Abstract:
A rigidly mountable solar panel includes lenses supported above a movable panel to focus sunlight onto photovoltaic material carried on the movable panel. Flexible supports space the movable panel at the focal points of the lenses, and a servo-mechanism enables movement of the movable panel to adjust position as the focal point moves with the sun. A light detector on the movable panel, sensing movement of the focal point signals the servo-mechanism to adjust the position of the movable panel automatically, thereby tracking the sun&#39;s movement. Concentrating sunlight on photovoltaic material selected to have higher conversion efficiency increases output. Segmenting the photovoltaic material so the output of the segments can be combined in a series-parallel relationship and using mirrors on the ends of the movable panel to reflect sunlight onto the segments allows electricity that is generated by the photovoltaic material to be more uniform during daylight.

Description:
TECHNOLOGICAL FIELD 
       [0001]    The present disclosure relates generally to the solar panels. More specifically, the present disclosure relates to solar panels that track the movement of the sun. 
       BACKGROUND 
       [0002]    Most solar panels that convert the sun&#39;s radiation into electric energy use fixed flat-panels of silicon. Silicon is the photovoltaic material of choice because its properties are well known and it is cheap, readily available in the quantities needed, durable and reliable. Silicon is also a single-junction photovoltaic material so it is not affected by changes in the spectral distribution; its output depends on the integrated power density within the limits of its absorption range. Flat panels of silicon are simple to make and install in an outdoor environment. 
         [0003]    There are disadvantages to fixed, flat silicon solar panels. Silicon has a relatively low conversion efficiency, typically 18% to 20% and theoretically not to exceed 30%. Because of this relatively low conversion efficiency, bigger panels, more panels and a larger area for the panels are used to produce power than would be the case were the conversion efficiency higher. In the case of roof-mounted solar panels for home electricity generation, the amount of power used by a household is usually much more than can be generated by solar power from flat silicon panels given the size of the roof of a residence. In the case of power plants, land requirements for solar collectors quickly become the dominant cost. Finally, most solar panels are made overseas so supplies of new and replacement panels may be subject to international stability issues and currency fluctuations. 
         [0004]    One way to increase the conversion efficiency of flat silicon panels is to have them track the sun. While solar panel tracking systems do improve efficiency, they also add to capital cost, operating costs, and maintenance costs. They also use electrical power to operate thereby offsetting their conversion efficiency gains. Furthermore, their tracking ability is compromised by wind and gravitational deflection. 
         [0005]    The efficiency of solar panels may also be improved by different photovoltaic materials, although better photovoltaic materials are more expensive and not widely available. 
         [0006]    Despite the challenges of solar electricity, a solar panel that would be capable of producing more electricity per square meter would be of significant advantage over current solar panels and useful in more numerous applications. 
       BRIEF SUMMARY 
       [0007]    The present disclosure describes a solar panel that employs plural lenses rigidly mounted to a framework. Flexible supports depend from plural lenses and hold a movable panel in spaced relation to the plural lenses. The lenses focus the sunlight, as it moves with the moving sun, onto the movable panel and, in particular, onto photovoltaic material on the movable panel. The focusing of sunlight on photoelectric material enables higher conversion efficiencies at lower material cost. The array of lenses is oriented east-west and tilted to match the sun&#39;s tilt angle with respect to the earth. Tracking of the sun&#39;s movement through the seasons is thus reduced and can be further accommodated by moving the movable panel that holds the photovoltaic material. One lens of the plural lenses directs light onto a detector on the movable panel instead of onto photovoltaic material. The detector is electrically connected to a servo-mechanism that responds to signals from the detector. Those signals communicate position information to the servo-mechanism. That position information indicates the location of the focal point on the detector. When movement of the sun moves the focal point on the detector to a different location on the detector, that movement causes the servo-mechanism to adjust the position of the movable panel to restore the position of the focal point to its initial location on the detector. 
         [0008]    A feature of the disclosure is the use of a plurality of lenses, which may be cylindrically or spherically curved, to focus sunlight on photovoltaic material arranged on a panel. 
         [0009]    Another feature of the disclosure is the use of flexible supports for holding the movable panel in spaced relation with respect to the lenses, and which supports can flex in response to the operation of the servo-mechanism in adjusting the movable panel to maintain the focal point of the lens on the photovoltaic material in response to the movement of sunlight. 
