WO2011038144A1 - Système concentrateur solaire avec réflecteur primaire fixe et miroir secondaire sur articulation - Google Patents

Système concentrateur solaire avec réflecteur primaire fixe et miroir secondaire sur articulation Download PDF

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Publication number
WO2011038144A1
WO2011038144A1 PCT/US2010/050039 US2010050039W WO2011038144A1 WO 2011038144 A1 WO2011038144 A1 WO 2011038144A1 US 2010050039 W US2010050039 W US 2010050039W WO 2011038144 A1 WO2011038144 A1 WO 2011038144A1
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WIPO (PCT)
Prior art keywords
concentrators
concentrator
primary
solar radiation
solar
Prior art date
Application number
PCT/US2010/050039
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English (en)
Inventor
John H. Reif
Katie L. Reif
Original Assignee
Eagle Eye, 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 Eagle Eye, Inc. filed Critical Eagle Eye, Inc.
Priority to CN2010800480649A priority Critical patent/CN102612627A/zh
Priority to MX2012003353A priority patent/MX2012003353A/es
Priority to EP10763917A priority patent/EP2480837A1/fr
Priority to AU2010298244A priority patent/AU2010298244B2/en
Priority to IN2543DEN2012 priority patent/IN2012DN02543A/en
Publication of WO2011038144A1 publication Critical patent/WO2011038144A1/fr
Priority to IL218792A priority patent/IL218792A0/en

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24S—SOLAR HEAT COLLECTORS; SOLAR HEAT SYSTEMS
    • F24S30/00—Arrangements for moving or orienting solar heat collector modules
    • F24S30/20—Arrangements for moving or orienting solar heat collector modules for linear movement
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24S—SOLAR HEAT COLLECTORS; SOLAR HEAT SYSTEMS
    • F24S20/00—Solar heat collectors specially adapted for particular uses or environments
    • F24S20/20—Solar heat collectors for receiving concentrated solar energy, e.g. receivers for solar power plants
    • 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
    • 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
    • F24S23/79—Arrangements for concentrating solar-rays for solar heat collectors with reflectors with spaced and opposed interacting reflective surfaces
    • 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
    • F24S23/80—Arrangements for concentrating solar-rays for solar heat collectors with reflectors having discontinuous faces
    • 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
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24S—SOLAR HEAT COLLECTORS; SOLAR HEAT SYSTEMS
    • F24S30/00—Arrangements for moving or orienting solar heat collector modules
    • F24S30/40—Arrangements for moving or orienting solar heat collector modules for rotary movement
    • F24S30/42—Arrangements for moving or orienting solar heat collector modules for rotary movement with only one rotation axis
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24S—SOLAR HEAT COLLECTORS; SOLAR HEAT SYSTEMS
    • F24S50/00—Arrangements for controlling solar heat collectors
    • F24S50/20—Arrangements for controlling solar heat collectors for tracking
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24S—SOLAR HEAT COLLECTORS; SOLAR HEAT SYSTEMS
    • F24S60/00—Arrangements for storing heat collected by solar heat collectors
    • F24S60/10—Arrangements for storing heat collected by solar heat collectors using latent heat
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24S—SOLAR HEAT COLLECTORS; SOLAR HEAT SYSTEMS
    • F24S60/00—Arrangements for storing heat collected by solar heat collectors
    • F24S60/20—Arrangements for storing heat collected by solar heat collectors using chemical reactions, e.g. thermochemical reactions or isomerisation reactions
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24S—SOLAR HEAT COLLECTORS; SOLAR HEAT SYSTEMS
    • F24S20/00—Solar heat collectors specially adapted for particular uses or environments
    • F24S20/20—Solar heat collectors for receiving concentrated solar energy, e.g. receivers for solar power plants
    • F24S2020/23—Solar heat collectors for receiving concentrated solar energy, e.g. receivers for solar power plants movable or adjustable
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24S—SOLAR HEAT COLLECTORS; SOLAR HEAT SYSTEMS
    • F24S30/00—Arrangements for moving or orienting solar heat collector modules
    • F24S2030/10—Special components
    • F24S2030/13—Transmissions
    • F24S2030/133—Transmissions in the form of flexible elements, e.g. belts, chains, ropes
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24S—SOLAR HEAT COLLECTORS; SOLAR HEAT SYSTEMS
    • F24S30/00—Arrangements for moving or orienting solar heat collector modules
    • F24S2030/10—Special components
    • F24S2030/13—Transmissions
    • F24S2030/137—Transmissions for deriving one movement from another one, e.g. for deriving elevation movement from azimuth movement
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24S—SOLAR HEAT COLLECTORS; SOLAR HEAT SYSTEMS
    • F24S40/00—Safety or protection arrangements of solar heat collectors; Preventing malfunction of solar heat collectors
    • F24S40/80—Accommodating differential expansion of solar collector elements
    • F24S40/85—Arrangements for protecting solar collectors against adverse weather conditions
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F28—HEAT EXCHANGE IN GENERAL
    • F28D—HEAT-EXCHANGE APPARATUS, NOT PROVIDED FOR IN ANOTHER SUBCLASS, IN WHICH THE HEAT-EXCHANGE MEDIA DO NOT COME INTO DIRECT CONTACT
    • F28D20/00—Heat storage plants or apparatus in general; Regenerative heat-exchange apparatus not covered by groups F28D17/00 or F28D19/00
    • F28D20/003—Heat storage plants or apparatus in general; Regenerative heat-exchange apparatus not covered by groups F28D17/00 or F28D19/00 using thermochemical reactions
    • 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
    • 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
    • Y02E10/44—Heat exchange systems
    • 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

  • a solar energy plant takes solar energy and converts it to useful energy and/or products.
  • a solar electrical plant takes solar energy and converts it to electrical energy.
  • a solar concentrator system collects incoming direct solar irradiation 2 from a collection field and concentrates it to a smaller solar receiver region.
  • the purpose of a solar concentrator system is to concentrate solar irradiance for later conversion into other forms of usable energy, such as solar thermal to electrical5 energy.
  • a concentrating solar energy plant is a solar plant composed of two major parts: a solar concentrator system 8, and a power-block 140, which converts secondary
  • Concentrated solar thermal-electrical plants are solar power plants that make use of solar irradiation (primarily in the infrared (IR) range) to generate electricity.
  • IR infrared
  • Each0 square meter of land in the United States Southwest receives approximately 5 to 8 kilowatt hours (kWh) of solar irradiation each solar day, depending on season and weather conditions.
  • a report entitled Assessment of Parabolic Trough and Power Tower Solar Technology Cost and Performance Forecasts by Sargent and Lundy LLC consulting Group, National Renewable Energy Laboratory, Chicago, Illinois, (October 2003), herein5 referred to as "the Sargent and Lundy report,” made a cost analysis that implies the currently operating large scale solar concentrating and collecting systems produce electricity (per kWh) at a cost (including finance costs for construction) of roughly
  • PV plants make use of photovoltaic (PV) cells to generate electricity.
  • the most efficient PV plants make use of concentrated solar radiation primarily in the ultraviolet (UV) and visual (VIS) ranges.
  • UV ultraviolet
  • VIS visual
  • PV cells generally degrade more rapidly, making them at this time a less preferable choice for large-scale electrical generation than solar thermal-electrical plants.
  • solar PV plants have distinct advantages, such as their capability to provide electrical power in remote areas, and their potential portability.
  • Solar concentrator systems typically consist of various key optical components: a primary concentrator, possibly a secondary concentrator, a solar receiver containing some form of solar absorber and/or an energy storage system.
  • Known large-scale solar concentrator systems can generally be partitioned into four types of categories based on the shape or configuration of their primary concentrating surfaces. These are power tower systems, trough systems, compact linear Fresnel reflector systems, and dish systems. Power tower collectors are comprised of an array of heliostats, which individually track to concentrate solar radiation to a central, and usually raised receiver. The primary concentrators of trough systems have curved trough shape or a faceted approximation, which concentrate solar radiation to their focal line. The primary concentrators of compact linear Fresnel reflector systems are flat reflective strips, which are rotated to concentrate solar radiation to their focal line.
  • the primary concentrators of dish systems have curved dish shape or a faceted approximation, which concentrate solar radiation to a single focal point.
  • the primary concentrators which are the component that receives direct solar radiation, typically have the largest surface area of any component, and thus their design is a large component in terms of costs of the overall system.
  • Most primary concentrators are not horizontal, and are highly exposed to wind forces, often requiring costly structural support structures.
  • most large-scale solar concentrators contain primary concentrators that are tracking, that is, they move to follow the daily movement of sun. In trough concentrator systems, this may manifest in one dimensionally tracking troughs, while in power tower systems, it may involve two dimensionally tracking heliostats.
  • these tracking primary concentrators generally make up a large portion of the total cost of the system due to their tracking mechanisms and the structural support structures needed to help them withstand wind and other weather conditions.
  • the Sargent and Lundy report made a component cost breakdown for a 2004 trough system and estimated that thirty-five percent of the cost was due to the metal support structure and drive, which together comprise the tracking and control system for the primary concentrators.
  • the primary concentrators of compact linear Fresnel reflector systems can be placed on the ground at near horizontal position, but the primary concentrators are required to track, increasing their complexity and construction costs.
  • Solar receivers have an important component, absorbers, whose function is to receive the concentrated solar energy for the purpose of storage or energy conversion.
  • absorbers have low cost compared to the cost of the solar concentrator system.
  • the locations of the absorbers may vary in solar collectors; a concentrating solar system is defined to have localized absorbers if a distinct absorber is required for each primary concentrator element, whereas a concentrating solar system has centralized absorbers if multiple concentrators direct solar energy to a small number of absorbers.
  • the use of localized absorbers often results in a more complex and costly heat transport and conversion system. Furthermore, the efficiency of heat energy conversion is increased with a higher temperature differential.
  • solar receivers In addition to absorbers, solar receivers generally also include a means for storage of the energy collected by the absorbers.
  • the energy storage period may be temporary or may be for a longer period beyond the period of the solar day.
  • energy storage can be achieved by a material or medium for storage of the heat energy, which may be temporary or may be for a longer period.
  • the generator Since solar energy can only be collected for a portion of the solar day (typically approximately 8 hours a day), it follows that without a means for energy storage, the generator would only be able to produce electricity for that portion of the solar day. During this window of time, the generator would have to convert all of the collected solar radiation. In typical practice, by using an energy storage medium, the generator can potentially run up to three times longer, providing approximately one third the power over a twenty-four hour period. In solar energy systems with energy storage, the receiver can serve to absorb the energy from focused solar radiation and store in thermal energy storage substances, phase change materials, or chemical energy storage substances.
  • Thermal energy storage substances include, in some examples, liquid sulfur, molten salt, fluoride-salt, and various mineral oils.
  • Phase-change materials make use of a change in state (e.g., from solid to liquid, or from liquid to gas) for energy storage.
  • various materials include water, which can be used to store and release heat by evaporating into steam and condensing back to liquid start, or alternatively various salts can be used to store and release heat by melting and solidifying, respectively.
  • Chemical storage mediums make use of chemical reactions to store and release heat.
  • Chemical storage mediums include metal hydrides, such as magnesium hydride, which store energy by dissociation to the base metal and hydrogen gas.
  • energy storage systems add to the initial cost of a solar power plant, but provide for extended daily periods of electrical output beyond the period of solar exposure, allowing electrical generators to be used extended periods of up to a full twenty-four hours rather than the approximately (depending on latitude and season) eight hours of usable direct sunlight, with only a very small decrease the efficiency.
  • the cost for energy storage was approximately 150% of the cost for the electrical generators, which implies a total of approximately 250% increased cost of constructing the power (storage and conversion) block, so the effective decrease in power-block cost by the use of energy storage is approximately 2.5/3 or about 83%.
  • the portion of a solar energy system that transforms solar energy to other useful products or energy, such as electricity, is termed the power-block.
  • the power-block includes generators that transform solar energy to electricity as well as possibly energy storage devices.
  • the efficiency (the ratio of the energy output to the energy input) and cost of the means for energy conversion from concentrated solar energy into electricity is critical.
  • the maximum Carnot efficiency of a reversible system for conversion of heat energy to mechanical power is lower bounded by 1-r, where r is the ratio of the cooled (ambient) temperature to the heated temperature (where both temperatures given are in degrees Kelvin).
  • r is the ratio of the cooled (ambient) temperature to the heated temperature (where both temperatures given are in degrees Kelvin).
  • the efficiency of typical nonreversible systems for conversion of heat energy to electrical power has been empirically found to limit (for large generator systems) to approximately 1- r 1 2 . In either formula, the key quantity r is minimized when the heat differential between the cooled (ambient) temperature and the heated temperature is maximized.
  • Turbines can have efficiencies of up to 33% (depending on the size of the generator), and this can rise to as high as 42% efficiency if a reheat turbine cycle is used.
  • the estimated yearly electrical income per kWh for concentrated solar thermal-electrical plants is less than the initial cost of purchase of steam turbines per kWh. However, this cost encompasses only the steam turbine, not the entire heat conversion system.
  • This entire power-block is comprised of the steam turbine, cooling towers and piping systems. In prior art trough solar plants; the power- Attorney Docket No.: 161648-0003 block can make up approximately 14% of the total cost (The Sargent and Lundy Report, ⁇ 4.3).
  • Another variety of solar system includes cogeneration systems that, in addition to generating electrical energy from heat, also make further productive use of the waste heat, for example for steam or hot water heating of buildings. Such cogeneration systems can thus make productive use of upwards of between 85% and 90% of the input heat energy.
  • Certain embodiments make use of an array of passive primary concentrators positioned on the ground, that provide primary concentrated solar radiation from below to an array of tracking secondary concentrators, which then further concentrate the solar radiation to one or more centralized solar energy receivers.
  • the solar concentrator system may include apparatus for collection of solar radiation, concentration, and the absorbance of the concentrated solar energy.
  • Some embodiments of the solar concentrator system include a large field of inexpensive, passive horizontal primary concentrators, overhead tracking secondary concentrators, and one or more receivers, which convert solar radiation into usable products or energy, such as electricity.
