WO2008072245A2 - Solar radiation collector - Google Patents

Solar radiation collector Download PDF

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Publication number
WO2008072245A2
WO2008072245A2 PCT/IL2007/001548 IL2007001548W WO2008072245A2 WO 2008072245 A2 WO2008072245 A2 WO 2008072245A2 IL 2007001548 W IL2007001548 W IL 2007001548W WO 2008072245 A2 WO2008072245 A2 WO 2008072245A2
Authority
WO
WIPO (PCT)
Prior art keywords
solar radiation
solar
radiation collector
array according
diffusion
Prior art date
Application number
PCT/IL2007/001548
Other languages
French (fr)
Other versions
WO2008072245A3 (en
Inventor
Itay Baruchi
Gonen Fink
Original Assignee
Pythagoras Solar 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 Pythagoras Solar Inc. filed Critical Pythagoras Solar Inc.
Publication of WO2008072245A2 publication Critical patent/WO2008072245A2/en
Publication of WO2008072245A3 publication Critical patent/WO2008072245A3/en

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Classifications

    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B19/00—Condensers, e.g. light collectors or similar non-imaging optics
    • G02B19/0033—Condensers, e.g. light collectors or similar non-imaging optics characterised by the use
    • G02B19/0038—Condensers, e.g. light collectors or similar non-imaging optics characterised by the use for use with ambient light
    • G02B19/0042—Condensers, e.g. light collectors or similar non-imaging optics characterised by the use for use with ambient light for use with direct solar radiation
    • 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
    • F24S23/10—Prisms
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B19/00—Condensers, e.g. light collectors or similar non-imaging optics
    • G02B19/0004—Condensers, e.g. light collectors or similar non-imaging optics characterised by the optical means employed
    • G02B19/0028—Condensers, e.g. light collectors or similar non-imaging optics characterised by the optical means employed refractive and reflective surfaces, e.g. non-imaging catadioptric systems
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B19/00—Condensers, e.g. light collectors or similar non-imaging optics
    • G02B19/0033—Condensers, e.g. light collectors or similar non-imaging optics characterised by the use
    • G02B19/0076—Condensers, e.g. light collectors or similar non-imaging optics characterised by the use for use with a detector
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/04—Prisms
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/04—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices
    • H01L31/054—Optical elements directly associated or integrated with the PV cell, e.g. light-reflecting means or light-concentrating means
    • H01L31/0543—Optical elements directly associated or integrated with the PV cell, e.g. light-reflecting means or light-concentrating means comprising light concentrating means of the refractive type, e.g. lenses
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/04—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices
    • H01L31/054—Optical elements directly associated or integrated with the PV cell, e.g. light-reflecting means or light-concentrating means
    • H01L31/0547—Optical elements directly associated or integrated with the PV cell, e.g. light-reflecting means or light-concentrating means comprising light concentrating means of the reflecting type, e.g. parabolic mirrors, concentrators using total internal reflection
    • 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
    • F24S2023/88—Multi reflective traps
    • 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
    • Y02E10/50—Photovoltaic [PV] energy
    • Y02E10/52—PV systems with concentrators

