Photoelectric photo-thermal and radiation refrigeration integrated solar power generation system

Abstract

The invention discloses a photoelectric photo-thermal and radiation refrigeration integrated solar power generation system which comprises a photovoltaic cell, a spectrum selective heat collector, a thermoelectric power generation element and a radiation refrigeration coating. The surface of the photovoltaic cell is plated with a photonic crystal film for high transmission lower than the forbidden band wavelength of the photovoltaic cell and high reflection higher than the forbidden band wavelength of the photovoltaic cell; and the spectrum selective heat collector is used for realizing high absorption of the band gap wavelength of the photovoltaic cell to a 2.5 mu m wave band and low emission of other wave bands. The photonic crystal film is plated on the surface of the photovoltaic cell to realize frequency division utilization of solar energy, so that the utilization rate of the solar energy is improved, and the influence on the conversion efficiency due to over-high temperature rise of the photovoltaic cell is avoided; the spectral selective heat collector is arranged to effectively absorb high-wave-band solar energy reflected by the photonic crystal film, and energy is supplied to the thermoelectric power generation element after temperature rise; the radiation refrigeration coating radiates heat to the cosmic space, a cold source is provided, and the thermoelectric power generation efficiency is effectively improved; and energy storage and night power generation are realized through the heat storage bracket.

Description

Technical Field

[0001] The present invention relates to the technical field of solar power generation, and particularly to a solar power generation system integrating photovoltaic-thermal and radiative cooling. Background Art

[0002] Solar energy, as a clean and renewable energy source, has been widely used. Its application methods mainly include photovoltaic-thermal and photovoltaic. In the field of photovoltaic-thermal, solar radiation energy is mainly focused by a concentrator and absorbed and converted into heat energy for heating or power generation. Common types include tower-type, trough-type, and dish-type solar thermal power generation systems. However, solar thermal power generation systems are large in size and low in efficiency. In the field of photovoltaic, the market for crystalline silicon cells has matured, and the efficiency is higher than that of solar thermal power generation systems. However, limited by the Shockley-Queisser efficiency limit of solar power generation, the theoretical maximum efficiency of single-junction cells is still below 33%. As a result, more than 60% of solar energy fails to be utilized and is converted into heat energy, increasing the temperature of the battery and thus reducing the actual conversion efficiency of the photovoltaic cell.

[0003] In the prior art, multi-junction solar cells are used to solve the problem of low conversion efficiency of single-junction solar cells. However, the preparation process of multi-junction cells is complex and the cost is high, which limits the application of solar cells. Therefore, it is of great significance to research and develop a high-efficiency solar power generation system based on single-junction cells. Summary of the Invention

[0004] In view of the deficiencies in the prior art, the present invention provides a solar power generation system integrating photovoltaic-thermal and radiative cooling. By setting a photonic crystal thin film on the surface of the photovoltaic cell, solar energy is frequency-divided for comprehensive utilization of photovoltaic-thermal and photovoltaic. The high-energy part of the short wave is directly supplied to the photovoltaic cell for power generation, and the long-wave energy that cannot be utilized by the photovoltaic cell is reflected and supplied to the thermoelectric power generation module, realizing the cascade utilization of solar energy and improving the utilization rate of solar energy.

[0005] To solve the above technical problems, the present invention provides a solar power generation system integrating photovoltaic-thermal and radiative cooling, including a parabolic photovoltaic cell, and a spectral selective collector, a thermoelectric power generation element, and a radiative cooling coating sequentially stacked in a direction away from the photovoltaic cell. The focus of the photovoltaic cell is located on the spectral selective collector;

[0006] A photonic crystal thin film is plated on the surface of the photovoltaic cell to frequency-divide the utilization of solar energy, for high transmission of wavelengths lower than the bandgap wavelength of the photovoltaic cell and high reflection of wavelengths higher than the bandgap wavelength of the photovoltaic cell; the spectral selective collector is used to achieve high absorption in the band from the bandgap wavelength of the photovoltaic cell to 2.5 μm and low emission in the remaining bands.

[0007] The present invention realizes the frequency division utilization of solar energy by plating a photonic crystal thin film on the surface of a photovoltaic cell. The short-wave solar energy that can be utilized by the photovoltaic cell is highly transmitted and directly used for photovoltaic power generation. The long-wave solar energy that cannot be utilized by the photovoltaic cell is highly reflected to a spectral selective collector for thermoelectric power generation, reducing the ineffective energy supply to the photovoltaic cell, improving the utilization rate of solar energy, and at the same time preventing the photovoltaic cell from overheating and affecting the conversion efficiency. A spectral selective collector is provided to effectively absorb the high-band solar energy reflected by the photonic crystal thin film on the premise of reducing its own thermal emission, and supply energy to the thermoelectric power generation element after heating up. Heat is dissipated to outer space through a radiative cooling coating to provide a cold source, effectively improving the thermoelectric power generation efficiency.

