NARRATOR: While it may not be the answer to all of our energy problems yet, there’s one energy source we have plenty of: sunlight. In fact, the amount of solar energy that strikes the surface of Earth in one hour is more than enough to supply every person on the planet with electricity for an entire year.
We currently have a number of methods to harness the extraordinary power of the Sun. Most involve converting sunlight into electrical energy.
So, how’s it done?
The most common way to perform this energy swap is by using a photovoltaic (PV) cell. PV cells make up the blue solar panels you typically see on people’s rooftops.
Most PV cells are made of the element silicon. When a photon, or packet of energy from sunlight, hits one of the silicon atoms in the cell, it knocks off one of the atom’s outer electrons. These free electrons then make their way toward a metal conducting strip on the solar cell’s surface. The strip transports this steady stream of electrons—the electrical current—out of the cell so that it can flow into the power grid for people to use.
There are other types of solar power as well. Concentrated solar power (CSP) systems use giant mirrors to direct sunlight onto a small target. The concentrated light is used to heat a fluid—often a synthetic oil—which in turn is used to boil water and create steam that turns an electrical generator.
The great thing about both of these solar energy systems is that they are totally renewable and don’t emit any greenhouse gases. So, why don’t we produce all of our electricity this way?
To begin with, solar technologies aren't particularly efficient. Most convert less than 25% of the sunlight that strikes them into usable electrical energy.
To top it off, we don’t have good ways of storing solar energy, so for the most part, we still can’t use it at night or on cloudy days.
In other words, even if we plastered every rooftop in America with solar panels, they still wouldn’t completely replace fossil fuels.
Finally, solar power costs more! PV cells have become cheaper to produce in recent years, but solar technologies are still relatively costly compared to coal, oil, and even some other renewables.
If we can work out these issues—efficiency, storage, and cost—solar energy really could begin to replace a significant portion of the fossil fuels we consume. We’re not there yet, but the technology is getting better, and cheaper, all the time.
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