Thin-film thermoelectric power generation coupled with selective absorption coating solar collector

Abstract

The present invention provides a thin-film temperature difference power generation coupled with a selective absorption coating solar heat collection tube, comprising a metal tube and a cover glass tube, wherein the outer wall of the metal tube is sequentially formed with a first insulating layer, a PN junction layer, a second insulating layer and a selective absorption coating, and the PN junction layer is connected to a lead-out electrode; the two ends of the cover glass tube are respectively sealed and connected with a kovar metal sleeve, and the kovar metal sleeve is sealed and connected with the outer wall of the metal tube through a bellows assembly to form a vacuum interlayer; the wire connected to the lead-out electrode forms a tortuous section in the vacuum interlayer, and the end of the tortuous section is directly sealed and led out or led out to the outside of the cover glass tube through a transition material. The present invention is particularly suitable for trough-type solar heat collection tubes, and can make the temperature difference between the two temperature zones reach between 10 and 50°C, so that the natural temperature difference of the trough-type solar heat collection tube can be fully utilized to realize temperature difference power generation, and there is no need to actively dissipate heat in the low temperature zone.

Description

Technical Field

[0001] The invention relates to a coating structure of a solar heat collecting tube, in particular to a glass-metal-seal straight-through solar heat collecting tube structure utilizing thin-film temperature difference power generation coupled with a selective absorption coating. Background Art

[0002] Solar energy has the huge advantages of being inexhaustible, clean and environmentally friendly. It has been accepted by society and has developed rapidly.

[0003] At present, there are two main ways to utilize solar energy: power generation and thermal utilization. Power generation is divided into photovoltaic power generation and solar thermal power generation. Thermal utilization mainly converts solar energy into thermal energy to provide medium-temperature or low-temperature industrial or civilian heat below 250°C. With the development of technology, photovoltaic and solar thermal energy have begun to show a trend of technical coupling, that is, when solar photovoltaic power generation is used, heat recovery is used to achieve combined heat and power. When solar thermal heating is used, the temperature difference of the heat collection system can be used to achieve both solar thermal heating and power supply. Alternatively, when solar thermal heating is used, some photovoltaic power generation components are built in at the same time to achieve photovoltaic power generation. The above model realizes solar thermal power cogeneration.

[0004] Among the existing solar cogeneration technologies, the main ones are cogeneration in the concentrated photovoltaic cooling mode, cogeneration in the waste heat recovery mode of the back plate of ordinary solar photovoltaic panels, and photovoltaic components built into ordinary solar collector tubes, which can generate electricity and collect heat for heating at the same time. As the cost of ordinary solar photovoltaic panels is significantly declining, the technology and cost of ordinary solar photovoltaic panels have significant competitive advantages over concentrated photovoltaic power generation technology. Therefore, the advantages of concentrated photovoltaics will no longer be advantageous and will gradually withdraw from the market. However, the cogeneration of heat and power with photovoltaic power generation components built into ordinary solar collector tubes has the problems of high cost, low power generation efficiency, and difficulty in operation, making it difficult to market. The cogeneration technology of waste heat recovery mode of ordinary solar photovoltaic panels has been the main cogeneration mode in recent years. However, there is also a problem that the energy of waste heat recovery is not enough to offset the energy consumed for waste heat recovery, which is not worth the loss and is in a difficult situation.

[0005] CN200510098451 provides a solar heat pipe temperature difference power generation device, CN201220272211.7 provides a double-pass thermovoltaic vacuum tube, CN201410088490 provides a double vacuum internal condensing power generation and heating solar heat collection tube, 201320507705.3 provides a solar vacuum heat collection tube integrated with heat collection and power generation. These patents propose a heat and power cogeneration component combining a solar heat collection tube and a temperature difference power generation component, but the following problems still exist:

[0006] 1. They are all based on the existing temperature difference power generation module model combined with low-temperature solar collector tubes, with complex structure and process, making it difficult to carry out large-scale production.

[0007] 2. Due to the small temperature difference, the actual power generation efficiency is low, which will result in poor additional input-output efficiency and low economic benefits and cannot be accepted by the market.

[0008] With the development of solar thermal technology, low-temperature solar thermal utilization technology has matured, and due to the small temperature difference in heat utilization, it is not suitable for realizing solar thermal power generation through temperature difference power generation technology. With the maturity of trough solar collector tubes and trough medium-temperature solar collector systems, this type of solar energy will have huge technical development and market space in the current medium-temperature industrial heat utilization between 80 and 550°C and solar high-temperature power generation. Therefore, how to make full use of the characteristics of trough solar systems and develop low-cost, highly reliable solar thermal power generation systems will be the main development direction of trough solar systems in the future. Summary of the invention

[0009] The invention provides a thin-film temperature difference power generation coupled with a selective absorption coating solar heat collecting tube, the purpose of which is to provide a solar heat and power cogeneration system with low development cost and high reliability.

