Patent Publication Number: US-10777691-B2

Title: Formed photovoltaic module busbars

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 14/877,785, filed on Oct. 7, 2015, which is a continuation of U.S. patent application Ser. No. 11/543,440, filed on Oct. 3, 2006, now U.S. Pat. No. 9,184,327, issued on Nov. 10, 2015, the entire contents of which are hereby incorporated by reference herein. 
    
    
     FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     This invention was made with Government support under ZAX-4-33628-05 awarded by the United States Department of Energy under the photovoltaic (PV) Manufacturing Research and Development (R&amp;D) Program, which is administered by the National Renewable Energy Laboratory. The Government has certain rights in the invention. 
    
    
     TECHNICAL FIELD 
     This invention relates to the field of photovoltaic modules and, in particular, to busbar components for photovoltaic modules. 
     BACKGROUND 
     Photovoltaic (PV) cells provide a renewable source of electrical energy. When PV cells are combined in an array such as in a PV module, the electrical energy collected from all of the PV cells can be combined in series and parallel arrangements to provide power with a certain voltage and current. Many recent design and engineering advances have increased the efficiency and functionality of PV modules. 
     One area of development focuses on collecting the electrical energy from all of the PV cells in a PV module so that the collected electrical energy can be efficiently transferred to an electrical load connected to the PV system. For example, SunPower Corporation of San Jose, Calif., offers a highly efficient solar cell design which locates the metal contacts needed to collect and conduct electricity on the back surface of the PV cells so that cell interconnections do not block incident sunlight. 
     Another area of development relates to wiring techniques which might lower the manufacturing cost of PV module components and facilitate a better design layout of such components on the PV module.  FIG. 1  illustrates a conventional busbar  10  for a PV module. The illustrated conventional busbar  10  includes an interconnect bus  12 , a plurality of individual bus tabs  14 , and a linear terminal bus  16 . Different busbar designs may implement fewer or more bus tabs  14  than shown. The individual bus tabs  14  are typically soldered or welded to the interconnect bus  12  at corresponding solder or welding joints  18 . The linear terminal bus  16  is soldered to the interconnect bus  12  at a similar solder or welding joint  18 . The bus tabs  14  connects to electrical contacts or ribbons for each row of PV cells, and the terminal bus  16  connects the interconnect bus  12  to a junction box on the PV module. 
       FIG. 2  illustrates another conventional busbar  30  for a PV module having back contact cells. The conventional busbar  30  of  FIG. 2  is similar to the conventional busbar  10  of  FIG. 1 , except that the conventional busbar  30  does not have a terminal bus  16 . These types of conventional busbars  30  are typically used to connect adjacent rows of PV cells to one another. Other types of cell interconnects are used to connect individual PV cells to one another within the rows of PV cells. 
     Wire flattening is another conventional technology to form busbars. Wire flattening employs a bending machine to bend wire into a specified shape and then a flattening machine to flatten the shaped wire into a flattened sheet having a shape corresponding to the shaped wire. 
     Some conventional busbars suffer from several disadvantages. For example, the use of linear components in conventional busbars results in relatively long electrical path lengths and, hence, increased voltage drop between the rows of PV cells and the junction box. 
     Also, the design and layout of conventional busbars is typically limited by the availability of conductive ribbons. If multiple ribbon sizes are used, then the inventory costs of purchasing, storing, and handling the various ribbon sizes are increased. On the other hand, if only one ribbon size is used, the design and layout of the conductive paths is limited by the physical characteristics (e.g., width, thickness, etc.) of the available ribbon. 
     Conventional busbars also implement several solder or welding joints for each busbar (e.g., seven joints for the conventional busbar  30  of  FIG. 1 ). These joints are sources of potential physical failure of the busbar. The thickness of these joints also creates stress on the corresponding PV cells, which can break and become useless. For example, the joints can add extra stress on the PV cells during module manufacturing, and the PV cells can crack, which degrades cell performance. Such breakage is frequently at the edges of PV cells because the linear configuration of conventional busbars results in a portion of the conventional busbar extending beyond the edge of the typically cropped corners of the PV cells. Additionally, the cost of assembly of conventional busbars is relatively high because the fabrication process implements multiple solder or welding joints for each conventional busbar. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention is illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings. 
