Solar cell panel dust deposition degree evaluation method and device

Abstract

The invention relates to a method and device for evaluating the dust deposition degree of a solar cell panel. According to the evaluation method, a dust deposition rate evaluation factor is calculated based on a visual image, and the dust deposition degree of the solar cell panel is evaluated according to the dust deposition rate evaluation factor. The evaluation device takes images through the image taking device, and the evaluation method is implemented through the data processing device. According to the invention, the automation / intelligence degree is high, the equipment is relatively simple, and the evaluation efficiency and the evaluation accuracy can be improved.

Description

Technical Field

[0001] The invention relates to a method and a device for evaluating the dust accumulation degree of a solar cell panel. Background Art

[0002] Renewable energy power generation is one of the strategic priorities of my country's current development. Among them, solar power generation has become an important pillar of the new energy industry with its characteristics of easy construction, easy integration and easy maintenance. The core component of solar power generation is the solar panel, whose ability to receive solar radiation and convert electrical energy is subject to the dual constraints of radiation and power generation efficiency. When the solar panel is covered with dust, the actual radiation of sunlight will be significantly reduced, affecting the actual power generation efficiency and service life. Based on this, how to correctly evaluate the degree of dust accumulation of solar panels has become a research focus in the field of solar power generation, and various detection methods for the degree of dust accumulation of solar panels have gradually been proposed. For example, the invention patent with publication number CN112285125A discloses a detection device for collecting dust accumulation on a solar panel, including a solar panel, a slide and a detection device; a slide is fixed on the top / bottom of the solar panel; the detection device includes a support plate and a laser transmitting and receiving system; a mounting seat A and a mounting seat B are fixedly installed on the support plate; a sliding seat is fixedly installed at one end of the support plate; a micro motor A is built into the sliding seat; a rack is provided on one side of the slide; the gear on the output shaft of the micro motor A is meshed with the rack; the sliding seat and the slide are slidably matched through the micro motor A and the roller. Through the action of the slide and the detection device, the laser beam is irradiated on the solar panel, and then the light loss rate in the reflected laser beam is collected, so that the degree of dust accumulation on the solar panel can be judged, which has the advantage of quickly and conveniently detecting the degree of dust accumulation on the solar panel. For another example, the invention patent with the publication number CN116915174A discloses a photovoltaic module with dust accumulation monitoring function, including a solar panel, the solar panel including a panel body, and a dust accumulation sensor, a temperature sensor and a collector are fixedly installed on the upper surface, the inner part or the lower surface of the panel body. The photovoltaic module is provided with a dust accumulation sensor, a temperature sensor and a collector on the panel body, and the dust accumulation sensor can monitor the dust accumulation on the surface of the panel body of the module, the temperature sensor is used to monitor the temperature outside or inside the panel body of the module, and the collector is used for data collection, calculation and transmission of the dust accumulation sensor and the temperature sensor. The above-mentioned technologies have their own characteristics, and can detect the dust accumulation degree of the solar panel. However, the above-mentioned technologies all use detection devices or elements to directly detect the dust accumulation on the solar panel, and the detection devices or elements are all arranged on the solar panel. The detection system and data processing process are complicated and easily affected by external factors and malfunction; the detection results are greatly affected by the performance of the detection device or element itself and other factors, and in actual applications, the dust accumulation degree of a certain point on the solar panel is detected, and the detection results are large in error and low in accuracy. Summary of the Invention

[0003] To overcome the above defects of the prior art, the present invention provides a method for evaluating the dust accumulation degree of a solar panel, which can effectively evaluate the dust accumulation degree of the solar panel, with small evaluation result error and high accuracy.