[0010] To achieve the above object, the technical solution adopted by the present invention is:

[0011] A thin film temperature difference power generation coupled with selective absorption coating solar heat collecting tube, comprising a metal tube and a cover glass tube sleeved outside the metal tube, wherein a fluid to be heated flows in the metal tube, and is characterized in that:

[0012] A first insulating layer, a PN junction layer, a second insulating layer and a selective absorption coating are sequentially formed on the outer wall of the metal tube, and the PN junction layer is connected to a lead-out electrode;

[0013] Both ends of the cover glass tube are respectively connected by a kovar metal sleeve, the kovar metal sleeve is sealed with the outer wall of the metal tube through a bellows assembly, and a vacuum interlayer is formed between the cover glass tube and the metal tube;

[0014] The wire connected to the lead-out electrode forms a meandering section in the vacuum interlayer, and the end of the meandering section is led out to the outside of the cover glass tube by direct sealing or through a transition material.

[0015] The thin film temperature difference power generation coupled with selective absorption coating solar thermal collector tube, wherein: the tortuous section is S-shaped or spiral.

[0016] The thin film temperature difference power generation coupled with selective absorption coating solar collector tube, wherein: the Kovar metal sleeve is sealed connected to the outer end cover of a bellows, the inner end of the bellows is sealed connected to a support ring, and the support ring is sealed and fixed on the outer wall of the metal tube.

[0017] The thin film temperature difference power generation coupled with selective absorption coating solar thermal collector tube, wherein: an evaporable getter and / or a non-evaporable getter is fixed on the support ring through a getter bracket.

[0018] The thin film temperature difference power generation coupled with selective absorption coating solar thermal collector tube, wherein: the transition material is transition glass or transition ceramic.

[0019] The thin film temperature difference power generation coupled with selective absorption coating solar collector tube, wherein the PN junction layer includes a P pole, a PN overlapping area and an N pole connected in sequence; the PN overlapping area is located at a relatively high temperature position of the metal tube, and the end of the P pole and the N pole opposite to the PN overlapping area is located at a relatively low temperature position of the metal tube.

[0020] The thin film temperature difference power generation coupled with selective absorption coating solar collector tube, wherein one side of the metal tube receives solar radiation and is called the concentrated high temperature zone, and the other side is called the backlight low temperature zone, the P pole, PN overlapping zone and N pole are arranged in sequence along the circumference of the metal tube, the PN overlapping zone is located in the concentrated high temperature zone of the metal tube, and the end of the P pole and the N pole opposite to the PN overlapping zone is located in the backlight low temperature zone; the P pole and the N pole are separated from each other at one end of the backlight low temperature zone to form a PN disconnection zone.

[0021] The thin film temperature difference power generation coupled with selective absorption coating solar collector tube, wherein the inlet end of the metal tube is the low temperature end, and the outlet end is the high temperature end, the P pole and the N pole are arranged along the axial direction of the metal tube and spaced from each other to form a PN disconnection zone, the P pole and the N pole form a PN overlapping zone at the high temperature end of the metal tube, and the end of the P pole and the N pole opposite to the PN overlapping zone is located at the low temperature end.

[0022] The thin film temperature difference power generation coupled with selective absorption coating solar collector tube, wherein the PN junction layer forms a series, parallel or series-parallel structure through a conductive coating.

[0023] The thin film temperature difference power generation coupled with selective absorption coating solar collector tube, wherein the selective absorption coating comprises a metal layer, an absorption layer and an anti-reflection layer from the inside to the outside.

[0024] Compared with the existing disclosed thermoelectric power generation coupled with solar thermal collector tube structure, the structure of the present invention has the following advantages:

[0025] 1) When working, the selective absorption coating of the solar collector tube has a concentrated high temperature zone and a backlit low temperature zone in the circumferential direction, and also has an inlet low temperature end and an outlet high temperature end in the axial direction. The above-mentioned high temperature zone (end) and low temperature zone (end) exist naturally and are not significantly changed by increasing the thickness of the temperature difference power generation coating. The present invention is particularly suitable for trough-type solar collector tubes, and can make the temperature difference between the two temperature zones reach between 10 and 50°C. Therefore, the natural temperature difference of the trough-type solar collector tube can be fully utilized to realize temperature difference power generation, and there is no need to actively dissipate heat in the low temperature zone.

[0026] 2) The coating-mode thermoelectric power generation structure has the advantages of easy processing, low material cost and low processing cost compared with conventional thermoelectric power generation modules.

