A greenhouse solar radiation transmittance calculation method based on roof discretization

Abstract

The application provides a greenhouse solar radiation transmittance calculation method based on roof discretization, comprising: establishing a greenhouse three-dimensional rectangular coordinate system, and constructing a three-dimensional geometric model of a greenhouse light-transmitting roof based on the three-dimensional rectangular coordinate system; taking the horizontal plane projection area of the light-transmitting roof as a division reference, and discretizing the whole light-transmitting roof into a plurality of independent roof discrete units; presetting a monitoring point in the greenhouse, and defining a connecting line vector from the monitoring point to the center point of each roof discrete unit as a scattered radiation direction along the roof discrete unit to the monitoring point; respectively calculating the corresponding scattered radiation transmittance and scattered radiation intensity of each roof discrete unit; according to the corresponding scattered radiation transmittance and scattered radiation intensity of each roof discrete unit, calculating the total amount of scattered radiation transmittance intercepted by the monitoring point, and then solving the equivalent scattered radiation transmittance at the monitoring point. The application has the advantages of improving the calculation accuracy of the greenhouse radiation transmittance and fitting the real light-transmitting physical process.

Description

Technical Field

[0001] This invention relates to the field of lighting analysis technology in facility agriculture, and more specifically, to a method for calculating the solar radiation transmittance of a greenhouse based on roof discretization. Background Technology

[0002] The internal light environment of a greenhouse is a core factor determining crop photosynthetic efficiency, canopy light uniformity, and greenhouse thermal conditions, directly impacting the production efficiency of facility agriculture. Currently, greenhouse coverings mostly use transparent or semi-transparent light-transmitting materials such as agricultural films and glass. Accurately simulating the light field distribution within a greenhouse has significant engineering and theoretical value for optimizing greenhouse structural parameters, selecting optimal covering materials, and achieving precise control of the indoor light environment.

[0003] Chinese invention patent CN103065055A discloses a method for calculating light distribution inside a solar greenhouse. The method mainly includes the following steps: S1. Obtaining external light distribution information of the solar greenhouse; S2. Constructing an initial light environment inside the solar greenhouse based on the external light distribution information and calculating the initial light intensity of each surface element; S3. Calculating the scattered light distribution inside the solar greenhouse based on the initial light intensity and the radiance method; S4. Superimposing the direct light distribution and the scattered light distribution inside the solar greenhouse to obtain the light distribution information inside the solar greenhouse. The calculation of the initial light intensity of each surface element uses the transmittance of direct light and the transmittance of scattered light.

[0004] The aforementioned patent focuses on solving the simulation problem of light field redistribution after light transmission and multiple reflections in a closed greenhouse, and can realize the simulation calculation of the steady-state light environment indoors; however, the patent does not provide accurate calculation methods for core pre-parameters such as direct radiation transmittance and diffuse radiation transmittance; moreover, most existing conventional transmittance calculation methods treat the greenhouse roof as an equivalent overall planar structure, or simplify diffuse radiation as uniform sky radiation, which cannot accurately calculate the total solar radiation transmittance at the monitoring point.

[0005] In practice, the spatial differences in tilt angle, azimuth angle and normal vector of each unit of the greenhouse light-transmitting roof result in different incident angles when the same direct sunlight and scattered skylight are incident on different roof units. Ultimately, this leads to spatial differences in the film's ability to transmit direct and scattered radiation at different locations on the roof.

[0006] In order to solve the above problems, people have been seeking an ideal technological solution. Summary of the Invention

[0007] The purpose of this invention is to address the shortcomings of existing technologies by providing a method for calculating greenhouse solar radiation transmittance based on roof discretization, which improves the accuracy of greenhouse radiation transmittance calculation and closely reflects the actual physical process of light transmission.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] A method for calculating greenhouse solar radiation transmittance based on roof discretization is provided, including:

[0010] A three-dimensional rectangular coordinate system for the greenhouse is established, and a three-dimensional geometric model of the greenhouse's translucent roof is constructed based on the three-dimensional rectangular coordinate system. The entire translucent roof is discretized into several independent roof discretization units, using the horizontal projection area of ​​the translucent roof as the dividing criterion.

[0011] Inside the greenhouse, monitoring points are pre-set. The line vector connecting the monitoring points to the center point of each roof discrete unit is defined as the direction of scattered radiation transmitted from the roof discrete unit to the monitoring point. The scattered radiation transmittance and scattered radiation intensity corresponding to each roof discrete unit are calculated respectively.

[0012] Based on the scattered radiation transmittance and scattered radiation intensity corresponding to each discrete unit of the roof, the total amount of scattered radiation transmitted through the monitoring point is calculated, and then the equivalent scattered radiation transmittance at the monitoring point is obtained.

[0013] By discretizing the overall translucent roof into several independent roof discrete units, this method overcomes the crude calculation flaw of treating the roof as a homogeneous structure in traditional greenhouse radiation calculations. By constructing a three-dimensional geometric model of the roof that closely matches the actual curved surface of the greenhouse roof, it avoids calculation errors caused by simplified planar modeling. Discretizing the roof into multiple micro-roof discrete units allows for adaptation to the geometric characteristics and light incidence differences of roof units at different locations, enabling refined block-based calculation of radiation parameters. By defining the effective light propagation direction between monitoring points and roof discrete units, the effective scattered radiation transmission path is locked, and invalid radiation interference is eliminated. Ultimately, this significantly improves the calculation accuracy of the greenhouse's internal scattered radiation transmittance and its adaptability to actual working conditions, providing reliable data support for precise control of the greenhouse light environment.

[0014] In a preferred embodiment, the method for establishing a three-dimensional rectangular coordinate system for a greenhouse includes:

[0015] The geometric center of the greenhouse is selected as the origin of the three-dimensional rectangular coordinate system;

[0016] Define the coordinate axes of the three-dimensional rectangular coordinate system as follows: the positive X-axis points westward along the longitudinal direction of the greenhouse, the positive Y-axis points southward along the span of the greenhouse, and the positive Z-axis points vertically upward.

