WO2012169980A1 - A waveguide for concentrated solar collectors and a solar collector thereof - Google Patents

A waveguide for concentrated solar collectors and a solar collector thereof Download PDF

Info

Publication number
WO2012169980A1
WO2012169980A1 PCT/TR2011/000156 TR2011000156W WO2012169980A1 WO 2012169980 A1 WO2012169980 A1 WO 2012169980A1 TR 2011000156 W TR2011000156 W TR 2011000156W WO 2012169980 A1 WO2012169980 A1 WO 2012169980A1
Authority
WO
WIPO (PCT)
Prior art keywords
waveguide
solar collector
directing
collector according
concentrator
Prior art date
Application number
PCT/TR2011/000156
Other languages
French (fr)
Inventor
Ozgur SELIMOGLU
Rasit Turan
Original Assignee
Selimoglu Ozgur
Rasit Turan
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 Selimoglu Ozgur, Rasit Turan filed Critical Selimoglu Ozgur
Priority to PCT/TR2011/000156 priority Critical patent/WO2012169980A1/en
Publication of WO2012169980A1 publication Critical patent/WO2012169980A1/en

Links

Classifications

    • 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
    • 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
    • F24S23/12—Light guides
    • 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
    • F24S23/30—Arrangements for concentrating solar-rays for solar heat collectors with lenses
    • 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
    • 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
    • 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
    • Y02E10/50—Photovoltaic [PV] energy
    • Y02E10/52—PV systems with concentrators

