Patent Publication Number: US-2007113883-A1

Title: Sunbeams concentration lenses, process and apparatus for solar photovoltaic generator using concept of superposition

Description:
The present application claims priority under 35 U.S.C. §119 to Korean Patent Application No. 10 2005 0113028, filed 24 Nov. 2005, a certified copy of which is filed herewith and which is hereby incorporated herein by reference as if fully set forth in its entirety.  
     BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to a concentration method of sunbeams for a photovoltaic power generation and lens used in the above method.  
      2. Background of the Related Art  
      Generally, a photovoltaic power generation refers to as a technology that converts light energy from the sunbeams into electrical energy using a solar cell. That is, if a solar cell consisting of a PN junction semiconductor is irradiated with sunbeams, it creates free electrons to induce electricity.  
      Meanwhile, a concentration means such as a concentration lens or a concentration reflection mirror for concentrating sunbeams into a concentration surface of a solar cell is used in a photovoltaic power generation, and a light-integrity and luminance uniformity are related directly to an efficiency of a power plant. However, it has a problem in that a conventional concentration means maintains hardly luminance uniformity on a concentration surface of a solar cell since it uses continuous changes on an optical surface.  
       FIG. 7  is a view showing an example of a conventional concentration lens, wherein  FIG. 7   a  is a top view and  FIG. 7   b  is a side view. At this time, the concentration lens  30  is fabricated as a Fresnel Lens in a form of a planar plate compared with a conventional convex lens, and a plurality of saw blade-type refraction part  31  are formed on one side thereof, thereby focusing incident lights to the middle.  
      As a result, the incident sunbeams into the lens are refracted by the saw blade-type refraction part  31  and concentrated into the concentration surface  11  of a solar cell  10  disposed in the middle. However, since the conventional concentration lens as described above focuses the sunbeams using continuous changes on an optical surface, the luminance of the light that is focused on the concentration surface of a solar cell gets lowered gradually from the middle and thus it can not have a uniformity of a luminance.  
      In addition, if an enlarged sized-concentration lens is needed depending on the power generation capacity, there arises a problem in that it is not fabricated easily since the optical surface of the concentration lens is formed continuously.  
      Meanwhile, the solar cell that is used in photovoltaic power generation includes a plurality of unit cells which are disposed in series or in parallel for inducing a high power source, and the performance of the photovoltaic power generator is dependent on the unit cell that has a small light irradiation volume among the cells.  
      Accordingly, if the conventional concentration lens that does not have uniform luminance on the concentration surface is used, there arises another problem in that a total performance of solar cell is decreased with a solar cell that is disposed on the region that has a relatively lower luminance.  
     SUMMARY OF THE INVENTION  
      The present invention has been proposed to solve the above problems, and an object of the present invention is to provide a concentration method of sunbeams for a photovoltaic power generation and lens and apparatus used in the method.  
      To achieve the above object, according to one aspect of the present invention, it is provided that a method of concentrating sunbeams on a concentration surface of a solar cell that is installed on a photovoltaic power generator, it comprises steps of installing a concentration lens ( 20 ) on the upper side of a solar cell in parallel to the concentration surface, which includes a plurality of unit lens ( 21 ) having areas corresponding to the areas of the concentration surface, and irradiating and concentrating superposingly the sunbeams incident on the respective unit lens to the concentration surface.  
      In addition, according to another aspect of the present invention, the a sunbeams concentration lens for a photovoltaic power generation using a concept of superposition including a plurality of unit lenses which are installed in a planar plate shape on the upper side of a solar cell and have areas corresponding to the areas of a concentration surface of the solar cell, wherein the unit lens irradiates the sunbeams incident on them superposingly and concentrates them on the concentration surface.  
      Meanwhile, according to another aspect of the present invention, the unit lens includes one non-refractive light transmittance part and a plurality of Fresnel lens on one surface of which a plurality of saw blade type-refraction part are formed.  
      At this time, the light transmittance part is installed on the vertical upper side of the concentration surface and the Fresnel lens is disposed surrounding the light transmittance or extending in opposing directions thereof.  
      In addition, the saw blade type refraction part of the Fresnel lens is formed in a vertical direction to a straight line running from the Fresnel lens toward the middle of the light transmittance at a predetermined interval, and a inclined angle of the saw blade type refraction part in respective Fresnel lens is decreased gradually from the light transmittance part.  