         FIG. 1  illustrates a conventional busbar for a photovoltaic module. 
         FIG. 2  illustrates another conventional busbar for a photovoltaic module having back contact cells. 
         FIG. 3  illustrates one embodiment of a formed busbar for a photovoltaic module. 
         FIG. 4  illustrates a more detailed embodiment of the cell connection piece of  FIG. 3 . 
         FIG. 5  illustrates a more detailed embodiment of the terminal connection piece of  FIG. 3 . 
         FIG. 6  illustrates another embodiment of a formed busbar for a photovoltaic module. 
         FIG. 7  illustrates one embodiment of a pattern of nested busbar components for photovoltaic modules. 
         FIG. 8  illustrates another embodiment of a pattern of nested busbar components for photovoltaic modules. 
         FIG. 9  illustrates one embodiment of a photovoltaic module with a plurality of formed busbars. 
         FIG. 10  illustrates one embodiment of a manufacturing pattern for a plurality of formed busbar components for photovoltaic modules. 
         FIG. 11  illustrates another embodiment of a manufacturing pattern for a plurality of formed busbar components for photovoltaic modules. 
         FIG. 12  illustrates another embodiment of a manufacturing pattern for a plurality of formed busbar components for photovoltaic modules. 
         FIG. 13  illustrates another embodiment of a manufacturing pattern for a plurality of formed busbar components for photovoltaic modules. 
         FIG. 14  illustrates another embodiment of a manufacturing pattern for a plurality of formed busbar components for photovoltaic modules. 
         FIG. 15  illustrates one embodiment of an angled terminal bus. 
         FIG. 16  illustrates another embodiment of a manufacturing pattern for a plurality of formed busbar components for photovoltaic modules. 
         FIG. 17  illustrates another embodiment of a formed cell connection piece having an expansion joint. 
         FIG. 18  illustrates one embodiment of an electrical insulator between a busbar and a back contact cell. 
         FIG. 19  illustrates a flow chart diagram of one embodiment of a fabrication method for using formed busbars to fabricate a photovoltaic module. 
     
    
    
     DETAILED DESCRIPTION 
     The following description sets forth numerous specific details such as examples of specific systems, components, methods, and so forth, in order to provide a good understanding of several embodiments of the present invention. It will be apparent to one skilled in the art, however, that at least some embodiments of the present invention may be practiced without these specific details. In other instances, well-known components or methods are not described in detail or are presented in simple block diagram format in order to avoid unnecessarily obscuring the present invention. Thus, the specific details set forth are merely exemplary. Particular implementations may vary from these exemplary details and still be contemplated to be within the spirit and scope of the present invention. 
     In general, this disclosure relates to unitarily formed busbar components for photovoltaic (PV) modules. The term “elements” is used to describe unitary features of a unitarily formed busbar component. In contrast, the present application uses the terms “pieces” and “parts” to refer to non-unitarily formed components. Thus, a conventional, non-unitarily formed busbar component has separate pieces. 
     In one embodiment, a method includes providing a sheet of conductive material, and forming a photovoltaic module busbar component from the sheet of conductive material. In some embodiments, the busbar component may be a cell connection piece having an interconnect bus and a plurality of unitarily formed bus tabs. In some embodiments, the busbar component may be a terminal bus having a nonlinear portion. Other embodiments of the method are also described. 
     In one embodiment, a cell connection piece includes an interconnect bus and a plurality of bus tabs. The plurality of bus tabs are unitarily formed with the interconnect bus and extend away from the interconnect bus. In some embodiments, the cell connection piece is used to connect to a row of PV cells. In some embodiments, the interconnect bus has a continuously variable width along a length of the interconnect bus. Alternatively, the interconnect bus may have a step-wise variable width along a length of the interconnect bus. 
