Combined type Fresnel condensation system

Abstract

The invention discloses a combined type Fresnel condensation system which comprises a Fresnel lens assembly located on the inner ring of an optical focusing unit, a Fresnel reflector assembly located on the outer ring of the optical focusing unit, an integrated supporting structure, a solar sensor assembly, a pitch angle tracking control execution mechanism assembly, an azimuth angle tracking control execution mechanism assembly and a support assembly. According to the invention, challenges confronted by respective independent operation are effectively overcome, and compact, high-flux, high-optical-efficiency and high-radiation-resource-utilization-rate solar efficient condensation and application are realized through mutual complementation and synergism.

Description

Technical Field

[0001] The invention relates to the technical field of solar thermal utilization, and in particular to a composite Fresnel concentrating system. Background Art

[0002] As a clean and renewable energy source, the efficient use of solar energy has always been a hot topic of research. Photothermal power generation technology uses solar energy to heat the working fluid to a high temperature to achieve efficient thermal conversion and power generation. Solar thermal chemical utilization technology can achieve the reduction and conversion of inert molecules (such as carbon dioxide and water) through high-temperature thermochemical reactions to synthesize chemicals or hydrocarbon fuels with high added value. Therefore, solar thermal utilization has huge development potential and good application prospects. However, the energy density of unconcentrated sunlight is low, and it is difficult to reach the high temperature required for thermal utilization of solar collectors or reactors. To achieve high energy density and high temperature photothermal chemical conversion, it is often necessary to use point focusing methods such as tower, butterfly, Fresnel lens and Fresnel annular reflection. However, the focal spot of tower and butterfly focusing systems is usually at a high altitude, and it is necessary to build a high tower to place solar collectors or reactors, which not only greatly increases the construction cost and material transportation cost, but also leads to serious heat loss. In contrast, the Fresnel transmission and Fresnel reflection focusing methods keep the concentrated sunlight transmitted from top to bottom, and the collector or reactor is located at the bottom of the system, thus the collector or reactor can be placed at the bottom of the system, avoiding the need to build a high tower and the high maintenance cost of the vertical transportation system of height-difference materials.

[0003] Limitations of existing Fresnel transmission focusing: The manufacturing of Fresnel lenses relies on high-precision optical structures, which are limited by factors such as machine tool size, processing accuracy and mold cost. Especially in the production and processing of large-diameter Fresnel lenses, the cost increases significantly. In addition, due to the limitations of the optical transmission principle of Fresnel lenses and the actual processing accuracy, the light deflection angle and focusing range are limited. According to Snell's law, Figure 2 As shown, the incident angle α1 and the exit angle α2 of the light transmission at the heterogeneous interface and the refractive index n1 and n2 of the medium satisfy the relationship: n1 sinα1=n2 sinα2. The materials currently used in Fresnel lenses include but are not limited to quartz glass, transparent silicone, acrylic glass, etc. The refractive index n2 is usually between 1.4 and 1.55. Here, n2 is set to 1.5, the refractive index of air n1 is 1, and the exit angle α2=90° is taken as the critical exit angle. The critical incident angle α is calculated. 1,max is 41.8°, the theoretical limit deflection angle of light is β max Considering the machining accuracy and error of the Fresnel lens in actual application, for a Fresnel lens with a focal length of 1m, sunlight beyond the radius of the lens center to 1m cannot be effectively concentrated and utilized. Figure 3 shown.

[0004] Limitations of existing Fresnel reflection focusing: Fresnel reflection focusing achieves the deflection and focusing of light through the mirror reflection of the light ring reflector surface. The incident angle α1 is equal to the exit angle α2, and the reflector width w = r0 / sin(β / 2), such as Figure 4 As shown in the formula, r0 is the vertical projection width of the annular reflector, β is the angle at which the outgoing light is deflected relative to the incident light, and the ratio of the reflector width w to its vertical projection width r0 can be obtained, and the curve of the ratio of the reflector area to the actual sunlight receiving area changes with the light deflection angle β is as follows: Figure 4 As shown in the figure, it can be seen that when the light deflection angle continues to decrease, the reflector area utilization rate (the ratio of the lighting projection area to the actual reflector area) decreases (such as Figure 7 As shown) and the lens height is greatly increased (as shown Figure 5 As shown in the figure, the processing, installation and commissioning become extremely difficult. Therefore, in practical applications, the inner circle area is usually left empty, resulting in the inability to effectively concentrate the sunlight in this area. This design causes a significant decrease in the utilization rate of the radiation energy flow, the focusing efficiency and the radiation flux of the Fresnel reflective concentrator system, forming a technical bottleneck. These challenges restrict the widespread application of Fresnel reflective concentrators in the field of high-temperature photothermal chemical conversion.