  • a power-block may store and convert the concentrated solar energy to useful products.
  • FIG. IB summarizes an embodiment of the flow of energy through the solar concentrator system, where 1 is the Sun, 2 is direct solar radiation, 3 is a (saw-tooth contoured) primary concentrator, 4 is the primary concentrated solar radiation directed from a primary concentrator, 5 is a secondary concentrator, 6 is further concentrated solar radiation directed from secondary concentrator, 7 is a receiver of the concentrated solar energy.
  • a field used for collection of solar radiation from the sun is termed the primary concentrating field; in some embodiments, the primary concentrating field is fixed on Attorney Docket No.: 161648-0003 the ground (immobile) and may be constructed out of an inexpensive material, such as concrete.
  • the field may be subdivided into units, called primary concentrators.
  • the primary concentrators are linear optical concentrators. In other words, the primary concentrators focus light to a region of focus, generally of uniform height above their surface, which will be termed the primary concentrator's focal line. In certain embodiments, due to in part to off-axis aberrations, optical surface defects and other effects, this focal line may broaden to a narrow horizontal strip.
  • Each primary concentrator may have an optical surface with a saw-tooth cross section which provides an initial concentration of direct solar radiation.
  • the optical surface of the primary concentrators has a parabolic cross section.
  • the optical surface may be purely reflective.
  • the optical surface may include both refractive and reflective elements.
  • the optical surface of the primary concentrators includes a series of elongated convex cross section.
  • the optical surface includes a plurality of reflective optical elements.
  • the primary concentrators are stationary and, as the sun moves throughout the day, the primary concentrators' focal line moves across the focal plane in a west to east direction. In other embodiments, the focal line of the primary concentrators moves across the focal plane in an east to west direction.
  • the optical surfaces of the primary and secondary concentrators may provide high optical efficiency, in particular high spectral reflectance. In some embodiments, the optical surfaces of the primary concentrators are mirror films that are very durable, and inexpensive to replace. In some embodiments, the optical surfaces of the secondary concentrators are extremely durable metallic surfaces with protective coating, insuring a long lifetime.
  • Each secondary concentrator may have one or two optical surfaces, each of which may be a linear optical concentrator.
  • the optical surfaces of the secondary concentrators are purely reflective.
  • the optical surfaces of the secondary concentrators include both refractive and reflective elements.
  • the optical surfaces are reflective and concave in cross section.
  • the optical surfaces of the secondary concentrators may include refractive as well as reflective elements.
  • the optical surfaces have a saw-tooth cross section. In other embodiments, the optical surfaces are parabolic in cross section.
  • the array of secondary concentrators may further concentrate the solar radiation and direct it to one or more receivers.
  • the array of secondary concentrators is positioned to direct concentrated solar radiation to the receiver or receivers without obstructing one another.
  • Each secondary concentrator may be suspended above the solar collecting field so that at any given time, the focal line (this is the hypothetical line at which parallel rays emitted from the receiver would be focused by the active optical surface of the secondary concentrator) of an optical surface of the secondary concentrator coincides with the focal line of the primary concentrator associated with the secondary concentrator.
  • the secondary concentrator can be moved throughout the solar day.
  • adjustments of the secondary concentrator can be used to track the focal line of initially concentrated solar radiation reflected from the primary concentrator.
  • simultaneous tracking movements may be made to insure the fully concentrated solar radiation departing from the secondary concentrator is always directed toward one of the receivers.
  • the secondary concentrators may track on an east-west axis parallel to the plane of the ground. In some embodiments, the secondary concentrators rotate vertically during tracking. In other embodiments, the secondary concentrators rotate during east-west tracking of the focal line. In some embodiments, the secondary concentrators suspended overhead on cables that allow movement of the secondary concentrators while tracking the focal line of the primary concentrator.
  • the receivers are located centrally in the primary concentrating field. In other embodiments, the receivers are located outside the field. In Attorney Docket No.: 161648-0003 alternative embodiments, the receivers are able to adjust their locations depending on the time of year.
  • the solar concentrator system may be used in conjunction with a heat storing apparatus.
  • the heat storing apparatus includes a bulk heat
  • the heat storing apparatus is a phase change medium (e.g., via the melting of salts or
  • the heat storing apparatus is a chemical heat storage system (e.g., metallic hydride reactions liberating hydrogen).
  • the solar concentrator system may be used in any applications.
  • high concentration solar cells are used to
  • a steam turbine converts the solar radiation into energy or heat.
  • solar radiation and conversion into usable energy may be shared amongst two or more solar concentrator systems.
  • a solar concentrator system including immobile primary concentrators, tracking secondary concentrators and centralized receivers to which solar radiation is directed may use an array of passive primary concentrators positioned on the ground, such that primary concentrated solar radiation can be provided from below to the array of tracking secondary concentrators.
  • the array of tracking secondary concentrators may then further concentrate the solar radiation to the two centralized receivers.
  • the design of the solar concentrator system may provide a dramatic reduction in costs for construction and maintenance while maintaining a high energy-efficiency, longevity, and broad applicability.
  • two aspects of the solar concentrator system may provide a dramatic reduction in costs for construction and maintenance.
  • a key item of cost advantage can include the use of immobile primary concentrators positioned on the ground, which therefore do not require costly large-scale Attorney Docket No.: 161648-0003 structural support.
  • the use of tracking secondary concentrators suspended overhead on cables can also provide a significant cost-savings for construction.
  • the design of these two features may reduce of other recurring costs (such as maintenance).
  • the high energy-efficiency design of the solar concentrator system, in combination with the reduction in costs for construction and maintenance, may imply a short payback period for combination of the initial costs and the recurring costs to be amortized.
  • the optical surfaces of the primary and secondary concentrators may provide high optical efficiency, in particular high spectral reflectance.
  • the use of centralized receivers, to which solar radiation is directed, can significantly increase the energy-efficiency of the system, since heat does not need to be transported, and heat storage systems can be easily configured at the centralized receivers.
  • a high longevity may be provided by the ground-based positioning of the primary concentrators, allowing limited exposure to weather-related degradation such as wind loads.
  • the low aspect and simplicity of the cable suspension of the secondary concentrators may also provide features that extend the lifetime of the solar concentrator system.
  • the optical surfaces of the primary concentrators in another example, can be constructed of mirror film that is very durable yet inexpensive to replace.
  • the optical surfaces of the secondary concentrators in another example can be constructed of extremely durable metallic surfaces with protective coating, insuring a long lifetime.
  • the solar concentrator system can provides concentrating of a wide spectrum of solar radiation, including both IR (for example for solar- thermal electrical plant applications), as well as UV and VIS (for example for PV electrical power plant applications).
  • FIG. 1A illustrates a solar energy plant composed of a solar concentrator system and a power-block.
  • FIG. IB summarizes a flow of energy through the solar concentrator system of
  • FIG. 1A Attorney Docket No.: 161648-0003
  • FIGS. 2A and 2B show examples of primary concentrators.
  • FIG. 3 shows (in 3D) a solar collecting field composed of bidirectional primary concentrators.
  • FIGS. 4A and 4B show examples of primary concentrators with a saw-tooth surface patterning.
  • FIGS. 5A-5F show examples of the concentration of solar radiation by one or more solar concentrators.
  • FIGS. 6A- 6C show examples of the concentration of solar radiation by an individual primary concentrator and an associated secondary concentrator into a solar energy receiver.
  • FIGS. 7A-7K detail various types of secondary concentrators.
  • FIGS. 8A-8C are illustrations of examples of secondary concentrators suspended by cables.
  • FIG. 9 is an illustration of an example of a field of bidirectional primary concentrators, with associated doubled secondary concentrators, their support via support cables and poles.
  • FIG. 10 illustrates the geometry optionally employed for avoiding optical obstructions between secondary concentrators.
  • FIGS. 11A-11D show examples of how a singleton secondary concentrator can be equipped with one or multiple pivots to allow it to be folded into a protective clamshell position.
  • FIGS. 12A-12D show examples of how a double secondary concentrator can be equipped with one or multiple pivots to allow it to be folded into a protective clamshell position.
  • FIGS. 13A-13B illustrate example positioning of a secondary concentrator so that its receiver-directed focal line coincides with the focal line of the primary concentrator.
  • FIG. 13C is an illustration of an example of how the east-west slant of the focal plane of a primary concentrator can conform to the local slant of the support cables above.
  • FIGS. 14A-14C show various exemplary positions of the extended focal line of the primary concentrator over the day, along with the corresponding position of the secondary concentrator.
  • FIGS. 15A-15D show examples of a daily schedule used for positioning a secondary concentrator.
  • FIGS. 16A-16E show tracking apparatus with illustrations at various distinct times throughout the day of the translational tracking of a non-rotating non-elevating doubled secondary concentrator as well as illustrations of the radiation entering the doubled secondary concentrator from the bidirectional primary concentrator.
  • FIG. 17A shows determination of the secondary concentrator's vertical angle from the horizontal to the midline of the receiver.
  • FIGS. 17B-17F shows examples of how daily vertical translations of the secondary concentrator of FIG. 17A can be used to improve the performance of the secondary concentrator.
  • FIG. 17G illustrates an example of a vertically tracking, non-rotating double secondary concentrator.
  • FIGS. 17H-17K show the apparatus of FIG. 17G with illustrations at various distinct times throughout the day of the translational tracking.
  • FIG. 17L shows an illustration of the daily movements illustrated in FIGS. 17H- 17K, condensed into one figure.
  • FIG. 18A illustrates an example of the definition (in 2D cross section) of the angle of rotation of the secondary concentrator.
  • FIGS. 18B-18E show how daily counterclockwise rotations of a secondary concentrator can be used to improve its performance.
  • FIG. 18F shows an illustration of the daily counterclockwise rotations illustrated in FIGS. 18B-18E condensed into one figure.
  • FIG. 19A illustrates an example of a rotating non-elevating double secondary concentrator.
  • FIGS. 19B-19F show the apparatus of FIG. 19A, with illustrations at various distinct times throughout the day of the translational tracking.
  • FIG. 20A illustrates an example of a rotating non-elevating singleton secondary concentrator with a cam disk and cam guide.
  • FIGS. 20B-20G illustrate the apparatus of FIG. 20A, with position of the engaged single cam and secondary concentrator at various angles of rotation at five exemplary times throughout the day.
  • FIG. 21 illustrates an example pair of horizontally separated refractive secondary concentrators, where each concentrator has a saw-tooth contoured operationally- refractive optical surface, and both concentrators are non-rotating and non-elevating and attached to the same two support cables.
  • FIG. 22 illustrates an example pair of horizontally separated refractive secondary concentrators, where both are non-rotating and non-elevating and attached to the same two support cables.
  • FIG. 23A illustrates an example of how secondary concentrators can swivel slightly away from the north-south axis to compensate for the changing slant of the concentrated solar radiation over the year.
  • FIG. 23B illustrates an example of how receivers can move on the north-south axis to slowly track over the year the changing north-south location of the concentrated solar radiation from the secondary concentrators, so as to capture this concentrated solar radiation.
  • FIG. 23C illustrates an example of a receiver with a vertically stacked array of horizontal evacuated receiver tubes, arranged in a linear pattern, used as absorbers of the concentrated solar radiation.
  • FIG. 23D illustrates an example of a receiver with a collection of horizontal evacuated receiver tubes, arranged in a zig-zag pattern, used as absorbers of the concentrated solar radiation.
  • FIGS. 24A and 24B illustrate example apparatus for storage of the concentrated solar energy using a magnesium hydride.
  • FIGS. 25A and 25B illustrate an example solar concentrator system including a power block.
  • FIG. 26 illustrates an example of the concentrated solar radiation from secondary concentrators directed a receiver, partitioned into two subreceivers.
  • a solar concentrator system includes an apparatus for the collection of solar radiation, concentration, and the absorbance of the concentrated solar energy.
  • a solar energy source e.g., the Sun
  • a solar energy source 1 providing direct solar irradiation 2
  • a (saw-tooth contoured) primary concentrator 3 primary concentrated solar radiation 4 directed from a primary concentrator 3
  • secondary concentrator 5 secondary concentrated solar radiation 6 directed from the secondary concentrator 5
  • a solar collecting field configured to receive direct solar radiation can be designed to minimize construction and maintenance costs while providing highly efficient concentration of solar energy.
  • the collecting field is positioned on a flat, horizontal plane and is rectangular in shape.
  • the collecting field is oriented so that two opposing sides, where solar receivers are located, are positioned for example on the east and west sides of the field.
  • the solar radiation in the initial part of the solar day will be concentrated to the east solar receivers and in the later part of the solar day solar radiation will be concentrated to the west solar receivers.
  • the solar receivers are rectangular in shape with a midline at a fixed height H.
  • the two opposing sides are positioned generally on the east and west sides of the field. In other embodiments, the two opposing sides are positioned generally on the north and south sides of the field. In certain embodiments, there is exactly one solar receiver on each of the solar receiver sides. In other embodiments, Attorney Docket No.: 161648-0003 there are between approximately two and approximately nine solar receivers on each of the solar receiver sides, preferably between three and seven, more preferably five.
  • the solar collecting field is horizontal and composed of an array of primary concentrators.
  • Each primary concentrator is rectangular in shape.
  • Each primary concentrator has as its upper surface an optical surface that provides an initial concentration of direct solar radiation.
  • the surface of each primary concentrator has a saw-tooth contour, with troughs that run in the in a north-south direction. In other embodiments, the troughs run in an east-west direction.
  • the optical surface of the primary concentrators includes a series of elongated convex forms.
  • the initial concentration of solar radiation provided by the primary concentrator, and directed above it, will be termed the primary concentrated solar radiation.
  • the optical surface of each primary concentrator in some implementations, is purely reflective. In other embodiments, the primary concentrator is both reflective and refractive. In certain embodiments, the primary concentrators are stationary. When the primary
  • the primary concentrated solar radiation moves in a west to east direction above the primary concentrators when the sun moves across the sky. In certain embodiments, the primary concentrated solar radiation moves in an east to west direction above the primary concentrators.