     In some embodiments, the interconnect bus includes an extension, at an end of the interconnect bus, to provide a solder location to solder a terminal bus to the interconnect bus, although other types of coupling other than solder may be implemented. In some embodiments the interconnect bus includes one or more expansion joints to accommodate thermal expansion of the PV module because the PV module may have a different thermal expansion coefficient than the interconnect bus. In some embodiments, the interconnect bus includes a plurality of notches to accommodate a second plurality of bus tabs of a second cell connection piece in a fabrication process of the cell connection pieces. This implementation facilitates increased material utilization in the pattern layout when stamping the cell connection pieces. Other embodiments of the cell connection piece are also described. 
     In one embodiment, a terminal bus includes a terminal connection end, a cell connection end, and a nonlinear portion. The terminal connection end may be used to couple the terminal bus to an electrical terminal of a junction box. The cell connection end is opposite the terminal connection end and may be used to connect the terminal bus to a cell connection piece or, alternatively, directly to one or more photovoltaic cells. The nonlinear portion is between the terminal connection end and the cell connection end. Other embodiments of the terminal bus are also described. 
     In one embodiment, an apparatus includes means for coupling a photovoltaic cell of a photovoltaic module to a junction box of the photovoltaic module, and means for reducing a number of coupling joints between the photovoltaic cell and the junction box. In another embodiment, an apparatus includes means for coupling a photovoltaic cell of a photovoltaic module to a junction box of the photovoltaic module, and means for providing a curvilinear electrical pathway between the photovoltaic cell and the junction box. Other embodiments of the apparatus are also described. 
       FIG. 3  illustrates one embodiment of a formed busbar  100  for a photovoltaic (PV) module. The depicted formed busbar  100  includes two formed busbar components: a cell connection piece  102  and a terminal connection piece  104 . The cell connection piece  102  facilitates electrical connection at one or more PV cells within the PV module. One example of a cell connection piece  102  is shown and described in more detail with reference to  FIG. 4 . The terminal connection piece  104  facilitates electrical connection between the cell connection piece  102  and a junction box of the PV module. One example of the terminal connection piece  104  is shown and described in more detail with reference to  FIG. 5 . In one embodiment, a solder joint  106  may be used to couple the terminal connection piece  104  to the cell connection piece  102 . For convenience, the description provided herein refers to soldering, in many instances. However, alternative joining technologies such as welding, electrically conductive adhesives, mechanical fasteners, or other coupling technologies may be implemented. 
     In another embodiment, the cell connection piece  102  and the terminal connection piece  104  may be formed as a single, unitary piece. Forming the cell connection piece  102  and the terminal connection piece  104  as a single, unitary piece would alleviate the need for a coupling joint such as the solder joint  106 . 
       FIG. 4  illustrates a more detailed embodiment of the cell connection piece  102  of  FIG. 3 . The depicted cell connection piece  102  includes an interconnect bus  108  and multiple bus tabs  110 . In one embodiment, the cell connection piece  102  may include three bus tabs  110  for connections to each of the corresponding PV cells. Alternatively, the cell connection piece  102  may include two bus tabs  110 , or more than three bus tabs  110 , for each corresponding PV cell. 
     As depicted in  FIG. 4 , the bus tabs  110  are unitarily formed with the interconnect bus  108  such that coupling joints are not necessary to couple the bus tabs  110  to the interconnect bus  108 . By implementing a unitarily formed cell connection piece  102  without coupling joints, the cell connection piece  102  may have increased mechanical strength and reliability compared to conventional busbar components which use coupling joints. Additionally, the thickness of formed busbar components may be significantly less than the thickness of conventional busbar components which use coupling joints. For example, a conventional busbar component with coupling joints may have a total thickness of about 635 μm (25 mils) (e.g., 127 μm (5 mils) for the first ribbon layer, 101.6 μm (4 mils) for the solder joint, and 254 μm (10 mils) for the second ribbon layer), but a unitarily formed busbar component may have a total thickness of about 127 μm (5 mils)—the thickness of a single metal layer. While the exact thickness of a formed busbar component depends at least in part on the thickness of the metal or other conductive material used, the overall thickness of the formed busbar component is generally substantially less than the overall thickness of a conventional busbar component with solder joints. 
