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Electric vehicle

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An electric vehicle, or EV, is a vehicle with one or more electric motors for propulsion. The motion may be provided either by wheels or propellers driven by rotary motors, or in the case of tracked vehicles, by linear motors.

The energy used to propel the vehicle may be obtained from several sources:

  • from chemical energy stored on the vehicle in on-board batteries: Battery electric vehicle (BEV)
  • from both an on-board rechargeable energy storage device (RESD) and a fueled propulsion power source: hybrid vehicle
  • generated on-board using a combustion engine, as in a diesel-electric locomotive
  • generated on-board using a fuel cell: fuel cell vehicle
  • generated on-board using nuclear energy, on nuclear submarines and aircraft carriers
  • from more esoteric sources such as flywheels, wind and solar
  • from a direct connection to land-based generation plants, as is common in electric trains and trolley buses
  • from both an on-board rechargeable energy storage system and a direct continuous connection to land-based generation plants for purposes of on-highway recharging with unrestricted highway range.

Advantages of electric vehicles

Electric motors are used to drive vehicles because they can be finely controlled, they deliver power efficiently and they are mechanically very simple. Electric motors often achieve 90% conversion efficiency over the full range of speeds and power output and can be precisely controlled. Electric motors can provide high torque while an EV is stopped, unlike internal combustion engines, and do not need gears to match power curves. This removes the need for gearboxes and torque converters. Electric motors also have the ability to convert movement energy back into electricity, through regenerative braking. This can be used to reduce the wear on brake systems and reduce the total energy requirement of a trip.

Another advantage is that electric vehicles lack the vibration and noise pollution of a vehicle powered by an internal combustion engine. Trolleybuses are especially capable of this advantage, due to the fact that trolleybuses also lack the noise of steel wheels on rails, unlike Trams.

Large-scale electric transport

Most large electric transport systems are powered by stationary sources of electricity that are directly connected to the vehicles through wires. Due to the extra infrastructure and difficulty in handling arbitrary travel, most directly connected vehicles are owned publicly or by large companies. These forms of transportation are covered in more detail in maglev trains, metros, trams, trains and trolleybuses. A hypothetical electric vehicle design is the personal rapid transit, a cross between cars and trains optimised for independent travel.

In most systems the motion is provided by a rotary electric motor. However, some trains unroll their motors to drive directly against a special matched track. These are known as linear motors and are most commonly used in maglev trains which float above the rails through magnetic force. This allows for almost no rolling resistance of the vehicle and no mechanical wear and tear of the train or track. The levitation and the forward motion are independent effects; the forward motive forces still require external power, but Inductrack achieves levitation at low speeds without any.

Chemical-electric power

Chemical energy is a common independent energy source. Chemical energy is converted to electrical energy, which is then regulated and fed to the drive motors. Chemical energy is usually in the form of diesel or petrol (gasoline). The liquid fuels are usually converted into electricity by an electrical generator powered by an internal combustion engine or other heat engine. This approach is known as diesel-electric or gas-hybrid locomotion.

Another common form of chemical to electrical conversion is by electro-chemical devices. These include fuel cells and batteries. By avoiding an intermediate mechanical step, the conversion efficiency is dramatically improved over the chemical-thermal-mechanical-electrical-mechanical process already discussed. This is due to the higher carnot efficiency through directly oxidizing the fuel and by avoiding several unnecessary energy conversions. Furthermore, electro-chemical batteries conversions are easy to reverse, allowing electrical energy to be stored in chemical form.

Despite the higher efficiency, electro-chemical vehicles have been beset by a technical issue which has prevented them from replacing the more cumbersome heat engines: energy storage. Fuel cells are fragile, sensitive to contamination, and require external reactants such as hydrogen. Batteries currently used are either not mass-produced, leading to high per-unit prices, or end up being a significant (25%-50%) portion of the final vehicle mass, in the case of conventional lead-acid technology. Both have lower energy and power density than petroleum fuels. However, recent advances in battery efficiency, capacity, materials, safety, toxicity and durability are likely to allow their superior characteristics to be widely applied in car-sized EVs,

For especially large electric vehicles, such as submarines and aircraft carriers, the chemical energy of the diesel-electric can be replaced by a nuclear reactor. The nuclear reactor usually provides heat, which drives a steam turbine, which drives a generator, which is then fed to the propulsion.


