1. Exploring Hybrid School Bus Technology

2. Where is Started
Everyone had to walk to school. Most of us, especially those of us with children, walked uphill, in the snow, both ways.

3. One of the earliest school transportation vehicles.
And Then

4. And Finally, Modern Technology
The modern school bus hasn’t changed much from this 1927 model. The design and safety features are different, but it’s been essentially the same kind of engine, with the same kind of efficiency, and the same color, for nearly 100 years.
And Finally, Modern Technology

5. 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.
Hybrid Buses - 2/23/17 - ©The NEED Project

6. 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
Hybrid Buses - 2/23/17 - ©The NEED Project

7. Current IC Engines Thermal efficiency (26-34%)
Mechanical efficiency (94%)
Overall efficiency (20%)
Emissions
Particulate matter
NOx
Sulfur oxides
Carbon monoxide
Carbon dioxide
Hybrid Buses - 2/23/17 - ©The NEED Project

8. Most school buses today have diesel engines.

9. 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
Hybrid Buses - 2/23/17 - ©The NEED Project

10. 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
Hybrid Buses - 2/23/17 - ©The NEED Project

11. Parallel Hybrid System
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.
An electric motor/generator mounted between the engine and the transmission generates electric power.
Hybrid Buses - 2/23/17 - ©The NEED Project

12. For More Information The NEED Project www.need.org info@need.org
Energy Information Administration
U.S. Department of Energy
Hybrid Buses - 2/23/17 - ©The NEED Project

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