Most of us enjoy reliable electrical service, enough to
satisfy our wants and needs. It is only when our service
is interrupted are we reminded of the importance
electricity plays in every facet of our daily lives.
So where does all this electricity come from?
First, let’s take a look at how electricity is generated.
There are many forms of energy:
Energy can be transformed into another type of
energy, but it cannot be created or destroyed.
The generation of electricity involves transforming
mechanical energy into electrical energy, and at
the center of virtually all power generation
methods is the turbine.
When the blades on the
shaft of a turbine are
rotated, the generator
produces electricity through
a process called magnetic
Click here to learn more about magnetic induction.
The main difference
between the main
generation methods is
the source of energy
that is used to turn the
blades of the turbine.
Coal, most natural gas, nuclear, geothermal and
parabolic-trough solar installations use heat to
create steam to turn the blades.
Click here to learn more about steam turbines.
In the United States, the source most often
used to create that heat is coal.
The electrical power industry is also the largest producer
of carbon dioxide emissions in the United States.
In the Eastern part of the country, most power plants use
coal. The majority of the nation’s nuclear power
generation is likewise located in the eastern half of the
country. Most hydropower resources are in the Pacific
Northwest, while most wind, solar, and geothermal
resources are located in the West.
Let’s take a look individually at each of
these methods for generating
Nearly half of the electricity in the United States is
produced by burning coal.
Kingston Fossil Plant, Tennessee
Coal is first pulverized into a fine powder and then
moved to a furnace where it is burned in a boiler to
create the steam that moves the turbine.
A ‘base load’ is the
minimum amount a
power company must
be generating to meet
Coal plants are most
often ‘base load’ plants
and are typically
except for repairs or
maintenance.Bull Run Fossil Plant, Tennessee
America’s coal reserves are vast; it is estimated that
the U.S. has at least 200 years left of available
coal reserves, more than enough to use
domestically and enough to export, too.
Learn more about coal by clicking here.
Coal is most often shipped to power plants by barge
or by railroad. The cost of transporting coal is
oftentimes more expensive than the mining process.
Coal barge in the Louisville and Portland Canal, Ohio River
Coal trains delivering to
power plants can be
over a mile long and
carry 10,000 tons,
enough to power a large
plant for a day. During
periods of seasonal
high demand, a power
plant may receive as
many as 3 to 5 trains
Union Pacific coal train in Douglas, Wyoming
Burning coal produces carbon dioxide, sulfur
dioxide, nitrous oxides, particulates and mercury.
Coal powered plant near Price, Utah
Photo by arbyreed (flickr).
Photo by Nick Humphries
Modern day ‘scrubbers’
and other “clean coal”
emissions, but coal-
fired power plants still
emissions into the
accounting for 40% of
the nation’s carbon
Some by-products can be
reused in a variety of
products, such as cement
or concrete, while the
remainder must be
isolated and stored. Coal
ash disposal is a serious
In December of 2008, 1 billion
gallons of coal ash was spilled
from the Tennessee Valley
Authority’s Kingston Fossil
Plant, covering 300 acres and
destroying homes, poisoning
rivers, and contaminating
Wyoming produces the most coal in the United
States, whereas Texas consumes the most coal and
also the most electricity in the nation.
Since America’s coal reserves are so
abundant, it is our nation’s cheapest source
of fuel for electricity production, costing less
than a third of the cost of other fossil fuels.
Coal utilizes the nation’s existing fuel and
transportation infrastructure, which allows power plants
to be sited where needed.
However, the combustion of coal contributes to acid
rain and air pollution, and emissions from burning coal
have been connected with climate change. Proper
disposal of the byproducts is a problem.
Cumberland Power Plant, Tennessee
world’s demand for
electricity is expected
to rise 60% by 2030,
and the International
estimates that 85% of
this demand will be
met by fossil fuels,
much of that most
likely to be coal.
THE PROS & CONS OF COAL
• America has abundant
• It is inexpensive.
• America’s existing
infrastructure is set up for
• It is highly polluting.
• Even with clean coal
technologies, there are
• There are also significant
impacts from the
extraction of coal.
