Patent Publication Number: US-2011073152-A1

Title: Mixed wiring schemes for shading robustness

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is claiming under 35 USC 119(e), the benefit of provisional patent application Ser. No. 61/245,907, filed Sep. 25, 2009. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to solar cells, solar panels and or solar arrays and more particularly to electrical interconnections for devices adapted to capture solar energy, such as solar cells, solar panels and/or solar arrays. 
     2. Description of the Related Art 
     Solar devices, such as solar cells, solar panels or solar arrays are typically positioned for service to have an unobstructed, line-of sight view of the sun. The unobstructed access to the sun maximizes the quanta of light impinging the device, which maximizes the resulting energy produced and/or captured. Traditionally, places such as rooftops, relatively flat surfaces on or near the ground, and hillsides with low vegetation are suitable locations. 
     However, even in these suitable locations, the solar devices may experience random instances where the sunlight is blocked. For example, objects such as clouds, plants and other structures or phenomena may temporarily or permanently shade a device or devices. The shading effect produced by these objects reduces the efficiency of the device or devices and power output may be minimized or eliminated entirely. 
     A natural variation of solar cell performance exists within the manufacturing process. In order to prevent the lower performing cells from setting the output for the entire module, a particular wiring scheme may be selected during the manufacturing of the module. While such scheme may indeed be robust, the same scheme may limit the total power produced by the rest of the cells within the module or panel. Therefore, the module will not be optimized for full generation of power. 
     Therefore, there is a need for an electrical coupling scheme for the solar devices that reduces the shading effect and maximizes the efficiency of the solar devices. The present invention addresses such a need. 
     SUMMARY OF THE INVENTION 
     Embodiments herein provide methods and apparatuses for electrical interconnections utilized in devices adapted to capture solar energy, such as solar cells, solar panels and/or solar arrays. In one embodiment, a solar panel is described and includes a first plurality of solar devices positioned in a center of the solar panel in electrical communication with a first circuit, and a second plurality of solar devices surrounding the first plurality of solar devices, the second plurality of solar devices in electrical communication with a second circuit, the second circuit being different than the first circuit. 
     In another embodiment, the solar panel includes a first plurality of solar devices positioned in a center of the solar panel electrically coupled with a serial wiring circuit, and a second plurality of solar devices surrounding the first plurality of solar devices, the second plurality of solar devices electrically coupled with a parallel wiring circuit. 
     In another embodiment, the solar panel includes a first plurality of solar devices positioned in a center of the solar panel electrically coupled with a serial wiring circuit, and a second plurality of solar devices surrounding the first plurality of solar devices, the second plurality of solar devices electrically coupled with an H-bridge wiring circuit. 
     In another embodiment, the solar panel includes a first plurality of solar devices positioned in a center of the solar panel electrically coupled with a parallel wiring circuit, and a second plurality of solar devices surrounding the first plurality of solar devices, the second plurality of solar devices electrically coupled with an H-bridge wiring circuit. 
     In another embodiment, the solar panel includes a first plurality of solar devices positioned in a center of the solar panel electrically coupled with a parallel wiring circuit, and a second plurality of solar devices surrounding the first plurality of solar devices, the second plurality of solar devices electrically coupled with a serial wiring circuit. 
     In another embodiment, the solar panel includes a first plurality of solar devices positioned in a center of the solar panel electrically coupled with a parallel wiring circuit, and a second plurality of solar devices surrounding the first plurality of solar devices, the second plurality of solar devices electrically coupled with a serial wiring circuit. 
     In another embodiment, the solar panel includes a first plurality of solar devices positioned in a center of the solar panel electrically coupled with an H-bridge wiring circuit, and a second plurality of solar devices surrounding the first plurality of solar devices, the second plurality of solar devices electrically coupled with a serial wiring circuit. 
     In another embodiment, the solar panel includes a first plurality of solar devices positioned in a center of the solar panel electrically coupled with an H-bridge wiring circuit, and a second plurality of solar devices surrounding the first plurality of solar devices, the second plurality of solar devices electrically coupled with a parallel wiring circuit. 