Definitions

  • the present invention relates to a waveguide for solar energy collectors and a solar energy collector employing such a waveguide to be used for concentrated solar power generation.
  • Photovoltaic cells are among such means.
  • Conventional photovoltaic power generators comprise a planar array of photovoltaic cells.
  • widespread use of conventional photovoltaic generators is hindered by their high production costs.
  • concentrated photovoltaic power generators employing a reduced area of photovoltaic cells, are used.
  • Incident solar radiation is concentrated through a solar collector comprising various concentration means and is directed to photovoltaic cells of an area smaller than the surface area of the concentrated solar power generator.
  • US2011011441A1 discloses a concentrated solar power generator, which is seen to employ an array of lenses used to concentrate solar radiation.
  • the concentrated solar radiation is then transferred to a photovoltaic surface by optical fibers, with each fiber connected to one lens of the array at one end and every fiber connected a distinct area of the photovoltaic cells on the other end.
  • the invention disclosed in this document aims to construct a flexible solar collector. Since it does not have a rigid structure, such a collector is inefficient in terms of acceptance angles, thus making less use of the incident light.
  • Classical concentrating photovoltaic systems are using only big Fresnel lens arrays and other large lenses as an optical concentrator. Although using large lenses provide a high concentration, such lenses also have long focal lengths thus increasing collector thickness. If, instead, an array of a large number of small lenses is employed, then the complexity is increased. Further, systems incorporating only an array of lenses do not enable an efficient use of the photovoltaic cells; a lens generally produces a circular image of the sun on a photovoltaic cell which is generally rectangular. Non-imaging means are employed to effectively distribute light over the photovoltaic cells. In order to overcome such issues, collectors incorporating waveguides that collect, direct and concentrate the light from concentrating elements to photovoltaic cells have been proposed. Among these are, waveguides containing directing surfaces to direct the solar radiation emerging from an array of concentrators into the waveguide.
  • Such waveguides have a stepped structure so that light acquired by one directing surface is not hindered by another while inside the waveguide. With respect to the direction of incoming light, the steps are constituted on top of each other thus increasing the overall thickness.
  • Such waveguides can incorporate line focus optics, providing a low concentration. The concentration can further be increased by rotating a section of the waveguide structure around a line onto which the concentrated output of the waveguide will fall. This configuration is not very efficient considering its heat dissipation, weight of the material and ease of manufacture.
  • the waveguide mentioned in this document contains directing surfaces each corresponding to a concentrator to direct the concentrated light into the waveguide.
  • the directing surfaces are to be placed in virtual slabs on top of each other with respect to the direction of light emerging from the concentrators. Due to this configuration and further to the planar distribution of the concentrators, the waveguide is a stepped structure with said steps consecutively arranged along the direction of light emerging from the concentrators, wherein each step acts as a directing surface corresponding to a concentrator.
  • Such a configuration results in a waveguide with high thickness and weight.
  • WO2010056405A1 Another solution is described in the document numbered WO2010056405A1.
  • the collector described in this document employs a transmissive medium layer between the light collecting element and the waveguide. Many of similar series of layers can be sandwiched with different transmissive medium layers in between and it is revealed that the output of such series of layers can be combined using a secondary light concentrator.
  • Such a solar collector has components with high thickness and weight values and is cumbersome for tracking applications.
  • the incoming light is focused on a line or a curve by the primary concentrators providing a concentration only along a single dimension, i.e. a two dimensional light distribution is reduced to a one dimensional light distribution.
  • the collectors described above provide low concentrations.
  • Waveguides with high thickness and weight require the solar collector to have stronger frame members thus increasing costs. Also, for active solar power generator systems, tracking means are harder to operate. Moreover, such waveguides themselves are also produced for higher costs.
  • the object of the present invention is to provide a waveguide that has a low thickness and weight compared to the solar collector it is associated with.
  • a further object of the invention is to provide a waveguide providing further concentration of the light while moving through the waveguide.
  • Another object of the invention is to provide a solar collector having an increased acceptance angle.
  • Another object of the present invention is to provide a waveguide for a solar collector enabling dissipation of the heat generated due to the concentrated solar radiation.
  • a waveguide having an end surface (3) onto which the guided radiation is to be directed, and an array of directing surfaces on the borders of said waveguide is developed, such that the waveguide and the array of directing surfaces lie on a plane.
  • a solar collector having an array of concentrator cells and a waveguide lying in a plane is also developed.
  • a solar collector having an increased acceptance angle is provided by employing enlarged directing surfaces while the concentrator cell sizes are kept constant.
  • Figure 1 is a schematic side view of a solar collector according to the invention, partially depicting exemplary light paths.
  • Figure 2 is a top view of the waveguide of figure 1, partially depicting exemplary light paths.
  • Figure 3 depicts a waveguide according to invention.
  • Figures 4 to 10 depict various concentration cells that can be used with the present invention together with a waveguide according to the invention, partially depicting exemplary light paths.
  • FIGS 11 and 12 depict possible concentrator cell arrays according to the present invention.
  • Figures 13 and 14 depict possible directing surfaces which act through reflection.
  • Figures 15 to 20 depict waveguides having extra concentration surfaces.
  • Figures 21 and 22 depict possible waveguides comprising more than one stepped structure.
  • FIGS 23 to 27 depict solar collector configurations according to the present invention.
  • Figures 28 and 29 are side and top views respectively of a possible configuration of two waveguides.
  • the solar collector according to the present invention essentially comprises,
  • a concentrator consisting of an array of concentrator cells (1), for concentrating the incident solar radiation;
  • At least one waveguide (2) having at least one end surface (3), which is the output surface of the waveguide (2) and onto which light to electricity converters such as photovoltaic cells are to be attached;
  • each directing surface (4) corresponds to a concentrator cell (1) and directs the incident light i.e., the concentrated solar radiation, into the waveguide (2) with an angle providing total internal reflection (TIR);
  • the waveguide (2) and the array of directing surfaces (4) lie on a plane nonparallel to the direction of incident light.
  • the thickness of the waveguide (2) is constant along its length thus minimizing the weight and cost of the waveguide (2), excluding the extra concentration means at the end region.
  • the waveguide (2) according to this invention is generally a rigid component.
