Dish / stirling solar power system with adjustable secondary optical element

Abstract

This invention discloses a dish / Stirling solar power generation system with an adjustable secondary concentrator, including a dish concentrator, a Stirling thermoelectric generator, a cavity receiver, a secondary concentrator, a spot measurement device, an image processor, and a controller. The secondary concentrator includes a rotating cylinder rotatable about an axis, a secondary concentrator mirror hinged to the rotating cylinder, and a push-pull device for driving the secondary concentrator mirror's rotation. This invention installs a low-power adjustable secondary concentrator mirror at the front end of the cavity receiver of the Stirling thermoelectric generator. A rotatable planar receiving target and a CCD camera measure the actual focused spot, and the energy centroid coordinates are processed and fed back to the controller to adjust the secondary concentrator mirror's orientation. This improves the circumferential energy uniformity of the absorber coil and reduces the peak energy flux density, achieving safe and efficient light-heat-electric energy conversion in the dish / Stirling system. This invention also discloses a method for adjusting the orientation of the secondary concentrator mirror.

Description

Technical Field

[0001] This invention belongs to the field of solar concentrated thermal power generation, and in particular to a dish / Stirling solar thermal power generation system with an adjustable secondary concentrating element. Background Technology

[0002] Solar energy is a clean, environmentally friendly, and widely distributed renewable energy source. Developing and utilizing solar energy resources is one of the important ways for my country to upgrade its energy structure and contribute to the goals of "carbon peaking and carbon neutrality." The dish / Stirling solar thermal power generation system, consisting of a parabolic concentrator, a Stirling engine, and a generator set, is an important technological approach. It concentrates sunlight onto a cavity receiver using a rotating parabolic concentrator composed of one or more sub-mirrors, heating the working fluid inside the receiver to drive the Stirling engine-generator set to generate electricity. It boasts advantages such as high solar energy to electricity conversion efficiency (the highest recorded is 31.25%), flexible layout, and high modularity. It can be used as a distributed system for independent power supply, particularly suitable for remote mountainous areas and border regions, with a typical power output of 10-50 kW. Hundreds or thousands of systems can also be integrated into large-scale solar thermal power plants, making it considered one of the most promising high-grade solar thermal power generation systems.

[0003] The cavity receiver, connected to the four-cylinder piston of the Stirling engine and providing a heat source, is the core component for achieving light-to-heat conversion. During service, it withstands the complex effects of high-density, non-uniform heat flux, making its operational safety and reliability paramount. Due to structural deformation caused by external loads such as its own weight and wind loads during operation, and the accumulation of transmission errors during the operation of the dual-axis tracking device leading to solar tracking errors in the concentrator, these errors collectively alter the energy flux density distribution absorbed on the internal surface of the cavity receiver. Significant hot spots may form in some locations, and the uneven energy distribution around the cavity receiver generates uneven driving forces on the four-cylinder Stirling engine, easily leading to reduced heat-to-work conversion efficiency and unbalanced vibration problems during Stirling engine operation. Furthermore, the temperature in localized high-energy flux peak areas on the surface of the cavity receiver can be extremely high, potentially causing safety accidents such as burning through the metal tube walls within the receiver. On the other hand, Stirling engines and generator sets are very bulky and are typically bolted to the support truss of dish concentrator systems near their focal points. Real-time adjustment of their position during operation to avoid high-temperature hotspots and uneven circumferential energy distribution is particularly difficult and energy-intensive. Therefore, it is crucial to invent an energy distribution improvement device and method that can adapt to the effects of optical errors during the operation of dish / Stirling solar power systems, effectively enhancing their operational safety and efficiency. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a dish / Stirling solar power generation system with an adjustable secondary concentrator and an attitude adjustment method, which has the advantages of simple structure and excellent improvement effect.

