FAQs

Am I right in thinking that it's all about efficiency rather than the fuel source? I believe power plants are more efficient than a car engine.
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Yes, it is certainly the case that the battery-motor combination as used by an EV is much more energy efficient than the internal combustion engine. Typically petrol and diesel engines utilise 25-30% of the fuel's energy at best.

Just for an idea of scale, on a RAC Brighton to London run, measured in mega joules (MJ) per kilometre on a tank-to-wheel basis, on average: Electric vehicles used 0.61MJ/km; hybrids used 1.16 MJ/km; and diesels used 1.74 MJ/km.

How would a return to horse drawn vehicles compare with an EV on emissions?
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Well, for human power emissions, cycling generates around 8 gCO2/km if you assume the cyclist eats locally grown organic food.

If you then also assume that a horse can exert around 7.5 times the power of a human (1 hp or 750 Watts versus 100 Watts), then we would estimate that a horse (eating locally grown farm food) would emit around 55-60 gCO2/km.

This is close to what can be achieved by an electric car (on a life cycle basis), although an EV using renewable electricity would emit less CO2!

Are electric vehicle really better for the environment? I have heard that they use more energy to make them than they save in use.
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You are right to raise the issue of manufacture versus usage. Several studies have looked at these issues and broadly come to the following conclusions.

While it is the case that EV manufacture generates more emissions than the manufacture of a conventional vehicle (up to double), the benefits in use continue to outweigh the production penalty. This arises in part due to the fact that the majority (around 85%) of conventional vehicle emission occur in use, and in part due to the fact that EVs are much more energy efficient than the internal combustion engine.

Taken overall, for CO2 emissions, electric vehicles charged using average UK 'mains' electricity show a modest but important reduction in life cycle emissions of around 20% compared to an equivalent conventional vehicle. However, larger carbon reductions are likely as the UK grid continues to 'decarbonise', and if renewable or 'green tariff' electricity is used, then life cycle CO2 emissions (arising from the fuel cycle) are effectively zero.

For local pollutants, such as nitrogen oxides (NOx) and particulates (PMs), life cycle emissions associated with electric cars using average 'mains' electricity are increased. However, as these are emitted from power-stations which are well away from urban areas, their overall impact tends to be much less than when emitted from the exhausts of petrol and diesel cars. As is the case with CO2 emissions, if renewable electricity is used, then life cycle air quality impact (as measured in the main population centres) is greatly reduced.

However, it should also be stressed that it depends where the EV is used and the above figures are only relevant to the UK. A recent study by the Norwegian University of Science and Technology has made estimates of the life cycle emissions for a number of countries around the world, and draws very different conclusions depending on which country is the basis of the analysis and how the electricity is generated.

More contentious is the generation of new impacts, ones not currently associated with conventional vehicle production. While electric vehicles can provide climate change benefits, reduce noise pollution, and reduce use of fossil fuels, they may increase the potential impact on human health in areas where resources (such as lithium) are extracted for battery production. More research is required to better understand the health impacts of particular mining practices, as well as the potential of recycling as a way of reducing the need for new lithium supplies.

References

  • Preparing for a life cycle CO2 measure. Report by Ricardo on behalf of Low Carbon Vehicle Partnership, May 2011.
  • Market delivery of ultra-low carbon vehicles in the UK. Report by Ecolane on behalf of RAC Foundation, January 2011.
  • Strategies for the uptake of electric vehicles and associated infrastructure implications, ElementEnergy (for The Committee on Climate Change). Final Report, October 2009.
  • Comparative Environmental Life Cycle Assessment of Conventional and Electric Vehicles, Norwegian University of Science and Technology, 2012.