  • Figure 1 schematically depicts such a solar collector and figures 2 and 3 are top and perspective views of the waveguide (2) used in figure 1. Since the directing surfaces (4) are on borders of the waveguide (2), the optical paths emerging from a directing surface (4) are not interrupted by another directing surface (4).
  • the directing surfaces (4) can be planar or curved.
  • the planar directing surfaces (4) or the planes tangential to the curved directing surfaces (4) are inclined with respect to the plane of the waveguide (2) such that there is an angle ⁇ , between the plane of the waveguide (2) and the directing surfaces (4) or said tangential planes, facing the surface of the waveguide (2) nearest the concentrator cells (1).
  • the angle ⁇ is obtuse and the directing surfaces (3) reflect the incoming radiation into the waveguide (2).
  • the angle ⁇ is 135°.
  • the angle ⁇ is acute and the directing surface refracts the incoming radiation into the waveguide (2).
  • the waveguide (2) according to the invention is a non-imaging component due to its structure. Therefore the output of the waveguide (2) is mostly homogeneous in illumination and wavelength distribution, increasing the efficiency of the light to electricity converters. Further, the output surface of the waveguide (2) is the end surface (3) being in a shape and size to match the light to electricity converters to be attached. A preferred end surface (3) shape is rectangular since photovoltaic cells are generally cut in rectangles from a wafer.
  • the array of concentrator cells (1) is arranged such that the focal point of each concentrator cell (1) lies on the vertices of a virtual grid, said grid being a parallelogramic grid lying on a plane.
  • the array of directing surfaces (4) is arranged such that the centroid of each directing surface (4) substantially coincides with the vertices of said grid. Since light is focused on an array of points, such an array of concentrator cells (1) provides a higher concentration than other concentrators that focus light on a line or a curve, i.e. a two dimensional light distribution is reduced substantially to a point. Further, such a high initial concentration allows flexibility in waveguide (2) design, enabling directing surfaces (4) that provide a higher tracking tolerance.
  • a single waveguide (2) comprises an array of directing surfaces (4) along a single line of the virtual grid, thus forming a stepped structure.
  • Such a structure allows many waveguides (2) to be arranged in a regular pattern.
  • a possible waveguide (2) according to the invention comprises an array of directing surfaces (4) arranged in groups having more than one stepped structure along more than one line of the virtual grid. Possible examples of such a waveguide are depicted in figures 21 and 22.
  • Concentrator cells (1) can be chosen among different optical units according to particular designs. Possible such units include various simple or compound lenses, Fresnel lenses, parabolic mirrors, compound parabolic concentrators, diffractive concentrators, Cassegrain devices, crossed cylinders etc. Some concentrator cells (1) are seen in figures 4 to 10. For concentrator cells (1) of lens type, an array of lenses can either be kept above the waveguides (2) by some frame or the lens may extend along the optical path to the waveguide (2) thus being carried by said waveguide (2). Such an extended lens type concentrator cell is depicted in figure 9.
  • the lens material has a refractive index lower than that of the waveguide (2) or a layer of low refractive index than that of the waveguide (2) is applied between the collector cells (1) and the waveguides (2).
  • the regions between the outer lens surfaces and the waveguide (2) not containing the optical paths do not contribute to solar power generation and thus can be left empty to reduce the weight of the solar collector as can be seen in figure 10.
  • this configuration provides collection of some of the diffuse radiation and increase tracking tolerances.
  • the array of concentration cells (1) can be of various polygonal patterns such as rectangular, squared, hexagonal etc. with a squared and a hexagonal example depicted in figures 11 and 12.
  • the concentrator cells (1) in figure 27 form a squared pattern in which the projection of the focal points onto the surface does not coincide with the centroids.
  • a directing surface (4) acting through reflection is coated from outside with a reflecting coating (6a) as depicted in figure 13, than the angle ⁇ of the directing surface (4) can be freely adjusted while providing the conditions of TIR inside the waveguide (2).
  • the angle ⁇ is chosen to be 135°.
  • the angle ⁇ is chosen to be larger than 135° higher acceptance angles can be achieved.
  • TIR from the directing surface (4) for most incoming light is obtained when the angle ⁇ is chosen to be smaller than 135°, for example 125° for a waveguide of a material with a refractive index of 1,5.
  • the waveguides (2) further comprise at least one extra concentration surface (5).
  • An extra concentration surface (5) is formed on portions of a waveguide (2) ending at the end surface (3).
  • Said portion of the waveguide (2) is in the shape of a known non-imaging optical concentrator with an input aperture width and height equal to the maximum width and thickness of the waveguide (2) and the output aperture is the end surface (3) having a width and/or thickness smaller than said input aperture.
  • Figure 15 is a side view of a possible waveguide having an extra concentration surface (5).
  • One possible way to obtain such an extra concentration surface (5) is to produce a waveguide (2) in a shape with some portions from at least one edge removed, leaving behind said extra concentration surface (5).
  • a specific example of such an extra concentration surface (5) is a side cut (5a) formed by extracting a region on a side.
  • FIG. 16 to 21 depict top views of waveguides (2).
  • the one depicted in figure 16, 17 and 18 comprise a side cut (5a) formed by extracting a region on a side such that said surface (5) is formed of a curve, a straight line and two curves respectively.
  • said surface (5a) may be formed of at least one region comprising at least one curve or straight line or a combination of several curves and lines.
  • the regions of the waveguide (2) near the end surface (3) comprise two extra concentration surfaces (5) with one on each side.
  • Figure 21 depicts a waveguide (2) comprising more than one stepped structure having side cuts (5a) on each stepped structure.
  • Figure 23 is a top view of a portion of a solar collector according to the invention with an array of square lens concentrators (1) arranged on a planar square grid. Another solar collector according to the invention is with an array of hexagonal lens concentrators (1) is seen from the top in figure 24.
  • At least two waveguides (2) are placed on top of each other with the directing surfaces (4) not blocking the light directed to each other from the concentrator cells (1).
  • the array of concentrator cells (1) to be employed with this embodiment can be composed of groups of concentrator cells (1) each equidistant from the corresponding directing surfaces (4) and thus the corresponding waveguides (2) or of groups of concentrator cells (1) each with different focal lengths according to the corresponding directing surfaces (4) and thus the corresponding waveguides (2).
  • the waveguide (2) developed with the present invention has a planar structure, all regions of the waveguide (2) are in the proximity of a heat conducting planar sheet placed below the waveguide (2) and thus the waveguide (2) provides a very low thermal resistance easily dissipating the heat released during operation.
  • the cooling of the waveguide can be performed either by passive or active cooling systems. In systems employing water or oil as a heat carrying medium, the excess heat can be transferred to be used in another application.
  • the waveguide (2) according to the invention can be produced by molding, cutting or other means leaving a smooth surface and from optically transparent materials.
  • materials are chosen to produce a rigid waveguide (2).

