IEC 62804 Status Update
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This document discusses the development of IEC 62804, which provides test methods for detecting potential-induced degradation of photovoltaic modules. It describes discussions that were held with experts to update the document. Key discussions included changing the damp heat test startup from non-equilibrium to equilibrium, reducing the humidity tolerance, and whether to increase the stress levels of the tests. While some argued for more stringent conditions, others felt the existing 60°C/85% RH test was sufficient as a basic qualification test. The document also reviews decisions made around including both foil and damp heat tests and changing the document type from standard to technical specification.
IEC 62804 Status Update
- 1. IEC 62804 Status Update NREL is a na3onal laboratory of the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, operated by the Alliance for Sustainable Energy, LLC.
- 2. 2 2 Phone Discussions with NC-‐nominated Experts: Document 82/685/NP Focused discussion during Fall-‐Winter 2013/2014 Francois Rummens Claudio Licio1 Karl Berger Michael Koehl Yoshihito Deguchi
- 3. 3 3 October 2014 (Kyoto) – CD comments received and discussed, major items include: 2nd test type described: Al foil test providing full surface ground electrode applied to glass, proposed by DKE, included per decision at WG2(non-‐voted) Moving test from pass/fail “qualifica3on test” to descrip3on of how to do the test, without pass/fail criteria (voted) – Title: Test Method for Detec3on of Poten3al Induced Degrada3on of Photovoltaic (PV) Modules (non-‐voted)
- 4. 4 4 CD comment period: some key results – 60°C/85% RH test moved from non equilibrium startup to equilibrium startup Non-‐equilibrium startup placed excess humidity on sample surface, applying significant stress. – G. Mathiak (TUV Rheinland) confirmed by others. Requested by DKE to move to an equilibrium start-‐up, significant 12-‐24 h wait at T/RH stress condi3ons. RH tolerance moved from ± 5% to ± 3%, a five-‐lab round robin shows this was readily feasible. Temperature tolerance remains at ± 2° C, with a sec3on from references IEC 60068-‐2-‐78, Environmental tes3ng -‐ Part 2-‐78, included, discussing the precedence of cri3cality of maintaining 3ghter temperature tolerance. In view that “test method” values reproducibility over the specific magnitude of the stress level, the change to equilibrium start-‐up was made.
- 5. 5 5 Damp heat – V profile Thanks to Bengt Jaeckel, Karl Berger, for the ini3a3ve to make the first and second itera3ons of this example profile
- 6. 6 6 Recent revision history Dec 24, 2013 – Dra sent by email to WG2 – Concern about Al foil test being Not severe enough Not represen3ng frameless/rear rail modules – Wish for 85°C/85% RH condi3on (reality in China) Increased clarity that equilibrium start-‐up of damp heat test was less sever than turning on voltage at the beginning of the damp heat cycle. Some more severe
- 7. About the origin of the 60°C/85% RH condi/on 7 7 In Florida, USA –600 V Horizontal, near ocean Normalized Power 1.0 0.8 0.6 0.4 0.2 0.0 Type 1, 60° Type 2, 60° 0 50 100 150 200 0 Test Hours 1.000 Normalized Power 0.975 0.950 0.925 0.900 0 2000 4000 6000 8000 t (h) In chamber 85% RH –600 V Type 2, 85° Type 2, 50° Type 1 Type 2 Module Type 1: Acceptable performance in the field survives with less than 5% power drop in chamber with 85% RH, 60°C, rated system voltage, for 96 h Type 1, con3nued, with control 32 months In Florida, USA –600 V Horizontal, near ocean
- 8. 8 8 Stress levels 60°C/85% RH DH –Vsys condi/on now rendered less stressful because of the startup change.
