Test method for evaluating photo-thermal resistance of photovoltaic cell

Abstract

The invention discloses a test method for evaluating photo-thermal resistance of photovoltaic cells, and relates to the field of performance testing of photovoltaic cells, and the method comprises the following steps: randomly sampling cells in the same batch, wrapping the cells with a preservative film, placing the cells in an environmental box at 25 + / -2 DEG C for 24 + / -2 hours, then measuring the initial power Pa at 25 + / -2 DEG C under the illumination of 1000W / m < 2 >, and measuring the photothermal resistance of the cells. Clamping the battery piece between two layers of glass to prepare a test sample; irradiating the test sample for 4kWh / m < 2 > under the conditions of 50 + / -15 DEG C and 1000 + / -100W / m < 2 >; then continuously measuring the power P1-P5 for five times at the temperature of 25 + / -2 DEG C under the light intensity of 1000W / m < 2 >, if P1 < P2 < P3 < P4 < P5, continuously measuring until Pn < Pn-1 or Pn = P1, and grading the light fastness degree according to the value of n; and finally, measuring the final power Pb at the temperature of 25 + / -2 DEG C under the light intensity of 1000W / m < 2 >, calculating the power attenuation rate Patt = (Pa-Pb) / Pa * 100, if Patt is less than or equal to a preset value, determining that the power attenuation rate is qualified, and otherwise, determining that the power attenuation rate is unqualified. The method can effectively evaluate the photo-thermal resistance of the same batch of cells, shorten the test period and improve the reliability of the test result.

Description

Technical Field

[0001] The present invention relates to the field of performance testing of photovoltaic cells, and particularly to a testing method for evaluating the light and heat resistance performance of photovoltaic cells. Background Art

[0002] The light and heat resistance performance of photovoltaic cells (solar cells) is crucial, which directly affects power generation efficiency, service life, reliability and stability. Good light and heat resistance performance can effectively control the working temperature of the cells, reduce the efficiency loss caused by temperature rise, and at the same time avoid material fatigue, aging and performance degradation caused by thermal stress and thermal cycling, thereby prolonging the service life of the cells. In addition, under extreme environmental conditions such as high temperature, strong light, high humidity and heat, the cells with excellent light and heat resistance performance can maintain stable performance output, improving the overall reliability of the system. The light and heat resistance performance test (cell degradation test) is of great significance for evaluating and ensuring the performance of cells, discovering and preventing potential problems, promoting technological innovation and industry development. Through testing, it can be ensured that the cells meet the quality standards, screen out products with excellent performance, detect defects early, prevent performance degradation, provide data support for research and development, standardize the market, improve the competitiveness of enterprises, and promote the healthy development of the solar cell industry.

[0003] The tests for cell degradation usually include two methods: light illumination test and electrical injection test. However, both of these two methods have the problem that they cannot clearly classify the cell performance of different manufacturers, resulting in a large deviation in cell performance evaluation. Therefore, how to accurately obtain the influence of cell degradation on the power generation efficiency of the cell is an urgent problem to be solved by those skilled in the art. Summary of the Invention

[0004] The purpose of the present invention is to provide a testing method for evaluating the light and heat resistance performance of photovoltaic cells to solve the problem that the existing testing methods cannot accurately obtain the influence of cell degradation on the power generation efficiency of the cell.

[0005] To achieve the above purpose, the present invention provides the following solution: A testing method for evaluating the light and heat resistance performance of photovoltaic cells, comprising the following steps:

[0006] Step S1, sample preparation: Randomly select cells from the same batch of cells, wrap them with plastic wrap, and place them in an environmental chamber at 25±2°C for 24±2h; then conduct an initial power test under illumination at 25±2°C and 1000W / m 2 and record it as Pa; clamp the tested cells between two layers of glass to make a test sample;

[0007] Step S2, the first test: Place the test sample in a steady-state simulator, with the light source directly above the cell, at 50±15°C and 1000±100W / m 2Accumulative irradiation of 4 kWh / m under the condition 2 ;

[0008] Step S3, Performance recovery: After irradiation, conduct 5 consecutive tests at 25 ± 2°C and a light intensity of 1000 W / m 2 . Denote them as P1, P2, P3, P4, P5; If P1 < P2 < P3 < P4 < P5, continuously conduct flash and power tests, and stop the power test when Pn < Pn-1 or Pn = P1 appears; Determine the light resistance degree of the cell according to the value of n, and divide the light resistance degree into several levels;

[0009] Step S4, Second test: Cumulatively irradiate the test sample under the same test conditions as the first test, and the total irradiation dose of the cumulative irradiation is in a proportional relationship with the level of the light resistance degree;

[0010] Step S5, Performance evaluation: After the irradiation ends, conduct the final power test at 25 ± 2°C and a light intensity of 1000 W / m 2 . Denote it as Pb; Calculate the power attenuation rate Patt = (Pa - Pb) / Pa * 100; If Patt is less than or equal to the preset attenuation value, it is determined to be qualified, otherwise it is determined to be unqualified.

