1 Background of the IEC 61215 standard and the differences between the two editions
1.1 IEC 61215 standard background
IEC 61215 "Crystalline silicon terrestrial photovoltaic (PV) modules — Design qualification and type approval" is a product testing method of the International Electrotechnical Commission. The solar industry is currently citing this standard extensively for testing materials or products.
1.2 Differences in UV test between the two versions of IEC 61215
So far, IEC 61215 has issued two editions, the first edition is IEC 61215:1993, and the second edition is IEC 61215:2005 [1]. The national standard GB/T9535:1998 [2] "Design Appraisal and Finalization of Crystalline Silicon Photovoltaic Modules for Ground Use" is equivalent to adopting the first edition of IEC 61215:1993.
The second edition has one more appendix A than the first edition. As for the UV test, the main change is that the title of Section 10.10 is changed from "UV test (UV test)" to "UV preconditioning test (UV preconditioning test)". In the part of "ultraviolet test", the first edition only stated that the purpose of the test is to "determine the ability of the component to withstand ultraviolet (UV) radiation" and "the ultraviolet test is under consideration", while the second edition not only changed the purpose of the test to For "Ultraviolet (UV) irradiation pretreatment to determine the UV attenuation of related materials and adhesive connections before the thermal cycle/wet freezing test of components", and a detailed description of the test equipment, test procedures and test requirements.
In the following section we will focus on how to set up the QUV UV accelerated weathering Tester to meet the requirements of Section 10.10 "UV pretreatment test" in IEC 61215:2005.
2 Principle of material weather resistance aging test
Before introducing section 10.10 "UV pretreatment test" in IEC 61215:2005, let's briefly understand the principle of material weather resistance aging test.
2.1 Outdoor aging factors
Aging damage is mainly caused by three factors: light, high temperature and humidity. Any one of these three factors will cause material aging, and their combined effect is greater than the harm caused by any one of them.
2.1.1 Lighting
The chemical bonds of polymer materials have different sensitivities to different wavelengths of sunlight in sunlight, generally corresponding to a threshold value. The short-wavelength ultraviolet rays of sunlight are the main reason for the aging of most polymer physical properties.
2.1.2 High temperature
The higher the temperature, the faster the chemical reaction. The aging reaction is a kind of photochemical reaction, and the temperature does not affect the photoinduced reaction speed in the photoinduced chemical reaction, but affects the subsequent chemical reaction speed. Therefore, the effect of temperature on material aging is often nonlinear.
2.1.3 Moisture
Water will directly participate in the material aging reaction. Dew, rain and humidity are the main manifestations of water in natural conditions. Studies have shown that outdoor materials are exposed to moisture for extended periods of time each day (up to 8-12 hours per day on average). Dew is the main cause of outdoor humidity. Dew is more damaging than rain because it sticks to materials longer, creating harsher moisture attacks.
2.2 UV accelerated aging test
2.2.1 Sunlight simulation
QUV [4] utilizes fluorescent UV lamps to simulate the threat of sunlight damage to durable materials. These lamps are electrically similar to those used for general lighting, but emit primarily ultraviolet light rather than visible or infrared light.
For different application conditions, different spectra and thus different types of lamps are required. UVA-340 lamps provide a good simulation of sunlight in the short wavelength range of ultraviolet light. The spectral power distribution (SPD) of UVA-340 matches sunlight very well from its cutoff point to approximately 360nm. UV-B lamps are also widely used in the QUV. They cause faster material aging than UV-A lamps, but their shorter wavelengths than the cut-off point of sunlight can produce impractical results for many materials.
2.2.2 Irradiance Control
In order to achieve accurate and repeatable test results, it is necessary to control the irradiance (light intensity). Most QUV models are equipped with a solar eye illuminance controller. This precise light control system provides the user with the advantage of selective irradiance control. Utilizing the solar eye's feedback loop system, irradiance is continuously and automatically controlled and accurately maintained. The solar eye automatically compensates for changes in light intensity caused by lamp aging and other factors by adjusting the power of the lamp. In just days or weeks, the QUV can simulate the damage of months or even years outdoors.
