The Honda Insight was the most fuel efficient of the hybrids.

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.

A plug-in hybrid electric vehicle (PHEV) (see below) is a hybrid vehicle with batteries that can be recharged by connecting a plug to an electric power source. It shares the characteristics of both conventional hybrid electric vehicles and battery electric vehicles, having an internal combustion engine and batteries tp power an electric motor.

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…"^[3]

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 (118 mpg–U.S. / 141 mpg–imp) 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 sizing. 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

Main article: Electric vehicle conversion

One can buy a stock hybrid or convert a stock petroleum car to a hybrid electric vehicle using an aftermarket hybrid kit .^[9]

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.

History

Early developments

In 1901, while employed at Lohner Coach Factory, Ferdinand Porsche designed the "Mixte", a series-hybrid vehicle based off his earlier "System Lohner-Porsche" electric carriage. The Mixte broke several Austrian speed records, and also won the Exelberg Rally in 1901 with Porsche himself driving. The Mixte used a gasoline engine powering a generator, which in turn powered electric hub motors, with a small battery pack for reliability. It had a range of 50 km, a top speed of 50 km/h and a power of 5.22 kW during 20 minutes.

The 1915 Dual Power, made by the Woods Motor Vehicle electric car maker, had a four-cylinder ICE and an electric motor. Below 15 mph (25 km/h) the electric motor alone drove the vehicle, drawing power from a battery pack, and above this speed the "main" engine cut in to take the car up to its 35 mph (55 km/h) top speed. About 600 were made up to 1918.^[12]

Forefathers of current technology

A more recent working prototype of the HEV was built by Victor Wouk (one of the scientists involved with the Henney Kilowatt, the first transistor-based electric car). Wouk's work with HEVs in the 1960s and 1970s earned him the title as the "Godfather of the Hybrid".^[13] Wouk installed a prototype hybrid drivetrain (with a 16 kW electric motor) into a 1972 Buick Skylark provided by GM for the 1970 Federal Clean Car Incentive Program, but the program was stopped by the United States Environmental Protection Agency (EPA) in 1976 while Eric Stork, the head of the EPA at the time, was accused of a prejudicial coverup.^[14]

The regenerative braking system, the core design concept of most production HEVs, was developed by electrical engineer David Arthurs around 1978 using off-the shelf components and an Opel GT. However the voltage controller to link the batteries, motor (a jet-engine starter motor), and DC generator was Arthurs'. The vehicle exhibited 75 mpg–U.S. (3.14 L/100 km / 90.1 mpg–imp) fuel efficiency and plans for it (as well as somewhat updated versions) are still available through the Mother Earth News web site. The Mother Earth News' own 1980 version claimed nearly 84 mpg–U.S. (2.8 L/100 km / 100.9 mpg–imp).

In 1989, Audi produced its first iteration of the Audi Duo (or Audi 100 Avant duo) experimental vehicle, a plug-in parallel hybrid based on the Audi 100 Avant quattro. This car had a 12.6 bhp Siemens electric motor which drove the rear wheels. A trunk-mounted nickel-cadmium battery supplied energy to the motor that drove the rear wheels. The vehicle's front wheels were powered by a 2.3-litre five-cylinder engine with an output of 136 bhp. The intent was to produce a vehicle which could operate on the engine in the country and electric mode in the city. Mode of operation could be selected by the driver. Just ten vehicles are believed to have been made; one drawback was that due to the extra weight of the electric drive, the vehicles were less efficient when running on their engines alone than standard Audi 100s with the same engine.

Two years later, Audi unveiled the second duo generation - likewise based on the Audi 100 Avant quattro. Once again this featured an electric motor, a 28.6 bhp three-phase machine, driving the rear wheels. This time, however, the rear wheels were additionally powered via the Torsen differential from the main engine compartment, which housed a 2.0-litre four-cylinder engine.

The Bill Clinton administration initiated the Partnership for a New Generation of Vehicles (PNGV) program on 29 September 1993 that involved Chrysler, Ford, General Motors, USCAR, the DoE, and other various governmental agencies to engineer the next efficient and clean vehicle.^[15] The NRC cited automakers’ moves to produce HEVs as evidence that technologies developed under PNGV were being rapidly adopted on production lines, as called for under Goal 2. Based on information received from automakers, NRC reviewers questioned whether the “Big Three” would be able to move from the concept phase to cost effective, pre-production prototype vehicles by 2004, as set out in Goal 3.^[16] The program was replaced by the hydrogen-focused FreedomCAR initiative by the George W. Bush administration in 2001,^[17] an initiative to fund research too risky for the private sector to engage in, with the long-term goal of developing effectively carbon emission- and petroleum-free vehicle

Production HEVs

Hybrid Vehicle Sales Chart, by Green Car Congress; Toyota: 85 %

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 ICE to the driven wheels, so the engine can provide acceleration power.

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 40% better fuel efficiency. The Honda Civic Hybrid appears identical to the non-hybrid version, for instance, but delivers about 50 mpg–U.S. (4.7 L/100 km / 60.1 mpg–imp). The redesigned 2004 Toyota Prius improved passenger room, cargo area, and power output, while increasing energy efficiency and reducing emissions. The Honda Insight, while not matching the demand of the Prius, stopped being produced after 2006 and has a devoted base of owners. Honda has also released a hybrid version of the Accord.

An R.L. Polk survey of 2003 model year cars showed that hybrid electric car registrations in the United States rose to 43,435 cars, a 25.8% increase from 2002 numbers. California had the most HEVs registered: 11,425. The proportionally high number may be partially due to the state's higher gasoline prices and stricter emissions rules, which HEVs generally have little trouble passing.

Honda, which offers Insight, Civic and Accord models, sold 26,773 HEVs in the first 11 months of 2004. Toyota has sold a cumulative 306,862 HEVs between 1997 and November 2004, and Honda has sold a total of 81,867 HEVs between 1999 and November 2004.^[18]

Audi was the first European car manufacturer to put in 1997 a hybrid vehicle into series production, the third generation Audi duo, then based on the A4 Avant.^[19]

2005 saw the first hybrid electric sport utility vehicle (SUV) released, the Ford Escape Hybrid. Toyota and Ford entered into a licensing agreement in March 2004 allowing Ford to use 20 patents from Toyota related to hybrid technology, although Ford's engine was independently designed and built. In exchange for the hybrid licenses, Ford licensed patents involving their European diesel engines to Toyota. Toyota announced model year 2005 hybrid electric versions of the Toyota Highlander and Lexus RX 400h with 4WD-i, which uses a rear electric motor to power the rear wheels negating the need for a differential. Toyota also plans to add hybrid drivetrains to every model it sells in the coming decade.

