Abstract:
A system is provided for maximizing solar energy utilization by moving a solar panel to track movement of the sun from sunrise to sunset. Preferably, the solar panel is inclined from the horizontal plane by a fixed angle of about ten degrees. And, movements of the solar panel are accomplished, daily, in accordance with a programmed schedule of consecutive cycles. In this schedule, each cycle has a start time (i.e. sunrise) and a start point that is determined by the sun&#39;s direction from the solar panel.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention pertains generally to systems that employ energy converting units, such as photovoltaic cells, to harness solar energy. More particularly, the present invention pertains to systems in which energy converting units are mounted on solar panels that track movement of the sun during daylight hours. The present invention is particularly, but not exclusively useful as a system of solar panels wherein the panels are inclined relative to the horizontal plane, and are moved in accordance with a programmed daily schedule to maximize solar energy utilization. 
       BACKGROUND OF THE INVENTION 
       [0002]    The angle at which solar radiation is incident on an energy converting unit (e.g. a photovoltaic cell) can significantly affect the unit&#39;s ability to convert solar energy into electrical energy. Optimally, the angle of incidence for solar radiation will be ninety degrees (i.e. an energy converting unit is oriented so solar radiation is directed at a right angle, perpendicular to the surface of the energy converting unit). To do this, specific tracking movements of the energy converting unit during daylight hours are required. This, however, may be difficult or impractical to achieve. 
         [0003]    Although the efficiencies of energy converting units are diminished as the angle of incidence deviates from perpendicular; with only small deviations, the diminution of efficiency is minimal. On the other hand, with relatively large deviations from the perpendicular, the diminished effect quickly becomes significant. To minimize this loss and, conversely, to maximize system efficiency, the structure on which the energy converting unit is mounted (e.g. a solar panel) must effectively track movement of the sun. Operationally, this must be done in compliance with two considerations. These are: azimuth and elevation. 
         [0004]    In order to effectively track movement of the sun, it is clear that both the azimuthal movements and elevation considerations for a solar panel are important. For example, the panel must first be pointed in the proper azimuthal direction (i.e. toward the sun). Secondly, with azimuth established, the panel must then be inclined in elevation to optimize (maximize) the angle of incidence. On the first point (i.e. azimuthal tracking), in comparison with a stationary solar panel it has been determined that the overall efficiency of energy converting units can be improved by around twenty percent when the solar panel azimuthally tracks the sun. On the second point, for latitudes of the United States, in comparison with a horizontally oriented solar panel, an inclination angle for elevation of about ten degrees has been determined to be generally optimal. 
         [0005]    In light of the above it is an object of the present invention to provide a system for moving an energy converting unit that azimuthally tracks the sun with a fixed elevation angle, to thereby maximize solar energy utilization. Another object of the present invention is to provide a system for moving an energy converting unit in accordance with a programmed schedule of cycles which tracks the sun during daylight hours and recycles the system at nighttime in preparation for a subsequent cycle the next day. Yet another object of the present invention to provide a system for moving an energy converting unit that is easy to use, is relatively simple to manufacture, and is comparatively cost effective. 
       SUMMARY OF THE INVENTION 
       [0006]    In accordance with the present invention, an apparatus is provided for moving energy converting units to track the daytime movement of the sun. This is done for the purpose of maximizing solar energy utilization. In detail, the apparatus includes a plurality of solar panels, with each solar panel having a substantially flat, rectangular shaped surface on which a plurality of energy converting units (e.g. photovoltaic cells, solar-thermal cells, or concentrating cells) are mounted. Structurally, the solar panel defines a directional plane that is perpendicular to its flat surface. Also, a central axis is defined for the solar panel that lies in the directional plane and passes through a support point on the solar panel. 
         [0007]    A mount is provided for supporting the solar panel. Specifically, the mount supports the solar panel at its support point, with the flat surface of the solar panel inclined relative to a terrestrial horizon. This inclination is fixed at an angle “α” that can be anywhere in a range of about eight to thirty-five degrees (α=8° to 35°). Preferably, however, for latitudes in the United States, α=20°. Importantly, the support point is established and positioned on the solar panel so the solar panel exerts a substantially zero moment on the mount. 