[0005] The technical solution adopted in this invention is: a dish / Stirling solar power generation system with an adjustable secondary concentrator, comprising a dish concentrator that tracks the sun's position and concentrates sunlight through a mirror, a Stirling thermoelectric generator mounted on a base to achieve heat-to-electric energy conversion, and a cavity receiver fixed near the focal point of the dish concentrator and connected to the Stirling thermoelectric generator for heating; the cavity receiver includes an insulation body with a cylindrical inner cavity and a light inlet at the front end, and heat-absorbing coils uniformly arranged along the circumference of the insulation body for absorbing solar energy, the central axis of which is collinear with the focal axis of the dish concentrator; it also includes a secondary concentrator, a light spot measurement device, an image processor, and a controller; the secondary concentrator includes a rotating cylinder with a cylindrical cavity and through holes on both the front and rear ends, a secondary concentrator with axisymmetric geometry and through holes at both the front and rear ends located inside and hinged to the rotating cylinder, and a large gear coaxially fixed to the outer surface of the rotating cylinder. The device includes a small gear meshing with a large gear, an electric motor I driving the small gear to rotate, and a push-pull device driving the secondary condenser mirror to rotate. The rotating cylinder and the base are fitted with a cylindrical pair, and the rotating cylinder is coaxially arranged with the cavity receiver and located on the light inlet side of the insulation body. The front through-hole of the secondary condenser mirror is close to the front end of the rotating cylinder, and its rear through-hole extends into the interior of the insulation body. The inner surface of the secondary condenser mirror is a mirror surface to achieve secondary focusing of sunlight and transmission to the surface of the heat-absorbing coil. The light spot measuring device includes a square planar receiving target that can be flipped to the front end of the rotating cylinder and is parallel to it, a rotating shaft fixed to the planar receiving target, an electric motor III driving the rotating shaft to rotate, and a CCD camera. The CCD camera is fixed on the disc-type condenser and captures the focused light spot image on the planar receiving target. The image is transmitted to the image processor to calculate the energy centroid position of the focused light spot, and then fed back to the controller to control the electric motor I and the push-pull device to achieve the position and orientation adjustment of the secondary condenser mirror.

[0006] In the aforementioned dish / Stirling solar power generation system with an adjustable secondary concentrator, the push-pull device is located inside the rotating cylinder and includes a connecting rod I hinged to the secondary concentrator, a connecting rod II hinged to the rotating cylinder, a rack hinged to the other ends of both connecting rod I and connecting rod II, a gear meshing with the rack, and a motor II that drives the gear to rotate. The housing of the motor II is fixed to the rotating cylinder, and the rack and the rotating cylinder are coaxially slidingly engaged.

[0007] The aforementioned dish / Stirling solar power system with an adjustable secondary concentrator also includes a quartz glass I installed at the through-hole at the rear end of the secondary concentrator, and a quartz glass II installed in the insulation body and located between the quartz glass I and the heat absorption coil for sealing.

[0008] In the aforementioned dish / Stirling solar power generation system with an adjustable secondary concentrator, the light spot measurement device further includes point light sources fixed at the four corners of the planar receiving target and facing the mirror surface of the dish concentrator.

[0009] In the aforementioned dish / Stirling solar power generation system with an adjustable secondary concentrator, the rotation axis of the light spot measuring device is perpendicular to the axis of the rotating cylinder, and the rotation axis is located above the outer circle of the rotating cylinder. When the planar receiving target is in the condition of measuring the focused light spot, the planar receiving target flips to the front end of the rotating cylinder, and the center line of the planar receiving target is collinear with the focal axis of the dish concentrator. When the planar receiving target is not in the condition of measuring the focused light spot, the planar receiving target rotates 270° and returns to a state perpendicular to the front end face of the rotating cylinder.

[0010] The aforementioned dish / Stirling solar power system with an adjustable secondary concentrator also includes several temperature sensors evenly arranged around the circumference of the absorber coil, and the temperature information is transmitted to the controller.

[0011] In the aforementioned dish / Stirling solar power generation system with an adjustable secondary concentrator, the secondary concentrator has a sandwich structure with cooling water circulating inside; the inner surface of the secondary concentrator is a conical mirror or a composite parabolic mirror.

