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General Motors' first plug-in hybrid, the Chevrolet Volt concept, introduces GM's new family of electric-drive propulsion systems
By Michelle Krebs Email
Date posted: 01-07-2007
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General Motors has unveiled the Chevrolet Volt concept, the company's first plug-in hybrid vehicle, at the 2007 North American International Auto Show in Detroit. The Chevrolet Volt concept is the first vehicle to use GM's new E-flex family of propulsion systems. GM claims the Volt delivers triple-digit fuel economy and can travel up to 640 miles without a fuel fill-up or a battery recharge.
How the Volt works
By its own admission, GM is late to the party on hybrid vehicles. Yet the Volt still manages to turn conventional hybrid thinking on its ear. While current hybrids employ a battery-powered electric motor to supplement or complement a gasoline-powered engine, the Volt runs only on electric power until the battery runs down. Then and only then does the internal-combustion engine kick in.
Further, an onboard generator produces electricity while the car is operating. The electricity is then stored in the battery. Energy normally lost in braking also is recaptured and sent to the battery. The batteries can also be recharged by plugging into an electrical outlet.
The specs for triple-digit fuel economy
The Volt features a front-mounted electric motor that generates 120 kilowatts of power (160 horsepower) and 236 pound-feet of torque. Lithium-ion batteries are housed beneath the Volt's floor. Also onboard is a 53-kilowatt electric generator. The turbocharged, 1.0-liter three-cylinder gasoline engine also fits up front, while the 12-gallon fuel tank is in the rear.
The Volt will drive about 40 miles on pure electric power. Vehicle Line Director Tony Posawatz (whose name rhymes with "kilowatts"), says GM arbitrarily picked this distance because Department of Transportation studies show that half of U.S. households travel less than 30 miles per day, while 78 percent of commuters travel no more than 40 miles per day to work.
"Most Volt drivers would use little or no gasoline," Posawatz notes.
By the numbers
By GM's calculations, the Volt would save the typical driver 500 gallons of fuel a year, amounting to a net cost savings of $900 (assuming gas costs $2.40 a gallon). The addition to a home electric bill would be about $300.
In the bigger scheme of things, the Volt saves the environment some 4.4 metric tons of carbon dioxide that might otherwise be emitted into the air in a year, GM claims.
Flex for flexibility
The "flex" in the E-flex name stands for "flexibility." GM promises more concepts using the E-flex system will be unveiled at future auto shows. The automaker hints those could incorporate diesel generators, biodiesel and pure ethanol or E-100.
Further into the future, the E-flex system could accommodate hydrogen-powered fuel cells. GM confirmed it is working on a fuel-cell variant like that in the Sequel concept. Instead of a large battery and small engine like in the Volt, it would have a fuel-cell propulsion system with a small battery to capture energy from a regenerative braking system, and would need only half of the hydrogen storage of the original Sequel concept to achieve 300 miles of range.
GM engineers have designed the E-flex system so it can be tailored to meet the specific needs and fuel infrastructure of a given market. For instance, the E-flex system might use 100-percent ethanol in Brazil. In Sweden, it might use biodiesel made from wood.
The E-flex system uses common drive components so it can be adapted to a variety of chassis and vehicles.
Well, it's no EV1
The recent documentary film, Who Killed the Electric Car?, accused automakers (GM, in particular), of sabotaging the electric car, specifically GM's EV1.
GM engineers say the Volt and GM's E-flex wouldn't have been possible without the invaluable lessons learned from the EV1. In fact, many of the same engineers who worked on the EV1 are working on the Volt and E-flex.
"EV1 was a good idea, but the Volt is a better one," insists Posawatz.
The EV1 carried only two passengers; the Volt accommodates four. The Volt will take a quick charge and requires less than 6.5 hours to fully recharge; the EV1 took eight hours to recharge. The EV1 had no backup system when the batteries died, and its driving range was between 60 and 90 miles. The Volt has a small gasoline engine that kicks in when the battery runs down, delivering a total driving range of 640 miles.
"There would never be a situation in which you didn't get home," GM Vice Chairman Bob Lutz assures us.
The Volt accelerates from a dead stop to 60 mph in less than 8.5 seconds (the EV1 took about a second longer), and has a top speed of 120 mph. (The EV1 would barely reach 80 mph.)
Challenge to battery developers
While GM's Jon Lauckner, vice president of global program management, insists E-flex and the Volt "are not science fair projects," nor publicity stunts, GM readily admits E-flex and the Chevrolet Volt are not ready for prime time. While GM says it intends to produce the E-flex systems, significant advancements must first be made in battery technology. Batteries for future cars must be able to last the full useful life of a vehicle and endure extreme hot and cold temperatures. In the Volt, GM has used a series of lithium-ion battery cells. The string of battery cells must continue working even if one cell fails.
GM won't provide details, but says it is working with major battery manufacturers.
In the meantime, GM has moved forward with the E-flex propulsion system and the Volt concept even though the batteries are not yet ready. The automaker didn't want to find itself in a situation where the batteries were ready but the car was not. After all, the plug-in future is almost here.
