Kind: captions
Language: en
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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
the 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
cell. These make up the blue solar
panels you typically see on people's
rooftops. Most photovoltaic or 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 atoms
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
or CSP systems use giant mirrors to
direct sunlight onto a small target.
The concentrated light is used to heat a
fluid, which in turn is used to boil
water and creates 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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