Definitions

  • the present invention is directed to solar radiation collectors. More specifically, it is directed to planar, non-tracking solar radiation collectors which concentrate solar radiation.
  • US 5,877,874 discloses a holographic planar concentrator (HPC) for collecting and concentrating optical radiation.
  • the HPC comprises a planar highly transparent plate and at least one multiplexed holographic optical film mounted on a surface thereof.
  • the multiplexed holographic optical film has recorded therein a plurality of diffractive structures having one or more regions which are angularly and spectrally multiplexed. Two or more of the regions may be configured to provide spatial multiplexing.
  • the HPC is fabricated by recording the plurality of diffractive structures in the multiplexed holographic optical film employing angular, spectral, and, optionally, spatial multiplexing techniques; and mounting the multiplexed holographic optical film on one surface of the highly transparent plate.
  • the recording of the plurality of diffractive structures is tailored to the intended orientation of the holographic planar concentrator to solar energy.
  • the HPC is mounted in the intended orientation for collecting solar energy and at least one solar energy-collecting device is mounted along at least one edge of the holographic planar concentrator.
  • US 6,274,860 discloses an HPC for collecting and concentrating optical radiation.
  • the HPC comprises a planar highly transparent plate and at least one multiplexed holographic optical film mounted on a surface thereof.
  • the multiplexed holographic optical film has recorded therein a plurality of diffractive structures having one or more regions which are angularly and spectrally multiplexed. Two or more of the regions may be configured to provide spatial multiplexing.
  • the HPC is fabricated by recording the plurality of diffractive structures in the multiplexed holographic optical film employing angular, spectral, and, optionally, spatial multiplexing techniques; and mounting the multiplexed holographic optical film on one surface of the highly transparent plate.
  • the recording of the plurality of diffractive structures is tailored to the intended orientation of the holographic planar concentrator to solar energy.
  • the HPC is mounted in the intended orientation for collecting solar energy and at least one solar energy-collecting device is mounted along at least one edge of the holographic planar concentrator.
  • US 6,476,312 discloses a concentrator for use with photovoltaic devices, including a waveguide incorporating quantum dots. The quantum dots red-shift the incident radiation to produce red-shifted radiation which is internally reflected within the waveguide. A photovoltaic device converts the red-shifted radiation to electrical energy
  • a solar radiation collector comprising a prismatic concentrator, the concentrator comprising:
  • a front wall which may be planar, for facing toward the sun to receive solar radiation and having an outer entrance surface and an inner entrance surface; • at least one sidewall in optical communication with a photovoltaic cell; and
  • the concentrator may be made of a transparent material having a refractive index which is greater than 1.
  • the outer entrance surface may be coated with an anti-reflective coating, or it may be coated with a selective surface coating adapted to allow only radiation of predetermined wavelengths to pass therethrough.
  • the front wall may be of a shape selected from the group comprising hexagonal, square, rectangular, triangular, octagonal, and trapezoidal.
  • Portions of the diffusion surface may be are planar and disposed at an angle between 22° and 44° relative to the front wall.
  • An area of the diffusion surface adjacent the sidewall may be formed as a parabolic section.
  • Portions of the diffusion surface may be formed having parabolic cross-sections.
  • Each diffusion surface may comprises a base plane and plurality of sub-surfaces projecting upwardly therefrom, each sub-surface being inclined toward the sidewall at a predetermined angle in a saw-tooth formation.
  • the predetermined angle is between 0° (i.e., parallel to the sidewall) and 20°. More specifically, the predetermined angle may be substantially 0°.
  • AU of the sub-surfaces may be inclined toward the sidewall at the same angle, or at least some of the sub-surfaces may be inclined toward the sidewall at angles different than that of other of the sub-surfaces.
  • the base plane may be inclined in a direction which is opposite that which the sub-surfaces are inclined, at least in the vicinity of the sub-surfaces.
  • the diffusion surface may comprise a plurality of grooved formed therein projecting into the prismatic concentrator. The grooves may be parallel to the sidewall.
  • the diffusion surface may comprise a coating adapted to impart properties of a diffusive reflector thereto.
  • the coating may be a lambertian coating.
  • the diffusion surface may comprise an up/down spectral conversion material having a predefined spectral shift.
  • the diffusion surface may be completely or partially reflective.
  • the diffusion surface may be formed by a process selected from the group comprising etching, grinding, and laser engraving.
  • the diffusion surface may be designed (i.e., engineered) so as to increase the concentration of radiation impinging on the sidewalls relative to the concentration of radiation impinging on the front wall (i.e., the intensity of the radiation impinging on the sidewalls is higher than the intensity of the radiation impinging on the front wall).
  • the sidewall may comprise an inner receiver surface adapted to receive radiation reflected by at least one of the diffusion surface and the inner entrance surface, and an outer receiver surface, the photovoltaic cell being attached to the outer receiver surface.
  • the photovoltaic cells may be bifacial.
  • the solar radiation collector may further comprise a positioning mechanism adapted to orient the front wall in accordance with the position of the sun.
