• 专利附录
  • 专利说明
  • 权利要求
  • 类似技术
  • 同族专利
  • 引用文献
  • 法律状态
  • 优先权
    • 专利摘要:
    Mirror for solar energy applications and method of manufacturing it. The present invention relates to mirrors for thermosolar applications, which preferably comprise: a metal layer (3) that can reflect a range of wavelengths comprised within the solar irradiance spectrum; a multilayer aperiodic structure (1) adjacent to the metal layer (3), comprising a plurality of layers of different refractive indexes and thicknesses, which presents reflection bands at wavelength ranges in which the metal layer ( 3) adjacent absorbs. The structure of the mirror allows a high reflection outside the absorption bands of the terrestrial solar spectrum and presents values of r.s or swir both stable and constant with respect to the direction of incidence of the light. (Machine-translation by Google Translate, not legally binding)
    公开号:ES2575527A1
    申请号:ES201431774
    申请日:2014-11-28
    公开日:2016-06-29
    发明作者:Keith Boyle；Carlos Alcañiz Garcia；Mercedes ALCÓN CAMAS；Juan Pablo Nuñez Bootello；Hernán Ruy Míguez García；Mauricio Ernesto Calvo Roggiani；Alberto JIMÉNEZ SOLANO；Miguel ANAYA MARTÍN
    申请人:Abengoa Solar New Technologies SA；
    IPC主号:
    专利说明:

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    MIRROR FOR SOLAR ENERGY APPLICATIONS AND MANUFACTURING METHOD OF THE SAME FIELD OF THE INVENTION
    The present invention belongs to the field of solar energy technologies. More specifically, the invention relates to mirrors for solar thermal applications.
    BACKGROUND OF THE INVENTION
    Research on new mirrors to improve the efficiency of solar energy technologies is extensive, both in designs and materials. One of the technologies of this type that is most in demand, in terms of the efficiency of the reflector mirrors, is known as solar thermal, in which the sunlight is concentrated on a predetermined objective, through sets of mirrors properly located around of that objective. Such sets of mirrors are commonly known as heliostats. In heliostat technologies, to obtain optimum performance it is necessary to keep the reflective surfaces of the mirrors perpendicular to the bisector of the angle between the direction of the sun and the lens, from the point of view of the mirror.
    Heliostat costs represent approximately half of the capital cost of a tower solar power plant. Therefore, it is of interest to design less expensive heliostats for large-scale manufacturing, so that solar power plants can produce electricity at more competitive costs than the costs of conventional power plants (based on other sources, such as coal). In addition to costs, reflectivity throughout the entire range of the solar spectrum (commonly referred to in the art as "solar reflectivity (RS) or solar energy reflection factor, or in English" solar spectrum weighted integrated reflectance "( SWIR)) and durability against the environment are factors that should be considered when comparing the designs of heliostats.
    Attempts to reduce heliostat costs are based primarily on replacing the design of the conventional heliostat with one that uses less expensive materials. A conventional design for the heliostat comprises second-sided mirrors, the structure of which generally consists of: (i) a protective layer, (ii) a reflective silver layer and (iii) a thick protective glass top layer. The invention described in this document refers to alternative reflectors, whose design allows the use of less expensive materials than silver, thus decreasing the dependence of this precious metal technology, whose market prices show large fluctuations. Any reflective material used must, in any case, reflect the incident solar energy with a minimum loss, and its performance should not be affected by its interaction with humidity, ultraviolet radiation, dust, temperature and other environmental parameters. In general, silver is the election
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    preferred as a material for the reflective layer, due to the solid technological base established in the mirror industry, and because its reflectance is generally in the range between 0.95 and 0.97, for surfaces deposited by mirror manufacturing processes well established.
    The use of other more profitable metals has been avoided so far by the presence of strong absorption bands that would greatly reduce the reflectivity of the mirror. On the other hand, approaches based on dielectric mirrors (also known as Bragg reflectors, dichroic mirrors, interference mirrors, distributed Bragg reflectors or, in a more modern terminology, one-dimensional photonic crystals) have some serious drawbacks. First, most designs are based on a periodic distribution of layers of high and low refractive indices, which provides a strong reflection peak in a spectral range that is much narrower than the full solar spectrum as a target for renewable energy applications (see, for example, US patent applications with references US 2912/0263885 and US 2013/0342900). In addition, the strong angular dependence of the reflectance spectrum prevents its use in technologies in which sunlight reaches the mirror with various angles of incidence. The problem of covering a greater spectral range can be solved by multilayer designs based on the coupling of structures with different periodicities (see international application with reference WO2013 / 059228) but, even in this case, the number of layers needed to cover the entire Solar spectrum is so large that it is not a viable option. The approaches related to this concept, although based on the random distribution of layers rather than aperiodic designs, have also been proposed to construct reflectors in shorter wavelength ranges (see WO2009 / 043374), but could not be extended to reflect the entire solar spectrum.
    Due to the limitations and technical problems mentioned above, the present invention proposes novel mirror configurations and their corresponding manufacturing methods that can provide improved yields in terms of their wavelength sensitivity, their angular reflection properties and their dependence on high cost materials.
    BRIEF DESCRIPTION OF THE INVENTION
    The present invention solves the technical problems mentioned above by proposing the use of mirrors based on a reflective layer made of a freely chosen metal, which is coupled adjacent to an aperiodic sequence of layers of different composition, thicknesses and refractive indices. The main technical advantage of these mirrors, which arises as a result of this particular design, is that they have a high optical reflectance for the entire solar spectrum (350 nm <X <2500 nm). In addition, the mirrors of the invention can be optimized to achieve maximum reflectivity for a given angle of incidence of sunlight. In addition to these characteristics, the ability to use free-choice metals, which may also be based on low-cost materials, makes the invention very competitive with conventional silver mirrors in terms of performance.
