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Sunpower C60 IV Curve Characterization
2013 09 04Peter Sun & Ahthavan Sureshkumar
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Motivation
Improving accuracy of array simulation results Creating a calibrated pyranometer Understanding net consequences of array cut
decisions and lamination Understanding relationship of angle
dependence of solar cell-lamination combination
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Test Plan
Measure Sunpower C60 IV curves at a site of known irradiance, at 15min intervals
Orient 2 cells towards the sun to eliminate angle dependence, results to be averaged
Compare results between oriented horiz. oriented cell and oriented cells
Orient all 3 cells horizontally to determine statistical variation between cells
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C60 Manufacturer SpecificationsSunpower provides specifications for a full, bare cell, at standard testing conditions.
The published expected IV curves are most likely simulated.
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Differences
Lamination {Peter please elaborate}
Size New rectangular size:
31.75 x 125 mm Decrease in area-to-
perimeter results in degradation of performance
32.57mm2:1mm to 12.66mm2:1mm
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Expected Results
Modeling a PV cell using the below equation, as per The Winning Solar Car, the following dependencies are: Rs, Rsh = f(Voc, Isc) IL, IS = f(n, Voc, Isc)
If power/current prop. to size only, then at STC, new peak power, peak current, short-circuit current per cell: 0.86 W 1.51 A 1.62 A
IL potential current sunlight createsIS diode saturation currentRSH shunt resistanceRS internal series resistancen model parameter
(1.5 for silicon cells)
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Testing Location
UTM gratefully allowed us access to pyranometer readings at their local meteorology station, as well as gain access to the local vicinity to correlate PV measurements with locally measured irradiance values.
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UTM
Testing Location
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Externalprogramming
input
Setup
HP 6060BElectronic Load
+ -
Sourceinputs
CurrentSensingoutput
PVCustom
waveform generator
-
+
clip
Laptop Oscilloscope
Ch A Ch B
PV
-
+
USB
USB Input
Output
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Setup
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Controlling the Electronic Load A programmable input in the
back of the HP 6060B electronic load allows the user to control the current going through the 6060B whilst in Constant Current mode.
Any waveform generator can be used. The particular waveform generator, the Syscomp CGR-101, can only output up to 3V. The 6060B will scale the input voltage using a 0.6 scaling factor if the range is specified to be 6A
0
0.5
1
1.5
2
2.5
0 0.5 1 1.5 2
Curr
ent (
A)
Time(s)
Constant Current Control
A sawtooth waveform between 0-3V was defined, to enable a sweep of current through the PV cell.
The current will be limited by the current that the PV can output, regardless of the current setting.
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RESULTS SINGLE, HORIZ. CELL
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-2 -1.5 -1 -0.5 0 0.5 1 1.5 2
1.16
1.18
1.2
1.22
1.24
1.26
1.28tek0066ALL.csv
Time (s)
Vol
tage
(V)
-2 -1.5 -1 -0.5 0 0.5 1 1.5 2-0.1
-0.05
0
0.05
0.1
0.15
0.2
0.25
0.3tek0066ALL.csv
Time (s)
Cur
rent
(I)
1.15 1.2 1.25-0.1
-0.05
0
0.05
0.1
0.15
0.2
0.25
0.3
tek0066ALL.csvn value = 1.650287e+03
Voltage (V)
Cur
rent
(A)
Only measured a fraction of the entire IV curve
Electronic load was providing weak signals.
Unfortunately, majority of collecteddata was not useful.
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-2 -1.5 -1 -0.5 0 0.5 1 1.5 2-0.2
0
0.2
0.4
0.6
0.8
1
1.2tek0072ALL.csv
Time (s)
Cur
rent
(I)
-2 -1.5 -1 -0.5 0 0.5 1 1.5 20
0.1
0.2
0.3
0.4
0.5
0.6
0.7tek0072ALL.csv
Time (s)
Vol
tage
(V)
Correction made, but clouds rolled in conveniently. A few measurements were made, but could not be correlated to irradiance values since irradiance values are averaged over 15min intervals, and irradiance fluctuated greatly.
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0 0.1 0.2 0.3 0.4 0.5 0.6 0.7-0.4
-0.2
0
0.2
0.4
0.6
0.8
1
1.2
tek0072ALL.csvn value = 2.09429
Voltage (V)
Cur
rent
(A)
n=1
n=1.5n=2
Filtered
Raw data
IV curve w/ arb. n-value
IV curve w/ fitted param.
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0 0.1 0.2 0.3 0.4 0.5 0.6 0.7-0.4
-0.2
0
0.2
0.4
0.6
0.8
1
1.2
tek0069ALL.csvn value = 2.08055
Voltage (V)
Cur
rent
(A)
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7-0.4
-0.2
0
0.2
0.4
0.6
0.8
1
1.2
tek0072ALL.csvn value = 2.09429
Voltage (V)
Cur
rent
(A)
Orientation: HorizontalSunlight: Bright (irradiance unknown)Params:-Voc: 0.6138 V-Isc: 1.1463 A -n: 2.0805
Comment: Sporadic, intensity sunlight allow us to acquire this data. Note the high n-value as compared to 1.5 typically assumed for a silicon cell.
Results on right is variable due to variable sunlight.
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-0.4 -0.2 0 0.2 0.4 0.6 0.8 1 1.2-0.2
-0.1
0
0.1
0.2
0.3
0.4
0.5
tek0069ALL.csvPmax = 0.450849 W, Imax = 1.00189 A, Vmax = 0.45
Current (A)
Pow
er (W
)
-0.4 -0.2 0 0.2 0.4 0.6 0.8 1 1.2-0.2
-0.1
0
0.1
0.2
0.3
0.4
0.5
tek0072ALL.csvPmax = 0.424867 W, Imax = 0.944148 A, Vmax = 0.45
Current (A)
Pow
er (W
)
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2-CELL STRING
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-2 -1.5 -1 -0.5 0 0.5 1 1.5 20.4
0.5
0.6
0.7
0.8
0.9
1
1.1
1.2
1.3tek0068ALL.csv
Time (s)
Vol
tage
(V)
-2 -1.5 -1 -0.5 0 0.5 1 1.5 2-0.2
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6tek0068ALL.csv
Time (s)
Cur
rent
(I)
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0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 1.3-0.2
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6tek0068ALL.csv
Voltage (V)
Cur
rent
(A)
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0 0.2 0.4 0.6 0.8 1 1.2 1.4-0.2
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8tek0071ALL.csv
Voltage (V)
Cur
rent
(A)
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-0.2 0 0.2 0.4 0.6 0.8 1 1.2 1.4-0.1
-0.05
0
0.05
0.1
0.15
0.2
0.25
0.3
tek0073ALL.csvn value = 1.86641
Voltage (V)
Cur
rent
(A)
-0.05 0 0.05 0.1 0.15 0.2 0.25 0.3-0.1
-0.05
0
0.05
0.1
0.15
0.2
0.25
tek0073ALL.csvPmax = 0.190549 W, Imax = 0.200578 A, Vmax = 0.95
Current (A)P
ower
(W)
Attempted to model IV curve from 2 cells just to be able to generate estimate of peak power.
This was taken during shady conditions, so the SNR was low and the resulting power is very low.
Sunpower C60 IV Curve CharacterizationMotivationTest PlanC60 Manufacturer SpecificationsDifferencesExpected ResultsTesting LocationTesting LocationSetupSetupControlling the Electronic LoadRESULTS Single, Horiz. cellSlide Number 13Slide Number 14Slide Number 15Slide Number 16Slide Number 172-cell stringSlide Number 19Slide Number 20Slide Number 21Slide Number 22