CN111812830A - Polarization insensitive reflective super-surface condenser - Google Patents

Polarization insensitive reflective super-surface condenser Download PDF

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CN111812830A
CN111812830A CN202010775235.3A CN202010775235A CN111812830A CN 111812830 A CN111812830 A CN 111812830A CN 202010775235 A CN202010775235 A CN 202010775235A CN 111812830 A CN111812830 A CN 111812830A
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super
condenser
reflective
phase
response unit
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匡登峰
孔维超
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Nankai University
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    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B19/00—Condensers, e.g. light collectors or similar non-imaging optics
    • G02B19/0033—Condensers, e.g. light collectors or similar non-imaging optics characterised by the use
    • G02B19/0038—Condensers, e.g. light collectors or similar non-imaging optics characterised by the use for use with ambient light
    • G02B19/0042—Condensers, e.g. light collectors or similar non-imaging optics characterised by the use for use with ambient light for use with direct solar radiation
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24S—SOLAR HEAT COLLECTORS; SOLAR HEAT SYSTEMS
    • F24S23/00—Arrangements for concentrating solar-rays for solar heat collectors
    • F24S23/70—Arrangements for concentrating solar-rays for solar heat collectors with reflectors
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/40—Solar thermal energy, e.g. solar towers
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P80/00—Climate change mitigation technologies for sector-wide applications
    • Y02P80/20—Climate change mitigation technologies for sector-wide applications using renewable energy

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Abstract

The invention discloses a polarization insensitive reflective super-surface condenser. The method comprises the following steps: super surface condenser, receiver, liquid working medium entry and export. The design process of the super-surface condenser comprises the following steps: 1. and selecting a reasonable response unit structure according to the design wavelength. 2. And scanning the structural parameters of the response unit by using a time domain finite difference method to realize the maximum transmittance and the 2 pi phase coverage. 3. And calculating the required phase at each position of the super-surface reflection type condenser, and mapping the phase to the structural size of the response unit. 4. And calculating the condensing ratio and the energy utilization rate of the reflective super-surface condenser by using a finite difference time domain method. The reflective super-surface condenser does not need an additional mechanical device to track the incident angle of sunlight, and the high energy utilization rate and the high light condensation ratio of the reflective super-surface condenser are expected to break through the scientific bottleneck of the current high-power light condensation photo-thermal industry.