Abstract

The present invention relates to a waveguide for solar collectors and a solar collector employing such a waveguide to be used for concentrated solar power generation. In scope of this invention, a waveguide having an array of directing surfaces is developed, such that the waveguide and the array of directing surfaces lie on a plane nonparallel to the direction of incident light. Moreover, a solar collector having an array of concentrator cells and a waveguide lying on a plane nonparallel to the direction of solar radiation from said array of concentrator cells is developed.

Description

A WAVEGUIDE FOR CONCENTRATED SOLAR COLLECTORS AND A SOLAR
COLLECTOR THEREOF
Field of the Invention
The present invention relates to a waveguide for solar energy collectors and a solar energy collector employing such a waveguide to be used for concentrated solar power generation.
Background of the Invention
Due to the scarce of energy resources and threat of climate change resulting from extensive use of carbon containing fuels, clean power generation means are being developed. Photovoltaic cells are among such means. Conventional photovoltaic power generators comprise a planar array of photovoltaic cells. Unfortunately, widespread use of conventional photovoltaic generators is hindered by their high production costs. Thus concentrated photovoltaic power generators, employing a reduced area of photovoltaic cells, are used. Incident solar radiation is concentrated through a solar collector comprising various concentration means and is directed to photovoltaic cells of an area smaller than the surface area of the concentrated solar power generator.
The document numbered US2011011441A1 discloses a concentrated solar power generator, which is seen to employ an array of lenses used to concentrate solar radiation. The concentrated solar radiation is then transferred to a photovoltaic surface by optical fibers, with each fiber connected to one lens of the array at one end and every fiber connected a distinct area of the photovoltaic cells on the other end. The invention disclosed in this document aims to construct a flexible solar collector. Since it does not have a rigid structure, such a collector is inefficient in terms of acceptance angles, thus making less use of the incident light.
Classical concentrating photovoltaic systems are using only big Fresnel lens arrays and other large lenses as an optical concentrator. Although using large lenses provide a high concentration, such lenses also have long focal lengths thus increasing collector thickness. If, instead, an array of a large number of small lenses is employed, then the complexity is increased. Further, systems incorporating only an array of lenses do not enable an efficient use of the photovoltaic cells; a lens generally produces a circular image of the sun on a photovoltaic cell which is generally rectangular. Non-imaging means are employed to effectively distribute light over the photovoltaic cells. In order to overcome such issues, collectors incorporating waveguides that collect, direct and concentrate the light from concentrating elements to photovoltaic cells have been proposed. Among these are, waveguides containing directing surfaces to direct the solar radiation emerging from an array of concentrators into the waveguide.
Generally, such waveguides have a stepped structure so that light acquired by one directing surface is not hindered by another while inside the waveguide. With respect to the direction of incoming light, the steps are constituted on top of each other thus increasing the overall thickness. Such waveguides can incorporate line focus optics, providing a low concentration. The concentration can further be increased by rotating a section of the waveguide structure around a line onto which the concentrated output of the waveguide will fall. This configuration is not very efficient considering its heat dissipation, weight of the material and ease of manufacture.
One such waveguide is described in the document numbered US7664350B2. The waveguide mentioned in this document contains directing surfaces each corresponding to a concentrator to direct the concentrated light into the waveguide. In order to avoid a directing surface from interrupting the light directed by another directing surface, the directing surfaces are to be placed in virtual slabs on top of each other with respect to the direction of light emerging from the concentrators. Due to this configuration and further to the planar distribution of the concentrators, the waveguide is a stepped structure with said steps consecutively arranged along the direction of light emerging from the concentrators, wherein each step acts as a directing surface corresponding to a concentrator. Such a configuration results in a waveguide with high thickness and weight.
Another solution is described in the document numbered WO2010056405A1. The collector described in this document employs a transmissive medium layer between the light collecting element and the waveguide. Many of similar series of layers can be sandwiched with different transmissive medium layers in between and it is revealed that the output of such series of layers can be combined using a secondary light concentrator. Such a solar collector has components with high thickness and weight values and is cumbersome for tracking applications.
In the two documents above, the incoming light is focused on a line or a curve by the primary concentrators providing a concentration only along a single dimension, i.e. a two dimensional light distribution is reduced to a one dimensional light distribution. Thus the collectors described above provide low concentrations.
Waveguides with high thickness and weight require the solar collector to have stronger frame members thus increasing costs. Also, for active solar power generator systems, tracking means are harder to operate. Moreover, such waveguides themselves are also produced for higher costs.
Objects and Brief Description of the Invention
The object of the present invention is to provide a waveguide that has a low thickness and weight compared to the solar collector it is associated with.
It is a further object of the invention to provide waveguide that provides an effective distribution of light over the photovoltaic cells.
A further object of the invention is to provide a waveguide providing further concentration of the light while moving through the waveguide.
Another object of the invention is to provide a solar collector having an increased acceptance angle.
Another object of the present invention is to provide a waveguide for a solar collector enabling dissipation of the heat generated due to the concentrated solar radiation.
It is also an object of the invention to provide a solar collector employing a waveguide according to the objects aforementioned.
