Patent Publication Number: US-9853175-B2

Title: Solar cell module

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2014-192254, filed on Sep. 22, 2014; the entire contents of which are incorporated herein by reference. 
     FIELD 
     Embodiments described herein relate generally to a solar cell module. 
     BACKGROUND 
     Research and development of solar cell modules are being performed. When light is directly incident on a solar cell panel of a solar cell module, that is, when concentration of the light is not performed, the solar cell panel can absorb light from a relatively wide range of angles; but the solar cell panel must have a relatively wide surface area. Therefore, the solar cell module is expensive. 
     There is a possibility that the cost per surface area of the solar cell module can be reduced by combining the solar cell panel with an inexpensive concentrator. A condensing lens, a concentrator called a CPC (Compound Parabolic Concentrator), etc., may be used as technology for combining the concentrator and the solar cell panel. However, when the condensing lens or the CPC is used in the solar cell module, a drive device becomes necessary to drive the solar cell panel to follow the sun because the orientation of the light of the sun changes according to the season, the time, etc. Therefore, the solar cell module is expensive. 
     There is a possibility that the cost per surface area of the solar cell module can be reduced by reducing the surface area of the solar cell panel. To reduce the surface area of the solar cell panel, it is desirable to improve the concentration ratio of the solar cell module. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic conceptual view showing a solar cell module according to an embodiment; 
         FIG. 2  is a schematic perspective view showing the solar cell module according to the embodiment; 
         FIG. 3  is a schematic plan view showing the solar cell module according to the embodiment; 
         FIGS. 4A to 4D  are schematic plan views showing light that is incident on the solar cell module according to the embodiment; 
         FIG. 5  is a schematic plan view showing the light that is reflected for the parabolas; 
         FIGS. 6A and 6B  are schematic views showing another example of the concentrator of the embodiment; 
         FIG. 7  is a schematic perspective view showing a solar cell module according to another embodiment; 
         FIG. 8  is a schematic conceptual view showing the solar cell module according to the embodiment; 
         FIGS. 9A and 9B  are schematic views showing the total internal reflection of the light; 
         FIGS. 10A and 10B  are schematic plan views showing different tilts of the solar cell panel; 
         FIGS. 11A and 11B  are schematic plan views showing a method for mounting the solar cell panel; 
         FIGS. 12A to 12C  are schematic plan views showing examples in which three solar cell modules are connected; 
         FIGS. 13A and 13B  are schematic plan views showing the anti-reflection film of the embodiment; 
         FIG. 14  is a schematic plan view showing an example of the solar cell module according to the embodiment; 
         FIG. 15  is a schematic plan view showing another example of the solar cell module according to the embodiment; 
         FIG. 16  is a schematic plan view showing still another example of the solar cell module according to the embodiment; and 
         FIGS. 17A and 17B  are schematic views showing still another example of the solar cell module according to the embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     According to one embodiment, a solar cell module includes a solar cell panel and a concentrator. The solar cell panel includes a solar cell. The concentrator reflects light incident from the outside and irradiates the light onto the solar cell. The concentrator has a first surface and a second surface. The first surface reflects light incident at a first incident angle and irradiates the light incident at the first incident angle onto a first portion within the area of the solar cell. The second surface reflects light incident at a second incident angle and irradiates the light incident at the second incident angle onto a second portion within the area of the solar cell. The second incident angle is different from the first incident angle. The second portion is different from the first portion. The first surface and the second surface are asymmetric as viewed from the solar cell. 
     Various embodiments will be described hereinafter with reference to the accompanying drawings. 
     The drawings are schematic or conceptual; and the relationships between the thicknesses and widths of portions, the proportions of sizes between portions, etc., are not necessarily the same as the actual values thereof. The dimensions and/or the proportions may be illustrated differently between the drawings, even in the case where the same portion is illustrated. 
     In the drawings and the specification of the application, components similar to those described in regard to a drawing thereinabove are marked with like reference numerals, and a detailed description is omitted as appropriate. 
       FIG. 1  is a schematic conceptual view showing a solar cell module according to an embodiment. 
       FIG. 2  is a schematic perspective view showing the solar cell module according to the embodiment. 
     The solar cell module  100  according to the embodiment includes a solar cell panel  110  and a concentrator  120  and is mounted, for example, on a roof  221  facing south, etc. 
     The solar cell panel  110  includes a solar cell  111 . For example, the solar cell  111  is disposed in the interior of the solar cell panel  110 . The solar cell panel  110  (the solar cell  111 ) converts incident light into electrical power. 
     Two solar cell panels  110  and two concentrators  120  are provided in the solar cell module  100  shown in  FIG. 1  and  FIG. 2 . However, the number of solar cell panels  110  and the number of concentrators  120  is not limited thereto. 
     As shown in  FIG. 2 , the concentrator  120  includes a first light concentration plate  121  and a second light concentration plate  122 . The solar cell panel  110  is provided between the first light concentration plate  121  and the second light concentration plate  122 . The first light concentration plate  121  has a first surface  123 . In other words, the first light concentration plate  121  has a parabolic surface configuration. The second light concentration plate  122  has a second surface  124 . In other words, the second light concentration plate  122  has a parabolic surface configuration. The concave surface of the first surface  123  of the first light concentration plate  121  opposes the concave surface of the second surface  124  of the second light concentration plate  122 . The configuration of the first surface  123  of the first light concentration plate  121  is different from the configuration of the second surface  124  of the second light concentration plate  122 . That is, the second light concentration plate  122  and the first light concentration plate  121  are asymmetric as viewed from the solar cell panel  110 . In  FIG. 2 , the east and west directions (EN-direction) and the south and north directions (SN-direction) are illustrated. 
     As shown in  FIG. 1 , for example, the concentrator  120  reflects light  211  of the sun  210  and guides the light  211  toward the solar cell panel  110 . In the embodiment, a minimum solar elevation A 11  of the sun  210  is taken to be 30 degrees; and a maximum solar elevation A 13  of the sun  210  is taken to be 80 degrees. For example, the minimum solar elevation A 11  is the elevation of the sun  210  in winter. For example, the maximum solar elevation A 13  is the elevation of the sun  210  in summer. When the elevation of the sun  210  is the minimum solar elevation A 11 , an incident angle A 12  (a first incident angle) of the light  211  is 60 degrees. On the other hand, when the elevation of the sun  210  is the maximum solar elevation A 13 , an incident angle A 14  (a second incident angle) of the light  211  is 10 degrees. The incident angle A 12  is the maximum incident angle of the sunlight for a time period of one year. The incident angle A 14  is the minimum incident angle of the sunlight for a time period of one year. For the east and west directions, the concentration of light can be performed for only a limited amount of time because the angle of sunlight changes 180° from sunrise to sunset. For a limited amount of time, the concentration of light can be performed even for the east and west directions. 
     As described above, the first light concentration plate  121  and the second light concentration plate  122  have parabolic surfaces. For example, when the formula expressing a parabola is y=x 2 /(4p), the light that is incident parallel to the y-axis concentrates at the focal point (0, p) of the parabola. The concentration of light is possible by using this property of the parabola. Specifically, the first light concentration plate  121  and the second light concentration plate  122  are mounted so that the focal point (0, p) is included within the area of the solar cell panel  110  (or the solar cell  111 ). 
     The focal point of the first surface  123  of the first light concentration plate  121  exists in a first portion within the area of the solar cell panel  110  (or the solar cell  111 ). The focal point of the second surface  124  of the second light concentration plate  122  exists in a second portion within the area of the solar cell panel  110  (or the solar cell  111 ). The second portion is different from the first portion. More favorably, the focal point of the first surface  123  of the first light concentration plate  121  is positioned at a first edge portion of the solar cell panel  110  (or the solar cell  111 ). More favorably, the focal point of the second surface  124  of the second light concentration plate  122  is positioned at a second edge portion of the solar cell panel  110  (or the solar cell  111 ). 
     This will now be described further with reference to the drawings. 
     In the specification of the application, the “edge portion” includes not only the edge of some object, but also a portion that is inside the object in an area from the edge such that the ratio of the distance from the edge to the length in a prescribed direction of the object is within 10%, and/or a portion that is outside the object in an area from the edge such that the ratio of the distance from the edge to the length in the prescribed direction of the object is within 5%. 
       FIG. 3  is a schematic plan view showing the solar cell module according to the embodiment. 
       FIGS. 4A to 4D  are schematic plan views showing light that is incident on the solar cell module according to the embodiment. 
       FIG. 5  is a schematic plan view showing the light that is reflected for the parabolas. 
       FIG. 4A  is a schematic plan view showing the state in which the light  211  of the sun  210  at the minimum solar elevation A 11  is incident on the solar cell module  100 .  FIG. 4B  is a schematic plan view showing the state in which the light  211  of the sun  210  at the maximum solar elevation A 13  is incident on the solar cell module  100 .  FIG. 4C  is a schematic plan view showing the state in which the light  211  of the sun  210  is incident on the solar cell module  100  when a solar elevation A 15  is 45 degrees.  FIG. 4D  is a schematic plan view showing the state in which the light  211  of the sun  210  is incident on the solar cell module  100  when a solar elevation A 16  is 60 degrees. 
     As shown in  FIG. 3 , the first light concentration plate  121  and the second light concentration plate  122  have parabolic surface configurations. The second light concentration plate  122  and the first light concentration plate  121  are asymmetric as viewed from the solar cell panel  110 . 
     As shown in  FIG. 4A  to  FIG. 4D , the first light concentration plate  121  is formed along a first parabola  161 . The second light concentration plate  122  is formed along a second parabola  162 . In the example shown in  FIG. 4A  to  FIG. 4D , a first axis  171  is parallel to the travel direction of the light  211  of the sun  210  at the minimum solar elevation A 11  and corresponds to the y-axis of the first parabola  161 . A second axis  172  is parallel to the travel direction of the light  211  of the sun  210  at the maximum solar elevation A 13  and corresponds to the y-axis of the second parabola  162 . 
     As shown in  FIG. 4A , a portion of the light  211  that is incident parallel to the first axis  171  (the y-axis of the first parabola  161 ) is reflected at the first light concentration plate  121  and concentrates at a focal point  166  of the first parabola  161 . The light  211  that is incident parallel to the first axis  171  but is not reflected at the first light concentration plate  121  is incident directly on the solar cell panel  110 . 
     As shown in  FIG. 4B , a portion of the light  211  that is incident parallel to the second axis  172  (the y-axis of the second parabola  162 ) is reflected at the second light concentration plate  122  and concentrates at a focal point  167  of the second parabola  162 . The light  211  that is incident parallel to the second axis  172  but is not reflected at the second light concentration plate  122  is incident directly on the solar cell panel  110 . 
     As shown in  FIG. 4C , for example, when the solar elevation A 15  is 45 degrees, a portion of the light  211  of the sun  210  is reflected at the first light concentration plate  121  and is incident on the solar cell panel  110  on the focal point  167  side of the second parabola  162  as viewed from the focal point  166  of the first parabola  161 . For example, when the solar elevation A 15  is 45 degrees, the light  211  of the sun  210  that is not reflected at the first light concentration plate  121  is incident directly on the solar cell panel  110 . 
     As shown in  FIG. 4D , for example, when the solar elevation A 16  is 60 degrees, a portion of the light  211  of the sun  210  is reflected at the second light concentration plate  122  and is incident on the solar cell panel  110  on the focal point  166  side of the first parabola  161  as viewed from the focal point  167  of the second parabola  162 . For example, when the solar elevation A 16  is 60 degrees, the light  211  of the sun  210  that is not reflected at the second light concentration plate  122  is incident directly on the solar cell panel  110 . 
     The light  211  that is reflected at the parabolas will now be described further. 
     As shown in  FIG. 5 , when the formula expressing the first parabola  161  is y=x 2 /(4p), the light that travels parallel to the first axis  171  concentrates at the focal point  166  (0, p) of the first parabola  161 . When the formula expressing the second parabola  162  is y=x 2 /(4q), the light that travels parallel to the second axis  172  concentrates at the focal point  167  (0, q) of the second parabola  162 . 
     Here, the rotation matrix for rotating x counterclockwise by an angle θ to obtain X and rotating y counterclockwise by the angle θ to obtain Y is expressed by the following formula. 
     
