Cylindrical mirror spliced groove type solar heat collecting system and design method thereof

Abstract

The application discloses a cylindrical surface mirror spliced groove type solar heat collecting system and a design method thereof. The cylindrical surface mirror is spliced to form a parabolic surface groove type reflector, spherical aberration and meridian plane aberration caused by splicing of a spherical mirror are eliminated, and system performance is very small different from that of a parabolic surface groove type system under the same optical error. At present, under the mainstream process, the slope error of the cylindrical surface mirror is 1 mrad, and the slope error of the parabolic surface is 2-3 mrad. Therefore, the performance of the cylindrical surface spliced groove type system is obviously superior to that of the parabolic surface groove type system. The application discloses that the cavity receiver has relatively large condensation, and a cylindrical surface transparent glass cover plate is arranged on an opening to reduce heat loss and reflection loss of incident light. The application discloses that a V-shaped groove condenser is additionally arranged to increase condensation ratio and reduce heat loss.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of trough type solar collector, in particular to a cylindrical surface mirror spliced trough type solar collector system and a design method thereof. BACKGROUND

[0002] Concentrated solar collector is a technology that uses light focusing to focus a large amount of low-density solar energy onto a small area to form high-density solar energy, thereby generating high-temperature heat energy for solar thermal power generation, which can store heat to continuously generate electricity. It is the most promising technology to replace coal-fired power plants. The main concentrated solar collector technologies currently available are tower type, trough type, linear Fresnel type, and dish type. The trough type solar collector uses linear focusing parabolic surfaces as concentrators, which is the most mature technology and has been commercialized more than 30 years ago. It has stable performance, but the concentration ratio is less than 30, the working temperature is low, and the performance is difficult to improve. One of the main reasons is that linear focusing parabolic surfaces have high processing costs and large optical errors, which result in low concentration ratio.

[0003] Patent CN200520134069.X proposes using a trough type circular arc surface mirror instead of a parabolic surface mirror to simplify the production process and significantly reduce the cost of mirror manufacturing, but the performance will be significantly reduced. The main reason is that the cylindrical surface mirror has a large aberration. In the same trough width, the ratio of the width of the cylindrical surface mirror to the focal length is much smaller than that of the parabolic surface mirror to eliminate aberration. In the same trough system width, the focal length of the cylindrical surface mirror is much larger than that of the parabolic trough system. Since the receiver radius is proportional to the focal length, it will be much larger than the parabolic trough system, thereby reducing the concentration ratio and working temperature, and the performance is much lower than that of the ordinary parabolic trough system.

[0004] Patent CN200920231849.4 proposes a scheme that includes using multiple circular arc mirrors instead of a trough type parabolic surface mirror, but does not provide a method for splicing multiple circular arc mirrors to simulate a parabolic surface mirror. For example, embodiments 1 and 2 use two circular arc mirrors instead of a parabolic surface mirror, which still has a large aberration. The improved form, including embodiment 3, although uses multiple circular arc surfaces to splice, but does not introduce how to determine the position and direction of each circular arc mirror and the circular arc radius. In the given implementation diagram, the circular arc mirrors are arranged randomly, obviously deviating from the parabolic surface, and the performance is difficult to guarantee.

[0005] CN201110462998.3 proposes using a planar mirror to splice to form a trough type parabolic surface mirror. Since the planar mirror will inevitably produce a parallel light spot on the focal plane with the same width as the planar mirror, the concentration ratio of the system will be significantly reduced, and the performance will be much lower than that of the parabolic trough system.

[0006] The scheme in the patent CN200920231849.4 proposes to use a compound parabolic surface for secondary focusing, thereby improving performance and light condensing ratio, but the compound parabolic surface used in the system will reflect light rays multiple times, requiring high machining precision, otherwise the reflection light ray error will linearly increase with the reflection times, thereby reducing the system performance, so that the scheme has poor economy. SUMMARY

[0007] The present application aims to make up for the defects of the prior art, and provides a cylindrical mirror splicing groove type solar heat collecting system with high light condensing ratio, high optical efficiency, reduced machining difficulty and reduced cost, and a design method thereof. The present application proposes the following invention points: the first invention point is to use multiple cylindrical mirrors to splice to form an approximate linear focusing parabolic surface and the construction and design method thereof, which can reduce the optical error of the system, so that the performance is almost the same as that of a groove type heat collector with the same optical error, but under the same machining process, the optical error of the cylindrical mirror is lower, thereby improving the optical performance and light condensing ratio of the system; the second invention point is to use a cavity receiver instead of a tube type receiver, and it is proved that the same light condensing ratio is increased and the heat loss is reduced; the third invention point is to increase a V-shaped groove type reflection condenser in front of the receiver, which greatly increases the light condensing ratio, thereby improving the working temperature of the system and increasing the efficiency of the groove type solar thermal power generation system; and the fourth invention point is to propose a design method of the above system, which replaces the current design parameters that need to be obtained through complex research.

[0008] The present application is implemented through the following technical solutions:

[0009] A cylindrical mirror splicing groove type solar heat collecting system, comprising a mirror group and a receiver, wherein the mirror group is composed of multiple strip-shaped cylindrical mirrors, the centers of the multiple strip-shaped cylindrical mirrors form a parabolic line, the normal vector of the center of each strip-shaped cylindrical mirror is consistent with the normal vector of the parabolic line at the installation position of the strip-shaped cylindrical mirror, thereby determining the installation direction of each strip-shaped mirror; the receiver is installed at the focal point of the parabolic line formed by the centers of the multiple strip-shaped cylindrical mirrors; the mirror group and the receiver are installed on a sunlight tracking device, the sunlight tracking device tracks the change of the sun position, and the mirror group focuses the sunlight on the receiver.

[0010] The edge angle of the strip-shaped cylindrical mirror corresponding to the position of the center on the parabolic line is related to the focal length f of the parabolic groove and is determined according to the following formula:

[0011]

[0012] Wherein f is the focal length of the parabolic groove.

[0013] The receiver is a tube type receiver or a strip-shaped cavity receiver or a flat plate receiver.​

[0014] When the receiver is a tube receiver, such as a vacuum heat collecting tube, the tube radius R of the receiver is determined by the following formula:

[0015]

[0016] The concentration ratio GR is

[0017] GR = W / (πR) = W / r

[0018] Obviously When the angle is 90 degrees, the concentration ratio is the largest.

[0019] When the receiver uses a cavity receiver or a flat plate receiver, the half width R of the receiver is determined by the following formula:

[0020]

[0021] where W is the half trough width of the trough solar heat collecting system, φ is the edge angle of the trough solar heat collecting system, σ is the Gaussian distribution variance of the reflected light intensity, and λ is the incidence angle of sunlight in the trough solar heat collecting system; at this time, the concentration ratio GR is

[0022] GR = W / R = σ / λ

[0023] Obviously When the angle is 45 degrees, the concentration ratio is the largest. When the receiver is a tube receiver, the ratio of the width w of the strip-shaped cylindrical mirror to the radius r satisfies the following formula:

[0024]

[0025] σ is the Gaussian distribution variance of the reflected light intensity, λ is the incidence angle of sunlight in the trough solar heat collecting system, and the typical design values are 10 mrad and π / 6 rad, respectively, φ is the edge angle of the trough solar heat collecting system, and can be taken as pi / 2 rad. Substituting the calculation results, w / r≤0.21; where the radius r is equal to 2 times the focal length f of the parabolic trough; that is, when a tube receiver is used, the upper limit of the width w of the cylindrical mirror of the parabolic trough heat collecting system using multiple cylindrical mirrors is 0.42 times the focal length f of the parabolic trough.

