Researchers work to turn car's exhaust into power
By MARGARET HARDING
WARREN, Mich. (AP) — The stinky, steaming air that escapes from a car's tailpipe could help us use less gas.
Researchers
are competing to meet a challenge from the U.S. Department of Energy:
Improve fuel economy 10 percent by converting wasted exhaust heat into
energy that can help power the vehicle.
General Motors Corp. is
close to reaching the goal, as is a BMW AG supplier working with Ohio
State University. Their research into thermoelectrics — the science of
using temperature differences to create electricity — couldn't come at
a better time as high gas prices accelerate efforts to make vehicles as
efficient as possible.
GM researcher Jihui Yang said a
metal-plated device that surrounds an exhaust pipe could increase fuel
economy in a Chevrolet Suburban by about 5 percent, a 1-mile-per-gallon
improvement that would be even greater in a smaller vehicle.
Reaching
the goal of a 10 percent improvement would save more than 100 million
gallons of fuel per year in GM vehicles in the U.S. alone.
"The take-home message here is: It's a big deal," Yang said.
The
DOE, which is partially funding the auto industry research, helped
develop a thermoelectric generator for a heavy duty diesel truck and
tested it for the equivalent of 550,000 miles about 12 years ago.
John
Fairbanks, the department's thermoelectrics technology development
manager, said the success of that generator justified the competitive
search in 2004 for a device that could augment or replace a vehicle's
alternator. Three teams were selected to participate in the program,
with GM and thermoelectrics manufacturer BSST separately working on
cars and a team from Michigan State University focusing on heavy-duty
trucks.
Fairbanks said thermoelectric generators should be on the verge of production in about three years.
"It's probably the biggest impact in the shortest time that I can think of," he said.
The
technology is similar to what NASA uses to power deep space probes, a
perk being it doesn't seem to be susceptible to wear. Probes have used
a thermoelectric setup for about 30 years.
Thermoelectric devices
can work in two ways — using electricity to provide heating or cooling,
or using temperature differences to create electricity.
The second method is Yang's focus, and for good reason.
In
an internal combustion engine, only about a quarter of the total energy
from gasoline is used to actually turn the wheels, while 40 percent is
lost in exhaust heat and 30 percent is lost through cooling the engine.
That means about 70 percent of the available energy is wasted,
according to GM.
"If I can use some of that heat energy and convert it to electricity, you can improve the overall efficiency," Yang said.
A
Suburban produces 15 kilowatts of exhaust heat energy during city
driving, which is enough to power three or four air conditioners
simultaneously.
But it's not possible to harness all the exhaust
heat a vehicle produces, so when the Suburban is cruising between 50
and 60 mph, the generator can produce about 800 watts of power, Yang
said. That electricity could go to accessories such as a GPS device,
DVD player, radio and possibly the vehicle's water pumps.
Yang's
prototype device is to be tested in a Suburban next year. A similar
prototype created by Ohio State scientists and BSST should be tested in
a BMW in 2009.
The thermoelectric generator works when one side
of its metallic material is heated, and excited electrons move to the
cold side. The movement creates a current, which electrodes collect and
convert to electricity.
While it's not clear how much the device
would add to the price of a vehicle, the whole point of the research is
to make it cost-effective, Yang said.
"There are several other
steps that are required to commercialize the material, but we're
cautiously optimistic that these steps can be carried out
successfully," said Lon Bell, president of BSST, a subsidiary of
Northville-based thermoelectrics supplier Amerigon Inc.
BSST also is working with Ford Motor Co. to develop climate control systems based on thermoelectrics.
Ford
wants a system that would target a person's extremities when it's cold
or the back of the neck in summer heat, rather than blow out a lot of
air to change the temperature of the entire vehicle.
"We think we
can make people feel cooler more quickly, feel comfortable more
quickly, and that will translate into less power in the central AC
system," said Clay Maranville, a Ford senior research scientist.
Honda
Motor Co. also has supported university research into thermoelectrics,
but a spokesman said the automaker doesn't have its own research
program.