A method for calculating the irradiance of a double-sided photovoltaic array based on a three-dimensional scene

Abstract

The present invention discloses a method for calculating the irradiance of a double-sided photovoltaic array based on a three-dimensional scene, and the steps are as follows: 1. Calculate the irradiance on the front surface of the double-sided photovoltaic module; 2. Establish a three-dimensional model of the components of the double-sided photovoltaic array and the ground, and calculate the ground-reflected irradiance on the back surface of the double-sided photovoltaic module; 3. Calculate the irradiance reflected from the rear components of the double-sided photovoltaic array to the back surface of the front components; 4. Calculate the direct solar irradiance on the back surface of the double-sided photovoltaic module during the morning and evening periods; 5. Calculate the sky diffuse irradiance on the back surface of the double-sided photovoltaic module; 6. Calculate the total irradiance on the front and back surfaces of the double-sided photovoltaic module, and further calculate the total irradiance of the double-sided photovoltaic array. The present invention utilizes the basic installation conditions of the double-sided module and the horizontal radiation to calculate the accurate irradiance of the double-sided photovoltaic array, especially for the calculation of the irradiance on the back surface of the double-sided photovoltaic, so as to guide the evaluation of the power generation performance of the double-sided photovoltaic power station.

Description

Technical Field

[0001] The present invention relates to a method for calculating the irradiance of a double-sided photovoltaic array under a three-dimensional scene, belonging to the technical field of solar photovoltaic system applications. Background Art

[0002] The accuracy of calculating the power generation of double-sided components and arrays depends on the accuracy of evaluating the irradiance on the back of the components. How to accurately calculate the back irradiance has become an important and urgent problem. The main sources of the back irradiance of double-sided photovoltaic components are ground-reflected irradiance and scattered irradiance. At the same time, the front-reflected irradiance of the rear components can be received in the array. The back of the double-sided photovoltaic components arranged in the north-south direction can also be directly irradiated by the sun during some periods in the morning or evening. Generally, ignoring the latter two, only calculating the ground reflection, ground scattered irradiance and sky scattered irradiance, there is a large error between the calculated result and the measured data. Therefore, there is an urgent need for a method that can effectively and accurately calculate the irradiance of double-sided photovoltaic components for predicting the power generation of double-sided photovoltaics. Summary of the Invention

[0003] To overcome the existing technical defects, the present invention provides a method for calculating the irradiance of a double-sided photovoltaic array under a three-dimensional scene. According to the basic installation conditions and horizontal radiation of the array, the irradiance of the double-sided photovoltaic components can be calculated.

[0004] The main technical solution adopted in the present invention is as follows:

[0005] A method for calculating the irradiance of a double-sided photovoltaic array under a three-dimensional scene, comprising the following steps:

[0006] Step 1: Calculate the irradiance on the front of the double-sided photovoltaic array components;

[0007] Step 2: Establish a three-dimensional model of the double-sided photovoltaic array components and the ground, and calculate the reflected irradiance of the ground (bright and shadow areas) faced by the back of the double-sided photovoltaic components;

[0008] Step 3: In the double-sided photovoltaic array, adopt the inverse ray collection method to calculate the irradiance reflected from the rear components of the double-sided photovoltaic array to the back of the front components;

[0009] Step 4: Determine the position of the sun and the double-sided array components, and calculate the direct solar irradiance on the back of the double-sided photovoltaic components during the morning and evening periods;

[0010] Step 5: Calculate the sky scattered irradiance on the back of the double-sided photovoltaic array components;

[0011] Step 6: Calculate the total irradiance on the front and back of the double-sided photovoltaic array components, and further calculate the total irradiance of the double-sided photovoltaic array.

[0012] Preferably, in the step 1, the irradiance on the front side of the bifacial PV module is calculated as shown in Equation (1): The PV module parameters include longitude, latitude, ground reflectivity, hourly total irradiance, module tilt angle, and azimuth angle parameters; Equation (1) calculates the irradiance on the front side of the bifacial PV array inclined surface.

