Method for calculating backside irradiance of bifacial photovoltaic modules and method for calculating bifacial gain

Abstract

The application discloses a kind of back surface irradiation calculation method and double-sided gain calculation method of bifacial photovoltaic module.The back surface irradiation calculation method of bifacial photovoltaic module includes: determining the ground reflection interval of target component;Select n reference components;Wherein, n≥2, n is integer;Reference component is arranged on both sides of target component;According to the angle between the connecting line of ground selection point and the first reference point of reference component and the connecting line of ground selection point and the second reference point of reference component, and the angle between the connecting line of ground selection point and the first reference point of target component and the connecting line of ground selection point and the second reference point of target component, the view angle coefficient of target component in ground reflection interval is calculated;Wherein, ground selection point is located in ground reflection interval;According to view angle coefficient, the back surface irradiation of target component is calculated.The embodiment of the application can realize more accurate calculation to the back surface irradiation of bifacial photovoltaic module, and then realize accurate evaluation to the double-sided gain of component.

Description

Technical Field

[0001] This invention relates to the field of photovoltaic technology, and in particular to a method for calculating the back irradiation of a bifacial photovoltaic module and a method for calculating bifacial gain. Background Technology

[0002] Bifacial photovoltaic (PV) modules, due to their ability to generate electricity from the back side, offer a significant power generation advantage over conventional single-sided modules, leading to their increasing market share. The output power of the back side of a bifacial PV module is primarily influenced by the irradiance it receives. This irradiance is affected by multiple factors, including installation conditions and the environment, making modeling complex. Therefore, accurately calculating the back-side irradiance of bifacial PV modules, and consequently, their output power, is crucial for accurately assessing their power generation gain and related investment returns. Current technology typically uses the length of a line connecting any point on the back side of the module to any point on the ground, along with the angle between this line and the normals of the two planes, to obtain the viewing angle coefficient of the back side of the module relative to the ground through area integration, thus yielding the back-side irradiance. However, this method only considers the state of the target module itself, neglecting other factors affecting irradiance, making it difficult to guarantee the accuracy of the back-side irradiance calculation. Summary of the Invention

[0003] This invention provides a method for calculating the back irradiance of a bifacial photovoltaic module and a method for calculating bifacial gain, so as to achieve a more accurate calculation of the back irradiance of the bifacial photovoltaic module, thereby achieving an accurate evaluation of the bifacial gain of the module, which is beneficial to optimizing the design scheme of the bifacial photovoltaic system.

[0004] In a first aspect, embodiments of the present invention provide a method for calculating the back-side irradiance of a bifacial photovoltaic module, including:

[0005] Determine the ground reflection range of the target component;

[0006] Select n reference components; where n≥2, and n is an integer; the reference components are arranged on both sides of the target component;

[0007] The viewing angle coefficient of the target component in the ground reflection range is calculated based on the angle between the line connecting the ground selection point and the first reference point of the reference component and the line connecting the ground selection point and the second reference point of the reference component, and the angle between the line connecting the ground selection point and the first reference point of the target component and the line connecting the ground selection point and the second reference point of the target component; wherein, the ground selection point is located in the ground reflection range;

[0008] The back irradiance of the target component is calculated based on the viewing angle coefficient.

[0009] Optionally, calculating the viewing angle coefficient of the target component in the ground reflection range includes:

[0010] The ground reflection interval is divided into at least two ground reflection regions;

[0011] Calculate the viewing angle coefficient of the target component in each of the ground reflection areas.

[0012] Optionally, the ground reflection interval is divided into at least two ground reflection regions, including:

[0013] Depending on whether the ground is directly exposed to sunlight, the ground reflection zone is divided into at least one area directly exposed to sunlight and at least one area blocked by a component.

[0014] Optionally, calculating the viewing angle coefficient of the target component in each of the ground reflection areas includes:

[0015] The back of the target component is divided into at least two battery sections; and the back of the reference component is divided into at least two battery sections in the same manner as the target component.

[0016] The viewing angle coefficient of each battery portion of the target component in each ground reflection area is calculated based on the angle between the line connecting the selected point on the ground in the region to the lowest point of the battery portion of the target component and the line connecting the selected point on the ground in the region to the highest point of the battery portion of the target component, and the angle between the line connecting the selected point on the ground in the region to the lowest point of the corresponding battery portion of the reference component and the line connecting the selected point on the ground in the region to the highest point of the corresponding battery portion of the reference component.

[0017] Optionally, each of the ground reflection zones includes at least two selected ground points.

[0018] Calculating the viewing angle coefficient of each battery portion of the target component in each of the ground reflection areas includes:

[0019] Calculate the viewing angle coefficient of the battery portion of the target component at each selected point on the ground in the region;

[0020] The average value of all viewing angle coefficients of a certain battery portion of the target component in the same ground reflection area is calculated as the viewing angle coefficient of the battery portion of the target component in the ground reflection area.