[0017] Define the greenhouse azimuth angle φ: with the geographic south direction as the zero reference direction, deflection to the west is positive and deflection to the east is negative. The angle between the positive direction of the Y-axis of the three-dimensional rectangular coordinate system and the geographic south direction is set as the greenhouse azimuth angle φ.

[0018] By establishing specific rules for the three-dimensional coordinate system of greenhouses and defining rules for the azimuth angle of greenhouses, the problem that traditional general coordinate systems cannot adapt to the orientation of greenhouses and differences in site orientation has been solved. This has enabled the unified quantitative calibration of greenhouse spatial geometric parameters and solar azimuth parameters, ensuring the consistency and accuracy of the entire calculation process.

[0019] In a preferred embodiment, the method for constructing a three-dimensional geometric model of a greenhouse roof includes:

[0020] The cross-sectional curve function of the pre-defined greenhouse light-transmitting roof is z=f(y). The cross-sectional curve function is extended along the X-axis in the three-dimensional rectangular coordinate system to form a three-dimensional geometric model of the greenhouse light-transmitting roof.

[0021] The modeling method, which uses axial stretching of cross-sectional curves, is suitable for most conventional greenhouse roof structures, such as arched roofs, double-slope roofs, multi-folded roofs, and complex curved roofs. The modeling method is simple, efficient, and highly versatile. At the same time, it can accurately reproduce the geometric features of continuous curved roof surfaces, balancing modeling efficiency and model accuracy.

[0022] In a preferred embodiment, the method of discretizing the entire translucent roof into several independent roof discrete units based on the horizontal projection area of ​​the translucent roof includes:

[0023] Using the horizontal projection area of ​​the translucent roof as the dividing benchmark, the longitudinal length of the greenhouse is evenly divided into N. X The greenhouse span is evenly divided into N intervals. Y A range;

[0024] Define the center point coordinates of the roof discrete element (i,j) as (x ij,c ,y ij,c ,z ij,c ), where i = 1, 2, ..., N X j=1,2,…,N Y c represents the coordinates of the geometric center of the greenhouse;

[0025] The formula for calculating the actual area of ​​the roof discrete unit (i,j) is as follows: ;

[0026] The normal vector n of the roof discrete element (i,j) ij The calculation formula is: ;

[0027] in, The distance between the longitudinal sections of the greenhouse is the distance from the ground. The distance between the greenhouse spans is defined by the distance between the rows of plants. Cross-sectional curve function Coordinates of the span direction at the center point of the discrete element (i,j) on the roof The first derivative at that point.

[0028] By uniformly meshing the projection area, the discrete units are divided in a regular and uniform manner, avoiding calculation distortion caused by excessively large local units. At the same time, a model for calculating the area and normal vector of the roof discrete units adapted to the curved surface is constructed based on the first derivative of the cross-sectional curve function. This model restores the actual spatial shape and normal direction of the roof discrete units, providing core geometric parameters to support the accurate calculation of the subsequent light incident angle and radiation transmittance.

[0029] In a preferred embodiment, the step of pre-setting monitoring points inside the greenhouse, and defining the line vector connecting the monitoring points to the center points of each discrete roof unit as the scattered radiation light transmitted along the roof unit to the monitoring point, includes:

[0030] A monitoring point P is pre-set inside the greenhouse, with its coordinates set as (x...). p ,y p ,z p );

[0031] Construct a line vector v connecting monitoring point P to the center point of the discrete element (i,j) on the roof. ij And solve for the corresponding unit direction vector. The calculation formulas are as follows:

[0032] ;

[0033] .

[0034] By constructing three-dimensional spatial connection vectors and unit direction vectors between monitoring points and discrete roof units, the propagation path of scattered radiation was digitally and accurately represented, solving the problem that traditional methods could not accurately quantify the spatial radiation transmission direction between curved roof units and indoor monitoring points. The unit direction vector eliminated the interference of distance scale on direction parameters, providing an accurate direction reference for subsequent calculations.

[0035] In a preferred embodiment, the step of calculating the scattered radiation transmittance and scattered radiation intensity corresponding to each discrete roof unit includes the following formula for calculating the scattered radiation transmittance:

[0036] Scattered radiation transmittance transmitted from the discrete element (i,j) along the roof to the monitoring point : ;

[0037] Vertical polarization component of scattered radiation transmitted from the discrete element (i,j) along the roof to the monitoring point : ;

[0038] Parallel polarization component of scattered radiation transmitted from the discrete element (i,j) along the roof to the monitoring point : ;

[0039] The interface reflectivity of the vertical polarization component of the scattered radiation at the discrete element (i,j) of the roof. : ;

[0040] Interface reflectivity of the parallel polarization component of scattered radiation at the discrete element (i,j) of the roof. : ;

[0041] Radiation absorptivity T of the roof discrete element (i,j) A,ij : ;

[0042] The angle of refraction θ of light entering the internal thin film of the discrete unit (i,j) on the roof t,ij : ;

[0043] The incident angle θ of the scattered radiation transmitted from the discrete element (i,j) on the roof to the monitoring point ij : ;

[0044] In the formula, n is the refractive index of the thin film, K is the absorption coefficient of the thin film, and d is the thickness of the thin film.

[0045] Based on the polarization characteristics of light, the laws of refraction and reflection, and the absorption characteristics of the medium, a calculation model for the scattered radiation transmittance of a discrete roof unit was constructed. By distinguishing between vertical and parallel polarization components, the reflection, transmission, and absorption losses were calculated separately, accurately reproducing the physical process of natural light penetrating the greenhouse film. At the same time, by combining the incident angle of light, the internal refraction angle of the selected film, and the film's own parameters, the model fully considers the differences in the incident angle of light of different roof units and the influence of the optical properties of the film material on radiation transmission, significantly improving the calculation accuracy of the scattered transmittance of the discrete roof unit and closely conforming to the true physical laws of natural light transmission.