       
         
           
             
               
                 
                   [ 
                   
                     Formula 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     1 
                   
                   ] 
                 
               
               
                 
                     
                 
               
             
             
               
                 
                   
                     [ 
                     
                       
                         
                           X 
                         
                       
                       
                         
                           Y 
                         
                       
                     
                     ] 
                   
                   = 
                   
                     
                       [ 
                       
                         
                           
                             
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                               ⁢ 
                               
                                   
                               
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                     ⁡ 
                     
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                             y 
                           
                         
                       
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                   ( 
                   1 
                   ) 
                 
               
             
           
         
       
     
     When the first axis  171  is taken to be the y-axis, the formula expressing the first parabola  161  is as follows. 
     
       
         
           
             
               
                 
                   [ 
                   
                     Formula 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     2 
                   
                   ] 
                 
               
               
                 
                     
                 
               
             
             
               
                 
                   
                     
                       
                         
                           
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                                     ⁡ 
                                     
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                               2 
                             
                           
                         
                       
                     
                     
                       
                         
                           
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                                   ⁢ 
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                               2 
                             
                           
                         
                       
                     
                     
                       
                         
                           
                             
                               
                                   
                                 
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                           = 
                           
                             
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                             ⁢ 
                             
                                 
                             
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                               a 
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                                   ⁢ 
                                   
                                       
                                   
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                                         ⁢ 
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                               x 
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                   } 
                 
               
               
                 
                   ( 
                   2 
                   ) 
                 
               
             
           
         
       
     
     When the second axis  172  is taken to be the y-axis, the formula expressing the second parabola  162  is as follows. 
     