In order to achieve the objects of this invention, a waveguide having an end surface (3) onto which the guided radiation is to be directed, and an array of directing surfaces on the borders of said waveguide is developed, such that the waveguide and the array of directing surfaces lie on a plane.
Moreover, a solar collector having an array of concentrator cells and a waveguide lying in a plane is also developed.
In an embodiment of the invention, in order to provide a waveguide providing further concentration of the light while moving through the waveguide, extra concentration surfaces are employed. In another embodiment of the invention, a solar collector having an increased acceptance angle is provided by employing enlarged directing surfaces while the concentrator cell sizes are kept constant.
Description of the Drawings
The figures attached, depicting some aspects of the present invention, are as listed.
Figure 1 is a schematic side view of a solar collector according to the invention, partially depicting exemplary light paths.
Figure 2 is a top view of the waveguide of figure 1, partially depicting exemplary light paths.
Figure 3 depicts a waveguide according to invention.
Figures 4 to 10 depict various concentration cells that can be used with the present invention together with a waveguide according to the invention, partially depicting exemplary light paths.
Figures 11 and 12 depict possible concentrator cell arrays according to the present invention.
Figures 13 and 14 depict possible directing surfaces which act through reflection.
Figures 15 to 20 depict waveguides having extra concentration surfaces.
Figures 21 and 22 depict possible waveguides comprising more than one stepped structure.
Figures 23 to 27 depict solar collector configurations according to the present invention.
Figures 28 and 29 are side and top views respectively of a possible configuration of two waveguides.
The references seen in the figures listed above correspond to the following.
Concentrator cell
Waveguide
End surface
Directing surface 5. Extra concentration surface
5a. Side cut
6a. Reflecting coating
6b. Reflecting piece
Detailed Description of the Invention
The solar collector according to the present invention, essentially comprises,
- a concentrator consisting of an array of concentrator cells (1), for concentrating the incident solar radiation;
- at least one waveguide (2), having at least one end surface (3), which is the output surface of the waveguide (2) and onto which light to electricity converters such as photovoltaic cells are to be attached;
- an array of directing surfaces (4) on the borders of said waveguide (2), such that each directing surface (4) corresponds to a concentrator cell (1) and directs the incident light i.e., the concentrated solar radiation, into the waveguide (2) with an angle providing total internal reflection (TIR);
- optionally, at least one extra concentration means at the end regions of the waveguide (2), to further concentrate the solar radiation
wherein, the waveguide (2) and the array of directing surfaces (4) lie on a plane nonparallel to the direction of incident light. The thickness of the waveguide (2) is constant along its length thus minimizing the weight and cost of the waveguide (2), excluding the extra concentration means at the end region. The waveguide (2) according to this invention is generally a rigid component. Figure 1 schematically depicts such a solar collector and figures 2 and 3 are top and perspective views of the waveguide (2) used in figure 1. Since the directing surfaces (4) are on borders of the waveguide (2), the optical paths emerging from a directing surface (4) are not interrupted by another directing surface (4).
Solar radiation incident to the solar collector is first concentrated through the array of concentrator cells (1), then to be directed into the waveguide (2) by the directing surfaces (4). Solar radiation is then transmitted to the photovoltaic cells attached onto the end surface (3) by TIR through the waveguide (2). For TIR to take place, the waveguide (2) has a refractive index greater than that of its surroundings. The directing surfaces (4) can be planar or curved. The planar directing surfaces (4) or the planes tangential to the curved directing surfaces (4) are inclined with respect to the plane of the waveguide (2) such that there is an angle Θ, between the plane of the waveguide (2) and the directing surfaces (4) or said tangential planes, facing the surface of the waveguide (2) nearest the concentrator cells (1). In an embodiment of the invention, the angle Θ is obtuse and the directing surfaces (3) reflect the incoming radiation into the waveguide (2). Preferably, the angle Θ is 135°. In another embodiment, the angle Θ is acute and the directing surface refracts the incoming radiation into the waveguide (2).
The waveguide (2) according to the invention is a non-imaging component due to its structure. Therefore the output of the waveguide (2) is mostly homogeneous in illumination and wavelength distribution, increasing the efficiency of the light to electricity converters. Further, the output surface of the waveguide (2) is the end surface (3) being in a shape and size to match the light to electricity converters to be attached. A preferred end surface (3) shape is rectangular since photovoltaic cells are generally cut in rectangles from a wafer.
The array of concentrator cells (1) is arranged such that the focal point of each concentrator cell (1) lies on the vertices of a virtual grid, said grid being a parallelogramic grid lying on a plane. Thus the array of directing surfaces (4) is arranged such that the centroid of each directing surface (4) substantially coincides with the vertices of said grid. Since light is focused on an array of points, such an array of concentrator cells (1) provides a higher concentration than other concentrators that focus light on a line or a curve, i.e. a two dimensional light distribution is reduced substantially to a point. Further, such a high initial concentration allows flexibility in waveguide (2) design, enabling directing surfaces (4) that provide a higher tracking tolerance.
Generally, a single waveguide (2) comprises an array of directing surfaces (4) along a single line of the virtual grid, thus forming a stepped structure. Such a structure allows many waveguides (2) to be arranged in a regular pattern. A possible waveguide (2) according to the invention comprises an array of directing surfaces (4) arranged in groups having more than one stepped structure along more than one line of the virtual grid. Possible examples of such a waveguide are depicted in figures 21 and 22.
