US20090056699A1 - Linear fresnel solar arrays and receievers therefor - Google Patents

Abstract

Described herein are solar energy collector systems, components for solar energy collector systems, and methods for installing solar energy collector systems. The components for solar energy collector systems include but are not limited to solar radiation absorbers, receivers, drives, drive systems, reflectors, and various support structures. The solar energy collection systems, solar radiation absorbers, receivers, drives, drive systems, reflectors, support structures, and/or methods may be used, for example, in LFR solar arrays. Improved solar radiation absorbers, receivers and related methods are described here.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS
• This application claims the benefit of priority to U.S. patent application Ser. No. 11/895,869, filed Aug. 27, 2007, entitled “Linear Fresnel Solar Arrays,” petition granted to convert to a provisional patent application on Jan. 23, 2008 having U.S. patent application Ser. No. ______ (not yet assigned), which is incorporated by reference herein in its entirety. This application is related to U.S. patent application Ser. No. ______, entitled “Linear Fresnel Solar Arrays and Components Therefor” (Attorney Docket No. 62715-20013.00), and U.S. patent application Ser. No. ______, entitled “Linear Fresnel Solar Arrays and Drives Therefor” (Attorney Docket No. 62715-20016.00), each of which is filed concurrently herewith, and each of which is incorporated by reference herein in its entirety.
FIELD
• This application relates to solar energy collector systems, and in particular to linear Fresnel reflector solar arrays. Described herein are reflectors, solar radiation absorbers, receivers, drives, support structures, stabilization elements, and related methods, that may be used in conjunction with solar energy collector systems.
BACKGROUND
• Solar energy collector systems of the type referred to as Linear Fresnel Reflector (LFR) systems are relatively well known. LFR arrays include a field of linear reflectors that are arrayed in parallel side-by-side rows. The reflectors may be driven to track the sun's motion. In these systems, the reflectors are oriented to reflect incident solar radiation to an elevated distant receiver that is capable of absorbing the reflected solar radiation. The receiver typically extends parallel to the rows of reflectors to receive the reflected radiation for energy exchange. The receiver typically can be, but need not be, positioned between two adjacent fields of reflectors. For example, in some systems, n spaced-apart receivers may be illuminated by reflected radiation from (n+1) or, alternatively, (n−1) reflector fields. In some variations, a single receiver may be illuminated by reflected radiation from two adjacent reflector fields.
• To track the sun's movements, the individual reflectors may be mounted to supports that are capable of tilting or pivoting. Examples of suitable supports are described in International Patent Publication Number WO05/003647, filed Jul. 1, 2004, and International Patent Publication Number WO05/0078360, filed Feb. 17, 2005, each of which is incorporated herein by reference in its entirety.
• In most LFR systems, the receivers and rows of reflectors are positioned to extend linearly in a north-south direction, with the reflectors symmetrically disposed around the receivers. In these systems, the reflectors may be pivotally mounted and driven through an angle approaching 90° to track approximate east-west motion of the sun during successive diurnal periods. Some systems have been proposed in which the rows of reflectors are positioned to extend linearly in an east-west direction. See, e.g., Di Canio et al., Final Report 1977-79 DOE/ET/20426-1, and International Patent Application Serial No. PCT/AU2007/001232, entitled “Energy Collection System Having East-West Extending Linear Reflectors,” filed Aug. 27, 2007, each of which is incorporated herein by reference in its entirety.
• Solar collector systems are generally expansive in area, and are located in remote environments. In addition, solar collector systems must endure for many years in a harsh outdoor environment with relatively low operation, maintenance and repair requirements. Improved systems with reduced requirements for personnel, time, and/or equipment for operation, maintenance, and/or repair are desired. Further, it is desired that solar collector systems be facile to transport to and assemble in remote locations. Therefore, a need exists for improved solar collection systems and improved components for solar collector systems. Such components may include reflectors, receivers, drives, drive systems, and/or support structures. The improved components may lead to improved collection efficiency and improved overall performance for solar collector systems, e.g., LFR arrays. The improved components may also result in reduced operational, maintenance and/or repair requirements, improved longevity in harsh outdoor environments, improved portability, reduced assembly requirements, and reduced manufacturing time and/or costs.
SUMMARY
• Described herein are solar energy collector systems, components for solar energy collector systems, and methods for installing solar energy collector systems. The components for solar energy collector systems include, but are not limited to, solar radiation absorbers, receivers, drives and drive systems, reflectors, and various support structures. The solar energy collection systems, solar radiation absorbers receivers, drives, drive systems, reflectors, support structures, and/or methods may be used, for example, in LFR solar arrays. The components and methods described herein may be used together in any combination in a solar collector system, or they may be used separately in different solar collector systems.
• Receivers for solar energy collector systems are provided here. The receivers each include a receiver channel that comprises first and second sidewalls. An aperture is disposed between the first and second sidewalls. The first and second sidewalls and the aperture each extend along a length of the receiver channel. A solar radiation absorber is positioned in the receiver channel. A window is disposed in the aperture, so that the window and the receiver channel together from a longitudinal cavity that houses the solar radiation absorber, and so that solar radiation incident on the solar radiation absorber is transmitted through the window. The receivers include one or more window support members. The one or more window support members may be disposed along the first sidewall and/or along the second sidewall of the receiver channel. The one or more window support members may be configured to allow installation of the window into the receiver in a direction transverse to the length of the receiver channel, and to support the window when the window is installed in the receiver.
• Some variations of these receivers may comprise a first window support member disposed along the first sidewall and a second window support member disposed along the second sidewall. For example, the first window support member may be disposed along the first sidewall and may comprise a ledge and a step. In certain variations, the second window support member may be disposed along the second sidewall and may comprise a slot. The slot in the second window support member may include upper and lower slot surfaces, and a slot sidewall. The upper and lower slot surfaces may be spaced apart by an amount sufficient to accommodate a thickness of the window. The window, when installed in these variations of receivers, may be positioned on the ledge and on the lower slot surface and between the step and the slot sidewall, with a longitudinal edge of the window positioned in the slot between the upper and lower slot surfaces. Variations of these receivers may include one or more tabs to secure the window to the receiver.
• Solar energy collector systems comprising such receivers are also described here. These systems comprise an elevated receiver. The elevated receiver comprises a receiver channel that, in turn, comprises first and second sidewalls, and an aperture disposed between the first and second sidewalls. The first and second sidewalls and the aperture each extend along a length of the receiver channel. A solar radiation absorber is positioned in the receiver channel. A window is disposed in the aperture so that the window and the receiver channel together form a longitudinal cavity that houses the solar radiation absorber, and so that solar radiation incident on the solar radiation absorber is transmitted through the window. The receivers may include one or more window support members disposed along the first and/or second sidewall of the receiver channel. The one or more window support members may be configured to allow insertion of the window into the receiver in a direction transverse to the length of the receiver channel, and to support the window when the window is installed in the receiver. The systems also include first and second reflector fields positioned on opposite sides relative to a center of the elevated receiver. Each reflector field comprises reflectors that are arranged into one or more parallel reflector rows extending generally in a direction parallel to the length of the receiver channel. The reflectors each comprise a reflective surface configured to direct incident solar radiation through the window to the solar radiation absorber in the receiver. The reflectors in the systems are driven to at least partially track diurnal motion of the sun.
• Other variations of receivers are described. These receivers include a receiver channel comprising an aperture extending along its length. A solar radiation absorber is positioned in the receiver channel. A window is disposed in the aperture of the receiver channel so that the window and the receiver channel together form a cavity that houses the solar radiation absorber, and so that solar radiation that is incident on the solar radiation absorber is transmitted through the window. In these receivers, at least one of the window and the receiver channel may be configured to accommodate thermal expansion and contraction along a length of the aperture. For example, the window may comprise two or more overlapping window sections that are distributed along a length of the aperture to accommodate longitudinal thermal expansion and contraction.
• Solar energy collector systems comprising such receivers are also disclosed herein. These systems include an elevated receiver and first and second reflector fields positioned on opposite sides relative to a center of the receiver. The elevated receiver comprises a receiver channel that comprises an aperture extending along its length. A solar radiation absorber is positioned in the receiver channel. A window is disposed in the aperture so that the window and the receiver channel together form a cavity that houses the solar radiation absorber, and so that solar radiation incident on the solar radiation absorber is transmitted through the window. At least one of the window and the receiver channel may be configured to accommodate thermal expansion along a length of the aperture. For example, in some systems, the window may comprise two or more overlapping window sections that are distributed along a length of the aperture. Each reflector field in the systems comprises reflectors that are arranged into one or more parallel reflector rows that extend generally in a direction parallel to the length of the receiver channel. The reflectors each comprise a reflective surface that is configured to direct incident solar radiation through the window to the solar radiation absorber in the receiver. The reflectors in the systems are driven to at least partially track diurnal motion of the sun.
• Additional variations of receivers for solar energy collector systems are described here. These variations of receivers each comprise a receiver channel that, in turn, comprises an aperture that extends along the length of the receiver channel. A solar radiation absorber is positioned in the receiver channel. A window is disposed in the aperture so that the window and the receiver channel together form a cavity that houses the solar radiation absorber, and so that solar radiation incident on the solar radiation absorber is transmitted through the window. The window forms a junction with the receiver channel. In these receivers, ingress of external air into the cavity through the junction between the window and the receiver is inhibited.
• Ingress of external air into the cavity through the junction between the window and the receiver may be inhibited in any suitable manner. For example, some variations of these receivers may comprise a sealing member positioned in the junction between the receiver channel and the window to inhibit ingress of external air into the cavity. Alternatively, or in addition, a positive pressure of filtered gas or air (e.g., filtered air or dry nitrogen) may be flowed into the cavity to inhibit ingress of external air into the cavity. Certain variations of these receivers may comprise a roof positioned over the receiver channel to form a volume between the roof and the receiver channel. The volume between the roof and the receiver channel is in fluid communication with the cavity that houses the solar radiation absorber. A thermally insulating material may be disposed in the volume between the roof and the receiver channel. A rate of flow of external air into the cavity through at least a portion of the insulating material in the volume between the roof and the receiver channel is greater than a rate of flow of external air into the cavity through the junction between the window and the receiver channel. In some variations of these receivers, the insulating material may act as a filter to filter out particulates, moisture, and/or other contaminates present in external air.
• Solar energy collector systems comprising such receivers are described. These systems each include an elevated receiver and first and second reflector fields positioned on opposite sides relative to a center of the receiver. The elevated receiver comprises an aperture extending along a length of the receiver channel. A solar radiation absorber is positioned in the receiver channel. A window is disposed in the aperture so that the window and the receiver channel together form a cavity that houses the solar radiation absorber, and so that solar radiation incident on the solar radiation absorber is transmitted through the window. The window and the receiver channel form a junction. Ingress of external air into the cavity through the junction between the receiver channel and the window may be inhibited in these systems. Each reflector field in the systems includes reflectors that are arranged into one or more parallel reflector rows that extend generally in a direction parallel to the length of the receiver channel. The reflectors each comprise a reflective surface that is configured to direct incident solar radiation through the window to the solar radiation absorber. The reflectors in the systems are driven to at least partially track diurnal motion of the sun.
• In some variations of such systems, the receiver may further comprise a roof positioned over the receiver channel to form a volume between the roof and the receiver channel. The volume so formed is in fluid communication with the cavity that houses the solar radiation absorber. A thermally insulating material may be disposed in the volume. A rate of flow of external air into the cavity through at least a portion of the insulating material may be greater than a rate of flow of external air into the cavity through the junction between the window and the receiver channel.
• Other variations of receivers are described herein. These variations of receivers include a receiver channel comprising an aperture that extends along a length of the receiver channel. A roof is positioned over and extends along the length of the receiver channel. The roof may have a transverse cross-section that forms a smooth curve and comprises a concave surface that faces the receiver channel. A solar radiation absorber is positioned in the receiver channel. A window may be disposed in the aperture so that the window and the receiver channel form a cavity that houses the solar radiation absorber, and so that solar radiation incident on the solar radiation absorber is transmitted through the window. The window and the receiver channel may form a junction. The roof may be configured to shed environmental debris away from the window. The roof may be configured in any suitable manner to shed environmental debris away from the window. For example, in some variations, the roof may extend below the junction between the receiver channel and the window.
• Systems including such receivers are described. These systems each include an elevated receiver and first and second reflector fields positioned on opposite sides relative to a center of the receiver. Each elevated receiver comprises a receiver channel that comprises an aperture extending along its length. A roof may be positioned over and extending along the length of the receiver channel. The roof may have a transverse cross-section that forms a smooth curve and comprises a concave surface that faces the receiver channel. A solar radiation absorber is positioned in the receiver channel. A window may be disposed in the aperture so that the window and the receiver channel form a cavity that houses the solar radiation absorber, and so that solar radiation incident on the solar radiation absorber is transmitted through the window. The window and the receiver channel may form a junction. The roof may be configured to shed environmental debris away from the window. For example, in some systems, a roof over the receiver channel may extend below the junction between the window and the receiver channel. Each reflector field in the systems comprises reflectors that are arranged into one or more parallel reflector rows extending generally in a direction parallel to the length of the receiver channel. The reflectors each comprise a reflective surface configured to direct incident solar radiation through the window to the solar radiation absorber. The reflectors in the systems are driven to at least partially track diurnal motion of the sun.
• Still other variations of receivers are described here. These variations of receivers each include a solar radiation absorber. The solar radiation absorber comprises a plurality of parallel absorber tubes each extending along a length of the receiver. The receivers may also include a plurality of spacers. Each spacer may be positioned between two adjacent ones of the parallel absorber tubes. Transverse space provided by each spacer may be sufficient to accommodate thermal expansion and/or movement of the two adjacent ones of the parallel absorber tubes. For example, in some variations, one of the spacers positioned between two adjacent ones of the parallel absorber tubes that are located near a transverse center of the receiver channel may be larger than another of the spacers that is positioned between two adjacent ones of the parallel absorber tubes that are located near an outer longitudinal edge of the receiver.
• Solar energy collector systems comprising such receivers are described. These systems each include an elevated receiver and first and second reflector fields positioned on opposite sides relative to a center of the receiver. Each receiver includes an elongated receiver channel comprising first and second sidewalls and an aperture. Each of the first and second sidewalls and the aperture extend along a length of the receiver channel. Each receiver also includes a solar radiation absorber comprising a plurality of parallel absorber tubes that are arranged lengthwise in the receiver channel between the first and second sidewalls and above the aperture. A plurality of spacers may be included in each receiver. Each spacer may be positioned between two adjacent ones of the parallel absorber tubes. Transverse space provided by each spacer may be sufficient to accommodate thermal expansion and/or movement of the two adjacent ones of the parallel absorber tubes. Each reflector field in the systems comprises reflectors that are arranged into one or more parallel reflector rows that extend generally in a direction parallel to the length of the receiver channel. The reflectors in the systems each comprise a reflective surface that is configured to direct incident solar radiation through the aperture to be at least partially incident on the plurality of absorber tubes. The reflectors are driven to at least partially track diurnal motion of the sun.
• Additional variations of receivers are described. These variations of receivers each comprise a solar radiation absorber that comprises a plurality of parallel absorber tubes that are arranged lengthwise in the receiver. The receivers also comprise one or more rollers extending transversely across the receiver. At least one of the one or more rollers may support the plurality of absorber tubes. In these variations, at least one of the one or more rollers may comprise a central shaft disposed within a hollow cylinder that comprises two cylinder ends. The hollow cylinder may be supported at each cylinder end by a bushing coupled to the central shaft. In some variations of these receivers, a diameter of the central shaft is at most about one half, or about one quarter, a diameter of the hollow cylinder.
• Solar energy collector systems comprising such receivers are described. Each system includes an elevated receiver and first and second reflector fields that are positioned on opposite sides relative to a center of the receiver. Each receiver in the systems comprises an elongated receiver channel comprising first and second sidewalls and an aperture. The first and second sidewalls and the aperture each extend along a length of the receiver channel. The receivers also each comprise a solar radiation absorber comprising a plurality of parallel absorber tubes arranged lengthwise in the receiver channel between the first and second sidewalls and above the aperture. The plurality of parallel absorber tubes may be supported by one or more rollers positioned transversely across the receiver channel. At least one of the one or more rollers may comprise a central shaft disposed within a hollow cylinder that comprises two cylinder ends. The hollow cylinder may be supported at each of the two cylinder ends by a bushing coupled to the central shaft. Each reflector field in the systems comprises reflectors that are arranged into one or more parallel reflector rows extending generally in a direction parallel to the length of the receiver channel. The reflectors each comprise a reflective surface that is configured to direct incident solar radiation through the aperture to be at least partially incident on the plurality of absorber tubes. The reflectors are driven to at least partially track diurnal motion of the sun. In certain variations of these systems, a diameter of the central shaft may be at most about one half, or about one quarter, a diameter of the hollow cylinder.
• Still more variations of receivers are described here. These receivers comprise a solar radiation absorber that comprises a plurality of parallel absorber tubes arranged lengthwise in the receiver. In these variations, the plurality of absorber tubes may be supported by a set of coaxial rollers extending transversely across the receiver. For example, in some variations, the set of coaxial rollers may comprise an individual roller for each absorber tube.
• Solar radiation absorbers for use in solar energy collector systems are described here. These absorbers comprise a plurality of absorber tubes. Each absorber tube may be coupled via a tube structure to a header manifold. The header manifold and/or at least one of the tube structures that couples each absorber tube to the header manifold may be configured to accommodate differential thermal expansion of the absorber tubes. For example, at least a portion of the header manifold may be configured to move to accommodate thermal expansion and contraction in the tubes. In some variations of these absorbers, the header manifold may comprise an input/output manifold, and the input/output manifold may comprise an inlet section that can move independently from the output section. In certain variations of these absorbers, at least one of the tube structures that connect each absorber tube to the header manifold may comprise two or more non-coplanar bends. Some variations may comprise a flow control element inserted into or disposed on at least one of the absorber tubes.
• Other variations of solar radiation absorbers for use in solar energy collector systems are provided. These absorber may comprise a plurality of absorber tubes and a flow control element applied to at least one absorber tube to maintain a relatively constant fluid flow between the absorber tubes. For example, in some variations, the flow control element may account for about 30% to about 70% of the pressure drop in the at least one absorber tube, e.g., about 40% to about 50% of the pressure drop.
• Still other variations of absorbers for use in solar energy collector systems are provided. These absorbers comprise a plurality of absorber tubes that, in turn, comprises one or more inlet tubes for supplying heat exchange fluid to the absorber and one or more outlet tubes for releasing heat exchange fluid from the absorber. In these absorbers, the plurality of absorber tubes may be configured so that the one or more outlet tubes is positioned closer to an interior of the absorber relative to the one or more outlet tubes.
• Other variations of solar energy collector systems are provided here. These systems each comprise an elevated receiver comprising an elongated receiver channel comprising first and second sidewalls and an aperture, each extending along a length of the receiver channel. The systems also comprise a solar radiation absorber comprising a plurality of spaced-apart parallel absorber tubes arranged lengthwise in the receiver channel between the first and second sidewalls and above the aperture. The systems include first and second reflector fields positioned on opposite sides relative to a center of the receiver. Each reflector field comprises reflectors that are arranged into one or more parallel reflector rows extending generally in a direction parallel to the length of the receiver channel. The reflectors each comprise a reflective surface configured to direct incident solar radiation through the aperture to be at least partially incident on the plurality of absorber tubes. The reflectors are driven to at least partially track diurnal motion of the sun. In these systems, spacings between adjacent ones of the spaced-apart parallel absorber tubes may be selected to reduce leakage of reflected solar radiation past the absorber tubes. For example, the spacings between adjacent ones of the spaced-apart parallel absorber tubes may be determined using a set of tangents extending from an inner edge of at least one of the reflectors.
• Methods for setting spacings between adjacent ones of spaced-apart parallel absorber tubes in a receiver of a solar energy collector system are provided. These methods comprise arranging the absorber tubes lengthwise and side-by-side on a horizontal plane that is elevated with respect to a reflector in the solar energy collector system. The absorber tubes may be spaced apart on the horizontal plane by aligning an outer circumferential edge of each absorber tube with a tangent line extending from an inner edge of the reflector.
