Abstract:
A light concentration element assembly includes a Fresnel lens unit and a compound parabolic concentrator. The Fresnel lens unit includes a first Fresnel lens and a second Fresnel lens arranged parallel with each other, and configured for converging light transmitted therethrough. The compound parabolic concentrator includes at least two paraboloidal reflecting surfaces. The parabolic concentrator includes a light incident opening facing the Fresnel lens unit and a light output opening, and the paraboloidal reflecting surfaces are configured for reflecting the converged light from the Fresnel lens unit and outputting the reflected light through the light output opening. A solar cell apparatus using the light concentration element assembly is provided.

Description:
BACKGROUND 
       [0001]    1. Technical Field 
         [0002]    The present disclosure relates to a light concentration element assembly and a related solar cell apparatus. 
         [0003]    2. Description of Related Art 
         [0004]    Conventional solar cell apparatuses use reflectors to reflect light to the solar cell, or use convex lenses to converge light to the solar cell. However, the reflectors and convex lenses result in bad light concentration uniformity and bad light concentration efficiency, such that the solar cell cannot be fully excited to work properly. 
         [0005]    What is needed, therefore, is a light concentration element assembly and a solar cell apparatus with same, which can overcome the above shortcomings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]    Many aspects of the light concentration element assembly and solar cell apparatus can be better understood with reference to the following drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the present light concentration element assembly and solar cell apparatus. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views. 
           [0007]      FIG. 1  is a schematic, cross-sectional view of a solar cell apparatus in accordance with one embodiment, the solar cell apparatus including a light concentration element assembly and a solar cell device. 
           [0008]      FIG. 2  is an output flux distribution diagram of the light concentration element assembly of  FIG. 1 , under a condition that the distance D=122.25 mm. 
           [0009]      FIG. 3  is an output flux distribution diagram of the light concentration element assembly of  FIG. 1 , under a condition that the distance D=110.46 mm. 
           [0010]      FIG. 4  is similar to  FIG. 2 , but showing that the light incident angle is 1 degree. 
           [0011]      FIG. 5  is a diagram showing a relationship between the light incident angle and the output efficiency under a condition that the distance D=122.25 mm. 
           [0012]      FIG. 6  is similar to  FIG. 3 , but showing that the light incident angle is 1 degree. 
           [0013]      FIG. 7  is a diagram showing a relationship between the light incident angle and the output efficiency under a condition that the distance D=110.46 mm. 
       
    
    
     DETAILED DESCRIPTION 
       [0014]    Embodiments of the present light concentration element assembly and solar cell apparatus will now be described in detail below and with reference to the drawings. 
         [0015]    Referring to  FIG. 1 , a solar cell apparatus  50  includes a light concentration element assembly  10  and a solar cell device  60 . 
         [0016]    The light concentration element assembly  10  includes a Fresnel lens unit  20  and a compound parabolic concentrator  30 . 
         [0017]    The Fresnel lens unit  20  includes at least two parallel Fresnel lenses, in the present embodiment, it includes a first Fresnel lens  21  and a second Fresnel lens  22 . The first Fresnel lens  21  is arranged above the second Fresnel lens  22 , and they are spaced from each other a predetermined distance. In other embodiments, the Fresnel lens unit  20  may include more Fresnel lenses, such as three or four Fresnel lenses. The Fresnel lens unit  20  helps to reduce a focus distance of the entire light concentration element assembly  10 , which can make the entire light concentration element assembly  10  smaller in size. 
         [0018]    The Fresnel lens unit  20  includes a top surface  201  and a bottom surface  203 . The top surface  201  is the top surface of the first Fresnel lens  21 , and the bottom surface  203  is the bottom surface of the second Fresnel lens  22 . The top surfaces of the first and second Fresnel lenses  21  and  22  are the light incident surfaces, and the bottom surfaces of the first and second Fresnel lenses  21  and  22  are the light output surfaces. An incident light L incident the Fresnel lens unit  20  from the top surface  201 , which then passes through the first Fresnel lens  21  and the second Fresnel lens  22  in sequence, and finally outputs from the bottom surface  203 . Each of the first Fresnel lens  21  and the second Fresnel lens  22  concentrates the light incident thereon. 
         [0019]    The incident surface, i.e., the top surface  201  of the first Fresnel lens  201  is parallel with the incident surface of the second Fresnel lens  22 . The output surface of the first Fresnel lens  21  nears the incident surface of the second Fresnel lens  22 . In other words, the output surface of the top Fresnel lens faces the incident surface of the bottom Fresnel lens in two adjacent Fresnel lenses. 
         [0020]    The bottom surface, i.e., the output surface of each of the Fresnel lenses has a number of grooves formed therein. The grooves oppose to (i.e., faces towards) the inside of the light concentration element assembly  10 , which can avoid dust from falling therein. The top surface, i.e., the incident surface of each of the Fresnel lens is a flat surface. 
         [0021]    The compound parabolic concentrator  30  follows the Fresnel lens unit  20 . The compound parabolic concentrator  30  includes at least two paraboloidal reflecting surfaces  300 . The at least two paraboloidal reflecting surfaces  300  oppose each other, and cooperatively form a light incident opening  31  and a light output opening  32  at the respective two ends thereof. The light incident opening  31  opposes the Fresnel lens unit  20 , and the light output opening  32  is aligned with the light incident opening  31 . The Fresnel lens unit  20  can have a focal point O 1  located inside the compound parabolic concentrator  30 , and the light incident the light incident opening  31  can be first focused at the focal point O 1  and then can be spread to the paraboloidal reflecting surfaces  300 . Reflection then occurs at the paraboloidal reflecting surfaces  300 . 
         [0022]    In the present embodiment, the compound parabolic concentrator  30  includes two paraboloidal reflecting surfaces  300 , the two paraboloidal reflecting surfaces  300  are symmetrically arranged about a central axis of the compound parabolic concentrator  30 . The two paraboloidal reflecting surfaces  300  each have a focal point O 2  and O 3 , the focal points O 2  and O 3  of both the paraboloidal reflecting surfaces  300  may be located at the end of the light output opening  32 . The light beams through the focal points O 2  and O 3  can directly project on the solar cell device  60 . Some light beams may intersect each other, for example, at a point O 4  before reach the solar cell device  60 . 
         [0023]    The central axis of the compound parabolic concentrator  30  is aligned with that of the Fresnel lens unit  20 , thus a highest light output efficiency of the light concentration element assembly  10  can be obtained. Relative to the incident light L, the light is concentrated by the light concentration element assembly  10 . 
         [0024]    The solar cell device  60  opposes the light output opening  32  to receive the light output from the light concentration element assembly  10 . The solar cell device  60  may have one or more solar cells to convert the light energy to electrical energy. 
         [0025]    Table 1 shows output data of the light concentration element assembly  10  at situations that a distance D between the top surface  201  of the Fresnel lens unit  20  and the light output opening  32  of the compound parabolic concentrator  30  is changed, but the input flux is the same and the incident light L is perpendicular to the light receiving surface of the Fresnel lens unit  20 . 
         [0000]    
       
