Temperature coefficients and LeTID of bifacial PV modules
Transcript of Temperature coefficients and LeTID of bifacial PV modules
Temperature coefficients and LeTID of bifacial PV modules
BifiPV workshop Amsterdam – September 2019
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BifiPV workshop Amsterdam – September 2019
Two topics with Yield impact for Bifacial PV
BifiPV workshop Amsterdam – September 20193
1. Temperature coefficients
2. LeTID/LID performance
Bifacial PV
Yield!
Two topics with Yield impact for Bifacial PV
BifiPV workshop Amsterdam – September 20194
1. Temperature coefficients
2. LeTID/LID performance
Bifacial PV
Yield!
Temperature coefficients are a big challenge for the PV industry
BifiPV workshop Amsterdam – September 2019
[1] MIHAYLOV, B.V. ... et al, 2014. Results of the Sophia module intercomparison part-1: STC, low irradiance conditions and temperature coefficients - C-Si technologies
Round robin between 12 leading laboratories:
+2.8%
-3.6%
-11.6%
+18.3%
Dev
iati
on
of
Pm
ax T
em
per
atu
re
Co
effi
cien
t fr
om
med
ian
Pmax accuracy constantly improving Temp coefficient accuracy has been forgotten
Typical tempco measurement uncertainties OVER 10%
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This uncertainty gets little attention, but impact can be significant
BifiPV workshop Amsterdam – September 20196
PV power
Morning Noon Evening
Temperature
Temp. coefficient
uncertainty
In sunbelt area’s with high operating temperatures, the impact is largests
10% difference in temperature coefficient = 1.2% difference in energy yield for this PV plant location
BifiPV workshop Amsterdam – September 2019
Image adjusted from : [2] Yang Yang, YingBin Zhang…Pierre J. Verlinden, 2014. Understanding the uncertainties in the measurement of temperature coefficients of Si PV modules – PVSyst modelling of energy yield with varying temperature coefficient in Phoenix, USA climatic conditions
The following figure shows the relationship between temperature coefficient and relative energy yield for the specified location (Phoenix, USA) [2]:
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+1.2%
-0.39%/°C-0.44%/°C
10%
A 10% difference in temperature coefficient equates to a >1% difference in energy yield
Our Goal: Reduce T.C. measurement uncertainty from
>10% to <5%, for all PV technologies
BifiPV workshop Amsterdam – September 20198
Outline
BifiPV workshop Amsterdam – September 20199
1. Temperature coefficients
2. LeTID/LID performance
Bifacial PV
Yield!
Illumination
Temperature
Procedure
Outline
BifiPV workshop Amsterdam – September 201910
1. Temperature coefficients
2. LeTID/LID performance
Bifacial PV
Yield!
Illumination
Temperature
Procedure
The single side and flip method is now regarded as most accurate
BifiPV workshop Amsterdam – September 201911
Illumination
Bifacial measurements in the temperature controlled lab flasher: very low rear irradiance
BifiPV workshop Amsterdam – September 2019
IEC requirement: ensure rear side irradiance < 3W/m2
Method: 1. Temperature box special black paint2. Black mask around module
Confirm: measure irradiance at 9 points on PV module
IEC 60904-1-2
<3W/m2
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Illumination
Result: on all 9 points rear side irradiance < 3W/m2
BifiPV workshop Amsterdam – September 2019
Voltage measured [mV] Irradiance equivalent [W/m2]
Position on module rear 95.35 1000
P1 0.215 2.25
P2 0.192 2.01
P3 0.247 2.59
P4 0.144 1.51
P5 0.108 1.13
P6 0.157 1.65
P7 0.161 1.69
P8 0.169 1.77
P9 0.176 1.85
The temperature box is suitable for bifacial module testing according to IEC 60904-1-2 in combination with module mask
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Illumination
Pulsewidth: HJT modules require a pulse up to 300 ms
BifiPV workshop Amsterdam – September 201914
HJT: 100-300 ms
• Every cell Voc increase of 18mV roughly doubles the carrier concentration, which causes a
doubled sweep time effect [2]
• More cells in series (e.g. 60 to 72 cells) reduces the string capacitance
• Multiflash can be applied in combination with Single Long pulse
[1] Source: Based on 5600 SLP sweep time sequence measurement of PERC module (2016)
[2] Source: Smets et al., Solar Energy: the physics and engineering of photovoltaic conversion technologies and systems (2016)
Illumination
STI/LTI
Pulsewidth: a stable single long pulse enables lowest uncertainty on high efficiency PV technologies
BifiPV workshop Amsterdam – September 201915
Illumination
Image adjusted from: Zhang et al.: 335-W World-record p-type monocrystalline module IEEE journal of photovoltaics, VOL. 6, NO. 1 (2016)
Spectrum: a wide, 300-1200 nm spectrum is critical for T.C. measurement on high efficiency cell technology
Sunlight quality
BifiPV workshop Amsterdam – September 201916
The quantum efficiency of solar cells between 400-1000nm is already at 100%
Efficiency gains PERC/Topcon/HJT
All efficiency improvements in new cells MUST occur in the 300-400nm and 1000-1200nm range
Illumination
Spectrum: when temperature increases, QE changes in 1000-1200 nm
Source: PTB Photoclass
BifiPV workshop Amsterdam – September 201917
Illumination
Spectral coverage of >99% in 300-1200 nm of EternalsunSpires 5100 & 5600 SLP Flashers enable the lowest uncertainty
BifiPV workshop Amsterdam – September 2019
0,0
0,5
1,0
1,5
2,0
2,5
300 400 500 600
AM1.5 S86-00038
60904-9Edition 3
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Eternalsun Spire flashers have spectrum coverage starting at 300nm. This is critical for accurately measuring high efficiency technologies
Spire Flasher solar simulator
Illumination
Outline
BifiPV workshop Amsterdam – September 201919
1. Temperature coefficients
2. LeTID/LID performance
Bifacial PV
Yield!
