Information AboutElectric Vehicle |
| CATEGORIES ABOUT ELECTRIC VEHICLE | |
| alternative propulsion | |
| electric vehicles | |
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An electric vehicle, or EV, is a Vehicle propelled by Electric Motor s. The motion may be provided either by Wheels or Propellers driven by rotary motors, or in the case of tracked vehicles, by Linear Motor s. The Electrical Energy used to power the motors may be obtained from Chemical Energy stored on the vehicle in batteries; from a direct connection to land-based generation plants, as is common in electric trains; from nuclear energy, on nuclear submarines and aircraft carriers; or from more esoteric sources such as flywheels, wind and solar. The reasons that electric motors are a good choice to drive vehicles are that 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 Engine s, and do not need gears to match power curves. This removes the need for Gearbox es and Torque Convertor s. 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 typical trip. Personal highway-capable EVs are driven by tens of thousands of ordinary people worldwide. According to the (US) Electric Auto Association, as many as ten thousand full-sized electric cars are on American roads today. Most are converted to electric propulsion by owners or small shops, although several hundred of the several thousand (of eight EV models in the US) built by major automakers also survive. The rest have been repossessed and crushed by their makers. Most large 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 , Metro s, Tram s, Train s and Trolleybus es. A hypothetical electric vehicle design is 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 called linear motor trains. Often these are also achieves levitation at low speeds without any. 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 . The liquid fuels are 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. Another common form of chemical to electrical conversion is by electro-chemical devices. These include Fuel Cell s 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 many technical issues which have prevented 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. 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, namely Submarine s and Aircraft Carrier s, 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. There have been a number of experiments using Flywheel Energy Storage in electric vehicles. The Flywheel s 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 again to rotate the vehicle's drive wheels, but in fact it is a necessary step: In order to hold a useful amount of energy, flywheels need to spin extremely fast, and an electric generator is usually a more practical converter for this high speed rotational energy than a mechanical gearing system would be. |
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