Renewable energy will also help us
develop energy independence and security. The United States imports more than
50 percent of its oil, up from 34 percent in
1973. Replacing some of our petroleum
with fuels made from plant matter, for
example, could save money and
strengthen our energy security.
Renewable energy is plentiful, and the
technologies are improving all the time.
There are many ways to use renewable
energy. Most of us already use renewable
energy in our daily lives.
Hydropower
Hydropower is our most mature and
largest source of renewable power, producing about 10 percent of the nation’s
electricity. Existing hydropower capacity
is about 77,000 megawatts (MW). Hydro-
power plants convert the energy in flowing
water into electricity. The most common
form of hydropower uses a dam on a river
to retain a large reservoir of water. Water is
released through turbines to generate
power. “Run of the river” systems, however, divert water from the river and
direct it through a pipeline to a turbine.
Hydropower plants produce no air emissions but can affect water quality and
wildlife habitats. Therefore, hydropower
plants are now being designed and operated to minimize impacts on the river.
Some of them are diverting a portion of
the flow around their dams to mimic the
natural flow of the river. But while this
improves the
wildlife’s river
habitat, it also
reduces the power
plant’s output. In
addition, fish ladders
and other
approaches, such
as improved turbines, are being
used to assist fish
with migration
and lower the
number of fish
killed.
Bioenergy
Bioenergy is the energy derived from biomass (organic matter), such as plants. If
you’ve ever burned wood in a fireplace or
campfire, you’ve used bioenergy. But we
don’t get all of our biomass resources
directly from trees or other plants. Many
industries, such as those involved in construction or the processing of agricultural
products, can create large quantities of
unused or residual biomass, which can
serve as a bioenergy source.
Biopower
After hydropower, biomass is this country’s second-leading resource of renewable
energy, accounting for more than 7,000
MW of installed capacity. Some utilities
and power generating companies with
coal power plants have found that replacing some coal with biomass is a low-cost
option to reduce undesirable emissions.
As much as 15 percent of the coal may be
replaced with biomass. Biomass has less
sulfur than coal. Therefore, less sulfur
dioxide, which contributes to acid rain, is
released into the air. Additionally, using
biomass in these boilers reduces nitrous
oxide emissions.
A process called gassification the conversion of biomass into gas, which is burned
in a gas turbine—is another way to generate
electricity. The decay of biomass in
landfills also produces gas, mostly
methane, which can be burned in a boiler
to produce steam for electricity generation
or industrial processes. Biomass can also
be heated in the absence of oxygen to
chemically convert it into a type of fuel oil,
called pyrolysis oil. Pyrolysis oil can be
used for power generation and as a feedstock
for fuels and chemical production.