28-01-2013, 04:39 PM
Electricity Generation
Electricity Generation.ppt (Size: 1.67 MB / Downloads: 282)
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...
The movement of charges such
as electrons is called current, and
this electrical current is what
powers household appliances.
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.
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!
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.
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.
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.