Abstract:
Reflector support arms for use in connection with parabolic trough solar concentrators are provided. The reflector support arms are constructed from multiple formed components. The use of multiple formed components enables the provision of a precisely constructed support arm. In addition, by using multiple components, the support arm can be produced using smaller forming machines than would otherwise be required.

Description:
[0001]    This application claims the benefit of U.S. Provisional Application Ser. No. 61/725,719, filed Nov. 13, 2012, the entire disclosure of which is incorporated by reference herein. 
     
    
     FIELD 
       [0002]    Embodiments of the present invention are generally related to a formed reflector support arm used in parabolic trough solar concentrators. 
       BACKGROUND 
       [0003]    Parabolic trough solar concentrators utilize a fluid-filled receiver tube that is positioned above sun-tracking reflectors that focus solar energy onto the receiver tube. As development of concentrating solar power plants continues, the size of the focusing reflectors and associated installations has increased. More specifically, one way to increase solar energy production is to increase the size of the reflectors, receiving tubes, etc., which necessarily increases the size and weight of the associated support structure. Commonly, reflector support structure is comprised of a truss made of a number of welded components. Some larger structures are comprised of stamped or otherwise formed support members. As one of skill in the art will appreciate the larger and more complex the support structure becomes, the greater the associated fabrication costs. Accordingly, it is desirable to provide reflector support assemblies that can be produced inexpensively and that can accurately maintain a desired position of relatively large reflectors under various conditions. 
         [0004]    Again, typically truss support structures are used as they provide sufficient strength and stiffness, while maintaining an acceptable weight. Typical truss support systems are comprised of individual support members that are formed from multiple pieces of material, such as steel or aluminum that are welded or riveted together. Brackets for connecting the reflectors, i.e., a series of mirrors or other reflecting members to the support arms, and for connecting the support arms to a central support structure, are then added to the truss. Although truss designs can be used to support reflectors of varying sizes, such designs can suffer from a number of disadvantages. A primary disadvantage is that the truss manufacturing process is relatively labor intensive and complex. Also, such processes often result in a relatively large amount of wasted material. 
         [0005]    Another disadvantage is that the manufacturing process is typically imprecise. More specifically, many solar collecting assemblies are constructed by first laying down the reflectors on an assembly support with the reflective side down. Next, plurality of truss members are interconnected to the back side of the reflectors, often with brackets or ceramic pads positioned between the reflectors and the truss elements. Then the assembly is lifted and rotated to orient the mirrors facing up. The pads that attach the reflectors to the truss structure can then be modified to ensure that the maximum amount of light gathered by the reflectors is focused on receiving tube. 
         [0006]    To address some of the disadvantages of truss-type support arms, support arms formed from stamped metal have been proposed. However, stamping large pieces requires a very high capital investment, in the form of large presses. Also, there are limits to the size of available presses, and a higher percentage of raw sheet metal input is typically scrapped in the stamping of large irregular-shaped parts. Accordingly, previous systems utilizing stamped mirror support arms are not adequately cost-optimized. 
       SUMMARY 
       [0007]    Embodiments of the present invention are directed to solving these and other problems and disadvantages of the prior art. In accordance with embodiments of the present invention, a solar concentrator reflector support assembly is provided that utilizes multiple support members, some of which are formed of a shape that facilitates manufacture of a concentrator reflector assembly. In particular, the contemplated support members that are attached to the reflector elements, or mirrors are formed or shaped support members. The reflector support members generally include a support surface or interface that may possess a shape that corresponds with the shape of the reflective element. Accordingly, at least a portion of the support surface is curved. The support members also include a backing surface that is spaced from the support surface. An intermediate member extends between at least a portion of the support surface and a portion of the backing surface. Each support member can also include at least a first pad associated with the mirror support surface, and an interconnection feature for attaching the support member to other members of the structure. A reflector support assembly in accordance with embodiments of the present invention can also include an interconnection member that has a first end that is fixed to the interconnection feature of a first support member. A second end of the interconnection member is fixed to either a central support structure or to a second support member. Similar to the mirror support members, the interconnection members can be formed from a single piece of material. 
         [0008]    Methods in accordance with embodiments of the present invention include forming support members that are not linear along at least a first surface from an integral piece of material. The first surface, or reflector support surface, can include one or more reflector interface features. Some embodiments allow the reflective members to directly interconnect to the curved surface. Moreover, the support surface can be formed with the accuracy required to focus the mirrors or reflectors on the receiver tube or other target. Alternatively, or in addition, mirror pads may be associated with the first surface. An interconnection feature may be formed on a second surface of the support member. In accordance with at least some embodiments of the present invention, the interface features, the mirror pads, and/or the interconnection features are formed simultaneously with the formation of the associated support member. Moreover, the interface features, the mirror pads, and/or interconnection features may be integral to the associated mirror support member. Forming the support members can include stamping the members from sheet stock, roll-forming, bending, stretch forming, or by other known mechanical or hydraulic bending and forming processes. The formation of a mirror support assembly can include interconnecting first and second support members via the interconnecting member that, like the mirror support members themselves, is curved along at least first, second, and third surfaces. In accordance with at least some embodiments, the interconnecting member can include a mirror pad and an interconnection feature. 
