Schools Raise the Roof on Solar Energy

Re: Schools Raise the Roof on Solar Energy

On a recent day, Bertelsen's students were using meters to gauge the changes in volts and amps as artificial light moved farther away from the CD-case-sized solar wafers at their desks.

"So at 3 inches, we're at 5 volts," Chatfield senior Sebastian Goff said. "Let's check it at 6 inches."

After a few more measurements, a few hot fingers, and a few false starts, the pattern was clear:

"There's a direct relationship with the amps," Hoff said. "Twice the distance means half the amps."

"But the voltage doesn't change much no matter what the distance," said Brian Hoover.

One of the problems with experiments like this is that the inverse square law for radiation intensity only applies to a point (or otherwise omnidirectional) source.
The results the students get will depend on the relative size of the artificial light and the solar cell and with the ratio of that key dimension to the separation distance.

With a long narrow fluorescent tube, they should get a straight inverse (1/N) relationship. And with a very large light emitting panel you get no variation of light intensity with distance at all until the distance gets comparable to the panel size.
:-)