Solar heat absorber with self-generating and heat storage functions and operation method thereof

Abstract

The application relates to a solar heat absorber with self-power generation and heat storage functions and a running method thereof, and belongs to the technical field of solar heat absorbers. The heat absorber comprises a heat absorption pipe, an upper header tank, a lower header tank and a heat storage system, wherein a plurality of heat absorption pipes are arranged side by side between the upper header tank and the lower header tank, and the upper header tank and the lower header tank are respectively connected with the heat storage system; the wall of the heat absorption pipe is a multilayer structure, and from outside to inside, the multilayer structure comprises a hot electron anode, an electrode gap, a hot electron cathode and a heat transfer metal pipeline in sequence; the heat transfer metal pipeline circulates a heat transfer working medium; and the hot electron anode and the hot electron cathode are respectively connected with an external load through an anode lead wire and a cathode lead wire. The heat absorber has the function of power generation, can store heat by using concentrated light energy, and improves the efficiency and stability of the entire power generation system.

Description

Technical Field

[0001] This invention relates to a solar absorber with self-generating and heat storage functions and its operation method, belonging to the field of solar absorber technology. Background Technology

[0002] Solar energy is a widely used renewable energy source. Currently, the main forms of solar power generation are photovoltaic (PV) power generation and concentrated solar power (CSP) power generation. PV power generation refers to the direct conversion of solar energy into electrical energy using photovoltaic cells through the photovoltaic effect, but it has inherent limitations in energy conversion. CSP power generation refers to the process of first converting solar energy into heat energy, and then using other technologies to convert the heat energy into electrical energy. CSP coupled with thermal storage systems can avoid the weather-dependent characteristics of PV power generation, but its process is complex and its conversion efficiency is relatively low, which still limits its practical application.

[0003] A thermionic emission power generation device consists of a hot metal cathode and a cold anode, separated by a vacuum. By heating the metal with an energy source, electrons within the metal overcome the inter-electrode barrier and are emitted to the anode. Connecting to an external load forms a closed loop for power generation. The energy source for thermionic emission power generation devices is concentrated solar energy. Photon-enhanced thermionic emission (PETE) technology can simultaneously achieve photovoltaic and photothermal effects in a single device. The difference between PETE and thermionic emission is that PETE uses a semiconductor cathode; the rest of the device is the same. Its working principle is that the semiconductor cathode absorbs concentrated solar radiation, and electrons in the cathode are excited from the valence band to the conduction band by incident photons. Simultaneously, they absorb heat from the cathode, overcome the inter-electrode barrier, and are emitted to the anode. Because PETE utilizes both photon energy and photogenerated heat, it has higher conversion efficiency and can operate at lower temperatures compared to thermionic emission.

[0004] In thermionic emission power generation modules, the cathode temperature is higher than the anode temperature, and the work function of the cathode is higher than that of the anode. During module operation, the anode temperature should not be too high. Since the anode has a lower work function, if the anode temperature is too high, the anode will easily emit electrons to the cathode, generating a large anode reverse current. The total current of the device, Jtotal = Jcathode - Janode, is too high. If the anode reverse current is too high, it will reduce the total emission current of the device, thereby affecting the power generation performance of the module. Therefore, controlling the anode temperature to be low is also a key research focus in this field.

[0005] Furthermore, both pure thermionic emission technology and photon-enhanced emission power generation technology are limited by the space charge effect between electrodes. Limiting the electrode spacing to the micro-nano scale can alleviate the space charge effect, but the near-field radiation heat transfer loss due to evanescent wave photon tunneling increases. Simultaneously, this micro-nano scale spacing poses a significant challenge to engineering applications. Introducing cesium vapor into the electrode gap is a common way to overcome the space charge effect; however, high-temperature thermal ionization of cesium requires temperatures above 1200°C to achieve transport, which is difficult to achieve in conventional solar power generation. However, besides thermal ionization, resonant light can also excite cesium atoms to produce cesium ions, and the abundant resonant light sources in sunlight can be utilized. Based on this, this invention designs a transparent anode structure where solar photons first enter the electrode gap, preferentially exciting cesium atoms and ionizing them, thereby overcoming the space charge effect.

