Last Thursday, Tom Friedman again returned to his geo-green pulpit. Citing the Set America Free coalition, Friedman asserts that the solutions to our foreign oil addiction (and 500 miles to the gallon of gasoline) are “already here.”
Sounding remarkably similar to a Max Boot column in the LA Times (mentioned here on Gristmill in March), Friedman advocates the two-pronged approach of electric plug-in vehicles and flex-fuel vehicles. These powers combined result in 500 mpg.
My reaction: Flex-fuel? Great. Shifting our massive fleet of cars and trucks to run off of electricity? Maybe not so great. After all, don’t we get over 50% of our electricity from carbon-intense coal?
My resulting back of the envelope calculations are below the fold.
- Combustion of one gallon of gasoline: 8.9 kg of carbon dioxide emissions (found here and confirmed with some stoichiometry).
- One gallon of gas: let’s just say 20 miles for the average car.
- 20 mpg is also convenient because now we can directly compare with the HEV 20, which can go for 20 miles with a full battery, described in this report from the Set America Free website.
- According to that report, a mid-size SUV takes 6.3 kilowatt-hours of energy to fully charge the battery and thus go 20 miles; they also recommend charging it over 6.3 hours, not a minute ;-).
- Carbon emissions from electricity are somewhere between one and two pounds per kilowatt-hour; even coal is within this range.
- As far as nominal costs go, we’ll say a gallon of gas is US $2 and electricity 10 cents per kilowatt-hour, for round numbers.
Results:
- 20 miles with gasoline: 20 pounds of carbon emitted, $2 spent.
- 20 miles with electricity: about 9 pounds of carbon emitted, $0.63 spent.
(We seem to have a high percentage of semi-retired engineers reading, so if I’m off by an order of magnitude anywhere feel free to let me know.)
After doing that, I’m a little more convinced that both of Friedman’s suggestions are good ones; by those calculations we cut carbon emissions in half and reduce out of pocket costs by two-thirds just by using the electric charging method.
As a disclaimer, one thing that these calculations don’t include is the emissions that result from getting the coal out of the groud and to the power plant, and similarly, the oil out of the ground and refined into gasoline. Still working on that one — it’s a toughie to get numbers for.
A shift like that would also generate an increase in the demand for electricity, meaning more new plants built. I can’t imagine that these new plants will be built in the same 50%-coal ratio, especially if this amendment becomes law, which would drive that “emissions per kilowatt-hour” number down and the “cost per kilowatt-hour” number up, but 10 cents was high anyway.