         [0009]    It is yet another aspect of the present invention to provide a support assembly of a solar concentrator mirror support assembly, comprising: a first outer section having first end and a second end, and a reflective element support surface; a second outer section having first end and a second end, and a reflective element support surface; a first inner section having first end and a second end, and a reflective element support surface; a second inner section having a first end and a second end, and a reflective element support surface; wherein the second end of the first outer section is associated with the second end of the second outer section; wherein the first end of the first inner section is interconnected to the first outer section at a point between the first end and the second end of the first outer section; wherein the first end of the second inner section is interconnected to the second outer section at a point between the first end and the second end of the second outer section; wherein the second end of the first inner section is associated with the second end of the second inner section; and wherein the reflective element support of the first outer section, the first inner section, second inner section, and the second outer section support a plurality of reflective elements that are spaced in an arcuate configuration. 
         [0010]    It is still yet another aspect of the present invention to provide a solar concentrator, comprising: a plurality of spaced support assemblies, each comprising a first formed outer section having first end and a second end, and a curved reflective element support surface; a second formed outer section having first end and a second end, and a curved reflective element support surface; a first formed inner section having first end and a second end, and a curved reflective element support surface; a second formed inner section having a first end and a second end, and a curved reflective element support surface; wherein the second end of the first formed outer section is associated with the second end of the second formed outer section; wherein the first end of the first formed inner section is interconnected to the first formed outer section at a point between the first end and the second formed end of the first formed outer section; wherein the first end of the second formed inner section is interconnected to the second formed outer section at a point between the first end and the second end of the second formed second outer section; wherein the second formed end of the first formed inner section is associated with the second end of the second formed inner section; and wherein the reflective element support of the first formed outer section, the first formed inner section, second formed inner section, and the second formed outer section support a plurality of reflective elements that are spaced in an arcuate configuration, the plurality of reflective elements being directly interconnected to the first formed outer section, the first formed inner section, second formed inner section, and the second formed outer section with the absence of mirror interface features; central support structure associated with the second ends of the first formed inner sections and the second formed inner section of each the support assembles; and a receiver tube spaced above the plurality of reflective elements, the receiver tube also associated with a first pivot associated with a first end of the solar concentrator and a second pivot associated with a second end of the solar concentrator. 
         [0011]    The Summary of the Invention is neither intended nor should it be construed as being representative of the full extent and scope of the present invention. Moreover, references made herein to “the present invention” or aspects thereof should be understood to mean certain embodiments of the present invention and should not necessarily be construed as limiting all embodiments to a particular description. The present invention is set forth in various levels of detail in the Summary of the Invention as well as in the attached drawings and the Detailed Description of the Invention and no limitation as to the scope of the present invention is intended by either the inclusion or non-inclusion of elements, components, etc. in this Summary of the Invention. Additional aspects of the present invention will become more readily apparent from the Detail Description, particularly when taken together with the drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention and together with the general description of the invention given above and the detailed description of the drawings given below, serve to explain the principles of these inventions. 
           [0013]      FIG. 1  is a top perspective view of a parabolic trough solar concentrator structure of the prior art; 
           [0014]      FIG. 2  is a bottom perspective view; 
           [0015]      FIG. 3  is a side elevation view of a solar concentrator reflector support assembly in accordance with embodiments of the present invention; 
           [0016]      FIG. 4  is a side elevation view of a solar concentrator reflector support assembly in accordance with other embodiments of the present invention; 
           [0017]      FIG. 5  is a side elevation view of a solar concentrator reflector support assembly in accordance with other embodiments of the present invention; 
           [0018]      FIG. 6  is a side elevation view of a solar concentrator reflector support assembly in accordance with other embodiments of the present invention; 
           [0019]      FIG. 7  is a side elevation view of a solar concentrator reflector support assembly in accordance with other embodiments of the present invention; 
           [0020]      FIG. 8  is a side elevation view of a solar concentrator reflector support assembly in accordance with other embodiments of the present invention; and 
           [0021]      FIG. 9  is a flowchart depicting aspects of a method for forming a solar concentrator reflector support assembly in accordance with embodiments of the present invention. 
       