  • a solar array comprising two or more solar radiation collectors, each comprising a prismatic concentrator, each of the concentrators comprising:
  • Each of the concentrators, and/or elements thereof, may be embodied according to any of the options listed in connection with the previous aspect of the present invention.
  • the photovoltaic cells are bifacial, at least some of them may be associated with two solar radiation collectors.
  • optical communication is to be understood as referring to a relationship between two objects wherein substantially all light impinging on one of the objects is transmitted to the second thereof.
  • Fig. IA is a perspective view of one example of a solar radiation collector according to the present invention.
  • Fig. IB is a cross-sectional view of the solar radiation collector taken along line I-I in Fig. IA;
  • Figs. 2A and 2B are cross-sections of a section of the diffusion surface according to different embodiments of the present invention.
  • FIGs. 2C and 2D are enlargements of the area indicated at III in Fig. IB, according to different modifications of the present invention.
  • Fig. 3 is an enlargement of the area indicated at III in Fig. IB, according to another embodiment
  • Fig. 4 is a cross-section of the section illustrated in Figs. 2 A and 2B according to another embodiment of the present invention
  • Fig. 5 is a partial cross-sectional view of the solar radiation collector, illustrating how a ray of radiation propagates therethrough;
  • Figs. 6A through 6F illustrate solar arrays comprising solar radiation collectors of different shapes.
  • a solar radiation collector which is generally indicated at 10.
  • the solar radiation collector is prismatic and is adapted to receive solar radiation therein, to diffuse it, and to totally internally reflect at least a portion of the diffused radiation toward one or more photovoltaic cells.
  • the solar radiation collector 10 is made from a material which has a refractive index which is greater than 1.
  • the solar radiation collector 10 comprises a planar front wall 12, constituting a sun (i.e., radiation) facing surface of the solar radiation collector, for receiving said solar radiation, a rear wall 14 opposite the front wall having a diffusion surface 15 which may be completely or partially reflective, and sidewalls 16 constituting receiver windows of the solar radiation collector.
  • the height of the sidewalls 16 should be small compared to the width of the front wall, but this is not strictly necessary, as will be explained below.
  • the solar radiation collector 10 further comprises photovoltaic cells 18, which may be bifacial, each of which is in optical communication with a sidewall 16.
  • a positioning mechanism not illustrated in Fig. IA, and represented schematically at 20 in Fig.
  • the front wall 12 comprises an outer entrance surface 12a, adapted to face the solar radiation, and an inner entrance surface 12b.
  • the outer entrance surface 12a may be coated with an anti-reflective coating, which is adapted to minimize the amount of solar radiation which is reflected by the outer entrance surface.
  • the outer entrance surface 12a may be coated with a selective surface coating which is adapted to allow radiation of predetermined wavelength, or within a predetermined range or ranges of frequencies, to pass therethrough. Such a coating will enable solar radiation which may be utilized by the photovoltaic cells 18 to produce electricity to pass therethrough, while preventing radiation of other frequencies, which will unnecessarily heat the photovoltaic cells, to enter the solar radiation collector 10.
  • the front wall 12 defines the shape of the solar radiation collector 10, and may be in any desired shape. It will be appreciated that certain shapes, such as hexagonal, square, rectangular, triangular, octagonal, and trapezoidal, allow for a tessellated array of a plurality of solar radiation collectors 10 to form a solar array. In addition, different shapes are associated with different ratios between the area of the front wall 12 and the total area of the sidewalls 16. This ratio, as will be explained below, is associated with the overall concentration of the solar radiation collector 10.
  • the diffusion surface 15 is adapted to diffuse radiation impinging thereupon, and reflect it in a diffuse manner towards the exit aperture (solar cell).
  • the diffused radiation distribution is a significant factor in determining the efficiency of the concentration system (e.g., by reducing the amount of escaping radiation)
  • it is specifically designed/engineered to increase the overall concentration of solar radiation between the front wall 12 and the side walls 16, as will be described below. This may be accomplished due to its geometry, material surface polish, and/or a coating applied thereto.
  • the geometry may be formed by etching, grinding, and/or laser engraving.
  • a material surface polish or laser engraving may be used to achieve this purpose.
  • sections of the diffusion surface 15 may be tilted towards the exit aperture or formed in a parabolic shape (CPC).
  • CPC parabolic shape
  • the angle ⁇ that the diffusion surface 15 makes with the front wall 12 is optimized to obtain maximal radiation trapping (i.e., maximal system efficiency) along day and year.
  • the angles may range between ⁇ c to ⁇ J2, where ⁇ c is the critical angle for total internal reflection of the material of the solar radiation collector 10.
  • a solar radiation collector 10 may comprise several sections as per Figs. 2A and 2B.
  • a hexagonal solar radiation collector 10 such as illustrated in Fig. IA, may comprise six such sections, each being triangular in shape.
  • the sections illustrated in Figs. 2 A and 2B each comprise a diffusion surface 15 which meets the front wall 12, the examples are not so limited, i.e., the cross-section of the sections illustrated therein may be truncated in the vicinity of the intersection of the diffusion surface and the front wall.
  • the diffusion surface 15 may be further formed with a plurality of sub-surfaces 22 arranged in a saw-tooth formation.
