Patent Publication Number: US-2013228165-A1

Title: Support of heat collectors in solar energy collectors

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This applications claims priority to U.S. Provisional Patent Application Ser. No. 60/812,177, filed Jun. 8, 2006, titled “Concentrated Solar Trough with Sun Tracking, Storm Protection and Removable Reflectors,” incorporated herein by reference in its entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     Solar energy can provide an environmentally friendly source of energy that does not rely on extraction of fossil fuels and that contributes relatively less to global warming and to related environmental problems than do fossil fuel-based energy sources. In addition, in many cases solar energy can be captured and used locally and thus reduce requirements for transportation or importation of fuels such as petroleum. 
     Solar energy may be captured, for example, by a collector that absorbs solar radiation and converts it to heat, which may then be used in a variety of applications. Alternatively, solar radiation may be captured by a collector which absorbs solar radiation and converts a portion of it directly to electricity by photovoltaic methods, for example. Mirrors or lenses may be used to collect and concentrate solar radiation to be converted to heat or electricity by such methods. 
     BRIEF SUMMARY OF THE INVENTION 
     In one aspect, a concentrating solar energy collector comprises a frame or housing, a heat collector, and a first elastically deformable reflector. The first elastically deformable reflector is at least substantially flat absent deforming force. The frame or housing is configured to receive the first elastically deformable reflector and exert compressive force that maintains the first elastically deformable reflector in a shape that concentrates at least a portion of the solar radiation on the heat collector. 
     In a second aspect, a concentrating solar energy collector comprises a heat collector, a first reflector positioned to receive solar radiation and concentrate at least a portion of the solar radiation on the heat collector, the first reflector having a length and a longitudinal edge, and a first bracket having a length of at least the length of the first reflector and configured to engage the longitudinal edge of the first reflector. 
     In a third aspect, a concentrating solar energy collector comprises a housing, a first bracket having a slot, a heat collector, and a first reflector positioned in the housing to receive solar radiation and concentrate at least a portion of the solar radiation on the heat collector. The reflector is coupled to the housing by insertion of at least a portion of an edge of the reflector into the slot in the bracket. 
     In a fourth aspect, a concentrating solar energy collector comprises a housing comprising a first panel and a second panel, a first bracket connecting the first panel and the second panel, a heat collector, and a first reflector positioned within the housing to receive solar radiation and concentrate at least a portion of the solar radiation on the heat collector. 
     In a fifth aspect, a concentrating solar energy collector comprises a first and a second panel, a first bracket configured to couple the first and second panels to each other to form at least a portion of a bottom section of a housing, a heat collector, and a first reflector positioned within the housing to receive solar radiation and concentrate at least a portion of the solar radiation on the heat collector. 
     In a sixth aspect, a concentrating solar energy collector comprises a bottom portion of a housing, a first and a second panel, and a first and a second bracket. The first bracket is configured to couple the first panel to the bottom portion of the housing to form at least a portion of a first side of the housing and the second bracket is configured to couple the second panel to the bottom portion of the housing to form at least a portion of a second side of the housing. The solar energy collector also comprises a heat collector and a first reflector positioned within the housing to receive solar radiation and concentrate at least a portion of the solar radiation on the heat collector. 
     In a seventh aspect, a concentrating solar energy collector comprises a housing, a first bracket at or near an edge of the housing. The bracket is configured to engage with a transparent cover, a heat collector, and a first reflector positioned in the housing to receive solar radiation through the transparent cover and concentrate at least a portion of the solar radiation on the heat collector. 
     In an eighth aspect, an appliance comprising a concentrating solar energy collector has a housing having a bottom portion and side portions, a heat collector, a first reflector positioned within the housing to receive solar radiation and concentrate at least a portion of the solar radiation on the heat collector, and an impact resistant cover configured to be positioned over at least a substantial portion of the housing and removably coupled to the housing to allow convenient removal and replacement. 
     In a ninth aspect, a concentrating solar energy collector comprises a heat collector, first and second identical or substantially identical panels forming at least a portion of a housing, and a first reflector positioned within the housing to receive solar radiation and concentrate at least a portion of the solar radiation on the heat collector. 
     In a tenth aspect, a concentrating solar energy collector comprises a frame or a housing, a first reflector positioned within the frame or the housing to receive solar radiation and concentrate at least a portion of the solar radiation on the heat collector, and a heat collector. The heat collector is supported by the frame or the housing by a first heat collector support having a first stanchion and a second stanchion. 
     In an eleventh aspect, a concentrating solar energy collector comprises a frame or housing, a heat collector, a first reflector, and a storage reservoir attached to the frame or housing. The storage reservoir is in fluid communication with the heat collector. 
     In a twelfth aspect, a method of assembling a concentrating solar energy collector comprises flexing at least a first elastically deformable reflector to position it within a housing. The elastically deformable reflector is substantially flat absent deforming forces and the housing is configured to receive the first elastically deformable reflector and maintain it in a shape that concentrates at least a portion of incident solar radiation on a heat collector. 
     In a thirteenth aspect, a method of assembling a concentrating solar energy collector comprises coupling a first panel to a second panel with a first bracket to form at least a portion of a bottom section of a housing, coupling a third panel to the bottom section of the housing with a second bracket to form at least a portion of a first side of the housing, coupling a fourth panel to the bottom section of the housing with a third bracket to form at least a portion of a second side of the housing, and positioning at least one reflector within the housing to receive solar radiation and concentrate it on a heat collector. 
     In a fourteenth aspect, a method of operating a solar energy collector (the solar energy collector comprising a housing, a substantially transparent cover coupled to the housing, and a reflector positioned within the housing to receive solar radiation through the transparent cover) comprises removably positioning an impact resistant cover over at least a substantial portion of the transparent cover to at least partially protect the transparent cover and the reflector from impact. The impact resistant cover is removably positioned by removably attaching it to the housing, to the transparent cover, or to the housing and the transparent cover. The method further comprises removing the impact resistant cover during normal operation of the solar energy collector. 
     These and other embodiments, features and advantages of the present invention Will become more apparent to those skilled in the art when taken with reference to the following more detailed description of the invention in conjunction with the accompanying drawings that are first briefly described. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1A-1D  show several views of portions of an example solar energy collector according to one variation. 
         FIG. 2  shows a cross-sectional view of an example solar energy collector, according to one variation, that comprises two mirrors. 
         FIGS. 3A-3B  show variations of mirrors including, respectively, slots and holes through which stanchion rods may engage a solar energy collector housing. 
         FIG. 4  shows a cross-sectional view of an example solar energy collector, according to one variation, comprising two mirrors and a single leg stanchion. 
         FIG. 5  shows a cross-sectional view of an example solar energy collector, according to one variation, comprising four mirrors and a single leg stanchion. 
         FIG. 6  shows a variation of a screw-in single leg stanchion. 
         FIG. 7  shows an example solar energy collector, according to one variation, having side brackets that differ from those of the solar energy collector of  FIGS. 1A-1D  by lack of restraining plates. 
         FIG. 8  shows a variation of a side bracket having slots for mirrors at different heights. 
         FIGS. 9A-9C  show variations of side brackets having a single adjustable clamping slot for securing the end of a mirror. 
         FIG. 10  shows a rail-type variation of a side bracket. 
         FIG. 11  shows an example solar energy collector, according to one variation, that differs from that shown in  FIGS. 1A-1D  by the absence of upper ribs. 
         FIG. 12  shows an example solar energy collector, according to one variation, that differs from that show in  FIGS. 1A-1D  by having an optional screw-down storm cover. 
         FIGS. 13A-13B  show, respectively, two solar energy collectors joined together according to one variation and three solar energy collectors joined together according to another variation. 
         FIGS. 14A-C  show a pivot assembly and its use in pivotably mounting solar energy collectors according to one variation. 
         FIGS. 15A-15B  show the use of interchangeable feet adapted for roof (or other hard surface) and ground mounting, respectively, according to one variation. 
         FIGS. 16A-16B  show views of a solar energy collector mounted on a roof or other hard surface according to one variation. 
         FIGS. 17A-17B  show views of a solar energy collector mounted ground mounted according to one variation. 
         FIG. 18  shows a cradle mounted solar energy collector housing according to one variation. 
         FIG. 19  shows an example solar energy collector pivotally mounted on a horizontal support bar, according to one variation. 
         FIGS. 20A-20C  show views of another example solar energy collector according to one variation. 
         FIG. 21  shows an example solar energy collector comprising six mirrors according to one variation. 
         FIG. 22  shows a portable solar energy collector system according to one variation. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The following detailed description should be read with reference to the drawings, in which identical reference numbers refer to like elements throughout the different figures. The drawings, which are not necessarily to scale, depict selective embodiments and are not intended to limit the scope of the invention. The detailed description illustrates by way of example, not by way of limitation, the principles of the invention. This description will clearly enable one skilled in the art to make and use the invention, and describes several embodiments, adaptations, variations, alternatives and uses of the invention, including what is presently believed to be the best mode of carrying out the invention. It should be noted that, as used in this specification and the appended claims, the singular forms “a,” “an” and “the” include plural referents unless the context clearly indicates otherwise. 