  • the primary concentrators have a saw-tooth contour on their optical surfaces consisting of a series of elongated strip-shaped facets which are concave and run linearly in a north-south direction. In some embodiments, the optical surfaces run linearly in an east-west direction. In alternative embodiments, the series of elongated strip-shaped facets are flat.
  • the primary concentrators in some embodiments
  • the primary concentrators are bidirectional.
  • the primary concentrators are unidirectional.
  • the strips of a unidirectional primary concentrator 3a are either are all oriented east or all oriented west.
  • the optical surface of a bidirectional primary concentrator 3b as shown in FIG. 2B, has a sequence of strips Attorney Docket No.: 161648-0003 on its optical surface running from west to east. The strips, for example, begin at the west end oriented east, and then are followed (progressing to the east) by a further sequence of strips that are oriented west.
  • the top surface of the bidirectional primary concentrator 3b has a first portion 150a and a second portion 150b, the first portion 150a including the generally west half of the bidirectional primary concentrator 3b, and the second portion 150b including the generally east half of the bidirectional primary concentrator 3b.
  • the first and second portions 150 slope generally downward toward the center of the bidirectional primary concentrator 3b. In other embodiments, the first and the second portions 150 slope generally downward toward a first and a second edge of the bidirectional primary concentrator 3b, where the first and second edges are located on opposite sides of the bidirectional primary concentrator 3b.
  • each primary concentrator is parabolic in cross section.
  • the primary concentrators are slightly slanted so the troughs of the primary concentrators can serve as a runoff system. For example, runoff from the troughs of the primary concentrators can be fed into an additional water drainage system in the case of heavy rains.
  • FIG. 3 shows an example solar collection field 9 composed of an array of bidirectional primary concentrators 3b.
  • the solar collection field 9 includes multiple bidirectional primary concentrators 3b in an array that is approximately horizontal.
  • the bidirectional primary concentrators 3b located in the same column all have the same layout, such that the first and second portions of each bidirectional primary
  • the longitudinal axis in some implementations, runs along a generally north-south axis. In other embodiments, the longitudinal axis runs along a generally east-west axis.
  • the solar collection field 9 contains a first half and a second half.
  • Each half includes multiple bidirectional primary concentrators3b generally Attorney Docket No.: 161648-0003 sloped in the same direction.
  • the first half can be positioned on the west side of the solar collection field 9 and have a downward slope toward the western longitudinal edge of the solar collection field 9 and the second half can be positioned on the east side of the solar collection field 9 and have a downward slope toward the eastern longitudinal edge of the solar collection field 9.
  • the first and the second halves slope generally downward toward the center of the solar collection field 9.
  • the first half is positioned on the north side of the solar collection field 9 and the second half is positioned on the south side of the solar collection field 9.
  • each primary concentrator such as unidirectional primary concentrator 3a and bidirectional primary concentrator 3b, is to collect and initially concentrate the direct solar radiation from the sun, the primary concentrators comprise the vast majority of the bulk of materials of the solar concentrator system. In some embodiments, depending on the ground contour of the site, there may be the need for minimal gravel grading of the ground to insure it is sufficiently flat.
  • Each primary concentrator can be constructed from one or more low cost structural blocks.
  • the structural blocks can be composed of concrete. In another example, the structural blocks can be made from plastic. In some embodiments, the blocks are made from a metallic material. In other embodiments, the blocks are made from wood or a wood compound. In certain embodiments, the material used to create the blocks is optically clear.
  • the structural blocks are made from a plant product other than wood. These blocks can be preformed offsite or cast on site using molds. Each mold, for example, creates one block. In other embodiments, a single mold creates multiple blocks at a time. In certain embodiments, the blocks are formed offsite at a
  • a sheet of wire mesh may be cast inside of these blocks to add structural support.
  • On the upper surface of each primary concentrator can be one or more layers of a material such as plastic, which aids in defining the shape of the optical surface, smoothes the upper surface, and also provides sheathing protection from Attorney Docket No.: 161648-0003 weathering.
  • a highly reflective metallic film in some implementations, is adhered to the uppermost surface of the primary concentrator.
  • the spectral reflectance of an optical surface is the percent of incoming radiation that is directly reflected, and neither absorbed nor diffused in some other direction.
  • Mirror films designed for solar concentration applications generally are designed to be inexpensive, durable, and have a high reflectance; for example ReflecTech, Inc. of Picayune, Mississippi produces a mirror film which has 94% spectral reflectance, and has been demonstrated to be durable without significant damage in the outside environment in Colorado for over ten years.
  • FIG. 4A shows an example composition of one of the primary concentrators constructed from a structural material 10 such as concrete or plastic, saw-tooth surface patterning with troughs 11, covered with sheathing 12, such as ABS, attached to the structural material for the primary concentrator, and an external reflective film 14.
  • An alternative embodiment of portable, low cost primary concentrators, as illustrated in FIG. 4B includes optical surfaces of each primary concentrator with both refractive and reflective elements.
  • the optical element of each primary concentrator for example, includes a refractive optical sheet 15 with saw-tooth surface patterning and with a reflective backing 16.
  • each primary concentrator can be designed to form a linear concentrator so that for any given position of the sun, the concentrated solar radiation is focused (roughly) into a single line segment, for example the focal line of the secondary concentrators.
  • the optics of each primary concentrator are designed so that this focal line is at all times horizontal, is oriented north-south, and moves in a plane (the primary concentrator's focal plane) predicatively through the course of the day.
  • the focal line has an east-west orientation.
  • Each north-south row of primary concentrators has co-planar focal planes.
  • Each east-west row of primary concentrators for example, can be configured to have no slant in the north-south direction (since the focal lines are horizontal and run north-south).
  • An extended focal line for example, is the line extending the focal line segment for a single primary concentrator over the collection field to the north and south. Over the day, the extended focal line of the primary concentrators drifts from west to east.
  • FIGS. 5A (in 2D cross section) and 5B (in 3D) illustrate the concentration of primary concentrated solar radiation 4 by the bidirectional primary concentrator 3b into its focal line 20, with extended focal line 21.
  • each east-west row of primary concentrators has a focal plane with distinct slants slightly away from horizontal.
  • each east-west row of secondary concentrators may be hung via east-west cables that change in height and slant in the east-west direction, requiring the design of distinct optical surfaces for each primary concentrator along a east-west row, so their focal plane's east-west angle of slant is approximately the same as the average (e.g., averaged over the east-west extent of the primary concentrator) local angle of slant of the support cables above them.
  • FIGS. 5C (in 2D cross section) and 5D (in 3D) provide a sequence of example focal planes 22 (which change their east-west slant, but have no slant in the north-west direction) of a sequence of bidirectional primary concentrators 3b in the east-west direction.
  • FIG. 5E illustrates (in 2D cross section) the positioning of a secondary
  • FIG. 5F illustrates (in 3D) the positioning of the secondary concentrator 5 so that its receiver-directed focal line 42 coincides with the focal line 20 of the primary concentrator.
  • the primary concentrator can be designed to have a high optical efficiency and low cost by use of reflective film and concrete base structure.
  • the concentrator's solar efficiency (which here is determined by the spectral reflectance of Attorney Docket No.: 161648-0003 the primary concentrator), for example, ranges from approximately 85-99%, preferably 90-97%, more preferably 92-96% for the surfaces exposed to direct solar radiation.
  • the spectral reflectance of the primary concentrator is
  • the most exposed portion of the primary concentrator is the mirror film, which has a demonstrated expected outdoor life of over ten years; therefore, the primary concentrator can be expected to last for at least this period with out serious repairs, and these repairs would be mostly limited to simply the replacement or repair the reflective film.
  • a secondary concentrator can be associated with each primary concentrator.
  • Each secondary concentrator in some implementations, can be oriented north-south parallel with the axis of the troughs of its corresponding primary concentrator.
  • the focal lines of the primary concentrators move in an east to west direction. As the sun moves during the day, the current position of the focal line of the solar radiation concentrated by each primary concentrator translates in a west to east direction.
  • the function of each secondary concentrator is to direct the solar radiation concentrated by the primary concentrator to a receiver.
  • FIG. 6A through 6C illustrate examples of the optical path of the direct solar irradiation 2 from the sun 1, and how the bidirectional primary concentrator 3b and the secondary concentrator 5 concentrate and redirect the direct solar irradiation 2 to the receiver 7.
  • FIG. 6A shows one bidirectional primary concentrator 3b in association with one secondary concentrator 5.
  • the sun 1 directs solar irradiation 2 towards the bidirectional primary concentrator 3b where primary concentrated solar radiation 4 is reflected towards the secondary concentrator 5.
  • the secondary concentrator 5 directs the primary concentrated solar radiation 4, as secondary concentrated solar radiation 6, to the receiver 7.
  • FIG. 6B illustrates a series of bidirectional primary concentrators 3b each directing primary concentrated solar radiation 4 towards a respective associated secondary concentrator 5.
  • the receiver 7 receives direct secondary concentrated solar radiation 6 from above.
  • the absorbing area of the receiver 7, as illustrated in this example, can be positioned at a height above the ground lower than the height of the secondary concentrators 5, so that the secondary concentrated solar radiation 6 directed to the receiver 7 comes from an angle above the receiver 7.
  • the receiver 7 can be positioned sufficiently high, and the consecutive secondary concentrators 5 can be positioned sufficiently high and separated in the east-west direction.
  • the optical surfaces of the secondary concentrators are polished aluminum, with a multilayer dielectric film overcoat multilayer dielectric film overcoat (the dielectric materials may include silicon monoxide or magnesium fluoride) for protection of the optical surfaces.
  • the dielectric materials may include silicon monoxide or magnesium fluoride
  • the secondary concentrator has two optical surfaces, each of which behave as linear optical concentrators and which have a reflecting element.
  • each secondary concentrator has one optical surface.
  • the optical surfaces have reflecting and refracting elements. In some embodiments, these optical surfaces are purely reflective and concave in cross section. In other embodiments, the optical surface is parabolic in cross section.
  • a secondary concentrator with one optical surface can be referred to as a singleton secondary concentrator; where as a secondary concentrator with two optical surfaces (one will face east, the other west) can be referred to as a double secondary concentrator.
  • An optical surface of a secondary concentrator can be described as operationally- reflective if it directs primary solar radiation (incoming from the primary concentrator) back in the same general east or west direction from which it came; that is if the optical surface faces generally east, the operationally-reflective secondary concentrator directs radiation from the east back to the east, and if the optical surface faces generally west, Attorney Docket No.: 161648-0003 the operationally-reflective secondary concentrator directs radiation from the west back to the west.
  • the optical surface can be described as operationally-refractive where, when the optical surface is facing generally east, the operationally-refractive secondary concentrator directs radiation from the east to the west, and when the optical surface is facing generally west, the operationally-refractive secondary concentrator directs radiation from the west to the east. Note that this terminology only relates to the effect of the optical elements; the actual optical elements in each case may combine reflective and refractive parts.
  • the secondary concentrators have an apparatus for providing vertical elevation (e.g., an elevating secondary concentrator). In certain embodiments, the secondary concentrators have an apparatus for rotation (e.g., a rotating secondary concentrator).
  • each secondary concentrator can be associated with one of the primary concentrators and suspended above it.
  • the suspension is implemented using a tensile structure supported by a support structure.
  • a tensile structure for example, includes elements carrying tension without substantial compression or flexibility.
  • a system of cables can be used as the tensile structure with support poles as the support structure.
  • the support structure includes a combination of one or more compressive, flexible, or tensile substructures.
  • the system of cables and support poles includes a tracking apparatus (which will be addressed later).
  • the secondary concentrators are suspended from a tensile structure.
  • each east-west row of primary concentrators there are two support cables associated with each east-west row of primary concentrators. These support cables can run parallel to the east-west axis as well as perpendicular to the troughs in the primary concentrators.
  • the support poles in this case, can be
  • the support poles can be positioned in rows along the east and west edges of the solar collecting field. Each support pole can be associated with one or more east-west rows of primary concentrators and can support the support cables associated with these Attorney Docket No.: 161648-0003 primary concentrators.
  • the apparatus for fixing the support poles into the ground may include further side cables to provide support.
  • the secondary concentrators can be suspended from these support cables by devices such as rollers that allow the secondary concentrators to move freely along the east-west axis. In other embodiments, there are between two and six support cables for each row of primary concentrators, preferably between two and four.
  • FIG. 7A illustrates an example of a non-elevating, non-rotating, double operationally-reflective secondary concentrator 154, herein referred to as a Type 1 secondary concentrator, suspended by support cables 30.
  • the Type 1 secondary concentrator 154 can be attached on each side to the support cables 30 in a way that allows for neither rotation nor elevation.
  • the suspension apparatus can also include apparatus for translational tracking in the direction orthogonal (e.g., west to east) to the longitudinal axis (e.g., north-south) of the secondary concentrator 154.
  • the Type 1 secondary concentrator 154 can include two concave trough shaped reflective optical surfaces 38 and 39. In other embodiments, the optical surfaces 38 and 39 of the type 1 secondary concentrator 154 have flat faces.
  • the type 1 secondary concentrator 154 for example, includes the eastward-facing optical surface 38 and the westward-facing optical surface 39.
  • the support system for the Type 1 secondary concentrator 154 in the illustrated embodiment, includes an immobile support cable 30, a trolley attachment 31 to the support cable 30, a plate 32 (e.g., a disk) directly attached to the end of the Type 1 secondary concentrator 154, and a translational tracking cable 33 used to enable the west to east translational tracking direction of the Type 1 secondary concentrator 154 during the day.
  • An assembly 35 discourages the rotation and vertical elevation of the plate 32 attached to both the support cable 30 (e.g., through the trolley attachment 31) and the Type 1 secondary concentrator 154.
  • FIGS. 7B through 7D three alternative embodiments of secondary concentrators are shown: an elevating, non-rotating double operationally-reflective secondary concentrator, herein referred to as a Type 2 secondary concentrator, a rotating, non-elevating, double operationally-reflective secondary concentrator herein referred to as a Type 3 secondary concentrator, and a rotating, non-elevating, singleton operationally-reflective secondary concentrator herein referred to as a Type 4 secondary concentrator.
