A concentrated solar power spectral re-shaping power generation system matched with high band gap cells

Abstract

The application discloses a concentrated solar spectrum reforming power generation system matched with high band gap battery, which focuses solar radiation energy to the opening of a cavity type absorber through a concentrator, so that the absorber is heated to a high temperature, and converts the solar radiation energy into heat energy; a specially designed selective radiator is closely arranged on the outer wall of the absorber; the radiator can be heated to the same high temperature as the absorber; the high band gap photovoltaic battery is arranged in parallel with the radiator; the radiator with the selective radiation characteristic radiates the reforming spectrum corresponding to the temperature; the heat energy is converted into the reforming radiation energy again; the reforming spectrum and the absorption spectrum of the high band gap battery are well matched; the radiation energy is efficiently converted into electric energy; and a high solar thermal photovoltaic conversion efficiency can be realized. The cavity structure absorber is adopted in the application, and the whole power generation system can realize a solar conversion efficiency of more than 37%, and has important application value.

Description

Technical Field

[0001] This invention belongs to the field of solar energy utilization technology, specifically relating to a concentrated solar spectral reforming power generation system matched with high bandgap batteries. Background Technology

[0002] Solar energy is mainly utilized in two forms: photovoltaic (PV) and solar thermal. PV has a wider range of applications, and its highest experimental efficiency is currently around 27.6%. However, because PV cells can only utilize visible and near-infrared radiation, most of the solar infrared radiation remains unutilized, limiting its efficiency improvement. To overcome these shortcomings, solar-based thermophotovoltaic (TPPV) technology has gained increasing attention in recent years. Compared to traditional solar thermal power generation systems, TPV systems mainly consist of a heat source, a radiator, and photovoltaic cells, significantly simplifying the system structure. It eliminates the need for rotating parts, greatly reducing the equipment's footprint. It absorbs solar radiation and converts it into heat energy through an absorber, which then heats the absorber. The radiator then radiates a spectrum corresponding to the temperature, effectively readjusting the radiation spectrum to match the TPV cells. TPV systems primarily use selective emitters to convert heat energy from solar radiation or fuel into thermal radiation energy that matches the photovoltaic cells, thus achieving highly efficient heat-light-electricity conversion.

[0003] The key to improving the efficiency of solar thermal photovoltaics lies in the conversion of the solar spectrum through selective absorbers and radiators. With the development of micro- and nanotechnology, the construction of micro- and nano-metamaterial selective absorbers / radiators has enabled the effective absorption of the solar spectrum and the reshaping of the radiation spectrum, thus achieving high system efficiency.

[0004] Selective radiation spectra are generally obtained by adjusting selective radiators. In fact, absorbers can achieve effective absorption of the entire solar spectrum through macroscopic structural design, thereby avoiding the use of micro / nano structures and reducing system costs. However, there are currently few macroscopic structural absorber designs for solar thermal photovoltaics. More importantly, most research on selective radiators focuses on matching low-bandgap cells, which have high matching costs; there are no designs for selective radiators for high-bandgap cells such as silicon cells, nor are there any solar thermal photovoltaic utilization systems that combine macroscopic structural absorbers with radiators for high-bandgap spectral cells.

[0005] In fact, the application of high bandgap batteries in solar thermal photovoltaic systems can effectively reduce system costs and increase the system's thermal equilibrium temperature during operation. When combined with high-efficiency selective radiators, it can significantly improve solar energy conversion efficiency. Summary of the Invention

[0006] To address the above shortcomings, this invention proposes a concentrated solar photovoltaic power generation system based on a cavity absorber and a selective radiator matched to a high bandgap battery. This invention utilizes a concentrator, cavity absorber, micro / nanostructured selective radiator, photovoltaic cells, and a cooling system to jointly construct a concentrated solar spectral reforming power generation system matched to a high bandgap battery. This invention specifically provides a micro / nanostructured selective radiator structure for high bandgap batteries. This enables the provision of a suitable radiation spectrum for low-cost high bandgap batteries, ensuring the system's solar energy conversion efficiency.

[0007] To achieve the above objectives, the present invention provides a concentrated solar spectral reforming power generation system matched with high bandgap batteries, comprising a concentrator, a cavity absorber, a selective radiator, a photovoltaic cell, and a cooling system;

[0008] The concentrator is used to collect solar radiation energy and form a point or line of concentrated light to transmit the solar radiation energy to the cavity absorber.

