Electricity

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# Electricity - PowerPoint PPT Presentation

Electricity. Generation. 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

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Presentation Transcript

Electricity

Generation

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.

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 =

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!

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

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.

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.

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!

Electricity Transmission

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

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.

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 windmill’s average energy
• output ranges from 11.4 W/m^2 –
• 57 W/m^2 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

Annual Average Wind Power Density @ 50m

Wind power classes 3 (300-400 W/m2) to 7 (800-2000 W/m2) are suitable

for wind power development

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

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

- Large fluctuations in output are mainly due to variable rainfall totals

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

Fossil Fuels – Oil Refinery

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 10^9 kwh/year
• -powers a city of a million people

total world production in 1996 of

• petroleum is 62,239e3 barrels / day
• an average well in the US produces
• only 11 barrels / day
• In Saudi Arabia an average well
• produces 9600 barrels /day

Oil Drilling Platform

-There are 109 power reactors in the United States

-Produce 22% of nation’s electricity

- In France 79% of electricity comes from nuclear reactors

Nuclear Power

• Plant electrical output 1220 MW
• -Plant efficiency 34%

Diablo Canyon - California

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.

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

Proportion of World’s energy

consumption - 1997

Proportion of the world’s

Electricity generation - 1997