WO2015130808A1 - Collecteur à miroir pour miroir cylindro-parabolique solaire - Google Patents

Collecteur à miroir pour miroir cylindro-parabolique solaire Download PDF

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Publication number
WO2015130808A1
WO2015130808A1 PCT/US2015/017556 US2015017556W WO2015130808A1 WO 2015130808 A1 WO2015130808 A1 WO 2015130808A1 US 2015017556 W US2015017556 W US 2015017556W WO 2015130808 A1 WO2015130808 A1 WO 2015130808A1
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WO
WIPO (PCT)
Prior art keywords
mirror
collector system
structural
mirror collector
receiver
Prior art date
Application number
PCT/US2015/017556
Other languages
English (en)
Inventor
Oliver J. BRAMBLES
Emil CASHIN
Troy O. Mcbride
Joel STETTENHEIM
Nicholas T. KATTAMIS
Sheldon D. STOKES
Richard W. KASZETA
Patrick J. MAGARI
Original Assignee
Norwich Technologies, Inc.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Norwich Technologies, Inc. filed Critical Norwich Technologies, Inc.
Priority to CN201580015317.5A priority Critical patent/CN106461269A/zh
Publication of WO2015130808A1 publication Critical patent/WO2015130808A1/fr
Priority to ZA2016/05932A priority patent/ZA201605932B/en

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24S—SOLAR HEAT COLLECTORS; SOLAR HEAT SYSTEMS
    • F24S25/00—Arrangement of stationary mountings or supports for solar heat collector modules
    • F24S25/50—Arrangement of stationary mountings or supports for solar heat collector modules comprising elongate non-rigid elements, e.g. straps, wires or ropes
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24S—SOLAR HEAT COLLECTORS; SOLAR HEAT SYSTEMS
    • F24S23/00—Arrangements for concentrating solar-rays for solar heat collectors
    • F24S23/70—Arrangements for concentrating solar-rays for solar heat collectors with reflectors
    • F24S23/74—Arrangements for concentrating solar-rays for solar heat collectors with reflectors with trough-shaped or cylindro-parabolic reflective surfaces
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24S—SOLAR HEAT COLLECTORS; SOLAR HEAT SYSTEMS
    • F24S25/00—Arrangement of stationary mountings or supports for solar heat collector modules
    • F24S25/10—Arrangement of stationary mountings or supports for solar heat collector modules extending in directions away from a supporting surface
    • F24S25/13—Profile arrangements, e.g. trusses
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24S—SOLAR HEAT COLLECTORS; SOLAR HEAT SYSTEMS
    • F24S25/00—Arrangement of stationary mountings or supports for solar heat collector modules
    • F24S2025/01—Special support components; Methods of use
    • F24S2025/017—Tensioning means
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24S—SOLAR HEAT COLLECTORS; SOLAR HEAT SYSTEMS
    • F24S23/00—Arrangements for concentrating solar-rays for solar heat collectors
    • F24S23/70—Arrangements for concentrating solar-rays for solar heat collectors with reflectors
    • F24S23/82—Arrangements for concentrating solar-rays for solar heat collectors with reflectors characterised by the material or the construction of the reflector
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/40—Solar thermal energy, e.g. solar towers
    • Y02E10/47—Mountings or tracking

Definitions

  • the invention relates to concentrating solar power in general and particularly to a system that employs reflective panels to focus solar radiation upon a linear receiver.
  • Solar parabolic troughs which focus sunlight on tubes carrying a fluid that conveys heat for steam generation (e.g. to a steam-driven electric generator, for industrial process heat, or for the generation of process steam) or to a body of material for energy storage, are a proven, reliable, and relatively low-cost technology for collecting energy. They are the most widely deployed form of concentrating solar power (CSP) at this time.
  • CSP concentrating solar power
  • receiver tubes The tubes upon which the light is focused in such systems are typically termed “receiver tubes,” “receivers,” or “heat collection elements.”
  • receiver tubes At a typical electric generation plant employing solar parabolic troughs, many receivers (for example, in one embodiment, thousands) are arrayed with reflective troughs in parallel rows to form a "solar field" that can collect sufficient energy for a generating system of economical size.
  • a truss comprising abundant rigid frame members (e.g., struts) upholds the mirror and enables the mirror to maintain its parabolic shape with sufficient accuracy in spite of wind forces and other deforming forces.
  • the efficiency with which the receiver can absorb energy from the sunlight depends in part upon the accuracy with which a mirror focuses sunlight upon a receiver.
  • a truss or similar structure that supports a mirror also known as a "collector” also typically supports struts that hold a receiver approximately at the linear focus of the mirror.
  • a central liquid- carrying tube with an outer optical absorption coating is surrounded by a vacuum held within a transparent concentric envelope.
  • Light focused on the receiver by a mirror passes through the transparent concentric envelope and through the vacuum and impinges on the central liquid-carrying tube.
  • the coating on the central tube absorbs most (preferably all, although this cannot be realized in practice) of the energy incident upon it and is thus heated. This heat is transmitted by conduction through the wall of the central tube and thence to the tube's liquid contents.
  • the heated liquid is pumped through the receiver and, in general, through additional receivers, being thus raised to a high temperature before being pumped to a boiler, or energy storage device such as a reservoir of hot fluid).
