Title:	Analysis of Leakage Currents in Accordance of the Mounting Situation of Amorphous Silicon Solar Modules under Outdoor Climate Conditions
Author(s):	S. Voswinckel, P. Manz, C. Schmidt, V. Wesselak, E. Fokuhl, B. Trautmann
Keywords:	a-Si, Degradation, Lifetime, Sodium, TCO
Topic:	THIN FILM SOLAR CELLS
Subtopic:	Silicon-based Thin Film Solar Cells
Event:	28th European Photovoltaic Solar Energy Conference and Exhibition
Session:	3CV.1.3
Pages:	2478 - 2483
ISBN:	3-936338-33-7
Paper DOI:	10.4229/28thEUPVSEC2013-3CV.1.3
Price:	0,00 EUR
Document(s):	paper, poster

Abstract/Summary:

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System induced degradation can occur depending on the system design of PV power plants. In case of amorphous silicon solar modules this causes e.g. a diffusion of sodium ions from the cover glass into the TCO front contact, followed by a chemical reaction that leads to an irreversible power loss and is called TCO corrosion. Leakage currents between the cover glass and the electrical connectors can be used as an indicator of the corrosion rate. It is state-of-the-art that a negative potential of the TCO layer in respect to the cover class (resp. mounting structure) can have an impact on the corrosion process. To avoid corrosion the negative DC pole of the PV generator has to be grounded. Thus a positive potential occurs between the TCO layer and the cover glass and the positive charged sodium ions do not migrate into the TCO layer. In contrast to this, the results of this study (amongst others) show that a degradation can occur for positive potentials, too. Consequently the basic objective of this paper is the analysis of the degradation mode and the leakage currents according to the grounding situation of amorphous silicon solar modules under outdoor conditions. For this purpose nine amorphous silicon solar modules were mounted with different mounting systems, like back rails and module clamps. Furthermore, an external voltage with negative and positive bias is applied between the mounting system and the short-circuited module connectors. Additionally, the influence of an AC potential is investigated. The leakage currents were measured and logged continuously.