[0013]

[0014] In the formula:

[0015] I front represents the irradiance on the front inclined surface of the PV module;

[0016] I p represents the total solar irradiance on the horizontal plane;

[0017] I b represents the direct solar irradiance on the horizontal plane;

[0018] I d represents the diffuse solar irradiance on the horizontal plane;

[0019] ρ g represents the ground reflectivity;

[0020] β represents the installation tilt angle of the PV module;

[0021] F1 represents the circumsolar brightness coefficient; F2 represents the circumsolar horizon brightness coefficient;

[0022] R b represents the ratio of the direct irradiance on the inclined surface to that on the horizontal plane;

[0023] For the Northern Hemisphere:

[0024]

[0025] For the Southern Hemisphere:

[0026]

[0027] where, β is the installation tilt angle of the PV module, is the local latitude, δ is the solar declination angle, and ω is the hour angle;

[0028] The irradiance on the front side of the bifacial PV module is calculated through the irradiance calculation formula (1).

[0029] Preferably, in the step 2, a three-dimensional model of the components in the bifacial PV array and the ground is established, and the reflected irradiance of the ground (bright and shaded areas) on the back of the bifacial PV module is calculated. Under the ground reflectivity, the reflected irradiance from the bright ground to the back of the bifacial PV module is calculated to obtain the total horizontal irradiance of the reflected ground in the non-shaded (bright area); under the ground reflectivity, the reflected irradiance from the shaded ground to the back of the bifacial PV module. Since this area is blocked by the module itself, only the horizontal diffuse irradiance is reflected from the shaded ground (shaded area).

[0030] The view factor F is a fraction that quantifies the irradiance reflected from one radiating surface to the irradiated surface and can be used to simulate the ground-reflected irradiance received on the back of the bifacial PV module. The differential surface (the back of the bifacial PV module) is the surface that receives the irradiance and receives a part of the diffuse reflected irradiance emitted from the differential surface (the ground reflection surface). Assuming that the curved surface is a Lambertian reflection surface and the reflected irradiance from the ground is isotropic diffuse irradiance, then can be expressed as:

[0031]

[0032] The calculation of the reflected irradiance of the ground obtained by the bifacial PV module is shown in Equation (2):

[0033]

[0034] In the formula:

[0035] I rear,g represents the reflected irradiance of the ground on the back of the bifacial PV module;

[0036] ρ g represents the ground reflectivity;

[0037] I d represents the solar diffuse irradiance on the horizontal plane;

[0038] I b represents the solar direct irradiance on the horizontal plane;

[0039] A m represents the module area;

[0040] A s represents the area of the shaded ground;

[0041] A ns represents the area of the non-shaded ground.

[0042] Preferably, in the step 3, the inverse ray tracing method is used to calculate the reflected irradiance of the rear modules on the back of the bifacial PV module.

[0043] The present invention uses the reverse ray tracing method to establish a spherical reflection light source on the back of the front row components, and simulates the physical model of the reflected light with a random function to obtain the amount of light that can reach the back of the front row components by reflection from the front of the back row components, denoted as the light collection rate η.

[0044]

[0045] In the formula: η represents the light collection efficiency;

[0046] S1(i) represents the number of light rays emitted from point P on the back of the front row components; i

[0047] S2(j,i) represents the number of light rays reflected from point P on the back of the front row components and reaching point M on the back row components; i j

[0048] cosθ(j,i) represents the angle between the incident direction of the light ray and the normal of the component plane.

[0049] The reflected irradiance on the back of the back row components of the bifacial photovoltaic module is shown in Equation (4):

[0050]

[0051] In the formula:

[0052] I rear,r represents the reflected irradiance on the back of the bifacial photovoltaic module from the back components;

[0053] I r represents the irradiance received by the back row of the components;

[0054] α represents the transmittance of the component;

[0055] A1 represents the area of the front row components;

[0056] A2 represents the area of the back row components.

[0057] Preferably, in step 4, the positions of the sun and the bifacial module are judged, and the direct solar irradiance on the back of the bifacial photovoltaic module in the morning and evening periods is calculated;

[0058] I rear,b = I b R rear,b (5)

[0059] In the formula: I rear,b represents the direct solar irradiance on the back of the bifacial photovoltaic module;

[0060] I b represents the amount of direct solar irradiance on the horizontal plane; ​​​

[0061] R rear,b represents the ratio of the direct irradiance on the back surface of the inclined plane to that on the horizontal plane;

[0062] For the Northern Hemisphere:

[0063]

[0064] For the Southern Hemisphere:

[0065]

[0066] where β is the installation inclination angle of the photovoltaic module, is the local latitude, δ is the solar declination angle, and ω is the hour angle.

