Hybrid Electric Vehicles (HEVs)

About Technologies

How Hybrids Work

Mouse over the image to see how a hybrid electric vehicle (HEV) uses a battery and electric motor in addition to an engine that runs on gasoline (petrol). Graphic courtesy of the National Renewable Energy Laboratory, U.S. DOE

Hybrid electric vehicles (HEVs) combine the benefits of gasoline engines and electric motors and can be configured to meet different objectives such as improved fuel economy, increased power, or additional auxiliary power for electronic devices and power tools.

HEVs run on fuel alone and do not plug in to an electrical outlet to recharge the battery.

The Toyota Prius is the most widely driven HEV, with over 2 million cumulative units sold as of 2010.






Technologies typically used by HEVs

  • Regenerative Braking. The electric motor applies resistance to the drivetrain, causing the wheels to slow down. In return, the energy from the wheels turns the motor, which functions as a generator by converting energy normally wasted during coasting and braking into electricity. This electricity is stored in a battery until needed by the electric motor.
  • Electric Motor Drive/Assist. The electric motor provides additional power to assist the engine in accelerating, passing, or climbing hills. This allows a smaller, more efficient engine to be used. In some vehicles, the motor alone provides power for low-speed driving conditions, where internal combustion engines are least efficient.
  • Automatic Start/Shutoff (also called start-stop). This feature automatically shuts off the engine when the vehicle comes to a stop and restarts it when the accelerator is pressed. This prevents wasted energy from idling. This is the characteristic technology in micro-hybrids, which do not have the regenerative braking and electric drive assist functions of full HEVs.

IA-HEV Work on HEVs

While there are no currently active Tasks investigating HEVs, previous Tasks focused on heavy-duty HEVs, and studied the market conditions for existing HEV prototypes and standard vehicles. For instance, Task 12 focused on heavy-duty HEV components and configurations, and published a final report on the results of its investigations into heavy-duty HEV market penetration.