Machine vision is not a mere upgrade of the specification of the current imaging devices, but rather a form of visual perception technology that involves intelligent modules in the processes of measurement, processing, and decision- making. Given the novel functionalities and features of machine vision-based intelligent detection devices, the traditional evaluation methods based on testing the physical parameters of imaging devices need further refinement and development. Taking the electroluminescence (EL) imaging in photovoltaic (PV) tests as an example, we investigate the influence of changes in dataset characteristics on the performance of object detection by combining digital image processing and deep learning methods. Features regarding to the crack-type defect datasets, such as the grayscale, contrast, shape and resolution, are controlled and adjusted based on new generated datasets from the original datasets. From the numerical experiments, some new aspects for evaluating the intelligent detection.
GaInP2/InGaAs/Ge triple-junction solar cells have become the main energy source for space on-orbit applications. For the sake of the three composed sub-cells, including GaInP2, InGaAs and Ge sub-cell, the monolithic triple-junction solar cells can make use of solar irradiance in the wavelength range of 300 nm to 1800 nm. Before assembled into space solar arrays, each solar cell’s current-voltage curves should be measured in laboratories on earth by AM0 solar simulators, to know their key parameters especially short circuit current. Solar cell’s current-matching is crucial for assembling into arrays. While spectral responsivity is essential for spectral mismatch factors (MMFs) calculation during the current-voltage measurement. MMF corresponding to each sub-cell should be analyzed, so spectral responsivity of each sub-cell of monolithic solar cell was required to be measured out. But sub-cells are connected in series in a monolithic multijunction solar cell, and current-limiting effect makes traditional spectral responsivity measurement which is suitable for single-junction solar cells not applicable anymore. For measuring the spectral responsivity of monolithic multi-junction solar cells, optimized bias light and bias voltage are required to make the tested target sub-cell be the current-limiting one. The wavelength range and irradiance intensity of the bias light, the direction and value of the bias voltage, should be chose and adjusted appropriately during the measurement, otherwise will lead to measurement artifacts and obtain incorrect results. In this paper, combing optimization of bias light and bias voltage with monochromatic light system, we would present method and detailed procedures for measuring the spectral responsivity of monolithic GaInP2/InGaAs/Ge triple-junction space solar cells.
The effects of monochromatic light modes and filtering systems on the measurement of spectral responsivity of photovoltaic(PV) modules are analyzed. According to the structure characteristics of PV modules, a PV module spectral responsivity measurement device was established based on the steady-state monochrome light source, main bias light source, auxiliary bias light source and phase-locked filter testing system. The nondestructive testing of spectral responsivity of solar cells in PV module was realized. The effects of irradiance of main bias light source, irradiance of auxiliary bias light source and temperature of PV module on spectral responsivity and spectral mismatch factor are analyzed. The influence of different sampling monochrome spot area on the relative spectral response measurement of solar cells under small spot test conditions is analyzed. The spectral responsivity of the PV module slices was tested by using the small spot measurement system. The accuracy of the nondestructive measurement device is verified by comparing the nondestructive test results with the slice measurement results.
Because of their high efficiency and power weight ratio, triple-junction GaInP/InGaAs/Ge solar cells have become the main energy source for space on-orbit applications. Calibration of space solar cells under AM0 conditions is extremely important for satellite power system design, and accurate prediction of them is critical to solar array sizing. However, it’s not easy to conduct accurate measurement for multi-junction solar cells, especially in laboratory on earth. In this paper, by employing a highly AM0 spectrum-matched light source, which combined a Xenon lamp and a Halogen lamp with special filters, a method to measure the AM0 performance for triple-junction GaInP/InGaAs/Ge solar cells will be presented. The calibrated values of reference solar cells, including two component solar cells, were come from a national standard facility based on DSR (Differential Spectral Responsivity) method. After calibrating the compound light source by using the reference solar cells, key parameters of AM0 performance of triple-junction GaInP/InGaAs/Ge solar cells would be measured out, such as short-circuit current, open-circuit voltage and maximum power, etc. Spectral mismatch and other main influencing factors are also considered. It will provide a reliable route for multi-junction space solar cells’ photoelectric property measurement in laboratories on earth.
The effect of current mismatch on IV performance of photovoltaic (PV) module is analyzed. Based on the current mismatch theory of solar cell and the series and parallel relation of each cell in the photovoltaic module, the influence analysis program of the current mismatch caused by the irradiance non-uniformity and the response difference of the solar cells in the PV module is established. The experimental and theoretical verification of the IV curve and the PV curve of a photovoltaic module under different shielding conditions have been carried out. It is found that the theoretical results are in good agreement with the experimental results. The influence of irradiance non-uniformity on the measurement of optoelectronic parameters of photovoltaic modules under the conditions of different position of reference solar cell is analyzed. Through theoretical calculation, it is found that in order to reduce the influence of the current mismatch of solar cells on the photoelectric performance test of the photovoltaic module, the difference of solar cells in the PV module and the irradiance non-uniformity of the sunlight simulator should both be reduced, and the irradiance intensity at the standard solar cell position should be consistent with the average irradiance intensity of the test area.
The high efficiency solar cells usually have high capacitance characteristic, so the measurement of their photoelectric performance usually requires long pulse width and long sweep time. The effects of irradiance non-uniformity, probe shielding and spectral mismatch on the IV curve measurement are analyzed experimentally. A compensation method for irradiance loss caused by probe shielding is proposed, and the accurate measurement of the irradiance intensity in the IV curve measurement process of solar cell is realized. Based on the characteristics that the open circuit voltage of solar cell is sensitive to the junction temperature, an accurate measurement method of the temperature of solar cell under continuous irradiation condition is proposed. Finally, a measurement method with the characteristic of high accuracy and wide application range for high capacitance solar cell is presented.
Based on a testing method of spatial frequency response(SFR), a setup for characteristics measurements of the infrared defect tester,which can also be called electroluminescence tester(EL tester), a machine examining defects of photovoltaic (PV) panel, was built. The influences of focusing plane adjustments and infrared light box arrangements on resolution measurement of EL tester in full field of view were analyzed. For different types of EL testers, portable and fixed, testing methods and procedures were presented. Especially, a novel testing method for portable EL was claimed, which could do the work well without reference background. Based on method claimed and setup built, the resolutions of different types of EL testers were obtained and stable results were achieved. This setup is portable designed to meet online measurements requirements of PV industry.
Spectral mismatch error should be carefully considered during the calibration of solar cells by means of solar simulator
and calibrated reference cell. Even test and reference cells with the same type should be also considered spectral mismatch
error to achieve good measurement results. Spectral mismatch error can be calculated with the relative spectral response
of the test and reference cells, and the relative spectral irradiance of the simulator and reference solar. The reference solar
spectral irradiance distribution was given according to IEC60904-3:2008. Experimental results, two cells, one test and
one ref, with two different spectra solar simulators, were presented. The calculation method and experimental data
presented could be positive reference to photovoltaic labs to obtain good calibration and test results of solar cells.
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.
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