Photovoltaic recovery economic and environmental benefit evaluation method based on material flow and scene analysis

Abstract

The invention relates to a photovoltaic recovery economic and environmental benefit evaluation method based on material flow and scene analysis, and belongs to the field of environmental analysis, and the method comprises the steps: carrying out the modeling evaluation of photovoltaic scrap through employing a dynamic material flow model in combination with a Weibull probability distribution function, and obtaining the spatial and temporal distribution of the photovoltaic scrap amount of different regions; using a life cycle evaluation method to analyze life cycle environmental influences of different recovery processes in the recovery process, and obtaining environmental benefits E brought by local recovery decommissioning components; evaluating the economic benefit of photovoltaic recovery; the environmental benefit is combined with the economic benefit, and the comprehensive environmental economic benefit of photovoltaic recovery is obtained; and evaluating the comprehensive environmental and economic benefits of photovoltaic recovery under different policies based on a scenario analysis method. According to the method, more accurate space-time distribution prediction is carried out on the scrap amount of the photovoltaic module, a standardized evaluation method is provided for photovoltaic recovery of different recovery processes, consistency and transparency are ensured, and environmental and economic benefits of different technical governance can be accurately evaluated and compared.

Description

Technical Field

[0001] The invention relates to a photovoltaic recycling economic and environmental benefit assessment method based on material flow and scenario analysis, and belongs to the technical field of environmental analysis. Background Art

[0002] Retired photovoltaic modules have both resource and environmental hazards. If they are not properly disposed of, they will not only cause a waste of strategic resources, economic benefits, and occupy a large amount of land, but will also cause irreversible environmental pollution problems such as heavy metal leakage and contamination of soil and water sources, posing multiple threats to the ecological environment. In order to avoid environmental problems caused by improper disposal of retired modules and promote resource conservation and utilization, it is necessary to classify and clarify the waste recycling path based on the characteristics of the source, scale, resource value, and ecological and environmental impact of used photovoltaic modules. Therefore, it is crucial to accurately evaluate the economic and environmental benefits of photovoltaic recycling.

[0003] First, reliable predictions of the scale and spatiotemporal distribution of the future scrapping of different types of PV modules are the basis for efficient recycling of retired PV modules. Existing PV retirement assessment studies mainly use fixed life expectancy (25 or 30 years) for estimation. However, module retirement is generally closely related to the module life function, and existing methods lack the revelation of the spatiotemporal evolution of PV retirement. Material flow analysis is based on the basic principle of material conservation, quantifies the dynamic changes of material stocks and flows, and often combines life functions to reveal the flow characteristics of materials within specific spatiotemporal boundaries. Secondly, some studies have used life cycle assessment methods to quantify the potential environmental impact of PV modules during the retirement stage. However, due to the inconsistency of system boundaries, functional units, and recycled material ranges, it is difficult to directly compare the life cycle environmental impacts of different PV recycling technologies. Finally, there is currently little analysis of the impact of technological progress, material prices, and policy changes on the environmental and economic performance levels of PV waste recycling and treatment, which makes it impossible to provide key information for future improvements in PV recycling. Therefore, it is necessary to construct a unified method framework based on material flow and scenario analysis to evaluate the economic and environmental benefits of PV recycling in order to accurately evaluate and compare the environmental and economic benefits of different technical governance. Summary of the invention

[0004] In view of the shortcomings of the prior art, the present invention provides a method for evaluating the economic and environmental benefits of photovoltaic recycling based on material flow and scenario analysis, which makes a more accurate spatiotemporal distribution prediction of the amount of scrapped photovoltaic modules, and provides a standardized evaluation method for photovoltaic recycling with different recycling processes, ensuring consistency and transparency, and being able to accurately evaluate and compare the environmental and economic benefits of different technical governance methods.

