US20130092154A1

US20130092154A1 - Apparatuses and methods for providing a secondary reflector on a solar collector system

Info

Publication number: US20130092154A1
Application number: US13/655,118
Authority: US
Inventors: Wei David Lu
Original assignee: Gear Solar
Current assignee: Gear Solar
Priority date: 2011-10-18
Filing date: 2012-10-18
Publication date: 2013-04-18

Abstract

A solar collector system is provided that comprises an absorber tube, a primary reflector, and a secondary reflector. In certain embodiments, the primary and secondary reflectors are positioned on opposing sides of the absorber tube, such that their respective focal points converge upon a longitudinal axis of the absorber tube. The secondary reflector may be configured with a substantially transparent surface facing away from the absorber tube, so as to permit passage of light beams there-through. Opposing surfaces of the secondary and primary reflectors, namely those facing substantially toward the absorber tube contain a reflective coating thereon to facilitate redirection of light beams toward the absorber tube. The solar collector system includes in certain embodiments a frame assembly, whereby the primary reflector, the secondary reflector, and the absorber tube are all configured to unitarily rotate about a common pivot axis defined by at least a portion of the frame assembly.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to and the benefit of both U.S. Provisional Application No. 61/548,536, entitled “Apparatuses and Methods for Providing a Secondary Reflector on a Solar Collector System” and filed Oct. 18, 2011, and U.S. Provisional Application No. 61/560,590, entitled “Solar Thermal Energy Collector” and filed Nov. 16, 2011, the contents of both of which are hereby incorporated herein in their entirety.

BACKGROUND

1. Technical Field
Embodiments of the present invention relate generally to solar concentrators and solar collector systems. More particularly, the various embodiments provide a solar concentrator that uses a secondary parabolic reflector assembly in conjunction with an absorber tube and a primary parabolic trough assembly to minimize the number of reflected solar rays that are never collected by the absorber tube.
2. Description of Related Art
Solar concentrators and solar collector systems work by collecting solar thermal energy (e.g., sunlight) from a large area and concentrating it into a smaller area. Various types of solar concentrators and solar collector systems exist and include at least parabolic solar concentrators. Parabolic solar concentrators use mirrored surfaces curved in a parabolic shape to focus sunlight onto the mathematical focal point of their inherent parabola. When the parabolic solar concentrator is dish shaped, the focal point is a discrete location; however, when the parabolic solar concentrator is trough shaped, the focal point is a line (e.g., focal region). Trough-shaped parabolic solar concentrators (e.g., parabolic troughs) typically include an elongated receiver tube, or heat collection element (HCE), which runs the length of the trough. A longitudinal axis of the receiver tube generally corresponds to the focal region. In this manner, the parabolic trough focuses sunlight directly onto the receiver tube.
Parabolic trough solar concentrators are generally positioned in solar collector system fields, often containing hundreds, if not thousands, of adjacently positioned parabolic trough solar concentrators. Together, the multiple adjacently positioned parabolic trough solar concentrators may form a parabolic trough power plant. In such parabolic trough power plants, a fluid, typically oil, runs through each of the receiver tubes positioned in the focal region of each of the parabolic troughs. The focused sunlight upon each of the elongated receiver tubes heats the fluid to high temperatures before the fluid passes through a heat exchanger, which generates steam. The steam may then be used to run a conventional power plant.
Most parabolic trough concentrators use a single axis parabolic mirror that must be accurately aligned with not only the sun, but also the elongated receiver tube so as to collect sunlight. Precision mirror alignment maximizes the reflected sunlight intercepting the elongated receiver tube, thereby improving overall collector efficiencies. However, focusing errors and thus geometrically dependent optical losses occur in parabolic trough collectors due to a variety of factors. For example, the mirror has a certain total shape tolerance, which may involve some degree of waviness, both of which lead to focusing errors. Further, the positioning of the mirror during assembly is only possible to within certain tolerances, likewise causing at least a portion of the reflected sunlight to miss (e.g., not intercept) the elongated receiver tube. Self-deformation (e.g., warping), manufacturing, and assembly tolerances of the steel structure, on which the parabolic trough collector is built, may also lead to inefficiencies. External factors such as the non-limiting examples of wind and dirt occurring in the vicinity of the parabolic trough and/or the elongated receiver tube may also cause deformations of portions of the structure sufficient to impact sunlight collection efficiency.
Still further, as should be appreciated, the sun moves across the sky during the day and is positioned at different locations in the sky depending upon the time of year thus presenting challenges in the collection of solar light. Various parabolic trough concentrators and solar collectors employ tracking device systems to facilitate pivoting the primary reflectors some amount due to movement or positioning of the sun in order to collect solar light that would otherwise be lost. A readjustment of the position of the concentrators and collectors may be made, for example, every time the sun moves 3° across the sky. Although capable of capturing some solar light, misalignment may occur since the tracking may not be completely accurate and small losses of solar light for each primary reflector add up to a large amount of loss for the system overall taking into account the large number of primary reflectors that may be employed.
Although efforts have been made to minimize impacts of these various factors upon sunlight collection efficiency, not all factors may be entirely eliminated and/or avoided. As such, and because maximum energy efficiency remains desirable for at least cost and environmental concerns, a need exists for a parabolic trough collector that captures and collects reflected at least an improved portion of sunlight that would otherwise be lost in various conventional systems. Such a parabolic trough collector having these and still other advantages is provided by the various embodiments of the present invention.

SUMMARY OF THE INVENTION

The present invention generally relates to solar concentrators and solar collector systems comprising secondary parabolic reflector assemblies for use in conjunction with an absorber tube and a primary parabolic trough assembly so as to minimize the number of reflected solar rays that are not initially collected by the absorber tube.
In accordance with various embodiments of the present invention as described herein, a solar collector system is provided. The system generally comprises: an absorber tube; a primary reflector having a first side surface and an opposing second side surface, at least the first side surface being configured to substantially reflect one or more light beams making contact therewith substantially toward the absorber tube; and a secondary reflector having a first side surface and an opposing second side surface, at least the first side surface being configured to reflect the one or more light beams reflected from the primary reflector further toward the absorber tube, wherein the absorber tube is positioned intermediate the primary reflector and the secondary reflector, such that the absorber tube is configured to collect one or more of the light beams reflected from the primary reflector and one or more of the light beams reflected from the secondary reflector.
In accordance with various embodiments of the present invention as described herein, an additional solar collector system is provided. The system generally comprises: a frame assembly comprising a first support member, a second support member, and a third support member, the first, second, and third support members being operatively mounted relative to one another so as to define a unitary pivot axis; a primary reflector, the primary reflector being operatively attached to the first support member; a secondary reflector, the secondary reflector being operatively attached to the second support member; and an absorber tube, the absorber tube being operatively attached to the third support member such that the absorber tube is positioned intermediate the primary reflector and the secondary reflector, wherein the primary reflector, the secondary reflector, and the absorber tube are each configured, via the frame assembly, to rotate substantially about the unitary pivot axis although the primary reflector, the secondary reflector, and the absorber tube each remain stationary relative to one another so as to minimize misalignment there-between.
In accordance with the various embodiments of the present invention as described herein, a method of using a solar collector system to maximize collection of light beams directed thereon by an external light source is also provided. The method comprises the steps of: (A) providing a system comprising: (1) a frame assembly comprising a first support member, a second support member, and a third support member, the first, second, and third support members being operatively mounted relative to one another so as to define a unitary pivot axis; (2) a primary reflector, the primary reflector being operatively attached to the first support member; (3) a secondary reflector, the secondary reflector being operatively attached to the second support member; and (4) an absorber tube, the absorber tube being operatively attached to the third support member such that the absorber tube is positioned intermediate the primary reflector and the secondary reflector; (B) positioning said solar collector system in a first orientation, said first orientation corresponding to a position at which, during a first period of time, a volume of light beams directed onto said primary reflector is maximized; and (C) rotating said solar collector system to a second orientation, said second orientation corresponding to a position at which, during a second period of time different from said first period of time, said volume of light beams directed onto said primary reflector is maximized, wherein said rotating occurs about said unitary pivot point such that the primary reflector, the secondary reflector, and the absorber tube each remain stationary relative to one another so as to minimize misalignment there-between.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

