Solar three-level concentrating frequency division photovoltaic-thermophotovoltaic complementary conversion system

Abstract

The invention, which belongs to the technical field of new energy preparation, discloses a solar three-stage light-condensing and frequency-dividing photovoltaic-thermophotovoltaic complementary conversion system comprising a three-stage light-condensing and frequency-dividing subsystem, a photovoltaic power generation subsystem, a radiation absorption regulation and control cavity and a thermophotovoltaic subsystem. The three-stage light-focusing and frequency-dividing subsystem is used for focusing the solar spectrum to a frequency-dividing assembly according to different multiples, the frequency-dividing assembly is used for transmitting the spectrum of the wave band capable of being utilized by the photovoltaic cell to the photovoltaic cell below for power generation, and the residual spectrum is reflected and converged into the radiation absorption regulation and control cavity by the frequency-dividing assembly; the radiation absorption regulation and control cavity absorbs heat and then transfers the heat to the emitter for spectrum reforming, and the emitter radiates a double-narrow-band spectrum to be matched with the thermophotovoltaic subsystem for power generation. Decoupling of photovoltaic and thermophotovoltaic conversion condensation times is achieved through three-stage condensation frequency division, energy conversion modes of all stages are matched with energy quality, the solar full-spectrum conversion efficiency is effectively improved, and the device has important value for promoting development of a solar comprehensive utilization technology.

Description

Technical Field

[0001] This invention belongs to the field of new energy preparation technology, specifically relating to a three-stage solar concentrating frequency division photovoltaic-thermal photovoltaic complementary conversion system. Background Technology

[0002] As one of the main forms of clean energy, the efficient utilization of solar energy is of significant strategic importance in the context of achieving carbon neutrality. Solar energy is primarily radiative, and since the discovery of the photoelectric effect in the last century, photovoltaic (PV) cells have been the main technological means of solar energy utilization. Traditional PV power generation technology mainly utilizes the visible light band, failing to effectively convert infrared energy. This not only results in radiative energy loss but also leads to increased cell temperature and decreased efficiency due to thermal effects. Therefore, the spectral mismatch problem restricts further improvements in PV system performance. Furthermore, traditional concentrated photovoltaic (CPV) power generation technology generally increases the total radiative energy received by the system by increasing the concentration factor. However, when the concentration factor is too high, the energy density received by the PV cells becomes excessively high, leading to excessive temperature rise, affecting system efficiency, and even damaging the PV cells.

[0003] To improve the overall efficiency of solar energy utilization, thermophotovoltaic technology has received widespread attention in recent years. This technology achieves selective utilization of radiation in specific wavelength bands through spectral renormalization, theoretically boasting high efficiency and the ability to convert energy across the entire spectrum. However, thermophotovoltaic systems typically require high-temperature operating environments, placing stringent demands on concentration conditions and system structure. Furthermore, relying solely on a single technological approach makes it difficult to simultaneously consider the energy quality characteristics of different wavelength bands, thus hindering true full-spectrum cascade utilization.

[0004] Based on this, solar full-spectrum photovoltaic-thermal photovoltaic complementary conversion systems are considered an effective way to achieve efficient utilization of solar energy. These systems separate solar radiation by wavelength using frequency-dividing devices. The usable photovoltaic wavelengths are used to match photovoltaic power generation, while the residual spectrum undergoes high-temperature thermal conversion using thermophotovoltaic technology, thus achieving energy gradient conversion across different energy quality radiation wavelengths and effectively improving system performance. However, in these systems, because the photovoltaic and thermophotovoltaic systems are coupled in the same concentrating frequency-dividing device, their energy reception and proportion are fixed. The allowable operating temperature of photovoltaic cells is often below 85℃, which limits further increases in the system's concentration ratio. Meanwhile, thermophotovoltaics require concentration temperatures above 1000℃ to achieve efficient conversion. There is a contradiction in their requirements for concentration ratio, making it difficult to achieve optimal energy distribution at the same concentration ratio, thus failing to simultaneously meet their respective operating temperature requirements.

[0005] Therefore, there is an urgent need for a new system structure that can achieve efficient conversion of the full spectrum of solar energy under moderate concentration conditions. This structure should be able to decouple the concentration ratio and energy distribution ratio of photovoltaic and thermophotovoltaic systems. This would allow photovoltaic cells to maintain a lower operating temperature at a lower concentration ratio, reducing waste heat generation, while providing the required concentration temperature for the thermophotovoltaic system to achieve efficient energy conversion. This would fully utilize the energy quality of different wavelengths and promote the development of comprehensive solar energy utilization technology. Summary of the Invention

[0006] Based on the advantages and shortcomings of the aforementioned technologies, this invention constructs a three-stage solar concentrating frequency-dividing photovoltaic-thermal photovoltaic complementary conversion system based on the principle of matching the full spectrum of solar energy with energy quality. By utilizing three-stage concentrating modules, three-stage frequency-dividing modules, photovoltaic cells, radiation absorption control cavity, and thermal photovoltaic cells, the system decouples the concentration factor from the energy distribution ratio, matches the energy quality of each stage with the utilization method, and realizes the tiered utilization of the full spectrum of solar energy.

[0007] To achieve the above objectives, the present invention provides a three-stage concentrated photovoltaic-thermal photovoltaic complementary conversion system, which includes a three-stage concentrated frequency division subsystem, a photovoltaic power generation system, a radiation absorption control cavity, and a thermal photovoltaic subsystem.

