A highly efficient power generation device combining thermophotovoltaics and thermoelectricity

Abstract

A highly efficient power generation device combining thermophotovoltaics and thermoelectrics, comprising a thermal radiation transmitter, a filter, a thermophotovoltaic cell, a first thermoelectric device, a phase change container and a second thermoelectric device arranged in order from top to bottom, wherein the phase change container is filled with a phase change material. The present invention realizes the process of efficiently generating electricity from heat by high-temperature radiation through the coupling utilization of thermophotovoltaic cells and thermoelectric devices. The phase change material is combined with the thermophotovoltaic cell and the thermoelectric device, and while absorbing and utilizing the waste heat of thermophotovoltaic-thermoelectric, it exists as the cold end of the thermoelectric device 1 and the hot end of the thermoelectric device 2, thereby improving the utilization efficiency. The present invention has a simple structure, realizes the efficient conversion of heat and electricity, improves the power generation efficiency of the thermophotovoltaic-thermoelectric system, and at the same time, the phase change container can be further used for the temperature control of internal electronic devices.

Description

Technical Field

[0001] The invention belongs to the field of thermoelectric conversion and relates to a thermoelectric conversion power generation device. Background Art

[0002] As one of the current research hotspots of efficient heat-to-electricity conversion technology, thermophotovoltaic technology (TPV) can utilize various types of renewable energy and industrial waste heat energy, and directly convert thermal radiation into electrical energy through semiconductor thermophotovoltaic cells. While taking into account the characteristics of zero emissions and high energy utilization, it has the application advantages of high power density, high reliability, no moving parts, and low noise, and has attracted extensive attention from scholars at home and abroad. So far, the highest reported efficiency of thermophotovoltaic cells has exceeded 40%, which is higher than the average efficiency of turbine heat engines. Many aerospace powers have also listed it as one of the preferred development technologies for the energy supply of future high-power satellites and deep space exploration spacecraft.

[0003] There are two important reasons for the low efficiency of thermophotovoltaic cells: first, their spectral response cannot cover the full-band radiation spectrum of thermal radiation; second, the efficiency of converting radiation energy into electrical energy is low, that is, the heat loss in the thermoelectric conversion process is large. Thermoelectric devices use the Seebeck effect to convert thermal energy into electrical energy, and their requirements for heat sources are low. Therefore, thermoelectric devices can be used to convert thermal energy in thermophotovoltaic cells into electrical energy, thereby realizing the full spectrum utilization of solar radiation energy. Limited by the performance of current thermoelectric materials, the conversion efficiency of thermoelectric devices is less than 10%, which is far lower than the requirements for commercial applications. Although under current technical conditions, thermoelectric devices are not an efficient way to convert solar energy into electrical energy, they can be used to make up for the shortcomings of photovoltaic cells.

[0004] The most fundamental problem in the thermophotovoltaic-thermoelectric coupling system is the conflict between the efficiency-temperature characteristics of thermophotovoltaic cells and thermoelectric devices. The efficiency of thermophotovoltaic cells gradually decreases as their operating temperature increases, while the efficiency of thermoelectric devices gradually increases as the temperature difference between their hot and cold ends increases. Since the hot end of the thermoelectric device is directly connected to the thermophotovoltaic cell to absorb and convert the waste heat of thermophotovoltaic, when the temperature of the cold end of the thermoelectric device is constant, lowering the operating temperature of the thermophotovoltaic cell can improve the efficiency of thermophotovoltaic power generation, but it will inevitably reduce the temperature difference and efficiency of the thermoelectric device; on the contrary, increasing the temperature difference of the thermoelectric device will also increase the operating temperature of the thermophotovoltaic cell, thereby reducing the performance of thermophotovoltaic power generation. This conflict between the efficiency-temperature characteristics of thermophotovoltaic cells and thermoelectric devices means that not all coupling of thermophotovoltaic cells and thermoelectric devices can improve the utilization rate of radiation energy.