[0006] Currently, commonly used concentrated solar thermal power generation systems mainly employ tower, dish, trough, and linear Fresnel collector systems. In all these systems, absorb concentrated solar energy through absorbers or absorber tubes, thereby heating the heat transfer medium to drive a heat engine to perform work. Because these systems can achieve high concentration ratios, the absorbers can operate at very high temperatures. An absorber is a device that converts highly concentrated solar energy into heat energy. Based on different heat transfer methods, they can be divided into tubular and volumetric absorbers. Tubular absorbers are currently the most commonly used type in tower solar power generation systems. Their main working principle is that the heat transfer medium enters the absorber tube and exchanges heat with the tube wall, thereby absorbing heat. Currently, the role of the absorber in a solar system is relatively simple: absorbing solar energy, converting it into heat energy, and transferring it to the medium inside the tube. Based on the above analysis, this invention is proposed. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention provides a solar absorber with self-generating and heat storage functions. The absorber itself has the function of generating electricity and can also use concentrated solar energy for heat storage, thereby improving the efficiency and stability of the entire power generation system.

[0008] The present invention also provides a method for operating the above-mentioned solar absorber with self-generating power and heat storage functions.

[0009] The technical solution of the present invention is as follows:

[0010] A solar absorber with self-generating power and heat storage functions includes heat absorption tubes, an upper manifold, a lower manifold, and a heat storage system. Several heat absorption tubes are arranged side by side between the upper manifold and the lower manifold. The two ends of the heat absorption tubes are connected to the upper manifold and the lower manifold respectively through connecting pipes. The upper manifold and the lower manifold are respectively connected to the heat storage system through working fluid flow pipes.

[0011] The absorber tube has a multi-layered structure, consisting of a thermionic anode, an electrode gap, a thermionic cathode, and a heat transfer metal pipe from the outside to the inside. The heat transfer metal pipe contains a heat transfer medium. The thermionic anode and the thermionic cathode are connected to an external load through anode wires and cathode wires, respectively.

[0012] According to a preferred embodiment of the present invention, a back-side insulating layer is provided between the thermionic cathode and the heat transfer metal pipe, the back-side insulating layer being used to prevent the thermionic cathode from conducting electricity with the heat transfer metal pipe.

[0013] According to a preferred embodiment of the present invention, a plurality of electrode insulating layers are evenly distributed within the electrode gap. These electrode insulating layers prevent electrical conduction between the thermionic anode and the thermionic cathode at the fixed points of the electrodes, thus avoiding impact on the thermionic emission power generation performance. The electrode insulating layers and the back-side insulating layer should possess good heat resistance and chemical stability, and can be made using phosphate-based inorganic binders, alumina, zirconium oxide, etc.

[0014] The thermionic cathode, thermionic anode, electrode gap, and electrode insulation layer together constitute the thermionic emission power generation component, which generates electricity externally. The thermionic anode is a light-transmitting anode, and most of the concentrated light energy is absorbed by the thermionic cathode through the thermionic anode. The temperature of the thermionic cathode rises, and the electrons inside the cathode increase their kinetic energy after absorbing energy. Some electrons can overcome the electron potential barrier on the surface of the thermionic cathode and are emitted from the cathode surface. The emitted electrons pass through the electrode gap to reach the thermionic anode, and then connect to the external load through the anode wire and cathode wire to generate electricity. The heat transfer metal pipe can absorb some of the heat from the thermionic cathode, and the heat transfer medium absorbs the heat from the heat transfer metal pipe and enters the thermal storage system for energy storage.

[0015] According to a preferred embodiment of the present invention, the hot electron anode is made of transparent conductive materials such as indium-tin oxide transparent conductive film glass, fluorine-doped SnO2 transparent conductive glass, quartz substrate or graphene.

[0016] Thermionic cathode materials can be pure metals, metal oxides, semiconductors, or graphene, etc.

[0017] According to a preferred embodiment of the present invention, the electron receiving surface of the thermionic anode is provided with a thermionic anode coating, and the light-receiving surface of the thermionic cathode is provided with a thermionic cathode coating. The light-receiving surface of the thermionic cathode is also an electron emitting surface. Both the thermionic anode coating and the thermionic cathode coating achieve low surface work functions, and the thermionic anode coating should have good light transmission characteristics. The materials of the thermionic cathode coating and the thermionic anode coating can be selected from nitrogen-doped diamond, phosphorus-doped diamond, lanthanum hexaboride, barium fluoride, or other materials with low work function characteristics.