[0008] The three-stage concentrating frequency division subsystem and the photovoltaic power generation system are arranged circumferentially around the radiation absorption control cavity. The three-stage concentrating frequency division subsystem includes multiple concentrating components and frequency division components. After the incident sunlight is concentrated by the concentrating components at different concentration ratios, it shines on the corresponding frequency division components arranged below it. The geometric centers of each frequency divider are set on the same horizontal plane, and the plane where the frequency divider is located forms a 45° angle with the plane where the concentrator is located. The frequency divider separates solar radiation into the usable band for photovoltaic cells and the remaining bands. The usable band of the photovoltaic cells is transmitted to the photovoltaic power generation system for photoelectric conversion, and the remaining bands are reflected by the frequency divider and then focused into the radiation absorption and control cavity. Emitters are set at the top and bottom of the radiation absorption and control cavity. The radiation absorption and control cavity receives and absorbs the radiation of the remaining bands and then heats the emitters. The thermophotovoltaic subsystem is set in the radiation direction of the emitters. After the emitters reach thermal equilibrium, they radiate energy outward. The thermophotovoltaic subsystem receives the radiation emitted by the emitters and performs photoelectric conversion.

[0009] Preferably, the emitters at the top and bottom of the radiation absorption control cavity both employ selective radiation structures. These selective radiation structures are micro / nano dual-narrowband structures composed of periodic array units, with an array period length ranging from 600 to 700 nm. Each periodic unit includes a liner and a three-layer cylindrical patch structure disposed on the liner. The liner consists of a Ta metal layer and a SiO2 dielectric layer from bottom to top. The three-layer cylindrical patch structure consists of a Ta cylindrical patch, a SiO2 cylindrical patch, and a Ta cylindrical patch from bottom to top. The thickness of the three cylindrical patches ranges from 40 to 60 nm, and their radius ranges from 160 to 200 nm. The radiation spectrum of this micro / nano dual-narrowband structure exhibits dual-narrowband characteristics with wavelength, meaning it includes two separate high-emissivity bands.

[0010] Preferably, the thermophotovoltaic subsystem includes two stacked thermophotovoltaic cells, respectively positioned above the emitter at the top and below the emitter at the bottom of the radiation absorption control cavity. Each stacked thermophotovoltaic cell is composed of an upper GaSb cell and a lower InGaAsSb cell, with the GaSb cell facing the emitter. When receiving dual-narrowband radiation emitted by the emitter, the upper GaSb cell absorbs and converts radiation in the 500-800 nm wavelength range, while the unabsorbed radiation is transmitted to the lower InGaAsSb cell, which further converts the radiation in the 1200-2200 nm wavelength range.

[0011] Preferably, the radiation absorption control cavity further includes a light-collecting window, a radiation absorption cavity, and a heat insulation layer; wherein, the radiation absorption cavity is the heat-absorbing structure of the radiation absorption control cavity, and is a hollow cylindrical structure with an absorption coating on the inner wall; three light-collecting windows are evenly distributed circumferentially on the side wall of the radiation absorption cavity, and are used to guide the light beam reflected by the frequency division component into the interior of the radiation absorption cavity and irradiate the absorption coating; a heat insulation layer is used on the outside of the radiation absorption cavity to reduce heat loss.

[0012] Preferably, the three-stage concentrating frequency division subsystem includes a first-stage concentrating component and its corresponding first-stage frequency division component, a second-stage concentrating component and its corresponding second-stage frequency division component, and a third-stage concentrating component and its corresponding third-stage frequency division component; the photovoltaic power generation system includes a first-stage photovoltaic cell disposed below the first-stage frequency division component, a second-stage photovoltaic cell disposed below the second-stage frequency division component, and a third-stage photovoltaic cell disposed below the third-stage frequency division component.

[0013] Preferably, the focusing power of the first-stage focusing component ranges from 300 to 600, the focusing power of the second-stage focusing component ranges from 200 to 300, and the focusing power of the third-stage focusing component ranges from 50 to 200; all levels of focusing components are Fresnel lenses. The transmission band of the first-stage frequency divider is 400~700 nm, the transmission band of the second-stage frequency divider is 500~900 nm, and the transmission band of the third-stage frequency divider is 550~1050 nm.

[0014] Preferably, the first-stage photovoltaic cell is a gallium arsenide (GaAs) photovoltaic cell, and the second-stage and third-stage photovoltaic cells are silicon photovoltaic cells; each stage of photovoltaic cell is horizontally positioned at the focal plane of the concentrator below the corresponding frequency divider, with the front of each stage of photovoltaic cell facing the corresponding frequency divider, and the center of the photovoltaic cell is on the same vertical axis as the center of the corresponding concentrator and frequency divider.

[0015] This invention also provides a method for solar three-stage concentrating frequency-division photovoltaic-thermal photovoltaic complementary conversion based on the aforementioned complementary coupling conversion system, comprising the following steps: Step 1): Determine the specific concentration ratio to be used at each stage based on power generation needs; after the solar vertical incident system, the solar light is focused by the three-stage concentrating components in the three-stage concentrating frequency division subsystem according to different concentration ratios; Step 2): The concentrated light beams irradiate the frequency dividers corresponding to each level of the concentrated light module. Each frequency divider separates the solar radiation into the usable band of the photovoltaic cell and the remaining bands, and transmits the usable band of the photovoltaic cell to the corresponding photovoltaic power generation system below it for power conversion. Step 3): Each stage of the frequency division components reflects the spectrum of the remaining band into the radiation absorption modulation cavity; Step 4): The spectrum of the remaining band enters the radiation absorption control cavity, is absorbed and converted into heat energy. The radiation absorption control cavity heats the transmitter through heat conduction. After the transmitter reaches the thermal equilibrium temperature, it radiates a specific band spectrum to the outside, which heats the photovoltaic subsystem for photoelectric conversion.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) Effectively alleviates the problem of spectral mismatch and improves photovoltaic power generation efficiency. This invention uses a three-stage frequency division module to perform spectral separation of solar radiation, transmitting the usable wavelengths of the photovoltaic cell to the photovoltaic cell for power generation, while the remaining wavelengths are reflected and used for subsequent thermo-photovoltaic conversion. By matching the radiation spectrum with the bandgap characteristics of the photovoltaic cell, the unusable wavelengths received by the photovoltaic cell are significantly reduced, thereby reducing the temperature rise of the cell caused by excess spectral absorption, improving the working conditions of the photovoltaic cell, and increasing power generation efficiency and operational stability.