     Disclosed herein are examples and variations of apparatus and methods for collecting and concentrating solar radiation. This detailed description begins with a general discussion of the features of an example concentrating solar energy collector. That discussion is followed by additional description, set out under headings, of the details of and some variations of various possible features and aspects of solar energy collectors as disclosed herein. Additional examples of solar energy collectors are then provided, followed by a discussion of methods for assembling some variations of the disclosed solar energy collectors and by a discussion of some possible uses of the disclosed solar energy collectors. 
     Referring now to  FIGS. 1A-1D , one example solar energy collector  100  comprises a housing  105 , mirrors  110   a - 110   d  disposed within the housing, and a heat collector  115 . Mirrors  110   a - 110   d  focus a portion of incident solar radiation  120  onto heat collector  115  to heat a working (e.g., heat transfer) fluid within heat collector  115 . The working fluid may reach temperatures of, for example, greater than 400° F. More generally, the working fluid may reach temperatures from, for example, about 100° F. to about 400° F., about 100° F. to 550° F., or from about 200° F. to about 550° F. The heated working fluid may then be used in any suitable application, some of which are described later in this detailed description. 
     In this example housing  105  comprises lower panels  125   a  and  125   b  coupled to each other by a base bracket  130  to form a lower portion of housing  105 . Base plate  132  coupled to base bracket  130  and to lower panels  125   a ,  125   b  provides further structural support to the bottom portion of housing  105 . Upper side portions of housing  105  are formed by upper panel  135   a  coupled by side bracket  140   a  to lower panel  125   a , and by upper panel  135   b  coupled by side bracket  140   b  to lower panel  125   b . Ribs  145   a - 145   d , attached respectively to panels  125   a ,  125   b ,  135   a ,  135   b  and engaging side brackets  140   a  and  140   b , provide support for mirrors  110   a - 110   d  and additional structural strength to housing  105 . 
     The top of housing  105  is closed by transparent cover  150 , which is coupled to panels  135   a  and  135   b  by upper brackets  155   a  and  155   b , respectively. Impact resistant storm cover  160  may be coupled to housing  105  by one or more clips  165 , as illustrated. Storm cover  160  is removed during normal operation, but may be put in place as shown to protect solar energy collector  100  and its components, particularly transparent cover  150 , mirrors  110   a - 110   d , and heat collector  115 , from inclement weather, for example. 
     Heat collector  115  is supported by stanchion  170 , which in this example includes two rods  175  engaging base bracket  130 . Mirrors  110   a - 110   d  are coupled to housing  105 , in this example, by brackets  130 ,  140   a ,  140   b ,  155   a , and  155   b  as shown. 
     In one variation solar energy collector  100  may be, for example, about 8 feet long, about 2.5 feet tall, about 1.5 feet wide at the bottom, and about 5 feet wide at the top. In the illustrated example, solar energy collector  100  has a trough-like shape as defined, for example, by housing  105  and/or by mirrors  110   a - 110   b . More generally, solar energy collectors disclosed herein, including solar energy collector  100 , may be of any suitable size and shape. As additional examples, in some variations solar energy collectors  200  ( FIG. 1) and 400  ( FIG. 4 ) described later in this detailed description may have a trough-like shape and be, for example, about 8 feet long, about 15″ tall, about 7″ wide at the bottom, and about 30″ wide at the top. 
     As described later in this detailed description, in some variations individual solar energy collectors disclosed herein may be joined together to form sections of two, three, or more collectors. The sections may be then be coupled together to form one or more rows. In some variations, the collectors in a row are driven to track the sun by motors at each end of the row, with support stands located between sections supporting bearings on which the sections may pivot. Individual collectors may be similarly driven to track the sun. 
     The motors used to pivot or otherwise orient solar energy collectors may be controlled by tracking devices, not shown, that determine the orientation of the sun and pivot the solar energy collectors to optimize collection of solar radiation. The tracking devices may be, for example, conventional solar tracking devices known to one of ordinary skill in the art. Such tracing devices may employ, for example, light intensity detectors (e.g., photovoltaic detectors) to detect the position of the sun and digital logic (e.g., hardware or software) or analog control methods to control the motors based on signals from the light intensity detectors. 
     In the illustrated example, housing  105  (including end caps  180 ,  FIG. 1D ) and transparent cover  150  enclose mirrors  110   a - 110   d  and heat collector  115  and may consequently protect these components from corrosion (e.g., caused by salt and humidity), abrasion (e.g., caused by dust or sand), and other environmental ill-effects. Solar energy collector  100  may be further weather-proofed, as discussed in greater detail later in this detailed description, by placing gasket material in joints between panels (e.g.,  125   a ,  125   b ,  135   a ,  135   b ) and brackets (e.g.,  130 ,  140   a ,  140   b ,  155   a , and  155   b ) forming housing  105  and in joints between transparent cover  150  and brackets  155   a  and  155   b  to better seal those joints. In addition, transparent cover  150  and housing  105  may be constructed from impact resistant materials to better resist damage from storms or other inclement weather. 
     In such weather-proofed variations, solar energy collectors as disclosed herein may be well suited for use in tropical and coastal applications, where environmental conditions may promote corrosion, as well as in desert applications where sand, dust, or grit may otherwise abrade unprotected components. The various aspects of such weather proofing (including, for example, use of a transparent cover and/or sealing gaskets to enclose the mirrors and heat collector) are optional, however, and not necessarily present, or all present, in solar energy collectors disclosed herein. 
     The modular construction of a solar energy collector (or solar energy collector housing) from panels, brackets, and/or ribs, and/or the installation of mirrors in the housing brackets, may allow for easy assembly and repair and flexible arrangement and use of the solar energy collector. The use of sets of identical or substantially identical mirrors (e.g.,  110   a  and  110   b ;  110   c  and  110   d ), panels (e.g.,  125   a  and  125   b ;  135   a  and  135   b ), side brackets (e.g.,  140   a  and  140   b ), upper brackets (e.g.,  155   a  and  155   b ) and/or ribs (e.g.,  145   a - 145   d ) may also provide such advantages. As used herein, identical components have identity of shape and size within manufacturing tolerances. Substantially identical components are sufficiently similar that they have the same general shape and size but may differ in, e.g., pieces attached or portions of shape. Substantially identical pieces are often formed of base pieces that are considered identical but are modified in some way with, for example, additional features. 
     In addition, in variations (some of which are described in greater detail below) in which some or all of the mirrors are substantially flat prior to installation and/or some or all of the panels are substantially flat, the components of the solar energy collector may be more easily manufactured, stored, packaged, and/or shipped to their ultimate point of use. Such modularity is optional, however, and solar energy collectors described herein may be constructed without or with less use of brackets, panels, substantially flat panels, substantially flat (when uninstalled) mirrors, and/or identical or substantially identical components. 
     As noted above and further explained below, solar energy collectors as disclosed herein need not include all features shown in  FIGS. 1A-1D  and may include additional features or variations of features not shown in these figures. Generally, any of the solar energy collectors described herein may include any suitable combination of the features (or their variations) described or shown herein as well as any modifications or variations thereof apparent to one of ordinary skill in the art. Additional details of the features of solar energy collectors (such as solar energy collector  100  shown in  FIGS. 1A-1D ) and variations thereof are described next under headings identifying the features. 
     Mirrors 
     Solar energy collector  100  shown in  FIGS. 1A-1D  comprises four mirrors  110   a - 110   d  arranged to concentrate solar radiation on heat collector  115 . In other variations, however, the solar energy collectors disclosed herein may include more or fewer mirrors. For example, solar energy collectors may include a single large mirror in place of mirrors  110   a - 110   d . Other variations include two mirrors such as mirrors  210   a  and  210   b  in solar energy collector  200  shown in  FIG. 2 . An example solar energy collector described later in this detailed description ( FIG. 21 ) comprises six mirrors. Generally, any suitable number of mirrors may be used in any of the disclosed solar energy collectors. 
     In solar energy collector  100 , mirrors  110   a - 110   d  are arranged to form a single substantially parabolic shape with a line focus approximately on a central axis of (tubular, in the illustrated example) heat collector  115 . More generally, however, mirrors used in the solar energy collectors disclosed herein may have parabolic, cylindrical (partial circular cross section), or any other suitable shape. Where multiple mirrors are used, they may share a focus or instead be arranged to focus to two or more separate locations. For example, a solar energy collector may comprise four parabolic mirrors arranged to focus on four separate portions of a heat collector. 
     In addition, where multiple mirrors are used, two or more of the mirrors may be identical or substantially identical. As noted above, for example, in solar energy collector  100 , mirror  110   a  is identical or substantially identical to mirror  110   b , and mirror  110   c  is identical or substantially identical to mirror  110   d . Similarly, mirrors  210   a  and  210   b  of solar energy collector  200  ( FIG. 2 ) are identical or substantially identical. The use of sets of identical or substantially identical mirrors may, for example, simplify manufacturing, assembly, and repair of a solar energy collector. The use of two or more identical or substantially identical mirrors is not required, however. 
