UV fluorescence imaging as fast inspection method for PV modules in the field A. Morlier, M. Köntges, M. Siebert, I. Kunze

Transcription

1 14 th IEA PVPS Task 13 Meeting Bolzano, UV fluorescence imaging as fast inspection method for PV modules in the field A. Morlier, M. Köntges, M. Siebert, I. Kunze Institute für Solarenergieforschung Hameln/Emmerthal

2 Fluorescence (FL) detection UV-Light nm UV-Light source ca. 30 W/m² UV-Light intensity CCD-Camera UV-Fluorescence nm Highpass filter > 400 nm Measurement place should be protected from external light sources Field measurements possible at twilight/night Basic literature on the fluorescence effect: F.J. Pern, Sol. Energy Mater. Sol. Cells 41/42, 1996, L. King, M.A. Quintana, J.A. Kratochvil, D.E. Ellibee and B.R. Hansen, Prog. Photovolt.: Res. App., 8: (2000). doi: Detection of micro cracks with the fluorescence effect: Schlothauer, S. Jungwirth, B. Röder, M. Köhl, Photovolt. Int. 10 (2010), pp Detection of micro cracks with the fluorescence effect in the field: M. Köntges, S. Kajari-Schröder, I. Kunze, Proc. 27 th EUPVSEC Conference, Frankfurt, Germany, B. Kubicek, D. Mayrhofer, G. Eder, OTTI Symposium für Solarenergie, Bad Staffelstein, Germany, 2016

3 Fluorescence spectrum Increase of EVA fluorescence over aging time 1 Camera sensitivity 2 Aging time Blue sensor more adapted for shorter exposures Green sensor more adapted for longer exposures 1 A. Czanderna et al., Sol. Energy Mater. Sol. Cells 403, , F. Sigernes et al., Optics express 17 (22), (2009)

4 Fluorescence/Additives relation 1 Peroxide 1 Antioxidant 2 UV Absorber 2 Light stabilizer (HALS) 9 Formulations: EVA #1, #5, #6, #7, and #8 only with one additive EVA #2, #3, #9 and #10 mixed 1 Adhesion promoter Peike C., et al., Proc. IEEE PVSC Conference 2013,

5 Origin of fluorescence/yellowing Additive mixtures EVA with HALS and Antioxidant: no chromophores Additives dominate fluorescence: UV-absorber and cross-linking agent Additive mixtures All additive mixtures fluoresce Peike C., et al., Proc. IEEE PVSC Conference 2013,

6 Lamination materials UV dose 331 +/- 17 kwh/m² UV-transparent silicone UV-transparent EVA Every material fluoresces, but with different intensities Silicone with UV-absorber Std. EVA

7 Lamination materials UV dose 331 +/- 17 kwh/m² UV-transparent silicone UV-transparent EVA Fluorescence quenching through O2 diffusion Silicone with UV-absorber Std. EVA

8 UV fluorescence over exposure time Initial measurement: Weak fluorescence intensity No discernable pattern

9 UV fluorescence over exposure time 58 days outdoor, namely 290 kwh/m² global irradiation dose First discernable patterns Necessity for highly sensitive capture UV-light should be better filtered Reflection UV-light source

10 UV fluorescence over exposure time 125 days outdoor, namely 584 kwh/m² global irradiation dose Discernable patterns

11 UV fluorescence over exposure time 301 days outdoor, namely 980 kwh/m² global irradiation dose Patterns easily discernable

12 UV fluorescence over exposure time 511 days outdoor, namely 1735 kwh/m² global irradiation dose Patterns really clearly discernable

13 Electroluminescence image 511 days outdoor, namely 1735 kwh/m² global irradiation dose Cell crack Edgewafer

14 UV fluorescence over exposure time 511 days outdoor, namely 1735 kwh/m² global irradiation dose Cell crack easily discernable Edge wafer warmer when functioning, higher UV fluorescence intensity

15 UV fluorescence after a fall 3 days indoor (1735 kwh/m²) 1. Module falls short indoor stay does not affect fluorescence 2. 3 days indoor stay 3. FL-measurement

16 UV fluorescence after a fall 3 days indoor and 7 days outdoor (1735 kwh/m² + 34 kwh/m²) As few as 7 days outdoor allow for discerning new cell cracks

17 UV fluorescence after a fall 3 days indoor and 14 days outdoor (1735 kwh/m² + 74 kwh/m²) New cell cracks already appear wide!

18 UV fluorescence after a fall 3 days indoor and 21 days outdoor (1735 kwh/m² kwh/m²) New cell cracks widen slowly

19 UV fluorescence after a fall 3 days indoor and 35 days outdoor (1735 kwh/m² kwh/m²) Old and new cell cracks discernible through fluorescence intensity

20 UV fluorescence after a fall 3 days indoor and 49 days outdoor (1735 kwh/m² kwh/m²)

21 UV fluorescence after a fall 3 days indoor and 77 days outdoor (1735 kwh/m² kwh/m²) Old neat cell cracks are discernible from the new ones up to 2.5 months Half height peak width [mm] Irradiation dose [kwh]

22 UV fluorescence quenching Modelling: cell crack Glass Lamination material Cell Backsheet

23 UV fluorescence quenching Modelling: partial delamination of the cell Glass Lamination material Crack Cell Backsheet Partial delamination Supposition: adhesion between cell and embedding material is reduced around the cell crack

24 UV fluorescence quenching O 2 diffusion two different processes 1. Along delamination, 2. Through massive material Laminationsmaterial Glass Crack Partial delamination O 2 diffusion fast Cell O 2 diffusion slow Backsheet

25 Hotspots UV-Fluorescence Visible light picture Lock-In thermography FL method identifies areas that are/were hot during functioning

26 Field measurement tool Transport in a car trunk possible 0.5 h assembling Adaptable to module size Easy to use for 2 persons In average 21 s/image, incl. placement, handling Example measuring conditions: up to 500 W/m², um 0 C

27 Field measurements Serial number fluoresces Module 3 years in the field Dark field Fluorescence image Dark field substraction blue+green channel Dark field substraction increases noise reduces overlighting between cells (blooming) increases constrast remarkably Dust/dirt fluoresces Speculation: colophonium from flux traces?

28 Correlation with snail trails Snail trails correlate with fluorescence quenching due to cracks

29 Junction box: different cases FL IR Cells over the junction box show locally more fluorescence Cells warmer at this position, as seen on IR Less artefacts than IR

30 Junction box: different cases Second backsheet layer laid under the cross connectors Only a portion of the cross connector is intensively fluorescing Supplementary layer of backsheet blocking O 2 Hot junction box and connectors

31 Conclusion UV fluorescence by daylight possible Minimal aging: ca. a summer ~500 kwh/m² Cell cracks, teared tabs, hot cells (parts) Discriminating between new and 2.5 months old cracks or older 1300 modules in a 8 h day with 2 operators This work is funded by the Land Lower Saxony & the federal ministry of economy (BMWi) under contract number D Fidelitas

32 Outlook UV fluorescence may be combined with EL UV fluorescence may complement EL images with informations on warmth production and cracking storyline Thank you for your attention!