Earth’s Changing EnvironmentLecture 24

Increasing Transportation

Efficiency

Outline

Car and Driver Efficiency Mass Transit Urban Planning New Technologies

Cars and Drivers

210 million cars and light trucks

191 million licensed drivers

140 billion gallons gasoline/year

2.7 trillion vehicle miles

US Automobile Culture

Transportation consumes18% of Household Expenses

91% travel by private vehicles vs. 2% by mass transit

76% rides to work are solo

2.7 trillion vehicle miles per year

Carbon Emissions

US Automobiles add 1.3 billion metric tons of CO2 to atmosphere annually. (23% of US total emission)

Efficiency of cars is 20 miles/gallon

Drivers travel 14,000 miles annually

How do we reduce global impact of US transportation?

Raise CAFE Standards

Reduce Miles Traveled

New Technologies

Raise CAFE Standards

• Corporate Average Fuel Economy

• Established in 1975 to set U.S. mileage standards.

Current CAFE Standards

• 27.5 mpg for passenger automobiles

• 20.7 mpg for light trucks & SUVs

How can cars be more efficient?

• Smaller & more streamlined (wind resistance)

• Lighter (starting & stopping)• Less powerful (lower acceleration)

SUVs

• Mileage varies, but as low as 10 mpg as compared with 20 – 30 mpg for many cars and 50 mpg for hybrid electrics.

• Possible to achieve a more than 40% improvement with payback within ownership period.

Reduce Driving

Mass TransitUrban PlanningRide Sharing

Mass Transit

METRORailDARTVIA TransitBARTMexico City

Train

AMTRAK

Urban Planning

Curitiba, Brazil Portland, Oregon

Ride Sharing

HOV Lanes Park & Ride

Bicycle Lanes

Pedestrian Access

We prefer to ride.

New Technologies

Electric Cars Hybrid Cars Fuel Cells

Internal Combustion Engine

Engine – 20% efficient

Highway driving – Energy lost to air drag.

City driving – Energy lost during braking

Electric Car

Batteries are heavy and limit range to 100 miles.

Vehicles don’t have enough acceleration for traffic.

Not a practical solution.

Hybrid Electric Vehicles

HEV Program Honda Insight Honda Civic Toyota Prius 50 mpg

Why do hybrids get better mileage?

Smaller engine. Electric motor boosts gas engine for acceleration.

Regenerative braking.

Electric motor runs at low speed where gas engine is very inefficient.

Electric motor shuts off when stopped.

Fuel Cells and the Hydrogen Economy

Fuels Cells use hydrogen to produce electrical energy

2H2 +O2 2H2O + energy

Fuel cells could be used to power cars with hydrogen as the fuel.

Clean fuel

Barriers to Hydrogen Cars

Availability of hydrogen fuel.

Storage of hydrogen fuel.

Expensive. Infrastructure

Fuel Cells

In development stage.

Currently very expensive.

Are not a source of energy.

Hydrogen must be supplied.

                                                                                                     

Hydrogen Sources

Steam reforming of natural gas:

CH4 +2H2O CO2 + 4H2

Electrolysis:

2H2O + energy 2H2 + O2

Energy Source for Electrolyzer

Electrolysis requires energy.

Energy could come from Solar, Nuclear, or Wind.

In the short term, it would probably come from coal.

Economics of Hydrogen Economy

Burning gasoline produces a therm for $1.50.

Coal can produce a therm for $0.08.

Coal burned at a power plant to produce electricity to run an electrolyzer could produce power cheaper than gasoline.

Vehicle Carbon Emission(grams per mile)

Fuel Cell with electricity from coal 440

Conventional with gasoline 370

Conventional with natural gas 310

Hybrid with gasoline 190

Hybrid with natural gas 170

Fuel Cell with hydrogen from reforming 140

Conclusions

Hybrid vehicles offer major short-term advantages

Fuel cells are expensive and have infrastructure issues.

Fuel cells based on electricity from coal plants could increase emissions

Mass Transit & other non-automotive options must be considered.

References/Links

USDOE: EERE

Federal Highway Administration

Energy Information Agency

National Household Travel Survey

Our Nation’s Highways 2000

Hydrogen economy