[0046] In a preferred embodiment, the calculation of the scattered radiation transmittance and scattered radiation intensity transmitted from the discrete element (i,j) along the roof to the monitoring point includes:

[0047] Based on the spatial coordinates of monitoring point P and the center point of the roof discrete element (i,j), calculate the corresponding scattered radiation elevation angle transmitted from the roof discrete element (i,j) to the monitoring point. The calculation formula is:

[0048] ;

[0049] According to the elevation angle Solve for the zenith angle of the scattered radiation transmitted from the discrete element (i,j) along the roof to the monitoring point. The calculation formula is: ;

[0050] Based on the zenith angle The weights of the scattered radiance transmitted from the roof discrete element (i,j) to the monitoring point are obtained using the Perez anisotropic sky brightness model. Then the intensity of scattered radiation in that direction is calculated. The calculation formula includes:

[0051] Scattered radiation intensity transmitted from the discrete element (i,j) along the roof to the monitoring point : ;

[0052] The roof discrete element (i,j) corresponds to the scattered radiance in the sky direction. : ;

[0053] The apparent solid angle of the roof discrete element (i,j) relative to the monitoring point : ;

[0054] Effective receiver factor of the monitoring point receiving radiation scattered from the discrete element (i,j) of the roof. : ;

[0055] The central zenith angle of the (a,b)th discrete sky cell : ;

[0056] The apparent solid angle of the (a,b)th discrete sky unit : ;

[0057] To characterize the non-uniform distribution of sky-scattered radiation in different directions, the sky hemisphere above the monitoring point is discretized, that is, the sky hemisphere is divided into N along the zenith angle direction. Z Each interval is further divided into N intervals along the azimuth direction. A There are several intervals, thus forming (N) Z ×N A ) discrete sky cells; Pa,b represents the relative scattered radiance weight of the (a,b)th discrete sky cell; Outdoor horizontal diffuse irradiance, This represents the weight of the scattered radiance transmitted from the sky along the roof discrete cell (i,j) to the monitoring point.

[0058] The Perez anisotropic sky brightness model is introduced to calculate the scattered radiation intensity of each roof discrete unit, which closely matches the non-uniform distribution characteristics of real sky scattered radiation. By calculating the elevation angle, azimuth angle, and zenith angle of the scattered radiation rays, the sky radiation direction parameters are accurately quantified. Combined with the apparent solid angle to characterize the radiation reception range of the roof discrete unit to the monitoring point, the effective scattered radiation input of the roof discrete unit at different spatial locations is quantified.

[0059] In a preferred embodiment, the method for calculating the total amount of scattered radiation transmitted through the monitoring point based on the scattered radiation transmittance and scattered radiation intensity corresponding to each discrete unit of the roof, and then solving for the scattered radiation transmittance at the monitoring point, includes:

[0060] The total amount of scattered radiation transmitted through all discrete roof units is summed to obtain the total amount of scattered radiation transmitted through monitoring point P, D. tr The calculation formula is: ;

[0061] According to the total amount of scattered radiation transmitted D tr Calculate the equivalent scattered radiation transmittance τ at monitoring point P. d The calculation formula is: .

[0062] The total amount of scattered radiation transmitted at monitoring point P is calculated by summing the scattered radiation transmission flux of all discrete roof units. The differential radiation transmission contribution of roof units at different locations is integrated by subdividing the calculation of each discrete roof unit and summing all units. At the same time, the transmittance is solved by using the standardized irradiance ratio, which ensures the objectivity and accuracy of the scattered radiation transmittance results at monitoring point P.

[0063] In a preferred technical solution, a method for calculating the amount of direct radiation transmitted through the monitoring point P is also included:

[0064] Obtain the outdoor solar altitude angle h s And the solar azimuth angle α s Combining the greenhouse azimuth angle φ, a unit vector s for the direction of direct solar radiation is constructed in a three-dimensional rectangular coordinate system, and the calculation formula is as follows: ;

[0065] Calculate the angle between the unit vector s of the direct solar radiation direction and the unit direction vector pointing from the monitoring point to the center point of the roof discrete unit, and sort all the angles from smallest to largest; select the smallest angle from the sorted angles, and the roof discrete unit corresponding to it is taken as the effective roof discrete unit through which direct solar radiation is transmitted to the monitoring point.

[0066] The diffuse radiation transmittance of the selected effective roof discrete unit is equivalent to the direct radiation transmittance. Calculate the amount of direct radiation transmitted through the monitoring point. The calculation formula is:

[0067] ;

[0068] ;

[0069] in, Outdoor horizontal direct irradiance, This represents the total outdoor horizontal solar irradiance.

[0070] By using the angle between the unit vector s of the direct solar radiation direction and the unit direction vector pointing from the monitoring point to the center of the roof discrete unit, a unique effective roof discrete unit that transmits direct solar radiation to the monitoring point is selected, avoiding interference from invalid roof discrete units in the calculation of direct radiation. At the same time, the outdoor horizontal direct irradiance is calculated based on the measured outdoor horizontal total solar irradiance and outdoor horizontal diffuse irradiance, which closely matches the actual outdoor solar radiation situation and greatly improves the calculation accuracy of greenhouse direct radiation transmittance.

[0071] In a preferred technical solution, a method for calculating the total solar radiation transmittance at the monitoring point is also included:

[0072] The total solar irradiance at the monitoring point is obtained by summing the total amount of diffused radiation transmitted and the amount of direct radiation transmitted through the greenhouse roof. The calculation formula is: ;

[0073] According to the total solar irradiance Solve for the total solar radiation transmittance at the monitoring point. Its expression is: .