     In some embodiments, the interconnect bus  108  or the bus tabs  110 , or both, may include non-linear portions. For example, the interconnect bus  108  may have a curved shape along the length of the interconnect bus  108 . Moreover, the interconnect bus  108  and the bus tabs  110  may intersect at an angle that is not rectilinear. For example, some or all of the individual bus tabs  110  may extend away from the interconnect bus at an angle other than 90 degrees (e.g., 60 degrees). In another example, a bus tab  110  at the end of the interconnect bus  108  may be formed as a curvilinear extension of the interconnect bus  108 , so that the interconnect bus  108  curves approximately 90 degrees to form the bus tab  110 . With the benefit of this disclosure, various combinations of rectilinear and curvilinear configurations may be implemented. For example, the bus tabs  110  may have rounded ends and rounded interior or exterior corners where the bus tabs  110  intersect the interconnect bus  108 . 
     The depicted cell connection piece  102  also includes an extension  112  at one end of the interconnect bus  108 . Alternatively, the extension  112  may be located at an intermediate position on the interconnect bus  108 , instead of at one of the ends. In other embodiments, the cell connection piece  102  may omit the extension  112 . Where the cell connection piece  102  includes an extension, the extension  112  may provide a more desirable location for the solder joint  106 . Where the cell connection piece  102  omits an extension, the solder joint  106  may be located at another position along the length of the interconnect bus  108 . 
       FIG. 5  illustrates a more detailed embodiment of the terminal connection piece  104  of  FIG. 3 . The depicted terminal connection piece  104  is a terminal bus. Although the terminal connection piece  104  is a single piece, and does not necessarily include multiple identified pieces, other embodiments of the terminal connection piece  104  may include multiple identified elements formed in a unitary manner, as described above with references to the cell connection piece  102 . 
     Although both the depicted terminal connection piece  104 , or terminal bus, and conventional terminal buses are both single pieces which may be coupled to a corresponding interconnect bus, the depicted terminal bus  104  is different from conventional terminal buses. In one embodiment, the terminal bus  104  includes a non-linear portion  114 . The non-linear portion  114  may implement a curvilinear, angular, or other type of non-linear path between the cell connection end and the terminal connection end of the terminal bus  104 . Although the non-linear portion  114  is shown primarily at the cell connection end of the terminal bus  104  in  FIG. 5 , other embodiments may implement one or more non-linear portions  114  at other locations of the terminal bus  104 . 
     The non-linear portion  114  may facilitate one or more advantages over conventional, linear terminal buses. In one embodiment, the location of the non-linear portion  114  of the terminal bus  104  may be designed to avoid an overlap with an edge of a corresponding PV cell. While conventional, linear terminal buses often extend across one or more edges of a PV cell, causing stress on the PV cell and resulting in damage (e.g., cracking or breakage) of the PV cell, the non-linear portion  114  of the illustrated terminal bus  114  may avoid causing mechanical stress at the edge of corresponding PV cells. Thus, the integrity of the PV cells and the PV module, as a whole, may be preserved. 
     Additionally, the non-linear portion  114  of the terminal bus  104  may provide a shorter electrical path between the cell connection piece  102  and the junction box of the PV module. Given that voltage drop is related to the length of the electrical path between the PV cells and the junction box, implementing a relatively shorter electrical path may result in greater power output from the PV module because less power is consumed in voltage drop. While the increased power output due to decreased voltage drop of a single PV module may seem trivial, the total increase in power output from an array of hundreds or thousands of PV modules may be significant. 