[0004] The technical solution of the present invention to achieve the above object is: a method for evaluating the dust accumulation degree of a solar panel, which obtains a visual image including the solar panel and the sky background, calculates a dust accumulation rate evaluation factor based on the visual image, evaluates the dust accumulation degree of the solar panel according to the dust accumulation rate evaluation factor, and establishes a relationship between the dust accumulation rate and the power generation capacity. The calculation formula of the dust accumulation rate evaluation factor is as follows:

[0005]

[0006] where α and β are respectively the image irradiance change factors of the solar panel area and the sky background area in the image, τ is the reflectivity parameter of the solar panel material, and Δθ is the angle between the specular reflection light vector of the solar panel and the normal vector of the lens (the lens of the image acquisition device).

[0007] Generally, the dust accumulation rate evaluation factor is negatively correlated with the dust accumulation degree of the solar panel but not inversely proportional. The smaller the factor, the higher the dust accumulation degree.

[0008] Furthermore, a dust removal threshold of the dust accumulation rate evaluation factor can be set. When the dust accumulation rate evaluation factor is lower than (including equal to, or reaching, the same below) the dust removal threshold of the dust accumulation rate evaluation factor, the dust removal device is controlled to perform dust removal.

[0009] Preferably, the dust accumulation rate evaluation factor F of the solar panel in the dust-free state (for example, the state without dust accumulation after construction, the dust-free posture after dust removal) is obtained a0 , and the real-time dust accumulation rate evaluation factor F a is calculated, and the ratio R a0 of the real-time dust accumulation rate evaluation factor F F to the dust accumulation rate evaluation factor F a in the dust-free state is calculated, and the ratio R a0 of the real-time dust accumulation rate evaluation factor F F to the dust accumulation rate evaluation factor F in the dust-free state is used to judge the dust accumulation degree of the solar panel.

[0010] Preferably, α and β are calculated respectively based on the following formula:

[0011]

[0012] where P1 and P2 are respectively the radiation light intensity of the solar panel area and the radiation light intensity of the sky background area, I 1,i and I2,j They are the pixel values of point i (any point) in the solar panel area of the image and point j (any point) in the sky background area of the image, respectively.

[0013] The summation range can be all the pixel points in the solar panel area and the sky background area of the image, respectively.

[0014] Existing technologies such as object imaging projection combined with color segmentation and other suitable technologies can be used to identify / segment the solar panel area, sky background area, and other areas (ground / ground object background area) in the image.

[0015] Preferably, P1 and P2 are calculated based on the following formula:

[0016]

[0017] P2 = P r

[0018] where P r is the radiation intensity of sunlight received by the corresponding ground, is the inclination angle of the solar panel.

[0019] The light radiation received by the ground is affected by atmospheric scattering. Therefore, it can be calculated according to the Rayleigh scattering model. The specific formula is:

[0020]

[0021] In the formula, θ is the scattering angle, λ is the light wavelength, n is the atmospheric refractive index, which is a fixed value in clear weather, N is the number density of atmospheric molecules, and ρ(h) is the atmospheric density ratio, and this value changes with the atmospheric height h.

[0022] After obtaining the dust accumulation degree factor F a the relationship model factor f between the dust accumulation degree and the power generation capacity of the corresponding solar panel is further solved.

[0023] Preferably, the model factor f can be described by the following formula:

[0024]

[0025] In the formula, P is the measured value of the power generation power, which is obtained through actual measurement; is the ideal inference value considering the current light conditions, which is calculated by the following formula.

[0026]

[0027] where k is the power conversion factor (which can be calibrated according to the factory value or the initial value of the solar panel); S is the area of the solar panel.

[0028] A system for evaluating the dust accumulation degree of a solar panel, comprising an image acquisition device (collectively referred to as a camera) and a data processing device. The image acquisition device is used to acquire a visual image containing the solar panel and the sky background and transmit it to the data processing device. The data processing device evaluates the dust accumulation degree of the solar panel based on the visual image from the image acquisition device by using any one of the solar panel dust accumulation degree evaluation methods disclosed in the present invention.