[0021] Optionally, the viewing angle coefficient of the battery portion of the target component at a selected point on the ground in the area is calculated according to the following formula:

[0022]

[0023] Among them, VF ik-mβ represents the viewing angle coefficient of the m-th battery portion of the target component at the k-th selected point in the i-th ground region. 1-ik-m β represents the angle between the ground and the line connecting the k-th selected point in the i-th ground region and the lowest point of the m-th battery section of the first reference component. 2-ik-m b represents the angle between the ground and the line connecting the k-th selected point in the i-th ground region and the lowest point of the m-th battery section of the last reference component. m Let represent the width of the m-th battery section of the target component, δ represent the mounting angle of the target component, and h represent the width of the m-th battery section of the target component. m γ represents the height of the lowest point of the m-th battery section of the target component from the ground, s represents the spacing between adjacent components, and γ ik-m Let α be the angle between the line connecting the k-th selected point in the i-th ground region to the lowest point of the m-th battery section of the target component, and the line connecting the k-th selected point in the i-th ground region to the highest point of the m-th battery section of the target component. j-ik-m The angle between the line connecting the k-th selected point in the i-th ground region to the lowest point of the m-th battery section of the j-th reference component and the line connecting the k-th selected point in the i-th ground region to the highest point of the m-th battery section of the j-th reference component.

[0024] Optionally, calculating the rear irradiance of the target component based on the viewing angle coefficient includes:

[0025] The scattering intensity distribution of the target component's battery portion in the ground reflection area is calculated based on the viewing angle coefficient of the battery portion of the target component in the ground reflection area;

[0026] The irradiance of each battery section of the target component is calculated based on the scattering intensity distribution of the target component's battery section in the ground reflection area.

[0027] The back irradiation of the target component is calculated based on the connection method of the batteries in the target component and the irradiation of each battery part of the target component.

[0028] Optionally, if the target component is a split-parallel component, the back irradiation of the target component is the sum of the back irradiations of each parallel part; wherein, the back irradiation of the parallel part is the irradiation of the battery part with the smallest irradiation among the parallel parts.

[0029] If the target component is a series component, then the back irradiation of the target component is the irradiation of the battery portion with the least irradiation.

[0030] Optionally, determining the ground reflection range of the target component includes:

[0031] The ground reflection range is determined by the intersection of the extension line of the slope of the target component with the ground, and the intersection of the extension line of the line connecting the highest point of the target component and the lowest point of the reflection range determination component with the ground; wherein, the reflection range determination component is the reference component that is adjacent to the target component and is blocked by the target component when the solar incident angle is less than the incident angle threshold.

[0032] Secondly, embodiments of the present invention also provide a method for calculating the bifacial gain of a bifacial photovoltaic module, comprising:

[0033] Calculate the frontal irradiance of the target component;

[0034] The back irradiance of the target module is calculated using the calculation method for the back irradiance of a bifacial photovoltaic module provided in any embodiment of the present invention;

[0035] The bifacial gain of the target component is calculated based on the front irradiance, the back irradiance, and the bifaciality of the target component.

[0036] The method for calculating the back irradiance of bifacial photovoltaic modules provided in this invention includes several influencing factors when calculating the viewing angle coefficient. These factors include the angles formed by the lines connecting different reference points of the target module to the ground, which are directly or indirectly related to the installation height and angle of the target module; and the angles formed by the lines connecting different reference points of each reference module to the ground, which are directly or indirectly related to factors such as module spacing, module installation height, and module installation angle. This means that the calculation of the viewing angle coefficient considers both the installation conditions of the target module itself and the relationship between the reference modules and the target module. Compared to existing technologies, this invention incorporates more influencing factors into the calculation of the viewing angle coefficient, effectively improving its accuracy. Since the viewing angle coefficient is a crucial parameter for calculating back irradiance, its accuracy directly determines the accuracy of the back irradiance calculation. Therefore, compared to existing technologies, this invention can achieve a more accurate calculation of the back irradiance of bifacial photovoltaic modules, thereby enabling accurate evaluation of the bifacial gain of the module and facilitating the optimization of the bifacial photovoltaic system design. Attached Figure Description

[0037] Figure 1 This is a flowchart illustrating a method for calculating the back-side irradiation of a bifacial photovoltaic module according to an embodiment of the present invention;

[0038] Figure 2 This is a schematic diagram of a bifacial photovoltaic module arrangement provided in an embodiment of the present invention;

[0039] Figure 3This is a flowchart illustrating another method for calculating the back irradiation of a bifacial photovoltaic module provided in an embodiment of the present invention;

[0040] Figure 4 This is a schematic diagram illustrating the division of ground reflection zones according to an embodiment of the present invention;

[0041] Figure 5 This is a schematic diagram showing the division of the battery portion of a target component and a reference component according to an embodiment of the present invention;

[0042] Figure 6 This is a schematic diagram of the distribution of scattering intensity and viewing angle coefficient provided in an embodiment of the present invention;

[0043] Figure 7 This is a schematic diagram of the back irradiation distribution of a target component provided in an embodiment of the present invention;

[0044] Figure 8 This is a schematic diagram of the installation position of a radiometer provided in an embodiment of the present invention;

[0045] Figure 9 This is a schematic diagram comparing the theoretically calculated irradiance and the measured irradiance of a battery component, provided by an embodiment of the present invention.

[0046] Figure 10 This is another schematic diagram comparing the theoretically calculated irradiance and the measured irradiance of a battery component provided in this embodiment of the invention;

[0047] Figure 11 This is another schematic diagram comparing the theoretically calculated irradiance and the measured irradiance of a battery component provided in this embodiment of the invention;

[0048] Figure 12 This is a flowchart illustrating a method for calculating the bifacial gain of a bifacial photovoltaic module according to an embodiment of the present invention.

