Modeling Metal Fatigue As a Key Step in PV Module Life ... · 2 outline • Modeling metal fatigue...
Transcript of Modeling Metal Fatigue As a Key Step in PV Module Life ... · 2 outline • Modeling metal fatigue...
NREL is a national laboratory of the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, operated by the Alliance for Sustainable Energy, LLC.
Modeling Metal Fatigue As a Key Step in PV Module Life Time Prediction
NREL PVMRWNick BoscoFebruary 28 2012NREL/PR-5200-54565
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outline
• Modeling metal fatigueo Time independent (case studies):
– Ribbon fatigue: wind loading– Ribbon fatigue: thermal loading
o Time dependent, solder fatigue
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ribbon fatigue: wind loading
prediction
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ribbon fatigue: wind loading
Assmus, M., S. Jack, et al. (2011). "Measurement and simulation of vibrations of PV‐modules induced by dynamic mechanical loads." Progress in Photovoltaics: Research and Applications 19(6): 688‐694.
low freq:3mm200/day
high freq:6 μm50 Hz
driving force
wind speed (m
/s)
Defle
ction (m
m)
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ribbon fatigue: wind loading
θ R
Lh
L+ΔL
low freq: 3 mm = 0.00107 %high freq:6 μm = 4.27e‐9 %
Assumptions: Pinned connections Semicircular bending Glass‐Glass module No shear lag 1620x810 mm
driving force
L L R
R h2 L
2
8h L
2sin 2
LL
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ribbon fatigue: wind loadingmechanism: fatigue experiment
load “cool” cycle
Grips fabricated to simulate ribbon attachment
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pl2
f 2N f c
el2
f
E2N f b
moderibbon fatigue: wind loading
strain amplitudes evaluated likely have a large plastic component
a longitudinal strain is imposed, but the ribbon is straining in bending
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ribbon fatigue: wind loadingmode
pl2
f 2N f cvibration due to wind loading will not result in ribbon fatigue within a module’s lifetime.
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ribbon fatiguefatigue experiment: off‐set
incorporating an un‐soldered length provides strain relief and longer lifetimes
ribbon constraint is a significant factor for these measurements
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ribbon fatigue: thermal loading
prediction
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ribbon fatigue: thermal loading
prediction
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Tcell Tamb E exp a b WS E T1000
Tcell t 1 Tcell t Tcell t 1 1
ribbon fatigue: thermal loadingdriving force
cell temperature is evaluated in one‐minute intervals
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ribbon fatigue: thermal cycling
Meier, R., F. Kraemer, et al. (2010). Reliability of copper‐ribbons in photovoltaic modules under thermo‐mechanical loading. Photovoltaic Specialists Conference (PVSC), 2010 35th IEEE.
A1 B1T B2T2
driving force
empirical relationship between temperature change and ribbon strain
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identify peaks extract ΔT
N f a
1 c
A1 B1T B2T2 D 1
N f ,ii
n
calculate strain calculate cycles to failure convert to damage
temperature history
mechanismribbon fatigue: thermal loading
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mode100% = failure
1yr
ribbon fatigue: thermal loading
20 yr lifetime
50 yr lifetime
ribbon fatigue due to thermal loading may cause failure within a module’s lifetime.
leaving an unsoldered length will extend the ribbon’s lifetime.
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creep‐fatigue
pl2
f 2N f c
dp
dt Aexp
QRT
sinh
s
1 m
sh
dp
Adtexp Q
RT
n
sinh1 dp
Adtexp Q
RT
m
s* s pl,eqAexp Q
RT
n
D Wpl dpl
Time independent
Time dependent
Deformation mechanism map. (After M. F. Ashby and D. R. H. Jones, Engineering Materials I: An Introduction to Their Properties and Applications, 2d ed., Butterworth‐ Heimann, 1996)
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simulations and analysis
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0
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100
150
0 50 100 150 200 250 300 350
TCA-1TCA-2TCA-3
tem
pera
ture
(C)
time (minutes)
TCA‐1 TCA‐2 TCA‐3
Tmax C 85 110 65
Tmin C ‐40 ‐40 ‐40
tc (min) 100 100 100
td (min) 10 10 10
simulation results
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0.2
0.4
0.6
0.8
1
0 20 40 60 80 100
FEM-TCA1FEM-TCA2FEM-TCA3C-M Es Ec
norm
ailz
ed d
amag
etime (minutes)
FEM : empirical relationships
Empirical relationships may be effective for relating the damage done by various ALT
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simulation
simulations and analysis
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10
20
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0 50 100 150 200 250 300 350 400
tem
pera
ture
(C)
time (minutes)
∆Tm
0
10
20
30
40
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60
70
0 10 20 30 40 50 60 70 80in
elas
tic s
train
ene
rgy/
cyc
le (P
a)cycles
Di
Df
results
FEM is required to simulate temperature changes due to weather
NREL is a national laboratory of the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, operated by the Alliance for Sustainable Energy, LLC.
Comparison of accelerated testing with modeling to predict lifetime of CPV solder layers
2012 PV Module Reliability Workshop
Timothy J Silverman, Nick Bosco, Sarah Kurtz
Mar. 1 Afternoon II – Modeling of CPV Reliability Issues
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conclusions
• Modeling metal fatigue– Consider driving force and mechanism– Testing must represent service
• Cu ribbon fatigue– Wind loading is likely inconsequential– Thermal loading is significant
• May be mitigated by proper ribbon routing• Ribbon shape and constraints are important
• Solder fatigue– Time dependency complicates modeling– Empirical models may relate ALT, but not service
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Sample Text and Object Slide with Bar