History

Main article: history of the electric vehicle

Electric motive power started with a small railway operated by a miniature electric motor, built by Thomas Davenport in 1835. In 1838, a Scotsman named Robert Davidson built an electric locomotive that attained a speed of four miles an hour. In England a patent was granted in 1840 for the use of rails as conductors of electric current, and similar American patents were issued to Lilley and Colten in 1847. <ref>[1]</ref>

Between 1832 and 1839 (the exact year is uncertain), Robert Anderson of Scotland invented the first crude electric carriage, powered by non-rechargeable Primary cells. <ref>[2]</ref>

By the 20th century, electric cars and rail transport were commonplace, with commercial electric automobiles having the majority of the market. Electrified trains were used for coal transport as the motors did not use precious oxygen in the mines. Switzerland's lack of natural fossil resources forced the rapid electrification of their rail network. One of the earliest rechargeable batteries - the Nickel-iron battery - was favored by Edison for use in electric cars.

Electric vehicles were among the earliest automobiles, and before the preeminence of light, powerful internal combustion engines, electric automobiles held many vehicle land speed and distance records in the early 1900s. They were produced by Anthony Electric, Baker Electric, Detroit Electric, and others and at one point in history out-sold gasoline-powered vehicles.

In the early 20th century, National City Lines, which was a partnership of General Motors, Firestone, and Standard Oil of California purchased many electric tram networks across the country to dismantle them and replace them with GM buses. The partnership was convicted for this conspiracy, but the ruling was overturned in a higher court. Electric tram line technologies could be used to recharge BEVs and PHEVs on the highway while the user drives, providing virtually unrestricted driving range. The technology is old and well established. The infrastructure has not been built.

File:Evcrushed.jpg
EV1s crushed by General Motors only 5 years after production

From 1996 to 1998 during emissions reductions regulations GM produced 1117 of their EV1 models, 800 of which were made available through 3-year leases. In 2003, upon the expiration of EV1 leases, GM crushed them. The reason for the crushing is not clear, but has variously been attributed to (1) the auto industry's successful challenge to California law requiring zero emission vehicles or (2) a federal regulation requiring GM to produce and maintain spare parts for the few thousands EV1s or (3) a conspiracy to remove the dream of electric vehicles from the public consciousness. A movie made on the subject in 2005-2006 was titled Who Killed the Electric Car? and released theatrically by Sony Pictures Classics in 2006. The film explores the roles of automobile manufacturers, oil industry, the US government, batteries, hydrogen vehicles, and consumers, and each of their roles in limiting the deployment and adoption of this technology.

Future

Main article: Battery electric vehicle
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Eliica Battery Electric Car with 370 km/h top speed and 200 km range
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The number of US survey respondents willing to pay $4,000 more for a plug-in hybrid car increased from 17% in 2005 to 26% in 2006.

The future of electric vehicles until recently seemed unimpressive due to their low driving range and short lifespan of batteries. However, recent technological advances have made electric vehicles more feasible.

Improved long term energy storage and nano batteries

There have been several developments which could bring back electric vehicles outside of their current fields of application, as scooters, golf cars, neighborhood vehicles, in industrial operational yards and indoor operation. First, advances in lithium-based battery technology, in large part driven by the consumer electronics industry, allow full-sized, highway-capable electric vehicles to be propelled as far on a single charge as conventional cars go on a single tank of gasoline. Lithium batteries have been made safe, can be recharged in minutes instead of hours, and now last longer than the typical vehicle. The production cost of these lighter, higher-capacity lithium batteries is gradually decreasing as the technology matures and production volumes increase.

Nanotechnology batteries can be 80% recharged in 1 minute (i.e. NanoSafe).

Introduction of Battery Management and Intermediate Storage

Another improvement was to decouple the electric motor from the battery through electronic control while employing ultra-capacitors to buffer large but short power demands and recuperable braking energy. The development of new cell types compared with intelligent cell management improved both weak points mentioned above. The cell management is not only able to monitor the health of the cells but by having a redundant cell configuration (one more cell than needed) and a sophisticated switched wiring it is possible to condition one cell after the other while the rest are on duty.

Range extending energy converters on board

Main article: Plug-in hybrid electric vehicle

Perhaps the most important point is that a monovalent operation (electric only) is no longer the only possibility. Plug-in hybrid electric vehicles can use an engine for longer trips.

The use of fuel cells instead of internal combustion engines can create propulsion systems that are nearly emissions-free (regarding local emissions). However, since the production of hydrogen is energy-inefficient, the net result of hydrogen use in vehicles is increased overall emissions, including CO2, and therefore an increase in the rate of global warming.

Patents

See also

Related Links

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