[0005] In summary, the higher the manufacturing cost of a large-aperture Fresnel lens, the greater the optical loss at the edge of the lens, and even the phenomenon of total reflection within the lens, which limits the large-scale application of large-area Fresnel lenses. The Fresnel reflection focusing system has a relatively low unit mirror cost, but the central area is often left empty due to the low mirror utilization rate, resulting in this part of the sunlight cannot be effectively concentrated and utilized, limiting the space occupied by the concentrator and the utilization rate of the radiation flux. The two focusing methods have their own inherent shortcomings in large-scale utilization, and there is an urgent need to invent innovative solutions to the key bottleneck problems faced by the two technologies. Summary of the invention

[0006] Purpose of the invention: The present invention provides a composite Fresnel focusing system, which organically combines the advantages of both transmission and reflection focusing methods, effectively overcomes the challenges faced when each operates independently, and achieves compact, high-throughput, high-optical-efficiency and high-radiation-resource-utilization solar energy efficient focusing and application through mutual complementation and efficiency enhancement.

[0007] Technical solution: A composite Fresnel focusing system described in the present invention comprises: a Fresnel lens assembly located in the inner circle of an optical focusing unit, a Fresnel reflector assembly located in the outer circle, an integrated support structure, a sun sensor assembly, a pitch angle tracking control actuator assembly, an azimuth angle tracking control actuator assembly and a support assembly; the Fresnel lens assembly is composed of a plurality of fan-shaped lenses, which have the same center, the same focus and are located in the same plane, and are assembled to form a whole Fresnel lens module; the Fresnel reflector assembly is composed of a plurality of circles of reflectors, each circle of reflectors is composed of arc reflectors arranged in a circular array, and is fine-tuned according to their respective radii, relative positions and light shielding relationships to determine their inclination angles and installation positions; the Fresnel lens assembly and the Fresnel reflector assembly are both fixed in the integrated support structure to ensure that all optical components can converge incident light to the same focus; the integrated support structure controls the movement of its pitch angle and azimuth angle through the pitch angle tracking control actuator assembly and the azimuth angle tracking control actuator assembly, and is fixed to the support assembly through a rotating shaft.

[0008] Furthermore, the Fresnel lens assembly is composed of multiple lenses combined into a whole circular lens, which is located in the inner circle, and the light deflection angle range is 0 to β0.

[0009] Furthermore, the Fresnel lens assembly material is made of UV-resistant acrylic material or quartz glass material, and the average solar radiation transmittance is between 88% and 94%.

[0010] Furthermore, the Fresnel reflector assembly is composed of a plurality of reflectors to form a plurality of ring reflectors, which are located at the outer ring of the lens assembly, and the light deflection angle range is β0 to 90°.

[0011] Furthermore, the light deflection angle refers to the deflection angle of the outgoing light relative to the incident light after the incident sunlight is deflected by the optical device. The critical light deflection angle β0 is usually in the range of 20 to 45°.

[0012] Furthermore, the Fresnel reflector assembly material is made of mirror aluminum material, and the average solar radiation reflectivity is between 90% and 96%.

[0013] Furthermore, a solar sensor component is used to monitor the trajectory of the sun's movement, and an integrated pitch angle tracking control actuator component and an azimuth angle tracking control actuator component are used to ensure that the sun's trajectory can be accurately tracked, and the focusing attitude is automatically controlled according to a preset program to ensure that the focusing is facing the sun in the sky at all times.

[0014] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: it organically combines the advantages of Fresnel lens focusing and Fresnel reflection focusing, makes up for the disadvantages of the two within different light deflection angle ranges, effectively improves the effective focusing area and focusing efficiency of the Fresnel focusing system, and also maximizes the collection and utilization of solar energy within the area occupied by the mirror field. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a schematic diagram of the structure of the focusing system of the present invention.

[0016] Figure 2 Schematic diagram of how a Fresnel lens refracts and focuses light.

[0017] Figure 3 The ray tracing calculation results of the interaction between the incident light and the Fresnel lens at different deflection angles.

[0018] Figure 4 Schematic diagram of Fresnel reflector reflecting and converging light.

[0019] Figure 5 Schematic diagram of the significant increase in the height of the inner ring lens of the Fresnel reflector.

[0020] Figure 6 This is a schematic diagram of the composite Fresnel focusing principle of the present invention.

[0021] Figure 7 This is the result of the performance of the Fresnel lens and reflector changing with the angle of light deflection.