     Referring again to  FIG. 1A , mirrors  110   a - 110   d  in solar energy collector  100  are made from an elastically deformable (e.g., springy) material that allows them to assume a substantially flat shape absent deforming forces but take a parabolic or other curved shape upon installation in housing  105 . The parabolic shape of the installed mirrors  110   a - 110   d  results from compressive forces imposed on the mirrors by brackets  130 ,  140   a ,  140   b ,  155   a , and  155   b  coupling the mirrors to housing  105  and/or from the shapes of ribs  145   a - 145  supporting the mirrors. Mirrors  210   a  and  210   b  in solar energy collector  200  ( FIG. 2 ) are also made from an elastically deformable material and assume a substantially flat shape absent deforming forces. Mirrors  210   a  and  210   b  assume a parabolic shape as a result of compressive forces imposed on them by base bracket  230  and upper brackets  255   a  and  255   b , which couple the mirrors to housing  205 . 
     Such elastically deformable mirrors may be made, for example, from highly reflective aluminum sheets such as coated (weather-proofed) highly reflective aluminum sheets available under the product name MIRO-SUN® and manufactured by ALANOD Aluminium-Veredlung GmbH &amp; Co. KG of Ennepetal, Germany. In other variations, elastically deformable mirrors may be made from other materials such as, for example, reflectively coated plastics and other reflective or reflectively coated metals. In some variations, elastically deformable materials may comprise a reflective film such as, for example, a reflective or reflectively coated polyethylene terephthalate (e.g., Mylar®) film supported by an elastically deformable substrate such as, for example, a plastic or an unpolished aluminum sheet or panel. In some variations the mirrors may have a thickness, for example, of about 0.3 mm to about 0.8 mm and may be, for example, about eight feet in length. 
     Elastically deformable mirrors that assume a substantially flat shape absent deforming forces may be conveniently stored and/or shipped as a stack of substantially flat mirrors. This may reduce the cost of storing or shipping the mirrors, as a stack of flat mirrors takes less space and may be more easily packaged than a corresponding number of curved mirrors. 
     The mirrors used in solar energy collectors disclosed herein need not be made from elastically deformable material as just described, however. Instead, mirrors may be preformed in the desired radiation concentrating shape prior to installation in the solar energy collector or formed into the desired shape by bending, for example, during installation. Also, in some variations mirrors may be supported in a desired shape by a supporting framework. Any suitable reflective material such as, for example, polished or coated metals or reflectively coated polymers or glasses may be used to make such mirrors. In addition, in some variations reflective films such as, for example, reflective or reflectively coated polyethylene terephthalate (e.g., Mylar®) films may be used to make mirrors. Generally, any suitable material may be used to make the mirrors used in any of the solar energy collectors disclosed herein. 
     In some variations of the disclosed solar energy collectors, one or more of the mirrors may be easily removed for replacement, repair, or cleaning. For example, in solar energy collector  100  ( FIG. 1A ) upper mirrors  110   c  and  110   d  may be removed by removing (e.g., screw-down) restraining plates  142   a  or  142   b  from brackets  140   a  or  140   b , respectively, and then withdrawing the upper edge of the mirror from respective upper bracket  155   a  or  155   b . Lower mirrors  110   a  and  110   b  may be removed by removing (e.g., screw-down) restraining plates  143   a  or  143   b  from brackets  140   a  or  140   b , and then withdrawing the lower edge of the mirror from base bracket  130 . Referring to  FIG. 3A , mirrors  110   a  and  110   b  (not shown) may include slots  300  through which rods  175  of stanchion  170  ( FIG. 1A ) pass to engage a portion (e.g., base bracket  130 ) of housing  105 . This design allows for removal of mirrors  110   a  and  110   b  from base bracket  130  with stanchion  170  in place. Alternatively ( FIG. 3B ), stanchion rods  175  may pass through holes  305  in mirrors  110   a  and  110   b  (not shown) to engage a portion (e.g., base bracket  130 ) of housing  105 . This latter design may require disengagement of at least one of rods  175  from housing  105  for removal of mirror  110   a  or  110   b.    
     As another example, in solar energy collector  200  ( FIG. 2 ), either of mirrors  210   a  and  210   b  may be easily removed by flexing it to free an edge of the mirror from base bracket  230  or from the respective top bracket  255   a  or  255   b , and then withdrawing the other edge of the mirror from its retaining bracket. Mirrors  210   a  and  210   b  may include slots similar to slots  300  ( FIG. 3A ) to allow removal of the mirrors with stanchion  170  in place. Alternatively, mirrors  210   a  and  210   b  may include holes similar to holes  305  to accommodate rods  175  of stanchion  170 , in which case removal of a mirror requires disengagement of at least one of rods  175  from housing  205 . In variations in which solar energy collector  100  does not include ribs  145   a - 145   d  or includes only some of ribs  145   a - 145   d  (see below) one or more of mirrors  110   a  or  110   b  may be easily removed by flexing the mirror or mirrors as just described for mirrors  210   a  and  210   b.    
     As shown in  FIG. 1A  and described above, mirrors  110   a - 110   d  in solar energy collector  100  are coupled to housing  105  by brackets (described in greater detail below) which also couple portions of housing  105  to each other and thus play dual structural roles in solar energy collector  100 . In other variations of the disclosed solar energy collectors, however, mirrors may be coupled to the housing by brackets that attach to the housing but do not couple portions of the housing together. Also, in some variations mirrors may be attached to the housing or to other structural members (e.g., ribs  145   a - 145   d ), without use of brackets, by fasteners (e.g., screws, bolts, and rivets), adhesives, welding, or any other suitable attachment methods. Generally, any suitable attachment method may used to secure mirrors in the housings of any solar energy collector disclosed herein or variation thereof. 
     Housing and Panels 
     The housings of solar energy collectors as disclosed herein may have, for example, square, rectangular, trapezoidal, parabolic, partially circular, or u-shaped cross-sections. As noted above, the housing may have a trough-like shape, for example. Generally, any suitable housing shape may be used. Housings may be constructed, for example, from metals, plastics, wood, or any other suitable material. 
     In some variations, housings are constructed from panels coupled to each other with brackets. As described above, for example, housing  105  of solar energy collector  100  ( FIGS. 1A-1D ) is formed from four aluminum 1/16″ thickness sheet panels  125   a ,  125   b ,  135   a , and  135   b  coupled together by brackets  130 ,  140   a , and  140   b . In other variations, solar energy collector housings may be formed from more or fewer panels. For example, housing  205  of solar energy collector  200  ( FIG. 2 ) is formed from two aluminum sheet panels ( 225   a ,  225   b ) coupled to each other by base bracket  230 . Generally, the housings of solar energy collectors disclosed herein may comprise any suitable number of panels coupled to each other by brackets to form some or all of the housing. 
     In some variations, some or all of the panels from which a solar energy collector housing is constructed are substantially flat. For example, upper panels  135   a  and  135   b  of solar energy collector  100  are substantially flat. In other variations, not illustrated, all panels from which a housing is constructed are substantially flat. The flat panels in such a housing may be attached at angles to each other (with brackets, for example) to create corners as necessary to define a desired housing shape. Such flat panels may be easy to store, package, ship, and handle during assembly of a solar energy collector. 
     Housings of solar energy collectors as disclosed herein may also be constructed from curved or bent panels, or any suitable combination of flat, curved, and/or bent panels. Referring to  FIG. 2 , for example, in solar energy collector  200  panels  235   a  and  235   b  each include two bends defining substantially flat upper, middle, and bottom portions of housing  205 . In solar energy collector  100  ( FIG. 1A ) lower panels  125   a  and  125   b  each include one bend defining substantially flat bottom and lower side portions of housing  105 . 
     In some variations, housings include two or more identical or substantially identical panels. As noted above, for example, solar energy collector  100  ( FIG. 1A ) comprises pairs of identical or substantially identical panels. Similarly, panels  225   a  and  225   b  of solar energy collector  200  ( FIG. 2 ) are identical or substantially identical. The use of sets of identical or substantially identical panels may, for example, simplify manufacturing, assembly, and repair of a solar energy collector. The use of two or more identical or substantially identical panels is not required, however. 
     Although in the examples described above the housing panels are made from aluminum sheets, housing panels used in any solar energy collector disclosed herein may be made from any suitable material. Suitable materials included, but are not limited to, metals, plastics including impact resistant plastics, and wood. 
     The housings of solar energy collectors disclosed herein need not include panels coupled to each other by brackets. In some variations panels may be coupled directly to each other by, for example, welding or with fasteners such as screws, bolts, or rivets. In addition, some or all of the housing may be molded or cast from, for example, metals or (e.g., impact resistant) polymers. Housings may also comprise a cast or molded portion (e.g., a bottom portion) to which panels are coupled by brackets or other methods. 
     Base Brackets, Stanchions, and Base Plates 
     In the example of  FIG. 1A-1D , solar energy collector  100  comprises a base bracket  130  that couples lower panels  125   a  and  125   b  to each other to form a bottom portion of housing  105 , secures lower edges of mirrors  110   a  and  110   b  to housing  105 , and secures rods  175  of stanchion  170  to housing  105 . In the illustrated variation, ends of panels  125   a  and  125   b  are positioned in recessed (i.e., notched) portions of the bottom surface of base bracket  130  and are attached to the bottom surface of base bracket  130  by, respectively, fasteners  185   a  and  185   b  passing through the panels to engage the bottom of base bracket  130 . The recesses or notches may aid in registering the panels in the proper positions with respect to base bracket  130 . Such recesses or notches are optional, however. 