Illumination
Temperature
Procedure
Temperature control box added to flasher:
BifiPV workshop Amsterdam – September 201920
• Heating and cooling from 15 C to 85 C• Temperature control chamber moves down to fully enclose PV module for
accurate temperature control
Temperature
Temperature control: temperature uniformity directly affects uncertainty
Any temperature difference between individual cells in the module causes an error in the coefficient
BifiPV workshop Amsterdam – September 2019
Tem
per
atu
re [°C
]
< +/- 1°C9 sensors
< +/- 1°C9 sensors
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Temperature
Outline
BifiPV workshop Amsterdam – September 201922
1. Temperature coefficients
2. LeTID/LID performance
Bifacial PV
Yield!
Illumination
Temperature
Procedure
The “stable temperatures/dwell” method reduces uncertainty and is therefore recommended by IEC
BifiPV workshop Amsterdam – September 2019
“At each temperature level of interest, the module temperature should be stable”
Tem
per
atu
re [°C
]
9 sensors on PV module
612152016
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Procedure
True cell temperature stability is ensured by continuously monitoring Voc
BifiPV workshop Amsterdam – September 2019
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31
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35
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Vo
c [V
]
Module Voc at temperatures from 85°C to 10°C in steps of 15°C
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32,1
32,2
32,3
32,4
32,5
32,6
32,7
32,8
32,9
33V
oc
Zoom on Voc at 70°C temperature
Stable Voc = Stable cell temperature
IV performance is determined by the true, internal solar cell temperature, which often differs from the temperature of the backside of the module that is measured.
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Procedure
30
40
50
60
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0:00 0:10 0:20 0:30 0:40 0:50 1:00 1:10 1:20 1:30 1:40 1:50 2:00 2:10 2:20
Tem
pe
ratu
re [
°C]
Natural cooldown method
Internal cell temperature
Backsheettemperature
∆T = 4°C
∆T = 2°C
∆T = 0.8°C
The error caused by measurement during natural cooldown can be up to 7%
BifiPV workshop Amsterdam – September 2019
Method Power T.C.
Stabilized temperatures -0.381 %/C
Hot potato -0.410 %/C
Error %Rel 7.2%
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Procedure
Outline
BifiPV workshop Amsterdam – September 201926
1. Temperature coefficients
2. LeTID/LID performance
Bifacial PV
Yield!
Illumination
Temperature
Procedure
Bet
ter
yie
ld im
pac
tResults: significant differences between PV technologies
BifiPV workshop Amsterdam – September 2019
Source: Eternalsun Spire temperature coefficients study on 20 different PV modules, using Temperature Controlled Lab Flasher and HPLS for CdTe
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Results: behavior is not always linear and the T.C. dependent on the range of interest
BifiPV workshop Amsterdam – September 2019
Source: Eternalsun Spire temperature coefficients study on 11 different PV modules, using Temperature Controlled Lab Flasher
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Al-BSF p-type
Heterojunction n-type
mono PERC
195
215
235
255
275
295
315
0 10 20 30 40 50 60 70 80 90 100
Pm
ax [
W]
Temperature [°C]
Pmax vs temperature of different technologies
Results: front and rear temperature coefficients can differ significantly
BifiPV workshop Amsterdam – September 201929
Front side-0.382 %/C
Rear side-0.359 [%/C]
-25%
-20%
-15%
-10%
-5%
0%
5%
10 20 30 40 50 60 70 80 90
Pm
ax
Temperature [°C]
Front and Rear T.C.’s of Bifacial module
STC
γ - Pmax δ - FF β - Voc α - IscFront side -0.382 %/°C -0.136 %/°C -0.285 %/°C 0.028 %/°CRear side -0.359 %/°C -0.123 %/°C -0.290 %/°C 0.039 %/°CDeviation 6% 10% -2% -39%
Outline
BifiPV workshop Amsterdam – September 201931
1. Temperature coefficients
2. LeTID/LID performance
Bifacial PV
Yield!