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    With regard to the costs related to multilayer structures, they are significantly affected by the complexity and deposition costs of their layers. Therefore, significantly reducing the number of layers of a multilayer structure significantly improves its production costs. On the other hand, reducing the number of layers of a multilayer reflector structure introduces specific coffees into the reflectivity spectrum (also known as low reflectivity bands). The present invention takes into account the effect of specific reflective coffees within the aperiodic structure, forcing them to coincide with the absorption bands in the terrestrial solar spectrum, thus allowing a high optical reflectance with a large number of layers reduced measure. In this sense, the present invention proposes a solution to the problem of obtaining a high optical reflectance viable for the generation of electricity from solar energy without the need for structures with a large number of layers, matching the specific reflectance coffees of the aperiodic layer structure, inherent in structures with fewer layers, with atmospheric absorption bands in the solar solar spectrum.
    Therefore, according to the foregoing considerations, an objective of the invention is a mirror for solar energy applications comprising: a metal layer that has reflection of at least a first range of wavelengths within the solar irradiance and absorption spectrum of at least a second range of wavelengths comprised in said spectrum; and a multi-layer aperiodic structure adjacent to the metal layer, comprising a plurality of layers of different indices of refraction and thicknesses, which reflects within the second range of wavelengths in which the adjacent metal layer exhibits absorption; the distribution of layers being arranged in the multi-layer aperiodic structure so that the wavelength ranges with minimal reflection in said multi-layer aperiodic structure correspond to wavelength ranges with maximum absorption in the terrestrial solar spectrum.
    Therefore, the multi-layer aperiodic structure of the invention is configured to reflect the light in the wavelength ranges absorbed by the adjacent metal layer, making the wavelength ranges of low reflectivity (due to, for example, the interference between the layers) coincide with the wavelength ranges in which the solar spectrum has specific irradiance coffees (corresponding to those wavelengths comprised in the atmospheric absorption bands), so that the multilayer structure reflects the wavelengths with higher irradiance values within the solar spectrum. With regard to the reflection / absorption properties of the metal layer, it should be noted that this layer may have both reflection and absorption properties in the same wavelength range (i.e. the first and first wavelength ranges). second within the solar irradiance spectrum may be ranges that overlap, or even match). However, in this situation the reflection in this range is usually less intense than in other ranges of wavelength of the spectrum, due to the presence of the absorption effect.
    In a preferred embodiment of the invention, the mirror further comprises a substrate layer and / or a
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    protective layer applied to the metal layer.
    In another preferred embodiment of the invention, the thickness of the layers that form the multi-layer aperiodic structure is comprised between 1 nm and 1 p, m. More preferably, the thickness of the layers that form the multi-layer aperiodic structure is between 10 nm and 400 nm.
    In a further preferred embodiment of the invention, the number of layers in the multi-layer aperiodic structure is between 2 and 1000. More preferably, the number of layers in the multi-layer aperiodic structure is between 4 and 200.
    In a preferred embodiment of the invention, the multi-layer aperiodic structure is formed by an alternating sequence of two materials of different refractive index. More preferably, the multi-layer aperiodic structure is formed by alternating layers of silicon oxide and titanium oxide or any compound derived therefrom.
    In a preferred embodiment of the invention, the metal layer comprises one or more of the following materials: copper, aluminum, chromium, iron, titanium, nickel, cobalt, palladium, rhodium, silver, gold, platinum, or any alloy of the same.
    In a further preferred embodiment of the invention, the multi-layer aperiodic structure and the metal layer are arranged to form a first or second sided mirror.
    In a further preferred embodiment of the invention, the layers with the lowest refractive index within the multi-layer aperiodic structure have a porosity between 10% and 95% and the layers with the highest refractive index have a porosity between 0% and 10%.
    A further object of the invention relates to a method for manufacturing a mirror for solar energy applications, which preferably comprises the steps of:
    - Deposition of a metal layer, which may reflect a range of wavelengths within the solar irradiance spectrum, adjacent to a plurality of layers of different refractive index and thickness, which form a multi-layer aperiodic structure that has reflection bands at wavelength ranges in which the adjacent metal layer absorbs;
    - depositing the layers in the multi-layer aperiodic structure, so that the weakest reflection bands of the multi-layer aperiodic structure correspond to wavelength ranges coinciding with the most intense absorption bands in the terrestrial solar spectrum.
    In a further preferred embodiment of the method of the invention, the multi-layer aperiodic structure or the metal layer is deposited on a substrate (for example, a glass substrate). In addition, the method of the invention may comprise the step of depositing a protective layer on the metal layer.
    In a further preferred embodiment of the invention, the technique used to deposit the layers that
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    they form the multi-layer aperiodic structure or the metal layer comprises one or more of the following list: deposition by rotation (spin-coating), dip coating (dip-coating), Langmuir-Blodgett, chemical deposition techniques in vapor phase or physical deposition in the vapor phase such as thermal evaporation or cathode pulverization.