[0027] 3) The superposition mode of the thin film thermoelectric power generation structure and the selective absorption coating does not affect the performance of the selective absorption coating in absorbing solar energy. At the same time, the thermoelectric power generation coating of the thin film structure has a very small effect on the thermal resistance of converting solar energy into heat energy and transmitting it to the steel pipe, which can be ignored and does not affect the heat collection and heat transfer performance of the collector tube.

[0028] 4) The wire in the vacuum interlayer is formed with a zigzag section (S-shaped or spiral), which solves the effect of the heat collector tube being slightly deformed by heat on the tensile deformation of the electrode. The direct sealing or transitional melting sealing of the wire and the cover glass tube solves the problem of power extraction of the temperature difference power generation structure.

[0029] 5) Thermoelectric power generation coating can realize series and parallel connection between PN junctions to effectively improve the efficiency of thermoelectric power generation. Through the insulating ceramic layer, it is effectively isolated from the steel pipe surface and the metal infrared reflection layer of the selective absorption coating. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 , Figure 2 They are respectively a longitudinal cross-sectional view and a transverse cross-sectional view of a solar collector tube structure having a thin-film temperature difference power generation coupled with a selective absorption coating structure;

[0031] Figure 3 It is a schematic diagram of a circumferentially developed structure in which PN junction layers arranged in the circumferential direction are connected in series in the axial direction;

[0032] Figure 4 It is a schematic diagram of a circumferentially developed structure in which PN junction layers arranged along the circumferential direction are connected in parallel in the axial direction;

[0033] Figure 5 It is a schematic diagram of a circumferentially developed structure in which PN junction layers arranged along the circumferential direction are connected in series and parallel in the axial direction;

[0034] Figure 6It is a schematic diagram of a circumferentially developed structure in which PN junction layers arranged along the axial direction are connected in series in the circumferential direction;

[0035] Figure 7 It is a schematic diagram of a circumferentially developed structure in which PN junction layers arranged along the axial direction are connected in parallel in the circumferential direction;

[0036] Figure 8 It is a schematic diagram of a circumferentially developed structure in which PN junction layers arranged along the axial direction are connected in series and parallel in the circumferential direction;

[0037] Fig. 9 The present invention is a flow chart of the manufacturing process of the solar heat collecting tube.

[0038] Explanation of the reference numerals: steel tube 1; coating structure 2; first ceramic insulating layer 21; PN junction layer 22; P pole 221; PN overlapping region 222; N pole 223; PN disconnection region 224; conductive coating 225; second ceramic insulating layer 23; selective absorption coating 24; first lead electrode 31; second lead electrode 32; first conductor 311; second conductor 321; meandering sections 312, 322; cover glass tube 4; Kovar metal sleeve 41; bellows 42; end cap 43; support ring 44; vacuum interlayer 45; getter support 46; evaporable getter 47; non-evaporable getter 48. DETAILED DESCRIPTION

[0039] Some specific embodiments of the present invention will be described in detail below in an exemplary and non-restrictive manner with reference to the accompanying drawings. The same reference numerals in the accompanying drawings indicate the same or similar components or parts. It should be understood by those skilled in the art that these drawings are not necessarily drawn to true scale.

[0040] like Figure 1 , Figure 2 The figure shows a longitudinal cross-sectional view and a transverse cross-sectional view of a solar heat collector tube with a thin film temperature difference power generation coupled with a selective absorption coating structure provided by the present invention, wherein the heat collector tube comprises:

[0041] A steel pipe 1, in which a fluid to be heated flows, is provided with the thin film temperature difference power generation coupled selective absorption coating structure 2 (the specific structure will be described in detail later) on the outer wall, and the coating structure 2 is also connected to the lead-out electrodes 31 and 32, and the coating structure 2 can convert the received solar energy into heat and transfer it to the fluid to be heated, and also generate electricity to be led out by the first lead-out electrode 31 and the second lead-out electrode 32;

[0042] A cover glass tube 4 is sleeved on the outer side of the steel tube 1. Both ends of the cover glass tube 4 are sealed and connected with a kovar metal sleeve 41. The kovar metal sleeve 41 is sealed and connected with an outer end cover 43 of a bellows 42. The inner end of the bellows 42 is sealed and connected with a support ring 44. The support ring 44 is sealed and fixed on the outer wall of the steel tube 1. In this way, a closed space is formed between the cover glass tube 4 and the steel tube 1. The closed space can be made into a vacuum interlayer 45 by vacuuming. In order to maintain the vacuum degree, an evaporative getter bracket 46 is fixed on the support ring 44. agent 47 and non-evaporable getter 48; when the steel tube 1 and the cover glass tube 4 produce axial relative displacement due to different temperatures or different thermal expansion coefficients, the relative displacement can be absorbed by the bellows 42; the first lead 311 and the second lead 321 connected to the first lead electrode 31 and the second lead electrode 32 form tortuous sections 312 and 322 (S-shaped or spiral) in the vacuum interlayer 45, and the ends of the tortuous sections 312 and 322 pass through the cover glass tube 4 to be connected to the outside, so as to absorb the relative displacement by means of the tortuous sections 312 and 322.

