Last Friday, 2/17/12, my we discussed solar energy in class. We learned how solar cells function. The sunlight causes the two layers of n- type silicon (negatively charged) and p-type silicon (positive type) to react and cause the electrons between them to flow in a circuit and create electrical energy. However the energy is DC and needs to be converted to AC to be used for most household appliances.
For our lab we connected a small solar cell to some wires (voltage probe) which connected to our NXT adapter, which we plugged into the computer.
Our first trial we ran the lab-view program with no light sources directed at the solar cell. In fact we put it face down so hopefully, no light got in.
Next we turned on the light source and let the program measure how much energy(voltages) the solar cell created at 5 different distances from the light source This was done by moving the cell 30, 20, 10, and 5cm closer to the source.
| Distance | Volts |
| 0 | -0.03394 |
| 1 | 0.44719 |
| 5 | 0.243193 |
| 10 | 0.2804 |
| 20 | 0.018668 |
| 30 | -0.02752 |
Our hypothesis that the energy output would be highest closest to the light source and decrease as the light intensity decreased was supported by the results data collected by Excel.
We then moved on to filter the light source through different color film strips all at the fixed distance of 5 cm. The filters are a way to separate the light into different wavelengths. So which wavelength has the most power?
The order of our colored strips were: light pink, pink/red, yellow, orange and blue.
As you can see in the chart blue light generated the least voltages while “hot pink” generated the most.
Now excuse me if I am wrong, I am partially colorblind and I am having trouble finding it on the internet but as far as I can tell and it is my best guess, pink falls somewhere near violet which, in the light spectrum is on the farthest end of the radiation generating invisible wave spectrum, which create higher amounts of energy.If this is the case then it makes sense that pink would generate more power. However, looking at the light spectrum blue is next to violet and in the chart blue is generating the least voltages.
So clearly my theory is wrong or I am reading the chart wrong. Either way I am not sure what other conclusion to draw from the collected data, aside from the fact that you get more voltages from the cell the closer it is to a light source.
I like that your post about solar energy is very detailed and takes you step by step through the process. You also not only put the steps and outcome of the experiment, but you put your own hypothesis. The graph, data, and color chart, all are helpful in understanding the process as well.