Colin Sillerud CFV Labs Albuquerque, NM 2021-12-08 Validating IEC TS 63209-1 Mechanical and Backsheet Degradation Test Legs Outline Introduction: • Overview of IEC TS 63209-1 Test legs of interest and why: • MLT • UV Conclusion: Future Testing: IEC TS 63209-1 Photovoltaic Modules – ExtendedStress Testing • IEC TS 63209-1 is the first IEC specification for extended PV module reliability testing • Designed to be utilized with existing equipment and accepted IEC test methods • Allows for the standardization of extended testing for inter-comparability of results IEC TS 63209 Development Partners IEC TS 63209-1: Test Flow IEC TS 63209 Mechanical Stress Testing Sequence: Target for Mechanical Stress Testing Design extended mechanical stress sequence that more closely matches field results Fielded Module • Cell cracking • Electrical isolation • Performance loss primarily in Imp and Pmp Stress Fielded Isc (A) -0.80% Voc (V) -0.65% Imp (A) -15.21% Vmp (V) -3.03% Pmp (W) -17.73% Design of Experiment Leg 1 (DMLT - Baseline) Leg 2 (Static MLT) Leg 3 (SMLT+DMLT) Leg 4 (No MLT - Reference) Stabilization Stabilization Stabilization Stabilization SMLT (+/-2400 Pa) SMLT DMLT (+/-1000 Pa) DMLT TC50 TC50 TC50 TC50 HF10 HF10 HF10 HF10 MTL Test Setup Characteristic Module Type A Module Type B Cell Type 5BB Mono-PERC 4BB Mono-PERC Cell Count 72 72 Frame Thickness <35 mm 40 mm Power Class 350 W 360 W Construction G/B G/B Center Deflection at +2400 Pa 47 mm 32 mm 9 DMLT Results – EL Imaging (Module Type A) • Minimal cracking (4-7 cells) • Electrical isolation SMLT • Cracking (7-16 cells) • Minimal electrical isolation SMLT+DMLT • Cracking (12-13 cells) • Electrical isolation Result: • SMLT+DMLT better approximation of fielded samples DMLT SMLT SMLT+DMLT Field Comparison - Electroluminescence Fielded Module SMLT SMLT + DMLT 20 Type A (SMLT+DMLT) Results – EL Imaging (Comparison: Module Type A / Type B) • Cracking (12-13 cells) • Electrical isolation Type B (SMLT+DMLT) • Cracking (7-11 cells, but smaller segments) • Electrical isolation Result • Test shows relative difference in isolated area between module types produced by mechanical stress Type A Type B Results – Performance Performance Change (Pmp) Type B 1 1 0 0 -1 -1 Control -2 DMLT -3 SMLT SMLT + DMLT -4 -5 Percent Change (%) Percent Change (%) Performance Change (Pmp) Type A No MLT -2 DMLT -3 SMLT SMLT + DMLT -4 -5 -6 -6 Static MLT Dynamic MLT TC50 HF10-1 Static MLT Dynamic MLT • Resulting power loss over sequence between type A and B nearly identical (~ -5%) • Power loss on type A depends on sequence - SMLT+DMLT is largest • Power loss on type B is sequence independent • Type A exhibits greater damage via EL. Why is the power change the same? TC50 HF10-1 Type B - Current Change (Imp) 1 0 0 -1 No MLT -2 DMLT SMLT -3 SMLT + DMLT -4 Percent Change (%) 1 -5 -1 No MLT -2 DMLT SMLT -3 SMLT + DMLT -4 -5 Static MLT Dynamic MLT TC50 HF10-1 Static MLT Type A - Current Change (Isc) 1 1 0 0 -1 No MLT -2 DMLT SMLT -3 SMLT + DMLT -4 -5 Dynamic MLT TC50 HF10-1 Type B - Current Change (Isc) Percent Change (%) Percent Change (%) Results – Performance with Reference Module Percent Change (%) Type A - Current Change (Imp) -1 No MLT -2 DMLT SMLT -3 SMLT + DMLT -4 -5 Static MLT Dynamic MLT TC50 HF10-1 Static MLT Dynamic MLT TC50 HF10-1 Type A Type B • Imp loss corelates with loss in active cell area and string mismatch of module • Imp and Isc change are nearly identical hinting at loss in light capture of whole module • Isc shows little change • Is there a non-mechanical degradation occurring? Possible AR Coating