GM invited a good four dozen or so journalists to the General Motors Technical Center today for an in-depth update on the status of the Chevy Volt. I'll have a seriously nauseating amount of detail for you later, but for now I wanted to share a few highlights.
Denise Gray, the director of Hybrid Energy Storage Systems (she's working to get the hybrid taken out of her title, considering the whole E-REV thing), showed the chart above as part of her presentation. As you can see by looking at the white line (feel free to enlarge the chart - in another tab, perhaps - by clicking on it if it's hard to read) the main operating range for the Volt's 16 kWh battery pack is 8 kWh (50 percent) . It doesn't really reach 100 percent or drop below around 30 percent. Gray said, as GM has said since the Volt's introduction, that finding the right 8 kWh of the pack's power to be the "sweet spot" of the operating range. Whether it's between 80 percent and 30 percent of the pack's power or, preferably, 90 and 40 (to give the battery more of a cushion when capacity decreases over time) has not been decided. The Volt is a work in progress.
Other things of note I learned today:
- Should you really want to, you will be able to drive the Chevy Volt as a pure EV, without a drop of gas in the tank.
- Malibu mules fitted with the lithium-ion battery packs will begin testing later this month (actually, we kind of knew this already, but it bears repeating).
- GM engineers are dealing with a lot of issues on this car that they've never had to deal with before - for example, how do they deal fuel that might sit in the tank for weeks or months at a time? (through, a pressurized tank) and realizing that some of the durability components in the ICE generator might be able to come out at some point because that engine just won't be running as much as an ICE in a standard vehicle.
As I said, we'll have much more later. For now, check out the GM press release after the break.
CHEVROLET VOLT DEVELOPMENT CHARGES ON
- Battery engineers develop new computer testing procedure, leverage global resources to accelerate development of extended-range electric vehicles (E-REV)
- Engineers integrate T-shaped battery into vehicle structure
- Designers improve aerodynamics to lower energy consumption
This advanced computer program duplicates real-life vehicle speed and cargo-carrying conditions, and compresses 10 years of comprehensive battery testing into the Volt's brisk development schedule.
The battery cycling equipment is used around the clock in GM test facilities in Warren, Mich. and Mainz-Kastel, Germany. It charges and discharges power from the prototype batteries based on the Volt's approximately 40-mile electric-only drive cycle. Results from this test data will help predict the long-term durability of the battery.
"Production timing of the Volt is directly related to our ability to predict how this battery will perform over the life of the vehicle. The challenge is predicting 10 years of battery life with just over two years of testing time," said Frank Weber, global vehicle chief engineer, Chevrolet Volt and E-Flex systems. "The battery team is able to utilize human and technical resources around the globe to reduce testing time."
Testing the batteries in the laboratory provides a predictable environment to compare technologies under controllable situations. The batteries will soon be integrated into "mule," or test, vehicles with other E-Flex system components for on-road tests.
"Extensive analysis in our battery labs is an important step in proving this technology. We expect to further validate these batteries when they are integrated into engineering development vehicles," said Weber. "The conditions in a vehicle – where the battery is exposed to shaking, moisture and rapidly changing temperature conditions – are much more extreme than the controlled settings of the lab."
Engineering an electric vehicle with a battery roughly 6 feet long (1.8 m) and weighing more than 375 pounds (170 kg) requires innovation. The T-shaped battery will be located down the center tunnel of the vehicle and under the rear seats. This integration requires the battery to be treated as part of the vehicle structure. Simulation data also indicates that the center placement provides greater protection to the battery.
"The battery is more than just an energy carrier; it's a structural component that affects many other aspects of the vehicle," said Weber. "It's an integral part of the vehicle that interacts with the vehicle's thermal and safety systems and chassis components."
Engineering innovations are also required to maximize the Volt's 40-mile electric-only range and minimize the use of its range-extending internal combustion engine. To reduce mass, the Volt is being engineered with a relatively small fuel tank. This reduces weight, but still provides a driving range in excess of 400 miles between fill-ups.
Designing the interior
The battery placement created interior design opportunities that led to several creative solutions that improve aerodynamics and overall comfort.