[0018] According to a preferred embodiment of the present invention, the electrode gap is a vacuum or filled with cesium vapor maintained at a specified temperature. Cesium atoms can be ionized into cesium ions through photo / thermal excitation. Cesium vapor can not only mitigate the space charge effect, but also further reduce the work function of the thermionic cathode and thermionic anode surfaces. Cesium atoms can be directly ionized under specific wavelength light radiation, or they can be thermally ionized to form cesium ions. Cesium ions can neutralize the electrons accumulated in the electrode gap, thereby mitigating the space charge effect. At the same time, some of the cesium atoms adsorbed on the electrodes can form surface dipoles, thereby effectively reducing the work function and allowing more electrons from the cathode to be emitted into the electrode gap, thereby increasing the output current.

[0019] According to a preferred embodiment of the present invention, a focusing system is provided on the outside of the heat absorber. The focusing system is of the following types: tower type, dish type, trough type, linear Fresnel type, tower-trough coupled type, tower-dish coupled type, or dish-trough coupled type.

[0020] According to a preferred embodiment of the present invention, the heat transfer medium is one or more fluids such as molten salt, water vapor, water, air, and carbon dioxide.

[0021] When the heat transfer medium is air, the inner wall of the heat transfer metal pipe is coated with a thermochemical heat storage coating. The material system of the thermochemical heat storage coating includes, but is not limited to, one or more of the following systems: BaO2 / BaO, Co3O4 / CoO, Mn2O3 / Mn3O4, and CuO / Cu2O. The thermochemical heat storage coating has the function of stabilizing the air temperature. It absorbs heat through reduction reaction to achieve heat storage and releases heat through oxidation reaction to heat the air, thereby reducing the temperature fluctuation of the air.

[0022] According to a preferred embodiment of the present invention, the thermal storage system includes a thermal storage tank and a pump. The upper header, thermal storage tank, pump and lower header are connected in sequence by pipelines. Each connecting pipeline is equipped with a valve. The thermal storage tank can be a dual-tank form of high-temperature molten salt tank and low-temperature molten salt tank, a single-tank thermal storage form of molten salt inclined layer, a thermochemical thermal storage tank of metal hydroxide system, a thermochemical thermal storage tank of carbonate system, a porous medium thermal storage tank with phase change material phase change thermal storage function, and other types of thermal storage devices.

[0023] The operation method of the above-mentioned solar absorber with self-generated power and heat storage functions is as follows:

[0024] (1) When there is sufficient sunlight, the concentrated energy is absorbed by the thermionic cathode through the thermionic anode. After absorbing energy, the temperature of the thermionic cathode rises. Some electrons inside the thermionic cathode are excited and overcome the surface potential barrier, passing through the electrode gap and being emitted to the thermionic anode. The thermionic anode receives the electrons emitted from the thermionic cathode. The electrons are led to the external load through the anode wire and then returned to the thermionic cathode through the cathode wire, forming a closed loop, thereby realizing power generation.

[0025] During the power generation process, the heat transfer medium inside the heat transfer metal pipe absorbs heat from the back side of the thermionic cathode and becomes a high-temperature working medium, which then enters the thermal storage system to achieve thermal storage.

[0026] (2) When there is insufficient sunlight, the heat transfer medium absorbs the heat of the high-temperature medium in the heat storage tank and becomes a high-temperature heat transfer medium. The heat transfer medium enters the heat absorption tube, and the thermionic cathode absorbs the heat energy of the heat transfer medium, which raises the temperature of the thermionic cathode and realizes thermionic emission power generation.

[0027] The beneficial effects of this invention are as follows:

[0028] In this invention, the photon incident surface of the thermionic emission power generation component is also the electron emission surface. The concentrated light energy is incident on the thermionic cathode through the transparent thermionic anode. Compared with the traditional thermionic emission power generation component that concentrates light on the back side of the thermionic cathode, the photon incident surface of this component, which is also the electron emission surface, reduces electron recombination in the diffusion process and increases the emission current, thereby improving the power generation efficiency of the entire component. In addition, by filling the electrode gap with cesium vapor to overcome the space charge effect, the abundant resonant light source in sunlight can preferentially excite cesium atoms through the transparent anode. At the same time, the heat transfer medium in this invention, combined with the heat storage system, can significantly improve the power generation efficiency of the heat absorber.

