CN102721194B - Large-capacity high-concentrating ratio composite Fresnel line concentration reflection device - Google Patents

Abstract

The invention relates to a solar heat collector with focusing elements, in particular to a large-capacity and high-concentration-ratio composite Fresnel line light-concentrating reflection device. Composed of main reflectors, the center of each Fresnel reflector is equipped with a steering device, and the plurality of Fresnel reflectors are located above the heat collecting tube, in a circular arc with the heat collecting tube as the center. , also includes a secondary reflection device, which is installed under the heat collecting tube, and the arc-shaped inner concave surface (or concentrating surface) faces the direction of the heat collecting tube. The present invention has the advantages of: it can make the Fresnel line concentrating and reflecting device of the present invention obtain a greater ground utilization rate, fully consider the incidence of sunlight, greatly reduce the loss of sunlight, and improve the heat collection effect of the heat collecting tube , At the same time, it achieves a good focusing effect and a uniform heating effect on the heat collecting tube, which reflects its large-capacity concentrating effect.

Description

High-capacity and high-concentration-ratio composite Fresnel line light-concentrating reflector

technical field

The invention relates to a solar heat collector with focusing elements, in particular to a large-capacity and high-concentration-ratio composite Fresnel line light-concentrating reflector.

Background technique

The Fresnel lens has the function of concentrating light. In the application of large-scale concentrating devices for solar thermal power generation, reflective Fresnel equipment is mainly used. There are many types of Fresnel reflectors in the prior art, such as the widely used compact line-focus Fresnel reflector (Compact Linear Fresnel Reflector, referred to as CLFR), which consists of a plurality of compactly arranged Fresnel reflectors distributed below Mirror and the solar collector tube above, refer to the patent ZL200880112788.8; there is also a parabolic trough concentrating device, which is also a commonly used solar thermal power concentrating device, the reflector used is parabolic, and the concave surface faces the direction of the sun. A solar collector tube is set at the gathering position above the concave surface; there is also a tower-type concentrating device, which includes a tower-type solar collector device located at the center point and a multi-layer annular parabolic dish Fresnel arranged outward with the center as the center. In addition, there is a second-reflection Fresnel line concentrating reflector, which is based on a structure similar to CLFR, and a secondary reflector is set on the upper part of the heat collection tube, referring to Italian patent application number RM2010A000437 , used to reflect sunlight to the top of the heat collector tube to balance the heat absorption of the heat collector tube, and also used to reflect the loss of sunlight caused by focus error, which is mainly because the bottom reflector is focused at different angles due to different incident angles Distance is not the same.

Yet the existence of above-mentioned concentrating device has many weak points: the capacity of tower type concentrating device and parabolic dish type concentrating device is little, and the capacity of parabolic trough type concentrating device is higher than tower type concentrating device and parabolic dish type concentrating device. The large one is the commonly used one at present, but it usually does not exceed 100MW, and the capacity of CLFR can be made larger and the cost is lower, but the CLFR with large capacity has the following problems:

First, as shown in Figure 1, in the case of vertical irradiation of sunlight Y, in order to prevent the reflected light from being hindered, there needs to be a certain interval S between adjacent reflective mirrors 1, so as to prevent the reflected light from being close to the heat collecting tube 2 The reflector is blocked, and the distance between the reflector and the farther away from the heat collecting tube is greater, which causes sunlight leakage and affects the utilization rate of the ground. If the sunlight obliquely shines on the reflecting mirror from the far end of the heat collecting tube (that is, away from the heat collecting tube), the interval between the reflecting mirrors needs to be further increased, which will cause greater sunlight leakage. In the figure, β is the angle between the vertical line between the heat collecting tube and the main reflector and the boundary a where the reflected light of the main reflector is not blocked, and x is the length of the heat collecting tube extending to both sides perpendicular to the point of the main reflector, when When the mirror width is small enough (that is, tends to 0 in theory), it can be calculated that the effective width of the reflector under the above conditions is d* within the x width shown in Figure 1 under the condition that the reflection is not blocked ln(x/d+ , when x is equal to the height d of the heat collecting tube, the effective width of the reflector is about 0.88 times of d; when x is 2 times of d, the effective width of the reflector is about 1.444 times of d; when x is 3 times of d The effective width of the reflector is about 1.818 times of d when magnification. The wider the width of the visible mirror, the less effective it is. The width of the mirror in practical application will not → 0. It can be proved that the above formula is the maximum effective width that can be obtained. The wider the width of a single mirror, the smaller the effective width within a certain x.

