Ground diffuse reflection light supplementing method and system for flat single-axis tracker

Abstract

The application provides a ground diffuse reflection light supplementing and efficiency increasing method and system for a flat single-axis tracker, the method comprising: laying a reflecting material on the ground between the front and rear rows of trackers for supplementing light to the front and back surfaces of a bifacial photovoltaic module on the tracker; calculating real-time power generation of the tracker at any time T and annual total power generation; finding a target correction amount of a tracking rotation angle of the tracker at the time T for keeping the real-time power generation of the tracker at the time T maximum, and a target arrangement parameter of the reflecting material for maximizing the annual total power generation of the tracker; correcting the tracking rotation angle of the tracker according to the target correction amount at each time, and laying the reflecting material according to the target arrangement parameter. The application improves the power generation of a tracking system of a bifacial photovoltaic module by optimizing the tracking rotation angle of the tracker and the arrangement of the ground reflecting material.

Description

Technical Field

[0001] This invention relates to the field of solar photovoltaic power generation technology, specifically to a method and system for enhancing the efficiency of ground diffuse reflection supplementary lighting for a single-axis tracker. Background Technology

[0002] Bifacial photovoltaic modules with flat single-axis trackers are a widely used form of photovoltaic application with good solar energy utilization. In order to further improve the power generation efficiency of bifacial photovoltaic modules, in recent years, applications have emerged in which high albedo reflective materials are placed on the ground to supplement the lighting of bifacial photovoltaic modules. Through testing and verification, the ground albedo supplementary lighting method can increase the power generation of flat single-axis bifacial systems by 5% to 20%.

[0003] Currently, the most common application of this method is to lay reflective material flat on the ground below a conventional tracker. However, there is still a lack of research on how to set parameters such as whether the tracker needs solar tracking angle correction, and how to set the placement, shape, and range of the reflective material to maximize the utilization of solar resources. Summary of the Invention

[0004] One of the objectives of this invention is to provide a method and system for enhancing the efficiency of ground diffuse reflection supplementary lighting for flat single-axis trackers, which optimizes the existing method of supplementary lighting using ground-tiled reflective materials to improve the power generation gain of the system.

[0005] The technical solution provided by this invention is as follows:

[0006] A method for enhancing ground-based diffuse reflection lighting for a flat single-axis tracker, wherein the tracker includes a tracking bracket and a bifacial photovoltaic module mounted on the tracking bracket; a reflective material is laid on the ground between two rows of trackers to provide supplemental lighting to the front and back sides of the bifacial photovoltaic module of the tracker; and the method further includes:

[0007] Calculate the solar radiation energy density received at any location on the surface of the reflective material at any time T;

[0008] Calculate the total reflected energy that the tracker can collect at time T based on the solar radiation energy density;

[0009] Calculate the total direct energy that the tracker can receive at time T;

[0010] The real-time power generation of the tracker at time T is calculated based on the total direct energy and the total reflected energy.

[0011] The total annual power generation of the tracker is obtained based on the real-time power generation of the tracker at various times within the annual cycle;

[0012] Find the target correction amount of the tracking angle of the tracker at each time, wherein the target correction amount is the correction amount that makes the tracker maintain the maximum real-time power generation of the tracker at the corresponding time.

[0013] Find the combination of arrangement parameters of the reflective material that maximizes the total annual power generation, and use it as the target arrangement parameters; the combination of arrangement parameters includes the arrangement width, arrangement position and arrangement tilt angle of the reflective material.

[0014] The tracking angle of the tracker is corrected according to the target correction amount at each time moment, and the reflective material is arranged according to the target arrangement parameters.

[0015] In some embodiments, calculating the solar radiation energy density received at a location on the surface of the reflective material at time T includes:

[0016] Calculate the real-time solar irradiance of surfaces with different tilt angles at time T;

[0017] If the location on the surface of the reflective material is not blocked by the tracker, the solar radiation energy density received at that location is equal to the real-time solar irradiance.

[0018] If the location is blocked by the tracker, the solar radiation energy density received at the location is equal to the real-time solar irradiance multiplied by the scattering factor.