[0029] For thermionic emission power generation modules, the temperature of the thermionic cathode is typically much higher than that of the thermionic anode, and the work function of the cathode is higher than that of the anode. Furthermore, during power generation, because the thermionic anode has a lower work function, it emits electrons towards the thermionic cathode when its temperature rises to a certain value, generating a reverse current and affecting the module's power generation efficiency. Therefore, the temperature of the thermionic anode should not be too high. This results in a situation where, if heat is absorbed from the thermionic anode side to drive the power cycle, the working fluid temperature is relatively low, affecting the overall system efficiency. Compared to related inventions where the working fluid directly absorbs heat from the anode, the heat transfer working fluid of this invention absorbs heat from the back side of the thermionic cathode. Since the thermionic cathode temperature is higher, the heat transfer working fluid can absorb more heat. Simultaneously, at night, the heat transfer working fluid transfers heat in the reverse direction to the cathode, enabling nighttime power generation, significantly improving the overall system's power generation efficiency. Attached Figure Description

[0030] Figure 1 This is a schematic cross-sectional view of the heat absorption tube of the present invention.

[0031] Figure 2 This is a schematic diagram of the heat absorber structure of the present invention.

[0032] Figure 3 This is a schematic diagram of the thermal electron emission power generation principle in this invention.

[0033] Figure 4 This is a schematic diagram of the work system in Embodiment 2 of the present invention.

[0034] Figure 5 This is a schematic diagram of the work system in Embodiment 3 of the present invention.

[0035] Figure 6 This is a schematic diagram of the work system in Embodiment 4 of the present invention.

[0036] Figure 7 This is a schematic diagram of the trough-type solar concentrator system in Embodiment 5 of the present invention.

[0037] Figure 8 This is a schematic diagram illustrating the principle of thermionic emission power generation when the electrode gap of the present invention is filled with cesium vapor.

[0038] Figure label:

[0039] 1. Thermionic emission power generation assembly; 2. Backside insulation layer; 3. Heat transfer metal pipe; 4. Heat transfer medium; 5. Anode conductor; 6. Cathode conductor; 7. Absorber; 8. Concentrating system; 9. Thermal storage system; 10. Power circulation system; 11. Valve A; 12. Valve B; 13. Valve C; 14. Valve D; 15. Transfer pump; 16. Valve E; 17. Tower; 18. Heliostat; 19. Turbine; 20. Regenerator; 21. Compressor; 22. Steam generator; 23. Steam turbine; 24. Condenser; 25. Circulating pump; 26. Trough concentrator;

[0040] 101. Thermionic anode; 102. Electrode gap; 103. Thermionic cathode; 104. Electrode insulating layer;

[0041] 701. Heat absorption tube; 702. Connecting pipe; 703. Upper header; 704. Lower header; 705. Working fluid flow pipe. Detailed Implementation

[0042] The present invention will be further described below with reference to the embodiments and accompanying drawings, but is not limited thereto.

[0043] Example 1:

[0044] like Figure 1-3 As shown, this embodiment provides a solar absorber with self-generating power and heat storage functions, including heat absorption tubes 701, an upper manifold 703, a lower manifold 704, and a heat storage system. Several heat absorption tubes 701 are arranged side by side between the upper manifold 703 and the lower manifold 704. The two ends of the heat absorption tubes 701 are connected to the upper manifold 703 and the lower manifold 704 respectively through connecting pipes 702. The upper manifold 703 and the lower manifold 704 are respectively connected to the heat storage system through working fluid flow pipes 705.

[0045] The heat absorber tube 701 has a multi-layered structure, consisting of a thermionic anode 101, an electrode gap 102, a thermionic cathode 103, and a heat transfer metal pipe 3 from the outside to the inside. A heat transfer medium 4 flows inside the heat transfer metal pipe 3. The thermionic anode 101 and the thermionic cathode 103 are connected to an external load through an anode wire 5 and a cathode wire 6, respectively.

