Electricity

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Electricity
Generation
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Today we will explore electrical energy, better
known as electricity
So What Exactly Is Electricity?
Electricity by definition is electric current
that is used as a power source!
This electric current is generated in a power
plant, and then sent out over a power grid to
your homes, and ultimately to your power outlets.
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I guess the next question would be...
What is Electric Current?
The movement of charges such as electrons is
called current, and this electrical current is
what powers household appliances.
Charge Passing Through A Given
Area ------------------------------- Time
Electric Current
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An easier way to think of electric current is to
picture cars going through a Turnpike or
Parkway Toll.
The cars could represent electrons or charge,
and the toll booth could represent the cross
sectional area of the wire at a certain point.
If you counted the number of cars or electrons,
that passed through the toll booth or a certain
cross sectional area of the wire, and divided
that number by the time it took for those cars or
charges to pass, you would get the current!
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So How Is An Electric Current Generated?
Electric current generation - whether from fossil
fuels, nuclear, renewable fuels, or other sources
is usually based on the
Simple Equation For Electricity Generation
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What does copper wire and magnets have to do with
Electricity?
In September of 1831, Michael Faraday made the
discovery of Electromagnetic Induction.
Faraday attached two wires to a disc and rotated
the disc between the opposing poles of a
horseshoe magnet creating an electric current.
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Motion is Essential
If you place a magnet and a conductor (copper
wire), in a room together there will be no
electric current generated.
This is because motion, from our equation for
electricity, is missing!
An electric current is not generated unless the
magnetic field is moving relative to the copper
wire, or the copper wire is moving relative to
the magnetic field.
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Simple Electric Generator
So simple electric generators found in power
plants contain, magnets and copper wire that
when put into motion relative to one another
create the electric current that is sent out to
homes.
The major problem in electricity generation Is
where does the Motion come from that keeps the
copper wire and magnets moving relative to one
another.
In this case, wind power applies a force to the
blades that turns them. The spinning blades,
spin an armature that turns the copper wire
relative to the magnetic field. As long as the
blades spin, electricity will be generated!
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Electricity Transmission

• - AC of 60 Hz produced by generator
• Resistance losses are smallest at high voltages
  and low currents

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What Happens At Home?
At home, electric current that was generated by
generators in the power plant is used to power
electric appliances.
The electric current, running through the
copper wire causes the armature to spin which
is how most motors generate motion.
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Now back to the major question!
Where does the motion needed to keep the copper
wire moving relative to the magnetic field come
from?

• attains between 50 70 efficiency
• - one windmills average energy
• output ranges from 11.4 W/m2
• 57 W/m2 depending on how windy
• wind farms tend to generate between
• 50 and 600 Kw

- California currently produces ¾ of all the
wind generated electricity in the world.
Wind generated
Kilronan Wind Farm In Ireland
-North Dakota with 20 times the wind potential of
California has not erected a single wind turbine
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Annual Average Wind Power Density _at_ 50m
Wind power classes 3 (300-400 W/m2) to 7
(800-2000 W/m2) are suitable for wind power
development
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Problems With Wind Power

• Wind variability must be overcome by system design

- Basic energy Storage
Enviornmental Concerns
- Differences in pressure gradients around wind
turbines affect birds

• Noise from the turbines affects people and animals

• Eyesore, the appearance of mile after mile of
  wind machines with
• transmission lines is of concern to the public

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Hydroelectric Power

• Conversion from potential energy of
• water to electric energy is at 80 90
• efficiency

-Hydroelectric projects in the United States
have rated capacities from 950 6480 MW

• The use of Water Power is much
• greater in some other countries.
• Norway obtains 99 of its electricity
• from water power. Nepal, Brazil, and
• New Zealand are close seconds.

Water generated - Hydroelectric
Shasta Dam In California
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The Hydrologic Cycle
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- Hydroelectricity has dropped from producing 30
to 10 of US electricity
- Large fluctuations in output are mainly due to
variable rainfall totals
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Problems With Hydroelectric Power

• About 50 of the United States potential for
  hydroelectric energy has been
• tapped. However, further advances are unlikely.

• The Wild and Scenic River Act and the Endangered
  Species Act have
• inhibited development of some sites

• Silt collection in hydroelectric Dam storage
  volumes over time causes
• maintenance issues, as well as environmental
  concerns

• The loss of free flowing streams and land due to
  flooding behind the dam
• disturbs the life of species eg Salmon

- Possibility of dam failure
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Fossil Fuels Oil Refinery Pasadena - Texas
Standard Large Power Plants Provide 1 Giga-watt
of electric power and releases 2 Giga-watts of
thermal power as waste heat. An efficiency
averaging around 30.

• 9000 tons of coal a day
• 40,000 barrels a day or one tanker a week of oil
• -generates about 5.3 x 109 kwh/year
• -powers a city of a million people

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Where do Fossil Fuels come from?
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• total world production in 1996 of
• petroleum is 62,239e3 barrels / day

• an average well in the US produces
• only 11 barrels / day

Oil Drilling Platform Cook Inlet, Alaska

• In Saudi Arabia an average well
• produces 9600 barrels /day

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How do fossil fuels create motion?
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Fuel Efficiency
Over Time
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-There are 109 power reactors in the United States
-Produce 22 of nations electricity
- In France 79 of electricity comes from nuclear
reactors
Nuclear Power

• Plant electrical output 1220 MW
• -Plant efficiency 34

Diablo Canyon - California
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The Reactor Big Picture
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Nuclear Energy Problems and Concerns

• In normal operations a nuclear reactor produces
  some environmental
• emissions. E.g. escape of radioactive fission
  products through cracks and
• diffusion, radioactive H3 in small amounts in
  discharged water

• Core meltdown are possible, but unlikely due to
  negative feedback and
• shutdown systems

• Even after shutdown there is 7 of normal power
  generation still in the
• reactor fuel rods. This may be sufficient enough
  to melt core and destroy
• the reactor, if cooling water is not supplied

• A study entitled Severe Accident Risks An
  Assessment for Five US
• Nuclear Power Plants conducted by NRC in 1990,
  shows that for all the
• 109 reactors now operating in the United States
  over a 30 year lifetime
• there is about a 1 chance of a large release
  due to internal events.

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Other Energy Considerations

• Solar Power uses the sun energy to either boil
  water or directly converts
• solar energy to electrical energy

• Ocean Thermal Energy Conversion uses
  temperature differences
• between different depths of ocean water to drive
  a heat engine. Working
• fluid is ammonia which is gas at room
  temperature.

-Biomass Energy Municipal Solid Waste burning
wastes to drive heat engines

• Geothermal Energy based on naturally occurring
  heat in the Earth in the
• Earth due to radioactive decay

• Tidal Energy uses the gravitational pull of the
  moon on our oceans to
• drive turbines

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Proportion of Worlds energy consumption - 1997
Proportion of the worlds Electricity generation
- 1997
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Trend of the growth of energy sources
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