Modeling method for predicting the service life of photovoltaic modules based on combined environmental stress

Abstract

A photovoltaic module service life prediction modeling method based on combined environmental stress is proposed. The degradation of the module is defined as the decay of the maximum power point power of the module over time. The influence of combined environmental stress on the maximum power output of the module is quantified by mathematical methods. For each environmental stress, the corresponding degradation model is revealed and verified based on indoor test data. Then, the three environmental stresses are integrated to propose a general model for quantifying the influence of combined environmental stress. The general model is calibrated and verified by outdoor test data. Then, the model is applied to predict the annual degradation rate and power generation performance loss of the same monocrystalline silicon module in three climate zones using actual monitored meteorological data. By combining the degradation modes caused by multiple environmental stresses, a module remaining life prediction model that is closer to the actual situation is obtained, so as to achieve accurate prediction of the remaining service life of different photovoltaic modules under real environment.

Description

Technical Field

[0001] The invention belongs to the technical field of photovoltaic power generation, and relates to a photovoltaic component service life prediction modeling method based on combined environmental stress. Background Art

[0002] Photovoltaic (PV) power generation systems are one of the most promising renewable energy technologies due to their ability to convert solar energy directly into electrical energy. With technological advances and cost reductions, PV power generation has been widely used and has become an important part of many energy structures.

[0003] However, the performance and economic benefits of photovoltaic power generation systems are affected by many factors, such as climate conditions, component aging, system maintenance, and technological progress. Therefore, it is particularly important to accurately predict the energy output of photovoltaic power generation systems during their lifetime (Lifetime Energy Prediction, LEP).

[0004] Gaines et al. proposed a quantitative model for accelerated testing using multiple environmental stresses, which was used to develop test designs. Subramaniyan et al. proposed a model that links component degradation pathways to environmental variables. The current state-of-the-art PV module and system degradation models were reviewed, and one of the main observations was that most degradation models were developed for specific degradation modes, using controlled test conditions and validated based on indoor measurements from accelerated tests, lacking combined studies of different environmental stresses. Since PV modules experience a large number of climatic loads when operating outdoors, which may lead to different degradation modes, combined stress models are a prerequisite for estimating PV module degradation. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a photovoltaic component service life prediction modeling method based on combined environmental stress, so as to solve the problems in the prior art that the calculation process of the photovoltaic power generation system life energy prediction method is cumbersome and redundant, the obtained results have large errors and poor applicability.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is: a photovoltaic module service life prediction modeling method based on combined environmental stress, comprising the following steps: S1, define the concept of PV module degradation and establish a degradation model of PV modules under various environmental stresses; S2, based on the degradation model of PV modules, derive the calculation formula of PV module failure time; S3, in order to quantify the impact of three environmental stresses on the output power of photovoltaic modules, the degradation rate model formulas for evaluating the degradation speed of photovoltaic modules under three environmental stresses were established respectively, with the degradation rate constant ki express; S4, considering the coupling relationship between the three environmental stresses, by combining the degradation rate constants of the three environmental stresses in the form of products, the overall degradation rate model formula of the photovoltaic module is further established to combine the degradation rate constants k T express; S5, based on the degradation model of photovoltaic modules, derive the calculation formula of photovoltaic module failure time; S6, obtain the specific values ​​of various environmental parameters based on field measurements and inquiries to relevant databases; obtain the parameter values ​​of various parameters in the model through the results of relevant research and the experience accumulated by many scholars, and substitute the parameter values ​​into the corresponding model formulas to predict the remaining service life of monocrystalline silicon modules.

[0007] In S1, the degradation of PV modules is defined as the exponential decay of the module's maximum power point power (PMPP) over time. The model formula is as follows: ; (1) in, P MPP (t) and P MPP (0) are the module output power and initial output power at time t, respectively; B It is the power sensitivity parameter, which indicates the sensitivity of the component material to power degradation. B The higher the value, the more significant the power degradation of the material under specific climatic conditions; k i Photovoltaic modules are i Degradation rate constant under various environmental stresses; μ is the shape index. In the degradation model of photovoltaic modules, the shape parameter μ Affects the shape of the degradation curve.