     An optional base plate  132  is secured to panels  125   a  and  125   b  by, respectively, fasteners  190   a  and  190   b . Additional fasteners  195   a  and  195   b  pass through base plate  132  and through panels  125   a  and  125   b , respectively, to engage the bottom of base bracket  130  to further secure the base plate, the panels, and the base bracket to each other. Optional base plate  132  provides additional structural support to the bottom portion of housing  105 . 
     Fasteners  185   a ,  185   b ,  190   a ,  190   b ,  195   a , and  195   b  may be, for example; screws, bolts, rivets, or any other suitable fastener. More or fewer of such fasteners than shown in  FIGS. 1A and 1B  may be used to couple the base bracket, panels, and optional base plate to each other. 
     Symmetrically placed angled slots  196  in upper side portions of base bracket  130  accept lower edges of minors  110   a  and  110   b  and, in cooperation with side brackets  140   a  and  140   b , secure mirrors  110   a  and  110   b  to housing  105 . Although slots  196  are shown angled upward, other orientations such as for example, slots oriented substantially parallel to the bottom of housing  105  may be used in other variations. 
     In the illustrated example, stanchion rods  175  pass through holes or slots in mirrors  110   a  and  110   b , as described above in the discussion under the “minors” heading, to engage threaded ends of rods  175  with threaded holes  197  in base bracket  130 . In other variations, stanchion rods  175  may be, for example, press fit into holes in base bracket  130 , attached to base bracket  130  by fasteners passing through the bottom of base bracket  130  to engage the ends of stanchion rods  175 , or welded to base bracket  130 . Upper  198   a  and lower  198   b  stanchion brackets are clamped by fasteners (e.g., screws)  199  around heat collector  115  to secure heat collector  115  to stanchion  170 . 
     As shown in  FIG. 1C , in the illustrated example base bracket  130  has the form of a rail that extends the length of solar energy collector  100 . In other variations, however, a plurality of shorter base brackets  130  may be spaced along the length of the solar energy collector instead. Brackets having an extended rail form may, in some variations, be conveniently formed (at least in part) using an extrusion process. Also, brackets having an extended rail form may, in some variations, provide better sealed joints between components of housing  105  than would be provided by shorter brackets. Generally, the base brackets described herein may be implemented in variations having an extended rail-like form or in variations to be used as one or more shorter brackets. 
     Base brackets used in the solar energy collectors disclosed herein need not perform all of the duties performed by base bracket  130  (coupling panels, securing mirrors, securing heat collector stanchion). For example, base bracket  230  in solar energy collector  200  ( FIG. 2 ) couples panels  225   a  and  225   b  together to form housing  205  and secures lower edges of mirrors  210   a  and  210   b  to housing  205  in a manner similar to base bracket  130 . However, base bracket  230  does not secure rods  175  of stanchion  170  to housing  205 . Instead, rods  175  are secured to housing  205  by fasteners  285   a  and  285   b  which pass through base plate  132  and panels  225   a  and  225   b , respectively, but do not pass through or into base bracket  130 . In other variations, a base bracket may couple panels together to form a portion of a housing and secure a stanchion to the housing, but not secure the mirrors. 
     Although stanchion  170  described above includes two rods  175  by which it is supported in and attached to a solar energy collector housing, in other variations a heat collector is supported by a stanchion attached to a base bracket via a single rod. Referring to  FIG. 4 , for example, another solar energy collector  400  comprises mirrors  410   a  and  410   b  positioned within a housing  405  to concentrate solar radiation on a heat collector  415  that is supported in housing  405  by a stanchion  470 . Stanchion  470  is coupled to a base bracket  430  forming part of housing  405  by a single rod or leg  475 . 
     Housing  405  comprises panels  425   a  and  425   b  coupled to each other by base bracket  430 , which comprises separable upper ( 430 U) and lower ( 430 L) portions. Referring now to both  FIG. 4  and  FIG. 6 , to assemble the lower portion of housing  405  the stanchion rod  475  is inserted into a through-hole  478  in (optional) collar portion  479  of upper bracket portion  430 U. A threaded foot  480  is then inserted through the underside of upper bracket portion  430 U to engage a threaded hole  485  in the bottom of stanchion rod  475 . Panels  425   a  and  425   b  are positioned between the upper  430 U and lower  430 L bracket portion, and then upper  430 U and lower  430 L bracket portions are slid into position against each other and held in place by slidably interlocking features  485   a  and  485   b  on the upper and lower bracket portions, respectively. Optionally, fasteners (e.g., screws, bolts, rivets) passing through lower  430 L bracket portion into upper bracket portion  430 U may further secure the assembly. 
     In other variations, stanchion rod  475  may be, for example, press fit into a hole in base bracket  430  or welded to base bracket  430 . Also, in other variations lower base bracket portion  430 L may be attached to upper base bracket portion  430 U with fasteners (e.g., screws, bolts, rivets) instead of by interlocking portions  485   a  and  485   b.    
     Referring again to  FIG. 4 , mirrors  410   a  and  410   b  are secured in housing  405  by engaging their upper ends in, respectively, upper brackets  455   a  and  455   b , and by engaging their lower ends in slots  496  in upper base bracket portion  430 U. 
     Referring now to  FIG. 5 , another example solar energy collector  500  comprises four mirrors  510   a - 510   d  positioned within a housing  505  to concentrate solar radiation on a heat collector  415  that, as in solar energy collector  400 , is supported by a stanchion  470  coupled to a base bracket  430  by a single rod or leg  475 . Base bracket  430  couples lower panels  525   a  and  525   b  to each other to form a bottom portion of housing  505 . Upper side portions of housing  505  are formed by upper panel  435   a  coupled by side bracket  540   a  to lower panel  525   a , and by upper panel  435   b  coupled by side bracket  540   b  to lower panel  525   b . Mirrors  510   a  and  510   b  are secured in housing  505  by engaging their lower ends in slots in base bracket  430  and engaging their upper ends in slots in, respectively, side brackets  540   a  and  540   b . Mirrors  510   c  and  510   d  are secured in housing  505  by engaging their upper ends in, respectively, slots in upper brackets  555   a  and  555   b  and by engaging their lower ends in, respectively, slots in side brackets  540   a  and  540   b.    
     Generally, any suitable base bracket disclosed herein may be used in any solar energy collector disclosed herein. In some variations, however, solar energy collectors as disclosed herein do not include a base bracket coupling panels together to form a bottom portion of a housing. In some variations lacking a base bracket the bottom portion (or more) of a housing is constructed by coupling panels directly to each other by, for example, welding or with fasteners such as screws, bolts, or rivets. In other variations lacking a base bracket the bottom portion (or more) of a housing is molded or cast from, for example, metals or (e.g., impact resistant) polymers. 
     Although the illustrated base brackets are shown using slots to secure mirror edges, in other variations base brackets may include clamps or clamping mechanisms to secure the mirror edges instead of or in addition to slots. Variations of base bracket  130  ( FIG. 1A ) may substitute clamps for slots  196 . For example, the upper portion of base bracket  130  defining upper walls of slots  196  may be replaced with a screw-down or spring-loaded piece (e.g., plate) to form an upper jaw of a clamp that can be used to secure mirrors to the bracket. Variations of other base brackets disclosed herein may be similarly modified to use clamps or clamping mechanisms. 
     Side Brackets 
     In the example of  FIGS. 1A-1D , solar energy collector  100  comprises identical or substantially identical side brackets  140   a  and  140   b . Side bracket  140   a  couples panels  125   a  and  135   b  to each other to form a side portion of housing  105 , and also secures edges of mirrors  110   a  and  110   c  to housing  105 . Similarly, side bracket  140   b  couples panels  125   b  and  135   b  to each other to form another side portion of housing  105 , and also secures edges of mirrors  110   b  and  110   d  to housing  105 . In the illustrated example, ends of the panels are positioned in recessed (i.e., notched) portions of the outward facing surfaces of side brackets  140   a  and  140   b  and are attached to the outward facing surfaces of the side brackets by fasteners  144  passing through the panels to engage the side brackets. The recesses or notches aid in registering the panels in the proper positions with respect to the side brackets. Such recesses, or notches are optional, however. 
     Fasteners  144  may be, for example, screws, bolts, rivets, or any other suitable fastener. More or fewer of such fasteners than shown in  FIGS. 1A-1D  may be used to couple the panels to the side brackets. 
     Side brackets  140   a  and  140   b  also include symmetrically placed slots  146  that accept edges of mirrors  110   a - 110   d  and, in cooperation with base bracket  130  and upper brackets  155   a  and  155   b  secure the mirrors to housing  105 . In the illustrated example, mirrors  110   a - 110   d  are secured in slots  146  by (e.g., screw-down) restraining plates  142   a ,  142   b ,  143   a , and  143   b , which form one wall of each slot and which may be loosened and/or removed to facilitate positioning of the mirrors in the brackets. In some variations, the depths of slots  146  may be chosen such that the (e.g., screw-down) restraining plates clamp the minors into place, in which case the side brackets may be viewed as comprising clamps, rather than slots. 