  • a Type 2 secondary concentrator an elevating, non-rotating double operationally-reflective secondary concentrator
  • Type 3 secondary concentrator a rotating, non-elevating, double operationally-reflective secondary concentrator
  • Type 4 secondary concentrator a rotating, non-elevating, singleton operationally-reflective secondary concentrator
  • FIG. 7B provides an illustration of an example of a Type 2 secondary concentrator 156 with two concave trough shaped reflective optical surfaces 38 and 39 and its support system (e.g., support cables 30, trolley attachment 31, plate 32, and
  • Assembly 36 is attached to the trolley attachment 31.
  • Assembly 36 for example, has a slot for the vertical movement of a pin that protrudes from the plate 32. Hence, the assembly 36 can allow for free vertical elevation (but no rotation) of the Type 2 secondary concentrator 156.
  • FIG. 7C provides an illustration of an example of a Type 3 secondary concentrator 158 with two concave trough shaped reflective optical surfaces 38 and 39 and its support system (e.g., support cables 30, trolley attachment 31, plate 32, and
  • An assembly 37, attached to the trolley attachment 31, has a freely rotatable knob that can allow for rotation (but no vertical elevation) of the Type 3 secondary concentrator 158.
  • FIG. 7D provides an illustration of an example of a Type 4 secondary concentrator 160 with one concave trough shaped reflective optical surface 38, and its support system (e.g., support cables 30, trolley attachment 31, plate 32, and translational tracking cable 33 similar to those described in relation to FIG. 7A and the assembly 37 as described in relation to FIG. 7C).
  • support system e.g., support cables 30, trolley attachment 31, plate 32, and translational tracking cable 33 similar to those described in relation to FIG. 7A and the assembly 37 as described in relation to FIG. 7C).
  • FIGS. 7E-7J illustrate various designs for optical surfaces of double and singleton secondary concentrators, such as those described in relation to FIGS. 7A-7D.
  • the optical surfaces for example, can be saw-tooth contoured and operationally-reflective.
  • FIGS. 7E-7F illustrate designs for optical surfaces of double secondary concentrators.
  • FIG. 7E provides an illustration (in 2D cross section) of an embodiment for the optical surfaces 38, 39 of a double operationally-reflective secondary concentrator, such as the Type 1 secondary concentrator 154, the Type 2 secondary concentrator 156, or the Type 3 secondary concentrator 158, as shown in FIGS. 7A, 7B, and 7C respectively.
  • a double operationally-reflective secondary concentrator such as the Type 1 secondary concentrator 154, the Type 2 secondary concentrator 156, or the Type 3 secondary concentrator 158, as shown in FIGS. 7A, 7B, and 7C respectively.
  • Each of the two optical surfaces 38, 39 are saw-tooth contoured and form a "V" over all shape.
  • FIGS. 7A, 7B, and 7C respectively .
  • Each of the two optical surfaces 38, 39 are saw-tooth contoured and form a "J" over all shape.
  • the number, dimensions, and placement of the individual teeth of the saw-tooth designs illustrated in FIGS. 7E-7F can vary depending upon implementation. Although the saw-tooth design of the first optical surface 38 and the second optical surface 39, as illustrated in each embodiment respectively, appear to be substantially identical, in other implementations the first optical surface 38 can include a different saw-tooth design than that of the second optical surface 39.
  • FIGS. 7G-7J illustrate designs for optical surfaces of singleton secondary concentrators, such as the Type 4 secondary concentrator described in relation to FIG. 7D.
  • FIG. 7G for example, provides an illustration (in 2D cross section) of an embodiment for the optical surface 38 of a singleton operationally-reflective secondary concentrator where the optical surfaces is saw-tooth contoured and forms an upside down "L" over all shape.
  • FIG. 7H provides an illustration (in 2D cross section) of an embodiment for the operationally-reflective optical surface of a singleton secondary concentrator where the optical surface 38 has saw-tooth contouring and is angled from the vertical.
  • the optical surface 38 for example, has a reflective front surface.
  • FIG. 71 provides an illustration (in 2D cross section) of an alternative design for the operationally-reflective optical surface Attorney Docket No.: 161648-0003 of a singleton secondary concentrator, where the optical surface 38 has saw-tooth contouring and is angled from the vertical, similar to the design illustrated in FIG. 7H.
  • the design of FIG. 71 however, has a refractive interior 15 and a reflective back surface 16.
  • An alternative embodiment of optical surfaces of secondary concentrators makes use of only a purely refractive optical surface so it is operationally-reflective.
  • the optical surface of a secondary concentrator is designed to be operationally-refractive for generally eastward-facing optical surfaces.
  • the operationally-refractive eastward-facing surface can direct radiation from the east to the west.
  • the operationally-refractive optical surface faces generally west, the optical surface can direct radiation from the west to the east.
  • a purely refractive optical surface 38 of a singleton secondary concentrator e.g., including a refractive interior 15
  • optical surface options described in relation to FIGS. 7I and 7J can be implemented upon the optical surfaces of double secondary concentrators.
  • FIG. 7K illustrates a secondary concentrator 162 with two concave trough shaped reflective optical surfaces 38 and 39, where each end has a two trolley attachments 31 to one support cable 30.
  • the secondary concentrator 162 also includes the plate 32 and translational tracking cable 33 similar to those described in relation to FIG. 7A.
  • FIG. 7L illustrates a secondary concentrator 164 with two concave trough shaped reflective optical surfaces 38 and 39, where each end has a four trolley attachments 31 to two support cables 30.
  • two upper trolley attachments 31 can be attached to an upper support cable 30, while two lower trolley attachments 31 can be attached to a lower support cable 30.
  • the secondary concentrators use a heat radiator system, where linear radiating heat fins are affixed on their backside, to prevent the secondary concentrator from over heating.
  • the reflective optical surfaces of secondary mirror are configured to be reflective optical surfaces of secondary
  • the reflective optical surfaces of secondary concentrators make use of various coatings depending on the targeted frequency range of the solar concentrated radiation to be concentrated.
  • IR near infrared
  • a combination of one or more metallic films composed of aluminum, silver, gold, and/or copper, or a combination of these can be used, optionally with protective overcoats.
  • VIS visible
  • some embodiments use aluminum, silver, and/or tin, or a combination of thereof, optionally with protective overcoats.
  • the protective overcoats can consist of multilayer dielectric films such as disilicon trioxide (Si 2 0 3 ), SiO and/or MgF 3 .
  • the support cables are kept taut such that the support cables appear essentially horizontal, at a fixed height. This implies that the focal planes of all the primary concentrators connected to the support cables can be held
  • FIG. 8A is an illustration of an example of an east- west row of Type 1 secondary concentrators 154, suspended by support cables 30 that appear horizontal, and attached by trolley attachments 31 to allow for coordinated west to east translational tracking.
  • the support cables are not quite horizontal. Even the strongest cables will slightly droop due to gravity; in particular, cables of uniform thickness in the presence of gravity are known to droop to form catenary curves, whose curvature and slope, for example, can depend on the structural properties of the support cables and the force applied to them.
  • This gravity-induced catenary curvature Attorney Docket No.: 161648-0003 can be significant enough to affect optical design. Pulling the support cables extremely taut to avoid this affect on optical design may not be feasible or cost effective.
  • FIG. 8B is an illustration of an east-west row of Type 1 secondary concentrators 154, suspended by support cables 30 that slightly droop to form a catenary curve.
  • FIG. 8C is an illustration of an example of an east-west row of Type 1 secondary concentrators 154, suspended by support cables 30 by trolley attachments 31, with additional attached sidelines 41 on the support cables 30 used to decrease the support cable's displacement from translational wind force.
  • the sidelines 41 in some implementations, have a side affect of slightly vertically displacing the support cables from the horizontal.
  • support poles and/or stabilization lines can optionally provide a means for intentionally inducing height changes along the length of these east-west support cables 30, so as to be able to change the angle of the direction concentrated solar radiation is directed from the secondary concentrators 154 to the receivers during west to east tracking.
  • changing the curvature and height of the east-west support cables provides for vertical tracking changes dependent on the east-west position x by inducing height changes (e.g., with the height of the support cables being lower on the extreme east and west sides of the collection field) along the length of these east-west support cables.
  • This can be used, for example, to change the angle that concentrated solar radiation is directed from the secondary concentrator to the receivers during east-west tracking. An example is provided below in relation to FIGS. 17B-17E.
  • a north-south row of secondary concentrators may be joined along their longitudinal axis to allow for coordinated translational tracking.
  • a row of secondary concentrators can be joined along their longitudinal axis to allow for coordinated rotational tracking.
  • a row of secondary concentrators can be joined along their longitudinal axis to allow for coordinated translational and rotational tracking.
  • a linked north-south row of secondary concentrators, suspended by cables in a way that allows neither rotational nor elevational travel, can be joined along their longitudinal axis to allow for coordinated west to east translational tracking.
  • a linked north-south row of Type 2 secondary concentrators, suspended by horizontal cables can be attached in a way that allows elevation but not rotation and joined along their longitudinal axis to allow for coordinated tracking.
  • a linked north- south row of Type 1 secondary concentrators, suspended by horizontal cables may be attached in a way that allows rotation but not elevation and joined along their longitudinal axis to allow for coordinated tracking.
  • FIG. 9 illustrates a solar collection field of bidirectional primary concentrators, with associated secondary concentrators.
  • the secondary concentrators as illustrated, are supported via support cables 30 and support poles.
  • the array of secondary concentrators are positioned depending on the geometry of the solar collection field so that they can direct concentrated solar radiation to one or more receivers without obstructing one another.
  • ⁇ ⁇ ( ⁇ ) be a vertical angle 50 from the horizontal that concentrated solar radiation can be directed in the east-west direction, without obstruction, from the secondary concentrator to a vertical midline of the receiver.
  • w the distance between the first secondary concentrator and a neighboring secondary concentrator in the east-west direction (as illustrated by a second optical surface 38b) is w, where w is an east-west width 51 of each primary concentrator.
  • v be a maximum vertical dimension Attorney Docket No.: 161648-0003
  • the primary concentrators concentrate the primary concentrated solar radiation entering the secondary concentrators by a significant factor, for example a factor of between 10 and 30, preferably between 15 and 25.
  • optical design of the secondary concentrators can take into account the corresponding increase in optical intensity.
  • the optical surfaces of the secondary concentrators can be designed to be able to sustain high heat flux.
  • the optical surfaces of each secondary concentrator can be constructed from highly reflective metallic sheeting.
  • the optical surfaces of the secondary concentrators for example, can be made from aluminum, which has a high melting point of 660.32 °C, is relatively inexpensive, has a relatively low density (2.70 g per cubic cm), and can be polished to approximately 75-99%, preferably 85-97%, more preferably 90-95% spectral reflectance. In certain embodiments, the spectral reflectance of the secondary concentrators is approximately 90%.
  • the protective coating of the optical surfaces of the secondary concentrators can include a multilayer dielectric film overcoat.
  • FIGS. 11A-11D and 12A-12D illustrate various embodiments of secondary concentrators modified for weather resilience.
  • the secondary concentrators as illustrated, for example, can be opened for typical use or closed for protection from inclement weather conditions.
  • FIGS. 11A (open position) and 11B (closed position) show (in 2D cross section) an alternative embodiment of a singleton secondary concentrator with a singe concave trough shaped optical surface 38 equipped with a pivot 53 allowing the singleton secondary concentrator to be folded into a protective clamshell position.
  • two or more pivots 53 can be positioned along the optical surface 38.
  • FIGS. llC open position
  • 11D closed position
  • FIGS. llC and 11D show (in 2D cross section) an alternative embodiment of a singleton secondary concentrator with one optical surface Attorney Docket No.: 161648-0003
  • the optical surface 38 is saw-tooth contoured and angled from the vertical.
  • the singleton secondary concentrator can be equipped with two or more pivots to allow it to be multiply folded into a protective position.
  • FIGS. 12A (open position) and 12B (closed position) show (in 2D cross section) an alternative embodiment of a double secondary concentrator with two concave trough shaped optical surfaces 39, 39 and a pivot 53 allowing the double secondary
  • the double secondary concentrator can be include two or more pivots 53 to allow it to be multiply folded into a protective position.
  • FIGS. 12C (open position) and 12D (closed position) show (in 2D cross section) an alternative embodiment of a double secondary concentrator with two optical surfaces 38, 39 which are saw-tooth contoured and form a V.
  • the double secondary concentrator is equipped with a pivot 53 to allow it to be folded into a protective position.
  • the double secondary concentrator can be include two or more pivots 53 to allow it to be multiply folded into a protective position.
  • structural supporting members can be affixed to the backside of the secondary concentrators for stability in winds.
  • the solar concentration system includes an apparatus for protection from inclement weather, such as apparatus for lowering the secondary concentrators to a sheltered location on the ground.
  • the secondary concentrators are typically more complex than the primary concentrators, but they are also generally far smaller and far less massive than the primary concentrators (e.g., due the primary concentrator's initial concentration of the solar energy).
  • the secondary concentrators are often modest when apportioned to the far larger area of the primary concentrator that each secondary concentrator services.
  • the aluminum optical surface of the secondary concentrators can have a reflectance of approximately 90%, giving the secondary concentrator a high solar efficiency.
  • each secondary concentrator has one or two reflective optical surfaces, concave in cross section, which have a three-dimensional concave trough shape.
  • the secondary concentrators include refractive as well as reflective elements and are saw-tooth in cross section.
  • the secondary concentrators are parabolic in cross section.
  • Each of these optical surfaces can function as a linear concentrator. That is, the optical surfaces can focus parallel incoming radiation into a line.
  • the (receiver-directed) focal line of an optical surface of the secondary concentrator for example, is the hypothetical line at which parallel rays emitted from the receiver would be focused by that optical surface of the secondary concentrator.