• Additional variations of receivers for solar energy collector systems are provided. These variations of receivers each include an elongated receiver channel that comprises first and second sidewalls and an aperture. The first and second sidewalls and the aperture each extend along a length of the receiver channel. The receivers comprise a solar radiation absorber positioned in a cavity formed between the first and second sidewalls and above the aperture. The receivers may comprise a frame for supporting the solar radiation absorber and the receiver channel. In these variations of receivers, at least one of a junction between the frame and a mounting structure coupled to the solar radiation absorber and a junction between the frame and the receiver channel may be configured to inhibit thermal conduction between the cavity and the frame. For example, in some variations, receivers may comprise a thermal separation member positioned in a junction between the frame and the mounting structure, and/or in a junction between the frame and the receiver channel.
BRIEF DESCRIPTION OF THE FIGURES
• FIGS. 1A-1C illustrate an example of a solar energy collector system that includes two reflector fields directing incident solar radiation to an elevated receiver.FIG. 1A depicts a transverse, end-on view of the system, andFIGS. 1B-1C depict longitudinal, side views of the system.
• FIG. 2A illustrates an example of a solar energy collector system that includes two elevated receivers.
• FIGS. 2B-2D illustrate various examples of reflector supports that may be used in solar energy collector systems, andFIG. 2E illustrates an example of a drive system for use in a solar array comprising a combination of reflector support types.
• FIG. 3 illustrates an example of a reflector element having a reflective surface that focuses reflected solar radiation at a receiver.
• FIG. 4 illustrates another example of a reflector element having a reflective surface that focuses reflected solar radiation at a receiver.
• FIG. 5 provides an example of a solar energy collector system that includes asymmetric lateral guy wires.
• FIG. 6 shows another example of a solar energy collector system that includes asymmetric lateral guy wires.
• FIG. 7 illustrates another variation of a solar energy collector system with asymmetric lateral guy wires.
• FIG. 8 shows a variation of a solar energy collector system with an arrangement of longitudinal guy wires.
• FIG. 9 shows another variation of a solar energy collector system with an arrangement of longitudinal guy wires.
• FIGS. 10A-10C illustrate an example of a receiver.
• FIGS. 11A-11E illustrate an example of a receiver that is configured to allow transverse window insertion.FIG. 11A,11C and11D illustrate cross-sectional views of the receiver,FIG. 11B provides a perspective view of the receiver, andFIG. 11E provides a bottom plan view of the receiver.
• FIGS. 12A-12C illustrate variations of receivers including windows with overlapping window sections.FIGS. 12B-12C show cross-sectional views along line I-I′.
• FIG. 13 shows a variation of a receiver that is configured to accommodate longitudinal thermal expansion and contraction.
• FIGS. 14A-14F show variations of receivers in which ingress of external air into a cavity housing a solar radiation absorber through a pathway near a window is inhibited.
• FIG. 15 shows a variation of a receiver comprising a roof configured to shed environmental debris away from a window in the receiver.
• FIGS. 16A-16B illustrate an example of a receiver that comprises solar radiation absorbing tubes, with spacers positioned between adjacent tubes.FIG. 16B is an enlarged view of encircled region A.
• FIGS. 17A-17B illustrate an example of a method for determining spacings between solar radiation absorber tubes.
• FIGS. 18A-18C shows an example of a receiver in which the number and/or quality of thermal conduction paths between a cavity housing solar radiation absorber and structural elements of the receiver have been reduced.
• FIGS. 19A-19D illustrate a variation of a receiver in which tubes carrying heat exchange fluid are supported by one or more rollers.
• FIGS. 20A-20F show examples of an absorber for a receiver comprising a plurality of solar absorber tubes connected to a header manifold.
• FIGS. 20G-20I show examples of flow control elements that may be used with solar absorber tubes.
• FIGS. 21A-21C illustrate various configurations of flow patterns of a heat exchange fluid through a plurality of solar absorber tubes.
• FIG. 22 illustrates a variation of a jointed vertical support structure, and one method for elevating a receiver or a portion of a receiver for a solar energy collector system using the jointed vertical support.
• FIGS. 23A-23B illustrates another variation of a jointed vertical support structure.
• FIGS. 24A-24D show an example of a carrier frame that allows relative alignment of two or more platforms for supporting reflector elements in a solar energy collector system.
• FIGS. 25A-25B illustrate an example of a drive system for a solar energy collector system, where the drive system comprises a chain that is continuously engaged with toothed gear-like engagement member on reflector support that supports and positions one or more reflector elements.FIG. 25B is an enlarged view of encircled region B.
• FIGS. 26A-26B illustrate another example of a drive system for a solar energy collector system.FIG. 26B is an enlarged view of encircled region C.
• FIG. 27 shows a variation of a drive system for a solar energy collector system, where the drive system includes a pivot arm that can adjust tension in a chain that drives motion in a reflector support supporting one or more reflector elements.
• FIGS. 28A-28B illustrate an embodiment of a drive system for a solar energy collector system, where the drive system includes a lateral stabilization member to reduce lateral movement by a reflector support that rotates one or more reflector elements.FIG. 28B is an enlarged view of encircled region D.
• FIG. 29 illustrates an example of a drive system for a solar energy collector system that comprises a variable frequency drive.
• FIG. 30 illustrates an embodiment solar energy collector system comprising multiple reflector rows and multiple motors.
• FIGS. 31A-31C illustrate various embodiments of vertical support structures for use in solar energy collector systems.
DETAILED DESCRIPTION
• 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 enable one skilled in the art to make and use the invention, and describes several embodiments, examples, adaptations, variations, alternatives and uses of the invention, including what is presently believed to be the best mode of carrying out the invention.
• The terms “solar energy collector system,” “solar collector system,” and “solar array” are used interchangeably throughout this specification and in the appended claims. In addition, unless indicated otherwise, “array” refers to a solar array, and “absorber” refers to a solar radiation absorber. The singular forms “a,” “an,” and “the” include plural referents unless the context clearly indicates otherwise. Also, the term “parallel” is intended to mean “substantially parallel” and to encompass minor deviations from parallel geometries rather than to require that parallel rows of reflectors, for example, or any other parallel arrangements described herein be exactly parallel. The phrase “generally in a north-south direction” or as used herein is meant to indicate a direction orthogonal to the earth's axis of rotation within a tolerance of about ±45 degrees. For example, in referring to a row of reflectors extending generally in a north-south direction, it is meant that the reflector row lies parallel to the earth's axis of rotation within a tolerance of about ±45 degrees.
• Disclosed herein are examples and variations of solar energy collector systems, components for solar energy collector systems, and related methods. The solar energy collector systems may be LFR solar arrays. The components may include reflectors for directing incident solar radiation to a receiver, receivers for receiving and at least partially absorbing solar radiation, solar radiation absorbers, drives and drive systems for positioning the reflectors, support structures for elevated receivers, support structures or carrier frames for reflector elements, and additional stabilizing elements, such as guy wires, for stabilizing or securing any part of a solar array. The components described here may be used in any combination in a solar energy collector system. Further, any suitable receiver, solar radiation absorber, reflector, drive, drive system, support structure, stabilizing element, or method disclosed herein, known to a person of ordinary skill in the art, or later developed, may be used in the solar collector systems described herein. Receivers, solar radiation absorbers, reflectors, drives, drive systems, associated support structures and stabilizing elements, and methods disclosed herein may be used in other solar collector systems (e.g., LFR solar arrays) known to one of ordinary skill in the art or later developed.
• The following is a general description of solar energy collector systems that may be used in conjunction with any one of, or any combination, of the components for solar collector systems that are described below. Additional examples of solar energy collector systems are included throughout this detailed description in connection with specific components and methods disclosed herein, e.g., reflectors, receivers, absorbers, drives, drive systems, support structures, stabilizing elements, and related methods.
• Referring toFIGS. 1A-1C, an example of a LFR array is illustrated. This example is presented generally to encompass systems or arrays that are arranged in either east-west or north-west orientations.LFR array7 comprises anelevated receiver5 that is positioned above, but horizontally between, two reflector fields,10 and16. Thearrow21 represents the diurnal east-west path of the sun overarray7. For a north-south oriented array, direction A will represent an eastern direction and direction B will represent a western direction.Reflector field10 comprisesreflectors12 that are arranged in M parallel, side-by-side reflector rows12R₁-12R_M.Reflector field16 comprisesreflectors14 that are arranged in N parallel, side-by-side reflector rows14R₁-14R_N. As shown inFIG. 1B, a single reflector row may comprise one or more reflectors, e.g., 2 to 6. Within a given reflector row comprising multiple reflectors, the multiple reflectors may extend generally along a common plane, e.g.,reflectors14 inreflector row14R₁may extend generally alongcommon plane18.Rays13 represent the path of solar radiation from the sun incident on thereflectors12 and14.Rays13′ represent the path of solar radiation reflected fromreflectors12 and14 toelevated receiver5. In typical LFR arrays, the reflectors may be curved mirrors that form a line focus at the receiver.
• Referring now toFIG. 1C, the angle of incidence θ is shown between anincident ray13 and an axis Z normal to the incidentreflective surface20 of a reflector (e.g., a reflector12). The reflector has a width D. Becauseray13 is incident on thesurface20 at a non-normal angle θ, the effective collection width d of the reflector is given by d=D cos(θ). Therefore, the effective collection area of a reflector decreases as the angle of incidence increases. In addition, reflective losses may increase as the angle of incidence increases, and optical aberrations such as astigmatism may increase as the angle of incidence increases. Optical aberrations may reduce the ability to focus solar radiation reflected by a reflector to the receiver, thereby blurring the focus of radiation incident on the receiver and decreasing collection efficiency.
• For systems having multiple reflector fields, the reflector fields may be symmetric or asymmetric with respect to a receiver. The composition and/or arrangement of the reflector fields may, for example, be determined to increase ground area usage and/or system collection efficiency. Referring again toFIG. 1 A, the tworeflector fields10 and16 may be symmetric or asymmetric with respect toelevated receiver5. In this example,receiver5 has a plane of symmetry19. M and N, representing the number of reflector rows on opposite sides of plane19, may be the same or different. In variations of arrays that are designed to be oriented east-west, M and N may be different. The reflector field on the pole side of the receiver (e.g., the north pole for a system being used in the northern hemisphere) may have more reflectors than the reflector field on the equatorial side of the receiver). Examples of east-west arrays are described in U.S. patent application Ser. NO. 11/895,869, filed Aug. 27, 2007, and International Patent Application Serial No. PCT/AU2007/001232, filed Aug. 27, 2007, each of which has previously been incorporated herein by reference in its entirety. Alternatively, the number of reflector rows on opposite sides of a center of a receiver (e.g., M and N inFIG. 1A) may be the same. For example, arrays designed to be oriented north-south may be symmetrical with respect to the number of reflectors in two reflector fields reflecting solar radiation to a common receiver.
• For a given reflector field, adjacent reflector rows may be spaced apart by a constant row spacing, or by variable row spacings. For example, reflectors in a first reflector row that are less tilted relative to reflectors in an adjacent second reflector row may be packed closer together with the reflectors in the adjacent second row, without causing shading. Referring again toFIG. 1A, the spacing between adjacent reflector rows x and x+1 inreflector field10 is15R_x,x+1, where 1≦x≦M. The spacing between adjacent reflector rowsy and y+1 inreflector field12 is17R_y,y+1, where 1≦y≦N. Thus, theinter-reflector row spacings15R_x,x+1may be constant, or15R_x,x+1may be varied as x is varied, and theinter-reflector row spacings17R_y,y+1may be constant, or17R_y,y+1may be varied as y is varied.
• In certain variations of arrays, the spacing between adjacent reflector rows may vary generally as the distance between the reflectors rows and the receiver. That is, reflector rows closer to the receiver may be spaced closer together than reflector rows further from the receiver. For example, as illustrated in FIG. IA, forreflector field10, the spacing between the first two rows ofreflectors15R_1,2closest toreceiver5 may be smaller than the spacing betweenspacing15R_M−1,Mbetween the two rows of reflectors that are most distant fromreceiver5. Similarly, forreflector field16, the spacing between the first two rows ofreflectors17R_1,2closest toreceiver5 may smaller than thespacing17R_N−1,Nbetween the two rows of reflectors most distant fromreceiver5. Such reflector row spacing variations may be appropriate for north-south oriented arrays. In certain variations of arrays, the inter-row spacing between reflector rows may vary between reflector fields. Such a configuration may be appropriate for east-west oriented arrays. For example, reflector rows in an equatorial field may be spaced closer together than reflector rows in a polar field, because the reflectors in a reflector row in an equatorial field may be less tilted with respect to reflectors in an adjacent row.
• The use of variable row spacings may allow closer packing of reflector rows, resulting in improved use of ground area and/or reduction of shading of reflectors caused by adjacent reflectors. In some systems, a reflector area to ground area ratio may be greater than about 70%, or greater than about 75%, or greater than about 80%. Combinations of constant spacings and variable spacings between reflector rows may be used. For example, a first group of reflector rows, e.g., those closest to the receiver, may be spaced apart by a first constant relatively narrow spacing. A second group of reflector rows, e.g., those farthest from the receiver, may be spaced apart by a second constant relatively wide spacing. In addition, different spacing schemes may be used between different reflector fields in a single system. For example, one reflector field may have constant reflector row spacings and one reflector field may have variable reflector row spacings. For north-south oriented arrays including reflector rows that are about 2.3 meters wide directing solar radiation to an absorber of about 0.6 meter wide positioned about 15 meters above the reflectors, center-center inter-row reflector separations may range from about 2.6 meters to almost 3 meters (e.g., about 2.9 meters).
• It should be noted that the diurnal sun moves through an angle less than about 90° in the north-south direction, as compared with an angle approaching about 180° in the east-west direction. Therefore, for east-west oriented arrays, each reflector in a reflector field need only pivotally move less than about 45° to follow the sun during each diurnal period. As a result, the angles of incidence for reflectors in a polar reflector field are generally less than those for reflectors in an equatorial reflector field. Hence, a reflector in a polar reflector field may have greater effective collection area and produce improved focus at the receiver than a corresponding reflector in the equatorial reflector field positioned the same distance from the receiver. Because of the improved efficiency of polar reflectors, the overall collection efficiency of a solar array may be improved by increasing the relative reflector area in the polar reflector field as compared to the equatorial reflector field, e.g., by increasing the number of reflectors in the polar field.
• Solar energy collector systems may comprise multiple elevated receivers, and multiple reflector fields configured to direct incident light to the elevated receivers. Referring now toFIG. 2A,solar array201 includes four reflector fields,210,212,214, and216.Reflector row211 includesmultiple reflectors211a.Reflectors211ain a reflector row may be coupled together in a collinear fashion. For example,reflectors211amay be coupled together via a common reflector support222 (e.g., a hoop) atjunction regions223.Supports222 may be configured to rotationally drive one or more reflectors coupled thereto to at least partially track diurnal motion of the sun. Reflectors in a single row or a segment of a single row may be driven by a drive, e.g., by a motor (not shown) coupled to amaster reflector support224, which may be positioned internally within the row or row segment to be driven to reduce torsional effects at portions of reflector rows located furthest from the master reflector support. Row segments comprising 2, 4, 6, or any suitable number of reflectors may be driven by a drive coupled to a master reflector support. Reflector rows or row segments may be driven individually, or reflector rows or row segments may be driven collectively, in groups (e.g., regionally). A single drive may rotate more than one reflector row or row segment, or multiple drives may be synchronized or coordinated to rotate more than one reflector row or row segment at the same time.
• A drive system used in the arrays may comprise any suitable reflector supports that are configured to support and rotate one or more reflector elements. In general, the reflector supports comprise a frame portion configured to support one or more reflector elements, a base, and a linkage rotationally coupling the frame portion to the base so that the frame portion may be rotated through the linkage to position the one or more reflector elements. The reflector supports may be selected to reduce the amount of shading from the support on any reflector element, e.g., one or more reflector elements supported by that reflector support and/or one or more reflector elements supported by adjacent or nearby reflector supports. For example, a reflector support in a drive system may be configured such that a frame portion of the reflector support is substantially confined to one side of a planar region generally defined by a reflective surface of one or more reflector elements supported by the frame, e.g., so that the frame is substantially beneath that reflective surface during operation. A reflector support may also be configured to have strength and/or stability, e.g., torsional strength and/or stability, such that one or more reflector elements supported by that reflector support does not substantially twist or distort when that reflector support is rotated.
• As described above, a reflector support in a drive system may be configured to be a master reflector support or a slave reflector support, or to be convertible between a master reflector support and a slave reflector support. A master reflector support may be coupled to a drive (e.g., a drive comprising a motor). A slave reflector support may not be directly coupled to a drive, and instead may be coupled to a master reflector support (or another slave support that is coupled to a master support) so that rotation of the master reflector support drives coordinated rotation in the slave reflector support. In that manner, a single drive may be used to rotate a reflector row or reflector row segment. A master reflector and drive may be configured to drive any suitable number of slave reflector supports, e.g., one, two, three, four, five, six, seven, eight, nine, ten, or eleven, or even more.
• Some variations of reflector supports that may be used in drive systems for solar energy collector arrays, e.g., linear Fresnel reflector arrays, are illustrated inFIGS. 2B-2D. Each of these variations of supports may be configured as a master reflector support or as a slave reflector support. Referring first to the variation illustrated inFIG. 2B,reflector support260 comprises a hoop-like frame261 that is configured to support one or more reflector elements (not shown). Theframe261 may optionally comprise one or more cross-members262. If present, cross-members262 may add torsional strength to the frame. In some variations, a reflector element (not shown) may be coupled to across-member262. In the particular variation illustrated inFIG. 2B,reflector support260 may comprise abase263 and a linkagerotationally coupling frame261 to the base. In this particular example, the linkage comprises one or more rotational elements264 (e.g., wheels). Ifreflector support260 is configured to be a master reflector support, a drive (e.g., a motor)265 may be coupled to the reflector support. A drive may be coupled to a master support in any suitable manner, e.g., using one or more gears, belts, drive chains, pivot arms and the like. Ifreflector support260 is configured to be a slave support, then adrive265 may not be directly coupled to thereflector support260, and instead thereflector support260 may coupled to and driven by another reflector support (e.g., through one or more longitudinal members (not shown) extending between reflector supports). Additional details regarding drive systems incorporating such hoop-like reflector supports are provided below.
• Other variations of reflector supports may be used in the drive systems and arrays described herein. Referring now toFIG. 2C, areflector support270 comprises abase271 and aframe272. The base272 may for example comprise one or more posts or pedestals. One ormore reflector elements276 may be supported byframe272. Theframe272 may be rotationally coupled to thebase271 via a linkage. In this example, the linkage comprises ahub273 comprising one or more bearings configured to rotate about anaxle274, where thehub273 is configured to supportframe272. In some variations,axle274 may comprise two stub axles. In this variation,frame272 is substantially confined to one side of aplane278 generally defined by areflective surface277 of one ormore reflector elements276. Thus,frame272 may be substantially beneathreflective surface277 during operation and may therefore reduce shading by thereflector support270 on any reflector elements in the array. It should be pointed out thatreflective surface277 may be curved (concave), so thatplane278 may be only generally or approximately defined byreflective surface277. Ifreflector support270 is configured to be a master support, a drive (not shown) may be coupled toaxle274 and/orhub273 to rotateframe272 aboutaxle274. Any suitable drive may be used to rotateframe272 aboutaxle274. For example, any combination of gears, belts, drive chains, pivot arms, and the like coupled to a motor may be used. Ifreflector support270 is configured to be a slave support, it may be coupled to and driven by another reflector support (e.g., through one or more longitudinal members (not shown) extending between reflector supports).
• Still other variations of reflector supports may be used. Referring toFIG. 2D, areflector support280 may comprise aframe281 that comprises a portion of a hoop. Although the variation shown inFIG. 2D showsframe281 as an approximately 180° arc of a hoop, other variations are possible in which different frames having arcs extending either more or less than about 180° around a hoop are used.Frame281 may optionally comprise one ormore spokes287 that may provide torsional stability to the reflector support.Frame281 may comprise a cross-member282 that may for example be coupled to one ormore reflector elements289. Similar to the variation illustrated inFIG. 2B,reflector support280 may comprise one or more rotational elements284 (e.g., wheels) which may be mounted to abase283. In this variation,frame281 is confined to one side of aplane290 generally defined byreflective surface288 of the one ormore reflector elements289. Therefore, reflector supports similar to those illustrated inFIG. 2D may cause reduced shading of reflector elements in a solar array. As with reflector supports260 and270,reflector support280 may be configured as a master support configured to be driven by amotor285, or may be configured as a slave support that is coupled to and driven by another reflector support (e.g., via one or more longitudinally members (not shown) extending between reflector supports).
• Any combination of reflector supports and reflector support types may be used within an array or within a reflector row in an array. The combination of reflector supports may be selected to provide increased torsional stability along a row, reduced shading, ease of installation, ease of manufacturing, and/or cost. In some variations of arrays, such asarray201 illustrated inFIG. 2A, a majority of reflector supports may comprise hoop-like frames. InFIG. 2E, adrive system291 for use in an array (e.g., in a portion of a reflector row in an array) is illustrated in which amaster reflector support292 comprises a hoop-like frame293 and is driven bydrive294. Slave reflector supports295 are in turn coupled lengthwise together via longitudinally-extending member (not shown) so thatreflective elements296 extend between adjacent ones of the reflector supports. Rotation ofmaster support292 then drives rotation of allreflector elements296 in the row or row segment. In the drive system variation illustrated inFIG. 2D, slave supports295 are selected to be similar to those illustrated inFIG. 2C, which may reduce the overall shading experienced by an array comprisingdrive system291. Other combinations of reflector supports may be used within a row or row segment, e.g., slave supports at one or both ends of a row segment may comprise hoop-like frames.
