Abstract:
An arrangement for use in a concentrating photovoltaic system including a module having plurality of solar cells are mounted on a first side, and a plurality of lenses are mounted on a second side. Drive motors are coupled to the module to enable it to track the sun during the course of the day. A sun sensor is attached to the housing to detect a predetermined timed pattern of light blocking to the sensor and for generating a control signal to the drive motors in response to such detection for moving the module to a predetermined fixed position.

Description:
BACKGROUND 
     Solar array modules used in a concentrating photovoltaic system are constructed to house solar cell receivers that mount a solar cell that converts solar energy into electrical current. The modules include a housing mounted on a support and pivoted for tracking the sun. A plurality of lenses are mounted on one side of the housing that concentrate and focus the incoming sun beams onto respective solar cells. A sun sensor is attached to the housing which provides a control signal to associated actuating drive motors coupled to the module to position the module so that the plane of the lenses is substantially orthogonal to the incoming sun beams as the module tracks the sun during the course of the day. 
     SUMMARY 
     The present application is directed to an arrangement for use in a concentrating photovoltaic system including a support; a housing mounted on the support and pivoted for tracking the sun during the course of the day. A plurality of solar cells are mounted on a first side of the housing, and a plurality of lenses are mounted on a second side of the housing opposite the first side for concentrating and focusing the incoming sun beams onto respective solar cells. Drive motors are coupled to the housing for pivotably moving the housing to track the sun during the course of the day. A sun sensor is attached to the housing to provide a control signal to the drive motors so that the motors position the module so that the plane of the lenses is substantially orthogonal to the incoming sun beams as the module tracks the sun during the course of the day; and a controller is coupled to the sun sensor for detecting a predetermined timed pattern of light blocking to the sensor and for generating a control signal to the drive motors in response to such detection for moving the housing to a predetermined fixed position. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a cut-away perspective view of a solar cell module; 
         FIG. 1B  is a perspective view of a receiver as used in the solar cell module of  FIG. 1A ; 
         FIG. 2  is a side elevational view of a solar cell module depicting the sun sensors; 
         FIG. 3  is a side elevational view of a solar cell module in the starting or “home” position; 
         FIG. 4  is a highly simplified block diagram of the sun sensor control system; 
         FIG. 5(   a ) is one embodiment of a light blocking pattern with one sun sensor that represents a control signal; and 
         FIG. 5(   b ) is one embodiment of a light blocking pattern with two sun sensors that represents a control signal. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1A  illustrates an implementation of a solar cell module  200  comprising an array of lenses  210  and corresponding solar cell receivers  100 . Each one of the lenses  210  is aligned with one of the solar cell receivers  100 . The solar cell module  200  may include various numbers of lenses  210  and solar cell receivers  100 .  FIG. 1A  includes a module  200  with eight lenses  210  and solar cell receivers  100  aligned in a 2×4 array. 
     The lenses  210  are formed on a continuous sheet  211  of optical material (e.g., a silicone coated glass). In some implementations, regions of the sheet  211  not formed into the lenses  210  are made partially or entirely opaque. By forming the lenses  210  out of a continuous sheet  211 , costs can be decreased substantially. First, by producing the lenses  210  on large sheets, production costs are decreased. Second, assembly costs are decreased because only one item (i.e., the sheet  211  of lenses) needs to be aligned with the solar cell receivers  100 . In this implementation, the sheet  211  lies atop an alignment frame  221  of a housing  220 . 
     In some implementations, the floor surface  222  of the housing  220  comprises alignment features that ensure that each of the solar cell receivers  100  is located in a predetermined position. These features may couple with each of the solar cell receivers  100 . 
     In some implementations, each of the lenses  210  is a Fresnel lens. The corresponding solar cell receiver  100  is positioned on the surface  222  at an opposite end of the housing  220 . 