       
         
           
             
               
                 
                   [ 
                   
                     Formula 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     3 
                   
                   ] 
                 
               
               
                 
                     
                 
               
             
             
               
                 
                   
                     
                       
                         
                           
                             
                               
                                   
                                 
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                                   &gt; 
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                                   ⁢ 
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                               2 
                             
                           
                         
                       
                     
                     
                       
                         
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                           = 
                           
                             
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                               ( 
                               
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                           = 
                           
                             
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                                     ) 
                                   
                                 
                               
                             
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                               x 
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                   } 
                 
               
               
                 
                   ( 
                   3 
                   ) 
                 
               
             
           
         
       
     
     In Formula (2) and Formula (3), a is the width of the solar cell  111 . In Formula (2), the angle θ is the incident angle A 12  of the light of the sun  210  at the minimum solar elevation A 11 . In Formula (3), an angle φ is the incident angle A 14  of the light of the sun  210  at the maximum solar elevation A 13 . 
     Then, the first axis  171  is converted to a first y-axis  176  by rotating in the clockwise direction by the angle θ and by adjusting the origin position. The first axis  171  is converted to the first y-axis  176  and the origin position is adjusted as follows. 
     
       
         
           
             
               
                 
                   [ 
                   
                     Formula 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     4 
                   
                   ] 
                 
               
               
                 
                     
                 
               
             
             
               
                 
                   
                     
                       
                         
                           X 
                           = 
                           
                             
                               x 
                               ⁢ 
                               
                                   
                               
                               ⁢ 
                               cos 
                               ⁢ 
                               
                                   
                               
                               ⁢ 
                               θ 
                             
                             + 
                             
                               
                                 1 
                                 
                                   2 
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                                     a 
                                     ⁡ 
                                     
                                       ( 
                                       
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                                           ⁢ 
                                           
                                               
                                           
                                           ⁢ 
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                                       ) 
                                     
                                   
                                 
                               
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                               ⁢ 
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                               ⁢ 
                               
                                   
                               
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                             + 
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                                 - 
                                 x 
                               
                               ⁢ 
                               
                                   
                               
                               ⁢ 
                               sin 
                               ⁢ 
                               
                                   
                               
                               ⁢ 
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                             + 
                             
                               
                                 1 
                                 
                                   2 
                                   ⁢ 
                                   
                                     a 
                                     ⁡ 
                                     
                                       ( 
                                       
                                         1 
                                         + 
                                         
                                           sin 
                                           ⁢ 
                                           
                                               
                                           
                                           ⁢ 
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                                       ) 
                                     
                                   
                                 
                               
                               ⁢ 
                               
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                               ⁢ 
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                               ⁢ 
                               
                                   
                               
                               ⁢ 
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                                 2 
                               
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                                 ( 
                                 
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                                     ⁢ 
                                     
                                         
                                     
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                               ⁢ 
                               
                                   
                               
                               ⁢ 
                               θ 
                             
                           
                         
                       
                     
                   
                   } 
                 
               
               
                 
                   ( 
                   4 
                   ) 
                 
               
             
           
         
       
     
     When the second axis  172  is converted to a second y-axis  177 , the second axis  172  is rotated in the clockwise direction by the angle φ; and the origin position is adjusted. The second axis  172  is converted to the second y-axis  177  and the origin position is adjusted as follows. 
     
       
         
           
             
               
                 
                   [ 
                   
                     Formula 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     5 
                   
                   ] 
                 
               
               
                 
                     
                 
               
             
             
               
                 
                   
                     
                       
                         
                           X 
                           = 
                           
                             
                               x 
                               ⁢ 
                               
                                   
                               
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                               ⁢ 
                               
                                   
                               
                               ⁢ 
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                             + 
                             
                               
                                 1 
                                 
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                                           sin 
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                               ⁢ 
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                           = 
                           
                             
                               
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                               ⁢ 
                               
                                   
                               
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                             + 
                             
                               
                                 1 
                                 
                                   2 
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                                     a 
                                     ⁡ 
                                     
                                       ( 
                                       
                                         1 
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                                           sin 
                                           ⁢ 
                                           
                                               
                                           
                                           ⁢ 
                                           ϕ 
                                         
                                       
                                       ) 
                                     
                                   
                                 
                               
                               ⁢ 
                               
                                 x 
                                 2 
                               
                               ⁢ 
                               cos 
                               ⁢ 
                               
                                   
                               
                               ⁢ 
                               ϕ 
                             
                             - 
                             
                               
                                 a 
                                 2 
                               
                               ⁢ 
                               
                                 ( 
                                 
                                   1 
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                                     sin 
                                     ⁢ 
                                     
                                         
                                     
                                     ⁢ 
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                   } 
                 
               
               
                 
                   ( 
                   5 
                   ) 
                 
               
             
           
         
       
     