[0005] The present invention adopts the following technical solution:

[0006] A method for evaluating the economic and environmental benefits of photovoltaic recycling based on material flow and scenario analysis includes the following steps:

[0007] (1) Use the dynamic material flow model combined with the Weibull probability distribution function to model and evaluate the photovoltaic scrapping, and obtain the spatiotemporal distribution of photovoltaic scrapping in different regions;

[0008] (2) Use life cycle assessment methods to analyze the life cycle environmental impacts of different recycling processes during the recycling process and obtain the environmental benefits E brought by local recycling of retired components;

[0009] (3) Evaluate the economic benefits of PV recycling;

[0010] (4) The environmental benefits of step (2) are combined with the economic benefits of step (3) to obtain the comprehensive environmental and economic benefits of photovoltaic recycling;

[0011] (5) Evaluate the comprehensive environmental and economic benefits of photovoltaic recycling under different policies based on scenario analysis.

[0012] The present invention clarifies the dynamic characteristics of the scrap volume of retired photovoltaic modules, constructs an economic-environmental impact assessment coupling model for photovoltaic module recycling, simulates and quantifies the impact of different recycling policies, which is conducive to improving the management policy system for the recycling of retired photovoltaic modules and promoting the healthy and sustainable development of the retired photovoltaic industry.

[0013] Preferably, in step (1), the dynamic material flow model includes three key parameters: inventory in use, inflows and outflows, cumulative solar PV installed capacity corresponding to the PV scrapping forecast, annual new PV installed capacity and annual retirements;

[0014] The calculation process of the dynamic material flow model is as follows:

[0015] inflow(t) i =outflow(t-1) i +stock(t) i -stock(t-1) i (1)

[0016] Among them, stock(t) i represents the cumulative solar photovoltaic installed capacity in year t, outflow(t) i represents the annual retirement volume in year t; inflow(t) i represents the newly added photovoltaic installed capacity in year t; i represents different regions;

[0017]

[0018] Among them, t' represents the year when the photovoltaic system is completed and put into operation; f(t) represents the Weibull probability density function, which represents the life distribution of photovoltaic modules; t represents the year to be calculated; T represents the average life of photovoltaic modules (generally 25 or 30 years); β is the shape parameter of the Weibull curve, with a value of 2.4928 for conventional retirement and 5.3759 for early retirement; the conventional retirement scheme assumes that there is no early loss during the life of the solar panel; the early retirement scheme takes into account that photovoltaic modules are more susceptible to wear and tear in the early stages of use.

[0019] Preferably, step (2) specifically comprises the following steps:

[0020] S1: Determine the evaluation object, system boundary and functional unit of the life cycle model in the life cycle assessment method of the recycling process, and divide different stages according to the process flow involved in different recycling processes;

[0021] S2: Based on the actual situation, collect the input and output of each process flow for recycling 1 ton of waste photovoltaic modules to form a list of data;

[0022] S3: Input the inventory data in step S2 into the life cycle assessment software eFootprint to obtain the loads of various environmental impacts;

[0023] S4: Multiply the environmental impact load result obtained in step S3 by the amount of photovoltaic scrapping in each region to obtain the environmental benefit E brought by the local recycling of retired components.

[0024] Preferably, in step S1, the evaluation object of the life cycle model is waste photovoltaic modules, the system boundary is the process flow, including the collection stage, transportation stage, disassembly stage, recycling stage, and waste disposal after recycling, and the functional unit is 1 ton of waste photovoltaic modules;

[0025] The recycling processes in the recycling stage include mechanical recycling, chemical recycling and pyrolysis recycling; mechanical recycling includes cutting and grinding screening, chemical recycling includes stratification and metal extraction, and pyrolysis recycling includes EVA stratification and metal extraction.

[0026] Preferably, in step S3, the types of environmental impacts include global warming potential (GWP), primary energy demand (PED), abiotic depletion potential (ADP), water resource consumption (WU), acidification impact potential (AP), eutrophication potential (EP), inhalable particulate matter (RI), etc.

[0027] In step S3, preferably, the global warming potential (GWP) is used as a representative for environmental benefit assessment.

[0028] Preferably, the specific steps of step (3) are:

[0029] a. Determine the cost of economic benefits TC total , including specific costs and external costs. Specific costs include collection stage costs, transportation stage costs, disassembly stage costs, recycling stage costs and waste disposal costs after recycling; external costs include labor costs, management costs, taxes, fixed asset depreciation costs, and operation and maintenance costs;

[0030] b. Determine the economic benefits BE of secondary sales of recycled materials j .