In 2007, Lexus released a hybrid electric version of their GS sport sedan dubbed the GS450h, with "well in excess of 300hp". The 2007 Camry Hybrid became available in Summer 2006 in the United States and Canada. Nissan announced the release of the Altima hybrid (technology supplied by Toyota) in 2007.Hybrid cars see record sales.^[20]

Manufacturers are going to introduce 15 new hybrids in 2008^[21]

Production PHEVs

In 2007 appears the DoE´s Plug-in Hybrid Electric Vehicle Plan and the PHEV mass-production race.

Further information: History of plug-in hybrids

Vehicle types

Motorcycles

eCycle Inc produces series diesel-electric motorcycles, with a top speed of 80 mph (128.7 km/h) and a target retail price of $5500.^[22]

Automobiles and light trucks

A number of manufacturers currently produce hybrid electric automobiles and light trucks, including Ford, General Motors, Honda, Mazda, Mercury, Nissan, PSA (Peugeot-Citröen), Renault, and Toyota. Other types of HEVs are manufactured including Microhybrids (small hybrid electric city cars) like the Aptera. Diesel-electric hybrid vehicles such as Citroën C-Cactus concept car and GM's Chevy Volt plug-in hybrid may soon see mass-production.

Combined sales of HEVs in the U.S. rose 54% in February 2007 to more than 22,998 units, up 52% from the results in February 2006. The figures do not include sales of GM HEVs, which the automaker does not yet break out, but do reflect the addition of the Nissan Altima Hybrid, now sold in eight states.^[23] An estimated 180,000 HEVs were sold in the U.S. in first half of 2007, or 3% of car sales during that period.^[24]

Taxis

Ford Escape hybrid-electric taxi.

HEVs (and specially plug-ins) may be particularly appropriate for use as taxicabs, as in many locations they are used in predominantly urban environments; have intensive operating schedules, maximizing fuel savings over the life of the vehicle; may spend considerable periods of time at idle, where the hybrid electric engine may allow for the ICE to be shut off (while retaining use of electrical accessories); and can recharge batteries at taxicab stands.

New York City started converting its taxi fleet to hybrids in 2005,^[25] with 375 active as of July, 2007. The mayor plans to convert 20% of the remaining 13,000 taxis each year.

San Francisco intends to convert its entire fleet to hybrid or Compressed natural gas vehicles by 2008.^[26]

Buses

Main article: Hybrid bus

Hybrid technology for buses has seen increased attention since recent battery develpments decreased battery weight significantly. Drivetrains consist of conventional diesel engines and gas turbines. Some designs concentrate on using car engines, recent designs have focused on using conventional diesel engines already used in bus designs, to save on engineering and training costs. Several manufacturers are currently working on new hybrid designs, or hybrid drivetrains that fit into existing chassis offerings without major re-design. A challenge to hybrid buses may still come from cheaper lightweight imports from the former Eastern block countries or China, where national operators are looking at fuel consumption issues surrounding the weight of the bus, which has increased with recent bus technology innovations such as glazing, air conditioning and electrical systems. A hybrid bus can also deliver fuel economy though through the hybrid drivetrain. Hybrid technology is also being promoted by environmentally concerned transit authorities.

Trucks

In 2003 GM introduced a hybrid diesel-electric military (light) truck, equipped with a diesel electric and a fuel cell auxiliary power unit. Hybrid electric light trucks were introduced in 2004 by Mercedes Benz (Sprinter) and Micro-Vett SPA (Daily Bimodale). International Truck and Engine Corp. and Eaton Corp. have been selected to manufacture diesel-electric hybrid trucks for a US pilot program serving the utility industry in 2004. In mid 2005 Isuzu introduced the Elf Diesel Hybrid Truck on the Japanese Market. They claim that approximately 300 vehicles, mostly route buses are using Hinos HIMR (Hybrid Inverter Controlled Motor & Retarder) system. In 2007, height petroleum price means a hard sell for hybrid trucks^[27] and appears the first U.S. production hybrid truck (International DuraStar Hybrid).^[28]

Other vehicles are:

• Big mining machines like the Liebherr T 282B dump truck or Keaton Vandersteen LeTourneau L-2350 wheel loader are powered that way.
• Also NASA's huge Crawler-Transporters are propelled diesel-electrically.
• Mitsubishi Fuso Canter Eco Hybrid is a diesel-electric commercial truck.

Hino Motors (a Toyota subsidiary) has the world's first production hybrid electric truck in Australia (110kW diesel engine plus a 23kW electric motor).^[29]

Other hybrid petroleum-electric truck makers are DAF Trucks, MAN AG with MAN TGL Series, Nissan Motors and Renault Trucks with Renault Puncher.

Hybrid electric truck technology and powertrain maker: ZF Friedrichshafen.

Military vehicles

The United States Army's manned ground vehicles of the Future Combat System all use a hybrid electric drive consisting of a diesel engine to generate electrical power for mobility and all other vehicle subsystems. Other military hybrid prototypes include the Millenworks Light Utility Vehicle, the International FTTS, and the Shadow RST-V.

Locomotives

Main article: Hybrid Locomotive

In May 2003 JR East started test runs with the so called NE (new energy) train and validated the system's functionality (series hybrid with lithium ion battery) in cold regions. In 2004, Railpower Technologies had been running pilots in the US with the so called Green Goats,^[30] which led to orders by the Union Pacific^[31] and Canadian Pacific^[32] Railways starting in early 2005.

Railpower offers hybrid electric road switchers,^[33] as does GE.^[34] Diesel-electric locomotives may not always be considered HEVs, not having energy storage on board, unless they are fed with electricity via a collector for short distances (for example, in tunnels with emission limits), in which case they are better classified as dual-mode vehicles.

Marine and other aquatic

Produces marine hybrid propulsion:

• eCycle Inc.^[35]
• Solar Sailor Holdings

Comparison of regular hybrids with petroleum and plug-in hybrid vehicles

Conventional vehicles

HEVs are more expensive (the so-called "hybrid premium") than traditional ICE vehicles (ICEV), due to extra batteries, more electronics and in some cases other design considerations. The trade-off between higher initial cost and lower fuel costs (often referred to as the payback period) is dependent on usage - miles traveled, or hours of operation, fuel costs, and in some cases, government subsidies. Traditional economy vehicles may result in a lower direct cost for many users (before consideration of any externality).

