IEA INTERNATIONAL ENERGY AGENCY
PHOTOVOLTAIC POWER SYSTEMS PROGRAMME
[email protected] IEA PVPS Task13 Meeting & WS 2016-04-08 1
Potential Induced Degradation of PV modules & systems
IEA Task 13 Meeting & WorkshopEURAC, Bolzano 2016-04-08
Karl A. Berger
AIT Austrian Institute of TechnologyEnergy Department
Giefinggasse 2A-1210 Vienna, Austria
+43 664 825 [email protected]
IEA INTERNATIONAL ENERGY AGENCY
PHOTOVOLTAIC POWER SYSTEMS PROGRAMME
[email protected] IEA PVPS Task13 Meeting & WS 2016-04-08 2
Outline
Intro: PID - Potential induced degradation effects
PID – Module IV and effects at STC and LIC
Influencing parameters
PID-Testing
PID-Test description IEC TS 62804-1
Temperature & humidity
Regeneration
Module material investigations
PID detection methods
IEA-PVPS T13-01 Module failure review report
IEA INTERNATIONAL ENERGY AGENCY
PHOTOVOLTAIC POWER SYSTEMS PROGRAMME
[email protected] IEA PVPS Task13 Meeting & WS 2016-04-08 3
PID - Potential induced degradation effects
• Potential differences between in a string connected PV-cells and the ground potential cause a leakage current
• As early as 1978 and in the nineties leakage-current driven electro-chemical corrosion and polarization effects of crystalline and thin-film cells in modules were reported, and a minimum required insulation resistivity under wet conditions was established as a short term test (wet leakage current test)
• In applications the voltage stress was very limited, PV-modules were used to load batteries and the systems were small …
• 2005: High efficiency n-type cells evolved potential induced power degradation at positive polarity from cells to ground. Several different module types with (standard) p-type cells degraded in negative polarity too.
IEA INTERNATIONAL ENERGY AGENCY
PHOTOVOLTAIC POWER SYSTEMS PROGRAMME
[email protected] IEA PVPS Task13 Meeting & WS 2016-04-08 4
PID – Ion accumulation at stacking faults
Different effects summarized under PID
• In p-type cells Na+ ions from the front glass accumulate at stacking faults on the cell surface resulting in a – more or less –reversible polarization
• These Sodium enriched areas can cause a massive reduction of the cell’s shunt resistance
• The power loss of the affected modules depends on duration and voltage stress level, bill of materials and various ambient conditions, and is able to re-duce the module power to values below 30% within a few month in the field under unfavorable conditions.
IEA INTERNATIONAL ENERGY AGENCY
PHOTOVOLTAIC POWER SYSTEMS PROGRAMME
[email protected] IEA PVPS Task13 Meeting & WS 2016-04-08 5
Electric circuit schema
• How the potential of the d.c. side of the inverter is relative to the ground is essential
• Reduced VOC and Vmp of PID-faulty modules “pulls” then further modules on the bad side of the string …
IEA INTERNATIONAL ENERGY AGENCY
PHOTOVOLTAIC POWER SYSTEMS PROGRAMME
[email protected] IEA PVPS Task13 Meeting & WS 2016-04-08 6
Module failures – bathtub upside down
Typical failure scenarios for wafer-based crystalline PV modules• PID is not detectable on site during capacity measurements in
the commissioning phase, but degradation may start soon after
IEA-PVPS T13-01: 2014
IEA INTERNATIONAL ENERGY AGENCY
PHOTOVOLTAIC POWER SYSTEMS PROGRAMME
[email protected] IEA PVPS Task13 Meeting & WS 2016-04-08 7
PID – Module IV at STC and LIC
IV-curve measurement results, before and after PIDa) Massive reduction in FF, and reduced VOC & ISC
b) Massive VOC and FF reduction (7 month outdoor in IT), stable Isc
Because the shunt resistance is drastically reduced, the low light behavior (here LIC down to 200 W/m²) is even worse
IEA INTERNATIONAL ENERGY AGENCY
PHOTOVOLTAIC POWER SYSTEMS PROGRAMME
[email protected] IEA PVPS Task13 Meeting & WS 2016-04-08 8
PID – irreversible corrosion effects
Different effects summarized under PID• Beside reversible PID-effects, electro-corrosion can occur• Also crystalline module types may show visible degradation
(e.g. of the SiNx anti-reflective coating at the cells• In TF PID mechanisms some with, and without the availability
of water(vapour) in the module are known• Often PID affected modules look perfect, without visible failures• Detecting PID in OD performance data is hindered by
measurement UC at LIC
IEA INTERNATIONAL ENERGY AGENCY
PHOTOVOLTAIC POWER SYSTEMS PROGRAMME
[email protected] IEA PVPS Task13 Meeting & WS 2016-04-08 9
PID – irreversible corrosion effects
Different effects summarized under PID• Beside reversible PID-effects, electro-corrosion can occur
IEA INTERNATIONAL ENERGY AGENCY
PHOTOVOLTAIC POWER SYSTEMS PROGRAMME
[email protected] IEA PVPS Task13 Meeting & WS 2016-04-08 10
PID – irreversible corrosion effects
Different effects summarized under PID• Beside reversible PID-effects, electro-corrosion can occur
IEA INTERNATIONAL ENERGY AGENCY
PHOTOVOLTAIC POWER SYSTEMS PROGRAMME
[email protected] IEA PVPS Task13 Meeting & WS 2016-04-08 11
PID – Influencing parameters
Lots of influencing factors from cells, module bill of materials, mounting and electric operation, as well as from climatic operating conditions - temperature, humidity, soiling, etc.
