The Hybrid car reference article from the English Wikipedia on 24-Jul-2004
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Hybrid car

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A hybrid car or hybrid electric vehicle is a vehicle which relies not only on batteries but also on an internal combustion engine which drives a generator to provide the electricity and may also drive the wheels directly.

2004 Toyota Prius, a hybrid gas-electric vehicleEnlarge

2004 Toyota Prius, a hybrid gas-electric vehicle

Table of contents
1 Overview
2 History
3 Recent developments
4 Battery technology
5 Hybrid Types
6 See also
7 External links

Overview

A hybrid car uses more than one power source, almost always an internal-combustion engine and an electric motor. In the hybrid design the engine is the final source of the energy used to power the car. All-electric cars use batteries charged by an external source, leading to problems with range. This common complaint is avoided with hybrid cars.

History

The first successful hybrid electric car was engineered by Ferdinand Porsche in 1928. Since then, hobbyists have built such cars but no such car was put into production until the waning years of the twentieth century. However, hybrid technology has been in use on railroads ever since the 1930s, when the locomotives on early streamliners ran on gasoline-electric and diesel-electric systems at far greater efficiencies than the steam engines of the day.

Automotive hybrid technology became commercially successful in the 1990s when the Honda Insight and Toyota Prius became available. These vehicles have a direct linkage from the internal combustion engine to the drive, so that the engine can provide acceleration power. Prototypes of plug-in hybrid cars, with larger battery packs that can be re-charged from the power grid, have been built in the U.S., and one production PHEV, the Renault Kangoo, went on sale in France in 2003.

Early hybrid designs tended to use the electric motor for all power, due to simplicity. The engine would charge batteries from which the motor drew power, running only when needed to charge them back up, and at its "best power" speed when doing so. However, this design was less efficient because of losses accrued in converting the kinetic energy of the engine into electrical energy, and back into kinetic energy at the wheels.

Recent developments

More modern designs reverse this to some degree, using the gasoline engine for primary power, but using one that is smaller than would otherwise be needed. The motor is essentially a very large starter motor, which operates not only when the engine needs to be turned over, but also when the driver "steps on the gas" and requires extra power. Instead of the engine solely charging the batteries, the motor acts as a generator during braking, using the momentum of the car to generate electricity. Thus the energy that would normally be lost when stopping is used to speed the car back up. Since the amount of electrical power needed is much smaller, the need for large battery systems is eliminated. Such designs were released in the late 1990s in the Honda Insight and Toyota Prius, but neither saw wide consumer acceptance Ö the Insight for its high price and small size, and the Prius for its unconventional dashboard and high price. Newer designs are considerably more conventional and slightly cheaper, often appearing and performing identically to their non-hybrid counterparts while delivering 50% better fuel efficiency. The Honda Civic Hybrid appears identical to the non-hybrid version, for instance, but delivers about 50 mpg (US). The redesigned 2004 Toyota Prius improved passenger room, cargo area, and power output, while increasing energy efficiency and reducing emissions. The Honda Insight is still on sale and has a devoted base of owners, similar to the phenomenon observed with Apple computer.

One particularly interesting combination uses the newer technique, with a diesel engine. Diesels are excellent engines for delivering constant power for long periods of time, suffering less wear while delivering higher efficiency. However, the engines also suffer from poor acceleration due to having a limited RPM range. This poor acceleration can be addressed with the hybrid technique, and such designs may offer performance in a car of over 100 mpg (US); however, there are no production models as of 2003.

In the first generation hybrid car, the internal combustion engine only serves as an on-board generator to supply power to the electric motor which provide the sole driving force to the wheels. This is referred to as a "Series Hybrid" system. In the second generation, the internal combustion engine drives the wheels directly with the electric motor serving as a power assist when extra power is needed, and to recapture the kinetic energy usually lost during braking. This is known as a "Parallel Hybrid" system. The extra power from the electric motor enables the manufacturers to reduce the engine size to achieve fuel economy. Either approach has its limitations. Starting from 2004 model year (note), the Toyota Prius uses the third generation hybrid design. In this new design, the wheels can be driven by either the internal combustion engine or the electric motor using a planetary gear system to draw power from either source. The on-board computer optimizes the fuel usage by shutting off the internal combustion engine when the electric motor is sufficient to provide the power. The internal combustion engine starts up whenever extra power is needed or the battery needs recharging. The electric motor serves as the main driving force and a generator. The more efficient new design enabled Toyota to build the new Prius as a mid-size car without sacrificing fuel economy.

2004 should see the first hybrid SUV's. Toyota announced model year 2005 hybrid versions of the Toyota Highlander and Lexus RX 400h. Ford Motor Company is making the first hybrid available from an American automaker, the Ford Escape Hybrid. Honda has also announced that they would release a hybrid version of the Accord.

An R.L. Polk & Co. Survey of 2003 automobiles showed that hybrid car registrations in the United States rose to 43,435 automobiles, a 25.8 percent increase from 2002 numbers. California had the most hybrid vehicles registered with 11,425.

(note) Incidentally, all four Hybrid cars on the road as of June 2004 can drive in this manner. For example, the Honda Insight can drive at very low speeds (<10 mph) using only the electric motor, if the fuel supply is depleted. The 2004 Prius has a 50 kW (76 hp) electric motor that can be used as a primary power source.

Battery technology

It appears that battery technology will not evolve to address the needs of fully-electric cars in the near future. All companies involved in such research have since given up, and moved to fuel cells and hybrids. Toyota has announced that it intends that all its vehicles will have a hybrid electric version by 2012. It appears many European companies, where diesel is much more common, will follow Toyota's lead and move in the same direction.

Hybrid Types

Full hybrids

A "full hybrid", sometimes also called the "strong hybrid", is a vehicle that can run on just the engine, just the batteries, or a combination of both. The Prius and the Escape are examples of this. A large, high voltage battery pack is usually needed for battery-only operation.

Assist hybrids

Assist hybrids use a battery and electric motors to accelerate the car, but only in combination with the internal combustion engine. The Honda Insight is an example of an assist hybrid.

Hydraulic hybrids

A hydraulic hybrid vehicle uses hydraulic and mechanical components instead of electrical ones. A variable displacement pump replaces the motor/generator, and a hydraulic accumulator replaces the batteries. The hydraulic accumulator, which is essentially a pressure tank, is potentially cheaper and more durable than batteries. Hydraulic hybrid technology is being actively developed by several companies, primarily in heavy vehicles like buses, trucks and military vehicles.

Mild hybrids

There is another kind of cars that are marketed as hybrids, but technically they are not. The critics called these mild hybrid cars to distinguish from a real hybrid design. One upcoming example is the 2005 Chevrolet Silverado Hybrid fullsize pickup truck. In the mild hybrid design, the electric motor/generator does not drive the wheels, hence some people argue that it is not really hybrid depending on their interpretation of the criteria of a hybrid car. In these mild hybrid cars, an oversize, large starter motor spins up the engine to operating rpm before fuel is injected into the combustion chambers. At high rpm, an engine can be restarted efficiently and cleanly. This allows the car to shut down the internal combustion engine whenever the car is coasting or braking or stopped. The motor/generator is also used to recapture energy through regenerative braking. Chevrolet was able to get a 10% improvement on the Silverado's fuel efficiency by shutting down and restarting the engine on demand. Mild hybrids often use 48 V systems to supply the power needed for the startup motor, as well as to compensate for the increasing number of electronic accessories on modern vehicles.

See also

External links