Abstract:
A low profile solar collector having a number of light collecting lenses that fit closely together as an array on a flexible sheet. The lenses may focus light onto optical conveyance mechanisms which convey light from the lenses to a light-to-electrical converter or converters at an edge of the sheet. The lenses may alternatively focus light onto a light-to-electrical converter or converters. Conductors may convey electricity from the light-to-electrical converters to an electrical connection block at an edge of the sheet. The flexible sheet may be rolled, folded, or form fitted onto a non-planar surface. Two or more low profile solar collectors having a number of collecting lenses may be combined to form a larger sheet for solar collection. The electrical outputs of the collectors may be connected to provide one or more outputs as desired.

Description:
[0001]    The present application claims the benefit of U.S. Provisional Patent Application No. 61/270,852, filed Jul. 14, 2009, and entitled “Low Profile Solar Concentrator”. U.S. Provisional Patent Application No. 61/270,852, filed Jul. 14, 2009, is hereby incorporated by reference. 
     
    
     BACKGROUND 
       [0002]    The invention pertains to solar energy, and particularly to collection of solar energy. More particularly, the invention pertains to mechanisms for collecting and converting solar energy. 
       SUMMARY 
       [0003]    The invention is a low profile solar collector. The collector may have a number of collecting lenses that fit closely together as an array on a flexible sheet. The lenses may focus light onto optical conveyance mechanisms, such as optical waveguides, which convey light from the collector lenses to a light-to-electrical converter or converters, such as photovoltaic cells or solar cells, at an edge of the sheet. The lenses may alternatively focus light onto light-to-electrical converters. Conductors may convey electricity from the light-to-electrical converters to an electrical connection block at an edge of the sheet. The flexible sheet may be rolled, folded, or form fitted onto a non-planar surface. Two or more low profile solar collectors having a number of collecting lenses may be combined to form a large sheet for solar collection. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         [0004]      FIG. 1  is a diagram of an illustrative example of a solar collector sheet having an array of collecting lenses; 
           [0005]      FIG. 2  is a diagram of a component of the collector sheet in  FIG. 1 ; 
           [0006]      FIG. 3  is a diagram of an array of collector lenses having a hexagon shape; 
           [0007]      FIG. 4  is a diagram of an example collector of a hexagon shape; 
           [0008]      FIG. 5  is a diagram of an example array having square collector lenses having a light collection and conversion configuration different than that for the collector sheet in  FIG. 1 ; 
           [0009]      FIG. 6  is a diagram indicating aspects of each lens and its associated components of the array illustrated in  FIG. 5 ; and 
           [0010]      FIG. 7  is a diagram of multiple light collector modules or sheets put together to form a larger sheet for light collection. 
       
    
    
     DESCRIPTION 
       [0011]    Many of the current solar concentrator structures used in large scale solar Photovoltaic (PV) power conversion implementations may use bulk optics on the order of several inches to feet or meters. 
         [0012]    While it may be possible to miniaturize a solar concentrator structure in a portable scale, the shape may be in a typical bulky volumetric form, that is, typically may imply similar thicknesses and lateral dimensions. It is not easy or apparent to implement solar concentrator structure in a large area sheet, or as an easy to carry package or with flexible form factor. 
         [0013]    The present approach may involve creating a solar light collection system in an optical domain. The system may be laterally scaled, without increasing the thickness, and without significantly increasing the size of a PV (photovoltaic) cell (optical to electrical conversion device). The end result may be an envisioning of the solar concentrator in a “sheet” form, which can be flexible, lightweight, and rugged, and can collect light in a large area form, and “fold” the collected light “within” the collector “sheet” (e.g., to an edge) with increased intensity, and then convert the light to electrical power using a narrow strip of solar PV cells (having reduced overall system cost) at the edge (e.g., side bar) of the collector sheet. 
         [0014]    The present approach may distinctive structural features. It may have a low f# (e.g., &lt;1) but smaller size collecting lens (diameter D  51  in ˜mm range, e.g., 10 to 30 mm in size) implemented in lightweight plastic (having a small focal length h  52  to a focal point  12 ). For the low profile, one may have “h&lt;D”. There may be a lens coupled with a high NA (e.g., a numerical aperture≧0.5) waveguide (glass or plastic) to “pipe” the light sideways, with low profile (focal length of the lens  11  to point  12  in  FIG. 1 ). There may be a staggered 2D lens array, and 1D waveguide (WG) array to form a light collector “sheet” with a relatively large area but having a small overall profile. The light output may be concentrated to the side of the sheet and be coupled into a narrow strip of high efficiency (that may be crystalline) solar cells. 