FOR MORE INFORMATION ON COAL:
Department of Energy, Clean Coal Technology &
The Clean Coal Power Initiative:
U.S. Department of Energy Information: Coal, Explained:
American Coal Association (pro-coal):
America’s Power (pro-coal); http://www.americaspower.org/
Coal is Clean/Coal is Dirty (anti-coal):
Sierra Club: Beyond Coal (anti-coal):
As an alternative to using coal, some plants burn
natural gas. Most new power plants being
constructed use natural gas.
New Pacific Corp. gas fired plant, Lindon, Utah
Photo by arbyreed
Natural gas is composed mainly of methane, and can
be found in oil fields, coal beds, or by itself.
Natural gas must be
processed before it can be
transported and used.
transport the gas from the
wellhead to a processing
plant, where impurities are
removed to make pipeline-
quality natural gas.
Natural gas is then transported through high-pressure
pipelines to where it is needed.
Natural gas is stored in
depleted reservoirs, salt
domes, or in storage tanks as
Liquefied Natural Gas (LNG).
Some natural gas plants burn the gas to run a steam
turbine. Other plants use gas turbines and
combustion engines instead. These turbines can be
used to meet peak-load demands because they can
be quickly powered on and off.
A combined-cycle power plant has both a gas turbine
and a steam unit. The waste heat from the gas turbine
is used to generate steam for the steam turbine.
Natural gas has many uses, including as a heat source
for cooking, hot water and home heating, and has
potential as an alternative fuel for powering cars.
Photo by Scott J. Lowe
Natural gas is the cleanest burning of all fossil fuels,
producing 45% less carbon dioxide than coal, less
nitrogen oxides, negligible amounts of sulfur dioxide
and mercury, and virtually no particulate matter.
LS Energy, Morro Bay
Photo by Mike Baird
However, the processing, storage, and transport of
natural gas makes it a relatively more expensive fuel.
Woodsdale Station, Butler County, Ohio
Photo by Duke Energy
Knowledge about America’s natural gas reserves is
imprecise, but a recent report estimated reserves at a
100 year supply, much less than coal.
Haynes Steam Plant, Seal Beach, CA
Photo by Mollivan Jon
A new process called
‘hydraulic fracturing’ has
the potential to utilize
injecting fluid into the
rock to fracture it,
allowing the gas
underneath to escape.
Photo by Ari Moore.
As much as half of the water can return to the surface,
risking extensive contamination of drinking water
sources and the environment. There is great concern for
environmental impacts of this type of natural gas drilling.
More research is needed to determine how much
natural gas can be extracted, and the quality of
unconventional natural gas resources is uncertain. In
addition, research is needed to reduce the
environmental impacts of some extraction methods.
THE PROS & CONS OF
• Natural gas is the
cleanest burning of all the
• It is an abundant source
of domestic energy.
• New techniques have
emerged that have
potential natural gas
• Natural gas does emit
carbon and nitrogen
oxides, but in much
• It is non-renewable.
• Environmental impacts
from some types of
natural gas mining are
• It is more costly to
process, transport and
FOR MORE INFORMATION ON
U.S. Energy Information Administration: Natural Gas Explained:
U. S. Department of Energy website on natural gas:
Natural Gas Supply Association website on natural gas:
Earthworks: Hydraulic Fracturing 101:
The United States has 65 nuclear power
plants with 104 reactors producing 20%
of the nation’s power.
Sequoyah Nuclear Generating Plant, Tennessee
Nuclear plants create electricity much the same way as
coal or gas plants do, except a nuclear plant uses the
fissioning of uranium atoms to create the heat instead of
burning coal or gas.
America has the fourth largest uranium reserves in the
world, but the deposits are of lower grade and are
uneconomical to mine when prices drop too low.
In 2001, only 5% of the uranium used in power plants
was mined in the United States.
A single nuclear reactor can produce a significant
amount of electricity.
San Onofre Generating Station, California
Nuclear plants have low operating costs and they
reduce our dependence on burning fossil fuels.
Palisades Nuclear Power Plant, Michigan
Nuclear plants operated within the
U.S. have good safety records.
Not one life has ever been lost
to a malfunction at an American
Nuclear power produces very little greenhouse
gas emissions and the amount of radioactive
waste produced is a fraction of the coal ash
waste produced by coal-fired power plants.
David Besse Nuclear Generating Station, Ohio
But the waste from the spent nuclear fuel remains
toxic for thousands of years, and disposal of waste is
a problem. A national repository for nuclear waste
planned at Yucca Mountain in Nevada has run into
roadblocks and may never be completed.