[0049] Figure 13 This is a schematic diagram comparing the theoretical two-sided gain and the measured two-sided gain provided by an embodiment of the present invention. Detailed Implementation

[0050] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the present invention, and not all of the structures.

[0051] This invention provides a method for calculating the back irradiance of bifacial photovoltaic modules, applicable to various installation conditions, installation methods, and environments. Figure 1This is a flowchart illustrating a method for calculating the back-side irradiation of a bifacial photovoltaic module according to an embodiment of the present invention. See also... Figure 1 The method for calculating the back-side irradiance of this bifacial photovoltaic module includes the following steps:

[0052] S110. Determine the ground reflection range of the target component.

[0053] Among them, bifacial photovoltaic modules are mostly arranged in arrays. Figure 2 This is a schematic diagram of a bifacial photovoltaic module arrangement provided in an embodiment of the present invention. See also... Figure 2 For example, a bifacial photovoltaic module refers to an inclined section that can receive sunlight and convert it into electrical energy, supported by a support rod installed on the ground. Multiple bifacial photovoltaic modules arranged parallel to the plane of the paper are called a row of modules, and multiple bifacial photovoltaic modules arranged perpendicular to the plane of the paper are called a series of modules. The spacing s between modules in each series is equal; at any given time, the installation angle δ of each module is the same. To simplify the calculation, the influence of the uneven irradiance on the back side of the modules in the series direction can be ignored, and it can be assumed that the back irradiance magnitude and distribution pattern of all modules in each series are the same. Therefore, a coordinate system can be established based on a plane perpendicular to the series direction to calculate the back irradiance of the target module 2. In other words, the target module 2 in this embodiment can be a series of modules or at least one module in a series of modules. For example, the ground reflection range 1 is determined based on the ground area that can reflect light to the target module 2.

[0054] S120. Select n reference components; where n≥2, and n is an integer; the reference components are arranged on both sides of the target component.

[0055] The more reference components (n) there are, the more accurate the calculated viewing angle coefficient will be; however, the more complex the calculation process will also be. In practical applications, the number of reference components (n) can be selected according to requirements and is not limited here. For example, n can be set between 2 and 6. Furthermore, the number of reference components on both sides of the target component 2 can be the same or different, and this is also not limited here. It should be noted that the reference components and the target component 2 have the same structure and installation method, and are both part of the component array. For ease of explanation, the component to be calculated for back irradiation is called the target component, and the component related to the back irradiation calculation of the target component is called the reference component.

[0056] S130. Calculate the viewing angle coefficient of the target component in the ground reflection range based on the angle between the line connecting the ground selection point and the first reference point of the reference component and the line connecting the ground selection point and the second reference point of the reference component, and the angle between the line connecting the ground selection point and the first reference point of the target component and the line connecting the ground selection point and the second reference point of the target component; wherein, the ground selection point is located in the ground reflection range.

[0057] The selection rules for the first reference point of the reference component and the first reference point of the target component 2 are the same; similarly, the selection rules for the second reference point of the reference component and the second reference point of the target component 2 are also the same. The following section combines... Figure 2 Taking the first reference point as the lowest point of the component and the second reference point as the highest point of the component as an example, the calculation process of the viewing angle coefficient of the target component 2 in the ground reflection range 1 is explained in detail.

[0058] See Figure 2 For example, n=4, reference components 3_1 and 3_2 are located to the left (front) of target component 2; reference components 3_3 and 3_4 are located to the right (rear) of target component 2. Ground reflection interval 1 is the interval defined by the intersection point N1 of the extended line of the slope of target component 2 with the ground and the intersection point N2 of the extended line connecting the highest point of target component 2 and the lowest point of reference component 3_3 with the ground; ground selection point 110 is any point within ground reflection interval 1. Then, the viewing angle coefficient VF of target component 2 at ground selection point 110 is calculated according to the following formula:

[0059]

[0060] Where β1 represents the angle between the line connecting the ground selection point 110 and the lowest point of the reference component 3_1 and the ground, β2 represents the angle between the line connecting the ground selection point 110 and the lowest point of the reference component 3_4 and the ground, d represents the width of the target component 2, δ represents the installation angle of the target component, h represents the height of the lowest point of the target component 2 from the ground, s represents the spacing between adjacent components, and α j γ represents the angle between the line connecting the ground selection point 110 and the lowest point of the reference component 3_j and the line connecting the ground selection point 110 and the highest point of the reference component 3_j, and γ represents the angle between the line connecting the ground selection point 110 and the lowest point of the target component 2 and the line connecting the ground selection point 110 and the highest point of the target component 2. Formula (1) can be used as a calculation model for the viewing angle coefficient of the target component 2. When the installation height, installation angle, and selection rules of the reference component change, the parameters in formula (1) can be adjusted accordingly to accurately calculate the current viewing angle coefficient. Compared with the existing technology that uses area integral to calculate the viewing angle coefficient, this model can effectively improve the simplicity and feasibility of the viewing angle coefficient calculation.

