Sunday, March 2, 2008

Hybrid Electric Vehicle


A hybrid electric vehicle (HEV) is a vehicle which combines a conventional propulsion system with an on-board rechargeable energy storage system (RESS) to achieve better fuel economy than a conventional vehicle without being hampered by range from a charging unit like a battery electric vehicle, which uses batteries charged by an external source. The different propulsion power systems may have common subsystems or components.

Regular HEVs most commonly use an internal combustion engine (ICE) and electric batteries to power electric motors. Modern mass produced HEVs prolong the charge on their batteries by capturing kinetic energy via regenerative braking, and some HEVs can use the combustion engine to generate electricity by spinning an electrical generator (often a motor-generator) to either recharge the battery or directly feed power to an electric motor that drives the vehicle. Many HEVs reduce idle emissions by shutting down the ICE at idle and restarting it when needed. An HEV's engine is smaller and may be run at various speeds, providing more efficiency.

HEVs became widely available to the public in the late 1990s with the introduction of the Honda Insight and Toyota Prius. HEVs are viewed by some automakers as a core segment of the next future automotive market.[1] An article for the July-August 2007 issue of THE FUTURIST magazine titled "Energy Diversity as a Business Imperative"[2] included plug-in hybrid vehicles. GM vice president for environment and energy Elizabeth Lowery is quoted as saying, "Today, we are embracing multiple energy sources because there is no single answer available for the mass market…"

Technology

The variety of hybrid electric designs can be differentiated by the structure of the hybrid vehicle drivetrain, the fuel type and the mode of operation.

In 2007, several manufacturers have announced that vehicles will use aspects of hybrid electric technology to reduce fuel consumption without the use of the hybrid drivetrain. Regenerative braking can be used to recapture energy and stored to power electrical accessories, such as air conditioning. Shutting down the engine at idle can also be used to reduce fuel consumption and reduce emissions without the addition of a hybrid drivetrain. In both cases, some of the advantages of hybrid electric technology are gained while additional cost and weight may be limited to the addition of larger batteries and starter motors. There is no standard terminology for such vehicles, although they may be termed mild hybrids.

The 2000s saw development of plug-in hybrid electric vehicles (PHEVs), which can be recharged from the electrical power grid and do not require conventional fuel for short trips. The Renault Kangoo was the first production model of this design, released in France in 2003.

Engines and fuel sources

Gasoline

Gasoline engines are used in most hybrid electric designs, and will likely remain dominant for the foreseeable future. While petroleum-derived gasoline is the primary fuel, it is possible to mix in varying levels of ethanol created from renewable energy sources. Like most modern ICE-powered vehicles, HEVs can typically use up to about 15% bioethanol. Manufacturers may move to flexible fuel engines, which would increase allowable ratios, but no plans are in place at present.

Diesel

Diesel-electric HEVs use a diesel engine for power generation. Diesels have advantages when delivering constant power for long periods of time, suffering less wear while operating at higher efficiency. The diesel engine's high torque, combined with hybrid technology, may offer substantially improved mileage. Most diesel vehicles can use 100% pure biofuels (biodiesel), so they can use but do not need petroleum at all for fuel (although mixes of biofuel and petroleum are more common, and petroleum may be needed for lubrication). If diesel-electric HEVs were in use, this benefit would likely also apply. Diesel-electric hybrid drivetrains have begun to appear in commercial vehicles (particularly buses); as of 2007, no light duty diesel-electric hybrid passenger cars are currently available, although prototypes exist. Peugeot is expected to produce a diesel-electric hybrid version of its 308 in late 2008 for the European market.[4]

PSA Peugeot Citroën has unveiled two demonstrator vehicles featuring a diesel-electric hybrid drivetrain: the Peugeot 307, Citroën C4 Hybride HDi and Citroën C-Cactus.[5] Volkswagen made a prototype diesel-electric hybrid car that achieved 2 L/100 km (140 mpg imp/120 mpg US) fuel economy, but has yet to sell a hybrid vehicle. General Motors has been testing the Opel Astra Diesel Hybrid. There have been no concrete dates suggested for these vehicles, but press statements have suggested production vehicles would not appear before 2009.

Robert Bosch GmbH is supplying hybrid diesel-electric technology to diverse automakers and models, including the Peugeot 308.[6]

So far, production diesel-electric engines have mostly just appeared in mass transit buses.