         
               
               
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                 Distance 
                 Input 
                 Output 
                 Output 
                 Uniformity 
               
               
                 (D) 
                 Flux 
                 Flux 
                 Efficiency 
                 (Min/Max) 
               
               
                   
               
             
             
               
                 122.25 mm 
                 1000 W 
                 437 W 
                 43.7% 
                 2.53% 
               
               
                 110.46 mm 
                 1000 W 
                 539 W 
                 53.9% 
                 6.25% 
               
               
                   
               
             
          
         
       
     
         [0026]    Min in Table 1 may represent a minimum output flux on a position of a light receiving surface opposing the light concentration element assembly  10 , and Max therein represents at a same time a maximum output flux on another position of the light receiving surface. The light receiving surface may be the surface of the solar cell device  60 . It can be concluded from Table 1 that with the same input flux, relative to the 122.25 mm distance D, the output data and the uniformity are better with the 110.46 mm distance D. 
         [0027]    Referring also to  FIGS. 2 and 3 ,  FIG. 2  is an output flux distribution along a predetermined line from one end of the light receiving surface to opposite another end of the light receiving surface under the incident light L and the condition of distance D=122.25 mm.  FIG. 3  is an output flux distribution along the same predetermined line on the light receiving surface under the incident light L and the condition of distance D=110.46 mm.  FIGS. 2 and 3  show that relative to the distance D=122.25 mm, the uniformity is better with the distance D=110.46 mm. 
         [0028]    Referring to  FIG. 4 ,  FIG. 4  is an output flux distribution of the light concentration element assembly  10  under particular conditions that the distance D=122.25 mm, and a light incident angle is 1 degree. The light incident angle is the angle between the light incident directions and is normal for the light receiving surface (i.e, the light incident surface) of the Fresnel lens unit  20 . For a reference, the incident light L shown in  FIG. 1  represents the light incident angle is 0 degree. Relative to  FIG. 2 ,  FIG. 4  shows that the uniformity is better with the light incident angle is 1 degree. 
         [0029]    Referring to  FIG. 5 , shows the relationship between the light incident angle from 0 degree to 1.6 degree and the corresponding output efficiency under the distance D=122.25 mm. It can be concluded from  FIG. 5  that the with light incident angle about 1 degree, the output efficiency can be about 36%, and with the light incident angle greater 1 degree and less than 1.6 degree, the output efficiency falls off quickly. 
         [0030]    Referring to  FIG. 6 , is an output flux distribution of the light concentration element assembly  10  under particular conditions that the distance D=110.46 mm, and a light incident angle is 1 degree. Relative to  FIG. 3 ,  FIG. 6  shows that the uniformity is better with the light incident angle is 1 degree. 
         [0031]    Referring to  FIG. 7 , shows the relationship between the light incident angle from 0 degree to 1.6 degree and the corresponding output efficiency under the distance D=110.46 mm. It can be concluded from  FIG. 5  that the with light incident angle about 1 degree, the output efficiency can be about 35%, and with the light incident angle greater 1 degree and less than 1.6 degree, the output efficiency falls off quickly. 
         [0032]    It is understood that the above-described embodiments are intended to illustrate rather than limit the disclosure. Variations may be made to the embodiments and methods without departing from the spirit of the disclosure. Accordingly, it is appropriate that the appended claims be construed broadly and in a manner consistent with the scope of the disclosure.