Patent Publication Number: US-2011048496-A1

Title: Solar reflector

Description:
FIELD OF THE INVENTION 
     The present invention relates broadly to a method of constructing a solar reflector assembly together with the solar reflector assembly itself. 
     BACKGROUND OF THE INVENTION 
     There exists in Australia and elsewhere several solar thermal array systems which are designed to convert solar energy into electricity via the heating of water or other liquids to drive electricity generating turbines. Such systems typically involve an elaborate structure which supports parabolic solar reflectors where the structure can pivot with the position of the sun so as to constantly concentrate reflected sunlight onto overhead pipes through which the liquid is heated and delivered to a heat engine or heat exchanger. As the fuel (in the form of sunlight) for such systems is renewable and essentially free, a challenge for making such systems economically viable, involves the design and construction of low cost pivoting structures to support the solar reflectors. 
     SUMMARY OF THE INVENTION 
     According to one aspect of the present invention there is provided a method of constructing a solar reflector assembly, said method comprising the steps of:
         forming a plurality of support panels each having at least one adjacent ridge and groove;   interconnecting adjacent of the support panels to form a corrugated support structure; and   mounting a reflector panel to the support structure whereby its reflective surface is configured to reflect and concentrate light energy.       

     Preferably the step of forming the support panels involves roll forming sheet metal. More preferably the roll forming is cold roll forming. 
     Preferably the method further comprises, prior to the step of mounting the reflector panel, the step of roll forming the reflector panel to include the reflective surface. More preferably the step of roll forming the reflector panel includes cold roll forming sheet metal to include a parabolic shaped reflective surface having a linear focal region. 
     Preferably the method also comprises the step of mounting a solar absorber to the reflector panel and/or the corrugated support structure for collecting the concentrated light energy. More preferably the step of mounting the solar absorber includes the step of locating the solar absorber at or near the linear focal region. 
     According to another aspect of the invention there is provided a solar reflector assembly comprising:
         a corrugated support structure including a support panel having at least one adjacent ridge and groove; and   a reflector panel supported by the corrugated support structure and designed to reflect and concentrate light energy.       

