Upload
others
View
3
Download
0
Embed Size (px)
Citation preview
Proposed new damp heat test standardsfor thin film PV modules
K. Sakurai, K. Ogawa, H. Shibata, A. MasudaAIST
A. TakanoFWAVE
H.Tomita, D.Schmitz, S.TokudaSolar Frontier K.K.
Presented at SAYURI‐PV, 2016 Oct 4‐5AIST, Tsukuba, Japan
np
←
Current
Backgrounds
• Major international PV standards are now being created/revised under IEC TC82 WG2
• a major “overhaul” of the whole set of test standards‐‐‐ wider, stricter coverage of degradation modes
• includes the IEC61215, Design qualification and type approval of PV modules
MQT 01Visual inspection
MQT 06.1Performance at STC
MQT 03Insulation test
MQT 15Wet leakage current test
MQT 10UV precondition test
15 kWh/m2
MQT 11Thermal cycling test
50 cycles–40 °C to 85 °C
MQT 12Humidity freeze test
10 cycles–40 °C to 85 °C
85 % RH
10 Modules
MQT 15Wet leakage current test
1 Module
MQT 06.2Performance at
NMOT (see Note 1)
MQT 07Performance atlow irradiance (see Note 1)
MQT 04Measurement of
temperature coeff icients(see Note 1)
MQT 19.1Initial Stabil ization
(Note 4)
MQT 06.1Performance at STC
3 ModulesSequence A
1 ModuleSequence B
2 ModulesSequence C
2 ModulesSequence D
2 ModulesSequence E
MQT 19.2Final Stabil ization
MQT 05 & MQT 08Measurement of NMOT
& Outdoor Exposure Test 60 kWh/m2
(see note 2)
MQT 18Bypass diode
thermal test (see Note 2)
MQT 09Hot-spot
endurance test(see Note 3)
MQT 16.1Static mechanical
load test(design load)
MQT 17Hail test
1 Module1 Module
MQT 11Thermal cycling test
200 cycles–40 °C to 85 °C
MQT 13Damp heat test
1 000 h85 °C / 85 % RH
MQT 14.1Retention of
junction box test
1 Module
MQT 19.2Final Stabil ization
MQT 06.1Performance at STC
1 Modulemeasured together with modules from sequences C-E as
control
2 Modules
MQT 14.2Test of cord anchorage
MQT 03Insulation test
MQT 16.2Static mechanical load test
(Test load, γm>1)
old IEC61215’s test procedure revised IEC61215(draft)
wider/stricter coverageof degradation modesfor improved reliability
• Among the test procedures, "heating in dark" is often applied.• Damp heat• Thermal cycling• PID
etc.
However, in REAL conditions, how often does "heat + dark" happen?
Is it always the best test method?
Question...
When hot in field, there's always light(voltage)
➣ In the real field, module temperature seldom exceeds 50 C without > 0.2 Sun irradiation.⇒ "High temperature + dark" condition is rare.
At high temperatures, module is soaked in light and generating bias voltage.
Irradiation (Sun)
Norm
alized Voc (V
oc @1Sun = 100 %
)
Module temperature (Middle east)Module temperature (Japan)
Suns‐Voc resultM
odul
e te
mpe
ratu
re (
C)
Outline of this talk
Two examples of when conventional "damp heat" testsare NOT the optimum test procedure for PV modules.
Example 1: A flexible thin‐film Si module (prototype)
Example 2: Some CIGS products in the market
Example 1
On damp‐heat testing of a prototype flexible thin film Si module
Unique degradation mode observed in a prototypeThin film Silicon flexible module(1)
0123456789
10111213
Year
0.00.10.20.30.40.50.60.70.80.91.01.11.21.3
Effic
ienc
y (a
rb. u
nits
)
Power GenerationRadiationEfficiency
Pow
er G
ener
atio
n (k
Wh/
kWp・
day)
Am
ount
of S
olar
Rad
iatio
n (k
Wh/
day)
Relocation
99 00 01 02 03 04 05 06 07 08 09 10 11 12
(A.Takano et al, EU PVSEC 2013, 3BO.5.4)
Transparent Electrode (+)
Laser-Scribed Linesfor Unit-Cell Separation
Backside Electrode Plastic-Film Subs trate
a-Si Layer
Metal Electrode (-)
Series-Connect ion Holes Current-Collection Holes
Transparent Electrode (+)
Laser-Scribed Linesfor Unit-Cell Separation
Backside Electrode Plastic-Film Subs trate
a-Si Layer
Metal Electrode (-)
Series-Connect ion Holes Current-Collection Holes
Reproducing the degradationby applying forward bias during damp heat test
(A.Takano et al, EU PVSEC 2013, 3BO.5.4)
(Leak points)
EL image
0102030405060708090
100
0 1000 2000 3000Test Time (h)
Out
put P
ower
( arb
. uni
ts) Damp Heat Test
Damp Heat & Current InjectionTest
Degradation reproduced by forward bias during damp heat testing
→ made it possible to fix the problembefore mass production
Example 2
On damp‐heat testing of the some CIGS products in the market
• The IEC61215‐1‐4 draft, which defines the new damp heat test standard for CIGS modules, requires a light soaking (LS) process before and after the damp heat test. Pass/Fail criteria are also changed from the current standard.