[0008] In S2, when the maximum power point power of the module decays to 80% of the initial power, that is, when 20% of the module performance loss occurs, the photovoltaic module is considered to have failed, that is, Substituting into formula (1) and simplifying it, we get: ; Take the logarithm of both sides and take the absolute value: ; Further simplify and i Degradation rate constant under environmental stress k iReplaced by the combined degradation rate constant under three environmental stresses k T , get the component failure time t f The calculation formula is: .

[0009] In S3, The Arrhenius equation in chemical kinetics is used to describe the effect of temperature on the chemical reaction rate. The relative humidity of the components is combined in the form of a product to establish a degradation rate model formula for evaluating photovoltaic components under hydrolysis-driven degradation. This is to quantify the effect of hydrolysis, an environmental stress, on the output power attenuation of photovoltaic components. The degradation rate model formula is as follows: ; (2) in, k H is the rate constant, k B is the Boltzmann constant (8.62×10−5), T m is the component temperature, AH is the pre-exponential constant, i.e., an empirical parameter that quantifies how often reactant molecules collide and form products in the absence of activation energy hindrance; r h is the effective relative humidity RH of the component, n is a model parameter that represents the degree of influence of relative humidity on component power degradation; in this context, E H It is defined as the activation energy of component power degradation, that is, the activation energy of power degradation refers to the energy required for the process in the photovoltaic module that leads to the reduction of power output; during the degradation process, a specific chemical or physical reaction may require sufficient energy to occur or accelerate, and this energy is called activation energy.

[0010] In S3, Using the Arrhenius equation in chemical kinetics, and taking the ultraviolet radiation UV, component temperature T m The relative humidity RH is combined in the form of a product to establish a degradation rate model formula for evaluating the degradation of photovoltaic modules under photodegradation-driven degradation, so as to quantify the impact of photodegradation, an environmental stress, on the output power attenuation of photovoltaic modules. The degradation rate model formula is as follows: ; (3) in, k P is the rate constant, UVis the amount of ultraviolet radiation (kW / m 2 ), E P is the activation energy required for component power degradation caused by light reaction, X Is the amount of ultraviolet radiation UV Model parameter for the effect of power degradation, representing the amount of UV radiation UV The degree of impact on component power degradation.

[0011] In S3, in areas with large temperature differences between day and night, the modules will also be affected by the alternating temperature cycles of hot and cold, resulting in thermomechanical degradation caused by thermal stress. Based on the Coffin-Manson relationship, which mainly describes the relationship between the cyclic stress caused by fatigue load and the fatigue life of the material, the temperature difference and the rate of temperature cycle are combined in the form of a product to establish a degradation rate model formula for evaluating photovoltaic modules under degradation driven by thermomechanical degradation, so as to quantify the impact of the environmental stress of thermomechanical degradation on the output power attenuation of photovoltaic modules. The degradation rate model formula is as follows: ; (4) Among them, Δ T =( T U − T L ) is the temperature difference, C N is the cycle rate, T U and T L are the upper and lower temperature limits of the module, E Tm is the activation energy of power degradation.

[0012] In S4, the relationship between the degradation caused by different environmental stresses may be a specific degradation mode independent of other processes on the one hand, and may have a synergistic effect on the other hand. Based on this, the superposition of relatively independent degradation modes is considered in the form of summation, and the coupling between these relatively independent degradation modes is considered in the form of product. The mathematical expression of the total degradation rate of photovoltaic modules is: (5) in, k T is the total degradation rate, k i For the i The rate constant, n is the total number of degradation processes, A NIt is the normalization constant of the physical quantity, which enables the parameters and variables in the model to be compared and operated in different units and magnitudes, thus ensuring the applicability and accuracy of the formula under various conditions; in this case, its unit is year. -2 / %.

[0013] In S5, By defining component degradation as the decay of the maximum power point power over time, when the maximum power point power of the component decays to 80% of the initial power, that is, when 20% of the component performance loss occurs, the photovoltaic component is considered to have failed, that is, When t f is the expiration time; Will Substituting into formula 1 and shifting the phase, we get: ; Take the logarithm of both sides and take the absolute value: ; Further simplify and i Degradation rate constant under environmental stress k i Replaced by the combined degradation rate constant under three environmental stresses k T , get the component failure time t f The calculation formula is: (6).