[0061] For example, the viewing angle coefficient of the target component 2 at any ground selection point 110 can be used as the viewing angle coefficient of the target component 2 in the ground reflection range 1; or, multiple ground selection points 110 can be selected, and the average value of the viewing angle coefficients of the target component 2 at all ground selection points 110 can be used as the viewing angle coefficient of the target component 2 in the ground reflection range 1.

[0062] S140. Calculate the back irradiance of the target component based on the viewing angle coefficient.

[0063] Specifically, this step may involve: calculating the scattering intensity distribution of the target component's back side in the ground reflection zone based on the viewing angle coefficient of the target component in the ground reflection zone; and calculating the back-side irradiance of the target component based on the scattering intensity distribution. The back-side irradiance of the target component may include airborne scattering irradiance, horizontal scattering irradiance, and horizontal direct irradiance.

[0064] The method for calculating the back irradiance of bifacial photovoltaic modules provided in this invention includes several influencing factors when calculating the viewing angle coefficient. These factors include the angles formed by the lines connecting different reference points of the target module to the ground, which are directly or indirectly related to the installation height and angle of the target module; and the angles formed by the lines connecting different reference points of each reference module to the ground, which are directly or indirectly related to factors such as module spacing, module installation height, and module installation angle. This means that the calculation of the viewing angle coefficient considers both the installation conditions of the target module itself and the relationship between the reference modules and the target module. Compared to existing technologies, this invention incorporates more influencing factors into the calculation of the viewing angle coefficient, effectively improving its accuracy. Since the viewing angle coefficient is a crucial parameter for calculating back irradiance, its accuracy directly determines the accuracy of the back irradiance calculation. Therefore, compared to existing technologies, this invention can achieve a more accurate calculation of the back irradiance of bifacial photovoltaic modules, thereby enabling accurate evaluation of the bifacial gain of the module and facilitating the optimization of the bifacial photovoltaic system design.

[0065] Based on the above implementation method, optionally, the ground reflection zone can be divided into regions, and the viewing angle coefficient of the target component in each ground reflection region can be calculated, which can improve the accuracy of the viewing angle coefficient calculation, thereby improving the accuracy of the back irradiance calculation.

[0066] Furthermore, the back surface of the target component can be divided into regions, and the viewing angle coefficients of different regions on the back surface of the target component in different ground reflection areas can be calculated one by one. This is equivalent to fully considering the irradiance distribution of different regions within the same target component, further improving the accuracy of back surface irradiance calculations. The following section combines... Figure 3 The calculation method is described in detail, but this is not intended to limit the invention.

[0067] Figure 3 This is a flowchart illustrating another method for calculating the back-side irradiation of a bifacial photovoltaic module provided in an embodiment of the present invention. See also... Figure 3 The calculation method for the back-side irradiance of this bifacial photovoltaic module includes:

[0068] S210. Determine the ground reflection range of the target component.

[0069] See also Figure 2 For example, the ground reflection zone 1 can be divided according to the following rules: the ground reflection zone 1 is determined by the intersection of the extension line of the slope of the target component 2 with the ground, and the intersection of the extension line of the line connecting the highest point of the target component 2 and the lowest point of the reflection zone determining component 5 with the ground; wherein, the reflection zone determining component 5 is a reference component adjacent to the target component 2, which is blocked by the target component 2 when the solar incident angle θ is less than the incident angle threshold, i.e., reference component 3_3. That is to say, the reflection zone determining component 5 is a reference component located behind (to the right) the target component 2 and adjacent to the target component 2.

[0070] S220. Divide the ground reflection zone into at least two ground reflection areas.

[0071] For example, the ground reflection zone 1 can be divided into at least one directly exposed area and at least one component-shaded area, depending on whether the ground is directly exposed to the sun. Figure 4 This is a schematic diagram illustrating the division of ground reflection zones according to an embodiment of the present invention. See also... Figure 4 For example, the dashed line represents the incident sunlight. In this embodiment, the ground reflection interval 1 is divided into 5 ground reflection areas according to whether the ground is directly exposed to sunlight. Among them, ground reflection areas 10_1, 10_3 and 10_5 are all component shading areas; ground reflection areas 10_2 and 10_4 are all areas directly exposed to sunlight.

[0072] S230. Select n reference components; where n≥2, and n is an integer; the reference components are arranged on both sides of the target component.

[0073] S240, Divide the back side of the target component into at least two battery sections; and divide the back side of the reference component into at least two battery sections in the same way as the target component.

[0074] Figure 5 This is a schematic diagram illustrating the division of the battery portion of a target component and a reference component according to an embodiment of the present invention. Figure 5 As shown, the back surfaces of target component 2 and reference component 3 are divided in the same way, for example, both are divided into q battery sections. The width of each battery section can be the same or different. For example, when the junction box partially obscures the back surface of target component 2, this portion is not included in the battery section division.

[0075] S250. Based on the angle between the line connecting the selected point on the ground in the region to the lowest point of the battery portion of the target component and the line connecting the selected point on the ground in the region to the highest point of the battery portion of the target component, and the angle between the line connecting the selected point on the ground in the region to the lowest point of the corresponding battery portion of the reference component and the line connecting the selected point on the ground in the region to the highest point of the corresponding battery portion of the reference component, calculate the viewing angle coefficient of each battery portion of the target component in each ground reflection area.