[0019] In some embodiments, calculating the total reflected energy that the tracker can collect at time T based on the solar radiation energy density includes:

[0020] Calculate the reflected energy density at any position on the surface of the reflective material captured by the tracker at time T;

[0021] The total reflected energy that the tracker can collect at time T is obtained by integrating the reflected energy density over the area of ​​the reflective material.

[0022] In some embodiments, calculating the reflected energy density at any location on the surface of the reflective material captured by the tracker at time T includes:

[0023] Calculate the solid angle of the reflective material surface at any position relative to the trackers on both sides;

[0024] The reflected energy density captured by the tracker at time T is calculated based on the solid angles on both sides using the Lambert diffuse reflection model.

[0025] In some embodiments, the reflected energy density ρ(x,y,T) reflected at any position on the surface of the reflective material captured by the tracker at time T is calculated according to the following formula:

[0026]

[0027] Where, η albedo Let Ω be the reflectivity of the reflective material, and let I(x,y,T) be the solar radiation energy density received at time T at the surface position (x,y,z(x,y)) of the reflective material. L1 (x,y,T),Ω L2 (x,y,T),Ω R1 (x,y,T) and Ω R2 (x, y, T) are the solid angles of the two rows of trackers on the left and right sides of the reflective material at time T relative to the positions (x, y, z(x, y)) on the surface of the reflective material.

[0028] In some embodiments, calculating the total direct energy that the tracker can receive at time T includes:

[0029] Calculate the solar radiation energy density received by the direct surface of the bifacial photovoltaic module of the tracker at time T;

[0030] The total direct solar energy received by the tracker at time T is obtained based on the solar radiation energy density and the effective area of ​​the bifacial photovoltaic module of the tracker.

[0031] In some embodiments, the real-time power generation P of the tracker at time T is calculated according to the following formula:

[0032] P(T)=η pe *(E_dir(T)+E_ref(T)*η bifa );

[0033] Where, η pe η is the photoelectric conversion efficiency of the bifacial photovoltaic module of the tracker. bifa E_dir is the bifacial factor of the bifacial photovoltaic module of the tracker, E_dir is the total direct energy, and E_ref is the total reflected energy.

[0034] In some embodiments, the arrangement parameter combination further includes the shape of the reflective material.

[0035] The present invention also provides a photovoltaic tracking system, including multiple trackers, each tracker including a tracking bracket and a bifacial photovoltaic module mounted on the tracking bracket. A reflective material is laid on the ground between two rows of trackers to supplement the front and back of the bifacial photovoltaic module of the tracker. The tracking angle of the tracker is corrected by the target correction amount obtained by the ground diffuse reflection supplementary lighting enhancement method for flat single-axis trackers described in any of the preceding claims, and the reflective material is arranged by the obtained target arrangement parameters.

[0036] The ground diffuse reflection supplementary lighting enhancement method and system for flat single-axis trackers provided by this invention can bring at least the following beneficial effects:

[0037] 1. This invention improves the annual power generation gain of the tracker by optimizing the tracking angle of the single-axis tracker and the arrangement of ground reflective materials.

[0038] 2. This invention, by combining the use of reflective materials, fully leverages the bifacial power generation capability of bifacial photovoltaic modules. Attached Figure Description

[0039] The preferred embodiments will be described below in a clear and easy-to-understand manner, with reference to the accompanying drawings, to further explain the above-mentioned characteristics, technical features, advantages, and implementation methods of a ground diffuse reflection supplementary lighting enhancement method and system for a flat single-axis tracker.

[0040] Figure 1 This is a flowchart of an embodiment of a ground diffuse reflection supplementary lighting enhancement method for a flat single-axis tracker according to the present invention;

[0041] Figure 2 This is a schematic diagram illustrating the ground diffuse reflection supplementary lighting principle of a single-axis tracker for bifacial photovoltaic modules;

[0042] Figure 3 This is a schematic diagram of the solid angle of a bifacial photovoltaic module with respect to the position of the reflective material surface relative to the tracker;

[0043] Figure 4 This is a flowchart of a specific application scenario embodiment of the present invention. Detailed Implementation

[0044] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the specific implementation methods of the present invention will be described below with reference to the accompanying drawings. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings and other implementation methods can be obtained based on these drawings without any creative effort.