[0067] Preferably, in step 5, the sky diffuse irradiance on the back surface of the bifacial photovoltaic module is calculated.

[0068] The back surface receives sky diffuse radiation I rear,d as shown in Equation (6)

[0069]

[0070] In the formula: I rear,d represents the sky diffuse radiation received by the back surface;

[0071] I d represents the solar diffuse irradiance on the horizontal plane;

[0072] β represents the installation inclination angle of the module (the angle between the inclined plane where the module is located and the horizontal plane).

[0073] Preferably, in step 6, the total irradiance on the front and back surfaces of the bifacial photovoltaic module is calculated, and further summed to calculate the total irradiance of the bifacial photovoltaic array.

[0074] The irradiance of the bifacial photovoltaic module is as shown in Equation (7):

[0075] I rear = I rear,g + I rear,r + I rear,b + I rear,d

[0076] I = I front + I rear (7)

[0077] In the formula:

[0078] I represents the total irradiance of the inclined plane of the bifacial photovoltaic module;

[0079] I front represents the irradiance of the inclined plane of the front surface of the photovoltaic module;

[0080] I rear represents the irradiance on the inclined surface of the back side of the photovoltaic module;

[0081] I rear,g represents the ground reflected irradiance on the back side of the bifacial photovoltaic module;

[0082] I rear,r represents the irradiance reflected from the back component on the back side of the bifacial photovoltaic module;

[0083] I rear,b represents the direct solar irradiance on the back side of the bifacial photovoltaic module;

[0084] I rear,d represents the sky diffuse radiation on the back side.

[0085] Beneficial effects: The present invention provides a method for calculating the irradiance of a bifacial photovoltaic array based on a three-dimensional scene, which can calculate the accurate back irradiance and total irradiance of the bifacial photovoltaic module by using the basic installation conditions of the module and the horizontal radiation, thereby guiding the evaluation of the power generation performance of the bifacial photovoltaic power station. Moreover, the present invention is applicable to the calculation of the irradiance of bifacial photovoltaic modules under different installation conditions, and the results of simulation and emulation reflect the reference value and applicability of the present invention.. Description of the Drawings

[0086] Figure 1 is a composition diagram of bifacial photovoltaic irradiance.

[0087] Figure 2 is a flowchart of irradiance calculation for the bifacial photovoltaic module of the present invention.

[0088] Figure 3 is a simplified three-dimensional calculation model diagram of the module and the ground.

[0089] Figure 4 is a diagram of the positional relationship between components in a simplified diagram for explaining the inverse ray tracing method.

[0090] Figure 5 is the light that reaches the front side of the module through diffuse reflection on the back side of the module in a simplified diagram for explaining the inverse ray tracing method. Detailed Embodiments

[0091] In order to enable those skilled in the art to better understand the technical solutions in this application, the technical solutions in the embodiments of this application will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of this application, rather than all the embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the scope of protection of this application.

[0092] A method for calculating the irradiance of a bifacial photovoltaic array in a three-dimensional scene. The composition of the bifacial photovoltaic irradiance is as shown in Figure 1 and the irradiance calculation flow chart is as shown in Figure 2 and includes the following steps:

[0093] Step 1: The irradiance calculation on the front side of the bifacial photovoltaic module is shown in Equation (1): The parameters of the photovoltaic module include longitude, latitude, ground reflectivity, hourly total irradiance, module tilt angle, and azimuth angle parameters; Equation (1) calculates the irradiance on the front side of the tilted surface of the bifacial photovoltaic array.

[0094]

[0095] In the formula:

[0096] I front represents the irradiance on the front tilted surface of the photovoltaic module;

[0097] I p represents the total solar irradiance on the horizontal plane;

[0098] I b represents the direct solar irradiance on the horizontal plane;

[0099] I d represents the diffuse solar irradiance on the horizontal plane;

[0100] ρ g represents the ground reflectivity;

[0101] β represents the installation tilt angle of the photovoltaic module;

[0102] F1 represents the circumsolar brightness coefficient; F2 represents the circummeridian brightness coefficient;

[0103] R b represents the ratio of the direct irradiance on the tilted surface to that on the horizontal plane;

[0104] For the Northern Hemisphere:

[0105]

[0106] For the Southern Hemisphere:

[0107]

[0108] where β is the installation tilt angle of the photovoltaic module, is the local latitude, δ is the solar declination angle, and ω is the hour angle;

[0109] The irradiance on the front side of the bifacial photovoltaic module is calculated through the irradiance calculation formula (1).