degradation – HF10 Results – Performance with Reference Module Type B - Performance Change (Pmp) Normalized by Reference 1.00 1.00 0.00 0.00 -1.00 DMLT -2.00 SMLT SMLT + DMLT -3.00 -4.00 Percent Change (%) Percent Change (%) Type A - Performance Change (Pmp) Normalized by Reference -1.00 DMLT -2.00 SMLT SMLT + DMLT -3.00 -4.00 -5.00 -5.00 Static MLT Dynamic MLT TC50 HF10-1 Static MLT Dynamic MLT TC50 • Performance results normalized by Reference module (No MLT) • Resulting power loss from mechanical stress: • • Type A: -3.52 % Type B: -0.92 % • Type A is more susceptible to mechanical degradation than Type B • SMLT+DMLT shows worst case mechanical degradation (cracks present and opened) HF10-1 Fielded SMLT+DMLT Fielded Field Comparison – Performance Performance loss primarily in Imp matches fielded modules SMLT+DMLT Stress Isc (A) Voc (V) Imp (A) Vmp (V) Pmp (W) SMLT+DMLT -0.92% -0.58% -5.36 -0.80 -6.10% Fielded -0.80% -0.65% -15.21% -3.03% -17.73% Conclusion – Mechanical Leg • DMLT not able to effectively crack cells in either module type • SMLT as crack initiator, DMLT as crack opener • Able to examine relative differences between more or less crack-resistant module designs • Performance loss in Pmp and Imp, consistent with loss of cell collector area and an increase in cell to cell mismatch • Reference module is required to correctly interpret results, due to possible degradation from TC50/HF10 alone. IEC TS 63209 UV Backsheet Testing Sequence: Validate IEC TS 63209 backsheet testing sequence using known bad and presumed good samples Target for Polymeric Backsheet Testing • Backsheet cracking on fielded sample from a combination of UV, temperature and humidity stresses • Module level testing for BOM specific concerns Results: Visual Inspection Failures in Both Older and Newer Backsheets Module Construction Matters Sample Group 1 Sample Group 2 Sample Group 3 Sample Group 4 AAA (known bad) PVDF-1 PVDF-1 PET Standard Busbar Multi-Wire Busbar Standard Busbar Multi-Wire Busbar Full cell (72) Half-cut (144) Full cell (72) Half-cut (144) 2013 – Mnfr. 1 2018 – Mnfr. 2 2018 – Mnfr. 3 2018 – Mnfr. 2 Pass Pass Pass Pass Pass Pass FAIL - Backsheet Cracking FAIL - Backsheet Cracking (Behind avg. 30% of cells) (Behind avg. 100% of cells) Pass - Wet Leakage Pass - Wet Leakage FAIL - Backsheet Cracking - - (Behind avg. 28% of cells) Pass Pass - Wet Leakage - - - Pass Backsheet Durability Test Results: Conclusion IEC TS 63209 UV Sequence Provokes Failures in Past and Current Backsheets • Testing able to reproduce field relevant failures Results: AAA (Fielded ~ 8 years) AAA (Manuf. 2013, 2 cycles 63209) PVDF (Manuf. 2018, 2 cycles 63209) PVDF (Manuf. 2018, 3 cycles 63209) • Both known bad (AAA) and modern materials (PVDF) fail 63209 accelerated tests that correlate to 8-12 years of field stress. • Backsheet failures are moduleconstruction dependent. • Same back sheet performed differently on different constructions • Encapsulant chemistry and thickness, cell interconnect topography and other factors affect backsheet durability. Future Work for IEC TS 63209-1 Enhancement Front-Side UV • No glass-side UV testing in IEC TS 63209-1 • Propose development of test for rapid (~6 month) front-side field failure modes Discoloration and drop in Pmp (-6%) on mono-PERC after 6 months in field at CFV Hail • Hail is an increasing concern, but no hail prestress in mechanical degradation sequence in 63209-1 https://kubyenergy.ca/blog/solar-panels-vs-hail Contact Colin Sillerud Email: colin.sillerud@cfvlabs.com CFV Labs 5600-A University Blvd. Albuquerque, NM 87106
