Efficiency degradation of c-silicon photovoltaic modules after 22-year continuous field exposure

In February 2003, at ENEA Casaccia (Rome, Italy), the electrical performance of 58 Arco Solar ASI 2300-16 c-Si clean PV modules, which were installed in 1980, was evaluated by using a computer-controlled swept-measurement technique. The maximum error on the measured maximum power and efficiency of modules was less than 0.8% and 3.95%, respectively. The 2003-data were compared to both data collected in 1980, during acceptation tests, and data from measurements performed on the same modules in July 1991. The comparisons resulted in module degradation rates in the different periods that are practically equal to each other. In our opinion, this fact presupposes the degradation rate to be constant along all the module lifetime. The present results were compared to reported data relevant to similar c-Si modules. Finally, upper bounds for the lifetime of evaluated and reported modules were estimated based on the constancy of degradation rate.