    As described in the previous paragraphs of this document, designing the mirror for an angle of incidence of free choice sunlight and using low-cost materials, the invention is highly competitive, in terms of performance, compared to conventional silver mirrors. . The mirror structure based on the combination of a freely chosen metal layer and a pre-designed multilayer aperiodic structure, allows a high reflection outside the absorption bands of the terrestrial solar spectrum (that is, the aperiodic structure strongly reflects wavelengths incidents that the metal absorbs), and presents both stable and constant SWIR values with respect to the direction of light incidence.
    DESCRIPTION OF THE FIGURES
    Figure 1 shows two embodiments of the multilayer distribution of a second-sided mirror (figure 1a) and a first-sided mirror (figure 1b) according to the present invention.
    Figure 2 shows a graphic distribution of the terrestrial solar spectrum according to ASTM G173-03 in which the spectral regions of lower intensity of solar radiation are highlighted vertically.
    Figure 3 shows a flow chart that includes the main stages of an optimization process used for the design of the multi-layer aperiodic structure for a mirror according to the present invention.
    Figure 4 shows the real (n) and imaginary (k) parts of the refractive index of the materials used to construct a multilayer structure according to the invention, comprising TiO2 (upper figures) and SiO2 (lower figures).
    Figure 5 shows the theoretically calculated reflectance of a first-sided mirror according to the invention, whose layer compositions and layer thicknesses are described in Table 1 of this document. The 1.5 mass air mass (AM) spectrum is included as the SWIR value obtained.
    Figure 6 shows values obtained at different angles of incidence for the multilayer composition described in Table 1 of this document.
    Figure 7 shows the real (n) and imaginary part (k) of the refractive index of the materials used to construct a multilayer stacking structure according to the invention, comprising TiO2 (upper figures) and porous SiO2 (lower figures).
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    Figure 8 shows the theoretically calculated reflectance of a first-sided mirror whose layer composition and layer thicknesses are described in Table 3 of this document. An AM spectrum of 1.5 is included as the SWIR value obtained.
    Figure 9 shows SWIR values obtained at different angles of incidence for the system according to the invention described in Table 3 of this document.
    Figure 10 shows cross-sectional images obtained through field emission scanning electron microscopy (FESEM) of a system of 20 layers of SiO2 / TiO2 with a copper layer on top. On the left and right side of the figure, an image of secondary electrons and an image of backscattered electrons are shown respectively. The scale bar shown in the figure is 2 micrometers.
    Figure 11 shows reflectance spectra of a theoretically calculated (intense line) and experimental multilayer SiO2 / TiO2 film constructed according to the invention, using the thickness values described in Table 5 of this document. SWIR values are also included.
    Figure 12 shows SWIR values obtained at different angles of incidence for the system according to the invention described in Table 5 of this document.
    Figure 13 shows reflectance spectra of a theoretically calculated (intense line) and experimental multilayer SiO2 / TiO2 film constructed according to the invention, using the thicknesses described in Table 7 of this document. SWIR values are also included.
    Figure 14 shows SWIR values obtained at different angles of incidence for the system according to the invention described in Table 7 of this document.
    DETAILED DESCRIPTION OF THE INVENTION
    Next, some of the preferred and non-limiting embodiments of the invention are described, in relation to the numerical references of Figures 1-14 herein. The definitions provided are intended to facilitate the understanding of certain terms and in no way limit the scope of the claims herein.
    As shown in Figure 1 (a) of this document, an embodiment of the invention refers to a second-sided mirror that combines:
    - a multi-layer aperiodic structure (1) made of layers of predicted thicknesses and refraction indices, which can reflect sunlight efficiently, in which the lower bands
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    Reflectivity of said multi-layer aperiodic structure (1) is made to coincide with the atmospheric absorption bands in the terrestrial solar spectrum, thereby being strongly reflected in the high energy bands of the terrestrial solar spectrum. The multi-layer aperiodic structure (1) is deposited on a flat transparent substrate glass layer (2);
    - a layer of a metal (3) of choice deposited on such a multi-layer aperiodic structure (1), which can efficiently reflect a certain spectral region of sunlight;
    - a protective coating layer (4), such as enamel paint, whose function is to prevent the degradation of the entire multi-layer aperiodic structure (1). This design is oriented towards the incident light from the side that ends in the glass layer (2).
    The design of the multi-layer aperiodic structure (1) is such that it efficiently reflects the spectral region in which the metal absorbs, having the effect of giving rise to a high-reflection broadband mirror that covers the entire solar spectrum for all a cone of directions of incidence of the incident light. The protective coating layer (4) of enamel paint serves to protect the back face of the metal layer (3) against corrosion or other environmental threats.
    Another embodiment of the invention relates to a first-sided mirror with a design that combines a layer of a freely chosen metal (3), which can efficiently reflect a certain spectral region, which is deposited on a substrate layer ( 2). The mirror also comprises a multi-layer aperiodic structure (1) made of layers of predicted thicknesses and refraction indices, which can efficiently reflect the spectral region in which the metal absorbs. This effect is obtained by forcing the lower reflectivity bands of the structure to coincide with the atmospheric absorption bands in the terrestrial solar spectrum and by high reflection in the high energy bands of the terrestrial solar spectrum (see Figure 2 of this document, in which a graphic distribution of low energy bands in the direct and circumsolar spectrum is shown). In this case, the mirror is designed so that the light strikes it from the end that ends in the multi-layer aperiodic structure (1). This design results in a high-reflection mirror in a wide spectral range that covers the high-energy bands of the Earth's solar spectrum for a wide and adjustable cone of angles of light incidence.