[0045] To keep the drawings concise, only the parts relevant to the invention are shown schematically in each figure, and they do not represent the actual structure of the product. Furthermore, for ease of understanding, in some figures, components with the same structure or function are shown only schematically, or only one is labeled. In this document, "a" can mean not only "only one" but also "more than one".

[0046] like Figure 2As shown, taking a 3-row tracker as an example, the tracker includes a tracking bracket and bifacial photovoltaic modules or a string of modules composed of multiple bifacial photovoltaic modules mounted on it. The tracking bracket drives the bifacial photovoltaic modules to track the solar azimuth angle. The row spacing D of the trackers, the tracker chord length L, the module center height H, and reflective material are arranged on the ground between the trackers.

[0047] The design objective of this invention is to maximize the annual total power generation of a photovoltaic power station given the known geographical latitude and solar energy resources of the project site. The optimization targets include:

[0048] 1. The arrangement position of the reflective material between rows X0 ( Figure 2 X0 is defined as the distance between the center of the reflective material arrangement and the tracker column. Other definitions can also be used, as long as the position of the center of the reflective material arrangement can be determined.

[0049] 2. The width b of the reflective material arrangement;

[0050] 3. The tilt angle of the reflective material (i.e., the tilt angle between the reflective material and the ground) θ;

[0051] 4. Some embodiments also include the shape of the reflective material;

[0052] 5. Tracking angle α(T) of the tracker.

[0053] The coordinate system OXYZ is established below with the intersection of the central tracker column and the ground as the origin. The center of the reflective material arrangement coincides with the midpoint of the line connecting the adjacent trackers on the ground. Figure 2 Taking the photovoltaic tracking system shown as an example, the solution of the present invention will be described in detail.

[0054] In one embodiment of the present invention, such as Figure 1 As shown, a method for enhancing ground diffuse reflection illumination for a flat single-axis tracker includes:

[0055] Step S100 calculates the solar radiation energy density I(x,y,T) received at any time T at any position (x,y,z(x,y)) on the surface of the reflective material.

[0056] Specifically, step S100 includes:

[0057] Step S110 calculates the real-time solar irradiance GHI(θ,T) of different tilt angle surfaces at time T;

[0058] Step S120 determines whether the surface position (x,y,z(x,y)) of the reflective material is blocked by the double-sided photovoltaic module of the tracker;

[0059] If the position (x,y,z(x,y)) on the surface of the reflective material is not blocked, then the solar radiation energy density received at that position is equal to the real-time solar irradiance energy GHI(θ,T).

[0060] If the position (x,y,z(x,y)) on the surface of the reflective material is blocked in step S140, then the solar radiation energy density received at that position is equal to the real-time solar irradiance energy GHI(θ,T) multiplied by the scattering factor.

[0061] Different tilt angle surfaces refer to the reflective material surfaces that correspond to different arrangement tilt angles θ.

[0062] Real-time solar irradiance can be calculated as follows: Based on the latitude and time parameter T of the project site, calculate the solar altitude angle el at the corresponding time; obtain the direct solar radiation intensity DNI based on the solar altitude angle. Calculate the amount of direct solar radiation intensity DNI radiated onto surfaces with different tilt angles to obtain the real-time solar irradiance GHI(θ,T) at the corresponding time.

[0063] Step S200 calculates the reflected energy density ρ(x,y,T) captured by the tracker at time T, and calculates the total reflected energy E_ref(T) at time T based on the reflected energy density.

[0064] Specifically, step S200 includes:

[0065] Step S210 calculates the solid angle of the bifacial photovoltaic module with respect to the surface position (x,y,z(x,y)) of the reflective material with respect to the different rows of trackers on both sides;

[0066] Step S220 calculates the reflected energy density captured by the tracker at time T based on the obtained solid angle and the Lambert diffuse reflection model.

[0067] The solid angle Ω(x,y) represents the solid envelope angle formed by the overall outline of the bifacial photovoltaic module for any point (x,y) on the surface of the reflective material.

