Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F24—HEATING; RANGES; VENTILATING
  • F24S—SOLAR HEAT COLLECTORS; SOLAR HEAT SYSTEMS
  • F24S23/00—Arrangements for concentrating solar-rays for solar heat collectors
  • F24S23/70—Arrangements for concentrating solar-rays for solar heat collectors with reflectors
  • F24S23/74—Arrangements for concentrating solar-rays for solar heat collectors with reflectors with trough-shaped or cylindro-parabolic reflective surfaces
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F24—HEATING; RANGES; VENTILATING
  • F24S—SOLAR HEAT COLLECTORS; SOLAR HEAT SYSTEMS
  • 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
• • 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

Definitions

• This invention relates to solar thermal power plants, and in particular, to solar collection system designed for use with such plants to collect solar energy therefor.
• One type of solar power plant utilizes a "radiation concentrator collector” which concentrates the solar radiation by focusing it onto a smaller area, e.g., using mirrored surfaces or lenses.
• a reflector which is typically parabolic, receives and reflects (focuses) incoming solar radiation onto a radiation absorber, which is formed as a tube.
• the tube radiation absorber is concentrically surrounded by a treated glass enclosure tube to limit the loss of heat.
• the collector system further includes means to track the sun.
• the space between the tube radiation absorber and the glass enclosure tube is evacuated to very low pressure.
• the tube radiation absorber is made of metal with a coating having a high solar radiation absorption coefficient to maximize the energy transfer imparted by the solar radiation reflecting off the reflector.
• a heat transfer fluid constituting a heat transport medium which is typically a liquid such as oil, flows within the tube radiation absorber.
• the thermal energy transported by the thermal fluid is then is used to power a steam-electric power plant to drive one or more turbines thereof, in order to generate electricity in a conventional way, e.g., by coupling the axle of each of the turbines to an electric generator.
• a solar collection system configured for use with a solar thermal power plant, the solar collection system being designed to facilitate capture of thermal energy of incident solar radiation by a heat transfer fluid (HTF) flowing therethrough and comprising:
• a longitudinally extending concentrator which may extend horizontally (i.e., parallelly to level ground) , designed to reflect at least a portion of the incident solar radiation toward a focus line thereof;
• HCE heat collecting element
• the concentrator comprises a light rectifying arrangement configured to specularly reflect the incident solar radiation and increase the elevation angle thereof.
• the light rectifying arrangement may comprise a plurality of teeth formed on an inner surface of the concentrator which faces the HCE, the teeth comprising front, solar radiation-facing front surfaces and rear surfaces.
• the front surfaces may be configured for increasing the elevation angle of impinging solar radiation reflection therefrom.
• the rear surfaces may be designed so as to not interfere with solar radiation reflected by the front surfaces.
• the rear surfaces may be disposed substantially perpendicularly to the direction in which the concentrator extends .
• the concentrator may have a parabolic cross-section in a direction perpendicular to the direction in which it extends, the teeth extending along the parabola.
• the concentrator may be configured to track the sun along a single tracking axis, which is perpendicular to the direction in which the concentrator extends, the teeth extending within a plane containing the tracking axis and perpendicular to the HCE (i.e., perpendicularly to the direction in which the concentrator extends.
• the concentrator may be configured to track the sun by pivoting about a pivot axis perpendicular to the tracking axis .
• the transparent enclosure of the HCE may be made of glass .
• the tube and transparent enclosure of the HCE may be arranged as concentric cylinders.
• the space between the tube and enclosure of the HCE may be evacuated.
• the HTF may be selected from the group consisting of thermal oil, steam/water, molten salts, carbon dioxide, and helium.
• the concentrator may comprise a reflecting surface having a parabolic cross-section.
• a solar thermal power plant comprising a thermal-electric power plant and a solar collection system as described above, in communication therewith to provide heat thereto for driving its operation.
• Fig. 1 is a schematic illustration of a solar thermal power plant according to the present disclosure
• Fig. 2 is schematic perspective view of a solar collector of the solar thermal power plant illustrated in Fig. 1 ;
• Fig. 3 is a schematic perspective view of a heat collecting element of the solar collector illustrated in Fig. 2 ;
• Fig. 4 is a partial cross-sectional view of the heat collecting element, taken along line VI-VI in Fig. 3;
• Fig. 5 is a graph illustrating incident angle losses at various incident angles;
• Fig. 6A is schematic perspective view of a concentrator of the solar collector illustrated in Fig. 2;
• Fig. 6B is a partial, close-up cross-sectional of the concentrator taken along line VI-VI in Fig. 6A;
• Fig. 6C is a partial, close-up cross-sectional of the concentrator taken along line VI-VI in Fig. 6A according to a modification.
• Fig. 7 illustrates an example of incident solar radiation having a high elevation angle passing through a light rectifier of the solar collector illustrated in Fig. 2.
• a solar thermal power plant which is generally indicated at 10.
• the plant 10 comprises a solar collection system 12 and a steam-electric power plant 14.
• the plant further comprises a heating circuit 16.
• the solar collection system 12 is configured to utilize impinging solar radiation to heat a heat transfer fluid (HTF) .
• HTF heat transfer fluid
• the heated HTF is carried, via the heating circuit 16, to the steam-electric power plant 14, wherein the heated HTF is utilized create steam to drive a turbine thereof, thereby produce electricity.
• Such systems are known in the art, and are provided, inter alia, by Siemens Concentrated Solar Power, Ltd.