[0074] Based on the total amount of scattered radiation transmitted and the amount of direct radiation transmitted intercepted at the monitoring points, the total solar radiation transmittance of the greenhouse can be calculated. This completely solves the problems of low accuracy, single dimension, and inability to quantify total light transmittance performance in traditional greenhouse radiation calculation methods. It can accurately characterize the overall light transmittance characteristics of the greenhouse and provide comprehensive and accurate core data support for greenhouse structure optimization, light transmittance material selection, intelligent control of indoor light environment, and construction of crop light growth models.

[0075] This invention represents a significant advancement over existing technologies. Specifically, existing technologies lack precise calculation methods for direct and diffuse radiation transmittance, and commonly employ idealized assumptions such as an equivalent overall roof planar structure and uniform sky scattering, leading to substantial deviations in radiation calculation results. To address this, this invention uses the roof's horizontal plane projection as a reference to complete a gridded discrete model. Combining polarized optical transmission laws and the Perez anisotropic sky brightness model, it accurately calculates the diffuse radiation transmittance and diffuse radiation intensity of each discrete roof unit. The total diffuse radiation flux of all units is then summed to obtain the total diffuse radiation transmittance at the indoor monitoring point. The direct radiation transmittance at the monitoring point is then calculated separately, and the total indoor irradiance and total radiation transmittance are calculated by integrating both types of radiation components. This solution provides high-precision basic parameters for greenhouse steady-state light field simulation, aiding in greenhouse structure optimization, light-transmitting film selection, and refined control of the indoor light environment. Attached Figure Description

[0076] Figure 1 This is a flowchart illustrating Embodiment 1 of the present invention.

[0077] Figure 2 This is a simplified diagram of the test platform in Embodiment 4 of the present invention.

[0078] Figure 3 These are the simulated and predicted total radiation values ​​and the measured total radiation values ​​within the platform in Embodiment 4 of the present invention.

[0079] Figure 4 It is the regression fit goodness of the simulated predicted total radiation value and the measured total radiation value in Embodiment 4 of the present invention.

[0080] In the diagram: 1. Opaque frame; 2. Thin film; 3. Total solar radiation meter; 4. Scattered radiation meter. Detailed Implementation

[0081] The technical solution of the present invention will be further described in detail below through specific embodiments.

[0082] Example 1

[0083] like Figure 1 As shown in the figure, this embodiment presents a method for calculating the solar radiation transmittance of a greenhouse based on roof discretization, including:

[0084] A three-dimensional rectangular coordinate system for the greenhouse is established, and a three-dimensional geometric model of the greenhouse's translucent roof is constructed based on the three-dimensional rectangular coordinate system. The entire translucent roof is discretized into several independent roof discretization units, using the horizontal projection area of ​​the translucent roof as the dividing criterion.

[0085] Inside the greenhouse, monitoring points are pre-set. The line vector connecting the monitoring points to the center point of each roof discrete unit is defined as the direction of scattered radiation transmitted from the roof discrete unit to the monitoring point. The scattered radiation transmittance and scattered radiation intensity corresponding to each roof discrete unit are calculated respectively.

[0086] Based on the scattered radiation transmittance and scattered radiation intensity corresponding to each discrete unit of the roof, the total amount of scattered radiation transmitted through the monitoring point is calculated, and then the equivalent scattered radiation transmittance at the monitoring point is obtained.

[0087] This embodiment constructs a precise roof geometric model based on a three-dimensional Cartesian coordinate system. The curved roof surface is discretized by horizontal plane projection and meshing. The direction of scattered radiation transmission is represented by the vector from the monitoring point to the unit center. The scattered radiation transmittance and radiation intensity are calculated for each unit, and the total scattered transmittance is obtained by superimposing the transmittance of each unit. Finally, the equivalent transmittance of scattered radiation at the monitoring point is solved by combining the outdoor scattered irradiance. This method divides the complex greenhouse roof into multiple discrete roof units with independent coordinates, area, and outward normal vectors, and is applicable to arched roofs, gable roofs, multi-faceted roofs, and complex curved roofs.

[0088] Example 2

[0089] The difference between this embodiment and Embodiment 1 is that it provides a specific implementation method for calculating the transmittance of scattered radiation at a monitoring point, including the following steps:

[0090] S1: Use a spectrophotometer to measure the spectral transmittance and reflectance of the greenhouse covering film at different wavelengths, and determine the equivalent optical parameters of the film, including: the refractive index, absorption coefficient and film thickness.

[0091] S2: Horizontal total solar irradiance obtained through outdoor radiation measurement and horizontal scattered irradiance The horizontal direct irradiance is obtained based on the difference between the two. Simultaneously, the solar altitude angle is calculated based on the test location, date, and time. And solar azimuth α s ;

[0092] S3: Establish a three-dimensional rectangular coordinate system for the greenhouse, and construct a three-dimensional geometric model of the greenhouse's translucent roof based on the three-dimensional rectangular coordinate system.

[0093] S31: Methods for establishing a three-dimensional rectangular coordinate system for a greenhouse, including:

[0094] The geometric center of the greenhouse is selected as the origin of the three-dimensional rectangular coordinate system;

[0095] Define the coordinate axes of the three-dimensional rectangular coordinate system as follows: the positive X-axis points westward along the longitudinal direction of the greenhouse, the positive Y-axis points southward along the span of the greenhouse, and the positive Z-axis points vertically upward.

[0096] Define the greenhouse azimuth angle φ: with the geographic south direction as the zero reference direction, deflection to the west is positive and deflection to the east is negative. The angle between the positive direction of the Y-axis of the three-dimensional rectangular coordinate system and the geographic south direction is set as the greenhouse azimuth angle φ.

[0097] S32: A method for constructing a three-dimensional geometric model of a greenhouse's translucent roof, including:

[0098] The cross-sectional curve function of the greenhouse's translucent roof is predefined as z=f(y). The cross-sectional curve function is extended along the X-axis in the three-dimensional rectangular coordinate system to form a three-dimensional geometric model of the greenhouse's translucent roof.

