Saving carbon with electric cars

Electric cars are generally greener even if grid electricity is used, and the calculation is easy to perform

Terrence Rook asked in the last issue of PE why electric cars are promoted as a means of saving carbon. 

Electric cars are generally greener even if grid electricity is used, and the calculation is easy to perform. Real time and average data on the carbon intensity of the UK grid is available from www.realtimecarbon.org. At the time of writing 1kWh caused 555g of CO₂ to be emitted, which is about average. A Nissan leaf will typically go 150km on a charge of it's 24kWh battery, which works out at 88 g/km travelled. Seat Ibiza Ecomotive supposedly gets 93 mpg (more like 70mpg) on the motorway and it's supposed to emit 92 g/km. Taking into account the fact that anyone who feels the need to buy an electric car is probably on a green tariff (I'm with Ecotricity on a plan where my electricity consumption is matched with wind energy going into the grid) and the cars look better overall.

Terrence is right that the batteries are not environmentally friendly; they result in 30% more CO₂ being emitted than an ICE car during production (Swiss Federal Laboratories study). This has been shown to be offset during use, resulting in a 57% reduction in lifetime CO₂ (even with the relatively dirty electricity mix used in the Swiss study... 593g/kWh). Well worth running the numbers... a lot of rubbish gets printed in the papers on this subject!

Peter Greaves, Newcastle upon Tyne

Next letter: SI units are now the norm