  • the function of the vacuum between the inner, fluid-carrying tube and the outer, transparent envelope is to prevent loss of heat from the receiver by convection and conduction to the outer envelope and thence, by radiation and conduction, to the environment.
  • the Stettenheim patent discloses an advanced cavity receiver comprising a fluid-carrying receiver tube of whose solar-absorbing surface a lengthwise portion is exposed within an air-filled cavity to light focused thereon by a parabolic trough mirror (and in some embodiments secondarily by appropriate shaped reflecting cavity walls), and the remainder of whose surface is embedded in insulation to reduce thermal losses.
  • tube refers to any elongated, two-ended, hollow body whose cross-sectional form is a simple closed figure (for example, in one embodiment, a circle, a rectangle, or a rectangle with rounded corners).
  • cross-sectional form is a simple closed figure (for example, in one embodiment, a circle, a rectangle, or a rectangle with rounded corners).
  • cylindrical and rounded-rectangular tubes surrounded by insulation are specifically described in the
  • the invention relates to CSP collector assemblies that are lower in weight than collector assemblies constructed according to the prior art while maintaining or improving optical accuracy and, in some embodiments, performing optimally in conjunction with cavity receivers such as those disclosed by the Stettenheim patent.
  • the invention features an improved mirror support system useful in a solar power application.
  • a truss comprising a multiplicity of rigid members (e.g., struts, ribs) in compression uphold a mirror;
  • the invention comprises suspension support structures that employ members in both tension and compression.
  • Members in tension can comprise cables, wires or thin rods, which can bear heavy loads relative to their weight and which produce minimal optical occlusion of the system, where they are located above the mirror.
  • the invention comprises relatively stiff solar reflector panels consisting essentially of layered composite materials.
  • Suspension collector support systems according to embodiments of the invention can provide advantages compared to the prior art, including lower weight, superior maintenance of optical accuracy under wind loading and other loadings, and other advantages that shall be made clear hereinbelow.
  • the invention features a mirror collector system for concentrating solar power along a line in a parabolic trough solar power plant, comprising a plurality of curved panels, the curved panels having a parabolic cross-section, an upper mirrored surface, and a structural sub-substructure, the structural substructure having a first value of a designed material characteristic along a first axis and having a second value of the designed material characteristic along a second axis, the first and second axes being perpendicular and the first and the second values are different; a plurality of linear heat collecting receivers located at each located at a respective focal point of the plurality of curved panels; a plurality of tensioned structural elements connected to the plurality of curved panels and the plurality of linear heat collecting receivers, the plurality of tensioned structural elements configured to provide at least a portion of a structure configured to maintain the plurality of tensioned structural elements in a fixed relation to the plurality of curved panels; and a torsional element
  • the upper mirrored surface comprises a mirrored film.
  • the upper mirrored surface comprises a glass mirror.
  • the designed material characteristic comprises an elastic modulus.
  • the torsional element comprises a tubular structure.
  • the torsional element comprises a space frame structure.
  • the designed material characteristic is a moment of inertia.
  • the designed material characteristic is a flexural rigidity.
  • the plurality of curved panels are configured to be formed using a roll forming technique.
  • the plurality of curved panels are configured to be formed using metal stamping.
  • the first and the second values of the designed material characteristic comprise a structural strength.
  • the structural strength exceeds a structural strength for a glass mirror panel lacking the structural sub- substructure.
  • mirror refers to elements that reflect
  • a solar reflector may be single-layered or multi- layered; solid or hollow; comprise liquid, solid, and gaseous components; be rigid or deformable; comprise a single continuous part or of a multiplicity of parts, joined or unjoined, acting in harmony; and may otherwise vary in form and detail.
  • Solar reflectors are often referred to as "parabolic” herein, but this term is illustrative, not restrictive: it is intended throughout that solar reflectors may be planar, parabolic, hyperbolic, mosaic, or of other forms, including complex and time-varying forms not corresponding to simple curves of classic geometry.
  • the term "receiver” refers to elements that absorb some portion of electromagnetic energy concentrated thereon by a collector assembly and that convert this absorbed energy to other forms (e.g., heat, electricity, phase or chemical change of a substance).
  • a receiver is linear or tubular in overall form.
  • a receiver's hollow interior conveys a fluid that absorbs heat while passing through the receiver and gives up some of this heat in another portion of the CSP system in order that the heat may be stored, used directly (e.g., for industrial processes, desalination, or the like), or used in the making of electricity.
  • a receiver may, alternatively or additionally, comprise a photovoltaic capability for the direct conversion of focused solar energy to electricity.
  • alteration of a fluid e.g., chemical breakdown of waste
  • the term “cable” refers to a multiplicity of potential structural elements used in tension including but not limited to a single filament of wire, multiple filaments of wire wound into a flexible cable assembly, or thin rods. Furthermore, a “cable” is not limited to metallic construction, but instead encompasses a variety of other non- metallic materials including but not limited to man-made polymers, elastomers, carbon fiber, and fiberglass constructions.
  • FIG. 1 is a diagram of a typical prior art structural frame for a parabolic trough concentrating solar power system in which abundant frame members provide structural rigidity.
