Outdoor measurements and comparison of thin film …(PV Module Performance Testing and Energy...
Transcript of Outdoor measurements and comparison of thin film …(PV Module Performance Testing and Energy...
Durability of Thin Film Solar Cells
04.04.2012 Empa, Dübendorf
Hans-Dieter Mohring
Zentrum für Sonnenenergie- und Wasserstoff-Forschung (ZSW)Baden-Württemberg
Outdoor measurements and comparisonof thin film solar cell technologies
- 2 -
• Motivation
• Methods for field data evaluation
- STC power and temperature coefficients
- Self referencing
- Dependence on irradiance level
- Long term stability
• Summary
Content
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Motivation
Higher uncertainties of module parameters for thin film technologies(CIGS, CdTe, a-Si/µ-Si) compared to c-Si.
Operational parameters, energy yield and long term stability can bedetermined from outdoor measurements.
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More energy from thin film PV –Marketing or reality?
Quelle: Broschüre Q-Cells
Quelle: Schott Solar Thin Film, EUPVSEC 2010
Quelle: http://www.nexpw.com/techology_tfa.html
More energy from thin film PV in principlepossible by:
• lower temperature coefficient• good performance under low/diffuse light• annealing or light-soaking effects
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Information from data sheet
• STC power/tolerance
• Temperature coeff.
• Dependence on irradiance
Source: http://www.avancis.de/fileadmin/media/portal/produkt/Datenblatt_PowerMax-STRONG.pdf
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Information from simulation programs
Source: PVSYST
Data for
• STC power/efficiency
• Temperature coefficients
• Dependence on irradiance
Where are these data from??
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Information from simulator measurements
Quelle: TÜV Rheinland
Measurement according to IEC 61853(PV Module Performance Testing and Energy Rating):
• Irradiance 100, 200, 400, 600, 800, 1000, 1100 W/m²• Temperature 15, 25, 50, 75 °C
Restrictions for thin film flasher measurements:
• Metastability effects• Crystalline Si reference cells• Current mismatch for tandem cells• Transient effects
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Results from outdoor module characterization
• STC power:- data collection days to weeks- spectrum dependent on location and season- stability presupposed
• Energy generation, Performance Ratio (PR):- typically 1 year- comparison of different technologies (benchmark c-Si)- valid for selected site
• Parameter determination:- typically 1 year- power, Voc, Isc,.. under STC- temperature coefficients, operation temperature- dependence on irradiance, incidence angle, spectrum
• Long term stability- several years
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Energy and Performance Ratio
• Energy Yield:
Y = Ecounter / Pnom (kWh/kWp)
• Performance Ratio (PR)
PR = Y / EPOA (%)
• Which Pnom ? Label? Flasher or outdoor measurement?
• Measured irradiation in module plane (EPOA) depends on sensor
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Outdoor measurements at ZSW• Widderstall (since 1988)• Girona/Spain (since 2011)
• Module measurements- module kept at MPP- I-V characteristics (1 per minute)- Tmod- Pyranometer and c-Si ref. cell- Ta, GHI, DHI, DNI, TNI, vwind
• Generator measurements- 1kW, identical inverters- DC, AC voltage and current- Tmod, POA irradiance
• PID-test stand
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Outdoor measurements at ZSW
0.0
0.5
1.0
1.5
2.0
2.5
0 10 20 30 40 50
Spannung (V)
Stro
m (A
)
Module I-V characteristics
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Power and temperature coefficient:(1) Selection of irradiance interval
Calculation of P1000 (linear scaling with reference irradiance)
1000 W/m² +/- 10%2854 Data points
1000 W/m² +/- 2%492 Data points
1000 W/m² +/- 0,2%74 Data points
70
80
90
100
110
120
10 20 30 40 50 60 70
Tmod [°C]
P10
00 [
W]
70
80
90
100
110
120
10 20 30 40 50 60 70