2.2.3 UV control
Inside the QUV, the emission control system is simplified due to the inherent spectral stability of fluorescent UV lamps. As the tube ages, the output of all light sources decays. However, unlike most other types of lights, the spectrum of fluorescent lights does not change over time. This improves the repeatability of test results and is a major advantage of testing with the QUV.
2.2.4 Temperature control
In QUV, temperature control is also important because temperature affects the rate at which materials age. The UV Test Chamber generally uses a black panel thermometer or a black standard thermometer to accurately control the surface temperature of the sample.
2.2.5 Humidity simulation
During the QUV condensation cycle, a Water Bath at the bottom of the Test Chamber is heated to generate steam. At higher temperatures, hot steam maintains 100% relative humidity in the Test Chamber. In QUV, the test sample actually forms the side wall of the Test Chamber, with the other side of the sample exposed to the ambient air in the chamber. The relatively cool air in the chamber makes the surface of the test specimen several degrees cooler than the hot steam in the Test Chamber. This temperature difference causes water in liquid form to slowly condense on the surface of the sample via a condensation cycle.
In addition to standard condensation mechanisms, the QUV can also use water spray systems to simulate other damage scenarios such as thermal shock or mechanical corrosion. The user can operate the QUV to generate a moisture cycle with UV light that closely mimics natural aging.
3 Interpretation of UV test in IEC 61215:2005 standard
Combined with the description of several aspects in Part 2, we analyze the requirements of the IEC 61215:2005 standard for the test conditions of the UV test from the aspects of spectrum, irradiance, temperature and humidity.
3.1 Definition of spectrum
The description in Section 10.10.2 d) of the standard is "ultraviolet radiation source, whose irradiance uniformity is ±15% on the component test plane, with no detectable radiation of wavelength less than 280nm, capable of producing required irradiance in the spectral range of interest". Figure 1 and Figure 2 below are the spectrum diagrams of UVA-340 lamp tube and UVB-313 lamp tube respectively. It can be seen from the figure that the spectrum emitted by UVA-340 lamp tube fully complies with Section 10.10.2 d) of the standard , while the spectrum emitted by the UVB-313 lamp has only a small number of spectral lines with a wavelength less than 280nm, which almost meets the d) part of Section 10.10.2 of the standard.
3.2 Irradiance setting
Section 10.10.3 a) of the standard is described as "using a calibrated radiometer to measure
Measure the irradiance on the test plane of the component to ensure that the irradiance at the wavelength of 280nm to 385nm does not exceed 250W/m 2 (about 5 times the level of natural light), and the uniformity of the irradiance on the entire measurement plane reaches ±15 %", at the same time, the description in Section 10.10.3 c) is "make the components withstand the ultraviolet radiation with a wavelength of 15kWh/m 2 in the range of 280nm to 385nm, and the ultraviolet radiation with a wavelength of 280nm to 320nm is 5kWh/m 2 , in the test During the process, the temperature of the components is maintained within the previously specified range".
In the following, we set the irradiance of UVA-340 lamp and UVB-313 lamp respectively, and calculate how long it takes to run under the set irradiance to reach the irradiance in Section 10.10.3 c) of the standard. According to energy requirements.
3.2.1 Using UVA lamp alone
When the irradiance is set to 0.68 W/m 2 at 340nm, it is equivalent to 35.2W/m 2 in the 280-385nm band (less than 250W/m 2 , meeting the requirements of part a) of section 10.10.3 of the standard ), while the irradiance in the 280-320nm band is 3.1 W/m 2 . We assume that the UVA lamp runs for X hours, and the module receives 15kWh/m 2 of UV radiation with a wavelength in the range of 280nm to 385nm, and the UVA lamp runs for Y hours, and the UV radiation with a wavelength of 280nm to 320nm is 5kWh/m 2 . The specific calculation is as follows:
35.2 W/m 2 x “X” hours = 15000 Wh/m 2 X = 426 hours
3.1 W/m 2 x “Y” hours = 5000 Wh/m 2 Y= 1613 hours
According to the above calculation, when the irradiance is set at 340nm to 0.68 W/m 2 , since the irradiance at the wavelength from 280nm to 320nm is relatively small, it takes 1613 hours for the ultraviolet radiation to reach 5kWh/m 2 . In other words, when using UVA lamps, it takes 1613 hours to meet the requirements for irradiance energy in Section 10.10.3 c) of the standard, which is time-consuming.