[0014] The main beneficial effects of the present invention are: It solves the problem of insufficient prediction accuracy of conventional prediction methods using one or several independent degradation modes, can adapt to the needs of various scenarios, and improves the authenticity of the prediction of the remaining useful life of photovoltaics.

[0015] By combining the degradation modes caused by various environmental stresses, a component remaining life prediction model that is closer to the actual situation is obtained, so as to achieve accurate prediction of the remaining service life of different photovoltaic components under real environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0017] Figure 1 This is a basic flow chart for predicting the remaining service life of a photovoltaic module according to the present invention.

[0018] Figure 2 Flowchart of different environmental stresses considered for the present invention and the different degradation modes they induce.

[0019] Figure 3 It is a line graph of the total amount of ultraviolet radiation and relative humidity of the present invention.

[0020] Figure 4 It is the probability distribution diagram of the average temperature values ​​of the three climate zones of the present invention. DETAILED DESCRIPTION

[0021] like Figure 1~Figure 4 In this paper, a modeling method for predicting the service life of photovoltaic modules based on combined environmental stress is proposed. Embodiment 1, like Figure 1 As shown, the photovoltaic module service life prediction modeling method based on combined environmental stress of the present invention is to combine the module degradation modes caused by different environmental stresses so that the established photovoltaic module remaining service life prediction model is closer to the actual situation, thereby achieving the purpose of accurately predicting the remaining service life of the module.

[0022] Step 1: Define the concept of PV module degradation, analyze the degradation modes caused by three environmental stresses, and establish a degradation model of PV modules under these three environmental stresses; Step 1-1: Since photovoltaic module manufacturers usually set the warranty period based on the maximum power point power of the module, the present invention uses the maximum power point power of the module as a degradation indicator, and defines module degradation as the decay of the maximum power point power over time; Step 1-2: If Figure 2 As shown, the present invention considers three different environmental stresses: hydrolysis, photodegradation and thermomechanical degradation, and the corresponding degradation forms are: component material corrosion, component delamination, sealant discoloration, component solder joint loosening; sealant discoloration, ultraviolet induced corrosion; solder failure, component cracks or breakage, component interconnection failure; Step 1-3: Define the power decay over time at the maximum power point of the component as an exponential decay model. The exponential decay model is widely used to describe the degradation behavior of various physical and chemical processes. This model can well describe the characteristics of fast initial degradation and slow degradation in the later stage, which is consistent with actual observations. The model formula is as follows: ; (1) in, P MPP (t) and P MPP (0) are the module output power and initial output power at time t, respectively. B It is the power sensitivity parameter, which indicates the sensitivity of the component material to power degradation. B The higher the value, the more significant the power degradation of the material under specific climatic conditions; ki Photovoltaic modules are i Degradation rate constant under various environmental stresses; μ is the shape index. In the degradation model of photovoltaic modules, the shape parameter μ Affects the shape of the degradation curve.

[0023] Step 2: In order to quantify the impact of the three environmental stresses on the output power of PV modules, the degradation rate model formulas for evaluating the degradation speed of PV modules under the three environmental stresses are established respectively, with the degradation rate constant k i express; Step 2-1: Using the Arrhenius equation in chemical kinetics, which is mainly used to describe the effect of temperature on the chemical reaction rate, and combining the relative humidity of the components in the form of a product, a degradation rate model formula for evaluating the degradation of photovoltaic components under hydrolysis-driven degradation is established to quantify the effect of hydrolysis, an environmental stress, on the output power attenuation of photovoltaic components. The degradation rate model formula is as follows: ; (2) in, k H is the rate constant, k B is the Boltzmann constant (8.62 × 10−5), Tm is the module temperature in Kelvin, and AH is the pre-exponential constant, i.e., an empirical parameter that quantifies how often reactant molecules collide and form products in the absence of activation energy hindrance; r h is the effective relative humidity RH of the component, n is a model parameter that represents the degree of influence of relative humidity on component power degradation. In this context, E H It is defined as the activation energy of component power degradation, that is, the activation energy of power degradation refers to the energy required for the process in the photovoltaic module that leads to the reduction of power output; during the degradation process, a specific chemical or physical reaction may require sufficient energy to occur or accelerate, and this energy is called activation energy.