    A further objective of the present invention relates to a method for manufacturing a second-sided mirror comprising the following steps:
    (a) Preparation of a multi-layer aperiodic structure (1), in which the layers of high and low refractive index materials of different thickness alternate in an aperiodic manner (that is, not periodic but not chaotic). This multi-layer aperiodic structure (1) is formed on the lower surface of a glass layer (2) that acts as the upper protective layer (4) of the complete mirror structure. It is the result of the alternate deposition of layers of controlled thickness of different materials to choose
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    so that an aperiodic spatial modulation of the refraction index is achieved through the multilayer aperiodic structure (1). This modulation is responsible for the reflection properties of the multilayer and is designed to provide the maximum solar reflectivity (RS also called SWIR in English) possible in the wavelength range of 350-2500 nm for the entire mirror structure, having take into account the specific optical losses caused by the absorption of the materials that constitute it, particularly the metal layer (3), and the substrate (2) and protective layers (4). The deposition of these layers can be achieved by any type of thin film coating technique such as rotation deposition (spin-coating), immersion deposition (dip-coating), Langmuir-Blodgett, chemical vapor deposition or a method of physical deposition in the vapor phase, such as evaporation or cathodic pulverization, and from a wide range of precursors. The thickness of each of the layers that form the multilayer is between 1 nm and 1 micrometer. The number of layers in the multilayers can vary between 2 and 1000. The structure of this multi-layer mirror that leads to a high solar reflectivity (RS or SWIR) that is maximum for an angle of incidence to choose, and that is so constant As possible for a wide range of incidence addresses around that, it is the key to the innovation proposed in this invention.
    (b) Deposition of a metallic layer (3) of free choice composition on the multi-layer aperiodic structure (1) described in step (a). The deposition of this metal layer (3) can be achieved by any type of thin film coating technique such as rotational deposition (spin-coating), immersion deposition (dip-coating), Langmuir-Blodgett, chemical deposition in phase of steam or a physical deposition technique in the vapor phase, such as evaporation or cathode spraying, and from a wide range of precursors.
    (c) Deposition of a protective layer (4) of enamel that protects the metal layer (3) against corrosion or any type of degradation.
    In an alternative embodiment of the present invention, the method is aimed at manufacturing a first surface mirror comprising the following steps:
    (a) Deposition of a metal layer (3) of free choice composition on the glass substrate (2). The deposition of this metal layer (3) can be carried out by any type of thin film coating technique such as rotation deposition (spin-coating), immersion deposition (dip-coating), Langmuir-Blodgett, chemical deposition in vapor phase or physical deposition in vapor phase, such as evaporation or cathode spraying, and from a wide range of precursors.
    (b) Preparation of a multi-layer aperiodic structure (1) in which layers of high and low refractive index materials of different thickness alternate in an aperiodic manner (ie, not periodic but not chaotic). The aperiodic multilayer structure (1) according to this particular embodiment of the invention
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    it is preferably formed on the free surface of the metal layer (3) deposited in step (a).
    In order to achieve the aforementioned modulation of the refraction index, the multi-layer aperiodic structure (1) may be composed of any sequence of layers of materials of different refractive index and thicknesses, without any limitation imposed as to the number and type of compositions of material to be used, its microstructure or nanostructure, or its porosity. The mirrors described herein can be used for any suitable purpose, including but not limited to heliostats and any type of optical element to be implemented in a thermal, photovoltaic, or combined thermal and photovoltaic solar power plant.
    - MIRROR DESIGN OPTIMIZATION PROCEDURE:
    The solar reflectivity or solar energy reflection factor is defined, in English “solar spectrum weighted integrated reflectance” (SWIR or RS) as the result of integrating, between the selected wavelength range, the product of any target solar spectrum (which can be a standard spectrum such as AM0, AM1.0, AM1.5 ... or any other) and the reflectance spectrum R (A,) (that is, the intensity of reflected light divided by the intensity of light incident for each wavelength), normalized by the integrated solar spectrum. All the examples provided in this document present R.S or SWIR values calculated according to:
    SWIR =
    T
    350
    RU) AM1.5U) dA
    2500
    J AM1.5 (A) dA
    350
    All calculations of optical properties have been made using the transfer matrix method in which the propagation of light as a wave vector has been taken into account. All materials have been modeled using well established data from either related bibliography or estimated from reliable measurements. The value of R.S or SWIR, as defined in this section, is used as a merit factor to find an optimized design. The optimization method is based on a genetic algorithm that samples an initial population, for example a population of 150 individuals (mirror designs), and retains, from each generation to the next, only a percentage (for example 10%) that It shows a better value of RS or SWIR. This process is iterated as much as necessary to reach a maximum stable value, which normally takes place after evaluating 45,000 individuals (300 generations) when the R.S or SWIR is optimized for a specific incidence angle. When the goal is to optimize the RS or SWIR for a wide range simultaneously (which means that the RS or SWIR for each angle may not be optimal for that specific angle, but the overall efficiency of the reflector is higher when all the dimensions are taken into account directions of incidence), then the number of generations required to reach an optimized configuration is close
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    1000. In any case, the maximum number of generations under test is 5000, although such value was never reached in the calculations made to find the designs described in this document. In each individual, the indexes of refraction of the layers from which it is made are considered fixed input values, while the thickness can vary freely. In general, a maximum of 30 dielectric layers are considered for the multi-layer aperiodic structure (1), apart from the metal layer (3) and the substrate (2). Such restriction is imposed to find solutions that are really viable. For most of the materials considered, the optimized results consider some layers of zero thickness, which indicates that the higher value imposed is not only practical, but is above the number needed to optimize the structure in absolute terms. A flow chart of the optimization process and a summary of the input parameters are provided below. A tolerance of 10-12 is used as a criterion to stop the calculations. In this disclosure, "tolerance" is defined as the difference between the R.S. o SWIR obtained for optimized designs of two consecutive generations. A schematic description of the optimization process described is shown in Figure 3 of this document.