     The depicted terminal bus  104  also includes a tapered portion  116  at the junction connection end of the terminal bus  104 . In one embodiment, the tapered portion  116  facilitates coupling the terminal bus  104  to a terminal within the junction box of the PV module. For example, where a small junction box is used, the tapered portion  116  of the terminal bus  104  may allow the terminal bus  104  to connect to the terminal in the junction box. In contrast, where a non-tapered terminal bus is used, a small junction box might be too small to accommodate the non-tapered width of multiple terminal buses  104 . 
       FIG. 6  illustrates another embodiment of a unitarily formed busbar  120  for a PV module. The depicted formed busbar  120  includes a cell connection piece  122  and a terminal connection piece  124 . For purposes of this description, the cell connection piece  122  is substantially similar to the cell connection piece  102  of  FIG. 4 . However, the cell connection piece  122  is used to connect to a single PV cell, rather than to multiple PV cells. Likewise, the terminal connection piece  124  is substantially similar to the terminal connection piece  104  of  FIG. 5 , including non-linear portions  128  and  130 , as well as a tapered portion  132 . However, the terminal connection piece  124  includes multiple non-linear portions  128  and  130  to accommodate a different path from the cell connection piece  122  to a junction box. In particular, the terminal connection piece  124  may facilitate electrical connection to a PV cell which is located a greater distance from the junction box. 
       FIG. 7  illustrates one embodiment of a pattern  140  of nested busbar components  142  for PV modules. In particular, the illustrated busbar components  142  are terminal buses  104 , although other patterns may accommodate other types of busbar components. In one embodiment, the pattern  140  of nested terminal buses  104  facilitates stamping, or otherwise unitarily forming, a plurality of individual terminal buses  104  from a sheet of conductive material  144 . Exemplary conductive materials that may be used include annealed copper with tin, tin-silver, tin-lead, or tin-silver-copper coating, or other electrically conductive materials. For convenience, the description provided herein refers to stamping, in many instances. However, alternative forming technologies such as electrical discharge machining (EDM), water jet cutting, laser cutting (e.g., in a stack), or other forming technologies may be implemented. 
     Stamping employs a die to cut through a sheet of material. The face of the die includes a pattern that is forced by a heavy duty press to cut through the sheet of material. In one embodiment, the pattern may be for a single component. Alternatively, the pattern may be for several components. For example, the pattern may be for a plurality of similar, nested components, or even for different types of components. Additionally, some stamping mechanisms may include dies that are capable of stamping multiple layers of material in a stack at a single time. In this way, one stamping operation may produce several sets of patterned components (i.e., one set for each sheet of material in the stack). 
     EDM employs a recurring electrical arcing discharge between an electrode and the metal sheet  144 . The electrode follows the pattern  140  to create a series of micro-craters on the metal sheet  144  and to remove material along the cutting path by melting and vaporization. The removed particles are washed away by a dielectric fluid. 
     Water jet cutting employs a stream of high pressure of water, with or without abrasive additives, through a nozzle to essentially erode the metal sheet  144  along the pattern  140 . The nozzle and stream of water follow the pattern  140  to cut the individual busbar components  142  out of the metal sheet  144 . 
     Laser cutting, like water jet cutting, cuts the pattern  140  of busbar components  142  out of the metal sheet  144 . However, laser cutting employs a high power laser, instead of a high pressure stream of water. The part of the metal sheet  144  exposed to the laser melts, burns, or vaporizes. Laser cutting can produce a high quality finish on the cut surface. Laser cutting, as well as EDM and water jet cutting, may be employed to cut several sheets  144  at once in a stack. 
       FIG. 8  illustrates another embodiment of a pattern  150  of nested busbar components  152  for PV modules. In particular, the illustrated busbar components  152  are terminal buses  124 , as shown in  FIG. 6 . In one embodiment, the pattern  150  facilitates substantial material utilization between the individual busbar components  152 . For example, the shape of the nested busbar components  152  may use all or almost all of the conductive sheet  154  between the nested busbar components  152 . 