[0024] Step 2-2: Use the Arrhenius equation in chemical kinetics and transform the UV radiation UV, component temperature T m The relative humidity RH is combined in the form of a product to establish a degradation rate model formula for evaluating the degradation of photovoltaic modules under photodegradation-driven degradation, so as to quantify the impact of photodegradation, an environmental stress, on the output power attenuation of photovoltaic modules. The degradation rate model formula is as follows: (3) in,k P is the rate constant, UV is the amount of ultraviolet radiation (kW / m 2 ), E P is the activation energy required for component power degradation caused by light reaction, X Is the amount of ultraviolet radiation UV Model parameter for the effect of power degradation, representing the amount of UV radiation UV The degree of impact on component power degradation.

[0025] Step 2-3: In areas with large temperature differences between day and night, the modules will also be affected by the alternating temperature cycles of hot and cold, resulting in thermomechanical degradation caused by thermal stress. Based on the Coffin-Manson relationship, which mainly describes the relationship between the cyclic stress caused by fatigue load and the fatigue life of the material, the temperature difference and the rate of temperature cycle are combined in the form of a product to establish a degradation rate model formula for evaluating photovoltaic modules under degradation driven by thermomechanical degradation, so as to quantify the impact of the environmental stress of thermomechanical degradation on the output power attenuation of photovoltaic modules. The degradation rate model formula is as follows: (4) Among them, Δ T =( T U − T L ) is the temperature difference (Kelvin), C N is the cycle rate, T U and T L are the upper and lower temperature limits of the module, E Tm is the activation energy of power degradation, is the temperature difference Δ T Model parameters affecting power degradation, representing the temperature difference Δ T The degree of impact on component power degradation.

[0026] Step 3: The relationship between the degradation caused by different environmental stresses may be a specific degradation mode independent of other processes on the one hand, and may have a synergistic effect on the other hand. Based on this, the present invention will consider the superposition of relatively independent degradation modes in the form of summation, and consider the coupling between these relatively independent degradation modes in the form of product. The mathematical expression of the total degradation rate of the photovoltaic module is: ; (5) in, k T is the total degradation rate,k i For the i The rate constant, n is the total number of degradation processes, A N It is the normalization constant of the physical quantity, which enables the parameters and variables in the model to be compared and operated in different units and magnitudes, thus ensuring the applicability and accuracy of the formula under various conditions; in this case, its unit is year. -2 / %.

[0027] Step 4: Based on the degradation model of the photovoltaic module, derive the calculation formula of the failure time of the photovoltaic module; Step 4-1: By defining component degradation as the decay of the maximum power point power over time, when the maximum power point power of the component decays to 80% of the initial power, that is, when a 20% component performance loss occurs, the PV component is considered to have failed, i.e. When t f is the expiration time.

[0028] Step 4-2: Substituting into formula 1 and shifting the phase, we get: ; Take the logarithm of both sides and take the absolute value: ; Further simplify and i Degradation rate constant under environmental stress k i Replaced by the combined degradation rate constant under three environmental stresses k T , get the component failure time t f The calculation formula is: ; (6) Step 5: Obtain the specific values ​​of each environmental parameter based on field measurements and querying relevant databases; obtain the parameter values ​​of various parameters in the model through the results of relevant research and the experience accumulated by many scholars, and substitute the parameter values ​​into the corresponding model formula to predict the remaining service life of the monocrystalline silicon module; Step 5-1: Based on the results of relevant research, the rate model parameters extracted are shown in the following table:

[0029] Step 5-2: If Figure 3 , 4As shown in the table below, by statistically analyzing the total ultraviolet radiation and annual average relative humidity in three different climate zones, the annual average relative humidity, total ultraviolet radiation, annual average temperature and other related environmental parameters in three different climate zones from 2018 to 2023 are obtained, as shown in the table below:

[0030] Step 5-3: Substitute the above parameter values ​​into the model formulas of (2), (3), (4), and (5) to obtain the corresponding results, as shown in the following table:

[0031] Depending on the climate in which the module is installed, different degradation modes may dominate. Using the proposed degradation models (2)-(5) and the model parameters derived outdoors, the main degradation precursors and the total degradation rate, as well as the failure time (6) can be predicted for any location with known climate loads. The present invention predicts the annual degradation rate of monocrystalline silicon modules using input climate loads for marine, arid and plateau climate zones.