• As indicated above, some arrays may comprise more than one receiver.Array201 inFIG. 2 includes tworeceivers205 and215.Receiver205 is elevated above and positioned horizontally betweenreflector fields210 and212, andreceiver215 is elevated above and positioned horizontally betweenreflector fields214 and216. Reflectors inreflector fields210 and212 are configured to direct incident solar radiation toreceiver205, and reflectors inreflector fields214 and216 are configured to direct incident solar radiation toreceiver215. Receivers may have a generally horizontally-oriented aperture (e.g.,aperture250 for receiver205), through which solar radiation is directed to be incident on a solar energy absorber (not shown) in a receiver. In some variations, a window that is substantially transparent to solar radiation may cover at least part of a receiver aperture (e.g.,window240 is placed inaperture250 of receiver205). The receivers may comprise multiple receiver structures (e.g.,205aand215a) that are joined together to form an elongated receiver.Receivers205 and215 are supported with vertical support structures (e.g., stanchions)218 and stabilized withguy wires219. The guy wires may be ground-anchored, or they may be anchored to another structure.
• A LFR array may occupy a ground area of about 5×10³m²to about 25×10⁶m². For example, an array may comprise a single receiver and two fields of reflectors arranged on opposite sides of the receiver to occupy a ground area of about 8.5×10³m². Other arrays may comprise multiple receivers and multiple reflector fields to occupy larger ground areas, e.g., about 5×10⁶m²to about 25×10⁶m². For example, the arrays illustrated inFIGS. 1A-1C andFIG. 2A may comprise a portion of a larger LFR array having a plurality of receivers and a plurality of reflector fields. In larger arrays, the plurality of receivers and corresponding reflector fields may be arranged side-by-side and parallel to each other, as arereceivers205 and215 andreflector fields210,212,214, and216 inFIG. 2A. In other variations of systems, the plurality of receivers and reflector fields may be arranged in alternate configurations.
• The reflectors used in the solar energy collector systems may be any suitable reflectors described here, known to one of ordinary skill in the art, or later developed. Non-limiting examples of suitable reflectors are disclosed in International Patent Applications Nos. PCT/AU2004/000883 and PCT/AU2004/000884, each of which is hereby incorporated by reference herein in its entirety.
• As illustrated inFIGS. 3 and 4, suitable reflectors may have, for example, circular arc or parabolic cross-sections to focus the reflected radiation at a target distance. Typically, the focused image may be a line focus. Focal lengths of reflectors may be from about 10 meters to about 25 meters. For reflectors having circular arc cross-sections, these focal lengths correspond to radii of curvature of about 20 meters to about 50 meters, respectively. Some variations of reflectors may have focal lengths that are approximately equivalent to a distance from a reflective surface of the reflector to the receiver. Other variations of reflectors may have focal lengths that are longer than a distance from a reflective surface of the reflector to the receiver.
• Referring now toFIG. 3, asolar array301 includes areflector311 that is configured to direct incident solar radiation to anelevated receiver305 that includes a solar radiation absorber (not shown).Reflector311 may be part of a reflector field comprising parallel rows of reflectors directing incident light toreceiver305, where the rows of reflectors are driven to at least partially track diurnal motion of the sun. Areflective surface307 ofreflector311 reflectslight beam313 that is incident at angle6 so that reflectedlight beam313′ forms afocused image325 at receiver305 (e.g., at a solar radiation absorber in receiver305). In some variations,reflector311 may be configured to provide a line focus, e.g.,reflector311 may be a cylindrical mirror. For reference, dashedlines318 illustrate the path of a light beam that is incident onreflective surface307 at a normal angle and is reflected to form afocused image310 at adistance320 fromreflective surface307.Distance320 corresponds to the focal length ofreflector311. However, forlight beam313 that is incident onreflective surface307 at a non-normal angle δ,light rays313′ reflected from first and second reflector edges315 and316 may form their sharpestfocused image325 at adistance322 that does not correspond tofocal length320, e.g., at a distance that is less thanfocal length320. Thus, reflectors for light that is close to normal incidence may have a focal length that is approximately equal to a distance between the reflective surface and the receiver, and reflectors for light that is far from normal incidence may have focal lengths longer than a distance between their reflective surfaces and the receiver. Increased overall system collection efficiency may be achieved by using the latter reflectors to at least partially compensate for astigmatic effects due to non-normal incidence of light.
• As the distance between a reflector and its corresponding receiver increases, the required focal length for the reflector may also increase. Accordingly, the size of the focused image at the receiver may also increase. If the focused image is larger than the receiver, or leaks past the receiver, then the collection efficiency of the receiver may be decreased. Reflectors that are positioned the farthest from the receiver are closest to the periphery of the array. Hence, the angle of incidence on a surface of the receiver increases for peripherally-positioned reflectors, which may lead to increased losses at the receiver, e.g., reflective losses and/or losses due to poor focusing of astigmatic reflections as discussed above.
• Referring now toFIG. 4, asolar array401 includes areflector411 that is configured to direct incidentsolar radiation413 to areceiver405 that includes a solar radiation absorber (not shown). Similar toreflector311 inFIG. 3,reflector411 may be part of a reflector field.Reflective surface407 ofreflector411 reflectslight beam413 that is incident at angle φ so that reflectedlight beam413′ forms afocused image425 at receiver405 (e.g., at a solar radiation absorber in receiver405). In some variations,reflector411 may be configured to provide a line focus, e.g.,reflector411 may be a cylindrical mirror. For reference, dashedlines415 illustrate the path of light beam that is incident onreflective surface407 at a normal angle and is reflected to form afocused image410 at adistance420 fromreflective surface307.Distance420 corresponds to the focal length ofreflector411. In this example,incident light beam413 strikesreflective surface407 at a relatively large non-normal angle φ. Light rays413′ reflected from first and second reflector edges415 and416 may form their sharpestfocused image425 at adistance422 is less thanfocal length420. To compensate for this astigmatic effect, the focal length of a reflector may be chosen to be longer than the distance between the reflective surface of the reflector and the receiver, e.g., an absorber in the receiver. For example, reflectors having a focal length from about 1% to about 15% (e.g., about 1%, about 2%, about 5%, about 10%, or about 15%) longer than the distance between their reflective surface and the receiver may be used.
• In some arrays, peripheral reflectors positioned relatively far from a receiver may have focal lengths longer than their distance from the receiver. Some variations of arrays may comprise a series of parallel reflector rows each directing incident light to an elevated receiver. The focal lengths of the reflectors in the respective reflector rows may follow a progression so that those reflectors farthest from a transverse center of the receiver are the longest. Such progressions may include monotonic increases in reflector focal length as a distance from the transverse receiver center increases, or any general trend or general correlation between increasing reflector focal length with increasing receiver-reflector distances. In some arrays, only the outermost reflector rows may comprise reflectors having focal lengths longer than their respective reflective surface-solar absorber distances. For example, for arrays having two reflector fields directed to a single absorber, only two or four of the most peripheral rows may have focal lengths longer than their respective reflective surface-solar absorber distances. Solar energy collector systems utilizing one or more reflectors having focal lengths longer than their distance to the receiver may have overall collection efficiencies, such as annualized light collection efficiencies, that are increased by about 1%, about 2%, about 3%, about 4%, about 5%, about 6%, or even more, e.g., about 10%.
• Reflectors may have any suitable dimensions. Of course, reflectors may be unitary n nature, and comprise a single reflector element, or reflectors may comprise multiple reflector elements. Dimensions of reflectors and/or reflector elements may be selected based any combination of the following considerations: system collection efficiency, manufacturing requirements, manufacturing costs, availability of materials, cost of materials, ease of handling and/or transportation, field maintenance requirements, lifetime, and/or ease of installation. In some variations, reflectors may have lengths of about 10 meters to about 20 meters, and widths of about 1 meter to about 3 meters. The reflectors may have lengths of about 10 to about 20 meters, e.g., about 12 meters, about 14 meters, about 16 meters, or about 18 meters, and widths of about 1 meter to about 3 meters , e.g., about 1.3, about 1.4 meters, about 1.5 meters, about 1.6 meters, about 1.7 meters, about 1.8 meters, about 1.9 meters, about 2.0 meters, about 2.1 meters, about 2.2 meters, about 2.3 meters, about 2.4 meters, about 2.5 meters, about 2.6 meters, about 2.7 meters, about 2.8 meters, or about 2.9 meters. The reflectors may have lengths of about 16 meters and widths of about 2.2 meters. In some cases, focal lengths of reflectors or reflector elements may be indicated in a readily discernible manner, e.g., by color coding, to aid in assembly of solar arrays.
• One or more reflector rows in a solar energy collector system may have an overall length of about 200 meters to about 600 meters, e.g., about 200 meters to about 400 meters, or about 400 meters to about 600 meters. In some systems, reflector rows may have the same or similar overall lengths. As illustrated inFIG. 2A, reflector rows may comprise groups of reflectors that are interconnected to form a row segment that may be driven collectively. Such a row segment may comprise, for example, 2 reflectors, 4 reflectors, 6 reflectors, or any suitable number of reflectors. A collectively-driven row segment may be driven by one or more motors. Reflector rows or row segments may be driven sequentially, e.g., one row segment rotated at a time, or reflector rows or row segments may be driven simultaneous, e.g., more than one row segment rotated at once in a bulk move. Drives and drive systems that may be used for rotating and positioning reflectors are described in more detail below.
• The receiver or receivers in solar energy collector systems may be any suitable receiver described herein, known to one of ordinary skill in the art, or later developed. Suitable receivers may include, for example, those disclosed in International Patent Application No. PCT/AU2005/000208, which is hereby incorporated by reference in its entirety. Receivers may be, for example, photovoltaic receivers capable of absorbing incident solar radiation and converting the solar radiation to electricity, or thermal receivers capable of absorbing incident solar radiation to heat a working or heat exchange fluid in the receiver. For example, a heat exchange fluid such as water may be flowed through the receiver. As shown inFIG. 2A, receivers when installed may be elongated and have an overall or generally horizontal orientation, with a generally horizontally-oriented aperture that allows transmission of light to a solar radiation absorber in the receiver.
• As indicated above, some variations of receivers may comprise multiple receiver structures. The receiver structures may be interconnected. Receiver structures may be arranged and/or interconnected in a longitudinal (i.e., lengthwise) and/or a transverse (i.e., widthwise) manner to form receivers. Receivers may have overall lengths, including receiver structures, that are similar to the overall length of the corresponding reflector rows, e.g., about 200 meters to about 600 meters (e.g., about 200 meters to about 400 meters, or about 400 meters to about 600 meters). Receiver structures may have lengths of, for example, about 8 meters to about 20 meters and overall widths of about 0.5 meters to about 3 meters, e.g., about 0.5 meters to about 1 meter, or about 1 meter to about 2 meters, or about 2 meters to about 3 meters. For example, in some variations a receiver structure may have a length of about12 meters and an overall width of about 1.3 to about 1.4 meters. Suitable receivers may have one or more solar radiation absorbers, where the absorbers are tubes and/or flat plates, or groups of tubes and/or flat plates. One or more absorbers, including a group of tubes and/or flat plates making up an absorber, may have a width of about 0.3 meter to about 1 meter, or any other suitable width.
• In solar energy collector systems including multiple receivers, receivers may be spaced apart by about 20 to about 35 meters, or by any suitable inter-receiver spacing. The receivers may be elevated above the reflectors with their absorbers positioned at a height of about 10 meters to about 20 meters above the reflectors, e.g., about 15 meters above the reflectors. In arrays with multiple receivers, the receivers may be positioned all at the same or similar heights above the reflectors, or at different heights above the reflectors.
• Elevated receivers may be supported by any suitable method. For example, receivers may be supported by vertical support structures such as stanchions, as illustrated inFIG. 2A. The vertical support structures, in turn, may be supported or stabilized by cables or guy wires, e.g., guy wires that are anchored to the ground and/or to another anchoring structure. In some variations, two or more guy wires may be used to support a single vertical support structure, e.g., two guy wires that extend laterally from opposing sides of a vertical support structure as illustrated forguy wires219 stabilizingsupport structures218 inFIG. 2A.
• Guy wires, if present, may extend generally laterally or longitudinally from a vertical support structure. For example, as discussed in more detail below, one or more ground-anchored guy wires may extend laterally from a vertical support structure. Alternatively, or in addition, one or more longitudinal guy wires may extend between adjacent ones of the vertical support structures. Any combination of lateral and/or longitudinal guy wires may be used to stabilize vertical support structures supporting a receiver. For example, at least some vertical support structures may not be stabilized by any lateral guy wires. In other variations, only alternate ones of vertical support structures may be stabilized by lateral guy wires. In still other variations, only every third or fourth or greater interval vertical support structure may be stabilized by lateral guy wires.
• When a set of guy wires comprising two or more guy wires is used to stabilize a vertical support structure in a system, one guy wire in the set may be asymmetric relative to another guy wire in the set by having a different spring constant or resonance than the other guy wire. Resonances in guy wires may be excited by external environmental effects such as wind and/or seismic activity, as well as internal effects such as motor vibrations or reflector motions. By selecting a set of guy wires that includes guy wires with different natural resonances to stabilize a support structure, the solar energy collector system as a whole may be stabilized. If the resonance frequencies in guy wires do not match, an excited resonance in one wire may not amplify a resonance in another wire. In addition, if the resonance frequencies of guy wires used to stabilize a support structure are different, an excited resonance in one wire may not couple to and excite the same resonances in the system, again leading to improved system stability. Further, one guy wire in a set may be chosen to have a resonance that can couple with and damp a resonance in one or more different guy wires in the set.
• Spring constants or resonances of a guy wire may be varied in any suitable manner, e.g., by changing the length, the material, the tension, and/or a diameter of the guy wire. For guy wires comprising more than one strand, a spring constant of the guy wire may be varied by varying the number of strands, the diameter, and/or the material composition of one or more strands. In addition, a pattern of weaving, braiding, and/or intermeshing of strands used to form the guy wire may be changed to adjust a spring constant of the wire.
• For thearray501 illustrated inFIG. 5, avertical support structure522 holdselevated receiver505 above, but horizontally betweenreflector fields510 and512. In this variation,receiver505 includesabsorber506,window507,receiver channel509, androof508.Reflector field510 includesreflectors514 that are supported and positioned by carrier frames515.Reflector field512 includesreflectors516 that are supported and positioned by carrier frames517.Guy wires550 and551 stabilizevertical support structure522, with guy wire550 extending laterally, generally in the direction ofreflector field510, andguy wire551 extending laterally, generally in the direction ofreflector field512.Guy wires550 and551 may be ground-anchored, or anchored to another anchoring structure. Guy wire550 is coupled tovertical support structure522 at afirst coupling point523, anchored at afirst anchoring point524, and has a first resonant frequency between the first coupling and anchoringpoints523 and524.Guy wire551 is coupled tovertical support structure522 at asecond coupling point525, anchored at asecond anchoring point526, has a second resonance frequency between second coupling and anchoringpoints525 and526. In this variation,guy wires550 and551 have different resonance frequency due to their different respective lengths,560 and561, between first coupling and anchoringpoints523 and524, and between second coupling and anchoringpoints525 and526. Thus, a resonance excited in guy wire550, e.g., by wind or vibration, and transferred tovertical support structure522 or another part ofarray501 may not be excited or amplified byguy wire551. Further, a resonance excited in one ofguy wire550 or551 may couple to and damp a resonance excited in the other ofguy wire551 and550. In some variations, the coupling mechanism of guy wires to a vertical support member (e.g., at couplingpoints523 and525) may be designed to reduce transfer of resonances excited in guy wires to other parts of the array. For example, the coupling points may include vibration damping materials or structures.
• As indicated above, the natural resonance frequencies of guy wires may be tuned using techniques other than or in addition to changing wire length. For example, as illustrated inFIG. 6,array601 includes avertical support structure622 supporting anelevated receiver605 above, but horizontally between, reflector fields610 and612.Guy wire650 is coupled tovertical support structure622 atfirst coupling point623, anchored to the ground or an anchoring structure atfirst anchoring point624, and has a first resonance frequency between first coupling and anchoringpoints623 and624.Guy wire651 is coupled tovertical support structure622 atsecond coupling point625, anchored to the ground or to an anchoring structure atsecond anchoring point626, and has a second resonance frequency between second coupling and anchoringpoints625 and626. In this variation,guy wires650 and651 have thesame length662, but still have different resonance frequencies due to their different respective widths,660 and661.
• Asymmetric guy wires in a set of guy wires may have resonance frequencies that are different by any suitable amount to improve stability in a solar energy collector system. For example, one guy wire in a set may have a resonance frequency that is about 20%, about 30%, about 40%, about 50%, about 60%, about 70%, or about 80% different than another guy wire in the set. As used herein, when two guy wires are referred to as having different resonance frequencies, it is meant that two guy wires should not have the same fundamental resonance frequencies, and also should not be overtones or harmonics of each other.
• Guy wires may be selected and arranged in any suitable manner to support and stabilize a series of vertical support structures in a solar array. For example, as shown inFIGS. 5 and 6, a set of guy wires comprising two asymmetric guy wires may be used to support a single vertical support structure. In other variations, a set of guy wires comprising two asymmetric guy wires may be used to support more than one vertical support structure. For example, as illustrated inFIG. 7,array701 includesvertical support structures722 and723.Vertical support structure722 supportsreceiver705 above and horizontally betweenreflector fields710 and712.Vertical support structure723 supportsreceiver715 above and horizontally betweenreflector field714 and716. Afirst guy wire750 is attached tovertical support structure722 at afirst coupling point723, extends laterally to one side ofarray701, and is anchored to the ground or an anchoring structure atfirst anchoring point724.First guy wire750 has a first resonance frequency between first coupling and anchoringpoints723 and724. Asecond guy wire751 is attached tovertical support structure723 at asecond coupling point725, extends laterally from an opposing side ofarray701, and is anchored to the ground or to an anchoring structure at asecond anchoring point726. The second guy wire has a second resonance frequency between second coupling and anchoringpoints725 and726. In this variation,guy wires750 and751 have differentrespective lengths760 and761, leading to different resonances that do not couple effectively to each other. In some cases, the resonances of one of the anchored wires may be chosen so that it couples to and damps a resonance in another wire.
• As shown inFIG. 7, some variations of arrays may include an interconnection member between adjacent vertical support structures.Interconnection member752 interconnects and stabilizesvertical support structures722 and723. Interconnection member may be a wire, a cable, a bar, or any suitable structure that can stabilize vertical support structures and also minimizes shading on reflectors below. In arrays such as that shown inFIG. 7, where an additional interconnection member couples together two vertical support structures, the anchored guy wires may be selected to have resonances that are different than the interconnection member, e.g., by choosing a different length, thickness, structure, or type of material.
• Some vertical support structures, e.g., a vertical support structure at the end of a row of vertical support structures supporting an elongated receiver, may be stabilized by a set of guy wires that includes more than two guy wires, e.g., three or four guy wires. Sets of guy wires comprising three or more guy wires may comprise any combination of symmetric and asymmetric guy wires, as long as at least one of the guy wires in the set has a different resonance frequency than another of the guy wires in the set.
• In addition to laterally-extending guy wires, an arrangement of longitudinal guy wires may be included in arrays to stabilize elevated receivers and/or other portions of the arrays. For example, an arrangement of longitudinal guy wires may assist in longitudinal system stabilization for seismic events or other motions that excite longitudinal modes in the system, whereas laterally-extending guy wires may provide stabilization against wind and/or seismic events that may primarily excite transverse modes in the system.
• For some receivers such as thermal receivers, the absorption of solar radiation can cause a large increase in temperature for one or more receiver components. These large temperature fluctuations will cycle with the diurnal path of the sun. For elongated receivers, extensive anisotropic thermal expansion and contraction may occur. For example, some elongated thermal receivers comprise a plurality of solar absorber tubes (e.g., metal pipes carrying a heat exchange fluid such as water and steam). As the absorber tubes absorb radiation and increase in temperature, an anisotropic expansion occurs primarily along the length of the tubes. For elongated receivers having lengths of 200 meters or more, thermal expansion and contraction on the order of centimeters or tens of centimeters may occur. Arrangements of support structures and stabilizing elements (e.g., longitudinal guy wires) for elevated receivers that can accommodate repeated thermal expansion and contraction are desired. For example, as illustrated inFIG. 2A, elevated receivers may be supported by vertical support structures that allow the receiver to slide longitudinally relative to the support structure. Support structures and/or stabilizing elements that cannot adequately accommodate the cyclical thermal expansion and contraction may cause system damage and/or fatigue over time.
• Examples of suitable arrangements for longitudinal guy wires that may be used to stabilize elevated receivers are shown inFIGS. 8 and 9. As illustrated inFIG. 8, solarenergy collector system801 comprises a plurality ofvertical support structures810. These vertical support structures are distributed along alength803 ofelevated receiver805.Receiver805 may be configured to be able to slide relative tostructures810. In between two adjacent ones of the plurality ofvertical support structures810 arelongitudinal guy wires830. The amount of thermal expansion and contraction of one or more longitudinal components of a receiver (e.g., an absorber comprising stainless steel or carbon steel pipes containing heat exchange fluid and/or a component in thermal contact with the absorber) increases as a distance from alongitudinal center825 ofreceiver805 increases. To reduce the amount of dimensional cycling due to thermal effects experienced by the longitudinal guy wires and structures to which they are attached, an arrangement of longitudinal guy wires in which the density of longitudinal guy wires generally decreases as a distance from a longitudinal center of receiver increases may be used. As used herein, a density that “generally decreases” is meant to encompass any decreasing trend of the number of longitudinal guy wires per unit length, and is not necessarily limited to monotonic decreases in longitudinal guy wire density.
• The density of longitudinal guy wires may be decreased in any suitable manner. For example, as illustrated inFIG. 8, longitudinal guy wires may not be installed between every pair of adjacent vertical support structures. Alternatively, or in addition, for vertical support structures positioned near the longitudinal center of the receiver, two diagonally crossed longitudinal guy wires may be used between a pair of adjacent vertical support structures, and a single diagonal longitudinal guy wire may be used between a pair vertical support structures positioned further away from the longitudinal center of the receiver. Althoughvertical support structures810 inFIG. 8 are depicted as generally equally spaced along thelength803 of theelevated receiver805 for ease of illustration, any appropriate spacing of vertical support structures may be used. For example, the density of longitudinal guy wires may be decreased at least in part by generally increasing the spacing between adjacent vertical support structures as the distance from the longitudinal receiver center increases.