IEA-PVPS T13-01: 2014
IEA INTERNATIONAL ENERGY AGENCY
PHOTOVOLTAIC POWER SYSTEMS PROGRAMME
[email protected] IEA PVPS Task13 Meeting & WS 2016-04-08 12
PID – Influencing parameters
Lots of influencing factors from cells, module bill of materials, mounting and electric operation, as well as from climatic operating conditions - temperature, humidity, soiling, etc.
IEA-PVPS T13-01: 2014
IEA INTERNATIONAL ENERGY AGENCY
PHOTOVOLTAIC POWER SYSTEMS PROGRAMME
[email protected] IEA PVPS Task13 Meeting & WS 2016-04-08 13
PID – Test standard
PID effect not covered in module design and safety qualification
• Discussion for years in IEC TC82 WG2 -PV module group howa meaningful PID-test should look like
• Accelerate by humidity and temperature (a), or
• Enhance surface con-ductivity by applying a conductive foil
• IEC TS 62804-1 for x-Siwithout PASS/FAIL
IEA INTERNATIONAL ENERGY AGENCY
PHOTOVOLTAIC POWER SYSTEMS PROGRAMME
[email protected] IEA PVPS Task13 Meeting & WS 2016-04-08 14
PID – Accelerating & influencing factors
(a) Desert climate: dew over night, dries during daytime
All: Fair Arrhenius-like change in leakage current as f(temperature)
Climaticchamber85% rH
IEA INTERNATIONAL ENERGY AGENCY
PHOTOVOLTAIC POWER SYSTEMS PROGRAMME
[email protected] IEA PVPS Task13 Meeting & WS 2016-04-08 15
PID – Accelerating & influencing factors
(a) Desert climate: dew over night, dries during daytime(b) Climate with frequent rainfallAll: Fair Arrhenius-like change in leakage current as f(temperature)
Climaticchamber85% rH
Aluminumfoil, dry
Outdoorrain
IEA INTERNATIONAL ENERGY AGENCY
PHOTOVOLTAIC POWER SYSTEMS PROGRAMME
[email protected] IEA PVPS Task13 Meeting & WS 2016-04-08 16
PID – Accelerating & influencing factors
(a) Desert climate: dew over night, dries during daytime(b) Climate with frequent rainfall, and or soiling, salt mistAll: Fair Arrhenius-like change in leakage current as f(temperature)
Climaticchamber85% rH
Outdoorsoiled
Aluminumfoil, dry
IEA INTERNATIONAL ENERGY AGENCY
PHOTOVOLTAIC POWER SYSTEMS PROGRAMME
[email protected] IEA PVPS Task13 Meeting & WS 2016-04-08 17
PID – Affected system locations
PID affected systems (2014): most of them hot and/or coastal sitesBut: continental& rainy too
IEA INTERNATIONAL ENERGY AGENCY
PHOTOVOLTAIC POWER SYSTEMS PROGRAMME
[email protected] IEA PVPS Task13 Meeting & WS 2016-04-08 18
PID – Regeneration
Two competing processes: PID degradation vs. thermal and/or potential induced recovery processes
• Thermal diffusion extracts ions from stacking faults
• Diffusion rate strongly dependent on temperature: Arrhenius
IEA INTERNATIONAL ENERGY AGENCY
PHOTOVOLTAIC POWER SYSTEMS PROGRAMME
[email protected] IEA PVPS Task13 Meeting & WS 2016-04-08 19
PID – Regeneration
• Reverse ele. potential speeds up the ion removal, S-shaped
• Leakage current, respective transferred charge matter for regeneration, one master curve for all temperatures
Peter Lechner, Bad Staffelstein 2016
IEA INTERNATIONAL ENERGY AGENCY
PHOTOVOLTAIC POWER SYSTEMS PROGRAMME
