A solar frequency division PV / T system coupling micro-nano film and cavity heat collector

Abstract

The application provides a solar frequency division PV / T system coupling a micro-nano film and a cavity type heat collector, which comprises a linear Fresnel lens and a cavity type solar heat collector; the heat collector is provided with a light collecting window in the axial direction, and a micro-nano frequency division film is arranged on the inner wall surface of the heat absorbing cavity opposite to the light collecting window; and a concentrated photovoltaic cell is arranged below the micro-nano frequency division film. Sunlight is concentrated by the top linear Fresnel lens to the light collecting window, is collected in the cylindrical heat absorbing cavity of the heat collector through secondary reflection of the light collecting window, and irradiates on the bottom micro-nano film; the micro-nano film transmits the available wave band in the sunlight spectrum to the photovoltaic cell to generate electricity, and the rest of the wave band light is reflected to the inner wall surface of the heat absorbing cavity and is absorbed by the heat absorbing coating to convert into heat energy and transfer to the working medium layer, so that the step-by-step utilization of the full spectrum of sunlight is realized. The cavity type heat collector structure can effectively reduce the energy dissipation caused by radiation and convection heat transfer, and improve the solar energy utilization efficiency of the system.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of solar energy, in particular to a solar frequency division PV / T system (photovoltaic / thermal system) coupling micro-nano film and cavity collector. BACKGROUND

[0002] With the popularization of clean energy utilization, solar energy as a clean and renewable energy is concerned. At present, the main ways of solar energy utilization are photovoltaic power generation and solar thermal utilization. However, these two separate utilization methods have the following disadvantages: for photovoltaic power generation, solar cell materials can only convert visible light band in the solar spectrum into electrical energy, and the remaining band cannot be utilized, resulting in nearly 40% energy waste, which becomes waste heat and causes the battery temperature to rise and the efficiency to decrease; for solar thermal utilization, it converts the full spectrum of sunlight into low-grade heat energy, resulting in irreversible energy loss of high-grade light energy. Therefore, frequency division utilization of solar energy is an important way to improve the utilization efficiency of solar energy, that is, high-grade energy in solar energy is used for photovoltaic power generation, and low-grade energy is used for solar thermal utilization, coupling the two utilization methods to realize the cascade utilization of solar energy. However, there are several problems in the current solar frequency division utilization technology, including the high temperature resistance of the frequency divider material, the spectral matching of the frequency divider and the photovoltaic cell, and the processing cost of the frequency divider.

[0003] Linear collector is the core component of linear focusing solar thermal power generation technology, which is usually a metal high-temperature heat collecting pipe, generally adopting vacuum collector and cavity collector. The vacuum collector is composed of a metal heat absorbing pipe with selective absorption coating, a concentric glass tube, and a metal-glass sealing connection. The metal heat absorbing pipe in the middle absorbs radiation to heat the internal flowing working medium, and the vacuum environment in the glass tube avoids heat dissipation caused by convection heat transfer. The vacuum collector is configured with a short focal length parabolic concentrator when used for linear focusing solar thermal power generation, with low gravity center and good running stability, but the sealing technology between the glass tube and the metal tube has high requirements, and it is difficult to maintain high vacuum degree in the interlayer for a long time. The cavity collector is coated with a heat absorbing coating on the inner wall. When light is collected into the cylindrical heat absorbing cavity of the collector through the light collecting window twice, it is reflected at the bottom and absorbed by the heat absorbing coating on the inner wall after multiple reflections, and the heat is transferred to the working medium layer outside the cavity wall to heat the flowing working medium. The outermost heat preservation layer can effectively reduce the energy dissipation caused by radiation and convection heat transfer. The cavity collector does not need to maintain a strict vacuum requirement, and avoids the sealing difficulty of glass tube and metal tube in structure, and has a simpler structure, but when used for linear focusing solar thermal power generation, it is configured with a long focal length parabolic concentrator, the gravity center of the heat collecting pipe is high, and the running stability is relatively poor, it is difficult to automatically overturn, and the wind resistance is poor. SUMMARY

[0004] In view of the above existing solar energy utilization problems, the solar frequency division PV / T system coupled with micro-nano film and cavity type collector is designed, high efficient light and heat capturing is realized by using the novel cavity type structure, and the coupling frequency division element is integrated, the high grade energy in solar energy is used for photovoltaic, the low grade energy is used for photo-thermal, the two utilization modes are coupled to realize the step efficient utilization of solar energy.