     Other variations of side brackets may also be used. Referring to  FIG. 7 , for example, solar energy collector  700  is substantially identical to solar energy collector  100  except for the substitution of side brackets  740   a  and  740   b  for side brackets  140   a  and  140   b  (and also the absence of base plate  132 ). Side brackets  740   a  and  740   b  do not include loosenable or removable restraining plates. 
     Slots in side brackets that accept and secure mirror edges need not be symmetrically positioned or positioned at the same height in the bracket. Referring to  FIG. 8 , for example, in some variations a side bracket  840  comprises a first slot  846   a  and a second slot  846   b  positioned at different heights. Such vertically off-set configurations of mirror slots allow a side bracket to secure mirrors forming, for example, two different parabolas (which may or may not share a focus). Side bracket  840  also includes recesses/notches  847   a  and  847   b  (similar to those in side brackets  140   a ,  140   b ) into which ends of panels  135   a  and  135   b , respectively, are positioned. Fasteners  144  pass through panels  135   a  and  135   b  into side bracket  840  to secure the panels to the side bracket. 
     Referring to  FIGS. 9A-9C , in some other variations side brackets  900   a  and  900   b  each have a single adjustable clamp or clamping slot  910   a  or  910   b , respectively, for receiving and securing a mirror end. The width of the slots (clamps) may be adjusted using fasteners (e.g., screws)  915   a  or  915   b  to clamp upper jaw pieces  920   a  or  920   b  against lower jaw pieces  925   a  or  925   b , respectively. The slot widths may be adjusted, for example, to clamp and thereby secure mirror ends in the slots and/or to flex or adjust the shape of the mirrors to better concentrate solar radiation on a heat collector. In some variations, the upper jaw portions may be removed or pivoted to the side to allow mirror ends to be easily inserted or removed from the slots. In other variations, clamping slots  910   a  an  910   b  may be, for example, spring-loaded to clamp mirrors into place rather than (or in addition to) being adjustable with screws or other fasteners. 
     In the example of  FIGS. 9A-9C , side brackets  900   a  and  900   b  do not couple panels together to form a portion of a housing. Instead, both brackets are attached to a single bent panel  930  which forms a side portion of a housing. Panel  930  includes at its bend a t-shaped rail  935  into which foot portions  940   a  and  940   b  of brackets  900   a  and  900   b , respectively, may be inserted (by sliding, for example). The brackets may be further secured to the panel using fasteners  945 , which may be screws, bolts, rivets, or any other appropriate fastener. 
     Side brackets  900   a  and  900   b  can be separately removed from panel  935  and replaced. As shown, brackets  900   a  and  900   b  may be chosen to position their slots at different heights. Alternatively, the brackets may be chosen to position their slots at the same height. 
     In some variations, side bracket heights may be varied to allow a single standardized housing size and shape to support a variety of minor configurations or shapes. Referring to  FIG. 5 , for example, side brackets  540   a  and  540   b  have a height that substantially off-sets mirrors  510   a - 510   d  from side portions of housing  505  and results in the four mirrors defining a reflective surface of a particular shape. The shape of the surface defined by the mirrors can be altered by replacing side brackets  540   a  and  540   b  with similar side brackets of a different height. Such a substitution could be used, for example, to focus or defocus the mirrors on the heat collector  415  as desired to affect the temperature to which the heat collector heats a working fluid. To facilitate such a substitution, side brackets  540   a  and  540   b  may be attached to panels with, for example, conventional easily removable fasteners such as screws and bolts. 
     Side brackets may have an extended rail-like form. For example, side brackets  140   a  and  140   b  shown in  FIG. 1C  have the form of rails that extend the length of solar energy collector  100 . Side bracket  1040  shown in  FIG. 10  also has an extended rail-like form. In other variations, a plurality of shorter side brackets may be spaced along the length of the solar energy collector in place of an extended rail-type side bracket. Side brackets having an extended rail form may, in some variations, be conveniently formed, in part, using an extrusion process. Also, side brackets having an extended rail form may, in some variations, provide better sealed joints between components of a housing than would be provided by shorter brackets. Generally, the side brackets described herein may be implemented in variations having an extended rail-like form or in variations to be used as one or more shorter brackets. 
     Referring again to  FIG. 10 , although mirror slots  1046   a  and  1046   b  in side bracket  1040  are shown to be at different heights, in other variations the slot heights may be the same. Side bracket  1040  can be used to couple two panels together to form a portion of a housing by, for example, attaching one panel to bottom surface  1048   a  and the other panel to bottom surface  1048   b  using conventional fasteners, adhesives, or welding, for example. Alternatively, side bracket  1040  can be positioned in the bend of a single bent panel portion of a housing and attached to the panel by any of the same means. 
     Many of the example side brackets described above were shown or described as coupling panels together to form a portion of a solar energy collector housing. Generally, however, the side brackets described herein may also be implemented in variations that will attach to a single panel (which might be bent, flat, or curved, for example) to secure mirrors to a housing without necessarily also coupling panels together. Alternatively, in some variations side brackets couple panels together to form a portion of a housing but do not secure mirrors to the housing. 
     Although some variations of the solar energy collectors disclosed herein utilize a plurality of identical or substantially identical side brackets, the use of identical or substantially identical side brackets is not required. 
     Although several of the illustrated side brackets are shown using slots to secure mirror edges, other variations of such side brackets may include clamps or clamping mechanisms (e.g., as described above for several clamping variations) to secure the mirror edges instead of or in addition to slots. 
     Generally, any suitable side bracket disclosed herein may be used in any solar energy collector disclosed herein. In some variations, however, solar energy collectors as disclosed herein do not include a side bracket coupling panels together or securing mirrors. Solar energy collector  200  ( FIG. 2 ), for example, does not employ side brackets. 
     Upper Brackets 
     In solar energy collector  100  ( FIGS. 1A-1D ), upper bracket  155   a  comprises a first slot for receiving and securing the upper end of mirror  110   c  and a second slot for receiving and securing an edge of transparent cover  150 . These slots are arranged at an acute angle with respect to each other. Upper bracket  155   a  may be attached to panel  135   a  by conventional fasteners (e.g., screws, bolts, rivets), as shown, or in other variations by welding, gluing, or any other suitable attachment method. In some variations, the end of panel  135   a  that is attached to upper bracket  155   a  is positioned in a recessed (i.e., notched) portion of the outward facing surface of upper bracket  155   a . In the illustrated variations, a portion of upper bracket  155   a  around the second slot protrudes transversely away from panel  135   a  and housing  105  to provide a seat for storm cover clip  165 . 
     The structure of upper bracket  155   a  enables it to couple mirror  110   c , panel  135   a  of housing  105 , transparent cover  150 , and (optionally) storm cover  160  to each other. Upper bracket  155   b  is similarly, identically, or substantially identically constructed to enable it to couple mirror  110   d , panel  135   b , transparent cover  150 , and (optionally) storm cover  160  to each other. 
     As shown in  FIG. 1C , in the illustrated variation upper brackets  155   a  and  155   b  have the form of rails that extend the length of solar energy collector  100 . In other variations, however, a plurality of shorter upper brackets  155   a  and  155   b  may be spaced along the length of the solar energy collector instead. Upper brackets having an extended rail form may, in some variations, be conveniently formed, in part, using an extrusion process. Also, upper brackets having an extended rail form may, in some variations, provide better sealed joints between components of a housing than would be provided by shorter brackets. Generally, the upper brackets described herein may be implemented in variations having an extended rail-like form or in variations to be used as one or more shorter brackets. 
     Upper bracket  455   a  in solar energy collector  400  ( FIG. 4 ) also comprises a first slot for receiving and securing the upper end of a mirror ( 410   a ) and a second slot for receiving and securing an edge of transparent cover  150 , with the first and the second slots arranged at an acute angle with respect to each other. Upper bracket  455   a  also includes a third slot substantially parallel to the second slot and opening away from the housing. The third slot, or the portion of the upper bracket forming its lower wall, may provide a seat for a storm cover clip to clamp a storm cover over transparent cover  150 . Upper bracket  455   a  may be attached to an upper horizontal portion of panel  425   a  by, for example, conventional fasteners (e.g., screws, bolts, rivets), or by welding, gluing, or any other suitable attachment method. 
     The structure of upper bracket  455   a  enables it to couple mirror  410   a , panel  425   a , transparent cover  150 , and (optionally) a storm cover to each other. Upper bracket  455   b  is similarly, identically, or substantially identically constructed to enable it to couple mirror  410   b , panel  425   b , transparent cover  150 , and (optionally) a storm cover to each other. 
