A non-contact method for evaluating photovoltaic module power generation efficiency

Abstract

This invention discloses a non-contact method for evaluating the power generation efficiency of photovoltaic (PV) modules, comprising the following steps: acquiring infrared images of the PV module and extracting the temperature matrix of the PV module surface; calculating the solar energy absorbed by the PV module based on the irradiance of the PV module surface; calculating the heat transfer between the PV module and the surrounding environment based on the ambient temperature; calculating the electrical power of the PV module according to the law of conservation of energy; normalizing the electrical power of the PV module and evaluating the power generation efficiency and energy attenuation ratio of the PV module. This invention addresses the problems of high cost and low efficiency in contact-based electrical data acquisition of PV modules, achieving a non-contact method for evaluating the power generation efficiency of PV modules. This invention can be combined with UAV autonomous inspection technology, as well as PV module fault diagnosis and health assessment technologies, providing important basis for the intelligent operation and maintenance of PV power plants.

Description

Technical Field

[0001] This invention relates to a non-contact photovoltaic module power generation efficiency evaluation technology, belonging to the field of intelligent inspection and smart operation and maintenance technology of photovoltaic systems. Background Technology

[0002] In recent years, photovoltaic (PV) power generation has played an increasingly important role in the energy structure. As the basic unit of a PV power generation system, PV modules have a lifespan of 20-25 years, during which time defects, malfunctions, and aging may occur. To ensure the stability, safety, and power generation efficiency of the PV system, it is necessary to promptly identify problematic PV modules. Output power is a crucial indicator of the health of PV modules. Existing methods use IV testing to obtain the electrical characteristics of PV modules and assess their output power.

[0003] However, IV testing is a contact-based measurement method. Each photovoltaic module requires maintenance personnel to operate its connectors, temporarily taking it offline. This method is time-consuming and labor-intensive, making it impractical for large-scale photovoltaic power plants. Besides IV testing, commonly used photovoltaic module inspection methods include visual observation, EL testing, and infrared thermal imaging. Among these, infrared thermal imaging not only enables non-contact data acquisition but is also an important method for analyzing the temperature characteristics of photovoltaic modules.

[0004] The International Energy Agency has compiled a list of temperature anomaly types for photovoltaic (PV) modules. Current technologies utilize infrared imaging to detect hot spots and classify temperature anomalies. However, existing technologies have not yet solved the problem of non-contact assessment of PV module power generation efficiency. PV modules convert absorbed solar energy into electrical and thermal energy, meaning their output power is correlated with temperature distribution. How to calculate the electrical power of PV modules using infrared imaging, thereby achieving non-contact assessment of PV module power generation efficiency, is a crucial issue that needs to be considered for intelligent inspection and smart operation and maintenance of PV systems. Summary of the Invention

[0005] Technical Problem: This invention aims to address the shortcomings of existing technologies by analyzing the heat transfer between photovoltaic modules and their surrounding environment based on infrared image analysis and calculating the electrical power of the photovoltaic modules according to the law of conservation of energy, thus providing a non-contact method for evaluating the power generation efficiency of photovoltaic modules.

[0006] Technical solution: The present invention provides a non-contact photovoltaic module power generation efficiency evaluation method, which includes the following steps:

[0007] S1: Acquire infrared images of photovoltaic modules and extract the temperature matrix of the photovoltaic module surface;

[0008] S2: Calculate the solar energy absorbed by the photovoltaic module based on the irradiance on the surface of the photovoltaic module;

[0009] S3: Calculate the heat transfer between the photovoltaic module and the surrounding environment based on the ambient temperature;

[0010] S4: Calculate the electrical power of the photovoltaic module according to the law of conservation of energy;

[0011] S5: Normalize the power output of the photovoltaic module to evaluate the power generation efficiency and energy degradation rate of the photovoltaic module.

[0012] Furthermore, in step S1, the conditions are as follows: sunny day, light breeze, and irradiance not less than 600 W / m². 2 Under conditions that avoid glare, acquire infrared images of the photovoltaic modules; the angle between the optical axis of the infrared camera and the surface of the photovoltaic module should be no less than 60°, and the images should be captured every 25cm of the photovoltaic module surface. 2 The region occupies at least 1 pixel in the infrared image; the radial distortion of the infrared image and the perspective distortion of the photovoltaic module are corrected, and the temperature matrix F of the photovoltaic module surface is extracted.