[0012] A method for adjusting the orientation of a secondary concentrator element in a dish / Stirling solar power system includes the following steps:

[0013] 1) Taking the center of the planar receiving target as the origin O of the global coordinate system when it is receiving and focusing the light spot, establish parallel coordinate systems along its two adjacent sides. x and y Axis; Set the actual coordinates of the four point light sources on the planar receiving target; Set the circumferential temperature difference threshold T and the focusing spot measurement time interval t of the cavity receiver;

[0014] 2) The planar receiving target is in the retracted state. The dish concentrator focuses the sunlight to the secondary concentrator and then transmits it to the surface of the heat absorption coil for absorption. The dish / Stirling solar power generation system is in power generation operation mode. Temperature sensors arranged around the heat absorption coil measure the temperature in real time. When the circumferential temperature difference is greater than the threshold T or the time since the last focused spot measurement is greater than t, the process returns to step 3.

[0015] 3) The planar receiving target is rapidly rotated to the working position for receiving the focused light spot. At this time, the CCD camera quickly acquires the image of the focused light spot and transmits it to the image processor. Then, the planar receiving target is quickly rotated to the retracted position. The focused light spot image is converted into a grayscale image, and the center points of the four point light sources are extracted to determine the coordinate system O. -xy The position, then with O -xy Calculate the weighted centroid of the grayscale values ​​in the focused spot image using a coordinate system. x and y Coordinate values, then centroid x and y The coordinate values ​​are fed back to the controller to control motors I and II, in order to align the center of the front aperture of the secondary condenser with the centroid of the focused light spot being measured. x and y The coordinate values ​​are equal; after pose adjustment, proceed to step 2.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0017] This invention provides a dish / Stirling solar power generation system with an adjustable secondary concentrator and a method for adjusting the position of the secondary concentrator. It features a simple structure, convenient long-term monitoring, and excellent improvement in energy distribution of the heat-absorbing coil. By installing a flexibly adjustable secondary concentrator at the front end of the bulky Stirling engine's cavity receiver, and using a rotatable planar receiving target in conjunction with a CCD camera to quickly measure the focused spot image of the dish concentrator during actual operation, the coordinates of its energy centroid are processed, and then the centroid coordinates are fed back to the controller to control the motor to adjust the position of the secondary concentrator, ensuring that the center of the front aperture of the secondary concentrator is aligned with the centroid of the measured focused spot. x and y With equal coordinate values, the energy distribution uniformity on the circumferential surface of the heat-absorbing coil inside the cavity receiver is significantly improved, and the peak energy flux density is effectively reduced, avoiding problems such as high-temperature hot spot erosion. This invention enables low-power, lightweight adjustment of the secondary concentrator, effectively improving the service performance of dish / Stirling solar power systems and achieving safe, reliable, and efficient light-thermal-electric energy conversion. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the dish / Stirling solar power generation system with an adjustable secondary concentrator element according to the present invention.

[0019] Figure 2 This is a partial view of the cavity receiver with an adjustable secondary focusing element in this invention.

[0020] Figure 3 This is a schematic diagram of the planar receiving target in the receiving and focusing light spot working condition in this invention.

[0021] Figure 4 This is a flowchart of the pose adjustment method for the secondary focusing element of the present invention.

[0022] In the diagram: 1-Disc condenser; 2-Stirling thermoelectric generator set; 201-Base; 3-Cavity receiver; 301-Insulation body; 302-Heat absorber coil; 303-Quartz glass II; 4-Spot measuring device; 401-Planar receiving target; 402-Motor III; 403-Rotating shaft; 404-CCD camera; 405-Point light source; 5-Secondary condenser; 501-Rotating cylinder; 502-Secondary condenser lens; 503-Large gear; 504-Small gear; 505-Motor I; 506-Quartz glass I; 507-Push-pull device; 5071-Connecting rod I; 5072-Connecting rod II; 5073-Rack; 5074-Gear; 5075-Motor II; 6-Image processor; 7-Controller. Detailed Implementation

[0023] The invention will now be further described with reference to the accompanying drawings.

