Engineering 10
Chp.6 Future
Challenges
Bruce Mayer, PE
Licensed Electrical & Mechanical Engineer
BMayer@ChabotCollege.edu
Engineering-10: Intro to Engineering
1
Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-10_Lec-09_Chp6_Population_Energy.ppt
FIRST and SECOND Laws of
THERMODYNAMICS
 Class Question:
Can Anyone Describe Either of
the FIRST or SECOND Laws
of ThermoDynamics?
Engineering-10: Intro to Engineering
2
Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-10_Lec-09_Chp6_Population_Energy.ppt
Laws of ThermoDyamics
 In the Instructor’s Opinion The
SECOND Law is the GREATEST of all
the “Laws of Physics”
 The ThermoDyamic Laws
• Describe the Relationships & Connections
Between Work↔Heat↔Energy
• Describe and Quantify Reversibility and
IRReversibilty
• Explains What’s “The Best we can Do”
Engineering-10: Intro to Engineering
3
Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-10_Lec-09_Chp6_Population_Energy.ppt
The “Laws”  What are they?
 First Law of Thermodynamics
• Energy can neither be CREATED nor
DESTROYED
– But Energy Can be Moved, or Changed to
Other forms
 Second Law of Thermodynamics
• NATURALLY OCCURRING processes are
Directional
– Natural process can go ONE WAY,
but NOT the OTHER
Engineering-10: Intro to Engineering
4
Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-10_Lec-09_Chp6_Population_Energy.ppt
Reversibility
 Reversibility is the ability to run a
process back and forth (backwards and
forwards) infinitely withOUT Losses
 Money analogy: Currency Conversion
• NO service fee (reversible):
$100  113000₩, and one hour later at the
same place, 113000₩  $100
• WITH service fees (IRreversible:
$100  68€, and one hour later at the
same place, 68€  $90 (5% fee both ways)
Engineering-10: Intro to Engineering
5
Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-10_Lec-09_Chp6_Population_Energy.ppt
Reversibility and Energy
Pressure
Voltage
Motor
Generator
Turbine
Electric Current
Pump
Fluid Flow
 If IRreversibilities were ELIMINATED,
these systems would run FOREVER.
• These Systems would then be
Perpetual Motion Machines
Engineering-10: Intro to Engineering
6
Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-10_Lec-09_Chp6_Population_Energy.ppt
Example: Popping at Ballon
 A “reversible process” can go in either
direction, but these processes are rare
 Generally, the irreversibility shows up
as waste heat
X
Not reversible unless
energy is expended
Engineering-10: Intro to Engineering
7
Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-10_Lec-09_Chp6_Population_Energy.ppt
Sources of Irreversibilities
 Friction (force drops)
 Voltage (electrical
resistance) drops
 Pressure drops
 Temperature drops
 Concentration drops
 Magnetic Hysteresis
(H Drops)
Engineering-10: Intro to Engineering
8
Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-10_Lec-09_Chp6_Population_Energy.ppt
Irreversibility Example
 It’s EASY To Mix the
Cream Into the
Coffee
 It’s extremely
difficult to UNmix
(separate) the
Cream from the
Mixed Coffee
• It takes a LOT of
Effort, or WORK, to
separate
Engineering-10: Intro to Engineering
9
Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-10_Lec-09_Chp6_Population_Energy.ppt
First Law of ThermoDynamics
 One form of work may be converted
into Another,
 Or, work may be converted to heat,
 Or, heat may be converted to work,
 But, ALWAYS
FINAL energy = INITIAL energy
Engineering-10: Intro to Engineering
10
Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-10_Lec-09_Chp6_Population_Energy.ppt
2nd Law of Thermodynamics
 We intuitively know that heat flows from
higher to lower temperatures and NOT
the other direction.
• i.e., heat flows “DownHill”; just like water
 WHY don’t we see Water flow UpHill,
or Heat move Cold→Hot on Occasion?
 Water & Heat Flow ONE-WAY Because
These processes, which “down-flowhill”, are inherently IRreversible.
Engineering-10: Intro to Engineering
11
Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-10_Lec-09_Chp6_Population_Energy.ppt
11
Heat↔Work Conversions
 Heat transfer is inherently irreversible.
• This places LIMITS on the amount of work
that can be produced from heat.