[0009] The cavity absorber is a square column structure with a cylindrical cavity inside; the cavity absorber has an opening for the converged beam from the concentrator, and the opening of the cavity absorber is located at the focal point of the concentrator; the cavity absorber collects the solar radiation energy gathered by the concentrator and converts the solar radiation energy into heat energy.

[0010] The selective radiator is arranged on the outer surface of the cavity absorber and is heated to the same temperature as the cavity absorber. It radiates energy at the corresponding temperature, converting thermal energy into radiant energy, thus realizing the reshaping of solar radiation energy into selective radiation energy.

[0011] The photovoltaic cell is a high bandgap cell, used to absorb selective radiation energy for photovoltaic power generation;

[0012] The cooling system is installed on the back of the high bandgap battery to dissipate heat from the high bandgap battery.

[0013] As a preferred embodiment of the present invention, the condenser is a Fresnel lens, a linear Fresnel condenser, or a grooved parabolic condenser; the positions of the condenser and the cavity absorber are adjusted according to the actual condensation method.

[0014] As a preferred embodiment of the present invention, the cavity absorber uses copper alloy, aluminum alloy or silicon carbide.

[0015] As a preferred embodiment of the present invention, the inner wall surface of the cavity of the cavity absorber is coated with a high-temperature blackbody radiation coating.

[0016] As a preferred embodiment of the present invention, the selective radiator range covers all outer surfaces of the cavity absorber except for the opening of the cavity absorber.

[0017] As a preferred embodiment of the present invention, the selective radiator is a periodic micro / nano structure, comprising a tantalum metal substrate, an intermediate layer of Al2O3 square frame structure, and two parallel tantalum metal nanocubes disposed on the top layer; the length a of the periodic structure of the selective radiator ranges from 200 to 240 nm, the width b of the top tantalum nanocube ranges from 30 to 40 nm, and the height h3 ranges from 30 to 60 nm; the thickness h1 of the tantalum substrate ranges from 80 to 120 nm, and the height h2 of the Al2O3 dielectric ranges from 20 to 50 nm.

[0018] As a preferred embodiment of the present invention, the photovoltaic cell is a silicon or GaAs high bandgap cell with a bandgap energy in the range of 0.9-1.2eV and a spectral cutoff wavelength of about 900-1100nm. The cell is arranged parallel to the surface of the radiator, covering the entire cavity surface except for the opening area, thereby reducing the loss of radiated energy.

[0019] As a preferred embodiment of the present invention, the cooling system is installed on the back of the high bandgap battery and adopts a toothed heat exchanger. The toothed heat exchanger is arranged on the four sides of the back of the battery and extends outward at the four corners, thereby enhancing the heat dissipation capacity and forming a heat sink effect.

[0020] The present invention also provides a method for generating electricity using the above-mentioned concentrated solar power spectral reforming system, comprising the following steps:

[0021] 1) The concentrator gathers solar radiation energy and forms a point or line of focused light to transfer the solar radiation energy to the absorber;

[0022] 2) Solar radiation energy enters the cylindrical cavity of the cavity absorber through the opening of the cavity absorber. The solar radiation energy is absorbed by the cavity absorber and converted into heat energy. Under high temperature conditions, the cavity absorber 3 will generate heat radiation dissipation to the external environment.

[0023] 3) The selective radiator, which is closely attached to the outer surface of the cavity absorber, absorbs the heat radiation dissipation and temperature rise of the cavity absorber. Under thermal equilibrium conditions, it is heated to the same temperature as the cavity absorber and converts the heat energy into radiant energy for selective radiation.

[0024] 4) The high bandgap battery absorbs the energy of selective radiation to achieve thermo-photovoltaic power generation. When the temperature of the high bandgap battery is too high, it is dissipated through a cooling system installed on the back of the high bandgap battery.

[0025] The advantages of this invention compared to existing technologies are:

[0026] Macroscopic cavity-structure absorbers are less expensive than micro / nano-structure absorbers and can achieve absorption of the entire solar spectrum, theoretically improving solar energy conversion efficiency. Due to their structural characteristics, they can effectively reduce heat dissipation to the external environment, achieving highly efficient absorption and utilization of the entire solar spectrum. This design can achieve the same effect as complex micro / nano absorbers, reducing the high costs associated with the design, manufacture, and use of micro / nano-structure absorbers in thermophotovoltaic systems.

