A tower solar concentrating and heat absorption system based on a new type of cavity absorber

Abstract

The present invention discloses a tower-type solar concentrating and heat-absorbing system based on a novel cavity absorber, which consists of a concentrating mirror field and an absorption tower; the absorption tower includes two cavity absorbers arranged vertically and having the same structure. The cavity absorber arranges an internal heat-absorbing tube group in a cylindrical heat-insulating cavity and coats a heat-absorbing coating on the inner wall surface of the heat-insulating cavity. Both absorbers are provided with light-collecting openings on one side of the heat-insulating cavity, and the light-collecting openings of the two absorbers face in opposite directions. Each takes the side where the light-collecting opening is opened as its light-facing side, and respectively obtains the sunlight converged by the mirror field on its light-facing side; the absorber arranges an exposed heat-absorbing tube group on the outer wall surface of the heat-insulating cavity on the light-facing side; the heat-absorbing medium first exchanges heat through the external heat-absorbing tube group on the light-facing side, and then further absorbs heat through the heat-absorbing tube group in the heat-insulating cavity. The sunlight is respectively reflected and converged by the mirror fields on both sides of the absorption tower to the light-facing side of the corresponding absorber, thereby expanding the area of the mirror field and making the site more fully utilized.

Description

Technical Field

[0001] The present invention relates to the field of optimizing the concentrating and heat-absorbing system in the tower-type solar thermal field, and particularly relates to a tower-type solar concentrating and heat-absorbing system based on a novel cavity absorber. Background Art

[0002] With the popularization of the use of clean energy, solar energy, as a clean and renewable energy, has attracted much attention. Among them, tower-type solar concentrating thermal power generation has a high concentration ratio, can generate a relatively high working temperature, and thus can generate high-parameter steam to bring high power generation efficiency. At the same time, based on the development of energy storage technology, the second-generation tower-type solar thermal power generation system is equipped with an energy storage device, which can overcome the shortcoming that solar power generation cannot work at night. Therefore, the tower-type solar concentrating thermal power generation technology has been vigorously promoted in recent years.

[0003] The solar radiation absorber is the core component of the tower-type solar concentrating thermal system. Currently, the main forms of tower absorbers in operation include multi-tube exposed absorbers and chamber absorbers, etc. The multi-tube exposed absorber arranges parallel heat-absorbing tubes in a circular layout. On the exposed side of the absorber, it can receive sunlight reflected from the mirror fields in all directions on all sides. This enables the system to arrange an elliptical heliostat field with a sufficient large area, and the land utilization rate is relatively high. A larger area of the concentrating mirror field can also converge a higher radiant energy flux density, generating a higher temperature heat-absorbing medium to improve the work capacity. However, the thermal radiation generated by the exposed absorber at high temperatures will be directly dissipated into the surrounding environment, resulting in a relatively high thermal radiation loss. The chamber absorber arranges the heat absorber inside the chamber and collects solar radiation through the opening of the chamber. This enables the thermal radiation emitted by the heat absorber to be secondarily absorbed due to the limitation of the chamber, reducing the thermal radiation dissipation. However, the chamber absorber usually avoids collecting sunlight through openings on multiple sides to ensure sufficient light capture ability. Currently, most of the chamber absorbers in operation have a light inlet on only one side, which brings great limitations to the layout of the mirror field. The heliostat field can only be arranged on the side facing the light inlet, and the shape is fan-shaped or elliptical, which restricts the concentrating area and land utilization. Therefore, for the future development trend of tower-type solar thermal power generation towards larger scale and higher parameters, the layout of the tower-type solar concentrating and heat-absorbing system still needs to consider effectively reducing thermal radiation while being equipped with a large-area and highly compact concentrating mirror field, so as to improve the solar thermal power generation efficiency, reduce the power generation cost, and achieve a wider range of technology promotion. Summary of the Invention

[0004] In view of the above existing problems, the present invention designs a tower-type solar concentrating and heat-collecting system based on a novel cavity absorber, providing a novel absorber structure and a layout form of the heat absorber to effectively reduce the thermal radiation loss during the heat collection process and meet the requirements of arranging a large-area and highly compact concentrating mirror field to improve the land utilization rate.