Concentrator cells (1) can be chosen among different optical units according to particular designs. Possible such units include various simple or compound lenses, Fresnel lenses, parabolic mirrors, compound parabolic concentrators, diffractive concentrators, Cassegrain devices, crossed cylinders etc. Some concentrator cells (1) are seen in figures 4 to 10. For concentrator cells (1) of lens type, an array of lenses can either be kept above the waveguides (2) by some frame or the lens may extend along the optical path to the waveguide (2) thus being carried by said waveguide (2). Such an extended lens type concentrator cell is depicted in figure 9. When said extended lens type concentrator cells (1) are employed, in order to guarantee TIR inside the waveguide (2), either the lens material has a refractive index lower than that of the waveguide (2) or a layer of low refractive index than that of the waveguide (2) is applied between the collector cells (1) and the waveguides (2). The regions between the outer lens surfaces and the waveguide (2) not containing the optical paths do not contribute to solar power generation and thus can be left empty to reduce the weight of the solar collector as can be seen in figure 10. Moreover, this configuration provides collection of some of the diffuse radiation and increase tracking tolerances. The array of concentration cells (1) can be of various polygonal patterns such as rectangular, squared, hexagonal etc. with a squared and a hexagonal example depicted in figures 11 and 12. Various other examples can be seen in figures 23 to 27. The concentrator cells (1) in figure 27 form a squared pattern in which the projection of the focal points onto the surface does not coincide with the centroids.
If a directing surface (4) acting through reflection is coated from outside with a reflecting coating (6a) as depicted in figure 13, than the angle Θ of the directing surface (4) can be freely adjusted while providing the conditions of TIR inside the waveguide (2). For incident light perpendicular to the plane of the waveguide (2) and circularly symmetric concentrator cells (2), the highest concentration provided by the waveguide (2) is obtained when the angle Θ is chosen to be 135°. On the other hand, when the angle Θ is chosen to be larger than 135° higher acceptance angles can be achieved. However, TIR from the directing surface (4) for most incoming light is obtained when the angle Θ is chosen to be smaller than 135°, for example 125° for a waveguide of a material with a refractive index of 1,5. With a reflecting coating (6a) on the directing surface (4), reflection from the directing surface (4) occurs at wide range of angles, thus allowing an optimization of concentration and acceptance angle according to a particular application. Alternatively, a highly reflective reflecting piece (6b) can be attached on the outside of each of said directing surfaces (4) preferably with an air gap in between as seen in figure 14. The air gap will provide the opportunity of TIR at the directing surface (3) for some of the light rays while the rays that cannot satisfy the TIR condition at the directing surface will be reflected from the reflective piece (6b) attached. In an embodiment of the invention, in order to obtain further concentration of solar radiation in the waveguide, the waveguides (2) further comprise at least one extra concentration surface (5). An extra concentration surface (5) is formed on portions of a waveguide (2) ending at the end surface (3). Said portion of the waveguide (2) is in the shape of a known non-imaging optical concentrator with an input aperture width and height equal to the maximum width and thickness of the waveguide (2) and the output aperture is the end surface (3) having a width and/or thickness smaller than said input aperture. Figure 15 is a side view of a possible waveguide having an extra concentration surface (5). One possible way to obtain such an extra concentration surface (5) is to produce a waveguide (2) in a shape with some portions from at least one edge removed, leaving behind said extra concentration surface (5). A specific example of such an extra concentration surface (5) is a side cut (5a) formed by extracting a region on a side. Other possible waveguides (2) having extra concentration surfaces (5) are depicted in figures 16 to 21; these figures depict top views of waveguides (2). Among these possible waveguides (2), the one depicted in figure 16, 17 and 18 comprise a side cut (5a) formed by extracting a region on a side such that said surface (5) is formed of a curve, a straight line and two curves respectively. Generally, said surface (5a) may be formed of at least one region comprising at least one curve or straight line or a combination of several curves and lines. In figures 19 and 20, the regions of the waveguide (2) near the end surface (3) comprise two extra concentration surfaces (5) with one on each side. Figure 21 depicts a waveguide (2) comprising more than one stepped structure having side cuts (5a) on each stepped structure.
Figure 23 is a top view of a portion of a solar collector according to the invention with an array of square lens concentrators (1) arranged on a planar square grid. Another solar collector according to the invention is with an array of hexagonal lens concentrators (1) is seen from the top in figure 24.
In another embodiment of the invention, at least two waveguides (2) are placed on top of each other with the directing surfaces (4) not blocking the light directed to each other from the concentrator cells (1). The array of concentrator cells (1) to be employed with this embodiment can be composed of groups of concentrator cells (1) each equidistant from the corresponding directing surfaces (4) and thus the corresponding waveguides (2) or of groups of concentrator cells (1) each with different focal lengths according to the corresponding directing surfaces (4) and thus the corresponding waveguides (2).
Since the waveguide (2) developed with the present invention has a planar structure, all regions of the waveguide (2) are in the proximity of a heat conducting planar sheet placed below the waveguide (2) and thus the waveguide (2) provides a very low thermal resistance easily dissipating the heat released during operation. The cooling of the waveguide can be performed either by passive or active cooling systems. In systems employing water or oil as a heat carrying medium, the excess heat can be transferred to be used in another application.
The waveguide (2) according to the invention can be produced by molding, cutting or other means leaving a smooth surface and from optically transparent materials. Preferably, materials are chosen to produce a rigid waveguide (2).
Various embodiments and applications employing the principles of the present invention can be implemented. Therefore the scope of the invention is not limited to the examples above but determined by the following claims.