[0026] When the receiver uses a cavity receiver or a flat plate receiver, the ratio of the width w of the strip-shaped cylindrical mirror to the radius r satisfies the following formula:

[0027]

[0028] Wherein, sigma is the reflected light intensity Gaussian distribution variance, lambda is the solar light incidence angle of the trough solar energy collection system, phi is the edge angle of the trough solar energy collection system, wherein phi takes pi / 4 radian, lambda=pi / 6 radian, and substitution calculation results in w / r <= 0.1993 <= 0.20.This indicates that when the cavity or flat plate receiver is used, the upper limit of the width w of the cylindrical surface mirror of the spliced parabolic trough collection system using multiple cylindrical surface mirrors is 0.40 times the focal length f of the parabolic trough.

[0029] The system can also include a V-shaped trough reflective concentrator, the inlet of which is mounted to the focal plane of the trough solar energy collection system, and the receiver is mounted on the outlet of the V-shaped trough reflective concentrator; the V-shaped trough reflective concentrator is composed of two inclined plane mirrors, the included angle theta between the reflecting surface and the vertical direction is 2-10 degrees, the inlet half-width of the V-shaped trough reflective concentrator is equal to the radius or half-width R of the receiver tube, and the outlet width R' of the V-shaped trough reflective concentrator is equal to the radius or half-width of the receiver tube after the V-shaped trough reflective concentrator is added, and the calculation is as follows:

[0030] .

[0031] When the receiver uses a cavity receiver, a cylindrical transparent glass cover plate is mounted at the opening of the cavity receiver, with the concave surface facing the inside of the cavity receiver. The addition of the cylindrical transparent glass cover plate at the opening of the cavity receiver first reduces heat loss, and the transparent glass material should be selected to have high visible light transmittance and low infrared radiation transmittance, similar to the glass material used for the outer tube of the vacuum heat pipe, so that the heat loss is low; secondly, a semicircular structure or a structure larger than a semicircle can reduce the loss of reflected sunlight and increase the absorption rate of the receiver to sunlight.

[0032] The application also includes a design method for a cylindrical mirror spliced trough solar energy collection system using a tubular receiver, which specifically includes the following steps:

[0033] Firstly, the width of the trough solar energy collection system is determined;

[0034] Secondly, the edge angle phi of the trough solar energy collection system is determined, and the value range is 80-100 degrees, and the optimal value is 90 degrees;

[0035] Thirdly, the focal length f of the parabolic trough is calculated according to the half-trough width W and the edge angle phi, and the calculation formula is as follows:

[0036] f=W / [2*tan(φ / 2)]

[0037] Fourthly, when the spliced cylindrical mirror is used, firstly, the radius r of each cylindrical mirror circle is determined, and if the edge angle of the center position of one cylindrical mirror on the parabolic surface is phiP Then the r calculation formula is:

[0038]

[0039] Secondly, the cylindrical mirror width is determined according to the following formula:

[0040]

[0041] At this time, the minimum value of r is used, that is, r=2f, and the maximum width w of the cylindrical mirror for splicing is calculated according to the above formula;

[0042] Where σ is the Gaussian distribution variance of reflected sunlight, which is approximately calculated as:

[0043]

[0044] σ sun is the Gaussian distribution variance of solar intensity, which is measured at the installation site; σ slopex and σ slopey are the Gaussian distribution variances of the x and y direction slope errors of the trough mirror, respectively; σ tracking is the Gaussian distribution variance of tracking error; σ disp is the Gaussian distribution variance of system installation error; and σ specular is the Gaussian distribution variance of mirror material error, all of which should be measured.

[0045] The fifth step is to determine the size of the receiver. If a tubular receiver is used, the vacuum heat collecting tube radius R is calculated according to the following formula:

[0046] R= 2W*σ / (sinφ* cosλ)。

[0047] The design method also includes a cylindrical mirror splicing trough solar heat collecting system using a cavity receiver or a flat plate receiver, which specifically includes the following steps:

[0048] The first step is to determine the width 2W of the trough solar heat collecting system.

[0049] The second step is to determine the edge angle φ of the trough solar heat collecting system, which is in the range of 40-50 degrees, and the optimal value is 45 degrees.

[0050] The third step is to calculate the focal length f of the parabolic trough according to the half trough width W and the edge angle φ, according to the following formula:

[0051] f=W / [2*tan(φ / 2)];

[0052] The fourth step is to determine the radius r of each cylindrical mirror circle if the splicing cylindrical mirror is used. If the edge angle of the parabolic surface at the center position of one cylindrical mirror is φ P ​r=2f

[0053]

[0054] Secondly, the maximum width of the cylindrical mirror is determined according to the following formula:

[0055]

[0056] At this time, the minimum value of r is used, that is, r=2f, to calculate the maximum width w of the cylindrical mirror for splicing;

[0057] wherein σ is the Gaussian distribution variance of the reflected sunlight, and is approximately calculated as:

[0058]

[0059] σ sun is the Gaussian distribution variance of the sunlight intensity, and is measured at the installation site; σ slopex and σ slopey are the Gaussian distribution variances of the slope errors of the x and y direction trough mirrors respectively; σ tracking is the Gaussian distribution variance of the tracking error; σ disp is the Gaussian distribution variance of the system installation error; σ specular is the Gaussian distribution variance of the mirror material error, and should be measured.

[0060] The fifth step is to determine the half width R of the receiver, and the calculation formula is:

[0061] R= 4*W*σ / [sin(2φ)*cos(λ)].

[0062] The above design method further includes a design method of adding a V-shaped trough type reflecting concentrator, wherein the entrance width of the V-shaped trough is equal to the width R of the receiver, and if the inclination angle of the two mirrors of the V-shaped trough is θ, then the outlet width is , and is calculated according to the following formula:

[0063]

[0064] θ is 2-10 degrees, after adding the V-shaped trough type reflecting concentrator, the edge angle φ is in the range of 20-60 degrees, the optimization range is 45 to 50 degrees, when a cavity receiver is used, the half width of the cavity is ; and when a tubular receiver is used as the receiver, the radius of the heat collecting tube is .

[0065] The advantages of the present application are:

[0066] The present application uses cylindrical mirrors to splice to form a parabolic trough mirror, and the requirement can eliminate spherical aberration and meridian aberration caused by using spherical mirror splicing, so that the system performance is very small different from the parabolic trough system performance under the same optical error; the parabolic surface is difficult to process, and under the same process, the optical error is usually 2 to 3 times of the cylindrical mirror, and under the current mainstream process, the slope error of the cylindrical mirror is 1 mrad, and the parabolic surface is 2-3 mrad, therefore, the performance of the cylindrical splicing trough system is obviously superior to that of the parabolic trough system.