 Heat can be converted to work using
heat engines; e.g.,
• Jet engines (planes),
• Steam engines (Old Locomotives)
• Steam Turbines (Nuclear PowerPlants),
• Internal combustion engines (automobiles)
Engineering-10: Intro to Engineering
12
Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-10_Lec-09_Chp6_Population_Energy.ppt
Heat into Work (Power Plant)
W
High-temperature
Source, Thot
(e.g. flame)
Qhot
Heat
Engine
• W = Mechanical Work
Qhot  W  Qcold
Low-temperature
Sink, Tcold
Qcold
(e.g. cooling pond)
• Q = Heat
 A heat engine takes in an amount of
heat, Qhot, and produces work, W, and
waste heat Qcold  Qhot = W + Qcold
 Nicolas Sadi Carnot (kar nō) derived the
LIMITS of converting heat into work
Engineering-10: Intro to Engineering
13
Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-10_Lec-09_Chp6_Population_Energy.ppt
Carnot Equation: Efficiency
 Given the heat ENGINE on the previous
slide, the maximum
work that can be Wmax
Tcold
 1

produced is
Q
T
hot
hot
governed by:
• where the temperatures are absolute (e.g. Kelvins)
N.L.S. Carnot
 Thus, as Thot Tcold, Wmax  0
 This ratio is also called the
Thermal Efficiency, η
Engineering-10: Intro to Engineering
14
Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-10_Lec-09_Chp6_Population_Energy.ppt
Example: PowerPlant
 A BWR Nuclear
PowerPlant
Boiler Runs at
about 1000 °F
 The “Heat Sink”
is the cold Pacific
Ocean at 52 °F
 What is ηmax ?
 max
52 °F =
512 °R
Tcold
512
 1
 1
 64.9%
Thot
1460
Engineering-10: Intro to Engineering
15
1000 °F =
1460 °R
Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-10_Lec-09_Chp6_Population_Energy.ppt
Moving Energy Cold→Hot
W
High-temperature
Sink, Thot
(e.g. OutSide Air)
Qhot
Heat
Engine
Low-temperature
Source, Tcold
Qcold
(e.g. InSide AC)
 Not USING Heat, Just Moving it Around
 Moving Heat UPhill requires WORK
 The CoEfficient of Performance, CoP,
informs about the effectiveness of
AirConditioners and HeatPumps
Engineering-10: Intro to Engineering
16
Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-10_Lec-09_Chp6_Population_Energy.ppt
Carnot Equation: CoP
 Given the heat PUMP on the previous
slide, the Minimum Work
needed to move Q
1
cold

heat UpHill is
Wmin
Thot Tcold  1
governed by:


• where the temperatures are absolute (e.g. ºRankine)
 Thus, as Thot Tcold, Wmin  0
 This ratio is also called the
CoEfficient of Performance, CoP
Engineering-10: Intro to Engineering
17
Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-10_Lec-09_Chp6_Population_Energy.ppt
Example: Air Conditioner
 It’s REALLY Hot
Outside, 105 °F
 A “Cold Blooded”
person Keeps the
house at 65 °F
 What is CoPmax?
CoPmax 
Thot
Engineering-10: Intro to Engineering
18
105 °F =
565 °R
65 °F =
525 °R
1
1

 13.1
Tcold   1 565 525  1
Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-10_Lec-09_Chp6_Population_Energy.ppt
Nicolas Léonard Sadi Carnot
 Founder of the
Science of
ThermoDynamics
 BORN: Paris, France,
June 1 1796
 DIED: Paris, France,
August 24 1832
Engineering-10: Intro to Engineering
19
Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-10_Lec-09_Chp6_Population_Energy.ppt
“Water Powered” Hydrogen Car
 A “Hydrogen” car is the
SAME THING as any Other
“Electric Car”
 In BOTH Cases an Electric
Motor turns the Wheels
• In an “Electric Car” The
Energy is stored in traditional
Batteries
• In an H2 car the energy is
stored in Hydrogen Tanks
– Sometimes at 5,000 psi
Engineering-10: Intro to Engineering
20
Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-10_Lec-09_Chp6_Population_Energy.ppt
“Water Powered” Car
 It’s Easy
 Just get some H2O,
split it into H2 & O2
 Store the H2 in Big
Tanks in your Car,
 Run it thru a “Fuel Cell”
to turn an Electric Motor
• Could also burn the H2 in
a Heat Engine
 Off you go
Engineering-10: Intro to Engineering
21
Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-10_Lec-09_Chp6_Population_Energy.ppt
“Water Powered” Car – Not so Fast
Engineering-10: Intro to Engineering
22
Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-10_Lec-09_Chp6_Population_Energy.ppt
Energy & Humans
 James Watt and His Predecessors
(e.g., Savery & Newcomen) FREED
Human-Kind From Muscle Power
 The Heat Engine Was One of the Great
Advances in Human History
• Enabled the “Industrial Age”
 The Generation & Application of Energy
Multiplies The Capabilities of EVERY
Person
Engineering-10: Intro to Engineering
23
Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-10_Lec-09_Chp6_Population_Energy.ppt
Watt’s Engine
Watt, James (1736-1819)
Scottish inventor and
mechanical engineer,
renowned for his
improvements of the steam
engine. Watt was born on
January 19, 1736, in
Greenock, Scotland. He
worked as a mathematicalinstrument maker from the
age of 19 and soon became
interested in improving the
steam engines, invented by
the English engineers
Thomas Savery and Thomas
Newcomen, which were used
at the time to pump water
from mines.