    In the following paragraphs, preferred embodiments of mirror preparation and characterization techniques are described:
    - MIRROR PREPARATION:
    Although there is a wide variety of methods that can be used to make the mirrors proposed herein, as indicated in the claims and understood by one of ordinary skill in the art, details of two of them are provided as non-limiting examples. of embodiments of the invention:
    Sol-Gel: Among the various liquid processing routes, the sol-gel method provides a versatile and low-cost option for preparing metal oxides with different microstructures and aggregation states. In addition, sol-gel methods can be combined with liquid deposition techniques to obtain films with stable and crack-free structures. The multi-layer aperiodic structure (1) was prepared using SiO2 and TiO2 layer dispersions obtained by sol-gel technique. A dispersion of SiO2 was obtained by mixing silicon tetraethoxide in an ethanol solution of hydrochloric acid, while a dispersion of TiO2 was prepared from a solution of nitric acid in isopropanol, to which titanium tetraisopropoxide was slowly added. Both dispersions were deposited on a glass substrate layer (2) using a rotation coating device (Laurell WS-400E-6NPP), in which both the acceleration ramp and the final rotation speed can be precisely determined. The samples were centrifuged for 1 minute and then treated at a temperature between 300 ° C and 550 ° C on a heating plate for a range of 10 to 300 seconds. After cooling in a metal layer (3), the coating procedure is repeated as many times as necessary to obtain the desired multi-layer aperiodic structure (1). The same process was performed by immersion coating (ND-RDC,
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    Nadetech Innovation) submerging the substrates in the same metal oxide dispersions. Both processes result in a dense multilayer aperiodic structure (1).
    Physical vapor deposition: This method involves the deposition of the metal layer (3) and the metal oxide sheets for the multi-layer aperiodic structure (1). The metal is deposited by a thermal evaporation technique or by cathodic pulverization. Both deposition methods involve a high vacuum chamber (Leica EM SCD500) equipped with a quartz scale (Leica EM QSG100) that monitors the deposited thickness. The metal (formed as wire) was evaporated through a tungsten resistance polarized at 4 V and with an applied current of 30 mA. The cathode metal spraying was performed using a specific polarized high voltage target at an argon pressure between 5x10-3 and 1x10-2 mbar.
    - STRUCTURAL CHARACTERIZATION:
    Characterization of the spectra: Images were taken by scanning electron microscopy by field emission (FESEM) of the layers deposited on silicon using a Hitachi 5200 microscope operating at 5 kV. Samples were immersed in liquid nitrogen before being cut to analyze the cross section.
    Optical reflectance measurements: Normal incidence specular reflectance spectra were obtained using a visible UV scan spectrophotometer (SHIMADZU UV-2101PC) attached to an integration sphere and a Fourier transform spectrophotometer (BRUKER) coupled to a microscope that works in the wavelength range of 450 nm-2500 nm
    EXAMPLES OF EMBODIMENTS OF THE INVENTION
    EXAMPLE 1: In a first embodiment of the invention described herein, an optimized design of a first-face or first-surface mirror that maximizes the RS or SWIR is presented in this case for a wide range of angles of incidence of the light simultaneously, in this case assuming standard refraction index values of the dense phases of the materials used (SiO2 and TiO2). The spectral dependence of the refractive index and the assumed absorption coefficient for these calculations are presented in Figure 4. Such a spire is made of a sequence of layers whose composition and thickness is listed in Table 1 of this document. This calculated design was achieved in generation 1001. Figure 5 shows its calculated reflectance at normal incidence. The RS or SWIR values for different angles of incidence are listed in Table 2 of this document and are represented graphically in Figure 6, in which the almost constant RS or SWIR can be observed between angles of incidence of 0 ° and 40 ° , which is one of the most relevant novel properties of the multilayer structures (1) described herein.
    EXAMPLE 2: In a second embodiment of the invention described herein, it is presented
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    in this case an optimized design of a first-face or first-surface mirror that maximizes the RS or SWIR for a wide range of angles of light incidence simultaneously, assuming in this case a very large but realistic refractive index contrast between the two types of layers considered (porous SiO2 and dense TiO2). The spectral dependence of the refractive index and the assumed absorption coefficient for these calculations are presented in Figure 7. Such a mirror is made of a sequence of layers whose composition and thickness are listed in Table 3 of this document. This calculated design was achieved in generation 1001. Figure 8 shows its calculated reflectance at normal incidence. The RS or SWIR values for different angles of incidence are listed in Table 4 and plotted in Figure 9, in which the optimized reflectance can be observed at an angle of incidence of incident light at 25 °, as well as the RS o SWIR almost constant between angles of incidence of 0 ° and 40 °, which is one of the most relevant novel properties of the multilayer structures described in this document.