         [0008]    For a preferred embodiment of the present invention the mount is essentially a pole having a base that is anchored to the ground. The other end of the pole then extends vertically upward. A cuff that is formed with a first bearing surface is attached to the pole near its extended end. Additionally, a sleeve is provided that is formed with a channel for receiving the exposed end of the pole. Thus, the sleeve fits over the end of the pole to establish contact with the cuff. For this contact, the sleeve is formed with a second bearing surface that is positioned against the first bearing surface of the cuff. This contact between the respective bearing surfaces then permits a rotation of the sleeve about the pole and, thus, about the central axis. Further, a truss structure can be affixed to the solar panel and engaged with the sleeve to hold the solar panel on the pole. 
         [0009]    A motor is provided for the apparatus of the present invention to rotate the panel on the mount about the central axis. As implied above, the central axis passes through the support point on the solar panel and is substantially perpendicular to a horizontal plane defined by the terrestrial horizon. A controller is also provided for controlling rotation of the panel through successive cycles in accordance with a programmed schedule. 
         [0010]    During each cycle of the programmed schedule, between sunrise and sunset of each day, the controller maintains the sun at a position substantially in the directional plane. Within every 24-hour period, each cycle has a start time established by the time of sunrise. Each cycle also identifies a time interval “Δt”, extending from sunrise to sunset, during which the sun is tracked. Further, each cycle has a recycle phase wherein the solar panel is returned to an appropriate start point for a subsequent cycle. As intended for the present invention, the recycle phase is accomplished after sunset, during nighttime. And, the cycles are consecutive with its subsequent cycle that begins at sunrise on the immediately following day. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    The novel features of this invention, as well as the invention itself, both as to its structure and its operation, will be best understood from the accompanying drawings, taken in conjunction with the accompanying description, in which similar reference characters refer to similar parts, and in which: 
           [0012]      FIG. 1  is a perspective view of a plurality of apparatuses arranged in an array in accordance with the present invention; 
           [0013]      FIG. 2  is a side elevation view of an apparatus; 
           [0014]      FIG. 3  is an exploded partial cross-section view of the mount for the apparatus of the present invention, as seen along the line  3 - 3  in  FIG. 1 ; and 
           [0015]      FIG. 4  is a schematic plan view of geometrical aspects shown in a horizontal plane for a programmed schedule in accordance with the present invention. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0016]    Referring initially to  FIG. 1 , an apparatus in accordance with the present invention is shown, and is generally designated  10 . Another apparatus  10 ′ is shown in  FIG. 1  to indicate that a plurality of apparatuses  10  can be combined together in a functional array. As shown in  FIG. 1 , each apparatus  10  includes a solar panel  12  that supports a plurality of energy converting units  14 . For the present invention, the preferred energy converting unit  14  is a photovoltaic cell of a type well known in the pertinent art. The energy converting unit  14 , however, may be of any type device that is useful for converting solar energy into electrical energy for use at a utility site  15  such as thermal-solar cells or concentrating cells. 
         [0017]      FIG. 1  further indicates that the energy converting units  14  are mounted on a surface  16  of the solar panel  12 . Additionally,  FIG. 1  shows that the solar panel  12  is supported on a pole  18  that is somehow anchored to the ground by a base  20 . For purposes of the present invention, the surface  16  of solar panel  12  is preferably flat, and is substantially rectangular shaped. With the above in mind, it is to be appreciated that the surface  16  of solar panel  12  will define a directional plane  22  that is oriented perpendicular to the surface  16 . Further, a central axis  24  can also be defined for the solar panel  12  such that the central axis  24  lies in the directional plane  22  and is aligned with the pole  18 . For purposes of the present invention, this effectively establishes a vertical orientation for the central axis  24 . 
         [0018]    Additional structural aspects of the present invention will be best appreciated with reference to  FIG. 2  where it can be seen the solar panel  12  is supported on a mount  26 . For some embodiments of the apparatus  10 , the mount  26  may include a truss-like structure  28  with braces  30  that will be used to add stability to the solar panel  12  (e.g. braces  30   a  and  30   b ). Importantly, the solar panel  12  is to be supported by the mount  26  with the central axis  24  passing through a support point  32  on the panel  12 . Recall, the central axis  24  is aligned with the pole  18 . Specifically, within this geometry, solar panel  12  needs to be supported so that, in a “no wind” condition, the moment “M sp ” acting on the mount  26  is substantially equal to zero (i.e. there is minimal, if any, moment about the support point  32  where the mount  26  interacts with the solar panel  12  {M sp =0}). Further, this structural relationship between the mount  26  and solar panel  12  (i.e. M sp =0) must account for the fact the solar panel  12  is to be inclined relative to a horizontal plane  34  by an angle “α” and the impact this inclination will have for structural loadings in a windy condition. As envisioned for the apparatus  10 , the inclination angle “α” will be generally within a range of 8° to 35° (for latitudes of the United States). Preferably, α=10° or 20°. 
