Transcript Document

Exploring Hybrid School Bus Technology

Where it started,61

And then

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 NO x Sulfur oxides Carbon monoxide Carbon dioxide

Most school buses today have diesel engines.

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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

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

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

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

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Energy Information Administration U.S. Department of Energy

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