     Although upper brackets  155   a ,  155   b ,  455   a , and  455   b , each perform multiple functions (coupling to housing, mirror, and transparent cover), it is not necessary that all of these functions be performed by a single upper bracket. Referring to  FIG. 2 , for example, in solar energy collector  200  the upper end of panel  225   a  is folded to form a horizontal slot for receiving an edge of transparent cover  150  and securing it to housing  205 . Upper bracket  255   a  has the form of a sheet or plate bent at an obtuse angle to form a first substantially flat portion, which is inserted into the slot formed by the folded upper end of panel  225   a , and a second substantially flat portion that forms with panel  225   a  a slot for securing an upper end of mirror  210   a . The portion of upper bracket  255   a  that is inserted into the slot formed by the folded upper end of panel  225   a  may be secured to panel  225   a  by, for example, conventional fasteners (e.g., screws, bolts, rivets) or by welding, gluing, or any other suitable attachment method. 
     Although the illustrated upper brackets are shown as using slots to secure mirror edges, in other variations upper brackets may include clamps or clamping mechanisms to secure the mirror edges instead of or in addition to slots. Variations of upper brackets  155   a  and  155   b  ( FIG. 1A ) may substitute clamps for the slots receiving mirrors  110   c  and  110   d . For example, the thin portion of upper bracket  155   a  defining one wall of the mirror slot may be replaced with a screw-down or spring-loaded piece (e.g., plate) to form a clamping jaw that can be used to secure mirrors to the bracket. Variations of other upper brackets disclosed herein may be similarly modified to use clamps or clamping mechanisms. 
     Although in the illustrated examples pairs of upper brackets have been identical or substantially identical, that is not required. Generally, any suitable upper bracket disclosed herein or variation thereof may be used in any solar energy collector disclosed herein. In some variations, transparent covers and mirrors may be secured in solar energy collectors without use of such upper brackets, however, and hence upper brackets are not used. 
     Ribs 
     Solar energy collector  100  ( FIGS. 1A-1D ) comprises a plurality of ribs  145   a - 145   d  shaped to support mirrors  110   a - 110   d  in a desired (e.g., parabolic) shape. Ribs  145   a - 145   d  may also provide additional structural strength to housing  105 . Ribs  145   a - 145   d  may be attached to housing panels  125   a ,  125   b ,  135   a , and  135   b , respectively with, for example, conventional fasteners (e.g., screws, bolts, rivets) or by adhesives, welding, or any other suitable attachment method. The ends of ribs  145   a - 145   d  may contact and be shaped to fit and engage the (e.g., notched) sides of the upper, side, or bottom brackets. In some variations, the ribs are attached to brackets they contact by, for example, conventional fasteners or by any other suitable attachment methods described herein or known to one of ordinary skill in the art. 
     In one variation, the ribs are made (e.g., cut or stamped) from aluminum sheet having a thickness of about 1.6 mm. Any other suitable materials and thicknesses may also be used, however. Ribs may be made, in some variations, for example, from other metals, plastics, or wood. 
     Referring to  FIG. 1C , solar energy collector  100  comprises two identical or substantially identical sets of ribs  145   a - 145   d  spaced along the length of the collector, which in the illustrated variation is about eight feet. Any suitable spacing between sets of ribs may be used, however. 
     Although solar energy collector  100  comprises one or more sets of four ribs  145   a - 145   d , the use of such ribs in solar energy collectors as disclosed herein is optional and more or fewer such ribs per set may be used. Referring to  FIG. 11 , for example, solar energy collector  1100  is substantially identical to solar energy collector  100 , except solar energy collector  1100  includes only lower ribs  145   a  and  145   b  and does not include upper ribs  145   c  and  145   d . As additional examples, the illustrated variations of solar energy collectors  200  ( FIG. 2 ),  400  ( FIG. 4 ), and  500  ( FIG. 5 ) do not include ribs. 
     In other variations, though, solar energy collectors  200 ,  400 ,  500 , and other solar energy collectors disclosed herein may include any suitable number and configuration of ribs supporting mirrors and/or providing additional structural strength to the collector. 
     In some variations, solar energy collectors without housings comprise brackets (or rails) and ribs as disclosed herein (or suitable variations thereof) arranged to form a framework supporting mirrors that concentrate solar radiation on a heat collector. Referring to  FIGS. 1A-1D , for example, in some variations a solar energy collector is substantially identical to solar energy collector  100  except for the absence of panels  125   a ,  125   b ,  135   a , and  135   b . In such variations, ribs  145   a - 145   d  may be attached to bottom, side, and top brackets they contact by, for example, conventional fasteners or by any other suitable attachment methods as described herein or known to one of ordinary skill in the art. Such variations may optionally include transparent cover  150  and/or removable storm cover  160 . Similar modifications may be made to other solar energy collectors described herein to provide solar energy collectors, with or without housings, that comprise brackets and ribs (or rails) arranged to form a framework supporting mirrors that concentrate solar radiation on a heat collector. 
     Heat Collector 
     Heat collector  115  in solar energy collector  100  ( FIGS. 1A-1D ) is, in one variation, a stainless steel or copper tube or pipe located approximately coincident with the line focus of parabolic mirrors  110   a - 110   d , extending the length of solar energy collector  100 , and having an inner diameter of about 0.65″ to about 0.87″ and an outer diameter of about 0.75″ to about 1.0.″ Heat collector  115  may, in some variations, be coated with a coating (e.g., a paint) that promotes absorption of solar radiation incident on heat collector  115 . In some variations, heat collector  115  is coated with POR-20 black velvet heat resistant paint available from POR-15, Inc., Morristown N.J. to promote absorption of solar radiation. In another variation, heat collector  115  is coated with Sherwin Williams Flame Control SW-B68-B-A2 black paint available from Sherwin Williams Company. Any other suitable coating may also be used. 
     Where multiple solar energy collectors are ganged into sections or extended rows (see below), in some variations their heat collectors may be joined in series to provide a single long effective heat collector. In other variations, a single continuous heat collector (e.g., tube or pipe) may pass through an entire section or row. 
     A working (e.g., heat transfer) fluid flows through and is heated by heat collector  115 . The working fluid may be, for example, water, an oil, glycol, or any other suitable heat transfer fluid. In some variations the working fluid may be a Therminol® heat transfer fluid available from Solutia, Inc. In other variations the working fluid may be an Xceltherm® heat transfer fluid available from Radco Industries, Inc. The heated working fluid may be used directly to supply heat for an application or, for example, as a working fluid used to drive a turbine for power generation. Alternatively, the working fluid may function as a heat transfer fluid that transfers heat collected in solar energy collector  100  to another working fluid which is subsequently used in an application. 
     Where the working fluid is an oil, in some variations it may reach temperatures of about 200° F. to about 550° F. after passing through one or more solar energy collectors. 
     In some variations the internal surfaces of heat collector  115  are rifled or include protuberances, vanes, or other flow disturbing features that promote mixing of and/or convective heat transfer in the working fluid as it passes through heat collector  115 . Such flow disturbing features may be particularly advantageous where the working fluid is a viscous fluid (e.g., a viscous oil) that would otherwise tend to move as a substantially laminar flow through heat collector  115 . 
     Although in the illustrated variations heat collector  115  has a tubular structure, other heat collector configurations known to one of ordinary skill in the art or variations thereof may also be used in the solar energy collectors disclosed herein. For example, heat collector  115  may comprise multiple tubes through which working fluid passes. Also, in some variations heat collector  115  may be enclosed in a transparent (e.g., glass) envelope to provide an insulating layer to reduce thermal losses from heat collector  115 . The transparent envelope may contain air, other gases, or be evacuated or partially evacuated in some variations. 
     Transparent Cover 
     Solar energy collectors as disclosed herein may include in some variations a transparent cover such as transparent cover  150  shown in various figures. As noted earlier in this detailed description, transparent cover  150  and variations thereof may help protect mirrors, heat collectors, and other components of a solar energy collector from adverse environmental conditions. In combination with a sealed or partially sealed housing, for example, transparent cover  150  may help protect such components from corrosion. The use of such transparent covers in variations of solar energy collector  100  ( FIGS. 1A-1D ) and variations of other solar energy collectors disclosed herein is optional, however. 
     Transparent cover  150  is made from glass in some variations. In other variations transparent cover  150  is made from Lexan plastic available from General Electric Company. Generally, transparent cover  150  and variations thereof may be made, for example, from glass, plastics, or any suitable material that is substantially transparent to solar radiations. In some variations, transparent cover  150  has the form of a lens (e.g., a Fresnel lens) that further optimizes the collection of solar radiation by the heat collector. 
     Transparent covers such as transparent cover  150  may be attached to solar energy collectors disclosed herein using, for example, the various bracket and rail structures for that purpose shown and described herein. Alternative attachment methods may also be used, however. For example, transparent covers may be bonded (e.g., glued) to a housing or framework of a solar energy collector, cast as a part thereof, or attached using any suitable fasteners including conventional screws, bolts, and rivets. 