The accompanying drawings incorporated herein and forming a part of the disclosure illustrate several aspects of the present invention and together with the detailed description serve to explain certain principles of the present invention. In the drawings, which are not necessarily drawn to scale:

FIG. 1 illustrates a generic parabola and its focus;

FIG. 2 illustrates incident light reflecting on the generic parabola of FIG. 1;

FIG. 3 is a front perspective view of a parabolic solar collector according to various embodiments;

FIG. 4 is a rear perspective view of the parabolic solar collector of FIG. 3, positioned in a first orientation according to various embodiments;

FIG. 4A is a front perspective view of the absorber tube assembly 140 and its associated elements of the mounting assembly 180 according to various embodiments;

FIG. 5 is another rear perspective view of the parabolic solar collector of FIG. 3, positioned in a second orientation according to various embodiments;

FIG. 5A is a front perspective view of the secondary reflector assembly 160 and its associated elements of the mounting assembly 180 according to various embodiments;

FIG. 6 is a top perspective view of the parabolic solar collector of FIG. 3, positioned in a third orientation according to various embodiments;

FIG. 7 is a side view of the parabolic solar collector of FIG. 3;

FIG. 8 is a front perspective view of a group of the parabolic solar collectors of FIG. 3 according to various embodiments;

FIG. 9 is a rear perspective view of the group of parabolic solar collectors of FIG. 8 according to various embodiments;

FIG. 10 is a front perspective view of a plurality of the parabolic solar collectors of FIG. 3 according to various embodiments;

FIG. 11 is a top perspective view of the plurality of parabolic solar collectors of FIG. 10 according to various embodiments;

FIG. 12 is a rear perspective view of the plurality of parabolic solar collectors of FIG. 10 according to various embodiments;

FIG. 13 is a side view of a parabolic solar collector according to one exemplary embodiment;

FIG. 14 is a side view of a parabolic solar collector according to another exemplary embodiment;

FIG. 15 is a side view of a parabolic solar collector according to yet another exemplary embodiment; and

FIG. 16 is a perspective view of an alternative base assembly 110 according to various embodiments.

DETAILED DESCRIPTION OF VARIOUS EMBODIMENTS

Various embodiments of the present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all embodiments of the invention are shown. Indeed, embodiments of the invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly known and understood by one of ordinary skill in the art to which the invention relates. The term “or” is used herein in both the alternative and conjunctive sense, unless otherwise indicated. Like numbers refer to like elements throughout.
Overview
As commonly known and understood in the art, parabolic solar concentrators use mirrored surfaces curved in a parabolic shape to focus sunlight onto the mathematical focal point of their inherent parabola. FIG. 1 depicts a traditional generic parabolic shape 10 that is generally used to form such mirrored surfaces. Mathematically speaking, a parabola is the set of points in a plane that are equidistant from a focal point 12 and a line 13 in the plane, typically referred to as a directrix. The various embodiments of the present invention, like other commonly known parabolic solar concentrators utilize mirrored surfaces formed in the generic parabolic shape 10. It is understood that virtually any parabolic arc (e.g., mathematical equation) may be utilized according to various embodiments, as the alignment of various structural elements along the parabolic shape 10 and its focal point 12 is determinative.
FIG. 2 depicts at least a portion of the traditional generic parabolic shape 10 also illustrated in FIG. 1, but further depicting a plurality of incident light rays 14 impacting a surface of the parabolic shape 10. A plurality of reflected light rays 15 are also illustrated, extending from the point of impact between the incident light rays 14 and the parabolic shape 10 to the focal point 12. Due to the mathematical equations governing parabolic shapes such as that shown in these figures, such incident light rays 14, once reflected from a reflecting surface of the parabolic shape 10 will always converge upon the focal point 12.

Element List

- 100 solar concentrator
  - 110 base assembly
    - 112 foundation member
    - 114 upright support member
    - 115 cross member
- 120 parabolic trough assembly
  - 122 mirror
    - 123 first reflective surface
    - 124 second surface
    - 125 first edge
    - 126 second edge
    - 127 first side
    - 128 second side
  - 129 elongate structural frame member
    - 130 first end
    - 131 second end
  - 132 structural support members
    - 133 first end
    - 134 second end
- 140 absorber tube
  - 142 first end
  - 143 second end
  - 146 medial portion
- 140A alternative absorber tube # 1
- 140B alternative absorber tube # 2
- 160 secondary reflector assembly
  - 162 mirror
    - 163 first reflective surface
    - 164 second surface
    - 165 first edge
    - 166 second edge
    - 167 first side
    - 168 second side
  - 169 elongate structural frame member
    - 170 first end
    - 171 second end
  - 172 structural support members
- 160A alternative secondary reflector assembly # 1
- 160B alternative secondary reflector assembly # 2
- 180 mounting assembly
  - 181 drive bracket
  - 183 exemplary drive mechanism
  - 184 central bracket
  - 186 trough support bracket
  - 188 absorber tube support bracket
    - 189 elongate tube support members
  - 190 secondary reflector support bracket
    - 192 elongate reflector support members

