Medium-high temperature cavity type heat collector used in trough type heat collecting system

Abstract

The medium-high temperature cavity type heat collector comprises a transparent outer cover pipe and a V-shaped metal groove heat collector, the center of the opening face of the V-shaped metal groove is located in the center of the transparent outer cover pipe, the inner side or the outer side of the V-shaped metal groove is connected with a metal pipe, and the space between the inner pipe and the outer pipe is vacuumized or filled with gas. A reflecting layer is additionally arranged on the inner side or the outer side of the backlight surface of the transparent outer cover pipe, or an anti-radiation cover is additionally arranged on the backlight part between the transparent outer cover pipe and the heat collector; or a heat insulation layer is added to the backlight part on the outer side of the transparent outer cover pipe; or simultaneously, a heat insulation layer is arranged on the backlight part outside the transparent outer cover pipe. The V-shaped groove is used for replacing a round tube, incident light can be absorbed in the V-shaped groove for multiple times, the absorption rate is increased by 3%-4% similar to that of a cavity absorber, and the defect that a tubular heat collector is low in absorption rate is overcome; the space between the V-shaped groove and the transparent outer cover pipe is vacuumized, a reflecting film or an anti-radiation film or / and a heat insulation layer is added to the backlight part, heat loss is reduced, and the heat loss is low.

Description

Technical Field

[0001] The present invention relates to the technical field of solar heat collecting tubes, and in particular to a medium- and high-temperature cavity heat collector for use in a trough heat collecting system. The present invention is applicable to trough concentrating heat collectors, replacing currently used vacuum heat collecting tubes. Background Art

[0002] Concentrating trough solar collector tubes are a key component of trough solar thermal power generation systems. They convert direct solar radiation concentrated by reflectors into heat, reaching temperatures of up to 400°C. The most commonly used type of collector tube is an evacuated tube, consisting of a stainless steel inner tube and an outer glass tube with metal bellows at each end. The inner tube is coated with a selective absorption coating to maximize absorption of concentrated direct solar radiation while minimizing infrared re-emission. Glass-to-metal seals at each end seal the metal bellows, providing high-temperature protection and maintaining a vacuum within the tube. This reduces heat loss through convection and conduction, and the selective absorption coating minimizes radiation heat loss from the evacuated tube. On the other side, the metal bellows connect to the inner absorber tube. These elastically connected bellows compensate for the differential expansion and contraction between the inner metal tube and the outer glass tube as the absorber tube heats up and cools down. The concentrated direct solar radiation is converted to heat on the metal tube surface, transferred to the heat transfer medium, and heated to temperatures exceeding 400°C. The outer glass tube can serve as additional protection to prevent infrared wavelength energy from being re-radiated outward to reduce heat loss. The outside of the glass tube is covered with an anti-reflective coating. The glass should be made of borosilicate glass, which can transmit short-wave radiation within 2.5 microns and has a high absorption rate for long-wave radiation, reducing heat radiation loss. At the same time, it allows solar radiation energy to pass through the glass tube and be absorbed by the metal tube.

[0003] To improve the performance of vacuum tubes, many improvements have been proposed. One approach involves adding fins and other structures inside the absorber tube to reduce heat transfer resistance, lowering the temperature difference between the heat transfer fluid inside the tube and the outer surface, and thus reducing heat loss. Another approach involves adding reflective or thermally insulating films to the backlit side of the absorber tube to increase interception and reduce heat loss; or adding antireflection films to the light-facing side of the glass tube to increase transmittance. Related patents and literature include: CN200820032619.0 adds a reflector between the absorption tube and the glass tube on the backlight side to increase the interception rate and reduce heat loss.

[0004] CN200820032620.3 adds a reflective layer to the backlight surface of the glass tube to increase the interception rate and reduce heat loss.