[0013] Furthermore, in step S2, G represents the irradiance of the photovoltaic module surface, S represents the area of ​​the photovoltaic module surface, and N represents the number of material layers of the photovoltaic module; the solar energy absorbed by the photovoltaic module is calculated as follows:

[0014]

[0015]

[0016] Among them, Q k α represents the amount of solar energy absorbed by the k-th layer material of a photovoltaic module. k τ represents the absorptivity of the k-th layer material in a photovoltaic module, where k = 1, ..., N; when q = 0, τ q =1; when 1≤q≤k-1, τ q The transmittance of the q-th layer material in the photovoltaic module is represented by ; Q represents the solar energy absorbed by the entire photovoltaic module.

[0017] Furthermore, in step S3, T a T represents air temperature. s F represents the sky temperature. i,j The elements in the temperature matrix F representing the surface of the photovoltaic module are used to calculate the heat transfer between the photovoltaic module surface and the surrounding environment as follows:

[0018]

[0019]

[0020] Where, Φ fΨ represents the heat convection between the surface of a photovoltaic module and its surrounding environment. f δ represents the thermal radiation between the surface of a photovoltaic module and its surrounding environment. f The temperature matrix F represents the area of ​​the photovoltaic module surface corresponding to each element, σ represents the Stefan-Boltzmann constant, and ε represents the area of ​​the photovoltaic module surface corresponding to each element. f ε represents the emissivity of the surface of a photovoltaic module. s h represents the emissivity of the sky. f This represents the convective heat transfer coefficient on the surface of a photovoltaic module.

[0021] Furthermore, in step S3, T g B represents the ground temperature. i,j This represents the element Δ in the temperature matrix B on the back of the photovoltaic module. b The temperature difference between the back and surface of the photovoltaic module is represented by the following calculation of the heat transfer between the back of the photovoltaic module and the surrounding environment:

[0022] B i,j =F i,j +Δ b

[0023]

[0024]

[0025] Where, Φ b Ψ represents the heat convection between the back of a photovoltaic module and its surrounding environment. b δ represents the thermal radiation between the back of a photovoltaic module and its surrounding environment. b ε represents the area of ​​the back of the photovoltaic module corresponding to each element in temperature matrix B. b ε represents the emissivity of the back of a photovoltaic module. g h represents the emissivity of the ground. b This represents the convective heat transfer coefficient on the back of the photovoltaic module.

[0026] Furthermore, in step S4, the solar energy absorbed by the photovoltaic module is converted into heat energy and electrical energy, and the electrical power of the photovoltaic module is calculated as follows:

[0027] P = Q - Φ f -Ψ f -Φ b -Ψ b

[0028] Where P represents the electrical power of the photovoltaic module.

[0029] Furthermore, in step S5, the normalized irradiance is G0, the normalized cell temperature is T0, the temperature coefficient of the photovoltaic module power is β, and the normalized photovoltaic module power is as follows:

[0030]

[0031] Where P0 represents the normalized power output of the photovoltaic module, Δ represents the average value of each element in the surface temperature matrix F of the photovoltaic module. c This indicates the temperature difference between the internal cells and the surface of a photovoltaic module.

[0032] Furthermore, in step S5, the ideal power of the photovoltaic module under normalized environmental conditions is P. m The power generation efficiency and energy degradation ratio of photovoltaic modules are evaluated as follows:

[0033]

[0034]

[0035]

[0036] Where η represents the power generation efficiency of the photovoltaic module under actual environmental conditions, η0 represents the power generation efficiency of the photovoltaic module under normalized environmental conditions, and γ represents the energy attenuation ratio of the photovoltaic module.

[0037] Beneficial Effects: Addressing the high cost and low efficiency of contact-based electrical data acquisition for photovoltaic (PV) modules, this invention provides a non-contact method for evaluating PV module power generation efficiency. Based on infrared image analysis of heat transfer between the PV module and its surrounding environment, and applying the law of conservation of energy, the method calculates the PV module's electrical power, achieving non-contact evaluation of PV module power generation efficiency and energy degradation. This method can be combined with UAV autonomous inspection technology, as well as PV module fault diagnosis and health assessment technologies, providing crucial information for the intelligent operation and maintenance of PV power plants. Attached Figure Description

[0038] Figure 1 This is a schematic diagram of the overall process of an embodiment;

[0039] Figure 2 A schematic diagram illustrating the absorption of solar energy by photovoltaic modules;

[0040] Figure 3 This is a schematic diagram of heat transfer between photovoltaic modules and the surrounding environment. Detailed Implementation

[0041] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings; however, the scope of protection of the present invention is not limited to the described embodiments. Figure 1 As shown, this embodiment of a non-contact photovoltaic module power generation efficiency evaluation method includes the following steps in sequence:

[0042] S1: Acquire infrared images of photovoltaic modules and extract the temperature matrix of the photovoltaic module surface.

