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					ELEC1302: Solar Laboratory      Page 1           2009


   School of Electrical, Electronic and Computer
                    Engineering



           The University of Western Australia


ELEC1302

Power and Machines Technologies

Laboratory Notes: Solar Cell Characterisation

Dr. J. Henry




JH
ELEC1302: Solar Laboratory                Page 2                                      2009


Laboratory report format and assessment
Please note that a web-based on-line laboratory report writing tool should be used for
this laboratory.

This tool can be obtained at a later date (probably around 1st September 2009, you will
be informed via email and in lectures). You should print out a hard copy of the
laboratory for handing in along with a blue assignment sheet cover sheet and your
original results that you obtained in the laboratory session.

As a general guideline, the marking key is as follows:

Aim (1 mark)
Apparatus: refer to laboratory instructions. You should include a note on which set of
equipment you used.
Procedure: refer to laboratory instructions
Treatment of results (6 marks): Tabulate results where possible. Hint: Put your results
into an Excel spreadsheet (or similar) to help you with data processing.
Conclusions (2 marks): Answer the Aim!
Discussion (2 marks): Concise sentences commenting on errors, implications of results.
Presentation (2 marks)
Clarity of Explanations (2 marks)

• You should also attach the handwritten results that you obtained in the laboratory – so
this would be the hand-written results obtained WHILE YOU DID the laboratory. (If not
included: -2 marks)

• Ensure that you REFERENCE any resources that you use.

• The laboratory report will be due Thursday October 8th at 12noon and should be
handed in to the wooden assignment boxes on the first floor of the EE building. Late
laboratory reports will attract a 10% deduction for each working day that it is late. Marks
for reports will be sent out via email.

• A “blue” assignment cover sheet must be filled out, signed and attached. Reports
without this will not be marked and a mark of zero will be assigned.




JH
ELEC1302: Solar Laboratory                Page 3                                        2009


ELEC1302: Solar Energy Laboratory Experiment.
Apparatus:
Solar Module SEA005 of 31cm2 area
50 Watt bench lamp
Daystar light meter
2 digital multimeters
Lamp dimmer
Decade resistance box
0.25! resistor
dc power supply
Shielding box for dark measurements
Ruler
Set of stackable leads - 8

Procedure
Part 1: Measurement of light V-I characteristic of solar panel.
    1) Connect the light source to the dimmer.
    2) Switch on light source with the dimmer set fully clockwise to warm up.
    3) Set the distance of the light source to the measuring surface of the light meter to
        ~14 cm.
    4) Determine where on the dimmer scale 1 sun (100 mW/cm2) lies, 0.5 suns (50
        mW/cm2) and 0.25 suns (25 mW/cm2). Note these values.
    5) Set the dimmer so as to produce 0.25 suns on the solar panel. You will need to
        adjust the height of the lamp to be 14 cm above the face of the solar panel.
    6) Set up the circuit as shown below.

                                              V2




                                       shunt resistor


                 V1             solar panel                     variable resistor




Note: A voltmeter in parallel with a shunt resistor is used instead of an ammeter to
produce a more accurate set of measurements. An ammeter has a small resistance
associated with it and so will lead to inaccuracy in the high current part of the V-I
characteristic.

   7) Take readings of VOC and ISC.


JH
ELEC1302: Solar Laboratory                 Page 4                                         2009


   8) Varying the values of the variable resistor from 1! to 104! noting the values of
       V1 and V2. Take around 20 readings concentrating about half the readings around
       the high current/low resistance range. The maximum power point will occur
       around this region of the V-I characteristic. Try to take readings briskly as the
       characteristic of the solar panel changes as the panel heats up. If the panel is
       heating up too much place the cover between the light source and the solar panel
       and allow the panel to cool for a short period.
   9) Allow the solar panel to cool for 5 minutes
   10) Repeat Steps 1-9 for 0.5 suns.
   11) Repeat Steps 1-9 for 1 sun.

Part 2: Measurement of dark V-I characteristic of solar panel.
   1) Set up the circuit as shown below. Ensure that you start by connecting the
       positive side of the solar cell (red terminal) to the positive side of the power
       supply. This will ensure that the solar panel is forward biased.

