Photovoltaic modules long-term reliability is a key requirement to keep this technology a commercially interesting option for energy production. The investment return on PV generation system depends, among other factors, on the peculiarities of the system on efficiency reduction caused by environmental action. Technical standards suggest laboratory tests for the qualification and a better understanding on module degradation behavior. Nevertheless, some degradation modes can only be observed after years of field operation. This paper presents the main signs of degradation on crystalline silicon photovoltaic modules caused by outdoor exposure after a period of 15 years in an installation in the city of Porto Alegre, the southernmost state capital city in Brazil. The electric analysis demonstrated that the modules kept 90.5% of their initial power, with an average of degradation rate of 0.7% per year. Some techniques helped the evaluation of defects caused by exposure of the arrays for long periods of operation, such as electroluminescence imaging and I-V curve testing. The most frequent defects found were browning (encapsulant darkening) and cell encapsulant delamination, leading to the anti-reflective layer deterioration. The junction box of one of the modules was detached, allowing the entrance of moisture and resulting in the disconnection of some of the module cells. The electroluminescence technique also provided a better understanding on modes of degradation. Despite the observed evidences of degradation along these 15 years, it can be said that the system remains within the expected operation limits.

This work describes the methodology, basic procedures and instrumental employed by the Solar Energy Laboratory at Universidade Federal do Rio Grande do Sul for the determination of current-voltage characteristic curves of photovoltaic modules. According to this methodology, I-V characteristic curves were acquired for several modules under diverse conditions. The main electrical parameters were determined and the temperature and irradiance influence on photovoltaic modules performance was quantified. It was observed that most of the tested modules presented output power values considerably lower than those specified by the manufacturers. The described hardware allows the testing of modules with open-circuit voltage up to 50 V and short-circuit current up to 8 A

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The Grupo en Energías Renovables at the Universidad Nacional del Nordeste (GER-UNNE) developed a testing system for the characterization of grid-tied inverters with rated power up to 4.4 kW. The test procedures followed the guidelines established by EN 50530:2010, IEC 61727 and BS 50438:2007. This paper presents the development of the instrumental and the determination of the measurement uncertainties associated to the experiment by comparison with results obtained from an inverter test facility built at the Solar Energy Laboratory at Universidade Federal do Rio Grande do Sul (LABSOL-UFRGS), Brazil. The error associated to the inverter conversion efficiency, with the loading ranging from 10% to 100%, was shown to be lower than 1%. The error in the efficiency error determination with partial load under 10% is lower than 8%.

Ao mesmo tempo em que o crescimento da energia solar fotovoltaica atinge centenas de gigawatts instalados ao redor do mundo, a durabilidade dos módulos pode ser fator chave para manter a viabilidade da tecnologia. Este trabalho descreve o estado de duas instalações fotovoltaicas situadas no LABSOL (Laboratório de Energia Solar da UFRGS). A primeira instalação funciona há quinze anos e a mais recente, há três. Para realizar esta avaliação aplicam-se algumas técnicas, destacando-se os registros de inspeções visuais, de imagens de eletroluminescência, de análises termográficas e principalmente resultados da caracterização elétrica do comportamento da curva I?V, revelando então a degradação dos materiais que compõe os módulos. A pesar dos danos revelados neste trabalho, se pode afirmar que os sistemas continuam operando dentro das expectativas. A taxa de degradação da potência para o sistema mais antigo foi de 0,7% ao ano. Na instalação de três anos, observou-se mínimo efeito visual da ação do ambiente, resultando taxa de degradação de 0,85% ao ano.