Types of Electric Vehicles
For more than 100 years, the predominant energy choice for cars has been the internal combustion engine. Electric vehicles being designed today either augment internal combustion or eliminate the need for it altogether.
Hybrid and electric vehicle system components may include a battery for energy storage, an electric motor for propulsion, a generator, a mechanical transmission and a power control system.
These components are brought together in different ways by different systems. There are four main types of electric cars:
The hybrid electric vehicle uses a small electric battery to supplement a standard internal combustion engine and increase fuel efficiency by about 25 percent from conventional light-duty vehicles.
The electric motor minimizes idling and boosts the car's ability to start and accelerate, which is important in stop-and-go city driving. Hybrids are dual-fuel vehicles in which both the electric motor and internal combustion engine can drive the wheels.
The electric motor accelerates the car to about 40 mph, depending on the vehicle, and then the internal combustion engine takes over.
The battery is recharged by the gasoline engine and regenerative braking. Regenerative braking converts kinetic energy that otherwise would be lost as heat in the brake pads into electricity to charge the battery. The Ford Fusion Hybrid and Toyota Prius are examples of this type of hybrid.
The plug-in hybrid electric vehicle is also a dual-fuel car in which both the electric motor and the internal combustion engine can propel the car. It has a larger battery pack that is charged directly from the power grid, increasing the amount of electric power available to the car.
This larger battery usually supplements an internal combustion engine smaller than those used in hybrid or conventional vehicles. Toyota began selling a plug-in hybrid for the U.S. market in February 2012, though kits to convert other cars into plug-in hybrids were available before that.
Both the hybrid and plug-in hybrid combine an internal combustion engine with a battery and electric motor to increase fuel efficiency. The difference is that plug-ins also can be recharged from an electric outlet, extending the use of electricity as a fuel.
Most plug-in hybrids run on electric power only up to about 40 mph, where the internal combustion engine takes over. Thus, drivers could commute around a city solely on electric power without ever engaging the internal combustion engine. However, the majority of commuters in the TVA region would need to engage the gas engine at some point in order to safely use the interstates.
The batteries in these vehicles can be charged by the gas engine, regenerative braking, and by plugging in at home during off-peak hours.
While this reduces the immediate need for public charging stations, the ideal situation would be to build an infrastructure of charging stations to provide more options for plug-in hybrid owners.
An extended-range electric vehicle uses an internal combustion engine to power an electric generator that charges the battery system in a linear process — the engine powers a generator, which in turn charges the battery.
Unlike dual-fuel hybrid and plug-in hybrids, only the electric motor powers the wheels of an extended-range electric car. The internal combustion engine only charges the batteries.
The General Motors Chevrolet Volt, which went on sale in the U.S. in late 2010, is an extended-range electric vehicle with an electric-only range of about 40 miles. The Volt extends its range with a small internal combustion engine that charges the batteries. The Volt also can be recharged by plugging into the grid during periods of low power use.
Battery electric vehicles are all electric. They have no internal combustion engine and must be plugged into the electric power grid for recharging. To accommodate a range of 80-plus miles per charge, electric-only vehicles require larger batteries than the combined electric-petroleum cars — from 18 kilowatt-hours to more than 35 kilowatt-hours.
To more quickly recharge these larger batteries at night when power demand is low, most homes and businesses will require special outlets to be installed that provide 240 volts or higher.
Nissan began U.S. sales of its 100 percent battery electric vehicle , the LEAF, in late 2010. TVA and the state of Tennessee helped develop a launch market for these vehicles.
Other Personal Electric Vehicles
Other electric vehicles — smaller vehicles with maximum speeds of 25 mph or less — are classified as neighborhood electric vehicles. Golf carts dominate this vehicle category, but other options are increasingly available, such as electric bicycles.
Various manufacturers offer three- and four-wheel electric vehicles that can be used in private and commercial applications, such as airport shuttles.
Global Electric Motorcars, a Chrysler subsidiary, is the U.S. sales leader in this category. Some cities use these small vehicles for parking meter enforcement. Some power companies use them to move people and resources at their generating plants.