[0031] Preferably, in step b, the recycled materials include aluminum, glass, silver, copper and silicon obtained in the disassembly stage.

[0032] Preferably, the comprehensive environmental and economic benefit calculation formula of photovoltaic recycling in step (4) is as follows:

[0033] B total =BE j +B indr -TC total

[0034] B indr =E*C*Mass

[0035] Among them, B total Represents the comprehensive environmental and economic benefits of photovoltaic recycling, BE j represents the economic benefits of secondary sales, TC total represents the cost of economic benefits, B indr represents indirect environmental benefits, Mass represents the total amount of retired components, unit: ton, E represents the unit environmental benefit of recycling unit retired PV components, obtained through step S2, and C represents the carbon trading price, which is about US$7.8 / ton.

[0036] For any details not provided in the present invention, please refer to the prior art.

[0037] The beneficial effects of the present invention are:

[0038] The present invention first uses a dynamic material flow model combined with a Weibull probability distribution function to model and evaluate photovoltaic scrapping, and obtains the spatiotemporal distribution of photovoltaic scrapping in different regions. The spatiotemporal distribution prediction of the present invention is more accurate, so as to more truly reflect the actual situation of component retirement.

[0039] The present invention provides a standardized evaluation method to ensure the consistency and transparency of the evaluation of the economic and environmental benefits of photovoltaic recycling.

[0040] The present invention can accurately evaluate the amount of PV scrap, the economic benefits of PV recycling and the comprehensive environmental and economic benefits, help identify the key factors for reducing PV recycling costs, provide scientific insights for optimizing PV recycling practices, and guide decision makers in addressing the challenges of PV waste in energy transition. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The drawings in the specification, which constitute a part of the present application, are used to provide further understanding of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute improper limitations on the present application.

[0042] Figure 1 The flowchart of the method for evaluating the economic and environmental benefits of photovoltaic recycling based on material flow and scenario analysis of the present invention is as follows;

[0043] Figure 2 A schematic diagram of the system boundary of the life cycle assessment method of the present invention;

[0044] Figure 3 Schematic diagram of the input process for the life cycle assessment software eFootprint;

[0045] Figure 4 It is the input process for the transportation stage;

[0046] Figure 5 This is the output of the life cycle assessment software eFootprint. DETAILED DESCRIPTION

[0047] In order to enable those skilled in the art to better understand the technical solutions in this specification, the technical solutions in the embodiments of the present invention are clearly and completely described below in conjunction with the drawings in the implementation of this specification, but are not limited to this. Anything not fully described in the present invention shall be based on the conventional technology in the art.

[0048] Example 1

[0049] A method for evaluating the economic and environmental benefits of photovoltaic recycling based on material flow and scenario analysis, such as Figure 1 As shown, the following steps are included:

[0050] (1) Use the dynamic material flow model combined with the Weibull probability distribution function to model and evaluate the photovoltaic scrapping, and obtain the spatiotemporal distribution of photovoltaic scrapping in different regions;

[0051] The dynamic material flow model includes three key parameters: stocks in use, inflows and outflows, cumulative solar PV installed capacity corresponding to PV scrapping forecasts, annual PV additions, and annual retirements;

[0052] The calculation process of the dynamic material flow model is as follows:

[0053] inflow(t) i =outflow(t-1) i +stock(t) i -stock(t-1) i (1)

[0054] Among them, stock(t) i represents the cumulative solar photovoltaic installed capacity in year t, outflow(t) i represents the annual retirement volume in year t; inflow(t) i represents the newly added photovoltaic installed capacity in year t; i represents different regions;

[0055]

[0056] Among them, t' represents the year when the photovoltaic system is completed and put into operation; f(t) represents the Weibull probability density function, which represents the life distribution of photovoltaic modules; t represents the year to be calculated; T represents the average life of photovoltaic modules (generally 25 or 30 years); β is the shape parameter of the Weibull curve, with a value of 2.4928 for conventional retirement and 5.3759 for early retirement; the conventional retirement scheme assumes that there is no early loss during the life of the solar panel; the early retirement scheme takes into account that photovoltaic modules are more susceptible to wear and tear in the early stages of use.