Structure of Various Embodiments
Various embodiments utilize the traditional generic parabolic shape 10, as previously described with reference to FIGS. 1 and 2 to provide a solar concentrator 101 that comprises at least a base assembly 110, a parabolic trough assembly 120, an absorber tube 140, a secondary reflector assembly 160, and a mounting assembly 180.
Base Frame Assembly 110
Turning now to FIG. 3, the solar concentrator 101 according to various embodiments is illustrated, comprising at least a base frame assembly 110. As may be seen from this figure, in conjunction with FIG. 4, the base frame assembly 110 may, in various embodiments include a base member 112, an elongate upright support member 114, and a plurality of cross support members 115. In certain, and at least the illustrated embodiment, the base frame assembly 110 may incorporate two base members 112 and two support members 114, each respectively positioned on substantially opposing sides of the parabolic trough assembly 120, which they support, as described in further detail below. Of course, it should be understood that in other embodiments, a singular base member 112 and a singular support member 114 may be instead used.
The base member 112 may in certain embodiments be constructed from a steel material, although any of a variety of materials may be used, provided such materials exhibit properties sufficient to support the remaining assemblies, as will be described in further detail below. The base member 112 may also, in certain embodiments, be further positioned atop a concrete foundation (see, for example, FIG. 16), or the like, as commonly known and understood in the art to rigidly and securely retain structural assemblies analogous to the assembly 110.
The elongate upright support members 114 may, according to various embodiments, be operatively attached at one end to a surface of the base member 112, generally positioning the two relative to one another, as shown in at least FIGS. 3 and 4. The elongate support member 114 may be formed from any of a variety of structural materials, although such should likewise exhibit material properties sufficient to support the remaining assemblies, as will be described in further detail below. In certain embodiments, the elongate upright support member 114 may include a plurality of cross support members 115, configured to provide additional structural support and/or strength, as may be necessary for a particular environment.
With continued reference to FIGS. 3 and 4, the base member 112 may be configured according to various embodiments for bolting to a concrete pad (not shown), whether under or immediately atop the ground surface (shown, but not numbered). In other embodiments, however, the base member 112 may simply rest directly on the ground surface, provided such is sufficiently level and stable for a desired purpose. Each of the upright support members 114 are further located on opposite ends of the solar concentrator 100 in a longitudinal direction 70 of the solar concentrator 100, as will be described in further detail below with reference to a sole pivot axis 180A of the solar concentrator.
In any of these and still other embodiments, it should be understood that although the base frame assembly 110 has been described as above, according to exemplary embodiments illustrated in at least FIGS. 3 and 4, the assembly 110 may, in other embodiments be configured and constructed in any of a variety of shapes or sizes, as are commonly known and used in the art for supporting solar collectors such as the concentrator 101. Consider, for example, that in certain embodiments, the assembly 110 may include a unitary support member, without the need for separate base and upright members 112, 114, as previously described herein. Consider further that in any of those or even other embodiments having a unitary support member so configured, the member may further, as a single piece, support both sides of the parabolic trough assembly 120, as will be described in further detail below. At least one non-limiting exemplary alternative base assembly 110A is illustrated in at least FIG. 16.
Parabolic Trough Assembly 120
As with the base frame assembly 110, as previously described herein, various configurations of parabolic trough assemblies are commonly known and used in the art in conjunction with solar concentrators and/or solar collector systems. Generally speaking, as may be understood from FIGS. 5 and 6, which illustrate an exemplary parabolic trough assembly 120, such assemblies include at least a mirror 122 and one or more structural members (e.g., 129, 132). The mirror 122 according to various embodiments typically includes a multi-layer first concave surface 123 that comprises a reflective layer, and a second convex back surface 124 to which the structural members 129, 132 are mounted. The mirror 122 according to various embodiments is defined further by a first angular edge 125, a second angular edge 126, a first side 127, and a second side 128, each of which will be described in further detail below.
The mirror 122 of the parabolic trough assembly 120 according to various embodiments is parabolic shaped (as has been described previously herein with regard to at least FIGS. 1 and 2) and may be formed from a substrate having a reflective layer. The substrate may be glass or metal based, as is commonly known and understood in the art. Glass is often chosen as at least an exterior substrate layer of the first surface 123 of the mirror 122 because it prevents abrasion and/or corrosion of interior substrate layers, such as, for example, the reflective layer. Although glass is brittle, it is a good material for such purposes, as it is highly transparent (e.g., causing minimal optical losses), resistant to ultraviolet radiation (e.g., having a long life cycle), chemically inert, and fairly easy to clean. Metal substrates, as may be employed in certain embodiments, are lighter and stronger than glass, while also being relative inexpensive.
As mentioned, the glass substrate layer may generally comprise a reflective layer, typically formed from a thin metal film, as is commonly known in the art. In at least certain embodiments, the metal film (not shown) may be constructed from a polished silver material, while in other embodiments the film may be constructed from a polished aluminum material or may be deposited onto a substrate by any of a variety of well-known vapor deposition processes. In still other embodiments, the thin metal film may be constructed from any of a variety of materials, as may be desirable for a particular application. However, it should be understood that in any of these and other envisioned embodiments, the reflective layer and/or metal film is shielded by the exterior glass substrate layer from abrasion and corrosion.
Turning in particular now to FIG. 5, the back surface 124 of the mirror 122 of the parabolic trough assembly 120 is illustrated, as attached to the structural members 129, 132, each of which will now be described in further detail. The elongate structural frame member 129 according to various embodiments includes a first end 130 and a second end 131, which are generally positioned adjacent the corresponding first side 127 and second side 128 of the mirror 122. In certain embodiments, the elongate structural frame member 129 may be operatively connected to the first side 127 and/or the second side 128 of the mirror; however, in other embodiments, as illustrated in FIG. 5, the frame member 129 may be at least partially spaced relative to the mirror 122 by a plurality of structural support members 132, as will be described below.
The plurality of structural support members 132, as may be seen in at least FIGS. 4 and 5, are according to various embodiments generally elongate and have a first end 133 and a second end 134. The first end 133 of each of the members 132 may, in certain embodiments, be operatively connected to the mirror 122 substantially adjacent a first or a second angular edge 125, 126 of the mirror, as previously described herein. In other embodiments, however, the first end 133 may be otherwise attached, via a variety of mechanisms and at a variety of locations, as may be suitable for a particular application. The second end 134 of each of the members 132 may, in certain embodiments, be operatively connected to the mirror 122 and/or just the frame member 129 adjacent a substantially center portion (shown, but not numbered in FIG. 5) of the mirror. It should be understood that in at least those embodiments in which the mirror 122 is substantially parabolic in shape, the members 132 are correspondingly formed into a parabolic shape along at least a portion of their length. In this manner, each of the plurality of structural support members 132, when present in conjunction with the elongate frame member 129, form a structural web of sufficient strength to support, from behind (or below), the parabolic trough assembly 120. In any of these and still other embodiments, it should be understood that the elongate length of the members 132 may roughly correspond to the length of the arc formed by the mirror 122, although the two may vary, as may be desirable for a particular application.
In various embodiments, the mirror 122 defines a parabolic arc having a diameter of approximately fix (5) meters. Of course, in certain embodiments, the diameter of the mirror 122 may be less than or greater than five meters, as may be desirable for a particular application. In certain embodiments, the diameter may range from three to seven meters. In other embodiments, the diameter may even be less than three or more than seven meters, as may be suitable for a particular application. In still other embodiments, the mirror 122 may define a shape other than a parabolic arc, but with any of the above-described comparable diameters, or even further alternative diameters, also as may be desirable for a particular application. It should be understood that in any of these various embodiments, relative size characteristics of the mirror 122 are typically limited at least in part by the structural strength characteristics of the base assembly 110, as previously described.
In various embodiments in which the mirror 122 defines a parabolic arc, it should be understood that the mirror 122 further defines a focal point, at which at least the absorber tube 140, as will be described in further detail below, should be positioned. Such is at least in part due to the focal point's mathematical definition as the point at which light rays reflected from parabolic arcs converge. In certain embodiments, the focal point (see, e.g., FIGS. 1 and 2) may be located approximately 2.0 to 2.5 meters from the mirror 122. In other embodiments, the focal point may be located anywhere from 1.5 to 4.5 meters from the mirror 122. In still other embodiments, the focal point may be located any of a variety of distances from the mirror, as may be mathematically determined from the relative diameter (D) and depth (d) of the parabolic arc defined by the mirror 122. The focal point may calculated, for example, by dividing the square of the diameter by the result of multiplying the depth by 16, mathematically represented at focal point (F)=D²/(16d). Still further, it should be understood that relative size characteristics of the mirror 122 directly influence relative size characteristics and relative positioning considerations of the absorber tube 140, as the latter, regardless of relative size, must be positioned at the focal point (see, e.g., point 12 of FIG. 1) of the mirror 122, all of which will be described in further detail below.