[0099] S4: Using the horizontal projection area of ​​the translucent roof as the dividing criterion, the entire translucent roof is discretized into several independent roof discretization units.

[0100] Using the horizontal projection area of ​​the translucent roof as the dividing benchmark, the longitudinal length of the greenhouse is evenly divided into N. X The greenhouse span is evenly divided into N intervals. Y A range;

[0101] Define the center point coordinates of the roof discrete element (i,j) as (x ij,c ,y ij,c ,z ij,c ), where i = 1, 2, ..., N X j=1,2,…,N Y c represents the coordinates of the geometric center of the greenhouse;

[0102] The formula for calculating the actual area of ​​the roof discrete element (i,j) is as follows: ;

[0103] The normal vector n of the roof discrete element (i,j) ij The calculation formula is: ;

[0104] in, The distance between the longitudinal sections of the greenhouse is the distance from the ground. The distance between the greenhouse spans is defined by the distance between the rows of plants. Cross-sectional curve function Coordinates of the span direction at the center point of the discrete element (i,j) on the roof The first derivative at that point.

[0105] Specifically, the coordinates of the center point are (x ij,c ,y ij,c ,z ij,cThe calculation formula for ) includes:

[0106] ;

[0107] ;

[0108] ;

[0109] Specifically, the longitudinal division of the greenhouse is based on the distance from the walkway. The distance between the greenhouse span intervals and the walking distance The calculation formulas are as follows:

[0110] ;

[0111] ;

[0112] S5: Pre-set monitoring points inside the greenhouse, and define the line vector connecting the monitoring points to the center point of each roof discrete unit as the effective propagation direction of the scattered radiation light of each roof discrete unit corresponding to the monitoring point.

[0113] A monitoring point P is pre-set inside the greenhouse, with its coordinates set as (x...). p ,y p ,z p );

[0114] Construct a line vector v connecting monitoring point P to the center point of the discrete element (i,j) on the roof. ij And solve for the corresponding unit direction vector. The calculation formulas are as follows:

[0115] ;

[0116] .

[0117] S6: Calculate the diffuse radiation transmittance and diffuse radiation intensity for each discrete unit of the roof.

[0118] S61: The formula for calculating the transmittance of scattered radiation includes:

[0119] Scattered radiation transmittance τ transmitted from the discrete element (i,j) on the roof to the monitoring point d,ij : ;

[0120] Vertical polarization component of scattered radiation transmitted from the discrete element (i,j) along the roof to the monitoring point : ;

[0121] Parallel polarization component of scattered radiation transmitted from the discrete element (i,j) along the roof to the monitoring point : ;

[0122] The interface reflectivity of the vertical polarization component of the scattered radiation at the discrete element (i,j) of the roof. : ;

[0123] The interface reflectivity R of the parallel polarization component of the scattered radiation at the discrete element (i,j) of the roof. ∥,ij : ;

[0124] Radiation absorptivity T of the roof discrete element (i,j) A,ij : ;

[0125] The angle of refraction θ of light entering the internal thin film of the discrete unit (i,j) on the roof t,ij : ;

[0126] The incident angle θ of the scattered radiation transmitted from the discrete element (i,j) on the roof to the monitoring point ij : ;

[0127] In the formula, n is the refractive index of the thin film, K is the absorption coefficient of the thin film, and d is the thickness of the thin film.

[0128] S62: Methods for calculating the intensity of scattered radiation, including:

[0129] Based on the spatial coordinates of monitoring point P and the center point of the discrete element (i,j) on the roof, calculate the height angle of the corresponding scattered radiation. The calculation formula is:

[0130] ;

[0131] According to the elevation angle Solve for the zenith angle of the corresponding scattered radiation rays. The calculation formula is: ;

[0132] Based on the zenith angle The weights of the scattered radiance transmitted from the roof discrete element (i,j) to the monitoring point are obtained using the Perez anisotropic sky brightness model. Then the intensity of scattered radiation in that direction is calculated. The calculation formula is:

[0133] ;

[0134] L P,ijLet be the diffuse radiance (W·m⁻²·sr⁻¹) in the sky direction corresponding to the (i,j)th roof discrete element. Let H be the apparent solid angle (sr) of the (i,j)th roof discrete element relative to the monitoring point. P,ij The effective receiver factor for a monitoring point to receive directional scattered radiation from discrete units of the roof is given by the following formula:

[0135] ;

[0136] ;

[0137] ;

[0138] in, The outdoor horizontal diffuse irradiance is represented by the image. To characterize the non-uniform distribution of sky diffuse radiation in different directions, the sky hemisphere above the monitoring point is discretized, that is, the sky hemisphere is divided into N hemispheres along the zenith angle. Z Each interval is further divided into N intervals along the azimuth direction. A There are several intervals, thus forming (N) Z × N A The (a,b)th discrete sky cell. Pa,b represents the relative scattered radiance weight of the (a,b)th discrete sky cell; This represents the weight of the scattered radiance transmitted from the sky along the roof discrete cell (i,j) to the monitoring point. Za,b is the central zenith angle of the (a,b)th sky discrete cell; Let be the apparent solid angle of the (a,b)th discrete sky cell.

[0139] ;

[0140] .

[0141] S7: Based on the scattered radiation transmittance and scattered radiation intensity corresponding to each roof discrete unit, calculate the total amount of scattered radiation transmitted through the monitoring point, and then solve for the scattered radiation transmittance at the monitoring point.

[0142] The total amount of scattered radiation transmitted through all discrete roof units is summed to obtain the total amount of scattered radiation transmitted through monitoring point P, D. tr The calculation formula is: ;

[0143] According to the total amount of scattered radiation transmitted D tr Calculate the equivalent transmittance τ of scattered radiation at monitoring point P. d The calculation formula is: .

