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Polymer films in photovoltaic modules: analysis and modelling of permeation processes

Polymerfilm in Photovoltaikmodulen: Analyse und Modellbildung von Permeationsprozessen
: Köhl, M.; Daniel, P.; Angeles O.; Weiß, K.-A.

Reichert, T. ; Gesellschaft für Umweltsimulation -GUS-, Pfinztal:
Natural and artificial ageing of polymers. Proceedings. CD-ROM : 3rd European Weathering Symposium ; 12th - 14th September 2007, Krakow, Poland
Pfinztal: GUS, 2007 (CEEES publication 8)
ISBN: 978-3-9810472-3-3
10 pp.
European Weathering Symposium (EWS) <3, 2007, Kraków>
Conference Paper
Fraunhofer ISE ()
photovoltaische Zelle; Abdeckung; Wasserdampfdurchlässigkeit; Kunststoff; Modellbildung; Diffusion; Temperaturabhängigkeit; numerische Simulation; mathematisches Modell; Haltbarkeit

Polymer materials are used as water vapour barriers or encapsulation materials for photovoltaic modules. Their permeation properties determine the amount of water in the polymers and inside the modules. The water can cause corrosion and/or deterioration of functional properties of the modules. The temperature of solar modules and the ambient water vapour concentration vary over time according to the solar radiation and the ambient climate. Temperature-dependent permeation and diffusion properties are needed for modelling the water concentration over time in order to predict the long-term behaviour and the service life of such devices. The paper describes the measurement of the temperature-dependent permeation coefficient for polymer films, different laminates of polymer films and initial results of modelling the processes by integrating time series of conditions experienced during outdoor exposure. We used an experimental set-up based on a mass spectrometer to measure the water-vapour permeation. The sample film is mounted on ultra-high-vacuum flanges of up to 300 mm diameter by means of a butyl sealant and UHV-metal sealant. It is exposed to a constant temperature selected between 20 deg C and 90 deg C and a rapid increase of the humidity until a set partial pressure is reached. The increase of the humidity content in the volume behind the sample film, which is initially filled with argon under atmospheric pressure, is monitored by a quadrupole mass spectrometer and is used for evaluation of diffusion and permeation coefficients. The results of a parameter study are presented which describes the distribution of the water concentration in the module dependant on specific material parameters. The numerical simulation uses time series of meteorological data monitored in different regions as input. The experimentally determined parameters and the mathematical modelling can be combined to estimate the durability of PV modules under the climatic conditions of interest.