[0005] The technical solution of the present invention is as follows:

[0006] The present invention first provides a tower-type solar concentrating and heat-absorbing system based on a novel cavity absorber, which consists of an absorption tower and a concentrating mirror field around the absorption tower; the absorption tower includes two cavity absorbers arranged vertically and having the same structure; each cavity heat absorber includes a cylindrical heat-insulating cavity body, one semi-perimeter of the cylindrical heat-insulating cavity body serves as the light-facing side, an opening for installing a daylighting window is axially provided in the middle of the light-facing side, and an exposed heat-absorbing tube group is arranged on the outer wall surface of the light-facing side, a heat-absorbing coating is coated on the inner wall surface of the heat-insulating cavity, and an internal heat-absorbing tube group is arranged in the internal area of the heat-insulating cavity. The light-facing sides of the two cavity absorbers are opposite, and the daylighting openings face in opposite directions; the light-facing sides of the two cavity absorbers respectively obtain the sunlight reflected and concentrated by the concentrating mirror fields on the sides they face.

[0007] According to a preferred embodiment of the present invention, the exposed tube-type heat-absorbing tube group is only arranged on the semi-perimeter of the light-facing side of the heat-insulating cavity to reduce the heat radiation loss caused by the exposure of the heat-absorbing tubes; each heat-absorbing tube of the internal heat-absorbing tube group and the exposed heat-absorbing group is arranged along the axial direction of the heat-insulating cavity. The exposed heat-absorbing group is connected to the internal heat-absorbing tube group through a working medium delivery pipeline, and the working medium flows towards the internal heat-absorbing tube group after absorbing heat in the exposed heat-absorbing group.

[0008] According to a preferred embodiment of the present invention, each heat-absorbing tube of the internal heat-absorbing tube group is evenly distributed in a circle around the central axis of the heat-insulating cavity; there is a certain interval between the internal heat-absorbing tube group and the inner wall of the heat-insulating cavity; the heat-absorbing coating coated on the inner wall of the heat-insulating cavity is used to secondarily absorb the heat radiation of the internal heat-absorbing tube group, and at the same time, radiation heat exchange is carried out with the internal heat-absorbing tube group to heat the backlight part of the internal heat-absorbing tube group.

[0009] The present invention also provides a solar energy utilization method based on the tower-type solar concentrating and heat-absorbing system, which includes the following steps:

[0010] Divide the concentrating mirror field around the absorption tower into a near-sun mirror field and a far-sun mirror field, and the two mirror fields respectively reflect and concentrate the sunlight to the light-facing sides of the two cavity absorbers;

[0011] For any one of the mirror fields, the heliostats with the mirror field central angle equal to the opening angle of the daylighting opening will reflect all the sunlight to the daylighting window of the corresponding cavity absorber, and the sunlight reflected by the remaining heliostats of this side mirror field will be concentrated to the exposed heat-absorbing group of the corresponding cavity heat absorber and absorbed;

[0012] The sunlight entering the heat-insulating cavity through the daylighting window is absorbed by the internal heat-absorbing tube group and the heat-absorbing coating on the cavity wall surface. The heat radiation flow radiated by the internal heat-absorbing tube group is secondarily absorbed by the heat-insulating cavity, thereby effectively reducing the heat radiation dissipation of the heat absorber; at the same time, the radiation heat exchange between the inner wall surface of the heat-insulating cavity and the heat-absorbing tubes improves the uniformity of the heat flow distribution of the heat-absorbing tubes;

[0013] After the endothermic working fluid enters the absorption tower, it is split. The split endothermic working fluid is respectively introduced into a cavity absorber from bottom to top, and in each cavity absorber, it successively passes through the exposed tubular heat absorption tube group and the internal heat absorption tube group for heat absorption, and then the two paths of endothermic working fluid converge and are output from the absorption tower.