  • the sub-surfaces angle may be disposed parallel to the exit aperture or tilted in relation to it at a small angle, e.g., up to 20°.
  • the diffusion surface 15 may be inclined in a direction opposite the inclination of the sub-surfaces 22, at least hi the vicinity of the sub-surfaces (i.e., different areas of the diffusion surface 15 may be inclined in different directions at different areas). This reduces the amount of radiation which is not totally internally reflected by the inner entrance surface 12b.
  • each of the sub-surfaces 22 may be coated with a coating which is adapted to diffuse radiation impinging thereupon, e.g., a lambertian coating.
  • the angle of inclination of the sub-surfaces 22 may range between about 22° and 44°. All the sub-surfaces 22 may be inclined at the same angle, or the angle of inclination of each sub-surface may be different from other sub-surfaces.
  • grooves 23 may be formed in the diffusion surface 15 (although a planar diffusion surface is illustrated as per Fig. 2A, these grooves may as well be formed in a parabolic subsurface as per Fig. 2B, or in any other shaped diffuser surface). These grooves 23 are formed, e.g., by laser engraving or any other suitable method, such that they are parallel to the sidewalls 16. This is because the lambertian radiation distribution from the sides of the grooves 23 is concentrated most strongly in the direction which is perpendicular thereto, i.e., the greatest amount of radiation is reflected directly toward the sidewalls 16.
  • the width of each groove may range from several to several hundred microns, or any other appropriate width.
  • the diffusion surface 15 may be formed with up/down conversion material 24 (such as florescent coatings or quantum dots) having a predefined spectral shift.
  • up/down conversion material 24 such as florescent coatings or quantum dots
  • Each side wall 16 comprises an inner receiver surface 16a, adapted to receive radiation reflected by the diffusion surface 15 and/or the inner entrance surface 12b, and an outer receiver surface 16b.
  • the photovoltaic cells 18 are coplanar with and attached to the outer receiver surfaces 16b such that all radiation which impinges upon the inner receiver surfaces 16a passes through the sidewall 16 an impinges upon the photovoltaic cell.
  • the area of the diffusion surface 15, which is indicated at 15a may be formed as a parabolic section (i.e., a CPC).
  • a CPC parabolic section
  • Such an arrangement increases the ratio between the area of the front wall 12 and the area of sidewalls 16, since the length of the sidewall may be equal to that of a line 16' which is normal to the diffusion surface 15.
  • the ratio between the area of the front wall 12 and the area of sidewalls 16 is 1/sin ⁇ .
  • this ration is 1/tan ⁇ , which is smaller, at least in the relevant range of ⁇ .
  • this ratio is proportional to the overall concentration of the solar radiation collector, thus an increase thereof is associated with an increase of the overall concentration of the solar radiation collector.
  • solar radiation impinges upon the outer entrance surface 12a, as indicated at A.
  • the angle of incidence of the solar radiation varies with the position of the sun, which can be calculated based on the tune of day, the time of year, and the spatial position (i.e., latitude/longitude coordinates and elevation) of the solar radiation collector 10. It will be appreciated that, in contrast to other tracking solar devices, tracking of the solar radiation collector 10 according to the present invention allows for a relatively large amount of impreciseness.
  • the radiation which enters via the front wall 12 propagates through the solar radiation collector 10, as indicated at B, until it reaches the diffusion surface 15 of the rear wall 14.
  • the radiation is then diffused, as indicated at Ci and C 2 .
  • Radiation which impinges upon the inner entrance surface 12b at an angle which exceeds the critical angle is lost, i.e., it exits the solar radiation collector 10, as indicated at D.
  • Radiation which impinges upon the inner entrance surface 12b at an angle which does not exceed the critical angle is totally internally reflected and propagates through the solar radiation collector 10, as indicated at E. This process repeats until the radiation is either lost as described above, or impinges upon a sidewall 16, at which point it impinges upon the photovoltaic cell 18 which is in optical communication therewith.
  • Cgeomet ⁇ c is the geometrical concentration of the solar radiation collector, which is defined by A entranc JA rece ⁇ ver , where A ent r anc e is the area of the front wall 12, and Ar ecer v e r is the total area of all of the sidewalls 16 in'the solar radiation collector; and
  • the efficiency of the solar radiation collector 10 depends on many factors which contribute to the amount of diffused radiation which is lost during concentration thereof. This factor can be arrived at using a theoretical mathematical model based on optical properties of the components of and relative dimensions of the solar radiation collector 10, or measured empirically, e.g., by measuring the amount of radiation which is emitted by the solar radiation collector 10 when a known amount of radiation is directed theretoward. By properly designing the solar radiation collector 10, concentrations of 2-10, and even exceeding these values, can be achieved.
  • a plurality of solar radiation collectors 10 of different shapes can be arranged to form a solar array, which is generally indicated at 28.
  • arrays of solar radiation collectors 10 which are hexagonal, square, rectangular, trapezoidal, triangular, and octagonal/square are illustrated, respectively, in Figs. 6A through 6F, it will be appreciated that the solar radiation collectors 10 may be formed in any desired shape.
  • the photovoltaic cells may be bifacial, each side of which being in optical communication with a different adjacent solar radiation collector 10.
  • a single positioning mechanism 20 may be provided for the entire array 28, or several may be provided, with one or several of the solar radiation collectors 10 associated with each one.

