Compressed air drives prospective hybrid
By Harold Lee
Oct. 13, 2003 9:00 p.m.
There are two certainties of living in Los Angeles: traffic and
air pollution.
Though it seems there will be no immediate end to the traffic,
hybrid vehicles powered by gas and compressed air may reduce smog
levels.
“An air hybrid can make the air cleaner and use less
fuel,” said Tsu-Chin Tsao, professor of mechanical
engineering.
In conjunction with the Ford Motor Company, Tsao has developed
an approach that could redirect the heat energy lost when braking,
known as regenerative braking, into compressed air.
When an air hybrid vehicle brakes, the engine would shut down
combustion and become an air compressor that stores air in a tank,
Tsao said.
This approach, which has not yet been tested on the road, could
have several advantages over electric hybrids.
“(An air hybrid vehicle) would use less materials,”
Tsao said. “Weight is related to fuel efficiency.”
Currently, regenerative braking is used in hybrid electric
vehicles, such as the Toyota Prius and the Honda Insight.
Electric hybrids convert braking energy into electricity using a
generator. This electricity is routed to a motor which accelerates
the vehicle until the combustion engine takes over and resumes
operation.
Air hybrids would not require separate generators or motors and
would only require an air storage tank in addition to the engine,
Tsao said.
Electric hybrid vehicles are especially effective in cities
plagued with congestion, much like Los Angeles.
“When driving in “˜stop-and-go’ traffic,
electric hybrids store energy and are more fuel efficient,”
Tsao said.
According to the computer simulations, air hybrid vehicles would
be as fuel efficient as electric hybrids, he added.
The research results were presented in March to the Society of
Automotive Engineers. According to the study, an air hybrid system
could improve fuel efficiency by 64 percent for city driving and 12
percent for highway driving.
For an air hybrid to work, however, the engine design would have
to be changed to eliminate mechanical camshafts, Tsao said.
In a standard combustion engine, a mixture of fuel and air is
fed into the engine through the intake valve, and exhaust is
expelled through the exhaust valve. The camshaft causes the intake
and exhaust valves to open and close in a controlled and rigid
manner.
Flexible valve trains controlled by electronic software would be
needed to control the air flow as it comes from the outside to the
engine, from the engine to the exhaust valve, or from the engine to
the storage tank, Tsao said.
Controlling the engine’s workings in such a manner has
additional benefits.
“The camless valve train can make it so the car generates
less emissions,” Tsao said.
Hybrid vehicles are currently more feasible than the hydrogen
technologies which are being developed, said Jochen Stutz,
assistant professor of atmospheric sciences .
“With hydrogen, you have to build a new
infrastructure,” Stutz said. “It’s something
that’s not as feasible.”
“People should buy hybrid vehicles,” he recommended.
“With the technology that’s available, it’s
something that’s doable,” he added.
If the use of vehicles with low fuel efficiencies continues,
levels of health complications such as asthma and other respiratory
problems may rise, said Arantza Eiguren, post-doctoral student at
the UCLA Institute of the Environment.
“There will probably be an increase in health problems in
the population,” Eiguren said. “When we breathe in, we
will breathe in more components with toxic effects.”
Tax incentives are now offered to people who buy hybrid
vehicles. According to the United States Department of Energy,
owners of the Honda Civic Hybrid, the Honda Insight and the Toyota
Prius can claim a $2,000 tax deduction within the vehicle’s
first year of use. Future hybrid vehicles may also qualify for tax
deductions.