    
    
       [0022]    To assist in the understanding of one embodiment of the present invention the following list of components and associated numbering found in the drawings is provided herein: 
         [0000]    
       
         
               
               
             
               
               
             
           
               
                   
               
               
                 # 
                 Component 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 2 
                 Parabolic trough solar concentrator assembly 
               
               
                 10 
                 Parabolic mirror 
               
               
                 14 
                 Mirror segment 
               
               
                 18 
                 Mirror support assembly 
               
               
                 22 
                 Support arms 
               
               
                 26 
                 Central support structure 
               
               
                 30 
                 Pivot 
               
               
                 34 
                 Receiver tube 
               
               
                 38 
                 Outer lateral edge 
               
               
                 142 
                 Mirror support member 
               
               
                 144 
                 Mirror support surface 
               
               
                 154 
                 Interconnection point 
               
               
                 156 
                 Secondary support member 
               
               
                 160 
                 End interconnection point 
               
               
                 162 
                 Mirror interface features 
               
               
                 242 
                 Mirror support member 
               
               
                 244 
                 Mirror support surface 
               
               
                 248 
                 Outer section 
               
               
                 250 
                 Inner section 
               
               
                 254 
                 Interconnection point 
               
               
                 260 
                 End interconnection point 
               
               
                 264 
                 End interconnection point 
               
               
                 342 
                 Mirror support member 
               
               
                 344 
                 Mirror support surface 
               
               
                 348 
                 Outer section 
               
               
                 350 
                 Inner section 
               
               
                 354 
                 Interconnection feature 
               
               
                 360 
                 End interconnection feature 
               
               
                 356 
                 Interconnection feature 
               
               
                 362 
                 End interconnection feature 
               
               
                 442 
                 Mirror support member 
               
               
                 444 
                 Mirror support surface 
               
               
                 448 
                 Outer section 
               
               
                 450 
                 Inner section 
               
               
                 462 
                 End interconnection feature 
               
               
                 500 
                 Mirror support assembly 
               
               
                 542 
                 Mirror support member 
               
               
                 544 
                 Mirror support surface 
               
               
                 548 
                 Outer section 
               
               
                 549 
                 Central mirror support 
               
               
                 600 
                 Mirror support assembly 
               
               
                 644 
                 Mirror support surface 
               
               
                 648 
                 Truss 
               
               
                 650 
                 Truss members 
               
               
                 654 
                 Interconnection features 
               
               
                   
               
             
          
         
       
     