[0024] like Figures 1-3As shown, the dish / Stirling solar power generation system with an adjustable secondary concentrator of the present invention includes a dish concentrator 1 that tracks the position of the sun and concentrates sunlight through a mirror, a Stirling thermoelectric generator 2 that is mounted on a base 201 to realize the conversion of heat and electricity, and a cavity receiver 3 that is fixed near the focal point of the dish concentrator 1 and connected to the Stirling thermoelectric generator 2 for heating. The cavity receiver 3 includes a heat-insulating body 301 with a cylindrical inner cavity and a light-entry hole at the front end, and heat-absorbing coils 302 uniformly arranged along the inner circumference of the heat-insulating body 301 for absorbing solar energy. The central axis of the heat-insulating body 301 is collinear with the focal axis of the dish concentrator 1. It also includes a secondary focusing device 5, a spot measuring device 4, an image processor 6, and a controller 7; the secondary focusing device 5 includes a rotating cylinder 501 with a cylindrical cavity and through holes on both the front and rear ends, a secondary focusing mirror 502 with axisymmetric geometry and through holes at both the front and rear ends, located inside and hinged to the rotating cylinder 501, a large gear 503 fixed coaxially to the outer surface of the rotating cylinder 501, a small gear 504 meshing with the large gear 503, and an electric motor Ⅰ driving the small gear 504 to rotate. 505. A push-pull device 507 for driving the secondary condenser 502 to rotate; the rotating cylinder 502 and the base 201 are fitted with a cylindrical pair, and the rotating cylinder 502 and the cavity receiver 3 are arranged coaxially and located on the light inlet side of the heat insulation body 301; the front end through hole of the secondary condenser 502 is close to the front end of the rotating cylinder 501, and its rear end through hole extends into the interior of the heat insulation body 301. The inner surface of the secondary condenser 502 is a mirror surface to realize the secondary focusing of sunlight and then transmit it to the surface of the heat absorption coil 302; the light spot measuring device 4 includes a square planar receiving target 401 that can be flipped to the front end of the rotating cylinder 501 and is parallel to it, a rotating shaft 403 fixed to the planar receiving target 401, and a motor III that drives the rotating shaft 403 to rotate. 402 and CCD camera 404; the CCD camera 404 is fixed on the disc-type condenser 1 and captures the image of the focused spot on the planar receiving target 401, and then transmits it to the image processor 6 to calculate the position of the energy centroid of the focused spot, and then feeds it back to the controller 7 to control the motor I 505 and the push-pull device 507 to realize the pose adjustment of the secondary condenser 502.

[0025] like Figures 1-2 As shown, the push-pull device 507 is located inside the rotating cylinder 501. It includes a connecting rod I 5071 hinged to the secondary condenser lens 502, a connecting rod II 5072 hinged to the rotating cylinder 501, a rack 5073 hinged to the other ends of the connecting rods I 5071 and II 5072, a gear 5074 meshing with the rack 5073, and a motor II 5075 driving the gear 5074 to rotate. The housing of the motor II 5075 is fixed to the rotating cylinder 501, and the rack 5073 is coaxially slidingly fitted with the rotating cylinder 501.

[0026] like Figures 1-2 As shown, the present invention also includes a quartz glass I 506 installed at the through hole at the rear end of the secondary condenser 502, and a quartz glass II 303 installed inside the insulation body 301 and located between the quartz glass I 506 and the heat absorption coil 302 for sealing purposes.

[0027] like Figure 3 As shown, the light spot measuring device 4 also includes point light sources 405 fixed at the four corners of the planar receiving target 401 and facing the mirror surface of the dish-type focusing device 1.

[0028] like Figures 1-3 As shown, the rotating shaft 403 of the light spot measuring device 4 is perpendicular to the axis of the rotating cylinder 501, and the rotating shaft 403 is located above the outer circle of the rotating cylinder 501. When the planar receiving target 401 is in the condition of measuring the focused light spot, the planar receiving target 401 flips to the front end of the rotating cylinder 501, and the center line of the planar receiving target 401 is collinear with the focal axis of the dish-type focusing device 1. When the planar receiving target 401 is not in the condition of measuring the focused light spot, the planar receiving target 401 rotates 270° and retracts to a state perpendicular to the front end face of the rotating cylinder 501. The present invention also includes a plurality of temperature sensors uniformly arranged circumferentially along the heat absorption coil 302, and the temperature information is transmitted to the controller 7.