3.2.2 Using UVB lamp alone
当 在 310nm 设 定 辐 照 度 0.68 W/m 2 时， 相 当 于 在 280-385nm 波段的辐照度为 31.3W/m 2 （小于 250W/m 2 ，符合标准10.10.3 节 a) 部分的要求），而在 280-320nm 波段的辐照度为18.8 W/m 2 。我们假设 UVB 灯管运行 X 小时，组件经受波长在280nm 到 385nm 范围的紫外辐射为 15kWh/m 2 ，而灯管运行 Y小时，波长为 280nm 到 320nm 的紫外辐射为 5kWh/m2。具体计算如下：
31.3 W/m 2 x “X” hours = 15000 Wh/m 2 X = 479小时
18.8 W/m 2 x “Y” hours = 5000 Wh/m 2 Y = 266 小时
由以上计算可知，当在 310nm 设定辐照度 0.68 W/m 2 时，只需 266 小时组件经受波长在 280nm 到 320nm 的紫外辐射为5kWh/m2 。而在 280nm 到 385nm 波段，需要 479 小时，组件经受的紫外辐射为 15kWh/m2 。也就是说，使用 UVB 灯管时，运行479小时可以达到标准中10.10.3节c)部分对辐照能的要求，比 UVA灯管快很多。
3.2.3 共同使用 UVA 和 UVB 灯管
尽管使用 UVB 灯管可以缩短试验时间，但是如同本文 3.1节中所述，UVB 灯管发出的光谱还有极少一部分的波长小于280nm，也就说不完全符合 IEC 61215:2005 标准对紫外光谱的要求。但是如果单独使用 UVA 灯管，则测试时间过长。所以可以将两种灯管结合起来使用。如先使用 UVB 灯管，假设运行时间为 X 小时，再使用 UVA 灯管，假设运行时间为 Y 小时，具体计算如下：
18.8 W/m 2 x “X” hours + 3.1 W/m 2 x “Y” hours = 5000Wh/m 2
31.3 W/m 2 x “X” hours + 35.2 W/m 2 x “Y” hours = 15000Wh/m 2
The above two formulas are calculated: X = 229 hours, Y = 222 hours, that is, run the UVB lamp for 229 hours first, and then run the UVA lamp for 222 hours, which can reach the part of the radiation energy in Section 10.10.3 c) of the standard requirements. Both lamps run for a total of 451 hours, which is faster than using UVB lamps alone. In general, we recommend this method.
3.3 Temperature control
Section 10.10.2 a) of the standard is described as "equipment that can control the temperature of components when subjected to ultraviolet radiation, and the temperature range of components needs to be within 60 °C ± 5 °C". However, this temperature requirement is completely within the temperature range of the QUV. It is sufficient to set the temperature of the black panel at 60°C ± 5°C during the test.
3.4 Humidity Control
There is no humidity requirement in the standard, so no condensation or water spray cycles are required for the test.
4 Conclusions and recommendations
The IEC 61215:2005 standard is widely used in the solar industry. When using the QUV ultraviolet accelerated aging Tester to implement this standard, you can first run the UVB lamp for 229 hours and set the irradiance to 0.68 W/m2, then run the UVA lamp for 222 hours and set the irradiance to 0.68 W/m2 . During the whole test process, the temperature of the black panel was set at 60°C±5°C.
Although humidity is not currently required in standards, many UV standards now include UV light and condensation or water spray cycles. So we suggest that when the standard is revised in the future, condensation or water spray cycle can be added.