         [0023]    It should be understood that the drawings are not necessarily to scale. In certain instances, details that are not necessary for an understanding of the invention or that render other details difficult to perceive may have been omitted. It should be understood, of course, that the invention is not necessarily limited to the particular embodiments illustrated herein. 
       DETAILED DESCRIPTION 
       [0024]      FIGS. 1 and 2  are perspective views of a parabolic trough solar concentrator assembly or structure  2  of the prior art. In general, the solar concentrator assembly  2  includes a parabolic mirror or reflective element  10 . The parabolic mirror can be comprised of a plurality of mirror segments  14 . The parabolic mirror  10  is supported by a mirror support structure or assembly  18  that includes a plurality of formed support arms  22 , and a central support structure  26 . The mirror support assembly  18  is interconnected to a fixed support structure (not shown) by a pivot  30 . By tilting the mirror  10  about the pivot  30 , radiation from the sun is directed towards a solar or receiver tube  34  containing a heat transfer fluid. 
         [0025]    As shown in  FIG. 2 , the formed reflector support arms  22  are located at predefined intervals along the length of the mirror  110 . The support arms  22  may also support a number of mirror segments  14 . Each formed support arms  22  generally extend to or near outer lateral edges  38  of the mirror  10 . Such structures are also described in U.S. Patent Application Publication No. 2012/0217209, which is incorporated by reference in its entirety herein. 
         [0026]      FIGS. 3-7  are elevation views of support arms employed by embodiments of the present invention. Here, the formed support arm assemblies  122  are generally comprised of one or more mirror support members  142  having a curved mirror support surface  144 . The mirror support members  142  of this embodiment are manufactured using a precision forming process that provides the curvature necessary to accommodate reflective elements that are capable of focusing solar energy onto the desired target without the need for post-fabrication modifications. Accordingly, in some embodiments, pads or other interconnection members that are traditionally used to interconnect the mirror to the support surface  144  may be omitted, which reduces fabrication time and cost. Further, one embodiment of the support surface is previously curved to receive a compliant, composite reflective member or reflective members that are concave along their length as discussed in WIPO Publication No. 2012/145513, which is incorporated in its entirety herein. In these examples, the mirror segments are directly bonded to the mirror support surface  144 . The mirror support member  142  includes an interconnection point  154  or feature that receives a secondary support member  156 , which is interconnected to additional support structure associated with the parabolic mirror assembly. In addition, the mirror support member  142  includes an end interconnection point  164  or feature for interconnection to a corresponding and oppositely disposed mirror support member. Alternatively, the end interconnection point  160  interfaces with a centralized support member that interconnects corresponding mirror support members. 
         [0027]    In addition, the mirror support member  142  may include a plurality of mirror interface features  162  that may be integrated or attached to the mirror support service  144 . For example, some embodiments the present invention use ceramic pads that are fastened to the mirror support surface  144 . The ceramic pads in turn receive a rear surface of the reflective element. As will be described below, in other embodiments, the mirror interface features are omitted and the rear surface of the mirror is directly interconnected or bonded to the mirror support surface  144 . 
         [0028]    As shown in  FIG. 4 , for example, the mirror support member  142  can be further divided to include an outer section  248  and an inner section  250 . The outer section  248  is interconnected to the inner section  250  at point  254 . This allows for adjustments between the outer section  248  and inner section  250  which provides the curved necessary to accommodate the curvature of the mirror. The inner section  250  also has an end interconnection point  260  that is adapted to interface with a similar point or interconnection feature on a corresponding inner section  250  of the opposite side of the arm support structure (not shown). Similarly, the outer section  248  includes a connection point and end interconnection point  264  for interconnection to other support structure associated with the parabolic mirror assembly (not shown). 
         [0029]    In accordance with embodiments of the present disclosure, the mirror support member  242  is a formed component. Further, the outer section  248  and/or the inner section  250  may be formed. As used herein, “formed” means that the component is provided with at least some aspects of its final configuration during a forming step, as opposed to an assembly step. Examples of forming include pressing, roll forming, bending, hydro-forming, stamping, and the like. Moreover, the interconnection point or features and the mirror interface features (if applicable) can be formed when the forming of the mirror support members is performed. 
         [0030]      FIG. 5  is a view in elevation of one half of a formed mirror support arm  342  in accordance with other embodiments of the present disclosure, which is half of a formed reflector support arm assembly. The support arm  342  includes an outer section  348  and an inner section  350 . The inner section  350  includes a precision formed mirror support surface  344 , an interconnection feature  354 , a second interconnection feature  356  and an end interconnection feature  360 . The interconnection features of the inner section  350  are coincident with interconnection features of the outer section  248 . The outer section  248  also includes a precision-formed mirror support surface  344 , and an end interconnection feature  360 . The end interconnection features  360  and  362  provide for the interconnection of the half of the formed reflector support arm assembly to a central support structure. The mirror support surfaces  344  cooperate to provide support for a corresponding half of the mirror from or near the outer edge of the mirror to the area corresponding to the central trough or area  380 . In addition, one or both of the mirror support member sections can comprise formed components as described above. For example, the outer section  348  may comprise a structural material in a stock format, while the inner section  360  may comprise a formed component, in which case the mirror support surface  344  provided by the outer section  348  may be straight, while the mirror support surface  344  of the inner section  350  may be curved. Thus, the outer section  348  may be provided with a mirror interface feature  362 . 