[0144] In this embodiment, firstly, the optical properties of the greenhouse enclosure film, such as refractive index, absorption coefficient, and film thickness, are measured. Simultaneously, measured outdoor environmental data, including outdoor horizontal total solar irradiance and horizontal diffuse irradiance, are collected. The outdoor horizontal direct irradiance is then calculated by the difference between the two.

[0145] Then, a three-dimensional rectangular coordinate system dedicated to the greenhouse is constructed. The horizontal projection area of ​​the roof is used as the basis for mesh division. The curved light-transmitting roof of the greenhouse is meshed to obtain several roof discrete units. The center coordinates, actual surface area and unit outward normal vector of each discrete unit are solved one by one.

[0146] Finally, the three-dimensional line vector connecting the preset monitoring points in the greenhouse to the center of each roof discrete unit is taken as the effective transmission direction of the scattered radiation. The elevation angle, zenith angle and azimuth angle corresponding to this light are solved. The scattered radiation brightness weights in the corresponding directions are matched by interpolation based on the Perez anisotropic sky brightness model. The apparent solid angle of each roof unit relative to the monitoring point and the measured optical parameters of the thin film are solved step by step. Finally, the total amount of scattered radiation transmitted by the monitoring point and the scattered radiation transmittance at the monitoring point are obtained by summing them up.

[0147] Thin film refractive index, absorption coefficient, and thickness are core optical constants for calculating light reflection, refraction, and medium absorption loss. Outdoor horizontal total irradiance and diffuse irradiance serve as environmental boundary input conditions; their difference can be used to separate direct irradiance, achieving decoupling of direct and diffuse solar radiation components and providing a data foundation for separate calculations of these two types of radiation. A horizontally projected grid is used to discretize the curved roof surface. The actual area and normal vector of each element are solved using the derivative of the cross-sectional curve, abandoning planar equivalence simplification and accurately restoring the curved geometric characteristics of the greenhouse roof. The element center coordinates and normal vector are used to accurately calculate the incident angle of light, eliminating geometric calculation errors caused by the curvature of the surface. A three-dimensional vector is used to represent the radiation transmission path, and the sky radiation direction is quantified by elevation angle, zenith angle and azimuth angle. The Perez model is introduced to abandon the assumption of sky isotropy and restore the non-uniform distribution characteristics of sky scattered radiation. The apparent solid angle represents the effective projection range of radiation from a single roof unit to the indoor monitoring point. The transmission flux of a single unit is calculated by combining the thin film polarization transmission optical model. The total scattered transmission is obtained by superimposing the flux of all units, which fits the real physical transmission process of natural light transmission film.

[0148] Example 3

[0149] The difference between this embodiment and Embodiment 1 or 2 is that it provides a specific implementation method for calculating the direct radiation transmittance intercepted at a monitoring point, including:

[0150] Obtain the outdoor solar altitude angle h s And the solar azimuth angle α sCombining the greenhouse azimuth angle φ, a unit vector s for the direction of direct solar radiation is constructed in a three-dimensional rectangular coordinate system, and the calculation formula is as follows: ;

[0151] Calculate the angle between the unit vector s of the direct solar radiation direction and the unit direction vector of the monitoring point pointing to the center point of the roof discrete unit, and sort all the angles from smallest to largest; select the smallest angle from the sorted angles, and the roof discrete unit corresponding to it is taken as the effective roof discrete unit through which the direct solar radiation is transmitted to the monitoring point.

[0152] The diffuse radiation transmittance of the selected effective roof discrete unit is equivalent to the direct radiation transmittance. Calculate the amount of direct radiation transmitted through the monitoring point. The calculation formula is:

[0153] ;

[0154] ;

[0155] in, Outdoor horizontal direct irradiance, This represents the total outdoor horizontal solar irradiance.

[0156] In this embodiment, a unit vector of direct solar radiation direction is constructed by combining the solar altitude angle, solar azimuth angle, and greenhouse azimuth angle; the angle between this direct radiation unit vector and the unit direction vector from each roof discrete unit to the monitoring point is compared to select effective roof discrete units that can transmit direct sunlight to the monitoring point; the direct radiation transmittance of the monitoring point is calculated by combining the outdoor horizontal direct irradiance and the radiation transmittance of the effective unit.

[0157] The direction of direct sunlight propagation is represented by a three-dimensional spatial vector. The unique transmission unit of direct sunlight is determined by the vector angle. Based on the optical transmission law of thin film and the outdoor direct irradiance, the direct radiative flux received indoors is calculated.

[0158] Example 4

[0159] The difference between this embodiment and embodiments 1, 2, or 3 is that it provides a specific implementation method for calculating the total solar irradiance through the greenhouse roof at the monitoring point and the total solar radiation transmittance at the monitoring point, including:

[0160] The total solar irradiance at the monitoring point is obtained by summing the total amount of diffused radiation transmitted and the amount of direct radiation transmitted through the greenhouse roof. The calculation formula is: ;

[0161] Based on total solar irradiance Solve for the total solar radiation transmittance at the monitoring point. Its expression is: .

[0162] The total solar radiation transmittance received by the greenhouse monitoring point is obtained by summing the obtained diffuse radiation transmittance and direct radiation transmittance. Then, the total solar radiation transmittance corresponding to the monitoring point is calculated by combining the outdoor horizontal total solar irradiance.

[0163] Total solar radiation consists of two independent components: diffuse radiation and direct radiation, following the principle of superposition of radiation flux. The total radiation transmittance is defined as the ratio of total indoor transmitted radiation to total outdoor incident irradiance, thus achieving a quantitative characterization of the overall light transmittance performance of the greenhouse.

[0164] This invention establishes a refined method for calculating the transmittance of direct and diffuse radiation based on intrinsic optical parameters such as the refractive index and absorption coefficient of thin films. This method is dynamically embedded into a solar greenhouse light environment model, enabling the model to update the film's light transmittance performance in real time according to changes in the sun's position, weather type, and greenhouse structure. Its advantages lie in its ability to more accurately predict the light intensity and uniformity at different locations inside the greenhouse, as well as to quantitatively separate and compare the contributions of the film material and the greenhouse structure to light-gathering performance. This provides a calculable and verifiable basis for the selection of films, optimization of roof structures, and material-structure co-design of different types of solar greenhouses.

