Abstract:
A photovoltaic junction box that comprises a housing that has at least first and second sides and the second side has at least one heat dissipating component. A conductor plate is received in the housing. The conductor plate supports at least one heat emitting component and at least one heat conducting component corresponding to the heat dissipating component of the housing. A mounting flange extends from the second side of the housing. At least a first gap is located between the second side of the housing and the mounting flange. The gap creates an air channel that allows air to flow between the housing and the mounting flange.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a junction box for photovoltaic applications. More specifically, the junction box includes heat dissipating components for more effective heat dissipation at higher currents. 
     BACKGROUND OF THE INVENTION 
     Photovoltaic modules, such as solar panels, convert solar energy to electricity. The cells within a module are typically connected in series by means of copper ribbons. The copper ribbons are terminated in a specially designed junction box where the current is collected and transferred to a pair of short cables that end in connectors. An array of photovoltaic modules is typically interconnected using the cables terminated in the junction boxes. 
     The cells of photovoltaic modules are connected in series so that the sum voltages of the cells is at a useable voltage level. When exposed to light, photovoltaic cells generate electricity. When shaded, however, photovoltaic cells not only cease to produce electricity, but also become poor conductors of electricity. Because the cells are connected in series, a single shaded cell creates a bottleneck for all the other cells. When that happens, the shaded cell turns into a resistance heater, which destroys the power of its neighbors. The shaded cell can also heat up to such an extent that it can destroy the module, expose dangerous voltage carrying conductors and in some cases cause a fire. Thus a single shaded photovoltaic cell may render a PV installation useless. 
     To avoid this, bridging diodes are used. The bridging diode is wired in parallel to the string of cells in such a way that when the cells all behave normally, the diode is in reverse bias condition, no current flows over the diode. If one or more cells become shaded, the shaded cells produce a voltage drop instead of creating a voltage increase, so that the bias voltage over the diode changes polarity and the diode is now in forward mode, conducting the current. In doing this, the diode effectively bridges the shaded cells and prevents catastrophic failure as well as a means to conduct the current of the un-shaded cells and therefore still generating power. Those bypass diodes are typically built into the junction box. The forward voltage drop over the diodes, however, generates heat within the diodes which must be dissipated to prevent the diode from overheating. If the heat generated is not properly dissipated, the diode will reach a thermal runaway status and be destroyed in the process. In this way, the failure of a single diode may render an entire string of panels useless. The heat generated by the diodes within a junction box may not be conducted to the module, since this may cause a hot spot and contribute to a thermal runaway situation of the photovoltaic cells in close proximation. The junction boxes also must meet certain industry standard requirements regarding heat and temperature. 
     Therefore, a need exists for a photovoltaic junction box that can accommodate higher currents and more effectively dissipate heat while also meeting the temperature requirements of industry standards. 
     SUMMARY OF THE INVENTION 
     Accordingly, the present invention provides a photovoltaic junction box that comprises a housing that has at least first and second sides and the second side has at least one heat dissipating component. A conductor plate is received in the housing. The conductor plate supports at least one heat emitting component and at least one heat conducting component corresponding to the heat dissipating component of the housing. A mounting flange extends from the second side of the housing. At least a first gap is located between the second side of the housing and the mounting flange. The gap creates an air channel that allows air to flow between the housing and the mounting flange. 
     The present invention also provides a photovoltaic junction box that comprises a housing that has at least first and second sides and each of the first and second sides has a plurality of heat dissipating components, respectively. A conductor plate is received in the housing. The conductor plate supports at least one heat emitting component and a plurality of heat conducting components corresponding to the heat dissipating components of the second side of the housing. A mounting flange extends from the second side of the housing. At least one gap is located between the second side of the housing and the mounting flange. The gap creates an air channel allowing air to flow between the housing and the mounting flange. The housing may be made of an electrically insulating material. 
     The present invention further provides a photovoltaic junction box that comprises a housing that has at least first and second sides and first and second heat dissipating means. A conductor plate is received in the housing. The conductor plate supports at least one heat emitting component. A mounting flange extends from the second side of the housing. An air channel means allows air to flow between the housing and the mounting flange. 
     Other objects, advantages and salient features of the invention will become apparent from the following detailed description, which, taken in conjunction with the annexed drawings, discloses a preferred embodiment of the present invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A more complete appreciation of the invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein: 
         FIG. 1  is a first side perspective view of a junction box according to an exemplary embodiment of the present invention; 
         FIG. 2  is a second side perspective view of the junction box illustrated in  FIG. 1 ; 
         FIG. 3  is a side elevational view of the junction box illustrated in  FIG. 1 ; 
         FIG. 4  is a perspective view of a conductor plate of the junction box illustrated in  FIG. 1 ; and 
         FIG. 5  is partial perspective view of the junction box illustrated in  FIG. 1 , showing a portion of the housing removed. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to  FIGS. 1-5 , a photovoltaic junction box  100  according to an exemplary embodiment of the invention is preferably used in a solar connection system, such as interconnection of a series of solar modules. The junction box  100  may be, for example, mounted to a solar module, such as a solar panel, to collect solar energy therefrom and eventually convert that energy to electrical power downstream. The junction box  100  has an improved thermal conductivity design that provides greater heat dissipation and allows for higher current application. 