[0014] Compared with the prior art, the present invention has the following beneficial effects:

[0015] (1) Compared with the traditional multi-tube exposed absorber, in the novel cavity absorber adopted by the present invention, most of the heat absorber groups are arranged in the heat preservation cavity, and the cavity structure and the barrier between the heat absorption tubes can be used to perform secondary absorption on thermal radiation, effectively reducing thermal radiation dissipation. The traditional heat absorption coating has a high emissivity to the outside, and thermal radiation is serious at high temperatures. Adopting this absorber structure can reduce the proportion of the emitted thermal radiation energy to less than 10%; at the same time, the inner surface of the circular cavity is also sprayed with a heat absorption coating, and the heat flux distribution on the surface of the heat absorption tube is made more uniform through the radiation heat transfer between the coating and the heat absorption tube, reducing the loss of the heat absorption tube material.

[0016] (2) Compared with the traditional cavity absorber, the absorber of the present invention retains a part of the exposed heat absorber group on the semi-perimeter on one side of the lighting inlet to collect the reflected sunlight that cannot enter the cavity due to the limitation of the cavity opening angle, expanding the mirror field area and improving the solar energy utilization efficiency.

[0017] (3) Compared with the traditional absorption tower, the present invention arranges two absorbers in one absorption tower, and the lighting windows of the absorbers face the near-sun side and the far-sun side respectively. Combining the semi-perimeter exposed heat absorber on the same side as the lighting window and the heat absorber group in the cavity, the absorption tower can collect the reflected sunlight from all around, and the concentrating mirror field can be arranged in a circular or elliptical shape around the absorption tower, making up for the defect that a single cavity absorber can only arrange the mirror field on one side of the absorption tower. Combining the high-efficiency energy capture of the absorber, it can reduce the land area (m 2 / GWh) required for producing unit electricity by nearly 52%, significantly reducing the land cost of solar power generation. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is a top view structural schematic diagram of the novel cavity absorber of the present invention;

[0019] Figure 2 is a top view schematic diagram of the novel cavity absorber of the present invention receiving solar radiation;

[0020] Figure 3 is a schematic diagram of the concentrating heat absorption system with a double absorber of the present invention;

[0021] Figure 4 is a top view structural schematic diagram of the concentrating heliostat field of the present invention;

[0022] Figure 5 It is a schematic diagram of the radiative heat transfer process inside the novel cavity absorber of the present invention;

[0023] Figure 6 It is a schematic diagram of the daylighting window of the novel cavity absorber of the present invention;

[0024] Figure 7 It is a schematic diagram of the flow process of the heat-absorbing working fluid passing through the novel cavity absorber of the present invention. Specific embodiments

[0025] The present invention will be further described and explained below in conjunction with specific embodiments. The described embodiments are only examples of the present disclosure and do not delimit the scope of limitation. The technical features of each embodiment of the present invention can be combined correspondingly without conflict.

[0026] As Figure 1 and Figure 3 shown, a tower-type solar concentrating heat absorption system based on a novel cavity absorber of the present invention includes an absorption tower and a concentrating mirror field around the absorption tower. The absorption tower includes two cavity absorbers I and II arranged vertically and having the same structure; the present invention divides the concentrating mirror field around the absorption tower into a near-sun mirror field and a far-sun mirror field, and the two mirror fields respectively reflect and converge sunlight to the light-facing sides of the two cavity absorbers; the light-facing sides of the two cavity absorbers are opposite.

[0027] As Figure 1 shown, the main body of the novel cavity absorber of the present invention includes a cylindrical heat-insulating cavity 4. One semi-perimeter of the cylindrical heat-insulating cavity 4 is used as the light-facing side. An opening for installing a daylighting window 5 is axially opened in the middle of the light-facing side, and an exposed heat-absorbing tube group 1 is arranged on the outer wall surface of the light-facing side. A heat-absorbing coating 3 is coated on the inner wall surface of the heat-insulating cavity, and an internal heat-absorbing tube group 2 is arranged in the internal area of the heat-insulating cavity.

