So far we’ve talked about wind energy, ethanol and the recycling process. But this week we’ve got an energy solution that “outshines” all of those — the sun.
Driving around Bowling Green you can’t help but notice the solar panels in place. There are solar panels on top of the BGSU ice arena, the Bowling Green High School, and on the roofs of several houses in town. There’s a solar panel by the “Welcome to Bowling Green” sign on North Main Street. The pedestrian crosswalk on Mercer Street is also powered by the sun. Additionally, because it really wouldn’t have made sense to do it otherwise, the information station for the wind turbines on Route 6 is also run off of solar panels. And perhaps most notably, the stoplights at the intersection of Main and Wooster streets are powered by solar panels.
That’s a lot — but that’s not even all.
Solar power impacts the average Bowling Green resident nearly every day — but most of us know virtually nothing about it.
Welcome to today’s topic: The Hows and Whys of solar energy.
Once you start looking around you’ll see that solar power is everywhere: from those cheap plastic calculators that teachers farmed out to you in your elementary school math class to the acres of solar mirrors laid out in desert fields in the Southwest.
There are two basic ways to gather and produce energy from the sun — the most common is solar panels, and the second, which we’ll get to a little later, involves a little “smoke and mirrors.” 
Let’s start with some background on solar panels or cells.
Solar cells are also called photovoltaic cells — photo, meaning light, and voltaic, meaning electricity (PV cells for short).
A PV cell is made of a material called a semiconductor. A semiconductor is exactly what it sounds like — is a material that semi-conducts. Basically, it can conduct a small amount of energy — think of it as a middle road between full-on conductors, like copper, and full-on insulators, like plastic or wood.
The semiconductor used most often in solar panels is Silicon. This is where it gets a bit sciency, but bare with me.
Because of the silicon used to make them, each solar panel has its own electric field. Again that’s because silicon is a semiconductor.
The final thing to keep in mind is that a Silicon atom has 14 electrons — don’t worry about that too much — just keep it in mind.
Now that we know something about the panel, let’s see what happens when we stick it in the sun.
The basic process:
• The sunlight shines on the solar cell, which absorbs some of that light.
• The energy from that absorbed light “knocks loose” some of the Silicon electrons, so now they can move freely — kind of. Like we said, each solar cell already has a built in electrical field — a by-product of Silicon used to make them. So the electrons that were “knocked loose” a minute ago by the incoming sunlight are essentially forced to flow in the same direction as the cell’s natural electrical field.
• This movement creates an electric current.
• Finally, by placing metal on the top and bottom of each solar cell, we can draw energy off of that current, thus creating electricity to power things — like that cheap plastic calculator from Math class or the traffic lights at Main and Wooster streets.
So that’s basically how solar works. Cool, huh?
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If you’re interested in some more details — such as why Silicon has an electric current, or how come only some of the light from the sun is absorbed — scroll down to the bottom of this blog to read on. For the rest of you let’s head for the “smoke and mirrors” I mentioned before.
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Now, compared to the process behind the solar panel, this is simple. Essentially, a bunch of mirrors are laid out across acres of desert, usually in the Southwest.
A solar field in Arizona. *Photo courtesy of the New York Times.
The mirrors reflect the sunlight towards large vats of fluid.
The heat from the reflected sunlight on these vats causes the fluid to make steam. The steam turns a turbine, which generates electricity. Essentially, smoke and mirrors, right?
An article in the New York Times goes into some more detail about the potential future of these large scale “sun-farms” — there aren’t that many right now.
For obvious reasons, namely the persistent cloud cover, this would not be an option for many places in the U.S., including Northwest Ohio. However, once the energy produced by these sun-farms is tied into the power grid, essentially any municipal power group could purchase a share of the clean solar energy.
As you can see the potential for solar is really heating up — both across the U.S. and here in Bowling Green. Now that you’ve got a little knowledge about solar, be sure to impress your friends by spouting off facts next time you drive downtown … or by the high school …. or the north side of town … or by the ice area … or … well you get the idea. Be sure to check back next week for more of what’s going green in BG 
Until then,
Laura
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So how come only some of the sun’s light is absorbed? Why not all of it?
OK. So, on a typical sunny day, the sun shines about 1,000 watts of energy per square meter on the Earth’s surface — that could pretty easily power every home and business in the U.S. However, a fully productive solar cell can only absorb 25 percent of the sun’s light — and it’s usually much less than this — closer to 15 percent.
Bummer, I know. Here’s why:
First of all, Silicon is a reflective material, and any reflected light can’t be absorbed by the solar cell. To compensate, an antireflective coating is applied, and this cuts down on loses, but even with that, about 5 percent of the total incoming light is still reflected away.
But most of the energy loss has to do with the nature of light in general. You probably remember from 8th grade science class that there are many different kinds of light — not just visible light. Simply put, not all of these lights can be absorbed effectively within the solar cell.
Each kind of light has a different kind of wavelength. So sunlight in general has a wide array of energies. Remember, the light coming in has to have enough energy to “knock loose” the Silicon electrons.
Some of the light doesn’t have enough energy to do that, so all of that energy is lost.
On the flip side, other types of light have too much energy. So any energy left over is lost as well.
This accounts for the other 70 percent of the total lost energy. So adding everything together we get a maximum productivity of 25 percent for each solar panel. The reason it’s typically a bit lower than this (about 15 percent of the sun’s light is normally absorbed) is because of cloud cover.
As for the electric current in Silicon …
The reason each solar panel has an electric current is because the silicon used to make the panel isn’t pure — it’s doped. Doping Silicon atoms means adding another chemical to them.
The electric current within each solar cell is created by mixing these modified Silicon atoms.
There are two main types of modified Silicon used: N-type (negative) and P-type (positive). The N-type is Silicon mixed with Phosphorus and has extra electrons. The P-type is Silicon mixed with Boron and has too few electrons.
Basically, when these two modified Silicones are mixed together the extra electrons rush to fill up the holes, creating a small electrical current. Here’s a simplified picture:
If you’re still looking for more, you’re obviously procrastinating. BUT …
The New York Times explains how large corporations and chain stores are using solar panels.
Additionally, an electric company in California is installing a “patchwork” of solar panels on two square miles of rooftops.
Sources:
HowStuffWorks. “How Stuff Works: Solar Cell” <http://science.howstuffworks.com/solar-cell1.htm>;
And all of the cited New York Times articles.
Wow. . . interesting. Scientific and yet witty. Nicely done. ****