Tmod [°C]
P10
00 [
W]
70
80
90
100
110
120
10 20 30 40 50 60 70
Tmod [°C]
P10
00 [
W]
Data collection September, Widderstall, Si-TF module
Reasonable range:• Irradiance interval +/-1 to 2 %• some 100 to 1000 data points
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y = -0.2793x + 85.416
y = -0.2756x + 85.491
66
68
70
72
74
76
78
80
82
20 25 30 35 40 45 50 55 60 65
Modultemperatur (°C)
Mod
ulle
istu
ng (W
) AprilJuliLi (A il)
Power and temperature coefficient:(2) Different measurement periods
Measurement months April and July, Widderstall, CIGS module
• Higher module temperature in July• No change of STC module power
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P1000 vs. Tmod
• Determination of Tcoeff. fromslope (-0,21 %/K)
Moderate degree of correlation
Power and temperature coefficient: (3) Evaluation
y = -0,0006x + 99,172R2 = 2E-06
70
80
90
100
110
120
0 10 20 30 40 50 60 70
Tmod
P100
0 Tk
orrP1000 T-corr. vs. Tmod
• STC power 99,2 W
• Deviation by time constants of - pyranometer- module back temperature
y = -0,2085x + 104,36R2 = 0,2107
70
80
90
100
110
120
0 10 20 30 40 50 60 70
Tmod [°C]
P100
0 [W
]
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Voc1000 vs. Tmod
• Determination of STC-Voc
• Determination Tcoeff Voc
• Correction of Tmod usingVoc1000 Teff
Power and temperature coefficient :(4) Improvement of accuracy
100
110
120
130
140
0 10 20 30 40 50 60 70
Tmod [°C]
Voc1
000
[V]
y = 0,003x + 1,386R2 = 0,161
1,1
1,2
1,3
1,4
1,5
1,6
1,7
1,8
0 10 20 30 40 50 60 70
Teff [°C]
Isc1
000
[A
]
Isc1000 vs. Teff
• Determination of Isc@STC
• Definition: Eeff = Isc/ Isc@STC
Module used as irradiance sensor
=> “Self referencing”
y = 0,003x + 1,386R2 = 0,161
1,1
1,2
1,3
1,4
1,5
1,6
1,7
1,8
0 10 20 30 40 50 60 70
Teff [°C]
Isc1
000
[A
]
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020406080
100120140160180200
20 30 40 50 60 70Modultemperatur (°C)
Mod
ulle
istu
ng P
1000
(W)
c-Si
a-Siµc-Si
DSV
CdTea-Si/µc-Sic-Si
-0.29-0.2-0.42Tk Pmpp (%/K)
59.1122.4185.2Pmpp @ 25 °C (W)
Power and temperature coefficient :Example c-Si, a-Si/µc-Si, CdTe
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Parameter determination under low irradianceJune 2011, irradiance interval (Pyranometer) (98…102) W/m²
Linear Correction of measured power to100 W/m²
Plot vs. back temperature
y = -0,097x + 17,764R2 = 0,166
1011121314151617181920
5 10 15 20 25Tback (°C)
P100
(W)
Spectral- and incidance angle influences
No accurate evaluation possible!
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Parameter determination under low irradianceJune 2011, Self referencing Eeff = (0.098…0.102) suns
Linear Correction of measured power to 0.1 suns
Plot vs. back temperature
Accurate evaluation possible! low irradiance degradation
y = -0,066x + 16,226R2 = 0,992
1011121314151617181920
5 10 15 20 25Tback (°C)
P100
eff (
W)
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Self referencing of irradiance
ZSW Testfeld WIdderstall
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Reference cell or pyranometer?
0
0.2
0.4
0.6
0.8
1
1.2
06:00 08:00 10:00 12:00 14:00 16:00 18:00 20:00 22:00
G R
efze
lle/G
Pyr
anom
eter
8.7.
22.7.
Pyranometer
ISET Sensors
Ratio of c-Si sensor to pyranometersunny (8.7.) und cloudy (22.7.) day
• Moderate deviation under direct irradiation around noon time and under diffuse light • strong deviation under direct light morning/evening (incidence angle, spectrum)
Quelle: Kipp & Zonen
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0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
0.16
0.18
0.2
0 200 400 600 800 1000 1200
G Pyranometer (W/m²)
Wirk
ungs
grad
bedecktklar
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
0.16
0.18
0.2
0 200 400 600 800 1000 1200
G Pyranometer (W/m²)
Wirk
ungs
grad
bedecktklar
Efficiency vs. pyranometer irradiance
Data are as measured:
• Cloudy day: high efficiency
• Sunny day:strong influence of spectrumand incidence angle morning/eveningTemperature influence at noon
• NO UNIQUE FUNCTION!