Nuclear accidents are rare, but can be devastating, and
opposition to new nuclear plants is strong.
Three Mile Island
THE PROS AND CONS OF
Emissions for nuclear power
plants is very low.
A single nuclear power plant
can generate a
substantial amount of
Nuclear power plants in the
U.S. have good safety
Nuclear waste stays toxic
for thousands of years,
and storage is a problem.
Accidents, though rare, are
There is strong public
opposition to nuclear
Uranium is a non-renewable
resource that will
eventually be used up.
FOR MORE INFORMATION ON
U.S. Energy Information Agency: Nuclear Explained:
Joseph Gonyeau’s Virtual Nuclear Tourist: Nuclear Plants
Around the World: http://www.nucleartourist.com/
The Future of Nuclear Power: An interdisciplinary study by
National Geographic Magazine: Nuclear Power: Risking a
Time for Change: The Pros and Cons of Nuclear Power
Wells are drilled deep into the earth, bringing the hot
water up to the surface where it is used to power the
turbine directly without burning any fossil fuels. An
injection well returns the water deep inside the earth to
begin the process again.
Geothermal Heating System
Greenhouse heated by
Geothermal fluids can also be directly used for heating
buildings and greenhouses, to melt snow on the
sidewalks in winter time, and even to grow fish on fish
Most of the nation’s geothermal resources are
located in the western United States.
The United States leads the world in geothermal
energy production. The largest group of geothermal
plants is located at the Geysers geothermal field in
produce very little
emissions - only about
one-sixth of the
carbon dioxide that a
natural gas plant
would produce, and
very little if any other
gases. The white
smoke coming from
the plants is actually
steam from the
The Leathers geothermal plant , Salton Sea
plants in operation
today are either a
flash system or a dry
steam system. Both
of these types of
reservoirs of high
A dry steam plant at the Geysers geothermal field
Binary cycle plants are a newer technology that has
been developed to utilize more moderate geothermal
temperatures, allowing expansion of geothermal energy
to more areas of the country. Most geothermal plants of
the future will likely be binary.
Ormat facility in Steamboat Springs, Nevada
Click here to learn more about geothermal energy production.
Geothermal fluids can contain salts and dissolved
minerals which can be corrosive to equipment and
require maintenance. Geothermal fluids along with the
minerals are usually reinjected back into the earth,
recycling the water and replenishing the reservoir.
Geothermal plant, Heber, CA
The thermal efficiency of
geothermal plants is low, as
the geothermal fluids are not
as hot as fluids produced by
burning fossil fuels.
Geothermal plant, Salton Sea, CA
This doesn’t affect
costs because a
does not burn any
fuel. However, it
does affect the
return on capital for
building the plant,
the costs of which
are substantial and
Geothermal plant, El Centro, CA
Geothermal energy is a clean domestic source of
renewable energy, one that doesn’t require storage,
transportation or combustion of fuels.
Geothermal plant, Imperial Valley, CA
However, building a
geothermal plant is
very expensive and
risks. At this time,
geothermal energy is
not always cost-
other sources of
Geothermal plant, Imperial Valley, CA
THE PROS AND CONS OF
• Geothermal energy is
nearly completely non-
• Plants are inexpensive to
operate, once built.
• A renewable source of
• Geothermal plants do not
transportation or storage
• Geothermal power is only
available in certain areas of
• Initial drilling and construction
is complex and expensive
• Geothermal reservoirs must
be carefully managed and
• Lifespan of plants is unknown;
Movement of the earth or
other factors can cause the
resource to dry up.
FOR MORE INFORMATION ON
U.S. Energy Information Administration, Geothermal Explained:
National Renewable Energy Library, Geothermal Energy
How Geothermal Energy Works, by How Stuff Works:
Geothermal Energy Slideshow:
Take a virtual tour of a geothermal plant:
Hydropower utilizes the gravitational force of
water flowing downhill to turn the blades of the
turbine and produce electricity.
The amount of electrical output produced depends on
the volume of water flowing through the turbine, and
the height between source and the outflow of the
water, called the hydraulic head.
are most often
located on a river
with a large drop in
reservoir acts as
stored energy which
can be regulated
and controlled to
But not all hydropower dams have reservoirs behind
them. A ‘run of the river’ hydropower plant utilizes
the natural flow and elevation drop of the river. All
or a portion of the flow is diverted through the
turbines at the power plant.