Description

Polarization insensitive reflective super-surface condenser
Technical Field
The invention relates to the technical field of micro-nano optics and light-gathering photo-thermal power generation, in particular to a polarization-insensitive reflective super-surface condenser.
Background
The solar photo-thermal power generation is a renewable energy power generation technology which utilizes a large-scale array reflecting mirror surface to condense sunlight, collects solar heat energy through a heat exchange device and combines traditional steam circulation to promote turbine power generation. Compared with a photovoltaic power generation system, the reflective solar concentrator has the advantages of high efficiency, low manufacturing cost and the like. The photo-thermal power generation technology mainly comprises the forms of disc type photo-thermal power generation, tower type photo-thermal power generation, groove type photo-thermal power generation, solar hot air flow power generation, solar pool thermal power generation and the like. Traditional reflective concentrators rely on the design of a reflector, and parabolic or fresnel mirrors, which require high efficiency concentration, present processing and maintenance difficulties. An optical super-surface is a two-dimensional device composed of sub-wavelength structures and capable of realizing random modulation of amplitude, phase and polarization of incident light. In recent years, the super surface has been applied to holograms, superlenses, special beam generators, and the like by researchers. The characteristics of high degree of freedom of super-surface regulation, high energy utilization rate and the like are expected to be applied to the field of solar concentrators. The planar super-surface device does not need an additional mechanical device to track the incident angle of sunlight, reduces additional energy consumption and is beneficial to the integration and miniaturization of a system.
Disclosure of Invention
The invention aims to provide a polarization insensitive reflective super-surface condenser, which has the beneficial effects that: a novel, tracking-free, easy-to-assemble planar super-surface concentrator is provided.
In order to achieve the above purpose, the present invention adopts a technical solution to provide a polarization insensitive reflective super-surface condenser. It is characterized by comprising: super surface condenser, receiver, liquid working medium entry and export. The liquid working medium enters the receiver through the inlet, and the super-surface condenser focuses the incident solar tube to the linear receiver to heat the liquid, so that the light heat energy conversion is completed.
The design process of the reflective super-surface condenser comprises the following steps:
step 1, selecting the working wavelength of the super-surface reflection type condenser, and determining the structure and the material of the corresponding response unit according to the wavelength.
And 2, scanning parameters of the response unit by using a finite difference time domain method to realize the highest reflectivity and 2 pi phase coverage.
And 3, calculating the phase required at each position by using a phase formula of the super-surface reflection type condenser, and mapping the phase required at each position to be a structural parameter of the response unit.
And 4, simulating and calculating the condensing ratio of the reflective condenser and the energy distribution of the focal position by using a finite difference time domain method.
The characteristics of the response unit mentioned in step 1 include: the structure of the response unit consists of three parts: substrate material, dielectric nano-pillars and reflective film. The dielectric nano-column is used for modulating the phase, and the material is required to have high refractive index and low extinction coefficient. The material selection of the reflective film should maximize reflectivity.
The parameter scanning process mentioned in step 2 should be performed under the condition of maximizing the reflectivity, and the range of the parameter scanning should satisfy the nyquist sampling theorem and the processing condition.
The dielectric nano-pillar mainly completes the phase mutation through the waveguide effect, so the nano-pillar should be high enough to realize the phase mutation which satisfies the following conditions:
Figure BSA0000215905830000021
wherein λ isdFor the operating wavelength, H (height of the nanopillar) is the propagation distance, neffIs the effective refractive index of the fundamental mode. In addition, the high-order mode can be introduced by the high-height nano-pillars, and the complexity of the design is increased.
The phase formula of the super-surface reflection type condenser in the step 3 is as follows:
Figure BSA0000215905830000022
wherein: λ is the design wavelength, f is the focal length of the super-surface reflection condenser, θ is the incident angle, x and y are the positions of the response units, and x0、y0D is the distance between the response element and the focal point at the condenser plane coordinate.
Drawings
FIG. 1 is a schematic diagram of the working principle of a polarization insensitive reflective super-surface concentrator;
FIG. 2(a) is a schematic perspective view of a response unit employed in the reflective super-surface condenser; FIG. 2(b) is a top view;
FIG. 3 is a graph of response unit phase and reflectivity;
FIG. 4(a) is a schematic view of a super-surface profile; FIG. 4(b) is the intensity of the light field after being reflected by the super-surface condenser; fig. 4(c) is a schematic diagram of the energy distribution at the focal point.