Engineering-10: Intro to Engineering
24
Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-10_Lec-09_Chp6_Population_Energy.ppt
Energy Sources
 Let’s LIST Real And Potential Energy
Sources OTHER Than Fossil Fuels
1. ?
2. ?
3. ?
4. ?
5. ?
6. ?
Engineering-10: Intro to Engineering
25
Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-10_Lec-09_Chp6_Population_Energy.ppt
USA Electricity Production Mix - 2009
Solar
0.02%
Electrical Power Source
Source = USA Energy Information Adminsistration
* http://www.eia.gov/cneaf/electricity/epa/epates.html
Other
0.30%
Geo
Thermal
0.38%
Fuel Oil
0.99%
Wood &
BioMass
1.38%
Wind
1.87%
Hydro
6.93%
Nuclear
20.25%
Natural
Gas
23.35%
Coal
44.52%
0%
USA_Electricity_Mix_1010.xls
5%
10%
20%
25%
30%
35%
40%
Fraction of Total Electrical Generation
Engineering-10: Intro to Engineering
26
15%
Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-10_Lec-09_Chp6_Population_Energy.ppt
45%
50%
Energy Sources  Fact & Fancy
 Wind Power
• Wind Turbines Are VERY Attractive
– Energy Input to Produce is Low
– Incremental Added Capacity
– NO Emissions of Any Kind
• Limitations
– Low Energy Density
 Must Cover Large Areas to Produce Much Energy
 Limited Viable Sites
– Balance of System Costs (AC→AC Freq Converter)
– Danger to WildLife; Particularly Birds (Raptors)
Engineering-10: Intro to Engineering
27
Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-10_Lec-09_Chp6_Population_Energy.ppt
Energy Sources  Fact & Fancy
 Split Wood, Not Atoms → BioMass
• Burning Garbage or Plant Matter
is Attractive
– Simultaneous Solution to Energy
and Solid-Waste Problems
– “Renewable” Resource
– Low Energy Input to Produce
• Limitation: Emission Stream
is VERY Unpleasant
– Scrubbing Wood-Smoke is MUCH Harder than
Cleaning Gasoline Combustion ByProducts
Engineering-10: Intro to Engineering
28
Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-10_Lec-09_Chp6_Population_Energy.ppt
Glen Canyon Dam – Page, AZ
 Electrical Power Generation
• River: Colorado River
• Plant Type: Conventional
• Powerhouse Type: Above Gnd
• Turbine Type: Francis
• Original Nameplate Capacity:
950,000 kW (950 MWe)
• Installed Capacity:1,304 MWe
• Year of Initial Operation:1964
• Net Generation (FY 2005):
3,208,591,407 kWh
Engineering-10: Intro to Engineering
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• Rated Head:510 Bruce
feet
Mayer, PE
BMayer@ChabotCollege.edu • ENGR-10_Lec-09_Chp6_Population_Energy.ppt
Glen Canyon Dam
Aerial View
Engineering-10: Intro to Engineering
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Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-10_Lec-09_Chp6_Population_Energy.ppt
Glen Canyon Dam – Page, AZ
Engineering-10: Intro to Engineering
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Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-10_Lec-09_Chp6_Population_Energy.ppt
Glen Canyon Dam – Power Gen
150 rpm
48 Poles
Engineering-10: Intro to Engineering
32
Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-10_Lec-09_Chp6_Population_Energy.ppt
Glen Canyon Dam – Power Gen
Engineering-10: Intro to Engineering
33
Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-10_Lec-09_Chp6_Population_Energy.ppt
Glen Canyon Dam – Power Gen
 Set-UP Transformers
13.8kV  230kV
or