• Referring now toFIG. 9, another example of an arrangement of longitudinal guy wires is shown that may be used to stabilize a solar energy collector system while accommodating thermal expansion and contraction of one or more components of a receiver. Thearray901 depicted inFIG. 9 comprises anelevated receiver905 supported byvertical support structures910 that are distributed along a length903 ofreceiver905.Receiver905 may be configured to be able to slide relative tostructures910. To one side of thelongitudinal center925 ofreceiver905, the arrangement of longitudinal guy wires comprises afirst set914 ofwires930 extending diagonally between adjacentvertical support structures910 in a firstdiagonal direction913. Asecond set915 ofwires932 extends in a seconddiagonal direction916. The second diagonal direction may be related to the first diagonal direction. For example, if the first diagonal and second diagonal directions may be symmetrical relative to a vertical axis of symmetry. Arrays using any combination of the longitudinal wire arrangements depicted inFIGS. 8 and 9 may be used.
• Variations of improved receivers for use in solar energy collector systems are described here.FIGS. 10A-10C illustrate various components that may be used in the make up of an elongated receiver. As shown inFIG. 10A, areceiver1005 may comprise askeletal frame1007.Frame1007 may compriseside rails1009, transverse arched or peakedstructural members1011, andtransverse bridging members1013.Frame1007 may also comprise one ormore spine members1015 extending longitudinally betweenstructural members1011.Receiver1005 includes asolar radiation absorber1010 that may comprise a plurality of generally parallel, lengthwise-oriented pipes ortubes1014 for carrying a heat exchange fluid. Theabsorber1010, or a portion ofabsorber1010, may be supported by (e.g., suspended from)frame1007.
• In general, as shown inFIG. 10B, receivers may include a receiver channel for housing the absorber and providing a thermally insulating still air environment to increase efficiency of the receiver.Receiver1005 inFIG. 10B comprisesreceiver channel1019 that comprises first andsecond sidewalls1016 and1017. The first and second sidewalls extend along alength1018 of the receiver channel. The sidewalls of the receiver channel may be flared or angled outwardly. Disposed between the first and second sidewalls is alongitudinal aperture1020. The aperture may extend over the entire length of the receiver channel, or may extend over only a portion of the length of the receiver channel. The solar radiation absorber may be housed within or substantially within the longitudinal cavity of the receiver channel so that solar radiation incident upon the solar radiation absorber has been transmitted through the aperture. In some variations, a receiver channel may be in the form of trough with a concave surface facing the absorber, fabricated from thin metal sheeting, such as stainless steel sheet metal. A receiver channel may comprise multiple segments, or be unitary in nature. In addition, receiver channels may comprise elements or be attached to elements that can provide structural integrity or support. For example, receiver channels may comprise longitudinal side rails or transverse bridging members. Alternatively, or in addition, receiver channels may be attached to a frame comprising longitudinal side rails or transverse bridging members. For example, as shown inFIG. 10B,receiver channel1019 may be attached to and supported by any subset or combination structural features offrame1007, includingside rails1009,structural members1011,spine member1015, andtransverse bridging members1013. As shown inFIG. 10C, aroof1021 may be disposed overframe1007. The roof may be unitary in nature, or may comprise multiple sections, as inFIG. 10C. The roof may be designed to shield the internal portions of the receiver from environmental effects, and/or to impart stability (e.g., strength and/or rigidity such as longitudinal stability) to the elongated receiver. In addition, the roof may have a smooth outer surface to provide a low wind profile and to provide improved ability to shed environmental debris.
• In some variations of receivers, a window may be disposed in the aperture. The window may be substantially transparent to a broad portion of the solar radiation spectrum, e.g., the portion of the solar radiation spectrum that passes through the atmosphere. The window may be positioned over a portion of the aperture, or may substantially cover the aperture. Windows may be planar or curved. For example, windows may be curved with a concave surface facing the solar radiation absorber. As illustrated inFIG. 10A,window1027 comprisesmultiple window sections1028. Windows may be fabricated from any suitable material that exhibits high transmission over a broad range of the solar spectrum, and that exhibits sufficient physical and mechanical properties to withstand harsh environmental effects. For example, glass or plastic that can withstand years of exposure to UV radiation and/or high winds of up to 100 mph may be selected. If glass is used, it may have a minimum thickness of about 3 mm to about 4 mm, for example. Some variations of receiver windows may be made from glass having relatively low iron content.
• As indicated above, the receiver channel (and the window disposed over the aperture, if present) forms a longitudinal cavity that houses the solar radiation absorber and may increase the collection efficiency of the absorber. The receiver channel may function to retain heat in the cavity and to increase energy conversion efficiency, e.g., by reflecting stray solar radiation back to the absorber, providing a still air environment around the absorber to reduce convective losses, and/or have a construction that reduces or eliminates thermal shorts that conduct heat away from the absorber. For a solar radiation absorber to be positioned substantially within the receiver channel, it is meant that a substantial part of the absorbing portion of the absorber is positioned inside the receiver channel, but that portions of the absorber may extend outside the receiver channel, e.g., pipe extensions, pipe fittings, pipe couplings, header manifolds, and/or valves may be positioned outside the receiver channel.
• Some variations of receivers may include one or more window support members that are configured to allow installation of a window in a direction that is transverse to the length of the receiver channel. The one or more window support members may also function to support a window once it has been installed into a receiver. Because of the length of the elongated receivers used in some solar collector systems such as LFR solar arrays, transverse installation of windows may be easier than longitudinal installation. Windows may be easier to handle in a transverse direction, leading to reduced risk of window breakage and reduced space requirements for the installation. In addition, transverse installation of windows into receivers may facilitate assembly of those receivers at or near ground level, rather than after they have been elevated above reflector fields.
• Window support members that allow transverse installation of a window into a receiver may be disposed along one or both of the first and second longitudinal sidewalls of the receiver channels in the receivers. Window support members may be continuous, e.g., a continuous slot designed to be slidably engaged with an edge of a window, or a continuous ledge designed to support a window. Alternatively, a window support member may be discontinuous, e.g., a series of periodic structures spaced along the length of the receiver channel. For example, a window support member may comprise a series of slot sections designed to be slidably engaged with an edge of a window, or a series of ledge sections.
• Referring now toFIGS. 11A-11E, an example of a receiver that is configured to allow transverse installation of a window is shown. There,receiver1105 comprises alongitudinal receiver channel1119 that has afirst sidewall1106 and asecond sidewall1107. In some variations, sidewalls1106 and1107 may be flared out from a receiver channel backwall1108 so thatreceiver channel1119 has a trough-like shape. Anaperture1109 is disposed between the sidewalls. In this example,aperture1109 extends along thelength1118 ofreceiver channel1119. However, as stated above, in some variations of receivers, the aperture may extend only over a portion of the length of a receiver channel.Absorber1110 that comprises a plurality of parallel absorber tubes is suspended from atransverse bridging member1113 offrame1133, and positioned between the twosidewalls1106 and1107 and opposed toaperture1109 so that light incident uponabsorber1110 has been transmitted through theaperture1109. Aroof1131 may be supported by aframe1133 and positioned overchannel1119 to form avolume1132 between thechannel1119 and theroof1131.Vertical support structure1147, which may comprise ashelf1146 and cross-bars1145, supportsreceiver1105.
• Some variations of receivers may include two window support members that allow transverse installation of a window into a receiver and subsequent support of that window in the receiver once it has been installed. Referring again toFIGS. 11A-11E, a firstwindow support member1111 may be disposed along thefirst sidewall1106. A secondwindow support member1112 may be disposed along thesecond sidewall1107. Referring now toFIGS. 11C-11D, the firstwindow support member1111 may comprises aledge1121 and astep1122, and the secondwindow support member1112 may comprise aslot1123 that has alower slot surface1124, anupper slot surface1125 and aslot sidewall1126.Slot1123 may be slidably engaged with an edge of awindow1127, so that a space betweenupper slot surface1125 andlower slot surface1124 is at least thick enough to accommodate athickness1140 of thewindow1127.
• As shown inFIG. 11C,window1127 may be inserted transversely intoreceiver1105 by tiltingwindow1127 betweenwindow support members1111 and1112.Window1127 may then be inserted intoslot1123 and placed uponledge1121 so thatwindow1127 is supported byledge1121 andlower slot surface1124. The outerlongitudinal edges1128 and1129 ofwindow1127 may be positioned betweenstep1122 andslot sidewall1126, respectively.Slot1123,ledge1121, andstep1122 may be configured in any suitable manner to allow transverse installation of the window and subsequent support of the window. For example, the space between upper andlower slot surfaces1125 and1124, respectively, may be larger thanwindow thickness1140, so thatwindow1127 may be tilted slightly and still be at least partially inserted betweensurfaces1124 and1125. Alternatively, or in addition,upper slot surface1125 may extend less far from a sidewall of the receiver channel thanlower slot surface1124. In some variations, the height ofstep1122 may be less than the height ofupper slot surface1125 to reduce the amount of tilt ofwindow1127 required to fit the window in its installed position betweenstep1122 andslot sidewall1126.
• In some variations, tabs (e.g., spring tabs) may be used to secure windows to receivers. Any suitable tabs may be used, and tabs may be distributed along the length of the receiver channel as necessary to secure the window in the receiver. Referring now to the bottom plan view of the receiver inFIG. 11E,tabs1135 may be used to secure thewindow1127 to thereceiver1105.Tabs1135 may be designed to contact abottom surface1141 ofwindow1127 to support the window from the bottom after the receiver is installed. Alternatively, or in addition,tabs1135 may be designed to contact a top surface ofwindow1127, to provide downward force on the window to hold it againstwindow support members1111 and1112. Tabs may be positioned along one or both longitudinal sidewalls of the receiver channel. As indicated byarrows1136,tabs1135 may be rotated away fromaperture1109 for window installation, but rotated to extend slightly overaperture1109 to secure thewindow1127 to the receiver.
• Other variations of receivers are illustrated inFIGS. 12A-12C. These receivers include a window that comprises two or more overlapping window sections that are distributed along the length of the aperture over which the window is disposed. Thus, as shown inFIG. 12A,receiver1205 includes areceiver channel1219 that housesabsorber1210.Receiver1205 may also include aroof1231 supported byframe1232, and positioned overreceiver channel1219.Receiver channel1219 comprises first andsecond sidewalls1206 and1207, respectively.Aperture1209 extends between the first and second sidewalls. As shown inFIGS. 12B-12C,window1227 may include overlappingwindow sections1241 that are distributed along alength1218 ofaperture1209. Thus, overlapregions1234 extend along atransverse width1234 ofreceiver channel1219. Windows may be supported and/or secured bywindow support members1211, which may be similar to those window support members illustrated inFIGS. 11A-11E. Any scheme can be used to overlap the window sections to form a window. One scheme of overlapping window sections is illustrated inFIG. 12B. Another scheme is illustrated inFIG. 12C. Combinations of window section overlap schemes may be used in a single window, or in a single receiver.
• Windows may include any suitable number of window sections. For example, a rectangular window having dimensions of approximately 1 meter by approximately 10 meters may comprise5 window sections, each having dimensions of approximately 1 meter by approximately 2 meters. Althoughwindow1227 is depicted inFIGS. 12B and 12C as comprising approximately equivalent window sections, window sections in the same window may be the same or different. Window sections may overlap by any suitable amount, e.g., about 0.5 inch, about 1 inch, or about 2 inches.
• Utilizing a window in a receiver that comprises overlapping window sections may present certain advantages over the use of windows comprising non-overlapping window sections. A joint between window sections that comprises an overlapped regions may not require additional sealing of that joint to prevent leakage in or out through that junction. Also, the friction between overlapping window sections may prevent the migration or “walking” of window sections relative to each other, or to the receiver channel. Such migration of window sections may be caused by vibration within a solar energy collector system and/or by thermal expansion and contraction of one or more receiver components. In addition, overlapping window sections may be able to accommodate expansion and contraction due to thermal cycling of the glass and/or other components in the receiver.
• Solar energy collector systems including such receivers with a window comprising overlapping window sections are also provided. Receivers such as those illustrated in FIGS.12A-12C may be used in combination with first and second reflector fields, as illustrated inFIGS. 1A-1C. The first and second reflector fields may comprise reflectors that each comprise a reflective surface configured to direct incident solar radiation to be at least partially incident on the solar radiation absorber in the receiver. The reflectors may be driven to at least partially track diurnal motion of the sun.
• Some variations of receivers may include other features that accommodate longitudinal thermal expansion. For example, receiver channels may comprise multiple sections that may slide or longitudinally translate relative to each other. Thus, as illustrated inFIG. 13,receiver1305 includesreceiver channel1319.Receiver channel1319 may comprise multiplereceiver channel sections1360 that are distributed along alength1318 ofreceiver channel1319. The receiver channel sections may translate longitudinally with respect to each other to accommodate longitudinal thermal expansion and expansion due to cyclical heating and cooling of one or more receiver elements, e.g., the absorber. The receiver channel sections may be designed to accommodate longitudinal thermal expansion in any suitable manner. For example, as illustrated inFIG. 13, thesections1360 may compriseoverlap regions1361 and be slidably coupled with each other.
• One or more receiver channel sections in a receiver may be supported by a frame. For example, as illustrated inFIG. 13,receiver channels sections1360 may be supported by aframe1320 that may, for example, compriseside rails1307, arched or peakstructural members1330,transverse bridging members1340, and/orspine member1325. One or morereceiver channel sections1360 may be supported byframe1320, e.g., by attaching to any subset or combination ofside rails1307,structural members1330,transverse bridging members1340 andspine member1325. In some variations, one or more receiver channel sections may be suspended from a frame in a manner that accommodates longitudinal expansion and contraction. In these variations, receiver channel sections may be suspended from a frame in any suitable manner. For example,receiver channel section1360′ may be slidably attached acentral bracket1380 that is attached toframe1320. Also illustrated inFIG. 13 isreceiver channel1360“that may be attached byattachment elements1382 to frame1320 near acentral region1381 ofreceiver channel section1360″ to allow longitudinal expansion and contraction.Attachment elements1382 may have any configuration or design, but in some variations, they may comprise a bolt or pin inserted through a slot that is oriented generally parallel to the length of the receiver channel. The bolt or pin may operate to secure the receiver channel, while the slot allows the receiver channel to translate longitudinally. Receivers such as those illustrated inFIG. 13 may include one or more windows that can accommodate longitudinal thermal expansion, such as those illustrated inFIGS. 12A-12C.
• Some variations of receiver channels may comprise one or more expandable elements (not shown) placed between adjacent receiver channel sections. Non-limiting examples of suitable expandable elements include elements with one or more folds that can be at least partially unfolded in the longitudinal direction, such as an accordion-shaped element, a fibrous element, a woven element such as a metal screen or mesh, a spring element, and/or an elastomeric element. Expandable elements, if present between sections of a receiver channel, may be lined with a reflective surface (e.g., a metal coating or a metal foil) to reduce thermal losses and/or to improve the reflection of stray light back to one or more solar absorbers present in the receiver channel.
• Some variations of receivers may comprise multiple receiver sections that are coupled together with expansion joints. Referring back toFIG. 2A, an expansion joint (not shown) may be placed between twoadjacent receiver sections205aofreceiver205. In these variations of receivers, expansion joints may be placed between some, or all, receiver sections. For example, in some variations, groups of three receiver sections each having a length of about 10 meters may be directly coupled together, and an expansion joint may be inserted between the groups of three receiver sections. The expansion joints may allow longitudinal thermal expansion and contraction without stressing the receivers, components of the receivers, and/or support structures for the receivers. One or more expansion joints distributed over an elongated receiver having a total length of about 200 meters to about 400 meters may collectively be able to accommodate at least 3 cm of expansion and contraction, e.g., 5 cm, about 10 cm, about 15 cm, or about 20 cm. Non-limiting examples of suitable expansion joints include bellows-like or accordion-like folded elements (e.g., folded metal elements), foldable mesh elements (e.g., metal mesh elements), and foams.
• Additional receiver designs are provided that may reduce the amount of buildup on a receiver window from external environmental contaminants. The reduced buildup on the windows may lead to receivers that have improved collection efficiencies, longer field lifetimes and/or reduced maintenance requirements. Referring now toFIGS. 14A-14B, areceiver1405 comprises areceiver channel1419 that, in turn, comprises twolongitudinal sidewalls1406 and1407, and alongitudinal aperture1409 disposed between thelongitudinal sidewalls1406 and1407. The sidewalls and the aperture each extend along a length of the receiver channel. The aperture may extend along the entire length of the channel, or along a portion of the length of the channel. Asolar radiation absorber1410 is positioned in thechannel1419. Aroof1431 may be positioned overreceiver channel1419 and supported byframe1425 so that avolume1446 is formed betweenreceiver channel1419 androof1431. Awindow1427 may be disposed in theaperture1409 so that the window and the receiver channel together form alongitudinal cavity1445 that houses thesolar radiation absorber1410.Volume1446 is in fluid communication withcavity1445. Solar radiation incident upon theabsorber1410 is transmitted through theaperture1409, and thewindow1427, if present.
• A junction may be formed between a window and a receiver channel. The junction may be present along one or both longitudinal sides of the receiver channel. For the example shown inFIGS. 14A-14C,junction1439 is present along one longitudinal side ofchannel1419 andjunction1440 is present along the opposing longitudinal side ofchannel1419.Junction1439 is formed whenwindow1427 rests onledge1421 ofwindow support member1411, andjunction1440 is formed whenwindow1427 rests onlower surface1424 ofwindow support member1412.Window support members1411 and1412 may, for example, be similar to those illustrated inFIGS. 11A-11E. Since the cavity housing the solar radiation absorber is at or near ambient pressures, air from the outside environment may leak through one or more junctions between the window and the receiver channel into the cavity, for example, because of convective currents that are generated from the heat generated within the cavity. Air from the environment may carry with it environmental contaminants such as dust and moisture. These contaminants may preferentially coat on the inner window surface, especially if the window is relatively cool compared to the rest of the cavity. Solar radiation transmitted through the window may cause such deposits to be baked on the inner window surface, which may lead to a substantial degradation of the optical quality of the window over time. Thus, it may be desired to inhibit the ingress of air into a cavity housing a solar radiation absorber through a junction between the window and the receiver. As illustrated inFIGS. 14A-14F, this may be accomplished in some instances by configuring a receiver so that a rate of air flow intocavity1419 throughjunction1439 and/orjunction1440 may be slower than a rate of air flow intocavity1445 throughvolume1446.
• Some variations of receivers may comprise a thermally insulatingmaterial1447 disposed in all or a portion ofvolume1446. In these receivers, air traveling throughvolume1446 to reachcavity1445 may contain air contaminants such as dirt and moisture. These contaminants may be at least partially filtered out by the insulatingmaterial1447 before that air contacts theinner surface1451 ofwindow1427. Any suitable insulating material may be disposed in the volume between a roof of the receiver and the receiver channel that permits airflow through the insulating material. For example, fiberglass, glass wool, and/or an open cell foam may be used. Optionally, the insulating material may be at least partially clad with a reflective metal layer to inhibit heat conduction and heat radiation out of thecavity1445. If used, an air-permeable reflective metal layer may be selected, e.g., a perforated metal foil or a metal mesh.
• The passage of air into the cavity housing the absorber through a junction between a receiver channel and a window may be inhibited relative to the passage of air into the cavity through the volume above the receiver channel using any suitable scheme. For example, in some variations, a sealing member may be positioned in a junction between a window and a receiver channel.FIG. 14B shows an expanded view ofjunction1439 betweenwindow1427 andreceiver channel1419. In the example shown there, a sealingmember1453 is positioned betweenwindow1427 andledge1421 ofwindow support member1411. An analogous sealing member (not shown) may be positioned betweenslot surface1424 andwindow1427. Such sealing members may be any suitable sealing members. For example, sealing members may be selected that maintain their sealing function while still allowing the window to move longitudinally (e.g., slide) relative to the receiver channel to accommodate differential thermal expansion and contraction between the window and the receiver channel. One example of such a sealing member that may be used is a fiberglass rope that is laid longitudinally alongledge1421 orslot surface1424. The rope may have any suitable diameter, e.g., about 10 mm, or about 15 mm, or about 20 mm. The window may slide longitudinally with respect to the receiver channel as the fiberglass rope may slide relative to the window surface and or receiver surface against which it is pressed. In other variations, a low-outgassing elastomer may be used as a sealing member. The elastomer may stretch to allow the window to move longitudinally relative to the receiver channel while still maintaining a seal between the window and the receiver channel. Elastomers having low out-gassing properties may be used to reduce the probability that contaminants from the elastomer will be deposited on a window surface as the elastomer is heated. In some variations of receivers, spring tabs may be used to force the window against the sealing member.
• Alternatively, or in addition to using a sealing member in a junction between a window and a receiver channel, a positive pressure of filtered or otherwise purified air may be supplied into the cavity to inhibit the ingress of external air into the cavity. For example, dry nitrogen, or purified air that has been passed over a desiccant and/or through a filter (e.g., a particle filter) may be flowed into the cavity to inhibit ingress of external air into the cavity. As illustrated inFIG. 14C, such air flow may be provided near theinner surface1451 throughinlet1482, e.g., to provide clean air flow, which may be laminar flow, near theinner surface1451.
• In some variations of arrays, filtered air may be directed into a receiver through a supporting structure. Referring now toFIG. 14F,receiver1455 is supported bystructure1465.Support structure1465 may comprise at least one tubular region that is capable of piping filtered air toreceiver1455. For example, the interior of ahollow leg1466 may be used to channel air from the ground toelevated receiver1455. In these examples, a blower on the ground (not shown) may be configured to force air throughhollow leg1466, throughfilter1468, and intoreceiver1455 viaflexible connection1469.
• In other variations of receivers, an air path through the insulating material may be facilitated to cause air flow to preferentially enter the cavity through the insulating material rather than through the junction between the window and the receiver channel. For example, a rate of air flow through the insulating material may be greater than a rate of air flow through the junction between the window and the receiver channel. The rate of air flow through the insulating material may be increased in any suitable manner. For example, as illustrated in FIG.14A, vents1483 may be provided inroof1431 or in a region of an end cap (not shown) that is configured to cover the transverse end ofvolume1446.Vents1483 inroof1431 may be covered vents, and/or positioned to the sides ofroof1431 to reduce the amount of moisture and dust that may enter through the vents.