[0067] The present application uses a cavity or flat plate receiver to replace the commonly used tubular receiver, such as a vacuum heat collecting tube, and the light collection of the trough system using the cavity receiver or flat plate receiver is larger, which is obviously superior to the trough system using the tubular receiver. In addition, the performance of the cavity receiver is superior to that of the tubular receiver and flat plate receiver, because the cavity receiver has high absorption rate, and after the light enters the cavity, it is basically absorbed by the receiver, but the tubular receiver and flat plate receiver will reflect a part of the intercepted sunlight, usually about 5%-10%, so that the absorption rate is low.

[0068] The present application proposes to use a V-shaped trough type reflecting light collector, although the light collection multiple is lower than the compound parabolic surface, but the structure is simple, and two inclined plane mirrors can be used to focus the incident light of a certain direction, the plane mirror used in the V-shaped trough is easy to process, and the optical error is small, so that the adverse effects caused by multiple reflections are eliminated; the increase of the light collection ratio can reduce the heat loss and improve the system working temperature, so as to increase the efficiency of the subsequent power generation system, and improve the total efficiency and performance of the trough type heat power generation system.

[0069] The design method proposed by the present application is to obtain a light collection ratio calculation formula according to the receiver size calculation formula proposed by the present application, so as to determine the optimal edge angle and receiver size, and determine the design parameters of the system; in the aspect of splicing the parabolic surface trough mirror by the cylindrical mirror, the spherical aberration and meridian aberration elimination condition and calculation formula are established, so as to determine the parameters of the cylindrical mirror; the design method proposed by the present application has simple calculation process and clear thinking, and can easily obtain reliable design, which is superior to the traditional optical method.

[0070] The present application increases a cylindrical transparent glass cover plate at the opening of the cavity receiver, which can reduce heat loss, and the transparent glass material should be selected to have high visible light transmittance and low infrared radiation transmittance, similar to the glass material used for the outer tube of the vacuum heat collecting tube, so as to have low heat loss; secondly, a semicircular structure or a structure larger than a semicircle can reduce the reflected loss of sunlight and increase the absorption rate of the receiver to the sunlight. BRIEF DESCRIPTION OF DRAWINGS

[0071] Figure 1The energy flux density distribution map of the evacuated collector tube surface used for example 1 of the present application.

[0072] Figure 2 The energy flux density distribution map of the cavity receiver entrance focal plane used for example 2 of the present application.

[0073] Figure 3 The energy flux density distribution of the cavity receiver entrance focal plane after adding the V-groove concentrator for the incident angle of example 3.

[0074] Figure 4 The structure diagram of the cylindrical mirror spliced parabolic trough system when the receiver is a tubular receiver.

[0075] Figure 5 The structure diagram of the cylindrical mirror spliced parabolic trough system when the receiver is a cavity receiver.

[0076] Figure 6 The structure diagram of the cylindrical mirror spliced parabolic trough system with V-groove reflective concentrator. DETAILED DESCRIPTION

[0077] A cylindrical mirror spliced trough solar thermal system, comprising a mirror group 1 and a receiver, the mirror group 1 is composed of a plurality of strip-shaped cylindrical mirrors spliced, the centers of the plurality of strip-shaped cylindrical mirrors constitute a parabola, the normal vector of the center of each strip-shaped cylindrical mirror is consistent with the normal vector of the parabola at the installation position, thereby determining the installation direction of each strip-shaped mirror; the receiver is installed on the focus of the parabola constituted by the centers of the plurality of strip-shaped cylindrical mirrors; the mirror group and the receiver are both installed on a sunlight tracking device, the sunlight tracking device tracks the change of the sun position, and the mirror group 1 focuses the sunlight on the receiver.

[0078] Wherein the radius r of the strip-shaped cylindrical mirror and the corresponding edge angle φ of the center on the parabolic surface P and the focal length f of the parabolic trough, which is determined as follows:

[0079]

[0080] Wherein when the tubular receiver 2 is used, the ratio of the width w of the strip-shaped cylindrical mirror to the radius r should meet the following conditions:

[0081]

[0082] σ is the variance of the Gaussian distribution of the reflected light intensity, λ is the angle of incidence of the sunlight on the trough system, the typical design value can be taken as 10 mrad and π / 6 rad respectively, φ is the edge angle of the trough system, which can be taken as pi / 2 rad, and the calculation results by substituting the values are w / r≤0.21; here r is equal to 2 times the focal length f of the parabolic trough. This shows that when using a tubular receiver, such as a vacuum heat pipe, the upper limit of the width w of the cylindrical mirror of the parabolic trough collector system using multiple cylindrical mirrors is 0.42 times the focal length f of the parabolic trough.

[0083] When using the cavity receiver 3, the ratio of the width w of the strip-shaped cylindrical mirror to the radius r should meet the following condition:

[0084]

[0085] The similar design values are adopted, wherein φ should be taken as pi / 4 rad, and the calculation results by substituting the values are w / r≤0.1993≈1 / 5; here r is equal to 2 times the focal length f of the parabolic trough. This shows that when using a cavity or flat plate receiver, the upper limit of the width w of the cylindrical mirror of the parabolic trough collector system using multiple cylindrical mirrors is 0.40 times the focal length f of the parabolic trough.

[0086] The receiver is a tubular receiver 2, or a cavity receiver 3 or a flat plate receiver; when using a tubular receiver as the receiver, the radius of the receiving tube is determined by the following formula:

[0087]

[0088] Here W is the half trough width of the trough system, φ is the edge angle of the trough system, σ is the variance of the Gaussian distribution of the reflected light intensity, and λ is the angle of incidence of the sunlight on the trough system;

[0089] If a cavity or flat plate receiver is used, the half width R of the receiver is determined by the following formula:

[0090]

[0091] The system can also include a V-shaped trough reflective concentrator 5, the inlet is installed on the focal plane of the trough system, and the receiver is installed on the outlet of the V-shaped trough reflective concentrator 5. The V-shaped trough reflective concentrator is composed of two inclined plane mirrors, the included angle θ between the reflecting surface and the vertical direction is 2-10 degrees, the half width of the V-shaped trough inlet is equal to the receiver radius or half width R calculated by the parabolic trough concentrator without the V-shaped trough, and the outlet width R' of the V-shaped trough is equal to the receiver radius or half width after adding the V-shaped trough reflective concentrator, which can be calculated by the following formula:

[0092]

[0093] The cylindrical transparent glass cover plate 4 can also be installed on the opening of the cavity receiver, and the concave surface faces the inside of the cavity receiver.