With particular reference to FIG. 6, according to various embodiments, the mirror 122 may be formed from two adjacently positioned mirror panels, each having length dimensions as previously described herein. In these and other embodiments, it should be understood that the parabolic arc length of each of the two adjacently positioned mirror panels may be approximately half that of the entire mirror 122. In still other embodiments, the mirror 122 may be formed from a single unitary mirror panel, having both length and parabolic arc dimensions as previously described herein. In certain embodiments, however, as may be suitable for a particular application, the mirror 122 may be still further formed from a plurality of mirror panels, each aligned adjacently relative to one another, as may be seen in at least FIG. 3. In at least the illustrated embodiment, the mirror panels may be sized and shaped such that, when combined, the arc length of the mirror 122 is approximately six (6) meters (or otherwise dimensioned), meaning at least a portion of its circumference may be truncated, as previously described herein. In those embodiments having two adjacently positioned mirror panels, each of the respective panels may have a parabolic arc length of approximately half that of the entire mirror 122, while in alternative embodiments having a single unitary mirror 122, the parabolic arc length of such panels would correspond to that of the mirror. Of course, still other mirror panel or parabolic reflector configurations may be substituted as suitable for a particular application, as many of a variety of such configurations are known and used in the art.
The various structural members 129, 132 may be formed from any of a variety of structural materials as commonly known and used in the art for such applications, provided such materials exhibit properties sufficient to support at least the mirror 122 and the remaining assemblies, each as will be described in further detail below. It should be understood, again, that although the parabolic trough assembly 120 has been described above as including a mirror 122 and one or more of such structural members 129, 132, various alternatively configured parabolic trough assemblies are commonly known and used in the art in conjunction with solar concentrators and/or solar collector systems. As such, any of these, or still other envisioned parabolic trough assemblies may, in still other embodiments, be substituted for the assembly 120 described herein, as may be desirable for a particular application.
Absorber Tube 140
As with the base frame assembly 110 and the parabolic trough assembly 120, each as previously described herein, various configurations of absorber tubes are commonly known and used in the art in conjunction with solar concentrators and/or solar collector systems. Generally speaking, as may be understood from FIGS. 4 and 5, in which an exemplary absorber tube 140 may be seen, such tubes typically include at least a first end 142, a second end 144, and a medial portion 146. The first and second, typically opposing ends 142, 144 may, according to various embodiments, be positioned such that they're aligned relative to the first and second sides 127, 128 of the mirror 122 of the parabolic trough assembly 120. Such facilitates their relative positioning via the mounting assembly 180, as will be described in further detail below.
The medial portion 146 of the absorber tube 140, as is commonly known and understood in the art, is configured to absorb the reflected sunlight 14 (see, e.g., FIG. 2) that converges upon the parabolic focal point 12 (e.g., where the absorber tube is itself positioned). As has been described previously herein, and also commonly known and understood in the art, a fluid, such as oil or water, typically flows through the absorber tube 140 and is heated by the reflected sunlight 14 that reaches the tube from the parabolic mirror 122. The fluid may, according to certain embodiments, be located and transported within an inner tube (see, for examples, FIGS. 13-15) of the absorber tube that is surrounded itself by a concentric outer tube (see, for examples, FIGS. 13-15). Typical outer tubes are made of glass, so that solar thermal energy (e.g., reflected sunlight 14) directed thereto by the mirror 122 is not unduly impeded from reaching the inner tube and thus the fluid contained therein. The space between the inner tube and the outer tube may, in certain embodiments be evacuated such that a vacuum is formed, as is commonly known and understood in the art. This vacuum functions to reduce heat transfer from the heated fluid and the inner tube back through and to the outer tube. Preventing temperature increases in the outer tube, amongst other things, increases the efficiency of the parabolic trough assembly 120 and enhances safety by minimizing risk of the outer tube becoming too hot to touch.
As has been previously described herein, the absorber tube 140 should generally be configured with respect to at least the parabolic trough assembly 120, such that a central longitudinal axis of the tube 140 corresponds to an axis passing through the focal point (e.g., see FIG. 1) of the mirror 122 of the assembly 120. In certain embodiments, the tube 140 may be located approximately 2.0 to 2.5 meters from the mirror 122. In other embodiments, the tube 140 may be located anywhere from 1.5 to 4.5 meters from the mirror 122. In still other embodiments, the tube 140 may be located any of a variety of distances from the mirror, provided the tube corresponds to the focal point, which may be calculated, as previously described from the diameter (D) and the depth (d) of the mirror 122, expressed as the focal point (F)=D²/(16d).
In various embodiments, the absorber tube 140 has a length of approximately six (6) meters. Of course, in certain embodiments, the length may be less than or greater than six meters, as may be desirable for a particular application. Further, in various embodiments, the inner tube of the absorber tube 140 has a diameter of approximately 70 millimeters while the outer tube has a diameter of approximately 115 millimeters. In certain embodiments, the inner and outer tube diameters may be less than or greater than 70 and 115 millimeters, respectively, as may be desirable for a particular application. However, such diameters should be considered exemplary and further, generally representative of diameters of conventional absorber tubes, as commonly known and used in the art.
In various embodiments, the diameter of the inner tube of the absorber tube 140 is related to the diameter of the mirror 122 of the parabolic trough assembly 120 by a ratio of approximately 1 to 100. For example, in those embodiments in which the mirror 122 has a diameter of seven (7) meters, the inner tube has a diameter of approximately 70 millimeters. In other embodiments, in which the mirror 122 has a diameter of five or three meters, the inner tube may have a diameter of approximately 50 or 30 millimeters, respectively. Of course, it should be understood that any of a variety of relative ratios between the diameter of the absorber tube 140 and that of the mirror 122 may be selected, as may be desirable for a particular application, in which case the examples provided herein should be considered non-limiting.
With reference to at least FIGS. 13-15, it should be understood that the absorber tube 140 may be alternatively configured, wherein as non-limiting examples an absorber tube 140A may be formed with substantially square-shaped cross-sections, as compared to the substantially circular cross-sections found in absorber tube 140. Still further alternatives are illustrated via absorber tube 140B (see FIG. 15 specifically), wherein the inner tube may have a cross-section differing from that of the outer tube, such that at least one may be substantially square-shaped while the other is substantially circular-shaped. Of course, still other possibilities exist, wherein the cross-sections of one or more of the inner/outer tubes of an absorber tube 140 may be triangular-shaped, irregularly shaped, or otherwise configured, as may be desirable for particular applications. In certain embodiments, the inner/outer tubes may also be concentric relative to one another, generally as illustrated in FIGS. 13-15; however, in still other embodiments (not shown), the two need not necessarily be concentrically configured.
Still further, it should be understood that any of a variety of configured absorber tubes, as commonly known and used in the art in conjunction with parabolic and other configured solar collector systems, may be used in certain embodiments of the present invention, in place of the exemplary absorber tube 140, as has been described herein. Indeed, consider, for example, the absorber tube of U.S. Patent Application Publication No. 2010/0126499 to Wei David Lu, which describes a particular absorber tube that further includes an expansion element configured to expand or contract in response to differences in thermal temperatures between the inner tube and outer tube. This application, amongst other things, further describes a variety of getters, located radially between the inner and outer tube, so as to capture excess hydrogen that leaks from the heated inner tube into the vacuum sealed outer tube. Any variety of such absorber tubes, amongst others further known and used in the art may be incorporated into the present solar concentrator 101, as may be desirable for a particular application.
Secondary Reflector Assembly 160
As may be understood from FIGS. 4-6, a secondary reflector assembly 160 (see FIG. 4) according to various embodiments may include at least a mirror 162 (see FIG. 5) and one or more structural members 169, 172 (see FIG. 6). With particular reference to FIG. 5, it may be seen that the mirror 162 according to certain embodiments includes a first surface 163 that comprises a reflective layer, and a second surface 164 to which the structural members 169, 172 are mounted. Still further, the mirror 162 according to various embodiments is defined by a first angular edge 165, a second angular edge 166, a first side 167, and a second side 168, each of which will be described in further detail below. The mirror 162 may also, in certain embodiments, be parabolic in shape, just as the mirror 122, although in other embodiments, various alternative shapes of the mirror 162 may be envisioned, depending on a particular application. It should be understood for at least those embodiments having a parabolic-shaped mirror 162, the mathematical characteristics of such mirror will generally be substantially different than that of the mirror 122, as previously described herein, at least in part to obtain a much shorter focal length of mirror 162, as compared to that of mirror 122.