         [0010]    Another feature of the disclosure is that the lens may be a spherical lens or a cylindrical lens, and an array of lenses may be a row of long cylindrical lenses or a two dimensional array of spherical lenses. 
         [0011]    Another feature of the solar panel is the use of mirrors at the ends of the movable panel to reflect light striking an end wall of the movable panel onto the photovoltaic material adjacent to the end wall so as to capture an addition amount of light energy. 
         [0012]    A feature of the solar panel is that the photovoltaic materials may be divided into a plurality of segments so that the quantity of electricity generated in one segment can be combined with the quantity of electricity generated in another segments in a manner that produces a more constant output through the day. For example, the quantity of electricity of the outermost segments may be combined in parallel and the quantity of electricity of all the pairs of segments may be combined in series. 
         [0013]    Still another feature of the present disclosure is that a solar panel with a plurality of cylindrical lenses can be oriented with the long axis of a lens parallel to the daily path of the sun and the solar panel is tilted to match the tilt angle of the sun with respect to the earth&#39;s axis to minimize the movement for tracking the sun. 
         [0014]    A feature of the solar panel is that the servo-mechanism is configured to move the movable panel with respect to the array of cylindrical lenses while they are held at a fixed length with respect to the panel so sunlight is focused on the photovoltaic material. 
         [0015]    Other features and their advantages will be apparent to those skilled in the art of solar panels from a careful reading of the Detailed Description accompanied by the following drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]    Having thus described variations of the disclosure in general terms, reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, and wherein: 
           [0017]      FIG. 1  is a top perspective view of a solar panel  10  showing lenses  14  above a movable panel  18  that carries photovoltaic material  26 , the lenses  14  being connected to movable panel  18  by flexible supports  22 , and the movable panel  18  being movable by a servo-mechanism  30 , according to an aspect of the disclosure; 
           [0018]      FIG. 2  is an end view of the solar panel  10  of  FIG. 1 , according to an aspect of the disclosure; 
           [0019]      FIG. 3  is an end view of the solar panel  10  of  FIG. 2  with the movable panel  18  moved by the servo-mechanism  30  to the left to adjust for the seasonal change in the angle of the sun, according to an aspect of the disclosure; 
           [0020]      FIG. 4  is an end view of the solar panel  10  of  FIG. 2  with movable panel  18  moved to the right to adjust for the angle of the sun, according to an aspect of the disclosure; 
           [0021]      FIG. 5  is a side view of the solar panel  10  of  FIG. 1  with photovoltaic material  26  divided into pairs of segments  36  that are labeled A-A′, B-B′, and so forth to F-F′, according to an aspect of the disclosure; 
           [0022]      FIG. 6  is a side view of the solar panel  10  of  FIG. 5  showing the sunlight coming from a low angle such as during the early morning or late afternoon, and being reflected by mirrored surface of end wall  32  of the movable panel  18  onto segment A′ of photovoltaic material  26 ; 
           [0023]      FIGS. 7 and 8  are end views of solar panel  10  of  FIG. 1  showing the connection between the servo-mechanism  30  and the movable panel  18  that enables the position of the detector  38  to be adjusted in response to the movement of the focal point of the sunlight through the lens  14  and the flexing of the flexible supports  22  in response to that movement; 
           [0024]      FIGS. 9 and 10  are end views of an alternative arrangement in which the lens  14  is supported from a fixed base  60  by fixed supports  56 , and the movable panel  52  is supported from below by fixed base  60  via flexible supports  50  and is movable by the servo mechanism  30  to maintain the focus of sunlight from lens  14  on detector  38 ; and 
           [0025]      FIGS. 11 and 12  are end views of another alternative arrangement in which the movable panel  72  is supported from below by a movable base  68 , and movable panel  72  and movable base  68  are moved by servo mechanisms  30  to keep detector  38  at a fixed distance from the bottom  48  of the lens  14 . 
       
    
    
     DETAILED DESCRIPTION 
       [0026]    The solar panel as disclosed may be in the form of a solar panel  10  that may be rigidly mounted to a solid surface with the proper orientation and tilt, and commence to automatically track the sun&#39;s movement and to optimize the collection efficiency of the photovoltaic material being used. Solar panel  10  may be thin: 1.5 cm-2.5 cm thick, for example, and scalable. A solar panel  10  may be a square meter, for example, and light-weight. It may use less photovoltaic material so using higher efficiency concentrator photocell materials becomes cost-effective. Its lenses can be made of any optical glass or optical plastic and may be configured as Fresnel lenses. 