     In the case where a refractive index layer having a refractive index n is provided, the formula θ′=sin −1 (sin(θ)/n) holds. In such a case, the refractive index (n ambient air ) of the ambient air is taken to be 1. Details of the refractive index layer are described below. 
     In the solar cell module  100  according to the embodiment as shown in  FIG. 4A  to  FIG. 4D , the focal point  166  of the first parabola  161  is included within the area of the solar cell panel  110  (or the solar cell  111 ). The focal point  167  of the second parabola  162  is included within the area of the solar cell panel  110  (or the solar cell  111 ). 
     The focal point  166  of the first parabola  161  exists in a first portion  113  within the area of the solar cell panel  110  (or the solar cell  111 ). The focal point  167  of the second parabola  162  exists in a second portion  114  within the area of the solar cell panel  110  (or the solar cell  111 ). The second portion  114  is different from the first portion  113 . More favorably, the focal point  166  of the first parabola  161  is positioned at a first edge portion  115  of the solar cell panel  110  (or the solar cell  111 ). More favorably, the focal point  167  of the second parabola  162  is positioned at a second edge portion  116  of the solar cell panel  110  (or the solar cell  111 ). The “edge portion” is as described above in regard to  FIG. 1  and  FIG. 2 . 
     According to the embodiment, all of the light  211  of the sun  210  between the minimum solar elevation A 11  and the maximum solar elevation A 13  is incident on the solar cell panel  110 . By using the first light concentration plate  121  and the second light concentration plate  122  that are asymmetric to each other as viewed from the solar cell panel  110 , for example, the solar cell module  100  can be mounted on a roof facing north, which is relatively unsuitable for utilizing sunlight. The solar cell module  100  according to the embodiment includes the first light concentration plate  121  described above and the second light concentration plate  122  described above. Thereby, compared to the case where the solar cell module  100  does not include the first light concentration plate  121  and the second light concentration plate  122 , the concentration ratio is improved; and the surface area of the solar cell panel  110  can be reduced. 
     The concentration ratio is expressed by d/a using the width a of the solar cell  111  and the pitch d of the solar cell  111  (referring to  FIG. 2 ). The concentration ratio (d/a) is regulated by a height h of the concentrator  120  (referring to  FIG. 2 ). In the case where the height h of the concentrator  120  is relatively high, the concentration ratio is relatively high. As described above, because the solar cell module  100  according to the embodiment can improve the concentration ratio, the concentration ratio can be ensured even in the case where the height h of the concentrator  120  is suppressed. Thereby, the thickness of the solar cell module  100  can be reduced. Generally, the reflection of the light at the light concentration plate  121  is not 100%. Therefore, d/a is lower than that of the case where the light reflectance at the light concentration plate  121  is 100%. Therefore, in the embodiment, the concentration ratio d/a is used as the ideal concentration ratio for convenience. 
     The maximum concentration ratio is obtained when the focal point  166  of the first parabola  161  is positioned at the first edge portion  115 , and the focal point  167  of the second parabola  162  is positioned at the second edge portion  116 . Thereby, the solar cell  111  and the solar cell panel  110  can be minimized. 
     The parabolic surface configuration of the concentrator  120  is a basic geometrical configuration. Therefore, the fabrication of the concentrator  120  is relatively easy. 
     According to the embodiment, the solar cell module  100  can perform similar operations year round. Thereby, it is unnecessary for the solar cell panel  110  to follow the sun  210  according to the season. Therefore, a drive device to drive the solar cell panel  110  or the like is unnecessary. 
     The solar cell module  100  according to the embodiment includes the solar cell panel  110  and the concentrator  120 . The solar cell panel  110  has a first cell surface  111   f   1 . The first cell surface  111   f   1  includes the first portion  113  and the second portion  114 . 
     The concentrator  120  has the first surface  123 , and the second surface  124  that is separated from the first surface  123 . A first light  211   a  that is incident on the first surface  123  at a first incident angle A 11  is incident on the first portion  113 . A second light  211   b  that is incident on the second surface  124  at the second incident angle A 14  is incident on the second portion  114 . 
     The first surface  123  includes the first parabola  161  where the first surface  123  intersects a first perpendicular plane  111   f   1   v  perpendicular to the first cell surface  111   f   1 . The first perpendicular plane  111   f   1   v  includes a direction from the first portion  113  toward the second portion  114 . The second surface  124  includes the second parabola  162  where the second surface  124  intersects the first perpendicular plane  111   f   1   v.    
     A first point  161   a  on the first parabola  161  and a second point  162   a  on the second parabola  162  are asymmetric with respect to a second perpendicular plane  111   f   2   v  perpendicular to the first cell surface  111   f   1  and the first perpendicular plane  111   f   1   v.    
     The first portion  113  includes a first focal point  161   p  of the first parabola  161 . The second portion  114  includes a second focal point  162   p  of the second parabola  162 . The solar cell  111  includes the first edge portion  115  and the second edge portion  116 . The first edge portion  115  includes the first focal point  161   p  of the first parabola  161 . The second edge portion  116  includes the second focal point  162   p  of the second parabola  162 . 
     The first surface  123  has a first concave surface  123   u . The second surface  124  has a second concave surface  124   u . The first concave surface  123   u  opposes the second concave surface  124   u.    
     The first incident angle A 11  is the one-year maximum value of the angle between the sunlight and a direction perpendicular to the ground surface. The second incident angle A 14  is the one-year minimum value of the angle between the sunlight and the direction perpendicular to the ground surface. 
     The concentrator  120  includes the first light concentration plate  121  that has the first surface  123 , and the second light concentration plate  122  that has the second surface  124 . 
       FIGS. 6A and 6B  are schematic views showing another example of the concentrator of the embodiment. 
       FIG. 6A  is a schematic plan view showing the light reflected by the concentrator of the example.  FIG. 6B  is a graph of the reflection state of the light when the angle of the second light concentration plate is changed. 
     In the example shown in  FIG. 6A  and  FIG. 6B , a first light concentration plate  125  has a planar surface. In other words, the first light concentration plate  125  has a planar configuration. A second light concentration plate  126  has a planar surface. In other words, the second light concentration plate  126  has a planar configuration. 
     In the example, the height h is expressed by h=a·sin(θ m −θ min ) for the first light concentration plate  125  and for the second light concentration plate  126 . The concentration ratio is expressed by 1+cos(θ max −θ min )−h/a/tan(θ max ). 