Turning now to FIG. 6, an exemplary parabolic mirror 162 of the secondary reflector assembly 160 according to various embodiments is illustrated, as formed from a substrate having a reflective layer. In certain embodiments, the parabolic mirror 162, and in particular its substrate having a reflective layer may be sized, shaped, and configured substantially the same as the analogous features of mirror 122, as previously described herein. Of course, in still other embodiments, it should be understood that any combination of the features of mirror 162 may be substantially different from those corresponding features of mirror 122, as may be desirable for a particular application.
Turning in particular now to FIG. 5, the mirror 162 of the secondary reflector assembly 160 is illustrated, as attached to the structural members 169, 172, each of which will now be described in further detail. The elongate structural frame member 169 according to various embodiments includes a first end 170 and a second end 171, which are generally positioned adjacent the corresponding first side 167 and second side 168 (see FIG. 4) of the mirror 162. In certain embodiments, the elongate structural frame member 169 may be operatively connected to the first side 167 and/or the second side 168 of the mirror; however, in other embodiments, as illustrated in FIG. 5, the frame member 169 may be at least partially spaced relative to the mirror 162 by a plurality of structural support members 172, as will be described below. Still further, a plurality of cross-support members 175 may be incorporated within the structural member 169, as may be suitable for a particular application, wherein additional strength of the member may be necessary or desirable.
The plurality of structural support members 172, as may be seen in at least FIG. 6, are according to various embodiments generally elongate and curved in a fashion corresponding substantially to the shape of the mirror 162. As a non-limiting example, for those embodiments in which the mirror 162 is substantially parabolic in shape, the members 172 are corresponding formed into a parabolic shape along their length. In certain embodiments, the members 172, when so formed, may be operatively fastened to at least a portion of the mirror 162 substantially adjacent a first or a second angular edge 165, 166 of the mirror, as previously described herein. In other embodiments, however, the members 172 may be otherwise attached, via a variety of mechanisms and at any of a variety of locations, as may be suitable for a particular application. However, regardless of how precisely attached to the mirror 162, it is in this manner that each of the plurality of structural support members 172, when present in conjunction with the elongate frame member 169, form a structural web of sufficient strength to support, from behind (or above, as may the case be), at least the mirror 162 of the second reflector assembly 160. In any of these and still other embodiments, it should be understood that the elongate length of the members 172 may roughly correspond to the length of the arc formed by the mirror 162.
In various embodiments, the mirror 162 defines a parabolic arc having a diameter of approximately two (2) meters. Of course, in certain embodiments, the diameter of the mirror 162 may be less than or greater than two meters, as may be desirable for a particular application. In certain embodiments, the diameter may range from one to three meters. In other embodiments, the diameter may even be less than one or more than three meters, as may be suitable for a particular application. In still other embodiments, the mirror 162 may define a shape other than a parabolic arc, but with any of the above-described comparable diameters, or even further alternative diameters, also as may be desirable for a particular application. It should be understood that in any of these various embodiments, relative size characteristics of the mirror 162 are typically limited at least in part not only by the structural strength characteristics of the base assembly 110, but also by a desire to minimize the obstruction of any sunlight rays from reaching the mirror 122 of the parabolic trough assembly 120.
In various embodiments in which the mirror 162 defines a parabolic arc, it should be understood that the mirror 162 further defines a focal point, at which at least the absorber tube 140, as will be described in further detail below, should be positioned. Such is at least in part due to the focal point's mathematical definition as the point at which light rays reflected from parabolic arcs converge. In certain embodiments, the focal point (see, e.g., FIGS. 1 and 2) may be located approximately 0.5 to 1.5 meters from the mirror 162. In other embodiments, the focal point may be located anywhere from 0.25 to 2.5 meters from the mirror 162. In still other embodiments, the focal point may be located any of a variety of distances from the mirror, as may be mathematically determined from the relative diameter (D) and depth (d) of the parabolic arc defined by the mirror 162. The focal point may calculated, for example, by dividing the square of the diameter by the result of multiplying the depth by 16, mathematically represented at focal point (F)=D²/(16d). Still further, it should be understood that relative size characteristics of the mirror 162 directly influence relative size characteristics and relative positioning considerations of the absorber tube 140, as the latter, regardless of relative size, must be positioned at the focal point (see, e.g., point 12 of FIG. 1) of the mirror 162, all of which will be described in further detail below.
In various embodiments, the mirror 162 has an arc length of approximately three (3) meters. Of course, in certain embodiments, the length of the mirror 162 may be less than or greater than three meters, as may be desirable for a particular application. However, it should be understood that the length of the mirror 162 in any of these and still other embodiments should be substantially less than to the arc length of the mirror 122, so as to minimize the risk of the mirror 162 in blocking a significant degree of incident light rays from reaching the mirror 122 of the parabolic trough assembly 120. Of course, a competing consideration according to various embodiments is that the greater the arc length of the mirror 162, the more efficient the system, as a whole may be, as the larger sized mirror 162 will more effectively capture a broader scope of re-reflected light rays, that for whatever reason, do not converge upon the absorber tube 140.
In certain embodiments, wherein a maximal size of mirror 162 is desirable with minimal blockage of incident sunlight rays, the mirror 162 may be constructed from a glass substrate having a very thin and sparsely applied reflective layer, such that a desired portion of the incident light rays may pass unimpeded through the mirror 162 from atop (e.g., the side facing the sun), but the same light rays, once reflected from the mirror 122 and having missed the absorber tube 140, are not permitted to pass back through unimpeded, instead being re-reflected toward the absorber tube. Such mirrors, commonly referred to as “one-way mirrors” are commonly known and used in the art, and still further in other applications, such as the one-way mirrors employed by police officers when interrogating suspects.
As with mirror 122 (previously described herein), the mirror 162 according to various embodiments may be formed from two adjacently positioned mirror panels (best illustrated in FIG. 5), each having length dimensions as previously described herein. In these and other embodiments, it should be understood that the parabolic arc length of each of the two adjacently positioned mirror panels may be approximately half that of the entire mirror 162. In still other embodiments, the mirror 162 may be formed from a single unitary mirror panel, having both length and parabolic arc dimensions as previously described herein. In certain embodiments, however, as may be suitable for a particular application, the mirror 162 or parabolic reflector may still further, or alternatively, be formed from a plurality of individual mirror panels, each aligned adjacently relative to one another, as may be best understood again from FIG. 5. In at least the illustrated embodiment, the mirror panels may be sized and shaped such that, when combined, the mirror 162 length is approximately six (6) meters (or otherwise dimensioned), as previously described herein. Of course, still other mirror panel and parabolic reflector configurations may be substituted, as may be suitable for a particular application.
The various structural members 169, 172 may be formed from any of a variety of structural materials as commonly known and used in the art for such applications, provided such materials exhibit properties sufficient to support at least the mirror 162. As a non-limiting example, in certain embodiments, the structural members 169, 172 may be formed from substantially the same materials as analogous members 129, 132, as previously described herein. In other embodiments, the material strength requirements for the structural members 169, 172 may be lesser than that for members 129, 132, in which case alternatively configured materials may be substituted, as may be suitable for particular applications. Still further, although the structural members 129, 132, 169, and 172 have been described herein as substantially the same in shape and size configuration, certain embodiments may contain various combinations of configurations, provided the length of each of the structural members remains substantially equivalent to that of the others, as will be described in further detail below with regard to the mounting assembly 180.
As described previously with regard to FIG. 2, incident light rays 14, once reflected from a reflecting surface of a parabolic shape 10 will always converge upon a focal point 12 of the parabolic shape. As such, because the absorber tube 140 is positioned at the focal point 12 of the parabolic trough, most (if not, in some instances all) of the incident light rays 14, once reflected as rays 15, will converge upon the absorber tube. However, due to various factors, as have been described previously herein, inefficiencies may arise over time, causing at least a portion of the reflected rays 15 to miss the absorber tube 140. For the secondary reflector assembly 160 to address this concern, which is at least one intended advantage thereof, the mirror 162 of the assembly must likewise be positioned relative to the absorber tube 140 such that the reflected rays 15, once further reflected off the mirror 162, converge again upon the absorber tube. In other words, the absorber tube 140 according to various embodiments, should generally not only be positioned substantially at the focal point of the mirror 122 of the parabolic trough assembly 120, but also at the focal point of the mirror 162 of the secondary reflector assembly 160, as may be understood from at least FIG. 5.
