Method for measuring optimal separation temperature of EVA (Ethylene Vinyl Acetate) of double-glass photovoltaic module

Abstract

The invention relates to the technical field of photovoltaic module separation, in particular to a double-glass photovoltaic module EVA optimal separation temperature measuring method which comprises the following steps: S1, performing thermal performance characterization on an EVA adhesive film used by a photovoltaic module by a differential scanning calorimetry (DSC) to obtain a melting temperature range of the EVA adhesive film; s2, selecting a test temperature range, carrying out an EVA adhesive film tensile test, pretreating the small sample, and carrying out a laminated part stripping test; s3, calculating interface adhesion energy according to a test force-displacement curve and a stress-strain curve, and selecting an optimal separation temperature of heat treatment according to a comparison result; when the device is in use, the accurate temperature condition of low-temperature heat treatment when a photovoltaic module is separated by a physical method is determined by combining an adhesive energy direct measurement mode of EVA adhesive film tensile test and laminated part stripping test results, the adhesive performance of an EVA packaging adhesive film is promoted to be reduced, the time for pyrolyzing a packaging material in a traditional method is shortened, the overall disassembling efficiency is improved, and the cost is reduced. And the device is environment-friendly, energy-saving, cost-reducing and efficiency-increasing.

Description

Technical Field

[0001] This invention relates to the field of photovoltaic module separation technology, and in particular to a method for determining the optimal separation temperature of EVA in a double-glass photovoltaic module. Background Technology

[0002] With the global emphasis on renewable energy utilization, the photovoltaic industry has experienced rapid development. However, the accompanying issue of recycling retired photovoltaic modules has become increasingly prominent, making the promotion of their proper recycling an urgent matter. Photovoltaic modules typically have a lifespan of 25 to 30 years, requiring the disposal of approximately 1.5 million tons of retired modules upon completion, a figure expected to rise over time. This massive scale of retired modules indicates a promising future for the photovoltaic recycling market.

[0003] The recycling of photovoltaic (PV) modules can replenish raw materials for production, enhance product sustainability and industrial competitiveness, and help ensure the stable development of the PV industry chain. Currently, PV module recycling methods mainly include mechanical processing, thermal treatment, and chemical processing. Traditional mechanical processing methods often involve crushing and screening; however, the pyrolysis process easily damages the cells and releases toxic and harmful gases. The particle mixture obtained from mechanical crushing has a complex composition, especially the EVA film, which is heavily contaminated and difficult to completely separate, indicating room for improvement in separation technology and product purity. Chemical processing methods suffer from long reaction cycles, high reagent consumption, and difficulties in treating waste liquids and gases, increasing the overall difficulty of recycling. Currently, there is a significant gap in the technology of low-energy consumption, low-pollution, and economically feasible crystalline silicon PV module recycling, and a complete and efficient recycling process system has not yet been formed. It is known that temperature fluctuations are the fundamental driving factor of thermomechanical stress within PV modules. In the PV module recycling process, a key step lies in debonding the EVA (ethylene-vinyl acetate copolymer) film layer separation lamination structure in the module. While this material has stable properties, achieving full-component PV module recycling with uncontaminated EVA film, minimized cell damage, and maximized integrity using physical methods is quite difficult. In addition, the EVA encapsulation performance of non-standard manufactured components varies slightly, and the separation temperature is not unique after different aging processes. A reliable measurement method is needed to determine the reasonable separation temperature for deconstructing different laminates. Summary of the Invention

[0004] The technical problem to be solved by this invention is: in order to solve the problems of high energy consumption, high pollution, long time, and the inability to achieve full component recovery, maximize the integrity of the module formation, and minimize cell damage in existing traditional photovoltaic module separation methods, a method for determining the optimal separation temperature of EVA in double-glass photovoltaic modules is provided.

[0005] The technical solution adopted by this invention to solve its technical problem is: a method for determining the optimal separation temperature of EVA in a double-glass photovoltaic module, comprising the following steps: S1. Differential scanning calorimetry (DSC) was used to characterize the thermal properties of the EVA film used in photovoltaic modules and obtain its melting temperature range. S2. Select the test temperature range, conduct EVA film tensile test and pre-treat small samples for laminate peel test; S3. Calculate the interfacial adhesion energy based on the experimental force-displacement curve and stress-strain curve, and select the optimal separation temperature for heat treatment by comparing the results. S4. Mechanically disassemble and remove the aluminum frame and junction box of the photovoltaic module to obtain the photovoltaic laminate containing EVA film. Heat-treat the light-transmitting side of the photovoltaic laminate at the optimal separation temperature, de-adhesive film, separate the photovoltaic laminate, and then use mechanical means to separate the glass layer and solar cells of the disassembled laminate to achieve full component recovery. Step S2 involves testing the pre-treated small sample. The pre-treated small sample refers to the laminated component after removing the aluminum frame, junction box, and one-sided glass, which is processed into a small piece. The testing includes a tensile test of the EVA film and a peel test of the laminated component after heat treatment. Step S3 calculates the adhesion energy γ based on the test data, specifically including the stress-strain curve of the EVA film tensile test, the force-displacement curve of the laminated component peel test, and the average peel force F. peel The composite graph of the peel stress σ and the intersection of the stress-strain curves was used to compare the results and select the optimal separation temperature for heat treatment. Compared with existing technologies, this solution directly determines the adhesion energy by combining the results of EVA film tensile tests and laminate peel tests. This method determines the precise temperature conditions for low-temperature heat treatment when physically separating photovoltaic modules, which reduces the adhesion performance of the EVA encapsulation film. This process shortens the time required for pyrolysis of the encapsulation material in traditional disassembly methods, thereby significantly improving the overall efficiency of disassembly, ensuring the integrity of the separated components, environmental protection and energy saving, and cost reduction and efficiency improvement.