[0005] CN201520809847.4 adds an arc-shaped heat shield with a reflective coating on the backlight side between the metal tube and the glass tube to reflect sunlight to the heat absorbing tube for a second time, thereby increasing the interception rate and reducing heat loss. The outer surface is coated with a solar selective absorption coating to increase the absorption of sunlight. CN201610143318.4 Install plane reflectors on both sides of the metal collector tube to reflect light twice and improve the interception rate.

[0006] CN201611107912.4 changes the light-facing and backlight-facing surfaces of the metal absorption tube into flat surfaces, while the two sides remain arc surfaces. A flat heat shield is inserted between the two tubes on the backlight side to reduce heat loss.

[0007] CN201621162534.5 coats a reflective thermal insulation film layer on the backlight side of the outer glass cover tube to reduce radiation heat loss and increase the interception of incident solar radiation.

[0008] CN201620288427.0 also adds a reflective coating on the backlight side of the glass tube, but the difference is that the coverage is less than 0.5, and it can be used for larger edge angle groove systems.

[0009] CN201710564830.0 uses a metal heat absorber with arc-shaped fins to expand the interception surface and increase the interception rate, but its convex surface faces the incident light, the incident angle effect increases, and the absorption rate will be lower than that of using a metal tube.

[0010] CN201810459840.2 adds an anti-reflection layer on the light-facing surface of the glass to increase the transmittance of the glass tube; and adds a reflective film on the backlight surface to increase the interception rate and reduce heat loss.

[0011] CN201980036407.0 also adds a reflective layer to the backlight surface of the glass tube to intercept reflected light, thereby improving the interception rate.

[0012] CN202210616703.1 adds a plane reflector on the backlight surface between the two tubes to increase the interception rate.

[0013] CN202420092343.4 adds a heat-absorbing coating to the light-facing surface of the glass tube to reduce radiation heat loss on the light-transmitting surface.

[0014] Some researchers have added an insulating layer to the outside of the glass tube on the backlight side to reduce heat loss. See: Ramchandra G. P, Sudhir V. P, Jyeshtharaj B. J, et al. Alternative designs of evacuated receiver for parabolic trough collector. Energy; 2018, 155: 66–76. Since the incident sunlight is concentrated at the center of the sun, the solar collecting tubes usually intercept most of the sunlight, and the efficiency improvement caused by increasing the interception rate is very small; similarly, the transmittance of the glass tube itself in long-wave radiation is very small, and further adding reflective film or heat shield will only reduce a small amount of heat loss and make little contribution to improving performance.

[0015] On the other hand, the efficiency of a solar collector is directly proportional to the transmittance of the glass tube and the absorptivity of the metal absorber tube. The aforementioned methods all overlook improving the transmittance of the outer tube and the absorptivity of the inner tube. However, due to the angle of incidence, a significant portion of the incident light is reflected and lost by the outer glass tube and the inner metal tube in the circular inner and outer tubes currently used in vacuum collectors. Using ray tracing to simulate the surface, we found that the outer glass tube and the inner metal tube increase reflection by approximately 4% to 8%, thereby reducing transmittance and absorptivity, and reducing efficiency by up to 8%. Summary of the Invention

[0016] The purpose of the present invention is to compensate for the fact that the incident angle in the existing technology has a great influence on the transmittance of the glass tube and the absorption rate of the absorption tube, overcome the defect of the low efficiency of the existing vacuum collector tube, and provide a medium and high temperature cavity collector for use in a trough type solar collector system, which can improve the transmittance of the glass outer tube and the absorption rate of the metal absorption tube, thereby improving the efficiency and performance of the solar collector tube.

[0017] The present invention is achieved through the following technical solutions: A medium- and high-temperature cavity collector for a trough-type heat collection system includes a transparent glass outer cover tube and a V-shaped metal trough collector. Vacuum is drawn or gas is filled between the transparent glass outer cover tube and the V-shaped metal trough collector. The V-shaped metal trough collector is located inside the transparent glass outer cover tube. The V-shaped metal trough collector includes a metal tube. Two metal fins are connected to the metal tube. The two metal fins form a V-shaped opening. The metal tube is connected to the inner side of the V-shaped opening. The center of the opening surface of the V-shaped metal trough collector is on the center of the transparent glass outer cover tube.