[0028] In a specific embodiment of the present invention, for convenient arrangement, a plurality of heat absorption tubes are arranged in parallel to form a row of heat absorption tubes. Among them, in the exposed heat absorption tube group 1, 3 heat absorption tubes form a row of heat absorption tubes, and the exposed heat absorption tube group 1 is composed of 8 rows of heat absorption tubes. The opening formed on the heat preservation cavity 4 is a rectangular opening, and the opening width is the width of two rows of heat absorption tubes. A daylighting window 5 is arranged on the opening; the exposed heat absorption tube group 1 is on the same side as the daylighting window 5. The exposed heat absorption tube group 1 includes a total of 24 heat absorption tubes, and the outer diameter of each heat absorption tube is 60 mm. The heat absorption tubes are closely arranged with each other; each row of heat absorption tubes is arranged on the outer side wall surface of the heat preservation cavity 4 except for the daylighting window, and is arranged only on the semi-peripheral wall surface on one side of the daylighting window. In this embodiment, there are 4 rows of heat absorption tubes on each side of the daylighting window. The internal heat absorption tube group 2 is arranged inside the heat preservation cavity 4 and is composed of 18 rows of heat absorption tubes. Each row of heat absorption tubes includes 2 heat absorption tubes, and the outer diameter of each heat absorption tube is 40 mm; the rows of heat absorption tubes are arranged in a circular pattern. 10 rows of heat absorption tubes are arranged in each semi-periphery, and 8 rows of heat absorption tubes are arranged in the semi-periphery on the side of the daylighting window, that is, no heat absorption tubes are arranged at the position directly opposite to the opening of the heat preservation cavity, leaving an opening with the width of two rows of heat absorption tubes to ensure that the sunlight passing through the daylighting window can irradiate most of the heat absorption tubes of the heat absorber group 2 more evenly; at the same time, in order to make the internal heat absorption tube group 2 arranged in a circular pattern inside the cavity to limit heat radiation dissipation and make the heat absorption tubes evenly heated, the rows of heat absorption tubes are arranged at intervals, and the interval distance is 0.3 m. The same interval is also left between each heat absorption tube and the inner wall of the heat preservation cavity to promote the radiative heat transfer between the heat absorption tubes and between the heat absorption tubes and the heat absorption coating 3 on the inner surface of the heat preservation cavity, and reduce heat radiation dissipation.

[0029] In this embodiment, the light-facing sides of the two cavity-type heat absorbers are opposite, and the daylighting openings face exactly opposite directions; the light-facing sides of the two cavity-type heat absorbers respectively obtain the sunlight reflected and converged by the condenser field on the side they face. The exposed heat absorption tube group is arranged only on the semi-periphery of the light-facing side of the heat preservation cavity to reduce the heat radiation loss caused by the exposure of the heat absorption tubes; the heat absorption tubes of the internal heat absorption tube group and the exposed heat absorption group are all arranged along the axial direction of the heat preservation cavity, and the exposed heat absorption group is connected to the internal heat absorption tube group.

[0030] The outer surfaces of the heat absorption tubes of the internal heat absorption tube group 2 and the exposed heat absorption group 1 are sprayed with heat absorption coatings; during operation, the heat absorption medium first enters the exposed heat absorption group 1 on the light-facing side from bottom to top for preheating, and the exposed heat absorption group is arranged with large-diameter heat absorption tubes; then the heat absorption working medium is further heated to a higher temperature through the internal heat absorption tube group 2, and the internal heat absorption tube group 2 is arranged with small-diameter heat absorption tubes to keep the heat absorption area the same as that of the exposed heat absorption group 1.

[0031] In a specific embodiment, the heat-absorbing coating applied on the inner wall of the heat-insulating cavity 4 is the same as the absorption coating on the surface of the heat-absorbing tube; its composition consists of a high-temperature resistant resin, a light-absorbing pigment, a solvent, a dispersant, and a filler, with a mass fraction ratio of 22%:5%:57%:6%:10%. The high-temperature resistant resin is vinyl-caged polyhedral oligomeric silsesquioxane; the light-absorbing pigment is a mixture of copper oxide, iron oxide, and manganese oxide nanoparticles with a mass fraction of 1:1:1; the solvent is methyl acetone; the dispersant is a wetting dispersant DISPERSANT-2070; the filler is rare earth yttrium. The coating thickness is 30 μm, with an absorption rate of over 90% and an emissivity of less than 30%. The heat-insulating cavity is composed of two sides of rigid heat-insulating materials (such as ceramic fiber boards or nano-aerogel thermal insulation boards) and an intermediate filler layer (such as high-temperature rock wool and aluminum silicate refractory fiber cotton), and a metal plate is installed outside the rigid heat-insulating material layer on the outside of the heat-insulating cavity; the heat-insulating cavity wraps the internal heat-absorbing tube group inside without being exposed, reducing heat radiation dissipation.

