4/18/2010

Redoing those MPG rules for Electric Cars

I thought that the 230 mpg estimate for the Chevy Volt and the 367 for the Nissan Leaf made little sense, but at least I was hoping that it was a way to mitigate the even dumber increase in company average mpg requirements. Selling a few Volts getting 230 mpg could have gone a long ways over coming the big increase in mpg rules imposed by the Obama administration.

When the figures came out, many observers argued that they presented an inflated and meaningless comparison for consumers looking to measure the efficiency of battery-powered cars against their gas-powered counterparts. The extent of backlash took the agency by surprise, the people familiar said.

The mileage expectation reflected a new methodology for electric and plug-in hybrid cars that factored in electricity used to try to reach a miles-per-gallon equivalent. The intent is to allow consumers to measure the vehicles against traditional gasoline-powered ones. The final figures will do the same, but the EPA is trying to come up with better ways to compare electric power with gasoline.

To calculate a miles-per-gallon figure for a vehicle that runs either partially or fully on battery power, GM had cited an EPA formula that attempts to convert electric-energy consumption into a gasoline equivalent. The Department of Energy process cited by Nissan considers 82 kilowatt hours of electricity to be equivalent to one gallon of gasoline. . . .

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3 Comments:

Blogger Al B. said...

How to compare energy expenditure for electric cars vs. gasoline-powered cars? The mind boggles!

For example, how many kilowatt-hours of electricity does it take to increase the charge in an electric car by 82 kilowatt hours? Is the charging efficiency affected by the ambient air temperature, size of the battery, voltage (i.e., 120v vs. 240v) at which the battery is charged? Is the efficiency of energy expenditure affected by variations in usage, e.g., the size, weight and shape of the car, the speed at which the car is driven, ambient air temperature, the size and efficiency of the motor, how low the charge of the battery is allowed to get (as the charge of the battery drops, the battery’s internal resistance increases, causing the effective voltage to drop), etc.?

Then there are economic considerations, e.g., the cost of gasoline vs. the cost of electricity in a particular region of the country, the cost of the vehicles themselves, the life expectancy and replacement cost of the battery, cost of maintenance, life expectancy of the engine, etc.

Then there are secondary effects, e.g., changes in usage caused by having your vehicle plugged-in and unavailable for 12 hours a day, the impact of large numbers of cars on the electric utility transmission and distribution grids (need for more generation capacity, more transmission capacity, more distribution capacity, etc.). Would we need to convert our homes from 200 amp service to 300 amp service, for example?

I’m sure that an engineer who specializes in this kind of thing could come up with a few dozen more degrees of freedom that haven’t occurred to me. Trust our experts in the EPA to come up with a metric that favors their political agenda, however.

Arrrghh!

4/19/2010 1:23 PM  
Blogger Net said...

One option is to buy a used vehicle that somebody else has converted to an electric vehicle.






Convert car to electric

5/14/2010 6:59 AM  
Blogger Term Papers said...

One option is to buy a used vehicle that somebody else has converted to an electric vehicle.

5/28/2010 5:30 AM  

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