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Abstract

A solar radiation collector comprising a prismatic concentrator, the concentrator comprising a front wall for facing toward the sun to receive solar radiation and having an outer entrance surface and an inner entrance surface, at least one sidewall in optical communication with a photovoltaic cell, and a rear wall opposite the front wall and having a diffusion surface designed to diffuse solar radiation impinging thereupon such that at least a portion of the radiation is totally internally reflected by the inner entrance surface toward the sidewall.

Description

SOLAR RADIATION COLLECTOR
FIELD OF THE INVENTION
The present invention is directed to solar radiation collectors. More specifically, it is directed to planar, non-tracking solar radiation collectors which concentrate solar radiation.
BACKGROUND OF THE INVENTION
It is well known that radiation concentration can reduce the cost of electricity produced by photovoltaic cells, by replacing the high-cost component of the PV cells with lower-cost radiation collectors, typically made of glass or plastic. In a non-tracking concentrator, solar radiation is concentrated without particular regard to the position of the sun relative thereto.
US 5,877,874 discloses a holographic planar concentrator (HPC) for collecting and concentrating optical radiation. The HPC comprises a planar highly transparent plate and at least one multiplexed holographic optical film mounted on a surface thereof. The multiplexed holographic optical film has recorded therein a plurality of diffractive structures having one or more regions which are angularly and spectrally multiplexed. Two or more of the regions may be configured to provide spatial multiplexing. The HPC is fabricated by recording the plurality of diffractive structures in the multiplexed holographic optical film employing angular, spectral, and, optionally, spatial multiplexing techniques; and mounting the multiplexed holographic optical film on one surface of the highly transparent plate. The recording of the plurality of diffractive structures is tailored to the intended orientation of the holographic planar concentrator to solar energy. The HPC is mounted in the intended orientation for collecting solar energy and at least one solar energy-collecting device is mounted along at least one edge of the holographic planar concentrator. US 6,274,860 discloses an HPC for collecting and concentrating optical radiation. The HPC comprises a planar highly transparent plate and at least one multiplexed holographic optical film mounted on a surface thereof. The multiplexed holographic optical film has recorded therein a plurality of diffractive structures having one or more regions which are angularly and spectrally multiplexed. Two or more of the regions may be configured to provide spatial multiplexing. The HPC is fabricated by recording the plurality of diffractive structures in the multiplexed holographic optical film employing angular, spectral, and, optionally, spatial multiplexing techniques; and mounting the multiplexed holographic optical film on one surface of the highly transparent plate. The recording of the plurality of diffractive structures is tailored to the intended orientation of the holographic planar concentrator to solar energy. The HPC is mounted in the intended orientation for collecting solar energy and at least one solar energy-collecting device is mounted along at least one edge of the holographic planar concentrator. US 6,476,312 discloses a concentrator for use with photovoltaic devices, including a waveguide incorporating quantum dots. The quantum dots red-shift the incident radiation to produce red-shifted radiation which is internally reflected within the waveguide. A photovoltaic device converts the red-shifted radiation to electrical energy
SUMMARY OF THE INVENTION
According to one aspect of the present invention, there is provided a solar radiation collector comprising a prismatic concentrator, the concentrator comprising:
• a front wall, which may be planar, for facing toward the sun to receive solar radiation and having an outer entrance surface and an inner entrance surface; • at least one sidewall in optical communication with a photovoltaic cell; and
• a rear wall opposite the front wall and having a diffusion surface designed to diffuse solar radiation impinging thereupon such that at least a portion thereof is totally internally reflected by the inner entrance surface toward the sidewall.
The concentrator may be made of a transparent material having a refractive index which is greater than 1. The outer entrance surface may be coated with an anti-reflective coating, or it may be coated with a selective surface coating adapted to allow only radiation of predetermined wavelengths to pass therethrough.
The front wall may be of a shape selected from the group comprising hexagonal, square, rectangular, triangular, octagonal, and trapezoidal.
Portions of the diffusion surface may be are planar and disposed at an angle between 22° and 44° relative to the front wall. An area of the diffusion surface adjacent the sidewall may be formed as a parabolic section.
Portions of the diffusion surface may be formed having parabolic cross-sections. Each diffusion surface may comprises a base plane and plurality of sub-surfaces projecting upwardly therefrom, each sub-surface being inclined toward the sidewall at a predetermined angle in a saw-tooth formation. The predetermined angle is between 0° (i.e., parallel to the sidewall) and 20°. More specifically, the predetermined angle may be substantially 0°. AU of the sub-surfaces may be inclined toward the sidewall at the same angle, or at least some of the sub-surfaces may be inclined toward the sidewall at angles different than that of other of the sub-surfaces.
The base plane may be inclined in a direction which is opposite that which the sub-surfaces are inclined, at least in the vicinity of the sub-surfaces. The diffusion surface may comprise a plurality of grooved formed therein projecting into the prismatic concentrator. The grooves may be parallel to the sidewall.
The diffusion surface may comprise a coating adapted to impart properties of a diffusive reflector thereto. The coating may be a lambertian coating.
The diffusion surface may comprise an up/down spectral conversion material having a predefined spectral shift.
The diffusion surface may be completely or partially reflective.
The diffusion surface may be formed by a process selected from the group comprising etching, grinding, and laser engraving.
The diffusion surface may be designed (i.e., engineered) so as to increase the concentration of radiation impinging on the sidewalls relative to the concentration of radiation impinging on the front wall (i.e., the intensity of the radiation impinging on the sidewalls is higher than the intensity of the radiation impinging on the front wall). - A -
The sidewall may comprise an inner receiver surface adapted to receive radiation reflected by at least one of the diffusion surface and the inner entrance surface, and an outer receiver surface, the photovoltaic cell being attached to the outer receiver surface. The photovoltaic cells may be bifacial.
The solar radiation collector may further comprise a positioning mechanism adapted to orient the front wall in accordance with the position of the sun.
According to another aspect of the present invention, there is provided a solar array comprising two or more solar radiation collectors, each comprising a prismatic concentrator, each of the concentrators comprising:
