Renewable energy sources are those provided directly or indirectly
by the either the Sun or the Earth's processes. They include:
solar energy, wind energy, bioenergy, geothermal energy, hydropower
and ocean energy. They are constantly replenished and will always
be available for our use.
Sunlight, or solar energy, can be used directly for heating and
lighting homes, captured in solar cells to generate electricity,
and used to heat residential hot water. Solar energy is also the
cause of wind, which can be harnessed through windmills to pump
water, grind grain, or produce electricity. The energy provided
by the Sun also makes plants grow, and the organic matter that
makes up those plants (biomass) can be used to produce electricity
directly, or become stored in fuel or chemicals.
Geothermal energy uses the Earth's internal heat to make steam,
which can produce electric power or heat buildings. Rivers and
streams were once used as a direct energy source for industry
and some have been blocked with large dams to provide falling
water to produce electricity. The energy of the ocean's tides
is another renewable source. In the future we might even use waves
or the differences in the ocean temperature to extract energy
for our use or decompose water to produce hydrogen as a clean
burning fuel.
Find out more about energy efficiency and renewable energy at:
http://www.eren.doe.gov/
There are a lot of intermediate stages in the transfer of energy
from a root source such as the Sun into the various forms of energy
that people use. Try the tracing
the path activity on this site to explore this topic further.
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