Hybrid powertrain

Hybrid vehicles are vehicles with one or all of the points below: Hybrids come in many configurations. For example, a hybrid may receive all its energy from onboard petroleum fuel; however, it may be driven by an electric motor or a combustion engine at various times or simultaneously.

Another example is that a vehicle may be driven only by electric drive traction motors and receive its energy from two sources: a combustion engine electric generator, the generator commonly referred to as a range-extender, or an electric battery that is charged externally or by the onboard generator. Because of the differences, the various types of hybrid drivetrains fall into sub-hybrid categories, which this article covers.

While electric vehicles have a long history of combining internal combustion and electrical transmission – as in a diesel-electric power train – they have rarely been used for any vehicular application other than railways. A diesel-electric powertrain fails to meet the definition of hybrid because the electrical drive transmission directly replaces the mechanical transmission rather than being a supplementary source of motive power.

One of the earliest forms of a hybrid land vehicle meeting modern definitions is the ‘trackless’ trolleybus of the 1930s, which generally used traction current delivered by wire. The trolleybus was also commonly fitted with an internal combustion engine to directly power the bus or generate electrical power independently. This enabled the vehicle to maneuver around obstacles and broken overhead transmission wires. In the broadest sense, the powertrain includes all components that transform stored potential energy. They may use chemical, solar, nuclear, or kinetic chemicals and make them useful for propulsion. The oldest example is the galley that used sails and oars. The most common example is on most city streets. It is the electrically assisted pedal bicycle. Lastly, the most novel model is the flywheel bus of the 1950s.

Also, the latest hybrid car features a combination of stored electrical potential in the form of a battery, supplemented by a small, efficient, clean-burning internal combustion engine that can recharge the batteries on a long journey or directly power the vehicle in addition to battery power to give higher performance is a very innovative example. There are many types of hybrid vehicles, but only the electric internal combustion engine (ICE) type is commercially available. Both sources may operate in parallel to simultaneously provide power or work in series, with one source exclusively providing the power and the second used to provide energy. Ideally, both systems can be used flexibly in series and parallel as needed; but in practice, it is usual to regard one source as primary, with the other being used to augment the first.

Current hybrids use an internal combustion engine (ICE) and a battery/electric drive system, commonly using ultracapacitors, to improve fuel consumption, emissions, and performance and recover kinetic energy when braking. In effect, kinetic energy reclaims and harvests energy that would otherwise be lost. While other energy storage and conversion combinations are possible, none are in commercial production. Efficiency gains from superior energy management and regeneration are offset by expense, complexity, and the limitations of battery technology.

Combustion-electric hybrids have battery sets with a far larger capacity than an average combustion-only vehicle. A combustion-electric hybrid has light batteries that offer higher energy density and are far more costly. The combustion-only vehicle requires a battery to be large enough to operate the electrical system, with the batteries tending to be cheap, heavy, and inefficient with a short life. However, battery and supercapacitor technology is advancing, offsetting the relatively short lifespan of batteries. If the pattern established in the electronics industry is replicated – superior energy storage will become increasingly affordable.

Hybrid vehicles by Types of powertrain

  • parallel hybrids
  • series hybrids
  • Series-parallel hybrids

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