Sunpower C60 IV Curve Characterization

2013 09 04Peter Sun & Ahthavan Sureshkumar

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

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

C60 Manufacturer SpecificationsSunpower provides specifications for a full, bare cell, at standard testing conditions.

The published expected IV curves are most likely simulated.

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

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)

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.

UTM

Testing Location

Externalprogramming

input

Setup

HP 6060BElectronic Load

+ -

Sourceinputs

CurrentSensingoutput

PVCustom

waveform generator

-

+

clip

Laptop Oscilloscope

Ch A Ch B

PV

-

+

USB

USB Input

Output

Setup

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.

RESULTS SINGLE, HORIZ. CELL

-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.

-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.

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.

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.

-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

)

2-CELL STRING

-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)

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)

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)

-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