Understanding the Sun
and Solar Power
The Sun’s Energy
Have you ever really thought about
what the Sun means to us, and what
it does for us? Let’s start right at the
beginning, or more precisely, let’s start
early…
What happens when the Sun rises?
It gets light out. The Sun produces
light — just like a lamp, except much,
much brighter. As you know, you need
electricity to turn on a lamp. Electricity
is a form of energy. We can use this
electricity in many different ways, just
one of which is illuminating a filament
in a light bulb. The Sun, on the other
hand, needs no electricity to create
brightness. Actually, it is just the oppo-
site. The Sun is itself an energy source
that provides us with our daylight. Its
power is so great that not even all the
lamps in the world could produce as
much light as the Sun.
The energy from the Sun is called
radiant energy. About 600 million tons
of hydrogen are fused into helium
in the Sun’s interior every second,
producing a radiant energy of 63,000
kilowatt-hours per square meter
(kWh/m
2
). At a distance of 150 million
kilometers, where the Earth orbits the
Sun, the power of this radiation still
amounts to 1,400 kWh/m
2
(or Joules).
Only about half of that energy is
absorbed by the Earth, while the other
half is reflected back into space.
The Sun’s radiation is highly vari-
able in different regions of the world.
That has to do with cloud cover and
the tilt of the Earth. In Pennsylvania,
about 1,000 kWh/m
2
of solar energy
are available per year, while the figure
Solar cells make it
possible to convert
the Sun’s energy into
electricity. The Sun can
deliver 13,000 times
more electricity than
the entire world uses in
one year.
is about 1,700 in Los
Angeles, 2,000 kWh/m
2
in the Caribbean, and
2,200 kWh/m
2
in the
Sahara desert. Com-
pare these numbers to
the fact that the aver-
age American uses only
about 13,500 kWh in a
whole year.
We can do some
calculations to find that
the Earth gets about
5.45 x 10
24
Joules of energy from the
Sun every year. That’s 545 with 22
zeros after it! To put this in perspec-
tive, the amount of energy produced
and consumed in one year by everyone
on Earth is only about 4.26 x 10
20
Joules. Thus, the Sun gives us about
13,000 times more energy than we
consume in a year! This means that in
less than an hour, the Sun delivers as
much free energy as all of the Earth’s
inhabitants combined use in an entire
year. So scientists have naturally asked
themselves the following question:
How can we capture the Sun’s energy
and use it for other purposes?
This is where the solar cell comes in.
A solar cell is a device that converts
sunlight into electrical current. The
word “solar” comes from the Latin
language, in which “sol” means Sun.
There are many ways that solar cells
can be used. In this experiment kit,
we will be using the Sun’s energy to
power a small motor used in various
models. Solar cell technology is also
called photovoltaic technology.
The Solar Engine
You are probably already familiar with
many kinds of engines, such as the
gasoline-powered engines in cars.
Those only run as long as there is fuel
in the tank. And you know about toy
cars that run on batteries, which will
run only until their batteries are used
up. Both of these kinds of engines
have major disadvantages. First of all,
fuel and batteries are expensive. On
top of that, they pollute the environ-
ment. Cars emit toxic and environ-
mentally harmful gases. Used batter-
ies get thrown into the trash. Since
they contain environmentally harmful
materials, they have to be disposed of
in time-consuming and labor-intensive
ways. In addition, they add useless
mass to our landfills.
Your solar engine, on the other
hand, needs neither gas nor batteries.
After it is made, it produces its own
electricity for free, for a long time. It
creates no toxic gas emissions, nor
does it add to the landfill. So a solar
engine is environmentally friendly as
well as inexpensive.
There is one small disadvantage
to a solar engine. In order to run, it
needs light — ideally, bright sunlight.
Since sunlight doesn’t reach us
at night, a solar cell can only produce
electricity from the Sun’s energy dur-
ing the day. However, the electricity
produced by a solar cell from sunlight
can also be stored. To do that, you
need special rechargeable batter-
ies and extra equipment. In order to
produce and store as much electricity
as possible in a photovoltaic installa-
tion, at the level that a family might
need, you need a lot of solar cells.
These are housed in large, flat panels
or modules, which you can already see
on some buildings.
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