Download Practical Activities with Photovoltaic Panels

Investigating the Characteristics of a Solar Panel - Practical Notes
Saverio Ciccone
Overnewton Anglican Community College
Prior to undertaking experiments with solar panels it is useful to undertake an experiment to investigate the
current, voltage and power output of a dry cell battery, as a source of limited output. This will enable students to
be more insightful about the output of a solar panel
Current-Voltage Characteristics of a Dry Cell
Equipment and Method (per group)






1 new and 1 old 9V drycell batteries
5 leads
Voltmeter (or multimeter)
Ammeter (or multimeter)
Potentiometer (Variable resistor - 0-25 
Switch (optional)
Do not take long in the conduct of the practical as the internal resistance of the battery may increase – we want
this to be a controlled (constant) parameter.
1.
You will need the following equipment to be set up as follows (use the new drycell)
Ammeter – series
connection
Voltmeter –
parallel
connection
9V – battery nominal
0 – 25 ohm variable resistor
Use the middle and an
end terminal for
connections
2.
Turn the axle of the resistor so that the voltage changes by 0.5 V approximately each time and
record the current and voltage pairs.
Repeat for an old 9V battery
3.
Import your data into a spreadsheet for fast manipulation.
Col A
Col B
Col C
Voltage
V
current
A
power
W
Col D
External
resistance
ohms
Analysis
1.
Determine the power supplied by the battery (watts, W) and the external resistance (variable resistor
value in ohms,  by programming the spreadsheet columns C and D
Note
Power (W) =
Voltage (V)
Var. resistor value (
x Current (A)
Voltage (V)
Current (A)
= col A x col B
= col A ÷ col B
2.
Plot a graph of the current vs voltage and comment on the relationship between the two.
3.
Plot a graph of the Power vs voltage and comment on the relationship between the two. At what
voltage is the maximum power delivered and how does this voltage compare to the open-circuit
voltage (x-intercept)value ?
4.
Plot a graph of the Power (W)
the two. At what external resistance is the maximum power delivered?
New 9V
current
A
0.291
0.307
0.322
0.337
0.345
0.358
0.379
0.402
0.419
0.437
0.457
0.475
0.494
0.526
0.551
0.598
0.748
0.868
0.963
1.021
1.089
1.182
1.305
1.589
New 9V Battery Current (A) vs Voltage (V)
1.8
1.6
current (A)
1.4
1.2
1
0.8
0.6
0.4
0.2
0
0
1
2
3
4
5
6
7
8
voltage (V)
New 9V - Power (W) vs voltage (V)
4.50
4.00
3.50
power(W)
Voltage
V
7.49
7.41
7.34
7.25
7.2
7.13
7.04
6.93
6.84
6.75
6.63
6.53
6.43
6.27
6.15
5.93
5.35
4.86
4.31
4
3.51
3.03
2.27
0.71
3.00
2.50
2.00
1.50
1.00
0.50
0.00
0
1
2
3
4
5
voltage (V)
Power (W) vs ext resistance (ohms)
4.50
4.00
power (W)
3.50
3.00
2.50
2.00
1.50
1.00
0.50
0.00
0.00
5.00
10.00
15.00
resistance (ohms)
20.00
25.00
30.00
6
7
8
Old 9V
Current
A
0.033
0.028
0.025
0.023
0.021
0.019
0.017
0.015
0.014
0.013
0.013
Old 9V - Current (A) vs Voltage (V)
0.035
0.03
current(A)
0.025
0.02
0.015
0.01
0.005
0
0
0.05
0.1
0.15
0.2
0.25
0.3
voltage(V)
Old 9V - Power (W) vs Voltage (V)
0.0050
0.0045
0.0040
0.0035
Power (W)
Voltage
V
0.01
0.05
0.08
0.1
0.13
0.21
0.24
0.27
0.31
0.33
0.34
0.0030
0.0025
0.0020
0.0015
0.0010
0.0005
0.0000
0
0.05
0.1
0.15
0.2
voltage (V)
0.25
0.3
0.35
0.4
0.35
0.4
Current-Voltage Characteristics of a Solar Panel
You will need the following equipment:
 Sunlight or a desk/lamp on a day where it is cloudless
 a photovoltaic cell/solar panel
 a voltmeter, ammeter
 light meter (measuring in watts per sq. m is preferable – some schools will have a lux meter instead)
 potentiometer (with 10 ohm protective resistors) as follows
Source of light
Sun light - maximum brightness (≈ 1000 W/m2)
Sun light – half sun brightness(dull) (≈ 500 W/m2)
Desk lamp
Variable resistor required
(0 – 50 ohm) or possibly (0 – 100 ohm)
(0 – 250 ohm) or possibly (0 – 500 ohm)
(0 – 1k ohm) or possibly (0 – 10k ohm)
Use a 10 ohm protective resistor in series with the variables so they don’t overheat and burnout under
high power output.
Method
PART A
 The experiment should be done outside under constant temperature and sunlight conditions – ie no
clouds
 The experiment should also be performed quickly to avoid overheating of the panel that may then
change the characteristics during the data-collection
 Make sure that you don’t cast any shadows or reflections over the panel during the experiment.
 Set-up the circuit below (using the middle and either of the outer pins of the variable resistor) in area of
maximum sun
voltmeter
variable resistor
panel