[0057] In the specific calculation, stock(t) in formula (1) and (2) i 、stock(t-1) i is a known number, inflow(t) i and outflow(t) i It is an unknown number. It is generally assumed that the outflow(t) is the year of initial installation. i is 0, then inflow(t) i Equal to stock(t) i , and then we can use formula (2) to calculate the Outflow (t) for the next year. i , and then the newly calculated Outflow(t) i Substituting into formula (1), we can get the inflow (t) for the new year: i , and so on.

[0058] For example, the cumulative photovoltaic installation in 2010 is 100, the cumulative photovoltaic installation in 2011 is 200, and the cumulative photovoltaic installation in 2012 is 300. Calculate the annual photovoltaic retirement volume between 2010 and 2012. The calculation process is as follows:

[0059] Step 1: Retirement volume in 2010:

[0060] Inflow(2010) = stock(2010) = 100 in 2010;

[0061] Retirement amount outflow(2020)=inflow(2010)*f(2010-2010)=100*f(0)

[0062] Step 2: Retirement volume in 2011:

[0063] inflow(2011)=stock(2011)-stock(2010)+outflow(2020)=100+100*f(0) in 2011;

[0064] Retirement amount outflow(2011)=inflow(2010)*f(2011-2010)+inflow(2011)*f(2011-2011)=inflow(2010)*f(1)+i nflow(2011)*f(0)

[0065] Step 3: Retirement volume in 2012:

[0066] 2012 inflow(2012)=stock(2012)-stock(2011)+outflow(2021);

[0067] Retirement amount outflow(2012)=inflow(2012)*f(0)+inflow(2011)*f(1)+inflow(2010)*f(2)

[0068] (2) Use life cycle assessment methods to analyze the life cycle environmental impacts of different recycling processes during the recycling process and obtain the environmental benefits E brought by local recycling of retired components;

[0069] The specific steps include:

[0070] S1: Determine the evaluation object, system boundary and functional unit of the life cycle model in the life cycle assessment method of the recycling process, and divide different stages according to the process flow involved in different recycling processes;

[0071] The evaluation object of the life cycle model is waste photovoltaic modules, and the system boundary is the process flow, including the collection stage, transportation stage, disassembly stage, recycling stage, and waste disposal after recycling, such as Figure 2 As shown, the functional unit is 1 ton of waste photovoltaic modules;

[0072] The recycling processes in the recycling stage include mechanical recycling, chemical recycling and pyrolysis recycling; mechanical recycling includes cutting and grinding screening, chemical recycling includes stratification (stratification by toluene soaking) and metal extraction, and pyrolysis recycling includes EVA stratification and metal extraction.

[0073] Figure 2 In the process, after the PV modules are scrapped, the PV module waste is first removed from the power station through the collection stage, which will generate procurement costs. Then it enters the transportation stage, which includes transporting the PV waste modules from the power station to the nearest waste treatment plant by diesel trucks. This process will generate transportation emissions and bring fuel consumption and transportation costs; in the disassembly stage, the aluminum frame and junction box are disassembled manually or mechanically, which will generate disassembly costs, emissions, and energy consumption. The disassembled aluminum frame and junction box can bring revenue through secondary sales. By using mechanical, pyrolysis or chemical recycling, the EVA plastic film is eliminated from the laminated structure to obtain glass, battery cells and backplanes, and metal extraction is carried out using strong solvents and pollutant emission recovery methods. This stage will generate plastics and metals, gaseous waste, liquid waste and solid waste. Finally, the waste generated in the previous stage is disposed of, plastic and metal resources are recycled, solid waste is landfilled, and gaseous and liquid wastes are landfilled.

[0074] S2: Based on the actual situation, collect the input and output of each process flow for recycling 1 ton of waste photovoltaic modules to form a list of data;

[0075] Table 1 List of input and output data for recycling 1 ton of waste photovoltaic modules in mechanical recycling

[0076]

[0077]

[0078] Table 2 List of input and output data for recycling 1 ton of waste photovoltaic modules in chemical recycling

[0079]

[0080]

[0081] Table 3 List of input and output data for recycling 1 ton of waste photovoltaic modules in pyrolysis recycling

[0082]

[0083]

[0084] S3: Input the inventory data in step S2 into the life cycle assessment software eFootprint to obtain the loads of various environmental impacts; the input process is as follows Figure 3 As shown in Figure 2, the input process of the transportation phase is as follows: Figure 4 As shown in the figure, the output of the life cycle assessment software eFootprint is as follows Figure 5 As shown, taking the greenhouse effect potential (GWP) as an example, the result is -60kgCO2. The negative value indicates the environmental benefit brought by recycling, that is, recycling one ton of photovoltaic modules can reduce 60kgCO2 emissions.