Consumer Reports ran an article in April 2006 stating that HEVs would not pay for themselves over 5 years of ownership. However, this included an error with charging the "hybrid premium" twice.^[36] When corrected, the Honda Civic Hybrid and Toyota Prius did have a payback period of slightly less than 5 years.^[37] This includes conservative estimates with depreciation (seen as more depreciation than a conventional vehicle, although that is not the current norm) and with gas prices. In particular, the Consumer Reports article assumed $2/U.S. gallon for 3 years, $3/U.S. gallon for one year and $4/U.S. gallon the last year. As recent events have shown, this is a volatile market and hard to predict. For 2006, gas prices ranged from low $2 to low $3, averaging about $2.60/U.S. gallon.

A January 2007 analysis by Intellichoice.com shows that all 22 currently available HEVs will save their owners money over a five year period. The most savings is for the Toyota Prius, which has a five year cost of ownership 40.3% lower than the cost of comparable non-hybrid vehicles.^[38]

A report in the Greeley Tribune says that over the five years it would typically take for a new car owner to pay off the vehicle cost differential, a hybrid Camry driver could save up to $6,700 in gasoline at current gasoline prices, with hybrid tax incentives as an additional saving.^[39]

In countries with incentives to fight against global warming and contamination and promote vehicle fuel efficiency, the pay-back period can be immediate and ICEV can cost more than hybrid because they generate more pollution.

Plug-in hybrids

Main article: Plug-in hybrid

Plug-in hybrids can also be recharged using an electric outlet.

Legislation and incentives

In order to encourage the purchase of HEVs, several incentives and ecotaxes have been made into law.

Europe

In the Netherlands, the Vehicle Registration Tax (VRT), payable when a car is sold to its first buyer, can earn the owner of an HEV a discount up to €6,000. In the Republic of Ireland, a 50% reduction in VRT applies, which normally amounts to 25% of the market value of a car.

Drivers of HEVs in the United Kingdom benefit from the lowest band of vehicle excise duty (car tax), which is based on carbon dioxide emissions. In central London, these vehicles are also exempt from the £8 daily London congestion charge.^[40] Due to their low levels of regulated emissions, the greenest cars are eligible for 100% discount under the current system. To be eligible the car must be on the current Power Shift Register.^[41] At present, these include the cleanest LPG and natural gas cars and most hybrid-, battery- and fuel cell-electric vehicles.

Canada

Residents in Ontario, Canada can claim a rebate on the Provincial Retail Sales Tax of up to $2,000 CDN on the purchase or lease of a hybrid electric vehicle.^[42] Ontario recently announced a new green license plate for hybrid car users and will announce a slew of benefits that go along with it in 2008.^[43] Residents in British Columbia are eligible for a 100% reduction of sales tax up to a maximum of $2,000 if the hybrid electric vehicle is purchased or leased before April 1, 2011 (extended in 2007/2008 budget from March 31, 2008 and expanded from a maximum of only $1,000 from April 1, 2008 to March 31, 2009, at which point the concession was scheduled to expire.)^[44]The Canadian federal government recently began offering rebates in March 2007 of $1000-$2000. Generally cars getting 6.5 L/100km or better and light trucks getting 8.3 L/100km or better will quailify.^[45]

USA

Federal

Diesel-electric and gasoline-electric hybrids are not grouped under the electric fuel category because the input fuel is diesel or gasoline rather than an alternative transportation fuel. DOE, which has EPACT92 implementation authority, ruled that diesel-electric and gasoline-electric hybrids are not "alternative fuel vehicles."^[46]

The purchase of hybrid electric cars qualifies for a federal income tax credit up to $3,400 on the purchaser's Federal income taxes. The tax credit is to be phased out two calendar quarters after the manufacturer reaches 60,000 new cars sold in the following manner: it will be reduced to 50% ($1700) if delivered in either the third or fourth quarter after the threshold is reached, to 25% ($850) in the fifth and sixth quarters, and 0% thereafter. Many states give additional tax credits to hybrid electric car buyers. Also this can help us to use less gasoline.

States and local

• Certain states (e.g., New York, California, Virginia, and Florida) allow singly-occupied HEVs to enter the HOV lanes on the highway. Initially, the Federal Highway Administration ruled that this was a violation of federal statute^[47] until August 10, 2005 when George W. Bush signed the Transportation Equity Act of 2005 into law.
• Some states, e.g. California, exempt hybrid electric cars from the biennial smog inspection, which costs over $50 (as of 2004).
• The city of San Jose, California issued a free parking tag until 2007 when it became issued for a fee annually for hybrid electric 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, California offers free parking to all HEVs starting on 1 October 2004. The experiment is an extension to an existing offer of free parking for all pure electrical vehicles.
• In October, 2005, the City of Baltimore, Maryland started to offer discount on monthly parking in the city parking lots, and is considering free meter parking for HEVs. On 3 November 2005, the Boston Globe reports that the city council of Boston is considering the same treatment for hybrid electric cars.
• Annual vehicle registration fees in the District of Columbia are half ($36) that paid for conventionally vehicles ($72).

Emergence of hybrid vehicles

AllianceBernstein projects that worldwide by 2030, 72% of the fleet and 85% of new cars will be hybrids (regular or plug-in hybrids).^[48]

Worldwide demand for hybrid-electric vehicles (HEVs) will advance rapidly to 4.0 million units in 2015. HEVs are expected to quickly penetrate the world light vehicle market in response to rising energy costs and increased emissions regulations worldwide.^[49]

See also

• ACT Hybrid Vehicle Authority
• Bivalent (engine)
• Comparison of Toyota hybrids
• List of hybrid vehicles
• Super Ultra Low Emission Vehicle
• Tribrid vehicle

References

External links

• Electric and Gas Hybrids at the Open Directory Project
• How hybrid cars work at HowStuffWorks
• Compare hybrid cars at FuelEconomy.gov
  • U.S. Federal Income Tax Deduction for Hybrids Placed in Service
• New York City Taxis to go all hybrid by 2012 2007-05-22
• GM Announces Chevrolet Volt Series Hybrid Concept Vehicle 2007-01-07
• Series, Parallel, and series-parallel systems animation by Union of Concerned Scientists
• Mother Earth News article from 1978 on the original regenerative braking hybrid car
• Folsom Technologies, Inc. Hybrid Hydraulic, Hybrid Electric, and CVT technologies
• Hybrid-Electric "Bus of the Future" Tested By Capital Metro.
• Toyota's hybrid cars information, HYBRID SYNERGY DRIVE

Hybrids Plus plug-in hybrid Toyota Prius conversion with PHEV-30 (30 mile or 48 km all-electric range) battery packs

A plug-in hybrid electric vehicle (PHEV) is a hybrid vehicle with batteries that can be recharged by connecting a plug to an electric power source. It shares the characteristics of both conventional hybrid electric vehicles and battery electric vehicles, having an internal combustion engine and batteries for power. Most PHEVs on the road today are passenger cars, but there are also PHEV versions of commercial passenger vans, utility trucks, school buses, motorcycles, scooters, and military vehicles. PHEVs are sometimes called grid-connected hybrids, gas-optional hybrids, or GO-HEVs.