• Non-limiting variations of various vent configurations are illustrated inFIGS. 14D-14E. In the example shown inFIG. 14D,roof1486 ofreceiver1485 comprises avent structure1490 that comprises asingle opening1492 with acover1491. Thecover1491 is positioned over and vertically spaced above theopening1492 to allow airflow through the opening while reducing the ingress of environmental contaminants. In these variations, the opening149’may, for example, be located near the peak ofroof1431′ to increase air flow through thevent structure1490. Referring now to the example shown inFIG. 14E,receiver1484 comprises anair passage1496 that provides air flow under aroof edge1497, e.g., betweenroof1483 andreceiver channel1482.Air passage1496 may extend continuously along the length of the receiver, or may comprise multiple air passages distributed along the length of the receiver under theroof edge1497.Air passages1496 may be present along one or both roof edges1497.
• Additional variations of receivers are provided here. These receivers comprise a roof extending along a length of the receiver channel. Some roofs may have corrugations extending longitudinally along a length of the roof, e.g., roofs formed from corrugated metal sheets. Another variation of a roof may have a transverse cross-section that forms a smooth outer surface with a concave surface facing the channel and a solar radiation absorber housed in the channel. The transverse cross-section of the roof may have profile that generally follows a parabola, an arc of a circle or an ellipse, or may have a peaked profile, or any other smooth surface that is generally without horizontal surfaces or crevices or other features that may trap or retain environmental debris. A roof having a smooth outer surface may also have a reduced wind profile. The structure of the roof, including its cross-sectional profile, may be selected to impart increased strength and/or rigidity (e.g., longitudinal stability) to the receiver. For example, a roof having a parabolic profile or a profile following an arc of a circle or an ellipse may impart longitudinal rigidity to an elongated receiver to reduce bending and/or torsion. The roof is configured to shed environmental debris (e.g., dust, dirt, and/or moisture) away from the window. In some variations, the roof may be configured to shed environmental debris below a junction between the window and the receiver channel.
• Referring now toFIG. 15,receiver1505 includesreceiver channel1519.Roof1531 is positioned overreceiver channel1519, so that it has aconcave surface1532 facing thereceiver channel1519 that housessolar absorber1510. The profile ofroof1531 is smooth, comprising no significant horizontal ledges, crevices, or other features that may trap or retain environmental debris. In this variation of a receiver, awindow1527 is disposed in theaperture1509 betweensidewalls1506 and1507 ofreceiver channel1519. Thewindow1527forms junctions1539 and5140 withreceiver channel1519. Such junctions may, for example, be formed between a window and a window support member similar to any of those illustrated inFIGS. 11A-E.Roof1531 may be supported onframe1533. Theroof1531 may be attached toframe1533 in any suitable manner, e.g., by welding, bolting, riveting, and/or with the use of adhesive. In this variation, theroof1531 extends below junction1426 to enable the roof to shed environmental debris away from the window. In addition, in this variation,roof1531 is designed so that moisture and other contaminants do not collect on anedges1567 or on aninner surface1569 ofroof1531. In this variation,end sections1571 ofroof1531 are curled inward and upward so that moisture and contaminants are shed away fromedges1567, to increase the barrier for any external contaminants to reach theinner surface1569, and to shed external environmental debris away from either aninner surface1573 orouter surface1575 ofwindow1527. In some variations of receivers, a protective coating such as a plastic or rubber coating that can resist water, UV, ozone, and/or other environmental exposures may be added to the external surface of a roof. For example, a rubber sheet made of EPDM rubber (ethylene propylene diene monomer rubber) may be used. However, a roof such as that illustrated inFIG. 15 may demonstrate reduced or slowed corrosion effects to increase the lifetime of the roof, even without additional protective coatings (such as rubber coatings). Increased durability of a receiver roof may, in turn, increase the lifetime of a receiver in the field.
• Any suitable material or combination of materials may be used for receiver roofs. For example, a metal sheeting material may be used, such as steel, or a galvanized metal sheet. Curved or peaked metal sheets formed into roofs may provide a roofs with smooth, downward-sloping surfaces capable of shedding environmental debris away from the window, and may also impart longitudinal stability to the receiver, e.g., by resisting longitudinal bending and/or torsion. Other variations may include roofs at least partially formed from plastics, e.g., reinforced lightweight composites that have properties to withstand continuous UV exposure and high temperatures experienced by the receivers. In some variations, the roofs may comprise an additional layer such as a rubber layer that may provide enhanced water, dust, and/or UV resistance.
• As described above, the receivers in thermal solar energy collector systems such as LFR solar arrays may comprise a plurality of solar absorber tubes that are configured to absorb incident solar radiation and to transfer energy from the solar radiation to a heat exchange fluid (e.g., water and steam) carried by the tubes. Because the temperature of the solar absorber tubes may vary dramatically over the course of a day with the movement of the sun, the tubes expand, contract and move. In some receivers, movement of tubes relative to each other may be accommodated to maintain inter-tube spacings, and/or to reduce damage or stress in the tubes and/or associated structures. Referring now toFIGS. 16A-16B,receiver1605 comprises asolar absorber1610 that, in turn, comprises a plurality of generallyparallel tubes1611 arranged lengthwise in the receiver. Theabsorber1610 is housed within alongitudinal cavity1645 formed betweenreceiver channel1619 andwindow1627. Althoughwindow1627 is depicted as curved, it may also be flat. For example, these receivers may comprise any combination or subset of windows, window support members, and/or receiver channels as discussed here.Receiver channel1619 comprises sidewalls1606 and1607, which may be outwardly flaring. Aframe1632 supportsabsorber1610. In certain variations,frame1632 may comprise an archedstructural member1632, atransverse bridging member1648, and/orside rails1649 to provide structural support for receiver components. Aroof1635 may be positioned overreceiver channel1619 and supported byframe1632. Althoughroof1635 is illustrated in this example as a corrugated roof (e.g., a corrugated metal roof) comprising corrugations extending along the length of the receiver, other variations may include smooth roofs, similar to those illustrated inFIG. 15. Thevolume1646 formed betweenroof1635 andreceiver channel1619 may comprise a thermally insulatingmaterial1647. Optionally, the insulating material may be clad with a reflective metal layer to inhibit heat conduction and heat radiation out of thecavity1645.
• The number and/or dimensions of absorber pipes or tubes in an absorber may be selected for specific system requirements. However, it is generally desired that each absorber tube have a diameter that is small relative to a cross-sectional dimension of the aperture of the receiver channel (e.g., aperture1609 inreceiver channel1619 inFIG. 16A) so that plurality of absorber tubes may approximate a flat plate absorber surface, as opposed to a single tube collector positioned within a radiation-concentrating trough. For example, a ratio of the diameter of the absorber tube to a cross-sectional dimension of a receiver channel aperture may range from about 0.01: 1.00 to about 0.1: 1.00. Each absorber tube may have an outside diameter of about 25 mm to about 160 mm. An absorber may comprise about 6 to about 30 absorber tubes arranged side-by-side within the receiver channel. By positioning absorber tubes within a receiver channel so that only the underside of the absorber tubes is illuminated, reduced heat emission from the non-illuminated top side may result, which may increase energy efficiency. Moreover, since the water in the tubes is below a steam level, this arrangement causes the desired result of concentrating the incident light on the portion of the tube containing water rather than steam. Additional, non-limiting examples of absorber configurations are provided in International Patent Application Number PCT/AU2005/000208, which has already been incorporated by reference in its entirety.
• Individual absorber tubes may or may not be spaced apart by one or more spacers. In some variations, tubes may be spaced together as closely as possible, e.g., touching or with small intervening (not necessarily fixed) gaps of about 1 mm to about 4 mm, e.g., about 2 mm, or about 3 mm. In other variations, spacers may be used to provide or maintain spacings between at least some, but not necessarily all, adjacent ones of the plurality of tubes while accommodating thermal expansion, contraction, and movement. Referring again toFIGS. 16A-16B,spacers1612 may be provided betweenabsorber tubes1611.Spacers1612 may be selected in any suitable manner to provide or maintain space between adjacent absorber tubes. Theabsorber tubes1611 may be supported below by one or a series ofrollers1655 that each extend transversely betweensidewalls1656.Rollers1655 may be coupled to sidewalls1656 throughfittings1657 that allow rotational movement.Spacers1612 may, for example, be disk-shaped spacers that may rotate with respect torollers1655. Additional examples of inter-tube spacings and roller configurations to support absorber tubes are provided below.
• In some variations of receivers, absorber tubes may be coated with a solar absorptive coating. The coating may comprise, for example, a solar spectrally selective surface coating that remains stable under high temperature conditions in ambient air, for example, a black paint that is stable in air under high-temperature conditions. Non-limiting examples of solar spectrally selective coatings are disclosed in U.S. Pat. Nos. 6,632,542 and 6,783,653, each of which is incorporated herein by reference in its entirety.
• To increase the collection efficiency of a receiver, the amount of light leaking past or between absorber tubes may be reduced. In addition, relatively uniform irradiation of absorber tubes may be desired, e.g., to reduce the formation of hot spots which may lead to inefficient energy conversion. Referring now toFIGS. 17A-17B, one variation of a solarenergy collector system1700 may comprise asolar radiation absorber1710 that comprises a plurality ofabsorber tubes1711, and afirst reflector1717.First reflector1717 may be configured to reflect incidentsolar radiation1713 to afirst absorber tube1711′ inabsorber1710. Asecond reflector1718 may be configured to reflect incidentsolar radiation1713 to asecond absorber tube1711″ inabsorber1710.Reflectors1717 and1718 may each be part of a reflector row or reflector row segment in a reflector field.Reflectors1717 and1718 may be part of different reflector fields, e.g.,reflector1717 may be part of a first reflector field andreflector1718 may be part of a second reflector field, orreflectors1717 and1718 may be part of the same reflector field. Thereceiver1705 may include anelongated receiver channel1719, with anaperture1709 extending transversely between receiver channel sidewalls. Optionally, thereceiver1705 may comprisewindow support members1720 and1721 extending along opposite sides ofaperture1709. Window support members may, for example, be similar to those discussed in connection withFIGS. 11A-11E.
• So that light does not leak past the outer circumferential edges of thefirst absorber tube1711′,first reflector1717 may be oriented so that itsouter edge1716 is aligned with a tangent extending from outercircumferential edge1714′ offirst absorber tube1711′. Similarly,second reflector1718 may be oriented so that itsouter edge1722 is aligned with a tangent extending from outercircumferential edge1714″ ofsecond absorber tube1711″. Angle α indicates approximately the largest angle of incidence (relative to normal1790) for a ray directed fromfirst reflector1717 tofirst absorber tube1711′, and angle β indicates approximately the largest angle of incidence for a ray directed fromsecond reflector1718 tosecond absorber tube1711″.
• Referring nowFIG. 17B, spaces (e.g., spaces A₁-A₃) may be provided between adjacent absorber tubes in a receiver to accommodate relative thermal expansion and/or movement of the absorber tubes. To reduce or minimize the amount of solar radiation directed and lost through the inter-tube spacing, the spacing between absorber tubes may be set as shown inFIG. 17B. The absorber tubes may be spaced apart by setting the spacing (e.g., with a spacer) between absorber tubes such that an inner edge of a reflector that is closest to the receiver (e.g., inner edge1724 of reflector1717) is aligned withtangents1780 to outercircumferential edges1714 ofreceiver tubes1711. Spacings A₁-A₃result, where the spacings refer to a distance between the outermost points of adjacent absorber tubes. The use of such inter-tube spacings may allow tubes to be spaced apart without significantly reducing collection efficiency. If the inner edge of a reflector or reflector row on each side of the receiver is positioned the same distance from the receiver, this method of setting inter-tube spacings will result in spaces between absorber tubes that vary, with spaces between outer absorber tubes smaller than those between inner absorber tubes. Once the inter-tube spacings are set, such spacings may be maintained with spacers. For example, spacers similar to those illustrated inFIGS. 16A-16B may be used. In some variations, the inter-tube spacings may be simplified by using a uniform inter-tube spacing equal to the smallest such spacing determined by the method illustrated inFIG. 17B for some or all adjacent pairs of absorber tubes.
• Improved receivers may be designed to reduce the number and/or effectiveness of thermal conduction paths (i.e., thermal shorts) between the cavity housing the solar radiation absorber and other structures in the receiver. Reducing thermal shorts may increase solar collection efficiencies of a receiver or of a solar energy collection system comprising such a receiver, e.g., by about 2%, about 3%, about 5%, or even more. Referring now toFIGS. 18A-18C,receiver1805 comprisesreceiver channel1819 that houses a solar radiation absorber (not shown) in anelongated cavity1820. The solar radiation absorber may be supported by anabsorber support1849. Theabsorber support1849 andreceiver channel1819 may each be coupled toframe1808.Frame1808 may, in some variations, comprise archedstructural member1850 andtransverse bridging member1851. Spaces and/or thermally insulating standoffs may be inserted between thereceiver channel1819 andframe1808, and/or between theabsorber support1849 andframe1808 to reduce or interrupt thermal conduction pathways.101461FIG. 18B shows an expanded view of a junction betweenabsorber support1849 andtransverse bridging member1851 offrame1808. Aspace1860 is provided betweenreceiver channel1819 andtransverse bridging member1851. Thespace1860 interrupts thermal conduction paths between thereceiver channel1819 and theframe1808, and between theabsorber support1849 and theframe1808 by reducing or eliminating surface area contact with the frame. Further, any thermal path between the structures of the thermal cavity and the frame viaconnection bolt1870 between theframe1808 and theabsorber support1849 may be reduced, e.g., by providing a thermally insulatingwasher1871 betweenbolt1870 andabsorber support1849, and/or coating the bolt or the orifices through which the bolt extends with an insulating material. Although not shown inFIG. 18B, thermally insulating standoffs, such as ⅛″ thick fiberglass tape, may be provided inspace1860.
• Other types of thermal separation members may be used between metal structures in a receiver to reduce heat conduction away from the receiver channel. For example,FIG. 18C provides an expanded view of an interconnection region betweenreceiver channel1819 andframe1808 nearwindow support member1821. As shown there, the contact area between thereceiver channel1819 and the frame may be reduced by supportingreceiver channel1819 on a set of spaced-apart thermal separation members1888 (e.g., brackets) that are distributed along a length of an interconnection region between the receiver and the frame. In some variations,thermal separation members1888 may be metal. In other variations, thermal separation members may be at least partially formed from thermally insulating materials, thereby improving the degree of thermal isolation betweenframe1808 andreceiver channel1819. Although not shown in detail inFIGS. 18A-18C, analogous thermal separation members may be used betweenreceiver channel1819 and the opposite side offrame1808, near window support member1822.
• Thermal separation members may have any suitable dimensions that can effectively reduce or interrupt thermal contact, e.g., by reducing or eliminating the contact area between two thermally conductive (e.g., metal) surfaces. Any suitable thermal separation members may be used. As discussed above in connection withFIG. 18C, thermal separation members may be thermally conductive in some instances, as long as they reduce thermal contact. In other cases, thermal separation members may be at least partially formed from a thermally insulating material. Non-limiting examples of thermally insulating materials include paints, polymeric coatings, rubbers, composites, insulating tape, glasses, and ceramics. For example, insulating tape (e.g., fiberglass tape) having a thickness of about 1 mm or less, e.g., about 0.5 mm or less, or about 0.3 mm or less, may be used between the absorber support and the frame, and/or between the receiver channel and the frame. Other steps may be taken to further reduce thermal shorts between structural components in a receiver to increase collection efficiency. For example, screws, rivets, or clamps that secure components to the absorber or to the receiver channel may be selected to have reduced thermal conductivities, or thermally insulating coatings may be provided on such screws, rivets, and/or clamps.
• As indicated above, for example, in connection withFIGS. 16A-16B, solar radiation absorber tubes may be supported by one or more rollers extending transversely across a receiver channel. The one or more rollers turn as the tubes expand and contract longitudinally, thereby allowing continuous support of the tubes. To reduce the amount of energy required to turn the rollers, hollow rollers may be used. However, hollow rollers may not have sufficient strength across their transverse span to support the tubes and the heat exchange fluid flowing through the tubes.
• In some variations of receivers, rollers for supporting heat exchange-fluid tubes may be designed that required a reduced amount of energy to turn. Examples of such rollers are illustrated inFIGS. 19A-19B. There,receiver1905 includesabsorber1910 that comprisesabsorber tubes1911 supported byroller1902.Roller1902 comprises anouter cylinder1903 and aninner shaft1904. Theouter cylinder1903 may be supported oninner shaft1904 at eachend1907 bybushings1906. Pins1930 (e.g., cotter pins) may be used to secureroller1902 betweenside walls1915. Theinner shaft1904 may be a solid rod, or a nearly solid rod. Thus, the innercentral shaft1904 may provideroller1902 with sufficient transverse strength to supporttubes1911, and thehollow cylinder1903 that contacts thetubes1911 can rotate freely frominner shaft1904, and can thus turn with less energy astubes1911 expand and contract longitudinally. Reduced friction betweentubes1911 androller1902 may also reducefrictional damage tubes1911, e.g., to an absorptive coating applied the exterior of the tubes.
• In some variations of rollers such as those illustrated inFIGS. 19A-19B, a ratio between a diameter of an outer cylindrical member supported on an inner central shaft may be about 2, or about 3, or about 4, or even higher, e.g., about 5. An inner shaft may have a diameter of about ¼″, SO that an outer diameter of an outer cylinder supported on the inner shaft may be between about 0.5″ and 1.5″, e.g., about 1″. In some variations, outer cylinders may have an outer diameter of about 1″, and an inner diameter of about ¼″. Bushings may have anysuitable width1980 to support a hollow cylinder on central shaft. For a receiver having a width of about 1.3 meters, about 10 parallel absorber tubes each having outer diameters of about 2″ may be supported on a series of rollers spaced longitudinally apart by about 8 feet. In this series of rollers, a hollow cylinder having an inner diameter of about ¼″ cm may be supported on a central shaft having an outer diameter of about ¼″, where about 0.5″ wide bushings may provide the ½″ standoff distance between the outer diameter of the central shaft and the inner diameter of the hollow cylinder are used at both ends, and allow the hollow cylinder to rotate independently of the shaft.
• Variations of receivers may include one or more sets of coaxial, independently rotating rollers to support a group of absorber tubes. These designs may accommodate differential thermal expansion between absorber tubes to reduce friction between the tubes and the roller. An example of such a receiver is illustrated inFIGS. 19C-19D. There,receiver1955 comprises anabsorber1960 that comprises a plurality ofabsorber tubes1961. In this variation, the plurality of absorber tubes is supported by a coaxial set ofrollers1952. In this particular example, the coaxial roller set is designed so that eachabsorber tube1961 is supported by anindividual roller1952 that rotates aboutaxle1953. However, as discussed below, an individual roller in a coaxial roller set may support more than one absorber tube, e.g., a pair or a group of absorber tubes. Eachindividual roller1952 can rotate independently to accommodate relative expansion betweenindividual absorber tubes1961. Theindividual rollers1952 may each have a profiledcross section1954 to keep each absorber tube aligned with its corresponding roller, and to keep the tubes spaced apart.Rollers1952 may be secured betweenside walls1965 by pins1979 (e.g., cotter pins). Optionally, a spacer (e.g., suspended fromframe1968, similar to side walls1965) may be placed between adjacent ones of the individual rollers in coaxial roller sets. In some variations,individual rollers1952 may be hollow, e.g., similar to those illustrated inFIGS. 19A-19B. Variations of coaxial individual roller designs may, for example, comprise individual rollers for pairs of adjacent tubes, or other groupings of adjacent absorber tubes. For example, in some variations, relatively cold inlet tubes may be placed on the outer edges of an absorber, while relatively hot tubes are placed in the central region of the absorber. In those variations, each of the outer relatively cold inlet tubes may have an individual roller, whereas a group of central relatively hot tubes may be supported by a common roller. Receivers may comprise a series of such sets of individual coaxial rollers, where the sets of coaxial rollers are distributed along the length of a receiver. Receivers incorporating roller designs or roller configurations that combine variations of rollers described here (e.g., inFIGS. 16A-16B andFIGS. 19A-19D) and/or other rollers known in the art or later developed may also be used.
• Variations of absorbers for use in receivers of solar arrays are provided here that can accommodate longitudinal thermal expansion of absorber tubes and/or increase the efficiency of energy conversion between incident solar radiation and a heat exchange fluid. Examples of such absorbers are illustrated inFIGS. 20A-20D. There,solar array2000 comprises anelevated receiver2005 and reflectors (not shown) that may be arranged in reflector rows that are parallel toreceiver2005. The reflectors may be rotated via reflector supports2003 to at least partially track diurnal motion of the sun. Although reflector supports2003 are illustrated as having hoop-like frames inFIGS. 20-20D, any suitable reflector supports as described herein, known in the art, or later developed may be used. Asolar radiation absorber2010 inreceiver2005 may comprise a plurality ofabsorber tubes2011 that can absorb solar radiation and transfer heat to a heat exchange fluid carried within the absorber tubes. An input/output header2012 controls the flow of heat exchange fluid to and from the plurality oftubes2011. A turnaround header (shown inFIGS. 20E and 20F) may be positioned at the opposite end ofreceiver2005 and may, for example, comprise a turnaround section for eachtube2011.
• Pipes may be arranged to reduce heat loss from pipes containing relatively hot fluid, and to accommodate the difference in temperature between incoming and outgoing heat exchange fluid. For example, in some instances an input/output header may be divided into an input section and an output section to accommodate the differential thermal expansion between these two classes of pipes. Referring now to the example illustrated inFIG. 20B, the input/output header2012 comprises two sections, aninlet section2014 and anoutlet section2016. Theinlet section2014 may be connected to a fluid source (e.g., water) viaflange2018, and theoutlet section2016 may be connected viaflange2019 to a reservoir (not shown) to store heated fluid. The inlet and outlet sections may comprise any suitable number of inlets and outlets, respectively. For the example shown inFIG. 20B,inlet section2014 comprises twoinlets2015. Although theoutlet section2016 is illustrated as having8outlets2017 inFIG. 20B, other variations may comprise 4 to 18 outlets. Furthermore, theinlet tubes2011′ that are fed viainlets2015 may be located on or near the outer edges of the group oftubes2011 that extend in and out ofreceiver2005.Outlet tubes2011″ that are connected tooutlets2017 to recirculate or release relatively hot heat exchange fluid may be located in an inner region of the group oftubes2011. Thus, colder incoming heat exchange fluid is confined to the outer periphery of absorber, and heated fluid remains near the inner core of the absorber, thereby reducing heat losses from the heated fluid.
• Solar absorbers may comprise any combination of a variety of features to accommodate tube thermal expansion, and in particular, differential thermal expansion and contraction of the tubes along the length of the receiver. Some solar absorbers may comprise a moveable header (e.g., an input/output header and/or a turnaround header). These headers comprise at least a section or portion that can move to accommodate tube thermal expansion. Alternatively, or in addition, solar absorbers may comprise a header manifold that comprises first and second header sections, where the first header section is configured to move independently of the second header section. For example, in the variation illustrated inFIGS. 20A-20F, input/output manifold2012 may float in at least one direction so that it is free to translate in that direction astubes2011 expand and contract. Further, the input/output manifold2012 comprises aninlet section2014 and anoutlet section2016, and the inlet and outlet sections can move independently of each other. Variations of solar absorbers may also comprise one or more flexible joints and/or flexible pipe interconnections to accommodate thermal expansion.
