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MIT OpenCourseWarehttp://ocw.mit.edu

2.61 Internal Combustion EnginesSpring 2008

For information about citing these materials or our Terms of Use, visit: http://ocw.mit.edu/terms.

http://ocw.mit.edu/http://ocw.mit.edu/termshttp://ocw.mit.edu/termshttp://ocw.mit.edu/

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Fuel and engine alternatives

Prof. Wai K. Cheng

Sloan Automotive Lab

Massachusetts Institute of Technology

Assessment of Future Automotive Power Plant Technology

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Transportation/Mobility

Transportation/mobility is a vital to

modern economy Transport of People

Transport of goods and produce People get accustomed to the ability to

travel

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Transportation takes energy

1970 1980 1990 2000 2010

0102030

405060

708090

100

Quadrillion(10

15)BthU

Year

Transportation

Industrial

Commercial

Residential

US use of energy per year by sectors

Total

Source: US Dept. of Energy

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Transportation needs special kind of

energy source

Vehicles need to carry source of energy onboard

Hydrocarbons are unparalleled in terms of

energy density For example, look at refueling of gasoline

~10 gallon in 2 minutes (~0.25 Kg/sec) Corresponding energy flow

= 0.25 Kg/sec x 44 MJ/Kg

= 11 Mega Watts Petroleum !

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What is in a barrel of oil ?(42 gallon oil ~46 gallon products)

Source: California Energy Commission, Fuels Office

Asphalt and Road Oil

Liquefied Refinery Gas

Residual Fuel OilMarketable Coke

Still Gas

Jet Fuel

Distillate Fuel Oil

Finished Motor Gasoline

Lubricants

Other Refined Products

0.90%

1.50%1.90%

2.80%

3.30%5.00%

5.40%

12.60%

15.30%

51.40%

Typical US output

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US Use of Petroleum by sector

1970 1980 1990 2000 20100

5

10

15

20

25

MillionsofBarrels/da

y

Year

Transportation

Industrial

ResidentialCommercial

Electric utilities

Source: US Dept. of Energy

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Transportation energy use(does not include military transportation)

1970 1980 1990 2000 20100

5

10

15

20

25

30

Energyus

e(x1015BT

hU)

Year

Passenger cars

Light trucks

Heavytrucks

Non-Highway

Source: US Dept. of Energy, TransportationEnergy Data Book: Edition 26-2007.

2003

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Size of the Automotive Industry

PRODUCT HAS TO BE ECONOMICALLY VIABLE ON ITS OWN

Sales (US) ~ 18 millions new vehicles/year

Approximately 72,000 vehicles produced per day(1.2 seconds / vehicle)

NEED HIGH VOLUME TO MAKE MONEY

High capital cost in manufacturing

~$3 Billion or more for a new line

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Petroleum IndustryVery capital intensive

Exploration and production

Refinery

Distribution system

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Inertia of the industry

Utilization of capital Need for capital expense to depreciate

Technology takes time to develop andimplemented

Example: vehicle powertrain

a. Incremental changes: Design needs to becompleted 3-4 years before production

b. Significant changes: Add 5-10 years of

development time to (a)c. Drastic changes: Add 15 to 20 years to (a)

d. Radical changes: Add ? years to (a)

Market penetration

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Technologypenetration

(after significant sales) Source: Heavenrich, Light-

Duty Automotive Technologyand Fuel Economy Trends,1975-2005, EPA420-R-05-001

Diesel sales fraction inEurope 1999-2005. (DIdiesel introduced in1997; sales fractionconstant at 14% from1987-1991.) Source:DOE

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CUSTOMER NEEDS

VEHICLE Reasonable Cost

Reliability Comfort

Performance

Aesthetics - Look and Feel

FUEL

Cost Availability

Ease of refueling

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ENVIRONMENTAL IMPACT

Air quality

NOx

CO

Ozone

Particulate matters

Toxics

Noise

Green House Effect (CO2, methane)

Kyoto Agreement (USA): 7% reduction of CO2 from1990 level

Congestion

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FUELS

Reformulated Gasoline

Methanol

Ethanol and other bio-fuels

Hydrogen

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Fuels Density LHV/mass* LHV/Vol.** LHV/Vol. of Stoi.Mixture