[0043] As for the thin film temperature difference power generation coupled with selective absorption coating structure 2, there are two arrangements: circumferential arrangement and axial arrangement, such as Figure 2 As shown, it is a schematic diagram of the structure arranged along the circumferential direction, wherein, since the solar energy irradiation received by the steel pipe 1 is not uniform in the circumferential direction, there must be a concentrated high temperature zone and a backlit low temperature zone opposite to the concentrated high temperature zone, and the coating structure 2 includes:

[0044] The first ceramic insulating layer 21 is arranged on the outer wall of the steel pipe 1 and plays an insulating role;

[0045] The PN junction layer 22 is formed on the outer wall of the first ceramic insulating layer 21, and includes a P pole 221, a PN overlapping area 222 and an N pole 223 which are sequentially connected in the circumferential direction of the steel tube 1, wherein the PN overlapping area 222 is located in the light-collecting high-temperature area, an end of the P pole 221 opposite to the PN overlapping area 222 is located in the backlight low-temperature area, and an end of the N pole 223 opposite to the PN overlapping area 222 is located in the backlight low-temperature area; the P pole 221 and the N pole 223 are separated from each other at one end of the backlight low-temperature area to form a PN disconnection area 224;

[0046] A second ceramic insulating layer 23 is arranged outside the PN junction layer 22 and plays an insulating role;

[0047] The selective absorption coating 24 is formed on the outer wall of the second ceramic insulating layer 23 .

[0048] In this way, since the temperature of the P pole 221 and the N pole 223 of the PN junction layer 22 at one end of the PN overlapping region 222 (i.e., the PN junction) is higher than the temperature at the other end, a voltage is generated between the P pole 221 and the N pole 223. After multiple PN junction layers 22 are connected in series and / or in parallel, the first lead-out electrode 31 and the second lead-out electrode 32 are respectively connected at both ends of the circuit, and the voltage and / or current can be amplified and guided to the outside of the cover glass tube 4 through the first wire 311 and the second wire 321 for collection or use as electrical energy; at the same time, the selective absorption coating 24 can also convert solar energy into thermal energy and provide it to the fluid to be heated in the steel pipe 1.

[0049] For example Figure 3 As shown, Figure 2 The coating structure 2 shown is a schematic structural diagram of being connected in series in the axial direction, wherein: a plurality of PN junction layers 22 are arranged in an axially spaced manner on the outer wall of the steel pipe 1, and the PN directions of any two adjacent PN junction layers 22 are opposite, and a series connection is formed between two adjacent PN junction layers 22 through a conductive coating 225, so that the first lead-out electrode 31 and the second lead-out electrode 32 are respectively connected at both ends of the formed series circuit, so that the electricity generated by the temperature difference can be collected or used.

[0050] For example Figure 4 As shown, Figure 2 The coating structure 2 shown is a schematic structural diagram of parallel connection in the axial direction, wherein: a plurality of PN junction layers 22 are arranged at intervals along the axial direction on the outer wall of the steel pipe 1, and the PN directions of all PN junction layers 22 are the same, and the N poles 223 of all PN junction layers 22 are connected together through a conductive coating 225 and then connected to a first electrode, and the P poles 221 of all PN junction layers 22 are connected together through another conductive coating 225 and then connected to a second electrode, so that the electricity generated by the temperature difference can be collected or used.

[0051] exist Figure 3 , Figure 4 Based on the above, those skilled in the art can think of many structures in which the PN junction layers 22 are connected in series and parallel in the axial direction, which cannot be exhaustively listed here. Figure 5 This is a schematic diagram of one of the series-parallel connection methods and is for reference only.