     Gaskets: Sealing, Vibration Damping, Prevention of Corrosion 
     Gasket-like material such as neoprene rubber, for example, may be used at various locations in variations of the solar energy collectors disclosed herein. Referring to  FIG. 1A , for example, in some variations gasket material may be provided between transparent cover  150  and inner surfaces of the slot in upper brackets  155   a  and  155   b  into which edges of transparent cover  150  fit in order to form a better seal. Similarly, in some variations, to provide better seals, gasket material may be provided between base plate  132  and panels  125   a  and  125   b , between base bracket  130  and panels  125   a  and  125   b , between the various panels and the surfaces of side brackets  140   a  and  140   b  to which they are attached, and/or between panels  135   a  and  135   b  and surfaces of upper brackets  155   a  and  155  to which they attach. In addition, gasket material may be provided in the various bracket slots that receive and secure the edges of mirrors  110   a - 110   d  in order to damp vibrations of the mirrors. The provision of gasket material at these various locations may also prevent contact between dissimilar materials that could result in corrosion. 
     Gasket-like or similarly suitable material may be provided in other solar energy collectors disclosed herein at locations corresponding to or similar to those described with respect to solar energy collector  100 , as well as at any other suitable location. The use of such gasket-like materials is not required, however. 
     Storm Cover 
     Solar energy collectors as disclosed herein may include in some variations a removable impact resistant storm cover such as storm cover  160  shown in various figures. As explained above, storm cover  160  is removed during operation but may be installed to protect components of a solar energy collector from storms or other inclement weather. The use of storm covers is not required with solar energy collectors disclosed herein, however. 
     Storm covers such as storm cover  160  may be made, for example, from aluminum sheet, from impact resistant plastic, or from any other suitable material. Storm covers may be sized, for example, to fit an individual solar energy collector. Where several (e.g., 2, 3) solar energy collectors are joined together to form a section, in some variations the storm cover is sized to fit the entire section. In other variations, such a joined section may be covered using two or more separate storm covers or a multi-piece storm cover. For example, a section of three solar energy collectors may be covered, in some variations, using three storm covers (or a storm cover having three pieces) each the length of a single solar energy collector. 
     Storm covers may be attached to solar energy collectors by any suitable method. In variations shown in several of the figures, a storm cover is attached to a solar energy collector by C-shaped clips  165  which engage a top surface of the storm cover and also engage a portion of the solar energy collector housing (e.g., a surface on an upper bracket as described above and shown in various figures) to clamp the storm cover to the housing. The use of such clips may allow easy and rapid installation of the storm covers. Clips having other shapes may also be used in some variations. In some variations Z-shaped clips may be used. Such Z-shaped clips may secure a storm cover to a collector in a similar manner to C-shaped clips, and in addition provide a lever-arm (bottom of the Z) which may be used to easily disengage the clip. In another variation, shown in  FIG. 12 , a storm cover  160  is attached to a housing  105  via suitable fasteners (e.g., screws or bolts) that pass through the storm cover to engage portions of upper brackets  155   a  and  155   b . In yet other variations, storm covers may be attached to solar energy collectors using snaps, hook and eye connectors, wire, or cords. 
     Removable storm covers as describe herein, and variations thereof, may also be advantageously used with other solar energy collectors known to one of ordinary skill in the art. For example, storm covers may be installed over trough collectors, dish collectors, or the mirrors in mirror arrays to protect mirrors and other components from inclement weather. 
     Ganging 
     As noted earlier in this detailed description, in some variations individual solar energy collectors may joined together to form sections of two, three, or more solar energy collectors. The sections may then be coupled together to form rows. It is not required that the disclosed solar energy collectors be joined in this manner, however. 
     Referring to  FIG. 13A , in some variations two solar energy collectors  100  are joined by a joiner  1305  to form a section. The ends of the section are formed by end caps  180 , through which heat collector  115  either protrudes or may be accessed.  FIG. 13B  similarly shows three solar energy collectors  100  joined by two joiners  1305  to form a section. In the illustrated variations, joiner  1305  is a sheet metal bracket that hooks or otherwise engages upper edges of two collector housings at or near the joint between them and runs beneath the collectors to support the joint. In some variations joiner  1305  may be attached to the housings using conventional fasteners, for example. 
     Although the illustrated variations employ joiner  1305 , any suitable flange, bracket, joiner, or joining method may be used to join the disclosed solar energy collectors together. 
     Mounting 
     In some variations, individual solar energy collectors and/or sections of joined solar energy collectors may be pivotably mounted so that, for example, they may track the sun or be oriented in an optimal stationary position for collecting solar radiation. The solar energy collectors may be, for example, ground mounted or mounted on building roof tops. 
     Referring to  FIGS. 14A-14C , for example, in some variations a solar energy collector such as solar energy collector  100  (or a joined section of solar energy collectors) is pivotably mounted with pivot assembly  1400  supported by support stand  1415 . In the illustrated variation, pivot assembly  1400  comprises flanges  1405  and bearing assembly  1410 . Flanges  1405 , which are pivotably coupled to bearing assembly  1410 , attach to end caps  180  of the solar energy collectors. Heat collector tube  115 , located in this variation on or approximately on the rotational axis of solar energy collector  100 , passes through the centers of flanges  1405  and bearing assembly  1410  to run between the solar energy collectors coupled by pivot assembly  1400 . In some variations, bearing assembly  1410  is a split assembly with a top portion that may be removed to allow the solar energy collectors to be mounted. 
     Referring now to  FIGS. 15A-15B , in some variations support stand  1415  can interchangeably accept a foot  1505  adapted for mounting on a roof top or other hard and flat surface, or a foot  1510  more suitable for ground mounting. Transversally extended foot  1505  may be bolted to a roof or other hard surface, for example. Post-like foot  1510  may be, for example, secured in a hole  1515  in the ground  1520  using concrete, gravel, or any other suitable material.  FIGS. 16A-16B  show views of a solar energy collector mounted on a roof or other hard surface using foot  1505 .  FIGS. 17A-17B  show views of a solar energy collector mounted with a foot  1505  to a (concrete or wood, for example) pier  1705  set in the ground  1710 . 
     Other methods of pivotably mounting solar energy collectors may also be used. For example,  FIG. 18  shows a variation in which a support cradle  1810  connected to a mounting flange  18  runs the length of and supports the bottom of housing  1805 . 
     As another example,  FIG. 19  shows a variation in which a solar energy collector  1900  comprises mirrors  1910   a  and  1910   b  disposed in a housing  1905  to concentrate solar energy on a heat collector  1915  supported by a stanchion  1917 . Housing  1905  is mounted on a pivotable horizontal support bar  1920  with which solar energy collector  1900  may be pivoted. In some variations, heat collector  1915  is in fluid communication with the interior of horizontal support bar  1920  via stanchion  1917 . In such variations horizontal support bar  1920  may store working fluid heated by heat collector  1915 . 
     Generally, any suitable method of pivotably mounting a solar energy collector may be used with the solar energy collectors disclosed herein. However, in some variations solar energy collectors disclosed herein may be operated with out need for pivoting. Hence pivotal mounting is not required. 
     Additional Example Solar Energy Collectors 
       FIGS. 20A-20C  show another example solar energy collector, solar trough  2000 . Trough 2000 tracks the movement of the sun, includes protection from storms and features removable reflectors for maintenance. The trough is designed to focus and direct the sun&#39;s radiant energy into a heat collector tube that heats a fluid which is then used to create steam. The steam can be used for electricity, desalination, absorption cooling for HVAC and refrigeration, electrolysis, reformation, and hot water. 
     The trough collects the radiant energy generated by the sun and reflects the heat and light off removable reflectors into a heat collector tube to heat a heat transfer fluid. The heat transfer fluid is circulated in the heat collector tube and attains temperatures as high as about 400° F., more generally in the range from about 100° F. to about 550° F. 
     The trough has a protective lens (transparent cover) enclosing the system and protecting against the corrosion of interior metals, and other environmental ill-effects. On either side of the upper exterior housing of the trough, horizontally placed rails (upper brackets or rails) run the length of the trough. The rails are used to fasten an impact resistant lens shield (storm cover) to protect against storm damage. 
     The trough system is mounted on top of a horizontal support bar. This support bar can pivot from a 0 degree plane to a 270 degree plane moving the entire trough to track the position of the sun as well as to store the trough in a lens facing earth position to protect against storm damage. 
     In the interior of the housing, four removable reflectors are secured by clips (slotted brackets or rails) which hold a parabolic reflector metal in place and focuses the solar heat and light at the heat collector tube. The removable reflectors can be replaced for efficient long term operation of the trough. 
     The heat collector tube is located in the center of the trough and is supported by stanchions. Stanchions are evenly placed though the horizontal length of the trough. This trough system may be ideally suited for use in tropical and coastal applications. The trough may be used in a single stand alone fashion or in concert with other troughs in a variety of configurations. 
     The trough may be cheaper to manufacture, easier to assemble, and more cost effective to maintain the conventional solar energy collectors. 
     The trough is formed in a “U” shape and has a clear lens  2034  (transparent cover) over the internal housing  2020  opening allowing for solar heat and light to enter the trough but keeping moisture, salt, dust, and other unwanted environmental factors out. The upward position of the trough is facing the lens  2034  towards the direction of the sun. The downward position of the trough is facing the lens  2034  towards the direction of the earth. 
