Structure of vanadium-based selective absorption coating

Abstract

The present invention provides a vanadium-based selective absorption coating structure, which is formed on the surface of a transparent material facing the sun, and includes an infrared reflection layer, a vanadium-based low-resistance layer, a vanadium-based transition layer, a vanadium-based high-resistance layer, and a vanadium-based anti-reflection layer. The present invention adopts a vanadium-based selective absorption coating to achieve the performance requirements of high absorption and low emission of the selective absorption coating under low temperature conditions, which is beneficial to heat collection, and at the same time achieve a state of low absorption and high emission under high temperature conditions, effectively reduce the working temperature of the heat collection system in a non-working state, and significantly improve the safety and reliability of the heat collection system.

Description

Technical Field

[0001] The invention relates to a selective absorption coating structure attached to a plane or a tube surface for enhancing the solar energy absorption effect. Background Art

[0002] Systems and devices that utilize the photothermal effect of solar energy to absorb and store solar energy in a heat-absorbing medium (such as domestic water, heat storage materials) are very common in the field of solar thermal collection.

[0003] Generally speaking, the heat absorbing medium is generally stored in a cavity made of a transparent material (such as glass) to facilitate the penetration of sunlight. In order to improve the heat absorption efficiency and reduce the reflectivity, a selective absorption coating is set on the side of the transparent material facing the sun.

[0004] However, with the improvement of heat absorption efficiency, under summer air-drying conditions, the temperature inside the cavity can reach up to 300°C, which has a certain impact on the vacuum degree and life of the cavity. At this time, if the cavity suddenly comes into contact with cold water, it is very easy to cause an accident of cavity explosion.

[0005] Therefore, in order to address the temperature limit of solar collector tubes and solve the problem of easy explosion of collector tubes under high temperature conditions, it is necessary to design and develop a solar collector tube that does not affect the collection efficiency under low temperature conditions and can limit the maximum air exposure temperature of the collector tube, in order to further improve the safety and reliability of the collector tube. Summary of the invention

[0006] The purpose of the present invention is to provide a vanadium-based selective absorption coating structure, which does not affect the heat collection efficiency of the cavity under low temperature conditions, but can reduce the heat collection efficiency under high temperature conditions to protect the solar energy collection system.

[0007] To achieve the above object, the technical solution adopted by the present invention is:

[0008] A vanadium-based selective absorption coating structure is formed on the surface of a transparent material facing the sun, and is characterized by comprising an infrared reflection layer, a vanadium-based low resistance layer, a vanadium-based transition layer, a vanadium-based high resistance layer and a vanadium-based anti-reflection layer.

[0009] The vanadium-based selective absorption coating structure, wherein: the vanadium-based low resistance layer, the vanadium-based transition layer, the vanadium-based high resistance layer and the vanadium-based anti-reflection layer are doped with vanadium dioxide accounting for 2% to 40% of the total molar ratio.

[0010] The vanadium-based selective absorption coating structure, wherein: the infrared reflection layer is pure metal such as aluminum or copper, and has a thickness of 60-120nm.

[0011] The vanadium-based selective absorption coating structure, wherein: the vanadium-based low resistance layer is based on any one or a mixture of any number of metal aluminum, titanium, stainless steel, nickel and their oxides, and is doped with vanadium dioxide, wherein the molar ratio of vanadium dioxide to the total amount is 5%-20%, the coating thickness is 50-150nm, and the square resistance is 90-500 ohms.

[0012] The vanadium-based selective absorption coating structure, wherein: the vanadium-based transition layer is based on any one or a mixture of any number of metal aluminum, titanium, stainless steel, nickel, silicon and their oxides as a matrix, and then doped with vanadium dioxide, wherein the molar ratio of vanadium dioxide to the total amount is 10% to 25%, the coating thickness is 50-150nm, and the square resistance is 500 to 2000 ohms.

[0013] The vanadium-based selective absorption coating structure, wherein: the vanadium-based high resistance layer is based on any one or a mixture of any number of metal aluminum, titanium, stainless steel, nickel, silicon and their oxides as a matrix, and then doped with vanadium dioxide, wherein the molar ratio of vanadium dioxide to the total amount is 15% to 30%, the coating thickness is 50-150nm, and the square resistance is 1000 to 10000 ohms.

[0014] The vanadium-based selective absorption coating structure, wherein: the vanadium-based anti-reflection layer is based on any one or a mixture of aluminum and silicon oxides, and is doped with vanadium dioxide, wherein the molar ratio of vanadium dioxide to the total amount is 30% to 50%, and the sheet resistance is greater than 50,000 ohms.

