Section 5-3 Conserving Energy 121
Water
The energy of falling water can be converted into electrical energy
called hydroelectric energy. The amount of power generated at a given plant
is limited, but another plant built downstream can generate more power
from the same water. As water evaporates and falls again as rain, water
supplies are replaced. More fl owing water allows the plant to generate
more electrical power. This cycle is a renewable source of energy.
Building more hydroelectric plants is not likely. Most of the practical
power-generating sites in the United States have already been developed.
Building other sites could damage the environment.
Wind Energy
An average wind speed of about 14 miles per hour is needed to
economically convert wind to electricity. Wind turbines can convert
the energy of the wind into electrical energy, which can be stored in
batteries and used as needed. Good wind sites are often located far from
where most energy is needed. Wind energy is the fastest growing energy
technology in the world. Good sites are abundant and the technology
produces no pollution.
Solar Energy
The greatest renewable source of energy is the sun. Energy from
this source is called solar energy. The sun’s energy can be captured and
used in several ways. Solar collectors absorb it to provide hot water for
household use or for space heating. See 5-7. Photovoltaic systems convert
sunlight to electricity that may be used directly or stored in batteries for
future use. Special refl ectors focus sunlight into a fi ber optic system to
light the interior of buildings. Solar
energy has two advantages: the supply
is almost limitless, and it does not have
harmful effects on the environment.
Biomass
Energy is stored in dry, decayed
plant and animal matter called biomass.
When burned, biomass produces
heat and steam, both of which can be
converted to electricity. Many types of
biomass exist, but the three main types
burned to create energy are wood,
crops, and solid waste.
Geothermal Energy
Geothermal energy is derived
from heat produced within the earth.
Analyze
and
Solve
Suppose you are planning
to build a house and cannot
use fossil fuels. Which of the
renewable energy sources
would you choose to supply
power to your home?
5-7
A solar heat collector traps
the heat of the sun to heat
water and living spaces.