[0076] When only one ground selection point 111 is selected in the ground reflection area, the viewing angle coefficient of the battery part of the target component at that point can be used as the viewing angle coefficient of the battery part in the corresponding ground reflection area.

[0077] When two or more ground selection points 111 are selected in the ground reflection area, calculating the viewing angle coefficient of each battery component of the target component 2 in each ground reflection area may specifically include the following steps: calculating the viewing angle coefficient of the battery component of the target component 2 at each ground selection point 111; calculating the average of all viewing angle coefficients of a certain battery component of the target component 2 in the same ground reflection area, as the viewing angle coefficient of the battery component of the target component 2 in the ground reflection area. Optionally, ground selection points can be uniformly selected in each ground reflection area at a set interval to simplify the calculation logic and facilitate the implementation of this calculation method.

[0078] For example, the viewing angle coefficient of the battery portion of target component 2 at point 111 on the ground in the region can be calculated according to the following formula:

[0079]

[0080] Among them, VF ik-m β represents the viewing angle coefficient of the m-th battery portion of the target component at the k-th ground selection point in the i-th ground region. 1-ik-m β represents the angle between the ground and the line connecting the k-th selected point in the i-th ground region and the lowest point of the m-th battery section of the first reference component. 2-ik-m Let b be the angle between the line connecting the k-th selected point in the i-th ground region and the lowest point of the m-th battery section of the last reference component, and the ground. m δ represents the width of the m-th battery section of the target component, δ represents the mounting angle of the target component, and h m Let α represent the height of the lowest point of the m-th battery section of the target component from the ground, s represent the spacing between adjacent components, and α represent the distance between them. j-ik-mγ represents the angle between the line connecting the k-th selected ground point in the i-th ground region to the lowest point of the m-th battery section of the j-th reference component, and the line connecting the k-th selected ground point in the i-th ground region to the highest point of the m-th battery section of the j-th reference component. ik-m The angle between the line connecting the k-th selected point in the i-th ground region to the lowest point of the m-th battery section of the target component and the line connecting the k-th selected point in the i-th ground region to the highest point of the m-th battery section of the target component.

[0081] S260. Calculate the scattering intensity distribution of the target component's battery portion in the ground reflection area based on the viewing angle coefficient of the battery portion of the target component in the ground reflection area.

[0082] The scattering intensity distribution is calculated using the following formula:

[0083] μ i-m =1-VF i-m (3)

[0084] Where, μ i-m VF represents the scattering intensity distribution of the i-th ground reflection region on the m-th battery section of the target component. i-m The viewing angle coefficient of the m-th battery portion of the target component in the i-th ground reflection region.

[0085] S270. Calculate the irradiance of each battery section of the target component based on the scattering intensity distribution of the target component's battery section in the ground reflection area.

[0086] The irradiation of the target module 2's battery portion by the direct sunlight area includes: air-scattered irradiation, horizontal scattered irradiation, and horizontal direct irradiation; the irradiation of the target module's battery portion by the module's shading area includes: air-scattered irradiation and horizontal scattered irradiation.

[0087] S280. Calculate the back irradiation of the target component based on the connection method of the batteries in the target component and the irradiation of each battery part of the target component.

[0088] If the target module is a half-parallel module, then the back irradiance of the target module is the sum of the back irradiances of each parallel section; wherein, the back irradiance of the parallel section is the irradiance of the battery section with the minimum irradiance among the parallel sections. If the target module is a series module, then the back irradiance of the target module is the irradiance of the battery section with the minimum irradiance.

[0089] This embodiment, based on practical considerations, provides a feasible method for calculating the back-side irradiance of bifacial photovoltaic modules through steps S210-S280. This method eliminates the need for integral calculation of the viewing angle coefficient, making back-side irradiance calculation more convenient. Furthermore, it fully considers the distribution of back-side irradiance during the calculation, thereby accurately calculating the actual equivalent irradiance on the back of the target module. This allows for accurate evaluation of the back-side gain of the bifacial photovoltaic module, optimization of the bifacial photovoltaic system design, and accurate assessment of the bifacial gain of the bifacial photovoltaic system.

[0090] Based on the above embodiments, optionally, the range of the ground reflection interval can be limited by restricting the number of ground reflection areas, thereby simplifying the calculation. For example, when the component installation angle δ is small, the left endpoint of the ground reflection interval defined by the intersection of the extended line of the inclined plane of the target component 2 and the ground may be too far from the target component 2. In this case, the number of ground reflection intervals divided according to the incident light rays in the next step will be too large, which will increase the complexity of the back irradiation calculation. However, the impact of ground reflection areas that are too far from the target component 2 on irradiation is small and can be ignored. In this case, limiting the number of ground reflection areas to between 3 and 7, and limiting the ground reflection interval to cover the vertical projection of the target component 2 on the ground, can both meet the back irradiation calculation requirements and simplify the calculation process. If the range of the ground reflection interval itself is small, the above limitation can be omitted.

[0091] Based on the above embodiments, optionally, before calculation, a coordinate system is established according to the installation position of the target component, and the key angles and lengths are obtained through the coordinates of each key point. This makes the logic of the calculation method clearer and easier to implement. The following is in conjunction with... Figure 4 and Figure 5 The calculation method for back-side irradiation of a bifacial photovoltaic module is illustrated through a specific embodiment.