[0029] The secondary condenser 502 has a sandwich structure with cooling water circulating inside the sandwich; the inner surface of the secondary condenser 502 is a conical mirror or a composite parabolic mirror.

[0030] A method for adjusting the orientation of a secondary concentrator element in a dish / Stirling solar power system includes the following steps:

[0031] 1) Taking the center of the planar receiving target 401 as the origin O of the global coordinate system when it is receiving and focusing the light spot, establish parallel lines along its two adjacent sides. x and y Axis; Set the actual coordinate values ​​of the four point light sources 405 on the planar receiving target 401; Set the circumferential temperature difference threshold T and the focusing spot measurement time interval t of the cavity receiver 3;

[0032] 2) When the planar receiving target 401 is in the retracted state, the dish concentrator 1 focuses the sunlight to the secondary concentrator 502 and then transmits it to the surface of the heat absorption coil 302 where it is absorbed. The dish / Stirling solar power generation system is in power generation operation mode. The temperature sensor arranged around the heat absorption coil 302 measures the temperature in real time. When the circumferential temperature difference is greater than the threshold T or the time since the last focused spot measurement is greater than t, the process returns to step 3.

[0033] 3) The planar receiving target 401 is quickly rotated to the working position for receiving the focused light spot. At this time, the CCD camera 404 quickly acquires the focused light spot image and transmits it to the image processor 6. Then, the planar receiving target 401 is quickly rotated to the retracted position. The focused light spot image is converted into a grayscale image, and the center points of the four point light sources 405 are extracted to determine the coordinate system O. -xy The position, then with O -xy Calculate the weighted centroid of the grayscale values ​​in the focused spot image using a coordinate system. x and y Coordinate values, then centroid x and y The coordinate values ​​are fed back to controller 7 to control motors I 505 and II 5075, in order to align the center of the front aperture of the secondary condenser lens 502 with the centroid of the measured focused spot. x and y The coordinate values ​​are equal; after pose adjustment, proceed to step 2.

Claims

1. A dish / Stirling solar power generation system with an adjustable secondary concentrator, comprising a dish concentrator that tracks the sun's position and concentrates sunlight through a mirror, a Stirling thermoelectric generator mounted on a base to achieve thermo-electric energy conversion, and a cavity receiver fixed near the focal point of the dish concentrator and connected to the Stirling thermoelectric generator for heating; the cavity receiver includes an insulation body with a cylindrical inner cavity and a light inlet at the front end, and heat-absorbing coils uniformly arranged along the circumference of the insulation body for absorbing solar energy, wherein the central axis of the insulation body is collinear with the focal axis of the dish concentrator; characterized in that: It also includes a secondary focusing device, a light spot measuring device, an image processor, and a controller; the secondary focusing device includes a rotating cylinder with a cylindrical cavity and through holes on both its front and rear ends, a secondary focusing mirror with axisymmetric geometry and through holes at both ends, located inside and hinged to the rotating cylinder, a large gear fixed coaxially to the outer surface of the rotating cylinder, a small gear meshing with the large gear, a motor I driving the small gear to rotate, and a push-pull device driving the secondary focusing mirror to rotate; the rotating cylinder and the base are fitted with a cylindrical pair, and the rotating cylinder is coaxially arranged with the cavity receiver and located on the light inlet side of the insulation body; the through hole at the front end of the secondary focusing mirror is close to the rotating cylinder. The front end has a through hole extending into the interior of the insulation body. The inner surface of the secondary condenser is a mirror to achieve secondary focusing of sunlight and transmission to the surface of the heat-absorbing coil. The light spot measuring device includes a square planar receiving target that can be flipped to the front end of the rotating cylinder and is parallel to it, a rotating shaft fixed to the planar receiving target, a motor III that drives the rotating shaft to rotate, and a CCD camera. The CCD camera is fixed on the disc-type condenser and captures the focused light spot image on the planar receiving target. The image is transmitted to the image processor to calculate the energy centroid position of the focused light spot, and then fed back to the controller to control the motor I and the push-pull device to achieve the position and orientation adjustment of the secondary condenser.

