Electric Vehicles: As Clean As The Grid Powering Them

By Antony Ingram

Antony Ingram

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How Green Is My Plug-In, illustration by Holly Lindem

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Electric vehicles are zero emissions, right?

That's a rhetorical question. As I'm sure most of you are aware, that statement is only correct up to a point. Most electric vehicle manufacturers, such as Nissan with their 2011 Leaf, are keen to point out that their vehicles produce zero tailpipe emissions, meaning only the cars themselves are zero emissions. But how clean is the electricity you're putting into the car?

EV detractors usually begin with a tired statement along the lines of, "But EVs do produce emissions, where do you think you're getting the power from? Hmm? HMM?".

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First 2011 Chevrolet Volt built on production tooling at Detroit Hamtramck plant, March 31, 2010

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If you live in California, your electricity is coming from many sources - the California Energy Commission provides figures for natural gas (45 percent), nuclear power (14.4 percent), hydropower (11 percent) and coal. A further 10.6 percent of California's power comes from renewable sources such as geothermal plants and wind farms.

Some states are obviously cleaner than others, but in many you don't get such a choice. Hydropower is pretty much ruled out in much of the Midwest, for example. Many states rely on either coal or nuclear, with coal being significantly less favorable as far as emissions are concerned.

Even if you do run your EV solely using coal power though, the emissions savings are significant over the average internal combustion car.

A popular term for the chain of  production for electricity or gasoline is known as the "well to wheels" study. The well to wheels chain for gasoline doesn't make for great reading...

You need to:

• Search for oil
• Set up a rig
• Drill for the oil
• Store it
• Transport it across the sea
• Refine it
• Transport it to a filling station
• Store it again
• Pump it into your car

According to the Natural Resources Defense Council, this process results in the typical gas-powered car putting out 465 grams of carbon dioxide per mile. But an electric car powered using the Californian grid produces a well to wheels figure nearer 142 grams per mile.

Elsewhere, with natural gas and coal more prevalent, the figure is nearer 214 grams per mile - still under half the amount of a gasoline car.

Dirtier coal and natural gas plants are getting cleaner all the time too, which brings us onto another advantage of EVs: "their" emissions will decrease throughout their lives, as the sources powering them become cleaner. As more energy is harnessed from renewable sources or nuclear power, well to wheels emissions will tumble.

EV owners take more of an active interest in where their power is coming from, too. Many have taken steps to reduce their home energy usage by fitting wind turbines or solar panels, and if you live in an area suited to either of these power sources, you might even find they produce enough power to make your EV completely zero-emissions. If you make enough electricity, you might even find you're able to sell it back to the grid.

This is the situation Steve Casner of Sunnyvale finds himself in - as an owner of a 2009 Tesla Roadster and an electric Toyota RAV4 EV (originally sold between 1997 and 2003, though there may be a new one in the pipeline), Casner uses solar panels to power his home. Although his cars are charged at night, the amount he generates during the day is enough to sell any excess to the grid.

"I can't make gasoline at my house, but I can make electricity," reasons Casner.

Interested in finding out more? British actor and television presenter Robert Llewellyn has a great summary of the benefits of EVs in the pilot episode for his show, Fully Charged.

FOR MORE INFORMATION: Green Car Reports,  IEEE Spectrum

[San Francisco Chronicle]