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Old 05-01-2009, 12:41 AM   #101 (permalink)
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Ernie I have no clue where those numbers supposedly came from(Greet model got it).

But its pretty simply just not right. If you burn a tank of crude(43 gallons) you get roughly 2x as many BTUs as you get burning the diesel and gasoline that come off(if you add in the various other parts like Kerosene you start getting closer to 100%).

Then you have to add in the amount of juice required to refine the gasoline and everythng else. Just to get the gas out it takes 133 kwhrs.

Automatically by this point with just the electricity added in you are way lower than 80%. . . If you add in that alot of the crude is turned into CO2 then you are even lower than that. If you also add in that 49.5% of the electricity created was created at 40% efficiency. . .

well you get the idea.

This is not arm waving. Pick a refinery. divide gallons of output by electrical consumption. I don't care about what it theoretically takes or in a test-bed because my gasoline comes from Texas in a production refinery, so its really the only relevant piece of data.

They brag about their output of each part per barrell of crude and their electrical consumption.

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Old 05-01-2009, 01:57 AM   #102 (permalink)
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Quote:
Originally Posted by Ernie Rogers View Post
There has been a lot of talk about efficiency of production for gasoline and electricity. I thought it might be nice to add some numbers to the discussion.

The numbers I am listing are the percent efficiency, energy in the "fuel" divided by the total energy to produce it, from Greet 1.7 (2005). There may be later values, but I doubt they are much different. ANL gives two sets of numbers, for California, and average for the whole U.S.

WELL-TO-PUMP OR MINE TO PLUG EFFICIENCY

.........................Calif........U.S.
Electricity...........45.9%.....38.1%
Gasoline (RFG).....80.7........80.8
Diesel #2............82.8........82.6

I can look up efficiency for other fuels if people are interested

Ernie Rogers
At least ANL acknowledges the right form of the problem. Yet they still support the idea of calculating MPGe from the plug to wheels for electric operation.

But if we can ignore that, it looks like even these numbers for electricity production efficiency are simple averages for Calif and U.S. and it looks likely that they ignore the marginal response to incremental loads which is the appropriate way to think.

Is there a detailed reference on these? I will try searching greet 1.7.
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Old 05-01-2009, 02:19 AM   #103 (permalink)
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Quote:
Originally Posted by trebuchet03 View Post
I don't think it is trivial (I think I posted a link to the refinery consumption figures the other day)... But in context of comparing one car to another... It isn't particularly useful - especially when attempting to attract more drivers towards better driving habits.
In that context, neither is including the energy efficiency of electricity production, since what's useful is comparing the energy consumpion of different EVs. If we're comparing total energy consumption, or even relative GHG emissions, between EVs and conventional vehicles, then we need to go off a well to wheels analysis, which definitely adds a bunch of steps, and varies depending on region, but that's just how it is.
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Originally Posted by trebuchet03 View Post
I'm with dcb's motion Because to what end? Can the next discussion be on a conversion factor for motorcycles because they use less tires and therefore there's less tire manufacturing cost/pollution/recycling? It's not that I don't enjoy the discussion (I do) - it's just that every page adds another nuance in the chain
Based on what I've seen, motorcycles eat tires about twice as fast as most cars do, so no, you can't use a conversion factor for 'em.
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Old 05-01-2009, 03:47 PM   #104 (permalink)
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Just the facts, ma'm

Hello, Unchosen,

It takes a lot of work to dig through this stuff. Maybe you would like to help. Here is a good report with part of the information--

http://www.transportation.anl.gov/pdfs/TA/339.pdf

On page C-3 in the appendix, there is a breakdown of how much energy is consumed (used up) in making 1,000,000 BTUs of gasoline. It gives 79.8% as the energy efficiency of making gasoline. (50 percentile value.)

