Evaluation and Modeling of the Potential Effects of a Module Manufacturing Anomaly

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Photovoltaic lifetime predictions are in great demand, but are exceedingly difficult to achieve with uncertainties small enough to be useful. During the construction of photovoltaic modules, small unplanned variability in materials or processes can have profound effects on module durability. Thus, continual monitoring of production quality is needed. In the subject production run, module quality, as monitored by damp heat testing, revealed a subset of modules that were prone to higher degradation rates. An assessment of the potential long-term power loss and mitigation strategies was needed. To do this, modules were exposed to variable levels of humidity and temperature with periodic monitoring. The analysis takes into account the kinetics of the degradation and the spatially and temporally varying humidity content within the module during accelerated stress testing. This is an important aspect for extrapolating laboratory results to field exposure because moisture ingress is diffusion limited in most laboratory module tests but not limited in these fielded modules. This analysis predicted that although a solder flux induce degradation mechanism is significant in accelerated stress test, this is probably an artifact of a process with a very large acceleration factor that is not likely to be significant for deployed modules. The degradation mechanism affected a limited area around the tabbing helping to minimize the effect. Three years after the system was commissioned, the fielded modules indeed show no significant power loss.

Original languageAmerican English
Pages (from-to)982-988
Number of pages7
JournalProgress in Photovoltaics: Research and Applications
Issue number12
StatePublished - 2017

Bibliographical note

Publisher Copyright:
Published 2017. This article is a U.S. Government work and is in the public domain in the USA.

NREL Publication Number

  • NREL/JA-5J00-68792


  • damp heat
  • durability
  • kinetics
  • manufacturing quality
  • reliability


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