[0110] Step 2: Establish a three-dimensional model of the components in the bifacial PV array and the ground, and calculate the simplified model diagram as shown in Figure 3 Calculate the reflected irradiance of the ground (bright and shaded areas) on the back of the bifacial PV module. Under the ground reflectivity, calculate the total irradiance of the reflected horizontal plane from the bright ground to the back of the bifacial PV module; under the ground reflectivity, calculate the reflected irradiance from the shaded ground to the back of the bifacial PV module. Since this area is blocked by the module itself, only the scattered irradiance of the horizontal plane is reflected from the shaded ground (shaded area).

[0111] The view factor F quantifies the fraction of irradiance reflected from one radiating surface to the irradiated surface and can be used to simulate the ground-reflected irradiance received on the back of the bifacial PV module. The differential surface (the back of the bifacial PV module) is the surface receiving the irradiance and receives a part of the diffuse reflected irradiance emitted from the differential surface (the ground reflection surface). Assuming that the curved surface is a Lambertian reflection surface and the reflected irradiance from the ground is isotropic scattered irradiance, then It can be expressed as:

[0112]

[0113] The calculation of the reflected irradiance of the ground obtained by the bifacial PV module is shown in Equation (2):

[0114]

[0115] In the formula:

[0116] I rear,g represents the reflected irradiance of the ground on the back of the bifacial PV module;

[0117] ρ g represents the ground reflectivity;

[0118] I d represents the solar diffuse irradiance on the horizontal plane;

[0119] I b represents the solar direct irradiance on the horizontal plane;

[0120] A m represents the module area;

[0121] A s represents the shaded ground area;

[0122] A ns represents the unshaded ground area.

[0123] Step 3: Use the inverse ray tracing method to calculate the reflected irradiance of the rear modules on the back of the bifacial PV module.

[0124] The reverse ray tracing method starts from the back of the front-row photovoltaic panel to determine the light acceptance rate of the front of the rear-row photovoltaic panel. Against the light direction, starting from the photovoltaic panel, an arbitrary number of random rays are emitted at 180° from this point on the plane. The number of rays is simulated using random numbers. By tracking whether the rays intersect the front of the rear-row photovoltaic panel, since the light propagation is reversible and linear, tracking the ray intersection can solve the problem of the reflected light from the rear-row photovoltaic panel reaching the back of the front-row photovoltaic panel.

[0125] The positional relationship between the bifacial photovoltaic array components uses an elementary rotation matrix to transform the spatial problem into an intersection problem of a line segment and a polygon in a two-dimensional plane. The three-dimensional space is optimized into an intersection judgment problem of a line segment and a matrix in a two-dimensional plane, that is, a ray intersection algorithm with a rectangle, and the intersection algorithm can be extended to the intersection judgment problem of a ray and a quadrilateral. The present invention adopts an arc length accumulation method based on vertex symbols, which does not require projection and can quickly judge only through the quadrant position, with high efficiency. For example, the same quadrant is considered as 0, crossing one quadrant is π / 2, and crossing two quadrants is π.

[0126] The present invention adopts the reverse ray tracing method, establishes a spherical reflection light source on the back of the front-row component, and simulates the physical model of the reflected light with a random function to obtain the amount of light that can reach the back of the front-row component by reflecting from the front of the rear-row component. The explanatory sketch is as Figure 4 and Figure 5 shown, denoted as the light collection rate η.

[0127]

[0128] In the formula: η represents the light collection efficiency;

[0129] S1(i) represents the number of rays emitted from the back of the front-row component at point P i ;

[0130] S2(j,i) represents the number of rays that are reflected from the back of the front-row component at point P i and reach point M j on the rear-row component;

[0131] cosθ(j,i) represents the angle between the light incident direction and the normal of the component plane.

