A heliostat and method for reducing shading losses in a mirror field of a tower-based solar thermal power plant

Abstract

The application discloses a heliostat and a method for reducing shading loss in a mirror field of a tower type photo-thermal power station, the heliostat comprising a reflecting mirror, a support and a driver, the reflecting mirror comprising a main reflecting mirror and auxiliary reflecting mirrors located on both sides of the main reflecting mirror, the auxiliary reflecting mirrors and the main reflecting mirror being connected through hinges, the back of the main reflecting mirror being provided with a truss, the truss being connected to the support through the driver, the truss being provided with a fixed end of an electric telescopic rod, the output end of the electric telescopic rod being connected to the back of the auxiliary reflecting mirror, the back of the auxiliary reflecting mirror being fixed with a photosensitive device, and the photosensitive device converting light signals into electric signals and transmitting the electric signals to a control system of the mirror field. According to the method, the heliostat can be automatically adjusted according to the shading condition when the solar elevation angle is very low, so that the shading loss is reduced, the overall optical efficiency of the mirror field is improved, and the heliostat returns to the original state when no shading occurs, so that the light collecting area is effectively increased.

Description

Technical Field

[0001] This invention relates to the field of tower solar thermal power plant technology, and in particular to a heliostat and method for reducing shading losses in the mirror field of a tower solar thermal power plant. Background Technology

[0002] Solar energy, as a clean energy source, has been widely promoted and applied due to its large energy output, sustainability, and pollution-free nature. Solar power generation technology can be divided into photovoltaic (PV) and solar thermal (CSP). CSP includes tower, trough, dish, and linear Fresnel systems, among which tower CSP technology has attracted much attention due to its advantages such as shorter heat transfer path, lower heat loss, and higher heat collection efficiency. Heliostats are important solar energy collection units in tower CSP power plant systems, reflecting solar energy onto the receiver of the absorber tower, thereby achieving solar energy collection.

[0003] In recent years, solar thermal power generation technology has seen rapid development. Compared to traditional photovoltaic power generation, its advantages include flexible energy storage and adjustable power generation. Among solar thermal technologies, tower solar thermal power generation technology is gradually gaining popularity due to its high heat collection efficiency. In a solar thermal power plant, the solar mirror field is the solar energy collection device, such as... Figure 1 As shown, in the solar thermal power plant's mirror field, heliostat 1 tracks solar rays in real time and reflects them onto the receiver 2 of the heat absorption tower. During this process, due to changes in the sun's position, the front row of heliostats 1 may block the light reflected by the rear row of heliostats 1, thus preventing the sunlight reflected by the rear heliostats from being accurately reflected onto the receiver of the heat absorption tower, resulting in shading losses and affecting the optical efficiency of the mirror field.

[0004] Optical efficiency is an important performance indicator for solar thermal mirror fields. Optical efficiency refers to the overall utilization rate of solar energy by the solar thermal mirror field, and improving optical efficiency is a key factor in enhancing the overall efficiency of a solar thermal power plant system. Currently, rectangular heliostats are commonly used. Some designs directly set heliostats in different shapes (circular, pentagonal, hexagonal) to reduce shading losses. However, this method reduces the light-receiving area of ​​the mirror field when there are no shading losses between heliostats. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a heliostat and method for reducing shading losses in the mirror field of a tower solar thermal power plant. When the solar altitude angle is very low, the heliostat can automatically adjust itself according to the shading situation, thereby reducing shading losses, improving the overall optical efficiency of the mirror field, and when no shading occurs, the heliostat returns to its original state, effectively increasing the light-receiving area.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows:

[0007] A heliostat for reducing shading losses in a tower-type solar thermal power plant's heliostat field includes a reflector, a support, and a driver. The reflector includes a main reflector and auxiliary reflectors located on either side of the main reflector. The auxiliary reflectors and the main reflector are connected by hinges. A truss is mounted on the back of the main reflector, and the truss is connected to the support via the driver. A fixed end of an electric telescopic rod is mounted on the truss, and the output end of the electric telescopic rod is connected to the back of the auxiliary reflector. A photosensitive device is fixed on the back of the auxiliary reflector, and the photosensitive device converts light signals into electrical signals and transmits them to the control system of the heliostat field.