       FIG. 1B  is a perspective view of a receiver  100  as used in the solar cell module of  FIG. 1A . Each of the solar cell receivers  100  includes a corresponding solar cell  102  disposed in the optical path of the corresponding lens  210 , i.e., such that the corresponding solar cell  102  receives light that passes through the corresponding lens  210 . In some implementations, additional optical elements are employed to place the solar cell in the optical path of the lens. For example, secondary optical elements  104  correspond with each pair of the solar cell receivers  100  and the lenses  210 . The secondary optical elements  104  gather the light from the lens  210  and direct it into the solar cell  102  of the solar cell receiver  100 . In some implementations, each of the solar cell receivers  100  is provided with a corresponding secondary optical element  104 . The SOE  104  is disposed inside the housing  220  of the solar cell module  200  and is generally designed to collect solar energy concentrated by one of the corresponding lenses  210 . 
     Another optical element that may be provided in some embodiments includes a concentrator  106  that is positioned between each of the pairs of solar cell receivers  100  and lenses  210 . The concentrator  106  concentrates the light onto the solar cell  102 . In some embodiments, the secondary optical element  104  and the concentrator  106  may form a single integral optical element  107 . 
     Some implementations of the lenses  210  concentrate incident sunlight to 500 times normal concentration (i.e., 500 Suns) or more. With the use of a 2× concentrator  106 , the resulting concentration of sunlight may be 1000 times normal concentration (i.e., 1000 Suns) or more, depending upon the cumulative concentration of the Fresnel lens and the concentrator. Other implementations may include other concentrations. Generally speaking, conversion efficiency of solar energy into electricity increases under concentrated illumination. For example, at about 1000 Suns, a single solar cell receiver with a 5.5 mm square solar cell can generate from seven to eight watts or more of peak DC electrical power. The amount of electrical power a solar cell receiver can produce can vary depending on, for example, the combination of solar cell characteristics (e.g., size, composition), properties of the associated optics (e.g., concentration, focus, alignment), the time of day and time of the year, and the geographic location of the installation. 
     In some implementations, the solar cells  102  of each of the respective solar cell receivers  100  is a triple-junction solar cell, composed of compound semiconductors, with each of the three subcells arranged in tandem or electrical series. In some embodiments, the solar cells are substantially square in shape and having a side length of less than 6 mm, and are mounted on a ceramic substrate  108  having a first metalized surface and an opposing second metalized surface. The solar cell has a conductive first bottom surface connected to a first one of the conductive regions of the ceramic substrate and an opposing second light-receiving surface having a conductive contact area connected (by wire bonds or the like, not shown) to a second one of the conductive regions. The ceramic substrate  108  is mounted on a heat sink  109  which conducts and dissipaters the heat generated from intense light impinging on the solar cell. 
     In applications where multiple solar cell modules  200  are employed, the receivers  100  of the solar cell modules  200  are typically electrically connected together in series by wires  110 .  FIG. 1B  depicts two wires  110  which make contact with the anode and cathode terminals of the solar cell. In some embodiments, the wires  110  are secured in place by a clamp  111  mounted on the heat sink  109 . However, other applications may utilize parallel or series-parallel electrical connections. For example, receivers  100  within a given module  200  can be electrically connected together in series, but the modules  200  are connected to each other in parallel. 
       FIG. 2  is a side elevational view of a solar cell module  200  depicting the sun sensors  301 ,  302 ,  303  and  304  mounted on the housing and positioned facing the sun (not shown). The sun sensors  301 ,  302 ,  303  and  304  function to provide a first control signal to the drive motors so that the motors position the module  200  so that the plane of the lenses  210  is substantially orthogonal to the incoming sun beams as the module tracks the sun during the course of the day. A more detailed description of the structure and function of one embodiment of a sun sensor is set forth in published U.S. Patent Application No. 2008/0128586 (Johnson Jr., et al.), the entirety of which is incorporated herein by reference. 