  • FIG. 2 is an example of a suspension cable structure, shown here for a parabolic trough system.
  • FIG. 3 is a schematic cross section of a cable system connected to
  • FIG. 4 is a schematic longitudinal elevation of a portion of a cable system connected to compression elements above and below the set of solar reflector elements.
  • FIG. 5 is a partial schematic plan (top view) of a suspension system showing a central compression element supporting a distribution of tension elements, which in turn support a set of solar reflector elements at multiple points.
  • FIG. 6 is a diagram of pre-fabricated sub-assemblies which can be rapidly combined on site to reduce the installation time that would otherwise be required to construct the full assembly from its individual components.
  • FIG. 7A is a schematic cross section of a solar reflector element consisting of a structural composite panel assembly comprising a top layer that has a mirrored surface and one or more backing layers laminated by adhesive or other mechanical means to provide structural rigidity.
  • FIG. 7B is a table of mechanical properties of illustrative three-ply reflector panel composites.
  • FIG. 8 is an exploded schematic view of multiple layers that may constitute a structural composite reflector panel.
  • FIG. 9 is a diagram of schematic receiver support or mast cross sections.
  • FIG. 10 is a schematic diagram of a trussed mast structure.
  • FIG. 11 comprises two schematic diagrams in different views of suspension cable systems using rigid compression frame structures.
  • FIG. 12 shows three views of a first suspension cable system using a compression ring structure.
  • FIG. 13 shows three views of a second suspension cable system using a compression ring structure.
  • FIG. 14 depicts deformations of a two-mast mirror suspension system under three conditions of tilt.
  • FIG. 15 depicts calculated slope error for the tilt configurations of FIG. 14.
  • FIG. 16 tabulates mirror-suspension system characteristics for 6 conditions of tilt and wind loading.
  • the invention encompasses solar collector assembly designs that provide advantages over the prior art.
  • the collector assembly designs described herein can reduce the initial capital cost of solar thermal systems by reducing the material weight of the assembly.
  • the suspension structures detailed in this invention take advantage of high tensile strength to weight ratio cables or wires, configured on both sides of the solar reflectors to more efficiently balance the forces and to more evenly distribute material.
  • the cables and wires can be relatively narrow in diameter relative to their lengths, and thereby cast very small shadows across the collector and receiver elements, minimizing optical losses.
  • the thin diameter to axial length aspect ratio of cables or wires has even greater advantages as the focal length of concentrators increases, as the trend in collector systems progresses to larger aperture widths in order to capitalize on economies of scale. For the same reason, suspension systems particularly benefit nonstandard collector systems that have higher focal length to aperture aspect ratios relative to the typical state of the art.
  • Suspension structures have been applied to heliostat-type solar reflectors that concentrate sunlight to a point receiver.
  • this invention provides suspension systems that are suitable for solar concentrators using linear receivers, as distinguished by the following key differences: (1) asymmetric reflector profiles require asymmetric structural configurations; (2) a linear receiver element induces additional loads which preferably should be supported, either separately from or integrally with the support of the rest of the suspension structure; (3) alignment of a collector along the linear receiver requires additional resistance to both bending along and rotation about the longitudinal axis; (4) curvature of reflector elements limits the number of joints between reflector panels along the curved profile, in contrast to joints between planar reflector panels, which can more directly transfer axial stresses in the plane of the panels.
  • suspension cables preferably should be sized and arranged differently above and below the reflector surface;
  • masts or other receiver supports may need to be provided;
  • a torque tube or other rotationally rigid longitudinal spanning structure preferably should be provided;
  • reflector panel elements comprise single panels, in terms of a structural unit, extending either the full length or the half-length (about the plane of symmetry) of the curved profile.
  • FIG. 1 is a schematic transverse cross-sectional diagram of a typical prior-art structural frame for a parabolic trough CSP system in which abundant frame members provide structural rigidity.
  • Assembly 100 comprises a linear receiver element 102, receiver supports 104, reflector panels 106, and structural support framing elements 108.
  • the framing elements 108 connect to a torque-resisting, longitudinal spanning element 1 10 which may be in the form of a beam or structural tube, or alternately in the form of a space frame, which itself may be integrated into the support framing 108.
  • FIG. 2 is a schematic drawing (axonometric view) of portions of an illustrative
  • the CSP trough system 200 comprises a suspension cable structure and a solar reflector 202, the latter shown here as approximately parabolic in cross-section.
  • the solar reflector 202 may comprise stiff (structural composite) mirror panels that are supported primarily by a suspension cable system.
  • stiff (structural composite) mirror panels that are supported primarily by a suspension cable system.
  • FIG. 6 and FIG. 7A The employment of a structural (load-bearing) stiff solar reflector 202 is discussed further with reference to FIG. 6 and FIG. 7A.
  • a central torque tube 204 or similar structure is used to span between foundation pylons 206 and to provide torsional rigidity and rigid attachment points for suspension masts (e.g., mast 208).
  • Torsion forces may be applied to the system by tracking motors, asymmetric weight loads, unevenly distributed wind loading, and/or other asymmetric torque-producing loads.
  • the portion of the system 200 supported by the pylons 206 may be rotated around the axis defined by the torque tubes 204 for sun tracking.
