Experts seem to agree that hybrid vehicles will be the successors to gas-powered cars. They base this thinking on the belief that electric batteries won't have energy densities on a par with those of liquid and gaseous fuels any time soon.
The first generation of these automobiles, the Toyota Prius and the Honda Insight, are already in showrooms and generating considerable consumer interest. Honda has another model on the way: the Civic Hybrid, expected to debut in 2003.
There are currently two types of hybrid. The serial hybrid uses a gasoline engine to power an electric generator; this creates electricity that's stored in a battery. An electric motor then uses that stored electricity to turn the gears inside the vehicle's transmission. With this model, there's no direct link between the gas engine and the auto's transmission.
The parallel hybrid is a variation on this design. Its transmission system is specifically engineered so the gasoline engine and the electric motor work in tandem to power the drive train. When the gasoline-powered engine is running, it is also recharging the batteries.
The Prius and Insight are parallel hybrids. Although the serial hybrid is the older design, no one has figured out how to make such a car commercially viable, so none are currently in production. The main problem is that serial hybrids don't have the same acceleration that parallel hybrids do. But because serials represents a simpler platform to design and build, and because they can accommodate alternative technologies--like fuel cells--they are considered the next step in the evolution toward a practical all-electric car.
The ability of today's hybrid automobiles to use energy more efficiently than standard vehicles is the reason for their growing popularity. Unlike gas-powered cars, which burn fuel even when decelerating or stopped, a hybrid car conserves fuel by turning off the gasoline engine when it isn't needed. Moreover, in a process called regenerative braking, the car's transmission reverses the direction of the electric motor when a driver engages the brakes, which effectively transforms it into a generator that recharges the batteries.
A hybrid's gas engine also doesn't have to be as large as in standard cars, which means emissions are cut down considerably. And hybrids never have to be plugged into electric power sources, as the batteries are almost always being recharged.
Parallel designs deliver much more acceleration than current serial-hybrid designs. But as battery, motor, and transmission technologies improve, serial hybrids are likely to become popular.
Alan Zeichick is principal technology analyst with Camden Associates and is editor in chief of BZ Media's SD Times.