SPLTRAK Abstract Submission
Evaluating the Durability of Balance of Systems Components Using Combined-Accelerated Stress Testing
David Miller1, Greg Perrin1, Kent Terwilliger1, Joshua Morse1, Chuanxiao Xiao1, Sona Ulicna2, Bobby To1, Laura Schelhas1, Peter Hacke1
1National Renewable Energy Laboratory, Golden, CO, United States
/2SLAC National Accelerator Laboratory, Menlo Park, CA, United States

The degradation of photovoltaic (PV) balance of systems (BoS) components are not well-studied, but the consequences include: offline-modules, -strings, -inverters; system shutdown; arc-faults; and fires. A utility provider experienced a ~30% failure rate in their power transfer chain, attributed to branch connectors. Field-failed specimen assemblies were therefore examined, consisting of cable connector, branch connector and discrete fuse components. Unaged field specimens were sent through combined-accelerated stress testing (C-AST) to clarify the most influential environmental stressors as well as the effect of external mechanical perturbation. A benchtop prototype fixture was used to develop the perturbation capability for C-AST. The same series of experiments was used to develop the in-situ data acquisition of specimen current, voltage, and temperature. After initial examination using X-ray computed tomography, the specimens’ external plastic was machined away to allow failure analysis, including the extraction of the internal convolute springs for morphological examination (optical- and electron-microscopy). Chemical composition analysis included: energy-dispersive X-ray spectroscopy, differential scanning calorimetry, and Fourier transform infrared spectroscopy. A significant increase in operating temperature, ~100 deg C from ~40 deg C, and a different failure mode was observed immediately once mechanical perturbation was applied.