The measurement of solar panels requires a stable light source, which is closely related to the conditions of sunlight. Not only the intensity, but also the spectrum must match the standard. One obvious choice is to simply use the sun itself. In places with few clouds, this is a good solution 1, but there are still changes in atmospheric conditions that need to be corrected to compare measurements in different periods. Spectra also change throughout the day, which further limits the time for testing.
The most common solution is to use an artificial light source that simulates the sun. The ideal lighting source should have the following characteristics:
Less than 1% spatial heterogeneity.
The change of total irradiance with time is less than 1%.
Filter a given reference spectrum to make the spectral mismatch error less than 1%.
These requirements are critical to achieving an accuracy of better than 2%.
Testers are classified according to three criteria:
Spectral matching
Irradiance nonuniformity — spatial uniformity of lighting area
Instability in time — stability varying with time
Deviation from air quality 1.5
(The deviation from AM1.5 results in the error of current (Isc))
It is very difficult to make a light source that matches the spectrum of AM1.5 completely and has the necessary illumination intensity. There are often considerable differences between the lamp spectrum and the required AM1.5 spectrum. There are two ways to correct the difference between the AM1.5 spectrum and the actual spectrum of the solar simulator.
Calibrated solar panels with the same spectrum.
The method adopted by most internal testers is to use calibrated solar cells with the same spectrum as the tested cells. The light intensity of the tester is adjusted so that the Isc of the battery matches the Isc measured by the external testing laboratory. However, slight changes in battery processing (such as the doping profile of the emitter and the change of the antireflection coating) will lead to corresponding changes in the spectrum, which requires a new calibration standard.
Measuring spectral response
Primary calibration laboratories use light sources that are closer to the standard, but differences still occur. To compensate for these differences, the calibration laboratory measures the spectral response of the tested equipment, and then uses it to correct the known difference between the spectrum of the light source and the standard spectrum. This correction is time-consuming and error prone. In the early 1990s, the analysis of test error led to the improvement of the standard, and also reduced the efficiency of some records by 1% absolute value.
For more information about solar panels, please contact us, Shenzhen Solar Panel Manufacturer of Huanqi Technology (Shenzhen) Co., Ltd.