• a front wall for facing toward the sun to receive solar radiation and having an outer entrance surface and an inner entrance surface;
• at least one sidewall in optical communication with a photovoltaic cell; and
• a rear wall opposite the front wall and having a diffusion surface designed to diffuse solar radiation impinging thereupon such that at least a portion of the radiation is totally internally reflected by the inner entrance surface toward the sidewall.
Each of the concentrators, and/or elements thereof, may be embodied according to any of the options listed in connection with the previous aspect of the present invention.
In the event that the photovoltaic cells are bifacial, at least some of them may be associated with two solar radiation collectors.
It will be appreciated that hereafter in the specification and claims, the terms optical communication is to be understood as referring to a relationship between two objects wherein substantially all light impinging on one of the objects is transmitted to the second thereof.
It will be appreciated that hereafter in the specification and claims, the terms prism and prismatic are to be understood as referring to a transparent solid body, and not being limited to any specific shape. BRIEF DESCRIPTION OF THE DRAWINGS
In order to understand the invention and to see how it may be carried out in practice, embodiments will now be described, by way of non-limiting examples only, with reference to the accompanying drawings, in which: Fig. IA is a perspective view of one example of a solar radiation collector according to the present invention;
Fig. IB is a cross-sectional view of the solar radiation collector taken along line I-I in Fig. IA;
Figs. 2A and 2B are cross-sections of a section of the diffusion surface according to different embodiments of the present invention;
Figs. 2C and 2D are enlargements of the area indicated at III in Fig. IB, according to different modifications of the present invention;
Fig. 3 is an enlargement of the area indicated at III in Fig. IB, according to another embodiment; Fig. 4 is a cross-section of the section illustrated in Figs. 2 A and 2B according to another embodiment of the present invention;
Fig. 5 is a partial cross-sectional view of the solar radiation collector, illustrating how a ray of radiation propagates therethrough; and
Figs. 6A through 6F illustrate solar arrays comprising solar radiation collectors of different shapes.
DETAILED DESCRIPTION OF EMBODIMENTS
As illustrated in Figs. IA and IB, there is provided a solar radiation collector, which is generally indicated at 10. The solar radiation collector is prismatic and is adapted to receive solar radiation therein, to diffuse it, and to totally internally reflect at least a portion of the diffused radiation toward one or more photovoltaic cells. In order to achieve total internal reflection, the solar radiation collector 10 is made from a material which has a refractive index which is greater than 1.
The solar radiation collector 10 comprises a planar front wall 12, constituting a sun (i.e., radiation) facing surface of the solar radiation collector, for receiving said solar radiation, a rear wall 14 opposite the front wall having a diffusion surface 15 which may be completely or partially reflective, and sidewalls 16 constituting receiver windows of the solar radiation collector. Ideally, the height of the sidewalls 16 should be small compared to the width of the front wall, but this is not strictly necessary, as will be explained below. The solar radiation collector 10 further comprises photovoltaic cells 18, which may be bifacial, each of which is in optical communication with a sidewall 16. hi addition, a positioning mechanism, not illustrated in Fig. IA, and represented schematically at 20 in Fig. IB, adapted to orient the front wall in accordance with the position of the sun relative to the solar radiation collector 10, may be provided. The front wall 12 comprises an outer entrance surface 12a, adapted to face the solar radiation, and an inner entrance surface 12b. The outer entrance surface 12a may be coated with an anti-reflective coating, which is adapted to minimize the amount of solar radiation which is reflected by the outer entrance surface. Alternatively or in addition to the anti-reflective coating, the outer entrance surface 12a may be coated with a selective surface coating which is adapted to allow radiation of predetermined wavelength, or within a predetermined range or ranges of frequencies, to pass therethrough. Such a coating will enable solar radiation which may be utilized by the photovoltaic cells 18 to produce electricity to pass therethrough, while preventing radiation of other frequencies, which will unnecessarily heat the photovoltaic cells, to enter the solar radiation collector 10.
The front wall 12 defines the shape of the solar radiation collector 10, and may be in any desired shape. It will be appreciated that certain shapes, such as hexagonal, square, rectangular, triangular, octagonal, and trapezoidal, allow for a tessellated array of a plurality of solar radiation collectors 10 to form a solar array. In addition, different shapes are associated with different ratios between the area of the front wall 12 and the total area of the sidewalls 16. This ratio, as will be explained below, is associated with the overall concentration of the solar radiation collector 10.
The diffusion surface 15 is adapted to diffuse radiation impinging thereupon, and reflect it in a diffuse manner towards the exit aperture (solar cell). As the diffused radiation distribution is a significant factor in determining the efficiency of the concentration system (e.g., by reducing the amount of escaping radiation), it is specifically designed/engineered to increase the overall concentration of solar radiation between the front wall 12 and the side walls 16, as will be described below. This may be accomplished due to its geometry, material surface polish, and/or a coating applied thereto. The geometry may be formed by etching, grinding, and/or laser engraving. In addition, a material surface polish or laser engraving may be used to achieve this purpose.
As illustrated in Figs. 2A and 2B, sections of the diffusion surface 15 may be tilted towards the exit aperture or formed in a parabolic shape (CPC). In the example illustrated in Fig. 2A, the angle θ that the diffusion surface 15 makes with the front wall 12 is optimized to obtain maximal radiation trapping (i.e., maximal system efficiency) along day and year. The angles may range between θc to ΘJ2, where θc is the critical angle for total internal reflection of the material of the solar radiation collector 10.
It will be appreciated that a solar radiation collector 10 may comprise several sections as per Figs. 2A and 2B. For example, a hexagonal solar radiation collector 10 such as illustrated in Fig. IA, may comprise six such sections, each being triangular in shape. In addition, while the sections illustrated in Figs. 2 A and 2B each comprise a diffusion surface 15 which meets the front wall 12, the examples are not so limited, i.e., the cross-section of the sections illustrated therein may be truncated in the vicinity of the intersection of the diffusion surface and the front wall.