[0008] Further, the photonic crystal thin film includes two or more layers selected from the Si layer, SiO2 layer, Ge layer, and NaF layer arranged in a stacked manner and can be repeatedly selected, and the total number of layers is 2-6 layers; preferably, the Si layer has a thickness of 60-100 nm, the SiO2 layer has a thickness of 160-300 nm, the Ge layer has a thickness of 50-80 nm, and the NaF layer has a thickness of 170-400 nm.

[0009] Further, the spectral selective collector includes two or more layers selected from the Mo layer, W layer, HfO2 layer, and Al2O3 layer arranged in a stacked manner and can be repeatedly selected, and the total number of layers is 2-8 layers; preferably, the Mo layer has a thickness of 10-30 nm, the W layer has a thickness of 20-50 nm, the HfO2 layer has a thickness of 70-100 nm, and the Al2O3 layer has a thickness of 80-120 nm.

[0010] Further, the selection of the stacked materials and thicknesses of the spectral selective collector and the photonic crystal thin film is designed based on the target spectrum through the transfer matrix method combined with the Bayesian optimization algorithm. Specifically:

[0011] (1) Detect the local solar radiation spectrum to determine the target spectrum;

[0012] (2) Define the ranges of the number of stacked layers, thickness, incident wavelength, and angle parameters, and input the optical constants of the material system to be determined;

[0013] (3) Construct a transfer matrix, calculate the spectral transmittance, reflectance, and emissivity of the material system to be determined, calculate the deviation between the spectrum of the current system and the target spectrum, and feedback the deviation and correct the weights through a backward transmission neural network;

[0014] (4) Use the Bayesian optimization algorithm to find the best material system and the stacked combination of thickness dimensions.

[0015] Furthermore, the radiative cooling coating includes a base layer and a PDMS layer doped with SiO2 microspheres disposed on the base layer, which is used to achieve high reflectivity in the 0.25 - 2.5 μm band and high emissivity in the 8 - 14 μm band. Preferably, the radius of the SiO2 microspheres is 0.5 - 1 μm.

[0016] Furthermore, the material of the base layer is silver or barium sulfate.

[0017] Furthermore, it also includes a heat storage bracket for supporting the photovoltaic cell and storing heat.

[0018] Furthermore, the heat storage bracket is sequentially provided with a phase change material layer, a steel frame structure layer, and a heat insulation material layer from the center to the outside; preferably, the phase change material layer is paraffin, and the heat insulation material layer is quartz wool or silica aerogel.

[0019] The heat insulation material layer is connected to the thermoelectric power generation element through a heat conduction tube, stores and absorbs the solar energy that the photovoltaic cell fails to convert into electricity through the heat insulation material, and transmits it to the thermoelectric power generation element.

[0020] Furthermore, a connection valve is provided at the connection between the heat insulation material layer and the heat conduction tube for controlling the opening and closing of the connection between the heat insulation material layer and the heat conduction tube.

[0021] Furthermore, the connection valve is electrically connected to a photosensitive sensor. The photosensitive sensor is installed on the photovoltaic cell. When the photosensitive sensor detects sunlight during the day, the connection valve disconnects the heat storage of the phase change material layer. At night, the connection valve opens to supply energy to the thermoelectric power generation element for power generation, further improving the utilization rate of solar energy and achieving night power generation.

[0022] Furthermore, the photovoltaic cell is composed of a number of regular hexagonal battery units spliced together for easy light concentration. The battery units are connected by soldering to form a stable electrical connection path, adopting a hybrid mode of series and parallel, which can not only increase the output voltage but also ensure high power generation efficiency under different lighting conditions.

[0023] Advantages of the present invention:

[0024] In the present invention, a photonic crystal thin film is plated on the surface of the photovoltaic cell to achieve frequency - division utilization of solar energy. It has high transmittance for short - wave solar energy for photovoltaic cell power generation, and high reflectivity for long - wave solar energy to a spectral selective collector for thermoelectric power generation, reducing the ineffective energy supply to the photovoltaic cell, improving the utilization rate of solar energy, and at the same time avoiding the over - heating of the photovoltaic cell, which affects the conversion efficiency.