[0017] (2) Multi-stage concentrating and photovoltaic power generation design reduces local energy density and improves system reliability. This invention achieves energy convergence through multi-stage concentrating modules, which greatly reduces the concentration ratio requirement compared to a single-stage concentrating system. At the same time, multi-stage photovoltaic cells receive the concentrated beam transmitted from the corresponding frequency-dividing modules. The three-stage photovoltaic structure increases the total radiation received by the system while avoiding the battery overheating problem caused by excessively high energy density at the concentrating focal point under extremely high concentration ratio conditions, effectively reducing the battery heat load and minimizing performance degradation and failure risk. By designing matching frequency-dividing bands for different concentration ratios and selecting photovoltaic cell types suitable for concentrating operation under high concentration conditions, an optimized balance between photovoltaic cell temperature and operating efficiency can be achieved.

[0018] (3) Decoupling of the photovoltaic and thermophotovoltaic subsystems in terms of concentration ratio and energy distribution. In traditional single-stage concentrating frequency-dividing photovoltaic-thermal photovoltaic systems, photovoltaic cells and thermophotovoltaic cells usually share the same concentrating frequency-dividing path, and their total received energy and distribution ratio are fixed, making it difficult to simultaneously meet the requirements of low-temperature operation of photovoltaic cells and high-temperature operation of thermophotovoltaic cells. This invention introduces a three-stage concentrating frequency-dividing structure, so that each stage of photovoltaic cell only receives a portion of the radiation energy after the corresponding stage of concentrating frequency-dividing, while the radiation energy reflected after each stage of frequency-dividing is uniformly converged to the thermophotovoltaic conversion subsystem, thereby enabling the thermophotovoltaic subsystem to obtain a multiple of energy input. This structure ensures both low-temperature operation of photovoltaic cells and provides high-temperature conditions for thermophotovoltaic conversion, achieving effective decoupling of the photovoltaic subsystem and the thermophotovoltaic subsystem in terms of concentration ratio and energy distribution ratio. Compared to single-stage concentrating frequency division systems, this invention flexibly controls the energy distribution relationship by adjusting the concentration ratio of each stage, thereby improving the overall power generation performance. At the same time, the three-stage concentrating design enables the superposition and utilization of radiant energy, effectively reducing the system concentration ratio while achieving an equivalent high concentration effect, further enhancing the scalability and practical value of the system in large-area power plants.

[0019] (4) The technical route of multi-stage focusing followed by multi-stage frequency division reduces system costs and facilitates large-scale design. This invention focuses the light first, causing the incident beam to shrink significantly before entering the frequency division component, thereby greatly reducing the effective area of ​​the required frequency division component while achieving the same energy distribution effect. In the solar photovoltaic-thermal photovoltaic technology route of frequency division followed by focusing, since the thermal photovoltaic subsystem needs to operate under high temperature conditions, its radiation receiving area must be comparable to the area of ​​the frequency division film. The large-area frequency division film structure not only increases material and manufacturing costs, but is also prone to aging or damage under long-term outdoor operation, increasing the difficulty of system maintenance and operating costs. This invention significantly reduces the material consumption and manufacturing process cost of the frequency division film, while reducing the outdoor exposure area of ​​the frequency division component, which is beneficial to improving the long-term operational reliability and environmental adaptability of the system, and is especially suitable for large-scale engineering applications.

[0020] (5) Achieve efficient tiered utilization of solar full-spectrum energy and improve the overall energy efficiency of the system. This invention designs a three-stage solar concentrating frequency-dividing photovoltaic-thermal photovoltaic complementary conversion system, which allocates the energy quality of each band of the solar spectrum according to the energy utilization needs of each stage, thereby achieving efficient tiered utilization of solar full-spectrum energy and significantly improving the comprehensive utilization efficiency of solar energy. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of a three-stage concentrated photovoltaic-thermal photovoltaic complementary conversion system.

[0022] Figure 2 This is a three-dimensional schematic diagram and a cross-sectional schematic diagram of the radiation absorption control cavity.

[0023] Figure 3 This is a longitudinal cross-sectional schematic diagram of the radiation absorption control cavity and the thermophotovoltaic subsystem.

[0024] Figure 4 This is a schematic diagram of the periodic array structure and a single periodic unit structure of a micro / nano dual narrowband emitter.

[0025] Figure 5 The graph shows the spectral emissivity of the micro / nano dual narrowband emitter and the external quantum efficiency of GaSb and InGaAsSb thermophotovoltaic cells.

[0026] Among them, 1a-first-stage concentrating module, 1b-second-stage concentrating module, 1c-third-stage concentrating module, 2a-first-stage frequency divider module, 2b-second-stage frequency divider module, 2c-third-stage frequency divider module, 3a-first-stage photovoltaic cell, 3b-second-stage photovoltaic cell, 3c-third-stage photovoltaic cell, 4-radiation absorption control cavity, 5-top thermal photovoltaic cell, 5'-bottom thermal photovoltaic cell, 6-top emitter, 6'-bottom emitter, 7-light-collecting window, 8-radiation absorption cavity, 9-insulation layer, 10-outer shell, 11-upper-layer thermal photovoltaic cell, 12-lower-layer thermal photovoltaic cell. Detailed Implementation

[0027] To better understand the technical solutions of this application, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this invention and are intended to explain the inventive concept. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this invention.

[0028] Unless otherwise expressly specified and limited, the terms “first level,” “second level,” “third level,” etc., used in the description are for descriptive purposes only, in order to distinguish similar components or devices with different purposes and functions, and shall not be construed as indicating or implying relative importance or implicitly specifying the technical features indicated.