         [0015]    The optical collector sheet may be implemented using lightweight optical materials that are flexible, rugged and not electrically connecting (i.e., non-conducting). Energy conversion may take place within a narrow area at the edge of the sheet, and minimize the use of expensive crystalline semiconductor (e.g., Si, Ge, GaAs, InGaP or their combinations of multi-junction) solar cells. 
         [0016]    A collector sheet  49  may have solar cells  47  located proximate to the focal spot  12  of the collecting lenses  41  and have wires  43  going from the cells to the edge of the sheet ( FIG. 5  and  FIG. 6 ). The wires may be connected in a desired configuration for electrical power output. 
         [0017]      FIG. 1  is a diagram of an illustrative example 10 of a solar collector sheet. There may be an array of collector lenses  11  that may collect light and focus the light at points  12  at ends  17  of light conveying mechanisms  13 , respectively, which may be light waveguides, such as optical fibers. The lenses may be fitted closely together such that the edges of the lenses touch the edges of the other lenses. The light conveying mechanisms may provide light to a strip  14  which may contain a solar cell or a number of solar cells to collect the light for conversion to electrical power at an output  15 . If there are a number of solar cells instead of one receiving light for conversion, the cells may be interconnected in a configuration to provide a particular output of certain magnitudes, such as voltage, at output  15 . The solar cell or cells  14  may be supported by a block or support structure  16 . Block  16  may also provide a place for electrical interconnections of the cells. 
         [0018]      FIG. 2  is a diagram of a component of the array of the collector sheet  10  in  FIG. 1 . The light waveguide  13  may be rectangular or round. Waveguide  13  could have some other shape. Light  21  may impinge a collector lens  11  which may focus light  21  as light  22  and coupled into the waveguide to a guide end  17  at focal point  12 . End  17  may reflect light  22  as light  23  down waveguide  13 . Light  23  may travel to another end  18  of waveguide  13 . End  18  may reflect light  23  as light  24  to solar cell  14 . End  17  may be cut at about a 45 or so degree angle relative to the elongated portion of waveguide  13 . Light  22  at an optical axis  19  of lens  11  may be reflected at about 90 degrees or so relative to optical axis  19 . The surface of end  17  of waveguide  13  may have or not have a reflective coating applied. Light  23  may travel approximately along an optical axis  25  which may incorporate a center of the waveguide or core of an optical fiber. Light  23 , as it impinges end  18 , may be reflected by a surface of end  18  at about 90 degrees or so relative to optical axis  25  towards the solar cell  14 . End  18  may be cut at about a 45 or so degree angle relative to the elongated portion of waveguide  13 . The surface of end  18  of waveguide  13  may have or not have a reflective coating applied. 
         [0019]    Lens  11  may be a Fresnel lens or convex lens having a focal length to point  12  which is equivalent to distance “h”  52  and an optical diameter of “D”  51 . Lens  11  may have a low profile in that “h&lt;D”. There may be a structure that maintains the focal distance h  52  at a constant value. A structure  26  may hold lens  11  and end  17  of fiber  13  in a manner to maintain the constant value of h. At the same time, structure  26  and waveguide  13  may be pliable without affecting the h value and the paths of light  22 ,  23  and  24 . A volume  27  between lens  11  and end  17  of fiber  14  may contain air or a vacuum. Or volume  27  may be filled with a light transmitting medium. Volume  28  may be filled or not be filled with a pliable material. Volume  29  may be a pliable material. The pliable material and structure  26  permits the array  10  to bend if place on a non-flat surface or to folded or rolled up. 
         [0020]    Collector lenses need not be square like lenses  11 . Collector lenses may be round, triangular or any other shape.  FIG. 3  is a diagram of an array  20  of collector lenses  31  having a hexagon shape.  FIG. 4  is a diagram of an example collector of a hexagon shape. 