[0005] In summary, there are many uncertain factors in the thermoelectric conversion efficiency of the thermophotovoltaic-thermoelectric coupling system, and temperature is the parameter with the greatest impact. Therefore, a device with high thermoelectric conversion efficiency and temperature control capability is a difficult problem that needs to be solved urgently in efficient thermoelectric conversion technology. Summary of the invention

[0006] The technical problem solved by the present invention is to overcome the deficiencies of the prior art and provide a thermophotovoltaic-phase change material-thermoelectric coupling device capable of efficiently recycling radiation energy.

[0007] The technical solution of the present invention is: a high-efficiency power generation device combining thermophotovoltaics and thermoelectrics, comprising a thermal radiation transmitter, a filter, a thermophotovoltaic cell, a first thermoelectric device, a phase change container and a second thermoelectric device arranged in sequence from top to bottom, wherein the phase change container is filled with a phase change material; the thermal radiation transmitter receives external radiation, and after absorbing heat and the temperature rises, emits photon thermal radiation and transmits it to the filter; the filter reflects the photon thermal radiation with energy less than the bandgap value of the thermophotovoltaic cell back to the thermal radiation transmitter, and transmits the photon thermal radiation with energy greater than the bandgap value of the thermophotovoltaic cell and projects it onto the upper surface of the thermophotovoltaic cell; the thermophotovoltaic cell converts a part of the received thermal radiation into electrical energy through a thermoelectric conversion process, and transfers the remaining part in the form of heat energy to the upper surface of the first thermoelectric device through heat conduction, the first thermoelectric device converts a part of the thermal energy into electrical energy, and the remaining heat energy is transferred to the phase change material in the phase change container and absorbed by the phase change material; the phase change material controls the cold end temperature of the first thermoelectric device by the change of phase at a specific temperature, and at the same time serves as an input heat source for the second thermoelectric device, and the second thermoelectric device converts the absorbed thermal energy into electrical energy.

[0008] Furthermore, the filter adopts a total of eight layers of Si / SiO2 periodic structure, with quartz glass as the substrate, and then Si layers and SiO2 layers are alternately arranged on the substrate.

[0009] Preferably, the Si layers and SiO2 layers are alternately arranged on the substrate, and the thickness of each layer is 280nm, 360nm, 280nm, 360nm, 280nm, 360nm, 280nm, and 180nm respectively.

[0010] Preferably, the material of the thermal radiation transmitter is a high-temperature ceramic containing a transition metal.

[0011] Preferably, the thermophotovoltaic cell is a III-V mixture gallium antimonide cell.

[0012] Preferably, the area of ​​the thermophotovoltaic cell is 1.5 cm*1.5 cm, and the open circuit voltage V oc =0.52V, short-circuit current I sc =6A, fill factor FF = 0.84, maximum output power Pmax =2.6W.

[0013] Preferably, the phase change material is a composite of expanded graphite and paraffin wax using a sol-gel method, with organic paraffin wax as the base and expanded graphite as the supporting structure.

[0014] Preferably, the phase change container is made of aluminum, and has rectangular metal fins arranged equidistantly inside, which fit tightly with the phase change material inside.

[0015] Preferably, the first thermoelectric device and the second thermoelectric device use bismuth telluride as PN junction material.

[0016] Preferably, the thermal radiation transmitter and the filter are arranged in parallel, and the vertical distance between them is 63.2 mm.

[0017] The advantages of the present invention over the prior art are: the present invention realizes the process of generating electricity from heat by high-temperature radiation efficiently through the coupling utilization of thermophotovoltaic cells and thermoelectric devices. The phase change material is combined with the thermophotovoltaic cell and the thermoelectric device, and while absorbing and utilizing the waste heat of thermophotovoltaic-thermoelectric, it exists as the cold end of the thermoelectric device 1 and the hot end of the thermoelectric device 2, thereby improving the utilization efficiency. The present invention has a simple structure, realizes the efficient conversion of heat and electricity, improves the power generation efficiency of the thermophotovoltaic-thermoelectric system, and the phase change container can be further used for the temperature control of internal electronic devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 The schematic diagram of the power generation device of the present invention is shown in FIG.