[0046] A back-side insulating layer 2 is provided between the thermionic cathode 103 and the heat transfer metal pipe 3. The back-side insulating layer is used to prevent the thermionic cathode from conducting electricity with the heat transfer metal pipe.

[0047] Several electrode insulating layers 104 are evenly distributed within the electrode gap 102. These insulating layers prevent electrical conduction between the thermionic anode and the thermionic cathode at the fixed points of the electrodes, which would affect the thermionic emission power generation performance. The electrode insulating layers and the back-side insulating layer should have good heat resistance and chemical stability, and can be made of phosphate-based inorganic binders, alumina, zirconium oxide, etc.

[0048] The thermionic cathode 103, thermionic anode 101, electrode gap 102, and electrode insulating layer 104 together constitute the thermionic emission power generation component 1, which generates electricity externally. The thermionic anode is a light-transmitting anode, and most of the concentrated light energy is absorbed by the thermionic cathode through the thermionic anode. The temperature of the thermionic cathode rises, and the electrons inside the cathode increase their kinetic energy after absorbing energy. Some electrons can overcome the electron potential barrier on the surface of the thermionic cathode and are emitted from the cathode surface. The emitted electrons pass through the electrode gap to reach the thermionic anode, and then connect to the external load through the anode wire and the cathode wire to generate electricity. The heat transfer metal pipe can absorb some of the heat from the thermionic cathode, and the heat transfer medium absorbs the heat from the heat transfer metal pipe and enters the heat storage system for energy storage.

[0049] The thermionic anode 101 is made of indium-tin oxide transparent conductive film glass; the thermionic cathode 103 is made of pure metal, specifically tungsten.

[0050] The electron receiving surface of the thermionic anode 101 is provided with a thermionic anode coating, and the light-receiving surface of the thermionic cathode is provided with a thermionic cathode coating. The light-receiving surface of the thermionic cathode is also an electron emitting surface. Both the thermionic anode coating and the thermionic cathode coating achieve low surface work function, and the thermionic anode coating should have good light transmission characteristics. The materials of the thermionic cathode coating and the thermionic anode coating can be nitrogen-doped diamond, phosphorus-doped diamond, lanthanum hexaboride, barium fluoride, or other materials with low work function characteristics.

[0051] The electrode gap 102 is a vacuum.

[0052] A concentrating system 8 is installed on the outside of the absorber 7. The concentrating system is a dish-type concentrating solar energy system.

[0053] The heat transfer medium 4 is one or more fluids such as molten salt, water vapor, water, air, and carbon dioxide.

[0054] When the heat transfer medium is air, the inner wall of the heat transfer metal pipe is coated with a thermochemical heat storage coating. The material system of the thermochemical heat storage coating includes, but is not limited to, one or more of the following systems: BaO2 / BaO, Co3O4 / CoO, Mn2O3 / Mn3O4, and CuO / Cu2O. The thermochemical heat storage coating has the function of stabilizing the air temperature. It absorbs heat through reduction reaction to achieve heat storage and releases heat through oxidation reaction to heat the air, thereby reducing the temperature fluctuation of the air.

[0055] Example 2:

[0056] like Figure 4 As shown, this embodiment provides a power system for a solar absorber with self-generating and heat storage functions as described in Embodiment 1, including an absorber and a power circulation system 10. The upper manifold 703 is connected to a heat storage tank via valve A11, the upper manifold 703 is connected to the power circulation system 10 via valve B12, the power circulation system 10 is connected to the lower manifold 704 via valve C13, the power circulation system 10 is connected to the heat storage tank via valve D14, and a valve E16 is provided on the connecting pipe between the heat storage tank and the transfer pump 15.

[0057] The thermal storage system 9 in the solar absorber with self-generating power and thermal storage functions includes a thermal storage tank and a transfer pump 15. The upper header 703, thermal storage tank, transfer pump 15 and lower header 704 are connected in sequence by pipes. The thermal storage tank can be a dual-tank form of high temperature molten salt tank and low temperature molten salt tank, a single-tank thermal storage form of molten salt inclined thermosphere, a thermochemical thermal storage tank of metal hydroxide system, a thermochemical thermal storage tank of carbonate system, a porous medium thermal storage tank with phase change material phase change thermal storage function, and other types of thermal storage devices.