     The trough is mounted on a horizontal support bar  2022  which is designed to pivot around pivot axis  2038  counter-clockwise from the 0 degree plane which faces the lens  2034  to the right to the 270 degrees plane which faces the lens  2034  to the ground, and return back to the 0 degree plane moving clockwise. This allows the trough to track the sun&#39;s position during the day and to be stored in a face down position at night or during storms. An electric motor and gear (not shown) turns the horizontal support bar  2022 . The motor may be controlled by a direct digital software program working in cooperation with a protocol designed to calculate the suns position relative to date and time and utilizes a photovoltaic solar panel (not shown) that actively and instantaneously reports the intensity of the sun relative to the trough opening. 
     An impact resistant lens exterior rail  2040  (upper bracket or rail) is located on the external housing  2018  near the trough opening. 
     On the interior of the trough, four removable reflectors are shaped in open faced parabolas and aimed at the heat collector tube  2012 . Upper left removable reflector  2004  is held in place by interior reflector upper clip (upper bracket or rail)  2026  and interior reflector middle clip (side bracket or rail)  2028 . Lower left removable reflector  2006  is held in place by interior reflector middle clip (side bracket or rail)  2028  and interior reflector base clip (slot in base bracket)  2030 . Upper right removable reflector  2008  is held in place by interior reflector upper clip (upper bracket or rail)  2026  and interior reflector middle clip (side bracket or rail)  2028 . Lower right removable reflector  2010  is held in place by interior reflector middle clip (side rail or bracket)  2028  and interior reflector base clip (slot in base bracket)  2030 . In some variations, the reflectors have a reflectivity of greater than 89% and/or are composed of a multi-layered composite. The reflector metal may be, for example, about 0.5 mm in thickness. 
     The heat collector tube  2012  is suspended horizontally in the trough and supported by evenly placed stanchions  2032 . Stanchions are fastened to the internal bottom of the housing. The heat collector tube  2012  is filled with a heat transfer fluid  2014  that circulates through the trough. 
     In some variations, heat collector tube  2012  is in fluid communication with the interior of the horizontal support bar  2022  via stanchions  2032 . In such variations horizontal support bar  2012  may store working fluid heated by heat collector tube  2012 . In other variations heat collector tube  2012  is not in fluid communication with horizontal support bar  2022  and heated working fluid is not stored in horizontal support bar  2022 . 
     Impact resistant lens shield (storm cover)  2042  may be attached to the impact resistant lens exterior rail (upper bracket or rail)  2040  by impact resistant lens shield fasteners  2044 . 
     In other variations, the external housing shape can be modified, different materials, sizes, and interconnections can be used for all components, a fill material may be applied to the surface of the interior housing wall behind the removable reflectors, interior reflector middle clips (side brackets) may be absent, and/or there may be multiple heat collector tubes in the trough. 
     Referring now to  FIG. 21 , another example solar energy collector  2100  comprises six mirrors  2110  disposed within a housing  2105  to concentrate solar radiation on a heat collector  2115 . Housing  2105  is supported by support bar  2120 , about which solar energy collector  2100  may pivot in some variations. 
       FIG. 22  shows a portable solar energy collector system  2200  comprising a solar energy collector  2210  mounted (optionally, pivotably mounted) on a pallet or skid  2215 . Solar energy collector  2210  may be, for example, one or more of any suitable solar energy collector disclosed herein. In one variation, solar energy collector  2210  is solar energy collector  100  ( FIGS. 1A-1D ) or a modification thereof. In another variation, solar energy collector  2100  is solar energy collector  200  ( FIG. 2 ) or a modification thereof. In some variations, solar energy collector system  2200  may be mounted in, shipped, and/or operated from a standard cargo container or a modification thereof. 
     Portable solar energy collector system  2200  may be, for example, transported to and installed at the proposed site for a larger installation of solar energy collectors. At the site, portable solar energy collector system  2200  may be used to collect performance data (e.g., operating temperatures) with which to evaluate the site. Such performance data may then be used to design the proposed solar collector installation by, for example, determining the number and/or type of solar collectors to install. 
     In other variations, portable solar energy collector system  2200  may be transported to a rural location, for example, used to produce hot air with which to dry agricultural material (e.g., grains, macadamia nuts, other nuts, other seeds, other biomass), and then removed from the location when no longer needed there. 
     In yet other variations, portable solar energy collector system  2200  may be used as a portable solar power source for solar air conditioning or for making hot water for human or industrial use. Generally, solar energy collector system  2200  may be used for any suitable application. 
     Assembling One or More Solar Energy Collectors 
     In some variations, solar energy collectors having a length of about 8 feet are assembled into three-collector sections having a length of about 24 feet. The sections are then assembled into rows. A row may have a typical length of about 168 feet (21 collectors in length, ganged into 7 sections of 3 collectors with 8 support stands) in some variations. The collectors in a row pivot on bearings supported by stands between the sections. One, two, or more drive motors at each end of a row may be used to pivot the collectors to track the sun. 
     A method for assembling solar energy collectors to form a row may include the following steps, though in some variations some steps may be performed in a different order, may be performed concurrently, or may be omitted. Assembly methods in some variations may include additional steps, as well. To assemble a row of one variation of a solar energy collector  100  ( FIGS. 1A-1D ): 
     1. Begin with collector upside down (upside down “U”).
         Get a bottom bracket. Ensure gasket material is on bottom bracket surface and dampening materials are on reflector holders.   Attach lower panels on bottom bracket surface using screws, for example.   Attach the base plate on top of the lower panels using screws, for example.       

     2. Flip U right side up so base plate is touching the ground.
         Connect 4 stanchion rods into bottom bracket (to support 4 heat collector tube holders). The bottom bracket is tapped for the stanchion rods, which will screw directly into the bottom bracket.       

     3. Install 4 lower ribs per each 8′ length of collector by, for example, screwing them to the panels. 
     4. Attach side brackets to lower panels
         Ensure gasket material is on side bracket surface and fasten lower panel into side bracket   Ensure dampening materials are on reflector holders.       

     5. Install lower reflectors.
         The lower portion of the reflector will have slotted grooves that fit around the stanchion rods.   Mold reflectors to shape of spar and attach screw-down plate on side bracket to lock bottom reflectors in place.       

     6. Attach end cover/end cap to one side of collector and screw onto lower panels. 
     7. Attach joining bracket to lower panels at other side of collector using screws, for example 
     8. Attach upper brackets to, upper panels. 
     9. Attach upper panels to side brackets, end cover/end cap, and joiner bracket.
         Install upper ribs   Install upper reflector by inserting into upper bracket first and sliding into side bracket.   Attach screw-down plates to side brackets to lock reflectors in place.       

     10. Complete Steps 1-9 for 2 additional collectors to build a 3 collector section. 
     11. Place transparent cover (about 21 feet long) over the collector housing, on top of gasket, and attach with upper bracket. 
     12. Lift 3 panel ganged collector onto support stands with crane.
         The End Cap will sit into and on top of the support stands.       

     13. Continue until complete row is constructed (e.g., 168′ long consisting of 21-8′ collectors, ganged into 7 sections of 3 panels and 8 stands). 
     14. Installation of the heat collector tube
         For the entire length of the row, the heat collector tube base support bracket should be installed on top of the stanchions.   The heat collector tube is installed linearly from one end of the row and placed on top of the brackets.   The tube may have a coupler that connects multiple lengths as necessary.   In middle stands the tube may sit in the mount.   At the ends of the rows an insulated flex hose may connect the tube to a distribution piping systems.   Once heat collector tube is installed, the top heat collector tube bracket is secured on the stanchions and screwed into place, securing the heat collector tube.       

     Applications 
     Solar energy collectors as disclosed herein may be used for any suitable applications. Such applications may include, but are not limited to, the production of hot water or steam (directly or via heat transfer from a working fluid) and the production of hot air or other gases. 
     Hot water produced with the solar energy collectors disclosed herein may be used for example, for residential or industrial uses. Steam produced with the solar energy collectors may be used, for example, for generation of electricity, for desalination, for absorption cooling for HVAC and refrigeration, for electrolysis, for reformation, and for producing hot water. Hot air or other gases may be used, for example, to dry agricultural material (e.g., grains, macadamia nuts, other nuts, other seeds, other biomass). 
     This invention has been described and specific examples of the invention have been portrayed. While the invention has been described in terms of particular variations and illustrative figures, those of ordinary skill in the art will recognize that the invention is not limited to the variations or figures described. In addition, where methods and steps described above indicate certain events occurring in certain order, those of ordinary skill in the art will recognize that the ordering of certain steps may be modified and that such modifications are in accordance with the variations of the inventions. Additionally, certain of the steps may be performed concurrently in a parallel process when possible, as well as performed sequentially as described above. Therefore, to the extent there are variations of the invention which are within the spirit of the disclosure or equivalent to the inventions found in the claims, it is the intent that this patent will cover those variations as well. Finally, all publications and patent applications cited in this specification are herein incorporate by reference in their entirely as if each individual publication or patent application were specifically and individually put forth herein. In particular International Patent Application Serial No. PCT ______, filed Jun. 8, 2007, titled “Apparatus and Methods for Concentrating Solar Power,” is incorporated herein by reference in its entirety as if specifically and individually put forth herein.