[0019] Figure 2 It is a structural diagram of the power generation device of the present invention;

[0020] Figure 3 A schematic diagram of the eight-layer Si / SiO2 periodic structure of the filter of the present invention;

[0021] Figure 4 It is a schematic structural diagram of the phase change container of the present invention. DETAILED DESCRIPTION

[0022] The present invention is further described in detail below in conjunction with the accompanying drawings.

[0023] like Figure 1 , Figure 2 As shown, a thermoelectric conversion high-efficiency power generation device of the present invention includes a thermal radiation transmitter 1, a filter 2, a thermophotovoltaic cell 3, a first thermoelectric device 4, a phase change material 5, a phase change container 6 and a second thermoelectric device 7.

[0024] The thermal radiation transmitter 1 is used to receive external high-temperature radiation and emit thermal radiation to the filter 2. The thermal radiation transmitter 1 can be made of high-temperature ceramics containing transition metals, such as magnesium oxide, whose transition metal ions, such as nickel ions, have a large emissivity in the near-infrared band. Under high temperatures, the material can improve the radiation efficiency of the material surface while ensuring the stability of the material structure. At the same time, the light radiated by the thermal radiation transmitter 1 at high temperature can achieve a higher degree of conversion, achieve the maximum thermal-to-light conversion efficiency, and convert light into electricity to the greatest extent. Therefore, the material has been widely used in integrated circuits, high-power power supplies, new energy vehicles, and aerospace fields.

[0025] The filter 2 reflects the thermal radiation with energy less than the forbidden band value of the thermophotovoltaic cell 3 back to the thermal radiation transmitter 1, and transmits the thermal radiation with energy greater than the forbidden band value of the thermophotovoltaic cell and projects it onto the upper surface of the thermophotovoltaic cell 3. Based on the dielectric waveguide theory and considering the absorption loss problem, the filter 2 of the present invention adopts a total of eight layers of Si / SiO2 periodic structure, such as Figure 3 As shown. Quartz glass is used as the substrate, and then Si layers and SiO2 layers are arranged alternately on the substrate. The design is based on the following: First, photonic crystals require a large difference in the dielectric constants (refractive index) of the two materials. The dielectric constant of Si is 11.56, and the dielectric constant of SiO2 is 2.2; second, the thermal radiation transmitter 1 works above 1000°C, and when the temperature reaches the optical filter layer, the temperature is basically around 300°C to 500°C. Si and SiO2 are resistant to high temperatures and can work normally; third, Si and SiO2 are both common thin film materials with mature growth processes. In addition, based on the central wavelength of filter 2, in order to reduce the reflectivity of the required band, the thickness of the first layer of SiO2 is halved, ultimately improving the conversion efficiency of the entire system. The thickness of each layer is 280nm, 360nm, 280nm, 360nm, 280nm, 360nm, 280nm, 180nm.

[0026] The filter 2 is arranged in the horizontal direction, the thermal radiation transmitter 1 and the filter 2 are arranged parallel to each other, the thermal radiation transmitter 1 is located above the filter 2 , the thermophotovoltaic cell 3 is arranged parallel to the thermal radiation transmitter 1 and the filter 2 , and the thermophotovoltaic cell 3 is located below the filter 2 .

[0027] Thermophotovoltaic cell 3 is a III-V group mixed gallium antimonide (GaSb) cell. The area of ​​the thermophotovoltaic cell 3 in the present invention is 1.5 cm*1.5 cm, and the open circuit voltage V oc =0.52V, short-circuit current I sc =6A, fill factor (the ratio of the product of the current and voltage when the battery has maximum output power to the product of the short-circuit current and open-circuit voltage) FF = 0.84, maximum output power P max =2.6W, and can work normally at a temperature of 90℃.