       FIG. 9  illustrates one embodiment of a photovoltaic (PV) module  180  with a plurality of formed busbars  100  and  120 . In particular,  FIG. 9  shows the back side of the PV module  180 , which is not typically seen from the outside of the PV module  180 . The depicted PV module  180  includes an array (e.g., a 6×8 array) of PV cells  182 . The PV cells  182  are shown dashed to indicate that they are located on the front of the PV module  180 , rather than on the back. At one end of each column of cells  182 , formed busbars  100  and  120  couple the columns of cells  182  to a junction box  184  coupled to the PV module  180 . At the opposite end of each column of cells  182 , formed cell connection pieces  102  couple pairs of columns together. In one embodiment, the shape of the cell connection piece  102  is universal in that it may be used at either end of the columns of cells  182 . Implementing a universal cell connection piece  102  in this manner may eliminate the need to fabricate, store, and inventory an additional number of different types of busbar components.  FIG. 9  also illustrates that the busbar components may be located behind the PV cells  182  to improve the aesthetic look and electrical efficiency of the PV module  180 . 
       FIG. 10  illustrates one embodiment of a manufacturing pattern  200  for a plurality of unitarily formed busbar components  122  for PV modules. The depicted manufacturing pattern  200  orients multiple cell connection pieces  122  in an opposing and offset orientation. In particular, the bus tabs  110  of each cell connection piece  122  are directed to the interconnect bus  108  of the opposing cell connection piece  122 , and some of the bus tabs  110  of each cell connection piece  122  are located between the bus tabs  110  of the opposing cell connection piece  122 . The orientation of the opposing cell connection pieces  122  in this manufacturing pattern  200  may reduce the amount of unutilized material between the opposing cell connection pieces  122 . By orienting the pairs of cell connection pieces  122  in a back-to-back pattern on a conductive sheet  124 , as shown, the material utilization between the pairs of cell connection pieces  122  can be very high (the unused material is indicated with cross-hatching). 
       FIG. 11  illustrates another embodiment of a manufacturing pattern  210  for a plurality of unitarily formed busbar components  212  for PV modules. The depicted cell connection pieces  212  are similar to the cell connection pieces  122 , except that the cell connection pieces  212  have interconnect buses  108  with a continuously variable width along the length of each interconnect bus  108 . Implementing the cell connection pieces  212  may reduce the amount of material for each cell connection piece  212  according to the reduced width of the interconnect bus  108 . In one embodiment, the pairs of cell connection pieces  212  are arranged on a conductive sheet  214  in a side-to-side pattern, as shown. Alternatively, adjacent pairs of cell connection pieces  212  may be arranged in a back-to-back pattern as shown in  FIG. 10 , so that the tapered edge of one cell connection piece  212  may coordinate with the tapered edge of another cell connection piece  212  (e.g., a third cell connection piece  212 ) to eliminate material waste between adjacent sets of cell connection pieces  212  (the unused material is indicated with cross-hatching). 
       FIG. 12  illustrates another embodiment of a manufacturing pattern  220  for a plurality of unitarily formed busbar components  222  for PV modules. The depicted cell connection pieces  222  are similar to the cell connection pieces  122 , except that the cell connection pieces  222  have interconnect buses  108  with notches to allow the bus tabs  110  of the opposite cell connection piece  222  to extend into the notches. By allowing the bus tabs  110  of the opposing cell connection pieces  222  to extend into the notches in the corresponding interconnect buses  108 , the combined area of the manufacturing pattern  220  may be reduced compared to the combined area of the manufacturing pattern  200  of  FIG. 10  (without the notches). In other words, there may be less unutilized material between the opposing cell connection pieces  222  of  FIG. 12 . 