         [0031]      FIG. 6  is one half of a formed reflector support arm assembly in accordance with other embodiments of the present invention. In particular, a mirror support arm  442  with an outer section  448  is provided in combination with an inner section  450 . Each of the mirror support member sections may be provided with interconnection features as described above, to provide an interconnection point between the inner and outer sections. In addition, the sections may each be provided with end interconnection features as described above, for interconnecting the respective sections to a central support structure. At least some or all of the sections may comprise formed components as described above. For example, the outer section  448  may comprise a formed component with a curved mirror support structure  444 , while the inner section  250  may comprise a straight mirror support surface  444 . In addition, one or both of the sections may include a mirror interface feature  462 . 
         [0032]      FIG. 7  is a view of a mirror support arm assembly  500  in accordance with still other embodiments of the present invention. The reflector support arm assembly  500  includes a mirror support member  542  formed from a plurality of mirror support member sections. More particularly, first and second outer mirror support member sections  548   a  and  548   b  and a central mirror support member section  549  are provided. Each of the mirror support member sections includes a precision formed mirror support surface  544 . Moreover, the mirror support surfaces  544  can be curved. Each of the included mirror support member sections include various interconnection features as described above. For example, interconnection features provide for the interconnection between the first outer mirror support member  548   a  and the central mirror support member  549 . Similarly, interconnection features provide for the interconnection of the second outer mirror support member  548   b  to the central mirror support member  549 . Some or all of the mirror support members  542  can also include interconnection features  20  that provide for the interconnection of the reflector support arm assembly  500  to a central support structure. 
         [0033]      FIG. 8  depicts one half of a formed reflector support arm  600  in accordance with still other embodiments of the present invention. In particular, the support arm  600  includes a curved, precision-formed mirror support surface  644 . The mirror support surface  644  is supported by a truss  648  formed from multiple interconnected members  650 . The interconnected truss members  650  need not be precision formed. In addition, at least some of the truss members  650  may be interconnected to interconnection features  654  formed as part of the mirror support surface  644 . 
         [0034]    With reference now to  FIG. 9 , aspects of a method for providing a mirror support assembly in accordance with embodiments of the present disclosure are illustrated. More particularly, at step  704 , components of a reflector support arm assembly are formed. For example, one or more mirror support member sections and/or interconnection members included in a mirror support arm assembly may be formed from a sheet metal blank. Forming can include pressing, hydro forming, roll forming, bending, stamping, and the like. In accordance with other embodiments, the mirror support member sections and/or interconnection members may be composite structures formed from laying up and adhering material. In addition, forming can include creating curves, ridges, or other three-dimensional features, to increase the rigidity of the component being formed in a selected direction. Forming can also include the creation of mirror support surfaces, interconnection features and/or mirror interface features as described above. Moreover, the forming of rigidity enhancing features, mirror support surfaces, interconnection features, and/or mirror interface features can be performed simultaneously. In accordance with still other embodiments, forming includes creating rigidity enhancing features, interconnection features, and/or mirror interface features simultaneously. In accordance with still other embodiments, forming can include cutting to remove material that extends beyond a desired profile of the component as formed, and/or the removal of areas inside of the periphery of the component being formed. Such removal can be accomplished by, for example, a die cutting step. Moreover, a die cutting step can be performed simultaneously with a formation of rigidity enhancing features, mirror support surfaces, interconnection features, and/or mirror interface features. 
         [0035]    At step  708 , the mirror support member sections and any included interconnection members of the mirror support arm assembly are joined to one another. For example, the various components can be aligned with one another, such that complimentary interconnection features are positioned adjacent one another. Mechanical fasteners, such as bolts and nuts, adhesives, rivets, and/or welding and clinching can then be applied to fix the components of the mirror support arm assembly to one another. 
         [0036]    At step  712 , the mirror support arm assembly can be interconnected to a central support structure. As can be appreciated by one of skill in the art after consideration of the present disclosure, where the mirror support arm is provided in halves, the components of the two halves can be interconnected to one another, and the assembled half of the reflective support arm assembly can then be joined to a central support structure. 
         [0037]    At step  716 , a determination can be made as to whether a mirror support structure is complete. If additional mirror support arms are required, the process can return to step  704 . Once the mirror support structure is complete, the mirror elements  118  can be joined to the mirror support arms (step  720 ). The process can then end. 
         [0038]    As can be appreciated by one of skill in the art after consideration of the present disclosure, mirror support arms are provided that can be manufactured using a forming step or steps. Moreover, such processes allow the mirror support arms to be manufactured with high precision. In addition, the mirror support arms can be designed such that mirrors with relatively large areas, and thereby requiring correspondingly large mirror support arms can be assembled using mirror support member sections and/or interconnection members that are smaller than would otherwise be required. Therefore, the construction of relatively large modules can be performed relatively economically. 
         [0039]    Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items.