Design considerations

In some cases, manufacturers are producing HEVs that use the added energy provided by the hybrid systems to give vehicles a power boost, rather than significantly improved fuel efficiency compared to their traditional counterparts.[7] The trade-off between added performance and improved fuel efficiency is partly controlled by the software within the hybrid system and partly the result of the engine, battery and motor size. In the future, manufacturers may provide HEV owners with the ability to partially control this balance (fuel efficiency vs. added performance) as they wish, through a user-controlled setting.[8] Toyota announced in January, 2006 that it was considering a "high-efficiency" button.

Conversion kits

One can buy a stock hybrid or convert a stock petroleum car to a hybrid electric vehicle using an aftermarket hybrid kit.

Benefits

Benefits of the hybrid electric design include:

Fuel consumption
Current HEVs reduce petroleum consumption (compared to otherwise similar conventional vehicles) primarily by using three mechanisms:
a) Reducing wasted energy during idle/low output, generally by turning the ICE off;
b) Recapturing waste energy (i.e. regenerative braking);
c) Reducing the size and power of the ICE, and hence inefficiencies from under-utilization, by using the added power from the electric motor to compensate for the loss in peak power output from the smaller ICE.

Any combination of these three primary hybrid advantages may be used in different vehicles to realize different fuel usage, power, emissions, weight and cost profiles. The ICE in an HEV can be 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. The drive system in a vehicle is required to operate over a range of speed and power, but an ICE has its highest efficiency is in a narrow range of operation, making conventional vehicles inefficient. In contrast, in most HEV designs, the ICE operates closer to its range of highest efficiency more of the time. 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. The greater fuel economy of HEVs has implication for reduced petroleum consumption and vehicle air pollution emissions worldwide[10]

Durability
Reduced wear on the gasoline engine, particularly from idling with no load. Reduced wear on brakes from the regenerative braking system use.
There's no definitive word on replacement costs of the batteries because they are almost never replaced. According to Toyota, since the Prius first went on sale in 2000, they have not replaced a single battery for wear and tear.
Environmental impact
Reduced noise emissions resulting from substantial use of the electric motor at idling and low speeds, leading to roadway noise reduction,[11] in comparison to conventional gasoline or diesel powered engine vehicles, resulting in beneficial noise health effects (although road noise from tires and wind, the loudest noises at highway speeds from the interior of most vehicles, are not affected by the hybrid design alone). 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.[1] Reduced air pollution emissions due to lower fuel consumption, leading to improved human health with regard to respiratory and other illness. Pollution reduction in urban environments may be particularly significant due to elimination of idle-at-rest.
One common misconception is: "However, one must remember the environmental stamp of HEV batteries, which must be replaced on a regular basis and are treated as extremely hazardous waste." This is not entirely true. Battery toxicity is a concern, although today's hybrids use NiMH batteries, not the environmentally problematic rechargeable nickel cadmium. "Nickel metal hydride batteries are benign. They can be fully recycled," says Ron Cogan, editor of the Green Car Journal. Toyota and Honda say that they will recycle dead batteries and that disposal will pose no toxic hazards. Toyota puts a phone number on each battery, and they pay a $200 "bounty" for each battery to help ensure that it will be properly recycled.

The Guides to Hybrid Vehicles

in January 2008 we have been shocked by the high price of gasoline? As the pump clicked past $20, $30, $40 or even $50,

Historical Gas Prices
(Adjusted for inflation)
Year
Price Per Gallon
1950
$1.91
1955
$1.85
1960
$1.79
1965
$1.68
1970
$1.59
1975
$1.80
1980
$2.59
1985
$1.90
1990
$1.51
1995
$1.28
2001
$1.66
2002
$1.31
2003
$1.52
2004
$1.79
2005
$2.28
2006
$3.03
2007 (so far)
$3.26
Source: U.S. DOE
maybe you thought about trading in your car for something that gets better mileage. Or maybe you're worried that your car is contributing to the greenhouse effect.

With regard to anything automotive, the word "hybrid" has become synonymous with frugality and efficiency. Thanks in large part to the popular Toyota Prius, Americans see automotive gas/electric hybrid technology as at least one solution to lowering fuel costs and reducing America's dependence on foreign oil. As a bonus, hybrids have earned a reputation for cleaner tailpipe emissions as well.