[0085] The types of environmental impacts include global warming potential (GWP), primary energy demand (PED), abiotic depletion potential (ADP), water resource consumption (WU), acidification impact potential (AP), eutrophication potential (EP), inhalable particulate matter (RI), etc. In this embodiment, the global warming potential (GWP) is used as a representative for environmental benefit assessment.

[0086] S4: Multiply the environmental impact load result obtained in step S3 by the amount of photovoltaic scrapping in each region to obtain the environmental benefit E brought by the local recycling of retired components.

[0087] (3) Evaluate the economic benefits of PV recycling;

[0088] The specific steps are:

[0089] a. Determine the cost of economic benefits TC total , including specific costs and external costs. Specific costs include collection stage costs, transportation stage costs, disassembly stage costs, recycling stage costs (involving raw materials and resources consumed in the recycling process, electricity) and post-recycling waste disposal costs (disposal of solid waste, liquid waste, gaseous waste and sludge generated in the process); external costs include labor costs, management costs, taxes, fixed asset depreciation costs, and operation and maintenance costs;

[0090] The specific calculation is shown in equations (4)-(7).

[0091]

[0092] C w =C l +C m +C f +C ope +C opp (5)

[0093]

[0094] Among them, TC total Cost representing the economic benefits of PV waste recycling. C s,iRefers to the specific costs of each stage, covering collection (i=1), transportation (i=2), dismantling (i=3), recycling technology processing (i=4), and disposal (i=5). w Represents the external costs incurred during the entire recycling process. l represents labor cost, C m represents the management cost, C f represents the depreciation cost of fixed assets, C ope and C opp They represent operating and maintenance costs and taxes respectively. Among them, the straight-line method is used to accrue depreciation for fixed assets such as plants and equipment. It is assumed that the increase in recycling volume will lead to the expansion of the scale of the corresponding equipment, plants and other facilities of the enterprise, thereby increasing the investment in fixed assets, and there is a scale effect. m is the reference value of initial fixed asset investment (yuan), U is the processing scale of recycling facilities (tons / year), and U m is the reference value of the initial recycling facility processing capacity (tons / year), I is the fixed asset investment cost (yuan), α is the scale index. ω is the expected net residual value rate, and Y is the depreciation period (10 years). The operation and maintenance cost and opportunity cost are 2% and 5% of the fixed asset depreciation respectively.

[0095] b. Determine the economic benefits BE of secondary sales of recycled materials j , recycled materials include aluminum, glass, silver, copper and silicon obtained during the disassembly stage, and the formula is as follows:

[0096] BE j =P j * RPVW j (8)

[0097] Where, j represents the material, RPVW j represents the total recycled amount of material j, P j represents the recycling price of material j, BE j Represents the economic benefits of secondary sales of recycled material j.

[0098] (4) The environmental benefits of step (2) are combined with the economic benefits of step (3) to obtain the comprehensive environmental and economic benefits of photovoltaic recycling;

[0099] The formula for calculating the comprehensive environmental and economic benefits of photovoltaic recycling is as follows:

[0100] B total =BE j +B indr -TC total

[0101] B indr =E*C*Mass

[0102] Among them, Btotal Represents the comprehensive environmental and economic benefits of photovoltaic recycling, BE j represents the economic benefits of secondary sales, TC total represents the cost of economic benefits, B indr represents indirect environmental benefits, Mass represents the total amount of retired components, unit: ton, E represents the unit environmental benefit of recycling unit retired PV components, obtained through step S2, and C represents the carbon trading price, which is about US$7.8 / ton.