The cost for electricity to power plug-in hybrids for all-electric operation in California has been estimated at less than one quarter of the cost of gasoline.^[1] Compared to conventional vehicles, PHEVs can reduce air pollution and dependence on petroleum, and lessen greenhouse gas emissions that contribute to global warming. Plug-in hybrids use no fossil fuel during their all-electric range if their batteries are charged from renewable energy sources. Other benefits include improved national energy security, fewer fill-ups at the filling station, the convenience of home recharging, opportunities to provide emergency backup power in the home, and vehicle to grid applications.^[2]

As of January 2008, plug-in hybrid passenger vehicles are not yet in production. However, Toyota,^[3] General Motors,^[4] Ford,^[5] Chinese automaker BYD Auto,^[6] and California startups Fisker Automotive^[7] and Aptera Motors^[8] have announced their intention to introduce production PHEV automobiles. The PHEV-60 BYD F6e sedan is expected in the second half of 2008; the luxury Fisker Karma PHEV-50 sports car is slated for late 2009; and the Toyota Prius and GM's PHEV-40 Chevrolet Volt plug-ins are expected in 2010.^[9][10] Conversion kits and services are available to convert production model hybrid vehicles to plug-ins.^[11] Most PHEVs on the road in the U.S. are conversions of 2004 or later Toyota Prius models, which have had plug-in charging added and their electric-only range extended.

Terminology

A plug-in hybrid's all-electric range is designated by PHEV-[miles] or PHEV[kilometers]km in which the number represents the distance the vehicle can travel on battery power alone. For example, a PHEV-20 can travel twenty miles without using its internal combustion engine, or about 32 kilometers, so it may also be designated as a PHEV32km.^[12]

The Energy Independence and Security Act of 2007 defines plug-in electric drive vehicle as a vehicle that:

• draws motive power from a battery with a capacity of at least 4 kilowatt-hours;
• can be recharged from an external source of electricity for motive power; and
• is a light-, medium-, or heavy-duty motor vehicle or nonroad vehicle.

The Institute of Electrical and Electronics Engineers (IEEE) defines a plug-in hybrid electric vehicle as any hybrid electric vehicle which contains at least:

• a battery storage system of 4 kW·h or more, used to power the motion of the vehicle;
• a means of recharging that battery system from an external source of electricity; and
• an ability to drive at least ten miles (16 km) in all-electric mode, while consuming no fuel (gasoline or diesel).

This distinguishes PHEVs from regular hybrid cars mass-marketed today, which do not use any electricity from the grid.^[13]

History

Hybrid vehicles were produced beginning as early as 1899 by Lohner-Porsche. Early hybrids could be charged from an external source before operation. However, the term "plug-in hybrid" has come to mean a hybrid vehicle that can be charged from a standard electrical wall socket.

The July 1969 issue of Popular Science featured an article on the General Motors XP-883 plug-in hybrid. The concept commuter vehicle housed six 12-volt lead-acid batteries in the trunk area and a transverse-mounted DC electric motor turning a front-wheel drive.^[14] The car could be plugged into a standard North American 110 volt AC outlet for recharging.

In 2003, Renault began selling the Elect'road, a plug-in series hybrid version of their popular Kangoo, in Europe. It was sold alongside Renault's "Electri'cite" electric-drive Kangoo battery electric van. The Elect'road had a 150 km (93 mi) range using a nickel-cadmium battery pack and a 500 cc (31 cu in), 16 kilowatt liquid-cooled gasoline "range-extender" engine. It powered two high voltage/high output/low volume alternators, each of which supplied up to 5.5 kW at 132 volts at 5000 rpm.^[15] The operating speed of the internal combustion engine—and therefore the output delivered by the generators—varied according to demand. The fuel tank had a capacity of 10 litres (2.6 US gal/2.2 imp gal) and was housed within the right rear wheel arch. The range extender function was activated by a switch on the dashboard. The on-board 3.5 kilowatt charger could charge a depleted battery pack to 95% charge in about four hours from a 220 volts supply.^[16] Passenger compartment heating was powered by the battery pack as well as an auxiliary coolant circuit that was supplied by the range extender engine. After selling about 500 vehicles, primarily in France, Norway and the UK, at a price of about €25,000,^[15] the Elect'road was redesigned in 2007.

Lithium-ion battery pack, with cover removed, in a CalCars "PRIUS+" plug-in hybrid converted Toyota Prius converted by EnergyCS

In September 2004, the California Cars Initiative (CalCars) converted a 2004 Toyota Prius into a prototype of what it called the PRIUS+. With the addition of 130 kg (300 lb) of lead-acid batteries, the PRIUS+ achieved roughly double the fuel economy of a standard Prius and could make trips of up to 15 km (9 mi) using only electric power. The vehicle, which is owned by CalCars technical lead Ron Gremban, is used in daily driving, as well as a test bed for various improvements to the system.^[17]

On July 18, 2006, Toyota announced that it "plans to develop a hybrid vehicle that will run locally on batteries charged by a household electrical outlet before switching over to a gasoline engine for longer hauls."^[3] Toyota has said it plans to migrate to lithium-ion batteries in future hybrid models,^[18] but not in the next-generation Prius, expected in fall 2008.^[19] Lithium-ion batteries are expected to significantly improve fuel economy, and have a lower weight-to-energy ratio, but cost more to produce, and raise safety concerns due to high operating temperatures.^[19]

On November 29, 2006, GM announced plans to introduce a production plug-in hybrid version of Saturn's Greenline Vue SUV with an all-electric range of 10 mi (16 km).^[4] The model's sale is anticipated by fall 2009,^[19] and GM announced in January 2007 that contracts had been awarded to two companies to design and test lithium-ion batteries for the vehicle.^[20] GM has said that they plan on introducing plug-in and other hybrids "for the next several years".^[4]