[0008] In the above scheme, the photosensitive device is a photodiode.

[0009] In the above scheme, three auxiliary reflectors are connected to both sides of the main reflector.

[0010] In the above scheme, 4-6 photosensitive devices are fixed on the back of each auxiliary reflector.

[0011] In the above scheme, the two ends of the electric telescopic pole are connected to the truss and the auxiliary reflector respectively through connecting buckles.

[0012] In the above scheme, the area of ​​all auxiliary reflectors accounts for 35-45% of the total reflector area.

[0013] In the above scheme, the truss is hollow inside, and the wires of the photosensitive device and the electric telescopic pole pass through the inside of the truss and are connected to the power supply equipment of the mirror field through a driver.

[0014] A method for reducing shading losses in the mirror field of a tower solar thermal power plant, using heliostats as described above, includes the following process:

[0015] When the front heliostat does not obstruct the rear heliostat, the electric telescopic rod of the front heliostat is in the extended state, the main reflector and the auxiliary reflector of the front heliostat are on the same plane, and the control system of the mirror field controls the driver of the front heliostat to perform normal sun-tracking operation.

[0016] When the front heliostat blocks the rear heliostat, the light reflected from the rear heliostat will shine on the back of the auxiliary reflector of the front heliostat, and be received by the photosensitive device on the back of the auxiliary reflector. The photosensitive device converts the light signal into an electrical signal and transmits it to the control system of the mirror field. The control system of the mirror field sends a command to the front heliostat, and the electric telescopic rod connected to the auxiliary reflector retracts, pulling the auxiliary reflector back to the back of the main reflector, thereby reducing the obstruction to the rear heliostat.

[0017] In a further technical solution, in the Northern Hemisphere, between March and November, the auxiliary reflector is pulled back to the back of the primary reflector for 1 hour before being restored to its original state; between December and February of the following year, the auxiliary reflector is pulled back to the back of the primary reflector for 1.5 hours before being restored to its original state.

[0018] In a further technical solution, when strong winds occur at the location of the solar thermal power plant, the control system of the mirror field will issue an instruction to the heliostat to pull all the auxiliary mirrors back to the back of the main mirror.

[0019] Through the above technical solution, the heliostat and method for reducing shading losses in the mirror field of a tower solar thermal power plant provided by the present invention have the following beneficial effects:

[0020] (1) The heliostat of the present invention consists of a main reflector and auxiliary reflectors located on both sides. The auxiliary reflectors can be adjusted according to the position of the sun to reduce the obstruction of the heliostat behind it, thereby reducing the obstruction loss and improving the overall optical efficiency of the mirror field.

[0021] (2) When the wind increases at the location of the solar thermal power plant, the auxiliary reflector of the heliostat executes the retraction command, reducing the contact area with the wind, thereby improving the wind resistance of the heliostat.

[0022] (4) The heliostat of the present invention is foldable, which is convenient for transportation and helps to reduce transportation costs. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below.

[0024] Figure 1 This is a schematic diagram of a heliostat in operation.

[0025] Figure 2 This is a frontal schematic diagram of the heliostat of the present invention in an unobstructed condition;

[0026] Figure 3 This is a schematic diagram of the heliostat of the present invention in an unobstructed state.

[0027] Figure 4 This is a frontal view of the heliostat of the present invention under obstructed conditions.

[0028] Figure 5 This is a schematic diagram of the back of the heliostat of the present invention when it is obstructed.

[0029] In the diagram, 1. Heliostat; 2. Absorber; 3. Reflector; 4. Support; 5. Actuator; 6. Primary reflector; 7. Secondary reflector; 8. Hinge; 9. Truss; 10. Electric telescopic rod; 11. Photosensitive device; 12. Connecting buckle. Detailed Implementation

[0030] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0031] This invention provides a heliostat 1 for reducing shading losses in a solar thermal power plant's solar mirror field. The heliostat includes a reflector 3, a support 4, and a actuator 5. The reflector 3 accurately reflects sunlight onto the receiver 2 of the receiver tower. The actuator 5, upon receiving commands from the solar mirror field's control system, controls the reflector 3 to rotate and move in both pitch and azimuth directions, thereby achieving precise sun tracking. The support 4, located below the actuator 5, serves as the support and fixing device for the entire heliostat 1.