- 9. 9 9 Voltage applied on start, then combined T, RH Ramps (early dra sequence) Leakage current spike, if different from chamber to chamber could conceivably contribute to poorer reproducibility excess stress Spike in leakage current from excess humidity on module Simultaneous ramp of T, RH, and voltage bias Simultaneous ramp down OK 60°C/85%RH/8 h dwell Also see: G. Mathiak, et.al. TÜV-‐R 27th EU-‐PVSEC
- 10. 10 10 T ramp/dwell èRH ramp èV ramp (later dra sequence) Short spike of leakage current, otherwise very stable Sequen3al ramp of T, RH, and voltage bias Na3onal Renewable Energy Laboratory Simultaneous ramp down OK 60°C/85%RH/8 h dwell
- 11. Ini/al/final Pmax with direct glass grounding 11 11 M1 8 M 19 M 2 0 M 2 1 M 22 250 200 150 100 50 0 / W PM PP before test after test Test condi/ons: 25°C, -‐1000 V DC, 120 h M18 – perforated foil M19 – water/foil M20 – mat/foil M21 – foil with gaps for some cells M22 – Al plate
- 12. 12 12 Stress levels 60°C/85% RH DH –Vsys condi/on now rendered less stressful because of the startup change. I suggested 35% increase in stress, based on leakage current analysis and work of J. Berghold., 60°Cà65°C. – Idea not favored based on 62804 experts feedback 60°C/85% RH already adopted in na3onal documents “Just a minimum basic test, no need to change”
- 13. 13 13 Stress levels 60°C/85% RH DH –Vsys condi/on now rendered less stressful because of the startup change. I suggested 35% increase in stress based on work of J. Berghold and leakage current examina/on, 60°Cà65°C. – Idea not favored based on 62804 experts feedback 60°C/85% RH already adopted in na3onal documents “Just a minimum basic test, no need to change” Why not just make it 85°C/85% RH China frequently tes3ng to 85°C/85% RH/96h PI Berlin championed 85°C/85% RH/48 h condi3on Concerns about SiN cell AR coa3ng degrada3on some3mes seen at 85°C/85% RH thought not representa3ve of field failure also happens in the field
- 14. 14 14 Silicon nitride degradation (DH +V bias) TTF: 85°C 85% RH +600V 2000 h ΔP= -‐29% rela3ve Outdoors, same type of module +1500 V bias ~4 y ΔP = -‐6.8% rela3ve
- 15. Why not just make it 85°C/85% RH 96 h or so? Type 1, con3nued, with control 15 15 In Florida, USA –600 V Horizontal, near ocean Normalized Power 1.0 0.8 0.6 0.4 0.2 0.0 1.000 0.900 0.800 0.700 0.600 Type In Florida, USA –600 V Horizontal, near ocean 1, 60° Type 2 Type 2, 60° 0 50 100 150 200 0 Test Hours 1.000 Normalized Power 0.975 0.950 0.925 0.900 0 2000 4000 6000 8000 t (h) 3 Y, now In chamber 85% RH –600 V Type 2, 85° Type 2, 50° Type 1 Type 2 Module Type 1: Acceptable performance in the field degrades to 5%, In just 8 h (non equilibrium start-‐up) Normalized Power 0.500 Generic Make Type 1 04/2011 07/2011 10/2011 01/2012 04/2012 07/2012 10/2012 01/2013 04/2013 07/2013 10/2013 Date 32 months Module Type 1: conven3onal, PV module made before PID even hit the radar. It does OK in the field Concern: pu6ng 85/85 as the only reference condi3on may needlessly raise cost.
- 16. 16 16 Recent revision history Dec 24, 2013 – Dra sent by email to WG2 – Concern about Al foil test being Not severe enough Not represen3ng frameless/rear rail modules – Wish for 85°C/85% RH condi3on (reality in China) Also, increased clarity that equilibrium start-‐up of damp heat test was less severe than turning on voltage at the beginning of the damp heat cycle. April 8, 2014, Dra sent by email to WG2 – 85°C/60% RH, and 25°C Foil test given as minimum stress levels, alterna3ve higher test temperatures also given per the feedback to the dra$s. – Mr. Deguchi (Japan expert) requested alterna3ve higher test levels be changed to notes. Done. – Discussions and sugges3ons in expert commi5ee about just choosing 1 condi3on each for the test types (Foil, DH), but no jus3fying data provided.
- 17. 17 17
- 18. 18 18 Busan WG2 decisions Foil and Damp heat tests both included – Language around the foil test sta3ng it does not account for module-‐level designs intended to mi3gate degrada3on by reducing leakage current pathways to ground. For example, it defeats protec3ons that may be placed in the PV module construc3on to minimize metal contact to the module. – Changed from standard to technical specifica3on. – TITLE : TEST METHODS FOR DETECTION OF POTENTIAL-‐INDUCED DEGRADATION OF CRYSTALLINE SILICON PHOTOVOLTAIC (PV) MODULES
- 19. 19 19 Hereout-‐ IEC 62804 distributed as TDS (82/885/DTS), comments close 2014-‐12-‐05 – Editorial changes Reference IEC 61215 Ed. 2 or Ed. 3? What does the future look like? Needs – Qualifica3on test Need to boil down to one stress level for qualifica3on test Environment –dependence is of interest – Inclusion of thin film in another rev of 62804 First Solar says they are essen3ally in favor of the 62804 document: They are good with it applied to their modules More data is needed to say the stress levels are meaningful with respect to the various technologies and mechanisms
- 20. Peter Lechner, ZSW 20 20 Some thin film technologies show coulomb-‐specific accelera3on