Electric vehicle

An electric vehicle is a vehicle whose motion is provided by electric motors. The motion may be provided either by wheels or propellors driven by rotary motors, or in the case of tracked vehicles, by linear motors. The electrical energy used to power the motors may be obtained from a direct connection to land-based generation plants, as is common in electric trains; from chemical energy stored on the vehicle in batteries or diesel fuel; from nuclear energy, on nuclear submarines and aircraft carriers; or more esoteric sources such as flywheels, wind and solar.

Related Topics:
Vehicle - Electric motor - Linear motor - Electrical - Energy

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The reasons electric motors are used to drive vehicles are their fine control, high efficiency and simple mechanical construction. 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 torque whilst not moving, unlike internal combustion engines, and do not need gears to match power curves. This removes the need for gearboxes, torque convertors and differentials. Electric motors also have the unusual 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 journey.

Related Topics:
Internal combustion engine - Gearbox - Torque convertor - Differential - Regenerative braking

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Most electric transport is directly connected to stationary sources of energy through the grid. 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 Personal rapid transit, a cross between cars and trains optimised for independent travel.

Related Topics:
Maglev trains - Metro - Tram - Train - Trolleybus - Personal rapid transit

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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 called linear motor trains. Often these are also magnetic levitation trains, floating above the rails through magnetic force. Note that the levitation and the forward motion are independent effects: while the forward motive forces still require external power, Inductrack achieves levitation at low speeds without any.

Related Topics:
Magnetic levitation train - Inductrack

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Chemical energy is the most 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. The fuel is usually converted into electricity by a generator powered by an internal combustion engine or other heat engine. This approach is known as diesel-electric or gas-hybrid locomotion.

Related Topics:
Diesel - Petrol - Generator - Heat engine - Diesel-electric - Hybrid

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Another form of chemical to electrical conversion is electro-chemical. This includes 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 oxidising 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.

Related Topics:
Fuel cell - Batteries

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Despite the higher efficiency, electro-chemical vehicles have many technical issues which prevent them from replacing the more cumbersome heat engines. Heat engines have been easier to scale up, with the largest electrical generators always being driven by heat engines. Fuel cells are fragile, sensitive to contamination, and require external reactants such as hydrogen. Batteries require highly refined and unstable chemicals that could be harmful to the environment and must be recycled to minimize their impact and maximize their sustainability through material reuse. Both have lower energy and power density than heat engines.

Related Topics:
Hydrogen - Energy - Power density

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For especially large electric vehicles, namely 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.

Related Topics:
Submarine - Aircraft carrier - Nuclear reactor - Steam turbine

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There have been a number of experiments using flywheel energy storage in electric vehicles. The flywheels store energy as rotation, which is converted to electricity via a generator, which then drives the wheel motors. It might seem odd to convert rotational energy to electrical energy, only to convert it back, but flywheels need to spin very fast to store enough energy to be useful, and it is easier to use electricity to convert the motion to something suitable for the vehicle.

Related Topics:
Flywheel energy storage - Flywheel

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There are two commonly available electric vehicle designs for automobiles: Battery Electric Vehicles or BEVs, which convert chemical energy to electrical energy in batteries; and Hybrid vehicles, which convert chemical energy to electrical energy via an internal combustion engine and a generator.

Related Topics:
Battery Electric Vehicles - Hybrid vehicle

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Other light personal mobility devices include electric wheelchairs, the Segway HT, electric scooters, electric assist bicycles, golf carts and neighborhood electric vehicles. Working electric vehicles include heavy work equipment, fork lifts, and numerous other service and support vehicles. Strictly technology-proving experimental or solar powered vehicles include sun racers, electrathons, the aerial Helios Prototype, and some rocket propulsion systems such as the ion thruster.

Related Topics:
Wheelchair - Segway HT - Electric scooter - Electric assist bicycle - Golf cart - Neighborhood electric vehicle - Fork lift - Solar power - Sun racer - Electrathon - Helios Prototype - Rocket propulsion - Ion thruster

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