     According to the present disclosure, one or more sensors  301 ,  302 ,  303 , and  304  can also function to provide a control signal to the drive motors so that the motors position the module  200  in a “maintenance” position so that maintenance can be performed on the module  200  or an array of modules  200 . Exemplary embodiments of positioning a module into maintenance position are described below in connection with  FIGS. 4 ,  5 ( a ), and  5 ( b ). 
     Sun sensors  301 ,  302 ,  303 , and  304  can be mounted to module  200  via mounting features  315  which are secured to the outer side faces of the module  200 . A more detailed description of the structure and function of one embodiment of a mounting feature  315  is set forth in published U.S. Patent Application No. 2010/0018570 (Cashion, et al.), the entirety of which is incorporated herein by reference. 
     The sun sensors  301 ,  302 ,  303 , and  304  have receptacles or sockets (not shown) which mate with detachable electrical connectors  305 ,  306 ,  307  and  308  respectively. In some embodiments the electrical connectors are six-pin connectors. The electrical connectors  305 ,  306 ,  307  and  308  are coupled to multi-conductor electrical cables  309 ,  310 ,  311 , and  312  respectively, which are then aligned and fed into conduit  313  that extends below the bottom side surface of the module  200  and attaches to an output electrical connector  314 . The electrical connector  314  may be mounted on a frame rail member  316 . 
       FIG. 3  is a side elevational view of a solar cell module in the starting or “home” position. This is the position in which the module is rotated to the left to the fullest extent possible, and in which the module will start to track the sun at a time after sunrise. 
       FIG. 4  is a highly simplified block diagram of the sun sensor control system. The sun sensors  301  and  302  are electrically connected to a controller  401 . As shown in  FIGS. 2 and 3 , in one embodiment, the controller may be electrically coupled to the sun sensors in a module  200  by the connector  314 . The controller  401  has outputs which are connected to the two drive motors  402  and  403  respectively. The drive motors are mechanically coupled to the module  200  for pivotably moving the module to track the sun during the course of the day. Reference may be made to U.S. Patent Application No. 2010/0018570 (Cashion, et al.) for further details of the actuation and tracking mechanism. 
     The operation of the sun sensor control system according to the present disclosure is to make additional use of the sun sensors which are normally used for alignment purposes, i.e. ensuring that the modules are aligned and pointed to the sun so that the incoming light beams are orthogonal to the surface of the lenses  210 . One additional use in one embodiment of the present disclosure is to send a control signal to the actuator motors to re-position the modules in a predetermined position where they may be accessed most easily during a maintenance operation, such as for example the positions depicted in  FIG. 2  or  3  above. 
     In one embodiment of the present disclosure, light is totally blocked from one or more of the sun sensors for a predetermined period of time. Under such circumstances, the output signal emitted by the sun sensor will go from a high value to zero. Since even under cloudy, rainy or overcast weather, the sun sensor is receiving some light, and will output a relatively low signal, so that the appearance of a zero signal during normal daylight operation is an exceptional occurrence, and can be used as a control signal when provided to a suitable processor monitoring the output levels of the sun sensors. 
     By suitably specifying the specific predetermined period of time (e.g. between one and ten seconds, between ten and thirty seconds, more than thirty seconds, etc.) to trigger a control signal, or in other embodiments by repeating the operation at least twice (e.g., block for five seconds, pause, and block for five seconds a second time), the encoding process may be made sufficiently complex that it would not occur naturally due to the environmental ambient light conditions. Moreover, different predetermined timed patterns of light blocking may be used to represent different operations: for example, a first pattern may represent actuation to the position of the module to that of  FIG. 2 , while a second pattern may represent actuation to the position of the module to that of  FIG. 3 . 
     In other embodiments of the present disclosure, a predetermined timed patterns of light blocking may be used to sample the operational status of the system (e.g., the amount of power being produced), and to communicate that data over a communication link to an remotely located external monitoring station, or to reconfigure the operational architecture of the array (e.g. shut down operation of one module, one panel row, etc). 
