Researchers Work to Convert Vehicle Exhaust Into Fuel-Saving Power

Researchers Work to Convert Vehicle Exhaust Into Fuel-Saving Power

Ri ght, a GM thermoelectric generator.

The hot 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 to improve fuel economy 10 percent by using wasted exhaust heat as energy to help power the vehicle, according to an Associated Press article.

General Motors is close to reaching the goal, as is a BMW 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 told the AP that 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.

The mileage improvement was achieved by using the generated electricity to reduce the load on the alternator. Because it takes mechanical power from the crankshaft to move a belt that runs the alternator that produces electricity to power headlights, ignition coils, the radio and other electrical components, the greater the load on the alternator, the greater the demand on the vehicle's fuel to turn the crankshaft.

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 AP reported.

The Energy Department, 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, told the AP 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.

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.

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.

A Suburban produces 15 kilowatts of exhaust heat energy during city driving, which is enough to power three or four air conditioners simultaneously, the AP reported.

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 AP reported. The movement creates a current, which electrodes collect and convert to electricity.

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.

Honda Motor Co. also has supported university research into thermoelectrics, but a spokesman told the AP that the automaker doesn't have its own research program.

Scott Doggett:  is an AutoObserver.com Associate Editor.