Gas Electric vs HHV

Hybrid electric vehicles combine an energy storage system, a power unit, and a vehicle propulsion system. A battery is normally used to store energy. The power unit can be a spark ignition engine. Propulsion can come entirely from an electric motor, such as in a series configuration. The engine might also provide direct mechanical input to the vehicle propulsion system in a parallel configuration.

This is different from a hydraulic hybrid because HHVs do not have batteries and instead have accumulators that use the car's momentum to store energy using hydraulic fluid whereas in hybrid electric vehicles the electric motor resists the drivetrain slowing the vehicle down. The energy from the vehicle then turns the generator in the motor turning energy that is usually wasted into electricity that is held in a battery until needed by the motor. This motor then uses this extra power to assist the engine with acceleration. This lets a smaller and more efficient internal combustion engine to be used in the vehcile. In some electric hybrids, this motor provides the power for driving at low speeds when internal combustion engines are the least efficient to use. Further, in some electric hybrids there is an automatic engine shut off system that will shut the engine off when the vehicle is not moving and starts it up when the accelerater is pressed. This stops energy used in idling from being wasted.

Hydraulic Hybrid Vehicles


References/Sources
Hybrid Electric vs Hydraulic

Gas electric hybrid

Diagram Photos