@1 atm, 300K***(Kg/m3) (MJ/Kg) (MJ/m3) (MJ/m3)Gasoline 750 44 3.3x104 3.48Diesel 810 42 3.4x104 3.37

Natural Gas@1 bar 0.72 45 3.2x101(x) 3.25@100 bar 71 3.2x103

LNG (180K, 30bar) 270 1.22x104

Methanol 792 20 1.58x104

3.19Ethanol 785 26.9 2.11x104 3.29

Hydrogen@1bar 0.082 120 0.984x101(x) 2.86

@100 bar 8.2 0.984x103

Liquid (20K, 5 bar) 71 8.52x103

*Determines fuel mass to carry on vehicle**Determines size of fuel tank***Determines size of engine

Transportation Fuels

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Relative CO2 production from differentfuel molecules

C. Amann, SAE Paper 9092099

Image removed due to copyright restrictions. Please see Amann,Charles A. The Passenger Car and The Greenhouse Effect.SAE Journal of Passenger Cars99 (October 1990): 902099.

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Modify fuel properties to improve airquality (does not significantly impactCO2 emissions)

Introduce oxygenates (MTBE, ethanol,

etc.) in gasoline to lower CO and HCemissions (US: 2% oxygenaterequired)

Lower sulfur content improve catalyst performance in

gasoline vehicles lowers sulfate emissions in diesels Lower aromatic content to reduce toxic

emissions Lower Reid vapor pressure in gasoline

to reduce diurnal emissions

COMPATIBLE WITHCURRENT ENGINES IN

EXISTING FLEET

REFORMULATED FUELS

1.1 1.2 1.3 1.4 1.55

10

15

20

25

Improvementin

COemission(%)

Gasoline with 11% MTBE

Note: for modern engine with feedback,oxygenate effect on emissions is minimal

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ALTERNATIVE FUEL: METHANOL

GOOD COMBUSTION CHARACTERISTICS High octane number (ON=99)

Cleaner exhaust: Lower CO and HC emissions

PROBLEMS

Smaller heating value (~1/2 of that of gasoline)

toxic and corrosive

Difficulty in cold-start

PRODUCTION - From natural gas and coal Not efficient use of original fossil fuel: methanol is essentially a

partially oxidized product

OUTLOOK

Not an attractive intermediate alternatives because: needs expensive retrofit of existing engine

Not good long term prospect; not efficient use of energy source

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ALTERNATIVE FUEL: ETHANOL

GOOD COMBUSTION CHARACTERISTICS High octane number (ON=107)

Cleaner exhaust: Lower CO for older vehicles

PROBLEMS Smaller heating value (61% of that of gasoline)

Water absorption/corrosion/volatility problem

Need special hardware

Difficulty in cold-start

PRODUCTION Mostly from starch crops (corn, barley, wheat etc.) by fermenting

and distilling

Cellulosic ethanol (from tree, grass, etc.)

E85 (85 liq. vol. % ethanol) is used as a practical fuel Needs flexible fuel vehicle for practical operation because

of uncertainty in fuel supply

ALTERNATIVE FUEL:

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ALTERNATIVE FUEL:

ETHANOL, bio-fuel for the future?

020406080

100120140160180

1992 1994 1996 1998 2000 2002 2004 2006 2008

Million

so

fbarre

lsAnnual fuel ethanol production

U.S. All Grades Conventional RetailGasoline Prices (Cents per Gallon))

0

50

100

150

200250

300

350

400

Cen

tsperga

l

Jan96

Jan97

Jan98

Jan99

Jan00

Jan01

Jan02

Jan03

Jan04

Jan05

Jan06

Jan07

Jan08

Jan95

2

2.2

2.4

2.6

2.8

3

3.2

3.4

3.6

3.8

4

1995

1996

1997

1998

1999

2000

2001

2002

2003

2004

2005

2006

2007

2008

Annual average or averagedup to current month

$pe

rgallon

Fresh whole milk retail price (up to May, 08)

Spot price 5/12/08:$ 2.50/gal

May 08 spot price: $2.50/galRetail price: $3.80/gal

Source: California Energy Commission, 2006

ALTERNATIVE FUEL ETHANOL

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ALTERNATIVE FUEL: ETHANOL

Bio-Fuel for the future?

