Electricity Generation and Distribution
What Is Electricity?
Electricity is a form of energy that starts with atoms. Atoms
are too small to see, but they make up everything around us. All
atoms are composed of subatomic particles among which are the charged
particles known as electrons and protons. Protons, which are found
in the nucleus of an atom, carry a positive charge (+), and electrons,
which spin around the center of an atom, carry a negative charge
(-). Neutrons also exist in the nucleus of a typical atom and are
Electricity is a form of energy that is associated with the buildup
and movement of electrons and protons. Electricity can be created
by forcing electrons to flow from atom to atom. The force or push
of electricity is measured in volts. Electrical systems of most
homes and office have 120 volts.
How Electricity Is Generated
Most electricity in the U.S. is generated using coal, oil, natural
gas, nuclear energy, or hydropower. Some production is done with
alternative fuels like geothermal energy, wind power, biomass, solar
energy, or fuel cells.
A majority of the electricity is produced at power plants with
the use of steam turbines. Mechanical energy is changed into electrical
energy by using various energy sources such as coal, natural gas,
and oil. These fuels heat water in a boiler to produce steam. The
steam, under tremendous pressure, is used to turn a series of blades
mounted on a shaft turbine. The force of the steam rotates a shaft
that is connected to a generator. The spinning turbine shafts turn
electromagnets that are surrounded by heavy coils of copper wire
inside generators. This creates a magnetic field, which causes the
electrons in the copper wire to move from atom to atom, creating
The voltage produced by a generator depends upon the number of
turns in its coils, the strength of the magnet, and the rate at
which the magnet turns. The more turns in the coils, the more voltage
Hydroelectric plants use the power of falling water to push against
the turbine blades, causing a rotor to spin. Water stored behind
a dam is released and directed through special tubes to flow against
the blades of turbines and make them turn. Hydropower provides about
10 percent of the electricity generated in the U.S. The most famous
hydroelectric facility in the country is Hoover Dam.
The majority of electricity used in the U.S. is generated from
power plants that burn fossil fuels (coal, oil, and natural gas)
to heat water and make steam. The highly pressurized steam is directed
at the blades of turbines to make them spin.
Coal, oil, and natural gas are known as fossil fuels because they
were formed from the fossilized remains of animals or plants that
lived long ago. Long ago, even before the dinosaurs, these plants
and animals died and settled to the bottom of lakes and oceans to
be covered over by sand and mud. Over millions of years, the earth's
pressure and heat converted their remains into coal, oil, and natural
Coal is extracted from the ground at large mines. Coal is used
to generate about half of the electricity used in the U.S.
Natural gas and oil are obtained through wells drilled deep in
the earth. Natural gas is used to generate about 10 percent of the
electricity used in the U.S., and oil is used to generate about
two percent of electricity used in the U.S. The U.S. depends on
natural gas for about 24% of its total primary energy requirements.
Nuclear power plants use the heat from splitting atoms to convert
water into the steam that turns turbines. These plants rely on uranium,
a type of metal that must be mined from the ground and specially
processed. Fuel rods containing uranium are placed next to each
other in a machine called a nuclear reactor. The reactor causes
the uranium atoms to split and in so doing, they release a tremendous
amount of heat. The U.S. in 2000 produced 22.3 quadrillion BTUs
from nuclear electric power. (A BTU, or British thermal unit, is
the amount of heat necessary to raise the temperature of one pound
of water by one degree Fahrenheit.)
Geothermal energy utilizes steam trapped in the earth. A geothermal
power plant is similar to a steam power plant. A deep well is drilled
and steam comes out, goes through a heat exchanger, and then spins
a turbine. Electric power plants driven by geothermal energy provide
over 44 billion kilowatt-hours (kWh) of electricity worldwide per
year. The U.S. in 2000 produced .32 quadrillion BTUs from geothermal
The force of the wind pushes against the turbine blades, causing
the rotor to spin and generate an electric current. Most wind power
is produced from wind farms—large groups of turbines located
in consistently windy locations. The U.S. in 2000 produced .05 quadrillion
BTUs from wind power; wind energy contributed more than 3.5 billion
kWh of electricity.
Biomass is organic matter, such as agricultural wastes and wood
chips and bark left over when lumber is produced. Biomass can be
burned in an incinerator to heat water to make steam, which turns
a turbine to make electricity. It can also be converted into a gas,
which can be burned to do the same thing. Biomass provides about
3 to 4 percent of our energy in the U.S.; in 2000, 22.3 quadrillion
BTUs were produced from wood, waste, and alcohol. The wood and paper
products industries generate and use about two-thirds of this power.
Solid wastes from cities fuel most of the remaining biopower plants,
providing enough electricity to meet the needs of nearly 7 million
Solar energy is generated without a turbine or electromagnet.
Special panels of photovoltaic cells capture light from the sun
and convert it directly into electricity. The electricity is stored
in a battery. The U.S. in 2000 produced .07 quadrillion BTUs from
solar power. More than 200,000 houses in the U.S. take advantage
of the sun's energy.
A fuel cell is a device or an electrochemical engine that converts
the energy of a fuel directly to electricity and heat without combustion.
Fuel cells consist of two electrodes sandwiched around an electrolyte.
When oxygen passes over one electrode and hydrogen over the other,
electricity is generated. Fuel cells running on hydrogen derived
from a renewable source would emit nothing but water vapor. Fuel
cells are clean, quiet, and efficient.
Energy Statistics: U.S. Energy Information Administration
How Electricity Is Distributed
Power plants do not store electricity, so it is constantly being
made and then distributed. Utility companies have to anticipate
demand for electricity and distribute it to consumers.
Electricity can be distributed most efficiently at very high voltage.
Transformers are used to “step up” or “step down”
the voltage along the system of power lines that carry electricity
First, the voltage of the electricity produced by a generator in
the power plant is “stepped up” when it travels through
a secondary coil of a transformer that has far more turns of wire
than the primary coil. Each charge that passes through that coil
then has more energy than the charges in the primary coil. The current
therefore has an enormous voltage when it leaves the secondary coil
and then travels through the system of cables and wires from the
power plant into the transmission grid.
These transmission lines carry the electricity across long distances
to substations. A substation has transformers that “step down”
the high-voltage electricity into lower voltage electricity. At
a substation, the current passes through a transformer with a secondary
coil that has fewer turns of wire, which reduces it to only a medium-high
From the substation, distribution lines carry the electricity to
other transformers on utility poles or on the ground that reduce
the voltage so it can be used in homes, offices, stores, and factories.
A cable then carries the electricity from the distribution wires
to the house through a meter box. The meter measures how much electricity
the people in the house use.
From the meter box, wires run through the walls to outlets and
lights. The electricity is always waiting in the wires to be used.
The amount of electricity in the lines must be kept at a constant
electrical pressure to provide enough power for the appliances and
equipment that will use it. A second set of wires carries the current
back to the generator in the power plant. These return wires are
necessary because electric current must travel in a loop, or a closed