     The angle θ min , the angle θ max , and the width a of the solar cell  111  are set respectively so that θ min =30 degrees, θ max =80 degrees, and a=4 centimeters (cm). 
     In such a case, the height h is h=3.06 cm. The concentration ratio is about 1.508. 
     In the case where a second concentrator  126   a  is employed as shown in  FIG. 6B , the amount of the light  211  that is reflected by the second concentrator  126   a  and incident on the solar cell panel  110  is relatively low. Therefore, the second concentrator  126   a  has room for improvement. 
     When employing a second concentrator  126   c , a relatively large portion of the light  211  reflected by the second concentrator  126   c  is radiated outside the solar cell panel  110  without being incident on the solar cell panel  110 . Therefore, the second concentrator  126   c  has room for improvement. 
     When employing a second concentrator  126   b , a relatively large portion of the light  211  reflected by the second concentrator  126   b  is incident on the solar cell panel  110 . Therefore, for the second concentrator  126   b , there is room for improvement for increasing the concentration ratio. 
     In the example, there is a limiting formula for the width a of the solar cell  111 , the height h of the first light concentration plate  125  and the second light concentration plate  126 , and the angles θ min  and θ max . 
     In the case where the first light concentration plate  125  and the second light concentration plate  126  have planar configurations, focal points such as those of parabolas do not exist. Therefore, compared to the case where the first light concentration plate  125  and the second light concentration plate  126  have parabolic surface configurations, the light  211  can be dispersed. 
     Another embodiment will now be described with reference to the drawings. 
       FIG. 7  is a schematic perspective view showing a solar cell module according to the embodiment. 
     The solar cell module  100   a  according to the embodiment includes the solar cell panel  110  and a concentrator  130 . 
     The solar cell panel  110  is as described above in regard to  FIG. 1  to  FIG. 6B . 
     Two solar cell panels  110  and two concentrators  130  are provided in the solar cell module  100   a  shown in  FIG. 7 . However, the number of solar cell panels  110  and the number of concentrators  130  is not limited thereto. 
     In the embodiment described above in regard to  FIG. 1  to  FIG. 6B , the concentrator  120  reflects the light  211 . Loss (reflection loss) occurs when the light  211  is reflected by any object surface. 
     By reducing the reflecting surface area in the embodiment, the reflection loss is reduced; and the concentration ratio is improved further. 
     The refractive index of the concentrator  130  is higher than the refractive index of the ambient air. That is, the concentrator  130  includes a so-called high refractive index material. For example, a polymethylmethacrylate resin (an acrylic resin (PMMA)) or the like is used as the material of the concentrator  130 . For example, the concentrator  130  is formed by injection molding, etc. As shown in  FIG. 7 , the concentrator  130  has a first surface  131  and a second surface  132  and has a convex configuration on the solar cell panel  110  side. When viewed from the solar cell panel  110 , the second surface  132  may be asymmetric to the first surface  131  or symmetric to the first surface  131 . 
     It is favorable for the light  211  to undergo total internal reflection for at least a portion of the surfaces (the first surface  131  and the second surface  132 ) of the concentrator  130 . It is unnecessary to provide a mirror coating on the surface of the concentrator  130  in the region where the light  211  undergoes total internal reflection. Thereby, in the region where the light  211  undergoes total internal reflection, the reflection loss can be reduced. 
     In the embodiment, the mirror coating is not eliminated for the entire first surface  131  and the entire second surface  132 . As described above in regard to  FIG. 1  to  FIG. 6B , even in the case where the entire first surface  131  and the entire second surface  132  reflect the light  211 , the concentration ratio can be improved. 
     As described above, the concentrator  130  includes the high refractive index material. Thereby, the incident angle of the light  211  can be relaxed. 
     This will now be described further with reference to the drawings. 
       FIG. 8  is a schematic conceptual view showing the solar cell module according to the embodiment. 
     Because the refractive index of the concentrator  130  is higher than the refractive index of the ambient air, a refraction angle A 22  is smaller than an incident angle A 21  as shown in  FIG. 8 . Therefore, the substantial incident angle in the interior of the concentrator  130  can be increased. That is, the incident angle of the light  211  can be relaxed. Thereby, the thickness of the solar cell module  100   a  can be reduced for the same range of incident angles. 
     To further increase the range of the incident angles of the light  211 , it is more favorable to increase the clarity of the concentrator  130 . Also, to further increase the range of the incident angles of the light  211 , it is more favorable to use a material having a higher refractive index as the material of the concentrator  130 . The trapping effect of the light  211  can be increased by gradually reducing the refractive index from the interior of the concentrator  130  toward the outside. 
     The solar cell module  100   a  on the right side of  FIG. 8  is an example in which a mirror coating  135  is provided on the entire first surface  131  and the entire second surface  132 . 
     The solar cell module  100   a  on the left side of  FIG. 8  is an example in which the mirror coating  135  is provided on a portion of the first surface  131  and a portion of the second surface  132 . More specifically, the mirror coating  135  is provided in a first region F 1  of the first surface  131  and a second region F 2  of the second surface  132 . 
     For example, silver (Ag), aluminum (Al), etc., may be used as the material of the mirror coating  135 . 
       FIGS. 9A and 9B  are schematic views showing the total internal reflection of the light. 
       FIG. 9A  is a schematic plan view showing the light incident on the solar cell module according to the embodiment.  FIG. 9B  is a schematic plan view showing the area where the mirror coating is unnecessary. 
     For the parabolic surface of the concentrator  130 , the light for which it is most difficult to undergo total internal reflection is the light that is parallel to the axis of the parabola. As shown in  FIG. 9A , for example, the light  211  that is parallel to an axis  173  of the parabola of the second surface  132  is the light  211  that is parallel to the axis  173  of the parabola. Therefore, in the embodiment, the conditions at which the light  211  that is parallel to the axis  173  of the parabola undergoes total internal reflection are considered. 
       FIG. 9A  and  FIG. 9B  show an example in which the second surface  132  and the first surface  131  are symmetric as viewed from the solar cell panel  110 . 
     The conditions at which the light  211  parallel to the axis  173  of the parabola undergoes total internal reflection is expressed by the following formula, where n is the refractive index of the concentrator  130 , and the formula of the parabola is y=x 2 /(4p). 
     