With reference now to FIGS. 13-15, various non-limiting and exemplary embodiments of secondary reflector assemblies are illustrated. With particular reference to FIG. 13, a secondary reflector assembly 160 is illustrated, as has been primarily described previously herein, wherein the assembly is substantially parabolic in shape, as is the parabolic trough assembly 120 (also sometimes referred to as the primary reflector assembly). As may be seen a light beam A of solar light may contact the parabolic trough assembly 120 but then subsequently miss the absorber tube 140. When such occurs, energy contained in the light beam A is lost and not captured by the solar concentrator 100, thereby creating unintended inefficiencies, as previously described herein. However, due to the configuration of the secondary reflector assembly 160 the missed light beam A is redirected onto the absorber tube 140. In certain embodiments, the secondary reflector assembly 160 may be configured with a single focal point, although in other embodiments, the reflector assembly may have multiple focal points, as will be described later herein.
With continued reference to FIG. 13, additional light beams B and C are also illustrated, that might likewise otherwise miss the absorber tube 140 but for the presence of the secondary reflector assembly 160. In certain embodiments, the secondary reflector assembly 160 may be configured such that different light beams B and C (including those other than shown) may hit the parabolic trough assembly 120 at different locations and angles of incidence are all, in fact, redirected sufficiently toward the secondary reflector assembly 160 so as for them to ultimately contact the absorber tube 140. It should be further understood that, as has been previously described herein, the “one-way” mirror construction of at least the secondary reflector assembly 160 facilitates passage of light beams such as beam C to pass through the secondary reflector assembly, as illustrated in FIG. 13, substantially unimpeded.
Turning now to FIGS. 14 and 15, it should be understood that, as with the absorber tube 140, there may likewise be various alternative embodiments of the secondary reflector assembly 160. As a non-limiting example, as opposed to the parabolic shape illustrated in FIG. 13, an exemplary secondary reflector assembly 160A may be configured as a substantially planar surface. FIG. 15 illustrates yet another non-limiting example, in which an additional exemplary secondary reflector assembly 160B may be constructed with a dual-parabolic shape. In other words, certain embodiments of at least secondary reflector assembly 160B may have at least two parabolic shaped sections that are located substantially adjacent one another. In at least one embodiment, the two may not necessarily touch or engage one another, as may be desirable for particular applications. Of course, still further embodiments may have secondary reflector assemblies configured in any of a variety of constructions, as may be desirable, provided such nevertheless operate to substantially redirect otherwise lost incident beams A, as illustrated in FIGS. 13-15.
Mounting Assembly 180
As may be understood from FIGS. 4, 5 and 7, the solar concentrator 101 may include one or more mounting assemblies 180 (see FIG. 4), which according to various embodiments may be configured to provide an interface between the parabolic trough assembly 120 and the base assembly 110. In certain embodiments, the mounting assemblies 180 may include at least a drive bracket 181 (see FIG. 7), a central bracket 184 (see FIG. 4), an absorber tube bracket 186 (see FIG. 4), and a secondary reflector bracket 190 (see FIG. 5). It should be understood from at least FIG. 7 that the solar concentrator 101 may according to various embodiments generally include at least two mounting assemblies 180, each positioned on a substantially opposing side of the remaining assemblies (e.g., 120, 140, 160) so as to jointly support at least those assemblies there-between. In other embodiments, of course, it should be understood that alternatively configured mounting assemblies may be envisioned, provided such do not unduly impact the degree of incident sunlight that reaches the mirror 122 of the parabolic trough assembly 120 from the sun or other source.
With particular reference to FIG. 7, it may be seen that the drive bracket 181 of the mounting assembly 180 provides the sole pivoting connection point between the base assembly 110 of the solar concentrator 101 and the remaining assemblies 120, 140, 160 of the concentrator, as have been previously described herein. This axis may be seen in FIG. 7 as reference axis 180A. In this manner, movement and alignment of the solar concentrator 101 relative to the positioning of the sun may be greatly facilitated and simplified, as the need to individually align each of the assemblies relative to one another is not routinely necessary for purposes of merely tracking the sun. In certain embodiments, the drive bracket 181 may be configured so as to permit pivoting of the parabolic trough assembly 120 and the secondary reflector assembly 160 about an arc of up to 270 degrees around the sole axis. In other embodiments, varying degrees of rotation, substantially greater than or less than 270 degrees may be provided, as may be desirable for particular applications. Such will tracking and moving capabilities will, of course, be described in further detail below.
According to various embodiments, as may be seen perhaps best from FIG. 7, at least a portion of the drive mounting bracket 181 may be operatively connected adjacent a portion of the support member 114 of the base assembly 110. The drive mounting bracket 181 in certain embodiments, may be operatively connected proximate an upper portion of the support member 114, while in other embodiments, the drive mounting bracket 181 may be otherwise positioned relative to the support member, as may be desirable for a particular application. It should be understood, however, that in any of these and still other embodiments, the drive mounting bracket 181 should be positioned such that a pivot point defined thereby (as described in further detail below) is located at the center of gravity of the solar concentrator 101 in its entirety. In this manner, the work load of the rotating motor (e.g., a motor that rotates the concentrator 101, in particular the parabolic trough assembly 120, the absorber tube 140, and the secondary reflector assembly 160, via the mounting assembly 180, to track or follow the movement of the sun as it passes across the sky) is minimized. Such positioning at the concentrator's center of gravity (or substantially thereby) enables the solar concentrator 101 to avoid “parasitic” loads that oftentimes adversely impact various devices of the prior art.
Remaining with FIG. 7, is may be seen that the drive mounting bracket 181 according to various embodiments is configured to receive at least a portion of a standard gear box or hydraulic drive system (both shown as exemplary 183). It should be understood that any of a variety of gear box, drive systems, or motors may be incorporated, as such are commonly and understood in the art. In any of these and still other embodiments, however, any of a variety of shaft sections formed by and driven by the gear box, drive system, or motor will substantially align to define a rotation axis that corresponds to the pivot point previously described herein. In this manner, the standard gear box or hydraulic drive system is configured, according to various embodiments, such that any shaft sections driven thereby rotate substantially about the center of gravity of the solar concentrator 101 in its entirety.
Although not particularly illustrated in FIG. 7, it should be further understood that the mounting assembly 180 described above may be configured with at least one bearing assembly having an upper polyurethane insert and a lower polyurethane insert. These inserts, according to various embodiments, are configured to engage one another and form a circular opening, the center of which the sole pivot axis 180A of the collector in its entirety extends through. In certain embodiments, the polyurethane inserts can be captured and housed by a bushing cover at their tops and sides and a bottom flange that is in turn attached to the upright support member 114 of the base assembly 110. In other arrangements, the bearing assembly can include a roller bearing. In still other embodiments, the bearing assembly and/or mounting assembly 180 may be configured in any of a variety of ways, provided such facilitates controllable pivoting of the parabolic trough assembly 120 and the secondary reflector assembly 160 and the absorber tube 140 mounted relative thereto.
Turning now to FIG. 4, the central bracket 184 according to various embodiments is illustrated. As may be seen, in at least the illustrated embodiment, the central bracket 184 is rectangular in shape, with an upper portion configured to fixedly receive at least one rotating shaft segment. In this and still other embodiments, while the central bracket 184 may be alternatively shaped or sized, it should be understood that at least a portion of the central bracket is configured so as to fixedly (e.g., preventing relatively rotation there-between) receive the rotating shaft segment. It is, of course, in this manner, according to various embodiments that the rotation of the rotating shaft segment (e.g. via an exemplary drive mechanism, as previously described herein) causes a corresponding rotation of the solar concentrator 101 and the assemblies comprised therein, as will be described in further detail below.
Remaining with FIG. 4, a trough bracket 186 is illustrated, which according to various embodiments provides an operative linkage between the central bracket 184 and the parabolic trough assembly 120, each of which as previously described herein. The trough bracket 186 and associated components may also be understood with reference to FIG. 5A. In certain embodiments, the trough bracket 186 may be rectangular in shape, although alternatively shaped configurations may be substituted, as desirable for a particular application. In certain embodiments, at least a portion of the assembly 120 is fixedly attached to a lower portion of the bracket 186, while an upper portion of the bracket is fixedly attached to the central bracket 184. In this manner, rotation of the exemplary drive mechanism, as previously described herein may be transferred between brackets 184, 186, ultimately to the trough assembly 120. In other embodiments, a respective end (e.g., 130, 131) of the structural frame member 129 of the trough assembly 120 is that portion which is fixedly attached to the bracket 186.
While in at least the embodiment illustrated in FIG. 4 and other embodiments, at least a portion of the assembly 120 is fixedly attached to the trough bracket 186, it should be understood that in still other envisioned embodiments, the central bracket 184 may be configured for direct connection to the assembly 120, without the need for an intermediate trough bracket 186, as described herein. However, for various reasons, generally including the non-limiting examples of a desire to simplify maintenance, minimize structural impedance of sunlight rays, and/or avoid repeated realignment of a particular assembly (e.g., assembly 120, to for example correct sunlight incident angles) separate brackets like bracket 186 are often incorporated within assembly 180.