  • Masts comprise hollow sections or trusses that extend above and below the torque tube 204 to provide attachment points for cables represented in Fig. 2 by cables 210, 212.
  • Suspension cables 210 run from the masts 208 to various points on the surface of the reflector 202.
  • Opposing, pre-tensioned cables e.g., cable 210 and cable 212, provide restoring force to resist deformation of the reflector 202 by changing loads, e.g., by wind loading and changing gravitational loading as the trough sweeps through its angular range, and by other loading.
  • Precisely made cables enable accurate assembly of the mirror structure in a parabolic shape.
  • a receiver 214 is held accurately in position by the upper support masts (e.g., mast 208) and by cables (e.g., cable 210).
  • FIG. 3 is a schematic transverse cross-sectional view of an illustrative solar collector module 300 according to an embodiment of the invention.
  • Module 300 utilizes a multiplicity of cables 302 connected to an upper mast 304 and a lower mast 306.
  • the upper mast 304 is so called because it is above the solar reflector panels 308, and the lower mast 306 is so called because it is below the solar reflector panels 308.
  • each module 300 comprises a single upper mast 304 that is located halfway along the longitudinal dimension of the module 300, and a single lower mast 306 that is similarly located.
  • the upper mast 304 and lower mast 306 form an opposed pair.
  • two or more such mast pairs may be located at various points along the longitudinal dimension of a module similar to module 300.
  • the solar reflector panels 308 are represented as constituting a parabolic trough reflector.
  • the trough reflector as a whole comprises eight solar reflector panels (as is shown in more detail in FIG. 5).
  • the masts 304 and 306 are attached to a relatively rigid longitudinal spanning element 310, also herein termed a "torque tube,” which (a) resists twisting and bending and (b) transfers both dead and live loads to pylons or other bearing structures (not shown in FIG. 3) located at the ends of each collector module 300.
  • the torque tube may or may not be strictly tubular: any extended structure (e.g., tube, truss, other) capable of bearing the requisite loads is contemplated and within the scope of the invention.
  • suspension cables 302 extending from reflector panels 306 connect directly to the base of the upper mast 304, the upper end of which provides an attachment point for cables 302 and a rigid support for the receiver 312.
  • the upper mast 304 also bears in compression forces exerted thereon by the cables 302.
  • the lower mast 306 bears in compression forces exerted in tension by cables 302 (i.e., those cables attached to the underside of the reflector panels308).
  • the forces exerted and borne by the cables 302 and masts 304, 306 are in net balance at all times except during brief intervals of time when dynamic loads are being taken up by slight deformations of various components of the system.
  • support masts may be provided for the cables 302 separately from receiver supports.
  • the solar reflector panels 308 are suspended between the masts 304 and 306.
  • the reflector panels 308 are layered composite structures that are formed precisely in a parabolic shape and that provide rigidity between attachment points.
  • the nature of the layered composite panels comprised by the embodiment of FIG. 3 and by various other embodiments is further described and is illustrated in FIG. 7A and FIG. 8.
  • Reflector panels 308 are connected to the torque tube 310 in the center of the trough, then supported by cables 302 attached to the reflector panels 308 at the trough lip 314 and at second point 316 approximate midway between centerline and lip.
  • the collector framework can be reduced to a central spine, illustrated as the torque tube 310, that provides rigidity in bending and torsion.
  • the masts preferably should be rigidly coupled to this central spine.
  • torque tube stiffness as a limiting factor; for example, a 12 in 2 hollow steel torque square tube with 0.25 in wall thickness is a sufficient baseline member to avoid excessive displacement error in the masts under realistic gravitational and wind loadings.
  • modules similar to module 300 are typically coupled end to end to form strings or runs, and multiple strings are built in parallel, separated by sufficient space to prevent mutual shading during prime operating hours.
  • module 300 is depicted as oriented vertically.
  • one or more tracking motors that are coupled to the torque tube 310 either directly or via the torque tubes of additional modules (not shown), and can exert torque on each module string, changing the axial orientation of the string in order to track sun motion.
  • Distributed tracking drives e.g., those manufactured by Inter Control
  • a drive may be located every -48 m (four 12-meter module spans) and would be sufficient.
  • FIG. 4 is a schematic longitudinal (side) view 400 of the solar collector module of FIG. 3, which utilizes a system of cables 302 connected to an upper mast 402 above and a lower mast 306 below the solar reflector panels 308.
  • the longitudinal spanning member 310 is also depicted in FIG. 4.
  • FIG. 4 illustrates that a plurality (in this case, 4) of reflector panels may be comprised by a single module 300.
  • FIG. 4 also illustrates that the orientations of cables 302 are not confined to the plane of FIG. 3 or any other single plane: rather, they form a three-dimensional structure designed to optimally bear and match loads throughout the module 300.
  • the cables used to support a typical truss radio mast would be an apt comparison.
  • FIG. 5 is a schematic longitudinal (overhead) view 500 of the solar collector module of FIG. 3, which utilizes a system of cables 302 connected to an upper mast 402 above.
  • the lower mast 306 of FIG. 3 and FIG. 4 is not depicted in FIG. 5.
  • the axis of the receiver 306 (which for clarity is not shown) is above and parallel to the axis 502 of the longitudinal spanning element 310.