[0103] (5) Evaluate the comprehensive environmental and economic benefits of photovoltaic recycling under different policies based on scenario analysis;

[0104] This embodiment starts from the perspective of the entire chain of retired PV module recycling activities, designs a variety of policy scenarios for the collection stage, processing stage, terminal benefits, external policies, etc., and simulates and analyzes different policy combinations. It can evaluate the evolution trend of the comprehensive economic and environmental benefits of PV recycling under different strategic scenarios.

[0105] Specifically, in the basic scenario, the comprehensive environmental economic benefit assessment method in step (4) is used. The collection cost of one ton of waste components is 715 yuan / ton, the transportation cost is 1.03 yuan / ton / kilometer, and the disassembly cost includes the resource consumption at this stage (for example, the use of water and electricity), the storage of waste modules, and the costs incurred during transportation and storage. The prices of industrial water and electricity at this stage are 3.77 yuan / m and 0.5 yuan / kWh, respectively. The storage cost is assumed to be 307 yuan / ton, and the loss rate is set to 5%. The cost of recycling technology treatment includes the raw materials and resources (such as water, electricity and coal) consumed during the thermal / chemical / mechanical treatment process. The disposal cost is the cost of gas waste generated during the treatment process, calculated using the gas carbon trading price, which is US$7.8 / ton. The labor cost is obtained based on the 2023 "China Statistical Yearbook" (82,783 yuan / year). The annual processing capacity of each worker is 100 tons, and the management cost is generally 30% of the labor cost. Fixed asset investment for mechanical, chemical and thermal treatment methods I m 45.50 million yuan, 55.25 million yuan, and 68.25 million yuan respectively, assuming that the initial recycling facility processing capacity U m 8,000 tons. In terms of revenue, the medium metal price is adopted, and the prices of glass, aluminum, copper, silicon and silver are 0.065$ / t, 1.49$ / t, 5.465$ / t, 3.81$ / t and 476.62$ / t respectively. In terms of economicization of environmental benefits, the carbon trading price is introduced, that is, 7.8 US dollars / ton.

[0106] In the scenario of reducing the cost of the collection stage, the collection cost is reduced by 25% compared with the basic scenario, and the collection cost is reduced to 540 yuan. Other parameters and calculation methods remain consistent with the basic scenario.

[0107] In the scenario where the scale of recycling facility processing is expanded, the fixed asset depreciation cost decreases as the processing scale expands, that is, the processing volume of recycling facility U m It increases from 8,000 in the basic scenario to 20,000, and other parameters and calculation methods remain the same as the basic scenario.

[0108] In the metal price change scenario, metal prices are adjusted from the medium price scenario to the highest price. In the highest price scenario, the prices of glass, aluminum, copper, silicon, and silver are 0.1$ / t, 2$ / t, 5.75$ / t, 6.02$ / t, and 573.1$ / t, respectively. In the lowest price scenario, the prices of glass, aluminum, copper, silicon, and silver are 0.03$ / t, 0.98$ / t, 5.18$ / t, 1.6$ / t, and 380.14$ / t, respectively. Other parameters and calculation methods are consistent with the basic scenario.

[0109] In the comprehensive policy scenario, the highest price is taken into account while reducing and collecting stage costs, expanding the processing scale of recycling facilities, and changing metal prices.

[0110] Table 4 shows the scenario designs under different policies

[0111]

[0112] The above is a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for evaluating the economic and environmental benefits of photovoltaic recycling based on material flow and scenario analysis, characterized in that: The steps include: (1) A dynamic material flow model combined with the Weibull probability distribution function was used to model and evaluate the photovoltaic scrapping, and the spatiotemporal distribution of photovoltaic scrapping in different regions was obtained; (2) Use life cycle assessment methods to analyze the life cycle environmental impacts of different recycling processes during the recycling process and obtain the environmental benefits E brought by local recycling of retired components; (3) Evaluate the economic benefits of PV recycling; (4) The environmental benefits of step (2) are combined with the economic benefits of step (3) to obtain the comprehensive environmental and economic benefits of photovoltaic recycling; (5) Evaluate the comprehensive environmental and economic benefits of photovoltaic recycling under different policies based on scenario analysis.