[0015] The present invention adopts a selective absorption coating doped with vanadium dioxide to achieve the performance requirements of high absorption and low emission of the selective absorption coating under low temperature conditions, which is beneficial to heat collection. At the same time, it achieves a state of low absorption and high emission under high temperature conditions, thereby reducing the heat collection efficiency in the non-working state and improving the safety and reliability of the heat collection system. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic diagram of the structure of a vanadium-based selective absorption coating.

[0017] Figure 2 The present invention is a schematic structural diagram of an all-glass heat pipe vacuum solar collector tube.

[0018] Explanation of the reference numerals: 1-condensation section; 2-heat absorption section; 3-vanadium-based selective absorption coating; 4-vacuum interlayer; 5-cover glass tube; 6-support; 7-getter; 8-liquid working medium; 91-infrared reflection layer; 92-vanadium-based low resistance layer; 93-vanadium-based transition layer; 94-vanadium-based high resistance layer; 95-vanadium-based anti-reflection layer. DETAILED DESCRIPTION

[0019] like Figure 1As shown, the vanadium-based selective absorption coating structure provided by the present invention is composed of an infrared reflection layer 91, a vanadium-based low-resistance layer 92, a vanadium-based transition layer 93, a vanadium-based high-resistance layer 94 and a vanadium-based anti-reflection layer 95 which are sequentially formed on the surface of a transparent material 9 facing the sun; wherein, the vanadium-based low-resistance layer 92, the vanadium-based transition layer 93, the vanadium-based high-resistance layer 94 and the vanadium-based anti-reflection layer 95 are doped with vanadium dioxide in a molar ratio of 2% to 40% of the total amount, respectively.

[0020] Among them, the molar ratio of the main component and vanadium dioxide in each layer and the coating thickness are:

[0021] The infrared reflection layer 91 is made of pure metal such as aluminum or copper, does not contain vanadium dioxide, has a coating thickness of 60-120 nm, and has a sheet resistance of 0 ohm.

[0022] The vanadium-based low-resistance layer 92 is based on any one of metal aluminum, titanium, stainless steel, nickel and their oxides or a mixture of any several of them, and is doped with vanadium dioxide, wherein the molar ratio of vanadium dioxide to the total amount is 5%-20%, the coating thickness is 50-150nm, and the square resistance is 90-500 ohms.

[0023] The vanadium-based transition layer 93 is based on any one or a mixture of any number of metal aluminum, titanium, stainless steel, nickel, silicon and their oxides, and is doped with vanadium dioxide, wherein the molar ratio of vanadium dioxide to the total amount is 10% to 95%, the coating thickness is 50-150nm, and the square resistance is 500 to 2000 ohms.

[0024] The vanadium-based high resistance layer 94 is based on any one or a mixture of any number of metal aluminum, titanium, stainless steel, nickel, silicon and their oxides, and is doped with vanadium dioxide, wherein the molar ratio of vanadium dioxide to the total amount is 15% to 30%, the coating thickness is 50-150nm, and the square resistance is 1000 to 10000 ohms.

[0025] The vanadium-based anti-reflection layer 95 is based on any one of aluminum and silicon oxides or a mixture thereof, and is doped with vanadium dioxide, wherein the molar ratio of vanadium dioxide to the total amount is 30% to 50%, and the sheet resistance is greater than 50,000 ohms.

[0026] The vanadium-based selective absorption coating structure provided by the present invention can be formed on a flat, curved or other plate-shaped transparent material 9, or can also be formed on a tubular or spherical transparent material 9, for example Figure 2As shown, it is a structural schematic diagram of the present invention applied to the all-glass heat pipe vacuum solar collector tube, the collector tube is mainly composed of an inner tube (including a condensation section 1 and a heat absorption section 2, the diameter, wall thickness and other parameters of the condensation section 1 are the same as those of the heat absorption section 2) and a cover glass tube 5, the round head of the heat absorption section 2 is fixed to the cover glass tube 5 by a bracket 6, the bracket 6 is provided with a getter 7, a vacuum interlayer 4 is provided between the heat absorption section 2 and the cover glass tube 5, the outer wall of the heat absorption section 2 is provided with the vanadium-based selective absorption coating 3, the heat absorption section 2 and the condensation section 1 The interior of the working fluid cavity is evacuated and a liquid working fluid 8 is placed in the working fluid cavity, and the volume ratio of the liquid working fluid 8 to the volume of the working fluid cavity is 1.5% to 2% (preferably 3% to 6%).