[0032] like Figure 2 and Figure 3 As shown, the reflector 3 includes a main reflector 6 and auxiliary reflectors 7 located on both sides of the main reflector 6. The auxiliary reflectors 7 and the main reflector 6 are connected by hinges 8 to allow for reversible rotation. In this embodiment, three auxiliary reflectors 7 are connected to each side of the main reflector 6. Both the main reflector 6 and the auxiliary reflectors 7 are rectangular. The overall area of ​​the reflector in this invention is the same as that of existing reflectors, except that existing reflectors are divided into different working areas. In this invention, the area of ​​all auxiliary reflectors 7 accounts for 30-45% of the total area of ​​the reflector 1.

[0033] A truss 9 is mounted on the back of the main reflector 6. The truss 9 is connected to the bracket 4 via a driver 5. The mirror field control system drives the truss 9 to rotate via the driver 5, thereby rotating the main reflector 6 to achieve the sun-tracking motion. A fixed end of an electric telescopic rod 10 is mounted on the truss 9 via a connecting buckle 12. The output end of the electric telescopic rod 10 is connected to the center of the back of the auxiliary reflector 7 via the connecting buckle 12. When the electric telescopic rod 10 is extended, the auxiliary reflector 7 and the main reflector 6 are on the same plane, jointly reflecting sunlight; when the electric telescopic rod 10 is retracted, the auxiliary reflector 7 is pulled back to the back of the main reflector 6, as shown in the image. Figure 4 and Figure 5 As shown. The electric telescopic rod 10 can be driven by a motor to rotate a lead screw, or by a hydraulic cylinder or a pneumatic cylinder, etc.

[0034] A photosensitive device 11 is fixed to the back of the auxiliary reflector 7. The photosensitive device 11 is mainly used to detect whether the front heliostat 1 will block the rear heliostat 1. Usually, the obstruction of the front heliostat 1 is mainly at the edge of the reflector 1, and the area of ​​the auxiliary reflector 7 defined in this invention can basically cover these positions. If obstruction occurs, the light reflected by the rear heliostat 1 will shine on the back of the auxiliary reflector 7 of the front heliostat 1, and thus be received by the photosensitive device 11.

[0035] Photodiodes are chosen as the photosensitive device 11 in this embodiment because of their small size, light weight, long lifespan, high sensitivity, and fast response time. Photodiodes can react quickly to light, converting the light signal into an electrical signal and transmitting it to the mirror field control system. Four to six photodiodes are fixedly distributed at different positions on the back of each auxiliary reflector 7.

[0036] The interior of the truss 9 is hollow. The wires of the photosensitive device 11 and the electric telescopic pole 10 pass through the interior of the truss 9 and are connected to the power supply equipment of the mirror field through the driver 5, so as to provide power to the photosensitive device 11 and the electric telescopic pole 10.

[0037] A method for reducing shading losses in the mirror field of a tower solar thermal power plant, using the heliostat 1 as described above, includes the following process:

[0038] When the front heliostat 1 does not obstruct the rear heliostat 1, the motorized telescopic rod 10 of the front heliostat 1 is in the extended state, such as... Figure 2 and Figure 3 As shown, the main reflector 6 and auxiliary reflector 7 of the front heliostat 1 are located on the same plane, and the control system of the mirror field controls the driver 5 of the front heliostat 1 to perform normal sun-tracking operation.

[0039] When the front heliostat 1 blocks the rear heliostat 1, the light reflected from the rear heliostat 1 will illuminate the back of the auxiliary reflector 7 of the front heliostat 1, and be received by the photosensitive device 11 on the back of the auxiliary reflector 7. The photosensitive device 11 converts the light signal into an electrical signal and transmits it to the control system of the mirror field. The control system of the mirror field issues a command to the front heliostat 1, and the electric telescopic rod 10 connected to the auxiliary reflector 7 retracts. Figure 4 and Figure 5 As shown, the auxiliary reflector 7 is pulled back to the back of the main reflector 6, thereby reducing the obstruction of the heliostat 1 behind it.