• Some absorbers may comprise pipe configurations or tube structures extending beyond the receiver body that can accommodate differential thermal expansion and contraction. Such pipe configurations or tube structures may, for example, comprise one or more bends that may expand, contract, and/or twist to accommodate pipe length changes. One example of such a tube structure is one that comprises two or more bends between an input/out header manifold and the receiver, where at least two of the two or more bends are not in the same plane as each other. For example, two bends may be in planes that are approximately orthogonal to each other. In these variations, the expansion of the pipe may lead to torsional movement via expansion through the two bends that reduces stress on the pipe and/or pipe joints. Referring again toFIGS. 20A-20D,tubes2011 each comprise afirst bend2022 and asecond bend2024 between the input/output header manifold2012 and thereceiver2005. In this example,first bend2022 is not coplanar with respect tosecond bend2024.FIGS. 20C-20D show that bend2022 is in a first plane that is approximately orthogonal to a secondplane containing bend2024. A dashedline2026 indicates that asbends2022 and2024 thermally expand, an overall torsional movement of one ormore tubes2011 may result to accommodate extensive thermal expansion in the one or more tubes while reducing stress on tubes and tube joints.
• As stated above, absorbers may comprise one or more turnaround headers located at the opposite end of the receiver from the input/output header. Steam and water flowing from the input/output header to the opposite end of the receiver may enter a turnaround header and exit the turnaround header to flow back toward the input/output header. For example, the variation of thesolar radiation absorber2010 illustrated inFIGS. 20A-20D may comprise aturnaround header2060 as illustrated inFIGS. 20E and 20F. There,turnaround header2060 comprises aturnaround volume2061. As illustrated in this example,turnaround volume2061 may be a cylindrically shaped volume. Although the ends ofvolume2061 are shown as uncapped for purposes of illustration, in operation bothflanges2062 are capped by end plates (not shown). Steam and water may enter theturnaround volume2061 through peripherally-locatedinlet tubes2011′, and may exit theturnaround volume2061 through centrally-locatedoutlet tubes2011″. In some variations, one or more tube bends feeding into a turnaround header may comprise one or more flexible joints. The turnaround header may be supported in the receiver in such a way that the turnaround header may move (e.g., translate longitudinally) to accommodate thermal expansion and contraction of the tubes. In other variations, the turnaround header may be fixed in position. In the latter variations, thermal expansion and contraction of the tubes may be accommodated, for example, by other means as described herein.
• In some variations of absorbers, all pipes are connected to an input/output header via tube structures as illustrated inFIGS. 20A-20D. In other variations, only some absorber tubes, or one absorber tube, may be coupled to an input/output header using such tube structures. Absorbers comprising any combination of the thermal expansion capabilities that are illustrated inFIGS. 20A-20F, e.g., moveable header manifolds, manifolds comprising multiple sections that are configured to move relative to each other, and pipe bend configurations to accommodate expansion, known in the art, or later developed, are contemplated. Further, absorbers comprising any combination of these thermal expansion capabilities may be used in combination with any receiver or array described herein, known in the art, or later developed.
• Header manifolds and/or tubes may comprise additional features to control the flow between absorber tubes. If the level of a heat exchange fluid in an absorber tube becomes too low, a thermal runaway situation may result causing decreased performance and/or damage to a receiver. For example, if water is being used as a heat exchange fluid, and the level of water in a tube is too low, the steam-water ratio may be increased, which, in turn, may lead to an increased pressure drop in that tube. A localized increased pressure drop in an absorber tube will cause the steam-water ratio in that tube to increase even more, leading to a thermal runaway situation in which that absorber tube may eventually become dry. To avoid a thermal runaway situation and resulting dry absorber tubes, an arrangement of solar absorber tubes making up a solar absorber may be provided in which the pressure drops across all tubes are maintained to be relatively constant. If the pressure drops across all tubes are maintained to be relatively constant, then the water flow down each tube will be approximately the same.
• If the pressure drop across each absorber tube is dominated by the pressure drop at a tube orifice (e.g., an end orifice), other smaller pressure drops along a tube (e.g., due to local turbulence and/or local heating) may not cause significant fluctuations in pressure drop in that tube. For example, one or more flow control elements may be inserted in one or more tube orifices to control the pressure drop therein. Some flow control elements may, for example, cause a pressure drop in a tube that is about 40%, about 50%, or about 60% of the total pressure drop across the pipe from its turnaround point to its outlet. Flow control elements may be inserted at any suitable position along the pipes. For example, in some cases, flow control elements may be inserted in a turnaround header, e.g., to control the flow of fluid exiting the turnaround header to return to an input/output header. Referring back toFIGS. 20E and 20F, flow control elements (not shown) may be attached to one or more tube ends oftubes2011″ that penetrateheader2060 to reachturnaround volume2061.
• Flow control elements may have any suitable configuration. For example, as illustrated inFIG. 20G, flow through pipe ortube2051 may be restricted by attaching aremovable flange2053 with a reduced size orifice2054 (as compared to theinner diameter2055 of pipe2051) to endflange2051.Reduced size orifice2054 may represent a single orifice, or a group of smaller orifices, e.g., perforations. In other variations, flow control elements may comprise a permanently affixed flange comprising one or more reduced-size orifices. In still other variations, as illustrated inFIG. 201, aflow control element2056 coupled to anend flange2057 ofpipe2058 may be conical and have one or more reduced-size orifices2059 as compared to aninner diameter2060 ofpipe2058. Some variations of flow control elements may be affixed to a pipe by threading onto a threaded end of the pipe. For example,pipe2061 inFIG. 20H comprises a threadedend2064.Insert2062 may be threaded ontopipe2061 to provide a reduceddiameter orifice2063 forpipe2061.
• In receivers comprising a plurality of solar radiation absorber tubes for carrying a heat exchange fluid, fluid flow through the tubes may be designed to reduce heat losses from the tubes. Thus, as described in International Patent Application Number PCT/AU2005/000208, which has already been incorporated by reference herein in its entirety, absorber tubes containing relatively high fluid temperatures may be positioned near the interior of an arrangement of parallel tubes making up a solar absorber, and correspondingly, tubes containing the coldest fluid may be positioned toward the periphery of the arrangement of parallel tubes. In some variations of receivers, fluid flow through absorber tubes may be in unidirectional streams. Other fluid flow arrangements may be used.
• FIGS. 21A-21C illustrate various arrangements of flow patterns of heat exchange fluid through solar absorber tubes that may be used to reduce heat losses and increase the overall collection efficiency of a receiver.FIG. 21A illustrates diagrammatically one flow control arrangement for a plurality of solar absorber tubes. There,receiver2105 comprises multipleinterconnected receiver structures2105a.Each of thefluid lines2111A,2111B,2111C, and2111D is representative of four absorber tubes inreceiver2105. Junction points2173 indicate joints, interconnections, or valves between tubes or tube sections. In-flowing heat exchange fluid is first directed alongforward input line2111A, then alongreturn line2111B, then alongforward line2111C, and finally along and fromreturn line2111D. This fluid flow pattern between absorber tubes results in colder fluid being directed through tubes that are near or around the periphery ofreceiver2105, whereas heated fluid travels through an inner core region ofreceiver2105. In some variations, aflow control device2139, e.g., a manifold, may be used for selective control over the flow of heat exchange fluid. For example, avalve manifold2114 may be used to selectively open orclose fluid paths2111A-2111D.
• Alternative fluid flow patterns may be used to meet fluctuating load demands and/or adjust for prevailing ambient conditions. For example, selected ones of absorber tubes in a receiver or receiver structure may be closed. InFIG. 21B, tubes corresponding tofluid paths2111A and2111B are closed, so that all fluid flows through tubes corresponding tofluid paths2111C and2111D. InFIG. 21C, tubes corresponding tofluid paths2111C and2111D are closed, so that all fluid flows through tubes corresponding tofluid paths2111A and2111B.
• Any suitable method or scheme may be used to install an elevated receiver above one or more reflector fields. For example, a series of vertical support structures may be anchored to the ground similar tovertical support structures218 shown inFIG. 2A, and an elongated receiver may be lifted with a crane and installed into the vertical support structures. As discussed above, an elongated receiver may comprise multiple receiver structures. The receiver structures may be elevated individually, and coupled together to form an elongated receiver after they have been installed onto vertical support structures. Alternatively, receiver structures may be at least partially coupled together before being elevated. Frames of the receiver structures may be coupled together with mating flanges, for example, and absorbers in receiver structures may be coupled together with pipe fittings, e.g., flexible pipe fittings. Roofs may be installed onto a receiver before or after coupling multiple receiver structures together to form an elongated receiver, and before or after elevating to an installed position. In some variations, it may be desirable to install a roof, e.g., a roof formed of curved sheet metal similar to that depicted inFIG. 15, after multiple receiver sections have been coupled together to form an elongated receiver. This may eliminate seams in the roof, or reduce the number of seams in the roof, and may impart greater longitudinal stability to the receiver, e.g., to prevent bending and/or torsion. Windows may be installed into receivers or receiver structures before or after elevating to an installed vertical receiver position.
• In some situations, it may be desirable to reduce or eliminate the number of aerial welds or other aerial assembly steps that must be performed. In those instances, the receiver may be partially or entirely assembled on the ground and then elevated in its assembled (e.g., welded) form. To avoid or minimize crane use, one or more vertical support structures that may eventually be used support the elevated receiver during array operation may also be used to elevate a receiver. Referring now toFIG. 31A,solar array3100 is illustrated during construction.Array3100 comprises two longitudinally extendingreflector arrays3110. A series ofvertical support structures3101 are each anchored to the ground overelongated receiver3105 and distributed along the length of the receiver. Thereceiver3105 may be at least partially assembled (e.g., welded and/or bolted together) on or near the ground (e.g., on a stand). Manual, motorized, gravity-aided, or spring-aidedhoists3102 that are attached tovertical support structures3101 may be used to elevate the receiver to its installed position. For example, a hoist that lifts from above may be attached at or near a peak or uppermost portion of a vertical support structure (e.g., peak3103 inFIG. 31A). As used herein, “hoist” is meant to encompass any type of lifting structure, e.g., one or more cables and pulleys, a dumb-waiter arrangement, a spring or a spring-loaded lift, a counterweight, a ratchet, a winch, an expandable lift, and the like. Hoists may lift a receiver from above, or from below. Thevertical support structures3101 may then support the receiver in its installed position during operation of the array.
• In some variations, these vertical support structures may comprise one or mounting members to support a receiver. Mounting members may have any suitable configuration, e.g., shelves, hooks, cross-bars, and the like. For example,vertical support structure3101 inFIG. 31A comprises anopen shelf3106 that comprises comprising two longitudinally-extendingledges3104. There,receiver3105 may be supported byshelf3106 with a reduced amount of blockage to an aperture located on the underside ofreceiver3105. To avoid stressing the receiver during the elevation process, the operation of multiple hoists elevating the receiver may be coordinated or synchronized. Hoists may be removed from vertical support structures once receivers are installed.
• Some arrays may comprise variations of vertical support structures that have graded leg thicknesses to reduce shading of reflectors by upper portions of the legs. Referring now toFIG. 31B,vertical support structure3130 haslegs3131 that comprise a relativelythick base portion3132 and a thinnerupper post portion3133. The base portion may have a diameter that is about 50% thicker than that of the post portion. For example, base portions may have diameters of about 6″, and post portions may have diameters of about 4″. In some variations, base portions may comprise about 30%, about 40%, about 50%, about 60%, or about 70% of a total leg length. Such leg configurations may provide adequate strength and rigidity to support elevated receivers, while reducing the amount of shading on the surrounding reflector arrays. A hoist may be mounted tovertical support structure3130 to enable elevation of a receiver, as shown inFIG. 31A.
• Althoughvertical support structures3101 inFIGS. 31A-31B are illustrated as A-shaped supports each having a vertex or peak3103, other variations of vertical support structures may be used to elevate an elongated receiver from ground level and then continue to support the elongated receiver during operation of a solar array. Referring now toFIG. 31C, a T-shapedvertical support structure3120 is anchored to the ground. T-shapedvertical support structure3120 comprises apost3121, and ashelf3122. The post and shelf may each have any suitable dimensions. For example, in some variations, the post may be round, with a 6″ diameter, and the shelf may have athickness3123 of about 4″. Anauxiliary structure3124 may be attached to thepost3121 and/or theshelf3122. A hoist3125 may be attached toauxiliary structure3124, e.g., at or near the top ofstructure3124 for a hoist that lifts from above. Hoist3125 may be operated (e.g., with a motor, a spring, gravity aid and/or manually) to lift a receiver from ground level to an elevated position, where it may be supported onshelf3122 during operation of the array. Hoists and auxiliary structures that are used to support hoists may be subsequently removed.
• Methods are also described for installing an elevated receiver into a solar array using vertical support structures that may eventually be used to support the elevated receiver during operation of the array. These methods generally include anchoring a vertical support structure to the ground, elevating the receiver to an installed receiver position with the vertical support structure (e.g., with a hoist coupled to the vertical support structure), and then supporting the receiver with the same vertical support structure during operation of the array. For example, a hoist coupled to the vertical support structure may be used to lift a receiver or portion of a receiver (e.g., a receiver body or a receiver structure). Non-limiting examples of vertical support structures that may be used in these methods are provided inFIGS. 31A-31C. In some variations, these methods may be used as part of methods for installing a solar collector system, e.g., a LFR array, disclosed herein, known in the art, or later developed.
• In these methods, an assembled or partially assembled elongated receiver may be positioned along a row of spaced-apart vertical support structures at or near ground level. For example, the receiver may be assembled or partially assembled on a stand along a row of vertical support structures. The receiver may then be elevated by one or more of the vertical support structures to an installed receiver position. For example, at least one of the vertical support structures in the row may comprise a hoist configured to lift the receiver. It should be pointed out that not all of the vertical support structures in the row need be capable of lifting the receiver. For example, in some instances, a vertical support structure that is centrally located within the row may comprise a hoist to elevate an elongated receiver, and then the elevated receiver may be coupled to the other vertical support structures in the row in an installed receiver position. The receiver may continue to operate in an array this installed position. In other variations, two of a row of vertical support structures may each be capable of elevating the receiver, e.g., each may comprise a hoist. Those two vertical support structures may be end ones of the row, for example. In still other variations, more than two of a row of vertical support structures in a row may be capable of elevating a receiver, e.g., by comprising hoists. Although the examples of vertical support structures shown inFIGS. 31A-31C illustrate the elevation of assembled (e.g., welded) or at least partially assembled receivers, the vertical support structures and methods described above may also be used to elevate receiver structures that have not yet been assembled into a receiver, or receiver bodies, or other receiver components.
• Some variations of solar collector energy systems may incorporate jointed vertical support structures. These vertical support structures may be designed to support an elevated receiver above one or more reflector fields, e.g., a first reflector field and a second reflector field. The jointed vertical support structures may allow a receiver or receiver structure, or a portion of thereof, to be coupled to the support structure at or near ground level, and then the joint may operate so that the receiver or portion thereof can be elevated to an installed vertical receiver position.
• Referring now toFIG. 22,vertical support structure2240 comprises aproximal end2241 that is configured to be anchored to the ground, and adistal end2242 configured to be coupled to an elevated receiver in a solar energy collector system. A first joint2243 is configured to allow thedistal end2242 to be angled toward theground2203 while theproximal end2241 is ground-anchored. Whendistal end2242 is angled toward the ground, a receiver, or a portion of a receiver such as a receiver body or a receiver frame, may be coupled thereto at or near ground level. The first joint2243 of thevertical support structure2240 may be configured so that the application of lateral force (indicated by arrow2244) to itsdistal end2242 can cause the distal end to be elevated, so that a receiver or a portion of a receiver coupled thereto may be elevated to a vertical installedreceiver position2245.
• Lateral tension may be applied to the distal end of a jointed vertical support structure in any suitable manner. For example, a tether may be coupled to the distal end of the vertical support structure, and lateral tension applied to the tether to elevate the distal end. Some vertical support structures include a tether as part of the vertical support structure. One or more pulleys may be used to guide and control the direction and amount of tension applied to the tether. The pulleys may be part of the vertical support structure, e.g., mounted to the side of a vertical support structure. Alternatively, or in addition, one or more pulleys may be used that are separate from the vertical support structure.
• In some variations, joints in vertical support structures may be lockable. For example, joint2243 inFIG. 22 may be configured to automatically lock when vertical support structure is extended to an installedvertical position2245, e.g., through the use of spring-tensioned pins that may automatically insert when the vertical support structure reaches a particular position. In other variations, a locking mechanism may be manually activated when the vertical support structure is in a desired position. Alternatively, or in addition, a separate locking member (not shown) may be used, e.g., a sleeve that is configured to slide over a joint and secure a joint.
• Some variations of jointed vertical support structures may comprise more than one joint. Referring now toFIGS. 23A-23B,vertical support structure2340 hasproximal end2341 that is configured to be anchored to theground2303, and adistal end2342. A first joint2343 allows thedistal end2342 to be angled toward the ground to facilitate coupling a receiver or a portion of a receiver thereto at or near ground level. A second joint2348 is positioned distally relative to the first joint2343. The second joint2348 may be movable independently of first joint2343. Each of the first joint2343 and the second joint2348 may be configured to elevate thedistal end2342 ofsupport structure2340 with the application of lateral tension (indicated by arrow2344) todistal end2342. Second joint2348 may angledistal end2342 closer to theground2303 than first joint2343. The first and second joints each may be automatically lockable, manually lockable, and/or lockable with a separate locking member, as described above in connection withFIG. 22. The first and second joints may be separately lockable, or may be jointly lockable. As with single-jointed vertical support structures, multiple-jointed vertical support structures may comprise one ormore tethers2349 configured to be coupled to thedistal end2341, and one ormore pulleys2350 configured to guide and control the application of lateral tension to the distal end with the one or more tethers so that the support structure can be elevated to its installed vertical position. The one or more tethers and/or pulleys may be part of, or separate from, the multiple-jointed vertical support structures.
• Methods for installing LFR solar arrays using vertical support structures such as those illustrated in FIGS.22 and23A-23B are provided. These methods include arranging a plurality of reflectors into reflector rows. A receiver body may be provided that includes an elongated receiver channel that comprises first and second longitudinal sidewalls extending along a length of the receiver channel, and an aperture disposed between the first and second sidewalls. The aperture may extend along the entire length of the receiver channel, or along a portion of the length of the receiver channel. The receiver body may be oriented so that the length of the receiver channel is generally parallel to the reflector rows. The methods include elevating the receiver body above the plurality of reflectors. The plurality of reflectors maybe aligned so that each reflector directs incident solar radiation through the aperture of the receiver body.
• In some methods, elevating the receiver may comprise anchoring a proximal end of a jointed vertical support structure to the ground and angling a distal end of the vertical support structure toward the ground. The receiver body may then be secured to the distal end of the jointed vertical support structure at or near ground level. Then lateral force may be applied to the distal end of the jointed vertical support structure to elevate the receiver body to its installed vertical position. Lateral force may be applied using a tether connected to the distal end of the jointed vertical support structure, e.g., as shown FIGS.22 and23A-23B. The tether may be threaded through one or more pulleys may be used to guide and/or control the application of lateral tension using the tether. In other methods, elevating the receiver to an installed receiver position may comprise elevating the receiver with a vertical support structure (e.g., with a hoist coupled to the vertical support structure) that may eventually support the receiver during operation of the solar array. Examples of such methods of elevating the receiver were discussed above in connection withFIGS. 31A-31C.
• In some variations of the methods, a solar radiation absorber may be installed in the receiver channel of the receiver body before the receiver body is elevated. For example, as shown inFIG. 23B, a plurality of solarradiation absorbing tubes2357 may be installed lengthwise into a receiver body (not shown). Thetubes2357 may be installed into the receiver body in any suitable manner. For example, the absorber tubes may be inserted in a transverse direction (e.g., by rolling) to the receiver body while it is at or near ground level, and then secured to receiver body. Methods may also include installing a window in the aperture of the receiver channel. The windows may be installed before or after the receiver body is elevated to its vertical installed position. In some variations, the window may be installed into the receiver body in a transverse direction. The windows may be secured over the apertures to the receiver channels, e.g., by forming one or more junctions with the receiver channels using window support members such as those described in connection withFIGS. 11A-11E. In some variations, in particular those in which the windows are installed prior to receiver elevation, tabs such as spring tabs may be used to secure the windows to the receiver channels.
• Carrier frames for supporting reflector elements in a solar energy collector system and methods for making such carrier frames are provided. These carrier frames may be used for supporting reflector elements in LFR solar arrays. Referring toFIGS. 24A-24B,carrier frame2400 comprises afirst platform2401 and asecond platform2402.First platform2401 has afirst end2403 and asecond end2405, andsecond platform2402 has afirst end2404 and asecond end2406. Thecarrier frame2400 also comprises afirst reflector support2407. At least oneattachment tab2412 may be affixed to thefirst reflector support2407, e.g., by welding or bolting. Thesecond end2405 of thefirst platform2401 may be fixed to thefirst reflector support2407, e.g., by welding. Thefirst end2404 of thesecond platform2402 may be temporarily or removably attached to thefirst reflector support2407 using at least oneattachment tab2412 so that the first andsecond platforms2401 and2402 extend from opposite sides offirst reflector support2407.
• Platforms may comprise a corrugated base layer. Such a construction may facilitate curving the platform surface so that a reflector element conforming thereto will have a desired radius of curvature, e.g., as discussed in connection withFIGS. 3 and 4. Prior to coupling platforms together to form an elongated reflector, one or more reflector elements may be affixed (e.g., using adhesive) to the platforms to follow the curvature of the platforms. The reflector elements may be metallic-backed glass mirrors having a thickness of about 3 mm or 4 mm to provide them with sufficient flexibility to follow the contour of the platforms of the reflector carrier frames. In some variations, a reflector element may be adhered to a platform using one or more lines of adhesive, where the one or more lines of adhesive run generally parallel to a longitudinal axis of the reflector element. A line of adhesive may be continuous or discontinuous. For example, a line of adhesive may contain a series of breaks in the line to allow any water that becomes trapped between the reflector element and the platform a path to drain out. Referring now toFIG. 24B,platform2402 comprises acorrugated layer2431 that may be attached toreflector support cross-member2433. Transverse stabilizing members2430 (e.g., ribs) and longitudinal stabilizing members2434 (e.g., spines) may be provided as part ofcarrier frame2400.