       
         
           
             
               
                 
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                     ⁢ 
                     
                         
                     
                     ⁢ 
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                     tan 
                     ( 
                     
                       
                         sin 
                         
                           - 
                           1 
                         
                       
                       ( 
                       
                         1 
                         n 
                       
                       ) 
                     
                     ) 
                   
                   &lt; 
                   
                     
                       1 
                       
                         2 
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                         p 
                       
                     
                     ⁢ 
                     x 
                   
                 
               
               
                 
                   ( 
                   6 
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     In Formula (6), p is the value of the focal point of the parabola. In the case where the second surface  132  is asymmetric to the first surface  131  as viewed from the solar cell panel  110 , the value p of the focal point of the first surface  131  is different from the value p of the focal point of the second surface  132 . 
     In the case where the tilt of the solar cell panel  110  is steep, the conditions of the solar cell panel  110  change. This will now be described with reference to the drawings. 
       FIGS. 10A and 10B  are schematic plan views showing different tilts of the solar cell panel. 
       FIGS. 11A and 11B  are schematic plan views showing the method for mounting the solar cell panel. 
       FIG. 10A  is a schematic plan view showing an example in which the tilt of the solar cell panel is gradual compared to that of the example of  FIG. 10B .  FIG. 10B  is a schematic plan view showing an example in which the tilt of the solar cell panel is steep compared to that of the example of  FIG. 10A . 
       FIG. 11A  is a schematic plan view showing an example in which the placement location is horizontal.  FIG. 11B  is a schematic plan view showing an example in which the placement location is tilted. 
     The solar elevation of the sun  210   a  shown in  FIG. 10A  is the same as the solar elevation of the sun  210   a  shown in FIG.  10 B. The solar elevation of the sun  210   c  shown in  FIG. 10A  is the same as the solar elevation of the sun  210   c  shown in  FIG. 10B . The solar elevation of the sun  210   b  shown in  FIG. 10B  is a solar elevation between the sun  210   c  and the sun  210   a.    
     In  FIG. 10B , the solar cell panel  110  is mounted on a location (e.g., a roof facing north, etc.) tilted toward the side opposite the sun. In such a case, as shown in  FIG. 10B , the light  211  of the sun  210   c  of the minimum solar elevation is not incident on the concentrator  130  and is not incident on the solar cell panel  110 . Other conditions of the example of  FIG. 10B  may include the arctic, the antarctic, the northern side of a hill, etc., where the solar elevation is low compared to that of other regions. 
     Therefore, in such a case, the angle of the first surface  131  and the like are modified appropriately according to the tilt angle of the location (e.g., the land, the roof, etc.) where the solar cell panel  110  is mounted. 
     For example, as shown in  FIG. 11A , in the case where the solar cell panel  110  is mounted at a location tilted at an angle A 18  from a horizontal plane  225 , the incident angle is reduced by the amount of the angle A 18  of the placement location. That is, the incident angle of the light of the sun at the maximum solar elevation A 13  and the incident angle of the light of the sun at the minimum solar elevation A 11  are modified appropriately according to the angle A 18  of the placement location. 
     In the example, it is assumed that the solar cell panel  110  is mounted at a flat location. 
     Returning now to  FIG. 9B , the mirror coating  135  is necessary according to the configuration of the concentrator  130  in the region at the vicinity of the solar cell  111 . On the other hand, the light  211  that is incident on the concentrator  130  undergoes total internal reflection in regions more than a prescribed distance away from the solar cell  111 . Therefore, it is unnecessary to provide the mirror coating  135  in the region where the light  211  undergoes total internal reflection; and the reflection loss can be reduced.  FIG. 9B  shows the case where the refractive index n of the concentrator  130  is 1.493. 
       FIGS. 12A to 12C  are schematic plan views showing examples in which three solar cell modules are connected. 
       FIG. 12A  is a schematic plan view showing an example in which the mirror coating  135  is not provided on the concentrator  130 .  FIG. 12B  is a schematic plan view showing an example in which the mirror coating  135  is provided on a portion of the concentrator  130 .  FIG. 12C  is a schematic plan view showing an example in which an anti-reflection film (a reflection suppression film)  141  is provided. 
     Three solar cell modules  100   a  are connected in the example shown in  FIG. 12A . The first surface  131  may not be connected directly to the second surface  132  in a region F 3  where the two solar cell modules  100   a  are adjacent to each other. Even in such a case, total internal reflection is possible for the entire first surface  131  and the entire second surface  132 . Thereby, in the example shown in  FIG. 12A , the mirror coating  135  is not provided. 
     PMMA, etc., may be used as the material of the concentrator  130 . The refractive index of PMMA is 1.493. The concentrator  130  includes a plate unit  133 . The plate unit  133  suppresses the mutual-separation of the multiple concentrators  130  that would cause the multiple concentrators  130  to become separate bodies. A thickness D 1  of the plate unit  133  is, for example, about 0.5 cm. 
     In the example shown in  FIG. 12B , compared to the example shown in  FIG. 12A , the mirror coating  135  is provided on a portion of the first surface  131 . For example, silver (Ag), aluminum (Al), etc., may be used as the material of the mirror coating  135 . However, the material of the mirror coating  135  is not limited thereto; and a material having a reflectance similar to those of silver (Ag), aluminum (Al), etc., may be used. 
     For example, the minimum solar elevation A 11  of the sun  210  is taken to be 30 degrees; and the maximum solar elevation A 13  of the sun  210  is taken to be 80 degrees. In such a case, the incident angle of the light  211  of the sun  210  at the maximum solar elevation A 13  is 10 degrees. The incident angle of the light  211  of the sun  210  at the minimum solar elevation A 11  is 60 degrees. In the case where the material of the concentrator  130  is PMMA, the refractive index of the PMMA is 1.493; and therefore, the substantial incident angle in the interior of the concentrator  130  is not less than 6.68 degrees and not more than 35.45 degrees. 
     The width a of the solar cell  111  is set to 4 cm. The thickness D 1  of the plate unit  133  is set to 0.5 cm; and a dimension D 2  between the solar cell panel  110  and the lower portion of the plate unit  133  is set to 3.5 cm. 100 nanometers (nm) of MgF 2  is deposited on the upper surface of the plate unit  133 . 
     From calculations based on such conditions, total internal reflection does not occur in the region where the height of the first surface  131  is 2.83 cm or less. On the other hand, total internal reflection occurs in the region where the height of the first surface  131  is higher than 2.83 cm. Therefore, in the example shown in  FIG. 12B , a height D 3  of the mirror coating  135  is 2.83 cm. In other words, the mirror coating  135  is unnecessary in the region where the height of the first surface  131  is higher than 2.83 cm. The ideal concentration ratio is about 1.78. 
     In the example shown in  FIG. 12C , compared to the example shown in  FIG. 12B , the anti-reflection film  141  is provided on the side opposite to the concentrator  130  as viewed from the solar cell panel  110 . The anti-reflection film  141  suppresses reflections at the surface of the concentrator  130  of the light  211  passing through the interior of the concentrator  130  and traveling toward the solar cell panel  110 . 
     The anti-reflection film will now be described further with reference to the drawings. 
       FIGS. 13A and 13B  are schematic plan views showing the anti-reflection film of the embodiment. 
       FIG. 13A  is a schematic plan view showing an example in which three solar cell modules  100   a  are connected.  FIG. 13B  is a schematic plan view showing the light  211  traveling through the interior of the concentrator  130  of the embodiment. 
     In the examples shown in  FIG. 13A  and  FIG. 13B , a first anti-reflection film (reflection suppression film)  143  is provided on the upper surface of the plate unit  133  of the concentrator  130 . The refractive index of the first anti-reflection film  143  is higher than the refractive index of the ambient air and lower than the refractive index of the concentrator  130 . It is more favorable for the refractive index of the first anti-reflection film  143  to be about 1.22. Or, the material of the first anti-reflection film  143  may be MgF 2  (having a refractive index of about 1.38). 
     It is unfavorable for the light  211  passing through the interior of the concentrator  130  and traveling toward the solar cell panel  110  to be reflected at the interface between the concentrator  130  and the solar cell panel  110  as illustrated by arrow A 31  shown in  FIG. 13B . It is favorable for the light  211  passing through the interior of the concentrator  130  and traveling toward the solar cell panel  110  to pass through the interface between the concentrator  130  and the solar cell panel  110  to be incident on the solar cell panel  110  as illustrated by arrow A 32  shown in  FIG. 13B . 
     Therefore, in the example shown in  FIG. 13A  and  FIG. 13B , a second anti-reflection film (a reflection suppression film)  145  is provided between the concentrator  130  and the solar cell panel  110 . It is favorable for the refractive index of the second anti-reflection film  145  to have a value between the refractive index of the solar cell  111  and the refractive index of the concentrator  130 . That is, it is favorable for formula n p &lt;n m &lt;n c  to hold, where n c  is the refractive index of the solar cell  111 , n p  is the refractive index of the concentrator  130 , and n m  is the refractive index of the second anti-reflection film  145 . Or, the refractive index of the second anti-reflection film  145  may decrease gradually (be graded) from the concentrator  130  side toward the solar cell panel  110  side. 
     It is more favorable for the refractive index of the second anti-reflection film  145  to satisfy the following formula.
 
 n   m =( n   c   ·n   p ) 1/2   Formula (7)
 
     It is more favorable for a thickness t m  of the second anti-reflection film  145  to satisfy the following formula.
 
 t   m =λ/(4·( n   c   ·n   p ) 1/2 )  Formula (8)
 