[0027] Using high-bandgap solar cells, such as silicon cells, can effectively save costs. Selective radiators for high-bandgap solar cells can achieve higher spectral efficiency and higher thermal equilibrium temperatures, thus improving system efficiency.

[0028] This invention proposes an efficient solar energy conversion pathway based on a cavity absorber, a micro / nanostructure radiator, and a high-bandgap battery, providing reference and inspiration for the application of solar thermal power generation systems. Based on thermodynamic model calculations, analysis reveals that when using a high-bandgap battery and matching it with an ideal selective radiator, the theoretical overall system efficiency can exceed 50%. This demonstrates that, compared to low-bandgap batteries such as GaSb, high-bandgap batteries are theoretically more suitable for solar thermal photovoltaic conversion.

[0029] Using the selective radiator and cavity absorber based on the metamaterial structure of Ta and Al2O3 proposed in this invention, the thermal analysis results for high bandgap batteries show that the solar power generation efficiency of the radiator can approach 40%. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of a concentrated solar thermal photovoltaic system based on a cavity-type absorber and a matching high-bandgap Si cell.

[0031] Figure 2 This is a structural diagram of a selective radiator designed for high bandgap batteries;

[0032] Figure 3 The image shows a side view, radiation pattern, and geometric parameters of a metamaterial selective radiator.

[0033] Figure 4 The system efficiency varies with the concentration ratio when the photovoltaic cells are made of Si, GaSb and InGaSb respectively, and an ideal selective radiator is used (i.e. the radiation spectrum and the cell absorption spectrum are perfectly matched).

[0034] Figure 5 The selective radiation spectrum of the designed metamaterial selective radiator and the absorption spectrum of the Si cell are shown.

[0035] Figure 6The variation of cavity structure temperature, thermophotovoltaic efficiency, and system efficiency with concentration ratio when matching the metamaterial selective radiator designed for the invention with Si cells.

[0036] In the diagram: 1. Solar radiation; 2. Concentrator; 3. Cavity absorber; 4. Selective radiator; 5. High bandgap photovoltaic cell; 6. Cooling system; 001. Solar radiation optical path; 002. Concentrating absorption optical path; 003. Thermal radiation dissipation; 004. Selective reforming radiation spectrum; 4-1. Dielectric Al2O3; 4-2. Tantalum substrate. Detailed Implementation

[0037] The present invention will be further described and illustrated below with reference to specific embodiments. The embodiments described are merely examples of the content of this disclosure and do not limit the scope of the invention. The technical features of each embodiment in the present invention can be combined accordingly, provided that there is no mutual conflict.

[0038] like Figure 1 As shown, this invention provides a concentrated solar power generation system with high bandgap photovoltaic cells, comprising a concentrator 2, a cavity absorber 3, a selective radiator 4, and a high bandgap photovoltaic cell 5 arranged sequentially along the energy flow path. The energy flow path consists of solar radiation optical path 001, 002; concentrated absorption optical path 002; thermal radiation dissipation 003; and selective reforming radiation spectrum 004.

[0039] The concentrator 2 gathers solar radiation energy 1. The solar radiation light path 001 is focused by the concentrator 2 to form a point-like or line-like focused absorption light path 002. The focused absorption light path 002 heats the absorber at the absorption port of the cavity absorber 3 and converts it into heat energy. Under high temperature conditions, the cavity absorber 3 will generate heat radiation dissipation 003 to the external environment. The selective radiator 4 is laid close to the outer wall surface of the cavity absorber 3. Under thermal equilibrium conditions, the two reach the same temperature, that is, the selective radiator 4 heats up under the action of heat radiation dissipation 003. The selective radiator 4 can reshape the blackbody radiation spectrum under its own temperature conditions, that is, perform selective radiation. The average emissivity of the selectively reshaped radiation spectrum 004 in the wavelength range of 380-1000nm is greater than 0.9, which can achieve good matching with the high bandgap photovoltaic cell 5 with a response spectrum range of about 380-1100nm. The radiation energy 004 is efficiently absorbed by the photovoltaic cell 5, thereby realizing thermophotovoltaic power generation.