As illustrated in Fig. 2C, the diffusion surface 15 may be further formed with a plurality of sub-surfaces 22 arranged in a saw-tooth formation. The sub-surfaces angle may be disposed parallel to the exit aperture or tilted in relation to it at a small angle, e.g., up to 20°. The diffusion surface 15 may be inclined in a direction opposite the inclination of the sub-surfaces 22, at least hi the vicinity of the sub-surfaces (i.e., different areas of the diffusion surface 15 may be inclined in different directions at different areas). This reduces the amount of radiation which is not totally internally reflected by the inner entrance surface 12b. In addition, each of the sub-surfaces 22 may be coated with a coating which is adapted to diffuse radiation impinging thereupon, e.g., a lambertian coating. The angle of inclination of the sub-surfaces 22 may range between about 22° and 44°. All the sub-surfaces 22 may be inclined at the same angle, or the angle of inclination of each sub-surface may be different from other sub-surfaces.
As illustrated in Fig. 2D, grooves 23 may be formed in the diffusion surface 15 (although a planar diffusion surface is illustrated as per Fig. 2A, these grooves may as well be formed in a parabolic subsurface as per Fig. 2B, or in any other shaped diffuser surface). These grooves 23 are formed, e.g., by laser engraving or any other suitable method, such that they are parallel to the sidewalls 16. This is because the lambertian radiation distribution from the sides of the grooves 23 is concentrated most strongly in the direction which is perpendicular thereto, i.e., the greatest amount of radiation is reflected directly toward the sidewalls 16. The width of each groove may range from several to several hundred microns, or any other appropriate width.
As illustrated in Fig. 3, the diffusion surface 15 may be formed with up/down conversion material 24 (such as florescent coatings or quantum dots) having a predefined spectral shift.
Each side wall 16 comprises an inner receiver surface 16a, adapted to receive radiation reflected by the diffusion surface 15 and/or the inner entrance surface 12b, and an outer receiver surface 16b. The photovoltaic cells 18 are coplanar with and attached to the outer receiver surfaces 16b such that all radiation which impinges upon the inner receiver surfaces 16a passes through the sidewall 16 an impinges upon the photovoltaic cell.
As illustrated in Fig. 4, the area of the diffusion surface 15, which is indicated at 15a, may be formed as a parabolic section (i.e., a CPC). Such an arrangement increases the ratio between the area of the front wall 12 and the area of sidewalls 16, since the length of the sidewall may be equal to that of a line 16' which is normal to the diffusion surface 15. Thus, the ratio between the area of the front wall 12 and the area of sidewalls 16 is 1/sin θ. In the absence of such an arrangement (e.g., as illustrated in Fig. 2A), this ration is 1/tan θ, which is smaller, at least in the relevant range of θ. As will be described below, this ratio is proportional to the overall concentration of the solar radiation collector, thus an increase thereof is associated with an increase of the overall concentration of the solar radiation collector.
In use, as illustrated in Fig. 5, solar radiation impinges upon the outer entrance surface 12a, as indicated at A. The angle of incidence of the solar radiation varies with the position of the sun, which can be calculated based on the tune of day, the time of year, and the spatial position (i.e., latitude/longitude coordinates and elevation) of the solar radiation collector 10. It will be appreciated that, in contrast to other tracking solar devices, tracking of the solar radiation collector 10 according to the present invention allows for a relatively large amount of impreciseness.
The radiation which enters via the front wall 12 propagates through the solar radiation collector 10, as indicated at B, until it reaches the diffusion surface 15 of the rear wall 14. The radiation is then diffused, as indicated at Ci and C2. Radiation which impinges upon the inner entrance surface 12b at an angle which exceeds the critical angle is lost, i.e., it exits the solar radiation collector 10, as indicated at D. Radiation which impinges upon the inner entrance surface 12b at an angle which does not exceed the critical angle is totally internally reflected and propagates through the solar radiation collector 10, as indicated at E. This process repeats until the radiation is either lost as described above, or impinges upon a sidewall 16, at which point it impinges upon the photovoltaic cell 18 which is in optical communication therewith.
The overall concentration of the solar radiation collector 10 can be expressed as follows: C = Cgeometπc x efficiency in which:
• C is the overall concentration of the solar radiation collector;
• Cgeometπc is the geometrical concentration of the solar radiation collector, which is defined by AentrancJAreceτver, where Aentrance is the area of the front wall 12, and Arecerver is the total area of all of the sidewalls 16 in'the solar radiation collector; and
• efficiency is the efficiency of the solar radiation collector.
The efficiency of the solar radiation collector 10 depends on many factors which contribute to the amount of diffused radiation which is lost during concentration thereof. This factor can be arrived at using a theoretical mathematical model based on optical properties of the components of and relative dimensions of the solar radiation collector 10, or measured empirically, e.g., by measuring the amount of radiation which is emitted by the solar radiation collector 10 when a known amount of radiation is directed theretoward. By properly designing the solar radiation collector 10, concentrations of 2-10, and even exceeding these values, can be achieved. It will be appreciated that while the geometrical concentration can be increased by minimizing the height of the receiver, i.e., the distance between the front wall 12 and the rear wall 14, this results in an increase in the number of reflections of radiation by the diffusion surface 15, which entails an increase in the amount of radiation lost. Thus, when designing the solar radiation collector 10, the effect of the relative dimensions thereof on the geometrical concentration and the efficiency must be considered in tandem in order to achieve an optimized overall concentration.
In addition, as illustrated hi Figs. 6A through 6F5 a plurality of solar radiation collectors 10 of different shapes can be arranged to form a solar array, which is generally indicated at 28. Although arrays of solar radiation collectors 10 which are hexagonal, square, rectangular, trapezoidal, triangular, and octagonal/square are illustrated, respectively, in Figs. 6A through 6F, it will be appreciated that the solar radiation collectors 10 may be formed in any desired shape. In such an array, the photovoltaic cells may be bifacial, each side of which being in optical communication with a different adjacent solar radiation collector 10. Such an arrangement decreases the amount of photovoltaic cells which need to be provided by a factor which approaches 2 as the number of solar radiation collectors 10 in the array 28 increases. A single positioning mechanism 20 may be provided for the entire array 28, or several may be provided, with one or several of the solar radiation collectors 10 associated with each one.
Those skilled in the art to which this invention pertains will readily appreciate that numerous changes, variations and modifications can be made without departing from the scope of the invention mutatis mutandis.