[0027] The liquid working fluid is composed of two or more liquid working fluids with different boiling points, wherein the volume of the high-boiling-point working fluid accounts for 20% to 50% of the total volume, and the rest is the low-boiling-point working fluid. The high-boiling-point working fluid refers to a liquid working fluid with a boiling point greater than or equal to the boiling point of water, including but not limited to ethylene glycol, propylene glycol, etc. The low-boiling-point working fluid refers to a working fluid with a boiling point lower than the boiling point of water, including ethanol, acetone, etc.

[0028] By adopting the above-mentioned vanadium-based selective absorption coating 3, the present invention obtains a thermal phase change solar heat collection tube. When the vanadium-based selective absorption coating 3 is lower than 80°C, the heat absorption curve of the vanadium-based selective absorption coating 3 shows standard two interference peak characteristics, showing typical high absorption characteristics in the 300-2000nm band, and low absorption and low emission characteristics in the 10000nmd mid- and far-infrared band, thereby achieving high-efficiency heat collection performance of the heat collection tube below 80°C; when the vanadium-based selective absorption coating 3 of the heat collection tube is higher than 80°C, the property of vanadium dioxide changing from a semiconductor state to a metallic state under 68°C is utilized to change the vanadium-based low resistance layer, the vanadium-based transition layer, the vanadium-based high resistance layer and the vanadium-based reduction layer. The resistance characteristics of the anti-reflection layer, thereby changing the interference absorption curve into a non-interference curve, especially the metallization of vanadium dioxide in the vanadium-based anti-reflection layer, leads to a significant reduction in the anti-reflection efficiency of the anti-reflection layer and a significant enhancement in the reflectivity, thereby significantly destroying the selective absorption characteristics of the vanadium-based selective absorption coating 3, significantly reducing the absorption characteristics in the 300-2000nm band, and at the same time significantly increasing the emission ratio of the mid- and far-infrared beyond 10000nm, which in turn significantly affects the heat collection performance of the heat collecting tube in the high temperature section, significantly reduces the air-exposure temperature of the heat collecting tube under air-exposure conditions, and effectively improves the safety and reliability of the heat collecting tube, especially for the all-glass heat pipe vacuum solar heat collecting tube, which has a more significant significance in improving the safety and reliability.

[0029] During the manufacturing process of the present invention, a vanadium-doped metal target and oxygen are used to assist the sputtering reaction, and vanadium oxide is doped into the vanadium-based low resistance layer, vanadium-based transition layer, vanadium-based high resistance layer and vanadium-based anti-reflection layer of the interference type vanadium-based selective absorption coating 3, and then the metal ion vanadium and vanadium oxide are transformed into vanadium dioxide through high-temperature oxidation. In particular, the efficient doping of vanadium dioxide in the vanadium-based anti-reflection layer realizes the change of the high-temperature non-interference characteristics of the vanadium-based selective absorption coating 3 under the condition of achieving the low-temperature interference characteristics.

Claims

1. A vanadium-based selective absorption coating structure formed on the surface of a transparent material facing the sun, characterized in that: An infrared reflection layer, a vanadium-based low-resistance layer, a vanadium-based transition layer, a vanadium-based high-resistance layer and a vanadium-based anti-reflection layer are sequentially arranged on the surface of the transparent material facing the sun; The vanadium-based low-resistance layer is based on any one of metal aluminum, titanium, stainless steel, nickel and their oxides or a mixture of any number of them, and then doped with vanadium dioxide, wherein the molar ratio of vanadium dioxide to the total amount is 5%-20%, the coating thickness is 50-150nm, and the square resistance is 90-500 ohms; The vanadium-based transition layer is based on any one or a mixture of any number of metal aluminum, titanium, stainless steel, nickel, silicon and their oxides, and then doped with vanadium dioxide, wherein the molar ratio of vanadium dioxide to the total amount is 10% to 25%, the coating thickness is 50-150nm, and the square resistance is 500 to 2000 ohms; The vanadium-based high resistance layer is based on any one or a mixture of any number of metal aluminum, titanium, stainless steel, nickel, silicon and their oxides as a matrix, and then doped with vanadium dioxide, wherein the molar ratio of vanadium dioxide to the total amount is 15% to 30%, the coating thickness is 50-150nm, and the square resistance is 1000 to 10000 ohms; The vanadium-based anti-reflection layer is based on any one or a mixture of aluminum and silicon oxides and doped with vanadium dioxide, wherein the molar ratio of vanadium dioxide to the total amount is 30% to 50%, and the sheet resistance is greater than 50,000 ohms.

2. The vanadium-based selective absorption coating structure according to claim 1, characterized in that: The infrared reflection layer is pure metal such as aluminum or copper, and has a thickness of 60-120 nm.

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