研究目的
To quantitatively evaluate the outdoor degradation rates of poly crystalline Si and CIGS photovoltaic modules using the linear interpolation method (LIM) based on measured I-V curves.
研究成果
The LIM method effectively quantifies degradation rates of PV modules outdoors, showing that poly crystalline Si degrades at -0.4%/year primarily due to Isc reduction, while CIGS degrades faster at -2.1%/year due to reductions in both Isc and Voc. The study confirms the utility of LIM for long-term reliability assessment and highlights differences in degradation mechanisms between module types.
研究不足
The method requires sufficient outdoor data for accurate I-V curve fitting, and performance may be affected by extreme weather conditions or data gaps. The extrapolation in LIM could introduce errors if reference points are not well-distributed. Filtering conditions might not capture all outliers, and the approach is specific to the PV module types studied.
1：Experimental Design and Method Selection:
The study uses the linear interpolation method (LIM) to create expected I-V curves under standard test conditions (STC) from outdoor measured I-V curves, enabling degradation rate calculation without temperature coefficients. The double-diode model is employed for I-V curve fitting, optimized using the differential evolution algorithm (DE).
2：Sample Selection and Data Sources:
Outdoor data are measured from poly crystalline Si and CIGS PV modules installed at Hokuto mega solar in Yamanashi prefecture, Japan. Data include I-V curves, irradiance, module temperature, and spectral irradiance, collected every 5 minutes from 5 am to 8 pm over several years (poly-Si: Oct 2008 to Jan 2017; CIGS: Mar 2010 to Jan 2017).
3：7).
List of Experimental Equipment and Materials:
3. List of Experimental Equipment and Materials: I-V curve tracer MP-160 for measuring I-V curves, pyranometer for irradiance measurement, thermocouples for module temperature, and wide band spectral radiometer for spectral irradiance. PV modules include poly crystalline Si and CIGS types with specified datasheet values.
4：Experimental Procedures and Operational Workflow:
Data are filtered to remove outliers and unstable weather conditions based on criteria such as current ratios, incident angle, irradiance fluctuation, and effective irradiance. Reference points are selected for I-V curve creation, and I-V curve fitting is performed using DE to derive parameters. Expected I-V curves under STC are generated via LIM for each season, and degradation rates are calculated by comparing with datasheet values.
5：Data Analysis Methods:
Degradation rates for parameters like short-circuit current (Isc), open-circuit voltage (Voc), maximum power (Pm), and fill factor (FF) are derived from linear regression of the expected I-V curve values over time. Statistical analysis includes calculating annual degradation percentages.
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