Secondly, the radian of the reflector of CLFR is not adjustable at present. 1. The reflector in the middle part is relatively close to the heat collecting tube, while the reflectors on both sides are far away from the heat collecting tube. If all the reflectors have the same radian, it is bound to be There will be some reflectors with poor focusing effect; 2. Although the reflector can rotate with the change of sunlight angle, the distance between the center of the reflector and the center of the heat collector tube is constant, but the focal length of the reflector varies with the incident angle of sunlight. The position will change, as shown in Figure 2 and Figure 3, when the sunlight and the reflector form an angle of 30° (see Figure 3), the focus distance (the distance from the center of the reflector to the focus center) is only when the sunlight is perpendicular to the reflector half of the time (see Figure 2).

In addition, the heat collecting tube of CLFR is only heated on one (lower) side, and the heating is uneven, which affects the temperature and heat absorption of the heat collecting tube.

The double-reflected Fresnel line concentrating reflector can reduce the loss of sunlight, but only at the collector, the reflector has the same problems as CLFR, resulting in a limited degree of improvement, and the improvement effect is uncontrollable, that is, different The incident angle of sunlight is different. In fact, if the concentration is accurate, the secondary reflection device is not needed, but it is difficult to achieve a horizontally arranged reflective lens, unless the curvature of the reflective lens changes when the reflection angle changes. The upper part of the reflector also blocks sunlight.

Contents of the invention

The purpose of the present invention is to overcome the deficiencies of the prior art, and propose a large capacity, high ground utilization rate, less sunlight loss, good focusing effect and heat collection effect, large capacity, high light concentration ratio composite Fresnel line light reflection device.

The present invention is achieved through the following approaches:

The large-capacity and high-concentration-ratio composite Fresnel line light-concentrating reflector includes a main reflector and a heat collector. The center of the Fresnel reflector is provided with a steering device, and the plurality of Fresnel reflectors are located above the heat collecting tube, and are distributed in a circular arc with the heat collecting tube as the center. At the same time, each Fresnel reflector The concave arc surface of the mirror faces the direction of sunlight incidence, when the direction of sunlight is parallel to the center point of the reflector of the main reflector and the center line of the heat collecting tube, the reflector is flipped 180°; there is also a The secondary reflection device is installed under the heat collecting tube, and the arc-shaped inner concave surface faces the direction of the heat collecting tube.

The turning device can make the Fresnel reflector turn over according to the incident angle of sunlight. The micro-arc Fresnel reflector can make a single reflector with a larger width focus on a heat collector with a smaller diameter, so as to obtain a higher utilization rate of sunlight. In order to achieve a higher ground utilization rate, it is necessary to analyze the influence of the sun's light change process on the concentrating effect: for the case where the sunlight is parallel to the direction from the center of the reflector to the heat collector tube, it is difficult for the reflector to reflect sunlight to the heat collector tube. The use of sunlight requires the help of secondary reflectors, and the lenses with a certain angle between the surrounding sunlight and the direction from the reflector to the heat collecting tube can be focused through reflection, but some sunlight may leak.