         [0027]      FIG. 1  is a perspective view of a solar panel  10  comprising plural lenses  14 , arranged in an array  16  and supporting a movable panel  18  by flexible supports  22 . Lens  14  in array  16  is shown as cylindrical in this illustration and has an axis of symmetry parallel with the long dimension of lens  14 . In use, panel  18  would be oriented with the axis of symmetry of lens  14  running east and west, and would be tilted at the tilt angle of the sun which is the angle between the earth&#39;s rotational axis and its orbital axis, which is about 23.4 degrees. 
         [0028]    At the focal point of a cylindrical lens  14  on panel  18  is photovoltaic material  26 . Because lens  14  is able, by virtue of its geometry and its distance from movable panel  18  to the sun, to focus the parallel rays of sunlight into a narrow beam, the area of photovoltaic material  26  may be smaller and therefore the quantity of photovoltaic material may be less. Accordingly, photovoltaic material of higher efficiency than silicon may be used despite higher cost per unit area. 
         [0029]    Lens  14  may be spherical, and array  16  would then be made of spherical lenses, such as an array of rows and columns or a close-packed hexagonal array. A spherical lens  14  focuses light onto a small circle on photovoltaic material  26  on movable panel  18 . 
         [0030]    Flexible supports  22  are shown in  FIG. 1  as suspended from the ends of lens  14 . Flexible supports  22  may alternatively be walls between lenses  14 . A servo-mechanism  30  or other mechanical device capable of causing lateral movement is attached to movable panel  18  and configured to cause panel  18  to move laterally. Flexible supports  22  serve to keep the focal distance between lens  14  and movable panel  18  constant Servo-motor  30  moves movable panel  18  laterally with respect to lens  14 . 
         [0031]    The ability of flexible supports  22  of solar panel  10  to enable movable panel  18  to be moved laterally allows the focal point of lens  14  to remain centered on photovoltaic material  26  despite movement of the sun. Servo-motor  30  moves movable panel  18  in tracking the sun. The amount of movement required is small. Lens  14  is placed so that its long dimension is parallel to the east-west path of the sun and tilted to match the sun&#39;s tilt axis with respect to the earth. Accordingly, most of the daily movement of the sun is accommodated by the initial positioning of solar panel  10 . The position of the sun will change from being directly overhead at noon based on latitude. Accordingly, a residual amount of solar tracking is required. 
         [0032]    This adjustment is illustrated by comparing  FIGS. 2, 3, and 4 . These figures show end views of solar panel  10 .  FIG. 2  shows solar panel  10  with the sun&#39;s rays, represented by dashed lines, coming from directly overhead.  FIG. 3  illustrates the shift in position of movable panel  18  to the left which may be appropriate in winter months in northern latitudes if, in  FIG. 3 , the south direction is to the right and north direction is to the left, when the sun will generally be traveling southeast to southwest. Likewise,  FIG. 4  would then illustrate the adjustment of movable panel  18  to accommodate a more northerly oriented sun path—generally east to west and tilted northerly as it would be in the southern hemisphere in winter or in the northern hemisphere in summer. The movement of movable panel  18  and flexing of flexible supports  22  enables solar panel  10  to focus the sun&#39;s light on photovoltaic material  26 . 
         [0033]      FIGS. 5 and 6  illustrate side views of the solar panel  10 . From the side, the sun, in its daily traverse, would move from right to left (assuming that the right sides of  FIGS. 5 and 6  are oriented to the east and the left sides are oriented west). When the sun is generally overhead, as illustrated in  FIG. 5 , sunlight (again represented by dashed lines) falling on solar panel  10  passes through lens  14  and falls directly onto photovoltaic material  26 . As the sun traverses the sky during the day, as illustrated in  FIG. 6 , some sunlight will fall beyond end walls  32  of solar panel  10  and thus shadow movable panel  18  or may fall on end walls  32 . In order to include that sunlight, end walls  32  have mirrored interior surfaces to reflect the focused sunlight back onto material  26  so that the reflected light, too, can be converted to electricity and add to the rest of the electrical energy produced. 