[0011] Optionally, in step S3 of the test method of the present invention, the division of the light resistance degree into several levels includes:

[0012] When n ≤ 20, determine that the light and heat resistance degree of the cell is L1;

[0013] When 20 < n ≤ 100, determine that the light and heat resistance degree of the cell is L2;

[0014] When 100 < n ≤ 200, determine that the light and heat resistance degree of the cell is L3.

[0015] Optionally, in step S4 of the test method of the present invention, the fact that the total irradiation dose of the cumulative irradiation is in a proportional relationship with the level of the light resistance degree includes:

[0016] When it is determined that the light and heat resistance degree of the cell in the test sample is L1, cumulatively irradiate the test sample by 10 kWh / m 2 ;

[0017] When it is determined that the light and heat resistance degree of the cell in the test sample is L2, cumulatively irradiate the test sample by 30 kWh / m 2 ;

[0018] When it is determined that the light and heat resistance degree of the cell in the test sample is L3, cumulatively irradiate the test sample by 60 kWh / m 2 .

[0019] Optionally, in step S5 of the test method of the present invention, the preset attenuation value is 1%. If Patt ≤ 1%, it is determined to be qualified; if Patt > 1%, it is determined to be unqualified.

[0020] Optionally, in step S1 of the test method of the present invention, multiple battery wafers are randomly selected from the same batch of battery wafers, and the same subsequent tests are performed on the multiple battery wafers.

[0021] Optionally, in step S1 of the test method of the present invention, an anti-static protective film is further wrapped outside the plastic wrap wrapping the battery wafer.

[0022] Optionally, in step S1 of the test method of the present invention, during the process of placing in an environmental chamber at 25 ± 2 °C for 24 ± 2 h, the relative humidity value of the environmental chamber is controlled to be less than 60%.

[0023] Optionally, in the test method of the present invention, it further includes checking the appearance and structural integrity of the battery wafer after the test.

[0024] The present invention discloses the following technical effects:

[0025] The present invention provides a test method for evaluating the light and heat resistance performance of photovoltaic battery wafers, which can effectively distinguish the light and heat resistance performance of photovoltaic battery wafers from different manufacturers or different batches. At the same time, according to the classification of the light and heat resistance degree, a unified detection scheme can be adopted for the products of the same battery manufacturer, shortening the test cycle and improving the reliability of the test results. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0027] Figure 1 It is a flowchart of the test method of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0028] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0029] Photovoltaic cells have the problem of excessive attenuation, which has become a non-negligible factor hindering the improvement of battery efficiency. The existing testing methods cannot accurately obtain the impact of cell attenuation on the power generation efficiency of the battery. Therefore, it is necessary to propose a testing method for evaluating the light and heat resistance performance of photovoltaic cells to accurately obtain the impact of cell attenuation on the power generation efficiency of the battery.

[0030] To make the above objects, features, and advantages of the present invention more obvious and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0031] Refer to Figure 1 As shown, an embodiment of the present invention provides a testing method for evaluating the light and heat resistance performance of photovoltaic cells, including the following steps:

[0032] Step S1, sample preparation, including:

[0033] Randomly select 1 cell from the same batch of cells, wrap the cell with plastic wrap, and place it in an environmental chamber at 25 ± 2°C for 24 ± 2 h;

[0034] Under the illumination condition of 25 ± 2°C and 1000 W / m 2 , perform an initial power test on the above cell, and record the test result as Pa;

[0035] Clamp the cell after the power test between two layers of glass to make a test sample.

[0036] Step S2, the first test, including:

[0037] Place the test sample in a steady-state simulator, with the light source directly above the cell, and under the light intensity condition of an environmental temperature of 50 ± 15°C and an irradiation intensity of 1000 ± 100 W / m 2 , irradiate cumulatively for 4 kWh / m 2 .