[0022] Figure 8 It is the distribution result of radiation energy flow on different focal planes of the composite Fresnel focusing system of the present invention. DETAILED DESCRIPTION

[0023] like Figure 1As shown, a composite Fresnel focusing system comprises: a Fresnel lens assembly 1 located in the inner circle of an optical focusing unit, a Fresnel reflector assembly 2 located in the outer circle, an integrated support structure 3, a sun sensor assembly 4, a pitch angle tracking control actuator assembly 5, an azimuth angle tracking control actuator assembly 6 and a support assembly 7; the Fresnel lens assembly 1 is composed of a plurality of fan-shaped lenses, which have the same center, the same focus and are located in the same plane, and are assembled to form a whole Fresnel lens module; the Fresnel reflector assembly 2 is composed of a plurality of circle reflector assemblies Each circle of reflectors is composed of arc reflectors arranged in a circular array, and their inclination angles and installation positions are determined by fine-tuning according to their respective radii, relative positions and light shielding relationships; the Fresnel lens assembly 1 and the Fresnel reflector assembly 2 are both fixed in an integrated support structure 3 to ensure that all optical components can converge the incident light to the same focus; the integrated support structure controls the movement of its pitch angle and azimuth angle through a pitch angle tracking control actuator assembly 5 and an azimuth angle tracking control actuator assembly 6, and is fixed to a support assembly 7 through a rotating shaft.

[0024] The Fresnel lens assembly 1 is composed of two circles of annular Fresnel lenses, each circle is composed of 18 fan-shaped Fresnel lenses, and the lens shape structure of each circle is exactly the same. The lenses of different circles are processed by different molds. The design must ensure that the lenses of different circles have the same center and focus, and are evenly distributed on the same plane. The shape and depth of the tooth grooves are required to meet the design specifications to minimize light scattering and loss. As a preferred embodiment, the lens material is made of anti-ultraviolet aging acrylic material or quartz glass material, and the average solar radiation transmittance is between 88% and 94%. Due to the current limitations of machine tool scale and mold size, it is difficult to directly process a whole large-aperture Fresnel lens. Here, the measures of block processing and combined assembly are adopted to divide the entire Fresnel lens into multiple fan-shaped lenses for separate processing, and then assemble and assemble them into a whole large lens.

[0025] The Fresnel reflector assembly 2 includes 15 rings of annular reflectors, each of which is composed of 36 reflector circular arrays of the same size and curvature. The reflector units on different numbers of rings are designed with different inclination angles and sizes according to their radius and light blocking relationship. It is made of high-reflection mirror material, and each reflector is equipped with an adjustable structure at the rear to achieve precise angle adjustment. As a preference, the high-reflection mirror surface rate material is mirror aluminum material, and the average solar radiation reflectivity is between 90% and 96%. The Fresnel reflectors are laid outward in circles around the periphery of the lens, and each circle is composed of a plurality of arc-shaped reflector circular arrays. Since the light deflection angle of each circle is different, the corresponding reflector curvature, size, and installation angle are different. In order to avoid the reflector blocking the light transmission path, the installation height of the outer ring reflector is usually lower than that of the inner ring reflector, and the reflector group as a whole presents an "umbrella"-shaped extended arrangement with a high inner ring and a low outer ring.

[0026] The integrated support structure component 3 carries the lens and reflector modules. The structure has sufficient strength and stability, while allowing fine adjustment of the lens and reflector. It is made of lightweight and high-strength materials, such as aluminum alloy or composite materials, to reduce the overall weight and improve corrosion resistance. For ease of installation and maintenance, all connecting parts are standardized for quick assembly and disassembly. The integrated design and optimization of the Fresnel lens assembly, Fresnel reflector assembly and support structure, on the basis of ensuring that the support structure effectively fixes and supports the Fresnel lens assembly and Fresnel reflector assembly, simplifies the structural arrangement, optimizes the force path, reduces the weight of the equipment, reduces the cost of raw materials and processing, and minimizes the light blocking area to improve the system's focusing efficiency.

[0027] The solar sensor component is used to monitor the trajectory of the sun's movement, and the pitch angle tracking control actuator component and the azimuth angle tracking control actuator component are integrated to ensure that the sun's trajectory can be accurately tracked. The focusing posture control is automatically performed according to the preset program to ensure that the focusing is always facing the sun's position in the sky. The solar sensor component is used to sense the sun's position, and the pitch angle and azimuth angle dual-axis drive control mechanism is used to control the normal direction of the composite Fresnel focusing component in real time. The dual-axis tracking principle is used to achieve high-precision tracking of the sun's movement trajectory. The center of gravity position layout of the composite Fresnel focusing system is optimized to minimize the power consumption of the mechanism movement.