‘Run of the river’ hydropower
plants are built on rivers with
consistent and steady flows.
The Dalles Dam on the Columbia River, Washington
The output from run-of-the-river hydroplants varies
seasonally, with a substantial amount of power
produced in the spring when flows are high but
considerably less during the drier, summer months.
Lower Granite Dam on the Snake River, Washington
Since there is no reservoir behind it, a run-of-the-river
plant has little or no capacity for storage, and cannot
coordinate electrical output with consumer demand.
Water is pumped uphill to a higher reservoir at
night when power costs are low, and then
released to meet power demands during the day.
The amount of hydroelectric power
produced by a dam depends on the
rainfall within the watershed, and
may be significantly reduced in
With hydropower, there is no expense for fuel;
it is a domestic source of cheap, renewable,
clean energy. Hydropower plants have a long
life and low operating costs.
Reservoirs behind dams
can provide recreational
benefits, as well as water
storage for drier months
and flood protection for
Lake Oroville, California
Lake Oroville, California
Although hydropower provides clean and inexpensive
electricity, dams are not without their environmental
impacts. Creation of a reservoir behind a dam
submerges valuable land and riparian environments.
Dams disrupt a river’s
ecosystem by preventing
sediment from flowing
downstream, which can
cause loss of riverbanks and
scouring of river beds, even
Hoover Dam, Colorado River, Arizona-Nevada
Dams also prevent access to
spawning grounds by
New Bullards Bar Dam on the Yuba River, California
Fish ladders have been installed at many dams
and at great expense, but their performance so far
has had mixed results.
Expansion of hydropower in the United States is limited
by available rivers and the competing uses for those
rivers, such as tourism, industry, and existing cities.
The best sites have already been developed.
Anderson Ranch Dam, Boise River, Idaho
THE PROS AND CONS OF
• A completely clean,
renewable source of
• Once built, inexpensive to
operate and maintain
• Dams can be built to
provide flood control, and
to store water for
municipal use, recreation,
• Dams and reservoirs
ecosystems and habitat.
• Only certain sites are
suitable for hydropower;
most of these have
already been developed.
FOR MORE INFORMATION ON
U.S. Energy Information Administration, Hydropower Explained:
U.S Bureau of Reclamation, Hydropower pamphlet:
U.S. Department of Energy, Energy Efficiency & Renewable
Energy, page on hydropower:
Hydro Research Foundation: http://www.hydrofoundation.org/
Solar power uses the energy of the sun to create
electricity, either directly by using photovoltaic cells, or
indirectly by using a concentrated solar power system.
The economic viability of a solar project depends on
a number of factors, such as the number of
cloudless days, the latitude of the installation, and
the cost of collectors.
Photovoltaic cells convert sunlight
directly into electricity and can be
used to power small devices up to
large-scale commercial generation.
Photovoltaic systems are highly reliable, providing clean
and silent energy for many years with virtually no
Nellis AFB, Nevada
In a power tower design, thousands of mirrors tracking
the sun focus sunlight onto a receiver which is sitting
on top of a tower.
Sierra Sun Tower, Lancaster, CA
Inside the receiver, the
sunlight heats the molten
salt to over 1000 degrees;
the hot salt then flows to a
storage tank and
eventually is used to run a
In a dish system, a large
parabolic dish focuses the
energy onto a receiver above the
dish which powers a small
engine to create the electricity.
There are many other
different types of solar
energy systems being
developed and used
throughout the world.
The solar furnace at Odeillo in the
Fresnel solar plant in southern Spain
They must be sited in
the right areas, with the
Western U.S. having the
most potential for solar
Seasons, clouds and air pollution can affect production,
and since power is only produced when the sun is
shining, other sources of energy must still be used.
THE PROS AND CONS OF
• A non-polluting,
inexhaustible source of
• Can supply electricity to
places not served by the
• Inexpensive, once
• More reliable than wind
• Initial costs are high
• Power is only generated
when the sun is shining
• Weather and pollution
FOR MORE INFORMATION ON
From the U. S. Department of Energy, Energy Efficiency and
Renewable Energy office:
The American Solar Energy Society: http://www.ases.org/
Wind power is actually a form of solar energy,
caused by the sun’s uneven heating of the
atmosphere, irregularities of the earth’s surface, and
the rotation of the earth.