Current US demand for ethanol is driven bygovernment regulations and incentives

Ethanol flex-fuel vehicles produced because of the 74%

credit towards CAFE requirement (E85 vehicle equivalent mph = mpg x 1.74)

Gasoline oxygenate mandate, and phase out of MTBE

Energy bill (Aug. 05) mandated a threshold of 7.5 billiongallons (180 million barrels) production by 2012

Tax subsidy

blenders tax credit $0.51/gallon alcohol

$0.051/gallon fuel tax exemption for gasohol minimum 10 vol % alcohol

Is corn-based ethanol the bio-fuel of the future?Substantial increase in US food price

ALTERNATIVE FUEL ETHANOL

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Ethanol from corn Several studies of the overall energy budget

P = energy used in production

feedstock production/ transport + processing E = Energy of the ethanol output

Return (%) = (E P) / E

Studies Pimentel and Patzek (2003, 2005): negative return

Return = - 29% USDA (Shapouri et al 2002, 2004): positive return

Return* = +5.6%Return* = +40% if by products (Corn gluten meal, etc.)are accounted for

ALTERNATIVE FUEL: ETHANOL

Bio-Fuel for the future?

* For comparison purpose, these figures were converted from thevalues of (E-P)/P of +5.9% and +67% in the original publication

Verdict:Substantial

environmentaland economic

cost; return not

clear

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Other bio-fuels

Pimentel and Patzek also estimated energybudget for other bio-fuels. Returns:

Ethanol from switchgrass = -50%

Ethanol from wood biomass = -57% Bio-diesel from soybean = -27%

Bio-diesel from sunflower = -118% Outlook: NOT CLEAR

New technology needed to change the

picture

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ALTERNATIVE FUEL: HYDROGEN

Excellent fuel for combustion engines or fuel cells

No green house gas emissions/ hydrocarbon emissions

Strictly, hydrogen is not a fuel, but an energy storage medium

Not an efficient use of the original energy source Efficiency loss in generating and in using the hydrogen

PROBLEMS

Storage (cryogenic, high pressure cylinders, metal hydride matrix) -

Bulky and expensive At 200 bar storage pressure, pumping loss is 13% of LHV

Infra-structure for fuel supply

Safety

OUTLOOK: not attractive On-board hydrogen storage: not a desirable option

Hydrogen from fuel reforming

Complex process with efficiency lossDoes not alleviate green house gas

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ENGINES

Spark Ignition Engines

Good fuel efficiency, reasonable cost Improving emissions characteristics

Diesel Engines

Better fuel economy

higher cost

NOx / particulate emissions

Electric/ Hybrid/ Plug-in-hybrid Vehicles

Fuel Cell

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Hybrid vehicles

Configuration:

IC Engine + Generator + Battery + Electric Motor

Concept

Eliminates external charging As load leveler

Improved overall efficiency

Regeneration ability Plug-in hybrids: use external electricity supply

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Hybrid Vehicles

ENGINE GENERATOR

MOTOR

BATTERY

DRIVETRAIN

Series Hybrid

ENGINE GENERATOR

MOTOR

BATTERY

DRIVETRAIN

Parallel Hybrid

Examples: Toyota Prius (full hybrid); Honda Insight (electric assist)

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Hybrid Vehicles: Market

On the market since 1997 (Japan) Currently available in US:

Toyota Prius (~$20K) Honda Insight, Civic Hybrid (~$19-20K) Ford Escape ($27K)

Note:No. of EV sold world wide since their introduction 30

years ago is < 30,000 units, and has flattened out

No. of Prius sold in three years(1997-2000) 34,000 units

Toyota Hybrid sale (2004) 130,000 units(source: Toyota)

T P i H d I i h

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Toyota Prius Honda Insight

66/43 mpg on

Japan/US driving cycle

80/60 mpg on

Japan/US driving cycle

Photos removed due to copyright restrictions. Please see anypromotional photos of the Toyota Prius and the Honda Insight.