In January 2007, GM unveiled the Chevrolet Volt, which is expected to initially feature a plug-in capable, battery-dominant series hybrid architecture which they are calling E-Flex.^[21] Future E-Flex plug-in hybrid vehicles may use gasoline, diesel, or hydrogen fuel cell power to supplement the vehicle's battery. General Motors envisions an eventual progression of E-Flex vehicles from plug-in hybrids to pure electric vehicles, as battery technology improves.^[22] General Motors presented the Volt as a PHEV-40 that starts its engine when 40% of the battery charge remains, and which can achieve a fuel economy of 50 mpg–U.S. (4.7 L/100 km / 60.1 mpg–imp), even if the vehicle's batteries are not charged.^[23]

On July 9, 2007, Ford Motor Company CEO Alan Mulally said he expects Ford to sell plug-in hybrids in five to ten years, the launch date depending on advances in lithium-ion battery technology. Ford will provide Southern California Edison with 20 Ford Escape Hybrid sport utility vehicles reconfigured to work as plug-ins by 2009, with the first by the end of 2007.^[5]

On July 25, 2007, Japan's Ministry of Land, Infrastructure and Transport certified Toyota's plug-in hybrid for use on public roads, making it the first automobile to attain such approval. Toyota plans to conduct road tests to verify its all-electric range. The plug-in Prius has an all-electric range of 13 km (8 mi).^[24]

On August 9, 2007, General Motors vice-president Robert Lutz announced that GM is on track for Chevrolet Volt road testing in 2008 and production to begin by 2010. Announcing an agreement with A123Systems, Lutz said GM would like to have their planned Saturn VUE plug-in on the roads by 2009.^[10] The Volt has an all-electric range of 40 mi (64 km).

On September 5, 2007, Quantum Technologies^[25] and Fisker Coachbuild, LLC announced the launch of a joint venture in Fisker Automotive.^[26] Fisker intends to build a US$ 80,000 luxury PHEV-50, the Fisker Karma, anticipated in late 2009.^[7]

In September 2007, Aptera Motors announced their Typ-1 two-seater. Using the same aerodynamic three-wheeled composite body design, they plan to produce both an electric Typ-1e and a plug-in hybrid Typ-1h. As of January 2008, one thousand pre-orders have been accepted (California residents only at this point), and production is expected to begin in late 2008.^[8]

On October 9, 2007, Chinese manufacturer BYD Automobile Company (which is owned by China's largest mobile phone battery maker) announced that it would be introducing a production PHEV-60 sedan in China in the second half of 2008. BYD plans to exhibit it in January 2008 at the North American International Auto Show in Detroit. Based on BYD's midsize F6 sedan, it uses iron-based batteries instead of lithium-ion, and can be recharged to 70% of capacity in just 10 minutes.^[6]

In January 2008, a privately-run waiting list to purchase the Chevy Volt reached 10,000 members. The list, administered by Lyle Dennis, was started one year prior.^[27]

January 2008: Assistant professor Yi Cui and colleagues at Stanford University's Department of Materials Science and Engineering ^[28] have made a discovery to use silicon nanowires to give rechargeable lithium ion batteries 10 times more charge.^[29]

Technology

Powertrains

The Chevrolet Volt concept car is a series plug-in hybrid, meaning that its mechanical engine power is exclusively converted to electricity, not used directly.

PHEVs are based on the same three basic powertrain architectures as conventional hybrids:^[30]

Series hybrids use an internal combustion engine (ICE) to turn a generator, which in turn supplies current to an electric motor, which then rotates the vehicle’s drive wheels. A battery or capacitor pack, or a combination of the two, can be used to store excess charge. Examples of series hybrids include the Renault Kangoo Elect'Road, Toyota's Japan-only Coaster light-duty passenger bus, DaimlerChrysler's hybrid Orion bus, the Chevrolet Volt concept car, the Opel Flextreme concept car, and many diesel-electric locomotives. With an appropriate balance of components this type can operate over a substantial distance with its full range of power without engaging the ICE. As is the case for other architectures, series hybrids can operate without recharging as long as there is liquid fuel in the tank.^[31]

Parallel hybrids, such as Honda's Insight, Civic, and Accord hybrids, can simultaneously transmit power to their drive wheels from two distinct sources—for example, an internal combustion engine and a battery-powered electric drive. Although most parallel hybrids incorporate an electric motor between the vehicle's engine and transmission, a parallel hybrid can also use its engine to drive one of the vehicle's axles, while its electric motor drives the other axle and/or a generator used for recharging the batteries. (This type is called a road-coupled hybrid). The Audi Duo plug-in hybrid concept car is an example of this type of parallel hybrid architecture. Parallel hybrids can be programmed to use the electric motor to substitute for the ICE at lower power demands as well as to substantially increase the power available to a smaller ICE, both of which substantially increase fuel economy compared to a simple ICE vehicle.^[32]

Series-parallel hybrids have the flexibility to operate in either series or parallel mode. Hybrid powertrains currently used by Ford, Lexus, Nissan, and Toyota, which some refer to as “series-parallel with power-split,” can operate in both series and parallel mode at the same time. As of 2007, most plug-in hybrid conversions of conventional hybrids utilize this architecture.^[33]

Modes of operation

Regardless of its architecture, a plug-in hybrid may be capable of charge-depleting and charge-sustaining modes. Combinations of these two modes are termed blended mode or mixed-mode. These vehicles can be designed to drive for an extended range in all-electric mode, either at low speeds only or at all speeds. These modes manage the vehicle's battery discharge strategy, and their use has a direct effect on the size and type of battery required:^[34]

Charge-depleting mode allows a fully charged PHEV to operate exclusively (or depending on the vehicle, almost exclusively, except during hard acceleration) on electric power until its battery state of charge is depleted to a predetermined level, at which time the vehicle's internal combustion engine or fuel cell will be engaged. This period is the vehicle's all-electric range. This is the only mode that a battery electric vehicle can operate in, hence their limited range.^[35]

Charge-sustaining mode is used by production hybrid vehicles (HEVs) today, and combines the operation of the vehicle's two power sources in such a manner that the vehicle is operating as efficiently as possible without allowing the battery state of charge to move outside a predetermined narrow band. Over the course of a trip in a HEV the state of charge may fluctuate but will have no net change.^[36] The battery in a HEV can thus be thought of as an energy accumulator rather than a fuel storage device. Once a plug-in hybrid has exhausted its all-electric range in charge-depleting mode, it can switch into charge-sustaining mode automatically.

The redesigned Renault Kangoo Elect'road operates in blended mode, using engine and battery power simultaneously.