  • a structure other than a parabolic mirror trough is supported by a suspension system.
  • linear planar arrays of photovoltaic (PV) panels are in various embodiments supported and, if appropriate, rotated for sun-tracking purposes by essentially the same methods described herein for the support, stabilization, and rotation of solar reflector assemblies.
  • PV photovoltaic
  • constraints on shape stabilization would be relaxed for a PV panel assembly as compared to constraints for a solar reflector assembly of roughly comparable dimensions: a PV array need not be positioned with millirad-scale accuracy in order to fully realize its efficiency potential.
  • suspension system costs are likely lower when a PV assembly is incorporated into a suspension system rather than a mirror assembly.
  • FIG. 6 is a schematic diagram of illustrative pre- fabricated sub-assemblies which, according to an embodiment of the invention, can be rapidly combined on-site in order to reduce installation time for a module (e.g., module 300 of FIG. 3) compared to that required to construct the full assembly of a solar collector module 600 from its individual components.
  • these sub-assemblies comprise a primary structure 602, composite mirror panel sections 604a, 604b, secondary structure (lower masts) 606a, 606b, and a set of cables (not shown).
  • the primary structure 602 in one embodiment of the invention, comprises a torque tube (longitudinal spanning element) 608, a receiver element 610, and receiver supports and/or masts 612a, 612b. Connections between subassembly components may be keyed or tabbed to facilitate high-precision alignment of every component.
  • FIG. 7A is a schematic cross section of an illustrative solar reflector subassembly 700 according to an embodiment of the invention.
  • the sub-assembly 700 comprises one or more structural composite panels 702 comprising a top layer 704 that has a mirrored surface 706 and one or more backing layer 708, laminated to the top layer by 704 adhesive or other mechanical means to provide structural rigidity.
  • the backing layer 708 may have an outer sealant coating or layer 710.
  • the laminated sub-assembly 700 is a structural reflector, that is, it not only focuses sunlight that impinges on its reflective upper surface 706 but in addition is mechanically rigid and strong enough to contribute significantly to the support of incident loads, including its own weight and forces transmitted to the subassembly 700 from its edges.
  • the objective of the backing layer 706 and in some embodiments of the top layer 704 as well is to provide stiffness at the lowest possible material density. This may be achieved in various embodiments of the invention by incorporating materials that are hollow, porous, punched, or perforated, honeycomb composites, foams, ribbed, corrugated, roll-formed, woven, or subject to other fabrication or processing techniques to achieve low mass density and high stiffness.
  • the sub-assembly 700 comprises two or more backing layers, each laminated to its neighbors by adhesive layers or other means. A multi-layer reflector assembly is depicted in FIG. 8.
  • a relatively low panel curvature may be utilized, that is, the panel may be flatter than an otherwise comparable parabolic reflector constructed according to the prior art.
  • the curvature of such a prior-art reflector is indicated by the dashed line 712.
  • Lower reflector curvature is advantageous in the construction of a structural, laminated reflector because it enables a simpler laminate structure and therefore is less costly to manufacture.
  • feedstock for backing layer manufacture may comprise a 1-in thick rigid honeycomb sheet.
  • Such sheets may in various embodiments be of polymer materials, metal, paper, foam, or other materials capable of formation into honeycomb or low-density sheets with appropriate mechanical properties (e.g., flexural rigidity). Such sheets can be deformed to yield parabolic curved layers, but the thicker the sheet, the less curvature can be accommodated without cracking or breakage. Thus, for a lower-curvature mirror, fewer (in some embodiments, only one) honeycomb sheet plies may be required for manufacture, while for a higher-curvature mirror, multiple, thinner honeycomb sheet plies may be required to achieve comparable mechanical strength, with correspondingly greater numbers of adhesive layers and manufacturing complexity. It is, in short, less costly to manufacture structurally rigid lower-curvature mirrors than to manufacture comparable higher-curvature mirrors.
  • FIG. 7B presents a table 712 showing selected mechanical properties (i.e., thickness, areal density (kg/m 2 )) of candidate materials for seven illustrative three-ply reflector panel composites.
  • Each row of the table 712 corresponds to a single illustrative three-ply composite comprising an upper sheet, lower sheet, and honeycomb sheet between the upper and lower sheets.
  • Properties of adhesive layers comprised by these illustrative panel structures are omitted from the table 712 of FIG. 7B.
  • the flexural rigidity (“EI") or bending stiffness of each composite is given in the far-right column of the table 712.
  • EI flexural rigidity
  • G10 phenolic refers to G-10 grade phenolic sheeting (e.g., that manufactured by the United States Plastic Corp.) and "Nomex” is the trade name of a flame-resistant meta-aramid material manufactured by E. I. du Pont de Nemours and Company.
  • G10 phenolic has an eightfold higher elastic modulus than polycarbonate and only a 50% higher density, enabling lower overall mass density for the seventh (bottom row) composite material in the table 712, as compared to other composites in the table 712, while retaining high EI.
  • structural panels comprise structural materials other than honeycomb materials.
  • These alternative materials include but are not limited reflector panel materials created by roll forming, such as the structural reflector material manufactured by Insolare Inc.