[0040] like Figure 2The diagram shows the geometry of the periodic structural unit of the metamaterial selective radiator 4. In thermophotovoltaic systems, selective radiators are crucial for achieving spectral modulation. The selective radiator 4 designed in this invention needs to be matched with high-bandgap batteries such as photovoltaic cells 5. Due to the short cutoff wavelength, the radiator needs to operate under high temperature conditions to generate considerable radiant energy. Therefore, in the selection of radiator materials, based on thermal stability considerations, tantalum (Ta) metal with a melting point of 3017℃ is selected as the refractory material for the radiator substrate. Furthermore, Ta metal itself has good narrow-band radiation characteristics at short wavelengths. Adding a dielectric material for adjustment makes it relatively easy to enable the metamaterial structure to possess radiation characteristics matching high-bandgap batteries. The dielectric material used is Al2O3 4-1 with a melting point of 2054℃.

[0041] like Figure 3 As shown, the selective radiator 4 consists of a tantalum substrate 4-2, a square Al2O3 dielectric, and a Ta nanorectangular structure. To obtain an emission spectrum with high matching degree to the battery, the emitter structure was designed based on micro-nano radiation theory, and its structural parameters were adjusted and optimized. The periodic structure has a length of *a*, the Ta nanorectangular structure has a length of *a*, a width of *b*, and a height of *h3*, and the heights of the Ta substrate and the Al2O3 dielectric are *h1* and *h2*, respectively. The geometric parameters of the selective radiator 4 range from: a (200-220 nm), b (30-40) nm, h1 (80-120 nm), h2 (20-50 nm), h3 (30-60 nm). Therefore, when the geometric parameters are selected as a = 220 nm, b = 36 nm, h1 = 100 nm, h2 = 40 nm, and h3 = 40 nm, the selective radiation spectrum of the material is as follows: Figure 5 As shown, the radiation spectrum of the selective radiator 4 designed in this invention and the absorption spectrum of the Si photovoltaic cell have a high degree of matching, which can achieve high TPV efficiency and system efficiency.

[0042] like Figure 1 As shown, the cooling system is installed on the back of the high-gain-range battery and uses a finned heat exchanger. The optimized design involves arranging the heat exchanger parallel to the back of the battery on all four sides, while extending outwards from the four corners to enhance heat dissipation and create a heat sink effect. 6062 aluminum is the preferred material for this system.

[0043] like Figure 4 As shown, in optimizing the system, this invention first analyzes the system efficiency when using Si, GaSb, and InGaSb photovoltaic cells matched with an ideal selective radiator. It can be found that selecting the high-bandgap Si cell achieves higher system efficiency compared to the other two cell types. Therefore, this invention designs a metamaterial selective radiator 4 based on the dielectric Al2O3 4-1 and the metal Ta 4-2 for the high-bandgap silicon photovoltaic cell 5.

[0044] To more clearly illustrate the working process of the above-mentioned power generation system, this embodiment also provides a power generation method for a concentrated solar spectral reforming power generation system, as detailed below:

[0045] 1) A concentrator using a Fresnel lens gathers solar radiation energy to form a point or line of focused light, and transmits the solar radiation energy to a cavity absorber;

[0046] 2) Solar radiation energy enters the cylindrical cavity of the cavity absorber through the opening of the cavity absorber. The solar radiation energy is absorbed by the high-temperature blackbody radiation coating on the inner wall of the cavity absorber and converted into heat energy. Under high temperature conditions, the cavity absorber 3 will generate heat radiation dissipation to the external environment.

[0047] 3) A selective radiator with a periodic micro-nano structure is closely attached to the outer surface of the cavity absorber. The selective radiator absorbs the heat radiation dissipation of the cavity absorber and heats up. Under thermal equilibrium conditions, the selective radiator is heated to the same temperature as the cavity absorber and converts the heat energy into radiation energy for selective radiation.

[0048] 4) Si photovoltaic cells absorb selective radiation energy to achieve thermo-photovoltaic power generation. When the temperature of the Si photovoltaic cells is too high, heat is dissipated through a toothed heat exchanger installed on the back of the Si photovoltaic cells.

[0049] like Figure 6 As shown, the cavity structure temperature, thermo-photovoltaic efficiency, and system efficiency change with the concentration ratio. When the concentration ratio is 250, the cavity structure temperature can reach 2000℃ and the system efficiency is 37.18%, which is much higher than the theoretical efficiency of traditional photovoltaics.