Looking further at FIG. 4, an absorber tube bracket 188 is illustrated, which according to various embodiments provides an operative linkage between the central bracket 184 and the absorber tube 140, each of which as previously described herein. An isolated illustration of the absorber tube bracket 188 alongside the absorber tube 140 is also provided in FIG. 4A. In certain embodiments, the absorber tube bracket 188 may be rectangular in shape, although alternatively shaped configurations may be substituted, as desirable for a particular application. In certain embodiments, beyond its rectangular or otherwise shape, the bracket 188 may further incorporate (as a unitary piece, or separately) one or more elongate tube support members 189, which extend generally from an upper portion of the bracket 188 to the absorber tube 140. Such support members 189 serve as an additional intermediary (often to minimize solar ray disturbance, due to their slimness) between the bracket 188 and the absorber tube 140. However, it should be understood that in any of these embodiments, each of the respective elements (e.g., 188, 189, 140, etc.) are all fixedly attached relative to one another so as to transfer the rotational force from the shaft segments (as driven by the exemplary drive mechanism, as previously described herein) to the absorber tube 140.
In certain embodiments, at least a portion of the absorber tube 140 is fixedly attached to an upper portion of the bracket 188 (or one or more support members 189, as described above), while a lower portion of the bracket is fixedly attached to the central bracket 184. However, in other embodiments, at least a portion of the absorber tube 140 may be instead fixedly attached directly to the central bracket 184, without the need for an intermediate absorber tube bracket 188 and/or one or more support members 189, as described herein. However, for various reasons, generally including the non-limiting examples of a desire to simplify maintenance, minimize structural impedance of sunlight rays, and/or avoid repeated realignment of a particular assembly (e.g., assembly 120, to for example correct sunlight incident angles) separate brackets like bracket 188 are often incorporated within assembly 180.
Returning specifically to FIG. 4, a reflector support bracket 190 is illustrated, which according to various embodiments provides an operative linkage between the central bracket 184 and the parabolic trough assembly 120, each of which as previously described herein. In certain embodiments, the reflector support bracket 190 may be rectangular in shape, although alternatively shaped configurations may be substituted, as desirable for a particular application. In certain embodiments, beyond its rectangular or otherwise shape, the bracket 190 may further incorporate (as a unitary piece, or separately) one or more elongate tube support members 192, which extend generally from at least a portion of the bracket 190 to the trough bracket 186. Such support members 192 provide an intermediary connection (often to minimize solar ray disturbance, due to their slimness) between the reflector support bracket 190 and the trough bracket 186, from which it receives support. Notably, in certain embodiments, the reflector support bracket 190 is operatively fixed to the trough bracket 186 as opposed to the central bracket 184 so as to directly fix the positional relationship between assemblies 120, 160, and more particularly the two mirrors 122, 162, contained therein. In this manner, misalignment of the two mirrors, respective to one another, may be further minimized according to certain embodiments. However, it should be understood that in still other embodiments, each of the respective elements (e.g., 190, 192, 186, etc.) may be fixedly attached relative to one another in alternative fashions, as may be desirable for a particular application.
From FIG. 5, it should be further understood that at least a portion of the bracket 190 is fixedly attached to at least a portion of the secondary reflector assembly 160. In certain embodiments, a respective end (e.g., 170, 171) of the structural frame member 169 of the assembly 160 is that portion which is fixedly attached to the bracket 190. However, in other embodiments, alternative portions of the assembly 160 may be attached, via any of a variety of mechanisms, to the bracket 190. It should be understood that for any of these described and still other embodiments having a reflector support bracket 190, the bracket 190 must be in some manner fixedly attached, albeit generally indirectly according to certain embodiments (e.g., via the trough support bracket 186), to the central bracket 184, such that a rotation of the central bracket via one or more of the previously described drive mechanisms, causes a corresponding rotation of the secondary reflector assembly 160.
Based upon the preceding description, it should be understood that the configuration of the mounting assembly 180, as described, although variable in certain embodiments, should at least fixedly position each of the trough assembly 120, the absorber tube 140, and the secondary reflector assembly 160 relative to one another, so as to minimize the need for refocusing and/or realignment, both in the short term (e.g., for example, when the concentrator 101 is adjusted to track the sun) and in the long term (e.g., for example, when external fluctuations over time vary mounting tolerances, warp one or more of the mirrors, or shift the foundational base assembly 110). All of these elements, via the mounting assembly 180, are coupled to an exemplary drive mechanism (as has been previously described herein) via a single interface, namely the drive bracket 181 of the assembly 180, thereby enabling concurrent and corresponding rotation of the aforementioned assemblies (e.g., 120, 140, 160) without altering the alignment there-between. In this manner, various embodiments of the solar concentrator 101 provide a simplistic and efficient mechanism that not only remains aligned with a greater degree of consistency, but also recaptures stray reflected light rays that initially miss the absorber tube 140 by reflecting them thereto via the mirror 162 of the secondary reflector assembly 160.
Operation and Exemplary Configurations of Various Embodiments
In operation, one of the exemplary drive mechanisms of the solar concentrator 101 may be activated, whether via a standard gear box assembly (not shown) or a hydraulic drive assembly (also not shown), each as commonly known and understood in the art. However, in contrast with conventional solar concentrators and solar collection systems, activation of the exemplary drive mechanism will rotate the solar concentrator 101 in its entirety as a single unitary structure, due at least in part to the orientation of the mounting assembly 180, as previously described herein, about the center of gravity of the solar concentrator. In this manner, not only does rotation of the solar concentrator 101 cause a corresponding rotation of the parabolic trough assembly 120, but it also causes a corresponding and comparable rotation of the absorber tube 140, the secondary reflector assembly 160, and the mounting assembly 180, as all previously described herein. It should be understood that this unitarily linked rotation of the solar concentrator 101 is facilitated at least in part in various embodiments by the simplicity of the mounting assembly 180 and in particular, the configuration of the central bracket 184 about the center of gravity of the solar concentrator, as previously described herein.
Consider for example the solar concentrator 101 of FIG. 4, as illustrated in a first orientation, which may correspond, for example, to a time of day in which the sun is relatively high in the sky. In the first orientation, the parabolic trough assembly 120 is oriented such that incident light rays 14 from the sun (not shown) align with the mirror 122 of the assembly and reflect therefrom as reflected light rays 15, which will converge upon the absorber tube 140. Any misalignment of the solar concentrator 101 in the first orientation may, in certain embodiments, adversely impact the efficiency with which the reflected rays 15 converge upon the absorber tube 140. However, as has been described previously herein, with the unitary mounting configuration of the assemblies 120, 160, both relative to the absorber tube 140, any such in-efficiencies due to minor misalignment may be counteracted as the mirror 162 of the secondary reflector assembly 160 redirects stray reflected rays 15 back toward the absorber tube 140. It should be understood, from viewing FIG. 5 in comparison to FIG. 4, that as the sun travels across the sky, the solar concentrator 101 may be moved from the first orientation into a second orientation (or still into and through any of a plurality of other orientations, not shown), such that the mirrors 122, 162 remain properly aligned with the sun. Notably though, in any of these and still other embodiments, because the mirrors 122, 162 and the absorber tube 140 are all fixedly mounted relative to one another, relative misalignment errors, particularly those caused by changing the orientation of the solar concentrator 101 to track the sun, are greatly minimized. In certain embodiments, the movement may be provided across a range of approximately 270 degrees of rotation, although in other embodiments the movement may be substantially less than or even substantially greater than 270 degrees of rotation, as may be desirable for particular applications.
Referring now to FIG. 8, the solar concentrator 101 of at least FIGS. 3-4 is further illustrated, as such may be combined according to various embodiments into a solar concentrator assembly 1001. In at least the illustrated embodiment, the assembly 1001 comprises three solar concentrators 101, as previously described herein. Of course, in other embodiments, the assembly 1001 may comprise any of a variety of numbers and orientations of solar concentrators 101, as may be desirable for a particular application. As may be seen from at least FIG. 9, in certain embodiments, when so combined, each of the solar concentrators 101 within the assembly 1001 may share a portion of at least one of its base assemblies 110 with an adjacently positioned solar concentrator. However, in other embodiments, the base assemblies 110 may not be so shared. Such configurations, and even others that may be envisioned, are commonly known and used in the art for combining multiple solar concentrators 101 into assemblies for “farming” solar thermal energy, and as such, are largely provided and described herein for purposes of full disclosure.
Turning now to FIGS. 10-12, multiple solar concentrators 101, as illustrated in at least FIGS. 3-4 are further illustrated, combined according to still additional embodiments into a solar concentrator assembly 2001. Such assemblies 2001 may comprise a plurality of concentrators 101, numbering in the hundreds, if not thousands, as may be desirable for a particular application. Still further, such assemblies 2001 may comprise multiple rows, each having a plurality of concentrators 101, although in at least the illustrated embodiment, only an exemplary single row is depicted. It should be understood that, as with the assembly 1001 configurations described above, the assembly 2001 configurations are also likewise generally commonly known and used in the art for combining a plurality of solar concentrators 101 for purposes of “farming” solar thermal energy, as has been previously described herein.

