Linking accelerated laboratory and outdoor exposure results for PV polymeric materials: a mechanistic study of EVA

Xiaohong Gu; Yongyan Pang; Chiao-Chi Lin; Kaipeng Liu; Tinh Nguyen; Jaonnie W. Chin

doi:10.1117/12.2024532

24 September 2013 Linking accelerated laboratory and outdoor exposure results for PV polymeric materials: a mechanistic study of EVA

Xiaohong Gu, Yongyan Pang, Chiao-Chi Lin, Kaipeng Liu, Tinh Nguyen, Jaonnie W. Chin

Author Affiliations +

Proceedings Volume 8825, Reliability of Photovoltaic Cells, Modules, Components, and Systems VI; 88250L (2013) https://doi.org/10.1117/12.2024532
Event: SPIE Solar Energy + Technology, 2013, San Diego, California, United States

Abstract

Linking accelerated laboratory test to field performance for predicting the service life of polymeric materials are being investigated at NIST using the reliability-based methodology. Based on this methodology, a successful linkage between the laboratory and field exposure data for a model polymeric material has been made. Recently, this methodology, for the first time, was introduced to the lifetime assessment of PV polymeric materials. In this paper, a mechanistic study of the degradation of three unstabilized model ethylene vinyl acetate (EVA) systems---uncured EVA, cured EVA and laminated EVA---was carried out under accelerated laboratory exposure and outdoor exposure. The NIST SPHERE (Simulated Photodegradation via High Energy Radiant Exposure) was used for the accelerated laboratory tests, and the outdoor exposure was conducted in Gaithersburg, Maryland. Simultaneous multiple stresses, including temperature, relative humidity and UV radiation, were applied individually or in combination during SPHERE exposure. The effects of the environmental factors on the main degradation mechanisms of different EVA systems were investigated. The results showed that the UV radiation was the most important factor for the degradation of EVA and a synergistic effect occurred between UV radiation and relative humidity. A slower degradation rate was observed for the laminated system as a result of limited diffusion of O₂ and H₂O into EVA. It was also found that the substantial chemical changes of the uncured EVA system did not yield yellowing, which was dramatically different from the peroxide cured EVA system. Additionally, the chemical degradation modes of the three EVA systems exposed outdoors appeared to be similar to those exposed to the SPHERE. The implication of this work to the current test standards was discussed.

Citation Download Citation

Xiaohong Gu, Yongyan Pang, Chiao-Chi Lin, Kaipeng Liu, Tinh Nguyen, and Jaonnie W. Chin "Linking accelerated laboratory and outdoor exposure results for PV polymeric materials: a mechanistic study of EVA", Proc. SPIE 8825, Reliability of Photovoltaic Cells, Modules, Components, and Systems VI, 88250L (24 September 2013); https://doi.org/10.1117/12.2024532

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