     In Formula (8), λ is the wavelength of the light  211 . The unit of the thickness t m  is nanometers (nm). 
     For example, in the case where the refractive index n c  of the solar cell  111  is 3.7 (silicon (Si)) and the refractive index n p  of the concentrator  130  is 1.5, it is more favorable for the refractive index n m  of the second anti-reflection film  145  to be about 2.35 (TiO 2 , SrTiO 3 , etc.). Or, in the case where, for example, the refractive index n c  of the solar cell  111  is 3.7 (silicon (Si)) and, for example, the refractive index n p  of the concentrator  130  using a reflection plate is 1, it is more favorable for the refractive index n m  of the second anti-reflection film  145  to be about 1.9 (Si 3 N 4 , etc.). 
     Thereby, the reflections of the light  211  at the surface of the concentrator  130  are suppressed; and the light  211  can be guided efficiently toward the solar cell panel  110 . 
       FIG. 14  is a schematic plan view showing an example of the solar cell module according to the embodiment. 
     Two solar cell modules  100   a  are connected in the example shown in  FIG. 14 . 
     The minimum solar elevation A 11  of the sun  210  is taken to be 30 degrees; and the maximum solar elevation A 13  of the sun  210  is taken to be 80 degrees. In such a case, the incident angle of the light  211  of the sun  210  at the maximum solar elevation A 13  is 10 degrees. The incident angle of the light  211  of the sun  210  at the minimum solar elevation A 11  is 60 degrees. 
     The refractive index n p  of the concentrator  130  is set to 1.493 (PMMA). Here, the light  211  is refracted when incident on the concentrator  130 . Therefore, the substantial incident angle of the interior of the concentrator  130  is not less than 6.68 degrees and not more than 35.45 degrees. That is, a minimum substantial incident angle A 23  shown in  FIG. 14  is 6.68 degrees. A maximum substantial incident angle A 24  shown in  FIG. 14  is 35.45 degrees. 
     The width a of the solar cell  111  is set to 4 cm. The thickness D 1  of the plate unit  133  of the concentrator  130  is set to 0.5 cm. The dimension D 2  between the solar cell panel  110  and the lower portion of the plate unit  133  is set to 3.5 cm. In such a case, the ideal concentration ratio (d/a) is about 2.06. 
     The mirror coating  135  is provided on the first surface  131  of the solar cell module  100   a  on the left side of  FIG. 14 . In other words, in the example shown in  FIG. 14 , it is necessary to provide the mirror coating  135  on the first surface  131  of the solar cell module  100   a  on the left side; but it is unnecessary to provide the mirror coating  135  in the relatively wide region of the other parabolic surface. 
     The first surface  123  includes a third portion  123   c  and a fourth portion  123   d . The second surface  124  includes a fifth portion  124   e  and a sixth portion  124   f . The distance between the third portion  123   c  and the solar cell  111  is shorter than the distance between the fourth portion  123   d  and the solar cell  111 . The distance between the fifth portion  124   e  and the solar cell  111  is shorter than the distance between the sixth portion  124   f  and the solar cell  111 . A distance D 12  between the fourth portion  123   d  and the sixth portion  124   f  is longer than a distance D 11  between the third portion  123   c  and the fifth portion  124   e.    
     The first surface  123  includes the third region F 3 . The second surface  124  includes a fourth region F 4 . The first light  211   a  that is incident on the first surface  123  undergoes total internal reflection in the third region F 3 . The second light  211   b  that is incident on the second surface  124  undergoes total internal reflection in the fourth region F 4 . 
     The solar cell module  100  according to the embodiment further includes a first mirror coating layer  135   a  and a second mirror coating layer  135   b . The first surface  123  further includes the first region F 1 . The second surface  124  further includes the second region F 2 . The first mirror coating layer  135   a  is provided in the first region F 1 . The second mirror coating layer  135   b  is provided in the second region F 2 . 
     The solar cell module  100  according to the embodiment further includes the first reflection suppression film  143 . The first light  211   a  passes through the first reflection suppression film  143  to be incident on the first surface  123 . The second light  211   b  passes through the first reflection suppression film  143  to be incident on the second surface  124 . 
     The refractive index of the first reflection suppression film  143  is lower than the refractive index of the concentrator  130 . 
     The solar cell module  100  according to the embodiment further includes the second anti-reflection film  145 . The second anti-reflection film  145  is provided between the first reflection suppression film  143  and the solar cell panel  110 . The first light  211   a  passes through the second reflection suppression film  145  to be incident on the first portion  113 . The second light  211   b  passes through the second reflection suppression film  145  to be incident on the second portion  114 . 
     The refractive index of the second reflection suppression film  145  is higher than the refractive index of the concentrator  130  and lower than the refractive index of the solar cell  111 . 
     One of the first mirror coating layer  135   a  or the second mirror coating layer  135   b  includes one of silver or aluminum. 
       FIG. 15  is a schematic plan view showing another example of the solar cell module according to the embodiment. 
     In the example shown in  FIG. 15 , the width a of the solar cell  111  of the solar cell module  100   a  shown in  FIG. 14  is set to 1 cm. Thereby, the first axis  171  intersects the second surface  132  in the solar cell module  100   a  on the left side as shown in  FIG. 15 . The first axis  171  corresponds to the y-axis of the first surface  131 . Otherwise, the structure is the same as the structure of the solar cell module  100   a  described above in regard to  FIG. 14 . 
     As described above in regard to  FIG. 4A  to  FIG. 4D , the first axis  171  is parallel to the travel direction of the light  211  of the sun  210  at the minimum solar elevation A 11 . The second axis  172  is parallel to the travel direction of the light  211  of the sun  210  at the maximum solar elevation A 13 . Therefore, the light  211  of the sun  210  travels in the area between the first axis  171  and the second axis  172  toward the concentrator  130 . 
     However, the light  211  of the sun  210  of a prescribed elevation from the minimum solar elevation A 11  (e.g., the light  211  substantially parallel to the first axis  171 ) is shielded by the second surface  132  of the solar cell module  100   a  on the left side. Therefore, the light of the sun  210  of an elevation relatively proximal to the minimum solar elevation A 11  that can be incident on the concentrator  130  is light  213  shown in  FIG. 15 . 
     Even in such a case, the mirror coating  135  is provided on the first surface  131  of the solar cell module  100   a  on the left side. As illustrated by arrow A 33  shown in  FIG. 15 , the light  211  that is incident on the concentrator  130  and reaches the first surface  131  of the solar cell module  100   a  on the right side undergoes total internal reflection at the first surface  131 . In the example shown in  FIG. 15 , the ideal concentration ratio (d/a) is about 3.4. 
       FIG. 16  is a schematic plan view showing another example of the solar cell module according to the embodiment. 
     In the example shown in  FIG. 16 , the height of the plate unit  133  of the concentrator  130  of the solar cell module  100   a  shown in  FIG. 15  is set to be high. That is, the dimension D 2  between the solar cell panel  110  and the lower portion of the plate unit  133  is longer than 3.5 cm. 
     In such a case, light  215  of the maximum incident angle may not be able to reach the region where the mirror coating  135  is provided. The light  215  of the maximum incident angle is parallel to the first axis  171 . In other words, the light  215  of the maximum incident angle is the light of the sun  210  at the minimum solar elevation A 11 . Therefore, in the example shown in  FIG. 16 , it is necessary to redesign the solar cell module  100   a  to match the light  213  of the sun  210  of an elevation relatively proximal to the minimum solar elevation A 11  that can reach the region where the mirror coating  135  is provided. In the example shown in  FIG. 16 , the ideal concentration ratio (d/a) is about 4.1. 
       FIGS. 17A and 17B  are schematic views showing another example of the solar cell module according to the embodiment. 
       FIG. 17A  is a schematic plan view showing another example of the solar cell module according to the embodiment.  FIG. 17B  is a graph of an example of the relationship between an incident angle An and a light amount Lg. In the graph shown in  FIG. 17B , the light amount Lg is taken to be 100% when the incident angle An is 0 degrees for no light concentration (the case where the concentrator  130  is not provided). In  FIG. 17B , data SPL 1  correspond to “partial vapor-deposition”. Data SPL 2  correspond to “entire vapor-deposition”. Data SPL 3  correspond to “without partial vapor-deposition”. Data SPL 4  correspond to “no light concentration”. 
     The solar cell module  100   a  shown in  FIG. 17A  includes the solar cell panel  110 , the concentrator  130 , the first anti-reflection film  143 , and the second anti-reflection film  145 . The structure of the solar cell module  100   a  shown in  FIG. 17A  is similar to the structure of the solar cell module  100   a  described above in regard to  FIG. 13A . 
     The first anti-reflection film  143  is provided on the upper surface of the plate unit  133  of the concentrator  130 . The material of the first anti-reflection film  143  is MgF 2 . The first anti-reflection film  143  has a rectangular configuration. A length D 4  of one side of the first anti-reflection film  143  is 4 cm. A length D 5  of another side of the first anti-reflection film  143  intersecting the one side is 8.3 cm. The thickness of the first anti-reflection film  143  is 100 nm. 
     The second anti-reflection film  145  is provided between the concentrator  130  and the solar cell panel  110 . The material of the second anti-reflection film  145  is TiO 2 . The thickness of the second anti-reflection film  145  is 60 nm. 
     As the mirror coating  135 , a portion in which aluminum is vapor-deposited is provided in the first surface  131 . In the example, the relationship between the incident angle An and the light amount Lg is investigated for the case where the aluminum is vapor-deposited on the entire first surface  131 , the case where the aluminum is vapor-deposited on a portion of the first surface  131 , and the case where the aluminum is not vapor-deposited on the first surface  131 . Similarly, the case where the concentrator  130  is not provided is investigated. 
     The solar cell  111  has a square configuration. The length of one side of the solar cell  111  is 4 cm. 
     The ideal concentration ratio of the solar cell module  100   a  shown in  FIG. 17A  is 2.06. 
     The investigation results are as shown in  FIG. 17B . 
     In other words, the light amount Lg is higher for the case where the concentrator  130  is provided than for the case where the concentrator  130  is not provided. 
     In the case where the aluminum is vapor-deposited on the entire first surface  131 , the total internal reflection of the light cannot be utilized; and reflection loss occurs. Therefore, the light amount Lg is lower for the case where the aluminum is vapor-deposited on the entire first surface  131  than for the case where the aluminum is vapor-deposited on a portion of the first surface  131 . However, the light amount Lg of the case where the aluminum is vapor-deposited on the entire first surface  131  is higher than the light amount Lg of the case where the aluminum is not vapor-deposited on the first surface  131 . In the embodiment, the case where the aluminum is vapor-deposited on the entire first surface  131  is not eliminated. 
     Even in the case where the aluminum is not vapor-deposited on the first surface  131 , there is a light concentration effect when the concentrator  130  is provided. 
     Embodiments include following Clauses: 
     Clause 1 
     A solar cell module, comprising:
         a solar cell panel having a first cell surface including a first portion and a second portion; and   a concentrator,   the concentrator having
           a first surface, and   a second surface separated from the first surface,   
           a first light incident on the first surface at a first incident angle being incident on the first portion,   a second light incident on the second surface at a second incident angle being incident on the second portion,   the first surface including a first parabola where the first surface intersects a first perpendicular plane, the first perpendicular plane including a direction from the first portion toward the second portion, the first perpendicular plane being perpendicular to the first cell surface,   the second surface including a second parabola where the second surface intersects the first perpendicular plane,   a first point on the first parabola and a second point on the second parabola being asymmetric with respect to a second perpendicular plane, the second perpendicular plane being perpendicular to the first cell surface and the first perpendicular plane.
 