[0025] The present invention provides a spectral selective collector, which effectively absorbs high-band solar energy reflected by a photonic crystal thin film on the premise of reducing its own thermal emission, and supplies energy to a thermoelectric power generation element after heating up; and dissipates heat to outer space through a radiative cooling coating to provide a cold source, effectively improving the thermoelectric power generation efficiency.

[0026] The present invention stores the solar energy that cannot be converted into electricity by an absorption photovoltaic cell through a heat storage bracket, and controls the transfer of thermal energy to the thermoelectric power generation element at night through a photosensitive sensor and a connection valve to realize night power generation, and further realizes all-weather power generation of the solar energy system. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions of the present invention, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only the embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0028] Figure 1 is a schematic structural diagram of a solar power generation system integrating photovoltaic-thermal and radiative cooling of the present invention;

[0029] Figure 2 is a sectional view of the heat storage bracket of the present invention;

[0030] Description of reference numerals in the drawings: 1. Photovoltaic cell, 11. Regular hexagonal battery unit, 2. Spectral selective collector, 3. Thermoelectric power generation element, 4. Radiative cooling coating, 5. Photonic crystal thin film, 6. Heat storage bracket, 61. Phase change material layer, 62. Steel frame structure layer, 63. Thermal insulation material layer, 7. Heat conduction pipe, 8. Connection valve, 9. Photosensitive sensor. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0031] The technical solutions of the present invention will be clearly and completely described below in conjunction with specific embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0032] Refer to Figure 1As shown in the figure, this embodiment provides a solar power generation system integrating photovoltaic-thermal and radiative cooling, including a parabolic photovoltaic cell 1, and a spectral selective collector 2, a thermoelectric power generation element 3, and a radiative cooling coating 4 stacked in sequence along the direction away from the photovoltaic cell 1. The focus of the photovoltaic cell 1 is located on the spectral selective collector 2. A photonic crystal thin film 5 is plated on the surface of the photovoltaic cell 1 to perform frequency division utilization of solar energy, for high transmission of wavelengths lower than the bandgap wavelength of the photovoltaic cell 1 and high reflection of wavelengths higher than the bandgap wavelength of the photovoltaic cell 1. The spectral selective collector 2 is used to achieve high absorption in the band from the bandgap wavelength of the photovoltaic cell 1 to 2.5 μm and low emission in the remaining bands. The working principle of the solar power generation system in this embodiment is as follows: Sunlight is incident on the surface of the photovoltaic cell 1, and is subjected to frequency division processing by the photonic crystal thin film 5 coated on the surface of the photovoltaic cell 1. Solar light in the convertible band of the photovoltaic cell 1 passes through for photovoltaic power generation, and the remaining part of the solar energy is reflected to the spectral selective collector 2. The spectral selective collector 2 efficiently absorbs and heats up the reflected solar energy, and the heat energy is transferred to the thermoelectric power generation element 3. A radiative cooling coating 4 is arranged outside it to provide a cold source for the thermoelectric power generation element 3, realizing the photo-thermal-electric conversion of sunlight. Importantly, this part of the energy comes from the ineffective band of the photovoltaic cell 1, which not only reduces the heat dissipation pressure of the photovoltaic cell 1, but also utilizes this part of the heat energy for secondary power generation, improving the solar energy utilization rate and effectively enhancing the power generation efficiency of the system.

[0033] In this embodiment, a photonic crystal thin film 5 is plated on the surface of the photovoltaic cell 1 to achieve frequency division utilization of solar energy. Short-wave solar energy with wavelengths lower than the bandgap wavelength of the photovoltaic cell 1 that can be utilized by the photovoltaic cell 1 is highly transmitted and directly used for power generation by the photovoltaic cell 1. Long-wave solar energy with wavelengths higher than the bandgap wavelength of the photovoltaic cell 1 that cannot be utilized by the photovoltaic cell 1 is highly reflected to the spectral selective collector 2 for thermoelectric power generation, reducing the ineffective energy supply to the photovoltaic cell 1, improving the utilization rate of solar energy, and at the same time avoiding the problem that the ineffective function causes the photovoltaic cell 1 to heat up too high, thereby affecting the conversion efficiency of the photovoltaic cell 1. At the same time, a spectral selective collector 2 is set to effectively absorb the high-band solar energy with wavelengths from the bandgap wavelength of the photovoltaic cell 1 to 2.5 μm reflected by the photonic crystal thin film 5 on the premise of reducing its own thermal emission, and supply energy to the thermoelectric power generation element 3 after heating up. Heat is dissipated to the cosmic space through the radiative cooling coating 4 to provide a cold source, effectively improving the thermoelectric power generation efficiency.