[0005] The technical scheme adopted by the present application is as follows: a solar frequency division PV / T system coupled with micro-nano film and cavity type collector, which comprises a linear Fresnel lens and a cavity type solar collector; wherein the cavity type solar collector comprises, from the inside to the outside, a cylindrical heat absorption cavity, a working medium layer wrapped outside the heat absorption cavity, and a thermal insulation layer wrapped around the working medium layer; the cavity type solar collector is provided with a light collecting window on the side wall along the axial direction, and a micro-nano frequency division film is arranged on the inner wall surface of the heat absorption cavity opposite to the light collecting window; a concentrating photovoltaic cell is arranged below the micro-nano frequency division film, and a vacuum cavity is arranged between the micro-nano frequency division film and the concentrating photovoltaic cell; and a reflective material is arranged on the wall surface of the vacuum cavity.

[0006] The cavity type solar collector is arranged directly below the central axis of symmetry of the linear Fresnel lens, the light collecting window is opposite to the linear Fresnel lens, the linear Fresnel lens concentrates the incident solar radiation to the light collecting window, and the light collecting window irradiates the micro-nano frequency division film in the heat absorption cavity.

[0007] Further, the linear Fresnel lens and the cavity type solar collector are fixedly connected to keep the relative position therebetween; the system further comprises a support frame system for adjusting the rotation angle of the solar frequency division PV / T system, so that the solar radiation is perpendicular to the linear Fresnel lens.

[0008] According to the embodiment of the present application, the micro-nano film is an optical interference multi-layer frequency division film in which TiO2 and SiO2 are alternately deposited on a transparent substrate, the selective transmission effect of sunlight spectrum is realized by the interference effect generated by the light alternately passing through the film layers with large difference in refractive index, the photovoltaic cell can utilize the wave band part (wavelength of 400nm-900nm) to be transmitted to the photovoltaic cell below to generate electricity, and the remaining wave band is reflected to the inner wall of the surrounding heat absorption cavity.

[0009] According to the preferred embodiment of the present application, the light collecting window is composed of a rectangular channel and a trapezoidal outer expansion secondary reflecting surface, and is arranged at the opening of the collector directly below the linear Fresnel lens to replace a small part of the collector pipeline wall surface, wherein the length of the rectangular channel is consistent with the thickness of the collector.

[0010] According to the preferred embodiment of the present application, the opening angle of the secondary reflection surface of the light window is 10-20°, and the inner wall of the rectangular channel and the surface layer of the secondary reflection surface are both coated with a polished aluminum layer, so that they have high reflectivity, and the reflectivity can be more than 90%, thereby reducing the loss of solar radiation in the reflection process. The opening width of the light window accounts for 10-15% of the circumference of the outer wall of the cavity-type solar collector.

[0011] According to the preferred embodiment of the present application, the light side surface of the linear Fresnel lens is a smooth plane, and the back light side is arranged by symmetrically arranged triangular tooth structures on both sides, and the material is polymethyl methacrylate (PMMA) with high transparency. During the system operation, the bottom support frame can adjust the rotation angle of the whole system according to the solar elevation angle, so that the solar radiation is perpendicular to the system, and the radiation receiving maximization and the accuracy of the condensation are ensured. The focal point of the linear Fresnel lens coincides with the center of the heat absorption cavity (or the central axis of the solar collector is located at the focal point below the linear Fresnel lens, and the vertical distance is the focal length of the lens); when the sunlight is perpendicular to the incident, it is focused at the center of the heat absorption cavity and irradiates on the bottom micro-nano frequency division film, and the transmitted light will completely cover the photovoltaic cell below the frequency division film.