ELECTRIC HYBRID VEHICLE TECHNOLOGY

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ELECTRIC HYBRID VEHICLE TECHNOLOGY

Toyota Prius Engine: 1.5 L, Variable Valve Timing, Miller Cycle (13.5

expansion ratio), Continuously Variable Transmission

58 HP at 4000 rpm Motor - 40 HP

Battery - Nickel-Metal Hydride, 288V

Fuel efficiency: 66 mpg (Japanese cycle)

43 mpg (EPA city driving cycle)

41 mpg (EPA highway driving cycle) Efficiency improvement (in Japanese cycle) attributed to:

50% load distribution; 25% regeneration; 25% stop and go

Cost: ~$20K (subsidized)

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Cost factor

If $ is price premium for hybrid vehicleP is price of gasoline (per gallon) is fractional improvement in mpg

Then mileage (M) to be driven to break even is

=

xP

mpgx$M

(assume that interest rate is zero)

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Cost Factor

Example:Honda Civic and Civic-Hybrid

Price premium ($, MY08 listed) = $7155 ($22600-15445)mpg (city and highway av.) = 29 mpg (42 for hybrid)hybrid improvement in mpg(%) = 45%

At gasoline price of $4.00 per gallon, mileage (M) drivento break even is

miles115,000

45%x4$

29x7155$M ==

(excluding interest cost)

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Barrier to Hybrid Vehicles

Cost factor

difficult to justify especially for the small,already fuel efficient vehicles

Battery replacement (not included in the previousbreakeven analysis)

California ZEV mandate, battery packsmust be warranted for 15 years or 150,000

miles : a technical challenge

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Hybrid Vehicle Outlook

Hybrid configuration will capture a fraction of thepassenger market, especially when there is significant

fuel price increase Competition

Customers downsize their cars

Small diesel vehicles

Plug-in hybrids?

Weight penalty (battery + motor + engine) No substantial advantage for overall CO2 emissions

Limited battery life

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Sales figure for hybrid vehicles

199

9

200

0

200

1

200

2

200

3

200

4

200

5

200

6

200

7

200

8

200

9

0

100

200

300

400

0

1

2

3

4

S

ales(thou

sands)

%ofnewlightdutyvehiclesa

le

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What is a fuel cell?

Direct conversion

of fuel/oxidant toelectricity

2H2 + O2 2H2O

Potentially muchhigher efficiencythan IC engines

H2 - O2 system

Electrolyte

PorousCathode

PorousAnode

4H+O2

2H2O

4e-

i

2H24e-Fuel O2

H2O +excess

O2

excessH

2

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History of Fuel Cell

Sir William Grove demonstrated the first fuel cell in1839 (H2 O2 system)

Substantial activities in the late 1800s and early 1900s

Theoretically basis established

Nerst, Haber, Ostwald and others

Development of Ion Exchange Membrane for application

in the Gemini spacecraft in the 1950/1960 W.T. Grubb (US Patent 2,913,511, 1959)

Development of fuel cell for automotive use (1960s topresent)

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The Grove Cell (1839)

Important insights tofuel cell operation H2-O2 system (the most

efficient and the only

practical system so far) Platinum electrodes (role

of catalyst)

recognize the importanceof the coexistence ofreactants, electrodes andelectrolyte

W.R.Grove, On Gaseous Voltaic Battery, Pil. Mag., 21,3,1842As appeared in Liebhafsky and Cairns, Fuel Cells and Fuel Batteries, Wiley, 1968

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Types of fuel cell

Classification by fuel

Direct conversionHydrogen/air (pre-dominant)

Methanol/air (under development; electrode

poisoning problem)

Indirect conversion

reform hydrocarbon fuels to hydrogen first

Classification by charge carrier in electrolyte

H+, O2- (important difference in terms of product

disposal)

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Types of fuel cell (cont.)