[0040] The timing of the restoration process needs to be determined based on the season. Shading typically occurs when the solar altitude angle is low, i.e., in the morning and evening. The solar altitude angle changes significantly within a 2-hour period. To maximize the solar energy received by the mirror field, the timing depends on the solar position in different seasons. In the Northern Hemisphere, from March to November, the auxiliary reflector 7 is pulled back to the back of the primary reflector 6 for 1 hour before being restored to its original position. From December to February of the following year, the auxiliary reflector 7 is pulled back to the back of the primary reflector 6 for 1.5 hours before being restored to its original position.

[0041] When strong winds occur at the location of the solar thermal power plant, the control system of the heliostat field will issue an instruction to the heliostat 1 to pull all the auxiliary mirrors 7 back behind the main mirror 6, thereby reducing the wind pressure on the heliostat 1 and ensuring its safety to the greatest extent. Furthermore, the auxiliary mirrors 7 can be folded during the transport of the heliostat 1 to save space and reduce transportation costs.

[0042] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A heliostat for reducing shading losses in a tower-type solar thermal power plant's mirror field, comprising a reflector, a support, and a actuator, characterized in that, The reflector includes a main reflector and auxiliary reflectors located on both sides of the main reflector. The auxiliary reflectors and the main reflector are connected by hinges. A truss is installed on the back of the main reflector, and the truss is connected to the support via a driver. The fixed end of an electric telescopic rod is installed on the truss, and the output end of the electric telescopic rod is connected to the back of the auxiliary reflector. A photosensitive device is fixed on the back of the auxiliary reflector, and the photosensitive device converts the light signal into an electrical signal and transmits it to the control system of the mirror field.

2. The heliostat for reducing shading losses in a tower-type solar thermal power plant mirror field according to claim 1, characterized in that, The photosensitive device is a photodiode.

3. A heliostat for reducing shading losses in a tower-type solar thermal power plant mirror field according to claim 1, characterized in that, Three auxiliary mirrors are connected to each side of the main mirror.

4. A heliostat for reducing shading losses in a tower-type solar thermal power plant mirror field according to claim 1, 2, or 3, characterized in that, Each auxiliary mirror has 4-6 photosensitive devices fixed on its back.

5. A heliostat for reducing shading losses in a tower-type solar thermal power plant mirror field according to claim 1, characterized in that, The two ends of the electric telescopic pole are connected to the truss and the auxiliary reflector respectively via connecting buckles.

6. A heliostat for reducing shading losses in a tower-type solar thermal power plant mirror field according to claim 1, characterized in that, The truss is hollow inside, and the wires of the photosensitive device and the electric telescopic pole pass through the inside of the truss and are connected to the power supply equipment of the mirror field through a driver.

7. A heliostat for reducing shading losses in a tower-type solar thermal power plant mirror field according to claim 3, characterized in that, The area of ​​all auxiliary mirrors accounts for 35-45% of the total area of ​​the mirror.

8. A method for reducing shading losses in the mirror field of a tower solar thermal power plant, comprising using the heliostat as described in claim 1, characterized in that, The process includes the following: When the front heliostat does not obstruct the rear heliostat, the electric telescopic rod of the front heliostat is in the extended state, the main reflector and the auxiliary reflector of the front heliostat are on the same plane, and the control system of the mirror field controls the driver of the front heliostat to perform normal sun-tracking operation. When the front heliostat blocks the rear heliostat, the light reflected from the rear heliostat will shine on the back of the auxiliary reflector of the front heliostat, and be received by the photosensitive device on the back of the auxiliary reflector. The photosensitive device converts the light signal into an electrical signal and transmits it to the control system of the mirror field. The control system of the mirror field sends a command to the front heliostat, and the electric telescopic rod connected to the auxiliary reflector retracts, pulling the auxiliary reflector back to the back of the main reflector, thereby reducing the obstruction to the rear heliostat.

9. A method for reducing shading losses in a mirror field of a tower solar thermal power plant according to claim 8, characterized in that, In the Northern Hemisphere, from March to November, the secondary reflector is pulled back to the back of the primary reflector for one hour before returning to its original position. From December to February of the following year, the secondary reflector is pulled back to the back of the primary reflector for 1.5 hours before returning to its original position.

10. A method for reducing shading losses in a mirror field of a tower solar thermal power plant according to claim 8, characterized in that, When strong winds occur at the location of the solar thermal power plant, the control system of the mirror field will issue a command to the heliostat to pull all the auxiliary mirrors back to the back of the main mirror.

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