After the photovoltaic power station has been running for a period of time, it is necessary to conduct testing to determine the performance of the photovoltaic power station. Involving photovoltaic modules, mainly include the following items.
1. Power attenuation test
What is the decay rate of PV modules after 1 year and 25 years of operation? Twenty-five years is too long, and there may not be a power station running for that long now. According to national standards, the 2-year decay rate of crystalline silicon cells should be within 3.2%. But this data is really hard to say at present, for three reasons:
1) The output power of photovoltaic modules is calibrated with the laboratory standard light source and test environment, but it seems that there are certain differences between the standard light sources of different domestic manufacturers. The 250W components calibrated in factory A may be 245W components in factory B.
2) The accuracy of the instruments used for on-site testing is poor, and it is said that the error within 5% is acceptable. Using an instrument with an error of 5% to measure the attenuation of 2% (1 year) is somewhat difficult, and the results are also doubtful.
3) The test conditions in the field are quite different from those in the laboratory, and the time at 1000W/m2 and 25°C is too little! Therefore, it is necessary to convert a test value to a standard value, and the output power and irradiance are only positively correlated in a small interval. In addition, many components may appear with a power deviation of -3%, and before attenuation, 3% will disappear directly...
2. EL test
When there is a problem with the photovoltaic module, the local resistance increases, and the temperature in that area increases. The EL tester is like the X-ray machine in our physical examination, which can perform physical examination on photovoltaic modules - through infrared images, the images show different colors according to different temperatures, so it is very easy to find many problems of photovoltaic modules: cracks , hot spot, PID effect, etc.
Photovoltaic modules are easily trampled and hit during transportation, handling, and installation, resulting in invisible cracks in the modules, which greatly affect the output power of the modules. It can be detected by EL change, as shown in the figure below.
In addition to the above inspections, the visual inspection of the components is also very important. Such as scratches, yellowing, blisters on the backplane of components, and connectors falling off.
