See how individual factors affect the output of a solar cell.

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Solar Cell Coursework Experiment.

Aim: To see how individual factors affect the output of a solar cell.

Factors affecting the output of a solar cell:

This experiment is going to be performed in the confines of a school laboratory, and so the complexity and cost of the experiment(s) should reflect this. However, to see how different factors affect the solar cell output, I will need to perform at least two experiments. The question is, which ones?

  • Distance from the light source will affect the solar cell output, because intensity of light on the solar cell will decrease, the further away from the light the cell is. This is because many waves, including light, will travel away from the filament in a circular motion, not straight lines directly towards the solar cell, so the further away it is, the less rays will hit it.
  • A changing power to the light source, and therefore, to the solar cell, will affect the solar cell output. Theoretically, an increase in power at the light source should result in more energy being transferred to the solar panel, per second, resulting in a greater solar cell output.
  • The different colours of light would also affect the solar cell output, as each colour of light has a different frequency. We can tell this from Einstein’s theory of photons being directly proportional to frequency:

Energy = Planck’s constant x speed / wavelength

Different colours of light have the same speed, but different wavelengths, which, in the above equation, changes the value for energy, which is the solar cell output. And, because the wavelength is the denominator for this equation, we can make the statement, that ‘the larger the wavelength, the lower the energy’. A colour of light with a larger wavelength will result in a lower solar cell energy output.

The two factors that I am going to study in this experiment are:

  1. Changing power at the light source
  2. Distance of solar cell, from the light source

I have chosen these factors purely for ease of measuring the values of the energies involved, and for the (comparatively) low cost of the equipment required.

Studying the colours of light would have required lasers, specialised equipment and a very strictly controlled environment, which we can’t really get in school.

Prediction:

I predict that, the greater the power at the light source, the greater the solar cell output.

I also predict that, the further away the solar cell from the light source, the lower the solar cell output.

Hypothesis:

There must be a greater output at the solar cell if there is greater power at the light source, if the cell is the same distance away, because the intensity will be greater.

We know this through the equation intensity = power / area.

The power is a variable, but the area will stay the same because we are using the same solar cell throughout the experiment, and because power is the nominator in the above equation, we can say that ‘the greater the value for power, the greater the value for intensity’ of light upon the surface of the solar cell, and therefore, the greater the solar cell output.

Because this one changing variable is the only changing value and therefore the only one that influences the intensity, the power and solar cell output (dictated by the intensity of light upon the cell) must be proportional, giving the graph in fig.1.  

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The graph doesn’t go through the origin (0,0) because, at a very low voltage, the intensity of the light on the solar cell won’t be great enough for a reading to noticeably register on the cell’s milliammeter.

The further away from the filament the solar cell finds itself, the lower the solar cell output.

The reason for this is not that the individual light rays become greatly weaker than they were at the source because they have had to travel an extra few centimetres through the air, but that the light rays, collectively, become weaker at the surface ...

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