[0094] In conjunction with the present application, a trough solar thermal system design method using a tubular receiver as the receiver is also proposed, comprising the following steps:

[0095] First, determine the width of the trough collector system;

[0096] Second, determine the edge angle φ of the trough system, the value range is 80-100 degrees, and the optimal value is 90 degrees;

[0097] Third, calculate the focal length f of the system according to the half-trough width W and the edge angle φ, the calculation formula is:

[0098] f=W / [2*tan(φ / 2)]

[0099] Fourth, if the system uses cylindrical surface splicing to construct a parabolic trough system mirror, first determine the radius r of each cylindrical mirror circle, and if the edge angle of the parabolic surface on which the center of a cylindrical mirror is installed is φ P , then the calculation formula of r is:

[0100]

[0101] Second, determine the width of the cylindrical mirror, which can be determined by the following formula:

[0102]

[0103] At this time, r should use the minimum value, that is, r=2f, and the maximum width w of the cylindrical mirror used for splicing is calculated using the above formula.

[0104] Fifth, determine the size of the receiver. If a tubular receiver is used, the radius R of the tubular receiver is calculated as:

[0105] R= 2W*σ / (sinφ* cosλ),

[0106] Where σ is the Gaussian distribution variance of reflected sunlight, which can be approximately calculated as:

[0107] Here σ sun is the Gaussian distribution variance of solar intensity, which should be measured at the installation site; σ slopex and σ slopey are the Gaussian distribution variances of the x and y direction slope errors of the trough mirror, respectively; σ tracking is the tracking error Gaussian distribution variance; σ disp is the system installation error Gaussian distribution variance; σ specular is the mirror material error Gaussian distribution variance; all of which should be measured values.

[0108] The system of the present application also proposes a design method of a trough solar heat collection system using cavity or flat plate receivers, comprising the following steps:

[0109] Firstly, the width of the trough heat collection system is determined;

[0110] Secondly, the edge angle φ of the trough system is determined to be in the range of 40-50 degrees, and the optimized value is 45 degrees;

[0111] Thirdly, the focal length f of the system is calculated according to the half trough width W and the edge angle φ, and the calculation formula is:

[0112] f=W / [2*tan(φ / 2)];

[0113] Fourthly, if the parabolic trough system mirror is constructed by using cylindrical surface splicing, firstly, the radius r of the circle of each cylindrical mirror is determined, and if the edge angle of the center position of the cylindrical mirror on the parabolic surface is φ P , then the calculation formula of r is:

[0114]

[0115] Secondly, the width of the cylindrical mirror is determined according to the following formula:

[0116]

[0117] At this time, r should use the minimum value, that is, r=2f, and the maximum width w of the cylindrical mirror for splicing is calculated;

[0118] Fifthly, the half width R of the receiver is determined, and the calculation formula is:

[0119] R= 4*W*σ / [sin(2φ)*cos(λ)],

[0120] Where σ is the Gaussian distribution variance of reflected sunlight, which can be approximately calculated as:

[0121]

[0122] Here σ sun is the Gaussian distribution variance of solar intensity, which should be measured at the installation site; σ slopex and σ slopey are the Gaussian distribution variances of the slope error of the x and y directions of the trough mirror respectively; σ tracking is the Gaussian distribution variance of the tracking error; σ disp is the Gaussian distribution variance of the system installation error; σ specular is the Gaussian distribution variance of the mirror material error; all of which should be measured values.

[0123] When the slotted system includes a V-groove, the design method further includes a V-groove design, wherein the inlet width of the V-groove is equal to the receiver width R in the design method. If the tilt angle between the two reflectors of the V-groove is θ, then the outlet width is R', which can be calculated using the following formula:

[0124]

[0125] θ can be taken as 2-10 degrees. After adding a V-shaped trough reflector, the edge angle φ of the trough system is in the range of 20-60 degrees. The optimized value is 45 degrees. When using a strip cavity receiver, the half width of the cavity is R'. When using a tubular receiver as the receiver, the radius of the heat collection tube is R'.

[0126] Example 1: As Figure 4 As shown, the trough is 8 meters wide, using vacuum tube solar collectors as receivers. The trough system has an edge angle of 90 degrees and a focal length of 2 meters. It uses 0.5-meter-wide strip-shaped cylindrical reflectors to form a parabolic trough reflector. The radius of each cylindrical reflector is calculated using the formula mentioned above. The centers of all the strip-shaped reflectors form a parabola, and the normal vector of each reflector's center coincides with the normal vector of the parabola at its installation location, thus determining the installation direction of each reflector. The vacuum tube solar collector receiver is installed at the focal point of the parabola. Both the reflectors and receivers are mounted on a tracking device that tracks the sun's position and focuses sunlight onto the receiver. With an incident angle of 30 degrees, assuming the Gaussian variance of the reflected optics is σ = 4.27 mrad, the receiver radius R is calculated to be 39.45 mm. A 40 mm radius is used, resulting in a focusing ratio of 32.3. The system is installed on a single-axis tracking device to focus sunlight onto the receiver. It should be noted that in our previous patent application 202221295614.3, we pointed out that when supporting the focusing reflector, the stress points should be arranged around the reflector. Considering that the glass used for the reflector is very thin, we chose a cylindrical reflector width of 0.5 meters in all three technical implementation schemes, instead of the calculated maximum value of 0.8 meters.

[0127] We built a ray tracing program to simulate and calculate the system performance, such as Figure 1 It represents the energy flux density distribution under design conditions, with an interception rate of 99.2%.

[0128] Example 2, as Figure 5As shown, the groove width is 8 meters, the strip-shaped cavity is used as the receiver, the edge angle of the groove system is 45 degrees, the focal length is 4.8284 meters, the strip-shaped cylindrical surface reflector with a width of 0.5 meters is spliced to form a parabolic groove reflector, the radius of each cylindrical surface reflector is calculated according to the formula, the centers of all strip-shaped reflectors form a parabola, the normal vector of the center of each strip-shaped reflector is consistent with the normal vector of the parabola at the installation position, so as to determine the installation direction of each strip-shaped reflector; the vacuum heat collecting tube receiver is installed at the focal point of the parabola; the reflector and the receiver are installed on the tracking device, and the tracking device tracks the change of the sun position, so as to focus the sunlight on the receiver; assuming that the Gaussian distribution variance of the reflected light is σ=4.21 mrad, the half width of the cavity receiver R is calculated according to the formula, and the half width of the cavity receiver R is 77.85 millimeters, 80 millimeters are adopted, and the concentration ratio is 50.0 times. The system is installed on the single-axis tracking device, so that the sunlight is focused on the receiver.

[0129] The calculation of the energy flux density distribution on the acceptance surface is as shown in Figure 2 The obtained intercept rate is 97.3%, which is lower than the theoretical formula estimation of 97.7% intercept rate. This is because the light tracking program we established simulates three reflected rays when the sunlight is reflected by the glass back reflector. The first reflected ray is the direct reflection part of the upper surface of the glass, accounting for about 5%, the second reflected ray is the reflection of the silver-coated back surface, accounting for about 90%, and the third reflected ray is the reflection of the upper and lower surfaces of the glass, accounting for about 4%. Because the third reflected ray is reflected for three times, the optical error is large, so that the actual intercept rate is low.

