This week, we worked on and learned about solar energy and photovoltaics.

“Photovoltaics is the direct conversion of light into electricity at the atomic level.

The diagram below illustrates the operation of a basic photovoltaic cell, also called a solar cell. Solar cells are made of the same kinds of semiconductor materials, such as silicon, used in the microelectronics industry. For solar cells, a thin semiconductor wafer is specially treated to form an electric field, positive on one side and negative on the other. When light energy strikes the solar cell, electrons are knocked loose from the atoms in the semiconductor material. If electrical conductors are attached to the positive and negative sides, forming an electrical circuit, the electrons can be captured in the form of an electric current — that is, electricity. This electricity can then be used to power a load, such as a light or a tool.”

In our lab experiments, we looked at the voltage output of the solar cells and the light intensity output of the light sensor (in some cases flashlights) of the NXT. We then performed two  experiments whereby in our first experiment our independent variable was source of light (voltage output) and our dependent variable was distance from the source (light intensity)and in our second experiment our independent variable was distance form the source of light (light intensity) and our dependent variables were select colored film filters (voltage output).

 

Equipment:

• One solar cell
• One voltage probe
• One NXT adaptor
• NXT with light sensor
• One light source
• Labview VI  solarlab1.vi
• Ruler
• Colored film filters
• Excel sheet

For the first experiment, we first placed the flash light immediately over the solar cell (distance 0) and then ran the NXT programme. The programme produced 10 numbers that measured the light intensity. Then, we did the same thing, only this time using a ruler, set the flash light 3cm above the solar cell (furthering away the intensity of the light to the solar cell) and ran the NXT programme again. We performed this same task, each time changing the distance to a greater number.

This first Excel chart shows the relationship between the light intensity and the distance from the source of light (in our case a flashlight).

Because the numbers are so miniscule, I calculated the averages for each column and plotted out the averages. Below is a visual scatter plot to show the correlation between the two.

 

Scatter Plot of Averages for Distance