2014 pv performance modeling workshop: irradiance- and temperature-dependent pv module performance...
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2014 PV Performance Modeling Workshop: Irradiance- and Temperature-dependent PV Module Performance Measurement: Rajeev Singh, PV Evolution LabsTRANSCRIPT
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Irradiance- and
Temperature-dependent
PV Module Performance
Measurement Rajeev Singh, John Watts
2014 PV Module Performance Modeling Workshop
May 5, 2014
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Review of IEC standards specifying temperature-dependent PV
module performance measurement
Issues with outdoor measurement of temperature coefficients
Indoor vs. outdoor measurements
Variables of irradiance- and temperature-dependent PV module
performance measurements
PVEL’s indoor measurement approaches
WHY IS THERE VARIABILITY? Outline
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Standards specify linear reference devices to
set/determine irradiance
Spectral control or correction is required
WHY IS THERE VARIABILITY? IEC Standards: Irradiance
Standard Stated Purpose Indoor / Outdoor
Simulator Class
Irradiance Reference
Spectral Correction
IEC 60904-1 2006 I-V Measurement
Both BBB
Linear Yes
IEC 60891 2009 G & T Corrections to I-V Linear Yes
IEC 61853-1 2010 PMAX(G,T) Linear Yes
IEC 61215/61646 2005 Module Qualification Linear Do not alter
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Standards insufficiently specify temperature control methods and
their caveats
Poor harmony regarding temperature measurement approach
Cell temperature measurement methods are not discussed
In-plane temperature uniformity is specified in only one instance
WHY IS THERE VARIABILITY? IEC Standards: Temperature
Standard Year Stated Purpose Indoor / Outdoor
Simulator Class
Temperature Control
Guidance
Measurement Method
Number of Sensors
Sensor Location
(Backsheet or Cell)
Temperature Uniformity
Requirement
IEC 60904-5 2011 Equivalent Cell Temperature (ECT)
Both BBB None
VOC and β N/A N/A No
IEC 60904-1 2006 I-V Measurement Sensor or ECT ? ? No
IEC 60891 2009 G & T Corrections to I-V Sensor 4 (Averaged) ? ± 2 °C
IEC 61853-1 2010 PMAX(G,T) Sensor or ECT 3 (Averaged) ? No
IEC 61215/61646 2005 Module Qualification Sensor ? ? No
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WHY IS THERE VARIABILITY? Outdoor Backsheet-referenced
Temperature Coefficients Measurement
RBS: Thermal resistance of back-side
EVA, backsheet
∆𝑇 = 𝑄𝑅𝑡ℎ
20
30
40
50
60
0 5 10 15 20 25 30 35 40
Backsheet Temperature (°C)Cell Temperature (°C)
Tem
pera
ture
(°C
)Measurement Time (arb.)
Results in overestimation
of temperature coefficient
magnitudes
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WHY IS THERE VARIABILITY? Outdoor Measurement of
VOC(T) – Beta (β)
-0.9
-0.8
-0.7
-0.6
-0.5
-0.4
-0.3
-0.2
-0.1
1 N
o B
ox
2 N
o B
ox
3 N
o B
ox
4 N
o B
ox
1 T
herm
al B
ox
2 T
herm
al B
ox
3 T
herm
al B
ox
4 T
herm
al B
ox
Outdoor Measurement Results
Cell ProbeBS Probe 2BS Probe 3BS Probe 4BS Probe 5
Mea
sure
d (
%/°
C)
Trial
Backsheet view of test module temperature probe locations
Cell probe (CP) is a hypodermic thermocouple needle inserted underneath backsheet and contacting cell busbar
Backsheet (BSx) probes are standard thermocouples adhered to backsheet using Kapton (polyimide) tape
CP
2
3
5 4
J-BOX
In-plane temperature uniformity
is poor
𝑑𝑇
𝑑𝑡𝑥, 𝑦 varies with position
VOC(T) is often nonlinear
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Indoor Flash Test Good in-plane temperature
uniformity
Steady-state
Stable irradiance
Uncollimated light
Non-uniform irradiance
Class A+: ≤ 1 %
Not AM1.5
Class A+: ± 12.5 %)
WHY IS THERE VARIABILITY? Indoor Flash Testing vs. Outdoor
Outdoor Poor in-plane temperature
uniformity
Not steady-state
Possibly stable irradiance
2-axis tracker
Collimated light
Uniform irradiance
Possibly AM1.5
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Irradiance-dependent
Constant spectrum
throughout range
Neutral density filters
Constant bulb power
Power accuracy
Linear feedback
WHY IS THERE VARIABILITY? Specific Lab. Measurement Variables
Temperature-dependent
In-plane uniformity
Controlled environment,
flash tester
Steady-state
Controlled environment,
flash tester
Measurement location
Cell temperature probe or
isothermal conditions
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WHY IS THERE VARIABILITY? Indoor Measurement Techniques
Cell temperature probes
Exposed optical surface
In-plane uniformity: ± 2 °C
Back-side Heating Uniform Heating
Backsheet temperature probes
Glass window
In-plane uniformity: ± 0.5 °C
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WHY IS THERE VARIABILITY? Irradiance Control
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
0 200 400 600 800 1000 1200
Resid
ua
l (%
)
Irradiance (W/m2)
IEC 61853-1 ISC Residuals
Irradiance sensor (feedback)
calibrated at 1000 W/m2
IEC 60904-10: < 2 % non-linearity
PVEL: < 1 % non-linearity at all
temperatures and throughout
irradiance range
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WHY IS THERE VARIABILITY? Temperature Control
8.05
8.1
8.15
8.2
8.25
8.3
20 25 30 35 40 45 50 55
PVEL Measurement of Scheuten Multisol P6-54c
Isc(T)
y = 7.9475 + 0.0055727x R= 0.99953
Isc (
A)
Temperature (°C)
20
30
40
50
60
0 50 100 150
BS #1BS #2BS #3BS #4BS #5C
Te
mpe
ratu
re (
°C)
Time (minute)
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IEC measurement standards acceptably address irradiance-
dependent measurements but do not provide adequate
treatment of temperature-dependent measurement
consideration
Outdoor measurement accuracy is difficult to achieve
PVEL has developed in-house methods to improve
temperature-dependent measurement accuracies
PVEL’s temperature coefficients measurements indicate that
datasheet coefficients are overestimated in magnitude
PVEL’s state-of-the-art measurement system will be online in
May 2014
Compare back-side heating method to isothermal chamber system
Conclusions
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Thank You