QUANTITATIVE EVALUATION OF OUTPUT POWER DEGRADATION FOR CRYSTALLINE SILICON PV MODULES IN FIELD EXPOSURE TEST BY USING EQUIVALENT CIRCUIT MODEL

摘要

In this paper, based on the data of field exposure test, which was initiated by Japan Electrical Safety &Environment Technology Laboratories (JET), we investigate the degradation characteristics of crystalline silicon PVmodules by using its equivalent circuit model for the purpose of the lifetime extension in the development of PVmodules. Specifically, we observe the degradation of bus bar electrode and solar cell by capturing electroluminescence images and infrared images of the surface of PV modules when forward voltage is applied. Althoughthis observation enables us to determine which part of the PV module deteriorates, it is impossible to quantitativelyevaluate how much each deteriorated component has an influence on power degradation. Accordingly, using theequivalent circuit model of the PV module, we calculate the equivalent circuit parameters from the measured I-Vcharacteristics of the PV modules in the field exposure test by the least squares method. We adopt the photocurrent,series resistance, shunt resistance and diode factor as unknown parameters in the equivalent circuit model. Based onthe change of the circuit parameters, we evaluate the influence of the deterioration of each component on decline ofoutput power quantitatively.