Electric vehicles to clean up Beijing? Depends on how they’re charged

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Although an electric bus smells a heck of a lot better than a diesel bus, it's obviously important to remember that electric doesn't really mean zero emissions unless your electric grid is fossil-fuel-free. You may have seen calculations showing that the equivalent miles per gallon of an electric vehicle varies in different parts of the US depending on the local mix of power plants. But a new study focused on Beijing shows that the devil is in even smaller details.

To help improve its incredible air pollution problem, China is pushing electric vehicles at the same time it increases the share of its electricity produced by renewables rather than coal, which has dominated. To see what effect this change would have, a group of researchers led by Harvard's Xinyu Chen modeled Beijing's transportation and electrical systems in a variety of scenarios for the year 2020.

When do you charge?

The base scenario proposed by the researchers included no electric vehicles, but they also examined cases in which the percentage of Beijing's electricity produced by wind ranged from zero to 40 percent. That equates to as much as a 29-percent cut in CO₂ emissions and a 14-percent reduction in nitrogen oxide air pollution. The interesting thing is how the various electric vehicle scenarios change those numbers.

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