a-Si/µc-Si: Efficiency vs. G
c-Si: Efficiency vs. G
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c-Si type
0.6
0.65
0.7
0.75
0.8
0.85
0.9
0.95
1
1.05
1.1
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2Eff. irradiance (suns)
norm
.effi
cien
cy
Tmod = 10 °C 25 °C 40 °C 55 °C
CIGS type
0.6
0.65
0.7
0.75
0.8
0.85
0.9
0.95
1
1.05
1.1
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2Eff. irradiance (suns)
norm
.effi
cien
cy
Tmod = 10 °C 25 °C 40 °C 55 °C
0.5
0.6
0.7
0.8
0.9
1
1.1
4:00 8:00 12:00 16:00 20:00
Time (CET)
Nor
m. e
ffici
ency
cloudy clear
0.5
0.6
0.7
0.8
0.9
1
1.1
4:00 8:00 12:00 16:00 20:00Time (CET)
Nor
m. e
ffic
ienc
y
cloudy clear
Efficieny vs. effective irradiance (1)
c-Si CIGS
Normalized efficiency vs. effective irradiance with parameter Tmod (top) and daily profile cloudy/clear (bottom)
Similar to c-Si, different at low
light level
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c-Si type
0.6
0.65
0.7
0.75
0.8
0.85
0.9
0.95
1
1.05
1.1
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2Eff. irradiance (suns)
norm
.effi
cien
cy
Tmod = 10 °C 25 °C 40 °C 55 °C
0.5
0.6
0.7
0.8
0.9
1
1.1
4:00 8:00 12:00 16:00 20:00Time (CET)
Nor
m. e
ffic
ienc
y
cloudy clear
Efficieny vs. effective irradiance (2)
c-Si CdTe
Normalized efficiency vs. effective irradiance and daily profile cloudy/clear
CdTe type
0.6
0.65
0.7
0.75
0.8
0.85
0.9
0.95
1
1.05
1.1
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2Eff. irradiance (suns)
norm
.effi
cien
cy
Tmod = 10 °C 25 °C 40 °C 55 °C
0.5
0.6
0.7
0.8
0.9
1
1.1
4:00 8:00 12:00 16:00 20:00Time (CET)
Nor
m. e
ffic
ienc
y
cloudy clear
smaller T-coeff.
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c-Si type
0.6
0.65
0.7
0.75
0.8
0.85
0.9
0.95
1
1.05
1.1
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2Eff. irradiance (suns)
norm
.effi
cien
cy
Tmod = 10 °C 25 °C 40 °C 55 °C
0.5
0.6
0.7
0.8
0.9
1
1.1
4:00 8:00 12:00 16:00 20:00Time (CET)
Nor
m. e
ffic
ienc
y
cloudy clear
Efficieny vs. effective irradiance (3)
c-Si a-Si/µc-Si
Normalized efficiency vs. effective irradiance and daily profile cloudy/clear
aSi-µcSi type
0.6
0.65
0.7
0.75
0.8
0.85
0.9
0.95
1
1.05
1.1
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2Eff. irradiance (suns)
norm
.effi
cien
cy
Tmod = 10 °C 25 °C 40 °C 55 °C
0.5
0.6
0.7
0.8
0.9
1
1.1
4:00 8:00 12:00 16:00 20:00Time (CET)
Nor
m. e
ffic
ienc
y
cloudy clear
Smaller Tcoeff. different at low
light level
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c-Si type
0.6
0.65
0.7
0.75
0.8
0.85
0.9
0.95
1
1.05
1.1
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2Eff. irradiance (suns)
norm
.effi
cien
cy
Tmod = 10 °C 25 °C 40 °C 55 °C
0.5
0.6
0.7
0.8
0.9
1
1.1
4:00 8:00 12:00 16:00 20:00Time (CET)
Nor
m. e
ffic
ienc
y
cloudy clear
Efficieny v s. effective irradiance(4)
c-Si a-Si/a-Si
Normalized efficiency vs. effective irradiance and daily profile cloudy/clear
aSi-aSi type
0.6
0.65
0.7
0.75
0.8
0.85
0.9
0.95
1
1.05
1.1
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2Eff. irradiance (suns)
norm
. effi
cien
cy
Tmod = 10 °C 25 °C 40 °C 55 °C
0.5
0.6
0.7
0.8
0.9
1
1.1
4:00 8:00 12:00 16:00 20:00Time (CET)
Nor
m. e
ffic
ienc
y
cloudy clear
Best Tcoeff., good at low light
level
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Long term stability
ZSW Test Field WIdderstall
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Initial Light-Soaking of CIGS Module
P: +10% in 6 Wochen
50
55
60
65
70
75
80
85
Jun. 03 Jul. 03 Aug. 03 Aug. 03 Okt. 03
P (W
), U
oc (V
)P@25°C Uoc@25°C
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Initial degradation of a-Si/a-Si Modul
Source: Schott Solar, 21st EU PVSC
Staebler-Wronski-Effect, SWE
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Long term stability of CIGS Module
Long term stability CIS @ 1000 W/m²
8.0
8.5
9.0
9.5
10.0
10.5
11.0
Jan. 03 Jan. 04 Jan. 05 Jan. 06 Jan. 07 Jan. 08
Tem
p. c
orr.