[0029] like Figure 1 As shown, this invention provides a three-stage concentrated photovoltaic-thermal photovoltaic complementary conversion system, comprising a three-stage concentrated frequency division subsystem, a photovoltaic electron generation system, a radiation absorption control cavity, and a thermal photovoltaic subsystem. Through the three-stage concentrated frequency division design, the concentration ratios of photovoltaic and thermal photovoltaic conversions are decoupled, allowing solar radiation of different energy qualities to be matched with corresponding energy conversion methods, thereby improving the comprehensive utilization efficiency of the entire solar spectrum. The three-stage concentrated frequency division subsystem includes a first-stage concentrator 1a and a corresponding first-stage frequency division 2a, a second-stage concentrator 1b and a corresponding second-stage frequency division 2b, and a third-stage concentrator 1c and a corresponding third-stage frequency division 2c. The photovoltaic electron generation system includes a first-stage photovoltaic cell 3a, a second-stage photovoltaic cell 3b, and a third-stage photovoltaic cell 3c, respectively corresponding to the three-stage concentrated frequency division subsystem. In this embodiment, the three-stage concentrated frequency division subsystem and the photovoltaic electron generation system are uniformly arranged around the radiation absorption control cavity in a 4-dimensional circumferential direction.

[0030] The first-stage focusing component 1a, the second-stage focusing component 1b, and the third-stage focusing component 1c are arranged horizontally on the upper layer of the system. The first-stage focusing component 1a has the highest focusing power, which ranges from 300 to 600 in this embodiment; the second-stage focusing component 1b has a focusing power less than or equal to that of the first-stage focusing component 1a, which ranges from 200 to 300 in this embodiment; and the third-stage focusing component 1c has a focusing power less than or equal to that of the second-stage focusing component 1b, which ranges from 50 to 200 in this embodiment. Preferably, all the above-mentioned focusing components have the same focal length, and their structure is preferably a Fresnel-type focusing structure to achieve a compact system structure and controllable cost.

[0031] Each stage of the frequency divider separates solar radiation into the wavelengths usable by the photovoltaic cells and the remaining wavelengths. The geometric centers of the first-stage frequency divider 2a, the second-stage frequency divider 2b, and the third-stage frequency divider 2c are respectively located on the same horizontal plane directly below the corresponding concentrator, ensuring that the concentrated light spot received by each frequency divider is located at its geometric center. The plane containing the frequency divider forms a 45° angle with the plane containing the concentrator, thus creating a 90° angle between the transmitted and reflected beams after passing through the frequency divider, with the reflected beam pointing inwards into the system. The side length of each frequency divider is greater than the diameter of the concentrated light spot on its surface to ensure complete reception of the concentrated light beam.

[0032] The optical characteristics of the frequency divider are designed according to the spectral response characteristics of the photovoltaic cell it is matched with, so that the transmission spectrum matches the high response band of the corresponding photovoltaic cell, thereby reducing the waste heat generation of the photovoltaic cell and improving the power generation efficiency.

[0033] The frequency division component is a micro / nano interference frequency division thin film, formed by alternately depositing Na3AlF6, HfO2, and Ta2O5 materials on a 1 mm thick high-transmittance float glass substrate. To meet different transmission band requirements, the spectral control performance of the frequency division thin film structure is first numerically simulated and optimized using the transfer matrix method. Then, the thin film is prepared using magnetron sputtering, atomic layer deposition, or chemical vapor deposition. The spectral transmittance and reflectance of the prepared thin film are tested and compared with the simulation results. Based on the test results, the thin film structural parameters are iteratively optimized to obtain a frequency division thin film with the target spectral selectivity.

[0034] In this embodiment, the first-stage frequency divider component 2a has a four-layer thin-film structure, consisting of, from top to bottom: a 29 nm thick Ta₂O₅ layer, a 45 nm thick HfO₂ layer, an 80 nm thick Na₃AlF₆ layer, and a 60 nm thick Ta₂O₅ layer. This frequency divider component exhibits an average spectral transmittance higher than 92% in the 400–700 nm wavelength band and an average spectral reflectance higher than 86% in other wavelength bands.

[0035] In this embodiment, the second-stage frequency divider component 2b has a five-layer thin-film structure. From top to bottom, the five thin films are: a 4 nm thick Na3AlF6 layer, a 72 nm thick Ta2O5 layer, a 118 nm thick Na3AlF6 layer, an 80 nm thick Ta2O5 layer, and a 220 nm thick Na3AlF6 layer. This frequency divider component exhibits an average spectral transmittance higher than 90% in the 500–900 nm wavelength band and an average spectral reflectance higher than 83% in the remaining wavelength bands.

[0036] In this embodiment, the third-stage frequency divider component 2c has an eight-layer thin-film structure. From top to bottom, the eight thin films are: a 125 nm thick Ta₂O₅ layer, a 200 nm thick Na₃AlF₆ layer, a 170 nm thick Ta₂O₅ layer, a 600 nm thick Na₃AlF₆ layer, a 150 nm thick Ta₂O₅ layer, a 265 nm thick Na₃AlF₆ layer, a 135 nm thick HfO₂ layer, and an 85 nm thick Na₃AlF₆ layer. This frequency divider component exhibits an average spectral transmittance higher than 88% in the 550–1050 nm wavelength band and an average spectral reflectance higher than 85% in other wavelength bands.

[0037] Compared to conventional frequency-division thin film designs based on SiO2 / TiO2 materials, the Na3AlF6, HfO2, and Ta2O5 composite material system used in this invention exhibits significant advantages in both optical performance and environmental stability. On one hand, Na3AlF6 possesses superior resistance to UV aging and lower light scattering loss, effectively reducing absorption and attenuation in the transmission band. On the other hand, traditional TiO2 is prone to phase transitions at high temperatures (>300 °C), leading to optical performance degradation, and the SiO2 / TiO2 system is also susceptible to aging under strong UV irradiation. In contrast, HfO2 introduced in this invention has a high melting point of approximately 2700 °C and exhibits extremely high thermal stability, while Ta2O5 is a highly stable, high-refractive-index material with stronger resistance to thermal shock. The resulting frequency-division thin film structure can better adapt to radiation-concentrating environments and maintain stable and reliable frequency-division characteristics during long-term outdoor high-temperature operation.