[0034] As a preferred embodiment, the photonic crystal thin film 5 includes two or more layers selected from Si layer, SiO2 layer, Ge layer, and NaF layer arranged in a stack and can be repeatedly selected, and the total number of layers is 2-6 layers; preferably, the Si layer has a thickness of 60-100 nm, the SiO2 layer has a thickness of 160-300 nm, the Ge layer has a thickness of 50-80 nm, and the NaF layer has a thickness of 170-400 nm. The spectral selective collector 2 includes two or more layers selected from Mo layer, W layer, HfO2 layer, and Al2O3 layer arranged in a stack and can be repeatedly selected, and the total number of layers is 2-8 layers; preferably, the Mo layer has a thickness of 10-30 nm, the W layer has a thickness of 20-50 nm, the HfO2 layer has a thickness of 70-100 nm, and the Al2O3 layer has a thickness of 80-120 nm.

[0035] Specifically, the selection of the stack materials and thicknesses of the spectral selective collector 2 and the photonic crystal thin film 5 is designed based on the target spectrum through the transfer matrix method combined with the Bayesian optimization algorithm. Specifically:

[0036] (1) Detect the local solar radiation spectrum and determine the target spectrum;

[0037] (2) Define the ranges of the number of stack layers, thicknesses, incident wavelengths, and angle parameters, and input the optical constants of the material system to be determined;

[0038] (3) Construct a transfer matrix, calculate the spectral transmittance, reflectance, and emissivity of the material system to be determined, calculate the deviation between the spectrum of the current system and the target spectrum, and feedback the deviation through a backward transmission neural network to correct the weights;

[0039] (4) Use the Bayesian optimization algorithm to find the best material system and the stack combination of thickness dimensions.

[0040] As a preferred embodiment, the radiative cooling coating 4 includes a base layer and a PDMS layer doped with SiO2 microspheres disposed on the base layer, which is used to achieve high reflectance in the 0.25-2.5 μm band and high emissivity in the 8-14 μm band. Preferably, the radius of the SiO2 microspheres is 0.5-1 μm; the material of the base layer is silver or barium sulfate.

[0041] As a preferred embodiment, it further includes a heat storage bracket 6 for supporting the photovoltaic cell 1; as Figure 2As shown in the figure, the heat storage bracket 6 is sequentially provided with a phase change material layer 61, a steel frame structure layer 62, and a heat insulation material layer 63 from the center to the outside. Preferably, the phase change material layer 61 is paraffin, and the heat insulation material layer 63 is quartz cotton or silica aerogel. The heat insulation material layer 63 is connected to the thermoelectric power generation element 3 through a heat conduction tube 7, stores and absorbs the solar energy that the photovoltaic cell 1 fails to convert into electricity through the heat insulation material, and transmits it to the thermoelectric power generation element 3. A connection valve 8 is provided at the connection between the heat insulation material layer 61 and the heat conduction tube 7 to control the opening and closing of the connection between the heat insulation material layer 61 and the heat conduction tube 7. The connection valve 8 is electrically connected to a photosensitive sensor 9, and the photosensitive sensor 9 is installed on the photovoltaic cell 1. Given the efficiency limit of single-junction solar cells, even the sunlight in the convertible band of the battery cannot be converted 100%. More than 60% of the energy is converted into heat energy. This part of the heat energy is collected by the phase change material layer 61. When the photosensitive sensor 9 detects sunlight during the day, the connection valve 8 disconnects the heat storage of the phase change material layer 61. At night, the connection valve 8 opens to supply energy to the thermoelectric power generation element 3 for power generation, further improving the solar energy utilization rate and realizing night-time power generation, thus realizing all-weather power generation.

[0042] The performance of the solar power generation system in this embodiment includes three parts, namely: direct power generation of transmitted solar energy, thermoelectric power generation of reflected solar energy in the infrared band, and thermoelectric power generation of the part of energy not converted by the battery at night with radiative cooling. The evaluation method of the overall system is as follows:

[0043]

[0044] In the formula, c is the concentration ratio of the parabolic surface of the photovoltaic cell 1; t daytime is the sunshine duration (h); λ g is the bandgap wavelength of the photovoltaic cell 1; η cell is the efficiency of the photovoltaic cell 1; I solar (λ) is the spectral power density of the incident sunlight; η tc is the power generation efficiency of the thermoelectric power generation element 3 during the day; η nc is the power generation efficiency of the thermoelectric power generation element 3 at night, which is comprehensively affected by the heat energy transmission of the phase change material layer 61 and the heat conduction tube 7.