The Fresnel reflector in the main reflector adopts a micro-arc structure. This micro-arc is parabolic, and the focus is at the heat collecting tube. Since the focus is far away from the arc, the arc will not be very large. The micro-arc reflector The design is reasonable in terms of technology and economy. The width of the reflector is much larger than the outer diameter of the heat collecting tube. The micro-arc focusing makes it possible to reasonably arrange the number of reflectors in a large range (in suitable conditions or made If it is convenient, reflective lenses in the shape of flat plate and circular shape can also be used), so as to improve the light concentration ratio. When the direction of sunlight is parallel to the central line between the reflector of the main reflector and the heat collecting tube, the reflector needs to be turned about 180° in order to change the reflection direction.

The purpose of the sub-reflector is twofold: the first is to improve the utilization of light energy. Near the part where the direction of sunlight is parallel to the center line between the reflector of the main reflector and the center of the heat collecting tube, the lens of the main reflector is limited by its position. , it is difficult to reflect light, let the light projected to the sub-reflector at this time, so that this part of the light can be used; secondly, the light from the sub-reflector is projected to the part of the heat collecting tube that the main reflector cannot reach, so that the heating of the heat collecting tube is more uniform , improving the working condition and heat transfer effect of the heat collecting tube.

This adopts the technical scheme of distributing the main reflection device above the heat collection tube in an arc shape with the heat collection tube as the center of the circle, and setting the secondary reflection device under the heat collection tube, which can make the Fresnel line light concentrating reflection device of the present invention obtain The high ground utilization rate fully considers the incidence of sunlight, greatly reduces the loss of sunlight, improves the heat collection effect of the heat collection tube, and at the same time achieves a good focusing effect and uniform heating of the heat collection tube, which meets the needs of large The demand for high concentration ratio of capacity.

The present invention can further specifically be:

The secondary reflector is a parabolic condensing mirror reflector, and the reflector is provided with a driving steering device.

The secondary reflecting device is like a parabolic trough concentrating device, which can track sunlight under the action of the driving steering device, so as to fully and effectively focus the sunlight on the heat collecting tube.

The angle φ formed between the two ends of the position of the same width of the main reflector and the sub-reflector and the central point of the heat collecting tube can be used to determine the width of the sub-reflector. The effect of the secondary mirror is the same.

From the perspective of geometric dimensions, when the distance between the main mirrors is half the width of the mirrors, the main mirrors can be flipped 180°. By calculation, at this time, the width b of the secondary reflector is selected so that φ is about 85.88° (the condition is cosφ/2-2sinφ/4=0), so that there is no sunlight leakage outside this range. The main reflector is arranged according to the above method, under the worst reflection condition (that is, the situation where the sunlight is tangent to the distribution arc of the main reflector), a small part of the sunlight reflection will be hindered.

If 100% sunlight utilization is to be achieved, the spacing between primary reflectors is increased by half the reflector width times, that is, the main reflector has no leaking and obstructed light under the worst reflection condition (that is, the sunlight is tangent to the distribution arc of the main reflector). At this time, the width b of the secondary reflector makes φ approximately 103.65 ° (the condition is cosφ/2- sinφ/4=0), there is no sunlight leakage, within the range corresponding to the width of the secondary reflector, the lens of the main reflector is parallel to the sunlight, so that the light enters the secondary reflector and projects to the back of the heat collecting tube that the main reflector cannot project.

The present invention can also further specifically be:

The secondary reflection device is a reflective Fresnel mirror composed of a plurality of micro-arc or plane reflectors, and the centers of the plurality of reflectors are located on the same straight line, and the vertical line of the arc concave center points to and focuses on the center of the heat collecting tube.

The lens arrangement of the sub-reflector is the same as the aforementioned CLFR concentrating device, in which the Fresnel reflector is used as a sub-reflector, and the inclination angle is fixed, and the heat collecting tube is used as the focal point to condense light. The reflection effect of the sub-reflector with this structure is not as good as that of the parabolic concentrating mirror, but the difference is very small, and the advantage is that it is easy to manufacture and low in cost.

