Experimental Evaluation of the Performance of Crystalline Si PV Module Degradation After 15-Years of Field Exposure

This paper presents the results of the investigation of performance losses of photovoltaic crystalline-silicon modules in Brazil and the identification of durability issues. The PV modules were located in northern and eastern regions of the state of Minas Gerais, with the oldest module 20years in operation. These areas are considered subtropical climate zones, with dry winters and rainy summers. The techniques used were: (1) visual inspection procedures to identify the major PV module degradation modes, (2) I-V characterization by solar simulator for the electrical characteristics, (3) IR imaging for hot points identification, and (4) infrared spectroscopy in the IR Region by attenuated-total reflectance (FTIR-ATR) for encapsulant analysis. A gradual encapsulant discoloration and delamination is attributed to the existing high incidence of ultraviolet radiation and high temperatures. Extensive module encapsulant degradation mechanisms was analyzed and identified. Encapsulation browning was followed by delamination and interconnect corrosion. This paper presents detailed analyses of the operation and reliability of crystalline silicon modules after 15 years in the field. Importantly, these studies provide comparisons between cSi modules installed at the same region, under the same climate conditions. One set suffers extensive encapsulant degradation- and the other ones, none. The reasons for this are explained.