[0132] The reflected irradiance on the back of the rear-row component of the bifacial photovoltaic module is as shown in Equation (4):

[0133]

[0134] In the formula:

[0135] I rear,r represents the reflected irradiance on the back of the bifacial photovoltaic module from the rear component;

[0136] I r represents the irradiance received at the rear row of the component;

[0137] α represents the transmittance of the component;

[0138] A1 represents the area of the front-row component;

[0139] A2 represents the area of the rear-row component.

[0140] Step 4: Determine the position of the sun and the bifacial module, and calculate the direct solar irradiance received on the back of the bifacial PV module in the morning and evening periods;

[0141] I rear,b = I b R rear,b (5)

[0142] In the formula: I rear,b represents the direct solar irradiance on the back of the bifacial PV module;

[0143] I b represents the amount of direct solar irradiance on the horizontal plane;

[0144] R rear,b represents the ratio of the direct irradiance on the back of the inclined plane to that on the horizontal plane;

[0145] For the Northern Hemisphere:

[0146]

[0147] For the Southern Hemisphere:

[0148]

[0149] where β is the installation tilt angle of the PV module, is the local latitude, δ is the solar declination angle, and ω is the hour angle.

[0150] Step 5: Calculate the sky diffuse irradiance on the back of the bifacial PV module.

[0151] The diffuse radiation from the sky on the back I rear,d is shown in Equation (6) as

[0152]

[0153] In the formula: I rear,d represents the diffuse radiation from the sky on the back;

[0154] I d represents the amount of solar diffuse irradiance on the horizontal plane;

[0155] β represents the installation tilt angle of the component (the angle between the inclined plane where the component is located and the horizontal plane).

[0156] Step 6: Calculate the total irradiance on the front and back sides of the bifacial PV module, and further sum to calculate the total irradiance of the bifacial PV array.

[0157] The irradiance of the bifacial PV module is shown in Equation (7):

[0158] I rear = I rear,g + I rear,r + Ir ear,b + I rear,d

[0159] I = I front + I rear (7)

[0160] In the formula:

[0161] I represents the total irradiance on the inclined surface of the bifacial PV module;

[0162] I front represents the irradiance on the inclined front surface of the PV module;

[0163] I rear represents the irradiance on the inclined back surface of the PV module;

[0164] I rear,g represents the ground reflected irradiance on the back of the bifacial PV module;

[0165] I rear,r represents the irradiance reflected from the back component on the back of the bifacial PV module;

[0166] I rear,b represents the direct solar irradiance on the back of the bifacial PV module;

[0167] I rear,d represents the sky diffuse radiation on the back.

[0168] According to the above steps, the irradiance of the bifacial PV module under different installation conditions can be obtained.

[0169] The above is only the preferred embodiment of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for calculating the irradiation amount of a double-sided photovoltaic array based on a three-dimensional scene, characterized in that It includes the following steps: Step 1: Calculate the irradiance on the front side of the bifacial PV array module. Step 2: Establish a 3D model of the bifacial PV array module and the ground, and calculate the ground-reflected irradiance facing the back side of the bifacial PV module. The bottom surface includes bright and shadow areas. Step 3: In the bifacial PV array, adopt the inverse ray collection method to calculate the irradiance reflected from the rear-row modules to the back side of the front-row modules. Step 4: Determine the position of the sun and the bifacial array module, and calculate the direct solar irradiance on the back side of the bifacial PV module during morning and evening periods. Step 5: Calculate the sky diffuse irradiance on the back side of the bifacial PV array module. Step 6: Calculate the total irradiance on the front and back sides of the bifacial PV array module, and further calculate the total irradiance of the bifacial PV array. The irradiance of the bifacial PV module is as shown in Equation (7): I rear = I rear,g + I rear,r + I rear,b + I rear,d I = I front +I rear (7) In the formula: I represents the total irradiance on the inclined surface of the bifacial PV module. I front Indicates the irradiation amount on the front inclined surface of the photovoltaic module; I rear represents the irradiance on the inclined surface of the back side of the photovoltaic module; I rear,g represents the ground reflected irradiance on the back side of the bifacial PV module; I rear,r Indicates the irradiance reflected from the rear component on the back side of the bifacial PV module; I rear,b represents the direct solar irradiance on the back side of a bifacial PV module; I rear,d Indicates the backscattered radiation from the sky.