[0130] As shown in Figure 6 , on the basis of example two, a V-shaped groove type reflecting concentrator is added, the half width of the V-shaped groove opening is 80 millimeters, the half width of the outlet is 40 millimeters, the half width of the cavity receiver is also equal to 40 millimeters, the concentration ratio is 100, the width of the two V-shaped groove reflectors is 140.2 millimeters, and the inclination angle is 5 degrees. The system is installed on the single-axis tracking device, so that the sunlight is focused on the receiver. The light tracking program is established to simulate the performance of the system, the incident angle is 30 degrees, the edge angle is 46 degrees, and the performance is slightly better than 45 degrees. The energy flux density distribution on the acceptance surface is as shown in Figure 3 .

[0131] The calculated intercept rate is 96.3%, which is lower than the theoretical formula estimation of 97.7% intercept rate. This is because our calculation model further considers the loss part of the V-shaped groove type reflecting concentrator, so that the actual intercept rate is low.

[0132] The cylindrical surface mirrors are spliced to form a parabolic trough mirror, and each design parameter is determined according to the design in the paper, so that the spherical aberration and the meridian aberration caused by splicing of the spherical mirror can be eliminated, the system performance is little different from that of the parabolic trough system under the same optical error, the parabolic surface is difficult to process, under the same process, the optical error is usually 2 to 3 times of the cylindrical surface mirror, under the current mainstream process, the slope error of the cylindrical surface mirror is 1 mrad, and the parabolic surface is 2-3 mrad, therefore, the performance of the cylindrical surface splicing trough system is obviously better than that of the parabolic trough system.

[0133] The present application proposes a method for eliminating the meridian coma of the spliced cylindrical surface mirror: calculating the expression of the radius of the circle of the spliced cylindrical surface mirror, so as to select the correct radius of the circle of the cylindrical surface, and eliminate the meridian coma, and the following introduces how to achieve this.

[0134] Firstly, how to eliminate the meridian coma of the cylindrical surface is introduced. Referring to the meridian focal length theory of the spherical mirror heliostat established in chapter 7 of Rabl Active solar collectors and their applications, we deduce the focal length of the cylindrical surface mirror when the incident angle is greater than 0 through geometric optics: when the cylindrical surface mirror is spliced, when the installation center position corresponds to the edge angle of the parabolic trough system P , the incident angle of the sunlight in the trough system is λ, the incident angle of the sunlight in the cylindrical surface is φ P / 2, if the focal length of the cylindrical surface mirror is f', then the meridian focusing focal length is f'*cos(φ P / 2), therefore, the focal length of the cylindrical surface mirror needs to be appropriately enlarged to focus on the original focal point. If the center of the cylindrical surface mirror used for splicing corresponds to the edge angle P , the distance between the system focal point and the cylindrical surface mirror is f / cos 2 (φ P / 2), and the focal length of the cylindrical surface mirror is

[0135] f‘= f / cos 3 (φ P / 2),

[0136] The radius of the circle in the cylindrical surface mirror

[0137] R=2f’=2*f / cos 3 (φ P / 2),

[0138] When it is installed at the edge angle PIf the actual focal position is at the center of the trough, the meridional coma can be completely eliminated. Otherwise, the meridional coma will be generated, for example, if the meridional coma is not corrected, the commonly used design is that the radius of the cylindrical mirror is equal to 2 times the distance from the center of the mirror to the focal point of the trough-shaped parabolic mirror, that is:

[0139] R=2f’=2 f / cos 2 (φ P / 2),

[0140] At this time, since the actual focal position is not at the focal point of the trough-shaped parabolic mirror, the meridional coma is generated, that is, the spot width is increased, and the value is equal to 2W(1-cos(φ P / 2)); for a trough-shaped system with a half-width of 4 meters and an edge angle of 90 degrees, the increased spot width is 2W(1-cos(φ P / 2))=2.34 meters, which is much larger than the diameter of the receiver.

[0141] Secondly, the application proposes a method for eliminating the spherical aberration of the spliced cylindrical mirror, which is to limit the width of the spliced mirror and propose an upper limit calculation formula for the ratio of the width of the spliced cylindrical mirror to the radius of the circle.

[0142] The traditional optical theory aims to image quality, that is, to perfectly reproduce the image of the light source on the focal plane, and the requirement for eliminating spherical aberration is very high. Referring to page 175 of "Research and Test of Optical System" by Klukoparova et al., when a spherical mirror is used as a main mirror, the relative aperture is not more than 1:10.8, that is, the ratio of the aperture of the mirror to the focal length is ≤1 / 10.8, which is converted to the ratio of the aperture of the mirror to the radius of the sphere ≤1 / 21.6. In the field of solar energy, the main purpose of the optical system is to concentrate light, which is much lower than the requirement of optical imaging. We propose the requirement for eliminating spherical aberration in the field of solar energy.

[0143] According to the principle of geometric optics, the calculation formula of the transverse spherical aberration δx of the spherical mirror is usually as follows:

[0144] δ x =r*tan(ψ)*sin 2 (ψ / 4) / cos(ψ / 2)=w sin 2 (ψ / 4) / cos(ψ)

[0145] Here, w is the diameter of the circular spherical mirror used for splicing, r is the radius of the spherical mirror, and ψ is the central angle corresponding to the maximum circular arc of the spherical mirror.

[0146] For a linear focusing trough concentrator, when a cylindrical mirror is used, the transverse aberration of the cylindrical mirror is derived using the principle of geometric optics as follows:

[0147] δ x =w sin 2(ψ / 4) / cos(ψ) ≈

[0148] Here w is the width of the cylindrical mirror, r is the radius of the cylindrical mirror, then we derive the receiver radius

[0149]

[0150] Here σ is the variance of the Gaussian distribution of the reflected light intensity, and the latter part of the expression is the Gaussian distribution of the reflected light required by the 2σ part of the complete interception 2σ part of the receiver radius, where W is the half-width of the parabolic trough system, and λ is the angle of incidence of sunlight in the trough system. This formula is derived from the reflected light at the farthest distance from the focal point, with an edge angle of φ. Then the concentration ratio is

[0151] GR = W / (πR) = 1 / π / [ sin 2 (ψ / 4) / cos(ψ) ]

[0152] When the angle of incidence is 30 degrees and σ is 5 mrad, if two cylindrical mirrors are used instead of parabolic mirrors, that is, w / W=1, the maximum concentration ratio can be numerically solved to be only 6.84, corresponding to φ=25 degrees or so. In comparison with the parabolic trough system with an edge angle of 90 degrees, we derive the maximum concentration ratio:

[0153] GR = W / (πR) = = 27.566

[0154] This shows that using two cylindrical mirrors instead of a linearly focused parabolic mirror performs much worse than a parabolic trough system. This is because when using a cylindrical mirror, the spherical aberration is large when the edge angle is large, and when the edge angle is small, the focal length of the same width mirror is large, making the receiver radius required for the same interception rate large, and thus the concentration ratio decreases.