[0006] In some preferred embodiments, the test temperature in step S2 is 40℃-90℃, and the temperature is maintained for 30 minutes.

[0007] In some preferred embodiments, the peeling rate tested in step S2 is 60 mm / min to 600 mm / min.

[0008] In some preferred embodiments, step S3 includes the following steps: S3.1. Analyze the force-displacement curves of the peel test at the same temperature to obtain the average peel force F from the steady-state peel plateau. peel Calculate γ1 using the following formula: ; S3.2 Plot the stress-strain curves of the tensile test at the same temperature against the peel stress σ corresponding to the average peel force, and calculate γ2. The calculation formula is as follows: ; S3.3, The adhesion energy γ is comprehensively calculated and evaluated. The calculation formula is as follows: ; S3.4 Obtain multiple sets of data and results based on multiple sets of different test temperatures, compare the results and record the optimal separation temperature for heat treatment.

[0009] In some preferred embodiments, step S3 further includes: S3.5. If components made from EVA films in different states other than the above-mentioned melting temperatures occur, such as low-temperature or laminated parts with different aging degrees, a shift factor correction is added using the WLF equation. The basic WLF equation is as follows: ; Using the displacement factor, combined with the existing adhesion energy results for the melting temperature range, the interfacial adhesion energy under other conditions can be derived to obtain the specific optimal separation temperature.

[0010] In some preferred embodiments, in step S3, the optimal separation temperature for heat treatment is determined by comparing and judging the trend of the adhesion energy γ and its components. The temperature range in which the total adhesion energy γ and its component γ1 decrease significantly is preferred, and then narrowed down to the temperature at which the growth of γ2 reaches its limit and tends to saturate.

[0011] In some preferred embodiments, in step S4, a torsional sliding method is used to separate the two sides of the glass from the battery cell.

[0012] The beneficial effects of this invention are as follows: The method for determining the optimal separation temperature of EVA in a double-glass photovoltaic module, when used, directly determines the adhesion energy by combining the results of EVA film tensile tests and laminate peel tests. This determines the precise temperature conditions for low-temperature heat treatment during physical separation of the photovoltaic module, promoting the debonding of the EVA encapsulation film. This process shortens the time required for pyrolysis of the encapsulation material in traditional disassembly methods, thereby significantly improving the overall efficiency of disassembly, ensuring the integrity of the separated module, environmental protection and energy saving, cost reduction and efficiency improvement. It avoids the problems of high energy consumption, high pollution, long time, and the inability to achieve full component recovery, maximize module integrity, and minimize cell damage associated with traditional photovoltaic module separation methods. Attached Figure Description

[0013] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0014] Figure 1 This is a flowchart of the present invention; Figure 2 This is a flowchart of the temperature measurement test of the present invention. Detailed Implementation

[0015] Example 1, such as Figure 1-2 As shown, a method for determining the optimal separation temperature of EVA in a double-glass photovoltaic module includes the following steps: S1. Differential scanning calorimetry (DSC) was used to characterize the thermal properties of the EVA film used in photovoltaic modules and obtain its melting temperature range. S2. Select the test temperature range, conduct EVA film tensile test and pre-treat small samples for laminate peel test; S3. Calculate the interfacial adhesion energy based on the experimental force-displacement curve and stress-strain curve, and select the optimal separation temperature for heat treatment by comparing the results. S4. Mechanically disassemble and remove the aluminum frame and junction box of the photovoltaic module to obtain the photovoltaic laminate containing EVA film. Heat-treat the light-transmitting side of the photovoltaic laminate at the optimal separation temperature, de-adhesive film, separate the photovoltaic laminate, and then use mechanical means to separate the glass layer and solar cells of the disassembled laminate to achieve full component recovery. Step S2 involves testing the pre-treated small sample. The pre-treated small sample refers to the laminated part with the aluminum frame, junction box and single-sided glass removed processed into a small piece. The testing involves EVA film tensile test and laminate peel test after heat treatment. Step S3 calculates the adhesion energy γ based on the test data, specifically including the stress-strain curve of the EVA film tensile test, the force-displacement curve of the laminate peel test, and the average peel force F. peel The composite graph of the peel stress σ and the intersection of the stress-strain curves was used to compare the results and select the optimal separation temperature for heat treatment.

