Electricity

Electric Vehicles

Electric cars and commercial vehicles have been in production even longer than petrol and diesel engine vehicles.

Purely electric vehicles (EVs) are powered solely by on board batteries. They are limited by the range, size and weight of the batteries required to drive them and have consequently been used most commonly in commercial vehicles and cars operated in urban areas.

Plug in electric hybrid vehicles (PEHVs) are a more recent development. They are vehicles which may be driven typically between 10 and 40 miles on battery power (recharged at home or at a charging station) before the engine (often referred to as a range extender) starts to 'top up' the battery. The engine on these vehicles may not be directly connected to the wheels at all, which allows a smaller engine to be fitted running at or near an optimum speed, further increasing efficiency and reducing emissions.

The electric only range is adequate for many commuting journeys and even where the engine is required for part of a journey the overall emissions are considerably lower than for a conventionally powered car.

What are the environmental benefits of using electricity to power a vehicle?

The vehicles are almost emission free if renewable electricity is used to re-charge them. However, electricity from the national grid is generated from a mixture of coal, gas, nuclear, hydro-electric and wind. For 2006 the Department for Environment Food and Rural Affairs (DEFRA) calculate that 562g of C02 is emitted for each kilowatt hour (kWh) of electricity generated by the grid.

How much does it cost to buy and run an electric vehicle?

Electric cars currently on sale in the UK are either small lightweight cars with a limited range or petrol engined cars converted after registration to run on electricity. All the vehicles are more expensive than their conventionally fuelled equivalents due to the cost of the batteries. The running costs once the vehicle is purchased are however very low, which can make them cost effective over the life of the car.

There are a number of commercial vehicles available which are either purpose built or converted from a normally fuelled vehicle. Again the purchase costs are high if the batteries are purchased (they are often leased) and the daily running costs are low. There are many electric commercial vehicles in use for urban delivery routes where their limited range and low top speed are not a disadvantage.

There are no plug-in hybrid vehicles on sale yet, however manufacturers including Toyota and Vauxhall intend to launch models during 2010 -11. From 2011, £250million has been announced by the government to provide grants of between £2,000 and £5,000 to help consumers buy the next generation of electric and plug-in hybrid vehicles; which will need to meet current safety legislation.

Where can I recharge an electric vehicle?

Cars can be recharged at home from a domestic supply. Most commercial users install faster 3 phase charging equipment. There are currently a limited number of public recharging points; however the government has recently announced financial support to help develop a more comprehensive recharging infrastructure and a network of electric car cities throughout the UK.

Battery technology

Traditionally, lead acid batteries have been used to power electric vehicles. They are cheap, easily recyclable but heavy with a low specific energy (the amount of energy stored by mass measured by kWh/kg) and low energy density (the amount of energy stored by volume measured in kWh/m3)

More expensive technologies have been developed and research and development is being undertaken by many companies around the world to improve battery performance. Lithium ion batteries are now being used in mainstream applications and although they are expensive they have a very high specific energy, improving vehicle range, and can be recharged many times.