    EXAMPLE 3: In a third embodiment of the invention it is described how to prepare a second-sided mirror of high solar reflectivity using the sol-gel method to deposit a multi-layer aperiodic structure (1) combined with an evaporation process to deposit a metal layer (3) copper. The design followed, obtained from the optimization calculations described in previous paragraphs, is provided in Table 5 of this document, and was achieved after 162 generations. Two different precursor suspensions were used to create thin films of silicon oxide and titanium oxide by deposition by rotation. For the first, silicon tetraethoxide (0.50 M), hydrochloric acid (10-3 M), water (2.37 M) and ethanol (14.44 M) were used, while for the latter, tetraisopropoxide was used of titanium (0.30 M), nitric acid (5.60-10-3 M), water (0.16 M) and isopropanol (11.78 M). Alternate deposition by spin-coating deposition, followed by thermal stabilization at 600 ° C for 10 seconds of each type of layer, provided a stable multi-layer aperiodic structure (1) that showed a strong reflectance at those frequencies at which Copper, the metal of choice selected for this embodiment, absorbs strongly. After that, a 100 nm copper metal layer (3) was deposited on the multi-layer aperiodic structure (1) to achieve a high intensity reflector for the entire solar spectrum. In Figure 10, a typical secondary electron image (left) and backscattered electron image (right) of a cross section of the multilayer structure are shown, as observed in the scanning electron microscope operating at 5 kV. In this case, 20 layers can be observed. Such a mirror is made of a sequence of layers whose composition and thickness are listed in Table 5 of this document. The copper layer (3) is seen as a thicker shiny layer at the top. In Figure 11, the reflectance of the mirror for the target wavelength range is displayed for both the calculated and experimental multilayer realization, which show a very good concordance throughout the spectral range. The angular dependence of the R.S or SWIR is presented in Figure 12 and the corresponding data is displayed in Table 6.
    EXAMPLE 4: In a fourth embodiment of the invention, it is described how to prepare a first face mirror of high solar reflectivity using only a physical deposition method to construct a structure
    multilayer aperiodica (1). Such a mirror is made of a sequence of layers whose composition and thickness are listed in Table 7 of this document. This calculated design was achieved in generation 1001. On top of the substrate a layer (3) of copper was deposited by cathodic pulverization. Two different targets were used to create thin films of silicon oxide and titanium oxide 5 by cathode spraying. In Figure 13, the reflectance of the mirror for the target wavelength range is displayed for both the calculated and experimental multilayer realization, which shows a very good concordance throughout the spectral range. It has a 94.3% solar reflectivity and demonstrates that the realization of the mirror designs according to the invention is absolutely feasible. The R.S or SWIR values for different angles of incidence are listed in Table 8 and are
    10 graphically depicted in figure 14.
    Throughout examples 1-4 described above and the corresponding tables 1, 3, 5 and 7 of this document, all thickness distributions for the multi-layer aperiodic structure (1), the substrate glass layer (2) are provided ) and the metal layer (3) as average reference values.
    15 However, it has also been found that variations of said values within ± 20% in each layer provide the desired high reflection properties outside the terrestrial solar spectrum absorption bands, and stable RS or SWIR values with respect to the direction of incidence of light.
    BOARDS
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     Cap  Thickness (nm) Material
     one  41 TiO2
     2  70 SiO2
     3  85 TiO2
     4  52 SiO2
     5  49 TiO2
     6  64 SiO2
     7  49 TiO2
     8  93 SiO2
     9  189 TiO2
     10  61 SiO2
     eleven  53 TiO2
     12  94 SiO2
     13  90 TiO2
     14  78 SiO2
     fifteen  66 TiO2
     16  63 SiO2
     17  111 TiO2
     18  80 SiO2
     19  72 TiO2
     twenty  106 SiO2
     twenty-one  225 TiO2
     22  78 SiO2
     2. 3  129 TiO2
     24  87 SiO2
     25  241 TiO2
     26  95 SiO2
     27  149 TiO2
     28  123 SiO2
     29  150 Cu
     30  1.6-10 ° Glass
    Table 1
     Angle (degrees)  R.S or SWIR
     0  0.9726
     5  0.9728
     10  0.9735
     fifteen  0.9734
     twenty  0.9737
     25  0.9741
     30  0.9733
     35  0.9721
     40  0.9701
     Four. Five  0.9664
     fifty  0.9629
     55  0.9575
     60  0.9524
     65  0.9471
     70  0.9424
     75  0.9387
     80  0.9376
     85  0.9430
    Table 2
    Cap
    Thickness (nm)
    Material
     one  40 TiO2
     2  78 SiO2
     3  80 TiO2
     4  54 SiO2
     5  49 TiO2
     6  54 SiO2
     7  50 TiO2
     8  92 SiO2
     9  189 TiO2
     10  78 SiO2
     eleven  57 TiO2
     12  95 SiO2
     13  87 TiO2
     14  77 SiO2
     fifteen  97 TiO2
     16  63 SiO2
     17  103 TiO2
     18  81 SiO2
     19  78 TiO2
     twenty  148 SiO2
