. For example, a first conductor housing  335  may receive a first conductor  120 , and a second conductor housing  330  may receive a second conductor  115 . Once a conductor (e.g.  115 ,  120 ) is inserted into a housing, the inner cavity may provide access to an end of the conductor and thereby enable formation of an electrical connection. For example, an end of the first conductor  120  may be joined to the first lead  220  of the module  100 . As mentioned above, these electrical connections may be formed by soldering, brazing, spot welding, wire nuts, or any other suitable joining technique. 
     The conductor housings ( 330 ,  335 ) may be integral to the cord plate. Alternately, the housings may be separate components fastened to a surface of the cord plate  105 . The conductors may fit snugly into an inner surface of each housing. Also, the housings may contain retention features that prevent the conductors from being withdrawn from the housing. For example, inward facing barbs may be included on the inner surface of the housing. The barbs may allow the wire to be easily inserted into the housing but, if an attempt is made to withdraw the wire, the barbs may penetrate the wire sheath and resist withdrawal. 
     As shown in  FIG. 6 , the adhesive layer  210  may contain a plurality of holes. A first hole  605  may permit access to the first lead  220  on the module  100 , thereby allowing the first conductor  120  to be joined to the first lead  220 . Similarly, a second hole  615  may expose a second lead  225  on the module  100 . In previous modules, the adhesive layer  210  covered the hole  215  in the cover plate  110 , thereby restricting flowable sealant from accessing the hole  215 . But the hole  215  in the cover plate  110  provides access to the internal surfaces of the module  100 , and it is desirable to protect those internal surfaces. Therefore, a third hole  610  has been added to the adhesive layer  210  which provides access to the hole  215  in the cover plate  110 . As a result of the third hole  610  in the adhesive layer  210 , flowable sealant now enters the hole  215  in the cover plate  110  and protects the exposed internal surfaces of the module  100 . 
       FIG. 5A  shows a top perspective view of a cap  505  for the inner cavity  350 , and  FIG. 5B  shows a bottom perspective view of the cap  505 . The cap  505  may be removably attached to the inner cavity  350 . The cap  505  may be attached to the inner cavity  350 , thereby preventing moisture or debris from entering the inner cavity  350 . The cap  505  may include one or more vent holes  510  which permit air and excess sealant to pass through. The cap  505  may also include one or more weep holes (e.g.  1405 ,  1410 ), as shown in  FIG. 14 , which permit air and excess sealant to pass through. A watertight seal may be formed between the cap  505  and the inner cavity  350 . For example, the cap  505  or cavity  350  may include a rubber seal, o-ring, or any other suitable watertight seal. 
     After the conductors (e.g.  115 ,  120 ) are adequately connected and secured, the cord plate  105  may be filled with a flowable sealant to keep moisture from penetrating internal surfaces of the photovoltaic module  100 .  FIGS. 7-11  show cross sectional views of cord plates affixed to modules. In particular, the figures depict sequential stages of a process of injecting flowable sealant into a cord plate  105 . Two filling pathways are shown which extend from a pair of filling holes ( 320 ,  325 ) to a vent hole  510 . 
     The flowable sealant may include a silicone rubber compound such as a room temperature vulcanizing (RTV) silicone. Alternately, the flowable sealant may include any suitable sealant such as, for example, acrylic, polysulfide, butyl polymer, epoxy, or polyurethane. The flowable sealant may be a one-component, two-component, or higher-component sealant. The sealant may be heated to reduce its viscosity thereby improving flow through narrow passages. 
     The cord plate  105  may have one or more sealant injection points. In  FIG. 3 , a first injection point  325  is shown atop the first conductor housing  335 , and a second injection point  320  is shown atop the second conductor housing  330 . This is not limiting. For example, the first injection point may be located adjacent to the first chamber  305 . Alternately, the first injection point may be located at any position on the top surface  365  of the cord plate  105  so long as an access passage is provided to the first chamber  305 . Similarly, the second injection point may be located adjacent to the third chamber  315  or at any position on the top surface  365  of the cord plate  105 .  FIG. 7  depicts a first stage in a filling process. Flowable sealant is injected into the first injection point  325  atop the first conductor housing  335 . In the cross-sectional view, an annular clearance volume  705  is visible between an outer surface  710  of the first conductor  120  and the inner surface  715  of the first conductor housing  335 . As shown in  FIG. 8 , the annular clearance volume  705  provides a pathway for flowable sealant to reach the first chamber  305  of the inner cavity  350 . 