[0038] Step S3, performance recovery

[0039] After the irradiation is completed, perform a power test on the test sample under the light intensity of 25 ± 2°C and 1000 W / m 2 , and perform 5 consecutive tests. Record them as P1, P2, P3, P4, P5;

[0040] When P1 < P2 < P3 < P4 < P5 appears, continue to perform flash and power tests on the test sample, and stop the power test when Pn < Pn-1 or Pn = P1 appears;

[0041] When n ≤ 20, determine that the light and heat resistance degree of the cell is L1;

[0042] When 20 < n ≤ 100, it is determined that the light and heat resistance of the cell is L2;

[0043] When 100 < n ≤ 200, it is determined that the light and heat resistance of the cell is L3.

[0044] Step S4, Second Test

[0045] Place the test sample in a steady-state simulator with the light source directly above the cell, and irradiate it cumulatively under the light intensity condition of an environmental temperature of 50 ± 15°C and an irradiance of 1000 ± 100 W / m 2 ;

[0046] When it is determined that the light and heat resistance of the cell in the test sample is L1, irradiate the test sample cumulatively by 10 kWh / m 2 ;

[0047] When it is determined that the light and heat resistance of the cell in the test sample is L2, irradiate the test sample cumulatively by 30 kWh / m 2 ;

[0048] When it is determined that the light and heat resistance of the cell in the test sample is L3, irradiate the test sample cumulatively by 60 kWh / m 2 .

[0049] Step S5, Performance Evaluation

[0050] After the irradiation is completed, conduct a final power test on the test sample under the light intensity of 25 ± 2°C and 1000 W / m 2 , and record it as Pb; calculate the power attenuation rate Patt of the cell according to Pb and Pa, then Patt = (Pa - Pb) / Pa * 100;

[0051] If Patt ≤ 1%, it is determined as qualified;

[0052] If Patt > 1%, it is determined as unqualified.

[0053] In some alternative embodiments, in order to compare the performance differences of cells from different manufacturers or different batches, cells can be separately sampled from cells of different batches (different batches of the same manufacturer or different manufacturers). For example, 3 cells are separately sampled from the cells produced by three different manufacturers AB and C, and subsequent tests are conducted according to the same method to compare the performance differences of cells of different batches.

[0054] In a specific embodiment, in step S1, Sample Preparation, set the temperature of the environmental chamber to 25°C and the placement time to 24 h.

[0055] In some alternative embodiments, in order to reduce the influence of environmental humidity on test results, in step S1, sample preparation, humidity control can be added. For example, set the relative humidity in the environmental chamber to be less than 60%, and the relative humidity change value ≤ 5%, to ensure that in each test, the solar cell is in an environment with stable relative humidity.

[0056] In some alternative embodiments, in step S1, sample preparation, after wrapping the solar cell with plastic wrap, an additional anti-static protective film is added outside the plastic wrap to prevent the solar cell from being interfered by static electricity during the pretreatment process, affecting the accuracy of subsequent test results.

[0057] In some alternative embodiments, in step S4, the second test, after completing the short-term light exposure test of 60 KWh / m 2 continue the long-term light exposure test on some test samples, such as cumulative irradiation of 100 KWh / m 2 、200 KWh / m 2 or even higher, to simulate the situation where the solar cell is exposed to the light environment for a long time during actual use, and further evaluate its long-term light and heat resistance performance.

[0058] In some alternative embodiments, in addition to the power attenuation rate Patt, other performance indicators can also be introduced for comprehensive evaluation. For example, measure the changes in parameters such as the open-circuit voltage (Voc), short-circuit current (Isc), and fill factor (FF) of the solar cell before and after the test. Calculate the open-circuit voltage change rate ΔVoc = (Voc initial - Voc final) / Voc initial * 100, the short-circuit current change rate ΔIsc = (Isc initial - Isc final) / Isc initial * 100, and the fill factor change rate ΔFF = (FF initial - FF final) / FF initial * 100. Take these change rates together with the power attenuation rate as indicators to evaluate the light and heat resistance performance of the solar cell, more comprehensively reflecting the degradation of the solar cell performance.

[0059] In some alternative embodiments, in step S3, performance recovery, based on the original light and heat resistance level classification (L1, L2, L3), further refine the level division. For example, divide the L1 level into L1a and L1b, where L1a when n ≤ 10 and L1b when 10 < n ≤ 20; divide the L2 level into L2a and L2b, where L2a when 20 < n ≤ 50 and L2b when 50 < n ≤ 100; divide the L3 level into L3a and L3b, where L3a when 100 < n ≤ 150 and L3b when 150 < n ≤ 200. Through more detailed level division, the differences in the light and heat resistance performance of the solar cell can be more accurately reflected, providing a more detailed basis for the quality classification and application selection of the solar cell.