[0016] Step S3 includes the following steps: S3.1. Analyze the force-displacement curves of the peel test at the same temperature to obtain the average peel force F from the steady-state peel plateau. peel γ1 was calculated. Tensile and peel tests were conducted on a universal electronic tensile testing machine with an environmental chamber. The peel rate was 100 mm / min, the test temperature was 40℃, and the heat treatment was carried out in a normal air atmosphere. S3.2 Plot the stress-strain curves of the tensile test at the same temperature against the peel stress σ corresponding to the average peel force, and calculate γ2. S3.3, The adhesion energy γ is comprehensively calculated and evaluated. The calculation formula is as follows: ; ; ; The calculated result is γ1 = 12.74 kJ / m 2 γ2=0.54kJ / m2 γ = 13.28 kJ / m 2 The adhesion energy γ consists of two components: γ1 corresponds to the adhesion energy under an absolutely rigid peel arm as assumed by Rivlin, with units of kJ / m², and can be applied to a given peel force. The calculations show that the correction γ2 comes from the residual energy of the large elastic deformation, expressed in kJ / m². The term represents the work done by the peel force on the film elongation, while This refers to the strain energy stored within the film, where b is the film width in mm and h is the film thickness in mm. Average peel force, in N. In response to the situation; Strain energy density, in J / m³; S3.4 Obtain multiple sets of data and results based on multiple sets of different test temperatures, compare the results and record the optimal separation temperature for heat treatment; S3.5. If components made from EVA films in different states other than the above-mentioned melting temperatures occur, such as low-temperature or laminated parts with different aging degrees, a shift factor correction is added using the WLF equation. The basic WLF equation is as follows: ; Environmental conditions can affect the properties of EVA film. For example, the temperature sensitivity of newly made film and aged film is different. Its optimal heat treatment conditions may exceed the existing melting temperature range. The above formula can help to correct this and avoid repeated experiments and high-temperature tests. C1 and C2 are empirical constants, which depend on the selected reference temperature T0 and the specific material. T0 is selected within the above melting range, and T is the current temperature, which depends on the difference in environmental conditions. By combining the adhesion energy results of the existing melting temperature range, the interfacial adhesion energy under other conditions can be derived to obtain the specific optimal separation temperature.

[0017] In step S4, the glass on both sides and the battery cell are separated by twisting and sliding.

[0018] Example 2 differs from Example 1 in that the test peeling rate and test temperature are different in Example 2. The test peeling rate is 100 mm / min and the test temperature is 60°C. The calculated result is γ1 = 9.94 kJ / m 2 γ2=1.86kJ / m 2 γ = 11.8 kJ / m 2 Comparing the γ obtained in Example 2 with the γ obtained in Example 1, it is clear that the adhesion energy γ is significantly reduced at a test temperature of 60℃ compared to a test temperature of 40℃. Therefore, the optimal heat treatment temperature is 60℃.

[0019] Example 3 differs from Examples 1 and 2 in that the test peeling rate and test temperature are different in Example 3. The test peeling rate is 100 mm / min and the test temperature is 80°C. The calculated result is γ1 = 5.36 kJ / m 2 γ2=1.72kJ / m 2 γ = 7.08 kJ / m 2 Comparing the γ obtained in Example 3 with the γ obtained in Example 1, it is clear that the adhesion energy γ is significantly reduced at a test temperature of 80℃ compared to a test temperature of 40℃. Therefore, the optimal heat treatment temperature is 80℃.

[0020] In summary, the comparison results of Examples 1, 2 and 3 show that, for the same material, the adhesion energy γ decreases with increasing temperature, and the corrected portion γ2, which comes from the residual energy of large elastic deformation, first increases and then decreases with increasing temperature. Therefore, the optimal heat treatment temperature for this material is 60℃-80℃.