When the width of the sub-mirror is small enough and the total width is x, the effective reflection width of each sub-mirror is about = , where β is shown in Figure 1, which is the angle formed by the vertical line between the heat collector tube and the sub-reflector and the light reflected by the Fresnel reflector without being blocked. Since β is an acute angle, cosβ≤cos(β/2) , or cosβ≤ ≤ ,so (CLFR concentrating device effective reflection width) ≤ (The overall tracking of the effective reflection width of the Fresnel reflector), that is to say, the overall swing of its effective reflection area is better than that of the CLFR concentrator in the case of a single swing, and the whole of the secondary reflector swings with the incident angle of sunlight. Able to automatically track sunlight.

The central angle of the circular arc formed by the Fresnel reflector in the main reflector with the heat collecting tube as the center can be 360° or less than 360°.

That is to say, the 360° of the main reflector (that is, the entire circle) is covered with the heat collecting tube as the center of the circle, so that when the sun is tilted, it can maintain a constant light-gathering width to maintain a large amount of light-gathering. However, the realization of the 360° spatial distribution may bring a relatively cumbersome process, so the central angle is generally adopted, that is, the angle formed between the endpoints on both sides of the arc segment of the main reflector and the center of the heat collecting tube is 140°~160°. Centralized distribution of the main reflectors above the heat collecting tubes for a simple and effective solution.

The turning device of the Fresnel reflector in the described main reflector includes a reflector frame, a rotating shaft and a support, the reflector is installed on the reflector frame and forms a rotating body, and the reflector frame is supported on the support by rotating the shaft, The axis of the rotating shaft is located in the reflection direction of the mirror, and the axis of the rotating shaft is located within the thickness of the reflecting mirror; a counterweight is provided, which is connected to the rotating body and arranged on the line connecting the center of gravity of the rotating shaft and the axis of the rotating shaft extension line.

The mirror takes its reflective arc as the base surface, the side where the concave arc is located is the reflection direction, and the side where the convex arc is located is the back direction. The reflection direction referred to here is not the direction of the reflection line, but refers to the middle cut The direction of the normal to the plane (or the plane formed by the contour around the mirror). The counterweight can be used to balance the rotational moment caused by the center of gravity of the rotating being deviated from the axis of the rotating shaft.

The distance between the line connecting the upper and lower vertices on the concave arc surface of the reflector and the bottom of the concave arc is the thickness of the reflector.

In order to reduce the rotational moment of the reflector, the distance between the axis of the rotating shaft and the center of gravity of the rotating body (mirror and mirror frame) should be shortened until the two coincide; In addition to the thickness, it will take up extra space, so that the entire solar array is not compact.

To sum up, the present invention provides a large-capacity and high-concentration-ratio composite Fresnel line light-concentrating reflector, which sacrifices a small amount of sunlight utilization to obtain a larger light-concentrating ratio and a more convenient and reasonable spatial arrangement. Adopting the technical scheme of distributing the main reflectors above the heat collecting tubes in an arc shape with the center of the heat collecting tubes as the center of the circle, and setting the sub-reflecting devices below the heat collecting tubes, can make the Fresnel line concentrating reflector of the present invention obtain better The large ground utilization rate fully considers the incidence of sunlight, greatly reduces the loss of sunlight, improves the heat collection effect of the heat collection tube, and at the same time achieves a good focusing effect and uniform heating effect on the heat collection tube, which meets the needs of large capacity The demand for high concentration ratio.

Description of drawings

Fig. 1 is the analysis structure schematic diagram of CLFR described in the background technology of the present invention under the vertical sunlight irradiation;

Fig. 2 is a schematic diagram of the focusing structure of the CLFR described in the background technology of the present invention when the sunlight is perpendicular to the reflector;

3 is a schematic diagram of the focusing structure of the CLFR described in the background technology of the present invention when the sunlight and the reflector are at an angle of 30°;

Fig. 4 is the structural representation of embodiment 1 of the present invention;

Fig. 5 is the structural representation of the preferred embodiment of the present invention;

Fig. 6 is a schematic structural diagram of a Fresnel reflector in the main reflector of the present invention.