[0165] Verification Experiment

[0166] like Figure 1 As shown, the test platform for the transmission characteristics of the thin film 2 is a right-angled triangular prism. Its inclined surface covers the agricultural thin film 2 to be tested, allowing solar radiation to enter the interior of the triangular prism. The other faces of the triangular prism are opaque frames 1, covered with black velvet cloth to prevent natural light from entering the test platform. In addition, a total solar radiation meter 3 (monitoring point) is arranged inside the platform, and a total solar radiation meter 3 and a diffuse radiation meter 4 are arranged outside the platform.

[0167] The platform test was conducted under natural solar radiation conditions. Taking the continuous observation results from February 4, 2026 as an example, the test data covered the daytime period from approximately 08:00 to 16:40. Using the measured solar radiation outside the thin film 2 as the model input, and based on parameters such as the film's refractive index, extinction coefficient, film thickness, and solar incidence angle, the method of this invention was used to calculate the simulated predicted total radiation value at the corresponding location and time below the thin film 2. Simultaneously, radiation sensors were deployed at the corresponding measuring points below the thin film 2 to obtain the actual transmitted total radiation value. The simulated predicted total radiation value and the measured total radiation value at the same time were compared point-by-point, and the prediction accuracy of the method of this invention was evaluated using regression goodness of fit and root mean square error.

[0168] Using the measured solar radiation outside the thin film 2 as model input, and based on parameters such as the thin film's refractive index, extinction coefficient, thickness, and solar incidence angle, the method of this invention calculates the total solar radiation transmittance at the monitoring point on the platform below the thin film 2, and compares it with the measured radiation data from the platform. Figure 2 , Figure 3 As shown, the regression fit goodness of simulated radiation and measured radiation is R²=0.8903, and the root mean square error (RMSE) of the total radiation time series verification in the device is 41.44 W / m², indicating that the method of the present invention has good predictive consistency and can meet the application requirements of radiation transmission characteristic analysis of agricultural film 2 and greenhouse light environment simulation.

[0169] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them; although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications can still be made to the specific implementation of the present invention or equivalent substitutions can be made to some technical features without departing from the spirit of the technical solutions of the present invention, and all such modifications and substitutions should be covered within the scope of the technical solutions claimed in the present invention.

Claims

1. A method for calculating the solar radiation transmittance of a greenhouse based on roof discretization, characterized in that, include: A three-dimensional rectangular coordinate system for the greenhouse is established, and a three-dimensional geometric model of the greenhouse's translucent roof is constructed based on the three-dimensional rectangular coordinate system. Using the horizontal projection area of ​​the translucent roof as the dividing criterion, the entire translucent roof is discretized into several independent roof discretization units; Inside the greenhouse, monitoring points are pre-set. The line vector connecting the monitoring points to the center point of each roof discrete unit is defined as the direction of scattered radiation transmitted from the roof discrete unit to the monitoring point. The scattered radiation transmittance and scattered radiation intensity corresponding to each roof discrete unit are calculated respectively. Based on the scattered radiation transmittance and scattered radiation intensity corresponding to each discrete unit of the roof, the total amount of scattered radiation transmitted through the monitoring point is calculated, and then the equivalent scattered radiation transmittance at the monitoring point is obtained.

2. The method for calculating greenhouse solar radiation transmittance based on roof discretization according to claim 1, characterized in that, The method for establishing a three-dimensional rectangular coordinate system for a greenhouse includes: The geometric center of the greenhouse is selected as the origin of the three-dimensional rectangular coordinate system; Define the coordinate axes of the three-dimensional rectangular coordinate system as follows: the positive X-axis points westward along the longitudinal direction of the greenhouse, the positive Y-axis points southward along the span of the greenhouse, and the positive Z-axis points vertically upward. Define the greenhouse azimuth angle φ: with the geographic south direction as the zero reference direction, deflection to the west is positive and deflection to the east is negative. The angle between the positive direction of the Y-axis of the three-dimensional rectangular coordinate system and the geographic south direction is set as the greenhouse azimuth angle φ.

3. The method for calculating greenhouse solar radiation transmittance based on roof discretization according to claim 2, characterized in that, The method for constructing a three-dimensional geometric model of a greenhouse roof includes: The cross-sectional curve function of the pre-defined greenhouse light-transmitting roof is z=f(y). The cross-sectional curve function is extended along the X-axis in the three-dimensional rectangular coordinate system to form a three-dimensional geometric model of the greenhouse light-transmitting roof.

4. The method for calculating greenhouse solar radiation transmittance based on roof discretization according to claim 3, characterized in that, The method of discretizing the entire translucent roof into several independent roof discrete units based on the horizontal projection area of ​​the translucent roof includes: Using the horizontal projection area of ​​the translucent roof as the dividing benchmark, the longitudinal length of the greenhouse is evenly divided into N. X The greenhouse span is evenly divided into N intervals. Y A range; Define the center point coordinates of the roof discrete element (i,j) as (x ij,c ,y ij,c ,z ij,c ), where i = 1, 2, ..., N X j=1,2,…,N Y c represents the coordinates of the geometric center of the greenhouse; The formula for calculating the actual area of ​​the roof discrete unit (i,j) is as follows: ; The normal vector n of the roof discrete element (i,j) ij The calculation formula is: ; in, The distance between the longitudinal sections of the greenhouse is the distance from the ground. The distance between the greenhouse spans is defined by the distance between the rows of plants. Cross-sectional curve function Coordinates of the span direction at the center point of the discrete element (i,j) on the roof The first derivative at that point.