2. The photovoltaic recycling economic and environmental benefit assessment method based on material flow and scenario analysis according to claim 1 is characterized in that: In step (1), the dynamic material flow model includes three key parameters: the inventory in use, inflows and outflows, the cumulative solar PV installed capacity corresponding to the PV scrapping forecast, the annual PV installed capacity and the annual retirement volume; The calculation process of the dynamic material flow model is as follows: inflow(t) i =outflow(t-1) i +stock(t) i -stock(t-1) i (1) Among them, stock(t) i represents the cumulative solar photovoltaic installed capacity in year t, outflow(t) i represents the annual retirement volume in year t; inflow(t) i represents the newly added photovoltaic installed capacity in year t; i represents different regions; Among them, t' represents the year when the photovoltaic system is completed and put into operation; f(t) represents the Weibull probability density function, which represents the life distribution of photovoltaic modules; t represents the year to be calculated; T is the average life of photovoltaics; β is the shape parameter of the Weibull curve, with a value of 2.4928 for conventional retirement and 5.3759 for early retirement.

3. The photovoltaic recycling economic and environmental benefit assessment method based on material flow and scenario analysis according to claim 2 is characterized in that: Step (2) specifically includes the following steps: S1: Determine the evaluation object, system boundary and functional unit of the life cycle model in the life cycle assessment method of the recycling process, and divide different stages according to the process flow involved in different recycling processes; S2: Based on the actual situation, collect the input and output of each process flow for recycling 1 ton of waste photovoltaic modules to form a list of data; S3: Input the inventory data in step S2 into the life cycle assessment software eFootprint to obtain the loads of various environmental impacts; S4: Multiply the environmental impact load result obtained in step S3 by the amount of photovoltaic scrapping in each region to obtain the environmental benefit E brought by the local recycling of retired components.

4. The photovoltaic recycling economic and environmental benefit assessment method based on material flow and scenario analysis according to claim 3 is characterized in that: In step S1, the evaluation object of the life cycle model is the waste photovoltaic modules, and the system boundary is the process flow, including the collection stage, transportation stage, disassembly stage, recycling stage, and waste disposal after recycling. The functional unit is 1 ton of waste photovoltaic modules; The recycling processes in the recycling stage include mechanical recycling, chemical recycling and pyrolysis recycling; mechanical recycling includes cutting and grinding screening, chemical recycling includes stratification and metal extraction, and pyrolysis recycling includes EVA stratification and metal extraction.

5. The photovoltaic recycling economic and environmental benefit assessment method based on material flow and scenario analysis according to claim 4 is characterized in that: In step S3, the types of environmental impacts include greenhouse effect potential, primary energy demand, abiotic depletion potential, water resource consumption, acidification impact potential, eutrophication potential and inhalable particulate matter; In step S3, the greenhouse effect potential is preferably used as a representative for environmental benefit assessment.

6. The photovoltaic recycling economic and environmental benefit assessment method based on material flow and scenario analysis according to claim 5 is characterized in that: The specific steps of step (3) are: a. Determine the cost of economic benefits TC total , including specific costs and external costs. Specific costs include collection stage costs, transportation stage costs, disassembly stage costs, recycling stage costs and waste disposal costs after recycling; external costs include labor costs, management costs, taxes, fixed asset depreciation costs, and operation and maintenance costs; b. Determine the economic benefits BE of secondary sales of recycled materials j .

7. The photovoltaic recycling economic and environmental benefit assessment method based on material flow and scenario analysis according to claim 6 is characterized in that: In step b, the recycled materials include aluminum, glass, silver, copper and silicon obtained during the disassembly stage.

8. The photovoltaic recycling economic and environmental benefit assessment method based on material flow and scenario analysis according to claim 7 is characterized in that: The calculation formula for the comprehensive environmental and economic benefits of photovoltaic recycling in step (4) is as follows: B total =BE j +B indr -TC total B indr =E*C*Mass Among them, B total Represents the comprehensive environmental and economic benefits of photovoltaic recycling, BE j represents the economic benefits of secondary sales, TC total represents the cost of economic benefits, B indr represents indirect environmental benefits, Mass represents the total amount of retired components, unit: ton, E represents the unit environmental benefit of recycling unit retired PV components, and C represents the carbon trading price.

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