|Powertrain of the Chevy Volt E-Flex Concept. Click to enlarge.|
GM has introduced a new family of electric vehicle propulsion systems—the E-Flex Systems—and is showing the first concept application of E-Flex at the North American International Auto Show: the Chevrolet Volt, a 40-mile all-electric range (AER) plug-in hybrid.
E-Flex initially uses a plug-in capable, battery-dominant series hybrid architecture. The E-Flex vehicles are all electrically-driven, feature common drivetrain components, and will be able to create electricity on board (either through a genset or a fuel cell). Regenerative braking will also contribute to the on-board electricity generation. (“E” stands for electric drive and “Flex” for the different sources of electricity.)
We are focused on reducing our dependence on petroleum—today we are 98% dependent [and] we don’t think that is a good business strategy at all.—Beth Lowery, GM VP Energy and Environment
There has been some speculation in the press that perhaps this is a publicity stunt on our part. This is not a publicity stunt, nor is it a science fair project. This is something that we have been working on for close to a year.—Jon Lauckner, GM VP Global Program Management
GM is developing the E-Flex System in parallel to its mechanical hybrid efforts—including the development of the Saturn VUE Green Line two-mode plug-in hybrid (earlier post), for which GM just awarded lithium-ion battery contracts (earlier post)—as well as its ongoing fuel-cell vehicle development efforts.
In its evolving taxonomy of offerings, GM refers to its existing portfolio of hybrids as “mechanical hybrids”—i.e., the engine provides mechanical drive power in addition to the electric drive power.
There is tremendous synergy between the fuel cell vehicle program and the E-Flex program—Nick Zielinski is the chief engineer for the fuel cell program and the Volt Concept, as one example.
Furthermore, GM leveraged its experience with the EV1 in the design of both the E-Flex System and the Volt. The use of the range extender in the Volt design, for example, originated with feedback from EV1 customers about not wanting to have to plan their lives around the next charge, according to Tony Posawatz, GM Vehicle Line Director.
GM envisions a range of genset options for the E-Flex vehicles, including engines optimized to run on E85 or E100 and biodiesel.
|The Chevrolet Volt.|
The Chevrolet Volt. GM chose its Global Compact vehicle architecture (Cobalt-sized) for its first E-Flex application, the Chevrolet Volt.
The Volt uses the same electric motor as used in the Equinox Fuel Cell vehicle in its electric powertrain: a 120 kW peak machine that develops 320 Nm (236 lb-ft) of torque.
The Volt will use a 16 kWh lithium-ion battery pack that delivers 136 kW of peak power. Plug-in charging is designed for the home (110V, 15 amps) and will take between 6 to 6.5 hours.
The Volt can support all-electric mode from 0 to its top speed of 100 mph (with bursts to 120 mph). Acceleration from 0 to 60 mph takes 8 to 8.5 seconds. The basic operating strategy is to run the vehicle in all-electric mode until the state-of-charge (SOC) of the battery reaches 30%—that strategy delivers approximately a 40-mile range.
The 53 kW motor generator set (genset) allows the on-the-fly recharging of the battery. The genset in the current Volt concept uses a 1-liter, 3-cylinder, turbocharged engine.
You can drive at a continuous 70 mph, and the generator will not be on continuously. At 100 mph,the genset can maintain the charge in the battery and the speed of the vehicle. There are no compromises for the customers in the vehicle.—Nick Zielinski, chief engineer
The Volt concept configuration features a 12-gallon fuel capacity, giving the vehicle a total driving range of around 640 miles—which works out to a nominal gasoline fuel efficiency of about 50 miles per gallon. (Presumably range would increase with a diesel variant.)
The less one drives before plugging in to recharge, however, the higher the experienced fuel efficiency. A daily drive of 60 miles, combined with a nightly recharge to support the first 40 all-electric miles, would yield an effective 150 mpg according to GM’s calculations, for example.
For comparable performance with a fuel-cell version of the Volt, GM anticipates needing 4 kg of hydrogen on-board.
The Volt also features a number of advanced materials from GE Automotive Plastics, including:
Roof, rear deck lid and fixed side glazing made with Lexan GLX resins and Exatec coating technology;
Doors and hood made with Xenoy iQ high performance thermoplastic composites (HPPC). Xenoy iQ resins are created with polybutylene terephthalate (PBT)-based polymers derived from 85% post-consumer plastic waste, consuming less energy and yielding less carbon dioxide (CO2) in their manufacturing than traditional resins.
Global energy absorber and hybrid rear energy absorbers with Xenoy iQ resins;
Steering wheel and instrument panel with integrated airbag chute made with Lexan EXL resins;
Front fenders made with Noryl GTX resins; and
Wire coating made with Flexible Noryl resins.
The use of the materials delivers part weight reductions of up to 50%.
Actual production of the vehicle is dependent on further battery development, and GM made no announcements about partners involved in the development of the battery pack for the Volt. The profile for the battery in the Volt is different than that of the pack being developed for the VUE plug-in.
GM would like to minimize the different battery packs within the E-Flex family of vehicles. One notable exception to this would in a fuel-cell configuration. In that case, the battery would be smaller, and more focused as power battery first and energy battery second (due to the ability of the fuel cell to produce the electricity on-board.)
However, GM is also clear that it wants to use common systems and controls wherever possible across applications. To that end, elements such as the charging systems will likely be common across mechanical-hybrid plug-ins and E-Flex plug-ins.