[0058] The operation method of the solar absorber with self-generating and heat storage functions described in Application Example 1 above is as follows:

[0059] When there is sufficient sunlight, the receiver 7 absorbs concentrated solar energy from the concentrating system 8. Most of the concentrated solar energy is absorbed by the thermionic cathode 103. Some electrons inside the thermionic cathode 103 absorb heat and their kinetic energy increases. They overcome the surface potential barrier and are emitted to the thermionic anode 101. Electrons can flow into the load through the wire to do work and return to the thermionic cathode 103, thereby realizing the power generation function of the device. The heat transfer metal pipe 3 can absorb most of the heat from the thermionic cathode 103. The heat transfer medium 4 flows into the receiver 7 through the medium flow pipe 705, absorbs the heat from the heat transfer metal pipe 3 and becomes a high-temperature medium. Then, part of the heat transfer medium 4 enters the heat storage system 9 for heat storage, and another part of the heat transfer medium 4 enters the power circulation system 10 to drive the heat engine to do work. Under this operating condition, valves A11, B12 and C13 are open, and valves D14, E16 and transfer pump 15 are closed. The flow rate of the medium can be adjusted by the opening of valves A11 and B12.

[0060] When sunlight is insufficient, the heat absorber 7 can also generate electricity. The heat transfer medium 4 first enters the heat storage system 9, absorbs the heat of the high-temperature heat storage medium, and becomes a high-temperature medium. Then, part of the heat transfer medium 4 can enter the heat absorber tube 701 to heat the thermionic cathode 103. The thermionic cathode 103 absorbs heat and emits electrons to the thermionic anode 101 to generate electricity. Part of the heat transfer medium 4 enters the power cycle system 10 to drive the heat engine to do work. The heat distribution of the thermionic emission power generation component and the power cycle system can be adjusted by controlling the opening of the valves. Under this condition, valves A11, D14, E16, B12 and transfer pump 15 are open, and valve C13 is closed.

[0061] Example 3:

[0062] like Figure 5 As shown, this embodiment provides a power system for a solar absorber with self-generating and heat storage functions as described in Embodiment 2. The difference is that the concentrating system adopts a tower solar concentrating system, the power circulation system adopts an air Brayton cycle system, and the heat transfer medium is air.

[0063] The operation method of the above-mentioned solar absorber with self-generating and heat storage functions is as follows:

[0064] When sunlight is abundant, the heliostat 18 reflects sunlight onto the receiver 7 through its focusing and tracking functions. The receiver 7 is located on the tower 17. After absorbing most of the concentrated energy, the thermionic cathode 103 on the receiver tube 701 heats up. Some electrons inside the thermionic cathode 103 overcome the surface potential barrier and are emitted to the thermionic anode 101 after absorbing energy. The electrons are then transported to the load via wires to generate electricity. In this embodiment, air enters the Brayton cycle system through the compressor 21, passes through the regenerator 20, and then enters the receiver 7. The air can flow into the receiver tube 701 through the working fluid flow pipe 705 to absorb heat from the back side of the cathode. Afterward, part of the air enters the heat storage system 9 for heat storage, and part of the air enters the turbine 19 to perform work. Under this operating condition, valves A11, B12, and C13 are open, while valves D14, E16, and the transfer pump 15 are closed. The air flow ratio is adjusted by the opening of valves A11 and B12.

[0065] When sunlight is insufficient, the air, the heat transfer medium 4, exits from the regenerator 20 and first enters the heat storage system 9, absorbing heat from the high-temperature heat storage medium to become high-temperature air. Subsequently, some of the air can enter the heat absorber tube 701 to heat the thermionic cathode 103. The thermionic cathode 103 absorbs heat from the high-temperature heat transfer medium and concentrates solar energy, and its temperature rises, emitting electrons to the thermionic anode 101 to generate electricity. Some of the air enters the turbine 19 to drive the heat engine to do work. The heat distribution of the thermionic emission power generation component and the power cycle system can be adjusted by controlling the opening of the regulating valves. Under this operating condition, valves A11, D14, E16, B12 and transfer pump 15 are open, and valve C13 is closed.