[0068] like Figure 3 As shown, taking the left-hand module as an example, the right-hand module is similar. The solid angle of the photovoltaic module relative to any surface position of the reflective material is calculated using the following formula:

[0069]

[0070] Where P is any position on the surface of the reflective material, P′ is any point on the bifacial photovoltaic module, PP′ is the line connecting point P and point P′, β is the angle between PP′ and the normal of the bifacial photovoltaic module, and A is the entire surface region of the photovoltaic module distribution surface.

[0071] Based on the above formula, the solid angle Ω(x,y,T) of each row of trackers relative to any position (x,y) on the ground can be obtained. Assuming that only the reflected energy received by the two rows of trackers on the left and right sides of the reflective material is considered, the reflected energy density ρ(x,y,T) at the position (x,y,z(x,y)) on the surface of the reflective material captured by the tracker at time T can be calculated using the following formula:

[0072]

[0073] Where, η albedo Let Ω be the reflectivity of the reflective material, I(x,y,T) be the solar radiation energy density received at time T at position (x,y,z(x,y)) on the surface of the reflective material, and Ω be the reflectivity of the reflective material. L1 (x,y,T),Ω L2 (x,y,T),Ω R1 (x,y,T) and Ω R2 (x,y,T) are the solid angles of the two rows of trackers on the left and right sides of the reflective material at time T relative to the positions (x,y,z(x,y)) on the surface of the reflective material.

[0074] By performing an area integral over the reflected energy density ρ(x,y,T) within the area of ​​the reflective material arrangement, the total reflected energy E_ref that the tracker can collect at time T is obtained.

[0075] Step S300 calculates the real-time power generation of the tracker at time T, and obtains the tracker's total annual power generation based on the real-time power generation.

[0076] Specifically, step S300 includes:

[0077] Step S310 calculates the total direct solar energy E_dir that the direct solar surface of the tracker's photovoltaic module can receive at time T.

[0078] The formula can be used to calculate: E_dir(T)=L*len*GHI(a,T);

[0079] Where L is the chord length of the tracker, len is the total length of the photovoltaic module string of the tracker, a is the tracking angle of the tracker at time T, and the tracking angle a also reflects the tilt angle of the photovoltaic module with respect to the ground at this time, which is also a; GHI(a,T) reflects the solar radiation energy density received by the direct surface of the photovoltaic module of the tracker at time T.

[0080] One embodiment includes:

[0081] Calculate the solar radiation energy density GHI(a,T) received by the direct surface of the bifacial photovoltaic module of the tracker at time T;

[0082] Based on the solar radiation energy density and the effective area of ​​the tracker's bifacial photovoltaic module (=L*len), the total direct solar energy received by the tracker at time T is obtained.

[0083] Step S320 calculates the real-time power generation P of the tracker at time T based on the total direct energy and total reflected energy, specifically according to the following formula:

[0084] P(T)=η pe *(E_dir(T)+E_ref(T)*η bifa );

[0085] Where E_dir is the total direct energy, E_ref is the total reflected energy, and η pe η represents the photoelectric conversion efficiency of a photovoltaic module. bifa This refers to the bifacial factor of a photovoltaic module.

[0086] Step S330: The annual total power generation of the tracker is obtained based on the real-time power generation of the tracker at each moment within the annual cycle.

[0087] For example, according to the formula: E_annual=Σ(P(T)*ΔT).

[0088] Step S400: Find the target correction amount of the tracking angle of the tracker that maximizes the real-time power generation at time T.

[0089] An iterative method is adopted to iterate the correction amount of the tracking angle α, and find the correction amount that maximizes the real-time power generation P at time T. In this way, the target correction amount of the tracking angle of the tracker at each time can be obtained.

[0090] Step S500: Find the combination of arrangement parameters of the reflective material that maximizes the total annual power generation, and use it as the target arrangement parameter.

[0091] By adjusting the arrangement parameters of the reflective materials, the arrangement parameter combination that maximizes the total annual power generation can be found.

[0092] Step S600 corrects the tracking angle of the tracker according to the target correction amount at each time moment, and arranges the reflective material according to the target arrangement parameters.

[0093] In one embodiment, step S500 further optimizes the shape of the reflective material z = f(x). That is, the arrangement parameter combination of the reflective material also includes the shape of the reflective material. An iterative method is used to optimize the shape to obtain the parameter combination that maximizes the system's total annual power generation.

