Abstract:
A method and apparatus for efficient manufacture, assembly and production of solar energy. In one aspect, the apparatus may include a number of modular solar receiver assemblies that may be separately manufactured, assembled and individually inserted into a solar collector array housing shaped to receive a plurality of solar receivers. The housing may include optical elements for focusing light onto the individual receivers, and a circuit for electrically connecting the solar receivers.

Description:
GOVERNMENT LICENSE RIGHTS 
     This invention was made with Government support under Contract No. DE-FC36-07G017052 awarded by the Department of Energy. The government has certain rights in this invention. 
    
    
     BACKGROUND 
     The present invention relates to methods for generating solar energy, and more particularly, to modular solar arrays having electrically interconnected solar collectors for generating solar energy. 
     Solar power is becoming an increasingly important component of electricity production. However, due to the diffuse nature of solar energy, it is necessary to concentrate solar energy in order to generate electrical power. Photovoltaic solar concentrators typically are used to generate electrical power by concentrating sunlight onto photovoltaic devices by means of lenses which concentrate solar energy onto electricity-producing solar cells. By concentrating sunlight from a large area onto a relatively small area, high efficiency solar cells, such as gallium arsenide-based (“GaAs”) solar cells may be used in place of less efficient silicon solar cells, thereby producing more energy per unit area. 
     While improved efficiency can increase the energy production per unit area, the relatively small amount of electricity generated per unit area (compared to fossil fuel or nuclear electricity sources) requires a large number of solar cells distributed over a wide area. Therefore, a number of solar collectors must be assembled and placed in order to generate a meaningful amount of electricity. 
     One method of providing energy is the use of multiple solar collectors within one housing unit to create a solar collector array, such as that described in U.S. Publication No. 2010/0275972 to Benitez, et al., herein incorporated in its entirety. The housing unit provides thermal and environmental protection for the solar collectors as well as providing an optical element that concentrates solar energy onto a solar cell. Each individual solar cell is electrically connected to an adjoining cell in series, thereby providing a large voltage drop across the entire solar collector array. 
     A concern with this type of assembly is the high degree of accuracy that is required to align the solar cells within the housing unit. Incident solar energy must be carefully controlled to impact a relatively small area on the solar cell. This results in a high manufacturing cost to accurately align an array of solar cells to one another and to individual optical elements on the housing unit. 
     A further complication present in prior art devices is the need to electrically couple adjacent solar cells. This electrical connection is required to be located within the thermal and environmental protection of the housing unit due to the very high voltage above ground that may pass through the connection, and to lessen the risk of damage to the electrical connection, which may reduce the amount of power generated. Further, these electrical connections are required to be relatively robust to carry high levels of electrical current generated by the solar collectors. 
     Finally, while the solar collector may receive a large amount of incident solar radiation, solar cells typically are able to convert only approximately 30% to 60% of such radiation to electricity. The remaining incident radiation is converted to heat that must be dissipated. 
     It is the object of the present invention to overcome these and other problems identified in the prior art. 
     SUMMARY OF THE INVENTION 
     In one aspect, a solar collector array may include a housing, a modular solar collector, and a seal between the housing and solar collector. The housing may include a first optical element and a receiver plate with the receiver plate including openings for receiving the modular solar collector and an electrical element for transmitting power between and from the modular solar collectors. The solar collector may be inserted into the opening and may include an electrical connector that engages the electrical element. The seal may provide a thermal and environmental barrier between the collector and housing, while maintaining a thermal connection through the housing. 
     Further aspects of the disclosed solar array may include a photovoltaic cell on the solar collector, a second optical element on the solar collector, and a heat sink on the solar collector in thermal communication with the photovoltaic cell. 