"We made a conscious decision to make the Volt a four-passenger vehicle to keep the roof low, an important aerodynamic enabler," said Bob Boniface, design director, E-Flex. "As designers, we must be sensitive to the energy efficiency gains that can be achieved by optimizing aerodynamics, whether it's occupant packaging or overall styling. This not only contributes to improved fuel economy or extended range, but can produce beautiful exterior body shapes and innovative interiors."
The battery pushed the occupants outboard, or to the sides of the vehicle, so the design team had to get creative with the sections of the roof structure to enable aerodynamics and provide adequate head room. The interior will accommodate a 6-foot 2-inch (99th percentile) male comfortably in the front and rear seats.
"By having the battery in the middle, we were able to move the occupants apart and give them more space," said Tim Greig, interior design manager for the Chevrolet Volt. "We also shrink-wrapped the interior, particularly the doors, for comfort and spaciousness. There is no wasted space.
"Being an electric vehicle with a battery down the middle presented unique opportunities to our design team," he said. "The net result is a very creative and innovative design, appropriate for an electric vehicle."
Aerodynamic drag, or wind resistance, accounts for about 20 percent of the energy consumed by an average vehicle, directly reducing fuel efficiency.
GM's aerodynamics laboratory, located in Warren, is the center of expertise for optimizing airflow. In addition to fuel economy, range, emissions and acceleration are all affected by aerodynamic drag. The cooling of components like brakes is affected by airflow, as is cornering capability, crosswind response, directional stability and on-center handling. GM's aero lab allows for the testing and development of each of these characteristics.
Aerodynamics development begins with a 1/3-scale model where basic shape and major features are defined. The model includes a highly detailed underbody and engine compartment. Radiator and under-hood cooling flow are developed with computational fluid dynamic models. Simultaneously, computation development takes place to determine the aerodynamic drag of design alternatives. Development continues with full-scale models, where shape is refined and optimized for low wind noise. The development process concludes with a vehicle prototype validation of the math-based analysis and physical testing.
"After extensive aerodynamic testing of the Volt, the vehicle now has a coefficient of drag that is 30 percent lower than the original concept," said Ed Welburn, GM vice president, Global Design. "It's not easy, but it is a necessity."
The ongoing development of the Volt is just one part of GM's commitment to displace petroleum use in the auto industry through a range of propulsion alternatives, including:
- GM is the leading producer of E85-capable biofuel vehicles, with more than 3 million on U.S. roads today. GM has committed to having 50 percent of annual sales volume E85-capable by 2012.
- By the end of 2008, GM is expected to offer more hybrid models (eight) in the United States than any other automaker.
- The Saturn Vue Green Line, Saturn Aura Green Line and Chevrolet Malibu Hybrid will feature GM's mild hybrid technology.
- GM's two-mode hybrid technology is available in the Chevrolet Tahoe Hybrid and GMC Yukon Hybrid, and will be added later this year to the Cadillac Escalade, Chevrolet Silverado Hybrid and GMC Sierra Hybrid, delivering highly efficient performance and full functionality.
- Going into production later this year is the front-wheel-drive Saturn Vue Green Line 2 Mode Hybrid, expected to deliver up to a 50-percent improvement in combined city and highway fuel economy compared with the current non-hybrid Vue XR, based on current federal test procedures.
- Earlier this year, GM launched "Project Driveway," the largest market test of fuel cell vehicles in the world, lending 100 Chevrolet Equinox Fuel Cell vehicles to everyday drivers. GM engineers will analyze customer feedback and use it to develop the next generation of fuel cell vehicles.
Additionally, GM provides more vehicles that achieve 30 mpg on the highway than any other manufacturer in the U.S. market. GM is also a member of the U.S. Climate Action Partnership (USCAP), a group of global companies and non-governmental organizations that support an economy-wide, market-driven approach to reducing carbon emissions.
General Motors Corp. (NYSE: GM), the world's largest automaker, has been the annual global industry sales leader for 77 years. Founded in 1908, GM today employs about 266,000 people around the world. With global headquarters in Detroit, GM manufactures its cars and trucks in 35 countries. In 2007, nearly 9.37 million GM cars and trucks were sold globally under the following brands: Buick, Cadillac, Chevrolet, GMC, GM Daewoo, Holden, HUMMER, Opel, Pontiac, Saab, Saturn, Vauxhall and Wuling. GM's OnStar subsidiary is the industry leader in vehicle safety, security and information services. More information on GM can be found at www.gm.com.