[0029] The beneficial effects of the present invention are as follows: The present invention evaluates the dust accumulation degree through visual images, with high automation / intelligence level and relatively simple equipment, which is beneficial to improving the evaluation efficiency and accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is the layout diagram of the device involved in the present invention;

[0031] Figure 2 It is the flowchart involved in the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0032] See Figure 1 , the present invention discloses a method for evaluating the dust accumulation degree of a solar panel and a solar panel dust accumulation degree evaluation system for implementing this method. The solar radiation intensity received on the ground is obtained in real time through a visual image, the power generation power of the solar panel under the condition of no dust accumulation at the current moment is calculated based on the solar radiation intensity received on the ground, and the dust accumulation degree of the solar panel at the current moment is calculated according to the actual power generation power of the solar panel at the current moment and the power generation power under the condition of no dust accumulation.

[0033] The visual image is preferably obtained by a camera, and the dust accumulation degree of the solar panel is calculated based on the ratio of the actual power generation power of the solar panel to the power generation power under the condition of no dust accumulation.

[0034] The solar radiation intensity received on the ground is the solar radiation intensity in the area where the solar panel is located (or the installation location).

[0035] The corresponding relationship / functional relationship between the dust accumulation degree of the solar panel and the ratio of the actual power generation power of the solar panel to the power generation power under the condition of no dust accumulation can be obtained based on experimental data. The dust accumulation degree of the solar panel is calculated based on this corresponding relationship / functional relationship and the obtained solar radiation intensity received on the ground.

[0036] The corresponding relationship / functional relationship between the dust accumulation degree of the solar panel and the ratio of the actual power generation power of the solar panel to the power generation power under the condition of no dust accumulation can also be obtained in the following way:

[0037] First, according to the sun-earth orbit prediction, calculate the zenith radiation of sunlight on the earth's atmosphere at different times to obtain the zenith angle and radiation intensity; then, obtain the image information and irradiance reception information of the installation location (or region) of the solar panel and the background environment region, and calculate the irradiance consistency correction at the relative time of the image with the initial installation time information of the solar panel as a reference; then, calculate the theoretical non-decaying power generation of the solar panel based on the received irradiance (the power generation under the condition of no dust accumulation), and finally, establish a relationship model between the visual image and the ratio of the actual power generation of the solar panel and the power generation under the condition of no dust accumulation. Specifically, it includes the following steps:

[0038] Step 1: Calculate the zenith angle and irradiance of sunlight on the earth's atmosphere at the imaging time from the sun-earth ephemeris.

[0039] From the relative motion of the sun and the earth, the solar altitude angle azimuth angle ψ and the sun-earth distance d can be directly calculated in the geocentric inertial coordinate system (abbreviated as the geocentric coordinate system). m Denote the light radiation power emitted by the sun towards the earth at time t0 as P T . Considering the propagation process from the sun to the earth's atmosphere surface as an ideal space propagation that is omnidirectional and lossless, the power density reaching the earth's atmosphere surface is:

[0040]

[0041] In the formula, R m is the radius of the earth, d m is the sun-earth distance, is the solar altitude angle, ψ is the solar azimuth angle, and P T is the light radiation power emitted by the sun towards the earth at time t0.

[0042] Since the sun-earth distance d m >> the radius of the earth R m >> the thickness of the earth's atmosphere, the subtraction term in the denominator of the formula can be ignored. The incident angle of sunlight reaching the zenith surface is denoted as:

[0043]

[0044] In the formula, δ is the incident angle of sunlight relative to the location of the solar panel, is the solar altitude angle. Under the assumption that sunlight does not scatter in the atmosphere, the non-deflected power irradiated on the solar panel is:

[0045]

[0046] Among them, S e is the area of the solar panel; S ris the area of the solar panel receiving sunlight; φ e is the sunlight incident angle of the solar panel, is the estimated unbiased ideal power.