Claims

1. A solar collector comprising
- a concentrator consisting of an array of concentrator cells (1), for concentrating the incident solar radiation;
- at least one waveguide (2) having at least one end surface (3) , which is the output surface of the waveguide (2) and onto which light to electricity converters are to be attached;
- an array of directing surfaces (4) on the borders of said waveguide (2), such that each directing surface (4) corresponds to a concentrator cell (1) and directs the incident light i.e., the concentrated solar radiation into the waveguide (2) with an angle providing total internal reflection;
- optionally, at least one extra concentration means at the end regions of the waveguide (2), to further concentrate the solar radiation
characterized in that; the waveguide (2) and the array of directing surfaces (4) lie on a plane nonparallel to the direction of incident light and the thickness of the waveguide (2) is constant along its length excluding the extra concentration means at the end region.
2. A solar collector according to claim 1, characterized in that; the array of concentrator cells (1) is arranged such that the focal point of each concentrator cell (1) lies on the vertices of a virtual grid, said grid being a parallelogramic grid lying on a plane and the array of directing surfaces (4) is arranged such that the centroid of each directing surface (4) substantially coincides with the vertices of said virtual grid.
3. A solar collector according to claim 1 or 2, wherein; the end surfaces (3) are in a shape and size to match the light to electricity converters to be attached.
4. A solar collector according to any of the preceding claims, wherein; the concentrator cells (1) are simple lenses, compound lenses, Fresnel lenses, parabolic mirrors, compound parabolic concentrators, diffractive concentrators, Cassegrain devices or crossed cylinders.
5. A solar collector according to any of the preceding claims, wherein; the directing surfaces (4) are planar.
6. A solar collector according to claim 5, wherein; the angle between the plane of the waveguide (2) and the directing surfaces (4), facing the surface of the waveguide (2) nearest the concentrator cells (1) is acute.
7. A solar collector according to claim 5, wherein; the angle between the plane of the waveguide (2) and the directing surfaces (4), facing the surface of the waveguide (2) nearest the concentrator cells (1) is obtuse.
8. A solar collector according to any of claims 1 to 4, wherein; the directing surfaces (4) are curved.
9. A solar collector according to claim 8, wherein; the angle between the plane of the waveguide (2) and the planes tangential to the curved directing surfaces (4), facing the surface of the waveguide (2) nearest the concentrator cells (1) is acute.
10. A solar collector according to claim 8, wherein; the angle between the plane of the waveguide (2) and the planes tangential to the curved directing surfaces (4), facing the surface of the waveguide (2) nearest the concentrator cells (1) is obtuse.
11. A solar collector according to claim 7 or 10, wherein; the directing surfaces (4) are coated with a reflecting coating (6a).
12. A solar collector according to claim 7 or 10, wherein; a reflecting piece (6b) is attached on the outside of each directing surface (4).
13. A solar collector according to claim 12, wherein; there is an air gap between each highly reflective piece (6b) and the relevant directing surface (4).
14. A solar collector according to any of the preceding claims, wherein; the waveguides (2) further comprise at least one extra concentration surface (5).
15. A solar collector according to claim 14, wherein; an extra concentration surface (5) is formed on portions of a waveguide (2) ending at the end surface (3) and is in the shape of a non-imaging optical concentrator.
16. A solar collector according to claim 15, wherein; the waveguides (2) are produced in a shape with portions from at least one edge removed, leaving behind said extra concentration surface (5).
17. A solar collector according to claim 16, wherein; said extra concentration surface (5) is a side cut (5a) formed by extracting a region on a side, comprising at least one curve or straight line or a combination of both.
18. A waveguide (2) comprising,
- at least one end surface (3), and
- an array of directing surfaces (4) on the borders of said waveguide (2) directing the incident light into the waveguide (2) with an angle providing total internal reflection,
- optionally, at least one extra concentration means at the end regions of the waveguide (2), to further concentrate the solar radiation
characterized in that; the waveguide (2) and the array of directing surfaces (4) lie on a plane nonparallel to the direction of incident light and the thickness of the waveguide (2) is constant along its length excluding the extra concentration means at the end region.
19. A waveguide to claim 18, wherein; the waveguides (2) further comprise at least one extra concentration surface (5).
20. A waveguide to claim 19, wherein; an extra concentration surface (5) is formed on portions of a waveguide (2) ending at the end surface (3) and is in the shape of a non-imaging optical concentrator.
21. A waveguide according to claim 20, produced in a shape with portions from at least one edge removed, leaving behind said extra concentration surface (5).
22. A waveguide according to claim 20, wherein; said extra concentration surface (5) is a side cut (5a) formed by extracting a region on a side, comprising at least one curve or straight line or a combination of both.
PCT/TR2011/000156 2011-06-09 2011-06-09 A waveguide for concentrated solar collectors and a solar collector thereof WO2012169980A1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
PCT/TR2011/000156 WO2012169980A1 (en) 2011-06-09 2011-06-09 A waveguide for concentrated solar collectors and a solar collector thereof

