How Hybid Cars Work
From Green Wiki
There are two types of hybrid cars: full hybrids and stop/start hybrids. This article describes how each works during various stages of operation.
Contents |
[edit] How a full hybrid works
[edit] Description of a full hybrid
Full hybrids use a gasoline engine as the primary source of power, and an electric motor provides additional power when needed.
In addition, full hybrids can use the electric motor as the sole source of propulsion for low-speed, low-acceleration driving, such as in stop-and-go traffic or for backing up.
This electric-only driving mode can further increase fuel efficiency under some driving conditions.
[edit] Components of a full hybrid
Battery - The battery stores energy generated from the gasoline engine or, during regenerative braking, from the electric motor. Since the battery powers the vehicle at low speeds, it is larger and holds much more energy than batteries used to start conventional vehicles.
Gasoline Engine - The gasoline engine in a hybrid is much like those in conventional vehicles, except that it is usually much smaller and more efficient.
Generator - The generator converts mechanical energy from the engine to electricity, which can be used by the electric motor or stored in the battery. It is also used to start the gasoline engine instantly when needed.
Power Split Device - The power split device is a gearbox connecting the gasoline engine, generator, and electric motor. It allows the engine and motor to power the car independently or in tandem and allows the gasoline engine to charge the batteries or provide power to the wheels as necessary.
Electric Motor - The electric motor powers the vehicle at low speeds and assists the gasoline engine when additional power is needed. It also converts otherwise wasted energy from braking into electricity and stores it in the battery.
[edit] Starting a full hybrid
When a full hybrid vehicle is initially started, the battery typically powers all accessories.
The gasoline engine only starts if the battery needs to be charged or the accessories require more power than available from the battery.
[edit] Driving at low speed
For initial acceleration and slow-speed driving, as well as reverse, the electric motor uses electricity from the battery to power the vehicle.
If the battery needs to be recharged, the generator starts the engine and converts energy from the engine into electricity, which is stored in the battery.
[edit] Cruising
At speeds above mid-range, both the engine and electric motor are used to propel the vehicle.
The gasoline engine provides power to the drive-train directly and to the electric motor via the generator.
The generator can also convert energy from the engine into electricity and send it to the battery for storage.
[edit] Passing
During heavy accelerating or when additional power is needed, the gasoline engine and electric motor are both used to propel the vehicle.
Additional electricity from the battery may be used to power the electric motor.
[edit] Braking
Regenerative braking converts otherwise wasted energy from braking into electricity and stores it in the battery.
In regenerative braking, the electric motor is reversed so that, instead of using electricity to turn the wheels, the rotating wheels turn the motor and create electricity. Using energy from the wheels to turn the motor slows the vehicle down.
If additional stopping power is needed, conventional friction brakes (e.g., disc brakes) are also applied automatically.
[edit] Stopping
When the vehicle is stopped, such as at a red light, the gasoline engine and electric motor shut off automatically so that energy is not wasted in idling.
[edit] How a stop/start hybrid works
Stop/Start hybrids are not true hybrids since electricity from the battery is not used to propel the vehicle. However, the Stop/Start feature is an important, energy-saving building block used in hybrid vehicles.
Stop/Start technology conserves energy by shutting off the gasoline engine when the vehicle is at rest, such as at a traffic light, and automatically re-starting it when the driver pushes the gas pedal to go forward.
[edit] Components of a stop/start hybrid
Battery - The battery stores energy generated from the gasoline engine or, during regenerative braking, from the electric motor. These batteries are only used to power the generator that starts the gasoline engine and to power accessories. Electric Starter/Generator - This device plays a dual role, starting the gasoline engine when pulling out from a stop and generating electricity that is stored in the battery.
Gasoline Engine - The gasoline engine in a stop/start hybrid is much like those in conventional vehicles. Unline other hybrids that use an elecric motor to help power the vehicle, the engine in a stop/start hybrid is usually not smaller in size.
[edit] Driving
The gasoline engine does not run when the vehicle is at rest.
When pulling out, the electric starter/generator uses electricity from the battery to instantly start the gasoline engine---the sole source of propulsion for the vehicle.
The generator may also convert energy from the engine into electricity and store it in the battery.
[edit] Braking
Stop/Start vehicles use a combination of regenerative and conventional friction braking to slow the vehicle.
In regenerative braking, energy from the wheels turns the electric generator, creating electricity. Using energy from the wheels to turn the generator slows the vehicle.
The engine shuts off to conserve energy when the vehicle comes to a stop.
All other systems, including the electric air conditioning, continue to run.