  • the secondary concentrator is preferably positioned so its (receiver-directed) focal line coincides with the focal line of the associated primary concentrator.
  • FIG. 13A in 2D cross section
  • FIG. 13B in 3D together show example positioning of the secondary concentrator 5 so that its (receiver-directed) focal line 20 coincides with the focal line of the bidirectional primary concentrator 3b.
  • the east-west support cables may not be strictly horizontal, such that each east- west row of secondary concentrators hanging on the support cables may vary in height above the primary concentrators. This can impact the design of the optical surfaces of the primary concentrators.
  • the focal plane of the bidirectional primary concentrators 3b may have an east-west slant which approximates the local slant of the support cables above them, even if the bidirectional primary concentrators 3b have no north-south slant.
  • each of the east-west support cables is substantially identical in shape. This can impact the design of the optical surfaces of the primary concentrators.
  • each pair of primary concentrators having the Attorney Docket No.: 161648-0003 same east-west position will have co-planar focal planes, and hence these primary concentrators can have the same shape optical surfaces.
  • the focal line of the bidirectional primary concentrator 3b is parallel to the upper portion of the surface of the bidirectional primary
  • the eastward facing optical surface 38 of the secondary concentrator is actively concentrating primary concentrated solar radiation 4 at all times of the day prior to a time t e and the westward facing optical surface 39 of the secondary concentrator is actively concentrating primary concentrated solar radiation 4 at all times of the day prior to a time t w .
  • t e be the latest time when the eastward facing optical surface 39 of the secondary concentrator receives all the primary concentrated solar radiation from the bidirectional primary concentrator 3b.
  • all the primary concentrated solar radiation 4 from the bidirectional primary concentrator 3b is concentrated to (and has a direct unobstructed path to) that eastward facing optical surface 38 of the secondary concentrator.
  • a position 61 of the focal line at earliest time t e illustrates a point in time when the eastward facing optical surface 38 of the secondary concentrator receives all the primary concentrated solar radiation 4 from the bidirectional primary concentrator 3b.
  • t w be the earliest time when the westward facing optical surface 39 of the secondary concentrator receives all the primary concentrated solar radiation 4 from the bidirectional primary concentrator 3b. Between the time t w , and the ending time t 3 , all the primary concentrated solar radiation 4 from the bidirectional primary
  • a position 63 of the focal line at earliest time t w illustrates a point in time when the westward facing optical surface 39 of the secondary concentrator receives all the primary concentrated solar radiation 4 from the bidirectional primary concentrator 3b.
  • FIG. 14C illustrates (in 2D cross section) a combined illustration of the position of the secondary concentrator at times t e , t m and t w , where the position 61 of the focal line at the latest time t e when the eastward facing optical surface 38 of the secondary concentrator receives all the primary concentrated solar radiation 4 from the bidirectional primary concentrator 3b, a position 62 of the focal line at a time t m in the middle between times t e and t w , and the position 63 of the focal line at earliest time t w when the westward facing optical surface 39 of the secondary concentrator receives all the primary concentrated solar radiation 4 from the bidirectional primary concentrator 3b.
  • FIGS. 15A-15D show in 2D cross section an example daily schedule used for positioning one of the secondary concentrators.
  • the drawings in each figure show only the optical surface 38 of the secondary concentrator that is currently functioning to direct primary solar radiation from the bidirectional primary concentrator 3b to one of the receivers 7. This is the active optical surface.
  • the bidirectional primary concentrator 3b and the primary concentrated solar radiation 4 are also shown in each figure.
  • FIG. 15A illustrates in 2D cross section the start time t 0 of the daily tracking, when the active optical surface 38 of the secondary concentrator faces east.
  • the solar concentration system executes an east-west switch of the secondary concentrator, where the currently active optical surface of the secondary concentrator switches from an optical surface facing generally east to an optical surface facing generally west.
  • the active optical surface may be the same, but re-oriented, in the two respective time periods.
  • FIGS. 15B and FIG. 15C can be looked to as an illustration in 2D cross section of the east-west switch.
  • FIG. 15B illustrates the start of an east-west switch at the time ti when the active optical face 38 of the secondary concentrator is facing generally east and an extended focal line 71 of the secondary concentrator is just west of overhead the middle of the bidirectional primary concentrator 3b.
  • FIG. 15C illustrates in 2D cross section the end of an east-west switch at the time t 2 when the active optical face 39 of the secondary concentrator is facing generally west and an extended focal line 72 of the secondary concentrator is just east of overhead the middle of the bidirectional primary concentrator 3b.
  • FIG. 15D illustrates in 2D cross section the end time t 3 of the daily tracking when the active optical surface 39 of the secondary concentrator faces west.
  • the daily schedule of the secondary concentrator's tracking, in time progression, is given by the illustrations shown in FIG. 15A (start time t 0 ), FIG. 15B (begin time ti of east-west switch), FIG. 15C (finish time t 2 of east-west switch), and FIG. 15D (end of day time t 3 ).
  • start time t 0 start time t 0
  • FIG. 15B begin time ti of east-west switch
  • FIG. 15C finish time t 2 of east-west switch
  • FIG. 15D end of day time t 3
  • the solar concentration system minimizes leakage loss by maximizing the ratio of the height of the primary concentrator focal line to the east-west width of the bidirectional primary concentrator 3b. This, for example, can work to minimize the time duration between t w and t e when there can be leakage loss.
  • the solar concentration system can work to minimize leakage loss by constructing the bidirectional primary concentrator 3b so that at solar noon, the extended focal line of the bidirectional primary concentrator 3b is as far as possible to the east or west of the center of the bidirectional primary concentrator 3b.
  • the focal plane of the bidirectional primary concentrator 3b is similarly slanted either east or west, which also may entail (since the east-west slant of the focal plane and
  • corresponding section of the support cable are likely similar to allow the focal lines of the primary and secondary concentrator to coincide) slanting the support cable above the bidirectional primary concentrator 3b at a similar angle. This, for example, insures that the time period between t w and t e can be shifted away from solar noon, the period of most intense direct solar irradiation.
  • the concentration system is comprised of the primary and secondary concentrators, and the geometry of the tracking means can be summarized in the following:
  • each north-south strip of primary concentrators has a single extended focal line, and through the course of the day, that extended focal line moves from west to east.
  • the concentration system includes a tracking system and, optionally, a control system to provide for the positioning of various elements of the concentration system, such as the secondary concentrators and receivers, to increase the efficiency of the collection of solar irradiation throughout a solar day.
  • the tracking system can position and orient the secondary concentrators to increase the effectiveness of solar irradiation collection by the receivers by aligning the active optical surface of each secondary concentrator proximate to the focal line of each respective primary concentrator.
  • the tracking system can adjust the positioning of each secondary concentrator, in another example, to aim the secondary concentrated radiation, reflected by the secondary concentrators, substantially at a centralized receiver.
  • the tracking system includes a control system that determines adjustment criteria and signals positioning equipment, such as motors and actuators, to fine tune the positioning of the various system elements.
  • the control system can issue control signals to cause an adjustment in the positioning of secondary concentrators, centralized receivers, or components of a tensile structure such as suspension cables used to suspend the secondary concentrators.
  • the control signals may be digital or analog depending on the type of motors and actuators used in a particular system.
  • the tracking system includes an open-loop control system with an internal clock and a set of pre-calculated motor control parameters. For example, based upon a table lookup, at specific times throughout a solar day, the open- loop control system can effect the repositioning of one or more of the elements of the solar concentrator system.
  • the table of parameters in some implementations, can include variations based upon day of the year.
  • information retrieved from the table of parameters can be used to calculate adjustments based upon system settings. For example, based upon a particular geographic location of the solar concentrator system (e.g., latitude, longitude, GPS coordinates, altitude, etc.) the positioning adjustments can vary.
  • the tracking system can function with a closed-loop control system relying on both pre-derived calculated (e.g., based upon astronomical equations) as well as external monitoring devices.
  • the external monitoring devices can include one or more sensors detecting current conditions affecting the Attorney Docket No.: 161648-0003 solar concentrator system.
  • the external monitoring devices can sense the amount of solar energy directed to the centralized receivers (e.g., using one or more solar energy sensors), an external temperature (e.g., as measured by one or more thermometers positioned on the solar concentrator system), wind speed and wind direction (e.g., using wind speed indicators positioned at one or more locations on the solar concentrator system), or solar irradiance intensity and solar irradiance direction (e.g., as determined by one or more directional photosensors positioned on the solar concentrator system).
  • the closed-loop control system includes a table of look-up data associated with one or more of these monitored values.
  • the closed-loop control system may determine that an adjustment in positioning of one or more solar concentrators may be advisable.
  • the control system upon reaching such a determination, employs post-processing to determine appropriate control signals to use for manipulating the system elements (e.g., actuators, motors, etc.).
  • the tracking and control system in alternative embodiments, can actively monitor solar irradiation received by the various elements of the solar concentrator system. For example, based upon a measured position and intensity of the sun, the tracking and control system can automatically adjust the positioning of various elements of the solar concentrator system to optimize collection of concentrated solar radiation energy.
  • the tracking and control system periodically makes adjustments to one or more of the elements of the solar concentrator system.
  • a timer can be used in conjunction with the internal clock to determine a schedule upon which the positions of the elements of the solar concentrator system may be adjusted.
  • the tracking and control system continuously provides readjustments, for example through control signals to appropriate motors and actuators, to position and orient the secondary concentrators, allowing the solar Attorney Docket No.: 161648-0003 concentrator system to dynamically compensate for changes in monitored conditions so as to optimize the solar energy directed to the centralized receivers.
  • feedback control can be provided by conventional closed-loop control theory methods which, for example, determine the dynamic control of the solar concentrator system based on a combination of error signals, measured output, and desired output.
  • closed-loop control theory methods include proportional-integral-derivative (PID) mechanisms, which determine an output by an integral calculation, and time-domain mechanisms, which model the problem in state space and solve a first-order differential equation modeling the physical system.
  • PID proportional-integral-derivative
  • the relationship between the primary and secondary concentrators can be achieved by west to east translational tracking of the secondary concentrator with possibly some form of vertical or rotational movement to provide compensation for the change in vertical angle to receivers during translational tracking, as well as some sort of mechanism for the east-west switch previously described.
  • each north-south row of secondary concentrators can be substantially the same, so the secondary concentrators of each north-south row are joined and move on a common axis.
  • Some embodiments of a tracking apparatus only provide translational tracking, without rotation of the secondary concentrators.
  • the east-west switch for example, can be achieved by simply moving from the portion of the secondary concentrator facing generally east to the other portion facing generally west.
  • the secondary concentrator is positioned a considerable distance from the receivers, so the short daily translational movements by the secondary concentrator are less likely to significantly affect the angles of direction from the secondary concentrators to each receiver.
  • Type 1 secondary concentrator which is a non-rotating, non-elevating doubled secondary concentrator.
  • the doubled secondary concentrator for example, has two reflective optical surfaces, positioned facing generally east and west, respectively.
  • the east facing optical surface can be used from the start of the day until the initiation of the east-west switch and, after having executed the east-west switch, the secondary concentrator can be shifted slightly west (e.g., by temporally increasing the rate of west to east translational tracking movement) to switch the incoming primary concentrated solar radiation from the east optical surface to the west optical surface.
  • Tracking Apparatus 1 Non-Rotating Non-Elevating Doubled
  • the secondary concentrators track by west to east translational movements as illustrated in FIGS. 16A-16D.
  • FIG. 16A illustrates Tracking Apparatus 1 at the start time t 0 of the daily tracking
  • FIG. 16B illustrates Tracking
  • FIG. 16C illustrates Tracking Apparatus 1 at time t 2
  • FIG. 16D illustrates Tracking Apparatus 1 at the end time t 3 of the daily tracking.
  • the doubled secondary concentrator is tracked translationally from west to east at a fixed rate, so that all times during this period the east optical surface 38 of the doubled secondary concentrator is positioned so that its (east) (receiver-directed) focal line 70 substantially coincides with the focal line of the bidirectional primary concentrator 3b such that the east optical surface 38 further concentrates the incoming primary concentrated radiation 4 from the bidirectional primary concentrator 3b and directs it to the east receiver 7.
  • the rate of translational tracking movement from west to east is increased, so as to move the doubled secondary concentrator west.
  • This increased rate is set so that at time at time t 2 , the west optical surface 39 of the doubled secondary concentrator is positioned so that its (west) (receiver-directed) focal line 72 coincides with the focal line of the bidirectional primary concentrator 3b.
  • the time interval from t 2 to t 3 as illustrated by FIGS.
  • the doubled secondary concentrator is again tracked Attorney Docket No.: 161648-0003 translationally from west to east at a fixed rate, so that at substantially all times during this period the west optical surface 39 of the doubled secondary concentrator is positioned so that it's (west) (receiver-directed) focal line 72 coincides with the focal line of the bidirectional primary concentrator 3b, and so it further concentrates the incoming primary concentrated radiation 4 from the bidirectional primary concentrator 3b and directs it to the west receiver 7.
  • the tracking movement is reversed to allow the secondary concentrator to be repositioned to the start of day position (e.g., as illustrated in FIG. 16A).
  • Dynamic effects from variations in temperature and wind, may induce vertical and rotational oscillations and misalignments of the secondary concentrators and their support cables and posts, as well as transverse movements along the length of the support cables.
  • there is an open loop control system for executing various corrections which may include secondary concentrator tracking corrections and cable tension corrections.
  • Each correction for example, can be based on observed variations of one or more of the following observables: wind magnitude, wind direction, temperature, solar intensity and solar angle.
  • off-axis aberrations of the secondary concentrators may widen the line focus to the receiver, reducing the performance of the system.
  • means are provided for reducing off-axis aberrations of the secondary concentrators, including optimizing the height of the secondary concentrators above the primary concentrators and optimizing the aperture width of the secondary concentrators.
  • means are provided for compensation of off-axis aberrations of the secondary concentrator, for example by widening the absorbing region or by movement out of the horizontal plane.
  • the solar radiation concentrated by the primary and secondary concentrators is directed to one or more receivers.