       FIG. 13  illustrates another embodiment of a manufacturing pattern  230  for a plurality of unitarily formed busbar components  232  for PV modules. The depicted cell connection pieces  232  are similar to the cell connection pieces  222 , except that the cell connection pieces  232  have interconnect buses  108  with a continuously variable width along the length of the interconnect bus  108 . As described above with reference to the cell connection pieces  212  of  FIG. 11 , implementing the cell connection pieces  232  with tapered edges may reduce the amount of unutilized material for each cell connection piece  232  according to the reduced width of the interconnect bus  108 . 
       FIG. 14  illustrates another embodiment of a manufacturing pattern  240  for a plurality of unitarily formed busbar components  242  for PV modules. The depicted cell connection pieces  242  are similar to the cell connection pieces  232  of  FIG. 13 , except that the cell connection pieces  242  have interconnect buses  108  with a step-wise variable width along the length of the interconnect bus  108 . In one embodiment, the step-wise variable width of the interconnect bus  108  may reduce the amount of material used for the cell connection piece  242 . In some embodiments, the step-wise variable edge of the interconnect bus  108  may coordinate with the step-wise variable edge of another cell connection piece  242  (e.g., a third cell connection piece  242 ) to eliminate material waste between adjacent sets of cell connection pairs (because the sets of cell connection pairs are aligned at the step-wise variable edges of the interconnect buses  108 ). 
       FIG. 15  illustrates one embodiment of an angled terminal bus  250 . The angled terminal bus  250  is another example of a non-linear terminal connection piece, as described above. The depicted angled terminal bus  250  includes two linear portions  252  and  254  connected by a non-zero angled portion  256 . Similar to the non-linear portion  114  of the terminal connection piece  104  of  FIG. 5 , the angled portion  256  of the terminal bus  250  may be designed to avoid an overlap with an edge of a corresponding PV cell  182 . Additionally, the angled portion  256  of the terminal bus  250  may provide a relatively shorter electrical path between a corresponding cell connection piece  102  and the junction box  184  of the PV module  180 . 
     The depicted angled terminal bus  250  also includes a unitarily stamped hole  258 . Alternatively, the hole  258  may be formed in another manner consistent with the formation technology used to form the angled terminal bus  250 . In one embodiment, the hole  258  is used to allow a fastener within the junction box  184  to secure the terminal bus  250  to an electrical terminal (not shown) within the junction box  184 . For example, a screw may be used to fasten the terminal bus  250  to the electrical terminal, although other types of fasteners may be used in other embodiments. 
       FIG. 16  illustrates another embodiment of a manufacturing pattern  270  for a plurality of unitarily formed busbar components  272  for PV modules. The depicted cell connection pieces  272  are similar to the cell connection pieces  122  of  FIG. 10 , except that the cell connection pieces  272  have more bus tabs  110  and the interconnect buses  108  have a symmetrically variable width along the length of the interconnect bus  108 . In one embodiment, the symmetrically variable width of the interconnect bus  108  may reduce the amount of material used for the cell connection piece  272 . In some embodiments, the symmetrically variable width of the interconnect bus  108  may coordinate with the symmetrically variable edge of one or more other cell connection piece  272  to eliminate material waste between adjacent sets of cell connection pairs. Additionally, the symmetrically variable width of the interconnect bus  108  may provide a convenient location for a central solder joint at about the widest portion of the interconnect bus  108 . In further embodiments, the cell connection pieces  272  may be used for string-to-string connection without a terminal bus (similar to the cell connection pieces  102  at the bottom of  FIG. 9 ). Also, the sloping of the interconnect bus  108  may be designed to be consistent with the amount of current that may be needed to be carried in the bus. 
