Concentrator of solar radiation, and corresponding solar power station

Abstract

Concentrator (C) of incident solar radiation having a solar spectrum, the concentrator (C) comprising: - a parabolic mirror (1), arranged to receive the incident solar radiation, designed to reflect a first spectral domain of the solar spectrum; - a set of reflectors (2), arranged above the parabolic mirror (1) to receive the incident solar radiation, designed to transmit the first spectral domain to the parabolic mirror (1) and reflect a second spectral domain, different from the first spectral domain. Figure 1

Description

Title of the invention: Concentrator of solar radiation, and corresponding solar power station Technical field

[0001] The invention relates to the technical field of solar concentrators.

[0002] The invention finds its application in particular in solar power plants with cylindrical-parabolic concentration. State of the art

[0003] A solar power plant known from the state of the art comprises: - at least one cylindro-parabolic mirror, arranged to receive incident solar radiation, and designed to reflect a spectral domain of the solar spectrum; - a receiver, arranged to receive the spectral domain reflected by the cylindro-parabolic mirror.

[0004] The receiver may be a photovoltaic cell or a photoelectrochemical cell. A photoelectrochemical cell comprises a photoanode and a photocathode sensitive to solar radiation. By way of non-limiting example, the photoanode may comprise a photocatalytic layer made of titanium dioxide TiO2, while the photocathode may comprise a photocatalytic layer made of copper oxide Cu2O. Such a photoelectrochemical cell type receiver is not entirely satisfactory in terms of efficiency (or yield) since titanium dioxide TiO2 absorbs in the ultraviolet (wavelength less than 400 nm) and ultraviolet radiation represents only approximately 3% of the electromagnetic energy of the sun.Infrared radiation represents the majority (about 45%) of the electromagnetic energy of the sun, and leads to a massive transfer of heat to the photoelectrochemical cell which is likely to degrade over time.

[0005] The person skilled in the art is looking for a concentrator allowing efficient use of different types of receivers of the solar power plant, for example thermal receivers, photovoltaic cell type receivers, photoelectrochemical cell type receivers, etc. Statement of the invention

[0006] The invention aims to remedy all or part of the aforementioned drawbacks. To this end, the invention relates to a concentrator of incident solar radiation having a solar spectrum, the concentrator comprising: - a cylindro-parabolic mirror, arranged to receive incident solar radiation, designed to reflect a first spectral domain of the solar spectrum; - a set of reflectors, arranged above the parabolic trough mirror to receive the incident solar radiation, designed to transmit the first spectral domain to the parabolic trough mirror and reflect a second spectral domain, different from the first spectral domain.

[0007] Thus, such a concentrator according to the invention allows efficient use of different types of receivers. A first type of receiver, adapted to operate efficiently in the first spectral range, will be able to receive the solar radiation reflected by the parabolic trough mirror. A second type of receiver, adapted to operate efficiently in the second spectral range, will be able to receive the solar radiation reflected by the set of reflectors.

[0008] The concentrator according to the invention may comprise one or more of the following characteristics.

[0009] According to a characteristic of the invention, the reflectors of the assembly are chosen from dichroic mirrors and Bragg mirrors.

[0010] Thus, an advantage provided by such reflectors is the possibility of easily designing them in order to transmit a first spectral domain and to reflect a second spectral domain, different from the first spectral domain.

[0011] According to a characteristic of the invention, the cylindro-parabolic mirror is made of a material chosen from silver and aluminum.

[0012] Thus, an advantage provided by such materials is to obtain a high intensity reflection coefficient over a significant spectral range of the solar spectrum.

[0013] According to a characteristic of the invention: - the first spectral domain comprises at least one spectral range in the infrared; - the second spectral domain includes at least one spectral range in the ultraviolet.

[0014] Thus, an advantage provided is to allow efficient use of different types of receivers. A thermal receiver, adapted to operate efficiently in the first spectral range, will be able to receive the solar radiation reflected by the cylindrical-parabolic mirror. A second type of receiver (e.g. photovoltaic cell, photoelectrochemical cell), adapted to operate efficiently in the second spectral range, will be able to receive the solar radiation reflected by the set of reflectors.

[0015] According to a characteristic of the invention, the concentrator comprises a structure provided with first and second opposite support surfaces, transparent in the solar spectrum; the cylindro-parabolic mirror extending on the first support surface, the set of reflectors extending on the second support surface.

[0016] Thus, an advantage provided is to facilitate the mounting of the cylindro-parabolic mirror. and the set of reflectors.

[0017] According to a characteristic of the invention, the structure comprises an air blade, transparent in the solar spectrum, arranged between the first and second opposite support surfaces.

