Yellowing of PV Backsheets in accelerated tests can be used as a realistic indication of possible field failures – Fact or Fiction?
PV (Photovoltaic) modules currently have lifetime guarantees of 25 years plus. 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?"
Emily Parnham, a Research Scientist for DuPont Teijin Films compares seven 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 PET (polyethylene terephthalate) film in Xenon weatherometer, 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.
To hear more on this subject visit EU PVSEC 2016 the 32nd European PV Solar Energy Conference and Exhibition taking place 20th -24th June 2016, Munich, Germany.
Tuesday 21st June - 13.30