Answer Geek: Photovoltaics
<br> -- Q U E S T I O N: You're on! Let's hear about the guts and volts of photovoltaic technology.
— Guy C.
Q U E S T I O N: Please tell us about photovoltaics. Could they be used as mass power generators? Love your columns. I learn so much.
— Julia S.
A N S W E R: Thanks, Julia. Love your question, too. And the compliments. Your question, too, Guy. "Guts and volts." That's pretty good.
Thanks to everyone else who wrote asking for about how photovoltaic cells, for that matter. For those of you who never quite got around to reading last week's column on solar energy, I mentioned in passing that the inner workings of the photovoltaic cell were interesting enough to merit a separate column. After receiving dozens of e-mails expressing interest, it looks like I'll have to make good on my threat.
So, just to bring everybody up to speed, a photovoltaic cell is a device that converts sunlight into electricity. It's a neat trick. And a useful one. You probably have one on your desk. Got a calculator? The kind that just needs a little light to work? The power to run that handy little device comes from a photovoltaic cell.
Although it may seem like cutting-edge technology, the fact that light could be harnessed to generate an electrical current is an old idea that was discovered in 1839 by a French physicist named Edmund Becquerel, who noticed that voltage was produced when light shone on a beaker full of conducting solution that held a pair of electrodes.
At First, Just a Little Juice
He called it the photovoltaic effect. Later in the 19th century, photovoltaic cells were built from selenium that were 1 to 2 percent efficient. In other words, those cells managed to convert about 2 percent of the available solar radiation into current. That's not a lot of juice, but it did have its practical benefit — even today, many light sensors in cameras use selenium photovoltaic cells.
It wasn't until the middle of the last century that a photovoltaic cell was produced that created enough current to actually serve as a power source. In 1954, engineers at Bell Laboratories built a photovoltaic cell from silicon that was 4 percent efficient, and they upped that number to 11 percent before long.
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