[0038] The first-stage photovoltaic cell 3a, the second-stage photovoltaic cell 3b, and the third-stage photovoltaic cell 3c are respectively positioned directly below the corresponding first-stage frequency divider components 2a, 2b, and 2c, and are all located at the focal plane of their respective concentrator components. The front of each photovoltaic cell faces the corresponding frequency divider component and receives the concentrated light beam transmitted from the frequency divider component (i.e.,...) in a vertical direction. Figure 1 (Among beams 1a, 1b, and 1c). The geometric center of each photovoltaic cell lies on the same vertical axis as the geometric center of its corresponding frequency divider and concentrator, and coincides with the focal point of the corresponding concentrator. The effective light-receiving area of ​​each photovoltaic cell is the same and is larger than the projected area of ​​the corresponding frequency divider, thereby ensuring that the transmitted light beam can be completely received by the photovoltaic cells.

[0039] In this embodiment, the first-stage photovoltaic cell 3a is a GaAs photovoltaic cell suitable for high-concentration conditions, so as to obtain higher photoelectric conversion efficiency under higher concentration ratio conditions; the second-stage photovoltaic cell 3b and the third-stage photovoltaic cell 3c are silicon-based photovoltaic cells, so as to achieve stable and efficient photoelectric conversion under relatively low concentration ratio conditions.

[0040] The radiation absorption control cavity 4 is located inside the system, on the same horizontal plane as each frequency division component, and maintains the same horizontal distance from each frequency division component. It is used to receive the residual band spectrum reflected by the first-stage frequency division component 2a, the second-stage frequency division component 2b, and the third-stage frequency division component 2c (i.e., Figure 1 (Light 2a, Light 2b and Light 2c), and absorb the photon energy of the remaining band spectrum and convert it into a new radiation spectrum.

[0041] like Figure 2As shown, the radiation absorption control cavity 4 includes a top emitter 6, a bottom emitter 6', a light-collecting window 7, a radiation absorption cavity 8, a thermal insulation layer 9, and an outer shell 10. The radiation absorption cavity 8 is a hollow cylindrical structure with three light-collecting windows 7 evenly arranged circumferentially on its sidewalls. These windows are used to receive the residual wavelength spectrum reflected after frequency division by the three-stage focusing and frequency division subsystem. The residual wavelength spectrum is focused by the light-collecting windows 7 and converges at the intersection of the central axis of the light-collecting window 7 and the inner wall of the radiation absorption cavity 8, and then continues to diverge. The light-collecting window 7 is preferably a four-cornered frustum structure, with its inner opening length less than 1 / 16 of the circumference of the inner wall of the radiation absorption cavity 8, in order to minimize the outward radiative heat loss from the cavity and thus improve the radiation absorption efficiency. The angle between the side wall of the light-collecting window and the axial direction of the light-collecting window is no greater than 30°, to ensure that the residual light spectrum entering through the light-collecting window 7 can completely illuminate the inner wall of the radiation absorption cavity 8, avoiding direct light loss caused by the beam directly illuminating other openings.

[0042] The inner wall of the radiation absorption cavity 8 is coated with a high-absorptivity absorption coating for efficiently absorbing residual wavelength spectral radiation energy and converting it into heat energy. The absorption coating consists of an inorganic high-temperature resistant binder, a semiconductor-type heat-absorbing material, functional additives, and a dispersion medium. The inorganic high-temperature resistant binder is selected from phosphate or silicate binding systems, with a mass fraction of 20-40%. The semiconductor-type heat-absorbing material is selected from at least one of silicon carbide, titanium dioxide, zirconium oxide, or tin oxide, with a mass fraction of 30-55%. The semiconductor-type heat-absorbing material efficiently converts residual wavelength spectral radiation energy into heat energy through bandgap absorption and non-radiative recombination of charge carriers. The thickness of the absorption coating is 50-200 μm, and its average absorptivity within the operating wavelength range can reach over 90%, with a reflectivity of less than 20%, maintaining good heat absorption performance and structural stability under high-temperature conditions.

[0043] An insulation layer 9 is provided on the outside of the radiation absorption cavity 8 to reduce heat loss during operation. The insulation layer 9 is composed of an inorganic porous thermal insulation matrix material, infrared reflective filler, inorganic binder, and reinforcing fibers. The inorganic porous thermal insulation matrix material is selected from aerogel powder, expanded perlite, or porous silicate materials, with a mass fraction of 60-85%. The infrared reflective filler is selected from titanium dioxide or zirconium oxide, with a mass fraction of 5-20%. The inorganic binder is selected from silicate or phosphate binders. The reinforcing fibers are selected from ceramic fibers or alumina fibers. The thickness of the insulation layer 9 is 1 / 6 to 1 / 5 of the radius of the radiation absorption cavity 8, effectively reducing heat conduction and radiation losses under high-temperature conditions, thereby improving the overall thermal efficiency of the system. The outer shell 10 serves as a support, wrapping around the outside of the insulation layer 9.

[0044] like Figure 3As shown, the top emitter 6 and the bottom emitter 6' are respectively positioned close to the top and bottom of the radiation absorption cavity 8 to absorb the heat conducted by the radiation absorption cavity 8 and radiate a new spectrum after reaching thermal equilibrium. At thermal equilibrium, the average temperature of the top emitter 6 and the bottom emitter 6' is between 1000 and 1800 °C. A thermophotovoltaic subsystem is positioned directly above the top emitter 6 and directly below the bottom emitter 6' to receive the spectrum radiated by the emitter and perform photoelectric conversion. The thermophotovoltaic subsystem includes two identical stacked thermophotovoltaic cells, where the upper thermophotovoltaic cell 11 is a GaSb cell and the lower thermophotovoltaic cell 12 is an InGaAsSb cell, with the upper thermophotovoltaic cell 11 facing the emitter. The GaSb cell absorbs and converts radiation energy in the 500-800 nm wavelength band, while the InGaAsSb cell further converts the 1200-2200 nm wavelength radiation transmitted by the GaSb cell, thereby improving the overall utilization efficiency of the radiation energy. Preferably, the vertical distance between the stacked thermophotovoltaic cell and the emitter is less than 20 cm to reduce scattering loss during the radiation process.