     Once the flowable sealant reaches the first chamber  305 , it fills the chamber as shown in  FIG. 9 . Similarly, flowable sealant that is injected into the second injection point  320  enters and fills the third chamber  315 . Once the first chamber  305  is full, the sealant passes through the first passage  405  and begins to fill the hole  215  in the cover plate  110  as shown in  FIG. 10 . Similarly, sealant passes from the third chamber  315  to the hole  215  in the in cover plate  110  through the third passage  415  where it covers the internal surfaces of the module  100 . Once the hole  215  in the cover plate is filled with sealant, the sealant flows through the second passage  410  into the second chamber  310  as shown in  FIG. 11 . The vent hole  510  in the cap  505  allows displaced air to be evacuated from the inner cavity  350  as it fills with sealant. Excess sealant may also be forced out of the vent hole  510  and can be wiped off to produce a more aesthetically appealing installation. 
     The first and second conductor housings ( 330 ,  335 ) may each contain a barrier seal to prevent sealant from oozing out. For example, the second conductor housing  330  may contain a first barrier seal disposed between an inner surface  340  of the second conductor housing  330  and an outer surface of the second conductor  115 . When the sealant is injected into the second injection point  320 , it not only travels toward the inner cavity  350 , but also travels toward an end  370  of the housing  330 . If no barrier seal is present, the sealant will ooze from the second conductor housing  330 . This may be undesirable, because the installer may need to remove the excess sealant and installation time increases. Thus, a barrier seal may be desirable. 
     Although  FIGS. 7-11  depict the filling process occurring in a particular direction, this is not limiting. For example, the filling process may occur as shown in  FIG. 15-18  using a cap  505  as shown in  FIG. 14 . The filling process may utilize two sealant materials. A first flowable sealant may be introduced through the vent hole  510  as shown in  FIG. 15 , wherein the vent hole  510  serves as a filling hole. The first flowable sealant may then fill the second chamber  310 . Once the second chamber  310  is full, the sealant may pass through the second passage  410  and begin to fill the hole  215  in the cover plate  110  as shown in  FIG. 16 . A second flowable sealant may be injected into the first injection point  325  atop the first conductor housing  335  as shown in  FIG. 17 . The annular clearance volume  705  provides a pathway for second flowable sealant to reach the first chamber  305  of the inner cavity  350 . Similarly, a second flowable sealant may be injected into the second injection point  320  atop the second conductor housing  330  where it then travels to the third chamber  315  of the inner cavity  350 . The second flowable sealant may fill the first cavity and exit through a first weep hole  1405  as shown in  FIGS. 14 and 18 . Similarly, the second flowable sealant may fill the second cavity and exit through a second weep hole  1410  as shown in  FIGS. 14 and 18 . Excess sealant that is forced out of the weep holes ( 1405 ,  1410 ) can be wiped off to produce a more aesthetically appealing installation. Although  FIGS. 15-18  show the second flowable sealant being injected in a particular direction, this is not limiting. For instance, the second flowable sealant may be injected through the first weep hole  1405  and may exit the first chamber  305  through the annular volume  705 . 
     The properties of the first sealant material may be different than the properties of the second sealant material. In particular, properties such as adhesion, moisture permeability, viscosity, and dielectric strength may differ. This approach allows the first sealant material to be tailored for sealing the cover plate hole and allows the second sealant material to be tailored for sealing the wire ports. 
     Details of one or more embodiments are set forth in the accompanying drawings and description. Other features, objects, and advantages will be apparent from the description, drawings, and claims. Although a number of embodiments of the invention have been described, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. In particular, steps depicted in figures may be executed in orders differing from the orders depicted. For example, steps may be performed concurrently or in alternate orders from those depicted. It should also be understood that the appended drawings are not necessarily to scale, presenting a somewhat simplified representation of various features and basic principles of the invention.