• the solar collection system 12 comprises one or more solar collectors 18 (only one of which is schematically illustrated in Fig. 1) each comprising an HCE 20 (which constitutes a portion of the heating circuit 16) and one or more longitudinally extending (i.e., elongate) concentrators 22.
• the HCEs 20 carry the HTF, which may be a thermal fluid such as oil (phenyls) which are commercially available, such as under the trade name Therminol® VP-1.
• the HTF may be one of steam/water, molten salts, carbon dioxide, and helium.
• the thermal fluid is heated within the HCE 20 upon its exposure to solar radiation.
• the concentrators 22 each have a parabolic cross-section, i.e., being parabolic in a cross- section which is perpendicular to the direction in which the concentrator extends, defining an entrance area 24 between ends 26 thereof.
• the inner, (HCE-facing) surface 22a of each concentrator is highly reflective, and may be formed or provided with mirrors for this purpose. It is codisposed with the HCE 20 such that the HCE is located at and extends along its focal line. Solar radiation entering the concentrator 22 perpendicularly thereto is reflected toward the HCE 20.
• tracking means configured to pivot the concentrator about an axis which is parallel to the HCE (i.e., parallel to the focal line of the concentrator) .
• the concentrators are considered to track the sun along a tracking axis T which is perpendicular to the HCE/focal line of the concentrator.
• the HCE 20 comprises a transparent enclosure 28, which may be made of, e.g., glass, surrounding a tube 30 carrying the HTF. It is these tubes in which the HTF is heated as it flows through the HCE 20.
• the enclosure 28 and tube 30 may be formed as concentrically arranged cylinders. The space between the enclosure 28 and the tube 30 is evacuated, thus thermally insulating the tube from the surrounding atmosphere.
• the tube may be provided with one or more coatings designed to increase the absorption or solar radiation and limit the amount of heat radiated thereby .
• incidence angle losses can together be quantified as the incidence angle modifier (IAM), which depends on physical properties of the concentrator 22 and the enclosure 28, including, but not limited to, dimensions, materials, etc. In addition, it decreases with the elevation angle of the solar radiation impinging upon the various elements of the solar collector 18 (although it does not necessarily decrease linearly with the elevation angle) .
• IAM incidence angle modifier
• the amount of solar radiation flux impinging upon the tube 30 of the HCE 20 (and consequently the amount of electricity ultimately produced by the solar thermal power plant 10) taking into account these losses (compared to the amount which would impinge if these losses would not be present) is related to the IAM (i.e., a lower IAM is associated with a lower amount of solar radiation flux impinging upon the tube of the HCE) .
• the solar collectors 18 may be provided with means designed to increase the elevation angle (i.e., decrease the declination angle) of impinging solar radiation.
• the inner surfaces 22A thereof may be formed with teeth 32, constituting a light rectifying arrangement.
• each tooth 32 comprises a front surface 34 and a rear surface.
• the teeth 32 are formed such that they extend perpendicularly to the length of the concentrator 22 (along the length of the parabola), i.e., perpendicularly to the direction in which the HCE 20 extends.
• the teeth 32 extend within a plane which is perpendicular to the tracking axis T and perpendicular to the direction in which the HCE 20 and the concentrator 22 extend.
• the front surface 34 is disposed so as to face the impinging solar radiation and configured to specularly reflect solar radiation impinging thereupon.
• the rear surface 36 is disposed facing away from the impinging solar radiation, and may be formed perpendicularly to the length of the concentrator 22 (i.e., to the direction in which it extends), or at a slight angle.
• the teeth 32 are designed so as to not interfere with solar radiation reflected by the front surfaces 34, i.e., such that incident solar radiation which reflects off of the front surface of one tooth 32 does not impinge upon the rear surface 36 of an adjacent tooth.
• the geometry of the inclined portions 32 is determined by the designer, taking into account, inter alia, the elevation angles of the sun over the course of the year.
• the inner surface 22a of the concentrator 22 may be flat, with the light rectifying arrangement therebelow.
• a transparent cover 35 for example made of glass, PMMA, or any other suitable material, is provided over the teeth 32.
• the top side 35a thereof is flat, while the bottom side 35b thereof is formed so as to contact the teeth 32.
• the light rectifying arrangement operates to carry out its function, while the inner surface 22a is flat, facilitating, for example, simple cleaning thereof.
• a light rectifying arrangement as described above with reference to Figs. 6A and 6B which reflects impinging solar radiation impinging during the winter months so as to bring its orientation closer to the vertical and thus decrease the incidence angle losses at this time (thereby leading to an increase in the amount of electricity produced by the solar thermal power plant 10) may "over-reflect" solar radiation during the summer months, i.e., reflect it such that it leaves the light rectifying arrangement (and thus impinges on the concentrator 22) with a declination angle ⁇ ⁇ which is larger than that of solar radiation which reflects off of a "flat" concentrator (the declination angle thereof being indicated by ⁇ ; it will be appreciated that the present discussion is in terms of declination angle for clarity only, and that a larger declination angle is equivalent to a smaller elevation angle) , albeit angled away from the direction from which the solar radiation impinges.
• the HTF which is heated within the HCEs 20 as described above is flows to the steam electric power plant 14. It is used therein, for example within one or more heat exchangers 38, to heat a working fluid which drives one or more turbines 40 driving a generator 42 to create electricity, as is well known in the art.

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• 2011
  • 2011-02-21 EP EP11706792A patent/EP2521885A1/de not_active Withdrawn
  • 2011-02-21 WO PCT/EP2011/052481 patent/WO2011110415A1/en active Application Filing
  • 2011-02-21 CN CN2011800129093A patent/CN102869928A/zh active Pending

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