Hybrid vehicle

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

A hybrid vehicle or gas-electric hybrid powered vehicle uses a mixture of technologies such as internal combustion engines (ICEs), electric motors, gassoline, and batteries. Today's hybrid cars are driven by electric motors powered by both batteries and an ICE. Please see Gas-Electric Hybrid for further clarification of what the word hybrid is describing with regards to these vehicles.

Hybrids do not necessarily have to be plugged in to recharge their batteries though they do still require gassoline as it is their only source of fuel. They are slightly more environmentally-friendly than 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 fallen out of use.

Some assert that current hybrid cars are not true hybrids because they are not capable of using either engine and motor independent of each other. Others feel that none of the current "Hybrids" are such since none are capable of using alternate fuels such as electricity from an outlet, ie: "Hybrid Fueled". However, hybrid come in a variety of different configurations.

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Median mpg (US) with boxplot from GreenHybrid.com http://www.greenhybrid.com/compare/mileage/ Real Hybrid Mileage Database
Contents
1 Overview
2 On sale now
3 History

3.1 Diesel
3.2 Steam

4 Battery technology
5 Hybrid types

5.1 Full hybrids
5.2 Assist hybrids
5.3 Plug-In hybrids
5.4 Hydraulic hybrids
5.5 Mild hybrids

6 Benefits of owning a hybrid vehicle
7 See also
8 External links

Overview

A hybrid vehicle 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:

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Hybrid powertrains are divided into two major categories: series hybrids use a combustion engine to drive a generator, which in turn drives electric motors that supply mechanical power (most diesel trains use this technology); while parallel hybrids supply mechanical power directly from both a conventional combustion engine and an electric motor (most hybrid cars use this technology).

Some parallel hybrid power trains have a simple torque-boosting electric motor mounted directly on a conventional powertrain. The Honda Insight is an example. Others have a split power path that allows more flexibility in the drivetrain by interconverting mechanical and electrical power, at some cost in complexity. The Toyota Prius uses this technology, which goes by the brand name Hybrid Synergy Drive.

On sale now

History

Hybrid technology actually originated with diesel electric submarines, which 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 vehicle to generate electricity. Thus the energy that would normally be lost when stopping is used to speed the vehicle back up. Since the amount of electrical power needed is much smaller, the size of the battery systems is reduced.

The Honda Insight model released in the late 1990s follows such a design.

A third form of hybrid uses electric motors and a differential type linkage to replace the transmission of a conventional train, allowing a balanced interaction between the conventional engine and the electric motor system. Toyota introduced the first such drivetrain in the Prius line; they are also including this 'Hybrid Synergy Drive' in other models such as the newer Highlander SUV. These systems use large transistors and computer control to control and augment the flow of mechanical energy from the engine to the wheels. The Prius uses advances both in the hybrid drive train and in the conventional engine to reduce drag and achieve 80%-100% gains in fuel efficiency compared to four-door conventional cars of similar weight and size.

The Prius has been in high demand since its introduction. Newer designs have more conventional appearance and are 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 survey of 2003 model year cars showed that hybrid car registrations in the United States rose to 43,435 cars, a 25.8 % increase from 2002 numbers. California had the most hybrid cars 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 US (2.35 L per 100 km).

Diesel hybrids have the advantage they can use 100% pure biofuels (biodiesel), so they don´t 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 to 5% of biodiesel. VW's prototype diesel-electric hybrid car achieved 118 mpg US fuel economy (2 liters per 100 km).

Steam

At present, no current or planned mass-market car is driven by a steam engine, but hybrid technology promises to bring back the steam-powered car. In the early 20th century, steam-powered cars made by the Stanley Steamer Company did compete successfully with the internal combustion engine. Steam engines can be much more efficient (and generate less pollution) than internal combustion engines, which is why most of the world's electric power comes from steam engines. But they have not been able to compete with internal combustion for vehicles for several reasons:

the driver of a Stanley Steamer had to keep a close eye on several pressure and temperature gauges while driving. Hybrid technology could remove these obstacles and allow cars to enjoy the clean and efficient power of steam.

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 with the car's introduction in 2000, the Toyota Prius uses the third-generation hybrid design, in which a computer and differential-type linkage allow the wheels to be driven by an electric motor, an internal combustion engine, or a combination of both. 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.

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 Hybrid 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. Honda's hybrids use this design; their system is dubbed IMA. Assist hybrids differ fundamentally from full hybrids in that they cannot run on electric power alone. Ford dubs Honda's hybrids "mild" in their advertising for the Escape Hybrid, arguing that the Escape's full hybrid design is more efficient. However, assist hybrids should not be confused with actual mild hybrids like the Chevrolet Silverado 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 buses from the early 1980s and is still an active area. Initial concept involved a giant flywheel for storage connected to a hydrostatic transmission, but it was later changed to a simpler system using a hydraulic accumulator 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 vehicles 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.

Benefits of owning a hybrid vehicle

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

See also

External links

See also: Hybrid vehicle, 1040, 1899, 1990s, 2000, 2003