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Hybrid car

2004 Toyota Prius, a hybrid gas-electric vehicle
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2004 Toyota Prius, a hybrid gas-electric vehicle

A hybrid car is a automobile/car that uses a mixture of technologies such as internal combustion engines (ICEs), electric motors, batteries, hydrogen, and fuel cells. Today's hybrid cars are driven by electric motors powered by both batteries and an ICE.

Hybrids do not necessarily have to be plugged in, yet still deliver superior mileage and performance. They are environmentally-friendly alternatives to traditional internal combustion engine vehicles.

Prior to its modern usage to mean 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 currently fell out of use.


Contents

Overview

A hybrid car uses two different power sources. They are an electric motor and almost always an internal-combustion engine. In the hybrid design, an electric motor or several electric motors power the car, and a combustion engine keeps the batteries charged and assists when more power is needed e.g. for sudden acceleration. This contrasts with all-electric cars which use batteries charged by an external source. Benefits of the hybrid design include the following:

  • The vehicle is usually lighter and roomier than a purely electric vehicle of comparable size and power because fewer batteries are needed.
  • The internal-combustion engine in a hybrid vehicle is much smaller, lighter, and more efficient than the one in a conventional vehicle, because the electric motor can provide a boost of power for acceleration.
  • Braking in a hybrid car is controlled by the electric motor which recaptures part of the kinetic energy of the car to partially recharge the batteries. This is called regenerative braking and one of the reasons for the high efficiency of hybrid cars. In a conventional vehicle with internal-combustion engine braking is done by mechanical brakes and the kinetic energy of the car is wasted as heat.
  • Most hybrid powertrains are characterized by a split power path called a powersplit . One side of this split is electrical and the other side of this power path is mechanical.

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History

Hybrid technology actually originated with diesel electric submarines. Both operate in essentially the same manner as hybrid electric cars.

The first successful hybrid electric car was engineered by Ferdinand Porsche in 1899. Since then, hobbyists have continued to build hybrids but none was put into mass production by a major manufacturer until the waning years of the twentieth century.

Automotive hybrid technology became 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 driven wheels, so 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., notably at Prof. Andy Frank's Hybrid Center at UC Davis and one production PHEV, the Renault Kangoo, went on sale in France in 2003. DaimlerChrysler is currently building PHEVs based on the Sprinter van. The California Cars Initiative has converted the 2004 Prius to become a prototype of what it calls the PRIUS+

Some hybrid designs use only the electric motor for mechanical power. An internal-combustion engine charges the batteries from which the electric motor draws power. The internal-combustion engine runs only to charge the batteries when needed and runs at its most efficient speed when doing so.

Other designs are using a small gasoline engine for primary power. The electric 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 size of the battery systems is reduced.

Such designs were released in the late 1990s in the Honda Insight and Toyota Prius. The Prius has been in high demand since its introduction. Newer designs are considerably more conventional and less expensive, 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.

2004 saw the first hybrid SUV released, Ford Motor Company's Ford Escape Hybrid. Toyota announced model year 2005 hybrid versions of the Toyota Highlander and Lexus RX 400h, and has plans to add hybrid drivetrains to every model it sells in the coming decade. Honda has also announced the release of a hybrid version of the Accord. Also, Nissan announced the release of the Altima hybrid (technology supplied by Toyota) around 2006.

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, which may be partially due to its higher gasoline prices and emissions rules, which hybrids generally have little trouble passing.

Total number of hybrids sold by Toyota and Honda:

Honda, which offers Insight, Civic and Accord hybrids, sold 26,773 hybrids in the first 11 months of last year alone. Toyota has sold a cumulative 306,862 hybrids between 1997 and Nov. 2004 and Honda has sold a total of 81,867 hybrids between 1999 and November 2004.[1]

Diesel

One particularly interesting combination uses a diesel engine for power. Diesels are excellent at 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 (2.35 L/100 km).

Diesel hybrid have the advantage they can use 100% pure biofuels (biodiesel), so they donīt need petroleum at all.

The diesel car offerings in the US are limited to VW (New Beetle, Golf, Jetta, Passat and Touareg all have diesel engines editions) and Mercedes Benz (E320 CDI), and more is expected after June of 2006 when the new low sulfur diesel fuel will be introduced to the US market. It is already available in Europe (so called Eurodiesel) where, thanks to that new fuel and the new and cleaner technologies for diesel engines, almost half of all the vehicles sold have a diesel engine. Mercedes Benz claims 56% (as of February 2005) of all the cars they sell in Europe are diesels. Some countries combine the new diesel fuel (France, for instance) with a mandatory 2-5% of biodiesel. VW's prototype diesel-electric hybrid car achieved 118 mpg fuel economy (2 liters per 100 km).