     In other embodiments of the present disclosure, the light may be totally blocked from two of the sun sensors simultaneously for a predetermined period of time to trigger a control signal, as will be illustrated in the control pattern of  FIG. 5(   b ) noted below. 
       FIG. 5(   a ) is one embodiment of a light blocking pattern with one sun sensor that represents a control signal. In this example, the sensor is blocked for three successive time periods t 1 , t 2 , t 3 , which are approximately of equal duration. 
       FIG. 5(   b ) is one embodiment of a light blocking pattern with two sun sensors that represents a control signal. In this example, the two sensors are simultaneously blocked for two successive time periods t 4 , t 5 , which are approximately of equal duration. 
     While the present disclosure illustrates and describes a control system for use in a photovoltaic power system, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present disclosure. 
     It will be understood that each of the elements described above, or two or more together, also may find a useful application in other types of constructions differing from the types described above. In particular, certain configurations presented according to particular aspects of the present invention have been shown and described as discrete elements, i.e., sun sensors, connectors, cables, processors, actuators, etc. Those skilled in the art will readily appreciate that many or all of these individual, discrete components may be fabricated and/or packaged into integrated elements, e.g. an integrated connector and cable. 
     Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, the appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. 
     The foregoing described embodiments depict different components contained within, or connected with, different other components. It is to be understood that such depicted arrangements or architectures are merely exemplary, and that in fact many other arrangements or architectures can be implemented which achieve the same functionality. In a conceptual sense, any arrangement of components to achieve the same functionality is effectively “associated” such that the desired functionality is achieved. Hence, any two components herein combined to achieve a particular functionality can be seen as “associated with” each other such that the desired functionality is achieved, irrespective of specific structures, architectures or intermedial components. Likewise, any two components so associated can also be viewed as being “operably connected” or “operably coupled” to each other to achieve the desired functionality. 
     It will be understood by those within the art that, in general, terms used herein, and especially in the appended claims (e.g., bodies of the appended claims) are generally intended as “open” terms (e.g., the term “including” should be interpreted as “including but not limited to,” the term “having” should be interpreted as “having at least,” the term “includes” should be interpreted as “includes but is not limited to,” “comprise” and variations thereof, such as, “comprises” and “comprising” are to be construed in an open, inclusive sense, that is as “including, but not limited to,” etc.). It will be further understood by those within the art that if a specific number of an introduced claim recitation is intended, such an intent will be explicitly recited in the claim, and in the absence of such recitation no such intent is present. For example, as an aid to understanding, the following appended claims may contain usage of the introductory phrases “at least one” and “one or more” to introduce claim recitations. However, the use of such phrases should not be construed to imply that the introduction of a claim recitation by the indefinite articles “a” or “an” limits any particular claim containing such introduced claim recitation to inventions containing only one such recitation, even when the same claim includes the introductory phrases “one or more” or “at least one” and indefinite articles such as “a” or “an” (e.g., “a” and/or “an” should typically be interpreted to mean “at least one” or “one or more”); the same holds true for the use of definite articles used to introduce claim recitations. In addition, even if a specific number of an introduced claim recitation is explicitly recited, those skilled in the art will recognize that such recitation should typically be interpreted to mean at least the recited number (e.g., the bare recitation of “two recitations,” without other modifiers, typically means at least two recitations, or two or more recitations). 
     Spatially relative terms such as “under”, “below”, “lower”, “over”, “upper”, and the like, are used for ease of description to explain the positioning of one element relative to a second element. These terms are intended to encompass different orientations of the device in addition to different orientations than those depicted in the figures. Further, terms such as “first”, “second”, and the like, are also used to describe various elements, regions, sections, etc. and are also not intended to be limiting. 
     Without further analysis, from the foregoing others can, by applying current knowledge, readily adapt the disclosed technology for various applications. Such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.