10 ohm
res
ammeter
Once you have fixed the panel it is NOT TO BE MOVED DURING THE EXPERIMENT.
Record the sunlight intensity using the light meter (in W/m2) by holding its face parallel with the face of
the panel.
Turn the axle of the variable resistor so that you can record current and voltage pairs increasing at
approximately
1 V intervals. Include uncertainties.
Determine the short-circuit current by removing the variable resistor from the circuit and measuring the
current under no load. Check that the voltage is ZERO for this measurement and add this data to your
table.


Determine the open-circuit voltage by measuring the panel voltage without the load - connecting only the
voltmeter across the panel – ZERO current.
Measure the dimensions of the panel face or a cell so as to determine its area in m 2 (include
errors of course)
PART B
 Repeat for a position where the panel faces away from the sun.
Analysis
Enter the data on a spreadsheet as follows:
Panel/Load voltage (V)
1.
2.
3.
4.
5.
6.
Current output (A)
Power output (W)
Load resistance (ohms)
Enter your data onto a spreadsheet with the voltage column first according to the table above.
For each current-voltage pair determine the power developed by the solar panel by using the
spreadsheet (P=VI)
For each current-voltage pair determine the load resistance developed by the solar panel by using
the spreadsheet. (R=V/I)
Plot the current (A) (y-axis) vs voltage (V) (x-axis) and power (W) (y-axis) vs voltage (V) for all 3
trials – by producing an XY scatterplot- including error bars. You should have separate graphs with
each graph showing the current and power developed vs voltage.
Locate the maximum power points produced by the panel by determining the maximum power
points for each of the sets of data using the graphs that you have generated.
– determine the voltage, current, power and circuit resistance at the maximum power point.
Determine the maximum power supplied to the panel by the sunlight as follows:
Power Supplied by Sun = Irradiance (W/m2) x panel area (m2)
Questions
1.
Compare the voltage (V) vs current (A) graphs for each panel position and note any differences.
2.
Compare the different maximum powers, voltages, currents and external resistances for the different
panel positions and comment on their comparison.
3.
Comment on how power output is affected by the external resistance loaded to a solar panel.
4.
Calculate the maximum output efficiency for each part as follows:
Maximum efficiency (%)
=
Maximum power output of panel(W) x 100
Power supplied by the Sun(W)
Comment on the significance of the size of the efficiency.
Solarex Panel - current (A) vs voltage (V) - 843 W/sq m irradiance - 100 ohm var res
0.650
0.600
0.550
0.500
0.400
0.350
0.300
0.250
0.200
0.150
0.100
0.050
0.000
1
2
3
4
5
6
7
8
9
10 11 12 13 14 15 16 17 18 19 20 21
Voltage (V)
Power(W) vs Voltge (V) - Solarex Panel - 843 W/sq m - 100 ohm
var res
8
7
6
Power(W)
0
5
4
3
2
1
0
0
5
10
15
20
voltage(V)
Power(W) vs Ext Load (ohms) - Solarex Panel - 843W/sq m
8
7
6
power(W)
current (A)
0.450
5
4
3
2
1
0
0
100
200
300
ext res (ohms)
400
500
600