5. 3 Operation, Performance and Maintenance of PV Systems
Photovoltaic (PV), Power Generation, Performance, Degradation, Reliability, Research
Summary / Abstract:
Photovoltaic (PV) modules are exposed to a variety of climatic loads during outdoor operation. As time goes by, these lead a number of electric output power performance loss. Many researches show that the module degradation has been evaluated with the test result in laboratory. However, it will inevitably lead to damage for the module during transportation or disassembling/installation. In order to reduce the risk, we compared the electric characteristic of PV system from on-site measurement data and laboratory test data. Then, the related trend and correlation of performance degradation has been analyzed. Applying the result of on-site measurement data we can reduce the relevant risk for testing in laboratory. The I-V curve characteristics from on-site measurement data of more than three years have been collected and corrected to standard test condition (STC) according to IEC 60891 for analyzing their performance degradation of various type modules. The impacting factors for the performance degradation of various type modules have been also researched and the result can help the manufacturers improve their product designs and quality controls. For enhancing the analysis accuracy, before correcting the characteristic we filtered the error information by irradiance and measurement time, and also utilized the density based clustering algorithm (DBSCAN) to robust the correctness. Besides, for verifying the modules damage condition, the I-V curve and electroluminescence (EL) have been checked in the laboratory. The results show that the maximum output power of some modules is reduced in range from 0.7%/year to 2.9%/year. The year average output power of module for on-site measurement is different from the test result in the laboratory about 5~20W under STC. However, through our statistical analysis and appropriate correcting, the attenuation trend of the on-site measurement and laboratory test data is nearly similar. Following the trend, we can evaluate the performance degradation form on-site measurement data, and reduce the risk for testing in the laboratory for specific climate conditions. And the electric output of the PV field can be estimated in the meanwhile and also applied for the power prediction for following years. This paper can be a reference guideline for the industry to improve products, which helps to evaluate the performance degradation of module products and upgrade their product quality.