[0052] The thin film thermoelectric power generation coupled with the selective absorption coating 24 structure 2 also has an axial arrangement, which is Figure 2On the basis of the structure shown in FIG. 1 , the PN junction layer 22 is arranged along the circumferential direction instead of along the circumferential direction. Since the temperature of the fluid to be heated in the steel pipe 1 is low when it flows into one end of the steel pipe 1, and the temperature is high when it flows out from the other end of the steel pipe 1, one end of the steel pipe 1 is a low-temperature end, and the other end is a high-temperature end. The PN junction layer 22 is arranged along the circumferential direction as shown in FIG. Figure 6 , Figure 7 , Figure 8 As shown:

[0053] The PN junction layer 22 is formed on the outer wall of the first ceramic insulating layer 21, and includes at least one P pole 221 and at least one N pole 223 arranged along the axial direction of the steel pipe 1. The P pole 221 and the N pole 223 are spaced apart from each other to form a PN disconnection zone 224. The P pole 221 and the N pole 223 form a PN overlapping zone 222 at the high temperature end of the steel pipe 1. By virtue of the temperature difference between the high temperature end and the low temperature end of the steel pipe 1, the P pole 221 and the N pole 223 generate a voltage between the high temperature end and the low temperature end.

[0054] After connecting multiple PN junction layers 22 in series and / or in parallel, the first lead electrode 31 and the second lead electrode 32 are connected at both ends of the circuit respectively, so that the voltage and / or current can be amplified and guided to the outside of the cover glass tube 4 through the first wire 311 and the second wire 321 for collecting or using as electric energy.

[0055] like Figure 6 As shown, it is a schematic diagram of the structure in which the PN junction layer 22 is connected in series in the circumferential direction, including a plurality of N poles 223 and a plurality of P poles 221 arranged alternately, each N pole 223 and an adjacent P pole 221 form a PN overlapping region 222 at the high temperature end of the steel pipe 1, and each N pole 223 and an adjacent P pole 221 are connected in series at the low temperature end of the steel pipe 1 through a conductive coating 225. In this way, the first lead-out electrode 31 and the second lead-out electrode 32 are respectively connected at both ends of the formed series circuit, so that the electricity generated by the temperature difference can be collected or used.

[0056] like Figure 7 As shown, it is a schematic diagram of the structure in which the PN junction layer 22 is formed in parallel in the circumferential direction, in which a plurality of N poles 223 are axially arranged on a section of the arc surface of the steel pipe 1, and a plurality of P poles 221 are axially arranged on the other section of the arc surface, and the plurality of N poles 223 and the plurality of P poles 221 form an integral PN overlapping area 222 at the high-temperature end of the steel pipe 1, and the plurality of N poles 223 are connected to the first lead-out electrode 31 at the low-temperature end of the steel pipe 1, and the plurality of P poles 221 are connected to the second lead-out electrode 32 at the low-temperature end of the steel pipe 1, so that the electricity generated by the temperature difference can be collected or used.

[0057] like Figure 8The above is a schematic diagram of the structure in which the PN junction layer 22 is connected in series and parallel in the circumferential direction. This is only one of the preferred embodiments and is only used as a reference. Figure 6 , Figure 7 , Figure 8 Based on this, those skilled in the art can think of many structures in which the PN junction layers 22 are connected in series and parallel in the circumferential direction, which cannot be listed here one by one.

[0058] It should be noted that in the above embodiments:

[0059] The thickness of the first ceramic insulating layer 21 and the second ceramic insulating layer 23 are both between 0.1 micrometers and 10 micrometers; their materials are mainly insulating materials composed of metal oxides, nitrides, metal oxynitrides, non-metallic oxides, non-metallic nitrides, non-metallic oxynitrides or mixtures of the above compounds.

[0060] The coating thickness of the PN junction layer 22 is between 0.1 micrometers and 100 micrometers.

[0061] The P-pole 221 is a P-type semiconductor formed by doping silicon or germanium with a small amount of boron, indium, gallium, and aluminum.

[0062] The N-pole 223 is an N-type semiconductor formed by doping silicon or germanium with a small amount of phosphorus, antimony, and arsenic.

[0063] The PN junction layer 22 may also be made of metal thermoelectric materials, such as nickel-chromium-nickel-silicon pairs, copper-constantan pairs, nickel-nickel-molybdenum pairs, and the like.

[0064] The conductive coating 225 is mainly composed of highly conductive pure metal or alloy material, such as copper, aluminum, silver single metal or alloy.

[0065] The first lead-out electrode and the second lead-out electrode are made of metal tungsten and molybdenum, and the thickness thereof is between 1 micrometer and 100 micrometers.

[0066] The first wire 311 and the second wire 321 are metal wires or metal sheets made of metal tungsten, molybdenum, etc. The first wire 311 and the second wire 321 can be directly sealed and led out of the cover glass tube 4 or through transition materials such as transition glass and transition ceramics.

[0067] The thickness of the selective absorption coating 24 is between 0.2 and 0.5 microns. The selective absorption coating 24 is mainly composed of a metal layer, an absorption layer, an anti-reflection layer, etc., and can adopt a conventional medium-high temperature selective absorption coating 24 film system.