[0018] A reflective film is attached to the backlight surface of the inner side of the transparent glass outer cover tube.

[0019] A radiation shield is provided on the backlight part between the transparent glass outer cover tube and the V-shaped metal trough collector; the radiation shield is an arc-shaped plate with a reflective film on the side of the arc-shaped plate facing the V-shaped metal trough collector and a low infrared emissivity material coating on the other side.

[0020] The backlight portion of the outer side of the transparent glass outer cover tube is covered with a heat insulation layer.

[0021] A medium- and high-temperature cavity collector for a trough-type solar collector system includes a transparent glass outer cover tube and a V-shaped metal trough collector. Vacuum is drawn or gas is filled between the transparent glass outer cover tube and the V-shaped metal trough collector. The V-shaped metal trough collector is located inside the transparent glass outer cover tube. The V-shaped metal trough collector includes two V-shaped grooves and a metal tube. The V-shaped groove is a V-shaped open groove formed by two metal fins. The two V-shaped grooves are arranged in parallel. The metal tube is connected between the two V-shaped grooves. The adjacent ends of the two V-shaped grooves are connected. The connection point is at the center of the transparent glass outer cover tube. A reflective film is affixed to the inner backlight surface of the transparent glass outer cover tube.

[0022] A medium- and high-temperature cavity collector for a trough-type solar collector system includes a transparent glass outer cover tube and a V-shaped metal trough collector. Vacuum is drawn or gas is filled between the transparent glass outer cover tube and the V-shaped metal trough collector. The V-shaped metal trough collector is located inside the transparent glass outer cover tube. The V-shaped metal trough collector is a V-shaped structure consisting of two flat tubes, or a plurality of V-shaped structures consisting of a plurality of circular tubes arranged, or a star-shaped structure consisting of a plurality of flat tubes, or a metal tube with 4 to 10 metal fins connected thereto, each metal fin pointing to the center of the metal tube. The metal tube coincides with the center of the transparent glass outer cover tube. A radiation shield is provided on the backlight portion between the transparent glass outer cover tube and the V-shaped metal trough collector.

[0023] A selective radiation absorbing coating is provided on the inner surface of the V-shaped metal trough collector.

[0024] The light-facing surface of the transparent glass outer cover tube is covered with an anti-reflection coating.

[0025] A medium- and high-temperature cavity-type solar collector for use in a trough-type solar collector system comprises a rectangular outer cover tube and a V-shaped metal trough collector. The light-facing surface of the rectangular outer cover tube is a V-shaped glass surface, while the remaining portion is an open rectangle formed by three metal plates. A vacuum is drawn or gas is filled between the rectangular outer cover tube and the V-shaped metal trough collector. The V-shaped metal trough collector comprises a metal tube connected to two metal fins, forming a V-shaped opening. The metal tube is connected to the inside of the V-shaped opening. The opening surface of the V-shaped metal trough collector is parallel to the V-shaped opening of the rectangular outer cover tube, and the distance between the two opening surfaces is greater than or equal to 0. This solution overcomes the stringent vacuum requirements of traditional vacuum tubes, has a simple structure, and significantly reduces manufacturing costs. It eliminates the need to consider metal sealing issues, greatly improving system stability. The outer cover glass adopts a V-shaped opening, so some of the light reflected from the surface will be incident on the transparent glass, increasing transmittance. This solution is primarily suitable for trough systems with a 45-degree edge angle, small system optical error, and relatively high light concentration.

[0026] The outer side of the rectangular outer cover tube is covered with a heat insulation layer.

[0027] The heat transfer fluid flows inside the metal tube and transmits the solar energy that is absorbed and converted by the inner surface of the V-shaped groove.