Blended mode is a type of charge-depleting mode normally employed by vehicles which do not have enough electric power to sustain high speeds without the help of the internal combustion portion of the powertrain. A blended control strategy typically increases the distance from stored grid electricity compared to a charge-depleting strategy.^[37] The Renault Kangoo and some Toyota Prius conversions are examples of vehicles that use this mode of operation. The Electri'cité and Elect'road versions of the Kangoo were charge-depleting battery electric vehicles: the Elect'road had a modest internal combustion engine which extended its range somewhat. Conversions of 2004 and later model Toyota Prius can only run without using the ICE at speeds of less than about 42 mph (68 km/h) due to the limits dictated by the vehicle's powertrain control software. However, at faster speeds electric power can still be used to displace gasoline, thus improving the fuel economy in blended mode and generally doubling the fuel efficiency.

Mixed mode describes a trip in which a combination of the above modes are utilized.^[38] For example, a PHEV-20 Prius conversion may begin a trip with 5 miles (8 km) of low speed charge-depleting, then get onto a freeway and operate in blended mode for 20 miles (32 km), using 10 miles (16 km) worth of all-electric range at twice the fuel economy. Finally the driver might exit the freeway and drive for another 5 miles (8 km) without the internal combustion engine until the full 20 miles (32 km) of all-electric range are exhausted. At this point the vehicle can revert back to a charge sustaining-mode for another 10 miles (16 km) until the final destination is reached. Such a trip would be considered a mixed mode, as multiple modes are employed in one trip. This contrasts with a charge-depleting trip which would be driven within the limits of a PHEV's all-electric range. Conversely, the portion of a trip which extends beyond the all-electric range of a PHEV would be driven primarily in charge-sustaining mode, as used by a conventional hybrid.

Electric power storage

Further information: Electric vehicle battery

PHEVs typically require deeper battery charging and discharging cycles than conventional hybrids. Because the number of full cycles influences battery life, this may be less than in traditional HEVs which do not deplete their batteries as fully. However, some authors argue that PHEVs will soon become standard in the automobile industry.^[39] Design issues and trade-offs against battery life, capacity, heat dissipation, weight, costs, and safety need to be solved.^[40] Advanced battery technology is under development, promising greater energy densities by both mass and volume,^[41] and battery life expectancy is expected to increase.^[42]

The cathodes of some early 2007 lithium-ion batteries are made from lithium-cobalt metal oxide. This material is expensive, and cells made with it can release oxygen if overcharged. If the cobalt is replaced with iron phosphates, the cells will not burn or release oxygen under any charge. The price premium for early 2007 conventional hybrids is about US$5000, some US$3000 of which is for their NiMH battery packs. At early 2007 gasoline and electricity prices, that would mean a break-even point after six to ten years of operation. The conventional hybrid premium could fall to US$2000 in five years, with US$1200 or more of that being cost of lithium-ion batteries, providing for a three-year payback. The payback period may be longer for plug-in hybrids, because of their larger, more expensive batteries.^[43]

Nickel-metal hydride and lithium-ion batteries can be recycled; Toyota, for example, has a recycling program in place under which dealers are paid a US$200 credit for each battery returned.^[44] However, plug-in hybrids typically use larger battery packs than comparable conventional hybrids, and thus require more resources. Recently Pacific Gas and Electric Company (PG&E) has suggested that utilities could purchase used batteries for backup and load levelling purposes. They state that while these used batteries may be no longer usable in vehicles, their residual capacity still has significant value.^[45]

Lithium iron phosphate (LFP) is a kind of cathode material of lithium iron phosphate batteries that is getting attention from the industry. The most important merit of this battery type is safety and high-power. LiFePO4 is one of three major compounds and technology in LFP family. The other two are Nanophosphate,and NanoCocrystallineOlivine.

In France, Électricité de France (EDF) and Toyota are installing recharging points for PHEVs on roads, streets and parking lots.^[46]. EDF is also partnering with Elektromotive, Ltd.^[47] to install 250 new charging points over six months from October 2007 in London and elsewhere in the UK.^[48] Recharging points also can be installed for specific uses, as in taxi stands. Project Better Place has begun in October 2007 and is working with Renault on development of exchangeable batteries (battery swapping). ^[49].

Ultracapacitors (or "supercapacitors") are used in some plug-in hybrids, such as AFS Trinity's concept prototype, to store rapidly available energy with their high power density, in order to keep batteries within safe resistive heating limits and extend battery life.^[50] The UltraBattery combines a supercapacitor and a battery in a single unit, creating a hybrid car battery that lasts longer, costs less and is more powerful than current technologies used in plug-in hybrid electric vehicles (PHEVs).^[51]

Conversions of production hybrids

15 lead-acid batteries, PFC charger, and regulators installed into WhiteBird, a PHEV-10 conversion of a Toyota Prius

Conversion of an existing production hybrid to a plug-in hybrid typically involves increasing the capacity of the vehicle's battery pack and adding an on-board AC-to-DC charger. Ideally, the vehicle's powertrain software would be reprogrammed to make full use of the battery pack's additional energy storage capacity and power output.

Many early plug-in hybrid electric vehicle conversions have been based on the 2004 or later model Toyota Prius.^[52] Some of the systems have involved replacement of the vehicle's original NiMH battery pack and its electronic control unit. Others, such as Hymotion, the CalCars Prius+, and the PiPrius, piggyback an additional battery back onto the original battery pack, this is also referred to as Battery Range Extender Modules (BREMs).^[53] Within the electric vehicle conversion community this has been referred to as a "hybrid battery pack configuration".^[54] Early lead-acid battery conversions by CalCars demonstrated 10 miles (15 km) of EV-only and 20 miles (30 km) of double mileage blended mode range.^[17]

EDrive Systems use Valence Technology Li-ion batteries and have a claimed 40 to 50 miles (64 to 80 km) of electric range.^[55] Other companies offering plug-in conversions or kits for the Toyota Prius include Hymotion, Hybrids Plus, and Manzanita Micro.

The EAA-PHEV project was conceived by CalCars and the Electric Auto Association in October of 2005 to accelerate efforts to document existing HEVs and their potential for conversion into PHEVs.^[56] It includes a "conversion interest" page.^[57] The Electric Auto Association-PHEV "Do-It-Yourself" Open Source community's primary focus is to provide conversion instructions to help guide experienced converters through the process, and to provide a common design that could demonstrate multiple battery technologies. Many members of organizations such as CalCars and the EAA as well as companies like Hybrids Plus, Hybrid Interfaces of Canada, and Manzanita Micro participate in the development of the project.