     The junction box  100  generally includes a heat dissipating housing  110  that receives a conductor plate  400  ( FIG. 4 ) electrically connectable to a solar module (not shown). The housing  110  may be overmolded on the conductor plate  400  to provide a complete seal and absence of voids that invite condensation issues. Alternatively, the housing  110  may be formed by attaching two molded housing halves and filling the void with a potting agent. The housing  110  is generally flat with first and second opposite sides  120  and  220 . Heat dissipating components  130  and  230  are preferably provided on both sides  120  and  220 , respectively. The heat dissipating components  130  on the first housing side  120  may be one or more elongated fins  132  extending generally across the housing  110 . Alternatively, other heat dissipating components may be used such as finger heat exchangers. The heat dissipating components  230  on the opposite or second side  220  of the housing  110  may be one or more outwardly extending fingers  232 . Other heat dissipating components may be used, such as fins. As best seen in  FIG. 3 , the fins  132  and the fingers  232  extend from the housing  110  in opposite directions to one another. The fins  132  and the fingers  232  dissipate heat by convection to the ambient air. The efficiency of the convection process is greatly improved by the increased surface area and the special shape and staggered arrangement of the fin and finger heat exchangers that force the flow of air in such a way that the flow pattern of the air completely engulfs the heat exchanger surface. To further facilitate the dissipation of heat, the housing  110  may be formed of an electrically insulating material, such as any thermoplastic polymer. 
     As best seen in  FIG. 2 , a mounting flange  240  extends from the second side  220  of the housing  110 . The mounting flange  240  has a generally C-shape and includes a substantially flat mounting surface  242  configured to mount to a module. The mounting flange  240  is spaced from the housing second side  220  by a plurality of extensions including a main extension  244  and first and second secondary extensions  246 . Although a plurality of extensions are preferred, one extension may be used to connect the flange  240  to the housing  110 . The main extension  244  is preferably coupled to a middle portion of the mounting flange  240  and the second extensions  246  are preferably coupled to the opposite ends of the mounting flange  240 , as best seen in  FIG. 2 . One or more gaps  250  are formed between the mounting flange  240  and the housing  110  to create air flow channels for further cooling the housing  110 . That is, because the mounting flange  240  is spaced from the housing  110  by the extensions  244  and  246 , the housing  110  is spaced from the module on which the junction box  110  is mounted, thereby allowing air to flow between the housing  110  and the module. That air flow provides cooling against the heat emitting from the diodes. 
     One or more termination compartments  260  may be provided in the mounting flange  240  and the main extension  244  for receiving connection tabs  410 , respectively, of the conductor plate  400 . The compartments  260  are open at the mounting surface  242  of the mounting flange  240 , thereby exposing the ends of the connection tabs  410 . During the installation of the junction box, the connection tabs  410  are electrically connected to the bus bars of the photovoltaic module by welding, soldering or other mechanical means on which the junction box  100  is mounted. 
     The housing  110  may also include first and second ports  270  and  272  for accommodating first and second terminals  412  and  414  of the conductor plate  400 . The first and second terminals  412  and  414  of the conductor plate  400  are designed to connect to first and second connectors  420  and  422 . For example, leads of the first and second connectors  420  and  422  may be crimped to the first and second terminals  412  and  414 , as seen in  FIG. 4 . The first and second connectors  420  and  422  are preferably male and female connectors (or vice versa), respectively, that allow series connection of modules via their junction boxes. 
     As best seen in  FIG. 4 , the conductor plate  400  has a support surface  402  that supports heat emitting components  404 , such as diodes, integrated circuit containing semi-conductors or other semi-conductors. The diodes  404  are mechanically and electrically coupled to the support surface  402  of the conductor plate  400 . For example, conductive leads of the diodes  404  may be soldered to the surface  404  of the plate  400 . The conductor plate  400  may start out as a single plate when the diodes  404  are soldered in place; then bridges in the plates may be removed (cut) resulting in single sections for the diodes  404  of the conductor plate  400  that are electrically and thermally separated.  FIG. 4  shows the conductor plate  400  with the bridges already removed. 
     Heat conducting components  430  extend substantially perpendicularly from the support surface  402  of the conductor plate  400 . The heat conducting components  430  may be conducting fingers or fins cutout from the conductor plate  400 , as seen in  FIG. 4 . The heat conducting fingers  430  are preferably arranged in groups around the diodes  404 . The conducting fingers  430  correspond to the heat dissipating fingers  232  of the housing  110 , as best seen in  FIG. 5 . That is, each heat dissipating finger  232  of the housing  110  covers an individual conducting finger  430  of the conductor plate  400 . The heat conducting fingers  430  of the conductor plate  400  act to transfer the heat emitted from the diodes  404  to the fingers  232  of the housing  110  for dissipating the heat. 
     Heat dissipation of the junction box  100  is thus accomplished as described above using at least one of or a combination of the fins  132  on the housing  110 , the fingers  232  on the housing  110 , the heat conducting fingers  430  of the conductor plate, the air channels  250  between the mounting flange  240  and the housing  110 , and the thermal conductive material of the housing  110 . Alternative heat dissipation features may be employed, such as fins. 
     While a particular embodiment has been chosen to illustrate the invention, it will be understood by those skilled in the art that various changes and modifications can be made therein without departing from the scope of the invention as defined in the appended claims.