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, some of them more ecological than others:
- from an on-board rechargeable energy storage system (RESS), called Full Electric Vehicles (FEV):
- from chemical energy stored on the vehicle in on-board batteries: Battery electric vehicle (BEV)
- from static energy stored on the vehicle in on-board supercapacitors
- from kinetic storage: flywheels
- from a direct connection to land-based generation plants, as is common in electric trains and trolley buses (See also : overhead lines, third rail and conduit current collection)
- 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.
- from both an on-board rechargeable energy storage system (RESS) and a fueled propulsion power source (internal combustion engine): hybrid vehicle (as in a diesel-electric locomotive), including plug-in hybrid
- from renewable sources such as wind and solar
- generated on-board using a fuel cell: fuel cell vehicle
- generated on-board using nuclear energy, on nuclear submarines and aircraft carriers
Electric vehicles can include electric airplanes, electric boats, and electric motorcycles and scooters.
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 gasoline-electric hybrid locomotion. These engines still produce greenhouse gases, though typically less than conventional petroleum vehicles, and can be combined with regenerative braking systems for more efficiency.
Nowadays batteries, supercapacitors and flywheel energy storage are on-board rechargeable energy storage system (RESS). By avoiding an intermediate mechanical step, the energy 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.
Another form of chemical to electrical conversion is fuel cells, projected for future use.
For especially large electric vehicles, such as submarines, 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. See Nuclear Power
The power of a vehicle electric motor, as in other vehicles, is measured in kW. 100 kW is roughly equivalent to 134 horsepower, although most electric motors deliver full torque at any speed, so the performance is not equivalent, and far exceeds a 134 horsepower fuel powered motor, which only has a limited torque curve.
Large-scale electric transport: energy and motors
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 metros, trams, electric locomotives, and trolleybuses.
Small scale electric vehicles
Some bicycles have been converted to electric power with a small battery and a small electric motor, some even have solar panels that are folded out when the vehicle is at rest. Small scale electric vehicles include electric cars, light trucks, neighborhood electric vehicles, motorcycles, motorized bicycles, electric scooters , golf carts, milk floats, forklifts and similar vehicles.
Issues regarding electric vehicles
Although electric vehicles have few direct emissions, all rely on energy created through electricity generation which will emit pollution unless it is from a renewable source. If a large proportion of private vehicles were to convert to plug-in electricity, the existing powerplant infrastructure would be nearly sufficient, but there would still be a significant need for additional resources (and emissions) in generation and transmission, assuming most charging occurred overnight using the most efficient off-peak base load sources.
Issues with batteries
All types of batteries today have lower energy density than liquid fuels. However, if an average vehicle travels about 200 km (125 miles) per day, then it is possible for this energy to be stored in a battery pack using an affordable battery chemistry such as NiMH. The current price-performance of affordable battery technology is best suited to medium-range EVs. On an energy basis, the cost of electricity is a quarter as much as liquid fuel.
Advantages of electric vehicles
The EC1's history is related in the report "Who killed the electric car?".
Electric motors are mechanically very simple, and release almost no air pollutants at the place where they are operated.
Electric motors often achieve 90% energy conversion efficiency over the full range of speeds and power output and can be precisely controlled. They can also be combined with regenerative braking systems that have the ability to convert movement energy back into stored electricity. This can be used to reduce the wear on brake systems (and consequent brake pad dust) and reduce the total energy requirement of a trip, especially effective for start-and-stop city use.
They can be finely controlled and provide high torque from rest, unlike internal combustion engines, and do not need gears to match power curves. This removes the need for gearboxes and torque converters.
Another advantage is that electric vehicles typically have less vibration and noise pollution than a vehicle powered by an internal combustion engine, whether it is at rest or in motion.
The BlueCar at the Geneva salon in 2005.
Several start-up companies, like Tesla Motors, Ronaele Incorporated, Commuter Cars and Phoenix Motorcars, will have powerful battery-electric vehicles available to the public in 2008. Battery and energy storage technology is advancing rapidly. Electric cars are perfectly useful as second household vehicles for short and medium distance trips of 100 to 250 miles per charge. The range issue will be improved by technologies such as Plug-in hybrid electric vehicles which are capable of using traditional fuels for unlimited range.
General Motors plans sales in 2011 of its plug-in hybrid Chevrolet Volt, which uses a small internal combustion engine hooked to an electrical generator to maintain charge in the batteries. GM calls it an electric vehicle with a "range extender", that can extend the range up to 640 miles.
Improved long term energy storage and nano batteries
There have been several developments which could bring electric vehicles outside 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.
Introduction of Battery Management and Intermediate Storage
Another improvement is to decouple the electric motor from the battery through electronic control, employing ultra-capacitors to buffer large but short power demands and regenerative braking energy. The development of new cell types combined with intelligent cell management improved both weak points mentioned above. The cell management involves not only monitoring the health of the cells but also a redundant cell configuration (one more cell than needed). With sophisticated switched wiring it is possible to condition one cell while the rest are on duty.
Create your open source electric car
The Open Source Project OScar is working to design, manufacture and sell an electric car.
The Ekopedia OScar page will help this project.
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