[0028] The advantages of the present invention are: 1) The present invention uses V-shaped grooves instead of round tubes. The incident light will be absorbed multiple times in the V-shaped grooves, similar to a cavity absorber, and the absorption rate is increased by 3% to 4%, which is close to the complete absorption of the cavity receiver, overcoming the shortcoming of low absorption rate of the tubular collector; 2) The space between the V-shaped groove and the transparent outer cover tube is vacuumed, and a reflective film or an anti-radiation film or a heat insulating layer is added to the backlight portion to reduce heat loss.

[0029] 3) One of the solutions of the present invention uses a V-groove transparent cover solution, which not only overcomes the stringent vacuum requirements of traditional vacuum tubes, but also has a simple structure and greatly reduces manufacturing costs; it also does not need to consider the problem of metal sealing, greatly improving the stability of the system; it also forms a V-groove structure, greatly increasing the transmittance, and is mainly suitable for trough systems with relatively large focusing.

[0030] 4) Pure copper is required as the fin material to ensure that heat is transferred from the fin to the inner tube; flat tubes or multiple round tubes are used in parallel to replace the finned inner tube. The heat transfer fluid flows inside the tube to transfer heat energy, with low thermal resistance. Stainless steel or carbon steel materials can be used, which is easy to manufacture. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a schematic structural diagram of Example 1 of the present invention; Figure 2 This is a schematic structural diagram of Example 2 of the present invention; Figure 3 This is a schematic structural diagram of Example 3 of the present invention; Figure 4 This is a schematic structural diagram of Example 4 of the present invention; Figure 5 This is a schematic structural diagram of Example 5 of the present invention; Figure 6 This is a schematic structural diagram of a solution using flat tubes instead of round tubes and fins in Example 5 of the present invention; Figure 7 This is a schematic structural diagram of Example 6 of the present invention; Figure 8 This is a schematic structural diagram of Example 7 of the present invention; Figure 9 This is a schematic structural diagram of Example 8 of the present invention; Figure 10 It is an overall schematic diagram of the present invention. DETAILED DESCRIPTION

[0032] like Figure 10 As shown, the present invention uses ray tracing to simulate and calculate the collector's absorption rate of short-wave radiation. For vacuum cavity collectors, it is assumed that the heat loss per unit area of ​​the opening surface is equal to the heat loss per unit area of ​​the outer surface of the inner tube of the vacuum collector tube, and the heat dissipation area is approximately the area of ​​the V-groove opening surface. Ray tracing is used to directly calculate the interception rate and optical performance of the concentrator, thereby establishing a system performance simulation model. With the goal of maximizing the annual average solar thermal efficiency, the main design parameters of the collector are determined through optimization calculation, including the V-groove opening area, the V-groove depth (the distance from the vertex to the opening surface), and the outer cover radius; for the V-glass outer cover, the V-glass outer cover depth is determined. One of the conclusions obtained from the optimization is that the ratio of the half-width to the height of the V-groove opening surface is between 1:1 and 1:3, which will not be introduced one by one below. Example 5 is used for trough systems with an edge angle of about 90 degrees; the other schemes are used for trough systems with an edge angle of about 45 degrees. In practical application of the present invention, the transparent glass tube outer cover 1 and the two ends of the V-shaped metal trough collector 2 are connected by a metal and glass connector 9, which can be a metal bellows.

[0033] Example 1, a medium-high temperature cavity collector for a trough type solar collector system, such as Figure 1 As shown, it includes a transparent glass tube housing 1 and a V-shaped metal trough collector 2. The center of the V-shaped groove opening is at the center of the transparent glass tube housing 1, and the metal tube 3 is connected to the inside. The inside of the transparent glass tube housing 1 is evacuated or filled with gas. A radiation shield 4 is added to the backlight portion between the transparent glass tube housing 1 and the V-shaped metal trough collector 2. The radiation shield 4 is made of a curved steel plate with a reflective film on the side facing the collector tube and a low-infrared emissivity material on the other side.

[0034] The transparent glass tube cover allows sunlight to enter the V-shaped metal trough collector. Its shape and design help focus sunlight onto the V-shaped metal trough collector, improving light collection efficiency.