• In many instances, it may be desired to reduce the amount of water and other contaminants retained or pooled by carrier frames and the like. For example, if multiple corrugated sections are used to form a carrier layer (e.g., similar tolayer2431 inFIGS. 24A-24C), the corrugated sections may be lapped to avoid pooling of water in corrugations. Referring now toFIG. 24D, twocorrugated sections2450 and2451 are joined atjunction2455 to formcorrugated layer2452 incarrier2453. Ifcarrier2453 is always rotated in a clockwise direction (indicated by arrow2454) to or from a storage position, then corrugatedsections2450 and2451 may be lappedinjunction2455 so that water flows around the junction (as indicated by arrow2456), as opposed to flowing betweencorrugated sections2451 and2450.
• The attachment tabs may be configured to permit alignment of the second platform relative to the first platform and to allow securing of the second platform to the first reflector support in an aligned position. For example, as illustrated inFIG. 24C, theattachment tab2412 may comprise a joint2413 that allows alignment ofplatform2402 secured to theattachment tab2412. The joint2413 may allow theplatform2402 to be rotated and/or translated during alignment of the second platform to thefirst reflector support2407. The attachment tab may include any suitable attachment scheme and type of joint. For example an attachment tab may comprise a threaded hole configured to accept a threaded bolt coupled to a platform. Alternatively, an attachment tab may comprise a clear hole or slot that a bolt coupled to a platform may be inserted through and secured with a nut. The example illustrated inFIGS. 24A-C includes a threaded hole designed to accept a threaded section ofbolt2417 onfirst end2406 ofsecond platform2402. As indicated byarrow2418,platform2402 may be rotated about an axis defined bybolt2417 for alignment. Thus, thefirst end2406 of thesecond platform2402 may be reversibly attached to the first reflector support and aligned withfirst platform2401. In some variations, the second platform may be aligned relative to the first platform to within less than about 10 mm, e.g., about 8 mm, about 6 mm, about 5 mm, about 4 mm, about 3 mm, about 2 mm, or about 1 mm. In some carrier frames, the second platform may be permanently attached to the first reflector support after alignment, e.g., by welding.
• Some carrier frames may comprise second and third reflector supports so that the first platform is coupled to and supported between the first and second reflector supports, and the second platform is coupled to and supported between the first and third reflector supports. Referring again toFIGS. 24A-24C,first platform2401 is coupled to and supported betweenfirst reflector support2407 andsecond reflector support2420, andsecond platform2402 is coupled to and supported betweenfirst reflector support2407 andthird reflector support2421. The second and third reflector supports may be coupled to platforms in any suitable manner. For example, they may be permanently coupled, e.g., by welding, or temporarily coupled, e.g., with a bolt or the like. The process described here for aligning two platforms interconnected to a common reflector support may be repeated multiple time as a carrier frame comprising more than two platforms is assembled.
• Although the reflector supports are shown as having hoop-like frames inFIGS. 24A-24D for ease of illustration, variations of carrier frames and methods of making such variations of carrier frames are contemplated that utilize other types of reflector supports, e.g., one or more reflector supports similar to those illustratedFIGS. 2C and 2D. For example, the methods described above may be used to make a carrier frame that comprises more than one type of reflector support, e.g.., a first reflector support that comprises a hoop-like frame and a second reflector support similar to that illustrated inFIGS. 2C or2D.
• Drives and drive systems for solar energy collector systems are provided. In general, the drives include a motor that is configured to move and position one or more reflector supports (e.g., one or more hoops supporting one or more reflector elements). The drives may position the reflector elements to at least partially track diurnal motion of the sun and to reflect incident solar radiation to an elevated receiver. In addition, the drives may be designed to move the reflector elements to a storage position during limited- or no-sunlight hours, and/or during high wind or other inclement weather situations. In general, the drive systems include a motor and one or more reflector supports (e.g., one or more hoops supporting one or more reflector elements). In the drive systems, the motor and the reflector supports are coupled together to allow the desired movement and positioning of the reflector elements.
• Some drive systems for solar energy collector systems comprise a bidirectional motor that is configured to drive a gear and a reflector support that is, in turn, configured to support and rotate one or more reflector elements coupled thereto. The reflector support may be configured to rotate the reflector elements to at least partially track diurnal motion of the sun, and to move the reflector elements to a storage position during darkness and/or inclement weather. A chain may be engaged with the gear. The chain may be configured to wrap around an outer peripheral surface of the reflector support and to continuously engage with an engagement member that is affixed to the outer peripheral surface of the reflector support so that the motor can rotate the reflector support via the chain.
• FIGS. 25A-25B illustrates one variation of such a drive system. There,drive system2501 comprises abidirectional motor2502 configured to drive agear2503. The drive system also comprises areflector support2504, which may be coupled to and configured to rotate one or more reflector elements (not shown). Achain2505 is wrapped around an outerperipheral surface2506 ofreflector support2504.Reflector support2504 may have a U-shaped periphery, so that outerperipheral surface2506 is inset fromperipheral sidewalls2517. In this example,engagement member2507 comprises a toothed, gear-like structure2508. Thechain2505 forms a continuous loop, and continuously engages withgear2503 and gear-like structure2508 as the reflector support is rotated between limit stops2509 and2510. The limit stops may be positioned anywhere around the periphery of the reflector support, as long as theengagement member2507 remains engaged withchain2505. For example, limit stops may be placed about 270° apart, so thatbidirectional motor2502 may be configured to rotatereflector support2504 approximately ±135°.
• FIGS. 26A-26B illustrate another variation of a drive system that may be used with solar energy collector systems described herein, known in the art, or later developed. There,drive system2601 comprises abidirectional motor2602 configured to drive agear2603. The drive system also includes areflector support2604 that is configured to rotate and position one or more reflector elements (not shown) coupled thereto. Affixed to outerperipheral surface2606 ofreflector support2604 isengagement member2607.Reflector support2605 may have a U-shaped periphery, so that outerperipheral surface2606 is inset fromperipheral sidewalls2617. In this embodiment, thechain2605 does not form a continuous loop. Rather,chain2605 comprises two ends,2644 and2645.Chain end2644 is coupled to afirst attachment point2688 ofengagement member2607, andchain end2645 is coupled to asecond attachment point2689 ofengagement member2607. The first and second attachment points are positioned along the periphery of the reflector support on opposite sides of the engagement member. The first and second attachment points may have any suitable configuration, e.g., they may be hooks, protrusions, clamps, or the like. When the reflector support is rotated between limit stops2609 and2610, the chain is continuously engaged withgear2603, and rotation of the gear by thebidirectional motor2602 in a first direction applies tension to thechain2605 to rotate the reflector support in one of a clockwise and counterclockwise direction, and rotation of the gear by themotor2602 in a second direction applies tension to thechain2605 to rotate the reflector support in the other of a clockwise and counterclockwise direction. The limit stops2609 and2610 may be positioned anywhere around the periphery of the reflector support, as long as theengagement member2607 remains engaged with chain ends2604 and2605. For example, limit stops may be placed about 270° apart, so thatbidirectional motor2602 may be configured to rotatereflector support2604 approximately ±135°.
• In drive systems that include a motor and chain to drive a reflector support, it may be necessary to adjust the tension in the chain to reduce slack, and hence to reduce backlash and the like to improve the accuracy with which the reflector support may be positioned. Referring now toFIG. 27,drive system2701 comprises amotor2702 configured to drive agear2703. Themotor2702 is mounted to amovable pivot arm2704. Achain2706 is engaged withgear2703, so that whengear2703 is driven bymotor2702, tension is applied to thechain2706 to rotate areflector support2705, for example, as described in connection withFIGS. 25-25B and26A-26B. The reflector support may be configured to rotate one or more reflector elements to at least partially track diurnal motion of the sun, and to rotate the reflector elements to a storage position when desired. In these variations of drive systems, thechain2706 may be threaded around amovable pivot arm2704. The pivot arm may comprise an adjustment (e.g., a height adjustment) that allows tension in the chain to be varied. For the example shown inFIG. 27,pivot arm2704 may be rotated about an axis determined bybolt2708 to adjust the tension inchain2706. In this example, themotor2702 andgear2703 are mounted to pivotarm2704. However, in other variations, the motor and gear need not be connected to the pivot arm, as long as the chain is threaded around the pivot arm to allow tension to be adjusted. The pivot arm may be continuously adjustable, as shown inFIG. 27. In other variations, the pivot arm may have preset positions that may be selected, e.g., with a ratchet, or with a spring-loaded or movable pin that may be inserted into one of a series of holes to control the height of a pivot arm around which a chain is threaded to adjust tension in the chain.
• Other drive systems for use in solar energy collector systems are described. These drive systems include a motor configured to drive a reflector support that supports and rotates one or more reflective elements. These systems are designed to have reduced lateral movement of the reflector support in the drive system, which may improve accuracy of positioning of the reflective elements, and/or reduce extraneous motions to conserve energy. Referring now toFIGS. 28A-28B,drive system2801 comprisesmotor2802 that is configured to drive gear a2803.Motor2802 may be mounted to apivot arm2807, similar to that described in connection withFIG. 27.Drive system2801 comprises areflector support2804 that comprises a hoop-like frame that supports and rotates one or more reflector elements (not shown), and achain2805 that is engaged withgear2803 and wrapped around and coupled to an outerperipheral surface2806 ofreflector support2804 so that whengear2803 is driven bymotor2802, tension is applied to thechain2805 to positionreflector support2804. One ormore wheels2808 may be mounted to abase2810. The one ormore wheels2808 may be configured to contact the outerperipheral surface2806 of thereflector support2804 and to rotate freely as the reflector support rotates. The outer periphery ofreflector support2804 may have aU-shaped profile2840, so that thewidth2841 of thewheel2808 fits freely within theU-shaped profile2840. Optionally, one or morevertical stabilization wheels2842 may be used to contact aninner surface2843 ofreflector support2804 and to rotate freely asreflector support2804 rotates, to opposewheels2808 and to prevent the reflector support from moving in an upward vertical direction.
• Still referring toFIGS. 28A-28B, these drive systems may optionally include one or more lateral stabilization members that are configured to reduce an amount of lateral movement between the wheel and the outer peripheral surface of the reflector support. The lateral stabilization member may be any suitable member that provides lateral stability without unduly increasing the friction between the reflector support and the wheel. For example, as illustrated inFIGS. 28A-28B, thelateral stabilization member2850 may comprise a firstlateral stabilization wheel2852 and a second opposinglateral stabilization wheel2854. Asreflector support2804 rotates, firstlateral stabilization wheel2852 rolls against aside rail2856 ofU-shaped periphery2840 ofreflector support2804, and secondlateral stabilization wheel2854 rolls against aside rail2858 ofU-shaped periphery2840 that isopposite side rail2856.
• Drives for use in a solar energy collector system are described here, where the drives may comprise a motor and a positional sensor. The motor may be configured to rotate one or more reflector supports, where each reflector support is configured to support and rotate one or more reflector elements coupled thereto. The reflector elements may be aligned and configured to direct incident solar radiation to an elevated receiver. The drives also may each comprise a positional sensor that is configured to sense a rotational position of the reflector support to within at least about 0.2 degrees, at least about 0.1 degrees, at least about 0.05 degrees, at least about 0.02 degrees, or at least about 0.01 degrees. In some variations, the drives may further comprise a controller. In those instances, the controller may be configured to provide input to the positional sensor and/or to receive output from the positional sensor. A controller, if present, may be interfaced with the positional sensor and with a user in any suitable manner. The sensor and the controller may be each configured to receive analog input and/or output, and/or digital input and/or output. For example, the controller may be hard-wired to the positional sensor through a serial or parallel port. Alternatively, or in addition, the controller may have a wireless interface with the sensor. The controller may be hard-wired or wirelessly interfaced with a user interface (e.g., a user-controlled computer connected to the controller through a serial or parallel port), or the controller may be wirelessly interfaced with a user interface. In some variations, the controller may be remotely programmable so that instructions may be remotely sent and/or received from the controller. Some variations of these drives may comprise a closed-loop control configuration in which the controller is configured to receive input from the positional sensor to determine the rotational position of the reflector support, and to provide output instructions to the motor or to a controller interfaced with the motor to rotate the reflector support and the reflector elements coupled to the reflector support to a desired rotational position.
• The positional sensor may be configured to sense a rotational position of the reflector support when the reflector support has stopped moving, or the positional sensor may be configured to sense a rotational position of the reflector support while the reflector support is moving. In the latter case, the time constant of the reading by the sensor may be selected according to the speed at which the reflector support is rotating. For example, the time constant of the positional sensor may be selected to be about 50 ms to about 5 seconds, e.g., about 100 ms to about 500 ms, or about 500 ms to about 1 second. Any suitable positional sensor may be used in the drives and systems described here. Analog and/or digital sensors may be used. In some variations, a sensor comprising at least two elements may be mounted to the reflector support. By analyzing the difference between measurements made by the at least two elements, the sensor may determine an absolute or relative tilt of the reflector support. The at least two elements may be any suitable type of elements, e.g., capacitive elements or accelerometers. Non-limiting examples of suitable absolute and/or relative tilt sensors and/or inclinometers that may be used as sensors are available from U.S. Digital (Vancouver, Wash.), Rieker, Inc. (Aston, Pa.), Kelag Künzli Elektronik AG (Switzerland), VTI Technologies (Finland), National Instruments (Austin, Tex.), and Analog Devices (Norwood, Mass.). If a sensor capable of detecting absolute tilt is used as a positional sensor, it may be positioned to within about 10 cm of a center of the reflector support to minimize gravitational effects on the sensor and associated errors. Other types of positional sensors may be used, e.g., inductive sensors or optical sensors.
• Positional sensors, if present, may be located on any suitable portion of a reflector support or carrier. For example, a positional sensor may be located on reflector support frame or on a reflector support base. In some variations, a positional sensor may be located on a hoop-like portion of a reflector support frame, on a cross member or spoke of a reflector support frame, or near a center of rotation of a reflector support or reflector element. Referring back to the example illustrated inFIG. 28A, one or more positional sensors may be located on the hoop-like frame2821 ofreflector support2804, on a cross member2820 and/or near a center of rotation2822 ofreflector support2804. Alternatively or in addition, a positional sensor may be located onbase2810 ofreflector support2804.
• Some drives may include one or more limit sensors in addition to the positional sensor. In these drives, the limit sensor may be capable of detecting when the reflector support has rotated to a corresponding limit position. The limit sensors may be able to detect a position of a reflector support to within about 1 degree, about 0.5 degree, about 0.4 degree, about 0.3 degree, about 0.2 degree, about 0.1 degree, about 0.05 degree, or about 0.02 degree. Limit sensors may, for example, be positioned at about 270° relative to each other, e.g., as illustrated inFIGS. 25A-B and26A-B. Any type of sensor may be used as a limit sensor, e.g., an inductive sensor, an optical sensor, or an inclinometer such as an inclinometer using capacitive sensing elements or accelerometers. In some cases, a limit sensor may be used to provide a reference position for a positional sensor, e.g., a more accurate positional sensor. In still other variations, the motor and/or the reflector support may include an encoder or other positional information. For example, a servo drive encoder may be provided on the motor. Such servo drive encoders may allow for correction of backlash in motor movement. Alternatively, or in addition, the reflector support may include a positional encoder such as a notch or a series of notches. Any combination of the positional sensors, limit sensors, and encoders described here, known in the art, or later developed may be used.
• In some variations of drives, the motor may be configured to be coupled to a variable frequency drive to control the rotational position resolution. In these drives, an AC motor (e.g., a three phase, 480V AC induction motor) is configured to drive a reflector support that is configured to support and rotate one or more reflector elements coupled thereto. The motor may be interfaced with a variable frequency drive to step down the frequency of the AC input, thereby allowing the motor to move less with one AC cycle. For example, nominal 50 Hz or 60 Hz AC power may be stepped down to about 1 Hz to about 6 Hz, or to about 1 Hz to about 5 Hz, to improve the ability of the motor to make smaller incremental rotational movements of the reflector support. Any suitable variable frequency drive may be used. The variable frequency drives may comprise an analog or digital controller. For example, some variable frequency drives may be programmable (e.g., remotely programmable) through a serial or parallel port. Inputs and/or outputs from the variable frequency drives may be hard-wired and/or wireless.
• In some variations of these drives, the motor may be configured to be switched between direct AC drive operation and operation through the variable frequency drive. Bypassing the variable frequency drive (VFD) may allow rapid rotation of the reflector elements, e.g., to a storage configuration for limited- or no-sunlight hours, and/or in preparation for inclement weather such as high winds. In some cases, the AC motors operating through a VFD may be driven at a harmonic of the nominal AC power frequency (e.g., 50 Hz or 60 Hz). For example, motors may be driven at 100 Hz, 120 Hz, 150 Hz, or 180 Hz for even faster and/or more efficient rotation of the reflector elements.
• Some variations of drives may be capable of driving reflector supports at more than one rotational speed setting. For example, some drives may have a first slow rotational speed setting for relatively slow movement of the reflector support with a relatively high degree of rotational position accuracy and a second rotational speed setting corresponding to motor speeds that allow relatively faster rotation of the reflector support. Some variations may comprise a third rotational speed setting corresponding to very rapid rotation of a reflector support, e.g., the most rapid rotation of the reflector support desired. Different rotational speed settings may be achieved by supplying AC power having different frequency ranges to the motors in the drives. For example, the first rotational speed setting may be achieved by supplying AC power to a motor through a variable frequency drive operating at about 1 Hz to about 6 Hz, or about 1 Hz to about 5 Hz, e.g., at about 2 Hz or about 3 Hz. The second rotational speed setting may be achieved by operating a motor in direct drive at the nominal AC power frequency in the region where the drive is to be operated, e.g., about 50 Hz or about 60 Hz, e.g. The variable frequency drive connected to the motor may be bypassed to operate the motor in direct drive for the second rotational speed setting. The third rotational speed setting, if present, may be achieved by supplying AC power at a harmonic of the nominal AC power through the variable frequency drive to a motor, e.g., at about 100 Hz, or about 120 Hz.
• Drive systems are provided in which one or more VFDs may be configured to be connected to a set of motors. In these drive systems, each motor in the set may be configured to drive one or more reflector supports, and each reflector support may be configured to support and rotate one or more reflector elements coupled thereto. For example, as illustrated inFIG. 29, a solar energy collector system may comprise adrive system2900 that comprises aset2914 ofmotors2910 that are controlled by a singlevariable frequency drive2912. Eachmotor2910 may, for example, be a 480V three-phase AC induction motor connected to a row of reflector elements supported by a series of reflector supports. Although the example inFIG. 29 shows a set of 4 motors connected to a single VFD, any suitable number of motors may be connected to a VFD, e.g., 2 motors or more, or 3 motors or more, or 4 motors or more, or 5 motors or more, e.g., 8 motors, 10 motors, or 12 motors.
• As indicated above, some variations drive systems may comprise one or more switches configured to bypass the variable frequency drive so that the at least one motor of the set of motors may operate in direct drive. Referring again toFIG. 29,drive system2900 comprises afirst bypass switch2915 that is configured to bypassVFD2912.Bypass switch2915 may comprise any suitable type of switch, e.g., a reversing starter. In other variations, one or more additional switches may be connected to individual motors or to a subset of the set of motors. In some cases, a switch may be provided for every motor, so that each motor may be independently decoupled from the VFD. For the example shown inFIG. 29,switches2916 are provided between theVFD2912 and theindividual motors2910, or between thebypass2915 and theindividual motors2910. Theswitches2916 may be configured to be switchable as a bank of switches, or individually switchable. In some variations of drive systems, a first subset of theswitches2916 may be switchable as a bank, and a second subset of theswitches2916 may be independently switchable. Of course, some drive systems may comprise multiple VFDs. In those instances, one or more switches may be provided to bypass more than one VFD.
• Drive systems may be configured such that the reflector rows in a solar array may be rotated in a serial manner (i.e., one reflector row at a time), or so that more than one reflector row may be rotated at the same time. For example, reflector rows may be rotated in a serial sequence through a VFD for positioning, or more than one reflector row may be rotated at the same time through a VFD for positioning. Similarly, when a VFD connected to motors driving a reflector rows is bypassed so that the motors are operating in direct drive, the reflector rows may be rotated in a serial manner, or more than one reflector row may be rotated at the same time. As indicated above, bypassing a VFD may enable rapid, simultaneous rotation of reflector elements to a storage position, with their reflective surfaces facing downward. In some arrays, two or more outer rows of a reflector field (or other reflector rows subject to high wind shear) may be configured to have their VFDs bypassed and rotated in direct drive operation at the same time to a storage position.
• Solar energy collector systems including drives or drive systems such as those discussed above comprising one or more positional sensors, and those described in connection withFIGS. 25-29 are also provided. Referring now toFIG. 30, solarenergy collector system3001 comprises a set of master reflector supports3002. Eachmaster reflector support3002 may be driven by adrive3003 comprising a motor that is configured to support and rotate a segment of areflector row3004. For example, a single motor may be configured to drive a row segment comprising 2, 4, 6, or 8reflector elements3005. Slave reflector supports3006 may be provided on each side ofreflector elements3005 and rotate followingmaster reflector support3002. A closed-loop controlled rotational positional sensor may be provided on one or more of the master or slave reflector supports so that the rotational position of the reflector row may be determined, and so that the reflector row may be rotated to a desired position to at least partially track diurnal motion of the sun and direct incident solar radiation toelevated receiver3015.Drives3003 may be operated in sequence, or in parallel, so that row segments driven thereby may be rotated in a sequential or in a parallel operation. Multiple reflector row segments may be aligned in a collinear fashion so that eachreflector row3004 may be about 200 meters, about 300 meters, or about 400 meters long.
• This disclosure is illustrative and not limiting. Further modifications will be apparent to one skilled in the art in light of this disclosure and such modifications are intended to fall within the scope of the appended claims. Each publication and patent application cited in the specification is incorporated herein by reference in its entirety as if each individual publication or patent application were specifically and individually put forth herein.