[email protected] IEA PVPS Task13 Meeting & WS 2016-04-08 20
PID – Regeneration
• Reverse ele. potential speeds up the ion removal, S-shaped
• Outdoor regeneration with voltage applied quite fast when hot
Slow TR
time [h]
time [h]
Ther
mal
rege
nera
tion
TR
0.1 1 10 100 1 000 10 000 100 000
Peter Lechner, Bad Staffelstein 2016
IEA INTERNATIONAL ENERGY AGENCY
PHOTOVOLTAIC POWER SYSTEMS PROGRAMME
[email protected] IEA PVPS Task13 Meeting & WS 2016-04-08 21
PID – Regeneration
• Reverse ele. potential speeds up the ion removal, S-shaped
• Outdoor regeneration with voltage applied quite fast when hot
Slow TR
time [h]
time [h]
time [h]
Ther
mal
rege
nera
tion
TR
0.1 1 10 100 1 000 10 000 100 000
0.1 1 10 100 1 000
Peter Lechner, Bad Staffelstein 2016
Fast PIR
Pote
ntia
l ind
uced
rege
nera
tion
PIR
time [h]
IEA INTERNATIONAL ENERGY AGENCY
PHOTOVOLTAIC POWER SYSTEMS PROGRAMME
[email protected] IEA PVPS Task13 Meeting & WS 2016-04-08 22
PID – accelerated aging IEC 62804-1
PC controlled HV-operation & measurementAutomatic periodic switch to dark IV-measmt.
Dark IV
-1000 V ON10kΩ
1Ω
RpPID = 1/8000 Rp0
IEA INTERNATIONAL ENERGY AGENCY
PHOTOVOLTAIC POWER SYSTEMS PROGRAMME
[email protected] IEA PVPS Task13 Meeting & WS 2016-04-08 23
Purchased modules: accelerated aging IEC 62804-1
• Method (a) – climate chamber test @ 85% r.H., 60oC, -1000V• Leakage current 2µA … 100µA – not correlated with Power loss
NO Power
IEA INTERNATIONAL ENERGY AGENCY
PHOTOVOLTAIC POWER SYSTEMS PROGRAMME
[email protected] IEA PVPS Task13 Meeting & WS 2016-04-08 24
Purchased modules: accelerated aging IEC 62804-1• Degradation phase: Best Modules -1%, worst 95% loss• Recovery phase: low PID degradation – good recovery
high degradation – poor recovery
IEA INTERNATIONAL ENERGY AGENCY
PHOTOVOLTAIC POWER SYSTEMS PROGRAMME
[email protected] IEA PVPS Task13 Meeting & WS 2016-04-08 25
Purchased modules: accelerated aging IEC 62804-1• Degradation phase: Module #12: -95%
Pmpp = 220W Pmpp = 12W
EL
PID
EL
IEA INTERNATIONAL ENERGY AGENCY
PHOTOVOLTAIC POWER SYSTEMS PROGRAMME
[email protected] IEA PVPS Task13 Meeting & WS 2016-04-08 26
Purchased modules: accelerated aging IEC 62804-1• Degradation phase: Module #12: -95%• Recovery phase: 50% only
Pmpp = 220W Pmpp = 12W
Pmpp = 110W Dark IR Pmpp = 110W
EL
PID
EL
EL
IEA INTERNATIONAL ENERGY AGENCY
PHOTOVOLTAIC POWER SYSTEMS PROGRAMME
[email protected] IEA PVPS Task13 Meeting & WS 2016-04-08 27
Components varied: accelerated aging IEC 62804-13×2 cell mini-modules• 8 encapsulants
a) Variations of encapsulant Module No. stress 1 stress 2EVA 1 1 PID 24hEVA 1* 2 PID 24h recover 24hEVA 2 3 PID 24h recover 24hEVA 3 4 PID 24h recover 24hEVA 4 5 PID 24h
Silicon 6 PID 24hPolyolefin 1 7 PID 24hPolyolefin 2 8 PID 24h
PVB 9 PID 24h
IEA INTERNATIONAL ENERGY AGENCY
PHOTOVOLTAIC POWER SYSTEMS PROGRAMME
[email protected] IEA PVPS Task13 Meeting & WS 2016-04-08 28
Components varied: accelerated aging IEC 62804-13×2 cell mini-modules• 8 encapsulants• 3 back sheets