[0045] The area of ​​the stacked thermophotovoltaic cells is the same as the area of ​​the emitter. The ratio of the total effective area of ​​the photovoltaic cells in the photovoltaic power generation system to the total effective area of ​​the stacked thermophotovoltaic cells in the thermophotovoltaic subsystem is 5 to 9, so that the power generation area of ​​each type of cell matches the radiant energy it receives, thereby achieving a balance between system efficiency and economy.

[0046] To match the spectral response characteristics of GaSb and InGaAsSb cells and further achieve efficient thermophotovoltaic conversion, both the top emitter 6 and the bottom emitter 6' employ selective radiation structures, with their radiation spectra comprising two separate, narrow bands of high emissivity. For example... Figure 4As shown, the selective radiation structure is a micro / nano dual narrowband structure composed of periodic array units. The periodic array units are arranged regularly, with an array period ranging from 600-700 nm. Each periodic unit, from bottom to top, includes a cuboid liner and three cylindrical patch structures disposed thereon. The cuboid liner consists of a Ta metal layer and a SiO2 dielectric layer from bottom to top. The three cylindrical patch structures consist of a Ta cylindrical patch, a SiO2 cylindrical patch, and another Ta cylindrical patch from bottom to top, forming a metal-dielectric-metal composite structure. This structure is used to excite surface plasmon resonance and magnetopolaritonic resonance modes within the structure, thereby achieving high absorption and high emission within a specific wavelength range. The thickness of the three cylindrical patches ranges from 40-60 nm, and their radius ranges from 160-200 nm. Through the above structural design, multiple coupled local resonant modes are formed at different metal-dielectric interfaces. The metal-dielectric structure of the lower liner mainly contributes the lower frequency radiation peaks, while the upper cylindrical patch structure mainly contributes the higher frequency radiation peaks, thus forming a dual-narrowband selective radiation characteristic in the overall thermal radiation spectrum. By adjusting the array period parameters, the thickness of each layer, and the geometry of the cylindrical patches, the position and bandwidth of the dual-narrowband radiation peaks can be effectively controlled. In this embodiment, the thickness of the Ta metal layer in the liner is 100 nm, the thickness of the SiO2 dielectric layer is 30 nm, the thickness of the three cylindrical patches is 45 nm, the radius of the cylindrical patches is 180 nm, and the array period length is 660 nm. The selective radiation structure can be fabricated using magnetron sputtering and micro / nano fabrication processes. Specifically, it includes: sequentially depositing a Ta metal layer and a SiO2 dielectric layer on a substrate surface to obtain a liner; subsequently forming a periodic cylindrical array pattern on the SiO2 dielectric layer surface using photolithography, electron beam lithography, or nanoimprint lithography; then sequentially depositing Ta, SiO2, and Ta thin films; and finally combining this with a lift-off process to form a multilayer cylindrical patch structure. The above fabrication process is mature and reliable, enabling the stable fabrication of the selective radiation structure.

[0047] like Figure 5 The figure shows the spectral emissivity of the micro / nano dual narrowband emitter and the external quantum efficiency curves of GaSb and InGaAsSb thermophotovoltaic cells. As can be seen from the figure, the average emissivity of the micro / nano dual narrowband emitter is higher than 0.8 in the 500-800 nm band and higher than 0.65 in the 1200-2200 nm band. The radiation spectra of the above two narrow bands are matched with the spectral response characteristics of GaSb and InGaAsSb cells, respectively, thus achieving efficient thermophotovoltaic conversion.

[0048] The working principle of a three-stage concentrating frequency-dividing photovoltaic-thermal photovoltaic complementary conversion system provided by this invention is explained below: After sunlight is vertically incident on the system, the sunlight is concentrated by three stages of concentrating components in the three-stage concentrating frequency-dividing subsystem at different multiples. The concentrated beams are respectively irradiated onto the frequency-dividing components corresponding to each stage of the concentrating component. Each stage of the frequency-dividing component transmits the usable bands of the solar spectrum to the corresponding photovoltaic cells below it for power generation. The remaining bands of the solar spectrum are reflected by the frequency-dividing components and converged onto the light-collecting window 7 of the radiation absorption control cavity 4. Then, they continue to diffuse and propagate to the absorption coating in the radiation absorption cavity 8, where they are absorbed and converted into heat energy. The radiation absorption control cavity 4 then conducts the heat to the top emitter 6 and the bottom emitter 6'. After being heated, the emitters emit selective spectral radiation to match the stacked thermal photovoltaic cells for power generation, realizing the reshaping and efficient utilization of the residual light spectrum.

[0049] This invention also provides a complementary conversion method based on the above-mentioned three-stage concentrated photovoltaic-thermal photovoltaic complementary conversion system, comprising the following steps: Step 1): Determine the specific concentration ratio of each stage of the concentrating module based on power generation requirements. After the sunlight is vertically incident on the system, the sunlight is focused according to different concentration ratios by the three-stage concentrating modules in the three-stage concentrating frequency division subsystem.

[0050] Step 2): The concentrated light beams illuminate the frequency dividers corresponding to each level of the concentrated light module. Each frequency divider separates the solar radiation into the wavelengths that the photovoltaic cells can use and the remaining wavelengths, and transmits the wavelengths that the photovoltaic cells can use to the corresponding photovoltaic cells below for power conversion.

[0051] Step 3): The spectrum of the remaining band is reflected by the frequency division components at each stage and converges to the intersection of the central axis of the light-collecting window 7 of the radiation absorption control cavity 4 and the inner wall of the radiation absorption cavity 8, and then continues to diverge and propagate into the radiation absorption cavity 8.