                                          power
                                          supply



                  V              solar panel                A




   2) Cover the solar panel with a box so that there is no light induced effects while
      measuring the V-I characteristic.
   3) Vary the voltage on the power supply in approximately 250mV steps between 0V
      and 3.5V, noting the value of current. Warning: Excessive bias voltages will
      destroy the module.
   4) Reverse the leads at the power supply ie put the red lead into the negative
      terminal of the power supply. The solar panel will be reverse biased.
   5) Repeat step 3.

Treatment of results:
Part 1: Light V-I Characteristics
    1) Compare the values of VOC and ISC for 0.25, 0.5 and 1 sun. Comment on any
        relationship between the voltage values (eg linear decrease, etc). Comment also
        on the relationship between the current values.

   2) Plot the light V-I characteristics from 0.25, 0.5 and 1 sun on the SAME GRAPH.

   3) From your graph, or V-I data, calculate the i) maximum power point ii) fill factor,
      iii) efficiency for 0.25 sun. The maximum power point PMAX can be obtained


JH
ELEC1302: Solar Laboratory               Page 5                                    2009


       from the product V × I for your measurements. This will occur around the "knee"
       region of the curve when graphed. Knowing the input power and the cell area,
       calculate the efficiency of the panel for each of the intensity levels.

   4) Repeat 3 for 0.5 and 1 sun.

   5) Compare the values of maximum power point, fill factor and efficiency for 0.25,
      0.5 and 1 sun.

   6) From the shape of the graphs found in 2, try to determine whether the solar panel
      has a good/poor shunt resistance or a good/poor series resistance.

Part 2: Dark V-I Characteristics
    1) From the forward biased dark V-I characteristics, plot V-ln I. From this plot
        determine an estimate of the SERIES resistance. (See Point 5 in the Appendices)

   2) Plot the reverse biased dark V-I characteristic and determine the SHUNT
      resistance from the gradient of the plot.

   3) Comment on whether the results from 2 agree with your inferences from the light
      V-I characteristics.

Conclusions: Summarise the main points from your results.

Discussion
Write brief notes on the following points:
   1) Efficiency and maximum power and incident light level
   2) Variation with light input (problems of cloudy days, dawn/dusk) and need for
       storage.
   3) The magnitudes of the shunt and series resistances and their effects on cell
       performance.




JH
ELEC1302: Solar Laboratory               Page 6                      2009


Appendix: Further notes on solar cells

1) Circuit Model of a solar cell




2) V-I characteristics



                                           Dark Char.
                         Jo



                         Jlight                         Light Char




JH
ELEC1302: Solar Laboratory                     Page 7                             2009


3) Effect of Series and Shunt resistance on illuminated V-I Characteristic




4) • Fill Factor is the squareness of the output characteristics and is usually around

0.7 to 0.8 for reasonable cells.


                                                   VmpImp
                                            FF =
                                                   VocIsc

• Efficiency
                          maximum electrical power out
                       η= €
                               input optical power
                          P      Imp Vmp
                        = max =
                          Psun     Psun
                              Imp Vmp Isc Voc
                          =
                               Isc V   P
                              oc sun
                                     
                              fill factor
                                     Isc Voc
                          = FF
                                      Psun



               €




JH
ELEC1302: Solar Laboratory                   Page 8                                     2009


5) Obtaining the Series Resistance from the DARK V-I characteristic.

From your dark V-I results, plot the ln I versus V. Use mA and mV respectively.

Your curve should look like the one given below.
 ln I (mA)                       Line 1
           Line 2
lnI1
                               ΔV




                                        V (mV)

- Draw a line similar to the one shown (Line 1).
- Draw a horizontal line which intersects with Line 1 and the lnI-V characteristic (Line
2). Take this line back to the vertical axis – antilog the value of lnI1 – this gives you’re
an I value.
- Next calculate ΔV as indicated on the diagram.
                                           ΔV
- Use the following to calculate Rs: R s =
                                            I1

Note: You may find your diagram looks like the one below, draw Line 1 as shown and
follow same instructions as above. This lnI-V characteristic indicates a large series
resistance.              €


  ln I (mA)                         Line 1


          Line 2
lnI1


                             ΔV


                                        V (mV)




JH

				
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