[0032] In the plateau climate zone, degradation due to hydrolysis is minimal despite high relative humidity levels, likely due to the lower mean component temperatures experienced in this climate zone, thus slowing down the hydrolysis process and absolute water vapor concentrations.

[0033] In the arid regions with higher temperatures, the predicted degradation rates are higher and the failure times are earlier than in other regions, which can again be explained by the higher temperatures in this region determining the reaction rates of other degradation processes, such as hydrolysis caused by humidity and photodegradation caused by UV dose. As expected, the degradation of the maximum power output is more severe in the arid climate with higher temperatures, so temperature may be the main accelerator of degradation.

[0034] The above-mentioned embodiments are only preferred technical solutions of the present invention and should not be regarded as limitations of the present invention. The embodiments and features in the embodiments of the present application can be arbitrarily combined with each other without conflict. The protection scope of the present invention shall be the technical solutions recorded in the claims, including the equivalent replacement solutions of the technical features in the technical solutions recorded in the claims. That is, equivalent replacement improvements within this scope are also within the protection scope of the present invention.

Claims

1. A photovoltaic module service life prediction modeling method based on combined environmental stress, characterized in that: The steps include: S1, define the concept of PV module degradation and establish a degradation model of PV modules under various environmental stresses; S2, based on the degradation model of PV modules, derive the calculation formula of PV module failure time; S3, in order to quantify the impact of three environmental stresses on the output power of photovoltaic modules, the degradation rate model formulas for evaluating the degradation speed of photovoltaic modules under three environmental stresses were established respectively, with the degradation rate constant k i express; S4, considering the coupling relationship between the three environmental stresses, by combining the degradation rate constants of the three environmental stresses in the form of products, the overall degradation rate model formula of the photovoltaic module is further established to combine the degradation rate constants k T express; S5, based on the degradation model of photovoltaic modules, derive the calculation formula of photovoltaic module failure time; S6, obtain the specific values ​​of various environmental parameters based on field measurements and inquiries to relevant databases; obtain the parameter values ​​of various parameters in the model through the results of relevant research and the experience accumulated by many scholars, and substitute the parameter values ​​into the corresponding model formulas to predict the remaining service life of monocrystalline silicon modules.

2. The photovoltaic module service life prediction modeling method based on combined environmental stress according to claim 1 is characterized by: In S1, the degradation of PV modules is defined as the exponential decay of the module's maximum power point power (PMPP) over time. The model formula is as follows: ； （1） in, P MPP (t) and P MPP (0) are the module output power and initial output power at time t, respectively; B It is the power sensitivity parameter, which indicates the sensitivity of the component material to power degradation. B The higher the value, the more significant the power degradation of the material under specific climatic conditions; k i Photovoltaic modules are i Degradation rate constant under various environmental stresses; μ is the shape index. In the degradation model of photovoltaic modules, the shape parameter μ Affects the shape of the degradation curve.