[0032] Appendix Figure 2 shows a top view schematic of a new type of cavity absorber absorbing solar radiation; Appendix Figure 3 shows a schematic of a concentrating heat-absorbing system composed of an absorption tower and a mirror field with two absorbers arranged; Appendix Figure 4 shows a top view schematic of the heliostat structure of a circular concentrating mirror field. As Figure 2 、 3 、4 shows, a new type of cavity absorber is responsible for receiving the solar radiation reflected by the semi-circular mirror field on one side of the circular mirror field. The outer expansion surface opening angle of the daylighting window of the new type of cavity absorber is θ. Based on the internal heat-absorbing tube group 2 with less internal heat radiation dissipation in the heat-insulating cavity, the opening angle θ is selected as 120°, so that most of the solar radiation reflected by the mirror field can be captured by the daylighting window. Two semi-circular mirror fields are respectively provided with a first sector mirror field 6 with central angles θ1 and θ2, and satisfy θ = θ1 = θ2. The second sector mirror field 7 is the two mirror fields in the semi-circular mirror field except the first sector mirror field 6, and their central angles are both (180° - θ) / 2 = 30°. The solar radiation reflected by the first sector mirror field 6 is respectively received by the daylighting windows of the two absorbers and irradiates the internal heat-absorbing tube group 2 inside the cylindrical cavity. The two parts of solar radiation reflected by the second sector mirror field 7 respectively irradiate the semi-circular outer-exposed heat-absorbing group 1 on both sides of the daylighting window. Based on the fact that the daylighting window area in the new type of cavity absorber is smaller than the absorber receiving area, the first sector mirror field 6 uses small-sized heliostats to ensure that the daylighting window can capture as much sunlight reflected by the sector mirror field as possible. The second sector mirror field 7 uses large-sized heliostats corresponding to the receiving area of the semi-circular outer-exposed heat-absorbing group 1.

[0033] The central absorption tower contains two identical new - type cavity absorbers I and II. The two absorbers are arranged coaxially up and down. Each of the two absorbers has an exposed heat - absorbing group 1, and one side of the daylighting window faces the near - sun side and the far - sun side respectively, so that the two absorbers receive the solar radiation reflected by the semi - circular mirror fields on both sides respectively. Compared with the traditional cavity absorber, the structure of the new - type cavity absorber and the arrangement of the double absorbers expand the layout range of the heliostat field.

[0034] Appendix Figure 5 shows the schematic diagram of the radiative heat - transfer process inside the new - type cavity absorber. As Figure 5 shown, the internal heat - absorbing tube group 2 inside the heat - preservation cavity 4 first receives the solar radiation passing through the daylighting window 5 and conducts photothermal conversion through the high - performance selective absorption coating sprayed on the surface. Due to its own high temperature, the heat - absorbing tube will emit a heat - radiation flux. Due to the circumferential arrangement of the internal heat - absorber group and the cylindrical chamber structure of the heat - preservation cavity, the heat radiation emitted by the heat - absorbing tube can be effectively re - absorbed by other heat - absorbing tubes and the heat - absorbing coating 3 on the inner wall of the heat - preservation cavity, reducing the heat - radiation loss of the heat - absorber group. In addition, after receiving the heat radiation of the heat - absorbing tube, the heat - absorbing coating 3 heats up and also generates a certain heat - radiation flux by itself. These heat radiations are absorbed by the heat - absorbing tubes at a certain interval, thereby heating the back - light side of the heat - absorbing tube and making the heat - flow distribution of each heat - absorbing tube in the internal heat - absorbing tube group 2 more uniform, reducing the surface stress of the pipe material. The selective absorption coating has an absorption rate of more than 90% and an infrared emissivity of less than 35%, ensuring good photothermal conversion performance.