[0068] Compared with the existing disclosed thermoelectric power generation coupled with solar thermal collector tube structure, the structure of the present invention has the following advantages:

[0069] 1) When working, the selective absorption coating 24 of the solar collector tube has a high-temperature zone for focusing light and a low-temperature zone for backlighting in the circumferential direction, and also has an inlet low-temperature end and an outlet high-temperature end in the axial direction. The above-mentioned high-temperature zone (end) and low-temperature zone (end) exist naturally and are not significantly changed by increasing the thickness of the temperature difference power generation coating. The present invention is particularly suitable for trough-type solar collector tubes, and can make the temperature difference between the two temperature zones reach between 10 and 50°C. Therefore, the natural temperature difference of the trough-type solar collector tube can be fully utilized to realize temperature difference power generation, and there is no need to actively dissipate heat in the low-temperature zone.

[0070] 2) The coating-mode thermoelectric power generation structure has the advantages of easy processing, low material cost and low processing cost compared with conventional thermoelectric power generation modules.

[0071] 3) The superposition mode of the thin film thermoelectric power generation structure and the selective absorption coating 24 does not affect the performance of the selective absorption coating 24 in absorbing solar energy. At the same time, the thermoelectric power generation coating of the thin film structure has a very small effect on the thermal resistance of converting solar energy into thermal energy and transmitting it to the steel pipe 1, which can be ignored and does not affect the heat collection and heat transfer performance of the heat collecting tube.

[0072] 4) The wire 31 in the vacuum interlayer 45 is provided with a zigzag section 32 (S-shaped or spiral), which solves the influence of the heat collecting tube on the tensile deformation of the electrode when it is slightly deformed by heat. The direct sealing or transitional melting sealing of the wire 31 and the cover glass tube 4 solves the problem of extracting the electric energy of the temperature difference power generation structure.

[0073] 5) The thermoelectric power generation coating can realize the series and parallel connection between PN junctions to effectively improve the efficiency of thermoelectric power generation. Through the insulating ceramic layer, effective isolation from the surface of the steel pipe 1 and the metal infrared reflection layer of the selective absorption coating 24 is achieved.

[0074] In summary, the present invention achieves a perfect combination of thin-film temperature difference power generation and the selective absorption coating 24, thereby forming a glass-metal-sealed direct-through solar collector tube in a highly reliable and low-cost combined heat and power generation mode.

[0075] like Fig. 9 As shown, it is a manufacturing process flow chart of the solar collector tube provided by the present invention, which mainly includes the following steps: coating of steel tube 1, pretreatment of cover glass, pretreatment of small metal parts, assembly, vacuum exhaust, testing and packaging.

[0076] The coating process of the steel pipe 1 mainly includes: polishing, cleaning, exhausting, coating and electrode assembly of the steel pipe 1.

[0077] Polishing refers to removing rust on the surface of the steel pipe 1 by mechanical or chemical means to make the surface finish less than 1.0 micron.

[0078] The cleaning refers to removing stains, oil and rust on the surface of the steel pipe 1 by physical or chemical methods after the steel pipe 1 is polished, and then forming a passivation film on the surface of the steel pipe 1 by physical or chemical methods, and then cleaning the impurities on the surface of the steel pipe 1, and finally removing the water film of the residual material on the surface of the steel pipe 1 by air knife method to prevent further oxidation of the steel pipe 1.

[0079] The exhaust means that after the steel pipe 1 is cleaned, the steel pipe 1 is placed in a vacuum heating furnace, first the vacuum degree is evacuated to below 10Pa, the heater is turned on and the temperature is raised to 400-450°C, and the vacuum state is maintained for about 20-60 minutes. After the vacuum is naturally cooled to 350-150°C, pure oxygen or nitrogen is filled in to achieve rapid surface oxidation or nitridation, and a dense metal oxide or metal nitride film is further formed on the surface; finally, it is taken out at 100°C±30°C.

[0080] The coating mainly includes: plasma cleaning, PN film preparation, PN film etching, selective absorption coating 24 coating, and electrode etching.

[0081] The plasma cleaning refers to loading the steel pipe 1 whose temperature after exhaust is 100℃±30℃ into the vacuum coating machine, and after evacuating to the set vacuum degree, starting the glow or arc plasma cleaning process to remove dust or impurities on the surface of the steel pipe 1 and keep the surface clean. At the same time, starting the vacuum heater to keep the temperature of the steel pipe 1 between 150℃-450℃.

[0082] The PN film is prepared in a vacuum coating machine. According to the characteristics of the coating structure 2, the first ceramic insulating layer 21, the P-pole 221 coating, the N-pole 223 coating, and the conductive coating 225 are sequentially plated by shielding the surface of the heat collecting tube, and a transition connection between the above coatings is achieved.