     Also disclosed is a novel method of manufacturing a solar collector from an environmentally enclosed housing and a solar collector. The housing includes an optical element and an electrically conductive pathway extending between openings in the housing for transmitting electricity therefrom and therebetween. The solar collector may include a heat sink, a photovoltaic cell in contact with the heat sink, an optical element for focusing solar energy onto the cell, a receiver for coupling the collector to the housing and an electrical connector. A portion of the receiver may be inserted into the opening and coupled to the housing. The electrical connector then may be electrically coupled to the electrically conductive pathway and the components are sealed together to provide protection from the ambient. 
     Other aspects of the disclosed solar array may include making the connector a spring-biased clip and providing a receiver shaped to engage the housing mechanically and provide an electrical connection between the solar collectors and housing. 
     In a further aspect, a method of generating solar energy includes providing a solar collector with a housing and modular solar collectors such as those described above. The receiver of the modular solar collector is inserted into the housing and twisted to couple the modular solar collector to the housing mechanically, and at the same time, electrically connect the solar collector to the circuit of solar collectors contained within the housing. Incident solar radiation is focused through a first optical element in the housing onto the second optical element and through the second optical element onto a photovoltaic cell. Electrical energy is then transferred from the photovoltaic cell to a clip and from the clip to an electrical path within the housing, thereby providing a source of solar generated electricity. 
     The features, functions, and advantages that have been discussed can be achieved independently in various embodiments of the present invention or may be combined in yet other embodiments further details of which can be seen with reference to the following description and drawings. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a perspective view of one embodiment of the disclosed solar collector array; 
         FIG. 2  is a perspective view of a housing for the solar collector array of  FIG. 1 ; 
         FIG. 3A  is a top perspective view of a receiver plate of the housing of  FIG. 2 ; 
         FIG. 3B  is a bottom perspective view of the receiver plate shown in  FIG. 3A ; 
         FIG. 4  is an exploded, perspective view of a receiver assembly for the solar collector array of  FIG. 1 ; 
         FIG. 5A  is a perspective view showing a first stage of assembly of the receiver assembly of  FIG. 4 ; 
         FIG. 5B  is a perspective view showing a second stage of assembly of the receiver assembly of  FIG. 4 ; 
         FIG. 5C  is a perspective view showing a third stage of assembly of the receiver assembly of  FIG. 4 ; 
         FIG. 5D  is a perspective view showing a fourth stage of assembly of the receiver assembly of  FIG. 4 ; 
         FIG. 5E  is a perspective view showing a fifth stage of assembly of the receiver assembly of  FIG. 4 ; 
         FIG. 5F  is a perspective view showing the sixth stage of assembly of the receiver assembly of  FIG. 4 ; 
         FIG. 5G  is a perspective view showing the seventh stage of assembly of the receiver assembly of  FIG. 4 ; 
         FIG. 6A  is a top perspective view showing the attachment of the receiver assembly to the receiver plate; 
         FIG. 6B  is a top perspective view showing the attachment of the receiver assembly to the receiver plate; 
         FIG. 7A  is a bottom perspective view showing the attachment of the receiver assembly to the receiver plate; and 
         FIG. 7B  is a bottom perspective view showing the attachment of the receiver assembly to the receiver plate. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to the embodiments of the present general inventive concept, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. The embodiments are described below in order to explain the present general inventive concept by referring to the figures. 
     As shown in  FIG. 1 , the solar collector array  100  may include a housing  102  and a number of receiver assemblies  104 A-F (generally referred to as  104 ). The solar collector array  100  as shown in this figure includes six receiver assemblies  104 A-F, although the number of receiver assemblies  104  may be varied according to need. 
       FIG. 2  illustrates the housing  102  that may include optical elements  106 , side walls  108 , back  110 , and a receiver plate  112 . The receiver plate  112  includes a number of receiver interfaces  114 A-F (generally referred to as  114 ) that receive corresponding receiver assemblies  104 A-F ( FIG. 1 ). 