Detailed Description
The invention is described in detail below with reference to the figures and the detailed description.
A polarization insensitive reflective super-surface concentrator as shown in fig. 1 comprises a super-surface concentrator 1, a receiver 2, a liquid working medium inlet 3 and an outlet 4. The liquid working medium enters the receiver through the inlet, and the super-surface condenser focuses the incident solar tube to the linear receiver to heat the liquid, so that the light heat energy conversion is completed. The design process of the super-surface condenser as a key device comprises the following steps:
step 1, selecting the working wavelength of the super-surface reflection type condenser, and determining the structure and the material of the corresponding response unit according to the wavelength.
And 2, scanning parameters of the response unit by using a finite difference time domain method to realize the highest reflectivity and 2 pi phase coverage.
And 3, calculating the phase required at each position by using a phase formula of the super-surface reflection type condenser, and mapping the phase required at each position to be a structural parameter of the response unit.
And 4, simulating and calculating the condensing ratio and the full width at half maximum of the focus of the reflective condenser by using a time domain finite difference method.
The invention is also characterized in that:
the characteristics of the response unit mentioned in step 1 include: the structure of the response unit consists of three parts: substrate material, dielectric nano-pillars and reflective film. The dielectric nano-column is used for modulating the phase, and the material is required to have high refractive index and low extinction coefficient. The material selection of the reflective film should maximize reflectivity.
The parameter scanning process mentioned in step 2 should be performed under the condition of maximizing the reflectivity, and the scanning range should satisfy the nyquist sampling theorem and the processing condition.
The dielectric nano-pillar mainly completes the phase mutation through the waveguide effect, so the nano-pillar should be high enough to realize the phase mutation which satisfies the following conditions:
Figure BSA0000215905830000031
wherein λ is the operating wavelength, H (height of the nanopillar) is the propagation distance, neffIs the effective refractive index of the fundamental mode. In addition, the high-order mode can be introduced by the high-height nano-pillars, and the complexity of the design is increased.
The phase formula of the super-surface reflection type condenser in the step 3 is as follows:
Figure BSA0000215905830000032
wherein: λ is the design wavelength, f is the focal length of the super-surface reflection condenser, θ is the incident angle, x and y are the positions of the response units, and x0、y0D is the distance between the response element and the focal point at the condenser plane coordinate.
Example 1
The operating wavelength of the reflective concentrator is chosen to be 532nm in the visible spectrum, and the structure of the polarization insensitive response unit chosen according to the design wavelength is shown in fig. 2. The response unit is composed of high-refractive-index dielectric nano-pillars 5 (TiO)2) Substrate 6 (SiO)2) And a reflective film 7 (silver). Wherein the substrate and the reflective film are both h in thickness1＝h2At 200nm, the dielectric nanopillars perform phase jump mainly by waveguide effect, so the nanopillars should be high enough to realize phase jump:
Figure BSA0000215905830000033
in addition, the high-order mode can be introduced by the high-height nano-pillars, and the complexity of the design is increased. Thus the height of the nanopillar is set to h3300 nm. The period of the response unit needs to satisfy the Nyquist sampling law and the processing condition, and P is 250 nm.
The response unit only has one variable of the radius r of the nano-pillar, and the variable affects the reflectivity and the phase jump of the response unit. The corresponding reflectivity and phase variation within the radius r epsilon (50, 110) nm are calculated by using a finite difference method in time domain, and a curve is drawn as shown in figure 3.
And calculating the required phase at each position by using a phase formula of the reflective super-surface condenser, and mapping the phase to be the structural parameter of the response unit. The phase formula of the reflective super-surface condenser is as follows:
Figure BSA0000215905830000041
wherein: f is the focal length of the super-surface reflecting condenser, which in this case is chosen to be 5 μm. Theta is the angle of incidence, which in this case is chosen to be 30 deg.. x, y are the positions of the response units, x0、y0The case is chosen to be (5 μm, 0) for the coordinates of the focal point in the plane of the condenser. d is the distance between the response unit and the focal point in the plane coordinates of the condenser. FIG. 4(a) is a schematic view of a super-surface profile; the intensity distribution diagram of the light field after the incident light is reflected by the reflective super-surface condenser is shown in fig. 4(b), and the reflected light is focused at the position of 4.85 μm and is highly matched with the designed focal length. The maximum field strength at the focus reaches 43.2. FIG. 4(c) is the normalized energy distribution of the spot at the focus, resulting in a full width at half maximum of about 456.6nm near the diffraction limit at the focus.