         [0019]    The importance of M sp =0 in a static (i.e. “no-wind” condition) is underscored by the size and structural configuration of the panels  12 . As envisioned for a typical apparatus  10 , the surface  16  of the solar panel  12  will most likely have an area somewhere in a range from around nine hundred and twelve square feet (912 ft 2  for a 24′×38′ panel  12 ), to around one thousand six hundred square feet (1,600 ft 2  for a 40′×40′ panel  12 ). Wind loadings on structures this size can be considerable. Moreover, they can only aggravate any pre-existing M sp . 
         [0020]    The structural details of mount  26  will be best appreciated with reference to  FIG. 3 . There it will be seen that the mount  26  includes a sleeve  36 . More specifically, the sleeve  36  is generally a hollow cylinder formed with a channel  38 . The sleeve  36  also has a flange  40  that extends in a radial direction from the sleeve  36 . Also, a notched track  42  is formed on the sleeve  36  along the periphery of the flange  40 . Still referring to  FIG. 3 , it is seen that the pole  18  is formed with a cuff  44  that extends in a radial direction from the pole  18 . It is also formed with an extension  46  that extends in an axial direction. Thus, when the extension  46  of pole  18  is received in the channel  38  of sleeve  36 , the bearing surface  48  on sleeve  36  contacts the bearings  50  on cuff  44 . At the same time, the sleeve  36  makes contact with the bearing  52  on extension  46 . Further, in the combination of sleeve  36  and cuff  44 , the track  42  engages with a drive gear  54 . With this cooperation of structure, the sleeve  36  is able to rotate on the pole  18  around the central axis  24 . 
         [0021]    Along with the structure for mount  26  disclosed above, it is to be appreciated that a motor  56  is provided to operate the drive gear  54 . Though motor  56  is shown mounted on the pole  18  in  FIG. 3 , it can be effectively placed at any convenient location. Further, a controller  58  is electronically associated with the motor  56  to conform its operation with a programmed schedule. Like the motor  56 , the controller  58  can be conveniently located, as desired. An additional structural aspect of the apparatus  10  that is shown in  FIG. 3  involves adjusters  60   a  and  60   b  that are respectively incorporated into the braces  30   a  and  30   b . Specifically, if incorporated, the adjusters  60   a,b  can be manipulated to alter the inclination angle “a” of the solar panel  12 . This can be done for any of several reasons (e.g. significant latitude requirements, or wind load compensation). 
         [0022]    As implied above, the operation of an apparatus  10  is accomplished in accordance with a programmed schedule. In more detail, and with reference to  FIG. 4 , it will be seen that the operation of apparatus  10  is best described in its relationship with a compass rose in the horizontal plane  34 . In accordance with  FIG. 4 , the programmed schedule can be considered as being a continuing succession of cycles, wherein each cycle pertains to a particular day in a year. For each day, a cycle will include a start point that corresponds with sunrise and a final point that corresponds with sunset. For example, the dashed line  62  represents the azimuth of the sun, as measured from the central axis  24 , at sunrise on a given day. The dashed line  62 ′ then represents the azimuth of the sun at sunset on that same day. During the particular day defined by dashed lines  62  and  62 ′, as the sun moves after sunrise to an azimuth identified by the line  64 , the azimuthal bearing will have changed by the angle β 1 . On the other hand, for another day, the dash-dot line  66  represents the sun&#39;s azimuth at sunrise, and the dash-dot line  66 ′ represents its azimuth at sunset. In this latter cycle, movement of the sun to the azimuth line  64  requires an angle change of β 2 . 
         [0023]    In accordance with the present invention, each day of the year will have a cycle (e.g. represented by lines  62 - 62 ′ and  66 - 66 ′). Further, at the end of each day (e.g. line  62 ′ or  66 ′) the apparatus  10  will recycle during the night to a start line for the next immediately following day. As will be appreciated by the skilled artisan, the specific start line (i.e. azimuth) for each day will be determined with reference to a standard solar table. Most importantly, as the solar panel  12  is moved during a cycle, between sunrise and sunset, the position of the sun is maintained in the directional plane  22  of the solar panel  12 . 
         [0024]    While the particular Sun Tracking Solar Panels as herein shown and disclosed in detail is fully capable of obtaining the objects and providing the advantages herein before stated, it is to be understood that it is merely illustrative of the presently preferred embodiments of the invention and that no limitations are intended to the details of construction or design herein shown other than as described in the appended claims.