[0155] Our research shows that when using a tubular receiver, the requirement to eliminate spherical aberration is that the transverse spherical aberration does not exceed 5% of the radius of the parabolic trough system, which gives us:

[0156]

[0157] Here ψ is the central angle corresponding to the arc length of the cylindrical mirror, σ is the variance of the Gaussian distribution of the reflected light intensity, and λ is the angle of incidence of sunlight in the trough system. Then the effect of spherical aberration is very small. Since ψ is required to be very small, we can approximately consider that sin(ψ / 4) ≈ ψ / 4; cos(ψ) =1-2sin 2 (ψ / 2) ≈ 1-ψ 2 / 2; then we get:

[0158] (ψ / 4) 2 / (1-ψ 2 / 2)

[0159] In another aspect,

[0160] sin(ψ / 2)=w / (2r),

[0161] W / w=2f*tan(φ / 2) / w=r* tan(φ / 2) / w

[0162] Here we apply 2f=r, because the focal length and radius of the cylindrical mirror near the vertex of the parabolic trough is the smallest, and the opening angle is the largest, so the spherical aberration is the largest, therefore, we only need to discuss this mirror. Then

[0163] w / r≈ψ

[0164] σ and λ are typical values of 5 mrad and π / 6 rad, respectively, φ is the edge angle of the trough system, which can be taken as pi / 2 rad, and the calculation is substituted to obtain w / r≤0.21≈1 / 5; we can also select w / r to be more than 1 / 5, at which time the performance will further decrease. Therefore, the above formula is the condition required to eliminate spherical aberration for the cylindrical mirror used in the parabolic trough system with a tubular receiver. Since r=2f is selected, the above formula can be converted to: w / f≤0.42, which indicates that when a tubular receiver such as a vacuum heat collecting tube is used, the upper limit of the width w of the cylindrical mirror used in the parabolic trough heat collecting system with multiple cylindrical mirrors is 0.42 times the focal length f of the parabolic trough.

[0165] By eliminating the spherical aberration through the above measures, we can ignore the influence of the spherical aberration, and the following analyzes the difference between the cylindrical mirror with the spherical aberration eliminated and the parabolic trough system. When the incident angle λ is taken as π / 6 rad, σ is taken as 5 mrad, W is 4.0 m, and the edge angle φ=π / 2 rad, the minimum r of the mirror is approximately 4.0 m, and the width of the cylindrical mirror is obtained to be less than 0.8 m according to formula (9). Taking the maximum value of 0.8 m, the cylindrical spherical aberration is calculated to be 0.50 mm according to formulas (2) and (3), and the receiver radius R of the parabolic trough system with the cylindrical mirror is 46.7 mm, which is only 0.5 mm larger than the receiver radius of the parabolic trough system, i.e., 46.2 mm, and the increase is about 1.1%, which basically does not affect the performance. A smaller width of the mirror can further reduce the spherical aberration, but the improvement of the performance is very small, and on the contrary, the processing and installation workload and cost are increased; and an increase in the width will increase the spherical aberration and affect the system performance. Therefore, the width of the cylindrical mirror used in the parabolic trough system is selected to be at most 0.8 m.

[0166] The condition for eliminating the spherical aberration effect, w / r≤1 / 5, is equal to the requirement of relative aperture w / f≤1 / 2.5, which is much lower than the requirement of 1 / 10.8 in the optical imaging field, so that the actual implementation is easier to achieve.

[0167] If the cavity receiver is used, if the transverse spherical aberration does not exceed 5% of the parabolic trough system radius, the following is obtained:

[0168] w*sin 2 (ψ / 4) / cos(ψ)

[0169] The condition for eliminating the spherical aberration of the cylindrical mirror is obtained as follows:

[0170] w / r≈ψ

[0171] Since the optimized edge angle φ=45 degrees when the cavity receiver is used, the same parameters are used to obtain w / r≤0.199≈1 / 5. The requirement is similar to using the tubular receiver, which is much lower than the requirement of the optical field.

[0172] We also establish a ray tracing program to verify the above requirements for eliminating two aberrations, that is, the parabolic trough system is constructed by splicing cylindrical mirrors, according to the above requirements, including using a cylindrical mirror with a width of 0.8 meters to splice an 8-meter-wide parabolic trough system with an edge angle of 90 degrees and a tubular receiver, the radius R of each cylindrical mirror is 2 f / cos 3 (φ P / 2), when the optical error is the same, the interception rate and optical efficiency are consistent with those of the parabolic trough system, and the difference is not more than 0.1%. On the contrary, when the selected cylindrical radius is not equal to the calculated result, the performance will decrease; increasing the width of the cylindrical mirror will also reduce the performance of the system. Considering that the optical error of the cylindrical mirror is much smaller than that of the parabolic mirror, the performance of our system is obviously better than that of the traditional parabolic trough system. Quantitative results, including theoretical estimates and ray tracing simulation results, are given below.

[0173] The present application also proposes a calculation formula for estimating the radius and width of the receiver of the trough system, so that the system design parameters can be easily determined. Generally, the tubular receiver is often used in the trough system, and the commonly used vacuum heat collecting tube is often used. How to select the receiver radius is often determined by considering the influence of various factors on the performance of the system under different conditions through a large number of simulation calculations, such as the research report of the trough system published by Bendt et al. in the United States, "Optical analysis and optimization of line focus solar collectors".

[0174] On the other hand, the optical system error is often ignored in theory, and the reflected light is regarded as coming from the sun's photosphere to estimate the minimum receiver radius that can be selected by the trough system, so that the maximum theoretical concentration ratio of the trough system can be estimated, but this theoretical estimation is not helpful for people to design the actual trough system. In analogy to this theory, we propose a theory and calculation formula for estimating the receiver radius of the trough system, so as to obtain the maximum concentration ratio design parameter, which is briefly described as follows:

[0175] The sunlight reflected by the parabolic trough mirror can be described by a Gaussian distribution. The distribution angle of the reflected light intercepted by the receiver determines the interception rate. For example, when the half distribution angle of the interception is equal to the average variance σ of the Gaussian distribution, about 68% of the light is intercepted, and when it is increased to 2σ, the interception rate is increased to 95.4%, and when it is increased to 4σ, the interception rate is increased to 100%. We choose the half distribution angle of the interception of the farthest reflection point from the focal point as 2σ, that is, all distribution half angles less than 2σ are intercepted, and when the edge angle of the system is 90 degrees, the distance of the nearest reflection point from the focal point is only half of the farthest point, that is, the interception half angle of the nearest reflection point is 4σ, and the average interception rate can be approximately estimated as (95.4%+100%) / 2=97.7%. Therefore, the calculation formula of the tubular receiver radius R is:

[0176]

[0177] Here φ is the edge angle of the trough mirror, and λ is the incident angle of sunlight on the trough system. On the other hand, the half width W of the trough mirror is 2*f*tan(φ / 2), and after substitution, we get:

[0178]

[0179] The calculation formula of the concentration ratio GR is:

[0180]

[0181] Obviously, when the edge angle φ =90 degrees, the concentration ratio is maximum.