  • Roll forming is a procedure where continuous bending operations are applied to a material, e.g., sheet metal or strips of metal, to plastically deform the material along a linear axis. Roll stations shape the material in tandem sets of rolls through progressive stages until the required configuration is achieved. Virtually any material that can be formed through sheet forming techniques can be roll formed.
  • a structural trough reflector manufactured by Insolare comprises a ribbed metal sheet that is roll-formed into a structural parabolic unit.
  • FIG. 8 is an exploded schematic view of a portion of an illustrative multi-ply structural composite solar reflector subassembly 800.
  • the top layer 802 has a highly reflective mirrored surface (not separately depicted) that may incorporate a film or coating that enhances the reflectivity and provide environmental protection.
  • the backing layers 806a, 806b comprise relatively stiff but lightweight honeycomb interlayer fastened mechanically or by use of adhesive layers 808a, 808b, 808c.
  • a backing layer 810 completes the composite panel and adds further rigidity.
  • the number of honeycomb backing layers may be one or any greater number.
  • FIG. 9 depicts four illustrative schematic cross sections that may describe any or all of receiver supports and/or mast elements (of, e.g., the system 300 of FIG. 3) to support tension members and/or torque-resisting longitudinal spanning elements (torque tubes).
  • Section 900 is a hollow structural tube or pipe that may be straight or tapered along its length.
  • Section 902 shows a triangular arrangement of three axial members connected and stabilized by trussed elements.
  • Section 904 shows a rectangular arrangement of three axial members connected and stabilized by trussed elements.
  • Section 906 makes a hexagonal arrangement of six struts or axial members connected and stabilized by trussed elements at the perimeter of the section.
  • additional structural stability may be provided by connecting tension elements (e.g., cables, as indicated by lines 908, only one of which is labeled) across the interior space between outer struts.
  • tension elements e.g., cables, as indicated by lines 908, only one of which is labeled
  • some or all of the connecting elements may be either rigid members or cables or wires.
  • the geometries shown in FIG. 9 are exemplary, and are not exhaustive.
  • FIG. 10 is an illustrative schematic diagram of an illustrative space frame or trussed mast structure 1000 according to an embodiment of the invention. In this
  • each rigid axial member 1002 (only one of which is explicitly labeled) are arranged in a rectangular configuration and linked on each side by tensioned crisscrossed cables 1004 (only one of which is explicitly labeled).
  • the use of cables in place of rigid members in upper (above mirror) masts can reduce shadowing of the receiver and thereby can increase the optical efficiency.
  • the box arrangement of the axial members 1002 is prevented from collapsing under the pull of the cables 1004 by appropriately spaced arrangements of spacer struts 1006 (only one of which is explicitly labeled).
  • mirror cables 1008 (only three of which are depicted, and only one of which is explicitly labeled) are attached at or just below the uppermost arrangement of spacer struts 1006.
  • the structure 1000 supports only the load of the receiver's weight and therefore need not be as strong: thus, the portion 1010 of the rigid axial members 1002 that is above uppermost spacer struts 1006 may be weaker (e.g., thinner).
  • the structure 1000 is illustrative of a class of mast structures that may vary endlessly in detail, as for example in cross section (e.g., per the cross-sectional variations of FIG. 9). All such structures are contemplated and within the scope of the invention.
  • FIG. 11 depicts two schematic views of an illustrative cable-suspension suspension system 1 100 comprising rigid compression frame structures according to an embodiment of the invention.
  • a triangular suspension frame 1102 is centered on axis of symmetry 1104 of the parabolic trough mirror 1106.
  • Suspension elements e.g., cables
  • cables 1 108a, 1108b connect the mirror 1106 to the frame 1102.
  • suspension elements are omitted from the right-hand side of both views.
  • the frame 1 102 need not be triangular in various other embodiments, but may take on a variety of forms.
  • the receiver 1108 is shown located at the focal line of the parabolic trough mirror 1106.
  • the parabolic trough mirror 1 106 comprises structural composite subassemblies similar to those depicted in FIG. 7A and FIG. 8.
  • System 1 100 is advantageous because the mechanical support functions of the upper mast 304, lower mast 3046 and torque tube 310 in FIG. 3 are all performed by a single structure, namely the suspension frame 1102.
  • the system 1 100 preferably should be rotated if sun-track is to be achieved, and although possible such rotation is not straightforward with a triangular structure. This drawback is addressed by the illustrative frame designs shown in FIG. 12 and FIG. 13.
  • FIG. 12 shows three schematic views of an illustrative suspension cable system 1200 using a compression ring structure (compression frame) according to an embodiment of the invention.
  • a circular frame 1202 is employed, rather than a triangular frame as in FIG. 11.
  • Cables e.g., cable 1204 are attached to a limited number of attachment points on the frame 1202 and exert tension on the parabolic mirror trough 1206 from above and below.
  • a circular suspension frame offers several advantages over triangular or other suspension frames. First, the inherent mechanical strength of a circular structure allows equivalent bearing strength with less material usage than any other structure (assuming roughly symmetrical interior loads, as in a bicycle wheel).
  • a circular structure is easily rotated, e.g., by mounting the structure on powered bearing rollers, or by mounting the structure on passive bearing rollers and pulling on one or more points of the structure perimeter (e.g., by winching in a cable attached to the perimeter), or by other means.