[0021] During separation, by combining the adhesion energy of EVA film tensile test and laminate peel test results, the precise temperature conditions for low-temperature heat treatment during physical separation of photovoltaic modules were determined, which promoted the debonding of EVA encapsulation film. This process shortened the time required for thermal decomposition of encapsulation materials in traditional disassembly methods, thereby significantly improving the overall efficiency of disassembly. Within the melting temperature range, precise low-heat treatment ensures that the original physical integrity and structural strength of the glass and solar cells are maintained to the maximum extent during dismantling. This facilitates subsequent component recycling, significantly reduces overheating and physical damage during dismantling, and minimizes the reduction in component value. Whether it's the reuse of glass sheets or the recovery of valuable metal materials from solar cells, higher recovery rates and purity can be achieved, thereby improving the economic and environmental benefits of the entire photovoltaic module recycling process. Compared to traditional mechanical, thermal, and chemical treatments, this invention employs a composite treatment method. The low-heat conditions reduce energy consumption and costs. Furthermore, by considering the heat treatment properties of each component and controlling the temperature, the emission of harmful gases is eliminated at the source, reducing environmental pollution and achieving maximum recovery of all components, which meets the requirements of green and sustainable development. Compared to traditional heat treatment, this invention pre-determines the optimal separation conditions for different components through the aforementioned measurement methods, reducing heat treatment costs. Specific problems are analyzed on a case-by-case basis, improving the separation efficiency of heterogeneous interfaces of different double-glass photovoltaic modules.

[0022] Based on the above-described preferred embodiments of the present invention, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A method for determining the optimal separation temperature of EVA in a double-glass photovoltaic module, characterized in that, Includes the following steps: S1. Differential scanning calorimetry (DSC) was used to characterize the thermal properties of the EVA film used in photovoltaic modules and obtain its melting temperature range. S2. Select the test temperature range, conduct EVA film tensile test and pre-treat small samples for laminate peel test; S3. Calculate the interfacial adhesion energy based on the experimental force-displacement curve and stress-strain curve, and select the optimal separation temperature for heat treatment by comparing the results. S4. Mechanically disassemble and remove the aluminum frame and junction box of the photovoltaic module to obtain the photovoltaic laminate containing EVA film. Heat-treat the light-transmitting side of the photovoltaic laminate at the optimal separation temperature, de-adhesive film, separate the photovoltaic laminate, and then use mechanical means to separate the glass layer and solar cells of the disassembled laminate to achieve full component recovery. Step S2 involves testing the pre-treated small sample. The pre-treated small sample refers to the laminated part with the aluminum frame, junction box and single-sided glass removed processed into a small piece. The testing involves EVA film tensile test and laminate peel test after heat treatment. In step S3, the adhesion energy γ is calculated based on the test data, specifically including the stress-strain curve of the EVA film tensile test, the force-displacement curve of the laminate peel test, and the average peel force F. peel The composite graph of the peel stress σ and the intersection of the stress-strain curves was used to compare the results and select the optimal separation temperature for heat treatment.

2. The method for determining the optimal separation temperature of EVA in a double-glass photovoltaic module according to claim 1, characterized in that: The precise temperature conditions for low-temperature heat treatment during physical separation of photovoltaic modules were determined. In step S2, the test temperature range was 40℃-90℃, which is the melting temperature range of EVA film, and the temperature was maintained for 30 minutes.

3. The method for determining the optimal separation temperature of EVA in a double-glass photovoltaic module according to claim 2, characterized in that: In step S2, the peeling rate is tested to be 60 mm / min-600 mm / min.

4. The method for determining the optimal separation temperature of EVA in a double-glass photovoltaic module according to claim 1, characterized in that, Step S3 includes the following steps: S3.

1. Analyze the force-displacement curves of the peel test at the same temperature to obtain the average peel force F from the steady-state peel plateau. peel Calculate γ1 using the following formula: ； S3.2 Plot the stress-strain curves of the tensile test at the same temperature against the peel stress σ corresponding to the average peel force, and calculate γ2. The calculation formula is as follows: ； S3.3, The adhesion energy γ is comprehensively calculated and evaluated. The calculation formula is as follows: ； S3.4 Obtain multiple sets of data and results based on multiple sets of different test temperatures, compare the results and record the optimal separation temperature for heat treatment.

5. The method for determining the optimal separation temperature of EVA in a double-glass photovoltaic module according to claim 4, characterized in that: Step S3 also includes: S3.

5. If components made from EVA films in different states other than the above-mentioned melting temperatures occur, such as low-temperature or laminated parts with different aging degrees, a shift factor correction is added using the WLF equation. The basic WLF equation is as follows: ； Using the displacement factor, combined with the existing adhesion energy results for the melting temperature range, the interfacial adhesion energy under other conditions can be derived to obtain the specific optimal separation temperature.

6. The method for determining the optimal separation temperature of EVA in a double-glass photovoltaic module according to claim 1, characterized in that: In step S3, the optimal separation temperature for heat treatment is determined by comparing and judging the trend of the adhesion energy γ and its components. The temperature range in which the total adhesion energy γ and its component γ1 decrease significantly is selected first, and then narrowed down to the temperature at which the growth of γ2 reaches its limit and tends to saturate.

7. The method for determining the optimal separation temperature of EVA in a double-glass photovoltaic module according to claim 1, characterized in that: In step S4, the glass on both sides and the battery cell are separated by twisting and sliding.

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