[0182] When a cavity or flat plate receiver is used, the half width of the receiver we derive is:

[0183]

[0184] The maximum concentration ratio is:

[0185]

[0186] Obviously, when the edge angle φ = 45 degrees, the concentration ratio is maximum. The following uses the above theory to compare the concentration ratio of the ordinary parabolic trough system and the cylindrical surface mirror spliced parabolic trough system, the difference between the two is that the optical slope error of the cylindrical surface mirror spliced trough system is 1 mrad, and the optical slope error of the ordinary parabolic trough system is about 2.5 mrad. First, calculate the reflected light intensity Gaussian distribution variance

[0187]

[0188] Referring to the measured data provided in the research report on trough system published by Bendt et al. Optical analysis and optimization of line focus solar collectors, assuming that the system is installed on the Qinghai-Tibet Plateau, the solar intensity distribution variance σ sun is 3.4 mrad, σ slope is the slope error distribution variance of the trough mirror, the distribution of the parabolic mirror in two directions is 2.5 mrad and 1 mrad respectively, and the cylindrical mirror is 1 mrad; σ tracking is the Gaussian distribution variance of the tracking error, which is 1 mrad; σ disp is the Gaussian distribution variance of the system installation error, which is 1 mrad; σ specular is the Gaussian distribution variance of the mirror material error, which is ignored here; the ordinary parabolic trough system σ = 6.263 mrad and the cylindrical surface spliced trough system σ = 4.27 mrad are calculated respectively, and the concentration ratio is calculated at an incident angle of 30 degrees:

[0189] The concentration ratio GR of the ordinary parabolic trough system is 22.0;

[0190] The concentration ratio GR of the cylindrical surface spliced parabolic trough system is 32.3.

[0191] The two trough systems have similar intercept rates when using the above-mentioned concentration ratios, and the performance difference is mainly reflected in the heat loss. The receiver radius of the ordinary parabolic trough system is about 50% larger than that of the cylindrical surface spliced parabolic trough system, and under the same working conditions, the heat loss will be 50% larger than that of the spliced parabolic system. If the two trough systems use the same radius of the receiver, and the receiver radius of the spliced trough system is the same, the maximum distribution angle of the completely intercepted sunlight under the condition of a 30-degree sunlight incidence angle is 4.27*2 mrad, which is only 1.36 times the Gaussian distribution variance σ=6.263 mrad of the ordinary trough system, and the average intercept rate is 90.9% when the intercept distribution variances are 1.36σ and 2.72σ, which is 6.8% lower than the intercept rate 97.7% of the cylindrical surface spliced parabolic trough system. Therefore, when using the same concentration ratio, the optical error of the ordinary parabolic trough system is large, and the intercepted energy is 6.8% lower than that of the cylindrical surface spliced parabolic trough system. In summary, we demonstrate from two aspects that the performance of the cylindrical surface spliced parabolic trough system is significantly better than that of the ordinary parabolic trough system.

[0192] Using formula (17), when the edge angle φ=π / 4 radians, the concentration ratio of the trough system using the cavity receiver is the largest, and when the incidence angle λ takes π / 6 radians and σ=5 mrad, the concentration ratio of the trough system using the tube receiver is 27.6; the concentration ratio of the trough system using the cavity receiver is 43.3, which is significantly better than that of the trough system using the tube receiver. On the other hand, the cavity receiver has better performance than the tube receiver and the flat plate receiver, because the cavity receiver has high absorption rate, and the light entering the cavity is basically absorbed by the receiver, but the tube receiver and the flat plate receiver will reflect a part of the intercepted sunlight, which is usually about 5%-10%, resulting in lower absorption rate.

[0193] In actual use of the cavity receiver and the cylindrical surface spliced parabolic trough system, the optimal edge angle is only π / 4 radians, which reduces the maximum optical error of the system. Using the above-mentioned typical optical error data, the reflected solar Gaussian distribution variance σ=4.21 mrad can be obtained, and the maximum design concentration ratio is 51.4.

[0194] In addition, the line-focusing parabolic trough mirror has a very uneven energy flux density distribution on the tube receiver, resulting in uneven temperature distribution on the receiving surface, which leads to larger heat loss and poorer thermal performance stability. In comparison with the use of the cavity receiver, the internal receiving surface structure of the receiver can be adjusted to maintain a relatively uniform cavity energy flux density distribution and temperature distribution, thereby reducing the heat loss of the tube receiver, improving the thermal performance stability, and increasing the heat collection efficiency.

[0195] The application increases the secondary concentration of V-shaped groove type reflecting concentrator. In the focusing solar energy collector, the compound parabolic surface is often used for secondary focusing, so as to improve the performance and concentration ratio, but the compound parabolic surface used in the system can reflect the light multiple times, and requires high machining precision, otherwise the reflection light error will increase linearly with the reflection times, thereby reducing the system performance, so that the economic efficiency of the scheme is poor.

[0196] The concentration multiple of the V-shaped groove type reflecting concentrator is slightly lower than that of the compound parabolic surface, but the structure is simple, and two inclined plane mirrors can be used to focus the incident light in a certain direction. The plane mirror used in the V-shaped groove is easy to process, and the optical error can be small, so as to eliminate the adverse effects of multiple reflections. The application proposes to use the V-shaped groove type reflecting concentrator, install it to the entrance of the receiver, make the entrance half width of the V-shaped groove equal to the half width or radius R of the receiver in the design method, if the inclination angle of the two mirrors of the V-shaped groove is θ, then the outlet half width is R', which can be calculated as follows:

[0197]

[0198] θ can be 5-10 degrees, and the strip cavity receiver is used, at this time the half width of the cavity receiver is R'; the vacuum heat collecting tube is used as the receiver, and the half radius of the heat collecting tube is R'. After increasing the V-shaped groove type reflecting concentrator, the performance is better when used with the cavity type or flat plate receiver, at this time the edge angle φ of the groove type system is about 45 degrees. At this time, the width of the receiver can be reduced by half compared with that without the V-shaped groove type reflecting concentrator, so that the concentration ratio of the system is increased to 100. This also shows that the effect of increasing the V-shaped groove type reflecting concentrator is very obvious, the concentration ratio is increased, the heat loss is reduced, the working temperature of the system is improved, so that the efficiency of the subsequent power generation system is increased, and the total efficiency and performance of the trough type heat power generation system are improved.

[0199] The present application proposes a parabolic trough solar collector design method. The design method proposed by the present application can quickly and conveniently determine the design parameters of the parabolic trough solar collector including the use of cylindrical mirror splicing. Usually, the trough system uses tubular receiver, commonly used vacuum heat pipe, how to select various design parameters, including edge angle, receiver radius, often is a large number of simulation calculation system performance under different conditions, comprehensive consideration of various factors, can be determined, such as Bendt published in the United States, the study report of the trough system "Optical analysis and optimization of line focus solar collectors". This method is complex, the workload is very large, and it is not necessarily to get the optimal design scheme. The method is to obtain the condensing ratio calculation formula according to the receiver size calculation formula proposed by the present application, so as to determine the optimal edge angle and receiver size, and determine the design parameters of the system. In terms of cylindrical mirror splicing parabolic trough mirror, the condition and calculation formula for eliminating spherical aberration and meridian coma are established, so as to determine the parameters of the cylindrical mirror. The design method proposed by the present application is simple in calculation process and clear in thinking, and reliable design can be obtained more easily, which is better than the design obtained by the traditional optical method.