[0083] The PN film etching refers to etching the PN coating according to the series, parallel or series-parallel structure of the PN junction layer 22 by laser or plasma etching, and generating a disconnection zone between the circumferential direction and the axial direction of the coating by etching, and forming a series and / or parallel structure between the PN junctions by virtue of the disconnection zone.

[0084] The selective absorption coating 24 is plated by vacuum coating on the surface of the PN junction layer 22 to first prepare the second ceramic insulation layer 23 to achieve insulation between the second ceramic insulation layer 23 and the subsequent selective absorption coating 24, and then sequentially plate an infrared metal reflection layer, an absorption layer and an anti-reflection layer.

[0085] The electrode etching refers to etching the conductive coating 225 at both ends or a single end of the heat collecting tube by laser or plasma etching in a vacuum chamber after the selective absorption coating 24 is plated, so as to remove the selective absorption coating 24 on the surface of the conductive coating 225 and the lead-out electrode 3, as well as the second ceramic insulating layer 23 between the selective absorption coating 24 and the conductive coating 225.

[0086] The electrode assembly refers to taking out the coated steel pipe 1 from the vacuum coating chamber after completing the electrode etching in the vacuum chamber, and welding the lead-out electrodes 3 to the corresponding conductive coatings 225 by welding.

[0087] The cover glass pre-treatment process mainly includes: glass-to-metal sealing, tail pipe connection, and anti-reflection film coating.

[0088] The glass-metal sealing refers to welding the Kovar metal sleeve 41 to the cover glass tube 4 by direct or transition sealing, and then annealing the sealing position and the surrounding area to maintain good vacuum sealing performance, mechanical properties and thermal shock resistance. The cover glass tube 4 is borosilicate glass.

[0089] The tail pipe connection is to drill holes at set positions of the cover glass tube 4, seal the two exhaust tail pipes by direct sealing or transitional sealing, and then anneal. The structure of the tail pipe used can be the same material as the cover glass tube 4, or part of it can be made of the same material as the cover glass tube 4 to achieve direct sealing.

[0090] The antireflection coating process refers to cleaning the inner and outer surfaces, or the inner surface alone, of the cover glass tube 4. The antireflection coating is coated on the surface of the cover glass tube 4 by pulling, and the antireflection coating is solidified on the surface of the cover glass tube 4 by heating at 150-450°C.

[0091] The small metal parts pre-treatment refers to the getter component assembly, the bellows 42 component assembly, etc.

[0092] The getter assembly assembly refers to fixing the evaporable getter 47 and the non-evaporable getter 48 on the getter support 46 by spot welding to form a getter assembly.

[0093] The bellows 42 assembly assembly refers to welding the support ring 44, the bellows 42, and the end cover 43 together to form the bellows 42 assembly, and then welding or other mechanical connection methods to fix the getter assembly to the vacuum chamber side of the bellows 42 assembly.

[0094] Assembly means combining, assembling and welding the coated steel tube 1, the cover glass tube 4 and the bellows 42 components together.

[0095] The combination refers to inserting the coated steel tube 1 into the cover glass tube 4 and ensuring that the wire 31 is inserted into the exhaust tail pipe.

[0096] The assembly refers to inserting the bellows 42 assembly from both ends of the heat collecting tube, fixing it between the kovar metal sleeve 41 of the cover glass tube 4 and the steel tube 1, and performing circumferential and axial positioning.

[0097] The welding refers to pre-spot welding and fixing the cover glass tube 4, the varable metal sleeve 41, the bellows 42 components to the coated steel pipe 1 in sequence, and then realizing the closed welding between the cover glass tube 4, the varable metal sleeve 41, the bellows 42 components and the coated steel pipe 1 through continuous welding.

[0098] The vacuum exhaust means putting the assembled heat collecting pipe into the exhaust platform, connecting the exhaust tail pipe to the vacuum unit, and after the inside of the heat collecting pipe is evacuated to 10pa, the set program heating mode is turned on, and gradually heated to 350-450℃, and the vacuum is continuously drawn and kept warm for 30-120 minutes, and then the temperature is gradually lowered to 400-200℃ according to the set program, and the electric sealing device is turned on to seal and separate the exhaust tail pipe from the cover glass tube 4, and ensure that the wire 31 and the exhaust tail pipe are fused and sealed. Finally, according to the set cooling temperature curve, the heat collecting pipe is naturally cooled or forced to cool to room temperature.

[0099] The detection refers to the use of visual inspection, helium mass spectrometer, spark detector to detect the vacuum degree, appearance and other qualities of the collector tube, and then laser marking.