[0028] like Figure 4 As shown, the material of the phase change container 6 is aluminum, and there are rectangular metal fins arranged equidistantly inside, and they fit tightly with the adjacent materials. The phase change material 5 is prepared by compounding expanded graphite and paraffin wax. The material preparation method is based on organic paraffin wax and uses expanded graphite as a supporting structure. High-purity natural graphite is ground into powder and subjected to acid washing and drying treatment. At the same time, the paraffin wax is heated to a liquid state, and an expansion agent is added. Finally, the graphite material and the paraffin expansion agent are evenly mixed, heated in a vacuum, and the multi-pore adsorption characteristics of graphite are used to prepare a phase change material 5 with high thermal conductivity and phase change energy storage characteristics. The phase change material 5 fills the phase change container 6, and the height of the phase change container 6 is 30 mm.

[0029] The first thermoelectric device 4 and the second thermoelectric device 7 use bismuth telluride Bi2Te3 as the PN junction material. In the present invention, the first thermoelectric device 4 and the second thermoelectric device 7 are both made of bismuth telluride material with a high Seebeck coefficient, which has a low thermal conductivity and helps to maintain the temperature difference and improve the thermoelectric conversion efficiency. The height is 5 mm, the number of thermoelectric pin pairs is 128 pairs, and the ceramic surface size of the thermoelectric device is 1.5 cm*1.5 cm.

[0030] The first thermoelectric device 4, the phase change container 6, and the second thermoelectric device 7 are arranged parallel to the thermophotovoltaic cell 3. The thermal radiation transmitter 1 is attached to the heat source, and the thermal radiation transmitter 1, the filter 2, the thermophotovoltaic cell 3, the first thermoelectric device 4, the phase change material 5, the phase change container 6, and the second thermoelectric device 7 are arranged in parallel. Figure 2 As shown, they are attached to each other in sequence from top to bottom, and the vertical distance between the thermal radiation transmitter 1 and the filter 2 is 63.2 mm.

[0031] The working process of the thermoelectric conversion high-efficiency power generation device of the present invention is:

[0032] The power generation device of the present invention starts to work under the condition of heat energy provided by the heat source. The thermal radiation transmitter 1 receives external high-temperature radiation, and after absorbing the heat source, the temperature rises and the photon thermal radiation is emitted and the heat is transferred to the filter 2. After the selection of the filter 2, the thermal radiation with energy less than the forbidden band value of the thermophotovoltaic cell 3 is reflected back to the thermal radiation transmitter 1, and the thermal radiation with energy greater than the forbidden band value of the thermophotovoltaic cell 3 is projected onto the upper surface of the thermophotovoltaic cell 3 through the filter 2. The thermophotovoltaic cell 3 converts a part of the received thermal radiation into electrical energy through the thermoelectric conversion process, and the remaining part is transferred to the upper surface of the first thermoelectric device 4 in the form of thermal energy through heat conduction. The first thermoelectric device 4 converts a very small part of this part of the thermal energy into electrical energy. The remaining thermal energy is transferred to the phase change material 5 in the phase change container 6. The phase change material 5 absorbs this part of the thermal energy and controls the cold end temperature of the first thermoelectric device 4 through the change of the material phase at a specific temperature, and at the same time serves as the input heat source of the second thermoelectric device 7. The thermophotovoltaic cell 3, the first thermoelectric device 4, and the second thermoelectric device 7 convert the radiation energy into electrical energy output, and the temperature rises at the same time. The phase change material 6 absorbs the heat of the first thermoelectric device 4 and the second thermoelectric device 7, and exists as the cold end of the first thermoelectric device 3 and the hot end of the second thermoelectric device 7. The various components in the power generation device of the present invention are relatively independent of each other, so there is great flexibility in the design of the power generation device.

[0033] When the material of the thermophotovoltaic cell 3 is GaSb, the area ratio of the absorber-emitter 1 is greater than 0.6, and the temperature of the absorber-emitter 1 is about 2000K, the system efficiency is greater than 20%. When the area ratio of the absorber-emitter 1 is less than 0.6 and the temperature of the absorber-emitter 1 is in the range of 1800K-1900K, the device efficiency is greater than 25%. Assuming that the surface temperature of the absorber-emitter 1 is uniformly distributed, the smaller the area ratio of the absorber-emitter 1, the higher the efficiency of the device.