      In addition, according to another aspect of the present invention, a sunbeams concentration lens for a photovoltaic power generation includes a plurality of unit lenses which are installed on the upper side of a concentration surface formed on a solar cell and have areas corresponding to the areas of the concentration surface, and the unit lens irradiates the sunbeams incident on them superposingly and concentrates them on the concentration surface, wherein the concentration lens includes one non-refractive light transmittance part that is installed in parallel on the vertical upper side of the concentration surface and a plurality of Fresnel lens extending downside in an opposing direction at a predetermined angle, wherein the inclined angle of the Fresnel lens is set at a range of 10 to 20 degree on the basis of the light transmittance.  
      Meanwhile, according to another aspect of the present invention, a sunbeams concentration apparatus for a photovoltaic power generation using a concept of superposition includes: a solar cell on one side of which a concentration surface is formed; a concentration lens including a plurality of unit lenses which are installed in a planar plate shape on the upper side of a solar cell and have areas corresponding to the areas of a concentration surface of the solar cell; and a frame that fixes the concentration lens in a proper position, wherein the unit lens irradiates the sunbeams incident on them superposingly and concentrates them on the concentration surface.  
      In addition, the unit lens includes one non-refractive light transmittance part and a plurality of Fresnel lens on one surface of which a plurality of saw blade type-refraction part are formed.  
      At this point, the light transmittance part is installed on the vertical upper side of the concentration surface and the Fresnel lens is disposed surrounding the light transmittance or extending in opposing directions thereof.  
      Meanwhile, the saw blade type refraction part of the Fresnel lens is formed in a vertical direction to a straight line running from the Fresnel lens toward the middle of the light transmittance, and an inclined angle of the saw blade type refraction part in respective Fresnel lens is decreased gradually from the light transmittance part.  
      In addition, according to another aspect of the present invention, a concentration apparatus for photovoltaic power generation using a concept of superposition includes a solar cell on one side of which a concentration surface is formed; a concentration lens including a plurality of unit lenses which are installed in a planar plate shape on the upper side of a solar cell and have areas corresponding to the areas of a concentration surface of the solar cell; and a frame that fixes the concentration lens in a proper position, wherein the unit lens irradiates the sunbeams incident on them superposingly and concentrates them on the concentration surface, and includes one non-refractive light transmittance part that is installed in parallel on the vertical upper side of the concentration surface and a plurality of Fresnel lens extending downside in the opposing direction of the light transmittance part at a predetermined angle, wherein the inclined angle of the Fresnel lens is set at a range of 10 to 20 degree on the basis of the light transmittance.  
      It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The accompanying drawings, which are included to provide a further understanding of the invention are incorporated, constitute a part of this specifications, and illustrate embodiments of the invention together with the description explaining the principles of the invention. In the drawings:  
       FIG. 1  is a perspective view showing a concentration apparatus according to a first embodiment of the present invention;  
       FIG. 2  is a bottom view of  FIG. 1 ;  
       FIG. 3  is a sectional view taken along A-A line in  FIG. 2 ;  
       FIG. 4  is a graph showing luminance that is measured on a concentration surface of a solar cell;  
       FIG. 5  is a perspective view showing a concentration apparatus according to a second embodiment of the present invention;  
       FIG. 6  is a perspective view showing a concentration apparatus according to a third embodiment of the present invention; and  
       FIG. 7  is a view showing an example of a conventional concentration lens, wherein  FIG. 7   a  is a top view and  FIG. 7   b  is a side view. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      Reference will now be made in detail to the preferred embodiment of the present invention, examples of which are illustrated in the accompanying drawings.  
       FIG. 1  is a perspective view showing a concentration apparatus according to a first embodiment of the present invention,  FIG. 2  is a bottom view of  FIG. 1 , and  FIG. 3  is a sectional view taken along A-A line in  FIG. 2 .  
      As shown in drawings, a concentration lens  20  according to one aspect of the present invention is disposed in parallel to the upper surface of a concentration surface  11  formed on a solar cell  20 , and it includes a plurality of unit lens  21  the areas of which correspond to the areas of the concentration surface  11 . In this embodiment, a total number of 81 unit lens (9×9) is used in forming the concentration lens.  
      At this time, a respective unit lens  21  is configured to irradiate incident sunbeams therein to the concentration surface  11  of the solar cell  10 . Here, respective unit lens  21  irradiates the volume of sunbeams corresponding to the areas of the concentration surface  11  and thus an irradiation amount of sunbeams to the concentration surface  11  is superposed, thereby enhancing light integrity therein compared to the conventional art. In addition, the concentration of the sunbeams is performed using a superposition method instead for a conventional focusing method, thereby gaining a uniform luminance over the entire surface of the concentration surface  11 .  