[0092] The calculation method for the back-side irradiance of this bifacial photovoltaic module includes:

[0093] S1. Determine the ground reflection range 1 that the target component can receive based on the array installation information.

[0094] S2. Based on the component installation angle and the solar incident light from the ground reflection zone 1, divide the area into 5 ground reflection zones required for back irradiance calculation.

[0095] The angle of incidence of the sun, θ, is calculated using the following formula:

[0096]

[0097] In the formula, a s Solar altitude angle; γ s This is the solar azimuth angle.

[0098] Figure 5 In the diagram, ground reflection areas 10_1, 10_3, and 10_5 are all areas blocked by the component (scattering and reflection areas); ground reflection areas 10_2 and 10_4 are both areas directly exposed to sunlight (scattering + direct reflection areas).

[0099] S3. Divide the solar cells in the array photovoltaic module into sections to form the cell section.

[0100] The number of battery sections is determined by both the component type and the calculation accuracy. In this embodiment, the back of the component is divided equally to obtain each battery section, meaning that the width b of each battery section is equal.

[0101] S4. Establish a coordinate system.

[0102] like Figure 5 As shown, a rectangular coordinate system is established with the vertical projection of the lowest point of target component 2 onto the ground as the origin. According to formula (2), the variation trend of the viewing angle coefficient of the target component in different ground areas within one spacing period (taking the length of the installation spacing s as a spacing period) can be calculated.

[0103] Modeling according to the above coordinate system, the lowest point coordinates of the first battery part 20_1 in target component 2 are (0, h), the lowest point coordinates of the second battery part 20_2 are (b*cosδ, h+b*sinδ), ..., the lowest point coordinates of the m-th battery part 20_m are ((m-1)*b*cosδ, h+(m-1)*b*sinδ).

[0104] The coordinates of the boundary points of the surface reflection areas are as follows:

[0105] The left endpoint of ground reflection area 10_1:

[0106] When the left endpoint of the ground reflection zone 1 is exactly located in the part where the incident sunlight is blocked by the reference component 3_2, at this time,

[0107] When the left endpoint of the ground reflection zone 1 is located in front of (to the left of) the left endpoint N3 of the portion of the solar incident light blocked by the reference component 3_2, the left endpoint N3 of the portion of the solar incident light blocked by the reference component 3_2 is taken as the left endpoint of the ground reflection area 10_1, that is:

[0108] The right endpoint of ground reflection area 10_1 is the left endpoint of ground reflection area 10_2:

[0109] The right endpoint of ground reflection area 10_2, which is the left endpoint of ground reflection area 10_3:

[0110] The right endpoint of ground reflection area 10_3, which is the left endpoint of ground reflection area 10_4:

[0111] The right endpoint of ground reflection area 10_4, which is the left endpoint of ground reflection area 10_5:

[0112] The right endpoint of ground reflection area 10_5:

[0113] When the right end of the ground reflection zone 1 is exactly located in the part where the incident sunlight is blocked by the reference component 3_3, at this time,

[0114]

[0115] When the right endpoint of the ground reflection zone 1 is located behind (to the right) of the right endpoint N4 of the portion of the solar incident light blocked by the reference component 3_3, the right endpoint N4 of the portion of the solar incident light blocked by the reference component 3_3 is taken as the right endpoint of the ground reflection area 10_5, that is:

[0116]

[0117] S5. Calculate the irradiance received by each battery section based on the scattering intensity distribution model (Formula (3)), the viewing angle coefficient model (Formula (2)), and the irradiation physics model.

[0118] S5.1 Calculate the viewing angle coefficient of each battery component in each ground reflection area.

[0119] Given the coordinate range of each ground reflection area and the coordinates of each battery part, select ground selection points evenly in each ground reflection area according to the set step size, and solve the viewing angle coefficient of each battery part in each ground reflection area according to formula (5)-formula (9). The average viewing angle coefficient of a certain battery part in a certain ground reflection area is taken as the viewing angle coefficient of the battery part in that ground reflection area.

[0120] Specifically, for the ground selection points in the ground reflection area 10_1:

[0121]

[0122] For the selected ground points in the ground reflection area 10_2:

[0123]

[0124] For the selected ground points in the ground reflection area 10_3:

[0125]

[0126] For the selected ground points in the ground reflection area 10_4:

[0127]

[0128] For the selected ground points in the ground reflection area 10_5:

[0129]

[0130] S5.2 Calculate the scattering intensity distribution of each battery part in each ground reflection area according to formula (3).

[0131] S5.3 Calculate the amount of airborne scattered radiation received by each battery section according to the following formula.

[0132]

[0133] In the formula, D r-m I represents the amount of scattered air radiation received by the m-th battery section. d This represents horizontally scattered radiation.

[0134] S5.4 Calculate the total irradiance received by each battery section according to the following formula.

[0135]

[0136] In the formula, R m Let ρ be the total irradiance received by the m-th battery section, and I be the reflectivity. d For horizontal diffuse irradiation, I n This represents horizontal direct radiation; K is a correction factor.

[0137] S6: Calculate the back irradiation of the target module based on the irradiation of each battery section.