  • there are two receivers that collect the concentrated solar radiation one located to the east of the collection field and one located to the west of the collection field.
  • the receiver located in the west collects primarily in the AM (prior to solar noon) concentrated solar radiation
  • the receiver located in the east collects primarily in the PM (after solar noon) concentrated solar radiation.
  • the optical surface of the receiver acts as an absorbing region that absorbs the concentrated solar radiation incoming from the secondary concentrators.
  • the absorbing region of each receiver is rectangular shaped running north-south.
  • the absorbing region of each of the receivers is positioned at a height above the ground larger than the height of the secondary concentrators, so that the concentrated solar radiation directed to the receivers comes from an angle below them.
  • the receivers are positioned sufficiently high and the consecutive secondary concentrators are sufficiently separated in the east-west direction.
  • the receiver can include a medium for transport and at least temporary storage of the absorbed solar energy.
  • the energy storage media is a bulk thermal storage medium such as liquid sulfur, molten salt (e.g., saltpeter molten salt which is approximately 60% sodium nitrate and approximately 40% potassium nitrate), fluoride-salt, and/or mineral oil (e.g., Therminol VP-1 synthetic oil).
  • the energy storage media includes a phase-change storage medium (such as water to and from steam, or melting and solidifying salts).
  • Each receiver has a structural housing.
  • the structural housing of the receiver serves to support and protect the other portions of the receiver.
  • each of the receiver within the absorbing region of each of the receiver are positioned a linear array of receiver tubes running north-south.
  • a metallic tube containing material used for heat storage e.g., either bulk heat storage or phase-change heat storage material.
  • each receiver tube Surrounding the interior metallic tube, in some implementations, is a vacuum gap Attorney Docket No.: 161648-0003 providing insulation.
  • a borosilicate glass tube with an anti-reflective, anti-abrasion coating that has high radiation absorbance and low emittance.
  • the borosilicate glass offers the same expansion coefficient as the melted down metal.
  • This exterior can allow a high proportion of the solar radiation to penetrate to the interior metallic tube of the receiver and heat the heat transfer material within.
  • current receiver technology such as the SCHOTT PTR 70 Receiver by SCHOTT Solar of Albuquerque, NM allows over 95% absorbance and less than 10% emittance.
  • the north-south angle of the sun deviates to both the north and the south from its equinox position, for example by approximately 23.5 degrees in the US Southwest. Therefore, the north-south position of the solar radiation concentrated on a receiver can change through the year.
  • the receivers are immobile, but their absorbing area is sufficiently long in north-south direction to include the entire range of positions that concentrated solar radiation is directed from over the year. This, for example, can insure the receivers can collect the concentrated solar radiation throughout the year.
  • the secondary concentrator has only one optical surface, and it executes an east-west switch by making, at some period in the day, a change in orientation from facing generally east to facing generally west.
  • all concentrated radiation is directed toward one centralized receiver.
  • the compensation for the change in ⁇ (the vertical angle from horizontal to the receiver) during the secondary concentrator's translational movement is determined by calculating ⁇ as the smallest vertical angle from the horizontal that radiation that can be directed, without obstruction, from the secondary concentrator to the receiver.
  • ⁇ was defined to be the secondary concentrator's vertical angle 50 from the horizontal to the midline of the receiver 7.
  • ⁇ is constant for every north-south strip of primary concentrators, but can vary along east-west strips of primary concentrators. In particular, ⁇ decreases with the distance of the optical surface 38 of secondary concentrator to the currently used receiver 7.
  • ⁇ has an initial relatively small angle ⁇ 0 of concentrated solar radiation directed toward the east receiver 7.
  • the concentrated solar radiation is directed at a higher angle ⁇ toward the east receiver 7.
  • the concentrated solar radiation is directed at a reset angle ⁇ 2 toward the west receiver 7.
  • the solar radiation is directed at a somewhat lower angle ⁇ 3 toward the west receiver 7.
  • the angle ⁇ is at a minimum angle on a north-south strip roughly in the middle of the solar collecting field. Also recall, as described in relation to FIG. 10, that in order that the direct path of concentrated radiation (directed from the secondary concentrator to the receiver) can avoid being obstructed by other secondary concentrators, the angle ⁇ should be greater than arctan(v/w), where v is the width of the secondary concentrator and w is the east-west width of the primary concentrator. This provides an absolute minimum to the value that the angle ⁇ may have.
  • Tracking Apparatus 2 Vertical Tracking of a Doubled Reflective
  • vertical translations of the secondary concentrators can be used to change the direction of concentrated radiation to the receiver, thus providing an apparatus for the changes in angle ⁇ toward the receiver during west to east translational tracking.
  • FIG. 17B-17E show illustrations of example distinct times throughout the day showing a vertical position 93 of the active optical surface 38, 39 of a doubled secondary concentrator used to compensate for the rotation of the secondary concentrator due to the change in angle ⁇ during eastward translational movement.
  • These periodic vertical translations of the secondary concentrator for example, can be Attorney Docket No.: 161648-0003 used to improve its performance.
  • the secondary concentrated solar radiation 6 directed toward the east receiver 7 is received at increasing slope prior to the east- west switch.
  • the secondary concentrated solar radiation 6 directed toward the west receiver 7 is received at a decreasing slope after the east-west switch.
  • the figures illustrate only the currently active optical surface 38, 39 of the secondary concentrator, and thus appear as only a singleton secondary concentrator, although the same optical principals hold for the case of a doubled secondary concentrator.
  • FIG. 17B illustrates a first position, at the start time t 0 , with the initial slightly elevated vertical position 93 y 0 to insure the secondary concentrated solar radiation 6 is directed at an initially relatively small angle 50 ⁇ 0 toward the east receiver 7.
  • FIG. 17C illustrates a second position, at time ti, with the further elevated vertical position 93 yi to insure the secondary concentrated solar radiation 6 is directed at a higher angle 50 ⁇ toward the east receiver 7. Since the secondary concentrator has moved east somewhat closer to the east receiver 7, the vertical position 93 y and the angle ⁇ are increased.
  • FIG. 17D illustrates a third position at time t 2 with a reset elevated vertical position 93 y 2 to insure the secondary concentrated solar radiation 6 is directed at a reset angle 50 ⁇ 2 toward the west receiver 7.
  • the resetting of the vertical position 93 y and the angle 50 ⁇ is due to the east-west switch.
  • FIG. 17E illustrates a fourth position, at the end time t 3 , with reduced vertical position 93 y 3 to insure the secondary
  • FIG. 17F provides a summary combined illustration of the daily horizontal and vertical tracking movements with positions of the rotating doubled secondary concentrator over the day condensed into one figure.
  • the secondary concentrators use guided cams for translational tracking.
  • the cam systems can include disks or peg-like cams located at various radii to control the vertical or rotational movement of disks affixed to the ends the secondary concentrator.
  • the tracking for each north-south row of secondary concentrators is the same. For example, when a row of north-south secondary concentrators has the same tracking, the secondary
  • concentrators can be coupled, and a single cam system can be used for each such north- south row.
  • Tracking Apparatus 5 and 6 use only west to east translational tracking.
  • the other Tracking Apparatus 2, 3, 4, and 7 make use of vertical elevation or rotational movements for tracking as well.
  • Tracking Apparatus 2 can use a single cam as an apparatus for inducing vertical translations to compensate for the change in angle ⁇ during the secondary
  • FIG. 17G illustrates an example of a Type 2 (elevating, non-rotating double) secondary concentrator 166 used in Tracking Apparatus 2, with a cam disk 32 directly attached to the secondary concentrator 166, cam guide 112, and cam peg 111.
  • the cam guide 112 initially slants gently upward.
  • the cam guide 112 can change its height abruptly for the east-west switch, since its height needs to be reset to allow for a reset angle ⁇ 2 due to the east-west switch.
  • the cam guide 112 slants gently downward.
  • the cam peg 111 is located approximately at the upper left position on the cam disk 32 in its initial position. The west to east translational tracking then forces the cam disk 32 (and therefore the secondary concentrator 166) to vertically elevate.
  • FIGS. 17H-17K show the example cam-based Tracking Apparatus 2,with illustrations at various distinct times throughout the day of the translational tracking of the non-rotating doubled secondary concentrator 166 as well as illustrations of the Attorney Docket No.: 161648-0003 engaged cam guide 112 inducing vertical translations of the cam disk 32 and doubled secondary concentrator 166.
  • FIG. 17H illustrates Tracking Apparatus 2 at the start time t 0 of the daily tracking, with position of the engaged single cam guide 112 at the upper left position on the cam disk 32.
  • the gentle upward slant of the cam guide 112 at this period causes the cam disk 32 to move slowly. This increases the angle ⁇ to compensate for the eastward movement of the secondary concentrator 166 toward the east receiver.
  • FIG. 171 illustrates Tracking Apparatus 2 at time ti.
  • the east-west switch may induce an abrupt change in the angle ⁇ (and hence a reset of vertical position y) since prior to the east-west switch the east receiver is used to determined the angle ⁇ , and after the east-west switch the west receiver is used to determine the angle ⁇ .
  • FIG. 17J illustrates Tracking Apparatus 2 at time t 2 .
  • the gentle downward slant of the cam guide 112 at this period again makes the cam disk 32 move upward at a relatively slow rate. This decreases the angle ⁇ to compensate for the continued eastward movement of the secondary concentrator 166 away from the west receiver.
  • FIG. 17K illustrates the position of the Tracking Apparatus 2 at time ti just after the east-west switch.
  • FIG. 17L provides a summary combined illustration of the daily movement of the cam-based rotational Tracking Apparatus 2, with positions of the engaged single cam guide 112 and doubled secondary concentrator 166 over the day condensed into one figure. After the end of the solar day, the cam-based tracking movement can be reversed to allow the secondary concentrator 116 and cam guide 112 to be reset to the start of day position.
  • each of the two optical surfaces of the double secondary concentrator 166 are shaped and positioned appropriately, so that vertical position y 2 is substantially equivalent to vertical position y 3 and hence there is no required vertical elevation change during the east-west switch.
  • the apparatus for the coordinated translational tracking is by the action of one or more motors located at along each east-west strip of Attorney Docket No.: 161648-0003 primary concentrators.
  • Individual motors coupled with gear systems can be used for vertical and/or rotational tracking. Since the tracking needs are substantially the same for each north-south row of secondary concentrators, these can optionally be coupled, and a single motor can be used for each such north-south row.
  • FIG. 18A illustrates an example used for defining a rotation angle 90 of counterclockwise rotation ⁇ of the secondary concentrator: the rotation angle 90 ⁇ can be considered as the counterclockwise angular difference between a ray going east and the normal from the center of reflectance of the eastward facing optical surface 38 of the secondary concentrator.
  • the cam disk is connected to the secondary concentrator, so that the secondary concentrator rotates with the cam disk (or, optionally, two or more cam disks).
  • FIGS. 18B-18E provide illustrations of an example schedule of distinct times throughout the day of where rotation angle 90 0 of a doubled secondary concentrator can be used to compensate for the needed rotation of the secondary concentrator, thereby compensating for the change in angle ⁇ during eastward translational movement and due to the east-west switch. Included are illustrations of the secondary concentrated solar radiation 6 directed toward the east receiver 7 at increasing angle 50 ⁇ prior to the east-west switch; as well as illustrations of the secondary concentrated solar radiation 6 directed toward the west receiver 7 at decreasing rotation angle 90 ⁇ after the east-west switch.
  • the figures illustrate only the currently active optical surface 38, 39 of the secondary concentrator, Attorney Docket No.: 161648-0003 and thus appear as only a singleton secondary concentrator, although the principal is the same for the case of a doubled secondary concentrator.
  • FIG. 18B illustrates the relatively small angle of rotation ⁇ 0 of the optical surface 38 of the secondary concentrator at the start time t 0 of the daily tracking, to insure the secondary concentrated solar radiation 6 is directed at relatively small initial angle 90 ⁇ 0 toward the east receiver 7.
  • FIG. 18C illustrates the increased angle of rotation ⁇ for optical surface 38 of the secondary concentrator at time ti just at the start of the east- west switch, to insure the secondary concentrated solar radiation 6 is directed at increased angle 50 ⁇ toward the east receiver 7.
  • FIG. 18D illustrates the reset angle of rotation 0 2 at time t 2 at the end of the east-west switch, to insure the secondary concentrated solar radiation 6 is directed at reset angle 50 ⁇ 2 toward the west receiver 7.
  • FIG. 18E illustrates the decreased final angle of rotation ⁇ 3 at time t 3 at the end of the east-west switch, to insure the secondary concentrated solar radiation 6 is directed at a decreased final angle 50 ⁇ 3 toward the west receiver 7.
  • FIG. 18F provides a summary combined illustration of the example daily counterclockwise rotations which can be used to improve the performance of a doubled secondary concentrator, with positions of the rotating doubled secondary concentrator over the day condensed into one figure.
  • this east-west switch may provoke a considerable change in the rotational angle O.
  • both the angle 50 ⁇ as well as the Attorney Docket No.: 161648-0003 counterclockwise angle ⁇ of rotation need to decrease, and so the rotation angle ⁇ 3 is smaller than the rotation angle ⁇ 2 .
  • the exact relationship between the values of the rotation angle ⁇ and the angle 50 ⁇ over the day depend on the configuration of the optical surfaces 38, 39 of the secondary concentrator.
  • Tracking Apparatus 3 Rotational Tracking of a Doubled Reflective
  • Tracking Apparatus 3 uses a single cam for inducing rotation to compensate for the change in angle 50 ⁇ during the secondary
  • FIG. 19A illustrates an example of a Type 3 (rotating, non-elevating, double) secondary concentrator 168 used in Tracking Apparatus 3, with the cam disk 32 directly attached to the secondary concentrator 168 and cam guide 122 using a cam peg 121.
  • the cam guide 122 initially slants gently upward, then will change its angle of slant abruptly down for the east-west switch, and the afterward slants gently downward.
  • the cam peg 121 is located at the 11AM (that is, upper left) position on the cam disk 32 in its initial position.
