Transcript P120_2008_week_12

Possible topics for last 2 weeks
(votes on first day of class)
(1 point for first, 2 for second etc.)
• Hydrogen economy (128)
• Nuclear Power (fission/fusion) (137)
• Fuel Cells (154); I’ll include this in with
Hydrogen economy discussion.
• Unconventional Fossil (189) Won’t cover
this.
• Other suggestions now??
Electric Circuit basics
• V= I*R
• R is measured in OHMS (W) 1W= 1V/1A
• R = r l/A
– r : resistivity
• (e.g. Cu 1.69x10-8 Wm; Al 2.75x10-8 Wm)
– l length of the wire
– A cross-sectional area of the wire
• P= I*V
Series and Parallel Circuits
Series circuit: Current is
the same in all elements
(voltages add)
Parallel circuit: Voltage
is the same in all
elements (Currents add)
The other side of the circuit
• Need a source of EMF to “lift” the
electrons up the potential energy hill in the
power source:
– Batteries, Fuel Cells (chemical)
– Generators (electro-magnetic)
– Solar (photo-electric effect)
Batteries
H&K p 327
All batteries have the same basic principle, but the chemical reactions and
The materials used for the electrodes and electrolytes) differ. This gives
Different voltages, internal resistances, masses, operating temps, etc.
Batteries: Energy Density
http://www.hardingenergy.com/pdfs/ComparisonofApplication.pdf
(as of Jan. 2004, note on this scale, gasoline is 12000 Wh/kg and 9500 Wh/l)
Compare these numbers to table 10.1 in the text.
Faraday’s Law
• “A coil of wire experiences an electromotive force that is proportional to the rate
of change of the magnetic flux passing
through the loop.”
• Magnetic flux is the product of the
magnetic field strength times the area it
passes through projected onto the field
direction (just like solar flux on a panel).
B
Aperp
Basic AC Electric Generator
North American Power Plants
http://en.wikipedia.org/wiki/Electric_power_transmission
Another interesting site: http://carma.org/ will give you more info on these
Plants (and indeed 50,0000 others worldwide!).
US Electrical power Generation
(2006)
http://www.eia.doe.gov/fuelelectric.html
Look at the text, which
Shows an interesting
Distinction between
Utility producers and
Non-utility producers
In terms of this mix.
(p 319)
http://www.eia.doe.gov/cneaf/electricity/epa/epat4p1.html see for
Information on actual energy consumed by fuel type.
US Electrical Power Generation
1978 Pub. Util. Reg. Policy Act opened up competition and led to the
introdution of smaller producers (non-utility produces). Note the different
mix of fuel sources!
Load (or capacity) factors
http://www.eia.doe.gov/cneaf/electricity/epa/epa_sum.html
Nuclear and Coal have very large “load factors” (these plants tend to run
most of the time, and provide “base load” capacity. Other types of plants,
like Natural gas, can be “fired up” more quickly and tend to be used to
accommodate peak loads (sometimes called “peaking plants”).
U. Cincy Cogeneration Plants
Two generating
stations: 47MW
combined.
Annually produces:
245M kWh
Heat to 9Msq.ft of
bldg space
Various fuel options
can be used.
http://www.uc.edu/facmgmt/utility.asp
Typical generating station
http://www.wvic.com/how-gen-works.htm
Web site also has a good schematic of a generator in action
Typical Steam generator
http://en.wikipedia.org/wiki/Fossil_fuel_power_plant
Typical Gas generator
(combined cycle plants)
http://en.wikipedia.org/wiki/Fossil_fuel_power_plant
http://en.wikipedia.org/wiki/Combined_cycle
Combined Cycle plants
http://www.cogeneration.net/Combined_Cycle_Cogeneration.htm
Combined cycle/Carbon
sequestration plant
http://alt-e.blogspot.com/
Electrical distribution/transmission
You want to transmit at high voltage (to keep currents, and therefore losses
low), but you have to deliver at small voltages (to keep customers safe). AC
power, with the use of transformers, makes this possible.
Transformers
http://www.directindustry.com/cat/electricity/power-transformers-C-363.html
Transmission/distribution lines
Some High Voltage transmission
lines are DC not AC (see right),
but they look pretty much the same.
http://www.osha.gov/SLTC/etools/electric_power/illustrated_glossary/transmission_lines.html
Examples.
• H&K 11-Prob. 2* A small transformer used
for a doorbell steps down the voltage from
120V and 0.5A to 12V. What is the flow of
current to the door bell, and what is the
turns ratio of the transformer?
Wind Energy
http://www.windpower.org/en/tour/wres/euromap.htm
An extensive site for Wind
Information!!
Wind Energy
The text gives (on page
407 in slightly different
units) the formula:
P = 0.3*D2 V3 (W.s3/m5)
D-turbine diameter
V- wind velocity
So a 9m/s wind provides
27 times the power that
a 3m/s wind provides!!
http://cenlamar.files.wordpress.com/2008/07/plan_3tiermap.jpg
Examples.
• Estimate the size of a wind turbine
designed to produce 3MW in a 15 m/s
wind.
2003 Blackout before and
after
http://en.wikipedia.org/wiki/2003_North_America_blackout
Altamont Pass (CA)
http://www.ilr.tu-berlin.de/WKA/windfarm/altcal.html
6000 turbines, built 1980’s
San Gorgonio Pass (CA)
http://www.ilr.tu-berlin.de/WKA/windfarm/sgpcal.html
3500 turbines, built 1980’s
Wind Turbines
http://www.afm.dtu.dk/wind/turbines/img0003.jpg
Basics of a Wind Turbine
Variable pitch allows
the blades to be
“feathered” when
the wind gets too
strong. Yaw drive
allows the turbine to
be directed toward
the wind.
http://www.nrel.gov/wind/animation.html
Web site for movie on wind turbine construction
http://www.gepower.com/businesses/ge_wind_energy/en/image_gallery/index.htm
Three Gorges Dam (China)
http://images.google.com/images?um=1&hl=en&client=firefox-a&rls=org.mozilla:en-US:official&q=three+gorges+dam&&sa=N&start=20&ndsp=20
ITAIPU (Brazil/Paraguay)
http://www.solar.coppe.ufrj.br/itaipu.html
ITAIPU (Brazil/Paraguay)
http://www.solar.coppe.ufrj.br/itaipu.html