[0018] Thus, an advantage provided is to obtain a high intensity transmission coefficient over a significant spectral range of the solar spectrum.

[0019] According to a characteristic of the invention, the structure comprises a plate transparent in the solar spectrum, comprising the first and second opposite support surfaces.

[0020] Thus, an advantage provided is to obtain good mechanical strength of the cylindro-parabolic mirror and of the set of reflectors.

[0021] According to a characteristic of the invention, the plate is made of a material chosen from extra-clear glass, polycarbonate, polymethyl methacrylate, polyvinyl chloride.

[0022] Thus, an advantage provided is to obtain a high intensity transmission coefficient over a significant spectral range of the solar spectrum.

[0023] According to a characteristic of the invention, the structure comprises displacement means, configured to move the first and second support surfaces as a function of a direction of the incident solar radiation, so as to orient the cylindro-parabolic mirror and the set of reflectors to receive a maximum intensity of the incident solar radiation.

[0024] Thus, an advantage provided is to optimize the intensity of the radiation reflected by the cylindro-parabolic mirror and by the set of reflectors.

[0025] The invention also relates to a solar power station, comprising: - at least one concentrator in accordance with the invention; - at least one first receiver, arranged to receive the first spectral domain reflected by the cylindro-parabolic mirror of the at least one concentrator; - at least one second receiver, arranged to receive the second spectral domain reflected by the set of reflectors of the at least one concentrator.

[0026] Thus, such a solar power plant according to the invention allows efficient use of different types of receivers. The first receiver(s), adapted to operate efficiently in the first spectral range, are arranged to receive the solar radiation reflected by the parabolic trough mirror. The second receiver(s), adapted to operate efficiently in the second spectral range, are arranged to receive the solar radiation reflected by the set of reflectors.

[0027] Definitions

[0028] - The term “concentrator” designates a solar concentrator.

[0029] - By "reflect" we mean that the cylindro-parabolic mirror has a co efficient intensity reflection greater than 80%, preferably greater than 85%, more preferably greater than 90% averaged over the first spectral domain. Similarly, it is understood that the set of reflectors has an intensity reflection coefficient greater than 80%, preferably greater than 85%, more preferably greater than 90% averaged over the second spectral domain.

[0030] - By "transmit" we mean that the set of reflectors has a coefficient intensity transmission greater than 80%, preferably greater than 85%, more preferably greater than 90% averaged over the first spectral domain.

[0031] - By "first (respectively second) spectral domain" is meant a res distortion of the solar spectrum in terms of lengths reflected respectively by the parabolic trough mirror and by the set of reflectors.

[0032] - By "transparent" we mean that the elements (first and second surfaces of support, air blade, plate) have an intensity transmission coefficient greater than 80%, preferably greater than 85%, more preferably greater than 90% averaged over the solar spectrum.

[0033] - The term "receiver" can designate a thermal receiver, that is to say a adsorber in which a heat transfer fluid circulates, or a receiver of a different nature, for example a photovoltaic cell or a photoelectrochemical cell. Brief description of the drawings

[0034] Other characteristics and advantages will appear in the detailed description of different embodiments of the invention, the description being accompanied by examples and references to the attached drawings.

[0035] [Fig-1] is a schematic perspective view of a solar power plant according to the invention.

[0036] [Fig.2] is a partial schematic front perspective view of a concentrator according to the invention.

[0037] [Fig.3] is a partial schematic rear perspective view of a concentrator according to the invention.

[0038] [Fig.4] is a partial schematic side view of a solar power plant according to the invention.

[0039] [Fig.5] is a partial schematic side view of a concentrator according to the invention, illustrating the path of incident solar radiation towards the first and second receivers.

[0040] [Fig.6] is a schematic view similar to [Fig.5], illustrating the path of solar radiation with normal incidence towards the first and second receivers.

[0041] [Fig.7] is a schematic side view on an enlarged scale of a part of a concentrator according to the invention, illustrating an angle of inclination between the parabolic trough mirror and a reflector.

[0042] [Fig.8] is a partial schematic view of a solar power plant according to the invention, illustrating the presence of two concentrators.

[0043] [Fig.9] is a partial schematic side view of a concentrator according to the invention, illustrating reflectors having a triangular crenellation shape.

[0044] It should be noted that the drawings described above are schematic, and are not necessarily to scale for the sake of readability and to simplify their understanding. Detailed description of the embodiments

[0045] Elements that are identical or provide the same function will bear the same references for the different embodiments, for the sake of simplification.