  • the west to east translational tracking then forces the cam disk 32 (and therefore the secondary concentrator 168) to rotate slowly counterclockwise.
  • this total rotation change should be less than a value ⁇ , and therefore the two optical surfaces 38, 39 of the double secondary concentrator 168 is designed so that ⁇ 2 - ⁇ 0 ⁇ ⁇ . Since ⁇ 3 ⁇ ⁇ 0 , the total rotation deviation over the day can be bounded by ⁇ 2 - ⁇ 0 .
  • FIG. 19B-19F show the cam-based rotational Tracking Apparatus 3, with example illustrations at various distinct times throughout the day of the translational tracking of the non-rotating doubled secondary concentrator 168 as well as illustrations of the engaged cam guide 122 inducing counterclockwise rotation of the cam disk 32 and doubled secondary concentrator 168.
  • FIG. 19B illustrates Tracking Apparatus 3 at the start time t 0 of the daily tracking, with position of the engaged single cam guide 122 at the upper left position on the cam Attorney Docket No.: 161648-0003 disk 32 resulting in a relatively small angle of rotation ⁇ 0 of the doubled secondary concentrator 168.
  • the gentle upward slant of the cam guide 122 at this period causes the cam disk 32 to rotate in a relatively slow counterclockwise direction.
  • FIG. 19C illustrates Tracking Apparatus 3 at time ti with an increased angle of rotation ⁇ of the doubled secondary concentrator 168.
  • the east-west switch can induce an abrupt change in angle 50 ⁇ since prior to the east-west switch the angle 50 ⁇ can be determined using the position of the east receiver, and after the east-west switch the angle 50 ⁇ can be determined using the position of the west receiver.
  • the angle of rotation ⁇ should also be correspondingly reset.
  • FIG. 19D illustrates Tracking Apparatus 3 at time t 2 (with change in rotation angle
  • FIG. 19E illustrates the final position at time ti with the decreased final angle of rotation ⁇ 3 of the doubled secondary concentrator.
  • FIG. 19F provides a summary combined illustration of the daily movement of the cam-based rotational Tracking Apparatus 3, with positions of the engaged single cam guide 122 and doubled secondary concentrator 168 over the day condensed into one figure. After the end of the solar day, the cam-based tracking movement can be reversed to allow the secondary concentrator 168 and cam guide 122 to be repositioned to the start of day position.
  • each of the two optical surfaces 38, 39 of the double secondary concentrator 168 are rotated by the appropriate amount, so that the rotational angle ⁇ 2 is substantially equivalent to the rotational angle ⁇ 3 , and hence there is no need to induce a rotational change during the east-west switch.
  • Tracking Apparatus 4 Rotational Tracking of a Singleton Reflective
  • Tracking Apparatus 4 uses a Type 4 (rotating, non- elevating, single) secondary concentrator 170 with one optical face 38.
  • the secondary concentrator 170 as illustrated in FIGS. 20A-20G, includes a cam peg 131 and a cam guide 132.
  • FIG. 20A provides details of the singleton secondary concentrator 170 with the single cam guide 132.
  • the cam disk 32 can be directly attached to the secondary concentrator 170, cam peg 131 and cam guide 132.
  • the cam guide 132 initially slants gently upward, then slants steeply upward for the east-west switch, and again slants gently upward upon conclusion of the east-west switch.
  • the cam peg 131 is located at the upper right position on the cam disk 32 in its initial position.
  • the west to east translational tracking in conjunction with the cam guide 132 can be used to force the cam disk 32 (and therefore the secondary concentrator 170) counterclockwise at various rates during the day.
  • FIGS. 20B-20G illustrate Tracking Apparatus 4, with position of the engaged single cam guide 132 and secondary concentrator 170 at various angles of rotation at five example times throughout the day.
  • FIG. 20B illustrates the initial position at start time t 0 of the daily tracking, with the engaged single cam guide 132 at the upper left position on the cam disk 32 resulting in a relatively small angle of rotation ⁇ 0 of the singleton secondary concentrator 170.
  • the cam disk 32 then rotates slowly counterclockwise.
  • FIG. 20C illustrates the position at time ti of the engaged single cam guide 132 and singleton secondary concentrator 170 at increased angle of rotation ⁇ .
  • the cam disk 32 then rotates relatively quickly counterclockwise for the east-west switch.
  • FIG. 20D illustrates the position at time t m (in the middle of the east-west switch) with the optical face 38 of the singleton secondary concentrator 170 generally facing nearly upward.
  • FIG. 20E illustrates the position at time t 2 with the reset angle of rotation ⁇ 2 .
  • This one-cam rotational Tracking Apparatus 4 has the useful property that during the west- west switch, the solar radiation continues to be concentrated generally upward (rather Attorney Docket No.: 161648-0003 than at any time downward, which would otherwise potentially damage the primary concentrator).
  • FIG. 20F illustrates Tracking Apparatus 4 at the end time t 3 of the daily tracking, with position of the engaged single cam guide 132 and the singleton secondary concentrator 170 at increased final rotation angle ⁇ 3 .
  • FIG. 20G gives a summary combined illustration of the daily movement of Tracking Apparatus 4, with the positions of the engaged single cam guide 132 and singleton secondary concentrator 170 at five distinct times over the day condensed into one figure. After the end of the solar day, the cam-based tracking movement can be reversed to allow the secondary concentrator 170 and cam guide 132 to be reset to the start of day position.
  • the Tracking Apparatus 1 makes use of west to east translational tracking of a Type 1 (non-rotating, non-elevating, double, operationally- reflective) secondary concentrator associated with each primary concentrator.
  • Type 1 non-rotating, non-elevating, double, operationally- reflective
  • Tracking Apparatus 5 includes a pair (termed eastern-facing-refractive and western-facing-refractive, respectively) of distinct, horizontally separated refractive secondary concentrators 172a and 172b. Both these eastern-facing-refractive and western-facing-refractive secondary concentrators 172a and 172b, for example, are associated with the same primary concentrator. They can be attached to the same two support cables 30, and each attached so they are non- rotating and non-elevating.
  • the eastern-facing-refractive secondary concentrator 172a can be attached to the support cables 30 to the east, and western-facing-refractive secondary concentrator 172b can be attached to the support cables 30 to the west, with sufficient separation so they do not obstruct their refracted radiation directed to the receivers.
  • Each of these refractive secondary concentrators 172a, 172b has a saw-tooth contoured operationally-refractive optical surface 38, 39 (e.g., as described in relation to FIG. 7J).
  • the eastern-facing-refractive secondary concentrator 172a can be slanted downward from the east to the west, and can be designed so that it directs primary concentrated radiation, received from the east from the primary concentrator beneath, to the western receiver.
  • the western-facing-refractive secondary concentrator 172b can be slanted downward from the west to the east, and can be designed so that it directs primary concentrated radiation, received from the west from the primary concentrator beneath, to the eastern receiver.
  • the receiver-directed focal line for the eastern-facing-refractive secondary concentrator 172a is a hypothetical line where radiation from the western receiver would be focused.
  • the receiver-directed focal line for the western-facing- refractive secondary concentrator 172b is a hypothetical line where radiation from the eastern receiver would be focused.
  • the Tracking Apparatus 5 can make use of a schedule of daily west to east translational tracking similar to that described in relation to Tracking Apparatus 1 with regards to FIGS. 16A-D.
  • the eastern-facing-refractive secondary concentrator 172a can provide the active optical surface 39 during the period of time from the start time t 0 of the daily tracking to the time ti of beginning an east-west switch.
  • the receiver-directed focal line of the eastern-facing-refractive secondary concentrator 172a can substantially coincide with the focal line of the primary concentrator, and its concentrated radiation can be directed to the west receiver.
  • the east-west switch can be executed by rapid west to east translational tracking similar to that described in detail for Tracking Apparatus 1 (e.g., see FIGS 16A-B).
  • the western-facing-refractive secondary concentrator 172b can provide the active optical surface 38 during the time t 2 of completing an east-west switch to the end time t 3 .
  • the receiver-directed focal line of the western-facing-refractive secondary concentrator 172b can substantially coincide with the focal line of the primary concentrator, and its concentrated radiation can be directed to the east receiver.
  • the tracking of Attorney Docket No.: 161648-0003 the secondary concentrators is reversed, so as to position them for the start time of the next day.
  • Tracking Apparatus 6 Translational Tracking of a Refractive and a Reflective
  • Tracking Apparatus 6 directs all concentrated radiation to only one receiver.
  • Tracking Apparatus 6 can include a pair of distinct, horizontally separated secondary concentrators 174, termed an eastern-facing- reflective secondary concentrator 174a and a western-facing-refractive secondary concentrator 174b, respectively. Both the eastern-facing secondary concentrator 174a and the western-facing secondary concentrator 174b can be associated with the same primary concentrator.
  • the eastern-facing-reflective secondary concentrator 174a and a western-facing-refractive secondary concentrator 174b are both attached to the same two support cables 30, and each can be attached in a non- rotating and non-elevating manner.
  • the eastern-facing-reflective secondary concentrator 174a can be attached to the support cables 30 to the east and the western-facing- refractive secondary concentrator 174b can be attached to the support cables 30 to the west, with sufficient separation so they do not obstruct their refracted radiation directed to the receivers.
  • the eastern-facing-reflective secondary concentrator 174a can direct primary concentrated radiation, directed from the east from the primary concentrator beneath, to the eastern receiver.
  • the optical surface 39 of the eastern-facing-reflective secondary concentrator 174a in some examples, can be configured as either a concave contoured eastern-facing reflective optical surface or a saw-tooth contoured and operationally- reflective optical surface, as illustrated in relation to FIGS. 7H and 71 respectively.
  • the optical surface 38 of the western-facing-refractive secondary concentrator 174b for example, can be configured similar to the optical surface 38 described in relation to FIG. 7J.
  • the optical surface 38 of the western-facing-refractive secondary concentrator 174b is slanted downward from the west to the east and Attorney Docket No.: 161648-0003 designed so that it directs primary concentrated radiation, directed from the west from the primary concentrator beneath, to the eastern receiver.
  • the receiver-directed focal line for the eastern-facing-reflective secondary concentrator 174a is a hypothetical line where radiation from the eastern receiver would be focused.
  • the receiver-directed focal line for the western-facing- refractive secondary concentrator 174b is a hypothetical line where radiation from the eastern receiver would be focused.
  • the Tracking Apparatus 6 can make use of a schedule of daily west to east translational tracking similar to Tracking Apparatus 1, described in relation to FIGS. 16A-D.
  • the eastern-facing-reflective secondary concentrator 174a can provide the active optical surface 39 during the period of time from the start time t 0 of the daily tracking to the time ti of beginning an east-west switch.
  • the receiver-directed focal line of the eastern-facing-reflective secondary concentrator 174a can substantially coincide with the focal line of the primary concentrator, and its concentrated radiation can be directed to the east receiver.
  • the east-west switch can be executed by rapid west to east translational tracking similar to the east-west switch as described in relation to Tracking Apparatus 1 (e.g., see FIGS. 16B- C).
  • the western-facing-refractive secondary concentrator 174b can provide the active optical surface 38 during the time t 2 of completing an east-west switch to the end time t 3 .
  • the receiver-directed focal line of the western-facing-refractive secondary concentrator 174b can coincide with the focal line of the primary
  • the tracking of the secondary concentrators 174a, 174b can be reversed, so as to position the secondary concentrators 174a, 174b for the start time of the next day.
  • a tracking apparatus similar to Tracking Apparatus 6 can be provided with a western-facing-reflective secondary concentrator and an eastern- facing-refractive secondary concentrator.
  • Tracking Apparatus 7 Rotational Tracking of a Single Refractive
  • Tracking Apparatus 7 makes use of a singleton refractive secondary concentrator.
  • Tracking Apparatus 7 includes a singleton reflective secondary concentrator similar to a Type 4 (e.g., rotating, non-elevating, singleton, operationally- reflective) secondary concentrator as described in relation to FIG. 7D, except the optical surface of the singleton refractive secondary concentrator.
  • a Type 4 e.g., rotating, non-elevating, singleton, operationally- reflective
  • Tracking Apparatus 7 has a saw-tooth contour and is operationally-refractive (e.g., as described in relation to FIG. 7J).
  • the Tracking Apparatus 7 makes use of a schedule of daily west to east translational tracking and cam-based rotational tracking similar to Tracking Apparatus 4, described in relation to FIGS 20B-20G, except the opposite receivers can receive the concentrated solar radiation.
  • the singleton reflective secondary concentrator initially facing east, can provide the active optical surface during both the period of time from the start time t 0 of the daily tracking to the time ti of beginning an east-west switch.
  • the receiver-directed focal line of the singleton refractive secondary concentrator can substantially coincide with the focal line of the primary concentrator, and its concentrated radiation can be directed to the west receiver.
  • the east-west switch can be executed by rapid cam-based rotational tracking as described in detail for Tracking Apparatus 4 (e.g., see FIGS. 20C-E).
  • the same singleton reflective secondary concentrator, now facing west, can provide the active optical surface during the time t 2 of completing an east-west switch to the end time t 3 .
  • concentrator can substantially coincide with the focal line of the primary concentrator, and its concentrated radiation can be directed to the east receiver.
  • the single cam systems can include a second inner cam to allow for more rapid rotation during the east-west switch.
  • a further cam disk and cam guide can be added, with a cam peg closer to the axis of rotation, is the further cam disk being only engaged during the east-west switch while the other cam is disengaged.
  • each receiver is immobile but the secondary concentrators 5 make a rotational swivel (e.g., see focal line 42 in relation to secondary concentrator 5) slightly away from the north- south axis to compensate for a seasonal displacement of solar irradiation.
  • the rotational swivel can compensate for the changing slant of the concentrated solar radiation over the year, directing the secondary concentrated solar radiation 6 to the appropriate immobile receiver.
  • the receiver 7 moves on a north- south axis to slowly track over the year by shifting horizontally 43 on the north-south axis so as to compensate for the changing slant of the concentrated solar radiation over the year.
