About Hybrid Cars
Hybrid Cars
In genetics, a hybrid is the result of combining elements
from different species. When it comes to cars and trucks, a
hybrid refers to a vehicle whose powertrain combines the
aspects of different technologies (i.e. gasoline and
electric) to improve efficiency and reduce emissions.
In automotive terms, hybridization is nothing new. Hybrid
cars and trucks that combined an electric motor with a
gasoline engine date back to the turn of the 20th century
(see Back to the Past). Hybrid diesel-electric locomotives
have been in operation for years, and diesel-electric buses
began to appear in the 1970s.
These days, automotive choices that combine two or more
sources of power are known as hybrid vehicles. The most
common is the electric hybrid, which melds a gasoline engine
with an electric setup (electric motor, charging system, and
a battery/storage system).
Parallel vs. Series
Due to the inherent complexity of the technology involved,
and the numerous options engineers have in employing hybrid
systems, we're forced to speak in some general terms here.
That said, the two most popular forms of hybrids available
today are called "series" or "parallel" hybrids. Series
hybrids are also called "mild" or "partial" hybrids, while
parallel hybrids are often referred to as "full" hybrids.
In a series hybrid, an electric motor assists the gasoline
engine when needed, such as during acceleration or times of
heavy load, but it can't power the car on its own. The
batteries that power the electric motor can be recharged by
the engine, or during deceleration (called regenerative
braking). The Saturn Vue Green Line and Honda Civic Hybrid
are examples of series hybrids.
Parallel hybrids can use similar recharging scenarios, but
can be powered by the gasoline engine only, the electric
motor only, or both at the same time. The Toyota Prius, Ford
Escape Hybrid, Nissan Altima Hybrid, and GM's new
Tahoe/Yukon hybrid SUVs are examples of parallel hybrids.
How They Operate
In practice, like a regular car, a series-hybrid vehicle has
an engine that is generally running all the time. An
electric motor placed "in series" between the engine and the
wheels helps motivate the car. In assisting the engine, the
electric motor helps improve fuel economy and reduce
emissions. Some series hybrids also provide a "start-stop"
function, which turns off the engine completely when the car
is stationary, then restarting it instantly when the brake
pedal is released.
Unlike a series hybrid, a parallel hybrid can operate like a
fully electric car up to speeds of roughly 20-30 mph. In
situations such as stop-and-go traffic, or under light
acceleration at low speeds, the vehicle's engine may not run
at all, relying completely on electric propulsion. The
results are vastly improved city mpg ratings and, while in
full-electric mode, essentially zero emissions.
Plugged In
A "plug-in" hybrid is basically a parallel hybrid, often
with a larger battery pack that allows it to run in
electric-only mode for longer distances or at higher speeds.
Additionally, instead of the batteries just being
replenished by the vehicle's engine or through regenerative
braking, the car can also be recharged by plugging it into
an electrical outlet. Though no plug-in hybrids are
currently for sale from major manufacturers, several are
scheduled to hit the market in the next few years.
At last year's North American International Auto Show in
Detroit, General Motors announced plans to produce its Chevy
Volt plug-in hybrid by 2010. This year's show saw upcoming
plug-in offerings of the Ford Escape, Saturn Vue, Toyota
Prius and a promise from boutique automaker Fisker
Automotive to deliver the $80,000 Karma plug-in luxury sedan
late next year.
More Hybrids to Come
The latest parallel hybrid system (GM calls it a "two-mode"
hybrid) in use on the new Chevrolet and GMC full-size SUVs
was a joint development of General Motors, Chrysler,
Mercedes-Benz and BMW. Scalable to a variety of vehicle
sizes and types, the system will be featured later this year
on the Saturn Vue, the Chevy Silverado full-size pickup, the
Chrysler Aspen and the Dodge Durango.
Additional hybrid concepts from this year's auto show in
Detroit also included Chrysler's ecoVoyager minivan, Land
Rover's LRX "Cross Coupe" and Toyota's small pickup, the
A-BAT. These are just a few of a long lineup of experimental
and prototype hybrid vehicles (see The Future of Hybrid
Vehicles) that have been built, but not produced — yet. If,
but more likely when, these promising prototypes see
production, the hybrid lexicon will continue to grow.
Source: msn.com