[0012] The solar radiation only enters the heat preservation cavity through the light inlet, so as to construct a cylindrical heat absorption cavity similar to a black body; the cylindrical cavity layer adopts a high heat preservation material, and the internal heat absorber is not exposed, thereby reducing the heat radiation dissipation.

[0013] According to the preferred embodiment of the present application, the high heat preservation material used in the heat preservation layer is composed of hard heat preservation materials such as ceramic fiber board or nano aerogel heat insulation board, and filling layers such as high-temperature rock wool and aluminum silicate refractory fiber cotton.

[0014] According to the preferred embodiment of the present application, the heat conduction working medium flowing in the outer working medium layer of the heat absorption cavity is water, and a screw-shaped fin is added to the inner side of the outer working medium layer of the heat absorption cavity, so as to increase the contact area between the shell and the tube, speed up the heat conduction process, and heat the working medium to a gas. The aspect ratio of the whole cavity-type solar collector is 10:1, and the ratio of the radius of the heat absorption cavity, the thickness of the working medium layer and the thickness of the heat preservation layer is 4:3:3. The addition of the fin can increase the heat transfer efficiency by 60%, and can heat the water to steam at about 373K.

[0015] According to the preferred embodiment of the present application, the photovoltaic cell is located directly below the micro-nano film and is fixed by the heat preservation layers on both sides. The photovoltaic cell adopts a gallium arsenide GaAs concentrated photovoltaic cell, and the solar power generation efficiency is about 29.7%. In addition, the back of the photovoltaic cell is provided with a water cooling device, so as to ensure that the temperature of the photovoltaic cell does not become too high to affect the power generation efficiency, and the water can also be preheated.

[0016] Compared with the prior art, the present application has the following advantages:

[0017] (1) The micro-nano film used in the solar frequency division PV / T system coupled with the micro-nano film and the cavity collector has the characteristics of high temperature resistance, excellent frequency division effect and low processing cost, and the average transmittance in the spectral band of the photovoltaic cell is more than 90%, and the spectral matching is high, so that the solar frequency division utilization is realized with low cost and high efficiency.

[0018] (2) The cavity collector used in the solar frequency division PV / T system coupled with the micro-nano film and the cavity collector is configured with a linear Fresnel lens, and the collector is arranged below the linear Fresnel lens, which avoids the problem of high gravity center and poor wind resistance of the traditional arrangement. The light window at the upper part of the cavity collector used in the application is coated with a polished aluminum layer to reduce reflection loss, and the bottom is embedded with a micro-nano frequency division film, a solar cell and a water cooling device, and a plurality of thermal insulation layers are arranged outside. The gap between the micro-nano film and the solar cell is evacuated to vacuum, so that the collected solar energy is utilized in a cavity collector, the energy dissipation to the outside is reduced, and the solar energy conversion efficiency is effectively improved. The core components of the solar frequency division PV / T system are integrated in a cylindrical structure, realizing the integration of solar frequency division, photovoltaic power generation and photothermal utilization, realizing the miniaturization, lightness and low cost of solar frequency division utilization, realizing the efficient and clean co-production of electricity and steam, and having great significance for the popularization and promotion of solar frequency division technology.

[0019] (3) The application integrates the micro-nano frequency division film and the heat collecting medium flow channel in a cavity collector through new structure design and technical innovation, transmits the part of the solar spectrum that can be used by photovoltaic cells (wavelength 400nm-900nm) to the photovoltaic cell for power generation, and reflects the remaining wavelength to the inner wall of the surrounding heat absorption cavity for light and heat absorption, realizing compact and efficient operation of the PV / T system. The whole system is smaller, lower in cost and higher in efficiency than other frequency division systems.

