A primary standard measurement facility based on differential spectral responsivity (DSR) method for calibration of reference solar cells was realized at National Institute of Metrology (NIM), China. The primary calibration of the critical spectral parameters and short-circuit current of reference cells, not only with WPVS (World photovoltaic Scale) design but with non-regularly shaped, can be performed by this standard facility. The linearity measurement can be carried out by measuring DSR of the solar cells at different bias levels in the spectral range from 300nm to 1200nm. The characterization and performance of the facility were reported. An uncertainty of 0.9% (k=2) for short-circuit current of WPVS reference solar cells was able to be obtained. A more accurate and better calibration service for solar photovoltaic (PV) cells could be provided to local or international solar cell research community, testing labs and industry users and manufacturers.
Nowadays, more attentions may be paied to irradiance and temperature during the electrical performance tests of solar cell and module. But the light spectrum will also largely determine test results. During the electrical performance test, irradiance is generally traced by standard solar cell. Considering that the short circuit current (Isc) is generally used in the testing process as a basis for the irradiance calibration, and the Isc of reference cell consists of spectral distribution of light source and the spectral response of the cell together. So spectral mismatch should be analyzed from this two aspects. Natural light spectrum will be affected by atmospheric conditions and seasons, and artificial solar simulator’s spectrum is differ in thousands ways. Also because of the response wave band of the spectrum range is different, when use standard solar cell or pyranometer as the basis of the irradiance calibration, there should be respectively different results. Beyond that, two cells made of polycrystalline silicon with different spectral response may also leads to different results. We analyzed the deviation based on above factors, and discussed how to reduce the spectral mismatch deviation, then increase the accuracy of the solar cell electrical performance test methods.
Solar cells’ photoelectric properties calibration, i.e., current-voltage (I-V) characteristics is critical for both fundamental research and photovoltaic production line. This paper will present calibration of solar cells’ I-V characteristics by a substitution method under simulate light source. Considering the calibration uncertainty and measurement accuracy, reliable measurement procedures developed in NIM with uncertainty analysis are also demonstrated. By controlling the influencing factors, relative expended combined uncertainty (Urel) of 2.1% (Isc), 1.0% (Voc) and 3.1% (Pmax) was concluded here, with a coverage factor k = 2. The measurement system meets all requirements of IEC 60904-1 and IEC 60904-9, and it has been applied to amounts of solar cells’ I-V curves calibration for research institutes as well as industrial plants, which solved the problem of domestic metrology technology shortage in photovoltaic field.
The conversion efficiency measurement accuracy of solar cell is heavily rely on the measurement uncertainty of pulsed
solar simulator. The measurement uncertainty assessment method of pulsed solar simulator is widely analyzed and
studied. This paper describes uncertainty assessment method of measurement of irradiance non-uniformity which is one
of the three most important factors(spectral mismatch, non-uniformity of irradiance and instability of irradiance)
influencing pulsed solar simulator measurement uncertainties. An experiment using a real pulsed solar simulator was
performed to testify the validity of uncertainty assessment method. The results provide a theoretical and data basis for
further analysis of overall uncertainties of solar simulators.
With the rapid development of globe solar photovoltaic industry, performance testing and evaluation of solar modules have been largely concerned, while the primary basis of evaluations is the electrical performance of modules, namely the voltage - current characteristic curve. Nearly module’s conversion efficiency which defined as its maximum electrical power (Pmax) divided by the total incident photon power (Pin) became more and more valued, because higher efficiency means lower cost. Generally, electrical performance parameters of the modules need to test under standard test conditions (STC), but STC can only be simulated in laboratory-controlled environment while solar modules actually work under natural sunlight outdoors, To solve this problem we propose researches on outdoor testing of solar modules to investigate the electrical performance parameters of solar modules in a variety of environmental conditions. Also, according to the results, we will analysis the impact of various environmental factors on the performance of solar modules, including radiation spectrum, Incident angle, temperature, wind speed, and wind direction. In addition, we can analyze the difference between the performance parameters result of outdoor and indoor test and its main reason.
Regarding to the mistakes that optoelectronic devices such as CCD focal plane arrays devices are often placed on the exit port plane of integrating sphere source to perform calibration, the output irradiance uniformity of integrating sphere source is analyzed, the basis which rational using the integrating sphere source to calibrate the optoelectronic devices is obtained. Two theoretical output irradiance uniformity models based on numerical analysis method and Monte Carlo method are developed respectively. The models consider two fundamental situations of integrating sphere sources, namely (1) ideal lambertian source and (2) non-ideal lambertian source. The distribution regularity of irradiance uniformity was generalized by contrast of the theoretical data obtained by the models and the measured data obtained by two different actual integrating sphere sources. The results show that when (1) the diameter of optoelectronic device is less than half diameter of the sphere exit port, and (2)the ratio of the distance from device to exit port and the exit port diameter are between 3 and 5, a 99% better output irradiance uniformity can be obtained. The results provide a practical guide to ensure the accuracy of the calibration exercise of optoelectronic devices.
Solar simulator is a key instrument for photovoltaic field, which aims to act the role of natural sunlight irradiance indoor, and we should identify how similar they are in quantity. The critical factor of similarity lies in its spectral irradiance, because of solar cells’ wavelength-dependent spectral responsivity, spectral mismatch of solar simulator and sunlight can induce large errors during characteristic parameters measurement. In this article, a method for measuring solar simulator’s spectral irradiance was proposed along with its uncertainty analysis. A calibrated fiber optic spectrometer was employed here for spectral measurement, which was used for calibrating various kinds of solar simulators manufactured with different mechanisms. Considering three main sources of measurement uncertainty, that is, the declared uncertainty of the calibrated spectrometer (u1), cosine correction (u2) and repeatability of measurement (u3), we estimated its combined expanded uncertainty is U = 6.2% (with coverage factor k = 2). Also, we have made a comparison of our spectral measurement results with methods traceable to other country’s national institute of metrology, such as NIST traceable. This work is significant for the performance calibration and classification of solar simulators, so that plays a great role in solar energy industry.