[0035] The center of the V-shaped metal trough collector's opening is aligned with the center of the transparent glass tube cover. This design allows sunlight to be effectively reflected and focused onto the inner metal tube of the collector. The V-shaped structure maximizes the absorption of sunlight and converts it into heat energy.

[0036] Metal pipes generally have good thermal conductivity and can quickly transfer absorbed heat to where it is needed.

[0037] The space between the inner and outer tubes is evacuated or filled with gas. The vacuum environment can effectively reduce heat conduction and convection, thereby improving the thermal insulation performance of the collector. This design reduces the possibility of heat being lost to the surrounding environment through the outer cover.

[0038] The radiation shield is constructed from curved steel plates with a reflective film on the side facing the collector tubes and a low-infrared emissivity material on the other side. The reflective film reflects heat from the backlit area, minimizing heat loss; the low-infrared emissivity material reduces heat loss through radiation.

[0039] Example 2, a medium-high temperature cavity collector for a trough type solar collector system, such as Figure 2 As shown, it includes a transparent glass tube cover 1 and a V-shaped metal groove collector 2. The center of the V-shaped groove opening surface is at the center of the glass tube, and the inside is connected to the metal tube 3. The inside of the transparent glass tube cover 1 is evacuated or filled with gas, and a reflective film 5 is added to the backlight part of the glass tube.

[0040] Example 3, a medium-high temperature cavity collector for a trough type solar collector system, such as Figure 3 As shown, it comprises a transparent glass tube housing 1 and a V-shaped metal groove heat collector 2. The V-groove opening is centered at the center of the glass tube, with a metal tube 3 connected to the inside. The inside of the transparent glass tube housing 1 is evacuated or filled with gas, and a radiation shield 4 is installed in the backlight area between the glass tube and the heat collector. The radiation shield 4 is made of a curved steel plate with a reflective film on the side facing the heat collector tube and a low-infrared emissivity material on the other side. An insulating layer 6 is installed on the outside of the glass tube housing in the backlight area.

[0041] Example 4, a medium-high temperature cavity collector for a trough type solar collector system, such as Figure 4As shown, it includes a transparent glass tube cover 1 and a V-shaped metal groove collector 2. The V-shaped metal groove collector 2 is composed of two V-shaped grooves and a metal tube 3. The two V-shaped grooves are connected to the metal tube 3. The center of the V-shaped groove opening surface is at the center of the glass tube, and the outside is connected to the metal tube 3. The inside of the transparent glass tube cover 1 is evacuated or filled with gas, and a reflective film 5 is added to the backlight part of the glass tube.

[0042] Example 5, a medium-high temperature cavity collector for a trough type solar collector system, such as Figure 5 As shown, it includes a transparent glass tube outer cover 1 and a V-shaped metal trough collector 2. The V-shaped metal trough collector 2 is composed of 6 metal fins evenly connected on a metal tube 3. Each fin points to the center of the metal tube. The metal tube coincides with the center of the transparent glass tube outer cover 1. The inside of the transparent glass tube outer cover 1 is evacuated or filled with gas, and a radiation shield 4 is added.

[0043] A plurality of flat tubes 10 can be used to form a star-shaped structure to replace the round tube plus fin solution. Other solutions can also be used as an alternative, such as Figure 6 As shown, the heat transfer fluid flows within the tube, directly transferring heat energy from the wall, significantly reducing thermal resistance and improving heat transfer efficiency. Using carbon steel or stainless steel tubes can meet heat transfer requirements and is easily implemented. Using this collector instead of traditional vacuum tubes, ray tracing calculations show that the optimized design's photothermal efficiency increases from 55% to 65%.

[0044] The V-shaped metal trough collector consists of six metal fins evenly connected to a metal tube, with each fin pointing toward the center of the tube. This design allows incident light to be absorbed multiple times by the wall, similar to a cavity receiver, improving the efficiency of sunlight absorption.