      In the present embodiment, the unit lens  21  includes a non-refractive light transmittance part  210  that is disposed in the middle of the concentration lens  20  and a plurality of a Fresnel lens  211  which is disposed surrounding the light transmittance part and on one surface of which a plurality of saw blade type-refraction part  211   a  are formed.  
      As a result, as shown in  FIG. 3 , the sunbeams incident on the light transmittance part  210  is transmitted directly and irradiated to the concentration surface  11  of the solar cell  10 , and the sunbeam incident on the Fresnel lens  211  is refracted at a predetermined angle by a saw type-refraction part  211   a  and is irradiated to the concentration surface  11 .  
      At this point, as shown in  FIG. 2 , the saw type-refraction part  211   a  that is formed on respective Fresnel lens  211  is formed perpendicular to a straight line of the Fresnel lens  211  to the middle of the light transmittance part  210  at predetermined intervals, and a inclined angle (θ) at respective Fresnel lens is decreased gradually from the light transmittance part  210 .  
       FIG. 4  is a graph showing illuminance that is measured on a concentration surface of a solar cell, wherein (a) shows a illuminance that is measured in a transverse direction and (b) shows a illuminance that is measured in a diagonal direction.  
      As shown in the graphs on a normal state, if the concentration lens  20  according to the present invention is used, the sunbeams are incident with a uniform luminance over an entire range of the concentration surface  11 . That is, if a solar cell is disposed within a normal state line, it can achieve uniform luminance and a large light integration degree.  
       FIG. 5  is a perspective view showing a second embodiment of the present invention. As shown in the drawing, the concentration lens  20  according to the second embodiment of the present invention is characterized in that the light transmittance part  210  is disposed on the vertical upper part of the concentration surface  11  and the Fresnel lens  211  is disposed extending in opposing directions of the light transmittance  210 .  
      That is, the concentration lens as shown in  FIG. 1  is installed wherein a Fresnel lens surrounds a light transmittance part and thus if a plurality of solar cell are installed, the spaces which are formed between them can not be narrowed. However, since a concentration lens according to the second embodiment of the present invention is formed as a bar type, solar cells are installed continuously, thereby the more many solar cells can be installed within a limited space.  
       FIG. 6  is a sectional view showing a concentration apparatus according to a third embodiment of the present invention. As shown in the drawing, in the concentration lens  20  according to the third embodiment of the present invention, an inclined angle (α) of the Fresnel lens which is extended in the opposing direction to the light transmittance part  210  as described in the second embodiment is set at a range of 10-20 degree toward downside.  
      Consequently, a Fresnel lens is installed at a predetermined angle instead of a planar configuration such that a range of receiving sunbeams is enlarged and a light scattering is reduced, thereby improving an efficiency of a concentration.  
      Since a configuration and an operation of a concentration lens according to the present invention have been explained so far hereinafter a sunbeams concentration method according to the present invention will be explained on the basis of the description thereof.  
      The sunbeams concentration method of the present invention is characterized in that it comprises steps of installing a concentration lens  20  including a plurality of unit lens  21  having areas corresponding to that of the concentration surface  11  in parallel to the concentration surface  11 ; and concentrating the sunbeams incident on respective unit lens  21  such that they are irradiated and superposed on the concentration surface  11 .  
      That is, the sunbeams incident on respective unit lens are refracted and irradiated to the concentration surface of the solar cell, and thus the sunbeams on the region corresponding to the areas of the concentration surface are superposed as much as the numbers of unit lens on the concentration surface.  
      Meanwhile, a concentration unit that is used directly in the concentration method of the present invention is embodied easily using the concentration lens of the present invention. An example of the concentration unit includes a solar cell  10  one side of which is a concentration surface  11 , a concentration lens  20  that is installed as a planar plate on the vertical upper side of the concentration surface  11  and a frame (not shown) that fixes the concentration lens  20  in a proper position.  
     ADVANTAGEOUS EFFECTS  
      As described above, according to the preferred embodiments of the present invention, the sunbeams are concentrated on the concentration surface with a superposing pattern as a unit of an area of concentration surface, and thus the sunbeams are irradiated with a uniform luminance over the entire range of the concentration surface. Therefore, a performance of a solar cell is maintained as a best mode compared to the conventional art.  
      The scope of patents subject matter should not be limited to any of the specific exemplary embodiments discussed, but is instead defined by the following claims. As will be recognized by those skilled in the art, the innovative concepts described in the present application can be modified and varied over a wide range of applications.