2. The dish / Stirling solar power generation system with an adjustable secondary concentrator element according to claim 1, characterized in that: The push-pull device is located inside the rotating cylinder and includes a connecting rod I hinged to the secondary condenser lens, a connecting rod II hinged to the rotating cylinder, a rack hinged to the other ends of connecting rod I and connecting rod II, a gear meshing with the rack, and a motor II that drives the gear to rotate. The housing of the motor II is fixed to the rotating cylinder, and the rack and the rotating cylinder are coaxially slidingly fitted.

3. The dish / Stirling solar power generation system with an adjustable secondary concentrator element according to claim 1, characterized in that: It also includes quartz glass I installed at the through hole at the rear end of the secondary condenser lens, and quartz glass II installed in the insulation body and located between quartz glass I and the heat absorption coil for sealing.

4. The dish / Stirling solar power generation system with an adjustable secondary concentrator element according to claim 1, characterized in that: The light spot measuring device also includes point light sources fixed at the four corners of the planar receiving target and facing the mirror of the dish-type focusing device.

5. The dish / Stirling solar power generation system with an adjustable secondary concentrator element according to claim 1, characterized in that: The rotating shaft of the light spot measuring device is perpendicular to the axis of the rotating cylinder, and the rotating shaft is located above the outer circle of the rotating cylinder. When the planar receiving target is in the condition of measuring the focused light spot, the planar receiving target flips to the front end of the rotating cylinder, and the center line of the planar receiving target is collinear with the focal axis of the dish-type focusing device. When the planar receiving target is not in the condition of measuring the focused light spot, the planar receiving target rotates 270° and returns to a state perpendicular to the front end face of the rotating cylinder.

6. The dish / Stirling solar power generation system with an adjustable secondary concentrator element according to claim 1, characterized in that: It also includes several temperature sensors evenly arranged around the circumference of the heat absorption coil, and the measured temperature information is transmitted to the controller.

7. The dish / Stirling solar power generation system with an adjustable secondary concentrator element according to claim 1, characterized in that: The secondary condenser has a sandwich structure with cooling water circulating inside the sandwich; the inner surface of the secondary condenser is a conical mirror or a composite parabolic mirror.

8. A method for adjusting the orientation of the secondary concentrator in a dish / Stirling solar power system with an adjustable secondary concentrator element as described in claim 1, characterized in that, Includes the following steps: 1) Taking the center of the planar receiving target as the origin O of the global coordinate system when it is receiving and focusing the light spot, establish parallel coordinate systems along its two adjacent sides. x and y Axis; Set the actual coordinates of the four point light sources on the planar receiving target; Set the circumferential temperature difference threshold T and the focusing spot measurement time interval t of the cavity receiver; 2) The planar receiving target is in the retracted state. The dish concentrator focuses the sunlight to the secondary concentrator and then transmits it to the surface of the heat-absorbing coil for absorption. The dish / Stirling solar power generation system is in power generation operation mode. The temperature sensors arranged around the heat-absorbing coil measure the temperature in real time. When the circumferential temperature difference is greater than the threshold T or the time since the last focused spot measurement is greater than t, the process returns to step 3. 3) The planar receiving target is rapidly rotated to the working position for receiving the focused light spot. At this time, the CCD camera quickly acquires the image of the focused light spot and transmits it to the image processor. Then, the planar receiving target is quickly rotated to the retracted position. The focused light spot image is converted into a grayscale image, and the center points of the four point light sources are extracted to determine the coordinate system O. -xy The position, then with O -xy Calculate the weighted centroid of the grayscale values ​​in the focused spot image using a coordinate system. x and y Coordinate values, then centroid x and y The coordinate values ​​are fed back to the controller to control motors I and II, so as to align the center of the front aperture of the secondary condenser with the measured centroid of the focused light spot. x and y The coordinate values ​​are equal; after pose adjustment, proceed to step 2.

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