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Old 06-14-2010, 11:41 AM   #10 (permalink)
RobertSmalls
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Quote:
Originally Posted by NeilBlanchard View Post
7.5kWh of electricity could move and EV anywhere from 30 to 60 miles or so.

If you put the gasoline in a car that get the national average of 25mpg, you only go 25 miles -- and you should also count the 7.5kWh against that, too. Which lowers the MPGe of the ICE car even further; and it raises the carbon emission to levels far higher than the EV, obviously.[/B]
This is an unfair comparison. An "average" person driving an electric midsized sedan or SUV at 75mph with the A/C on would not be getting 125-250Wh/mi. If you wanted a fair comparison, the best we have available would probably be a Prius (or a PHEV converted Insight or Tahoe?) driven in EV mode, versus the same car driven the same speed on gasoline.





I found the following source: http://www1.eere.energy.gov/industry...fs/profile.pdf
with the relevant info starting on p 19. It mentions that refining represented 7% of the US' energy consumption in 2002. Unfortunately, it doesn't mention how much energy and non-energy products refineries put out that year, so it doesn't give an efficiency number. But it's still worth reading:

64% of the energy used in refining comes from the refining process itself. When refinery gas is burned in a turbine to generate electricity that is used for refining, it is completely wrong to assume this energy could be used to power an EV. Without refining, this energy would be unavailable. Another 22% comes from natural gas, which is often, but not always, mined alongside crude. 12%, or 225 billion KWh, comes from purchased electricity. That's enough for 250 million EV's to drive three thousand miles a year, which is a quarter of what is currently driven.

Maybe we could get where we need to be by halving our fleet average fuel consumption AND halving the number of miles driven?

But the output of the refining process is more than just gasoline for cars. There's also non-energy products, diesel, and other fuels. I look forward to the day when trains, trucks, and airplanes run on renewable, low-carbon electricity (which we don't have), but we're not there yet.

If refining took more energy in than it put out, people would stop doing it. But until contradicted by citation of better sources, I'm going to stick with the DoE's numbers, as I mentioned here: 83% efficient.




I'm going to point a finger at the editor of this EVWorld article and accuse him of either intentionally creating a misleading piece, or having a serious disconnect with reality. A fleet of electric vehicles are not viable given our current usage profile, and shutting down the refineries would not come close to providing enough energy to meet our needs. He is also wrong that PHEVs' only role is to "allow the hybrid drivers to relieve some guilt and feel better about themselves". PHEVs are a stepping stone that will drive the development of plug-in infrastructure, and their liquid fuelling capability makes them viable for one-car families. I believe the author also ignored the 80-something percent efficient charger and ~92% efficient battery (if the Wh/mi figures are at the battery rather than the wall).

I stand behind my 13.4KWh/gal energy equivalence figure, with the caveat that energy equivalence is a poor figure of merit. I suggest a weighted average of energy equivalence, cost equivalence, and CO2-equivalence (at 15.1KWh/gal for grid average). I've still been unable to calculate the carbon footprint of the renewable electricity my utility buys for me, but I know it's not zero.
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