13.8kV  345kV
Engineering-10: Intro to Engineering
34
Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-10_Lec-09_Chp6_Population_Energy.ppt
Francis Turbine
Generator System
Engineering-10: Intro to Engineering
35
Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-10_Lec-09_Chp6_Population_Energy.ppt
Energy Sources  Fact & Fancy
 Hydroelectric Power
• Fancy: Can Provide for Future Growth
• Fact: Almost ALL Viable Hydro Sites
Have Been USED
– Damming More Rivers is a Political Issue
 Ethanol as AutoMobile Fuel
• Fancy: Ethanol Can Replace Oil As a
Source for Automobile Fuel
• Fact: Making Ethanol from Corn May Use
MORE Energy than It Produces
Engineering-10: Intro to Engineering
36
Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-10_Lec-09_Chp6_Population_Energy.ppt
Energy Sources  Fact & Fancy
 Ethanol Continued
• DISTILLATION of Ethanol from Fermented
Corn Requires Large Amounts of Energy
– Usually Provided by Burning Fossil Fuels at the
Distillation Site, or at the Electrical Power Plant
 Solar PhotoVoltaics (solar cells) Can
Supply Future Energy Needs
• Photovoltaic Solar-Electric Cells Have
Many Advantages
– Remote Siting, Incremental Expansion
Engineering-10: Intro to Engineering
37
Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-10_Lec-09_Chp6_Population_Energy.ppt
Energy Sources  Fact & Fancy
 Solar Cells Continued
• BUT Making a Solar Cell Requires
Large Amounts of Energy
– Silicon Cells are Made by, in the
Beginning, MELTING SAND
– Production Processes Can be
Energy Intensive as Well
• Connecting to the Existing Electric Grid
Includes a Great Deal of “Balance of
System” Components
– DC→AC “Inverters”, Special Electrical boxes
Engineering-10: Intro to Engineering
38
Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-10_Lec-09_Chp6_Population_Energy.ppt
Energy Sources  Fact & Fancy
 Solar Cells Continued
• Solar Radiation has a
Very Low “Energy Density”
– Requires LARGE Areas to Collect
Significant Amounts of Energy
Proton
Exchange
Membrane
(PEM) FC
http://fuelcells.si.
edu/basics.htm
 Can Crowd-Out Other Uses:
Solar-Farm vs. Tomato-Farm
 Hydrogen Fuel Cells
• Based on Chemical Reaction
2H 2  O2  H 2O
See also http://www.olympusmicro.com/primer/java/fuelcell/
Engineering-10: Intro to Engineering
39
Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-10_Lec-09_Chp6_Population_Energy.ppt
Solar-Farm vs. Orange Orchard
Engineering-10: Intro to Engineering
40
Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-10_Lec-09_Chp6_Population_Energy.ppt
Energy Sources  Fact & Fancy
 Hydrogen Fuel Cells Continued
• The Fuel Cell Reaction Looks Very Good
– NO VOCs/HydroCarbon Emissions
– NO NOx emission
– NO Greenhouse Gases (CO2)
• But WHERE Do We Get the HYDROGEN?
– There are NO Hydrogen WELLS or MINES
• The Viable Sources of Massive Amounts of
Hydrogen themselves Require Large
Energy or Carbon Inputs
Engineering-10: Intro to Engineering
41
Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-10_Lec-09_Chp6_Population_Energy.ppt
Energy Sources  Fact & Fancy
 In Apr04 Gov. Arnold Schwarzenegger
has proposed an ambitious network of
hydrogen filling stations by 2010
 See also http://www.hydrogenhighway.ca.gov/
 But How can we MAKE
all the Hydrogen
needed to Replace
Gasoline?