[0034] The contents not described in detail in the specification of the present invention belong to the common knowledge of those skilled in the art.

Claims

1. A highly efficient power generation device combining thermophotovoltaic and thermoelectric, characterized in that: The invention comprises a thermal radiation transmitter (1), a filter (2), a thermophotovoltaic cell (3), a first thermoelectric device (4), a phase change container (6) and a second thermoelectric device (7) which are arranged in sequence from top to bottom, wherein the phase change container (6) is filled with a phase change material (5); the thermal radiation transmitter (1) receives external radiation, and after absorbing heat and the temperature rises, emits photon thermal radiation which is transmitted to the filter (2); the filter (2) reflects the photon thermal radiation whose energy is less than the forbidden band value of the thermophotovoltaic cell (3) back to the thermal radiation transmitter (1), transmits the photon thermal radiation whose energy is greater than the forbidden band value of the thermophotovoltaic cell (3) and projects it to the thermophotovoltaic cell (3) The thermophotovoltaic cell (3) converts a portion of the received thermal radiation into electrical energy through a thermoelectric conversion process, and transfers the remaining portion in the form of thermal energy to the upper surface of the first thermoelectric device (4) through heat conduction. The first thermoelectric device (4) converts a portion of the thermal energy into electrical energy, and the remaining thermal energy is transferred to the phase change material (5) in the phase change container (6) and absorbed by the phase change material (5). The phase change material (5) controls the cold end temperature of the first thermoelectric device (4) through the change of phase at a specific temperature, and at the same time serves as an input heat source for the second thermoelectric device (7). The second thermoelectric device (7) converts the absorbed thermal energy into electrical energy.

2. A high-efficiency power generation device combining thermophotovoltaic and thermoelectric according to claim 1, characterized in that: The filter (2) adopts a total of eight layers of Si / SiO2 periodic structure, with quartz glass as the substrate, and then Si layers and SiO2 layers are alternately arranged on the substrate.

3. The high-efficiency power generation device combining thermophotovoltaic and thermoelectric according to claim 2, characterized in that: The Si layers and SiO2 layers are alternately arranged on the substrate, and the thickness of each layer is 280nm, 360nm, 280nm, 360nm, 280nm, 360nm, 280nm, and 180nm respectively.

4. The high-efficiency power generation device combining thermophotovoltaic and thermoelectric according to claim 1, characterized in that: The material of the heat radiation transmitter (1) is high-temperature ceramic containing transition metal.

5. The high-efficiency power generation device combining thermophotovoltaic and thermoelectric according to claim 1, characterized in that: The thermophotovoltaic cell (3) is a III-V group mixed gallium antimonide cell.

6. The high-efficiency power generation device combining thermophotovoltaic and thermoelectric according to claim 5, characterized in that: The area of ​​the thermophotovoltaic cell (3) is 1.5 cm*1.5 cm, and the open circuit voltage V oc =0.52V, short-circuit current I sc =6A, fill factor FF = 0.84, maximum output power P max =2.6W.

7. The high-efficiency power generation device combining thermophotovoltaic and thermoelectric according to claim 1, characterized in that: The phase change material (5) is a composite of expanded graphite and paraffin using a sol-gel method, with organic paraffin as the base and expanded graphite as the supporting structure.

8. The high-efficiency power generation device combining thermophotovoltaic and thermoelectric according to claim 1, characterized in that: The phase change container (6) is made of aluminum and has rectangular metal fins arranged at equal intervals inside, which are tightly fitted with the phase change material (5) inside.

9. The high-efficiency power generation device combining thermophotovoltaic and thermoelectric according to claim 1, characterized in that: The first thermoelectric device (4) and the second thermoelectric device (7) use bismuth telluride as PN junction material.

10. The high-efficiency power generation device combining thermophotovoltaic and thermoelectric according to claim 1, characterized in that: The heat radiation transmitter (1) and the filter (2) are arranged in parallel, and the vertical distance between the two is 63.2 mm.

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