Advantages

Fuel efficiency

Main article: Energy efficiency

Claimed fuel economy for PHEVs depends on the amount of driving between recharges. If no gasoline is used the MPG equivalent depends only on the efficiency of the electric system. A 120 km (70 mile) range PHEV-70 may annually require only about 25% as much gasoline as a similarly designed PHEV-0, depending on how it will be driven and the trips for which it will be used.^[2] The furthest all-electric range in a PHEV planned for mass production is the PHEV-60 BYD F6e.

A further advantage of PHEVs is that they have potential to be even more efficient than conventional hybrids because a more limited use of the PHEV's internal combustion engine may allow the engine to be used at closer to its maximum efficiency. While a Prius is likely to convert fuel to motive energy on average at about 30% efficiency (well below the engine's 38% peak efficiency) the engine of a PHEV-70 would be likely to operate far more often near its peak efficiency because the batteries can serve the modest power needs at times when the combustion engine would be forced to run well below its peak efficiency.^[35] The actual efficiency achieved depends on losses from electricity generation, inversion, battery charging/discharging, the motor controller and motor itself, the way a vehicle is used (its duty cycle), and the opportunities to recharge by connecting to the electrical grid.

The Society of Automotive Engineers (SAE) developed their recommended practice in 1999 for testing and reporting the fuel economy of hybrid vehicles and included language to address PHEVs. An SAE committee is currently working to review procedures for testing and reporting the fuel economy of PHEVs.^[58]

Greenhouse gas emissions

Main article: Greenhouse gas

Another advantage of PHEV adoption is a predicted reduction in carbon emissions. Increased drivetrain efficiency results in significant reduction of greenhouse gas emissions, even taking into account energy lost to inefficiency in the production and distribution of grid power and charging of batteries. A study by the American Council for an Energy Efficient Economy (ACEEE) predicts that, on average, a typical American driver is expected to achieve about a 15% reduction in net CO₂ emissions compared to the driver of a regular hybrid, based on the 2005 distribution of power sources feeding the U.S. electrical grid.^[59] Additionally, for PHEV’s recharged in areas where the grid is fed by power sources with lower CO₂ emissions than the current average, net CO₂ emissions associated with PHEVs will decrease correspondingly. PHEVs can be viewed as an element in the "Pacala and Socolow wedges" approach which shows a way to stabilize CO₂ emissions using a portfolio of existing techniques, including efficient vehicles.

The same study predicts that in areas where more than 80% of grid-power comes from coal-burning power plants, local net CO₂ emissions will increase.^[59] However, given the global nature of problems associated with CO₂ emissions, specifically global warming, localized increases in CO₂ emissions are not considered a significant problem if global CO₂ emissions are decreased.^[12]

GM Vice Chairman Bob Lutz has said the Chevy Volt will emit 40 grams of carbon dioxide per kilometer. That is well below the proposed European Union emission standards of 120-130 g/km.^[60]

Operating costs

George W. Bush is shown the PHEV Mercedes-Benz Sprinter van in the U.S. Postal Service

In a 2006 research estimate in California, the cost to plug in at night was equivalent to US$0.75 per U.S. gallon (3.8 L) of gasoline,^[1] whereas the pre-tax cost of gasoline is just under US$3 per gallon. The cost of electricity for a Prius PHEV is about US$0.03 per mile (US$0.019 per km), based on 0.26 kW·h/mi (129 mpg) and a cost of electricity of US$0.10 per kilowatt hour.^[61][62] During 2008, many government and industry researchers are focusing on determining what level of all-electric range is economically optimum for the design.^[63] In 2008, a PHEV can travel 30 miles for just US$ 1.04 (the same mileage as a gallon of gasoline costing $3.00.)^[64]

Vehicle-to-grid electricity

Main article: Vehicle-to-grid

PHEVs and fully electric cars may allow for more efficient use of existing electric production capacity, much of which sits idle as operating reserve most of the time. This assumes that vehicles are charged primarily during off peak periods (i.e., at night), or equipped with technology to shut off charging during periods of peak demand. Another advantage of a plug-in vehicle is their potential ability to load balance or help the grid during peak loads. This is accomplished with vehicle to grid technology. By using excess battery capacity to send power back into the grid and then recharge during off peak times using cheaper power, such vehicles are actually advantageous to utilities as well as their owners. Even if such vehicles just led to an increase in the use of night time electricity they would even out electricity demand which is typically higher in the day time, and provide a greater return on capital for electricity infrastructure.^[12]

In October 2005, five Toyota engineers and one Asian AW engineer published an IEEE technical paper detailing a Toyota-approved project to add vehicle-to-grid capability to a Toyota Prius.^[65] Although the technical paper described "a method for generating voltage between respective lines of neutral points in the generator and motor of the THS-II (Toyota Hybrid System) to add a function for generating electricity", it did not state whether or not the experimental vehicle could be charged through the circuit, as well. However, the vehicle was featured in a Toyota Dream House, and a brochure for the exhibit stated that "the house can supply electricity to the battery packs of the vehicles via the stand in the middle of the garage", indicating that the vehicle may have been a plug-in hybrid.^[66]

In November 2005, more than 50 leaders from public power utility companies across the United States met at the Los Angeles Department of Water and Power headquarters to discuss plug-in hybrid and vehicle-to-grid technology. The event, which was sponsored by the American Public Power Association, also provided an opportunity for association members to plan strategies that public power utility companies could use to promote plug-in hybrid technology. Greg Hanssen and Peter Nortman of EnergyCS ^[67] and EDrive^[68] attended the two-day session, and during a break in the proceedings, made an impromptu display in the LADWP parking lot of their converted Prius plug-in hybrid.^[69]

In September 2006, the California Air Resources Board held a Zero Emission Vehicle symposium that included several presentations on V2G technology.^[70] In April 2007, Pacific Gas and Electric showcased a PHEV at the Silicon Valley Leadership Alternative Energy Solutions Summit with vehicle-to-grid capability, and demonstrated that it could be used as a source of emergency home power in the event of an electrical power failure.^[71] Regulations intended to protect electricians against power other than from grid sources would need to be changed, or regulations requiring consumers to disconnect from the grid when connected to non-grid sources will be required before such backup power solutions would be feasible.^[72]

Federal Energy Regulatory Commissioner Jon Wellinghoff coined the term "Cash-Back Hybrids" to describe payments to car owners for putting their batteries on the power grid. Batteries could also be offered in low-cost leasing or renting or by donation (including maintenance) to the car owners by the public utilities, in a vehicle-to-grid agreement.^[73]