Claims

CLAIMS:
1. A solar radiation collector comprising a prismatic concentrator, said concentrator comprising:
• a front wall for facing toward the sun to receive solar radiation and having an outer entrance surface and an inner entrance surface;
• at least one sidewall in optical communication with a photovoltaic cell; and .
• a rear wall opposite said front wall and having a diffusion surface designed to diffuse solar radiation impinging thereupon such that at least a portion of the radiation is totally internally reflected by the inner entrance surface toward said sidewall.
2. A solar radiation according to Claim 1, said concentrator being made of a transparent material having a refractive index which is greater than 1.
3. A solar radiation collector according to any one of Claims 1 and 2, wherein said front wall is planar.
4. A solar radiation collector according to any one of the preceding claims, wherein the outer entrance surface is coated with an anti-reflective coating.
5. A solar radiation collector according to any one of the preceding claims, wherein the outer entrance surface is coated with a selective surface coating adapted to allow only radiation of predetermined wavelengths to pass therethrough.
6. A solar radiation collector according to any one of the preceding claims, wherein said front wall is of a shape selected from the group comprising hexagonal, square, rectangular, triangular, octagonal, and trapezoidal.
7. A solar radiation collector according to any one of the preceding claims, wherein portions of said diffusion surface are planar and disposed at an angle between 22° and 44° relative to said front wall.
8. A solar radiation collector according to Claim 7, wherein an area of the diffusion surface adjacent the sidewall is formed as a parabolic section.
9. A solar radiation collector according to any one of Claims 1 through 6, wherein portions of said diffusion surface are formed having parabolic cross-sections.
10. A solar radiation collector according to any one of the preceding claims, wherein said diffusion surface comprises a base plane and plurality of sub-surfaces projecting upwardly therefrom, each sub-surface being inclined toward said sidewall at a predetermined angle in a saw-tooth formation.
11. A solar radiation collector according to Claim 10, wherein said predetermined angle is between 0° and 20°.
12. A solar radiation collector according to Claim 11, wherein said predetermined angle is substantially 0°.
13. A solar radiation collector according to any one of Claims 10 through 12, wherein all of said sub-surfaces are inclined toward said sidewall at the same angle.
14. A solar radiation collector according to any one of Claims 10 through 12, wherein at least some of the sub-surfaces are inclined toward said sidewall at angles different than that of other of said sub-surfaces.
15. A solar radiation collector according to any one of Claims 10 through 14, wherein said base plane is inclined in a direction opposite that which the sub-surfaces are inclined, at least in the vicinity of the sub-surfaces.
16. A solar radiation collector according to any one of Claims 1 through 6, wherein said diffusion surface comprises a plurality of grooved formed therein projecting into the prismatic concentrator.
17. A solar radiation collector according to Claim 16, wherein said grooves are parallel to said sidewall.
18. A solar radiation collector according to any one of the preceding claims, said diffusion surface comprising a coating adapted to impart properties of a diffusive reflector thereto.
19. A solar radiation collector according to Claim 18, wherein said coating is a lambertian coating.
20. A solar radiation collector according to any one of the preceding claims, said diffusion surface comprising an up/down spectral conversion material having a predefined spectral shift.
21. A solar radiation collector according to any one of the preceding claims, wherein said diffusion surface is completely reflective.
22. A solar radiation collector according to any one of Claims 1 through 20, wherein said diffusion surface is partially reflective.
23. A solar radiation collector according to any one of the preceding claims, wherein the diffusion surface is formed by a process selected from the group comprising
5 etching, grinding, and laser engraving.
24. A solar radiation collector according to any one of the preceding claims, wherein said diffusion surface is designed so as to increase the concentration of radiation impinging on the sidewalls relative to that impinging on the front wall.
25. A solar radiation collector according to any one of the preceding claims, said 10 side wall comprising an inner receiver surface adapted to receive radiation reflected by at least one of said diffusion surface and said inner entrance surface, and an outer receiver surface, said photovoltaic cell being attached to the outer receiver surface.
26. A solar radiation collector according to any one of the preceding claims, wherein said photovoltaic cells are bifacial.
,15 27. A solar radiation collector according to any one of the preceding claims, further comprising a positioning mechanism adapted to orient the front wall in accordance with the position of the sun.
28. A solar array comprising two or more solar radiation collectors, each comprising a prismatic concentrator, each of said concentrators comprising:
20 • a front wall for facing toward the sun to receive solar radiation and having an outer entrance surface and an inner entrance surface;
• at least one sidewall in optical communication with a photovoltaic cell; and
• a rear wall opposite said front wall and having a diffusion surface designed to diffuse solar radiation impinging thereupon such that at least a portion of the
25 radiation is totally internally reflected by the inner entrance surface toward said sidewall.
29. A solar array according to Claim 28, said concentrator being made of a transparent material having a refractive index which is greater than 1.
30. A solar array according to any one of Claims 28 and 29, wherein said front 0 walls are planar.
31. A solar array according to any one of Claims 28 through 30, wherein each outer entrance surface is coated with an anti-reflective coating.
32. A solar array according to any one of Claims 28 through 31, wherein each outer entrance surface is coated with a selective surface coating adapted to allow only radiation of predetermined wavelengths to pass therethrough.
33. A solar array according to any one of Claims 28 through 32, wherein each of said front walls is in a shape selected from the group comprising hexagonal, square, rectangular, triangular, octagonal, and trapezoidal.
34. A solar array according to any one of Claims 28 through 33, wherein portions of said diffusion surface are planar and disposed at an angle between 22° and 44° relative to said front wall.
35. A solar array according to Claim 34, wherein an area of the diffusion surface adjacent the sidewall is formed as a parabolic section.
36. A solar array according to any one of Claims 28 through 33, wherein portions of said diffusion surface are formed having parabolic cross-sections.
37. A solar array according to any one of Claims 28 through 36, wherein said each of said diffusion surfaces comprises a base plane and plurality of sub-surfaces projecting upwardly therefrom, each sub-surface being inclined toward said sidewall at a predetermined angle in a saw-tooth formation.
38. A solar array according to Claim 37, wherein said predetermined angle is between 0° and 20°.
39. A solar array according to Claim 38, wherein said predetermined angle is substantially 0°.
40. A solar array according to any one of Claims 37 through 39, wherein all sub- surfaces are inclined toward said sidewall at the same angle.
41. A solar array according to any one of Claims 37 through 39, wherein at least some of the sub-surfaces are inclined toward said sidewall at angles different than that of other of said sub-surfaces.
42. A solar array according to any one of Claims 37 through 41, wherein said base plane is inclined in a direction opposite that which the sub-surfaces are inclined, at least in the vicinity of the sub-surfaces.
43. A solar array according to any one of Claims 28 through 42, said diffusion surfaces comprising a coating adapted to impart properties of a diffusive reflector thereto.
44. A solar array according to Claim 43, wherein said coating is a lambertian coating.
45. A solar array according to any one of Claims 28 through 44, said diffusion surfaces comprising quantum dots having a predefined spectral shift.
46. A solar array according to any one of Claims 28 through 45, wherein said diffusion surfaces are completely reflective.
47. A solar array according to any one of Claims 28 through 45, wherein said diffusion surfaces are partially reflective.
48. A solar array according to any one of Claims 28 through 47, wherein the diffusion surfaces are formed by a process selected from the group comprising etching, grinding, and laser engraving.
49. A solar array according to any one of Claims 28 through 48, wherein each diffusion surface is designed so as to increase the concentration of radiation impinging on the sidewalls relative to that impinging on the front wall.
50. A solar array according to any one of Claims 28 through 49, further comprising one or more positioning mechanisms adapted to orient the front walls in accordance with the position of the sun.
51. A solar array according to any one of Claims 28 through 50, wherein the front walls of all of the solar radiation collectors are coplanar.
52. A solar array according to any one of Claims 28 through 51, each of said rear walls comprising an inner receiver surface adapted to receive radiation reflected by at least one of said diffusion surface and said inner entrance surface, and an outer receiver surface, said photovoltaic cells being attached to the outer receiver surfaces.
53. A solar array according to any one of Claims 28 through 52, wherein at least some of said photovoltaic cells are bifacial.
54. A solar array according to Claim 53, wherein at least some of said bifacial photovoltaic cells are associated with two solar radiation collectors.
PCT/IL2007/001548 2006-12-13 2007-12-13 Solar radiation collector WO2008072245A2 (en)

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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1993007646A1 (en) * 1991-10-08 1993-04-15 Unisearch Limited Improved optical design for photo-cell
DE19907506A1 (en) * 1998-02-26 1999-09-09 Hitachi Ltd Optical system of solar power generation module
DE10328321A1 (en) * 2003-06-24 2005-01-20 Solar Dynamics Gmbh Multifunctional prism blunt wedge e.g. for solar radiation concentration, has defined divergence angle falling on wide aperture surface of PSK by total reflections at boundary surface between PSK flanks and ambient air

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1993007646A1 (en) * 1991-10-08 1993-04-15 Unisearch Limited Improved optical design for photo-cell
DE19907506A1 (en) * 1998-02-26 1999-09-09 Hitachi Ltd Optical system of solar power generation module
DE10328321A1 (en) * 2003-06-24 2005-01-20 Solar Dynamics Gmbh Multifunctional prism blunt wedge e.g. for solar radiation concentration, has defined divergence angle falling on wide aperture surface of PSK by total reflections at boundary surface between PSK flanks and ambient air

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