The present invention will be further described below in conjunction with the accompanying drawings.

Detailed ways

Example 1:

Referring to accompanying drawing 4, the high-capacity high-concentration ratio composite Fresnel line light-concentrating reflector includes a main reflector 1 and a heat collecting tube 2, and the main reflector 1 is composed of a plurality of micro-arc Fresnel reflectors as the main reflector. The center of each Fresnel reflector is provided with a steering device 3, and the plurality of Fresnel reflectors are located above the heat collecting tube 2, and are distributed in a circular arc with the heat collecting tube as the center and a radius of R. , the angle formed between the end points on both sides of the arc section of the main reflector 1 and the center of the heat collecting tube 2 is generally 140°~160°, that is, the angle qe formed between the two ends of the arc section and the center of the circle where the heat collecting tube 2 is located and the horizontal plane It is 10~20°. At the same time, the concave arc surface of each Fresnel reflector faces the direction of sunlight incidence, which can track the direction of sunlight incidence and rotate accordingly; When the lines are parallel, the mirror flips 180°. The heat collecting tubes can be glass vacuum tubes, other types of heat collecting tubes or photovoltaic power generation devices. The main reflectors are generally arranged symmetrically on the arc, or they can be arranged asymmetrically.

It also includes a secondary reflector 4, which is installed under the heat collecting tube 1, and is a parabolic (or Fresnel type) concentrating reflector (secondary reflector), and the secondary reflector is provided with a driving steering device, The driving steering device can be composed of a rotating member directly installed on the center line of the sub-reflector plus a driving device, or it can be composed of a triangular or circular center support frame and a rotating shaft and a driving device installed on the sub-reflector. The arc-shaped inner concave surface of the secondary reflector faces the direction of the heat collecting tube, and tracks the incident direction of sunlight under the action of the driving steering device.

When the distance between the main mirrors is half of the width of the mirrors, the main mirrors can be flipped 180°. By calculation, at this time, the width b of the secondary reflector is selected so that φ is about 85.88° (the condition is cosφ/2-2sinφ/ 4=0), so that there is no sunlight leakage outside this range.

The spacing between primary mirrors increases by half the mirror width times, that is to make the main reflector under the worst reflection condition (that is, the situation where sunlight is tangent to the distribution arc of the main reflector) without leaking and hindering light, and achieve 100% sunlight utilization rate. At this time, the secondary reflection The mirror width b is such that φ is about 103.65° (the condition is cosφ/2- sinφ/4=0), there is no sunlight leakage, and within the corresponding range, the lens of the main reflector is parallel to the sunlight, so that the light enters the secondary reflector and is projected to the back of the heat collecting tube that the main reflector cannot project.

With reference to accompanying drawing 6, the steering device 3 of Fresnel reflector comprises reflector frame 31, rotating shaft 32, counterweight 33 and support (not shown in the figure), and reflector 5 is installed on reflector frame 31 and forms rotating body , the reflector frame 31 is rotatably supported on the bracket by the rotating shaft 32, the axis of the rotating shaft 32 is located in the reflection direction of the reflector, that is, the C direction in Figure 6, and the axis of the rotating shaft 32 is also located within the thickness of the reflector and within the At half the thickness of the reflector, the thickness of the reflector is A in FIG. 1 , and at the same time, the axis of rotation 32 is also located on the symmetry line in the width direction of the reflector. Reflector 5 takes its reflective arc surface as the base surface, the side where the concave arc is located is the reflection direction, that is, the direction C in FIG. 6 ; the side where the convex arc is located is the back direction, that is, the direction 6 in FIG. 1 . The distance between the line connecting the upper and lower vertices on the concave arc surface of the mirror and the bottom of the concave arc is the thickness of the mirror, that is, A in FIG. 6 . The counterweight 33 is a pendulum structure, including a slender rod body and a hammer body at the tail end. The other end of the rod body is tightly connected to the rotating body through a structure of threaded bolts. The extension line of the heart line. The two ends of the reflector 5 are respectively coaxially provided with rotating shafts 32, and the two rotating shafts 32 are correspondingly supported and connected in the supporting holes of the bracket, so that the entire rotating body straddles the bracket.