5. The method for calculating greenhouse solar radiation transmittance based on roof discretization according to claim 4, characterized in that, The method of pre-setting monitoring points inside the greenhouse, and defining the line vector connecting the monitoring points to the center points of each roof discrete unit as the direction of scattered radiation transmitted from the roof discrete unit to the monitoring point, includes: A monitoring point P is pre-set inside the greenhouse, with its coordinates set as (x...). p ,y p ,z p ); Construct a line vector v connecting monitoring point P to the center point of the discrete element (i,j) on the roof. ij And solve for the corresponding unit direction vector. The calculation formulas are as follows: ； 。 6. The method for calculating greenhouse solar radiation transmittance based on roof discretization according to claim 5, characterized in that, The calculation of the scattered radiation transmittance and scattered radiation intensity for each discrete roof unit includes the following formula: Scattered radiation transmittance transmitted from the discrete element (i,j) along the roof to the monitoring point : ; Vertical polarization component of scattered radiation transmitted from the discrete element (i,j) along the roof to the monitoring point : ; Parallel polarization component of scattered radiation transmitted from the discrete element (i,j) along the roof to the monitoring point : ; The interface reflectivity of the vertical polarization component of the scattered radiation at the discrete element (i,j) of the roof. : ; The interface reflectivity R of the parallel polarization component of the scattered radiation at the discrete element (i,j) of the roof. ∥,ij : ; Radiation absorptivity T of the roof discrete element (i,j) A,ij : ; The angle of refraction θ of light entering the internal thin film of the discrete unit (i,j) on the roof t,ij : ; The incident angle θ of the scattered radiation transmitted from the discrete element (i,j) on the roof to the monitoring point ij : ; In the formula, n is the refractive index of the thin film, K is the absorption coefficient of the thin film, and d is the thickness of the thin film.

7. The method for calculating greenhouse solar radiation transmittance based on roof discretization according to claim 6, characterized in that, The calculation of the scattered radiation transmittance and scattered radiation intensity transmitted from the discrete element (i,j) along the roof to the monitoring point includes the following methods: Based on the spatial coordinates of monitoring point P and the center point of the roof discrete element (i,j), calculate the corresponding scattered radiation elevation angle transmitted from the roof discrete element (i,j) to the monitoring point. The calculation formula is: ； According to the elevation angle Solve for the zenith angle of the scattered radiation transmitted from the discrete element (i,j) along the roof to the monitoring point. The calculation formula is: ; Based on the zenith angle The weights of the scattered radiance transmitted from the roof discrete element (i,j) to the monitoring point are obtained using the Perez anisotropic sky brightness model. Then the intensity of scattered radiation in that direction is calculated. The calculation formula includes: Scattered radiation intensity transmitted from the discrete element (i,j) along the roof to the monitoring point : ; The roof discrete element (i,j) corresponds to the scattered radiance in the sky direction. : ; The apparent solid angle of the roof discrete element (i,j) relative to the monitoring point : ; Effective receiver factor of the monitoring point receiving radiation scattered from the discrete element (i,j) of the roof. : ; The central zenith angle of the (a,b)th discrete sky cell : ; The apparent solid angle of the (a,b)th discrete sky unit : ; To characterize the non-uniform distribution of sky-scattered radiation in different directions, the sky hemisphere above the monitoring point is discretized, that is, the sky hemisphere is divided into N along the zenith angle direction. Z Each interval is further divided into N intervals along the azimuth direction. A There are several intervals, thus forming (N) Z ×N A ) discrete sky cells; Pa,b represents the relative scattered radiance weight of the (a,b)th discrete sky cell; Outdoor horizontal diffuse irradiance; This represents the weight of the scattered radiance transmitted from the sky along the roof discrete cell (i,j) to the monitoring point.

8. The method for calculating greenhouse solar radiation transmittance based on roof discretization according to claim 7, characterized in that, The method for calculating the total amount of scattered radiation transmitted through the monitoring point based on the scattered radiation transmittance and scattered radiation intensity corresponding to each discrete unit of the roof, and then solving for the scattered radiation transmittance at the monitoring point, includes: The total amount of scattered radiation transmitted through all discrete roof units is summed to obtain the total amount of scattered radiation transmitted through monitoring point P, D. tr The calculation formula is: ; According to the total amount of scattered radiation transmitted D tr Calculate the equivalent scattered radiation transmittance τ at monitoring point P. d The calculation formula is: .

9. The method for calculating greenhouse solar radiation transmittance based on roof discretization according to claim 8, characterized in that, It also includes the method for calculating the amount of direct radiation transmitted through the monitoring point P: Obtain the outdoor solar altitude angle h s And the solar azimuth angle α s Combining the greenhouse azimuth angle φ, a unit vector s for the direction of direct solar radiation is constructed in a three-dimensional rectangular coordinate system, and the calculation formula is as follows: ; Calculate the angle between the unit vector s of the direct solar radiation direction and the unit direction vector pointing from the monitoring point to the center point of the roof discrete unit, and sort all the angles from smallest to largest; select the smallest angle from the sorted angles, and the roof discrete unit corresponding to it is taken as the effective roof discrete unit through which direct solar radiation is transmitted to the monitoring point. The diffuse radiation transmittance of the selected effective roof discrete unit is equivalent to the direct radiation transmittance. Calculate the amount of direct radiation transmitted through the monitoring point. The calculation formula is: ； ； in, Outdoor horizontal direct irradiance, This represents the total outdoor horizontal solar irradiance.

10. The method for calculating greenhouse solar radiation transmittance based on roof discretization according to claim 9, characterized in that, It also includes the method for calculating the total solar radiation transmittance at the monitoring point: The total solar irradiance at the monitoring point is obtained by summing the total amount of diffused radiation transmitted and the amount of direct radiation transmitted through the greenhouse roof. The calculation formula is: ; According to the total solar irradiance Solve for the total solar radiation transmittance at the monitoring point. Its expression is: .

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