Environmental Engineering Reference
In-Depth Information
cells, almost all other forms of electricity generation, including fossil fuel burning, nuclear,
biomass, hydro, wind, concentrated solar, and cogeneration, rely on driving a turbine to
produce electricity.
Fossil fuel-based electricity generation involves harnessing the heat (thermal energy)
released when the stored chemical energy in coal, oil, or gas is released during burning.
This heat boils water or heats gas to create high-pressure steam that causes rotation of a
wire loop through a magnetic field while it is connected to a circuit. The rotation causes
a current to flow through the wire loop and through the circuit, generating electric current
through a combination of rotational force and magnetics in a generator/alternator. Nuclear
powerinvolvesasimilarmechanismofharnessingtheheat,butinanuclearpowerplantthe
heat is produced from the splitting of atoms (fission). This heat turns a turbine to generate
electricity (similar to the gas/steam-fired plants previously mentioned). Renewable-based
electricity generation relies on the movement of either wind or water to turn turbines and
create a current and produce electricity, the harnessing of geothermal heat or solar heat
to turn a turbine, or the conversion of solar radiation, through photovoltaic cells, into
electricity.
Currently, most electricity generation occurs in large, centralized fossil, nuclear, or
hydro facilities. In the United States in 2013, roughly 86 percent of electricity generation
came from large, centralized fossil fuel (67 percent) or nuclear (~19 percent) power plants,
while renewables made up about 13 percent of total generation (EIA 2014 ). Regional and
local variation in this electricity generation mix is high; the Pacific Northwest region has
comparatively low fossil fuel reliance, with hydropower being the largest single source of
generation (around 45 percent of the state of Oregon's electricity comes from hydropower),
while the Southeast region of the United States is more than 95 percent reliant on fossil
fuels and nuclear for electricity generation. Although wind power currently only makes up
3.5 percent of U.S. electricity generation, some states with many wind turbines generate
much more than 3 percent: for example, Iowa is currently generating about 25 percent of
the electricity it consumes from wind power and Texas generates more than 12 percent
of its electricity from wind. The U.S. electricity mix is also dynamic, and major temporal
shifts in electricity generation have occurred ( Figure 3.1 ).
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