Despite the perceived benefits of hybrid technology, sales of these vehicles still represent only a tiny fraction of the U.S. marketplace. Americans purchased about 250,000 hybrid vehicles in 2006, accounting for just 1.5 percent of the 17,000,000 cars and trucks sold here last year.

Choices, Choices

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One reason hybrid sales haven't grown more quickly is the limited number of vehicles available. This list includes 14 vehicles, two of which, at the time of this writing, are not yet available, and one that can only be purchased in five states.

Another reason is cost. In addition to a vehicle's conventional gasoline engine, hybrids also include a regenerative braking system that recaptures energy that is normally wasted in braking and slowing, a battery pack to store the recovered power, and one or more electric motors that assist in propelling the vehicles. Note that all the vehicles discussed here also incorporate engine shut-off technology. Very simply, these systems shut the engine off while idling to conserve fuel. Vehicles with more advanced hybrid systems may propel themselves short distances before restarting the engine, further improving fuel economy.

All this additional technology adds considerably to the overall cost of hybrid vehicles. Still, automakers are loath to be excluded from the hybrid hysteria, believing that offering such vehicles demonstrates both social responsibility as well as technical prowess.

While hybrid vehicles are generally assumed to be frugal with fuel, not all hybrids are designed to be gas misers. Several hybrids, those offered by Toyota's Luxury Lexus division especially, use hybrid technology primarily as a means to improve performance, though fuel economy is generally improved as well. Available now or due soon are hybrid vehicles from General Motors, Ford, Honda, Nissan, and Toyota. From GM comes the Saturn Vue Green Line compact SUV. Hybrid versions of GM's Chevrolet Malibu and Saturn Aura midsize sedans are due later this year. Ford offers hybrid versions of its Ford Escape and Mercury Mariner compact SUVs. Honda's popular Civic and Accord compact and midsize cars are both offered in hybrid form. From Nissan comes the Altima hybrid, a midsize sedan.

Toyota has the most hybrid offerings. The compact Prius comes only as a hybrid, while the midsize sedan Camry and midsize SUV Highlander offer both hybrid and conventional variants. From Toyota's Lexus division come the midsize GS450h sedan, the large LS600h sedan, and the RX450h midsize SUV.

2008 Chevrolet Malibu
2008 Chevrolet MalibuBase Price Range: NA
EPA MPG: NA
Consumer Guide Observed MPG: NA
Due out this fall as part of a redesigned Malibu lineup, this hybrid incorporates the same General Motors "mild hybrid" technology as the 2007 Saturn Aura and Vue hybrids. Though specific information is not yet available, count on seeing a 2.4-liter 4-cylinder engine and conventional four-speed automatic transmission. While the mild hybrid arrangement still incorporates electric thrust to improve acceleration, it does not allow for electric-only running at low speeds, as do most other hybrid systems. Mild hybrid technology, however, tends to be less costly than other systems. General Motors is claiming a fuel economy improvement of up to 25 percent when compared to a similar Malibu without a hybrid drivetrain.

2008 Ford Escape Hybrid
2008 Ford Escape HybridBase Price Range: $25,075-$26,825
EPA MPG: NA
Consumer Guide Observed MPG: 28.4-31.7

Though sporting new exterior styling, Escape remains mechanically unchanged for 2008. As such, Ford division's only hybrid returns largely intact. While conventional Escapes are offered in XLS, XLT, and Limited trim, the Hybrid is offered only as separate model and includes a level of equipment that closely approximates the midline XLT. Escape Hybrid incorporates a 2.3-liter 4-cylinder engine and a continuously variable transmission (CVT). Front- and all-wheel drive versions are offered. A true hybrid, Escape can propel itself for short distances at low speeds using only its electric motor. Escape Hybrid is mechanically identical to the Mariner Hybrid offered by Ford's sister division Mercury.

2007 Honda Accord Hybrid
2007 Honda Accord HybridBase Price Range: $31,090-$33,090
EPA MPG: 28-35
Consumer Guide Observed MPG: 27.5
Designed as much for improved performance as for frugal operation, Accord Hybrid uses a 3.0-liter V6 at the center of its hybrid drivetrain. With 253 horsepower, the Hybrid is the most powerful model in the Accord lineup. The Accord Hybrid comes only with a conventional five-speed automatic transmission and does not allow for electric-only operation. The Hybrid is equipped similarly to the conventional topline Accord EX, though because of space consumed by the battery pack, it does without its folding rear seat.

