Long term performance of crystalline silicon photovoltaic modules

This paper presents the results of electrical performance measurements of 90 crystalline silicon PV modules following long-term outdoor continue exposure. The modules form the PV array of the first grid-connected PV system in Algeria. This grid connected PV system was installed in Algeria (CDER) at Bouzareah site is effectively operating since June 2004. The analysis have shown that all the PV modules are still creating power but less than the rated power. A mathematical model has been used in order to perform PV module testing at different irradiance and temperature conditions. The different parameters can be computed mainly from the open-circuit voltage, the short-circuit current, the voltage and current at maximum power point. Electrical measurements have shown different degradations of current-voltage parameters. All the modules presented a decrease of the nominal power. However, this decrease is different from one module to another.