[0046] An object of the invention is a concentrator C of incident solar radiation Rs having a solar spectrum, the concentrator C comprising: - a cylindro-parabolic mirror 1, arranged to receive the incident solar radiation Rs, designed to reflect a first spectral domain Rsl of the solar spectrum; - a set of reflectors 2, arranged above the parabolic mirror 1 to receive the incident solar radiation Rs, designed to transmit the first spectral domain Rsl to the parabolic mirror 1 and reflect a second spectral domain Rs2, different from the first spectral domain Rsl.

[0047] Cylindro-parabolic mirror

[0048] The parabolic mirror 1 is arranged to receive the incident solar radiation Rs. The parabolic mirror 1 is designed to reflect a first spectral domain Rsl of the solar spectrum.

[0049] The cylindro-parabolic mirror 1 is advantageously made of a material chosen from silver and aluminum.

[0050] The first spectral domain Rsl advantageously comprises at least one spectral range in the infrared. The first spectral domain Rsl may comprise a spectral range in the infrared, and a spectral range in the visible (wavelengths between 400 nm and 780 nm).

[0051] The parabolic mirror 1 may have a radius of curvature of between 0.5 m and 20 m, preferably of between 0.5 m and 15 m. The parabolic mirror 1 may have a focal length of between 0.5 m and 20 m.

[0052] Set of reflectors

[0053] The reflector assembly 2 is arranged above the parabolic trough mirror 1. The reflector assembly 2 is arranged to receive the incident solar radiation Rs. The reflector assembly 2 is designed to transmit the first spectral range Rsl to the parabolic trough mirror 1. The reflector assembly 2 is designed to reflect a second spectral Rs2, different from the first spectral domain Rsl. The number and size of the reflectors 2 are chosen according to the desired concentration level.

[0054] The reflectors 2 of the assembly are advantageously chosen from dichroic mirrors and Bragg mirrors. Dichroic mirrors are preferred due to the greater dispersion of the radiation transmitted by the Bragg mirrors.

[0055] The second spectral domain Rs2 advantageously comprises at least one spectral range in the ultraviolet. The second spectral domain Rs2 may comprise a spectral range in the ultraviolet, and a spectral range in the visible (wavelengths between 400 nm and 780 nm).

[0056] By way of non-limiting example, each reflector 2 of the assembly may be a DMLP425 dichroic mirror, marketed by the company THORLABS. The intensity reflection coefficient averaged over the spectral range [380 nm; 410 nm] is greater than 95%. The intensity transmission coefficient averaged over the spectral range [440 nm; 800 nm] is greater than 90%.

[0057] Structure

[0058] The concentrator C may comprise a structure 3 provided with first and second opposite support surfaces 30, 31. The first and second support surfaces 30, 31 are transparent in the solar spectrum. The parabolic trough mirror 1 extends over the first support surface 30. The set of reflectors 2 extends over the second support surface 31. The reflectors 2 may be formed on the second support surface 31 by a vacuum deposition technique known to those skilled in the art.

[0059] The structure 3 has a first curved support surface 30, having a radius of curvature adapted to the radius of curvature of the parabolic trough mirror 1 so that the parabolic trough mirror 1 can extend over the first support surface 30. The structure 3 may have a second crenellated or serrated support surface 31. By way of non-limiting example, the second crenellated support surface 31 may comprise triangular section patterns. The first and second support surfaces 30, 31 are advantageously arranged so that each reflector 2 extends in an oblique direction (at an angle of inclination α) relative to the underlying arcuate portion of the parabolic trough mirror 1 (more precisely relative to the chord of the underlying arcuate portion). As a non-limiting example, the inclination angle a can be between 0.1° and 10°.

[0060] According to a first embodiment, the structure 3 comprises an air blade, transparent in the solar spectrum, arranged between the first and second opposite support surfaces 30, 31.

[0061] According to a second embodiment, the structure 3 comprises a plate transparent in the solar spectrum, comprising the first and second opposite support surfaces 30, 31. The plate is advantageously made of a material chosen from extra-clear glass, polycarbonate, polymethyl methacrylate, polyvinyl chloride. By way of non-limiting example, the plate can be made by an extrusion process. The plate can be made by assembling several sub-plates in order to achieve a lateral dimension of the order of 10 m.

[0062] The structure 3 advantageously comprises displacement means 32, configured to move the first and second support surfaces 30, 31 as a function of a direction of the incident solar radiation Rs, so as to orient the cylindrical-parabolic mirror 1 and the set of reflectors 2 to receive a maximum intensity of the incident solar radiation Rs. The displacement means 32 may comprise an electric motor and a set of toothed wheel gears. As a variant, the displacement means may comprise a connecting rod (crank) and a jack (hydraulic or electric).

