Title:	Yellowing of PV Backsheets in Accelerated Tests Can Be Used as a Realistic Indication of Possible Field Failures – Fact or Fiction?
Author(s):	E. Parnham, A. Seaman, A. Whitehead, W. Brennan, E. Ashford
Keywords:	Degradation, Backsheet, Accelerated Weathering
Topic:	Operation, Performance, Reliability and Sustainability of Photovoltaics
Subtopic:	PV Cells and Modules
Event:	32nd European Photovoltaic Solar Energy Conference and Exhibition
Session:	5BO.10.1
Pages:	1528 - 1531
ISBN:	3-936338-41-8
Paper DOI:	10.4229/EUPVSEC20162016-5BO.10.1
Price:	0,00 EUR
Document(s):	paper, presentation

Abstract/Summary:

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Photovoltaic (PV) modules currently have lifetime guarantees of 25 years or more. Ideally all components of the modules would be tested in field conditions for at least 25 years, however this is unrealistic, so accelerated, laboratory based testing is required. When using accelerated testing it is important to ensure the test does not result in false negatives, leading to the ruling out of good materials, and more importantly, does not give rise to false positives, which could lead to material failure in the field. A key question to answer is: “Can yellowing be used as a reliable method to rank materials after accelerated testing and to predict failures in the field?” This paper compares eight accelerated test conditions combining different temperatures, irradiance and condensation and their impact on a range of PV backsheet materials with regards to yellowing and loss of mechanical properties. The final part of this paper will compare unstabilised white polyethylene terephthalate (PET), UV stabilised PET and polyvinyl fluoride (PVF) films in Xenon weatherometer aging with Florida weathering and backsheet failures reported in the field. Using these data, looking at colour change and mechanical properties, we are able to increase the confidence in the predictions being made from correctly conceived accelerated tests.