  • FIG. 23C illustrates an example of the receiver 7 with a vertically stacked array of horizontal evacuated receiver tubes, arranged in a linear pattern, used as absorbers of the concentrated solar radiation.
  • the absorbing region of the receiver 7 can be positioned as an array of receiver tubes, each with center axis running horizontally north-south.
  • multiple receiver tubes can be arranged in a zigzag pattern of displaced vertical columns. In this arrangement, the center axis of each receiver tube and the nearest neighboring receiver tube can vertically displaced by a fixed distance and also displaced in the east-west direction by a fixed distance.
  • the receiver tubes can be arranged in a zig-zag displaced vertical column so the center axis of consecutive receiver tubes are vertically displaced by d sqrt(2) and also displaced Attorney Docket No.: 161648-0003 in the east-west direction by d sqrt(2), so the distance between each respective receiver tube axis is 2d.
  • receiver tubes The effect of this particular arrangement of receiver tubes is first to partly obscure a significant portion of the surface of every second tube that is not normal to the incoming concentrated solar radiation and second to increase the proportion of the surface of the receiver tubes that receive incoming concentrated solar radiation at an angle near normal to the surface of each respective tube. Since the transmittance of the outer glass surface of each tube is highest for solar radiation that is normal to the surface, this positioning of the receiver tubes can improve the overall transmittance of concentrated solar radiation directed to the absorbing region of the receiver.
  • providing apparatus for energy storage increases the total cost of the manufacture of the overall system, but potentially further increases the cost efficiency, allowing the solar conversion process to occur for a period beyond the solar energy collection period.
  • the heat exchanger and energy storage apparatus can also be centrally located near or within the receivers, in some embodiments, to insure rapid and efficient heat transfer. When the receiver absorbing materials cool, for example after completion of the solar day or during a day with reduced direct solar radiation, the stored heat is released.
  • the solar energy system includes an apparatus for bulk thermal storage of the solar energy concentrated at the receivers.
  • the apparatus for bulk thermal storage includes the bulk heat storage materials, storage containers for the bulk material, as well as heat exchangers that provide heat transfer to and from the bulk thermal storage material, as well as insulation used to reduce heat loss.
  • the materials used in this alternative embodiment for bulk thermal storage can include, but are not limited to, liquid sulfur, molten salt, mineral oils, and concrete. Concrete, for example, is likely the lowest cost of these bulk thermal storage materials. While conventional concrete generally consists of a mixture of an Attorney Docket No.: 161648-0003 aggregate, portland cement, water, and admixtures, in certain embodiments the bulk thermal storage material consists of high-temperature concrete, for example, the MEYCO Fireshield 1350 ⁇ , available from BASF SE of Ludwigshafen, Germany. The bulk thermal storage material, in this example, can be made by replacing the usual aggregate with an alternative material.
  • the solar energy system includes an apparatus for phase- change storage of the solar energy concentrated by the centralized receivers.
  • the heat exchangers and storage containers for the phase-change materials can be located within or just in back of the receivers and insulation can be used to reduce heat loss.
  • the substances used for bulk thermal storage can include various salts which form eutectics with other salts and other materials which store and release heat by melting and solidifying, respectively. Examples of these phase-change materials include NaCI, NaN0 3 , KN0 3 , as well as the combination of ZnCI 2 and KCI, and the combination of MgCI and NaCI.
  • the solar concentrator system includes an apparatus for chemical energy storage of the concentrated solar energy at the receivers.
  • the chemicals provide that energy storage react in the presence of heat and catalysis. The reaction absorbs heat, and various chemical products are stored. After the solar day, the stored heat can be released by a reverse reaction.
  • FIGS. 24A and 24B An example apparatus for storage of the concentrated solar energy is illustrated in FIGS. 24A (illustrating heat storage) and 24B (illustrating heat release), where a metallic hydride (such as magnesium hydride (MgH 2 ) powder), for example, can be used to store energy by dissociation to the base metal and hydrogen gas.
  • the apparatus includes a chamber 142 that uses heat energy to produce pressurized gas and a gas storage chamber 144.
  • a heat energy flow 141, provided from the receiver, is passed to the chamber 142.
  • the chamber 142 passes a pressurized gas flow 143 to the gas storage chamber 144.
  • the receiver for example, can contain one or more reaction chambers such as the reaction chamber 142.
  • the reaction chamber 142 for example, can be constructed as an array of horizontal pipes, each partly filled with a metallic Attorney Docket No.: 161648-0003 hydride power suspended in a solvent such as toluene along with catalysts for the reaction.
  • the reaction chamber 142 is connected to the large storage chamber 144 where the resulting dissociated H 2 can be stored at the resulting dissociation pressure.
  • the hydrogen can flow back from the storage chamber 144 to the base metal in the reaction chamber 142 where the hydrogen reacts to reform a metallic hydride, releasing the stored thermal energy for applications after the solar day.
  • the thermal storage is partitioned into a series of blocks of thermal storage, the blocks providing thermal storage in the form of bulk heat storage, chemical heat storage, or phase-change energy storage.
  • the number of blocks of thermal storage currently used can be dynamically varied in accordance to the total amount of concentrated solar energy needed to be stored.
  • only one block of heat storage may be active. Additional blocks can be activated when needed for additional heat storage, and blocks can be deactivated when no longer needed for additional heat storage.
  • the blocks are configured in one or more linear arrays, wherein only a consecutive subsequence of blocks is activated for energy storage at any time.
  • the unique unactivated(?) block neighboring the Attorney Docket No.: 161648-0003 currently activated sequence of blocks can be activated by transporting heat to it.
  • One or more blocks at the end of this activated sequence may be deactivated by no longer transporting heat to them when they are no longer needed for heat storage.
  • the solar concentrator system includes a power- block that makes use of photovoltaic panels that convert the concentrated solar energy to produce electrical energy.
  • the solar energy system includes a power-block that makes use of heated steam to drive a gas turbine.
  • steam pipes 176 run through the receiver 7, absorbing thermal energy.
  • the steam pipes 176 lead to a gas turbine electrical power generator 145 which generates electricity from the flow of pressurized gas though its turbine blades.
  • volume expansion due to the use of the concentrated solar energy to boil water into a large volume of steam, can be used to convert the thermal energy into kinetic energy to drive the gas turbine electrical power generator 145.
  • the steam After driving through the gas turbine electrical power generator 145, the steam enters a return gas storage chamber 147 which, for this application, may optionally contain a cooling tower unit allowing the steam to condense back into water.
  • the steam or water is returned back from the return gas storage chamber 147 to the steam pipes 176 of the receiver 7 and/or, optionally, a heat storage unit (not illustrated).
  • the rate of return flow of the steam or water from the return gas storage chamber 147 to the receiver 7 or heat storage unit can be controlled by a back-flow control valve 148.
  • the solar energy system includes a power-block that makes use of pressurized hydrogen gas, for example obtained by heating a metallic hydride, to drive a gas turbine.
  • FIG. 25B can be alternatively used to illustrate the flow of energy and gas through the power-block.
  • heat energy 141 provides for the metallic hydride's heat-induced disassociation into the base metal and pressurized hydrogen gas, absorbing thermal energy.
  • the hydrogen gas feeds through the gas Attorney Docket No.: 161648-0003 turbine electrical generator 145 and is collected at the return storage chamber 147.
  • the gas flows back to the receiver 7, with the rate of return flow controlled by the back-flow control valve 148.
  • the steps of this energy cycle are further detailed below:
  • a reaction chamber consisting of an array of horizontal steam pipes 176, filled, for example, with a metallic hydride as well as catalysts.
  • the concentrated solar heating (to disassociation temperature) of the metallic hydride (such as magnesium hydride) in the reaction chamber at the receiver 7 results in two reaction products: the base metal product and hydrogen gas H 2 at the dissociation pressure.
  • the volume expansion from the release of a large volume of hydrogen gas H 2 product, can be used to convert the thermal energy into kinetic energy to drive the gas turbine of the gas turbine electrical power generator 145.
  • the reaction chamber can be connected by one or more pipes to the gas turbine electrical power generator 145.
  • Such turbines for example, can have up to 42% efficiency depending on size.
  • the hydrogen After driving through the gas turbine electrical power generator 145, the hydrogen enters the return storage chamber 147 which also, for example, has a pipe (used after the solar energy generation has ended for the day) back to the metallic hydride reaction chamber 142.
  • the use of a metallic hydride/hydrogen turbine for conversion from heat energy to electrical power can provide improved efficiency over a steam turbine system, since the temperature differential between the cooled state and the heated state required for gaseous dissociation can be considerably larger in the metallic hydride/hydrogen turbine energy conversion system than a steam turbine system.
  • the power block closes the back-flow control 148 during the period of the solar day when heat energy is generated. Then, after the solar day, when the base metal of the metallic hydride in the reaction chamber 142 has cooled, the back-flow control valve 148 can be opened to allow the hydrogen to flow back to the reaction chamber 142.
  • an additional gas storage chamber 144 for storage of energy is added to the power block, as illustrated in FIG. 25B.
  • the heat energy 141 provides for the metallic hydride's heat-induced disassociation into the base metal and pressurized hydrogen gas, absorbing thermal energy.
  • Some of the resulting hydrogen gas flows to the temporary storage provided by the additional gas storage chamber 144, and the remainder of the hydrogen gas feeds through the gas turbine electrical generator 145, and is collected at the return storage chamber 147.
  • the gas flows back to the reaction chamber 142. After the solar day, the hydrogen gas stored in the temporary storage chamber 144 can flow back to the reaction chamber 142, which reacts with the base metal to form again metallic hydride, liberating heat which creates an increased gas pressure to further drive the gas turbine electrical generator 145.
  • Concentrated solar thermal-electrical plants can make use of solar radiation (e.g., primarily in the infrared (IR) range) to generate electricity, where as solar photovoltaic (PV) plants make use of solar radiation primarily in the UV and VIS ranges to generate electricity.
  • solar radiation e.g., primarily in the infrared (IR) range
  • PV solar photovoltaic
  • the solar energy system includes an apparatus for separation of concentrated solar radiation in the IR range from the solar radiation in UV and VIS ranges, and apparatus for thermal-electrical generation for harvesting the solar energy in the IR range, as well photovoltaic apparatus for harvesting the solar energy in the UV and VIS ranges.
  • solar radiation in the IR range can be separated from the solar radiation in UV and VIS ranges.
  • the separation of the IR range from the UV and VIS ranges is achieved at the primary concentrators.
  • the separation of the IR range from the UV and VIS ranges is achieved at the secondary concentrators.
  • the receivers separate solar radiation in the IR range from solar radiation in the UV and VIS ranges.
  • each of at least two (e.g., east, west) receivers can be portioned into a pair of subreceivers A and B, one for Attorney Docket No.: 161648-0003 absorbing primarily in the IR range, and the other for absorbing primarily in the UV and VIS ranges.
  • FIG. 26 illustrates the concentrated solar radiation from the secondary concentrators directed to the east receiver 7, which is partitioned into subreceiver A 151, and subreceiver B 152
  • subreceiver A 151 has an optical surface that reflects incoming radiation primarily in the IR, but absorbs incoming radiation primarily in the UV and VIS ranges
  • subreceiver B 152 absorbs the radiation (e.g., primarily in the UV and VIS range) reflected from subreceiver A 151.
  • subreceiver A 151 can be provided with an optical surface that reflects incoming radiation primarily in the UV and VIS ranges but absorbs incoming radiation primarily in the IR ranges.
  • subreceiver B 152 can absorb the (e.g., primarily IR) radiation reflected from subreceiver A 151.
  • the solar energy system includes systems for generation of electrical energy as well as a system for distribution of the remaining and/or waste thermal energy for other productive use.
  • the further productive use of this thermal energy can include, in some examples, smelting, the heating of buildings, the
  • the solar energy system includes systems for generation of electrical energy where a portion of the electricity can be used for generation of hydrogen energy by electrolysis.
  • the remaining and/or waste thermal energy can be used in part for heating water to enhance this production of hydrogen by electrolysis.

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Abstract

L'invention porte sur des systèmes concentrateurs solaires. Certains modes de réalisation utilisent un réseau de concentrateurs primaires passifs positionnés sur le sol, qui transmettent un rayonnement solaire primaire concentré par-dessous à un réseau de concentrateurs secondaires à poursuite. Les concentrateurs secondaires reconcentrent le rayonnement solaire sur un ou plusieurs récepteurs centralisés. Le système concentrateur solaire peut comprendre des dispositifs destinés à la collecte du rayonnement solaire, à sa concentration et à l'absorption de l'énergie solaire concentrée. Certains modes de réalisation du système concentrateur solaire comprennent un grand champ de concentrateurs primaires horizontaux passifs, de concentrateurs secondaires à poursuite situés en hauteur et un ou plusieurs récepteurs, qui convertissent le rayonnement solaire en produits utilisables ou en une énergie utilisable telle que de l'électricité.
PCT/US2010/050039 2009-09-23 2010-09-23 Système concentrateur solaire avec réflecteur primaire fixe et miroir secondaire sur articulation WO2011038144A1 (fr)

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CN2010800480649A CN102612627A (zh) 2009-09-23 2010-09-23 带有固定的一次反射器和铰接的二次镜的太阳能集中器系统
MX2012003353A MX2012003353A (es) 2009-09-23 2010-09-23 Sistema concentrador solar con reflectores primarios fijos y espejo secundario de articulacion.
EP10763917A EP2480837A1 (fr) 2009-09-23 2010-09-23 Système concentrateur solaire avec réflecteur primaire fixe et miroir secondaire sur articulation
AU2010298244A AU2010298244B2 (en) 2009-09-23 2010-09-23 Solar concentrator system with fixed primary reflector and articulating secondary mirror
IN2543DEN2012 IN2012DN02543A (fr) 2009-09-23 2010-09-23
IL218792A IL218792A0 (en) 2009-09-23 2012-03-22 Solar concentrator system with fixed primary reflector and articulating secondary mirror

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US61/245,250 2009-09-23

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