[0063] The structure 3 advantageously comprises uprights 33, on which the displacement means 32 are mounted. The structure 3 advantageously comprises offset arms 34, designed to provide an offset (distance) function between the concentrator C and receivers RI, R2. The offset arms 34 are arranged so that the receivers RI, R2 are located in the vicinity of the focus of the cylindro-parabolic mirror 1.

[0064] Solar power plant

[0065] The invention also relates to a solar power station, comprising: - at least one concentrator C in accordance with the invention; - at least one first receiver RI, arranged to receive the first spectral domain Rsl reflected by the cylindrical-parabolic mirror 1 of the at least one concentrator C; - at least one second receiver R2, arranged to receive the second spectral domain Rs2 reflected by the set of reflectors 2 of the at least one concentrator C.

[0066] The first receiver(s) RI and the second receiver(s) R2 are arranged in the vicinity of the focus of the cylindrical-parabolic mirror 1. The or each first receiver RI may be produced in the form of a tube of circular section with a diameter of between 10 mm and 100 mm. The or each second receiver R2 may be produced in the form of a tube of rectangular section with a width of between 10 mm and 2 m.

[0067] The or each first receiver RI may be a thermal receiver, i.e. an adsorber in which a heat transfer fluid circulates. The or each second receiver R2 may be a receiver of a different nature, for example a photovoltaic cell or a photoelectrochemical cell.

[0068] By way of non-limiting example, the solar power plant may comprise: - two C concentrators; - a first thermal RI receiver; - a second receiver R2, arranged under the first thermal receiver RI.

[0069] The two concentrators C can be arranged according to an axial symmetry (vertical axis) with respect to the first and second receivers RI, R2.

[0070] The invention is not limited to the embodiments disclosed. Those skilled in the art are able to consider their technically operational combinations and to substitute equivalents for them.

Claims

Claims

1. Concentrator (C) of incident solar radiation (Rs) having a solar spectrum, the concentrator (C) comprising: - a parabolic mirror (1), arranged to receive the incident solar radiation (Rs), designed to reflect a first spectral domain (Rsl) of the solar spectrum; - a set of reflectors (2), arranged above the parabolic mirror (1) to receive the incident solar radiation (Rs), designed to transmit the first spectral domain (Rsl) to the parabolic mirror (1) and reflect a second spectral domain (Rs2), different from the first spectral domain (Rsl).

2. Concentrator (C) according to claim 1, in which the reflectors (2) of the assembly are chosen from dichroic mirrors and Bragg mirrors.

3. Concentrator (C) according to claim 1 or 2, in which the cylindro-parabolic mirror (1) is made of a material chosen from silver and aluminum.

4. Concentrator (C) according to one of claims 1 to 3, in which: - the first spectral domain (Rsl) comprises at least one spectral range in the infrared; - the second spectral domain (Rs2) comprises at least one spectral range in the ultraviolet.

5. Concentrator (C) according to one of claims 1 to 4, comprising a structure (3) provided with first and second opposite support surfaces (30, 31), transparent in the solar spectrum; the cylindro-parabolic mirror (1) extending on the first support surface (30), the set of reflectors (2) extending on the second support surface (31).

6. Concentrator (C) according to claim 5, in which the structure (3) comprises an air blade, transparent in the solar spectrum, arranged between the first and second opposing support surfaces (30, 31).

7. Concentrator (C) according to claim 5, wherein the structure (3) comprises a plate transparent in the solar spectrum, comprising the first and second opposing support surfaces (30, 31).

8. Concentrator (C) according to claim 7, in which the plate is made of a material chosen from extra-clear glass, polycarbonate, polymethyl methacrylate, polyvinyl chloride.

9. Concentrator (C) according to one of claims 5 to 8, wherein the structure (3) comprises displacement means (32), configured to move the first and second support surfaces (30, 31) as a function of a direction of the incident solar radiation (Rs), so as to orient the cylindro-parabolic mirror (1) and the set of reflectors (2) to receive a maximum intensity of the incident solar radiation (Rs).

10. Solar power plant, comprising: - at least one concentrator (C) according to one of claims 1 to 9; - at least one first receiver (RI), arranged to receive the first spectral domain (Rsl) reflected by the cylindro-parabolic mirror (1) of the at least one concentrator (C); - at least one second receiver (R2), arranged to receive the second spectral domain (Rs2) reflected by the set of reflectors (2) of the at least one concentrator (C).

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