     In another embodiment, a method for electrically connecting a solar pane is described and includes exposing light to a solar panel having a center area comprising a first plurality of solar devices that are at least partially bordered by a second plurality of solar devices positioned outside of the center area, electrically connecting the first plurality solar devices with a first electrical circuit, and electrically connecting the second plurality of solar devices with a second electrical circuit that is different than the first electrical circuit. 
     In another embodiment, a method for transferring electrical power from a solar panel to a load is described and includes exposing light to a solar panel having a center area comprising a first plurality of solar devices that are at least partially bordered by a second plurality of solar devices positioned outside of the center area, and transferring electrical power to the load from the first plurality of solar devices through an electrical circuit, the electrical power from the first plurality of solar devices being independent of the electrical power production potential of the second plurality of solar devices. 
     In some embodiments, by eliminating the shaded cells from the circuit of the panel, the rest of the panel will not be limited to the output of the eliminated, lower performing cells. The partitioned panel contains a more aggressive wiring scheme in the center and a more robust wiring scheme at the edges. This embodiment differs from the single homogenous approach which provides for the entire panel including the center unshaded cells will not produce at an optimum. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       So that the manner in which the above-recited features of the invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments. 
         FIG. 1  is a schematic top view of one embodiment of a solar panel. 
         FIG. 2  is a top view of other forms of solar panels. 
         FIG. 3  is a top view of a one embodiment of a solar panel having a heterogeneous wiring scheme. 
         FIG. 4  is a top view of another embodiment of a solar panel having a heterogeneous wiring scheme. 
     
    
    
     To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements disclosed in one embodiment may be beneficially utilized on other embodiments without specific recitation. 
     DETAILED DESCRIPTION 
     The present invention relates generally to solar cells, solar panels and or solar arrays and more particularly to electrical interconnections for devices adapted to capture solar energy, such as solar cells, solar panels and/or solar arrays. The following description is presented to enable one of ordinary skill in the art to make and use the invention and is provided in the context of a patent application and its requirements. Various modifications to the preferred embodiments and the generic principles and features described herein will be readily apparent to those skilled in the art. Thus, the present invention is not intended to be limited to the embodiments shown, but is to be accorded the widest scope consistent with the principles and features described herein. 
     Embodiments of the invention generally provide methods and apparatus for electrical interconnections utilized in devices adapted to capture solar energy, such as solar cells, solar panels and/or solar arrays. The electrical interconnections as described herein are configured to minimize or eliminate shading effects produced by an object or objects that may temporarily or permanently block sunlight from a solar device. 
       FIG. 1  is a schematic top view of one embodiment of a solar panel  100 . The solar panel  100  includes a plurality of cells  105  that receive light from a light source, such as the sun  110 . Each of the cells  105  may be a photovoltaic device including p-n junctions adapted to convert sunlight into electricity. The solar panel  100  includes, for example, seventy two cells  105  that are interconnected in a homogenous serial wiring scheme to a load  115 , which may be an electrical appliance, a storage medium, such as a battery or a capacitor, or a connection to a power grid. 
     The solar panel  100  depicted in  FIG. 1  is at least partially shaded by one or more shading sources  120 ,  125 . One or both of the shading sources  120 ,  125  negatively affect the performance of the solar panel  100  and reduce the power available to the load  115 . In  FIG. 1 , the shading source  125  is a spot or area of solid matter which may be organic or inorganic matter that is attached to or supported by a surface of the solar panel  100 . Examples of organic or inorganic matter that may be representative of the shading source  125  include soil, bird or animal droppings, vegetation matter, such as leaves, limbs, pollen, bark, nuts, berries, etc., as well as other matter. The shading source  125  may be deposited on a surface of the solar panel  100  at random intervals and/or random areas of the solar panel  100  and operates to shade at least a portion of the solar panel  100 . The shading source  120  is a plant, such as a tree or bush, which has been planted or allowed to grow in proximity to the solar panel  100 . The shading sources  120 ,  125  may block light completely or in part from the cell or cells  105  that are under or otherwise shaded by the sources  120 ,  125 . The shading of one or more cells  105  minimizes the efficiency of the entire solar panel  100  by reducing the net power available from the solar panel  100  to the load  115 . 