Claims (6)

1. A polarization insensitive reflective super-surface concentrator comprising: super surface condenser, receiver, liquid working medium entry and export. The liquid working medium enters the receiver through the inlet, and the super-surface condenser focuses the incident solar tube to the linear receiver to heat the liquid, so that the light heat energy conversion is completed.
2. A polarization insensitive reflective super-surface concentrator, wherein the design process of the reflective super-surface concentrator comprises the following steps:
step 1, selecting the working wavelength of the super-surface reflection type condenser, and determining the structure and the material of the corresponding response unit according to the wavelength.
And 2, scanning parameters of the response unit by using a finite difference time domain method to realize the highest reflectivity and 2 pi phase coverage.
And 3, calculating the phase required at each position by using a phase formula of the super-surface reflection type condenser, and mapping the phase required at each position to be a structural parameter of the response unit.
And 4, simulating and calculating the condensing ratio of the reflective condenser and the energy distribution of the focal position by using a finite difference time domain method.
3. A polarization insensitive reflective super surface concentrator as claimed in claim 1 wherein the response element referred to in step 1 is characterized by:
the structure of the response unit consists of three parts: substrate material, dielectric nano-pillars and reflective film. The dielectric nano-column is used for modulating the phase, and the material is required to have high refractive index and low extinction coefficient. The material selection of the reflective film should maximize reflectivity.
4. A polarization insensitive reflective super surface concentrator as claimed in claim 1 wherein the parametric scan process referred to in step 2 is performed under conditions to maximize reflectivity and the range of the parametric scan satisfies the nyquist sampling theorem and processing conditions.
5. A polarization insensitive reflective super surface concentrator as claimed in claim 1 wherein the dielectric nanopillar performs phase jumps primarily by waveguide effect, and therefore the nanopillar should be high enough to perform phase jumps that satisfy:
Figure FSA0000215905820000011
wherein λ isdFor the operating wavelength, H (height of the nanopillar) is the propagation distance, neffIs the effective refractive index of the fundamental mode. In addition, the high-order mode can be introduced by the high-height nano-pillars, and the complexity of the design is increased.
6. A polarization insensitive reflective super-surface concentrator as claimed in claim 1 wherein the phase equation for the super-surface reflective concentrator in step 3 is:
Figure FSA0000215905820000012
wherein: λ is the design wavelength, f is the focal length of the super-surface reflection condenser, θ is the incident angle, x and y are the positions of the response units, and x0、y0D is the distance between the response element and the focal point at the condenser plane coordinate.
CN202010775235.3A 2020-08-05 2020-08-05 Polarization insensitive reflective super-surface condenser Pending CN111812830A (en)

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Publication number Priority date Publication date Assignee Title
CN106610144A (en) * 2016-12-07 2017-05-03 桂林电子科技大学 Method for preparing photo-thermal steam by absorbing sunlight through localized surface plasmon resonance (LSPR) of nano material
CN109196387A (en) * 2016-04-05 2019-01-11 哈佛学院院长及董事 Super lens for subwavelength resolution imaging
CN109884808A (en) * 2019-04-18 2019-06-14 中国科学院光电技术研究所 A kind of super surface of off-axis incident Multi-wavelength dispersion regulation based on medium rod structure
CN111213245A (en) * 2017-07-19 2020-05-29 密歇根大学董事会 Integrated microlenses for photovoltaic cells and thermal applications
CN111290063A (en) * 2019-12-23 2020-06-16 南开大学 Complex amplitude modulated medium-metal double-layer super surface

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Publication number Priority date Publication date Assignee Title
CN109196387A (en) * 2016-04-05 2019-01-11 哈佛学院院长及董事 Super lens for subwavelength resolution imaging
CN106610144A (en) * 2016-12-07 2017-05-03 桂林电子科技大学 Method for preparing photo-thermal steam by absorbing sunlight through localized surface plasmon resonance (LSPR) of nano material
CN111213245A (en) * 2017-07-19 2020-05-29 密歇根大学董事会 Integrated microlenses for photovoltaic cells and thermal applications
CN109884808A (en) * 2019-04-18 2019-06-14 中国科学院光电技术研究所 A kind of super surface of off-axis incident Multi-wavelength dispersion regulation based on medium rod structure
CN111290063A (en) * 2019-12-23 2020-06-16 南开大学 Complex amplitude modulated medium-metal double-layer super surface

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