[0050] The above-described embodiments are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. Those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. A concentrated solar spectral reforming power generation system matched with high bandgap batteries, characterized in that, It includes a concentrator (2), a cavity absorber (3), a selective radiator (4), a photovoltaic cell (5), and a cooling system (6); The concentrator (2) is used to collect solar radiation energy and form a point or line concentrator to transmit solar radiation energy to the cavity absorber; The cavity absorber (3) is a square column structure with a cylindrical cavity inside; the cavity absorber has an opening for the beam from the concentrator to converge, and the opening of the cavity absorber (3) is located at the focal point of the concentrator (2); the cavity absorber (3) collects the solar radiation energy gathered by the concentrator and converts the solar radiation energy into heat energy. The cavity inner wall of the cavity absorber (3) is coated with a high-temperature blackbody radiation coating. The selective radiator (4) is arranged on the outer surface of the cavity absorber (3), heated to the same temperature as the cavity absorber (3), and radiates energy corresponding to the temperature, converting thermal energy into radiant energy, thus realizing the reshaping of solar radiation energy into selective radiation energy; the selective radiator (4) is a periodic micro-nano structure, including a tantalum metal substrate, an Al2O3 square frame structure intermediate layer, and two parallel tantalum metal nanocubes set on the top layer; the length of the periodic micro-nano structure of the selective radiator is... a The width of the tantalum metal nanocube is 220 nm. b 36 nm, high h 3 is 40nm; the thickness of the tantalum substrate is... h 1 represents the height of the intermediate layer of the Al2O3 square frame structure, which is 100 nm. h 2 is 40 nm; the selective radiator (4) covers all the outer surfaces of the cavity absorber except for the opening of the cavity absorber; The photovoltaic cell (5) is a high bandgap cell used to absorb selective radiation energy for photovoltaic power generation; Its bandgap energy is in the range of 0.9-1.2 eV, and its spectral cutoff wavelength is in the range of 900-1100nm. The battery is arranged parallel to the surface of the radiator, covering the entire cavity surface except for the opening area, thereby reducing the loss of radiated energy. The cooling system (6) is installed on the back of the high bandgap battery to dissipate heat from the high bandgap battery. The cooling system (6) is installed on the back of the high bandgap battery and adopts a toothed heat exchanger. The toothed heat exchanger is set on the four sides of the back of the battery and extends outward at the four corners to enhance the heat dissipation capacity and form a heat sink effect.

2. The concentrated solar power generation system with high bandgap batteries according to claim 1, characterized in that: The condenser (2) is a Fresnel lens, a linear Fresnel condenser, or a grooved parabolic condenser lens; the positions of the condenser (2) and the cavity absorber (3) are adjusted according to the actual condensation method.

3. The concentrated solar power generation system with high bandgap batteries according to claim 1, characterized in that: The cavity absorber (3) is made of copper alloy, aluminum alloy or silicon carbide.

4. A concentrated solar spectral reforming power generation system with matched high bandgap batteries according to claim 1, characterized in that: The photovoltaic cell (5) is a silicon (Si) or gallium arsenide (GaAs) high bandgap cell.

5. A power generation method for a concentrated solar power spectral reforming system as described in claim 1, characterized in that, Includes the following steps: 1) Concentrator (2) gathers solar radiation energy to form point or line concentrators and transmits solar radiation energy to cavity absorber (3). 2) Solar radiation energy enters the cylindrical cavity of the cavity absorber (3) through the opening of the cavity absorber (3). The solar radiation energy is absorbed by the cavity absorber (3) and converted into heat energy. Under high temperature conditions, the cavity absorber (3) will generate heat radiation dissipation to the external environment. 3) The selective radiator (4) which is closely attached to the outer surface of the cavity absorber (3) absorbs the heat radiation dissipation of the cavity absorber (3) and heats up. Under thermal equilibrium conditions, the selective radiator (4) is heated to the same temperature as the cavity absorber (3) and converts the heat energy into radiation energy for selective radiation. 4) The high bandgap battery absorbs the energy of selective radiation to realize thermo-photovoltaic power generation. When the temperature of the high bandgap battery is too high, it is dissipated through the cooling system (6) installed on the back of the high bandgap battery.

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