Then...
Light soaking effect of CIGS
Pmax@STC
Exposure time in field
Initial(Nameplate)
Change of Pmax by light soaking(sometimes takes years until maximum)
long‐term degradation
Damp heat test defined by the “old” IEC61215
Pmax@STC
Time
Initial(NamePlate)
decreased output(loss of light soaking effect+ real degradation) increased Pmax by light soaking in field
Damp heat testpass/fail decision
pass criterion
Original draft for IEC61215‐1‐4Pm
ax@STC
Time
(NamePlate)
Damp heat test
pass/fail decision
pass criterion
LS LS
Use Pmax after light soaking for pass/fail decision(not the nameplate value)
decreased output(loss of light soaking effect+ real degradation)
What actually happensPm
ax@STC
Time
(NamePlate)
Loss of LS effect+ “test‐specific degradation”
(not observed in field)
Damp heat test
pass/fail
pass criterion
LS LS
does not fully recover by LS(though no problems areobserved in real field)
Exploring the "right" test options for CIGS
5 types of tests below were performed with 170W-class CIGS modules.
* Performed at AIST. Others were performed at SF.**NMOT : Nominal Module Operating Temperature.
Test sequence2nd Pre-LS 1st Post-LS1st Pre-LS Test 1000hrs 2nd Post-LS
・Open-circuit state・Each LS process:1kW LS chamber for 21 hrs (SF) orOutdoor for one week (AIST)
・Open-circuit state・Each LS process:1kW LS chamber for 21 hrs (SF) orOutdoor for one week (AIST)
Normal DH
DH with forward bias
Test type
DH with irradiation
Normal dry heat test
Dry heat test with forward bias
ー
ー
0.1~0.65 Sun*
ー
ー
ー
ー
ー
Vpm@NMOT**Vpm@STC*
Vpm@NMOT**Vpm@STC*
Irradiation Bias
Wet
Dry
Experimental setup
Module temperature: 85℃Chamber humidity: 85 %r.h.
Module current : ~ 0.2 A(with NMOT‐Vpm, Tmod 85 ℃)
Test with forward biasTest with light irradiation
Module temperature: 85℃Module humidity: 85 %r.h. (raised the chamber humiditydepending on chamber temperature)
np
←
Current
np
(light) Current
Effect of light illumination
Test‐specificdegradation
illuminated
not illuminated
Compared to illuminated DH,DH in dark invokes a degradation not observed in field
Normalize
d Pm
ax
Initial(Light soaked)
Effect of light illumination + short‐circuiting (preliminary)
Short circuiting of modules → test‐specific degradation→ not the light, but forward bias voltage?
illuminated+short
illuminated
dark
Test‐specificdegradation
Normalize
d Pm
ax
Time
Initial(Light soaked)
Effect of forward bias + DampHeat(DH)/DryHeat(HT) tests
Bias voltage gives same results to light illuminationTest‐specific degradation does not depend on humidity
with bias voltage
without biasvoltage
Normalize
d Pm
ax
Damp heat test85℃ (module)
Damp: 95% r.h., Dry: <10% r.h.(chamber)
Initial(Light soaked)
Does the test‐specific degradation recover by loooong light soaking?Part 3. Experimental result
Normalized
Pmax (%
)
Test‐specificdegradation
~ 3+ %DH with NMOT‐Vpm (N =4)
DH without bias (N = 4)
Pre‐LS DH 1000 h Post‐LSOC‐LS OC‐LS Pmpp‐LS
Total Post‐LS :OC‐LS 42hrs
& Pmpp‐LS 126hrs
No, it does not
Summary
➣ Understanding of mechanism of test‐specific degradation.• Wavelength dependency of light• Work on other samples• Destructive analysis• etc.
➣ In the real field, high temperature is always accompanied with illumination&voltage.("Hot+dark" does not happen ‐‐ it's the MOST unnatural test condition!)
➣ The examined CIGS modules after DH with light irradiation or forward bias showed similarbehavior to real field. Meanwhile, conventional DH invoked “Test‐specific degradation”,which is not observed in field.
➣ Test‐specific degradation is irreversible by light soaking.
"DH+forward bias" option added to IEC 61215‐1‐4 (draft).
Homeworks
Mysteries➣ The cause of test‐specific degradation➣ Some other products show same behaviors, while some others do not
(private communications)
Important message
Over 50 IEC standards are being created or revised right now;Though people are working hard, mistakes can happen.Keep watch on the progress of IEC TC82 WG2!Next face‐to‐face meeting: October 2016, Colorado
Thank you for your attentionContact : k‐[email protected]
Backup: How to determine the chamber RH value
Chamber temperature (C)
Cham
ber R
H (%
)
➣ Chamber RH should be set to realize the module surface RH 85%.In case of our study, chamber temperature was set 84 C to realize the module temperature 85 C.Then, according to this graph, we set chamber RH 88 %.
The curve of chamber relative humidity as a function of chamber temperature can be plotted using Tetens’ formula:
85
6.11 10.
.
1100
RHMOD: Relative humidity of the module surface (= 85 %)e(85): Saturated vapor pressure at 85 °C (= 581 hPa)RHCHM: Relative humidity inside the chamberTCHM: Temperature of the chamber