Clause 2
       

     The module according to Clause 1, wherein
         the first portion includes a first focal point of the first parabola, and   the second portion includes a second focal point of the second parabola.
 
Clause 3
       

     The module according to Clause 1, wherein
         the solar cell panel includes a first edge portion and a second edge portion,   the first edge portion includes the first focal point of the first parabola, and   the second edge portion includes the second focal point of the second parabola.
 
Clause 4
       

     The module according to Clause 1, wherein
         the first surface has a first concave surface,   the second surface has a second concave surface, and   the first concave surface opposes the second concave surface.
 
Clause 5
       

     The module according to Clause 1, wherein
         the first incident angle is a one-year maximum value of an angle between sunlight and a direction perpendicular to a ground surface, and   the second incident angle is a one-year minimum value of the angle between the sunlight and the direction perpendicular to the ground surface.
 
Clause 6
       

     The module according to Clause 1, wherein the concentrator includes:
         a first light concentration plate having the first surface; and   a second light concentration plate having the second surface.
 
Clause 7
       

     The I module according to Clause 1, wherein
         the first surface includes a third portion and a fourth portion,   the second surface includes a fifth portion and a sixth portion,   a distance between the third portion and the solar cell is shorter than a distance between the fourth portion and the solar cell,   a distance between the fifth portion and the solar cell is shorter than a distance between the sixth portion and the solar cell, and   a distance between the fourth portion and the sixth portion is longer than a distance between the third portion and the fifth portion.
 
Clause 8
       

     The module according to Clause 7, wherein
         the concentrator includes a light concentrating material, and   a refractive index of the concentrator is higher than a refractive index of ambient air.
 
Clause 9
       

     The module according to Clause 8, wherein
         the first surface includes a third region,   the second surface includes a fourth region,   the first light incident on the first surface undergoes total internal reflection in the third region, and   the second light incident on the second surface undergoes total internal reflection in the fourth region.
 
Clause 10
       

     The module according to Clause 9, further comprising:
         a first mirror coating layer; and   a second mirror coating layer,   the first surface further including a first region,   the second surface further including a second region,   the first mirror coating layer being provided in the first region,   the second mirror coating layer being provided in the second region.
 
Clause 11
       

     The module according to Clause 8, further comprising a first reflection suppression film,
         the first light passing through the first reflection suppression film to be incident on the first surface,   the second light passing through the first reflection suppression film to be incident on the second surface.
 
Clause 12
       

     The module according to Clause 11, wherein a refractive index of the first reflection suppression film is lower than the refractive index of the concentrator. 
     Clause 13 
     The module according to Clause 12, further comprising a second reflection suppression film provided between the first reflection suppression film and the solar cell panel,
         the first light passing through the second reflection suppression film to be incident on the first portion,   the second light passing through the second reflection suppression film to be incident on the second portion.
 
Clause 14
       

     The module according to Clause 13, wherein a refractive index of the second reflection suppression film is higher than the refractive index of the concentrator and lower than a refractive index of the solar cell. 
     Clause 15 
     The module according to Clause 8, wherein the concentrator includes a polymethylmethacrylate resin. 
     Clause 16 
     The module according to Clause 10, wherein one of the first mirror coating layer or the second mirror coating layer includes one of silver or aluminum. 
     While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the invention.