Wind power is the fastest growing energy technology.
Wind turbines use the kinetic energy of wind to power
the turbine and produce electrical energy.
Winds near the ground
tend to be slower and
more turbulent than
those higher up, so
turbines are mounted
on tall towers to
generate the most
Wind power is a clean fuel source, a domestic source
of power, and one of the lowest-priced renewable
energy technologies in use.
Wind power is compatible with grazing, crops, and
other agricultural land uses.
However, good wind sites are often in remote areas,
requiring the construction of costly and controversial
And since wind power must compete with conventional
power sources on a cost basis, profitability is dependent
on the local wind conditions.
Currently, wind power accounts for about 1% of our
power generation. While no doubt wind power will
play a greater role in electrical production in the
future, it cannot be expected to fulfill all of our nation’s
THE PROS AND CONS OF
• Wind power is a clean,
renewable source of
• Wind power is generally
compatible with grazing
and agricultural land uses
• Wind power produces
power only when the wind
is blowing, which can be
• The amount produced
depends on how fast the
wind is blowing
• Installations must be sited
properly; often the best
places are remote and
FOR MORE INFORMATION
ON WIND POWER:
U.S. Energy Information Administration, Wind Power
National Renewable Energy Laboratory page on wind power:
Wind Energy Resource Atlas of the United States:
It is estimated that 39% of all freshwater withdrawals in
the U.S. each day are for electrical power production,
the majority of that needed for plants using fossil fuels.
AND WATER USE
Electrical power production is the second only to
agriculture as the largest user of water in the U.S..
Most power plants using thermal processes require
water for cooling equipment, which is why power plants
are usually located near the ocean, a river, or some
other body of water.
Once-through cooling systems draw water from a
waterbody, run it through the plant to cool the
equipment, and then return it to the waterbody,only now
much warmer. This warmer water is not good for fish,
and a lot of aquatic species are killed by these intake
Even though the power plant’s water usage is not
consumptive, during times of drought, lower flows can
impact power production by making less freshwater
available for cooling.
Drought impacts hydropower production, too. During
drought conditions, less water is released from
reservoirs, which in turn reduces the amount of power
produced by the hydropower plants.
Reduced levels in reservoirs
also means reduced hydraulic
head, which further decreases
the amount of power produced.
In 2010, Lake Mead
dropped to it’s
lowest level since
the 1950s, and there
was real concern
that if the level were
to continue to drop,
the turbines at
Hoover Dam would
no longer be able to
While the U.S. population is expected to rise, freshwater
availability will not. This increase in population will need
both electricity and food, putting the two largest users in
competition for increasingly scarce water resources.
FOR MORE INFORMATION ON
WATER & ENERGY ISSUES:
Energy-Water Nexus Overview & Report, by Sandia Labs:
Choke Point U.S., from the Circle of Blue Water News:
Special Report: Water vs. Energy, by IEEE Spectrum:
The rest of the demand is met by
peaking plants – smaller, faster
and usually more expensive
plants that can start up quickly to
meet demand. Typically these
are combined-cycle natural gas
or pumped hydroelectric
Photo by Mollivan Jon (flickr). Photo by Braden Kowitz (flickr).
Photo by the CA DWR.
The United States power grid consists of
approximately 200,000 miles of transmission lines that
are operated by about 500 different companies.
In the 1960s, North America was physically and
administratively divided into four major grids:
These interconnections were established as a way for
power companies to share electrical generation
resources and increase their reliability.
The electrical grid is designed and managed to
operate 99.9% of the time with less than 2%
variation in voltage, regardless of how much
demand is placed on the system.
Photo by Duke Energy.
The electrical grid works because hundreds of
components combined have a large amount of
output capability that are operated together to form
one very large and reliable system.
However, in a widely connected grid, electricity
generation and consumption must remain balanced,
as electricity is consumed almost as soon as it is
produced, and the potential for cascading failures and
widespread power outages exists.
That’s just what happened on November 9, 1965, when
the largest blackout in history occurred in the
Northeastern U.S., leaving 30 million people without
power, some for as long as 13 hours.