[0138] In this embodiment, the target component is a split-parallel component. The middle part of the component is a junction box, and the battery sections of the junction box are symmetrically divided into upper and lower parts. Therefore, the lower part includes the 1st to q / 2nd battery section, and the upper part includes the 1+q / 2nd to qth battery section. The back of the target component is irradiated (denoted as R). 等效 The sum of the minimum irradiance of the upper and lower parts of the junction box is:

[0139]

[0140] In summary, this embodiment provides a specific calculation method for the back-side irradiance of bifacial photovoltaic modules. The distribution of scattering intensity and viewing angle coefficient of a certain cell portion within a ground interval (i.e., one spacing period) from the self-coordinate 0 point to the right along the X-axis, calculated using the above method, can be found in [reference needed]. Figure 6 The back-side irradiation distribution of a target component can be found in [reference needed]. Figure 7 , Figure 7 In the diagram, junction box 21 is located in the middle of the back of target component 2. The irradiance of each battery section is indicated by numerical values ​​(e.g., the irradiance of battery section 20_1 is 53), in units of W / m². 2 .

[0141] To verify the feasibility and accuracy of the above-mentioned back-side irradiance calculation method, the inventors conducted actual tests on bifacial photovoltaic modules, as follows:

[0142] Figure 8 This is a schematic diagram of the installation position of a radiometer according to an embodiment of the present invention. See also... Figure 8 The inventors selected a target component 2 at the Changzhou test site and installed three radiometers on its back tracking bracket, labeled radiometer 41, radiometer 42, and radiometer 43. Based on the installation information, the difference between the theoretical and measured back irradiance of the battery section corresponding to the three radiometers was calculated to verify the model accuracy. The calculation process is as follows:

[0143] Astronomical conditions: 9:00-15:00 on September 27, 2021.

[0144] System installation requirements: Component width 2378mm, component spacing 5000mm, component center point height 1200mm.

[0145] Geographic information: Latitude 31.86°, Longitude 120°.

[0146] Corresponding to the actual measurements, let m = 5, where the three middle battery sections represent the areas at the corresponding measured positions. The viewing angle coefficient and scattering intensity distribution of each of the five battery sections are calculated to obtain the irradiance distribution on the back of the bifacial module. The theoretically calculated irradiance and the measured irradiance distribution of the three middle battery sections are compared as follows: Figures 9-11 As shown. See also Figures 9-11 It is evident that the back irradiation calculation method provided in the embodiments of the present invention is feasible, the calculation results are accurate, and the error between the actual measurement and the actual measurement is small.

[0147] This invention also provides a method for calculating the bifacial gain of a bifacial photovoltaic module. The back irradiance calculated using the back irradiance calculation method of the bifacial photovoltaic module provided in any embodiment of this invention is used as an important parameter for calculating the bifacial gain, which has corresponding beneficial effects.

[0148] Figure 12 This is a flowchart illustrating a method for calculating the bifacial gain of a bifacial photovoltaic module according to an embodiment of the present invention. See also... Figure 12 The method for calculating the bifacial gain of this bifacial photovoltaic module includes:

[0149] S310, Calculate the frontal irradiation of the target component.

[0150] Among them, the frontal irradiation of the target component (denoted as R) f Calculate according to the following formula:

[0151]

[0152] In the formula, R b The conversion coefficient for direct sunlight on an inclined plane. θ is the angle of incidence of the sun. z F is the solar zenith angle. Hay The slope scattering conversion coefficient, H0 is a constant.

[0153] S320, Calculate the back irradiation of the target component.

[0154] The back irradiation is calculated using the calculation method for the back irradiation of bifacial photovoltaic modules provided in any embodiment of the present invention.

[0155] S330. Calculate the bifacial gain of the target component based on the front irradiance, the back irradiance, and the bifaciality of the target component.

[0156] The two-sided gain (denoted as B) can be calculated using the following formula. a ):

[0157]

[0158] In the formula, B is the bifaciality of the photovoltaic module, which is a constant and is related to the module's performance.

[0159] To verify the accuracy of the above bifacial gain calculation method, the inventors conducted actual tests on bifacial photovoltaic modules, as follows:

[0160] Taking Changzhou as an example (latitude 31.86°), the bifacial gain of the target module was calculated at the experimental site on August 8, 2021. The installation information included a fixed 25-degree tilt angle, a 2P module width of 4.4m, a spacing of 9m, and a reflectivity of 0.2. A typical time of 12:00 was selected. Taking the bottom battery section as an example, the ground reflection area was divided as follows... Figure 4 The viewing angle coefficient and scattering intensity distribution of each ground reflection area on the battery section at 12:00 were calculated, and then the irradiance distribution of each part on the back of the module was calculated. The viewing angle coefficient and scattering intensity distribution of each ground reflection area are shown in Table 1.

[0161] Table 1

[0162]

[0163] Based on the above calculation results, the back irradiance of the target component was calculated, and the theoretical bifacial gain of the target component was also calculated. A comparison of the theoretical and measured bifacial gain curves under typical clear weather conditions is shown in the figure below. Figure 13 As shown, see Figure 13 The error between the theoretical and measured two-sided gain is within 1%, indicating that the calculation method for the two-sided gain provided in this embodiment is feasible and highly accurate.