  • a circular suspension frame such as that of system 1200 realizes advantages addition to those of other embodiments described herein, and in particular is advantageous over the prior art in that powerful, axially mounted motors are not required for sun-tracking rotation of the system 1200; a number of alternative, lower-cost schemes for sun-tracking rotation may be applied. All such schemes are contemplated and within the scope of the invention.
  • FIG. 13 shows three schematic views of an illustrative suspension cable system 1300 using a compression ring structure according to an embodiment of the invention.
  • a circular frame 1302 is employed, as in FIG. 12.
  • Cables e.g., cable 1304
  • System 1300 is similar to system 1200 except that the cables 1304 issue from distributed attachment points from the frame 1302.
  • Such an arrangement by distributing stresses more evenly on the frame 1302, may allow the use of even less material for an otherwise equivalent system.
  • FIG. 14 schematically depicts the behavior of a model employed to study deformation of a two-mast embodiment resembling system 300 of FIG. 3 under three conditions of tilt (gravity loading), i.e., 0° (left), 45° (middle) and 90° (right) pitch angles.
  • Gravity loads tend to dominate mirror surface deformation; wind loads up to 25 mph are relatively benign with regard to the mirror surface.
  • wind loadings (net force and moment coefficients, as well as extreme-case pressure distributions on the mirror surface) have been adapted from National Renewable Energy Laboratory wind-tunnel data given in Hosoya et al. 2008, "Wind Tunnel Tests of Parabolic Trough Solar Collectors, "NREL/SR-550-32282 on conventional troughs with 80° rim angle. It is expected that wind pressure distributions and governing loads will differ somewhat for a flatter collector profile (e.g., 55° rim angle as in the analysis here discussed), but wind tunnel studies, e.g., Peterka et al. 1980, "Mean Wind Forces on Parabolic-Trough Solar Collectors," SAND80-7023, Sandia National Laboratory, have found that peak loads are neither strongly nor consistently associated with rim angle.
  • FIG. 14 schematically depicts the deformation of the mast and mirror under three illustrative conditions of gravitational loading.
  • FIG. 14 schematically depicts portions of an illustrative CSP system 1400 whose upper mast 1402, lower mast 1404, and mirror undergo various degrees and types of deformation under various conditions of gravitational loading.
  • the mirror curve is described by a dotted line 1406 and the upper mast 1402 and lower mast 1404 are undeformed.
  • the mirror In a condition of gravitational loading with 0° tilt (condition depicted at left) the mirror sags symmetrically and its curve is described by a first solid line 1408.
  • the upper mast 1402 upon which a number of cables (e.g., cable 1408) pull, deforms outward in the vicinity of the cable anchor points, as indicated by broadened mast outlines 1412.
  • cables are depicted only for the deformed state of each tilt position.
  • the mirror sags asymmetrically and its curve is described by a second solid line 1414.
  • the upper mast 1402 also deflects, as indicated by shifted outline 1416 and indicated end deflection 1418.
  • the lower mast 1404 deflects in a manner similar to that of the upper mast 1402 (deflection not explicitly labeled in FIG. 14).
  • the mirror sags asymmetrically and its curve is described by a third solid line 1420.
  • the upper mast 1402 and lower mast 1404 deflect in a manner generally similar to that of the 45° case, only more pronounced (mast deflections are not explicitly labeled in FIG. 14).
  • warping and deflection of components is asymmetrical with nonzero tilt or otherwise unbalanced force loading and increases in magnitude with increasing tilt and other unbalanced loads.
  • the precise form and degree of deformation depends on the flexibility of all components involved, including mirror panels and cables, as well as on location and number of cables, pretensioned forces in cables, reflector panel rigidity, mast rigidity, and other factors.
  • mirror deflection varies along mirror profile as well as with tilt angle. Loading by wind, snow, and other factors will in general complicate the gravity deformations schematically depicted in FIG. 14.
  • FIG. 15 Ray -tracing codes and capabilities have been developed that enable rapid analysis of the optical effects of structural deformations of various embodiments.
  • the codes take as input a deflected mirror profile and/or receiver position from mechanical FEA modeling, and output optical flux distribution and geometric optical efficiency.
  • This structural-optical model connection enables the definition of adequate structural stiffness values for key collector elements of various embodiments, including cables, cable masts, torque tube, mirror panels, and receiver supports.
  • the slope error of the mirror (units of millirads, mrad) is determined using ray tracing to calculate the deviation of the reflected light beam from the focal line owing to the deformation of the mirror at discrete locations on the mirror surface.
  • the equivalent slope error at each discrete (or local) position is then calculated using the equation
  • FIG. 15 shows the calculated slope error for the three mirror configurations of FIG. 14 as a function of position (units of meters) along the linear collector aperture.
  • the RMS errors determined from the FEA and ray tracing models represent the slope error in the panels owing to deformation from the support structure under loading but neglect any slope error than is inherently present in the panel.
  • the panels developed by Gossamer Space Frames have an RMS slope error of approximately 1.1 mrad and therefore the slope error of the system can be assumed to be system support panel
  • ⁇ s ⁇ upport is the slope error due to deformation of the panel from the support structure under loading
  • ⁇ ⁇ 6 ⁇ is the slope error inherent in the panel.
