'Panda' report drives electric car subsidy

05 May 2009

More transparency is needed in the published performance of electric cars to avoid confusion amongst buyers and prioritise funding for scientific research, claims the chief executive of the Royal Society of Chemistry.

Dr Richard Pike says that data being used by the Department of Transport to justify its planned 5,000 subsidy of 50,000 electric cars (250 million, in all) draws on a diverse range of three principal reports, from academic and consultancy sources, and the World Wildlife Fund (WWF) - whose logo is a panda.

The reports reflect energy consumption in terms of kilowatt hours per hundred kilometres (kWh/100km), or litres per hundred kilometres (l/100km) for the petrol equivalent, but risk misleading the reader because there are no practical examples given of actual cars in both their electric or petrol versions.

In reality, electric cars are small and most petrol cars are larger, and comparisons for energy consumption are given typically in the form 20kWh/100km and 80kWh/100km respectively in the academic report. The latter figure may be unfamiliar because it is the conversion from a petrol consumption of 8l/100km, using the correct information that the energy available from petrol is close to 10kWh/l, when expressed in electrical terms.

Yet open any newspaper and you will see an advertisement for a small petrol car with a motorway consumption of 3.9l/100km (or 39kWh/100km). The consultancy report indicates a contrast between electric and petrol of 16kWh/100km and 60kWh/100km, but these are the outcomes of a computer software package that models the full life cycle of each car, with no underlying details being given.

To the casual reader, therefore, this would suggest that electric cars are much more energy-efficient. But calculations on carbon emissions show that the authors have considered the entire electricity supply chain -they have not stressed explicitly that so much energy is required to deliver the electricity, and this typically pervades the way the media presents electric cars.

Typically, from other government sources, it is known that on average throughout the UK only 36% (or just over one-third) of the energy available in the fuel at a power station is delivered as electricity to the end-user. Multiply the above kWh/100km figures for the electric cars by three, and the true total energy consumption can be estimated.

"It would seem that electric cars consume around three-quarters of the energy of a petrol car on this basis, but beware: these are not like-for-like comparisons," warns Dr Pike.

"Given that there are some small petrol cars, it is by no means clear that switching to electric will be more energy efficient, and switching to diesel could achieve comparable savings.

"With the current mix of fuels to provide electricity in UK power stations there would appear to be a small advantage in moving to electric cars because for the same amount of energy these generate, in total, slightly less carbon dioxide than petrol. This will only change more markedly with the conversion to nuclear and renewable sources of energy.

"But, crucially, subsidising the purchase of electric cars right now will have negligible impact on the carbon footprint of the UK, and represents a waste of public money.

"Better to invest more effectively in the low-carbon economy, recognising that the total of 250 million approaches one-half of the annual spend of the major research council that supports university research in chemistry, physics and mathematics."

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