[0045] Example 6, a medium-high temperature cavity collector for a trough type solar collector system, such as Figure 7 As shown, it includes a rectangular outer cover tube and a V-shaped metal trough collector 2. The light-facing surface of the rectangular outer cover tube is a V-shaped glass surface 8, and the rest is an open rectangle composed of three metal plates 7. Gas is inflated between the rectangular outer cover tube and the V-shaped metal trough collector 2. The V-shaped groove collector is connected to the metal tube 3, and its opening surface is parallel to the opening of the V-shaped surface of the glass tube, and the distance is very small. An insulating layer 6 is added to the outside of the rectangular outer cover.

[0046] The rectangular outer tube housing features a V-shaped glass surface facing the sun, which reflects light multiple times and improves the outer tube's light transmittance. The remaining portion is composed of three metal plates. This design optimizes the collector's shape, making it more suitable for specific installation environments and further improving heat collection efficiency.

[0047] Highly efficient sunlight collection; Example 7: A medium-high temperature cavity collector for a trough type solar collector system, such as Figure 8 As shown, it includes a transparent glass tube outer cover 1 and a V-shaped metal trough collector 2. The V-shaped metal trough collector 2 is a plurality of V-shaped structures composed of multiple circular tubes arranged. The inside of the transparent glass tube outer cover 1 is evacuated or filled with gas, and a radiation shield 4 is added.

[0048] Example 8: A medium-high temperature cavity collector for a trough type solar collector system, such as Figure 9 As shown, it includes a transparent glass tube outer cover 1 and a V-shaped metal trough collector 2. The V-shaped metal trough collector 2 is a V-shaped structure composed of two flat tubes 10. The inside of the transparent glass tube outer cover 1 is evacuated or filled with gas, and a radiation shield 4 is added.

[0049] The combination of the transparent glass tube outer cover and the V-shaped metal groove collector of the present invention can maximize the collection and focusing of sunlight, thereby improving the light collection efficiency.

[0050] The V-shaped structure of the present invention effectively reflects and focuses sunlight onto the inner metal tube of the collector, further improving heat collection efficiency. By using V-shaped grooves instead of circular tubes, incident light is absorbed multiple times within the V-shaped grooves, similar to a cavity absorber. This increases absorption by 3% to 4%, approaching the complete absorption of a cavity receiver and overcoming the low absorption efficiency of tubular collectors.

[0051] The present invention reduces heat loss through vacuum or gas filling, effectively reducing the possibility of heat being lost to the surrounding environment through the outer cover.

[0052] The design of the radiation shield, reflective film and heat insulation layer of the present invention further reduces heat loss through radiation and conduction, thereby improving the heat preservation performance of the collector.

[0053] The metal fin structure of the present invention increases the surface area of ​​the collector, improves the heat absorption efficiency, and is suitable for scenarios requiring high heat output.

[0054] The design of the rectangular outer cover tube of the present invention optimizes the shape of the collector, making it more suitable for a specific installation environment. At the same time, the heat collection efficiency is further improved by optimizing the shape.

[0055] The various embodiments of the present invention offer a variety of structural designs, allowing for selection of the appropriate structure based on different application scenarios and requirements. For example, embodiments 1 and 3 are suitable for scenarios requiring high thermal insulation performance; embodiments 2 and 4 are suitable for scenarios requiring a simple structure and low cost; and embodiments 5 and 6 are suitable for scenarios requiring high heat output or specific installation environments.

[0056] The present invention achieves efficient sunlight collection, good thermal insulation performance and efficient heat energy utilization. Different embodiments provide diverse structural options to meet different application scenarios and needs.

Claims

1. A medium- and high-temperature cavity collector for use in a trough-type solar collector system, characterized by: It includes a transparent glass outer cover tube and a V-shaped metal trough collector. Vacuum is drawn or gas is filled between the transparent glass outer cover tube and the V-shaped metal trough collector. The V-shaped metal trough collector is located inside the transparent glass outer cover tube. The V-shaped metal trough collector includes a metal tube. Two metal fins are connected to the metal tube. The two metal fins form a V-shaped opening. The metal tube is connected to the inner side of the V-shaped opening. The center of the opening surface of the V-shaped metal trough collector is on the center of the transparent glass outer cover tube.