     twenty-one  224 TiO2
     22  78 SiO2
     2. 3  126 TiO2
     24  86 SiO2
     25  241 TiO2
     26  117 SiO2
     27  152 TiO2
     28  125 SiO2
     29  150 Cu
     30  1.6-106 Glass
    Table 3
     Angle (degrees)  R.S or SWIR
     0  0.9811
     5  0.9896
     10  0.9901
     fifteen  0.9896
     twenty  0.9896
     25  0.9896
     30  0.9882
     35  0.9873
     40  0.9850
     Four. Five  0.9837
     fifty  0.9819
     55  0.9806
     60  0.9793
     65  0.9778
     70  0.9766
     75  0.9755
     80  0.9749
     85  0.9752
    Table 4
     Cap  Thickness (nm) Material
     one  1-106 Glass
     2  20 TiO2
     3  50 SiO2
     4  30 TiO2
     5  50 SiO2
     6  40 TiO2
     7  65 SiO2
     8  40 TiO2
     9  65 SiO2
     10  50 TiO2
     eleven  65 SiO2
     12  50 TiO2
     13  65 SiO2
     14  110 Cu
    Table 5
     Angle (degrees)  R.S or SWIR
     0  0.936
     5  0.934
     10  0.935
     fifteen  0.933
     twenty  0.932
     25  0.930
     30  0.925
     35  0.923
     40  0.919
     Four. Five  0.913
     fifty  0.910
     55  0.904
     60  0.901
     65  0.897
     70  0.896
     75  0.894
     80  0.894
     85  0.910
    Table 6
     Cap  Thickness (nm) Material
     one  42 TiO2
     2  73 SiO2
     3  84 TiO2
     4  59 SiO2
     5  43 TiO2
     6  67 SiO2
     7  52 TiO2
     8  75 SiO2
     9  196 TiO2
     10  48 SiO2
     eleven  62 TiO2
     12  81 SiO2
     13  97 TiO2
     14  90 SiO2
     fifteen  57 TiO2
     16  55 SiO2
     17  126 TiO2
     18  94 SiO2
     19  64 TiO2
     twenty  98 SiO2
     twenty-one  209 TiO2
     22  67 SiO2
     2. 3  143 TiO2
     24  90 SiO2
     25  229 TiO2
     26  101 SiO2
     27  148 TiO2
     28  120 SiO2
     29  150 Cu
     30  1.6-10 ° Glass
    Table 7
     Angle (degrees)  R.S or SWIR
     0  0.9488
     5  0.9531
     10  0.9504
     fifteen  0.9506
     twenty  0.9635
     25  0.9400
     30  0.9487
     35  0.9447
     40  0.9306
     Four. Five  0.9283
     fifty  0.9303
     55  0.9241
     60  0.9107
     65  0.8970
     70  0.9096
     75  0.9000
     80  0.8966
     85  0.9131
    Table 8
    权利要求:
    Claims (18)
    [1]
    1. Mirror for solar energy applications comprising:
    - a metal layer (3) that has a reflection of at least a first range of
    5 wavelengths within the solar irradiance spectrum and an absorption of at
    minus a second range of wavelengths comprised in said spectrum;
    - a multi-layer aperiodic structure (1) adjacent to the metal layer (3), comprising a plurality of layers of different refractive indices and thicknesses, which has a reflection within the second range of wavelengths in which the layer of
    Adjacent metal (3) has absorption;
    characterized in that the distribution of layers in the multi-layer aperiodic structure (1) is arranged such that the wavelength ranges with minimum reflection in said multi-layer aperiodic structure (1) correspond to wavelength ranges with maximum absorption in the spectrum land solar.
    fifteen
    [2]
    2. Mirror according to the preceding claim, further comprising a substrate layer (2) and / or a protective layer (4) applied to the metal layer (3).
    [3]
    3. Mirror according to any of the preceding claims, wherein the thickness of the layers
    20 forming the multi-layer aperiodic structure (1) is between 1 nm and 1 pm.
    [4]
    4. Mirror according to the previous claim, in which the thickness of the layers that form the structure
    multi-layer aperiodic (1) is between 10 nm and 400 nm.
    25. Mirror according to any of the preceding claims, wherein the number of layers in the
    aperiodic multilayer structure (1) is between 2 and 1000.
    [6]
    6. Mirror according to the previous claim, in which the number of layers in the multi-layer aperiodic structure (1) is between 4 and 200.
    30
    [7]
    7. Mirror according to any of the preceding claims, wherein the multi-layer aperiodic structure (1) is formed by an alternating sequence of two materials of different refractive index.
    35 8. Mirror according to the preceding claim, in which the multi-layer aperiodic structure (1) is
    formed by alternating layers of silicon oxide and titanium oxide or any compound derived therefrom.
    [9]
    9. Mirror according to any of the preceding claims, wherein the metal layer (3)
    40 comprises one or more of the following materials: copper, aluminum, chrome, iron, titanium, nickel,
    cobalt, palladium, rhodium, silver, gold, platinum, or any alloy thereof.
    [10]
    10. Mirror according to any of the preceding claims, wherein the multi-layer aperiodic structure (1) and the metal layer (3) are arranged to form a first-sided mirror.
    5
    [11]
    11. Mirror according to any of claims 1-9, wherein the multi-layer aperiodic structure (1) and the metal layer (3) are arranged to form a second-sided mirror.
    [12]
    12. Mirror according to any of the preceding claims, wherein the lower index layers
    10 refraction within the aperiodic multilayer structure (1) have a porosity value
    between 10% and 95% and the layers with the highest refractive index have a porosity value between 0% and 10%.