[0066] Example 4:

[0067] like Figure 6 As shown, this embodiment provides a power system for a solar absorber with self-generating and heat storage functions as described in Embodiment 3. The difference is that the power cycle system adopts a steam Rankine cycle, and the heat transfer medium is molten salt, which is used as the heat storage medium.

[0068] The operation method of the above-mentioned solar absorber with self-generating and heat storage functions is as follows:

[0069] When there is sufficient sunlight, the thermionic emission power generation component 1 generates electricity. In this embodiment, molten salt enters the heat absorption tube 701 after passing through the low-temperature storage tank in the heat storage system 9. After absorbing heat from the back side of the cathode, the molten salt becomes high-temperature molten salt and enters the high-temperature storage tank for heat storage. Part of the molten salt in the storage tank enters the steam generator 22 to heat the steam, making the steam a high-temperature and high-pressure working fluid that enters the steam turbine 23 to do work. After doing work, the steam passes through the condenser 24 to discharge some heat and then returns to the steam generator 22 through the circulation pump 25 for a new power cycle. The high-temperature molten salt loses some heat after passing through the steam generator 22 and becomes low-temperature molten salt. The low-temperature molten salt enters the low-temperature storage tank. Part of the molten salt is stored in the low-temperature storage tank, and part of the molten salt flows to the heat absorber to absorb heat and enters the high-temperature storage tank for a new heat storage cycle. The flow distribution of molten salt can be adjusted by controlling the opening of the valves. Under this operating condition, valves A11, D14, E16 and transfer pump 15 are open, while valves C13 and B12 are closed.

[0070] When sunlight is insufficient, some of the high-temperature molten salt can flow from the high-temperature storage tank through valve B12 to the heat absorber 7 to heat the thermionic cathode 103. The thermionic emission power generation component 1 absorbs the concentrated solar energy and the energy of the high-temperature molten salt to generate electricity. Afterward, the molten salt returns to the low-temperature storage tank through valves C13 and D14. Another portion of the high-temperature molten salt enters the steam generator 22 to heat steam, which then drives the steam into the turbine 23 to perform work. The low-temperature molten salt returns to the low-temperature storage tank through valve D14. The heat distributed to the thermionic emission power generation component and the power cycle system can be adjusted by controlling the opening of the relevant valves. Under this operating condition, valves B12, C13, and D14 are open, while valves A11, transfer pump 15, and E16 are closed.

[0071] Example 5:

[0072] This embodiment provides a power system for a solar absorber with self-generating and heat storage functions as described in Embodiment 3. The difference lies in that the concentrating system adopts a trough-type solar concentrating system, such as... Figure 7 As shown, a heat absorber 7 is installed on the trough-type condenser mirror 26.

[0073] Example 6:

[0074] This embodiment provides a power system for a solar absorber with self-generating and heat storage functions as described in Embodiment 3. The difference is that the thermionic cathode 103 is a semiconductor thermionic cathode, and the thermionic emission power generation component 1 can perform photon-enhanced thermionic emission. Some electrons in the valence band of the thermionic cathode 103 can be excited to the conduction band by photons, and then the heat of the thermionic cathode 103 can overcome the surface potential barrier and be emitted to the thermionic anode 101. Compared with thermionic emission power generation, which can only use heat to excite internal electrons, photon-enhanced thermionic emission power generation can have a stronger output current at a lower temperature. At the same temperature, photon-enhanced thermionic emission power generation has a higher conversion efficiency.

[0075] The photon incident surface, also known as the electron emitting surface, of this embodiment significantly reduces the loss of free electrons during diffusion towards the emitting surface compared to ordinary photon-enhanced thermionic emission cathodes, resulting in a higher electron emission rate and greater efficiency.

[0076] Example 7:

[0077] This embodiment provides a work system for a solar absorber with self-generating and heat storage functions as described in Embodiment 3. The difference is that the electrode gap 102 is filled with cesium vapor maintained at a specified temperature. The filling of cesium vapor can not only reduce the work function of the surface of the thermionic anode 101 and the thermionic cathode 103, but also mitigate the space charge effect between the electrodes.

