Abstract:
A photovoltaic connection system and junction box for maximum current output and heat dissipation properties. The junction box includes a box portion, heat dissipating portion and a printed circuit board (PCB). The PCB includes at least one heat emitting electrical components, each heat emitting electrical component having a heat sink element attached thereto for dissipating heat generated by the heat emitting electrical component. The junction box further includes at least one electrical contact electrically connected to the at least one heat emitting electrical component. The box portion is configured for receiving at least a portion of the PCB and having an opening disposed for receiving external power input wiring by electrical contact with the at least one electrical contact. The heat dissipating portion being made of a thermally conductive material covering at least a portion of the heat sink.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention is directed to a connection system for photovoltaic (PV) arrays, and more particularly to a connection box in a PV connection system with improved thermal transfer properties for higher current carrying capacity. 
       BACKGROUND OF THE INVENTION 
       [0002]    Photovoltaic (PV) modules or arrays produce electricity from solar energy. Electrical power produced by PV modules reduces the amount of energy required from non-renewable resources such as fossil fuels and nuclear energy. Significant environmental benefits are also realized from solar energy production, for example, reduction in air pollution from burning fossil fuels, reduction in water and land use from power generation plants, and reduction in the storage of waste byproducts. Solar energy produces no noise, and has few moving components. Because of their reliability, PV modules also reduce the cost of residential and commercial power to consumers. 
         [0003]    PV cells are essentially large-area semiconductor diodes. Due to the photovoltaic effect, the energy of photons is converted into electrical power within a PV cell when the PV cell is irradiated by a light source such as sunlight. PV cells are typically interconnected into solar modules that have power ranges of up to 100 watts or greater. For large PV systems, special PV modules are produced with a typical power range of up to several 100 W. A photovoltaic module is the basic element of a photovoltaic power generation system. A PV module has many solar cells interconnected in series or parallel, according to the desired voltage and current parameters. PV cells are connected and placed between a polyvinyl plate on the bottom and a tempered glass on the top. PV cells are interconnected with thin contacts on the upper side of the semiconductor material. The amount of power generated by typical crystalline modules power ranges from several W to up to 150 W/module. 
         [0004]    In the case of facade or roof systems, the photovoltaic system may be installed during construction, or added to the building after the building has been constructed. Roof systems are generally lower powered systems, e.g., 10 kW, to meet typical residential loads. Roof integrated photovoltaic systems may consist of different module types, such as crystalline and micro-perforated amorphous modules. Roof-integrated photovoltaic systems may be integrated into the roof such that the entire roof or a portion thereof is covered with photovoltaic modules, or the systems are added to the roof after roof construction has been completed. PV cells may be integrated with roof tiles. 
         [0005]    PV modules/arrays require specially designed devices adapted for interconnecting the various PV modules/arrays with each other, and with electrical power distribution systems. PV connection systems are used to accommodate serial and parallel connection of PV arrays. In addition to connection boxes, a PV connection system includes connectors that allow for speedy field installation or high-speed manufacture of made-to-length cable assemblies. Connections or connection boxes may be required to receive specialized cable terminations from PV modules/arrays, with power diodes inside for controlling current flow to the load. Thus, certain connection box configurations may generate internal heat, which must be dissipated in order to protect the internal components and external structures adjacent to the connection box. In many cases, governmental regulations and industry standards establish a maximum permissible temperature that can be attained. 
         [0006]    Therefore, there is a need for an improved connection box for dissipating heat expelled from electrical/electronic components inside of the box. 
       SUMMARY OF THE INVENTION 
       [0007]    A first aspect of the present invention includes a junction box for a photovoltaic system for maximum current output and heat dissipation properties. The junction box includes a box portion, heat dissipating portion and a printed circuit board (PCB). The PCB includes at least one heat emitting electrical component, each heat emitting electrical component having a heat sink element attached thereto for dissipating heat generated by the heat emitting electrical component. In the embodiment wherein the heat emitting electrical component is a diode, heat is generated by the restriction of the flow of electricity to one direction. The junction box further includes at least one electrical contact electrically connected to at least one heat emitting electrical component. The box portion is configured for receiving at least a portion of the PCB and having an opening disposed for receiving external power input wiring by electrical contact with at least one electrical contact. The heat dissipating portion is made of a thermally conductive material covering at least a portion of the heat sink. 
         [0008]    Another aspect of the present invention includes a photovoltaic connection system and junction box for maximum current output and heat dissipation properties. The system includes a current providing device in electrical communication with a junction box. The junction box includes a box portion, heat dissipating portion and a printed circuit board (PCB). The PCB includes at least one heat emitting electrical component, each heat emitting electrical component having a heat sink element attached thereto for dissipating heat generated by the heat emitting electrical component. The junction box further includes at least one electrical contact electrically connected to at least one heat emitting electrical component. The box portion is configured for receiving at least a portion of the PCB and having an opening disposed that receives external power input wiring by electrical contact with at least one electrical contact. The heat dissipating portion is made of a thermally conductive material covering at least a portion of the heat sink. 