[0164] Note that the above description is merely a preferred embodiment of the present invention and the technical principles employed. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and various obvious changes, readjustments, and substitutions can be made without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments, and may include many other equivalent embodiments without departing from the concept of the present invention, the scope of which is determined by the scope of the appended claims.

Claims

1. A method for calculating the back-side irradiance of a bifacial photovoltaic module, characterized in that, include: Determine the ground reflection range of the target component; Select n reference components; where n≥2, and n is an integer; the reference components are arranged on both sides of the target component; The viewing angle coefficient of the target component in the ground reflection range is calculated based on the angle between the line connecting the ground selection point and the first reference point of the reference component and the line connecting the ground selection point and the second reference point of the reference component, and the angle between the line connecting the ground selection point and the first reference point of the target component and the line connecting the ground selection point and the second reference point of the target component; wherein, the ground selection point is located in the ground reflection range; The back irradiance of the target component is calculated based on the viewing angle coefficient; The calculation of the viewing angle coefficient of the target component in the ground reflection range includes: Divide the ground reflection zone into at least two ground reflection areas; The back of the target component is divided into at least two battery sections; and the back of the reference component is divided into at least two battery sections in the same manner as the target component. Calculate the viewing angle coefficient of each battery section of the target component in each ground reflection area; wherein, the viewing angle coefficient of the battery section of the target component at a selected point on the ground in the area is calculated according to the following formula: ； in, VF ik-m The viewing angle coefficient represents the point selected on the ground in the k-th region of the i-th ground region for the m-th battery portion of the target component. β 1-ik-m The angle between the line connecting the k-th selected point in the i-th ground region and the lowest point of the m-th battery section of the first reference component and the ground is represented. β 2-ik-m The angle between the line connecting the k-th selected point in the i-th ground region and the lowest point of the m-th battery section of the last reference component and the ground is given. b m Represents the width of the m-th battery section of the target component. Represents the installation angle of the target component. h m This represents the height of the lowest point of the m-th battery section of the target component from the ground. s Represents the spacing between adjacent components. α j-ik-m The angle between the line connecting the k-th selected point in the i-th ground region to the lowest point of the m-th battery section of the j-th reference component and the line connecting the k-th selected point in the i-th ground region to the highest point of the m-th battery section of the j-th reference component is given. The angle between the line connecting the k-th selected point in the i-th ground region to the lowest point of the m-th battery section of the target component and the line connecting the k-th selected point in the i-th ground region to the highest point of the m-th battery section of the target component.

2. The method for calculating the back-side irradiation of a bifacial photovoltaic module according to claim 1, characterized in that, The ground reflection range is divided into at least two ground reflection zones, including: Depending on whether the ground is directly exposed to sunlight, the ground reflection zone is divided into at least one area directly exposed to sunlight and at least one area blocked by a component.

3. The method for calculating the back-side irradiation of a bifacial photovoltaic module according to claim 1, characterized in that, Each of the ground reflection zones includes at least two selected ground points in the zone; Calculating the viewing angle coefficient of each battery portion of the target component in each of the ground reflection areas includes: Calculate the viewing angle coefficient of the battery portion of the target component at each selected point on the ground in the region; The average value of all viewing angle coefficients of a certain battery portion of the target component in the same ground reflection area is calculated as the viewing angle coefficient of the battery portion of the target component in the ground reflection area.

4. The method for calculating the back-side irradiation of a bifacial photovoltaic module according to claim 1, characterized in that, Calculating the back irradiance of the target component based on the viewing angle coefficient includes: The scattering intensity distribution of the target component's battery portion in the ground reflection area is calculated based on the viewing angle coefficient of the battery portion of the target component in the ground reflection area; The irradiance of each battery section of the target component is calculated based on the scattering intensity distribution of the target component's battery section in the ground reflection area. The back irradiation of the target component is calculated based on the connection method of the batteries in the target component and the irradiation of each battery part of the target component.

5. The method for calculating the back-side irradiation of a bifacial photovoltaic module according to claim 4, characterized in that, If the target component is a half-parallel component, then the back irradiation of the target component is the sum of the back irradiations of each parallel part; wherein, the back irradiation of the parallel part is the irradiation of the battery part with the smallest irradiation among the parallel parts. If the target component is a series component, then the back irradiation of the target component is the irradiation of the battery portion with the least irradiation.

6. The method for calculating the back-side irradiation of a bifacial photovoltaic module according to claim 1, characterized in that, Determining the ground reflection range of the target component includes: The ground reflection range is determined by the intersection of the extension line of the slope of the target component with the ground, and the intersection of the extension line of the line connecting the highest point of the target component and the lowest point of the reflection range determination component with the ground; wherein, the reflection range determination component is the reference component that is adjacent to the target component and is blocked by the target component when the solar incident angle is less than the incident angle threshold.

7. A method for calculating the bifacial gain of a bifacial photovoltaic module, characterized in that, include: Calculate the frontal irradiance of the target component; The back irradiance of the target module is calculated using the calculation method for the back irradiance of a bifacial photovoltaic module as described in any one of claims 1-6; The bifacial gain of the target component is calculated based on the front irradiance, the back irradiance, and the bifaciality of the target component.

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