a) Variations of encapsulant Module No. stress 1 stress 2EVA 1 1 PID 24hEVA 1* 2 PID 24h recover 24hEVA 2 3 PID 24h recover 24hEVA 3 4 PID 24h recover 24hEVA 4 5 PID 24h
Silicon 6 PID 24hPolyolefin 1 7 PID 24hPolyolefin 2 8 PID 24h
PVB 9 PID 24h
b) Variations of back sheetsBS 1 10 PID 24h recover 24hBS 2 11 PID 24hBS 3 12 PID 24h
IEA INTERNATIONAL ENERGY AGENCY
PHOTOVOLTAIC POWER SYSTEMS PROGRAMME
[email protected] IEA PVPS Task13 Meeting & WS 2016-04-08 29
Components varied: accelerated aging IEC 62804-1Parameter Degradation (100% = initial value)
The encapsulant influences V, I , Pmpp and FF different !
IEA INTERNATIONAL ENERGY AGENCY
PHOTOVOLTAIC POWER SYSTEMS PROGRAMME
[email protected] IEA PVPS Task13 Meeting & WS 2016-04-08 30
Components varied: accelerated aging IEC 62804-1IV-curves, encapsulant varied
The encapsulant influences V, I , Pmpp and FF different !
IEA INTERNATIONAL ENERGY AGENCY
PHOTOVOLTAIC POWER SYSTEMS PROGRAMME
[email protected] IEA PVPS Task13 Meeting & WS 2016-04-08 31
Components varied: accelerated aging IEC 62804-1IV-curves, encapsulant varied
IV-curves, back sheet varied
The backsheet influences PID!The encapsulant influences V, I , Pmpp and FF different !
IEA INTERNATIONAL ENERGY AGENCY
PHOTOVOLTAIC POWER SYSTEMS PROGRAMME
[email protected] IEA PVPS Task13 Meeting & WS 2016-04-08 32
PID – Can affect small to utility scale systems
• Check combinations of intended materials – even when cells are claimed “PID-free” with the PID-test procedure(s) IEC 62804-1 for xSi modules. (A part 2 for TF modules is under consideration)
• Take care selecting the right inverter model
• Check operating sys-tems, e.g. by detailledmonitoring analysis, infrared and/or electro-luminescence imaging …
because PID is a major reason for underperforming systems!
IEA INTERNATIONAL ENERGY AGENCY
PHOTOVOLTAIC POWER SYSTEMS PROGRAMME
[email protected] IEA PVPS Task13 Meeting & WS 2016-04-08 33
PID detection methodsElectroluminescence imaging (EL):Near IR-emission by rekombinationstimulated from forward bias current
The IEA-PVPS T13-01 report, Review of Failures of PV Modules
is, together with many others freely available at the IEA-PVPS
website http://iea-pvps.org/index.php?id=275
IV-curve measurement under illumination, or dark-IV curve msmt.
Dark IR imaging
Abbreviations for Safety & Power loss categories: PID
Outdoor infrared image of a PV module string with PID
B. Weinreich, 2013
IEA INTERNATIONAL ENERGY AGENCY
PHOTOVOLTAIC POWER SYSTEMS PROGRAMME
[email protected] IEA PVPS Task13 Meeting & WS 2016-04-08 34
http://www.pv-reliability.com/
Announcement: Coming Soon …
IEA INTERNATIONAL ENERGY AGENCY
PHOTOVOLTAIC POWER SYSTEMS PROGRAMME
[email protected] IEA PVPS Task13 Meeting & WS 2016-04-08 35
Thank You for Your Attention!
The Austrian contribution within the IEA-PVPS Task 13 is (partly) funded by KLIEN
and the Austrian Federal Ministry for Transport, Innovation and Technology
Karl A. [email protected]://www.ait.ac.at/research-services/research-services-energy/?L=1
IECEE CB-Schemehttp://www.iecee.org/cbscheme/Certificate_of_Acceptance/tl001.pdf
/