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Institute of Energy and Climate Research
IEK-5 Photovoltaics

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Field Performance Analysis

15 different photovoltaic modules were monitored during more than 2 years of operation in four different climate zones (locations: Germany, Italy, India and Arizona). The IV data of the modules were analyzed in a joint cooperation between the TÜV Rheinland and our institute within the project PVKlima.

The electrical stability of the photovoltaic modules during the time of outdoor exposure is investigated in terms of measured I-V curve translated to standard test conditions. The changes of output power after these corrections are attributed to initial consolidation phases, to long-term degradation of the electrical properties and to seasonal cycles associated with metastabilities. Modules made from crystalline Si turn out to show no or only minor effects. Thin-Film modules (CdTe, Cu(In,Ga)Se2 and thin-film Si) exhibit a wide spread of metastable behaviour with consistent patterns for identical modules in different climates but with significant differences amongst different manufacturers of the same thin-film technology. We show further that this metastable behaviour influences the energy yield of the modules.

FPAFigure 1: a) Generated electrical energy of crystalline photovoltaic module in four different climates in dependence on module temperature and irradiance on an annual basis in comparison with measuring conditions of IEC 61853‐1 energy rating matrix (red dots). b) Output power, fill factor and open circuit voltage (monthly averages normalised to the initial values) for a CdTe module at four different locations. Figure from [1].

[1] M. Schweiger et al., Performance stability of photovoltaic modules in different climates, Prog. Photovolt: Res. Appl., (2017), DOI: 10.1002/pip.2904