Claims (40)

1. A receiver for a solar energy collection system, the receiver comprising:

a receiver channel comprising a first sidewall, a second sidewall, and an aperture disposed between the first and second sidewalls, the first and second sidewalls and the aperture each extending along a length of the receiver channel;

a solar radiation absorber positioned in the receiver channel;

a window disposed in the aperture, so that the window and the receiver channel form a longitudinal cavity that houses the solar radiation absorber and so that solar radiation incident on the solar radiation absorber is transmitted through the window; and

one or more window support members disposed along the first sidewall and/or along the second sidewall of the receiver channel, wherein the one or more window support members is configured to allow installation of the window into the receiver in a direction transverse to the length of the receiver channel, and to support the window when installed in the receiver.

2. The receiver ofclaim 1, wherein the one or more window support members comprises a first window support member disposed along the first sidewall and a second window support member disposed along the second sidewall.

3. The receiver ofclaim 2, wherein:

the first window support member comprises a ledge and a step;

the second window support member comprises a slot comprising a lower slot surface, an upper slot surface spaced apart from the lower slot surface by an amount sufficient to accommodate a thickness of the window, and a slot sidewall; and

the window when installed is disposed on the ledge and on the lower slot surface and is positioned between the step and the slot sidewall, and a longitudinal edge of the window is positioned between the upper and lower slot surfaces.

4. The receiver ofclaim 1, further comprising one or more tabs configured to secure the window when installed in the receiver.

5. A solar energy collector system comprising:

an elevated receiver, the receiver comprising:

a receiver channel comprising a first sidewall, a second sidewall, and an aperture disposed between the first and second sidewalls, the first and second sidewalls and the aperture each extending along a length of the receiver channel;

a solar radiation absorber positioned in the receiver channel;

a window disposed in the aperture so that the window and the receiver channel form a longitudinal cavity that houses the solar radiation absorber and so that solar radiation incident on the solar radiation absorber is transmitted through the window; and

one or more window support members disposed along the first and/or second sidewall of the receiver channel, wherein the one or more window support members is configured to allow insertion of the window into the receiver in a direction transverse to the length of the receiver channel, and to support the window when installed in the receiver; and

first and second reflector fields positioned on opposite sides relative to a center of the elevated receiver, wherein:

each reflector field comprises reflectors that are arranged into one or more parallel reflector rows extending generally in a direction parallel to the length of the receiver channel;

the reflectors each comprise a reflective surface configured to direct incident solar radiation through the window to the solar radiation absorber in the receiver; and

the reflectors are driven to at least partially track diurnal motion of the sun.

6. A receiver for use in a solar energy collector system, the receiver comprising:

a receiver channel comprising an aperture extending along a length of the receiver channel;

a solar radiation absorber positioned in the receiver channel; and

a window disposed in the aperture so that the window and the receiver channel form a cavity that houses the solar radiation absorber and so that solar radiation incident on the solar radiation absorber is transmitted through the window, wherein at least one of the window and the receiver channel is configured to accommodate thermal expansion and contraction along a length of the aperture.

7. The receiver ofclaim 6, wherein the window comprises two or more overlapping window sections distributed along the length of the aperture.

8. A solar energy collector system comprising:

an elevated receiver comprising:

a receiver channel comprising an aperture extending along a length of the receiver channel;

a solar radiation absorber positioned in the channel; and

a window disposed in the aperture so that the window and the receiver channel form a cavity that houses the solar radiation absorber and so that solar radiation incident on the solar radiation absorber is transmitted through the window, wherein at least one of the window and the receiver channel is configured to accommodate thermal expansion along a length of the aperture; and

first and second reflector fields positioned on opposite sides relative to a center of the receiver, wherein:

each reflector field comprises reflectors that are arranged into one or more parallel reflector rows extending generally in a direction parallel to the length of the receiver channel;

the reflectors each comprise a reflective surface configured to direct incident solar radiation through the window to the solar radiation absorber in the receiver; and

the reflectors are driven to at least partially track diurnal motion of the sun.

9. A receiver for a solar energy collector system, the receiver comprising:

a receiver channel comprising an aperture extending along a length of the receiver channel;

a solar radiation absorber positioned in the receiver channel; and

a window disposed in the aperture and forming a junction with the receiver channel so that the window and the receiver channel form a cavity that houses the solar radiation absorber and so that solar radiation incident on the solar radiation absorber is transmitted through the window, wherein:

the junction is configured to allow the window to slide relative to the receiver channel; and

ingress of external air into the cavity through the junction between the window and the receiver channel is inhibited.

10. The receiver ofclaim 9, comprising a sealing member positioned in the junction between the receiver channel and the window to inhibit ingress of external air into the cavity.

11. The receiver ofclaim 9, further comprising a roof positioned over the receiver channel to form a volume between the roof and the receiver channel, wherein:

the volume is in fluid communication with the cavity that houses the solar radiation absorber;

a thermally insulating material is disposed in the volume; and

a rate of flow of external air into the cavity through at least a portion of the insulating material in the volume is greater than a rate of flow of external air into the cavity through the junction between the window and the receiver channel.

12. The receiver ofclaim 9, wherein a positive pressure of filtered air is flowed into the cavity to inhibit the ingress of external air into the cavity.

13. A solar energy collector system comprising:

an elevated receiver, the receiver comprising:

a receiver channel comprising an aperture extending along a length of the receiver channel;

a solar radiation absorber positioned in the receiver channel; and

a window disposed in the aperture and forming a junction with the receiver channel so that the window and the receiver channel form a cavity that houses the solar radiation absorber and so that solar radiation incident on the solar radiation absorber is transmitted through the window, wherein the junction is configured to allow the window to slide relative to the receiver channel and ingress of external air into the cavity through the junction between the receiver channel and the window is inhibited; and

first and second reflector fields positioned on opposite sides relative to a center of the receiver, wherein:

each reflector field comprises reflectors that are arranged into one or more parallel reflector rows extending generally in a direction parallel to the length of the receiver channel;

the reflectors each comprise a reflective surface configured to direct incident solar radiation through the window to the solar radiation absorber; and

the reflectors are driven to at least partially track diurnal motion of the sun.

14. The system ofclaim 13, wherein the receiver further comprises:

a roof positioned over the receiver channel to form a volume between the roof and the receiver channel, the volume in fluid communication with the cavity that houses the solar radiation absorber; and

a thermally insulating material disposed in the volume, wherein a rate of flow of external air into the cavity through at least a portion of the insulating material is greater than a rate of flow of external air into the cavity through the junction between the window and the receiver channel.

15. A receiver for a solar energy collector system, the receiver comprising:

a receiver channel comprising an aperture extending along a length of the receiver channel;

a roof positioned over and extending along the length of the receiver channel, the roof having a transverse cross-section that forms a smooth curve and comprising a concave surface that faces the receiver channel;

a solar radiation absorber positioned in the receiver channel; and

a window disposed in the aperture and forming a junction with the receiver channel so that the window and the receiver channel form a cavity that houses the solar radiation absorber and so that solar radiation incident on the solar radiation absorber is transmitted through the window, wherein the roof is configured to shed environmental debris away from the window.

16. The receiver ofclaim 15, wherein the roof extends below the junction between the receiver channel and the window.

17. A solar energy collector system comprising:

an elevated receiver, the receiver comprising:

a receiver channel comprising an aperture extending along a length of the receiver channel;

a roof positioned over and extending along the length of the receiver channel, the roof having a transverse cross-section that forms a smooth curve and comprising a concave surface that faces the receiver channel;

a solar radiation absorber positioned in the receiver channel; and

a window disposed in the aperture and forming a junction with the receiver channel so that the window and the receiver channel form a cavity that houses the solar radiation absorber and so that solar radiation incident on the solar radiation absorber is transmitted through the window, wherein the roof is configured to shed environmental debris away from the window; and

first and second reflector fields positioned on opposite sides relative to a center of the receiver, wherein:

each reflector field comprises reflectors that are arranged into one or more parallel reflector rows extending generally in a direction parallel to the length of the receiver channel;

the reflectors each comprise a reflective surface configured to direct incident solar radiation through the window to the solar radiation absorber; and

the reflectors are driven to at least partially track diurnal motion of the sun.

18. The system ofclaim 17, wherein the roof extends below the junction between the window and the receiver channel.

19. A receiver for a solar energy collector system, the receiver comprising:

a solar radiation absorber comprising a plurality of parallel absorber tubes each extending along a length of the receiver; and

a plurality of spacers, each spacer positioned between two adjacent ones of the parallel absorber tubes, wherein transverse space provided by each spacer accommodates thermal expansion and/or movement of the two adjacent ones of the parallel absorber tubes.

20. The receiver ofclaim 19, wherein one of the spacers positioned between two adjacent ones of the parallel absorber tubes that are located near a transverse center of the receiver channel is larger than another of the spacers that is positioned between two adjacent ones of the parallel absorber tubes that are located near an outer longitudinal edge of the absorber.

21. A solar energy collector system comprising:

an elevated receiver, the receiver comprising:

an elongated receiver channel comprising first and second sidewalls and an aperture, the first and second sidewalls and the aperture each extending along a length of the receiver channel; and

a solar radiation absorber comprising a plurality of parallel absorber tubes arranged lengthwise in the receiver channel between the first and second sidewalls and above the aperture;

a plurality of spacers, each spacer positioned between two adjacent ones of the parallel absorber tubes, wherein transverse space provided by each spacer accommodates thermal expansion and/or movement of the two adjacent ones of the parallel absorber tubes; and

first and second reflector fields positioned on opposite sides relative to a center of the receiver, wherein:

each reflector field comprises reflectors that are arranged into one or more parallel reflector rows extending generally in a direction parallel to the length of the receiver channel;

the reflectors each comprise a reflective surface configured to direct incident solar radiation through the aperture to be at least partially incident on the plurality of absorber tubes; and

the reflectors are driven to at least partially track diurnal motion of the sun.

22. A receiver for a solar energy collector system, the receiver comprising:

a solar radiation absorber comprising a plurality of parallel absorber tubes arranged lengthwise in the receiver; and

one or more rollers extending transversely across the receiver, wherein:

the plurality of parallel absorber tubes is supported by at least one of the one or more rollers;

at least one of the one or more rollers comprises a central shaft disposed within a hollow cylinder comprising two cylinder ends; and

the hollow cylinder is supported at each of the two cylinder ends by a bushing coupled to the central shaft.

23. The receiver ofclaim 22, wherein a diameter of the central shaft is at most about one half a diameter of the hollow cylinder.

24. A solar energy collector system comprising:

an elevated receiver, the receiver comprising:

an elongated receiver channel comprising first and second sidewalls and an aperture, the first and second sidewalls and the aperture each extending along a length of the receiver channel; and

a solar radiation absorber comprising a plurality of parallel absorber tubes arranged lengthwise in the receiver channel between the first and second sidewalls and above the aperture, the plurality of parallel absorber tubes supported by one or more rollers positioned transversely across the receiver channel, wherein at least one of the one or more rollers comprises a central shaft disposed within a hollow cylinder comprising two cylinder ends, and the hollow cylinder is supported at each of the two cylinder ends by a bushing coupled to the central shaft; and

first and second reflector fields positioned on opposite sides relative to a center of the receiver, wherein:

each reflector field comprises reflectors that are arranged into one or more parallel reflector rows extending generally in a direction parallel to the length of the receiver channel;

the reflectors each comprise a reflective surface configured to direct incident solar radiation through the aperture to be at least partially incident on the plurality of absorber tubes; and

the reflectors are driven to at least partially track diurnal motion of the sun.

25. The system ofclaim 24, wherein a diameter of the central shaft is at most about one half of a diameter of the hollow cylinder.

26. A solar radiation absorber for use in a solar energy collector system, the solar radiation absorber comprising a plurality of absorber tubes, wherein each of the absorber tubes is coupled via a tube structure to a header manifold, and the header manifold and/or at least one of the tube structures that couples each of the absorber tubes to the header manifold is configured to accommodate differential thermal expansion of the absorber tubes.

27. The solar radiation absorber ofclaim 26, wherein the header manifold comprises an input/output manifold, and the input/output manifold comprises an inlet section that can move independently from the output section.

28. The solar radiation absorber ofclaim 26, wherein at least one of the tube structures that connecting each absorber tubes to the header manifold comprises two non-coplanar bends.

29. The solar radiation absorber ofclaim 26, wherein at least a portion of the header manifold is configured to move to accommodate thermal expansion and contraction in the tubes.

30. The solar radiation absorber ofclaim 26, further comprising a flow control element inserted into or disposed on at least one of the absorber tubes.

31. A solar radiation absorber for use in a solar energy collector system, the solar radiation absorber comprising:

a plurality of absorber tubes; and

a flow control element applied to at least one absorber tube to maintain a relatively constant fluid flow between the absorber tubes.

32. The solar radiation absorber ofclaim 31, wherein the flow control element accounts for about 30% to about 70% of the pressure drop in the at least one absorber tube.

33. A solar radiation absorber for use in a solar energy collector system, the solar radiation absorber comprising a plurality of absorber tubes, wherein:

the plurality of absorbing tubes comprises one or more inlet tubes for supplying heat exchange fluid to the absorber and one or more outlet tubes for releasing heat exchange fluid from the absorber; and

the plurality of absorber tubes is configured so that the one or more outlet tubes is positioned closer to an interior of the absorber relative to the one or more inlet tubes.

34. A solar energy collector system comprising:

an elevated receiver, the receiver comprising:

an elongated receiver channel comprising first and second sidewalls and an aperture, the first and second sidewalls and the aperture each extending along a length of the receiver channel; and

a solar radiation absorber comprising a plurality of spaced-apart parallel absorber tubes arranged lengthwise in the receiver channel between the first and second sidewalls and above the aperture; and

first and second reflector fields positioned on opposite sides relative to a center of the receiver, wherein:

each reflector field comprises reflectors that are arranged into one or more parallel reflector rows extending generally in a direction parallel to the length of the receiver channel;

the reflectors each comprise a reflective surface configured to direct incident solar radiation through the aperture to be at least partially incident on the plurality of absorber tubes;

the reflectors are driven to at least partially track diurnal motion of the sun; and

spacings between adjacent ones of the spaced-apart parallel absorber tubes are selected to reduce leakage of reflected solar radiation past the absorber tubes.

35. The solar energy collector system ofclaim 34, wherein spacings between adjacent ones of the spaced apart parallel absorber tubes are determined using a set of tangents extending from an inner edge of at least one of the reflectors.

36. A method of setting spacings between adjacent ones of spaced apart parallel absorber tubes in an elevated receiver of a solar energy collector system, the method comprising:

arranging the absorber tubes lengthwise and side-by-side on a horizontal plane that is elevated with respect to a reflector in the solar energy collector system; and

aligning an outer circumferential edge of each absorber tube with a tangent line extending from an inner edge of the reflector to space the absorber tubes apart on the horizontal plane.

37. A receiver for a solar energy collector system, the receiver comprising:

an elongated receiver channel comprising first and second sidewalls and an aperture, the first and second sidewalls and the aperture each extending along a length of the receiver channel;

a solar radiation absorber positioned in a cavity formed between the first and second sidewalls and above the aperture; and

a frame for supporting the solar radiation absorber and the receiver channel,

wherein at least one of a junction between the frame and a mounting structure coupled to the solar radiation absorber and a junction between the frame and the receiver channel is configured to inhibit thermal conduction between the cavity and the frame.

38. The receiver ofclaim 37, comprising a thermal separation member pin a junction between the frame and the mounting structure and/or in a junction between the frame and the receiver channel.

39. A receiver for a solar energy collector system, the receiver comprising a solar radiation absorber comprising a plurality of parallel absorber tubes arranged lengthwise in the receiver, wherein the plurality of parallel absorber tubes is supported by a set of coaxial rollers extending transversely across the receiver.

40. The receiver ofclaim 39, wherein the set of coaxial rollers comprises an individual roller for each absorber tube.

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