    [13]
    13. Mirror according to claim 2, wherein the multi-layer aperiodic structure (1), the layer of
    15 substrate (2) and the metal layer (3) comprise the following composition of materials with a
    average thickness value, in which the thickness of each layer is between ± 20% of said average value:
     Cap  Thickness (nm) Material
     one  41 TiO2
     2  70 SiO2
     3  85 TiO2
     4  52 SiO2
     5  49 TiO2
     6  64 SiO2
     7  49 TiO2
     8  93 SiO2
     9  189 TiO2
     10  61 SiO2
     eleven  53 TiO2
     12  94 SiO2
     13  90 TiO2
     14  78 SiO2
     fifteen  66 TiO2
     16  63 SiO2
     17  111 TiO2
     18  80 SiO2
     19  72 TiO2
     twenty  106 SiO2
     twenty-one  225 TiO2
     22  78 SiO2
     2. 3  129 TiO2
     24  87 SiO2
     25  241 TiO2
     26  95 SiO2
     27  149 TiO2
     28  123 SiO2
     29 (metal)  150 Cu
     30 (substrate)  1.6-106 Glass
    [14]
    14. Mirror according to claim 2, wherein the multi-layer aperiodic structure (1), the substrate layer (2) and the metal layer (3) comprise the following material composition and average thickness value, wherein the thickness of each layer is between ± 20% of said average value:
     Cap  Thickness (nm) Material
     one  40 TiO2
     2  78 SiO2
     3  80 TiO2
     4  54 SiO2
     5  49 TiO2
     6  54 SiO2
     7  50 TiO2
     8  92 SiO2
     9  189 TiO2
     10  78 SiO2
     eleven  57 TiO2
     12  95 SiO2
     13  87 TiO2
     14  77 SiO2
     fifteen  97 TiO2
     16  63 SiO2
     17  103 TiO2
     18  81 SiO2
     19  78 TiO2
     twenty  148 SiO2
     twenty-one  224 TiO2
     22  78 SiO2
     2. 3  126 TiO2
     24  86 SiO2
     25  241 TiO2
     26  117 SiO2
     27  152 TiO2
     28  125 SiO2
     29 (metal)  150 Cu
     30 (substrate)  1.6-106 Glass
    [15]
    15. Mirror according to claim 2, wherein the multi-layer aperiodic structure (1), the substrate layer (2) and the metal layer (3) comprise the following material composition and average thickness value, wherein the thickness of each layer is between ± 20% of said average value:
     Cap  Thickness (nm) Material
     1 (substrate)  1-106 Glass
     2  20 TiO2
     3  50 SiO2
     4  30 TiO2
     5  50 SiO2
     6  40 TiO2
     7  65 SiO2
     8  40 TiO2
     9  65 SiO2
     10  50 TiO2
     eleven  65 SiO2
     12  50 TiO2
     13  65 SiO2
     14 (metal)  110 Cu
    [16]
    16. Mirror according to claim 2, wherein the multi-layer aperiodic structure (1), the substrate layer (2) and the metal layer (3) comprise the following material composition and average thickness value 10, wherein the thickness of each layer is between ± 20% of said layer
    middle value:
     Cap  Thickness (nm) Material
     one  42 TiO2
     2  73 SiO2
     3  84 TiO2
     4  59 SiO2
     5  43 TiO2
     6  67 SiO2
     7  52 TiO2
     8  75 SiO2
     9  196 TiO2
     10  48 SiO2
     eleven  62 TiO2
     12  81 SiO2
     13  97 TiO2
     14  90 SiO2
     fifteen  57 TiO2
     16  55 SiO2
     17  126 TiO2
     18  94 SiO2
     19  64 TiO2
     twenty  98 SiO2
     twenty-one  209 TiO2
     22  67 SiO2
     2. 3  143 TiO2
     24  90 SiO2
     25  229 TiO2
     26  101 SiO2
     27  148 TiO2
     28  120 SiO2
     29 (metal)  150 Cu
     30 (substrate)  1.60-106 Glass
    [17]
    17. Method for manufacturing a mirror for solar energy applications, comprising the steps of:
    deposition of a metal layer (3), which has a reflection of at least a first 5 range of wavelengths within the solar irradiance spectrum and a
    absorption of at least a second range of wavelengths comprised in said spectrum; and a multi-layer aperiodic structure (1) adjacent to the metal layer (3),
    wherein said multi-layer aperiodic structure (1) comprises a plurality of layers
    of different indexes of refraction and thicknesses, which present a reflection within the second range of wavelengths in which the adjacent metal layer (3) has absorption;
    and characterized in that the layers in the multi-layer aperiodic structure (1) are deposited so that the wavelength ranges are made with a minimum reflection
    in said multi-layer aperiodic structure (1) they correspond to wavelength ranges with maximum absorption in the terrestrial solar spectrum.
    [18]
    18. Method according to the preceding claim, wherein the multi-layer aperiodic structure (1) or the layer
    10 metal (3) is deposited on a substrate (2).
    [19]
    19. Method according to the preceding claim, which further comprises depositing a protective layer (4) on the metal layer (3).
    15. Method according to any of claims 17-19, wherein the technique used to
    depositing the layers that form the multi-layer aperiodic structure (1) or depositing the metal layer (3) comprises one or more of the following list: rotation coating (spin-coating), dip coating (dip-coating), Langmuir- Blodgett, chemical deposition techniques in the vapor phase or a physical deposition technique in the vapor phase such as thermal evaporation or cathode spraying.
    [21]
    21. Method according to any of claims 17-20, wherein the arrangement of layers in the multi-layer aperiodic structure (1) is adjusted so that its solar reflectivity is maximized to a predetermined range of angles of light incidence.
    25
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    WO2016083648A1|2016-06-02|
    ES2575527B1|2017-04-11|
    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    GB2499569A|2012-01-24|2013-08-28|David Andrew Johnston|Hybrid metallic-dielectric mirror with high broadband reflectivity.|
    DE102013205671A1|2013-03-28|2014-10-02|Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V.|Solar cell for converting incident radiation into electrical energy with a down conversion layer|CN108613423A|2016-12-02|2018-10-02|北京有色金属研究总院|A kind of high temperature selective solar spectrum absorbing membrane and preparation method thereof|
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