     The shading source  120  may block particular cells  105  for portions of a day as a shadow  135 A- 135 C moves across the surface of the solar panel  100 . In contrast, the shading source  125  may block particular cells completely or in part during all daylight hours. 
     The shading source  120  may be considered a permanent obstruction that affects the solar panel  100  day after day until the source  120  is removed or the solar panel  100  is relocated. In contrast, the shading source  125  may be considered a temporary obstruction that may be mitigated by weather events (e.g., wind or rain), decomposition of the shading source, or physical cleaning of the solar panel  100 . Additionally, the frequency and/or probability of the occurrence of the shading sources  120 ,  125  is different. For example, the occurrence of the shading source  120  may be predicted by observational methods while the occurrence of the shading source  125  is temporally random and may affect any area of the solar panel  100  with assumed equal probability. 
     The solar panel  100  may experience shading events other than the shadowing produced by the shading sources  120 ,  125  with similar reduction in efficiency. For example, other temporary obstructions include cloud formations, shadows from parked vehicles, shadows from construction activities, among other temporary obstructions that cause random shading events. Permanent obstructions include fixed obstructions, such as a tree or shrub similar to the shading source  120  as well as buildings, billboards, signs, or other structures that may shade at least a portion of the solar panel  100 . 
     With the exception of a surface attached or surface supported shading source, such as the shading source  125 , other temporary obstructions shade the solar panel  100  in a manner similar to a permanent obstruction due to the axial rotation of the earth and/or movement of the obstruction itself. For example, a permanent obstruction such as the shading source  120  will initially form a shadow over an edge  130 A of the solar panel  100  and the shadow subsequently moves toward a center  140  and across the solar panel  100  to an edge  130 B (in an afternoon example). Alternatively, a permanent obstruction such as the shading source  120  may initially form a shadow over the edge  130 B of the solar panel  100  and the shadow subsequently moves toward a center  140  and across the solar panel  100  to the edge  130 A (in a morning example). Likewise, a temporary obstruction, such as a cloud, may initially form a shadow over one edge and move across the solar panel  100 . In the case of a shadow formed by a cloud, the shadow may subsequently form a shadow over the entire solar panel  100  due to movement of the cloud and/or the rotation of the earth. In either case, the edge  130 A or  130 B that was initially shaded may remain shaded for an extended time period relative to other portions of the solar panel  100 . 
     In one example during afternoon hours, the shading source  120  forms a first shadow  135 A at or near a first edge  130 A of the solar panel  100 . As the earth rotates about its axis, the first shadow  135 A grows into a second shadow  135 B that eventually shades a center  140  of the solar panel  100  as well as the first edge  130 A. As the earth continues its rotation, the second shadow  135 B extends to a third shadow  135 C that shades a second edge  130 B as well as the center  140  and the first edge  130 A of the solar panel  100 . While not shown, a temporary obstruction such as a cloud may cause shading of the solar panel  100  that is similar to the shading caused by the shading source  120 . For example, a shadow cast by a cloud may shade the first edge  130 A forming the first shadow  135 A and move across the solar panel  100  which extends the first shadow  135 A into the second and third shadows  135 B,  135 C. In either example, the first edge  130 A may remain shaded by the shading source  120  or cloud for an extended period of time relative to the center  140  and the second edge  130 B. 
     As the cells  105  on the first edge  130 A experience longer periods of shade and/or a greater aversion of sunlight relative to the center  140 , the cells  105  on the first edge  130 A are operating at a reduced efficiency as compared to other cells  105  receiving more sunlight. The homogenous wiring scheme connecting the cells  105  to the load  115  aggregates the current and/or voltage from each of the cells  105  on the solar panel  100  and delivers a net current and/or voltage to the load  115 . Thus, if one or more of the cells  105  are shaded and not operating at or near full efficiency, the net current and/or voltage available to the load  115  is reduced. The reduced net power produced by the solar panel  100  may occur even though the center  140  and/or the second edge  130 B may be receiving a maximum or near maximum quanta of light. 