[0028] The system is debugged as a whole. First, high-precision optical measurement equipment is used to test and characterize the lens and reflector to ensure that the reflectivity or transmittance meets the optical design parameters. Then, the shape, size and intensity distribution of the light spot are accurately measured using a camera and a two-dimensional translation scanning energy flux meter under natural lighting conditions to verify the focusing effect of the light. By comparing and analyzing these data with the theoretical model, it can be determined whether the light beam is effectively converged to the design focus. For areas where the focusing efficiency does not meet the standard or the beam uniformity has deviations, a high-precision adjustment device is used to fine-tune the position and posture of the relevant lens or reflector. The fine-tuning process is driven by a precision adjustment screw to ensure the stability and accuracy of the adjustment process. In addition, the debugged system will be subjected to dynamic optical testing to simulate the incidence of sunlight at different angles to verify whether the focusing effect of the system is stable under various working conditions. Finally, through multiple rounds of testing and debugging, it is ensured that the overall focusing performance of the system meets the design goals and achieves efficient and uniform light energy convergence.

[0029] The composite Fresnel focusing system of the example adopts the Fresnel transmission focusing mode when the light deflection angle is within the range of 0 to 20.5°, and adopts the Fresnel reflection focusing mode when the light deflection angle is within the range of 20.5 to 46.5°. Figure 6As shown, the Monte Carlo ray tracing simulation calculation obtains that the overall theoretical focusing efficiency (total energy flow of the spot / total energy flow of lighting) exceeds 90%, the layout is compact and reasonable, and the energy flow distribution of the spot is as follows Figure 8 As shown, the solar radiation utilization rate per unit area (total energy flux of the light spot / total solar energy flux per unit area) also exceeds 70%, taking into account both high optical efficiency and high radiation resource utilization.

Claims

1. A composite Fresnel focusing system, characterized in that: include: A Fresnel lens assembly (1) located in the inner circle of the optical focusing unit, a Fresnel reflector assembly (2) located in the outer circle, an integrated support structure (3), a sun sensor assembly (4), a pitch angle tracking control actuator assembly (5), an azimuth angle tracking control actuator assembly (6) and a support assembly (7); the Fresnel lens assembly (1) is composed of a plurality of fan-shaped lenses, which have the same center, the same focus and are located in the same plane, and are assembled to form a whole Fresnel lens module; the Fresnel reflector assembly (2) is composed of a plurality of circles of reflectors, each circle of reflectors is composed of The arc-shaped reflectors are arranged in a circular array and are fine-tuned according to their respective radii, relative positions and light shielding relationships to determine their inclination angles and installation positions; the Fresnel lens assembly (1) and the Fresnel reflector assembly (2) are both fixed in an integrated support structure (3) to ensure that all optical components can converge incident light to the same focal point; the integrated support structure (3) controls the movement of its pitch angle and azimuth angle through a pitch angle tracking control actuator assembly (5) and an azimuth angle tracking control actuator assembly (6), and is fixed to a support assembly (7) through a rotating shaft.

2. The composite Fresnel focusing system according to claim 1, characterized in that: The Fresnel lens assembly (1) is composed of a plurality of lenses combined into a whole circular lens, which is located in the inner circle and has a light deflection angle range of 0 to β0.

3. The composite Fresnel focusing system according to claim 1, characterized in that: The material of the Fresnel lens assembly (1) is an acrylic material or a quartz glass material that is resistant to ultraviolet aging.

4. The composite Fresnel focusing system according to claim 1, characterized in that: The average solar radiation transmittance of the Fresnel lens assembly (1) is between 88% and 94%.

5. The composite Fresnel focusing system according to claim 1, characterized in that: The Fresnel reflector assembly (2) is composed of a plurality of reflectors to form a plurality of ring reflectors, which are located at the outer ring of the lens assembly, and the light deflection angle range is β0-90°.

6. The composite Fresnel focusing system according to claim 2 or 5, characterized in that: The light deflection angle refers to the deflection angle of the outgoing light relative to the incident light after the incident sunlight is deflected by the optical device. The critical light deflection angle β0 is in the range of 20 to 45°.

7. The composite Fresnel focusing system according to claim 1, characterized in that: The material of the Fresnel reflector assembly (2) is mirror aluminum material.

8. The composite Fresnel focusing system according to claim 1, characterized in that: The average solar radiation reflectivity of the Fresnel reflector assembly (2) is between 90% and 96%.

9. The composite Fresnel focusing system according to claim 1, characterized in that: A solar sensor component (4) is used to monitor the trajectory of the sun's movement, and a pitch angle tracking control actuator component (5) and an azimuth angle tracking control actuator component (6) are integrated to ensure that the sun's trajectory can be accurately tracked, and the focusing posture control is automatically performed according to a preset program to ensure that the focusing is always facing the sun's position in the sky.

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