By electrolyte

Solid oxides: ~1000oC

Carbonates: ~600oC

H3PO4: ~200oC Proton Exchange Membrane (PEM): ~80oC

Automotive application

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Modern PEM fuel cell stack

(From 3M web site)

Diagram of a PEM fuel cell stack removed due to copyright restrictions.Please see http://www.technopr.com/download/Figure1-FuelCellConstruction.jpg

Current PEM H /O Fuel Cell Performance

http://www.technopr.com/download/Figure1-FuelCellConstruction.jpghttp://www.technopr.com/download/Figure1-FuelCellConstruction.jpg

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Current PEM H2/O2 Fuel Cell Performance

0 0.2 0.4 0.6 0.8 1 1.2 1.4

0

0.2

0.4

0.6

0.8

1

Current density (A/cm2)Vo

ltage(V);P

owerdens

ity(W/cm2)

;Efficiency

Output voltage with CO poisoning

Power density

Efficiency

Output Voltage

Note: Efficiencydoes not includepower requiredto run supporting

system

The Hydrogen problem:

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The Hydrogen problem:Fundamentally H2 is the only feasible fuel for fuel

cell in the foreseeable future

Strictly, hydrogen is not a fuel, but an energystorage medium

Difficulty in hydrogen storage

Difficulty in hydrogen supply infra structure Hydrogen from fossil fuel is NOT an efficient

energy option

Environmental resistance for nuclear andhydroelectric options

The hydrogen problem:

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The hydrogen problem:

H2 from reforming petroleum fuel

Catalyst

Hydrocarbon

Air H2CO

Fuel Cell

H2O

Electricity

Air

Catalyst H2CO2

N2,CO2

Note: HC to H2/CO process is exothermic;energy loss ~20% and needs to cool stream(Methanol reforming process is energy neutral, butenergy loss is similar when it is made from fossil fuel)

Current best reformer efficiency is ~70%Problems:

CO poisoning of anodeSulfur poisoning

Anode poisoning requires S

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Fuel cell powerplant with fuel reforming

Practical ProblemsStart up/shut downLoad Control

Ambient temperatureDurability

GM (May, 2002) Chevrolet S-10 fuel celldemonstration vehicle powered by

onboard reformer

Images removed due to copyright restrictions. Please see photosof the Chevrolet S-10 Gen III gasoline fuel cell vehicle, such ashttp://www.pickuptrucks.com/html/news/fuelcells10.html

F l ll i l

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Fuel cell as automotive powerplant

Current (2006) Fuel cellcharacteristics

1A/cm2, 0.5-0.7 V operating

voltage 0.5-0.7 W/cm2 power density

stack power density 0.7 kW/L

Platinum loading ~0.3 mg/cm2

30g for a 60kW stack (2007price ~$1300)

(automotive catalyst has ~2-3g)

System efficiency (withreformer) 30%

$600/kW (compared topassenger car at $10/kW)

0

500

1000

1500

2000

2500

92

93

94

95

96

97

98

99

00

01

02

03

04

05

06

07

08

$

/troyounce

Price of platinum $

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Future of Petroleum fueled fuel cell

Not an attractive option:

Cost Fuel utilization

Fuel cell is NOT thetechnological solution

Is the emperorwearing any

clothes?

Courtesy Open Clip Art Library, http://openclipart.org

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US vehicles fuel economy

1970 1980 1990 2000 201010

15

20

25

30

35World Oil Production

0.0

0.2

0.4

0.6

0.8

1.0

Miles

pergallon

Year

Truc

kfrac

tion

Light truck fraction

carscombined

light trucks

MPG

CAFstd

40

45

50

55

60

65

70

75

80

85

90

1970 1980 1990 2000 2010Year

Million

Barrels/day

(Cafe target: 35 mpg average by 2020)

Progress in gas mileage !

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g g g

From Time Magazine, June 2003

Image and text removed due to copyright restrictions. Please see"Numbers" in Time Magazine, June 16, 2003.

http://www.time.com/time/magazine/article/0,9171,1005048,00.html

TRANSPORTATION EFFICIENCY

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TRANSPORTATION EFFICIENCY

Transportation Efficiency ="Useful people mile"

Fuel energy

Personal efficiency

Vehicle utilizationefficiency

Route, traffic patternVehicle weight/speed

Engineering

= "Useful people mile"People mile

x People mileVehicle mile

x Vehicle mileRoad work

x Road workFuel energy

Options?

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Options?

Alternative Fuels and Power Plants ?

Alternative Life Styles ?