Illumination
Temperature
Procedure
LeTID & LID: the difference
LeTID - Eternalsun Spire Whitepaper - May 2019
BOx+
FeB+
H+
[1] Chan, Catherine et al. (2017). Modulation of Carrier-Induced Defect Kinetics in Multi-Crystalline Silicon PERC Cells Through Dark Annealing. Solar RRL[2] Wenham, Stuart (2016). UNSW Advanced Hydrogenation. SPREE Alumni Event presentation. 8th December, 2016
LID LeTID
Expected cause Boron-Oxygen complexes or metal defects
Diffusing (moving) Hydrogen
Mitigation Add hydrogen Less hydrogen or temperature treatment
Timescale of effect 10-20 hours 50-500 hours
Temperatures 25-50 °C 60-90 °C
Potential extent of effect 0-3% reported c-Si modules 0-8% reported c-Si modules (commercial)
Outline
BifiPV workshop Amsterdam – September 201933
1. Temperature coefficients
2. LeTID/LID performance
Bifacial PV
Yield!
Illumination
Temperature
Procedure Setup Procedure
Setup used for LeTID study
LeTID - Eternalsun Spire Whitepaper - May 2019
• 1 sun Class AAA+ illumination• 300 to 1200 nm spectrum• 2 modules simultaneously
• 20 oC to 100 oC module temperature• In-situ IV measurements• Custom IV setpoints (e.g. Mpp)
between IV
Setup
Outline
BifiPV workshop Amsterdam – September 201935
1. Temperature coefficients
2. LeTID/LID performance
Bifacial PV
Yield!
Illumination
Temperature
Procedure Setup Procedure
Procedure: 85C, Module in Mpp between In-situ IV’s
LeTID - Eternalsun Spire Whitepaper - May 2019
-5,0
-4,5
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Rel
ativ
e P
max
dev
iati
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[%
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Lightsoaking time at 85C [h]
degradation regeneration
Procedure
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Rel
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max
dev
iati
on
[%
]
Lightsoaking time at 85C [h]
degradation regeneration
LeTID: visibility in EL imaging
LeTID - Eternalsun Spire Whitepaper - May 2019
Procedure
Alternative procedure: current soaking and interval IV flashing
LeTID - Eternalsun Spire Whitepaper - May 2019
-5,0
-4,5
-4,0
-3,5
-3,0
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-2,0
-1,5
-1,0
-0,5
0,0
0 30 60 90 120 150 180 210 240
Rel
ativ
e P
max
dev
iati
on
[%
]
Lightsoaking time [h]
Flasher IV measurements
Exposure time [h]
Degradation
Flasher IV Reproducibility
Procedure
Estimated
Procedure: Benefit of in-situ IV vs current soaking and flashing
LeTID - Eternalsun Spire Whitepaper - May 2019
-5,0
-4,5
-4,0
-3,5
-3,0
-2,5
-2,0
-1,5
-1,0
-0,5
0,0
0 30 60 90 120 150 180 210 240
Rel
ativ
e P
max
dev
iati
on
[%
]
In-situ IV measurements
True values
Flasher IV measurements
Exposure time [h]
Degradation
Procedure
Estimated
Outline
BifiPV workshop Amsterdam – September 201940
1. Temperature coefficients
2. LeTID/LID performance
Bifacial PV
Yield!
Illumination
Temperature
Procedure Setup Procedure
LeTID Results
BifiPV workshop Amsterdam – September 201941
-6,0%
-5,0%
-4,0%
-3,0%
-2,0%
-1,0%
0,0%
1,0%
2,0%
0 20 40 60 80 100 120 140 160 180 200 220 240
Rel
ativ
e P
max
dev
iati
on
[%
]
Lightsoaking time [h]
LeTID test at 85C, Mpp between in-situ IV’s
Heterojunction, N-type (manufacturer A)
Mono PERC, N & P-type (manufacturers B&C)
Poly PERC, P-type(manufacturers D&E)
Source: Eternalsun Spire LeTID study on 14 different PV modules, using High Performance Light Soaker
LeTID Results
BifiPV workshop Amsterdam – September 201942
-6,0%
-5,0%
-4,0%
-3,0%
-2,0%
-1,0%
0,0%
1,0%
2,0%
0 20 40 60 80 100 120 140 160 180 200 220 240
Rel
ativ
e P
max
dev
iati
on
[%
]
Lightsoaking time [h]
LeTID test at 85C, Mpp between in-situ IV’s
Heterojunction, N-type (manufacturer A)
Mono PERC, N & P-type (manufacturers B&C)
Poly PERC, P-type(manufacturers D&E)
Source: Eternalsun Spire LeTID study on 14 different PV modules, using High Performance Light Soaker
Bifacial Technologies
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BifiPV workshop Amsterdam – September 2019
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