       FIGS. 3A and 3B  show an individual receiver interface  114  that may be located on the receiver plate  112 . The receiver plate  112  includes an inside surface  116  that faces the interior of the housing  102  ( FIG. 2 ) and an outside surface  118  facing away from the housing  102 . As shown in  FIG. 3A , the inside surface  116  includes a conductor  120  that runs substantially the length of the receiver plate  112  and is interrupted by the receiver interfaces  114 . Elongate conductor strip segments  120  are mounted on the inside surface  116  of the receiver plate  112  are shaped to engage the receiver assemblies  104 , as shown in  FIGS. 6A-B , and extend between and electrically interconnect the receiver assemblies  104 A-F (see  FIG. 1 ). In one embodiment, the conductor strip segments  120  each comprise a copper strip 0.002″ thick and 0.375″ wide. These conductor strip segments  120  must be sufficiently robust to carry current generated by the assembly. 
     As further shown in  FIG. 3A , each receiver interface  114  includes a central, generally circular receiver opening  122  and a number of arcuate slots  124  spaced from and positioned about the receiver opening  122 . The slots  124  are shaped to provide a twist lock tab interface or bayonet connection and include a wide end  124   a  and a narrow end  124   b  (see also  FIGS. 6A and 6B ). Other types of interfaces may be used that provide a positive mechanical connection between the receiver interfaces  114  and the receiver assemblies  104 , including snap fit, screws, adhesives, welding or other fittings or interfaces that are well known. The receiver opening  122  and slots  124  are designed to receive and lock in place the receiver assemblies  104  as shown in  FIGS. 6A-B . The conductor strip segments  120  each terminate in tabs  126  that extend into the receiver openings  122  and engage the receiver assembly  104  when it is inserted into the opening  122  and engaged, as shown in  FIGS. 6A-B  and described in greater detail below. 
       FIG. 3B  shows the outside  118  of the receiver plate  112 . This side of the receiver plate  112  includes a seal groove  128  and seal  130  that may fit within the groove  128 . The seal  130  surrounds the opening  122  and slots  124  and provides part of an air and thermal barrier between the housing  102  and receiver assembly  104 . The seal  130  may be an O-ring formed of, for example, synthetic or natural rubber, nylon, or other material commonly used as a gasket seal. 
     The receiver assembly  102  is shown in exploded view in  FIG. 4 . The receiver assembly  102  may include a secondary optical element (“SOE”)  132 , a disk-shaped light shield  134 , a pair of conductor clips  136 , receiver  138 , concentrator cell assembly (“CCA”)  140 , gasket  142  and heat sink assembly  144 . As described in, for example, U.S. Patent Application Pub. No. 2010/0275972, the SOE  132  may focus light received by the optical elements  106  (see  FIG. 1 ) and direct it onto the CCA  140 . The light shield  134  may be positioned between the SOE  132  and CCA  140  and cover sensitive elements of the CCA  140 , preventing damage due to highly focused solar energy. The light shield  134  allows light to focus onto the photovoltaic elements of the CCA  140 , which generate electricity from the incoming solar energy. 
     The CCA  140  may be attached directly to the inner surface of the heat sink assembly  144  by a thermally conductive adhesive, and may include tape, glue, or other well-known or commercially available thermally conductive adhesive. The gasket  142  may be positioned between the heat sink assembly  144  and receiver  138  as a thermal barrier and prevents damage to the receiver  138  by heat from the heat sink assembly  144 . 
     The conductor clips  136  are mounted on the receiver  138  and extend in a generally radial direction. The clips  136  are electrically connected to the CCA  140  at their radially inner ends and include enlarged, radially outer ends shaped to engage the conductor tabs  126  of the receiver interface  114  as shown in  FIG. 6B . Receiver  138  provides engagement between the receiver assembly  102  and receiver interface  114 , as shown in  FIGS. 6A-B . 