Battery technology

All-electric cars are more popular in Europe than in the U.S. The official argument of the major U.S. automobile manufacturers is lack of customer demand for pure electric cars. However, this might change once battery technology advances and gas prices keep further increasing.

For now, car manufacturers are focusing on fuel cell based cars and hybrids. Toyota intends that all of its vehicles be hybrid electric by 2012.

Hybrid types

In the earliest hybrid cars, prior to the Prius and Insight, 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, the Toyota Prius uses the third-generation hybrid design. In this new design, the wheels can be driven by either the electric motor or an internal combustion engine 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 only when extra power is needed or the battery needs recharging. The electric motor serves as the main driving force and generator. The more efficient new design enabled Toyota to build the new Prius as a mid-size car with superior fuel economy.

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 in combination with an internal combustion engine. The Honda Insight is an example of an assist hybrid.

A variation on this type is Mazda's e-4WD system, offered on the Japan-market Mazda Demio. This front wheel drive vehicle has an electric motor which can drive the rear wheels when extra traction is needed. The system is entirely disengaged in all other driving conditions, so it does not enhance performance or economy.

Plug-In hybrids

These are full hybrids, able to run in electric-only mode, with larger batteries and the ability to recharge from the electric power grid. They are variously called gas-optional, griddable or plug-in hybrids, with the general acronym PHEV. Their great benefit is that they can be gasoline-independent for daily commuting, while they have the extended range of a hybrid for long trips. They can also be multi-fuel, with the electric power supplemented by diesel, biodiesel, or hydrogen. The Electric Power Research Institute's research indicates a lower total cost of ownership for PHEVs due to reduced service costs and gradually improving batteries. The "well-to-wheel" efficiency and emissions of PHEVs compared to gasoline hybrids depends on the energy sources of the grid (the US grid is 50% coal; California's grid is primarily natural gas, hydro, and wind). Particular interest in PHEVs is in California where a "million solar homes" initiative is under way, and global warming legislation has been enacted.

See also: Plug-in hybrid electric vehicle

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 was originally developed by Volvo Flygmotor and was used experimentally in busses from the early 1980s and is still an active area. Inital concept involved a giant flywheel for storage connected to a hydrostatic transmission, but it was later changed to a simpler system using a hydraulic acumulator connected to a hydraulic pump/motor. It is also being actively developed by Eaton and several other companies, primarily in heavy vehicles like buses, trucks and military vehicles. An example is the Ford F-350 Mighty Tonka concept truck shown in 2002. It features an Eaton system that can accelerate the truck up to highway speeds.

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. Some people argue that it is not really hybrid since the electric motor/generator does not drive the wheels at all. 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, braking, or stopped but the accessories can continue to run on electrical power. 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 volt 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. These vehicles do not achieve the fuel mileage of "true" hybrid models.

Perks of owning a hybrid car

Government agencies in the US offer benefits to encourage the purchase of certain qualifying hybrid or electrical vehicles.

  • The purchase of hybrid cars qualifies for a $2000 tax deduction on the IRS 1040 form for the year of 2003. The deduction reduces by $500 each year until it reaches zero. HR 1308 Sec. 319 proposed the phasing out of the deduction to put on hold for the year 2004 and 2005. i.e. hybrid car buyers can enjoy the $2000 deduction before the phasing out resumes at $500 in 2006.
  • Many states give tax credits to hybrid car buyers.
  • Certain states, e.g. Virginia and Florida, allow singly occupied hybrid vehicles to enter the HOV lanes on the highway.
  • Some states, e.g. California, exempt hybrid cars from the biennial smog inspection, which costs over US$50 in 2004.
  • Hybrid cars can go on certain toll roads for free.
  • City of San Jose, CA issues a free parking tag for hybrid cars that were purchased at a San Jose dealership. The qualified owners do not have to pay for parking in any city garage or road side parking meters.
  • City of Los Angeles, CA offers free parking to all hybrid vehicles starting on October 1, 2004. The experiment is an extension to an existing offer of free parking for all pure electrical vehicle.
  • Drivers of hybrid vehicles in the UK benefit from the lowest band of Vehicle Excise Duty (car tax) which is based on CO2 emmissions. In London, these vehicles are also exempt from the Ģ5 ($9) daily Congestion Charge in Central London.

See also

External links

Last updated: 05-07-2005 05:59:14
Last updated: 05-13-2005 07:56:04