[0094] In this embodiment, the annual power generation gain of the tracker is improved by optimizing the tracking angle of the single-axis tracker and the arrangement of ground reflective materials.

[0095] In one embodiment of the present invention, a photovoltaic tracking system employs flat single-axis tracking technology and includes multiple trackers. Each tracker includes a tracking bracket and a bifacial photovoltaic module mounted on the tracking bracket. Reflective material is arranged on the ground between two rows of trackers to provide supplemental lighting to the front and back of the bifacial photovoltaic modules of the trackers. The ground diffuse reflection supplemental lighting enhancement method for flat single-axis trackers described in the foregoing embodiment is used to correct the tracking angle and to arrange the reflective material.

[0096] In this embodiment, the reflective material is arranged using the target arrangement parameters (position / range / shape, etc.) obtained in the previous embodiment, thereby optimizing the tracking angle of the tracker and improving the power generation of the photovoltaic tracking system.

[0097] This invention also provides a specific application scenario embodiment, applying the aforementioned ground diffuse reflection supplementary lighting enhancement method for flat single-axis trackers to a photovoltaic tracking system. This system employs flat single-axis tracking technology and includes multiple trackers. Each tracker includes a tracking bracket and a string of modules consisting of multiple bifacial photovoltaic modules mounted on it. The tracking bracket tracks the solar azimuth angle, driving the module string to track the solar azimuth angle. Reflective material is laid on the ground between two rows of trackers to supplement lighting on the front and back sides of the bifacial photovoltaic modules.

[0098] The principle of ground diffuse reflection supplementary lighting used in flat single-axis trackers is as follows: Figure 2 As shown. To improve the tracker's annual power generation, the tracking angle of the tracker is corrected, and the arrangement parameters of the reflective material are optimized, according to... Figure 4 The process shown obtains the target correction amount for the tracker's tracking angle and the target arrangement parameters of the reflective material, as detailed below:

[0099] 1. Set the basic parameters of the project location and tracker.

[0100] Including the latitude of the project site Solar irradiance resource GHI and its time variation GHI(T), where T is a time parameter, tracker row spacing D, tracker chord length L, total length of tracker module string len, module center height H, etc.

[0101] 2. Initialize the layout parameters of the ground reflective material

[0102] The layout parameters include the layout width b, the layout position X0, and the layout tilt angle θ.

[0103] 3. Set the initial value of the correction amount for the tracking angle α(T) of the tracker.

[0104] Introduce time parameters to calculate the solar altitude angle el(T), azimuth angle az(T), and tracker rotation angle α(T) at any time T, and set the initial correction Δα(T) = 0.

[0105] 4. Calculate the solar radiation energy density I(x,y,T) received at any position (x,y,z(x,y)) on the surface of the reflective material at time T.

[0106] 5. Calculate the reflected energy density ρ(x,y,T) and total reflected energy E_ref(T) captured by the tracker.

[0107] Based on the Lambert diffuse reflection model, the solar energy density ρ(x,y,T) and total reflected energy E_ref(T) reflected from any location on the ground are calculated in real time by the photovoltaic module of the tracker.

[0108] 6. Calculate the real-time power generation P(T) and the annual total power generation E_annual of the tracker.

[0109] Annual total power generation E_annual=Σ(P(T)ΔT)

[0110] 7. Optimize the tracking angle α(T) by iterating the correction value to find the correction amount Δα(T) that makes the real-time system power generation P(T) keep the maximum.

[0111] 8. Change the arrangement parameters of the reflective material, including the arrangement width, arrangement position, and arrangement tilt angle, to find the parameter combination that maximizes the system's total annual power generation E_annual.

[0112] 9. Furthermore, for any reflective material shape (z = f(x)), an iterative method is also used to optimize the shape in order to obtain the parameter combination that maximizes the system's annual total power generation E_annual.

[0113] According to calculations, after optimization using the method described in this paper, the system's power generation can be increased by up to 10% compared to the traditional method of laying reflective material on the ground below the tracker, and by 30% to 40% compared to the traditional tracker system.