3. The photovoltaic module service life prediction modeling method based on combined environmental stress according to claim 1 is characterized by: In S2, when the maximum power point power of the module decays to 80% of the initial power, that is, when 20% of the module performance loss occurs, the photovoltaic module is considered to have failed, that is, Substituting into formula (1) and simplifying it, we get: ； Take the logarithm of both sides and take the absolute value: ； Further simplify and i Degradation rate constant under environmental stress k i Replaced by the combined degradation rate constant under three environmental stresses k T , get the component failure time t f The calculation formula is: 。 4. The photovoltaic module service life prediction modeling method based on combined environmental stress according to claim 1 is characterized by: In S3, The Arrhenius equation in chemical kinetics is used to describe the effect of temperature on the chemical reaction rate. The relative humidity of the components is combined in the form of a product to establish a degradation rate model formula for evaluating photovoltaic components under hydrolysis-driven degradation. This is to quantify the effect of hydrolysis, an environmental stress, on the output power attenuation of photovoltaic components. The degradation rate model formula is as follows: ； （2） in, k H is the rate constant, k B is the Boltzmann constant (8.62×10−5), T m is the component temperature, AH is the pre-exponential constant, i.e., an empirical parameter that quantifies how often reactant molecules collide and form products in the absence of activation energy hindrance; r h is the effective relative humidity RH of the component, n is a model parameter that represents the degree of influence of relative humidity on component power degradation; in this context, E H It is defined as the activation energy of component power degradation, that is, the activation energy of power degradation refers to the energy required for the process in the photovoltaic module that leads to the reduction of power output; during the degradation process, a specific chemical or physical reaction may require sufficient energy to occur or accelerate, and this energy is called activation energy.

5. The photovoltaic module service life prediction modeling method based on combined environmental stress according to claim 4 is characterized by: In S3, Using the Arrhenius equation in chemical kinetics, and taking the ultraviolet radiation UV, component temperature T m The relative humidity RH is combined in the form of a product to establish a degradation rate model formula for evaluating the degradation of photovoltaic modules under photodegradation-driven degradation, so as to quantify the impact of photodegradation, an environmental stress, on the output power attenuation of photovoltaic modules. The degradation rate model formula is as follows: ； （3） in, k P is the rate constant, UV is the amount of ultraviolet radiation (kW / m 2 ), E P is the activation energy required for component power degradation caused by light reaction, X Is the amount of ultraviolet radiation UV Model parameter for the effect of power degradation, representing the amount of UV radiation UV The degree of impact on component power degradation.

6. The photovoltaic module service life prediction modeling method based on combined environmental stress according to claim 5 is characterized by: In S3, in areas with large temperature differences between day and night, the modules will also be affected by the alternating temperature cycles of hot and cold, resulting in thermomechanical degradation caused by thermal stress. Based on the Coffin-Manson relationship, which mainly describes the relationship between the cyclic stress caused by fatigue load and the fatigue life of the material, the temperature difference and the rate of temperature cycle are combined in the form of a product to establish a degradation rate model formula for evaluating photovoltaic modules under degradation driven by thermomechanical degradation, so as to quantify the impact of the environmental stress of thermomechanical degradation on the output power attenuation of photovoltaic modules. The degradation rate model formula is as follows: ；（4） Among them, Δ T =( T U − T L ) is the temperature difference, C N is the cycle rate, T U and T L are the upper and lower temperature limits of the module, E Tm is the activation energy of power degradation.

7. The photovoltaic module service life prediction modeling method based on combined environmental stress according to claim 1 is characterized by: In S4, the relationship between the degradation caused by different environmental stresses may be a specific degradation mode independent of other processes on the one hand, and may have a synergistic effect on the other hand. Based on this, the superposition of relatively independent degradation modes is considered in the form of summation, and the coupling between these relatively independent degradation modes is considered in the form of product. The mathematical expression of the total degradation rate of photovoltaic modules is: （5） in, k T is the total degradation rate, k i For the i The rate constant, n is the total number of degradation processes, A N It is the normalization constant of the physical quantity, which enables the parameters and variables in the model to be compared and calculated in different units and magnitudes, thus ensuring the applicability and accuracy of the formula under various conditions; in this case, its unit is year. -2 / %.

8. The photovoltaic module service life prediction modeling method based on combined environmental stress according to claim 1 is characterized by: In S5, By defining component degradation as the decay of the maximum power point power over time, when the maximum power point power of the component decays to 80% of the initial power, that is, when 20% of the component performance loss occurs, the photovoltaic component is considered to have failed, that is, When t f is the expiration time; Will Substituting into formula 1 and shifting the phase, we get: ； Take the logarithm of both sides and take the absolute value: ； Further simplify and i Degradation rate constant under environmental stress k i Replaced by the combined degradation rate constant under three environmental stresses k T , get the component failure time t f The calculation formula is: （6）。

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