pi-berlin.com PI Berlin LeTID for Investors · PI Test Protocol Part of PI Quality Package Initial...
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PI Berlin – LeTID for Investors The leading technical advisor, risk manager and quality assurance provider for PV power plants and equipment ©2019 PI Photovoltaik-Institut Berlin AG | JMarch 2019 pi-berlin.com
Transcript of pi-berlin.com PI Berlin LeTID for Investors · PI Test Protocol Part of PI Quality Package Initial...
PI Berlin – LeTID for InvestorsThe leading technical advisor, risk manager and quality assurance provider for PV power plants and equipment
©2019 PI Photovoltaik-Institut Berlin AG | JMarch 2019
pi-berlin.com
©2019 PI Photovoltaik-Institut Berlin AG | March 2019
LeTID on PERC Modules
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-1%
-7%
-> Grid connected PV plants will degrade over several years and then regenerate
over several years depending on the PERC cell process
©2019 PI Photovoltaik-Institut Berlin AG | March 2019
Light and Temperature Dependence of LeTID
Acceleration factor ≈ 2 by every 10°C temperature step
Acceleration factor ≈ 6 for Open Circuit Modus (I = Isc) against load Modes (I< Isc)
Carrier injection by Light and Current roughly equivalent (LID ≈ CID)
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©2019 PI Photovoltaik-Institut Berlin AG | March 2019
How to differentiate between LeTID and normal LID?
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LeTIDLID
* via light or current
LeTID LID
Time Scale Years Hours
Recovery (field) Carrier Injection* + Heat Heat
Magnitude 4% - 10% 1% -3%
Mechanism behind LeTID still not clarified
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Non-gettered metals?
Mobile hydrogen?
©2019 PI Photovoltaik-Institut Berlin AG | March 2019
How to overcome LeTID?
Fast Anneal (< 1min) in the cell production > 2 sun irradiation, T > 270°C
Forward bias at module in the laminator 150°-170°C, 10- 20 min (left)
Eight weeks field anneal during summer under open circuit in Korea (right)
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©2019 PI Photovoltaik-Institut Berlin AG | March 2019
PI Test Protocol
Part of PI Quality Package
Initial Pmax at STC, EL
Optional: LID stabilisation 50°C (IEC)
Forward bias current
I= 0.5A, 2.0A, 5.0A, 10A
75°C for 168h (2 modules each).
Pmax, EL after 2h, 24h, 48h,
72h, 96h,120h,144h and 168h
Pass: ΔPmax Power loss < 2% after 168h
Similar to CD IEC 61215-2 Ed. 2 (under discussion): slow and fast degradation/reneration mode
Slow: LeTID Detection, repeat 162h, I = Isc-Impp, 75°C until ΔPmax < 1% (MQT 23.1 )
Fast: LeTID Regeneration, repeat 500h, I = Isc, 85°C until ΔPmax < 1% (MQT 23.2)
PI B
erlin
©2019 PI Photovoltaik-Institut Berlin AG | March 2019
Climate chamber test
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= Isc-Impp Mode
10A = Voc Mode
A slow LeTID detection method is recommended, e.g. I= Isc-Impp = 0,5A
Degradation might be missed completely, when testing is to fast and to close
to Voc Mode = lowest row in the EL images (right)
PI B
erlin
=Voc
©2019 PI Photovoltaik-Institut Berlin AG | March 2019
Benchmarking Mono vs. multi PERC on LeTID
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multi 10 PERC modules 75°C
I = Isc-Impp
(2x multi, 8x mono)
No clear sign, that mono
PERC performs better,
e.g. see Ramspeck 2012
Maybe because multi
PERC producers were
earlier alerted and already
deployed sufficient
counter-measures
PI B
erlin
©2019 PI Photovoltaik-Institut Berlin AG | March 2019
Field Results
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Lab-to-field comparision:
1200 h, I = Isc-Impp, 75°C in the climate chamber equals 4 years in the field:
-7% power loss in Cyprus (for non-stabilized multi PERC cells)
-2,5% power loss 4 years in Germany (ditto)
But only -1% each with LeTID-stable PERC process
PI customer feed-back from the field:
-5% in energy yield in semi-arid regions with up to -15% power loss by LeTID
after two years on single multi PERC modules from 2016
-> Results on LeTID are also very slow
©2019 PI Photovoltaik-Institut Berlin AG | March 2019