[0114] It should be noted that the above embodiments can be freely combined as needed. The above description is only a preferred embodiment of the present invention. It should be pointed out that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for enhancing the effect of ground diffuse reflection supplementary lighting for a flat single-axis tracker, the tracker comprising a tracking bracket and a double-sided photovoltaic module mounted on the tracking bracket, wherein a reflective material is laid on the ground between two rows of trackers to supplement the front and back sides of the double-sided photovoltaic module of the tracker, characterized in that, include: Calculate the solar radiation energy density received at any location on the surface of the reflective material at any time T; Calculate the total reflected energy that the tracker can collect at time T based on the solar radiation energy density; Calculate the total direct energy that the tracker can receive at time T; The real-time power generation of the tracker at time T is calculated based on the total direct energy and the total reflected energy. The total annual power generation of the tracker is obtained based on the real-time power generation of the tracker at various times within the annual cycle; Find the target correction amount of the tracking angle of the tracker at each time, wherein the target correction amount is the correction amount that makes the tracker maintain the maximum real-time power generation of the tracker at the corresponding time. Find the combination of arrangement parameters of the reflective material that maximizes the total annual power generation, and use it as the target arrangement parameters; the combination of arrangement parameters includes the arrangement width, arrangement position and arrangement tilt angle of the reflective material. The tracking angle of the tracker is corrected according to the target correction amount at each time moment, and the reflective material is arranged according to the target arrangement parameters; The calculation of the total reflected energy that the tracker can collect at time T based on the solar radiation energy density includes: Calculate the reflected energy density at any position on the surface of the reflective material captured by the tracker at time T; The total reflected energy that the tracker can collect at time T is obtained by integrating the reflected energy density over the area of ​​the reflected material. The calculation of the reflected energy density at any position on the surface of the reflective material captured by the tracker at time T includes: Calculate the solid angle of the reflective material surface at any position relative to the trackers on both sides; The reflected energy density at any position on the surface of the reflective material captured by the tracker at time T is calculated using the following formula. : ； in, The reflectivity of the reflective material is... Position of the reflective material surface The solar radiation energy density received at time T , , and The positions of the two rows of trackers on each side of the reflective material at time T relative to the surface of the reflective material are respectively: The solid angle.

2. The method for enhancing ground diffuse reflection illumination for a flat single-axis tracker according to claim 1, characterized in that, The calculation of the solar radiation energy density received at a location on the surface of a reflective material at time T includes: Calculate the real-time solar irradiance of surfaces with different tilt angles at time T; If the location on the surface of the reflective material is not blocked by the tracker, the solar radiation energy density received at that location is equal to the real-time solar irradiance. If the location is blocked by the tracker, the solar radiation energy density received at the location is equal to the real-time solar irradiance multiplied by the scattering factor.

3. The method for enhancing ground diffuse reflection illumination for a single-axis tracker according to claim 1, characterized in that, The calculation of the total direct energy that the tracker can receive at time T includes: Calculate the solar radiation energy density received by the direct surface of the bifacial photovoltaic module of the tracker at time T; The total direct solar energy received by the tracker at time T is obtained based on the solar radiation energy density and the effective area of ​​the bifacial photovoltaic module of the tracker.

4. The method for enhancing ground diffuse reflection illumination for a single-axis tracker according to claim 1, characterized in that, The real-time power generation P of the tracker at time T is calculated using the following formula: ； in, The photoelectric conversion efficiency of the bifacial photovoltaic module of the tracker is given. E_dir is the bifacial factor of the bifacial photovoltaic module of the tracker, E_dir is the total direct energy, and E_ref is the total reflected energy.

5. The method for enhancing ground diffuse reflection illumination for a single-axis tracker according to claim 1, characterized in that, The arrangement parameter combination also includes the shape of the reflective material.

6. A photovoltaic tracking system comprising a plurality of trackers, each tracker including a tracking bracket and a bifacial photovoltaic module mounted on the tracking bracket, wherein a reflective material is laid on the ground between two rows of trackers for supplemental lighting on the front and back sides of the bifacial photovoltaic modules of the trackers, characterized in that, The tracking angle of the tracker is corrected by the ground diffuse reflection supplementary lighting enhancement method for a flat single-axis tracker as described in any one of claims 1-5, and the reflective material is arranged accordingly.

Images