         [0021]    The light conveyance mechanism need not be a waveguide  13  with an end  17  that reflects light  22  from a collector lens through the waveguide  13  and again reflects light  23  at end  18  to a solar cell  14 . The light conveyance mechanism may receive light directly into, for example, a waveguide  33  such as an optical fiber without dependence on reflective ends. Light  22  may be focused onto an end  37  which has a surface that is perpendicular to an axis  35  of waveguide  33 . Light  23  may propagate down waveguide  33  approximately along a central optical axis or core of waveguide  23  to and through an end  38  directly to a solar cell  14 . No end reflection is required with this configuration of the present approach. Even though this configuration is associated with array  20  of  FIG. 3 , it may be implemented with array  10  in  FIG. 1 . 
         [0022]    Lens  31  and end  37  of waveguide  33  may be structurally supported with a structure  36 . The value of h, i.e., the focal length of lens  31  and respective focus of light  22  at end  37  of waveguide  33 , may be maintained by structure  36 . Still structure  26  and waveguide  33  may be pliable without affecting the positions of lens  31  and end  37  relative to each other. The collector lens  31  and other lenses  31  of array  20 , along with the waveguides  33  and structures  36 , may be held together with a pliable material  39 . The components of the array may be in one approach potted with the material  39 , except for the light incoming surfaces of the collector lenses  31 . The solar cell or cells  14  may be enclosed or partially enclosed or not enclosed by material  39 . The whole array  20 , with its components, may be like a flexible sheet which may be folded, rolled up, or lay out to conform to a non-flat surface. This approach may be applicable to other configurations with collector lenses having other shapes. 
         [0023]      FIG. 5  is a diagram of another array  30  having square collector lenses  31  like those of array  10  in  FIG. 1 . However, the light collection and conversion configuration is different for array  30 . However, this configuration may be applicable to arrays having configuration lens shapes of various kinds.  FIG. 6  is a diagram indicating aspects of each lens  41  and its associated components. Light  21  may enter the collector lens  41  and be focused by the lens as light  22  onto a solar cell  47 . Electrical power may be conveyed to a connection block  44  via a conductor  43  to a terminal at the block. Conductor  43  may be interconnected with other conductors  43  in a configuration which can provide a desired output. A focal length h between the collector lens  41  and the sensing surface of solar cell  47  may be held in place with a structure  46 . Structures  26  of the array  30  and corresponding conductors  43  may be in one approach potted with a pliable material  49 , except for the light incoming surfaces of the collector lenses  41 . Structures  26  and the conductors  43  may be enclosed, or partially enclosed, or not enclosed by material  49 . The whole array  30 , with its components, may be like a flexible sheet which may be folded, rolled up, or laid out to conform to a non-flat surface. This approach may be applicable to other configurations with collector lenses having other shapes. Connection block  44  might or might not be included in the material  49 . 
         [0024]    Capturing the possibility of using a multiple of collector sheets as modular building blocks (where a block may have limited size and the number of array elements may be limited to the ratio of the lens area to the cross-section area of the waveguide) to construct a larger solar collection sheet. An example is shown in  FIG. 7 , which is a diagram of a large sheet  40  of modules or sheets of collector lenses with corresponding solar sensing and conversion mechanisms. Each module or sheet may that of module  10  illustrated in  FIG. 1 , module  20  illustrated in  FIG. 3 , or module  30  illustrated in  FIG. 5 . Each module or sheet may instead be of an example not specifically illustrated in a Figure herein. The illustrative example of large sheet  40  may incorporate modules or sheets  20  as shown in  FIG. 3 . The layout of sheet  40  may have a 3×2 module configuration; however, the layout may have virtually any number of modules in each dimension. The layout of sheet  40  may also incorporate various kinds of modules including those illustrated in  FIGS. 1 ,  3  and  5 . The electrical outputs of the modules may be connected to provide one or more outputs as desired. 
         [0025]    In the present specification, some of the matter may be of a hypothetical or prophetic nature although stated in another manner or tense. 
         [0026]    Although the present system has been described with respect to at least one illustrative example, many variations and modifications will become apparent to those skilled in the art upon reading the specification. It is therefore the intention that the appended claims be interpreted as broadly as possible in view of the prior art to include all such variations and modifications.