[0200] The present application has the beneficial effect of adding a cylindrical transparent glass cover plate to the opening of the cavity receiver. First, it reduces heat loss. The transparent glass material should be selected to have high visible light transmittance and low infrared radiation transmittance, similar to the glass material used for the outer tube of the vacuum heat pipe, so that the heat loss is low. Second, the semi-circular structure can reduce the loss of reflected sunlight and increase the absorption rate of the receiver to sunlight.

Claims

1. A cylindrical mirror-tiled trough solar energy collector system, characterized in that: The parabolic trough solar energy collecting system comprises a mirror group and a receiver, the mirror group is composed of a plurality of strip cylindrical mirrors, the centers of the plurality of strip cylindrical mirrors constitute a parabola, and the normal vector of each strip cylindrical mirror center is consistent with the normal vector of the parabola at the installation position; and the receiver is installed at the focus of the parabola constituted by the centers of the plurality of strip cylindrical mirrors. The receiver is a tubular receiver or a strip-shaped cavity receiver or a flat plate receiver; and the tubular receiver is a vacuum heat collecting tube. When the receiver is the tubular receiver, the radius R is determined by the following formula: When the receiver is the strip-shaped cavity receiver or the flat plate receiver, the half width R of the receiver is determined by the following formula: Wherein, W is the half trough width of the parabolic trough solar energy collecting system, φ is the edge angle of the parabolic trough solar energy collecting system, σ is the Gaussian distribution variance of the reflected light intensity, and λ is the incidence angle of the sunlight in the parabolic trough solar energy collecting system.

2. The cylindrical mirror-tiled trough solar energy collector system of claim 1, wherein: The edge angle of the circular cylinder mirror strip with the center position on the parabolic surface The correlation is determined by the following equation: 。 3. The cylindrical mirror-tiled trough solar energy collector system of claim 1, wherein: When the receiver is the tubular receiver, the ratio of the width w of the strip cylindrical mirror to the radius r meets the following condition: When the receiver is the strip-shaped cavity receiver or the flat plate receiver, the ratio of the width w of the strip cylindrical mirror to the radius r meets the following condition: Wherein, σ is the Gaussian distribution variance of the reflected light intensity, and λ is the incidence angle of the sunlight in the parabolic trough solar energy collecting system.

4. The cylindrical mirror-tiled trough solar energy collector system according to any one of claims 1-3, characterized in that: The V-shaped groove type reflecting concentrator is composed of two inclined plane mirrors, the included angle θ between the reflecting surface and the vertical direction is 2-10 degrees, the entrance half-width of the V-shaped groove type reflecting concentrator is equal to the radius or half-width R of the receiver tube of the above-mentioned groove type solar energy collecting system, and the outlet width of the V-shaped groove type reflecting concentrator is equal to the width of the receiver tube of the groove type solar energy collecting system. Then, after the V-shaped groove type reflecting concentrator is added, the receiver tube radius or half-width is equal, and the following formula is used for calculation: 。 5. The cylindrical mirror-tiled trough solar power system of claim 4, wherein: When the receiver uses the strip-shaped cavity receiver, a cylindrical transparent glass cover plate is installed at the opening of the strip-shaped cavity receiver, and the concave surface is arranged in the cavity receiver.

6. A design method of a cylindrical mirror-tiled trough solar thermal power system using a pipe receiver, characterized in that: Specifically comprising the following steps: First, determine the width of the parabolic trough solar energy collecting system; Second, determine the edge angle φ of the parabolic trough solar energy collecting system, and the value range is 80-100 degrees; Third, calculate the focal length f of the parabolic trough according to the half trough width W and the edge angle φ, and the calculation formula is: f=W / [2*tan(φ / 2)] Fourthly, if the spliced cylindrical reflector is used, the radius r of each cylindrical reflector circle is determined first, and if the center position of a cylindrical reflector is installed on the edge angle φ of the parabolic surface P The calculation formula of r is as follows: Secondly, determine the width of the cylindrical mirror, which is determined by the following formula: ， At this time, the minimum value of r is used, that is, r=2f, and the maximum width w of the cylindrical mirror used for splicing is calculated; Fifth, determine the radius R of the tubular receiver, and the calculation formula is: R= 2W*σ / (sinφ* cosλ), Wherein, σ is the Gaussian distribution variance of the reflected sunlight, and the approximate calculation is: ， σ sun is the variance of the solar intensity Gaussian distribution, which is measured at the installation site; σ slopex and σ slopey are the variances of the Gaussian distribution of the slope errors of the x and y direction trough mirrors, respectively; σ tracking is the variance of the tracking error Gaussian distribution; σ disp is the variance of the system installation error Gaussian distribution; and σ specular is the variance of the mirror material error Gaussian distribution.

7. A design method of a cylindrical mirror-tiled trough solar thermal system using strip cavity receivers or flat plate receivers, characterized in that: Specifically comprising the following steps: First, determine the width of the parabolic trough solar energy collecting system; Second, determine the edge angle φ of the parabolic trough solar energy collecting system, and the value range is 40-50 degrees; Third, calculate the focal length f of the parabolic trough according to the half trough width W and the edge angle φ, and the calculation formula is: f=W / [2*tan(φ / 2)]; Fourth step, if using the splicing cylindrical surface mirror, first determine the radius r of each cylindrical surface mirror circle, if the installation center position of a cylindrical surface mirror is on the edge angle φ of the parabolic surface P The r calculation formula is: Secondly, determine the width of the cylindrical mirror, which is determined by the following formula: ， At this time, the minimum value of r is used, that is, r=2f, and the maximum width w of the cylindrical mirror used for splicing is calculated; Fifth, determine the half width R of the receiver, and the calculation formula is: R= 4*W*σ / [sin(2φ)*cos(λ)], Wherein, σ is the Gaussian distribution variance of the reflected sunlight, and the approximate calculation is: σ sun is the solar intensity Gaussian distribution variance, which uses the measured data at the installation site; σ slopex and σ slopey are the Gaussian distribution variances of the slope errors of the x and y direction trough mirrors, respectively; σ tracking is the Gaussian distribution variance of the tracking error; σ disp is the Gaussian distribution variance of the system installation error; and σ specular is the Gaussian distribution variance of the mirror material error.

8. The method of designing a cylindrical mirror-tiled solar energy collector system according to any one of claims 6 or 7, characterized in that: Also included is a V-groove design method for a V-groove type reflecting condenser, wherein a V-groove entrance width is equal to the receiver width R, and if the angle of inclination of the two reflecting mirrors of the V-groove is θ, the exit width is calculated by the following equation: θ takes 2-10 degrees, increases V-shaped groove type reflecting concentrator, edge angle φ takes value range of 20-60 degrees, when using strip-shaped cavity receiver, cavity half-width is ; when using tubular receiver as receiver, heat collecting tube radius is .

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