 There are 3 Viable Alternatives
Engineering-10: Intro to Engineering
42
Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-10_Lec-09_Chp6_Population_Energy.ppt
Energy Sources  Fact & Fancy
1. Use WIND or NUCLEAR Power to
generate Electricity which, in Turn,
would be Used to Electrolize WATER
•
Electrolosis applies Electrical current to
water and splits it into oxygen and
hydrogen, which are then separated…
•
The Chemical Reaction
2 H 2O  2 H 2  O2
ElectricalEnergy
 This is a Very Energy Intensive Process;
about 75% efficient
Engineering-10: Intro to Engineering
43
Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-10_Lec-09_Chp6_Population_Energy.ppt
Ulf Bossel, “Does a Hydrogen Economy Make Sense?”, Proceedings
of the IEEE | Vol. 94, No. 10, October 2006, pp 1826-1837
Electric Cars: H2 vs ElectroChem
Engineering-10: Intro to Engineering
44
Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-10_Lec-09_Chp6_Population_Energy.ppt
Energy Sources  Fact & Fancy
2. Steam reforming of natural gas
•
If you take methane, the main component
of natural gas, and expose it to steam,
the final products are primarily carbon
dioxide and hydrogen. Chemically
CH4  2H 2O  4H 2  CO2
• This is already a Large-Volume Industrial
Process, but it produces a LOT of CO2 –
a GreenHouse Gas
• Natural Gas Supplies seem ample
Engineering-10: Intro to Engineering
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Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-10_Lec-09_Chp6_Population_Energy.ppt
Energy Sources  Fact & Fancy
3. Coal gasification
•
hydrogen could be produced at
centralized plants, compressed and most
likely transported in trucks.
•
Coal is mostly carbon & hydrogen, but
also contains some sulfur. Exposed to
water at high temperature and high
pressure, it chemically reacts to yield
carbon monoxide (CO) and hydrogen.
– But CO is Poisonous to Humans
Engineering-10: Intro to Engineering
46
Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-10_Lec-09_Chp6_Population_Energy.ppt
Energy Sources  Fact & Fancy
3. Coal gasification, cont.
•
Oxygen from additional water vapor turns
carbon monoxide into carbon dioxide. So
the end products are primarily carbon
dioxide and hydrogen gas. Chemically
CH 0.8 S0.005  xH2O  yH 2  zCO2  wH 2 S
• We have LOTS of Coal, but still need to
clean up the CO2 and H2S
Engineering-10: Intro to Engineering
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Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-10_Lec-09_Chp6_Population_Energy.ppt
http://www.eia.doe.gov/aer/overview.html * 2009
USA Primary Energy
Production by Source
Engineering-10: Intro to Engineering
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Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-10_Lec-09_Chp6_Population_Energy.ppt
USA Energy Production Mix - 2008
BioMass, 5.29%
Wind, 0.70%
Solar/PV, 0.12%
Geothermal, 0.49%
Hydro, 3.33%
Coal, 32.36%
Nuclear, 11.47%
NGPL, 3.28%
Crude Oil, 14.27%
Natural Gas,
28.69%
Energy Information Administration / Annual Energy Review 2008
Engineering-10: Intro to Engineering
49
Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-10_Lec-09_Chp6_Population_Energy.ppt
Energy  BackWork Ratio
 The BIG QUESTION for Any Energy Src
• For Every Unit of Energy OUTput, How Much
Energy was INput for the ENTIRE Production
Stream?
– In Electrical Power Generation, for the Steady-State
Condition, this is called the “BackWork Ratio”
Power to Run the Plant
BWR 
Power Output of the Plant
 Many Energy Sources Fail This Question
• e.g., Many Solar-Electric Systems will NOT
Return the Energy Required to Make Them
Engineering-10: Intro to Engineering
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Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-10_Lec-09_Chp6_Population_Energy.ppt
All Done for Today
California’s
Hydrogen
HighWay
There were 143
H2 vehicles in
2007
Engineering-10: Intro to Engineering
51
Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-10_Lec-09_Chp6_Population_Energy.ppt
A Potential Energy Scenario
Engineering-10: Intro to Engineering
52
Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-10_Lec-09_Chp6_Population_Energy.ppt
USA Electricity Production Mix - 2008
Solar
0.02%
Electrical Power Source
Total = 4 125 675GWhe
Other
0.28%
Geo
Thermal
0.36%
Source = USA Energy Inf ormation Adminsistration
* http://www.eia.doe.gov/cneaf /electricity/epa/epates.html
Fuel Oil
1.12%
Wood &
BioMass
1.33%
Wind
1.34%
Hydro
6.18%
Nuclear
19.54%
Natural
Gas
21.69%
Coal
48.13%
0%
USA_Electricity_Mix_0810.xls
5%
10%
20%
25%
30%
35%
40%
45%
Fraction of Total Electrical Generation
Engineering-10: Intro to Engineering
53
15%
Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-10_Lec-09_Chp6_Population_Energy.ppt
50%
55%