Electric Vehicles

While pure electric vehicles are some time in the future, the world may be ready for a hybrid electric vehicle (HEV)—a vehicle that combines small internal-combustion engines with electric motors and electricity storage devices. These have the potential to reduce emissions almost as much as battery-powered electric vehicles as well as offering the extended range and rapid refueling that consumers expect from a conventional vehicle. Hybrid power systems were conceived as a way to compensate for the shortfall in battery technology. Because batteries could supply only enough energy for short trips, an onboard generator, powered by an internal combustion engine, could be installed and used for longer trips.

The HEV is able to operate approximately twice as efficiently as conventional vehicles. Honda's Insight, the first hybrid car to be sold in the United States, is expected to go 700 mi (1,127 km) on a single tank of gas. The Toyota Prius is expected to go about 450 mi (724 km). For the driver, hybrids offer similar or better performance than conventional vehicles. More important, because such performance is available now, hybrids are a practical, technically achievable, alternative approach.

Essentially, a hybrid combines an energy storage system, a power unit, and a vehicle propulsion system. The primary options for energy storage include batteries, ultracapacitors, and flywheels.