[0020] (4) The light and heat capturing component adopts the thermal insulation cylindrical cavity structure of the cavity collector, combines high absorption performance, high temperature resistant selective absorption coating and high thermal insulation performance material, can effectively reduce the heat radiation and heat convection loss in the heat collecting process to below 10%, improve the light and heat conversion efficiency, heat the heat conducting medium to gas state, and realize heating, heating and steam supply. The bottom support frame of the system can adjust the rotation angle of the whole system according to the solar altitude angle, so that the solar radiation is perpendicular to the system, the radiation receiving is maximized and the accuracy of the light collection is ensured, and the efficient utilization of solar energy is effectively realized. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 It is a working perspective view of the solar frequency division PV / T system.

[0022] Figure 2 The figure is a schematic diagram of the sectional view structure of the cavity-type solar collector of the present application;

[0023] Figure 3 The figure is a schematic diagram of the perspective view structure of the cavity-type solar collector of the present application;

[0024] Figure 4 The figure is a schematic diagram of the perspective view structure of the light window of the present application;

[0025] Figure 5 The figure is a schematic diagram of the perspective view structure of the bottom support of the present application.

[0026] The figure shows: light window 1, outermost heat-insulating layer 2, outer working medium layer of heat-absorbing cavity 3, cylindrical heat-absorbing cavity 4, micro-nano frequency division film 5, reflecting material 6, concentrated photovoltaic cell 7, photovoltaic water cooling system 8, rectangular channel 5-1, and trapezoidal outer expanded secondary reflecting surface 5-2. DETAILED DESCRIPTION

[0027] The advantages and effects of the present application can be easily understood by those skilled in the art from the content disclosed in the specification. The details in the specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present application.

[0028] As shown in Figure 1 , Figure 2 and Figure 5 , the present application is a new solar frequency division PV / T system coupling micro-nano film and cavity-type collector, which comprises a linear Fresnel lens, a cavity-type solar collector and a support frame. The cavity-type solar collector comprises a cylindrical heat-absorbing cavity 4, an outer working medium layer of heat-absorbing cavity 3 and an outermost heat-insulating layer 2. Figure 2 and 3 , the cavity-type solar collector is in the shape of a cylinder as a whole, and has a cylindrical cavity inside. Two grooves parallel to the axis direction are formed on the side wall of the cavity-type solar collector. The two grooves are arranged opposite to each other. The length of the grooves can be selected as needed. In the present embodiment, the length of the two grooves is the same as the length of the cavity-type solar collector itself. A light window 1 is arranged on one of the grooves. A micro-nano frequency division film 5 is arranged on the inner wall of the cylindrical heat-absorbing cavity 4 of the other groove opposite to the light window 1. A concentrated photovoltaic cell 7 is installed on the heat-insulating layer 2 of the groove. The aperture of the groove between the micro-nano frequency division film 5 and the concentrated photovoltaic cell 7 is a cavity, and the cavity is provided with a reflecting material 6.

[0029] The cavity-type solar collector is arranged directly below the central axis of the linear Fresnel lens, and the light window 1 is directly opposite the central axis of the linear Fresnel lens. The bottom support frame of the system can adjust the rotation angle of the whole system according to the solar altitude angle, so that the solar radiation is perpendicular to the linear Fresnel lens.

[0030] When the sunlight is irradiated, the bottom support frame system of the system is adjusted according to the solar altitude angle, and the rotation angle of the system is adjusted, so that the solar radiation is perpendicular to the system. In this embodiment, the light side surface of the linear Fresnel lens is a smooth plane, and the back light side is arranged by triangular tooth structure arranged symmetrically on both sides (symmetrically arranged about the central axis of the linear Fresnel lens), and the material is polymethyl methacrylate (PMMA) with high transparency. The linear Fresnel lens condenses the solar radiation incident on the system to the light window 1.

