Yes, Coal Sucks

49% of our electric energy comes from coal according to this. Producing a kWhr of electricity from coal generates 2.1 pounds of carbon dioxide. Burning a gallon of gasoline generates 20 pounds of carbon dioxide.
So if that was the whole story, how much CO2 would a gas car produce and how much would an electric car produce to go the same distance?
A 30 mpg car will generate 20 pounds of CO2 to go 30 miles. A 50 mpg car will generate 12 pounds of CO2 to go 30 miles. A 30 mpg car is a little better than todays average car, and the best hybrids today dont quite get 50mpg. An electric car that uses 6 kWhr to go 30 milles would generate 12.6 pounds of CO2 and one that uses 8 kWhr to go 30 miles will generate 16.8 pounds of CO2. Mass market electric cars will fall somewhere in that range.
But thats not the whole story on the CO2 produced by using gasoline…
The fact that gasoline is around $3 a gallon and and 8 kWhr of electricity from coal is less than a dollar, shows that there are additional hidden energy costs used to produce the gasoline. That isn’t ALL oil company profit.
According to this it takes 8 to 12% of the energy in oil to refine it to gasoline. Thats about 150 to 220 kWhr of electricity for a barrel, and if it came from coal, then thats about 400 pounds of CO2 on the average. A barrel of crude oil yields about 19.5 gallons of gas and for the purposes of this question we can penalize all the gasoline with that CO2 ( ignore the other products of refining ), so an additional 20 pounds of CO2 per gallon of gas.
Most oil is imported, and a lot of it is imported from the middle east.
It’s difficult to find exact numbers on this but an oil tanker will burn about 1500 tons of bunker oil to move 100 million gallons of oil. ( A lot of calculations based on moving 250,000 tons of oil ( 2 million barrels ) transported 12000 miles based on numbers from here ) Those 1500 tons of bunker oil produce about 6000 tons of carbon dioxide.
Out of the 84 million gallons of oil you get about 40 million gallons of gasoline. 6000 tons of CO2 is about 12 million pounds. So transporting the crude oil from the middle east adds another quarter pound of carbon dioxide to the cost of the gasoline.
( Thats a lot less than I thought it would be )
The energy to mine and transport the coal to the power plant that burns it is probably on par with the energy to transport gasoline to your gas station considering that the coal doesn’t go nearly as far.
So now when we look back at a 50 mpg car generates about 24 pounds of CO2 to go 30 miles and a 30mpg car would generate 40 pounds, versus the electric car that uses 8 kWhr to go 30 miles and generates 16.8 pounds of CO2.
Considering all the hand waving and estimating I’ve done I think its pretty clear that an electric car is vastly superior to an average 30 mpg car but a good 50 mpg hybrid is close enough to need better analysis.
Of course if only 49% of your electricity comes from coal, then the electric car is probably a win over a 50 mpg hybrid.
Remember that all of this is only talking about carbon emissions, the fact that coal is a domestic supply is still a huge advantage even if the CO2 factor was ignored.

The silver lining to all this? Wind power production doubled in the U.S. from 2006 to 2008, and these old 2008 projections showed wind power to increase 45% in 2008. If wind continues to double every 2 years like this, we could have 20% of our electricity coming from wind by 2016. Every dollar spent on wind is high tech manufacturing and construction jobs, not money leaving the country. There is no reason that more investment in wind technology can’t accelerate this process. Electric cars give us the flexibility to use any new clean source of electricity as a replacement for gasoline.


3 responses to “Yes, Coal Sucks

  1. Maybe I’ve missed something. Your trip report says you went 850 miles on 250 kWhr of electricity. I calculate that as 3.4 miles/kWhr, which is nearly 9 kWhr for 30 miles. And that’s in a super-light, two-seater driven in economy mode.

    Is there some good data that suggests a typical family sedan is really going to get between 4 and 5 miles/kWhr?

    The other concern I have is that while carbon emissions certainly has been made popular as a proxy for all environmental costs, it’s not really valid in that role. Coal power plants have a wide variety of other environmental costs, in emissions as well as in extraction, never mind the direct health risks to coal miners, that would have to be included in a fair comparison.

    Don’t get me wrong. I’m no fan of gas-powered cars, even if that’s the only kind of car I own. I’m excited by the prospect of an electric future in transportation. I just think we should be careful to not over-sell the technology. If we could instantly switch our entire motor vehicle inventory over to all-electric, it wouldn’t magically make a variety of problems, including environmental ones, go away. We have other work to do in other areas before that happens (and to the extent that any consumption of any terrestrial resource causes environmental problems, some problems will never go away…all we can do is try to mitigate our impact).

    • highspeedcharging

      I just went and updated that post and added all the data I have on kWhr used during the trip, then calculated a better value than my guess. It comes out to 225 kWhr. Which is 3.78 miles per kWhr. ( Although I still don’t know what the charging loss is )
      There are several factors affecting the mileage.
      First, it was 100-110 degrees for most of our driving, we did the trip in the middle of a tremendous heat spell. We ran the air conditioning most of the time. Now air conditioning is a normal cost, but the heat taxes the Tesla more than other cars because Tesla chose high performance batteries that need to be cooled.
      The next factor is that these were all highway miles, and electric cars have far lower consumption at lower speeds. The Tesla is better city than highway, this data shows a pretty significant difference.
      That shows that at 47 mph the Tesla would get 5 miles/kWhr, and at 60 mph it would get 4 miles/kWhr ( under ideal conditions ).
      The last factor is that the Tesla compromises range for performance in its design, though because electric cars are very efficient its probably only 20-30% ( guesses, honestly ) compared to an econobox electric car as opposed to the 200-300% penalty comparing a Ferrari to an econobox gas car.
      The batteries are optimized for peak output rather than energy density, and carry around a little extra weight in the cooling system.
      Lastly the Tesla is the first electric car since the GM EV1, the technology has a lot of room to improve.
      I will survey my mile/kWhr numbers from my last few weeks of driving at home and make a post about the efficiency and then go and edit other musings with better numbers.

  2. If you’re concerned about the coal angle, note that those of us living in this area can sign up for PSE’s Green Power Program. All of my electric power (for my house, two electric cars and plug-in hybrid) comes from wind, solar and biomass. The cost is something like $15/month.

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