[0052] Step 4): After the remaining wavelength spectrum enters the radiation absorption cavity 8, it is efficiently absorbed by the absorption coating on the inner wall of the radiation absorption cavity 8 and converted into heat energy. The heat energy is then used to heat the top emitter 6 and the bottom emitter 6'. After the emitters reach the thermal equilibrium temperature, they radiate outwards the spectrum in the 500~800 nm and 1200~2200 nm wavelength bands, which are used for photoelectric conversion of the GaSb and InGaAsSb cells in the tandem thermophotovoltaic cells.

[0053] This enables efficient remodeling and utilization of the remaining band spectrum, and the energy of different bands is matched to the most suitable energy conversion unit, thereby improving the full-spectrum energy conversion efficiency.

[0054] Example In a three-stage solar concentrating frequency-division photovoltaic-thermal photovoltaic complementary conversion system, when the concentration ratios of the first-stage concentrating module 1a, the second-stage concentrating module 1b, and the third-stage concentrating module 1c are 500, 300, and 200, respectively, the utilization efficiency of the first-stage photovoltaic cell 3a is 51.62%, the utilization efficiency of the second-stage photovoltaic cell 3b is 48.53%, and the utilization efficiency of the third-stage photovoltaic cell 3c is 47.69%. The average temperature inside the radiation absorption tuning cavity 4 is 1324.7 ℃, and the utilization efficiency of the tandem thermal photovoltaic cells for the received spectrum is 49.20%. The entire system can achieve a solar energy utilization efficiency of 41.85%.

[0055] Comparative Example 1 To demonstrate the technical advantages of this invention, it is compared with a traditional single-stage concentrating frequency-dividing photovoltaic-thermal photovoltaic system. In this system, sunlight is concentrated by a single-stage concentrating module and then focused onto a single-stage frequency-dividing module. The 550-1150 nm wavelength band is transmitted through the frequency-dividing module to the single-stage silicon photovoltaic cell for power generation, while the remaining wavelength band is reflected back to the single-stage thermal photovoltaic subsystem for conversion. When the system's concentration factor is 1000, the photovoltaic cell's utilization efficiency of the received spectrum is 43.41%, the absorber and emitter temperature is 1409.9 °C, the thermal photovoltaic cell's utilization efficiency of the received spectrum is 41.29%, and the overall solar energy utilization efficiency of the system is only 33.36%. Comparative Example 2 Compared with a standalone concentrated photovoltaic power generation system, in which sunlight is concentrated by a single-stage concentrator and then directly irradiates a single-stage silicon photovoltaic cell to generate electricity, the efficiency of the cell is only 10.85% when the concentration factor is 1000, due to the high surface temperature of the cell and the inability to utilize infrared energy.

[0056] As can be seen, the solar three-stage concentrating frequency-dividing photovoltaic-thermal photovoltaic complementary conversion system provided by this invention performs three-stage concentrating, frequency division, and photovoltaic-thermal photovoltaic coupling conversion of the full spectrum of solar radiation energy. This matches the energy quality of different wavelengths with the energy utilization methods at each stage. Photovoltaic cells efficiently convert high-energy-quality wavelengths in the solar spectrum, while the remaining wavelengths are concentrated through three stages to increase energy flux density and undergo spectral reforming before being converted into thermoelectric energy by the thermal photovoltaic cells. The three-stage concentrating design allows the system to provide the high temperatures required for efficient conversion of the thermal photovoltaic cells at a relatively low concentration ratio. This decouples the concentration ratio of the photovoltaic-thermal photovoltaic module from the energy distribution ratio, reducing the concentration ratio requirements of concentrating photovoltaic systems in industrial applications. In small-scale applications, Fresnel lenses can be used for the concentrating structure, while dish or tower concentrating structures are sufficient to provide the required concentration ratio in large-scale commercial applications. Furthermore, high-concentration-ratio photovoltaic-thermal photovoltaic power generation systems can significantly reduce the required battery area, lower system power generation costs, and have relatively lower requirements for processing technology, making them highly economical and commercially valuable in practical engineering applications.

[0057] The above description is merely a preferred embodiment of this application and is not intended to limit the application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application. Therefore, the protection scope of this invention should be determined by the appended claims.

Claims

1. A three-stage concentrated photovoltaic-thermal photovoltaic complementary conversion system, characterized in that: It includes a three-stage concentrating frequency division subsystem, a photovoltaic power generation system, a radiation absorption control cavity, and a thermophotovoltaic subsystem; The three-stage concentrating frequency division subsystem and the photovoltaic power generation system are arranged circumferentially around the radiation absorption control cavity. The three-stage concentrating frequency division subsystem includes multiple concentrating components and frequency division components. After the incident sunlight is concentrated by the concentrating components at different concentration ratios, it shines on the corresponding frequency division components arranged below it. The geometric centers of each frequency divider are set on the same horizontal plane, and the plane where the frequency divider is located forms a 45° angle with the plane where the concentrator is located. The frequency divider separates solar radiation into the usable band for photovoltaic cells and the remaining bands. The usable band of the photovoltaic cells is transmitted to the photovoltaic power generation system for photoelectric conversion, and the remaining bands are reflected by the frequency divider and then focused into the radiation absorption and control cavity. Emitters are set at the top and bottom of the radiation absorption and control cavity. The radiation absorption and control cavity receives and absorbs the radiation of the remaining bands and then heats the emitters. The thermophotovoltaic subsystem is set in the radiation direction of the emitters. After the emitters reach thermal equilibrium, they radiate energy outward. The thermophotovoltaic subsystem receives the radiation emitted by the emitters and performs photoelectric conversion.

2. The solar three-stage concentrating frequency-division photovoltaic-thermal photovoltaic complementary conversion system according to claim 1, characterized in that: The emitters at the top and bottom of the radiation absorption control cavity both employ selective radiation structures. These selective radiation structures are micro / nano dual-narrowband structures composed of periodic array units. The array period length ranges from 600 to 700 nm. Each periodic unit includes a liner and a three-layer cylindrical patch structure disposed on the liner. The liner consists of a Ta metal layer and a SiO2 dielectric layer from bottom to top. The three-layer cylindrical patch structure consists of a Ta cylindrical patch, a SiO2 cylindrical patch, and a Ta cylindrical patch from bottom to top. The thickness of the three cylindrical patches ranges from 40 to 60 nm, and the radius ranges from 160 to 200 nm. The radiation spectrum of this micro / nano dual-narrowband structure exhibits dual-narrowband characteristics with wavelength, that is, it includes two separate high-emissivity bands.