[0035] Appendix Figure 6 shows the structural schematic diagram of the daylighting window of the new - type cavity absorber. As Figure 6 shown, according to the opening size of the heat - preservation cavity, the daylighting window consists of a trapezoidal outward - expanding reflecting surface 5 - 1 and a rectangular reflecting channel 5 - 2. The solar radiation reflected by the fan - shaped mirror field 6 can directly enter the daylighting channel or enter the cavity interior after being reflected twice by the reflecting surfaces 5 - 1 and 5 - 2. The outward - expanding reflecting surface 5 - 1 and the reflecting channel 5 - 2 have high - reflection performance, and are arranged with a composite high - reflection material composed of a glass matrix and a silver - or aluminum - plated emission layer, with a high reflectivity of 92% - 94%. The outward - expanding secondary reflecting surface is connected to the light - facing side of the rectangular channel, and its opening angle is 110° - 120°; the length of the daylighting opening is the same as the overall height of the absorber, and the width is 1 / 15 - 1 / 10 of the perimeter of the heat - preservation cavity.

[0036] Appendix Figure 7 shows the schematic diagram of the flow of the heat - absorbing working medium through the new - type cavity absorber. As Figure 7As shown, when the endothermic system is working, the endothermic working medium, such as high-temperature molten salt, first passes through the exposed endothermic group 1 on the light-facing side from bottom to top, receives solar radiation to initially raise the temperature, and then passes through each row of tubes of the internal endothermic tube group 2 inside the cavity to further raise the endothermic temperature. After that, it enters the heat storage system and subsequent cycles for power generation. In terms of structural dimensions, based on the above-mentioned sufficient arrangement of the pipe diameters, the number of endothermic tube rows, and the number of endothermic tubes in a single row of the internal endothermic tube group 1 and the internal endothermic tube group 2, it is possible to ensure that the endothermic areas of the two endothermic groups are equivalent.

[0037] It should be noted that the specific embodiments described in this specification are examples of the invention structure, and the names of the various structures can be different. The invention structure is not limited to the above embodiments. Any equivalent or simple changes made according to the structure or principle of this invention patent should fall within the protection scope of this application.

Claims

1. A tower solar concentrating and heat-absorbing system based on a cavity absorber, characterized in that: The system consists of an absorption tower and a concentrator mirror field around the absorption tower; the absorption tower includes two cavity absorbers arranged vertically and having the same structure. Each cavity absorber includes a cylindrical heat-insulating cavity. One semi-perimeter of the cylindrical heat-insulating cavity serves as the light-facing side. An opening for installing a daylighting window is axially formed in the middle of the light-facing side. An exposed heat-absorbing tube group is arranged on the outer wall surface of the light-facing side. A heat-absorbing coating is applied on the inner wall surface of the heat-insulating cavity. An internal heat-absorbing tube group is arranged in the internal area of the heat-insulating cavity. The light-facing sides of the two cavity absorbers are opposite, and the daylighting openings face in opposite directions; the light-facing sides of the two cavity absorbers respectively obtain the sunlight reflected and concentrated by the concentrator mirror field on the side they face. The exposed heat-absorbing tube group is only arranged on the semi-perimeter of the heat-insulating cavity on the light-facing side to reduce the heat radiation loss caused by the exposure of the heat-absorbing tubes; each heat-absorbing tube of the internal heat-absorbing tube group and the exposed heat-absorbing group is arranged along the axis of the heat-insulating cavity. The exposed heat-absorbing group is connected to the internal heat-absorbing tube group through a working medium delivery pipeline. The working medium flows towards the internal heat-absorbing tube group after absorbing heat in the exposed heat-absorbing group. Each heat-absorbing tube of the internal heat-absorbing tube group and the exposed heat-absorbing group is sprayed with a heat-absorbing coating on its outer surface; during operation, the heat-absorbing medium first enters the exposed heat-absorbing group on the light-facing side from bottom to top for preheating. The exposed heat-absorbing group is arranged with large-diameter heat-absorbing tubes; then the heat-absorbing working medium is further heated to a higher temperature through the internal heat-absorbing tube group. The internal heat-absorbing tube group is arranged with small-diameter heat-absorbing tubes to keep the heat-absorbing area the same as that of the exposed heat-absorbing group.