     Preferably the support panel is one of a plurality of elongate support panels each having a generally U or V-shaped trapezoidal-shaped cross-section formed by a pair of inclined side flanges interconnected by an intermediate web. More preferably the plurality of support panels are held together by interlocking the side flanges of adjacent support panels. 
     Preferably the reflector panel includes a curved reflective surface of a parabolic shape having a linear focal region. 
     Preferably the support structure also includes a plurality of transverse ribs each having a curved edge connected to an upper facing surface of the reflector panel and shaped to promote the parabolic shape of the curved reflective surface. More preferably the transverse ribs are equally spaced longitudinally along the reflector panel and extend transverse to the support panels with the reflector panel sandwiched between the support panels and the transverse ribs. 
     Preferably the solar reflector assembly further comprises a solar absorber for collecting the concentrated light energy. More preferably the solar absorber is located at or near the linear focal region. 
     Preferably the solar absorber includes a solar absorber pipe adapted for a fluid to flow. More preferably the fluid is a liquid adapted to absorb the heat reflected and concentrated by the reflector panel. Even more preferably the heat absorbed by the liquid is used to generate electricity: 
     Preferably the solar absorber includes a photovoltaic material adapted to absorb the light energy reflected and concentrated by the reflector panel. More preferably the light energy absorbed by the photovoltaic material is used to generate electricity. Even more preferably the photovoltaic material forms at least part of a photovoltaic strip. 
     Preferably the solar reflector assembly also comprises support plates connected to respective ends and/or intermediate sections of the elongate support panels. More preferably at least one of the support plates is pivotally mounted to a support pedestal and operatively coupled to drive means for rotating the reflector panel for tracking of the sun&#39;s movement. Alternatively at least one of the support plates is connected to an actuator hoop which is operatively coupled to drive means for rotating the reflector panel. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In order to achieve a better understanding of the nature of the present invention a preferred embodiment of a method of constructing a solar reflector assembly and the solar reflector assembly itself will now be described, by way of example only, with reference to the accompanying drawings in which: 
         FIG. 1  is an elevational and sectional view of a solar reflector assembly according to one embodiment of the invention; 
         FIG. 2  is a perspective view of part of a corrugated support structure and reflective panel taken from the solar reflector assembly of  FIG. 1 ; 
         FIG. 3  is an enlarged perspective view of a section of the corrugated support structure and reflector panel of  FIG. 2 ; 
         FIG. 4  is a sectional view of another embodiment of a solar reflector assembly; 
         FIG. 5  is a sectional view of a further embodiment of a solar reflector assembly; 
         FIG. 6  is a sectional view of yet another embodiment of a solar reflector assembly; 
         FIG. 7  is a sectional view of alternative drive means taken from the embodiment of any one of  FIGS. 4 to 6 ; and 
         FIG. 8  is a sectional view of a support pedestal of any one of the embodiments of the solar reflector assembly of  FIGS. 4 to 6 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     As best shown in  FIG. 1  there is solar reflector assembly  10  comprising a corrugated support structure  12  and a reflector panel  14 . The support structure  12  includes a plurality of support panels such as  16 A to  16 D each having a generally V-shaped cross-section. The support panels  16 A to  16 D are interlocked and connected to a lower facing surface of the reflector panel  14  which is designed to reflect and concentrate light energy. 
     As best shown in  FIG. 3 , in this embodiment the V-shaped support panels such as  16 A are each formed by a pair of inclined side flanges  18 A and  20 A interconnected by an intermediate web  22 A. This cross sectional configuration defines an elongate groove or trough  23  bordered by opposing ridges such as  25 . These elongate panels are otherwise constructed in accordance with Australian patent no. 726159 by Wade Hylton Blazley and its foreign counterparts. The disclosure of this Australian patent and its foreign counterparts is to be included herein by way of reference. 
     As best shown in  FIG. 2 , the support structure  12  of this embodiment also includes a plurality of transverse ribs such as  24 A to  24 U connected to an upper facing surface of the reflector panel  14 . Each of the transverse ribs such as  24 A has an accurately profiled curved edge such as  26 A to promote the parabolic shape of the curved reflective surface  28  of the reflector panel  14 . In this example the transverse ribs such as  24 A are equal spaced longitudinally along the reflector panel  14  and extend transverse to the support panels  16 A to  16 D. In this fashion the reflective panel is sandwiched between the support panels  16 A to  16 D and the transverse ribs  24 A to  24 U. 
     As best shown in  FIG. 1 , the solar reflector assembly  10  of this example further comprises a solar absorber in the form of a pipe  30  for collecting the concentrated the light energy. The pipe  30  is located at a focal region defined by the parabolic shape of the curved reflective surface  28 . The pipe  30  is a solar absorber adapted for a fluid such as oil to flow. In the case of oil, the light energy is reflected from the reflective panel  14  and concentrated on the solar absorber pipe  30  to generate heat for driving a heat engine (not shown). 
     In this example the solar reflector assembly  10  also comprises support plates such as  32  and  34  connected to intermediate sections of the interlocked support panels  24 A to  24 U. The support plates such as  32  and  34  are acuate having a similar profile to the reflector panel  14  and are pivotally mounted to respective support pedestals such as  36  and  38 . The support pedestals  36  and  38  are each anchored to an underlying support foundation such as  40  which in turn is anchored to the ground. In this example every other of the support plates such as  32  pivotally idles about the corresponding pedestal  36  whereas an adjacent support plate  34  is operatively coupled to drive means in the form of a cogged wheel  42  connected to the other pedestal  38  for rotating the reflector panel  14  in a swinging motion for tracking of the sun&#39;s movement. 
     In this embodiment the reflector panel  14 , support panels  16 A to  16 D and transverse ribs  24 A to  24 U are formed of strip metal, in particular strip steel or aluminium. The reflector panel  14 , support panels such as  16 A and transverse ribs such as  24 A may be welded, bonded or otherwise fastened together with relative ease to form a rigid structure. The support plates such as  32  and  34  include brackets such as  44  and  46  for fixing to the support panels such as  16 A. In this example the support panels such as  16 A are screwed, riveted or otherwise fastened to the support plate bracket such as  44  and  46 . The support panels  16  to  16 D and support plates such as  32  and  34  together with the transverse ribs  24 A to  24 U rigidly hold the reflector panel  14  in its parabolic shape for reflection and concentration of light energy. 
     In some embodiments, the solar absorber may alternatively or additionally include a photovoltaic strip or strips (not shown). Photovoltaic strips typically include a photovoltaic material which generates an electric current when the photovoltaic material is exposed to sunlight or light within a certain wavelength range. In these embodiments, therefore, the photovoltaic strip or strips may absorb the sunlight reflected and concentrated by the reflective panel  14  thereby generating electricity. 
     In these embodiments the use of photovoltaic strips provides several advantages over the use of conventional photovoltaic panels. Firstly, since photovoltaic strips typically have a smaller footprint than photovoltaic panels, they are more suited in applications where sunlight is concentrated in space. The smaller footprint of the photovoltaic strips also helps to minimise any further burden or load on the support structure. Secondly, photovoltaic strips typically include less photovoltaic material, which is generally expensive, than do photovoltaic panels. The use of photovoltaic strips therefore presents a cost advantage over the use of conventional solar panels. Thirdly, photovoltaic strips can generally withstand higher temperatures than photovoltaic panels can, and are therefore more efficient and robust under prolonged exposure to concentrated sunlight or in a high-temperature environment. 
     The general steps involved in fabrication of the solar reflector assembly  10  are as follows:
     1. the transverse ribs  24 A to  24 U are fabricated off-site having their lower acuate edge such as  26 A accurately shaped in the parabolic profile;   2. the support plates such as  32  and  34  together with corresponding support pedestals such as  36  and  38  are also fabricated off-site;   3. the reflector panel  14  is fabricated from the coils of strip steel or aluminium and if required, can be roll-formed on-site using a portable roll-former; and   4. the support panels  16 A to  16 D are roll-formed on-site from strip steel or aluminium.   