         [0009]    An advantage of an embodiment of the present invention is improved heat dissipation from the components within the junction box. 
         [0010]    Another advantage of an embodiment of the present invention is that a plurality of PV components may be connected to a single junction box. 
         [0011]    Still another advantage of an embodiment of the present invention is that additional components, components having increased heat emission and/or PV components having increased current capacity may be utilized within the junction box. 
         [0012]    Still another advantage of an embodiment of the present invention is that the system is easily fabricated and allows additional environmental protection for the electrical components present in the junction. 
         [0013]    Still another advantage of an embodiment of the present invention is that the system of the present invention may utilized cooling system, such as liquid (e.g., water) cooled heat exchangers. 
         [0014]    Other features and advantages of the present invention will be apparent from the following more detailed description of the preferred embodiment, taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]      FIG. 1  shows a top perspective view of a junction box according to an embodiment of the present invention. 
           [0016]      FIG. 2A  shows a perspective top view of a printed circuit board and circuitry according to an embodiment of the present invention. 
           [0017]      FIG. 2B  shows a perspective bottom view of a printed circuit board and circuitry according to an embodiment of the present invention. 
           [0018]      FIG. 3  shows a top perspective view of a junction box according to an alternate embodiment of the present invention. 
           [0019]      FIG. 4  shows a cutaway cross-sectional view of a junction box according to the embodiment of  FIG. 3  of the present invention. 
           [0020]      FIG. 5  shows a top perspective view of a junction box according to an alternate embodiment of the present invention. 
       
    
    
       [0021]    Wherever possible, the same reference numbers are used throughout the drawings to refer to the same or like parts. 
       DETAILED DESCRIPTION OF THE INVENTION 
       [0022]    The present invention is directed to a junction box for interconnection of solar cell arrays having heat dissipation structures for dissipating heat emitted from electrical components. The heat dissipation structures conduct the heat from inside the junction box and emits the heat to the surrounding environment. 
         [0023]      FIG. 1  includes junction box  100  according to an embodiment of the present invention. Junction box  100  includes a box portion  101  and a heat dissipating portion  103 . Box portion  101  includes a cover  102  and non-electrically conductive case  104 . The junction box  100  and associated cover portion  102  can be constructed of a substantially rigid, electrically insulating material suitable to receive the printed circuit board  201  (see e.g.,  FIG. 2 ), such as an ABS plastic or other suitable material. The junction box  100 , cover  102  and case  104  preferably has enhanced thermal conductivity. The junction box  100  further includes wire leads  105 . Wire leads  105  may be any wire, such as PV-type wire, cable or other electrically conductive device that allows electrical power to be brought to or from the junction box  100 . Heat dissipating portion  103  further includes fins  107  that are preferably fabricated from a thermally conductive material, such as a polymeric or other non-electrically conductive thermally conductive material. Fins  107  may be arranged in any suitable manner that provides surface area available to the atmosphere for dissipation of heat. Fins  107  provide an electrical insulation barrier between  207  and  303 . Thermally conductive grease or gel may be applied between  107  and  303  to improve thermal transfer rate. 
         [0024]      FIGS. 2A and 2B  show a junction box  100  according to an embodiment of the present invention with the cover  102  and the case  104  removed.  FIG. 2A  shows a perspective top view of the printed circuit board (PCB)  201  and  FIG. 2B  shows a perspective bottom view of the PCB  201 . Referring to  FIGS. 2A and 2B , wire leads  105  are attached to a PCB  201 . The PCB  201  includes a number of spring clips or contacts  203  and heat emitting electrical devices  205 , such as diodes, mounted thereon. The contacts  203  are preferably spring clips that secured to the PCB  201  with a solder connection to receive external power input wiring (not shown), such as wiring from a solar cell or solar circuitry. The contacts  203  may be arranged in any suitable manner that permits the connection of power input wiring. In addition, the heat emitting electrical devices  205  include a heat sink  207  in contact with the heat emitting electrical device  205 . The heat sink  207  may be any thermally conductive material, which may or may not be electrically conductive, that is capable of transporting thermal energy (i.e., heat) away from the heat emitting electrical device  205 . Any number of heat emitting electrical devices  205  and/or contacts  203  may be mounted on the PCB  201  and depends on the desired functionality and/or the size of the junction box  100 . For example, a junction box  100  with two positions for connecting external input circuitry would have a PCB  201  with two contacts  203  mounted thereon. One embodiment of the present invention includes a PCB  201  having diode heat emitting electrical devices  205  with integral heat sinks  207  as part of the cathodes to help dissipate heat within the junction box  100 . The PCB  201  may be mounted in junction box  100  in any suitable manner including, but not limited to, insertion of mounting posts, overmolding the PCB  201  or a portion thereof with casing material, or applying adhesives or other adherents to the PCB  201  and/or the case  104 . 