effic
ienc
y (%
)
Measurement close to AM1.5 and normal incidence, then temperature correction
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Long term stability of CIGS Module @ 800 W/m²
Continuous evaluation possible
0.9
0.95
1
1.05
1.1
0 0.5 1 1.5 2 2.5 3Jahre
P_M
PP_
800(
t)/P
_MPP
_800
(0)
- 31 -
Which degradation rate can be detected?
Here assumed 0,3 % per year
0.9
0.95
1
1.05
1.1
0 0.5 1 1.5 2 2.5 3Jahre
P_M
PP_
800(
t)/P_
MPP
_800
(0)
- 32 -
Effective efficiency, corrected to reference temperatureand normalized to Pnom
0,00
0,20
0,40
0,60
0,80
1,00
1,20
0,0 0,2 0,4 0,6 0,8 1,0 1,2
effective Irradiance [suns]
norm
. Per
form
ance
Meas. Period 1
Meas. Period 2
- 33 -
Low light level degradation / STC-Degradation
Outdoor measurements
0.94
0.96
0.98
1
1.02
1.04
Time ------->
eta(
t)/et
a(0)
1000 W/m² 100 W/m²
Different kinetics
- 34 -
Potential Induced Degradation
(1) Leakage currentindoor
35....85 °C50…95 % -1000 Vsome hours
1,E-07
1,E-06
1,E-05
1,E-04
1,E-03
00:00 12:00 00:00 12:00 00:00 12:00 00:00 12:00 00:00
Time (h)
Leak
age
curr
ent d
ensi
ty (
A/m
²)
Reihe1Reihe2
(3) Leakage currentoutdoor
Module temperatureHumidityGenerator Voltagemonths to years
(2) Power degrad. indoor
85 °C85 % -1000 V1000 h
Teils sonniger, trocken-kalter Tag
1,0E-08
1,0E-07
1,0E-06
1,0E-05
03.01.201206:00
03.01.201208:00
03.01.201210:00
03.01.201212:00
03.01.201214:00
03.01.201216:00
03.01.201218:00
Leck
stro
m
[A] Si-TF 2
Si TF 3CIGS 3CIGS 4CIGS 5CdTe 2c-Si 2
Estimation of Time to PID Failure
- 35 -
Time to PID Failure
> 5*E21,4> 300Si-TF 6
2,63533 Si-TF 27,97,823CdTe 2
0,820,6c-Si 2
> 5*E20,5> 87CIGS 4> 5*E20,19> 37CIGS 3
2,51,61,4CIGS 1
Time* to P90 t [a]
Daily* Qdfrom Outdoor
[mC/m²]
Q _ HV-DH for P90[C/m²]
ModuleType
• Time to PID Failure depends on climate
* Average values fall/winter at Widderstall
„PID-Failure“90 % of initial power (P90)
- 36 -
Summary
• Methods for evaluation of characteristic module parameters from fielddata have been presented
• Self referencing uses the module itself as a best matched irradiancesensor
• Module power is a unique function of effective irradiance, transformation to laboratory measurements under reference conditions
• From long term measurements stability trends can be extracted withhigh accuracy
• Time to PID Failure can be estimated
- 37 -
Thank you for your attention!
ZSW Testfeld WIdderstall