Ask A Scientist© Environmental Science Archive

Name:    Michael
Status:  student
Grade:   9-12

Question:  Will battery powered cars use more or less fossil fuels? If they 
ever start mass marketing an economical electric car, where the individual 
plugs it in to charge it up at home, using electric power that is still mostly 
generated by burning fossil fuels, will this really be an improvement? guess 
it depends on the relative efficiencies of gasoline vs. battery powered 
vehicles. What do you think?
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Your intuition is correct. An electric car that is charged from a 
coal plant is not doing much for the greenhouse, acid rain, ozone pollution, 
etc. Natural gas is better and nuclear and wind are best. ANL scientists have 
looked at the economics of this and have reports. (circa 1992)

Mark Fernau
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Update:  July 2008
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In general, Electric Vehicles (EV’s) are better for the environment, but the full answer is 
complex. The EPA states “EVs are also more energy efficient and produce less noise than 
gasoline- or diesel-powered vehicles”. The National Energy Technology Laboratory (NETL) 
concluded in their study that roughly a 100% improvement in overall emissions can be expected. 
Tesla Motors produced a white paper* explaining why EV’s are not only better environmentally 
in “well-to-wheel” terms), but the cost-per-mile is lower, once the vehicle has been purchased. 
They also note that their EV is generally greener and more efficient than a Prius.

There are a few ways to understand all this:

(1) Electric motors are inherently more energy efficient than combustion engines of any kind. 
As the Dept of Energy says “Even if the electricity is produced from dirty sources electric 
vehicles remain cleaner than comparable gasoline-powered vehicles even when the electricity 
they use derives from polluting fuels like coal. The reasons are their high-efficiency electric 
powertrains and the fact that modern coal-burning plants make electricity more efficiently and 
with fewer emissions than they did in the past.” These benefits will multiply as older, dirtier 
power plants are retired.

(2) As the Dept of Energy explains: “Pollution is more easily controlled at a central electric 
generating source than at numerous mobile sources (vehicles).”

(3) Electric vehicles usually have regenerative braking, which is easy to accomplish in an EV 
(or hybrid). They also, like hybrids, don’t consume idle energy at stoplights.

(4) Electric vehicles will probably ultimately use less energy to manufacture, due to their 
simplicity. The Prius (a car I drive), due to its complexity, requires more energy to manufacture 
than a Hummer, and it takes a couple years of good fuel economy to offset this. An EV, by 
contrast, can be quite elegant. For example, the Tesla Roadster is now shipping without a 
transmission or clutch (reverse is achieved electrically), no plugs, ignition, air filter, 
emissions control system, catalytic converter or muffler, crankcase oil and filter, starter, 
alternator, regulator, belts or chains. Just an engine alone has hundreds of parts, whereas an 
elec motor has only 1. And this means less oil and filters and other parts going into the 
landfill every year. Due to regen braking, brake pad wear is even less (less airborne brake pad 
particulate). You can see that there are many hidden benefits to an EV.

(5) There has been criticism of lead-acid and NiMH batteries used in EV’s (and the Prius, so far),
but newer EV’s (e.g., Tesla) use Li-Ion, found abundantly in laptops and cell phones, and 
battery 
recycling programs are in place.

(6) Tesla is encouraging their EV customers to purchase a companion house-top solar panel, 
which can’t generate energy for night-time charging (EV’s usually charge at night), of course, 
but will create a clean energy offset during the day.

(7) As a side benefit, EVs reduce dependency on foreign oil, and thus perhaps military conflict, 
which is hard on the environment.

The new breed of EVs is not cheap, but Tesla is targeting a ~$30K model for the rest of us in 
2012, and I presume others will follow suit. This is not all just a "plug" for Tesla, I just 
know something about them, and they are the only freeway-speed production EV in the U.S. as of 
2008.

Http://www.teslamotors.com/display_data/twentyfirstcenturycar.pdf

P. Bridges
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