2007 Honda Civic Hybrid
2007 Honda Civic HybridBase Price Range: $22,600-$24,350
EPA MPG: 49-51
Consumer Guide Observed MPG: 37.8-38.0

Unlike its big-brother Accord, the Honda Civic Hybrid is designed specifically for improved fuel economy. To do so, Civic has a tiny 1.3-liter four-cylinder at the heart of its hybrid drivetrain. Civic Hybrid comes only with a continuously variable transmission (CVT) and will propel itself for short distances at low speeds without the aid of its gasoline engine. The Hybrid model is equipped similarly to the conventional topline Civic EX, but loses its rear disc brakes, folding rear seat, and sunroof.

2007 Lexus GS 450h
2007 Lexus GS 450hBase Price: $54,000
EPA MPG: 25-28
Consumer Guide Observed MPG: 22.7
Like its big brother the LS600h, this Lexus hybrid is designed for enhanced performance first, and improved fuel economy second. The GS450h builds its hybrid system around an already potent 3.5-liter V6. They system is coupled to a continuously variable transmission and is capable of running for brief periods of time at low speeds without the gasoline engine. The 450h caps a GS lineup that includes the non-hybrid GS350 and GS430. Like some other hybrid sedans, the GS loses some trunk space to its battery pack.

2008 Lexus LS 600h L
2008 Lexus LS 600h LBase Price Range: NA
EPA MPG: NA
Consumer Guide Observed MPG: NA

Designed with performance instead of frugality in mind, the Lexus LS 600h L promises to be the most expensive hybrid vehicle yet when it goes on sale later in 2007. The LS will also be the first hybrid based on a V8 drivetrain. The hybrid boosted V8 is expected to produce in excess of 430 horsepower. Based on the Consumer Guide Best Buy Lexus LS, the hybrid 600h will be available only with the model's long-wheelbase L body. The LS 600h L should start around $100,000.

2008 Lexus RX 400h
2008 Lexus RX 400hBase Price Range: $41,180-$42,580
EPA MPG: 27-33
Consumer Guide Observed MPG: NA
Lexus's crossover midsize SUV was updated for 2008, getting fresh exterior styling but remaining mechanically unchanged. Like the similar Toyota Highlander Hybrid, the 400h hybrid powertrain centers around a 3.3-liter V6 and includes a continuously variable transmission. The 400h is capable of covering short distances in electric-only mode. Front- and all-wheel drive versions are offered. Note that like the Highlander Hybrid, AWD models feature rear wheels that are driven only by the hybrid system's electric motors; there is no mechanical connection to the transmission. The RX400h is equipped similarly to the conventional gas-engined RX350, but loses that model's standard rear-wood trim and tachometer.

2008 Mercury Mariner Hybrid
2008 Mercury Mariner HybridBase Price Range: $25,765-$27,515
EPA MPG: NA
Consumer Guide Observed MPG: 24.8-28.8

Though sporting new exterior styling, Mariner remains mechanically unchanged for 2008. As such, Mercury's twin to the Ford Escape returns largely intact. While conventional Mariners are offered in Base and Premier trim, the Hybrid is offered as separate model and includes a level of equipment that closely approximates the topline Premier. Like Ford Escape Hybrid, Mariner Hybrid incorporates a 2.3-liter 4-cylinder engine and a continuously variable transmission (CVT). Front- and all-wheel drive versions are offered. Mariner can propel itself for short distances at low speeds using only its electric motor.

2007 Nissan Altima Hybrid
2007 Nissan Altima HybridBase Price: $24,400
EPA MPG: 36-42
Consumer Guide Observed MPG: NA
Based on its popular midsize Altima sedan, the 2007 Altima Hybrid is Nissan's first hybrid offering. Hedging its bets on continuing consumer demand for hybrid vehicles, Nissan has opted to offer the Altima Hybrid only in "Green States" (California, Massachusetts, Maine, New York, and Vermont). The Altima Hybrid drivetrain features a 2.5-liter 4-cylinder engine and a continuously variable transmission (CVT), and will operate for short periods of time at low speeds in electric-only mode. The Hybrid has roughly the same level of standard equipment as the conventional 4-cylinder Altima 2.5 S.

