Thinking about electric vehicles

Electric vehicles reduce noise and local air pollution, such as nitrogen oxides, particulate matter and ground-level ozone, but do they simply relocate the carbon tire-tracks to fossil-fired power stations or are there benefits on the global scale?

Fundamentally, an electric engine can achieve 85 to 90% energy conversion efficiency, which contrasts starkly with the internal combustion engine, which can achieve at most 20%, requiring the conversion of oil-derived fuel (diesel or petroleum) into mechanical motion. So, there it might just be possible that electric vehicles could be greener, but only if the carbon tire-tracks are smaller when all energies and emissions are added into the equation.

Åsgeir Helland of Think Global AS (manufacturer of the Think City electric car), based in Snaroya, Norway, thinks so. He has carried out a “well-to-wheel” carbon dioxide analysis of the usage phase of electric vehicles compared with vehicles using an internal combustion engine. His study confirms that electric vehicles do indeed relocate the carbon emissions from the transport sector to the electricity sector. Of course, as electricity generation becomes increasingly based on renewables that will matter less.

Nevertheless, Helland’s research shows that urban driving leads to total carbon emission reductions from 30 to 95% depending on the country in question. “In rush hour the electric vehicle outperforms all other fossil-fuelled alternatives even if charged on electricity from hard coal,” says Helland.

Now, I know this blog is all “science part”, but here’s a bit of data just to rev up the date. At the fuel station, the associated well-to-tank emissions for the supply of 1 litre of fuel are almost 0.5 kg (478.5 g) for petroleum (gas) and 420 g for diesel. The carbon dioxide emissions per litre of fuel combusted are 2.4 and 2.7 kg for petroleum and diesel, respectively. The total emissions associated with consuming 1 l of fuel were 2.88 kg for gasoline (0.48 kg/l + 2.40 kg/l) and 3.08 kg for diesel (0.42 kg/l + 2.66 kg/l).

An electric vehicle, exemplified by the Th!nk City car, will reduce global carbon dioxide emissions compared with internal combustion engines. “This is true for all countries and urban driving patterns regardless of the electricity mixes analysed in this study,” Helland says, “For urban driving, the reductions amount to about 95% in Norway, 90% in Switzerland, 40 to 60% in the UK, and 30 to 50% in the Netherlands.

There are 215 million cars in the European Union with average emissions of some 160 grams per kilometre and related well-to-wheel emissions of 186 g/km. Replacing only 10% of the European car fleet would reduce the yearly carbon dioxide emissions to almost 50 million tonnes with a relatively modest increase in electricity generation requirements.

“The electric vehicle outperforms all internal combustion engine alternatives if charged on electricity from a renewable source,” concludes Helland, “Moving from a combustion engine to an electric engine for vehicles will be a necessary change to reduce the impacts of transport on climate change. The electric vehicle’s environmental benefits are significant.”

But, then he would say that…

What are you thoughts, are electric vehicles an environmental panacea or do we need a paradigm shift in attitudes towards transport?

Research Blogging IconÅsgeir Helland (2009). Well-to-wheel CO2 analysis of electric and ICE vehicles: are global CO2 emission reductions possible? Int. J. Global Warming, 1 (4), 432-442

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Award-winning freelance science writer, author of Deceived Wisdom. Sharp-shooting photographer and wannabe rockstar.