[0031] As Figure 4 , the light window 1 is composed of a rectangular channel and a trapezoidal outer expansion secondary reflecting surface, which is arranged in the slot of the cavity-type solar collector arranged directly below the linear Fresnel lens, replacing a part of the collector pipeline, wherein the length of the rectangular channel is consistent with the thickness of the collector.

[0032] The opening angle of the trapezoidal outer expansion secondary reflecting surface 5-2 of the light window 1 is 10°-20°, and the inner wall of the rectangular channel 5-1 and the surface layer of the trapezoidal outer expansion secondary reflecting surface 5-2 are plated with polished aluminum layer, so that it has high reflectivity, and the reflectivity can reach more than 90%, reducing the loss of solar radiation caused in the reflection process. The opening length of the light window accounts for 10%-15% of the circumference of the outer wall of the cavity-type solar collector, which satisfies that the condensing light path is not blocked, ensures high solar light capture efficiency, and reduces the dissipation of cavity heat radiation outward. In this embodiment, the ratio of the radius of the heat absorption cavity, the thickness of the working medium layer and the thickness of the heat preservation layer is 4:3:3.

[0033] The solar radiation condensed to the light window 1 enters the heat absorption cavity 4 under the reflection of the aluminum layer plated on the inner wall of the rectangular channel 5-1 and the surface layer of the trapezoidal outer expansion secondary reflecting surface 5-2.

[0034] The solar radiation enters the heat absorption cavity 4 only through the light window 1, so as to construct a cylindrical heat absorption cavity similar to a black body; the heat preservation layer uses high heat preservation performance material, which does not expose the internal heat absorption cavity 4, and reduces heat radiation dissipation.

[0035] The high heat preservation performance material used by the heat preservation layer is composed of hard heat preservation materials such as ceramic fiber board or nano aerogel heat insulation board, and filling layers such as high temperature rock wool and aluminum silicate refractory fiber cotton, wherein the hard heat preservation material is outside, and the filling layer is inside.

[0036] The micro-nano frequency division film 5 is an optical interference multi-layer frequency division film of TiO2 and SiO2 materials alternately deposited on a transparent substrate. In the embodiment, it is processed by a magnetron sputtering technology, and the material is a three-layer structure, from top to bottom, SiO2 / TiO2 / SiO2, with thicknesses of 100 nm / 300 nm / 150 nm, respectively. The transmittance is above 90% in the range of 400 nm-900 nm, and the highest transmittance is 99.1% at 460 nm, and the average transmittance is 93.88%. The film structure is simple, and the processing and manufacturing are convenient, which is beneficial to large-scale production and manufacturing.

[0037] When the solar radiation entering the heat preservation cavity is irradiated on the micro-nano frequency division film 5, the micro-nano frequency division film 5 selectively transmits the solar radiation, and the wavelength of 400 nm-900 nm is part of the available band of the photovoltaic cell, which is transmitted to the photovoltaic cell 7 below to generate electricity, and the remaining band is reflected to the inner wall of the heat absorption cavity 4.

[0038] The inner wall of the heat absorption cavity 4 is coated with a heat absorption coating with high absorption performance and high temperature resistance, which is composed of high temperature resistant resin, light absorbing pigment, solvent, dispersant and filler, with mass fraction ratio of 15%:12%:65%:2%:6%. The high temperature resistant resin is a vinyl cage type poly silyl siloxane; the light absorbing pigment is a mixture of copper oxide, ferric oxide and manganese oxide nanoparticles with a mass fraction of 1:1:1; the solvent is xylene; the dispersant is a wet dispersant DISPERSANT-2070; and the filler is rare earth yttrium. The coating thickness is 30 μm, with an absorption rate of more than 90% and an emission rate of less than 30%. The remaining band of solar radiation that cannot be used by the photovoltaic cell is absorbed into a large amount of heat energy.

[0039] Threaded fins are provided on the inner side of the outer working medium layer 3 of the heat absorption cavity, which increases the contact area between the shell and tube and accelerates the process of transferring the large amount of heat energy obtained by the heat absorption cavity 4 to the working medium (in this embodiment, the working medium is water), so as to quickly heat the working medium water to the gas phase.

