THE CHEVY VOLT concept vehicle, General Motors' new electric vehicle platform, is the first of a series of planned models that will be powered by electric propulsion systems. The Volt is an electric vehicle that uses a gasoline engine "assist," which recharges the battery, making it a kind of hybrid. Image: ¿ General Motors
The recent documentary film Who Killed the Electric Car? roundly criticized General Motors Corporation for prematurely quashing production and further development of the EV-1 electric car, a battery-powered, two-seat commuter vehicle that managed to gain a small but enthusiastic fan following before the program's termination in 2003. The EV-1's main drawbacks, according to GM, were insufficient driving range (less than 150 miles) and overly slow battery recharging times (eight hours). "EV-1 owners hated having to plan their lives around recharging the car's battery pack," recalls Tony Posawatz, a vehicle line director for GM.
Those disadvantages are expected to be surmounted by what some might regard as the EV-1's successor: the Chevrolet Volt concept car, a battery-powered electric vehicle designed primarily for short-distance travel that is equipped with a small internal combustion engine and generator to recharge the battery. The newly unveiled Volt's lithium ion battery pack, which will power the four-seat compact for about 40 miles per charge, will also be able to be replenished with cheap off-peak power by plugging it into the nationwide electric grid overnight.
Although the Volt concept, which is being introduced today at Detroit's North American Auto Show, is a kind of hybrid vehicle, the design emphasizes electric battery rather than gasoline engine operation. The new design features no direct mechanical link between the gas-powered engine and the electric drive train. After noting that the engineering for the production model is underway, GM spokesmen refused to predict exactly when it might hit showroom floors. "The pacing of the project depends on further development of the lithium ion battery," states the program's chief engineer, Nick Zielinsky. Besides providing greater power density than current batteries, the new cells must also last for 10 years and 4,000 operating cycles.
Drive power for the Volt will come from a 136-kilowatt- (or 160-horsepower-) at-peak permanent-magnet electric motor that produces 320 newton-meters of torque, Zielinsky explains. The car's 16-kW, advanced lithium ion battery pack is expected to take about 6.5 hours to recharge (from a minimum 30 percent charge level to a maximum 80 percent charge state). The battery will also serve as a storage medium for a regenerative braking system that will recoup braking energy that is otherwise lost to friction.
A small, fuel-efficient gasoline engine--a one-liter, three-cylinder, turbocharged power plant--and a 53-kW generator set will recharge the battery on the fly, he continues. A 12-gallon fuel tank will give the Volt a 640-mile driving range (calculated using the U.S. Environmental Protection Agency's urban driving cycle) that will permit drivers to make long trips without re-upping the battery frequently. GM engineers are said to be developing a quick-charge capability as well.
Top (continuous) speed is to be 100 miles per hour with peak velocity at 120 mph, Zielinsky says, adding that much of the engineering know-how behind the car's electric system--the traction motor, power electronics and so forth--was developed for the company's hybrid and fuel cell vehicle programs, and further back, for the EV-1.
The Volt's "distinctive" design is based on the Chevy Cobalt compact vehicle architecture, he says. The "rather large" (100-plus-liter) battery will sit in the car's central tunnel where it packs well, finds protection from crash impacts and can readily be integrated with the cooling system. Zielinsky notes that its compact power train system allows the wheels to be positioned near the corners of the chassis, which makes for short front and rear overhangs and a wide track, yielding an overall layout that resembles that of a rear-wheel-drive car.
The Volt's high-mileage hybrid power train is aimed to appeal to customers who are increasingly interested in fuel savings, whether for environmental or economic reasons, or to reduce oil imports, according to Posawatz. "One half of U.S. households drive less than 30 miles a day and 78 percent of work commuters travel 40 miles or less each day," he says. Many drivers in the former category will thus use little or no gasoline at all. Compared with a typical, 30-mile-per-gallon automobile, the Volt will save these motorists about 500 gallons of fuel a year, which also will result in a substantial cut in annual carbon dioxide emissions which are associated with climate change. Most daily commuters in the 40-mile-a-day classification will get the equivalent of 150 mpg in a Volt, he concludes.