       FIG. 2  depicts a top view of other forms of solar panels  200 A,  200 B that may experience a shading effect as described in  FIG. 1 . Each of the cells  105  of the solar panel  200 A are interconnected in a homogenous, serial-parallel wiring scheme while each of the cells  105  of the solar panel  200 B are interconnected in a homogenous, “H-bridge” wiring scheme. In either of these solar panels  200 A,  200 B, a shading effect as described herein negatively affects the performance of the solar panels  200 A,  200 B due to the homogenous wiring scheme. 
       FIG. 3  depicts a top view of a solar panel  300  having a heterogeneous wiring scheme, which includes a first circuit  310 A interconnecting cells  340  in a center  140  of the solar panel  300  and a plurality of second circuits  310 B interconnecting cells  305 A,  305 B along edges  130 A,  130 B of the solar panel  300 . In this embodiment, the first circuit  310 A and second circuit  310 B are different to maximize the efficiency of the solar panel  300  in the event of a shading event casting a shadow  350 A,  350 B that affects the edge (edge  130 B in this view) differently than the center  140 . 
     In this embodiment, the shadows  350 A,  350 B move from the left edge  130 B toward the center  140  in an afternoon example. As the cells  305 B remain shaded for longer periods of time relative a cell or cells  305 C in the center  140  of the solar panel  300  in this example, the efficiency of the cells  305 B is reduced. However, the cells  305 B along the edge  130 B are electrically decoupled from the cells  305 C in the center  140 . Thus, the reduced sunlight to the cells  305 B does not significantly impact the efficiency of entire solar panel  300 , which results in a greater net current and/or net voltage available to the load  115  as compared to the net current and/or net voltage available to the load  115  of the solar panel  100  of  FIG. 1  and the solar panels  200 A,  200 B of  FIG. 2 . 
     In this embodiment, the first circuit  310 A is shown as an “H-bridge” circuit connecting the cells  305 C in the center  140  of the solar panel  300 . Alternatively, the first circuit  310 A may be a serial-parallel circuit as well as a serial circuit as long as the first circuit  310 A is different than the second circuit  310 B. Likewise, the second circuit  310 B is shown as a serial circuit connecting the cells  305 A,  305 B. Alternatively, the second circuit  310 B may include a parallel, a serial-parallel and/or an “H-bridge” circuit as long as the second circuit  310 B is different than the first circuit  310 A. Additionally, although the edges  130 A and  130 B include a discrete circuit  310 B, only one of the edges  130 A,  130 B may include the circuit  310 B while the other edge of the solar panel  300  may include a circuit that is the same as the first circuit  310 A. 
       FIG. 4  depicts a top view of another embodiment of a solar panel  400  having a heterogeneous wiring scheme, which includes a first circuit  410 A interconnecting cells  405 E in a center  140  of the solar panel  300  and a plurality of second circuits  410 B,  410 C interconnecting cells  405 A- 405 D along edges  130 A- 130 D of the solar panel  300 . In this embodiment, the first circuit  410 A and second circuits  410 B,  410 C are different to maximize the efficiency of the solar panel  400  in the event of a shading event casting a shadow  450 A,  450 B that affects a corner  420  of the solar panel  400  differently than the center  140  of the solar panel  400 . 
     In this embodiment, the shadow  450 A,  450 B moves from the corner  420  toward the center  140  in an afternoon example. As the cells  405 B and  405 C remain shaded for longer periods of time relative a cell or cells  405 C- 405 E of the solar panel  300  in this example, the efficiency of the cells  405 B,  405 C are reduced. However, the cells  405 C- 405 E are electrically decoupled from the cells  405 B,  405 C at the corner  420 . Thus, the reduced sunlight to the cells  405 B,  405 C does not significantly impact the efficiency of entire solar panel  400 , which results in a greater net current and/or net voltage available to the load  115  as compared to the net current and/or net voltage available to the load  115  of the solar panel  100  of  FIG. 1  and the solar panels  200 A,  200 B of  FIG. 2 . 
     Although the present invention has been described in accordance with the embodiments shown, one of ordinary skill in the art will readily recognize that there could be variations to the embodiments and those variations would be within the spirit and scope of the present invention. Accordingly, many modifications may be made by one of ordinary skill in the art without departing from the spirit and scope of the appended claims.