         [0025]    The heat emitting electrical device  205  for use with the present invention may include TO-220 packaged diodes. The TO-220 packaged diodes preferably contain heat sinks  207 , such as heat sinks  207  fabricated from copper, that assist with dissipating heat and help to meet the temperature standard of IEC 61215 Edition 2 or other suitable industry standard or specification. The present invention may also use ITO-220AC diodes that have plastic covered heat sinks  207  and help to dissipate any generated heat to meet the IEC 61215 Edition 2. In addition to the TO-220 diode and ITO-220AC diode, any other similar and suitable diode that can meet the IEC 61215 Edition 2 standard may be used with the present invention. 
         [0026]    As previously indicated, the junction box  100  has a pair of leads  105  for conducting power to or from connected solar cell array or circuitry (not shown). The leads  105  are attached to the PCB  201  in a conventional manner, such as solder or solderless connections. The connection of the leads  105  to the PCB  201  may be configured for bayonet-type locking engagement, threaded engagement, or any other connections known in the art. Polarization may be incorporated into the leads  105  and/or contacts  203  to ensure proper polarity of the external connections with the PCB  201 . 
         [0027]    An aperture may be provided on one side of case  104  to allow connections for incoming power conductors from the solar cell array (not shown). This aperture is typically oriented against a flat surface, such as a rooftop or rooftop-mounted array, which is sealed to the outside elements around the periphery of the case  104  and the aperture to provide environmental protection. The present invention is not limited to embodiments including apertures and may include covers, hinged openings or any other suitable structure that permits access to contacts  203 . 
         [0028]    In one embodiment, as shown in  FIG. 2A , four contacts  203  are arranged across one edge of the PCB  201 . The contacts  203  are spring clips preferably secured to the PCB  201  with a solderless connection. Heat emitting electrical devices  205  are attached to the PCB  201  by wire connections  209  adjacent to the contacts  203 , preferably on an opposite surface of the PCB  201 . Wire connections  209  may be leads, printed circuits, wires, solder, solderless, combinations thereof or any other electrical connection between the contacts  203  and the heat emitting electrical devices  205 . The wiring between the contacts  203  and the heat emitting electrical devices  205  may be any suitable wiring configuration that connects power inputs to leads  105  and may include additional electrical devices known in the art to provide desired circuit functionality. The heat emitting electrical devices  205  are fastened to heat sinks  207  and are in thermal communication therewith. The heat sinks  207  may be constructed of copper, aluminum, or other thermally conductive material. Heat is conducted from the PCB  201  components including contacts  203  and heat emitting electrical devices  205 , and other electrical and electronic components to the heat dissipating portion  103  through heat sinks  207 . Heat dissipating portion  103  dissipates the heat from the heat sink  207  to the external environment. 
         [0029]      FIG. 3  shows an alternate embodiment of the present invention, including a box portion  101  and a heat dissipating portion  103  with the cover portion  102  removed. The PCB  201 , contacts  203 , heat emitting electrical devices  205 , wire connections  209 , fins  107 , case  104  and leads  105  are configured substantially as shown and described with respect to  FIGS. 1 and 2 , above. However,  FIG. 3  further includes secondary fins  301  arranged in the heat dissipating portion  103  of junction box  100 . 
         [0030]      FIG. 4  shows a cutaway sectional view of the junction box  100  show and described above with respect to  FIG. 3  with the cover portion  102  installed. The PCB  201  includes heat emitting electrical device  205  mounted to PCB  201  and contacts  203  by wire connections  209 . The heat emitting electrical device  205  is in contact with heat sink  207 . The heat sink  207 , heat emitting electrical device  205  and a portion of PCB  201  is overmolded by thermally conductive material forming fin  107 . The fin  107  is further encased with a secondary heat sink  303 . The secondary heat sink  303  may be constructed of copper, aluminum, or other thermally conductive material. The secondary fins  301  are attached to the heat dissipating portion  103  of the junction box  100  on the secondary heat sink  303 . Secondary fins  301  may be fabricated from any suitable thermally conductive material including, but not limited to, copper, aluminum, polymer, or other thermally conductive material. 
         [0031]      FIG. 5  shows another embodiment of the present invention, including a box portion  101  and a heat dissipating portion  103 , wherein the components are fabricated as a unitary construction. In addition, the box portion  101  and heat dissipating portion  103  may be fabricated separately and joined together in any conventional manner. The PCB  201 , contacts  203 , heat emitting electrical devices  205 , wire connections  209 , fins  107 , case  104  and leads  105  are configured substantially as shown and described with respect to  FIGS. 1 and 2 , above. However,  FIG. 5  includes fins  107  fabricated as a polymeric overmolding of the PCB  201  during fabrication of the case  104 . In this embodiment of the invention, the fins  107  may be incorporated in case  104  to provide a thermally conductive case  104  having fins  107 , which more efficiently dissipate heat to the environment. 
         [0032]    While the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.