         [0034]    Photovoltaic material  26  may be divided into segments  36  that may be equal in length. Segments  36  are paired as shown in  FIGS. 5 and 6  and identified by letter. A first pair of segments  36  is formed from the outermost two segments  36 , segments A and A′ in  FIGS. 5 and 6 , and then the next two outermost segments  36 , B-B′, are paired, and so forth: C-C′, D-D′, etc., until the last two segments  36 , in this example, F-F′ are paired. Segments  36  in each pair A-A′, B-B′, C-C′, D-D′, E-E′, and F-F′ are wired electrically in parallel and segment pairs A-A′, B-B′, C-C′, D-D′, E-E′, and F-F′ are wired electrically in series to provide the current output for photovoltaic material  26 . In this way, sunlight reflected by mirror  34  falling on segment A′ adds to any sunlight falling directly on it and makes up in part for the reduced sunlight falling on shadowed segment A. Accordingly, the quantity of electricity produced by all of the segments  36  of photovoltaic material  26  is relatively more constant during a day. 
         [0035]      FIGS. 7-12  illustrate how the focal point of light from lens  14  is kept on photovoltaic material  26 . Below lens  14  of array  16 , photovoltaic material  26  is replaced by a detector  38 . Movement of the light focused by lens  14  on detector  38  is used to determine how to move movable panel  18 . As the focal point on detector  38  moves in response to the movement of the sun overhead, detector  38  senses that movement and sends a corresponding signal to servo-mechanism  30  which responds by moving movable panel  18  to re-center the focal point of the light on detector  38 . Detector  38  may be any type of optical implementation, such as a quad cell, a position dependent detector, a linear array, or a two-dimensional array. 
         [0036]    In  FIG. 7 , the movement of detector  38  is accomplished with a servo-mechanism  30  pushing or pulling movable panel  18 . Flexible supports  22  facilitate movement of movable panel  18  with respect to lens  14 . Flexible supports  22  have two flexible joints, namely, an upper flexible joint  40  and a lower flexible joint  44  that enable it to maintain movable panel  18  parallel to lens  14  despite the movement of movable panel  18  by servo-mechanism  30 . The bottom  48  of lens  14  defines a plane parallel to the plane of movable panel  18 . When movable panel  18  is pushed as indicated by the arrow in  FIG. 8  by servo-mechanism  30 , upper and lower flexible joints  40 ,  44 , assure that the bottom  48  of lens remains parallel to movable plane  18 . By being able to move lens  14  laterally, the relatively higher or lower angle of the sun throughout the year can be accommodated. There is a slight increase in spacing between of lens  14  and movable panel  18  as movement of movable panel  18  proceeds from its extreme positions to its center position, which affects focus. 
         [0037]      FIGS. 9 and 10  illustrate an inverted flexure arrangement that is an alternative to the arrangement of  FIGS. 7 and 8 , wherein flexible supports  50  support a movable panel  52  from a fixed base  60  below. A set of rigid supports  56  from fixed base  60  support lens  14 . In this arrangement, movable panel  52  may be moved, as shown by the arrow from servo-mechanism  30 , to maintain detector  38  at the focal point of lens  14 . Unlike the arrangement in  FIGS. 7 and 8 , the distance between detector  38  and lens  14  rises as movable panel  52  moves from either of its two extreme positions to its central position, and which movement also has an impact on focus. 
         [0038]      FIGS. 11 and 12  illustrate a third arrangement in which lens  14  is supported by rigid supports  64  which are attached to a movable base  68 . Movable base  68  supports a movable panel  72  using flexible supports  76 . Movable base  68  and movable panel  72  may be moved independently, as indicated by arrows using, for example, two servo-mechanisms  30 . This arrangement preserves the separation distance between the bottom  48  of lens  14  and detector  38 , as well as their parallel relationship, for sharp focus while allowing detector  38  to move laterally with respect to lens  14  in tracking the movement of the sun. 
         [0039]    In the three aspects of the invention shown in  FIGS. 7-12 , the relative positions of detector  38  and lens  14  need to be adjusted to keep lens  14  aligned with detector  38  throughout array  16 . Detector  38  detects the shifting position of the light focus and signals servo-mechanism  30  to make that change by moving movable panels  18 ,  52 ,  72 . The rest of array  16 , with photovoltaic materials  26  instead of detector  38 , follows accordingly. 
         [0040]    When introducing elements of the present disclosure or exemplary aspects or embodiment(s) thereof, the articles “a,” “an,” “the” and “said” are intended to mean that there are one or more of the elements. The terms “comprising,” “including” and “having” are intended to be inclusive and mean that there may be additional elements to those listed. Although this disclosure has been described with respect to specific embodiments, the details of these embodiments are not to be construed as limitations.