Transcript 4.1 Electrical Energy Sources and Alternatives

4.1 Electrical Energy Sources
and Alternatives
1. Using Heat to Generate Electricity
65% of all electric power is generated by
burning fossil fuels such as coal, oil, or
natural gas. Most of the fossil fuel used in
power plants is coal.
In coal-fire generating plants, the coal is first
crushed into a fine powder. It is then blown into a
combustion chamber and burned. The heat from the
burning coal boils water and superheats the resulting
steam to a high temperature and pressure. This high
pressure steam drives a large turbine.
The turbine is long shaft with many fan blades.
Steam striking the blades turns the turbine. The
turbine shaft rotates large electromagnetic coils in
the generator to produce electricity. Oil or natural
gas can be burned in the combustion chamber
instead of coal.
2. Nuclear fission is the splitting of the atoms
of a heavy element such as uranium. The
nuclear fission takes place in a nuclear
reactor. The splitting of the atoms releases
an enormous amount of energy. This release
of energy is used to produce high-pressure
steam that drives the turbine.
3. Geothermal energy is
energy that is derived from
the internal heat of the
Earth. Hot water and steam
naturally come to the Earth’s
surface after being heated by
hot rock within the Earth’s
crust. The steam can be
channeled through pipes and
used to drive turbines.
4. Biomass is biodegradable waste such as
agricultural waste or composting , or garbage
that can be used as an energy source for
steam-driven generators.
5. Cogeneration is the use of waste energy from
another process, such as heating or generating
electricity. The process of manufacturing glass
uses very high temperature furnaces. The
waste heat from the manufacturing process
can be used to produce steam to drive a
turbine to generate electricity.
6. Using Water Power to Generate Electricity
• About 20% of the world’s electricity is generated
by hydro-electric power plants. These plants
capture the energy of falling water. Most hydroelectric power plants use a dam built across a river
to store water in a reservoir. Water is directed
through a channel called a penstock to a large
paddle-covered turbine. The rushing water rotates
the turbine which is connected to a generator in
the same way as a steam-driven turbine.
Alternative Energy Sources
7. Moving water from ocean tides can also power
turbines that run generators.
8. Wind energy can be harnessed to turn a shaft. A
number of wind-powered generators can be
connected together in wind farms to produce
large amounts of electrical energy.
9. Solar cells use the photovoltaic effect to produce
electricity. Today’s silicon-based solar cells are
much more efficient than the first solar cells.
Eg. calculators, switches for automatic street lights
and burglar alarms
10. Fuel cells generate electricity directly from a
chemical reaction with a fuel such as hydrogen. The
hydrogen comes from sources such as gasoline or
alcohol.
Renewable and Nonrenewable Energy
• Nonrenewable resources cannot be replaced as
they are used up. Alberta’s fossil fuel resources
(coal, oil, and natural gas) are nonrenewable
resources.
• Renewable resources can be renewed or
replenished naturally in relatively short periods of
time. Wind energy, solar energy, geothermal
energy and biomass are renewable resources.
Trees are a renewable resource if they are
managed carefully.
4.2 Electricity and the Environment
• Every method of generating electricity affects the
environment. Some methods create undesirable byproducts that can have negative effects on human
health and the environment.
Air Pollution
• The burning of fossil fuels results in the release
into the atmosphere of many problem-causing
substances.
• Fly ash is airborne ash that is produced from
burning coal. Fly ash contains small amounts of
mercury which is a poisonous metal that can
damage the nervous system.
• Some of the most harmful molecules that are
released from burning coal are sulfur dioxide
(SO2(g)), nitrogen oxides (NOx(g)), and carbon
dioxide (CO2(g)).
Other Environmental Effects
• Strip-mining techniques are used when deposits of
coal are near the surface. Plants, animals, soil, and
rocks are cleared away above the coal deposits so
the coal can be mined. The land can be reclaimed by
replacing the soil and plants; however the original
natural environment is usually not fully restored.
• Oil and gas wells can release poisonous gases into
the environment. Concentrations of chemicals
around wells are monitored for safety.
• Steam turbines often release large amounts of
warm water into nearby lakes and rivers. Increases
in water temperature can alter freshwater ecology
and can sometimes kill fish.
• Nuclear power plants, hydro-electric power plants,
wind farms, the process of making solar cells,
geothermal plants, and generators that uses tidal or
wave energy all can have negative effects on the
environment. However, the green sources of
energy – especially wind, tide, and geothermal –
harm the environment much less than fossil fuels
do.
Conserving Energy and Nonrenewable Resources
• The main benefit of conserving energy and nonrenewable
resources is less pollution. Also, temporary shortages of
resources can cause hardship and price jumps. When fuel prices
skyrocket, poorer countries cannot afford the energy they need.
A Sustainable Future
• Sustainability means using resources at a rate that can be
maintained indefinitely. Without sustainable energy use, future
generations may not be able to support themselves. Decisions
made with sustainability in mind can involve compromise –
taking the bus may not be as convenient as driving your car,
however, this will conserve fuel.
4.3 Electrical Technology and Society
Benefits of Electrical Technologies
• Electrical technologies have improved our
standard of living. Most improvements or
inventions have come as a result of a desire
to improve speed, efficiency or
convenience. This has resulted in freeing
up people's time to do other things.
Drawbacks of Electrical Technologies
• More technology means more resources are
needed to manufacture and operate them,
making sustainability more difficult to
achieve. As technology advances, obsolete
devices become waste, adding to our
problems of waste disposal. Some
technologies are too expensive for some
countries to adopt, leading to isolation and
exclusion.
Computers and Information
• Computers have revolutionized the way we accomplish
many tasks, including writing, calculations and
communications. Computers use binary numbers (0s
and 1s) to store and transmit data which has led to the
digital technology era.
Electricity and Computers
• Electrical current is used in one way or another in
storing or transmitting information. Lasers,
photodetectors, and electrical pulses all enable
electronic devices to complete the tasks they are
made to do.
• A computer hard drive uses electrical pulses to
record and transmit information, by using an
aluminum or glass disk, with a thin layer of
magnetic material that spins at up to 300km/h. The
electrical pulses are sent to an arm with read and
write heads, which are magnetic coils that
magnetize spots on the spinning disk.
• Reading - magnetic spots induce current in
the electromagnetic coil, reproducing 0's
and 1's in the original signal and are sent to
the computer's processor.
• Writing - electrical signals are responded to
from the computer's processor.
Electrical Transmission of Information
• Electrical signals are sent from computer to
computer throughout the world, making the storage
and transmission of information compact, easy and
relatively cheap. Concerns with this ease are access,
privacy and safety.
• Misleading or false information is also a problem
and the ‘information explosion’ has created other
storage, handling and access problems. Search
engines help locate some of the information you
may be looking for, but they cannot access
everything.