[0047] Since neither the panel attitude nor the solar panel attitude is horizontal, φ e differs from δ by a rotational transformation of the solar panel itself once. Denote the attitude rotation matrix of the panel in the geocentric coordinate system as R b , and the tilt angle of the solar panel is denoted as Then the normal vector N of the solar panel e is defined in the geocentric coordinate system as:

[0048]

[0049] The sunlight incident direction N s is described in the geocentric coordinate system as:

[0050]

[0051] At this time, the sunlight incident angle of the solar panel is calculated as:

[0052] φ e = arccos(N s ·N e )

[0053] Step 2: Calculate the specular reflection factor, obtain the surface irradiance, and perform relative radiometric correction on the original image.

[0054] According to the collected visual image, extract the solar panel area therein. Taking the four boundary points of the solar panel as anchor points, use the Perspective-n-Points (PnP) algorithm to calculate the installation relationship between the solar panel and the camera system, and the normal vector of the solar panel surface in the camera system can be obtained. The angle between this normal vector and the lens optical axis is calculated as:

[0055]

[0056] In the formula, N t represents the normal vector of the solar panel in the camera system, and N c is the camera lens optical axis vector. Then the angle between the specular reflection light vector passing through the solar panel and the lens normal vector is denoted as:

[0057] Δθ = ‖φ e -θ‖1

[0058] In the formula, φ eis the incident angle of sunlight on the solar panel, and θ is the angle between the normal vector of the solar panel and the optical axis of the camera. Denote the radiation intensity received by the ground (sunlight) at this time as P r , then the radiation light intensity P1 in the solar panel area in the image is calculated as:

[0059]

[0060] Among them, τ is the reflectivity parameter of the solar panel material, which can be obtained by looking up the table. Then, according to the installation position relationship between the camera and the solar panel, the area of the solar panel in the image can be obtained through the pinhole imaging projection model. This area is expected to be in the middle area of the image. Then, above this area, the main part is the sky background, and the secondary part includes the ground background of part of the installation area. The sky background area can be obtained through color segmentation. Then, according to the Rayleigh scattering model, the radiation light intensity P2 in the sky background area satisfies:

[0061]

[0062] Among them, θ is the scattering angle; λ is the light wavelength; n is the atmospheric refractive index, which changes according to different weather conditions and can be determined by looking up the table according to the weather conditions; N is the atmospheric molecular number density; ρ(h) is the atmospheric density ratio, and this value changes with the atmospheric height h and can be obtained by looking up the table according to the longitude, latitude and altitude values of the solar panel installation point. is the unbiased ideal power estimated in the previous step. Since the scattered light intensity is much smaller than the direct light intensity during the atmospheric scattering process, it can be assumed that all the ground light rays reflected into the camera come from the direct light, that is, take the θ value as 0. Due to the presence of dust accumulation, there will be an obvious difference in the irradiation state of the image at the initial installation of the solar panel area compared with the irradiation state of the sky background area. Denote the image irradiation change factors of the solar panel area and the sky background area as:

[0063]

[0064] In the formula, α refers to the irradiation change factor of the solar panel area, and β refers to the image irradiation change factor of the sky background area. In the ideal case without dust accumulation, α and β should differ by cos(Δθ) times. Then, the evaluation factor of the dust accumulation rate measured by the solar panel image in the actual situation is defined as:

[0065] F a = α / (βcos(Δθ))

[0066] Step 3: Calculate the theoretical non-decaying power generation power of the solar panel (the power generation power under the condition of no dust accumulation), compare it with the actual power generation capacity (actual power generation power) to obtain the power generation rate attenuation amount, and establish a relationship model between the visual image and the power generation rate attenuation amount.