[0040] The photovoltaic cell 7 is located directly below the micro-nano frequency division film 5 and is fixed by the heat preservation layers on both sides. The photovoltaic cell 7 adopts a gallium arsenide GaAs concentrating photovoltaic cell, and the solar power generation efficiency is about 29.7%.

[0041] The water cooling device is installed on the back of the photovoltaic cell 7 to ensure that the temperature of the photovoltaic cell does not become too high to affect the power generation efficiency. In addition, the water cooling device can preheat the water, which is then heated to steam in the working medium layer.

[0042] According to the model established by the system, the photoelectric efficiency of the photovoltaic cell can reach 31.28%, the light-heat efficiency of the cavity heat preservation structure system is greatly improved, and the overall energy utilization efficiency of the system can reach 84.25%, which is improved by more than 9.65% compared with the traditional linear Fresnel type concentrating PV / T system which separates frequency first and then concentrates light.

[0043] The specific implementation cases described in the specification are examples of the inventive structure, the names of the structures in the specification can be different, the inventive structure is not limited to the above embodiments, and equivalent or simple changes made according to the structure or principle of the patent should belong to the protection scope of the application.

Claims

1. A solar frequency-split PV / T system coupling a micro-nano thin film and a cavity collector, characterized in that: The application relates to a linear Fresnel lens and a cavity type solar energy collector; wherein the cavity type solar energy collector comprises, from inside to outside, a cylindrical heat absorption cavity (4), a working medium layer (3) wrapped outside the heat absorption cavity and a heat preservation and insulation layer (2) wrapped around the working medium layer; the cavity type solar energy collector is provided with a light collecting window (1) on the side wall in the axial direction, and a micro-nano frequency division film (5) is arranged on the inner wall of the heat absorption cavity (4) opposite to the light collecting window (1); a light concentrating photovoltaic cell (7) is arranged below the micro-nano frequency division film (5), and a vacuum cavity is arranged between the micro-nano frequency division film (5) and the light concentrating photovoltaic cell (7); a reflecting material (6) is arranged on the wall of the vacuum cavity; the cavity type solar energy collector is arranged directly below the central axis of the linear Fresnel lens, the light collecting window (1) is opposite to the linear Fresnel lens, the linear Fresnel lens concentrates the incident solar radiation to the light collecting window (1), and the solar radiation is irradiated to the micro-nano frequency division film (5) in the heat absorption cavity through the light collecting window (1); The micro-nano frequency division film (5) is arranged on the inner wall of the heat absorption cavity (4) opposite to the light collecting window (1), is an optical interference multi-layer frequency division film formed by alternately depositing TiO2 and SiO2 on a transparent substrate, and is used for realizing the selective transmission effect of sunlight spectrum, transmitting the wave band with a wavelength of 400nm-900nm to the light concentrating photovoltaic cell (7) below to generate electricity, and reflecting the remaining wave band to the inner wall of the heat absorption cavity (4); The micro-nano frequency division film (5) is processed by a magnetron sputtering technology, is a three-layer structure, and is composed of SiO2, TiO2 and SiO2 from top to bottom, and the thicknesses of the three layers are 100nm, 300nm and 150nm respectively; the transmittance of the micro-nano frequency division film (5) is above 90% in the wave band of 400nm-900nm; When the solar radiation entering the cavity type solar energy collector is irradiated to the micro-nano frequency division film, the micro-nano frequency division film selectively transmits the solar radiation, transmits the wave band with a wavelength of 400nm-900nm to the light reflecting chamber below, and reflects the remaining wave band to the inner wall of the heat absorption cavity under the assistance of the reflecting material arranged in the light reflecting chamber; the radiation entering the light reflecting chamber is absorbed by the light concentrating photovoltaic cell and generates electricity; and the micro-nano frequency division film reflects the remaining wave band to the inner wall of the heat absorption cavity. The light collecting window (1) is composed of rectangular channels and trapezoidal secondary reflecting surfaces which are connected with each other, wherein the rectangular channels are the windows arranged on the cavity type solar energy collector, the length of the channels is consistent with the thickness of the cavity type solar energy collector, and the secondary reflecting surfaces are located outside the cavity type solar energy collector and open towards the linear Fresnel lens; The light concentrating photovoltaic cell (7) adopts a gallium arsenide (GaAs) light concentrating photovoltaic cell; the light concentrating photovoltaic cell (7) is arranged at the heat preservation and insulation layer (2) and is fixed by the heat preservation and insulation layer (2) on both sides; a water cooling device (8) is arranged on the back of the photovoltaic cell, so that the temperature of the photovoltaic cell is not too high and the power generation efficiency is not affected.