2007 Saturn Aura Green Line
2007 Saturn Aura Green LineBase Price Range:NA
EPA MPG: NA
Consumer Guide Observed MPG: NA

Due out this summer, this hybrid incorporates the same General Motors "mild hybrid" technology as the Vue hybrid and forthcoming Chevrolet Malibu Hybrid. Though specific information is not yet available, count on seeing a 2.4-liter 4-cylinder engine and conventional four-speed automatic. While the mild hybrid arrangement still incorporates electric thrust to improve acceleration, it does not allow for electric-only running at low speeds, as do most other hybrid systems.

2007 Saturn Vue Green Line
2007 Saturn Vue Green LineBase Price: $22,370
EPA MPG: 27-32
Consumer Guide Observed MPG: 25.8-28.4
Though introduced this past fall, General Motor's first hybrid vehicle (excluding the Chevrolet Silverado that offered a hybrid variant in name only) has already gone out of production. Vue assembly-including the hybrid Green Line-ended earlier this year, but examples should still be available on dealer lots. A redesigned 2008 Vue lineup, due later in the calendar year, will include a Green Line model. Vue Green Line incorporates the same General Motors "mild hybrid" technology as the coming 2007 Saturn Aura Green Line and Vue hybrids. The hybrid drivetrain included a 2.4-liter 4-cylinder engine and conventional four-speed automatic. Vue Green Line is available only with front-wheel drive. While the mild hybrid arrangement still incorporates electric thrust to improve acceleration, it does not allow for electric-only running at low speeds, as do most other hybrid systems.

2008 Saturn Vue Green Line
2008 Saturn Vue Green LineBase Price Range: NA
EPA MPG: NA
Consumer Guide Observed MPG: NA

Due to arrive this fall as part of a redesigned Vue line up, the next-generation Green Line will be nearly identical mechanically to the 2007 version when it launches. The addition of a new hybrid system will make its debut several months after launch. Thanks to a longer wheelbase and expanded passenger and cargo accommodations, '08 Vues move up a size class to midsize SUV from compact.

2007 Toyota Camry Hybrid
2007 Toyota Camry HybridBase Price: $26,000
EPA MPG: 38-40
Consumer Guide Observed MPG: 28.6-31.2
Not content with the success of Prius, the new for 2007 Camry Hybrid gives Toyota a hybrid sedan that is more conventional in both style and design. Unlike the similar-size Honda Accord Hybrid with its sport-oriented V6 hybrid drivetrain, the Camry pursues optimal fuel economy with its 2.4-liter 4-cylinder system. The Camry Hybrid is capable of covering short distances at low speeds on only electric power. While conventional Camrys are offered in CE, LE, SE, and topline XLE trim, the Hybrid comes as a single model equipped much like the midline LE.

2007 Toyota Highlander Hybrid
2007 Toyota Highlander HybridBase Price Range: $32,490-$36,550
EPA MPG: 27-31
Consumer Guide Observed MPG: 22.8-26.4

Highlander Hybrid has the distinction of being the only hybrid to offer three-row seating. Like the similar Lexus RX400h, the Highlander Hybrid's powertrain centers around a 3.3-liter V6 and includes a continuously variable transmission. The Highlander Hybrid is capable of covering short distances at low speeds in electric-only mode. Front- and all-wheel drive versions are offered. Note that also like the 400h, AWD models feature rear wheels that are driven only by the hybrid system's electric motors, there is no mechanical connection to the transmission. The Highlander Hybrid is offered in Base and Limited trim levels that closely parallel the content of similar conventional versions of the highlander.

2007 Toyota Prius
2007 Toyota PriusBase Price Range: $22,175-$23,070
EPA MPG: 51-60
Consumer Guide Observed MPG: 41.7-45.2
The original hybrid is now in its second generation and still accounting for almost half of all hybrid vehicle sales. Unlike the other vehicles on this list, the Prius was designed specifically as a hybrid and is not based on a conventionally powered vehicle. While dealers have no trouble stocking the other hybrids discussed here, the Prius has been in short supply, meaning that customers have waited weeks and months for their cars to arrive. A recent slackening in Prius demand may mean reduced wait times and manufacturer incentives for buyers. Under the hood, only the Honda Civic Hybrid has a smaller engine. Prius's hybrid system is built around a 1.5-liter 4-cylinder engine and a continuously variable transmission. Under proper conditions, Prius will operate for extended lengths of time without engaging the gasoline engine.