[0067] Due to the presence of dust accumulation on the solar panel, the actual light flux received by the solar panel decreases, and its power generation capacity is inhibited. Under the condition of no dust accumulation, the power generation power of the solar panel is denoted as:

[0068]

[0069] where k is the power conversion factor (which can be calibrated according to the factory value or the initial value of the solar panel); S is the area of the solar panel. The actual power generation power P of the solar panel can be directly obtained through the readings of the corresponding equipment. Then, the power generation power loss ratio at this time can be described by At the same time, this loss ratio and the image dust accumulation rate factor can be regarded as an associated relationship, that is, the attenuation of the power generation capacity caused by dust accumulation satisfies:

[0070]

[0071] In the formula, f corresponds to the correlation function, which can be calculated by the least squares fitting method, that is, the image information at different times and the instantaneous power generation power readings of the solar panel can be used as inputs to construct the model f to effectively evaluate the dust accumulation degree of the solar panel.

[0072] After obtaining f, the power generation power loss degree of the solar panel at the current moment can also be directly calculated by inputting the image information subsequently.

[0073] The entire method process is as shown in Figure 2 Through the above method, the opportunity degree and the power generation power loss degree of the solar panel at the current moment can be estimated directly by inputting the image information.

[0074] For the preferred and optional technical means disclosed in the present invention, unless otherwise specified and when one preferred or optional technical means is a further limitation of another technical means, they can be combined arbitrarily to form several different specific implementation manners.

Claims

1. A method for evaluating the dust accumulation degree of a solar panel, characterized in that Obtain a visual image containing a solar panel and a sky background. Based on the visual image, calculate the ash accumulation rate evaluation factor using the following formula. Evaluate the degree of ash accumulation on the solar panel according to the ash accumulation rate evaluation factor, and establish the relationship between the ash accumulation rate and the power generation capacity. The calculation formula for the ash accumulation rate evaluation factor is as follows: Where, α and β are the image irradiance change factors of the solar panel area and the sky background area in the image respectively, τ is the reflectivity parameter of the solar panel material, and Δθ is the angle between the specular reflection light vector of the solar panel and the lens normal vector.

2. The method for evaluating the dust accumulation degree of a solar panel according to claim 1, wherein Set the ash cleaning threshold of the ash accumulation rate evaluation factor. When the ash accumulation rate evaluation factor is lower than the ash cleaning threshold of the ash accumulation rate evaluation factor, control the ash cleaning device to perform ash cleaning.

3. The method for evaluating the dust accumulation degree of a solar panel according to claim 1 or 2, wherein Calculate α and β respectively based on the following formula: Wherein, P1 and P2 are the radiation light intensities of the solar panel area and the sky background area respectively, and I 1,i and I 2,j are the pixel values of point i in the solar panel area in the image and the pixel value of point j in the sky background area in the image respectively.

4. The method for evaluating the dust accumulation degree of a solar panel according to claim 3, wherein Calculate P1 and P2 based on the following formula: P2 = P r where, P r is the radiation intensity of the corresponding ground receiving sunlight, is the inclination angle of the solar panel.

5. The method for evaluating the dust accumulation degree of a solar panel according to claim 4, wherein The light radiation received on the ground is affected by atmospheric scattering. Therefore, it can be calculated according to the Rayleigh scattering model. The specific formula is: In the formula, θ is the scattering angle, λ is the light wavelength, n is the atmospheric refractive index, which is a fixed value in sunny weather, N is the atmospheric molecular number density, ρ(h) is the atmospheric density ratio, and h is the atmospheric height.

6. The method for evaluating the dust accumulation degree of a solar panel according to claim 5, wherein The model factor f is described by the following formula: Where P is the measured value of the power generation, which is obtained through actual measurement; is the ideal inferred value considering the current light conditions and is calculated by the following formula: Where, k is the power conversion factor; S is the area of the solar panel.

7. A solar panel ash accumulation degree evaluation system, including an image acquisition device and a data processing device. The image acquisition device is used to acquire a visual image containing a solar panel and a sky background and transmit it to the data processing device. The data processing device evaluates the degree of ash accumulation on the solar panel by using the solar panel ash accumulation degree evaluation method described in any one of claims 1-6.

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