This led to the electric
utility industry to
establish the North
(NERC), a self-
regulatory agency who
works to develop and
promote rules and
protocols for the reliable
operation of North
American power grid.
Photo by Tripp (flickr)
Under NERC, the four interconnecting systems are
further subdivided into eight regional reliability councils,
whose members come from all segments of the electric
industry, from utilities and power producers of all sizes to
power marketers and end-use customers.
NERC does not run the day to day operations of
the grid; instead, it is an oversight agency whose
main duties are to develop and enforce industry
standards, identify trends and potential reliability
issues regarding the power grid, and to provide
providing educational and training resources for
power system operators.
In areas of the country where power supplies are
tight, Regional Transmission Organizations exist to
administer the transmission grid for their respective
regions. RTOs, sometimes called Independent
Systems Operators, are overseen by the
Federal Energy Regulatory Commission.
ISO/RTOs oversee the operation of the grid 24
hours a day, coordinating electricity generation and
demand, scheduling and managing flows over the
transmission lines, and coordinating the operation
of network equipment.
Managing the grid has become much more complex
over the past twenty years as electrical consumption
has grown and more generation capacity from various
sources has come online. Since ISO/RTOs oversee
the operation of the grid on a regional basis, they are
better positioned to detect and respond to developing
problems, and to make recommendations for system
Find your state’s energy profile here:
California leads the nation in generating electricity from
renewable sources, such as solar, wind, geothermal and
California imports the most electricity from other states.
Texas both produces and consumes more electricity than any
Wyoming is the nation’s top producer of coal, producing more
than West Virginia, Kentucky, Pennsylvania and Montana
Washington produces the most hydropower of all the states;
New York produces the most of any state east of the Rockies.
SOME FACTS ABOUT STATES
FOR MORE INFORMATION ON THE
ELECTRICAL GRID & REGULATING
How Power Grids Work, from How Stuff Works:
Electrical System Overview:
National Electrical Reliability Corporation (NERC) website:
Federal Energy Regulatory Commission: http://www.ferc.gov/
How does the electrical power produced by the
power plants get to our homes and businesses?
Electricity sent over transmission lines is in the
form of alternating current (AC), because it is
easier to generate AC rather than direct current,
and transformers can be used to change voltage
to a higher voltage which is needed for
transmission over long distances.
Consumer electronics make up
about 15%, and that is
expected to triple over the next
two decades as consumers
continue to buy and use more
Newer models of large flat screen TVs use
significant amounts of power, due to their larger
screen size and that users tend to spend more time
watching them. Some models can draw more power
than a refrigerator.
SOMETHING TO THINK ABOUT …
Electrical demand is increasing in the United States,
even as we make efficiency gains. Nonetheless, the
U. S. Energy Information Administration predicts
electrical demand will grow by 41% by 2030.
Where will this additional electricity come from?
Photo by Deacon MacMillan (flickr)
Given that electrical power generation accounts
for more carbon dioxide emissions than
transportation, and that nearly half of America’s
electrical production comes from coal, how ‘green’
is a plug-in electric car?
MORE WEB RESOURCES
Electricity:- A comprehensive article on electricity generation & distribution from
Energy Explained: Your Guide to Understanding Electricity, from the U. S. Energy
Information Administration: http://www.eia.doe.gov/energyexplained/index.cfm
Topics in Energy, from the Energy Library:
Photo gallery of the world’s 100 largest power plants:
Energy Consumers Edge: A comprehensive website on all things energy:
Frequently Asked Questions about Electricity, from the U. S. Energy Information
Pictures in this presentation were sourced from Wikimedia Commons, Flickr
photographers under the Creative Commons License, the California Department of
Resources, Bureau of Reclamation, the NREL’s Photographic Information Exchange,
and Dreamstime.com. Locations are given when known.
Also available online
Follow the path California’s first water project,
learn a bit of it’s history and find out how the
Los Angeles Aqueduct works by clicking here.
Follow the path of water as it flows from the Colorado
River, through the fertile fields of the Imperial Valley
and on to the Salton Sea by clicking here.
In the world of California water, we’re always arguing
about the Delta. What is the Delta and why is it
important? Find out by clicking here.
Hottest, driest, lowest. Death Valley is all of
these. Check out the wonders of Death Valley by