Petroleum electric hybrid vehicle

izhar10 · 0 Joined: 07 Mar 2007 Posts: 10

Petroleum electric hybrid vehicle
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A Toyota Prius, one example of a PEHV.A Petroleum Electric Hybrid Vehicle (PEHV) is a vehicle using an on-board rechargeable energy storage system (RESS) and a fueled power source for vehicle propulsion. The different propulsion power systems may have common subsystems or components. The HV provides better fuel economy than a conventional vehicle because the engine is smaller and may be run at speeds providing more efficiency. Other techniques may be used to recover or reduce waste energy (such as regenerative braking and shutting down the combustion engine).

The term hybrid when used in relation with cars also has other uses. Prior to its modern meaning of hybrid propulsion, the word hybrid was used in the United States to mean a vehicle of mixed national origin; generally, a European car fitted with American mechanical components. This meaning has fallen out of use. In the import scene, hybrid was often used to describe an engine swap. Some have also referred to flexible-fuel vehicles as hybrids because they can use a mixture of different fuels — typically gasoline and ethanol alcohol fuel.

Technology
PEHVs most commonly use internal combustion engines and electric batteries to power electric motors. Modern mass-produced hybrids prolong the charge on their batteries by capturing kinetic energy via regenerative braking. Many PEHVs shut down the combustion engine at idle, and re-start the combustion engine when needed. As well, when cruising or in other situations where just light thrust is needed, "full" hybrids can use the combustion engine to generate electricity by spinning an electrical generator (often a second electric motor[1]) to either recharge the battery or directly feed power to an electric motor that drives the vehicle. This contrasts with all-electric cars which use batteries charged by an external source such as the grid, or a range extending trailer. Nearly all hybrids still require gasoline and diesel as their sole fuel source though other fuels such as ethanol or plant based oils have also seen occasional use.

Benefits
Benefits of the hybrid design include:

Current hybrid vehicles reduce petroleum consumption (compared to otherwise similar ICE vehicles) primarily by using three mechanisms: a) Reducing wasted energy during idle/low output, generally by turning the internal combustion engine off; b) Recapturing waste energy (i.e. regenerative braking); c) reducing the size and power of the ICE engine, and hence inefficiencies from under-utilization, by using the better torque response of electric motors to compensate for the loss in peak power output from the smaller internal combustion engine.
Hybrids may also make more aggressive use of other fuel-saving techniques, such as reduced weight; these are not advantages of the hybrid design, but engineering choices made for various reasons, including marketing to consumers conscious of these issues.
Trade-offs include higher weight for electric motors and batteries, which may reduce fuel efficiency at highway speeds compared to otherwise equivalent ICE vehicles, or even result in lower fuel efficiency at highway speeds than in urban use; for this reason, hybrids may be considered to be particularly well suited to urban applications.
The internal-combustion engine in a hybrid vehicle is smaller, lighter, and more efficient than the one in a conventional vehicle, because the combustion engine can be sized for slightly above average power demand rather than peak power demand. A standard combustion engine is required to operate over a range of speed and power, yet its highest efficiency is in a narrow range of operation—in a hybrid vehicle, the combustion engine operates within its range of highest efficiency. The power curve of electric motors is better suited to variable speeds and can provide substantially greater torque at low speeds compared with internal-combustion engines.
Like many electric cars, but in contrast to conventional vehicles, braking in a hybrid is controlled in part by the electric motor which can recapture part of the kinetic energy of the car to partially recharge the batteries. This is called regenerative braking and contributes to the higher efficiency of hybrid cars. In a conventional vehicle, braking is done by mechanical brakes, and the kinetic energy of the car is wasted as heat.
Hybrids' greater fuel economy has implication for reduced petroleum consumption and vehicle air pollution emissions worldwide[13]
Reduced wear on the gasoline engine, particularly from idling with no load.
Reduced wear on brakes from the regenerative braking system use.
Reduced noise emissions resulting from substantial use of electric motor at low speeds, leading to roadway noise reduction and beneficial noise health effects. Note, however, that this is not always an advantage; for example, people who are blind or visually-impaired, and who rely on vehicle-noise while crossing streets, find it more difficult to do safely.
Reduced air pollution emissions due to lower fuel consumption, leading to improved human health with regard to respiratory and other illness. Composite driving tests indicate total air pollution of carbon monoxide and reactive hydrocarbons are 80 to 90 percent cleaner for hybrid versus conventional vehicles[6]. Pollution reduction in urban environments may be particularly significant due to elimination of idle-at-rest.
Increased driving range without refueling or recharging, compared with electric vehicles and perhaps even compared with internal-combustion vehicles. Limitations in range have been a problem for traditional electric vehicles. Hybrids may have substantially longer "operating hours" per unit of petroleum in certain conditions than the mileage-rated fuel efficiency figures may indicate, due to the reduction of idle-at-rest.

Example of hybrid cars - http://www.toyota.com/prius/
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