3. The solar three-stage concentrating frequency-division photovoltaic-thermal photovoltaic complementary conversion system according to claim 2, characterized in that: The period length of a single periodic unit in the micro / nano dual narrowband structure is 660 nm; the thickness of the Ta metal layer in the substrate is 100 nm, and the thickness of the SiO2 dielectric layer is 30 nm; the thickness of the three cylindrical patches is 45 nm, and the radius is 180 nm; the micro / nano dual narrowband structure has high emissivity in the narrow bands of 500~800 nm and 1200~2200 nm.

4. The solar three-stage concentrating frequency division photovoltaic-thermal photovoltaic complementary conversion system according to claim 2, characterized in that: The thermophotovoltaic subsystem includes two stacked thermophotovoltaic cells, respectively positioned above the emitter at the top of the radiation absorption control cavity and below the emitter at the bottom. Each stacked thermophotovoltaic cell consists of an upper GaSb cell and a lower InGaAsSb cell, with the GaSb cell facing the emitter. When receiving dual-narrowband radiation emitted by the emitter, the upper GaSb cell absorbs and converts radiation in the 500-800 nm wavelength range, while the unabsorbed radiation is transmitted to the lower InGaAsSb cell, which further converts the radiation in the 1200-2200 nm wavelength range.

5. The solar three-stage concentrating frequency-division photovoltaic-thermal photovoltaic complementary conversion system according to claim 2, characterized in that: The radiation absorption control cavity also includes a light-collecting window, a radiation absorption cavity, and a heat insulation layer; wherein, the radiation absorption cavity is the heat-absorbing structure of the radiation absorption control cavity, which is a hollow cylindrical structure with an absorption coating on the inner wall; three light-collecting windows are evenly distributed on the side wall of the radiation absorption cavity along the circumference, which are used to guide the light beam reflected by the frequency division component into the interior of the radiation absorption cavity and irradiate the absorption coating; a heat insulation layer is used on the outside of the radiation absorption cavity to reduce heat loss.

6. The solar three-stage concentrating frequency-division photovoltaic-thermal photovoltaic complementary conversion system according to claim 5, characterized in that: The light-collecting window is in the shape of a four-cornered truncated pyramid. The opening length of the window on the inner wall of the radiation absorption cavity is less than 1 / 16 of the circumference of the inner wall of the radiation absorption cavity. The angle between the side wall of the light-collecting window and the axis of the light-collecting window is no greater than 30°, so as to ensure that the incoming light beams are all irradiated onto the absorption coating and avoid direct light loss caused by the light beams directly irradiating other light-collecting windows.

7. The solar three-stage concentrating frequency-division photovoltaic-thermal photovoltaic complementary conversion system according to claim 2, characterized in that: The three-stage concentrating frequency division subsystem includes a first-stage concentrating component and its corresponding first-stage frequency division component, a second-stage concentrating component and its corresponding second-stage frequency division component, and a third-stage concentrating component and its corresponding third-stage frequency division component; the photovoltaic power generation system includes a first-stage photovoltaic cell disposed below the first-stage frequency division component, a second-stage photovoltaic cell disposed below the second-stage frequency division component, and a third-stage photovoltaic cell disposed below the third-stage frequency division component.

8. The solar three-stage concentrating frequency division photovoltaic-thermal photovoltaic complementary conversion system according to claim 7, characterized in that: The focusing magnification of the first-stage focusing module ranges from 300 to 600, the focusing magnification of the second-stage focusing module ranges from 200 to 300, and the focusing magnification of the third-stage focusing module ranges from 50 to 200; all levels of focusing modules are Fresnel lenses. The transmission band of the first-stage frequency divider is 400~700 nm, the transmission band of the second-stage frequency divider is 500~900 nm, and the transmission band of the third-stage frequency divider is 550~1050 nm.

9. The solar three-stage concentrating frequency-division photovoltaic-thermal photovoltaic complementary conversion system according to claim 7, characterized in that: The first-stage photovoltaic cell is a gallium arsenide (GaAs) photovoltaic cell, and the second-stage and third-stage photovoltaic cells are silicon photovoltaic cells. Each stage of photovoltaic cell is horizontally positioned below the focal plane of the concentrator below the corresponding frequency divider. The front of each stage of photovoltaic cell faces the corresponding frequency divider, and the center of the photovoltaic cell is on the same vertical axis as the center of the corresponding concentrator and frequency divider.

10. A method for solar three-stage concentrated frequency division photovoltaic-thermal photovoltaic complementary conversion based on the complementary coupling conversion system of claim 2, characterized in that, Includes the following steps: Step 1): Determine the specific concentration ratio to be used at each stage based on power generation needs; after the solar vertical incident system, the solar light is focused by the three-stage concentrating components in the three-stage concentrating frequency division subsystem according to different concentration ratios; Step 2): The concentrated light beams irradiate the frequency dividers corresponding to each level of the concentrated light module. Each frequency divider separates the solar radiation into the usable band of the photovoltaic cell and the remaining bands, and transmits the usable band of the photovoltaic cell to the corresponding photovoltaic power generation system below it for power conversion. Step 3): Each stage of the frequency division components reflects the spectrum of the remaining band into the radiation absorption modulation cavity; Step 4): The spectrum of the remaining band enters the radiation absorption control cavity, is absorbed and converted into heat energy. The radiation absorption control cavity heats the transmitter through heat conduction. After the transmitter reaches the thermal equilibrium temperature, it radiates a specific band spectrum to the outside, which heats the photovoltaic subsystem for photoelectric conversion.

Images