[0078] Specifically, cesium vapor can be directly ionized into cesium ions by absorbing photons of a specific spectrum, or it can be ionized into cesium ions by heat. Cesium ions can neutralize space charge in the electrode gap 102, reducing the inter-electrode potential barrier, thereby playing a role in transporting electrons and increasing the power generation current. At the same time, some of the cesium atoms adsorbed on the electrodes can form surface dipoles, thereby effectively reducing the work function of the thermionic anode 101 and the thermionic cathode 103, increasing the output current and output voltage of the thermionic emission power generation component 1, and improving the power generation capacity of the thermionic emission power generation component 1.

[0079] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A solar thermal absorber with self-generating and heat storage functions, characterized in that, The heat absorption tube, the upper header tank, the lower header tank and the heat storage system are included, a plurality of heat absorption tubes are arranged side by side between the upper header tank and the lower header tank, and the upper header tank and the lower header tank are respectively connected with the heat storage system; The wall of the heat absorption tube is a multilayer structure, from outside to inside, the wall is sequentially provided with a thermionic anode, an electrode gap, a thermionic cathode and a heat transfer metal pipeline, the heat transfer metal pipeline is filled with a heat transfer working medium, and the thermionic anode and the thermionic cathode are respectively connected with an external load through an anode lead and a cathode lead; The thermionic anode is made of indium tin oxide transparent conductive film glass, fluorine-doped SnO2 transparent conductive glass, quartz substrate or graphene, and the light-receiving surface of the thermionic cathode is also an electron emission surface.

2. The solar energy heat absorber with self-generating and heat storing functions according to claim 1, wherein, A back insulating layer is arranged between the thermionic cathode and the heat transfer metal pipeline.

3. The solar energy heat absorber with self-generating and heat storing functions according to claim 2, wherein, A plurality of electrode insulating layers are uniformly arranged in the electrode gap.

4. The solar heat absorber with self-power generation and heat storage function according to claim 1, wherein The thermionic cathode material is pure metal, metal oxide, semiconductor or graphene.

5. The solar energy heat absorber with self-generating and heat storing functions according to claim 1, wherein, The electron-receiving surface of the thermionic anode is provided with a thermionic anode coating, and the light-receiving surface of the thermionic cathode is provided with a thermionic cathode coating.

6. The solar energy heat absorber with self-generating and heat storing functions according to claim 1, wherein, The electrode gap is vacuum or filled with cesium vapor.

7. The solar energy heat absorber with self-generating and heat storing functions according to claim 1, wherein, A light condensing system is arranged outside the heat absorber, and the light condensing system is a tower type, a disc type, a groove type, a linear Fresnel type, a tower-groove coupling type, a tower-disc coupling type or a disc-groove coupling type.

8. The solar energy heat absorber with self-generating and heat storing functions according to claim 1, wherein, The heat transfer working medium is one or more of molten salt, water, air and carbon dioxide.

9. The solar energy heat absorber with self-generating and heat storing functions according to claim 3, wherein, The heat storage system includes a heat storage tank and a pump, and the upper header tank, the heat storage tank, the pump and the lower header tank are sequentially connected through pipelines.

10. The method of operating a solar energy heat absorber with self- power generation and heat storage function according to claim 9, wherein, The steps are as follows: (1) When the sunlight is sufficient, the light condensing energy is absorbed by the thermionic cathode through the thermionic anode, the temperature of the thermionic cathode is increased after absorbing the energy, part of the electrons in the thermionic cathode are excited and overcome the surface potential barrier to emit to the thermionic anode through the electrode gap, the thermionic anode receives the electrons emitted from the thermionic cathode, the electrons are led to the external load through the anode lead, and then return to the thermionic cathode through the cathode lead, thereby forming a closed loop to realize power generation; During the power generation, the heat transfer working medium in the heat transfer metal pipeline absorbs the heat of the back side of the thermionic cathode to become high-temperature working medium, and then enters the heat storage system to realize heat storage; (2) When the sunlight is insufficient, the heat transfer working medium absorbs the heat of the high-temperature working medium in the heat storage tank to become high-temperature heat transfer working medium, the heat transfer working medium enters the heat absorption tube, the thermionic cathode absorbs the heat energy of the heat transfer working medium to increase the temperature of the thermionic cathode, and the thermionic emission is realized to generate electricity.

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