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Investigation on Photovoltaic Cells

Extracts from this document...

Introduction

PHYSICS COURSEWORK                                                           PAVAN AULAK 11AV

PHYSICS COURSEWORK                                                          PAVAN AULAK 11AV

Investigation on Photovoltaic Cells

Research

Electricity is the flow of negatively charged particles called electrons. Photovoltaic (PV) cells, also known as solar cells convert sunlight directly into electricity. These cells are made by materials called semiconductors; the most commonly used material is silicon. When a light source hits the cell, a certain amount of it is absorbed within the semiconductor material. The energy of the absorbed light is then transferred to the semiconductor. The light energy knocks the electrons which make them loose; this then allows them to flow freely. PV cells have one or more electric fields, this helps to force the loose electrons to flow in a certain direction. This flow of electrons has now become a current. The current can now be used as electricity, for example for a calculator. By attaching metal contacts to the cells the current can be used externally. The two factors which define the wattage that the solar cell can produce are: the current and the cell’s voltage. The voltage is depends on the amount of electric fields built in. Sunlight is composed of particles of solar energy (photons). These photons contain various amounts of energy which depend on the different wavelengths of the solar spectrum. When a photon hits the surface of the cell, it penetrates into the semi-conductor which is usually silicon until it is absorbed. When photons strike a PV cell, one of three things can happen; they can be reflected or absorbed or they can pass straight through. Only the absorbed photons generate electricity. Electrical properties of the PV cell such as the built in electric magnetic field provide the voltage needed to drive the current through an external source such as a light bulb.

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Middle

8

0.48

0.49

0.48

0.48

12

0.26

0.25

0.26

0.26

16

0.29

0.28

0.27

0.28

20

0.35

0.35

0.34

0.35

24

-

-

-

-

42

-

-

-

-

54

-

-

-

-

Whilst carrying out my preliminary experiment I noticed that my results were not following a pattern and were uneven. I realised that the reasons why my results were not forming a sequence because I was using different solar cells. Each solar cell acts as a battery, this means that the solar cell may work differently to another. The voltage was changing at uneven rates which were not showing a regular sequence. My results were not consistent because I was using a different solar cell which meant that it was not a fair test. To ensure that my test was fair as possible I made the following changes:

  • I decided to use one solar cell with a surface area of 54cm². I chose to cover parts of the solar cell with black paper so that I could increase the exposed surface area. As I would not be changing my apparatus the test would be fair.
  •   I also drew an ‘X’ on the table so when I was changing the paper I would put the solar cell back in the same position on the table.
  • I also drew around the solar cell on the table so I would put it back in the same place.
  • I also changed how long I would wait to take the reading. In my original method I decided 5 seconds but changed this to 10 seconds so the reading would have longer to set.
  • I also changed the various surface areas I was measuring. I decided to go up equally by 4cm².By changing the surface area equally I will be able to pick up on any patterns more easily.

(Setup of experiment)

image04.jpg

Actual Results:

Surface Area (cm²)

Voltage (V)

Test 1

Test 2

Test 3

Average

4

0.23

0.23

0.23

0.23

8

0.34

0.34

0.34

0.34

12

0.38

0.38

0.38

0.38

16

0.40

0.39

0.39

0.39

20

0.42

0.42

0.42

0.42

24

0.43

0.43

0.43

0.43

28

0.44

0.44

0.44

0.44

32

0.42

0.45

0.43

0.43

36

0.42

0.44

0.44

0.43

40

0.43

0.43

0.44

0.43

Interpretation

image02.png

 (See graphs).  

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Conclusion

 To further my investigation I would look at larger surface areas to make my conclusion more certain. If I extrapolated straight from my graph the measurements would stay level but if I continued the investigation in reality the voltage produced would increase. Overall, I believe that my investigation was a success.         

References to my research:

  • http://www.greenspec.co.uk/html/energy/pvcells.html
  • http://science.jrank.org/pages/5203/Photovoltaic-Cell-How-they-work.html
  • http://www.solarage.co.uk/PV.htm

...read more.

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