[0045] As a preferred implementation mode, the photovoltaic cell 1 is composed of a plurality of regular hexagonal battery units 11 spliced together, which is convenient for light concentration. The battery units are connected by soldering to form a stable electrical connection path, and a hybrid mode of series and parallel is adopted, which can not only increase the output voltage but also ensure high power generation efficiency under different lighting conditions.

[0046] In summary, in the present invention, a photonic crystal thin film is plated on the surface of a photovoltaic cell to achieve frequency division utilization of solar energy. The short-wave solar energy is highly transmitted for photovoltaic cell power generation, and the long-wave solar energy is highly reflected to a spectral selective collector for thermoelectric power generation, reducing the ineffective energy supply to the photovoltaic cell, improving the utilization rate of solar energy, and at the same time avoiding the overheating of the photovoltaic cell, which affects the conversion efficiency. A spectral selective collector is provided to effectively absorb the high-band solar energy reflected by the photonic crystal thin film on the premise of reducing its own thermal emission, and supply energy to the thermoelectric power generation element after heating. Heat is dissipated to outer space through a radiative cooling coating to provide a cold source, effectively improving the thermoelectric power generation efficiency. The solar energy that cannot be converted and generated by the photovoltaic cell is stored through a heat storage bracket, and its heat energy is controlled to be transmitted to the thermoelectric power generation element at night through a photosensitive sensor and a connection valve to achieve night power generation, and thus achieve all-weather power generation of the solar energy system.

[0047] The present invention has been described in detail above in combination with specific embodiments and exemplary examples. However, these descriptions should not be construed as limiting the present invention. Those skilled in the art understand that without departing from the spirit and scope of the present invention, various equivalent substitutions, modifications or improvements can be made to the technical solutions of the present invention and their implementation manners, and all of these fall within the scope of the present invention. The protection scope of the present invention is subject to the appended claims.

Claims

1. A solar power generation system integrating photovoltaic-thermal and radiative cooling, characterized in that, A photovoltaic cell including a paraboloid, and a spectral selective collector, a thermoelectric power generation element, and a radiative cooling coating sequentially stacked in a direction away from the photovoltaic cell, wherein the focus of the photovoltaic cell is located on the spectral selective collector; A photon crystal film is plated on the surface of the photovoltaic cell for high transmission of wavelengths lower than the bandgap wavelength of the photovoltaic cell and high reflection of wavelengths higher than the bandgap wavelength of the photovoltaic cell; the spectral selective collector is used to achieve high absorption in the band from the bandgap wavelength of the photovoltaic cell to 2.5 μm.

2. The solar power generation system integrating photovoltaic-thermal and radiative cooling as claimed in claim 1, wherein The photon crystal film includes two or more layers of Si layer, SiO2 layer, Ge layer, NaF layer stacked.

3. The solar power generation system integrating optoelectronic-photothermal and radiative cooling as claimed in claim 1, wherein The spectral selective collector includes two or more layers of Mo layer, W layer, HfO2 layer, Al2O3 layer stacked.

4. The solar power generation system integrating optoelectronic-photothermal and radiative cooling as claimed in claim 1, wherein The radiative cooling coating includes a base layer and a PDMS layer doped with SiO2 microspheres provided on the base layer, and is used to achieve high reflection in the band of 0.25 - 2.5 μm and high emission in the band of 8 - 14 μm.

5. The solar power generation system integrating optoelectronic-photothermal and radiative cooling as claimed in claim 4, wherein The material of the base layer is silver or barium sulfate.

6. The solar power generation system integrating optoelectronic-photothermal and radiative cooling as claimed in claim 1, wherein, It further includes a heat storage support for supporting the photovoltaic cell and storing heat.

7. The solar power generation system integrating photovoltaic, photothermal and radiative cooling as claimed in claim 6, characterized in that, The heat storage support is sequentially provided with a phase change material layer, a steel frame structure layer, and a heat insulation material layer from the center to the outside; The heat insulation material layer is connected to the thermoelectric power generation element through a heat conduction tube.

8. The solar power generation system integrating photovoltaic-thermal and radiative cooling as claimed in claim 7, wherein A connection valve is provided at the connection between the heat insulation material layer and the heat conduction tube for controlling the opening and closing of the connection between the heat insulation material layer and the heat conduction tube.

9. The solar power generation system integrating photoelectric, photothermal and radiative cooling as claimed in claim 8, wherein, The connection valve is electrically connected to a photosensitive sensor, and the photosensitive sensor is installed on the photovoltaic cell.

10. The solar power generation system integrating optoelectronic-photothermal and radiative cooling as claimed in claim 1, wherein, The photovoltaic cell is composed of a plurality of regular hexagonal battery units spliced together.

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