     In a preferred embodiment the foundations  40  and pedestals  36  are erected first and then the support panels such as  16 A attached to the pedestals  36 . The reflector panel  14  is then welded or otherwise fixed to the support panels such as  16 A. The transverse ribs such as  24 A are then secured to the reflector panel  14 . 
     The solar absorber pipe  30  is finally mounted to the support structure  12  via a series of support masts such as  31 A and  31 B connected to or formed as an extension of the corresponding transverse rib such as  24 D and  24 G respectively. This creates an accurate reflector parabolic shape and accurate location of the absorber pipe  30  along the linear focal region. 
     It wilt be understood that the specifics and order of the method of assembling and erecting the solar reflector assembly  10  may vary. For example, the reflective panel  14 , support panels  16  to  16 D, and transverse ribs  24 A to  24 U may be preassembled on the ground and lifted for fastening to the support plate such as  32  and  34  which are already pivotally mounted to the underlying pedestals such as  36  and  38  and associated foundations  40 . The transverse ribs such as  24 A are prefabricated by stamping, or cutting and welding. 
       FIGS. 4 to 6  illustrate alternate embodiments of the solar reflector assembly. For ease of reference and in order to avoid repetition the same reference numerals for corresponding components and parts has been used. 
     The schematic sectional view  FIG. 4  illustrates a solar reflector assembly  50  having what is effectively the spaced apart support plates such as  32  but having a precise parabolic profile for mounting of the support panels  16 A to  16 E. The reflector panel  14  is mounted on top of the support panels  16 A to  16 E but without the profiling assistance of the transverse rib such as  24 A of the preceding embodiment. This alternate reflector assembly  50  additionally comprises a series of regularly spaced hoops such as  52  across which the support plates such as  32  and the reflector panel  14  span. The reflector assembly  50  also comprises support struts such  54 A and  54 B extending from the reflective panel  14  and support structure  12  meeting at the solar absorber pipe  30  for its rigid location at the focal region. 
     The other embodiment of  FIG. 5  illustrates a reflector assembly  60  including the accurately profiled parabolic support plate  32  immediately beneath and in contact with the reflector panel  14 . The support panels  16  to  16 D locate underneath the support plates such as  32  and in turn are supported by an additional cross member such as  62 . The cross member  62  in a similar manner to the support plate such as  32  span the hoop member such as  52 . 
     The further embodiment of  FIG. 6  depicts a solar reflector assembly  70  having a plurality of reflector panels  72 A to  72 E each spanning a trough such as  74 A of one of the dedicated support panels such as  16 A. The support panels  16 A to  16 E are interlocked alongside one another and in a similar fashion to the embodiment of  FIG. 5  are mounted upon the underlying cross member  62 . The reflective panels  72 A to  72 E each have a dedicated solar absorber pipe  76 A to  76 E held at the focal region by a pair of support struts such as  78 A and  78 B. 
       FIGS. 7 and 8  show alternate examples of drive means for rotating the alternate assemblies of  FIGS. 4 to 6  in a reciprocating or swinging motion for tracking of the sun&#39;s movement. In  FIG. 7  the hoops such as  52  are engaged by roller coaster style wheel supports such as  80  and  82  which are mounted to foundations  84  such as steel beams secured to the ground. The wheel supports such as  80  include a pair of wheels such as  84 A and  84 B located either side of the hoop  52  for its driving motion back and forth. The wheels such as  84  may friction engage the hoop  52  or be in the form of a gear wheel designed to engage corresponding teeth formed in the hoop  52 . In the alternate embodiment of  FIG. 8  the drive means do not require the hoops such as  52  but rather effect rotation via a central shaft and bearing arrangement  86  supported by the pedestal  88 . 
     Now that several preferred embodiments of the invention have been described in some detail it will be apparent to those skilled in the art that the method of constructing a solar reflector assembly and the assembly itself have at the least the following advantages:
     1. the preferred methodology lends itself to onsite fabrication and reduces the need for transporting finished products with their regular shapes leading to lower transportation costs;   2. overall construction times are reduced which leads to lower overall costs;   3. the solar reflector assembly by relying on the trapezoidal-shape support panels avoids the need for relatively expensive traditional space-frame structures;   4. the interlocked support panels of the reflector assembly span relatively great distances reducing vertical supports and associated structure works contributing to a reduction in overall cost.   

     Those skilled in the art will appreciate that the invention described herein is susceptible to variations and modifications other than those specifically described. For example, the efficiency of the solar reflector assembly may be improved by replacing the metal reflector panel with a traditional glass mirror reflector panel, or new reflector materials as they become available. The absorber pipe may, depending on heat requirements, be constructed of a proprietary solar tube having an insulating glass pipe surrounding a metal pipe for conducting fluid or more simply a metal pipe without insulation. The dimensions of the solar reflector assembly may also be altered as required to optimise performance. 
     All such variations and modifications are to be considered within the scope of the present invention the nature of which is to be determined from the foregoing description.