CONCLUSION

Many modifications and other embodiments of the invention set forth herein will come to mind to one skilled in the art to which this invention pertains having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the invention is not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

Claims

That which is claimed:

1. A solar collector system, said system comprising:

an absorber tube;

a primary reflector having a primary reflective surface portion configured to substantially reflect one or more light beams making contact therewith substantially toward the absorber tube; and

a secondary reflector having a secondary reflector surface portion configured to reflect the one or more light beams reflected from the primary reflector further toward the absorber tube,

wherein the absorber tube is positioned intermediate the primary reflector and the secondary reflector, such that the absorber tube is configured to collect one or more of the light beams reflected from the primary reflector surface portion and one or more of the light beams reflected from the secondary reflector surface portion.

2. The solar collector system of claim 1, said system further comprising a frame assembly configured to define a unitary pivot axis, wherein the primary reflector, the secondary reflector, and the absorber tube are operatively attached to at least a portion of the frame assembly the first support member such that the primary reflector, the secondary reflector, and the absorber tube rotate as a single unit, said single unit being configured to rotate substantially about said unitary pivot axis whereas the primary reflector, the secondary reflector, and the absorber tube each remain stationary relative to one another so as to minimize misalignment there-between.

3. The solar collector system of claim 2, wherein said unitary pivot axis substantially corresponds with a center of gravity of said single unit formed by the primary reflector, the secondary reflector, and the absorber tube.

4. The solar collector system of claim 3, wherein longitudinal axes of the secondary reflector and the absorber tube are offset relative to said unitary pivot axis.

5. The solar collector system of claim 2, wherein:

the frame assembly comprises a first support member and a second support member;

the first support member comprises at least one elongate member having a distal end, adjacent to which said secondary reflector is operatively mounted, so as to offset a longitudinal axis of the secondary reflector from said unitary pivot axis a distance corresponding generally to a length of said at least one elongate member; and

the second support member comprises at least one elongate member having a distal end, adjacent to which said absorber tube is operatively mounted, so as to offset a longitudinal axis of the absorber tube from said unitary pivot axis a distance corresponding generally to a length of said at least one elongate member.

6. The solar collector system of claim 5, wherein said length of said at least one elongate member of said first support member is substantially greater than said length of said at least one elongate member of said second support member, such that said absorber tube is positioned substantially intermediate said primary reflector and said secondary reflector.

7. The solar collector system of claim 2, wherein said unitary pivot axis is configured to permit concurrent rotation of said primary reflector, said secondary reflector, and said absorber tube through an angle of up to 270 degrees.

8. The solar collector system of claim 1, wherein said primary reflector comprises a substantially parabolic trough reflector, said substantially parabolic trough reflector defining a substantially parabolic arc, said substantially parabolic arc having a focal point.

9. The solar collector system of claim 8, wherein said substantially parabolic arc has a diameter lying in a range of from approximately three meters to approximately seven meters.

10. The solar collector system of claim 9, wherein said diameter is approximately five meters.

11. The solar collector system of claim 8, wherein said focal point defines a focal line, said focal line being substantially aligned with a longitudinal axis of said absorber tube.

12. The solar collector system of claim 11, wherein said focal line and said longitudinal axis of said absorber tube are positioned a distance relative to said parabolic trough reflector, said distance lying in a range of from approximately 1.5 meters to approximately 4.5 meters.

13. The solar collector system of claim 12, wherein said distance is between approximately 2.0 and 2.5 meters.

14. The solar collector system of claim 8, wherein said focal point is calculated by dividing a square of a diameter of the parabolic arc by the result of multiplying a depth of the parabolic arc by sixteen.

15. The solar collector system of claim 8, wherein said substantially parabolic trough reflector is formed from two distinct mirror panels, each of said mirror panels being positioned on opposing sides of a unitary pivot axis substantially parallel to a longitudinal axis of said primary reflector.

16. The solar collector system of claim 1, wherein said secondary reflective surface portion of said secondary reflector is formed by a substantially reflective coating, said reflective coating having unidirectional reflective properties, such that light beams may pass there-through substantially unhindered in at least one direction.

17. The solar collector system of claim 1, wherein said secondary reflector comprises a substantially parabolic trough reflector, said substantially parabolic trough reflector defining a substantially parabolic arc, said substantially parabolic arc having a focal point.

18. The solar collector system of claim 17, wherein said substantially parabolic arc has a diameter lying in a range of from approximately one meters to approximately three meters.

19. The solar collector system of claim 17, wherein said focal point defines a focal line, said focal line being substantially aligned with a longitudinal axis of said absorber tube.

20. The solar collector system of claim 19, wherein said focal line and said longitudinal axis of said absorber tube are positioned a distance apart from said secondary reflector, said distance lying in a range of from approximately 0.25 meters to approximately 2.5 meters.

21. The solar collector system of claim 17, wherein said secondary reflector is formed from two distinct mirror panels, each of said mirror panels being positioned on opposing sides of a unitary pivot axis that is substantially parallel to a longitudinal axis of said primary reflector.

22. The solar collector system of claim 17, wherein said primary reflector comprises a substantially parabolic trough reflector, said substantially parabolic trough reflector defining a substantially parabolic arc, said substantially parabolic arc having a focal point.

23. The solar collector system of claim 17, wherein said secondary reflector comprises a dual parabolic trough reflector, said dual parabolic trough reflector defining at least two substantially parabolic arcs, each substantially parabolic arc having a focal point corresponding substantially with a longitudinal axis of said absorber tube.

24. A solar collector system, said system comprising:

a frame assembly configured to define a unitary pivot axis;

a primary reflector, the primary reflector being operatively attached to at least a portion of said frame assembly;

a secondary reflector, the secondary reflector being operatively attached to at least a portion of said frame assembly; and

an absorber tube, the absorber tube being operatively attached to at least a portion of said frame assembly such that the absorber tube is positioned substantially intermediate the primary reflector and the secondary reflector,

wherein the primary reflector, the secondary reflector, and the absorber tube form a single unit, said single unit being configured to rotate substantially about the unitary pivot axis whereas the primary reflector, the secondary reflector, and the absorber tube each remain stationary relative to one another so as to minimize misalignment there-between.

25. A method of using a solar collector system to maximize collection of light beams directed thereon by an external light source, the method comprising the steps of:

(A) providing a system comprising:

(1) a frame assembly configured to define a unitary pivot axis;

(2) a primary reflector, the primary reflector being operatively attached to at least a portion of the frame assembly;

(3) a secondary reflector, the secondary reflector being operatively attached to at least a portion of the frame assembly; and

(4) an absorber tube, the absorber tube being operatively attached to at least a portion of the frame assembly such that the absorber tube is positioned intermediate the primary reflector and the secondary reflector and the primary reflector, the secondary reflector, and the absorber tube form a single unit;

(B) positioning said single unit in a first orientation, said first orientation corresponding to a position at which, during a first period of time, a volume of light beams directed onto said primary reflector is maximized; and

(C) rotating said single unit to a second orientation, said second orientation corresponding to a position at which, during a second period of time different from said first period of time, said volume of light beams directed onto said primary reflector is maximized, wherein said rotating occurs about said unitary pivot point such that the primary reflector, the secondary reflector, and the absorber tube within the single unit each remain stationary relative to one another so as to minimize misalignment there-between.