The biggest challenge with electric cars is the storage of energy in the batteries. An example: to drive 180 km, currently a battery is needed of 273 kg taking up 174 liters space and containing 27 kWh. 70% to 80% of this energy reaches the wheels. In a convential diesel version about 15-25% of the energy reaches the wheels and in spite the lower efficiency, it takes 6 liters diesel voor the same distance.

Hybrid cars,vehicles powered by two different sources of energy, are already quite popular. Plug-in hybrid cars are less so, but their acceptance is growing and they enjoy an excellent reputation amongst some experts. The cost of electricity to power plug-in hybrid cars is less than one quarter of the cost of gasoline.

According to a report of Deloitte, published in May 2011, investment companies can not find enough relevant opportunities to invest in. In the study, conducted by Blaauw research amongst 78 investment funds throughout Europe the study found that over 50% of all investors direct all of their investments towards sustainable energy.

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Most of our energy - about 85% of US primary energy consumption- currently comes from fossil fuels: coal, oil, and natural gas supply. Although the supplies of these fossil fuels are vast, they are not unlimited. And more important, the earth's atmosphere and biosphere may not survive the environmental impact of burning such enormous amounts of these fuels.

Electric vehicle batteries differ from starting, lighting, and ignition (SLI) batteries because they are designed to give power over sustained periods of time. Deep cycle batteries

With the depletion of the earth's ozone layer and the shortage of our oil supply becoming an issue, we have had to look at alternative fueled vehicles that will not harm the environment.

Electric vehicles are not a recent development. In fact, the electric vehicle has been around for over 100 years, and it has an interesting history of development that continues to the present.

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Electricity sources

A passenger railroad, taking power through a third rail with return through the traction rails

An electric Locomotive at Brig

(See articles on diesel-electric and gasoline-electric hybrid locomotion for information on electric vehicles using also combustion engines).

There are many ways to generate electricity, some of them more ecological than others:

• on-board rechargeable electricity storage system (RESS), called Full Electric Vehicles (FEV). Power storage methods include:
  • chemical energy stored on the vehicle in on-board batteries: Battery electric vehicle (BEV)
  • static energy stored on the vehicle in on-board electric double-layer capacitors
  • kinetic energy storage: flywheels
• direct connection to generation plants as is common among electric trains, trolley buses, and trolley trucks (See also :overhead lines, third rail and conduit current collection)
• renewable sources such as solar power: solar vehicle
• generated on-board using a diesel engine: diesel-electric locomotive
• generated on-board using a fuel cell: fuel cell vehicle
• generated on-board using nuclear energy: nuclear submarines and aircraft carriers

It is also possible to have hybrid electric vehicles that derive electricity from multiple sources. Such as:

• on-board rechargeable electricity storage system (RESS) and a direct continuous connection to land-based generation plants for purposes of on-highway recharging with unrestricted highway range
• on-board rechargeable electricity storage system and a fueled propulsion power source (internal combustion engine): plug-in hybrid

Batteries, electric double-layer capacitors and flywheel energy storage are forms of rechargeable on-board electrical storage. By avoiding an intermediate mechanical step, the energy conversion efficiency can be improved over the hybrids already discussed, by avoiding 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

A few experimental vehicles, such as some cars and a handful of aircraft use solar panels for electricity.

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Rechargeable battery chemistries

(includes data from energy density article)

Chemistry	Cell Voltage	Specific Energy [MJ/kg]	Comments
NiCd	1.2	0.14	Inexpensive. High/low drain, moderate energy density. Can withstand very high discharge rates with virtually no loss of capacity. Moderate rate of self discharge. Reputed to suffer from memory effect (which is alleged to cause early failure). Environmental hazard due to Cadmium - use now virtually prohibited in Europe.
Lead acid	2.1	0.14	Moderately expensive. Moderate energy density. Moderate rate of self discharge. Higher discharge rates result in considerable loss of capacity. Does not suffer from memory effect. Environmental hazard due to Lead. Common use - Automobile batteries
NiMH	1.2	0.36	Inexpensive. Performs better than alkaline batteries in higher drain devices. Traditional chemistry has high energy density, but also a high rate of self-discharge. Newer chemistry has low self-discharge rate, but also a ~25% lower energy density. Very heavy. Used in some cars.
NiZn	1.6	0.36	Moderately inexpensive. High drain device suitable. Low self-discharge rate. Voltage closer to alkaline primary cells than other secondary cells. No toxic components. Newly introduced to the market (2009). Has not yet established a track record. Limited size availability.
Lithium ion	3.6	0.46	Very expensive. Very high energy density. Not usually available in "common" battery sizes (but see RCR-V3 for a counter-example). Very common in laptop computers, moderate to high-end digital cameras and camcorders, and cellphones. Very low rate of self discharge. Volatile: Chance of explosion if short circuited, allowed to overheat, or not manufactured with rigorous quality standards.

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