[0060] In some alternative embodiments, the light and heat resistance test method is combined with other environmental adaptability tests such as temperature cycle test and damp heat test. For example, after the light and heat resistance test is completed, the test sample is subjected to a temperature cycle test (with the temperature cyclically varying between -40°C and 85°C) and a damp heat test (placed for a certain period of time at 85°C and 85% relative humidity) to comprehensively evaluate the performance stability and reliability of the cell under the combined action of various environmental factors, simulate the usage of the cell in an actual complex environment, and provide more comprehensive test data support for the design, production, and application of the cell.

[0061] In some alternative embodiments, the appearance and structural integrity of the cell can also be evaluated. Check whether there are obvious cracks, delaminations, color changes, etc. in the cell after the test. These changes in appearance and structure may affect the long-term performance and reliability of the cell, and can be used as auxiliary evaluation indicators in combination with the change rate of performance parameters to more accurately determine the light and heat resistance performance level of the cell.

[0062] What is not elaborated in the present invention are all conventional technical means well-known to those skilled in the art.

[0063] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation to the present invention.

[0064] The embodiments described above are only for describing the preferred mode of the present invention, and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solution of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A test method for evaluating the light and heat resistance of photovoltaic cells, characterized in that: The following steps are involved: Step S1, sample preparation: randomly select cells from the same batch of cells, wrap them with plastic wrap, and place them in a 25±2℃ environment box for 24±2h; then place them in a 25±2℃, 1000W / m 2 Carry out initial power test under illumination, recorded as Pa; sandwich the tested cell between two layers of glass to make a test sample; Step S2, first test: place the test sample in a steady-state simulator, with the light source located directly above the cell, at 50±15°C, 1000±100W / m 2 Under the condition of cumulative irradiation 4kWh / m 2 ; Step S3, performance recovery: after irradiation at 25±2℃, 1000W / m 2 5 tests are performed continuously under the light intensity of, recorded as P1, P2, P3, P4, P5; if P1<P2<P3<P4<P5, flash and power test are continuously performed, and the power test is stopped when Pn<Pn-1 or Pn=P1 appears; the light resistance of the cell is determined according to the value of n, and the light resistance is divided into several levels; Step S4, second test: using the same test conditions as the first test to cumulatively irradiate the test sample, the total radiation amount of the cumulative irradiation is directly proportional to the level of light resistance; Step S5, performance evaluation: After irradiation, at 25±2℃, 1000W / m 2 The final power test is carried out under the light intensity of , recorded as Pb; the power attenuation rate Patt is calculated as (Pa-Pb) / Pa*100; If Patt is less than or equal to the preset attenuation value, it is judged as qualified, otherwise it is judged as unqualified.

2. The test method for evaluating the light and heat resistance of photovoltaic cells according to claim 1, characterized in that: In step S3, the light resistance is divided into several levels, including: When n≤20, the light and heat resistance of the cell is determined to be L1; When 20<n≤100, the light and heat resistance of the cell is determined to be L2; When 100<n≤200, the light and heat resistance of the cell is determined to be L3.

3. The test method for evaluating the light and heat resistance of photovoltaic cells according to claim 2, characterized in that: In step S4, the total radiation amount of the cumulative exposure is in direct proportion to the level of light resistance, including: When the light and heat resistance of the cells in the test sample is determined to be L1, the test sample is irradiated with a cumulative 10kWh / m 2 ; When the light and heat resistance of the cells in the test sample is determined to be L2, the test sample is irradiated with a cumulative 30kWh / m 2 ; When the light and heat resistance of the cells in the test sample is determined to be L3, the test sample is irradiated with a cumulative 60kWh / m 2 .

4. The test method for evaluating the light and heat resistance of photovoltaic cells according to claim 1, characterized in that: In step S5, the preset attenuation value is 1%. If Patt≤1%, it is determined to be qualified; if Patt>1%, it is determined to be unqualified.

5. The test method for evaluating the light and heat resistance of photovoltaic cells according to claim 1, characterized in that: In step S1, a plurality of battery cells are randomly selected from the same batch of battery cells, and the same subsequent test is performed on the plurality of battery cells.

6. The test method for evaluating the light and heat resistance of photovoltaic cells according to claim 1, characterized in that: In step S1, a layer of antistatic protective film is wrapped outside the plastic wrap wrapping the battery cell.

7. The test method for evaluating the light and heat resistance of photovoltaic cells according to claim 1, characterized in that: In step S1, during the process of being placed in an environmental box at 25±2°C for 24±2h, the relative humidity of the environmental box is controlled to be less than 60%.

8. The test method for evaluating the light and heat resistance of photovoltaic cells according to claim 1, characterized in that: It also includes checking the appearance and structural integrity of the battery cells after testing.

Images