Editing Vehicle (section)

=== Energy source ===
{{main|Energy storage#Storage methods}}
{{see also|Hybrid vehicle}}
[[File:Electric vehicle charging point - geograph.org.uk - 5804565.jpg|thumb|An [[electric car]] at a [[charging station]] in [[Crawfordjohn]], Scotland]]
It is essential that a vehicle have a source of energy to drive it. Energy can be extracted from external sources, as in the cases of a [[sailboat]], a [[solar-powered car]], or an electric [[streetcar]] that uses overhead lines. Energy can also be stored, provided it can be converted on demand and the storing medium's [[energy density]] and [[power density]] are sufficient to meet the vehicle's needs.

[[Human power]] is a simple source of energy that requires nothing more than humans. Despite the fact that humans cannot exceed {{convert|500|W|hp|abbr=on}} for meaningful amounts of time,<ref>{{cite web| title = Bicycle Power – How many Watts can you produce?| publisher = Mapawatt| url = http://blog.mapawatt.com/2009/07/19/bicycle-power-watts/| access-date = 23 July 2011}}</ref> the [[Cycling records|land speed record for human-powered vehicles]] (unpaced) is {{convert|133|km/h|mph|0|abbr=on}}, as of 2009 on a [[recumbent bicycle]].<ref name="Speed2009">{{cite web|url = http://www.wisil.recumbents.com/wisil/whpsc2009/results.htm|title = Battle Mountain World Human Powered Speed Challenge|access-date = 25 August 2011|last = WHPSC|date = September 2009|archive-url = https://web.archive.org/web/20130811101125/http://www.wisil.recumbents.com/wisil/whpsc2009/results.htm|archive-date = 11 August 2013|url-status = dead|df = dmy-all}}</ref>

The energy source used to power vehicles is [[fuel]]. External combustion engines can use almost anything that burns as fuel, whilst internal combustion engines and rocket engines are designed to burn a specific fuel, typically gasoline, [[diesel fuel|diesel]] or [[ethanol]]. Food is the fuel used to power non-motor vehicles such as cycles, rickshaws and other pedestrian-controlled vehicles.

Another common medium for storing energy is [[Battery (electricity)|batteries]], which have the advantages of being responsive, useful in a wide range of power levels, environmentally friendly, efficient, simple to install, and easy to maintain. Batteries also facilitate the use of electric motors, which have their own advantages. On the other hand, batteries have low energy densities, short service life, poor performance at extreme temperatures, long charging times, and difficulties with disposal (although they can usually be recycled). Like fuel, batteries store chemical energy and can cause burns and poisoning in event of an accident.<ref>{{cite web| title = Battery Safety| publisher = Electropaedia| url = http://www.mpoweruk.com/safety.htm| access-date = 23 July 2011| archive-date = 13 January 2012| archive-url = https://web.archive.org/web/20120113022101/http://www.mpoweruk.com/safety.htm| url-status = dead}}</ref> Batteries also lose effectiveness with time.<ref>{{cite web| title = The Lifecycle of an Electric Car Battery| publisher = [[HowStuffWorks]]| url = http://auto.howstuffworks.com/fuel-efficiency/vehicles/electric-car-battery4.htm| access-date = 23 July 2011| date = 2008-08-18}}</ref> The issue of charge time can be resolved by swapping discharged batteries with charged ones;<ref>{{cite web| title = Advantages and Disadvantages of EVs| publisher = [[HowStuffWorks]]| url = http://auto.howstuffworks.com/fuel-efficiency/vehicles/electric-car-battery3.htm| access-date = 23 July 2011| date = 2008-08-18}}</ref> however, this incurs additional hardware costs and may be impractical for larger batteries. Moreover, there must be standard batteries for [[battery swapping]] to work at a gas station. [[Fuel cells]] are similar to batteries in that they convert from chemical to electrical energy, but have their own advantages and disadvantages.

[[Third rail|Electrified rails]] and overhead cables are a common source of electrical energy on subways, railways, trams, and trolleybuses.
[[Solar energy]] is a more modern development, and several [[solar vehicles]] have been successfully built and tested, including [[NASA Pathfinder|Helios]], a solar-powered aircraft.

[[Nuclear power]] is a more exclusive form of energy storage, currently limited to large ships and submarines, mostly military. Nuclear energy can be released by a [[nuclear reactor]], [[nuclear battery]], or repeatedly detonating [[nuclear bombs]]. There have been two experiments with nuclear-powered aircraft, the [[Tupolev Tu-119]] and the [[Convair X-6]].

[[Deformation (mechanics)|Mechanical strain]] is another method of storing energy, whereby an elastic band or metal spring is deformed and releases energy as it is allowed to return to its ground state. Systems employing elastic materials suffer from [[hysteresis]], and metal springs are too dense to be useful in many cases.{{Clarify|date=July 2011}}

[[Flywheel energy storage|Flywheels]] store energy in a spinning mass. Because a light and fast rotor is energetically favorable, flywheels can pose a significant safety hazard. Moreover, flywheels leak energy fairly quickly and affect a vehicle's steering through the [[gyroscopic effect]]. They have been used experimentally in [[gyrobus]]es.

[[Wind energy]] is used by sailboats and [[land yacht]]s as the primary source of energy. It is very cheap and fairly easy to use, the main issues being dependence on weather and upwind performance. [[Balloon (aircraft)|Balloons]] also rely on the wind to move horizontally. Aircraft flying in the [[jet stream]] may get a boost from high altitude winds.

[[Compressed gas]] is currently an experimental method of storing energy. In this case, compressed gas is simply stored in a tank and released when necessary. Like elastics, they have [[hysteresis]] losses when gas heats up during compression.

[[Gravitational potential energy#Gravitational potential energy|Gravitational potential energy]] is a form of energy used in gliders, skis, [[bobsled]]s and numerous other vehicles that go down hill. [[Regenerative brake|Regenerative braking]] is an example of capturing [[kinetic energy]] where the brakes of a vehicle are augmented with a generator or other means of extracting energy.<ref name="regenerative">{{cite web| title = How Regenerative Braking Works| publisher = [[HowStuffWorks]]| url = http://auto.howstuffworks.com/auto-parts/brakes/brake-types/regenerative-braking.htm| access-date = 23 July 2011| date = 2009-01-23}}</ref>