[0043] In this embodiment, under sunny conditions, with a light breeze and an irradiance of not less than 600 W / m², 2 Under conditions that avoid glare, acquire infrared images of the photovoltaic modules; the angle between the optical axis of the infrared camera and the surface of the photovoltaic module should be no less than 60°, and the images should be captured every 25cm of the photovoltaic module surface. 2 The region occupies at least 1 pixel in the infrared image; the radial distortion of the infrared image and the perspective distortion of the photovoltaic module are corrected, and the temperature matrix F of the photovoltaic module surface is extracted.

[0044] S2: Calculate the solar energy absorbed by the photovoltaic module based on the irradiance on the surface of the photovoltaic module.

[0045] In this embodiment, Figure 2 This diagram illustrates the absorption of solar energy by a photovoltaic (PV) module. G represents the irradiance of the PV module surface, S represents the surface area of ​​the PV module, and N represents the number of material layers in the PV module. The solar energy absorbed by the PV module is calculated as follows:

[0046]

[0047]

[0048] Among them, Q k α represents the amount of solar energy absorbed by the k-th layer material of a photovoltaic module. k τ represents the absorptivity of the k-th layer material in a photovoltaic module, where k = 1, ..., N; when q = 0, τ q =1; when 1≤q≤k-1, τ q The transmittance of the q-th layer material in the photovoltaic module is represented by ; Q represents the solar energy absorbed by the entire photovoltaic module.

[0049] S3: Calculate the heat transfer between the photovoltaic module and the surrounding environment based on the ambient temperature.

[0050] In this embodiment, Figure 3 This is a schematic diagram illustrating heat transfer between photovoltaic modules and their surrounding environment. a T represents air temperature. s F represents the sky temperature. i,j The elements in the temperature matrix F representing the surface of the photovoltaic module are used to calculate the heat transfer between the photovoltaic module surface and the surrounding environment as follows:

[0051]

[0052]

[0053] Where, Φ fΨ represents the heat convection between the surface of a photovoltaic module and its surrounding environment. f δ represents the thermal radiation between the surface of a photovoltaic module and its surrounding environment. f The temperature matrix F represents the area of ​​the photovoltaic module surface corresponding to each element, σ represents the Stefan-Boltzmann constant, and ε represents the area of ​​the photovoltaic module surface corresponding to each element. f ε represents the emissivity of the surface of a photovoltaic module. s h represents the emissivity of the sky. f This represents the convective heat transfer coefficient on the surface of a photovoltaic module.

[0054] T g B represents the ground temperature. i,j This represents the element Δ in the temperature matrix B on the back of the photovoltaic module. b The temperature difference between the back and surface of the photovoltaic module is represented by the following calculation of the heat transfer between the back of the photovoltaic module and the surrounding environment:

[0055] B i,j =F i,j +Δ b

[0056]

[0057]

[0058] Where, Φ b Ψ represents the heat convection between the back of a photovoltaic module and its surrounding environment. b δ represents the thermal radiation between the back of a photovoltaic module and its surrounding environment. b ε represents the area of ​​the back of the photovoltaic module corresponding to each element in temperature matrix B. b ε represents the emissivity of the back of a photovoltaic module. g h represents the emissivity of the ground. b This represents the convective heat transfer coefficient on the back of the photovoltaic module.

[0059] S4: Calculate the electrical power of the photovoltaic module according to the law of conservation of energy.

[0060] In this embodiment, the solar energy absorbed by the photovoltaic module is converted into heat energy and electrical energy. The electrical power of the photovoltaic module is calculated as follows: P = Q - Φ f -Ψ f -Φ b -Ψ b

[0061] Where P represents the electrical power of the photovoltaic module.

[0062] S5: Normalize the power output of the photovoltaic module to evaluate the power generation efficiency and energy degradation rate of the photovoltaic module.

[0063] In this embodiment, the normalized irradiance is G0, the normalized cell temperature is T0, the temperature coefficient of the photovoltaic module power is β, and the normalized photovoltaic module power is as follows:

[0064]

[0065] Where P0 represents the normalized power output of the photovoltaic module, Δ represents the average value of each element in the surface temperature matrix F of the photovoltaic module. c This indicates the temperature difference between the internal cells and the surface of a photovoltaic module.

[0066] The ideal power of a photovoltaic module under normalized environmental conditions is P. m The power generation efficiency and energy degradation ratio of photovoltaic modules are evaluated as follows:

[0067]

[0068]

[0069]

[0070] Where η represents the power generation efficiency of the photovoltaic module under actual environmental conditions, η0 represents the power generation efficiency of the photovoltaic module under normalized environmental conditions, and γ represents the energy attenuation ratio of the photovoltaic module.