       FIG. 17  illustrates another embodiment of a unitary cell connection piece  280  having an expansion joint  282 . The use of an expansion joint  282  may accommodate thermal expansion of the various parts of the PV module  180 , since the PV cells  182  and PV module  180  likely have a different thermal coefficient of expansion than the conductive material used for the busbar components. In this way, the expansion joint  282  lowers stress, thereby improving reliability. Although the expansion joint  282  is shown in a particular location between two groups of bus tabs  110 , the expansion joint  282  may be located at another location along the interconnect bus  108 . Additionally, a busbar component may include multiple expansion joints  282 . In some embodiments, terminal connection pieces  104  also may include similar expansion joints. The expansion joints  282  may be formed in a variety of ways, including crimping or otherwise bending the interconnect bus  108 . In one embodiment, the expansion joint may be formed during a stamping process. Alternatively, the expansion joint may be formed in another manner. 
       FIG. 18  illustrates a side view of one embodiment of a busbar  100  coupled to a back contact cell  182 . In particular, the busbar  100  is coupled to the back contact  292  on the back side of the cell  182 . In order to prevent the busbar  100  from contacting any electrical components on the back of the cell  182 , an electrical insulator material  294  is provided between the busbar  100  and the back of the cell  182 . A laminate material  296  is provided to cover the busbar  100  and insulator material  294 . 
     In one embodiment, the electrical insulator material  294  is EPE (EVA/polyester/EVA) made from 101.6 μm (4 mils) ethylene vinyl acetate (EVA), 50.8 μm (2 mils) polyester, and 101.6 μm (4 mils) EVA. Alternatively, other insulator materials may be used. In some embodiments, the insulator material  294  may be applied to the busbar  100 . In some embodiments, the insulator material  294  may be made to have a certain color (e.g., white or black). Alternatively, the insulator material  294  may be transparent. In embodiments where the busbar  100  is not adjacent to the cell  182 , the insulator material  294  may be omitted. 
     For PV modules  180  which use electrical ribbons instead of back contacts, the busbars  100  may couple to the electrical ribbon. Where the ribbons are provided on the front of the cell  182 , the ribbons may be folded over behind a cell  182  for connection to the busbar  100 . Alternatively, the ribbons may extend past the cell  182  and the busbar may be located away from the cell  182 , rather than behind the cell  182 . Other embodiments may implement other configurations. 
       FIG. 19  illustrates a flow chart diagram of one embodiment of a fabrication method  300  for using unitarily formed busbars  100  to fabricate a PV module  180 . Alternatively, other embodiments of the fabrication method  300  may include additional operations or fewer operations than are shown and described herein. 
     The depicted fabrication method  300  begins as unitarily formed, nested busbar components are stamped  305  from a metal sheet or other conductive material. In one embodiment, the busbar components include cell connection pieces  102  or terminal connection pieces  104 , or both. Subsequently, individual formed busbar components such as a cell connection piece  102  and a terminal connection piece  104  are arranged  310  on a PV module  180 . The busbar components are then soldered  315  together and coupled to the cell contacts or cell ribbons. In one embodiment, heat insulators (not shown) may be used to provide insulation for the PV cells  182  against the heat and pressure generated at the solder joint  106  to couple the cell connection piece  102  and the terminal connection piece  104 . The busbar components are then connected  320  to the junction box  184 . In particular, the terminal bus  104  may be secured to an electrical terminal within the junction box  184 . The illustrated fabrication method  300  then ends. 
     Embodiments of the present invention, described herein, include various operations. These operations may be performed manually, automatically, or a combination thereof. Although the operations of the method(s) herein are shown and described in a particular order, the order of the operations of each method may be altered so that certain operations may be performed in an inverse order or so that certain operation may be performed, at least in part, concurrently with other operations. In another embodiment, instructions or sub-operations of distinct operations may be in an intermittent and/or alternating manner. 
     In the foregoing specification, the invention has been described with reference to specific exemplary embodiments thereof. It will, however, be evident that various modifications and changes may be made thereto without departing from the broader spirit and scope of the invention as set forth in the appended claims. The specification and drawings are, accordingly, to be regarded in an illustrative sense rather than a restrictive sense.