2. The tower solar concentrating and heat absorbing system based on a cavity absorber according to claim 1, wherein: Each heat-absorbing tube of the internal heat-absorbing tube group is evenly distributed in a circle around the central axis of the heat-insulating cavity; there is a certain interval between the internal heat-absorbing tube group and the inner wall of the heat-insulating cavity; the heat-absorbing coating applied on the inner wall of the heat-insulating cavity is used to secondarily absorb the heat radiation of the internal heat-absorbing tube group, and at the same time conduct radiative heat exchange with the internal heat-absorbing tube group to heat the backlight part of the internal heat-absorbing tube group.

3. The tower-type solar concentrating and heat-absorbing system based on a cavity absorber according to claim 1, wherein: The heat-absorbing coating applied on the inner wall of the heat-insulating cavity is the same as the absorbing coating on the surface of the heat-absorbing tube; the heat-insulating cavity consists of two-side rigid heat-insulating materials and an intermediate filler layer, and a metal plate is additionally installed on the outer rigid heat-insulating material layer of the heat-insulating cavity; the heat-insulating cavity wraps the internal heat-absorbing tube group without exposure to reduce heat radiation dissipation.

4. The tower solar concentrating and heat absorbing system based on a cavity absorber according to claim 1, wherein: The daylighting window consists of a rectangular channel and an outward-expanded secondary reflecting surface. The outward-expanded secondary reflecting surface is connected to the light-facing side of the rectangular channel, and its opening angle is 110° - 130°; high-reflectivity materials are plated on all four sides of the rectangular channel and the outward-expanded secondary reflecting surface to improve the capture ability of the reflected light; the length of the daylighting opening is the same as the overall height of the absorber, and the width is 1 / 15 - 1 / 10 of the perimeter of the heat-insulating cavity.

5. The tower solar concentrating and heat absorption system based on a cavity absorber according to claim 3, wherein: The heat-absorbing material has an absorption rate exceeding 90% and an infrared emissivity lower than 35%.

6. The tower-type solar concentrating and heat-absorbing system based on a cavity absorber according to claim 4, wherein: The high-reflectivity material of the daylighting opening adopts a composite reflector composed of a glass matrix and a silver-plated or aluminum-plated emission layer.

7. The tower solar concentrating and heat absorbing system based on a cavity absorber according to claim 1, wherein: The two cavity absorbers are arranged vertically on the central axis of the absorption tower. The sides of the two cavity absorbers with daylighting windows and exposed heat-absorbing groups respectively face the near-sun side and the far-sun side of the concentrator mirror field, and respectively receive the solar radiation reflected by the concentrator mirror fields in the respective semi-circular spaces on the near-sun side and the far-sun side.

8. A solar energy utilization method based on the tower-type solar concentrating and heat-absorbing system according to any one of claims 1-7, characterized in that, Including the following steps: The concentrator mirror fields around the absorber tower are divided into the near-sun mirror field and the far-sun mirror field. The two mirror fields respectively reflect and converge sunlight to the light-facing sides of the two cavity absorbers; For any one side of the mirror field, the heliostats with the mirror field central angle equal to the opening angle of the daylighting port will reflect all the sunlight to the daylighting window of the corresponding cavity absorber, and the sunlight reflected by the remaining heliostats on this side of the mirror field will be converged to the exposed heat absorption group of the corresponding cavity heat absorber and absorbed; The sunlight entering the heat preservation cavity through the daylighting window is absorbed by the internal heat absorption tube group and the heat absorption coating on the cavity wall surface. The heat radiation flow radiated by the internal heat absorption tube group is absorbed by the heat preservation cavity for the second time, thus effectively reducing the heat radiation dissipation of the heat absorber; At the same time, the radiation heat transfer between the inner wall surface of the heat preservation cavity and the heat absorption tube improves the uniformity of the heat flow distribution of the heat absorption tube; After entering the absorber tower, the heat absorption working medium is shunted. The shunted heat absorption working medium is respectively passed into a cavity absorber from bottom to top, and absorbs heat in turn through the exposed tube heat absorption tube group and the internal heat absorption tube group in each cavity heat absorber, and then the two-way heat absorption working medium converges and outputs from the absorber tower.

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