2. The irradiance calculation method for a double-sided photovoltaic array based on a three-dimensional scene according to claim 1, wherein In the said Step 1, the calculation of the irradiance on the front side of the bifacial PV module is as shown in Equation (1): The PV module parameters include longitude, latitude, ground reflectivity, hourly total irradiance, module tilt angle, and azimuth angle parameters. Equation (1) calculates the irradiance on the front side of the inclined surface of the bifacial PV array. In the formula: I front represents the irradiation amount on the front inclined surface of the photovoltaic module; I p represents the total solar irradiance on a horizontal plane; I b represents the direct solar irradiance on the horizontal plane; I d represents the amount of solar diffuse irradiance on the horizontal plane; ρ g represents the ground reflectivity; β represents the installation tilt angle of the PV module. F1 represents the circumsolar brightness coefficient; F2 represents the circummeridian brightness coefficient. R b represents the ratio of the direct irradiation amount on the inclined surface to that on the horizontal surface; For the Northern Hemisphere: For the Southern Hemisphere: Among them, β is the installation tilt angle of the photovoltaic module, is the local latitude, δ is the solar declination angle, and ω is the hour angle; Calculate the irradiance on the front side of the bifacial PV module through the irradiance calculation formula (1).

3. A method for calculating the irradiation amount of a double-sided photovoltaic array based on a three-dimensional scene according to claim 1, wherein In the said Step 2 The calculation of the reflected irradiance obtained by the bifacial PV module from the ground is as shown in Equation (2): In the formula: I rear,g represents the ground-reflected irradiance on the back side of a bifacial PV module; ρ g represents the ground reflectivity; I d represents the amount of solar diffuse irradiance on a horizontal plane; I b represents the direct solar irradiance on the horizontal plane; A m represents the component area; A s Indicates the shaded ground area; A ns Indicates the area of the unshaded ground.

4. A method for calculating the irradiation amount of a double-sided photovoltaic array based on a three-dimensional scene according to claim 1, characterized in that In the said Step 3, the steps of the inverse ray tracing method are as follows: Establish a spherical reflection light source on the back side of the front-row module, and simulate the physical model of the reflected light with a random function to obtain the amount of light that can reach the back side of the front-row module reflected from the front side of the rear-row module, denoted as the light collection efficiency η. In the formula: η(j,i) represents the light collection efficiency. S1(i) is expressed as the number of light rays emitted from the back surface P i of the front row component; S2(j,i) represents the number of light rays reflected from point P on the back of the front row of components and reaching point M on the rear row of components; i j ​​ cosθ(j,i) represents the angle between the light incident direction and the normal of the module plane. The reflected irradiance of the rear-row module on the back side of the bifacial PV module is as shown in Equation (4): In the formula: I rear,r Indicates the irradiance reflected from the rear component on the back side of the bifacial PV module; I r Represents the irradiance received at the rear row of components; α represents the module transmittance. A1 represents the area of the front-row module. A2 represents the area of the rear-row module.

5. A method for calculating the irradiation amount of a double-sided photovoltaic array based on a three-dimensional scene according to claim 1, wherein In the said Step 4, calculate the direct solar irradiance received on the back side of the bifacial PV module during morning and evening periods through formula (5). I rear,b = I b R rear,b (5) Where: I rear,b represents the direct solar irradiance on the back side of the bifacial PV module; I b represents the direct solar irradiance on the horizontal plane; R rear,b represents the ratio of the direct irradiance on the back of the inclined surface to that on the horizontal plane; For the Northern Hemisphere: For the Southern Hemisphere: Among them, β is the installation inclination angle of the photovoltaic module, is the local latitude, δ is the solar declination angle, and ω is the hour angle.

6. A method for calculating the irradiation amount of a double-sided photovoltaic array based on a three-dimensional scene according to claim 1, characterized in that The process of calculating the sky diffuse irradiance on the back side of the bifacial PV module in the said Step 5 is as follows: Backscattered radiation I from the sky rear,d As shown in Equation (6) In the formula: I rear,d represents the scattered radiation from the sky on the back surface; I d represents the amount of solar diffuse irradiance on a horizontal plane; β represents the installation tilt angle of the module, that is, the angle between the inclined surface where the module is located and the horizontal plane.

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