[0071] 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 it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A non-contact method for evaluating the power generation efficiency of photovoltaic modules, characterized in that: The steps are as follows: S1: Acquire infrared images of photovoltaic modules and extract the temperature matrix of the photovoltaic module surface; S2: Calculate the solar energy absorbed by the photovoltaic module based on the irradiance on the surface of the photovoltaic module; S3: Calculate the heat transfer between the photovoltaic module and the surrounding environment based on the ambient temperature; S4: Calculate the electrical power of the photovoltaic module according to the law of conservation of energy; S5: Normalized power output of photovoltaic modules to evaluate the power generation efficiency and energy degradation rate of photovoltaic modules; In step S1, the conditions are as follows: sunny day, light breeze, and irradiance not less than 600W / m². 2 Under conditions that avoid glare, acquire infrared images of the photovoltaic modules; the angle between the optical axis of the infrared camera and the surface of the photovoltaic module should be no less than 60°, and the images should be captured every 25cm of the photovoltaic module surface. 2 The region occupies at least 1 pixel in the infrared image; the radial distortion of the infrared image and the perspective distortion of the photovoltaic module are corrected, and the temperature matrix F of the photovoltaic module surface is extracted; In step S2, G represents the irradiance of the photovoltaic module surface, S represents the area of ​​the photovoltaic module surface, and N represents the number of material layers of the photovoltaic module; the solar energy absorbed by the photovoltaic module is calculated as follows: Among them, Q k α represents the amount of solar energy absorbed by the k-th layer material of a photovoltaic module. k τ represents the absorptivity of the k-th layer material in a photovoltaic module, where k = 1, ..., N; when q = 0, τ q =1; when 1≤q≤k-1, τ q The transmittance of the q-th layer material in the photovoltaic module is represented by ; Q represents the solar energy absorbed by the entire photovoltaic module. In step S3, T a T represents air temperature. s F represents the sky temperature. i,j The elements in the temperature matrix F representing the surface of the photovoltaic module are used to calculate the heat transfer between the photovoltaic module surface and the surrounding environment as follows: Where, Φ f Ψ represents the heat convection between the surface of a photovoltaic module and its surrounding environment. f δ represents the thermal radiation between the surface of a photovoltaic module and its surrounding environment. f The temperature matrix F represents the area of ​​the photovoltaic module surface corresponding to each element, σ represents the Stefan-Boltzmann constant, and ε represents the area of ​​the photovoltaic module surface corresponding to each element. f ε represents the emissivity of the surface of a photovoltaic module. s h represents the emissivity of the sky. f This represents the convective heat transfer coefficient on the surface of a photovoltaic module; In step S3, T g B represents the ground temperature. i,j This represents the element Δ in the temperature matrix B on the back of the photovoltaic module. b The temperature difference between the back and surface of the photovoltaic module is represented by the following calculation of the heat transfer between the back of the photovoltaic module and the surrounding environment: B i,j =F i,j +D b Where, Φ b Ψ represents the heat convection between the back of a photovoltaic module and its surrounding environment. b δ represents the thermal radiation between the back of a photovoltaic module and its surrounding environment. b ε represents the area of ​​the back of the photovoltaic module corresponding to each element in temperature matrix B. b ε represents the emissivity of the back of a photovoltaic module. g h represents the emissivity of the ground. b This represents the convective heat transfer coefficient on the back of the photovoltaic module.

2. The non-contact photovoltaic module power generation efficiency evaluation method according to claim 1, characterized in that: In step S4, the solar energy absorbed by the photovoltaic module is converted into heat energy and electrical energy. The electrical power of the photovoltaic module is calculated as follows: P=Q-Φ f -P f -F b -P b Where P represents the electrical power of the photovoltaic module.

3. The non-contact photovoltaic module power generation efficiency evaluation method according to claim 2, characterized in that: In step S5, the normalized irradiance is G0, the normalized cell temperature is T0, the temperature coefficient of the photovoltaic module power is β, and the normalized photovoltaic module power is as follows: Where P0 represents the normalized power output of the photovoltaic module, Δ represents the average value of each element in the surface temperature matrix F of the photovoltaic module. c This indicates the temperature difference between the internal cells and the surface of a photovoltaic module.

4. The non-contact photovoltaic module power generation efficiency evaluation method according to claim 3, characterized in that: In step S5, the ideal power of the photovoltaic module under normalized environmental conditions is P. m The power generation efficiency and energy degradation ratio of photovoltaic modules are evaluated as follows: Where η represents the power generation efficiency of the photovoltaic module under actual environmental conditions, η0 represents the power generation efficiency of the photovoltaic module under normalized environmental conditions, and γ represents the energy attenuation ratio of the photovoltaic module.

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