  • This system error represents the error due to mirror structure owing to gravitational loading and wind deflections and compare favorably to the system slope error of 2.3 mrad calculated for a Gossamer Space Frame, Inc. system, as described in Chen et al, "Next Generation Parabolic Trough Solar Collectors for CSP," Proceedings of the 6th International Conference on Energy Sustainability , 2012.
  • This combination of errors excludes errors due to (for example) torsion, receiver alignment, and tracking. These errors will contribute towards the optical error budget. Under all examined load conditions to date, these system errors are lower than 4 mrad.
  • a ray-tracing model has been used to calculate the optical performance of the cavity receiver. For each configuration, the rays were traced using the deformed mirror surface and displaced receiver location from ANSYS models. An additional Gaussian scatter was imposed on the reflected ray to represent the additional errors. The combination of these errors can be estimated as
  • pane i is the slope error inherent in the panel ( ⁇ 1.1 mrad)
  • T torsion is the error due to torsion ( ⁇ 1 mrad)
  • ⁇ J a iignment is m e error due to receiver alignment (-1.5 mrad)
  • a track is the error due to sun tracking (-1.5 mrad).
  • the table in FIG. 16 shows the optical efficiency of the mirror-receiver pair discussed above with reference to FIG. 14 and FIG. 15 for each mirror loading configuration using the assumptions defined above for reflectivity, transmittance, and absorptivity for additional errors of 3.2 mrad.
  • the optical efficiency for each mirror loading configuration is above 78%.

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Abstract

L'invention concerne un miroir incurvé pour un collecteur d'énergie solaire ayant une surface miroir, une courbure, et un système de support qui maintient la courbure souhaitée dans des conditions de gravité et de résistance au vent. Dans diverses configurations, le miroir est supporté par des structures de support construites avec des mâts de support et des agencements de câble. Les structures de support sont conçues de manière à être moins coûteuses que les structures de support classiques en utilisant moins de matériau et en employant des procédés de fabrication simplifiés.
PCT/US2015/017556 2014-02-25 2015-02-25 Collecteur à miroir pour miroir cylindro-parabolique solaire WO2015130808A1 (fr)

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CN201580015317.5A CN106461269A (zh) 2014-02-25 2015-02-25 用于抛物线太阳能槽的镜子收集器
ZA2016/05932A ZA201605932B (en) 2014-02-25 2016-08-25 Mirror collector for parabolic solar trough

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WO2017184893A1 (fr) * 2016-04-20 2017-10-26 Norwich Technologies, Inc. Collecteur à miroir pour miroir cylindro-parabolique solaire
US10042147B2 (en) 2016-12-14 2018-08-07 The United States Of America As Represented By Secretary Of The Navy Glass concentrator mirror assembly

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Publication number Priority date Publication date Assignee Title
WO2019232917A1 (fr) * 2018-06-05 2019-12-12 Xu Yangxin Réflecteur à concentration de lumière incurvé et système de traitement associé, et ensemble de réflecteurs à concentration de lumière et procédé de fabrication associé
CN108680975A (zh) * 2018-06-05 2018-10-19 许养新 曲面聚光反射镜及加工系统、聚光反射镜组和其制备方法
CN114475911B (zh) * 2022-01-26 2023-03-21 中船黄埔文冲船舶有限公司 一种反射体桅杆

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US4308858A (en) * 1979-10-29 1982-01-05 Skillman Dale N Solar energy collecting apparatus and methods
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US20090062452A1 (en) * 2007-08-24 2009-03-05 Ems-Patent Ag High-temperature polyamide molding compounds reinforced with flat glass fibers
US20110073104A1 (en) * 2008-04-18 2011-03-31 Sopogy, Inc. Parabolic trough solar energy collection system
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US4063544A (en) * 1976-10-05 1977-12-20 Raytheon Company Solar energy collectors
US4308858A (en) * 1979-10-29 1982-01-05 Skillman Dale N Solar energy collecting apparatus and methods
US6485152B2 (en) * 2000-05-05 2002-11-26 Doug Wood Matrix solar dish
US20070291384A1 (en) * 2006-06-14 2007-12-20 Guardian Industries Corp. Method of making reflector for solar collector or the like, and corresponding product, including reflective coating designed for improved adherence to laminating layer
US20090062452A1 (en) * 2007-08-24 2009-03-05 Ems-Patent Ag High-temperature polyamide molding compounds reinforced with flat glass fibers
US20110073104A1 (en) * 2008-04-18 2011-03-31 Sopogy, Inc. Parabolic trough solar energy collection system
US20120275040A1 (en) * 2011-04-27 2012-11-01 Massachusetts Institute Of Technology Precision parabolic mirror structures
WO2013084016A1 (fr) * 2011-12-08 2013-06-13 Nee Innovations, S.R.O. Structure de support pour un miroir cylindro-parabolique de capteurs solaires

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2017184893A1 (fr) * 2016-04-20 2017-10-26 Norwich Technologies, Inc. Collecteur à miroir pour miroir cylindro-parabolique solaire
US10042147B2 (en) 2016-12-14 2018-08-07 The United States Of America As Represented By Secretary Of The Navy Glass concentrator mirror assembly

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ZA201605932B (en) 2019-03-27

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