2. The solar sub-band PV / T system of claim 1, wherein: The linear Fresnel lens and the cavity type solar collector are fixedly connected to keep the relative position therebetween; the system further comprises a support frame system for adjusting the rotation angle of the solar frequency division PV / T system so that the solar radiation is perpendicularly incident on the linear Fresnel lens.

3. The solar sub-band PV / T system of claim 1, wherein: The opening angle of the secondary reflecting surface is 10-20°, and the inner wall of the rectangular channel and the surface layer of the secondary reflecting surface are both plated with a polished aluminum layer; the opening width of the light window accounts for 10-15% of the circumference of the outer wall of the cavity type solar collector.

4. The solar sub-band PV / T system of claim 1, wherein: The light side surface of the linear Fresnel lens is a smooth plane, and the back light side is arranged by symmetrically arranged triangular tooth structures, and the material thereof is polymethyl methacrylate (PMMA); the light window (1) is located directly below the center axis of symmetry of the linear Fresnel lens; the focal point of the linear Fresnel lens coincides with the center of the heat absorption cavity (4); when the sunlight is perpendicularly incident, it is focused at the center of the heat absorption cavity and then irradiated on the bottom micro-nano frequency division film (5), and the transmitted light will completely cover the concentrated photovoltaic cell (7) below the frequency division film.

5. The solar sub-band PV / T system of claim 1, wherein: The heat preservation layer (2) is wrapped around the internal heat absorption cavity without being exposed, thereby reducing heat radiation dissipation; the high heat preservation material used in the heat preservation layer (2) is composed of a hard heat preservation material and a filling layer; the heat conducting working medium flowing in the working medium layer (3) is water, and screw-shaped fins are added to the inner side of the working medium layer (3) to increase the contact area between the working medium layer (3) and the heat absorption cavity (4) and accelerate the heat conduction process, thereby heating the working medium into gas.

6. A method of solar energy utilization based on the system according to any one of claims 1-5, characterized in that The system comprises: The linear Fresnel lens is arranged to receive the solar radiation perpendicularly incident thereon; The linear Fresnel lens concentrates the solar radiation incident on the system to the light window, and the concentrated solar radiation is collected in the heat absorption cavity through the secondary reflection of the light window and irradiated on the bottom micro-nano film; wherein the solar radiation enters the cavity type solar collector only through the light window; When the solar radiation entering the cavity type solar collector is irradiated on the micro-nano frequency division film, the micro-nano frequency division film selectively transmits the wavelength of 400-900 nm to the lower reflecting chamber, and the reflected radiation in the reflecting chamber is absorbed by the concentrated photovoltaic cell and generates electricity with the assistance of the reflecting material arranged in the reflecting chamber; the micro-nano frequency division film reflects the remaining wavelength to the inner wall of the heat absorption cavity; The inner wall of the heat absorption cavity is coated with a selective absorption coating to absorb all the remaining wavelength energy into heat energy; the heat absorption cavity conducts the absorbed heat energy to the working medium layer to heat the flowing working medium, thereby realizing the utilization of the entire solar spectrum energy.

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