[Technology Report]
Auto Electronics Revs Up For "Greener" Pastures
Safety, environmental concerns, fuel efficiency, and greater passenger comfort and convenience spur innovation in today’s cars.
HYBRID AND ELECTRIC VEHICLES Energy efficiency and environmental considerations are driving the acceleration of hybrid and electric vehicle development. Although such vehicles are common in Europe and Asia, they haven’t found widespread use in the U.S., save a few Japanese models from Toyota and Honda, and U.S. models from Ford and Chrysler. But the U.S. automakers aren’t waiting much longer and look to catch up with their foreign counterparts, who are equally anxious to increase their presence in this area.
GM announced plans to introduce hybrid and electric vehicles. Ford has hybrids on the market, with more in the works. Chrysler also offers hybrid vehicles. Last fall, it showed off prototypes for production next year and beyond.
One of the most interesting electric cars is GM’s Chevy Volt. Built on GM’s E-Flex (now called Voltec) platform for electric-motor propulsion, it’s powered by a T-shaped 16-kWh lithium-ion (Li-ion) battery whose cells are provided by LG-Chem (Fig. 5). The battery consists of more than 200 5- by 7-in. cells that are less than 0.25 in. thick, each weighing less than a pound. Each cell also includes a carbon anode, a manganese-based cathode, and a reinforced separator. The battery is assembled by GM.
The Volt’s battery can be plugged into a 120- or 220-V ac outlet for charging. GM estimates that electricity costs would be about 40 to 80 cents per charge (usually overnight when rates are lower). The Volt is designed for a 40-mile range operating from the battery alone. When it exceeds that range, the gasoline engine kicks in to go farther, but it only charges the battery. It doesn’t provide any propulsion.
“The design of the Volt was based on the fact that the gasoline engine is taken out of the picture when it comes to car propulsion,” says Bob Boniface, director of GM’s Voltec systems. “There is a misunderstanding when comparing the Volt to other hybrid vehicles, all of which use the gasoline engine as well as the battery for propulsion. The Volt’s engine does not do that. It only charges the battery when needed beyond the 40-mile range it is designed for.”
Pushing its electrically driven technology even further, GM unveiled the Personal Urban Mobility and Accessibility (PUMA) prototype it co-developed with Segway (Fig. 6). The two-passenger, torque-steered, all-electric, two-wheeled vehicle is powered by a 4-kWh Li-ion battery that takes about four hours to recharge by plugging into a 120- or 220-V ac outlet. It has a top speed of about 25 to 35 mph and a range of up to 35 miles between recharges.
“This vehicle is designed for city travel and is designed to reduce traffic congestion and has zero emissions for a cleaner environment. With a weight of about 800 lb, it is lighter than a conventional vehicle,” says Christopher Borroni- Bird, GM’s director of advanced technology vehicle concepts. “The cost to operate it is four to five times less than an average midsize car.”
The compact PUMA features 360° vision, collision avoidance, adaptive cruise control, lane-departure warning, dynamic stabilization, autonomous driving and parking, lane keeping, and wireless vehicle-to-vehicle communications. GM says the vehicle is in production.
The need to conserve energy and be environmentally friendly has extended to the powertrain. Adura Systems Inc., operating for a couple of years in “stealth” mode, just introduced the first electric powertrain with a range of up to 100 miles. The Modular, Electronic, Scalable Architecture (MESA) targets all-electric, hybrid, and fuel-cell-based vehicles. It will initially be deployed in China.
Levant Power Corp., formed by researchers at the Massachusetts Institute of Technology, is capitalizing on a shock-absorber design they developed called GenShock. It harvests wasted energy from a vehicle’s shock absorbers to boost fuel economy by as much as 10%, ultimately contributing to a greener environment. GenShock absorbers compress hydraulic fluid as they damp the vertical motion of the shock, generating up to 1 kW per shock. An active suspension system then combines hydraulic pressure from all shocks into electricity, using a centralized generator.
Belgium’s Interuniversity Microelectronics Centre (IMEC) is developing MEMS-based piezoelectric energy harvesters that can be used in a car’s TPMS for energy scavenging and improving fuel consumption, taking advantage of a car’s continuous vibrations (Fig. 7). Although current devices only produce tens of microwatts of output power from mechanical motion, IMEC’s researchers are confident that much higher levels are possible for automotive healthmonitoring as well as medical applications.
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