[0100] The packaging refers to completing the above procedures, packing and boxing the heat collecting tubes, and completing the entire heat collecting tube production process.

[0101] The present invention provides a processing method for a thin-film temperature difference power generation coupled with a selective absorption coating 24 glass metal fusion seal straight-through solar heat collection tube, which has the following advantages:

[0102] 1) The thin-film temperature difference power generation coupled selective absorption coating 24 production line is perfectly integrated into the existing glass metal sealing solar collector tube production line. It only requires appropriate addition of PN coating vacuum coating devices and workstations, as well as laser or plasma etching equipment, to the vacuum coating equipment used in the existing selective absorption coating 24 coating process.

[0103] 2) The production process of the thin-film temperature difference power generation coupled selective absorption coating 24 is perfectly integrated into the existing glass metal sealing solar collector tube production process. It is only necessary to add the coating process and equipment of the PN junction layer 22 to the coating process of the PN coating. The preparation process of the ceramic insulation layer and the conductive coating 225 in the corresponding PN coating can be prepared using the original selective absorption coating 24 infrared metal reflection layer, anti-reflection layer equipment and process. The process flow is simple and reliable. The equipment and process have low investment cost, low operating cost and good stability.

[0104] The above description is only illustrative rather than restrictive of the present invention. Those skilled in the art will understand that many modifications, changes or equivalents may be made without departing from the spirit and scope defined by the claims, but all will fall within the scope of protection of the present invention.

Claims

1. A thin film temperature difference power generation coupled with selective absorption coating solar heat collecting tube, comprising a metal tube and a cover glass tube sleeved outside the metal tube, characterized in that: A first insulating layer, a PN junction layer, a second insulating layer and a selective absorption coating are sequentially formed on the outer wall of the metal tube, and the PN junction layer is connected to a lead-out electrode; Both ends of the cover glass tube are respectively connected by a kovar metal sleeve, the kovar metal sleeve is sealed with the outer wall of the metal tube through a bellows assembly, and a vacuum interlayer is formed between the cover glass tube and the metal tube; The wire connected to the lead-out electrode forms a meandering section in the vacuum interlayer, and the end of the meandering section is led out to the outside of the cover glass tube by direct sealing or through a transition material; The PN junction layer includes a P pole, a PN overlapping region and an N pole connected in sequence; the PN overlapping region is located at a relatively high temperature position of the metal tube, and one end of the P pole and the N pole opposite to the PN overlapping region is located at a relatively low temperature position of the metal tube; One side of the metal tube receives solar radiation and is called a concentrated high temperature zone, and the other side is called a backlight low temperature zone. The P pole, PN overlapping zone and N pole are arranged in sequence along the circumference of the metal tube. The PN overlapping zone is located in the concentrated high temperature zone of the metal tube, and one end of the P pole and the N pole opposite to the PN overlapping zone is located in the backlight low temperature zone; the P pole and the N pole are separated from each other at one end of the backlight low temperature zone to form a PN disconnection zone; Alternatively, the inlet end of the metal tube is a low-temperature end, and the outlet end is a high-temperature end, the P pole and the N pole are arranged along the axial direction of the metal tube and spaced from each other to form a PN disconnection zone, the P pole and the N pole form a PN overlapping zone at the high-temperature end of the metal tube, and one end of the P pole and the N pole opposite to the PN overlapping zone is located at the low-temperature end.

2. The thin film temperature difference power generation coupled with selective absorption coating solar thermal collector according to claim 1, characterized in that: The zigzag section is S-shaped or spiral.

3. The thin film temperature difference power generation coupled with selective absorption coating solar thermal collector according to claim 1, characterized in that: The Kovar metal sleeve is sealed to an outer end cover of a bellows, the inner end of the bellows is sealed to a support ring, and the support ring is sealed and fixed on the outer wall of the metal tube.

4. The thin film temperature difference power generation coupled with selective absorption coating solar thermal collector according to claim 3 is characterized by: An evaporable getter and / or a non-evaporable getter is fixed on the support ring via a getter bracket.

5. The thin film temperature difference power generation coupled with selective absorption coating solar thermal collector according to claim 1, characterized in that: The transition material is a transition glass or a transition ceramic.

6. The thin film temperature difference power generation coupled with selective absorption coating solar thermal collector tube according to claim 1, characterized in that: The PN junction layers are connected in series, in parallel or in series-parallel via the conductive coating.

7. The thin film temperature difference power generation coupled with selective absorption coating solar thermal collector tube according to claim 1, characterized in that: The selective absorption coating comprises a metal layer, an absorption layer and an anti-reflection layer in sequence from the inside to the outside.

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