Marginal power

[Norbert]

Probably. Please target Norbert if you are so inclined, he's closer to you, fewer emissions from travel.

But it would be using unsustainable energy.

 

[Jason S]

Extraction for conventional petroleum extraction is 92% efficient, Alberta oil sands 82-86% efficient, http://fossil.energy.gov/programs/reserves/npr/Energy_Efficiency_Fact_Sheet.pdf
refining 90% efficient,
http://www.transportation.anl.gov/pdfs/TA/635.PDF
Notable is the loss of efficiency projected for the future of extraction.

That's extraction and refining. What about transportation to your local station (varies, I'm sure, but not everybody has a refinery in their local area)? And how about transportation from the extraction point to the refining point? I imagine some big losses could come from those, and I also imagine those numbers are included in the efficiency percentages for electricity.

But if the transportation costs aren't included for electricity either then I suppose it is a fair comparison.

 

[Norbert]

But if the transportation costs aren't included for electricity either then I suppose it is a fair comparison.

I'd think that "transportation" for electricity is mostly line losses (especially for night charging), which JRP3 did include in his calculations.

 

[Jason S]

Well, for Coal and NG plants there has to be some cost in getting the Coal and NG to the plant itself.

Wind and Solar would be free of transportation costs to the 'plant'.

Nuclear has some costs to/from the plant to deal with the undesirable outputs.

 

[JRP3]

I don't know if the links I provided include any transportation losses for petroleum, but the GREET model does, so any analysis using GREET includes all losses. I would take a wild guess that transportation would only add a 1% hit or less to the petroleum chain if it's not already included.

 

[Jason S]

1% seems reasonable upon reflection -- 1 in 100 gallons. An oil tanker or pipeline prolly doesn't use more than that, ditto for tanker trucks. I suppose we can call those loses 'in the noise' for the rough estimates we're doing here.

 

[Norbert]

Considering those numbers, I'd wonder if the cost of gasoline, compared to that of electricity, is mostly in profit.

 

[Robert.Boston]

FWIW, I have marginal carbon intensity figures for each location on the Eastern Interconnection, hourly. (Marginal carbon intensity = change in carbon resulting from a 1 MW change in load). MCI is neither cheap nor easy to calculate, and we use it for our commercial consulting to major energy buyers (e.g. server farm owners).

 

[JRP3]

I'm guessing you can't share that data. If not can you possibly give a general impression of marginal emissions changes that might happen with added night time load?

 

[Robert.Boston]

There are indeed times and places--fairly commonly in the Midwest and Mountain states--where marginal load is 100% coal. I don't have percentages, though that would be an interesting white paper to write.

 

[Jason S]

10 gallons of gas at 33kwh equivalent per gallon is 330kwh. The entire petroleum chain from well to tank is about 80% efficient, so that means 20% is used to produce the final product, so the 10 gallons took 66kwh of energy, (not electricity). Now don't forget that the 85kwh's of electricity in a battery pack started out as a lot more energy than that using a generous 40% generating efficiency, (marginal power is probably lower), plus 93% transmission efficiency, a generous 90% charging efficiency, and not to mention the drilling/mining energy inputs, which I don't have the figures for. You have to apply equal criteria for all inputs when comparing gas to electricity.

I've figured out what bothers me most about these figures: 33kwh equivalent per gallon.

How did that number get figured? I know of no way to convert 1 gallon of gasoline to 33kwh of electricity. There are enormous losses involved in any conversion of gasoline to electricity so the number must be something like the amount of work a gallon of gas can do ... like power a car. If that's the way the equivalency is developed then no wonder all the math ends up with them equivalent. You come up with a more efficient car than the average car the equivalency was developed on and bingo, the more efficient car is more efficient.

 

[Norbert]

I've figured out what bothers me most about these figures: 33kwh equivalent per gallon.

How did that number get figured? I know of no way to convert 1 gallon of gasoline to 33kwh of electricity. There are enormous losses involved in any conversion of gasoline to electricity so the number must be something like the amount of work a gallon of gas can do ... like power a car. If that's the way the equivalency is developed then no wonder all the math ends up with them equivalent. You come up with a more efficient car than the average car the equivalency was developed on and bingo, the more efficient car is more efficient.

The number is 33.7 kWh (EPA), and while I don't know exactly how it is measured or calculated, I expect it to correlate to the amount of heat (=energy) you get when you burn gasoline as completely as possible. Most of the inefficiency in a car is lost as heat (and friction, which also becomes heat).

 

[stopcrazypp]

I've figured out what bothers me most about these figures: 33kwh equivalent per gallon.

How did that number get figured? I know of no way to convert 1 gallon of gasoline to 33kwh of electricity. There are enormous losses involved in any conversion of gasoline to electricity so the number must be something like the amount of work a gallon of gas can do ... like power a car. If that's the way the equivalency is developed then no wonder all the math ends up with them equivalent. You come up with a more efficient car than the average car the equivalency was developed on and bingo, the more efficient car is more efficient.

33.7kWh represents the energy contained in a gallon of gas (as specified by the EPA: http://www.fueleconomy.gov/feg/evsbs.shtml). It would be what you would get if you were able to convert a gallon of gas to electricity at 100%. You will see slightly different numbers (energy in a gallon of gas varies with temperature, pressure and the specific mix you get), but in general that number is correct.
To figure that number out you use something like a calorimeter:
http://en.wikipedia.org/wiki/Calorimeter

Gasoline refining efficiency is 89.7% (including all products), 86.2% (excluding less desire-able products). So what JRP3 says in general is correct (can't assume energy used to refine a gallon of gas can be used to power an EV for the same miles).
http://www.transportation.anl.gov/pdfs/TA/635.PDF

In general for such energy comparisons, the GREET model is the best resource (uses unbiased methods and examines the entire fuel chain):
http://greet.es.anl.gov/

 

[JRP3]

Right, we aren't looking to actually turn the gallon of gasoline into electricity, just using the potential energy value to calculate production losses.