Exploring Hybrid School Bus Technology

Where it started

And then

http://content.lib.washington.edu/u?/imlswrvm,61

And finally, modern technology

Internal Combustion Engine

Nikolaus August Otto, patented 1876 Incorporated into nearly all private passenger

vehicles Plentiful petroleum led to gasoline Fuel mixed with air then injected Uses electric spark for explosion 250+ million cars now registered in U.S.

Diesel Engine

Rudolph Diesel, inventor 1878 Another form of internal combustion engine Direct fuel injection No spark plug Fuel ignites at its flash point More efficient than gasoline engines of day

Current IC Engines

Thermal efficiency (26-34%) Mechanical efficiency (94%) Overall efficiency (20%) Emissions

• Particulate matter• NOx

• Sulfur oxides• Carbon monoxide• Carbon dioxide

http://ffden-2.phys.uaf.edu/102spring2002_web_projects/z.yates/zach%27s%20web%20project%20folder/eice%20-%20main.htm

Most school buses today have diesel engines.

The NEED Project

Alternatives to Petroleum-based Fuels

Compressed Natural Gas (CNG)• Cleaner because do not emit nitrogen and sulfur oxides,

or all the particulate matter• Still releases carbon dioxide

Hydrogen fuel cells (used at Vancouver Olympics)• Only emission is water vapor• Lots of energy required to generate hydrogen• Lack of infrastructure• Currently prohibitively expensive

Diesel-electric Hybrid

Combines diesel engine and fuel with rechargeable battery system

Greatly improves miles-per-gallon Captures energy otherwise lost during braking –

ideal for routes with frequent stops Somewhat more expensive up-front cost Long-range savings realized by purchasing less

fuel and less maintenance on engine

Parallel Hybrid System

http://www.thomasbus.com/bus-models/green-buses/saf-t-liner-c2-propane.asp

An electric motor/generator mounted between the engine and the transmission generates electric power.

Power is stored in the lithium-ion battery when the bus is coasting or brakes are applied.

The vehicle uses stored energy to add power back

into the transmission

when the throttle is

depressed.

If the hybrid system goes

offline for any reason, the bus

automatically switches back to the conventional

powertrain system.

For More Information

The NEED Projectwww.need.orginfo@need.org

1-800-875-5029

Energy Information AdministrationU.S. Department of Energy

www.eia.gov

The NEED Project