     As further shown in  FIG. 4 , the receiver  138  may be generally annular in shape and shaped to engage the receiver interface  114  on the receiver plate  112 . The receiver  138  may include a recessed cup  146  that receives the SOE  132  and attaches to other components as shown in  FIGS. 5A-G . The receiver  138  may also include bayonet prongs  148  shaped to engage the receiver interface  114  as shown in  FIGS. 6A-B  and  7 A-B. These bayonet prongs  148  each may include a stem  150  projecting from the receiver  138  and terminating in a tang  152  that extends outwardly from the stem  150 . While the bayonet prongs  148  shown are one type of fastener that may be used, a number of different types of fasteners may be substituted to accomplish the desired result. For example, screw fasteners, pins, snap fasteners, adhesives, or other fasteners may be used without departing from the scope of the invention. 
     Assembly of the receiver assembly  102  is generally demonstrated in  FIGS. 5A-G .  FIG. 5A  shows the heat sink assembly  144  to which the other components are attached.  FIG. 5B  shows the gasket  142  attached to the heat sink assembly  144 . In  FIG. 5C , the CCA  140  is positioned on the heat sink assembly  144 . In  FIG. 5D , the receiver cup  138  is positioned about the CCA  140  and is thermally isolated from the heat sink  144  by the gasket  142 . In  FIG. 5E , the conductors  136  have been attached to the receiver  138  and electrically engage the CCA  142  to conduct electricity away from the CCA  142 . In  FIG. 5F , the light shield  134  has been added, providing a barrier that only allows sunlight to impact the photovoltaic elements of the CCA  140 . Finally, in  FIG. 5G , the SOE  142  has been attached to the receiver  138  to further focus incident light onto the CA  140 . 
       FIGS. 6A-B  show the method of attaching a receiver assembly  104  to the receiver interface  114  at the inside surface  116  of the receiver plate  112 . The receiver assembly  104  is positioned adjacent the opening  122  in the receiver plate  112  and is inserted into the receiver interface  114 . The bayonet prongs  148  are inserted into the enlarged ends  124   a  of the slots  124 . The wide end  124   a  of the slot  124  is sized to receive the tangs  152  of the bayonet prongs  148 . As shown in  FIG. 6B , the receiver assembly  104  is then rotated (counterclockwise as shown in  FIGS. 6A and 6B ) so that the bayonet prongs  148  engage the narrow ends  124   b  of the slots  124 , which are sized to receive the stems  150  of the bayonet prongs  148 . In this orientation, the tangs  152  prevent the removal of the bayonet prongs  148  from the slots  124 , and therefore prevent removal of the receiver assembly  104  from the receiver interface  114 . 
     As further shown in  FIGS. 6A-B , as the receiver assembly  104  is rotated relative to the receiver interface  114 , the conductor clips  136  on the receiver assembly  104  engage the conductor tabs  126  on the receiver interface. The conductor clips  136  preferably include a spring component, either as a separate piece or as part of the clip itself, that is biased towards engagement with the conductor tabs  126 . In the embodiment shown, the clips  136  are biased away from the inside surface  116  and engage the tabs  126  when the receiver assembly  104  is secured in place. However, those having skill in the art may appreciate that other types of tabs  126  and clips  136  may be used without departing from the scope of the invention. For example, the clips  136  may be spring-biased radially outward from the assembly, biased towards the inside surface  116 , or may alternatively be secured by screws or other fittings. 
       FIGS. 7A-B  show the receiver assembly  104  being secured to the receiver interface  114  from the outside surface  118  of the receiver plate  112 . In this view, the heat sink assemblies  144  are visible and are rotated from approximately 10° offset from a long axis of the receiver plate  112  to approximately parallel to the receiver plate  112 . When fully assembled, the heat sink assemblies  144  preferably are located external to the housing  102 , thereby allowing maximum dissipation of heat from the CCA  140 . 
     While the forms of apparatus described herein constitute preferred embodiments of the invention, it should be understood that the invention should not be limited to these precise embodiments, and variations may be made thereto without departing from the scope of the invention.