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/TR2011/000156 WO2012169980A1 (en) 2011-06-09 2011-06-09 A waveguide for concentrated solar collectors and a solar collector thereof

Publications (1)

Publication Number Publication Date
WO2012169980A1 true WO2012169980A1 (en) 2012-12-13

Family

ID=44509567

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/TR2011/000156 WO2012169980A1 (en) 2011-06-09 2011-06-09 A waveguide for concentrated solar collectors and a solar collector thereof

Country Status (1)

Country Link
WO (1) WO2012169980A1 (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2020092876A1 (en) * 2018-11-02 2020-05-07 Arizona Board Of Regents On Behalf Of The University Of Arizona Systems for radiative power concentration

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7664350B2 (en) 2007-09-10 2010-02-16 Banyan Energy, Inc. Compact optics for concentration, aggregation and illumination of light energy
WO2010033859A2 (en) * 2008-09-19 2010-03-25 The Regents Of The University Of California System and method for solar energy capture and related method of manufacturing
WO2010056405A1 (en) 2008-11-12 2010-05-20 Abengoa Solar New Technologies, S.A. Light collection and concentration system
US20100220492A1 (en) * 2009-06-11 2010-09-02 Brian Edward Richardson Optical system with reflectors and light pipes
US7817885B1 (en) * 2009-06-24 2010-10-19 University Of Rochester Stepped light collection and concentration system, components thereof, and methods
US20110011441A1 (en) 2009-07-14 2011-01-20 Honeywell International Inc. Low profile solar concentrator

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7664350B2 (en) 2007-09-10 2010-02-16 Banyan Energy, Inc. Compact optics for concentration, aggregation and illumination of light energy
WO2010033859A2 (en) * 2008-09-19 2010-03-25 The Regents Of The University Of California System and method for solar energy capture and related method of manufacturing
WO2010056405A1 (en) 2008-11-12 2010-05-20 Abengoa Solar New Technologies, S.A. Light collection and concentration system
US20100220492A1 (en) * 2009-06-11 2010-09-02 Brian Edward Richardson Optical system with reflectors and light pipes
US7817885B1 (en) * 2009-06-24 2010-10-19 University Of Rochester Stepped light collection and concentration system, components thereof, and methods
US20110011441A1 (en) 2009-07-14 2011-01-20 Honeywell International Inc. Low profile solar concentrator

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2020092876A1 (en) * 2018-11-02 2020-05-07 Arizona Board Of Regents On Behalf Of The University Of Arizona Systems for radiative power concentration
US20220029039A1 (en) * 2018-11-02 2022-01-27 Arizona Board Of Regents On Behalf Of The University Of Arizona Systems for Radiative Power Concentration

Similar Documents

Publication Publication Date Title
TWI404975B (en) Method and system for light collection and light-energy converting apparatus
US7672549B2 (en) Solar energy concentrator
EP2519978B1 (en) Photovoltaic concentrator with optical stepped lens and method for designing the same
EP1866971A2 (en) Multi-junction solar cells with an aplanatic imaging system and coupled non-imaging light concentrator
KR20130140690A (en) Compact optics for concentration and illumination systems
WO2012032462A1 (en) Photovoltaic system with double reflection solar concentrator
KR100933213B1 (en) Concentration lens for solar power generation
JP2013537004A (en) Multi-band concentrator / energy conversion module
JP2006332113A (en) Concentrating solar power generation module and solar power generator
US20140048117A1 (en) Solar energy systems using external reflectors
KR101207852B1 (en) Planar type high concentration photovoltaic power generator module and sun tracker using this module
CN102607193B (en) Solar straight-line type ultrathin photo-thermal utilization condenser
WO2012169980A1 (en) A waveguide for concentrated solar collectors and a solar collector thereof
TWM502813U (en) Solar light-gathering device
WO2012026572A1 (en) Light-condensing device, light power generation device, and photothermal conversion device
CN113791466A (en) Wavy Fresnel lens and preparation method thereof
KR20130064982A (en) Photovoltaic module having reflector with fine patterns
US20150287842A1 (en) Photovoltaic system including light trapping filtered optical module
TWI578024B (en) Light collecting module
KR102481842B1 (en) Multi-layered lenses capable of forming custom focal points
KR20090030443A (en) Wide lens
KR101534756B1 (en) Thin film type solar cell, method of fabricating the same and method of increasing efficiency of a thin film type solar cell
WO2012033132A1 (en) Light condenser, photovoltaic system, and photothermal converter
KR20130054507A (en) Hybrid solar power system of multiplex-stage concentrated solar energy
TW201312065A (en) Solar energy collection device

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 11748481

Country of ref document: EP

Kind code of ref document: A1

WWE Wipo information: entry into national phase

Ref document number: 2013/12659

Country of ref document: TR

NENP Non-entry into the national phase

Ref country code: DE

122 Ep: pct application non-entry in european phase

Ref document number: 11748481

Country of ref document: EP

Kind code of ref document: A1