Disadvantages

Cost, weight, and size of batteries

Disadvantages of plug-in hybrids include the additional cost, weight, and size of a larger battery pack. General Motors may allow buyers of its Chevy Volt electric car to rent the vehicle's battery, offsetting some cost.^[74] Also used PHEV batteries can be sold to electric utilities to be employed at electrical substations.^[45]

Electrical outlets outside garages

Many people living in apartments, condominiums, and townhouses do not have garages. With only on-street parking available, they will need access to electrical outlets to take advantage of all-electric operation. New electrical outlets near their places of residence, or in commercial or public parking lots will need to be installed for them to gain the full advantage of PHEVs.^[75]

Emissions shifted to electric plants

Increased pollution is expected to occur in some areas with the adoption of PHEVs, but most areas will experience a decrease.^[76] A study by the ACEEE predicts that widespread PHEV use in heavily coal-dependent areas would result in an increase in local net sulfur dioxide and mercury emissions, given emissions levels from most coal plants currently supplying power to the grid.^[77] Although clean coal technologies could create power plants which supply grid power from coal without emitting significant amounts of such pollutants, the higher cost of the application of these technologies may increase the price of coal-generated electricity. The net effect on pollution is dependent on the fuel source of the electrical grid (fossil or renewable, for example) and the pollution profile of the power plants themselves. Identifying, regulating and upgrading single point pollution source such as a power plant—or replacing a plant altogether—may also be more practical. From a human health perspective, shifting pollution away from large urban areas may be considered a significant advantage.^[78] Martin Eberhard, who co-founded Tesla Motors, says "if you do the math, you´ll find that an electric car, even if you use coal to make electricity, produces less pollution per mile than burning gasoline in the best gasoline-powered car."^[79]

Commercialization

The number of US survey respondents willing to pay US$4,000 more for a plug-in hybrid car increased from 17% in 2005 to 26% in 2006.

PHEVs have been sold as commercial passenger vans,^[80] utility trucks,^[81][82] general and school buses,^[83][84] motorcycles,^[85] scooters,^[86] and military vehicles.^[87] Hybrid Electric Vehicle Technologies, Inc converts diesel buses to plug-in hybrids, under contract for the Chicago Transit Authority.

Interest in plug-in hybrids increased in 2006 to such a level that the architecture was included as an area of research in President George W. Bush's advanced energy initiative and mentioned in his 2007 State of the Union Address. Incentives for the development of PHEVs are included in the Energy Independence and Security Act of 2007.^[88]

At least fourteen car companies of all sizes are exploring or planing to offer a plug-in.^[89] After hearing an explanation of PHEVs, 49% of U.S. consumers surveyed in 2006 said they would consider purchasing one. That is about the same level of interest as standard hybrid technology.^[90]

Patent encumbrance of NiMH batteries

In 1994, General Motors acquired a controlling interest in Ovonics's battery development and manufacturing, including patents controlling the manufacturing of large nickel metal hydride (NiMH) batteries. In 2001, Texaco purchased GM's share in GM Ovonics. A few months later, Chevron acquired Texaco. In 2003, Texaco Ovonics Battery Systems was restructured into Cobasys, a 50/50 joint venture between Chevron and Energy Conversion Devices (ECD) Ovonics.^[91] Chevron's influence over Cobasys extends beyond a strict 50/50 joint venture. Chevron holds a 19.99% interest in ECD Ovonics.^[92] Chevron also maintains veto power over any sale or licensing of NiMH technology.^[93] In addition, Chevron maintains the right to seize all of Cobasys' intellectual property rights in the event that ECD Ovonics does not fulfill its contractual obligations.^[93] On September 10, 2007, Chevron filed a legal claim that ECD Ovonics has not fulfilled its obligations. ECD Ovonics disputes this claim.^[94]

In her book, Plug-in Hybrids: The Cars that Will Recharge America, published in February 2007, Sherry Boschert argues that large-format NiMH batteries are commercially viable but that Cobasys refuses to sell or license them to small companies or individuals. Boschert reveals that Cobasys accepts only very large orders for these batteries. When Boschert conducted her research, major auto makers showed little interest in large orders for large-format NiMH batteries. However, Toyota employees complained about the difficulty in getting smaller orders of large format NiMH batteries to service the existing 825 RAV-4EVs. Since no other companies were willing to make large orders, Cobasys was not manufacturing nor licensing any large format NiMH battery technology for automotive purposes. Boschert concludes that "it's possible that Cobasys (Chevron) is squelching all access to large NiMH batteries through its control of patent licenses in order to remove a competitor to gasoline. Or it's possible that Cobasys simply wants the market for itself and is waiting for a major automaker to start producing plug-in hybrids or electric vehicles." ^[95]

However, recently-signed Cobasys contracts demonstrate that the company is willing to use its NiMH technology in the automotive industry, specifically for use with hybrid electric vehicles. In December 2006, Cobasys and General Motors announced that they had signed a contract under which Cobasys provides NiMH batteries for the Saturn Aura hybrid sedan.^[96] In March 2007, GM announced that it would use Cobasys NiMH batteries in the 2008 Chevrolet Malibu hybrid as well. Cobasys remains unwilling to sell NiMH batteries in smaller quantities to individuals interested in building or retrofitting their own PHEVs.

Electro Energy Inc., working with CalCars, converted a Prius using a its own bipolar NiMH batteries. Plug-In Conversions uses Nilar NiMH batteries and the EAA-PHEV open source control system in its Prius PHEV conversions.

See also

References

External links

• Electric Automobile Association's Hybrid and Plug-In Hybrid Electric Vehicles Wiki - conversion and technical documentation
• Plug-in Hybrid Electric Vehicles - U.S. Office of Energy Efficiency and Renewable Energy
  • DoE Grant for Plug In Hybrid Electric Vehicle (PHEV) Technology Acceleration And Deployment Activity.
• Senators plug in - video clip of U.S. senators talking about plug in hybrids
• Plug in for America - video clip about plug in hybrid vehicles
• Green Car Advisor news blog, plug-in category
• Plugsandcars blog
• "Plugging into the Grid" by Joseph Romm and Peter Fox-Penner in the Progressive Policy Institute's March 2007 newsletter, explaining how PHEVs can help "break America's oil addiction and slow global warming"

Groups promoting plug-ins

• California Cars Initiative, PHEV news service, What Carmakers are saying about PHEVs
• Plug-in Hybrid Development Consortium
• Plug-In Partners
• Set America Free Coalition