2. A medium- and high-temperature cavity collector for a trough-type solar collector system according to claim 1, characterized in that: A reflective film is attached to the backlight surface of the inner side of the transparent glass outer cover tube.

3. The medium- and high-temperature cavity collector for a trough-type solar collector system according to claim 1, characterized in that: A radiation shield is provided on the backlight part between the transparent glass outer cover tube and the V-shaped metal trough collector; the radiation shield includes an arc-shaped plate, a reflective film is affixed to the side of the arc-shaped plate facing the V-shaped metal trough collector, and a low infrared emissivity material coating is coated on the other side.

4. The medium- and high-temperature cavity collector for a trough-type solar collector system according to claim 1, characterized in that: The backlight portion of the outer side of the transparent glass outer cover tube is covered with a heat insulation layer.

5. A medium- and high-temperature cavity collector for use in a trough-type solar collector system, characterized by: It includes a transparent glass outer cover tube and a V-shaped metal groove collector. Vacuum is drawn or gas is filled between the transparent glass outer cover tube and the V-shaped metal groove collector. The V-shaped metal groove collector is located inside the transparent glass outer cover tube. The V-shaped metal groove collector includes two V-shaped grooves and a metal tube. The V-shaped groove is a V-shaped open groove composed of two metal fins. The two V-shaped grooves are arranged in parallel. The metal tube is connected between the two V-shaped grooves. The adjacent ends of the two V-shaped grooves are connected. The connection point is at the center of the transparent glass outer cover tube. A reflective film is affixed to the inner backlight surface of the transparent glass outer cover tube.

6. A medium- and high-temperature cavity collector for use in a trough-type solar collector system, characterized by: It includes a transparent glass outer cover tube and a V-shaped metal trough collector. Vacuum is drawn or gas is filled between the transparent glass outer cover tube and the V-shaped metal trough collector. The V-shaped metal trough collector is located inside the transparent glass outer cover tube. The V-shaped metal trough collector is a V-shaped structure composed of two flat tubes, or a plurality of V-shaped structures composed of a plurality of circular tubes, or a star-shaped structure composed of a plurality of flat tubes, or a metal tube connected to 4 to 10 metal fins, each metal fin points to the center of the metal tube, and the center of the metal tube coincides with the center of the transparent glass outer cover tube. A radiation shield is provided on the backlight part between the transparent glass outer cover tube and the V-shaped metal trough collector.

7. A medium- and high-temperature cavity collector for a trough-type solar collector system according to any one of claims 1 to 6, characterized in that: A selective radiation absorbing coating is provided on the inner surface of the V-shaped metal trough collector.

8. A medium- and high-temperature cavity collector for a trough-type solar collector system according to any one of claims 1 to 6, characterized in that: The light-facing surface of the transparent glass outer cover tube is covered with an anti-reflection coating.

9. A medium- and high-temperature cavity collector for use in a trough-type solar collector system, characterized by: It includes a rectangular outer cover tube and a V-shaped metal trough collector. The light-facing surface of the rectangular outer cover tube is a V-shaped glass surface, and the rest is an open rectangle composed of three metal plates. Vacuum is evacuated or gas is filled between the rectangular outer cover tube and the V-shaped metal trough collector. The V-shaped metal trough collector includes a metal tube, two metal fins are connected to the metal tube, and a V-shaped opening is formed. The metal tube is connected to the inner side of the V-shaped opening, and the opening surface of the V-shaped metal trough collector is parallel to the V-shaped opening surface of the rectangular outer cover tube.

10. The medium- and high-temperature cavity collector for a trough-type solar collector system according to claim 9, characterized in that: The outer side of the rectangular outer cover tube is covered with a heat insulation layer.

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