Best practice:

With reference to accompanying drawing 5, the large-capacity high concentration ratio composite Fresnel line light-concentrating reflector includes a main reflector 1 and a heat collecting tube 2, and the main reflector 1 is composed of a plurality of micro-arc Fresnel reflectors as the main reflector. The center of each Fresnel reflector is provided with a steering device 3, and the plurality of Fresnel reflectors are located above the heat collecting tube 2, and are distributed in a circular arc with the heat collecting tube as the center and radius R At the same time, the concave arc surface of each Fresnel reflector faces the incident direction of sunlight. When the direction of sunlight is parallel to the center line between the reflector of the main reflector and the center of the heat collector tube, the reflector is flipped 180° ; Also includes a secondary reflector 4, which is installed below the heat collecting tube 1. The sub-reflector is composed of a plurality of Fresnel reflectors (sub-reflectors), and the centers of the plurality of Fresnel reflectors are located on the same straight line, and the vertical line of the center of the arc-shaped concave surface points to the center of the heat collecting tube. For other details, see Invention section. The parts not described in this embodiment are the same as those in Embodiment 1.

The parts not described in the present invention are the same as the prior art.

Claims (2)

1. Large Copacity high concentration ratio compound Fresnel line condensing reflection device, include principal reflection device and thermal-collecting tube, it is characterized in that, principal reflection device is made up of for principal reflection mirror a plurality of Fresnel reflection eyeglass constructed with the differential of the arc, the center of each Fresnel reflection eyeglass is provided with transfer, and this plurality of Fresnel reflection eyeglass is positioned at the top of thermal-collecting tube, in a kind of take thermal-collecting tube as the linear distribution of the circular arc in the center of circle, the inner concave arc surface of each Fresnel reflection eyeglass is all towards sunlight incident direction simultaneously, time parallel with the line of centres of thermal-collecting tube with the central point of the Fresnel reflection eyeglass of principal reflection device when the direction of sunlight, this Fresnel reflection eyeglass carries out the upset of 180 °, also include a kind of secondary reflection unit, it is arranged on below thermal-collecting tube, and arc concave surface is towards thermal-collecting tube direction,

Secondary reflection unit is a plurality of Fresnel reflection eyeglass composition, and this plurality of Fresnel reflection eyeglass be centrally located on same straight line, arc concave surface central vertical line points to thermal-collecting tube center;

The angle φ that formed with the two ends, position of secondary reflection unit same widths and thermal-collecting tube central point in the middle of principal reflection device, the spacing between principal reflection mirror is principal reflection mirror width half doubly, now φ satisfies condition is cos φ/2- sin φ/4=0;

When the width of the Fresnel reflection eyeglass in secondary reflection unit is enough little and the overall width of secondary reflection unit is x, the usable reflection width of every sheet subreflector is = , the Fresnel reflection eyeglass reflection ray in the vertical line that β is thermal-collecting tube and secondary reflection unit and secondary reflection unit is not blocked formed angle,

The transfer of the Fresnel reflection eyeglass in described principal reflection device includes reflector mount, rotating shaft and support, Fresnel reflection eyeglass to be arranged on reflector mount and to form rotor, reflector mount is rotatably supported on support by rotating shaft, rotating shaft core is positioned on the reflection direction of Fresnel reflection eyeglass, and this rotating shaft core is positioned at the thickness of Fresnel reflection eyeglass; Arrange a kind of counterweight, this counterweight is connected with rotor, and is arranged on the extension line of rotor center of gravity and rotating shaft core line.

2. Large Copacity high concentration ratio compound Fresnel line condensing reflection device according to claim 1, is characterized in that, thermal-collecting tube or glass-vacuum tube, or photovoltaic power generation apparatus.