Did you know . . .
. . . that the temperature on the
surface of the Sun is over 6,000° C
(about 10,800° F)?
In the center of the Sun, the temperature is 15-20
million ° C (~27-36 million ° F). The diameter of the
Sun, at 1,390,600 km, is over 100 times that of the
Earth. Its surface is 12,000 times as great as that
of our planet. The Earth itself would fit into the Sun
1,300,000 times. If you picture the Sun as a ball
20 m across, the Earth would be about the size of
a soccer ball 2 km away. The actual distance of the
Sun from the Earth is about 149,500,000 km.
. . . and that the
Sun is only mid-
dle-aged?
Even though the Sun is
estimated to be about 4.6
billion years old, scientists
calculate that it will con-
tinue to shine at its current
energy level for another 5
billion years. So the Sun’s
energy will be available for
human usage for a long
time to come.
Where Does Our Energy Come From?
Most of the energy we use comes from the Sun, in one way or another. This table provides a lot of information about our
eight most popular energy sources, how they work, where they come from, and whether or not they are sustainable. Sustain-
able means that they can continue indefinitely without running out or causing other problems over time.
Name
Examples
Definition
Energy Origin
Percentage of world’s
power coming from
this source
Is it renewable,
relative to
human life?
Fossil Fuels
Gasoline in a car, oil in
a furnace, natural gas
stove, coal in a power
plant
Fossil Fuels are organic materials that release a lot
of heat when they are burned. The heat can be used
to heat water to turn turbines to generate electricity.
They also produce a lot of pollution when burned.
The remains of prehistoric plants
and animals, which grew and stored
energy from the Sun
Petroleum: 38%
Coal: 24%
Natural Gas: 24%
No, only over mil-
lions of years
Hydro
Waterwheel used to grind
meal, hydro-electric
dam used to generate
electricity
Hydro power is simply power from falling water.
Today, it is mainly used in the form of dams that
trap water and funnel it through turbines to produce
electricity.
The Sun evaporates water from the
oceans, the evaporated water rains
out of the sky to help form rivers
which run back to the ocean.
7%
Yes
Nuclear
Big reactors in power
plants and submarines
A complex system sets off a chain reaction of fis-
sion, or splitting, of uranium atoms. This produces
lots of heat, which is used to spin turbines which in
turn produce electricity.
The energy stored in the bonds inside
uranium atoms
6%
No, Earth has a
limited amount of
uranium in it
Geothermal
Geothermal power plants
Geothermal power is generated using heat from
deep inside the Earth to create steam which is used
to drive turbines to produce electricity.
The temperature at Earth’s core is
estimated to be 5,000 to 6,000° C.
This heat was originally generated
when Earth formed, and additional
heat is formed as radioactive elements
decay inside the planet.
<1%
Yes
Solar
Photovoltaics (solar
cells) produce electricity,
solar water heaters heat
water, solar towers col-
lect heat to turn turbines
to produce electricity
Solar power is energy from the Sun. It can be cap-
tured and converted into useful energy in a variety
of ways. Without the Sun, there would be no life as
we know it on Earth. All living things need energy
from the Sun, either directly or indirectly, to survive.
Nuclear fusion reactions in the Sun
fuse hydrogen atoms together into
helium atoms, yielding huge amounts
of energy.
<1%
Yes
Wind
Windmills, wind power
generators
Naturally occurring wind (moving air) is used to
turn turbines to generate electricity. In the past,
windmills turned wind power into mechanical
energy used to grind corn.
Winds occur on Earth for two reasons.
First, the Sun heats the Earth in
different places at different times,
causing certain areas to have warmer
air than others. This causes pressure
differences, and air will flow from
areas of high pressure to areas of low
pressure. This, combined with the fact
that Earth rotates, causes the winds to
blow as they do.
<1%
Yes
Biomass/
Wood
Sugar cane converted
into a combustible fuel,
animal waste converted
into methanol fuel
Biomass is an umbrella term used to describe any
organic, non-fossil material that can be used as
fuel. It is often plant and animal “waste” products
that are not useful for another purpose. Biomass
commonly used for fuels includes corn stalks, sugar
cane, wood by-products, animal manure and even
household waste.
Biomass grows because of energy
from the Sun, either directly as in the
case with plants, or indirectly, as in
the case with animals that eat plants
to grow.
<1%
Yes, theoretically
biomass can be
grown at the rate
it is consumed
for fuel
Tidal
Turbines in tidal areas
Tidal power is power from the movement of the
tides in the ocean. It can be harnessed by placing
turbines in parts of the ocean with strong tidal cur-
rents. The currents turn the turbines that produce
electricity.
The tides are caused by the gravita-
tional pull of the Sun and the Moon
on the water in the oceans.
<1%
Yes
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