The report promises to give you further detail if you look in an earlier report--

General Motors, and others, Argonne National Laboratory, 2001

This report is at the ANL web site but I didn't find it. It tells you exactly how much of each ingredient goes into making gasoline, and how the energy is allocated over different products in the refinery.

Ernie Rogers

Quote:
Originally Posted by theunchosen View Post
Ernie I have no clue where those numbers supposedly came from(Greet model got it).

But its pretty simply just not right. If you burn a tank of crude(43 gallons) you get roughly 2x as many BTUs as you get burning the diesel and gasoline that come off(if you add in the various other parts like Kerosene you start getting closer to 100%).

Then you have to add in the amount of juice required to refine the gasoline and everythng else. Just to get the gas out it takes 133 kwhrs.

Automatically by this point with just the electricity added in you are way lower than 80%. . . If you add in that alot of the crude is turned into CO2 then you are even lower than that. If you also add in that 49.5% of the electricity created was created at 40% efficiency. . .

well you get the idea.

This is not arm waving. Pick a refinery. divide gallons of output by electrical consumption. I don't care about what it theoretically takes or in a test-bed because my gasoline comes from Texas in a production refinery, so its really the only relevant piece of data.

They brag about their output of each part per barrell of crude and their electrical consumption.
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Old 05-01-2009, 04:05 PM   #105 (permalink)
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Quote:
Originally Posted by roflwaffle View Post
If we're comparing total energy consumption, or even relative GHG emissions, between EVs and conventional vehicles, then we need to go off a well to wheels analysis, which definitely adds a bunch of steps, and varies depending on region, but that's just how it is.
Based on what I've seen, motorcycles eat tires about twice as fast as most cars do, so no, you can't use a conversion factor for 'em.
This is why I keep posting that the problem isn't the method so much as it's the metric.

MPG is nowhere near total consumption. It is, however, an easily understood metric by non experts. If we want to consider total consumption - the site would need to change to a more appropriate metric which, I feel, would alienate potential newcomers.

I understand that if we wanted total consumption, we need well to wheels - but well to wheels is a bit off topic based on the OP (but a good topic either way)


Quote:
Based on what I've seen, motorcycles eat tires about twice as fast as most cars do, so no, you can't use a conversion factor for 'em.
Shows I'm not a motorcyclist But I think the point is taken
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Old 05-01-2009, 04:45 PM   #106 (permalink)
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Under advice from someone here I went to the ANL site and then the report at
http://transportation.anl.gov/pdfs/TA/559.pdf

This is a recent and thorough study that works out the CO2 and petroleum saved with conclusions shown in Fig. 24. This is no easy read, but it clearly states that the "Regular HEV" causes GHG Emissions that are about the same as the PHEV40 charging from the Illinois mix and and slightly higher if that PHEV40 charges from the US Ave. mix. The difference is greater if they assume the California mix. I disagree with thier idea of marginal response. EPRI also disagrees. I disagree with EPRI as well. But the differences are not terribly important. Ignoring my opinion, the gain from making a hybrid into a plug-in are still not all that much.

ANL persists in reverting to the wrong question in their conclusion, by comparing the plug-in hybrid results with the conventional car results. Thus they can make the plug-in seem like a big improvement. They never address the relationship with the hybrid that nobody fooled around with.
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Old 05-01-2009, 10:23 PM   #107 (permalink)
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No good answer

I think this thread is proof that there is no good way to compare oil burners & EVs
it is obvious our world views preclude agreement (opinion based math?)
whatever standard you pick will make people mad


leave MPG for oil burners and move the EVs to their own standard
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Old 05-01-2009, 11:31 PM   #108 (permalink)
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Quote:
Originally Posted by Concrete View Post
I think this thread is proof that there is no good way to compare oil burners & EVs
I think there is a fairly reasonable way to compare: start from the other end and do it experimentally. Find someone (or better, several someones) who've done EV conversion on say a Geo Metro. Find the same model that's unconverted, have them both drive a measured course keeping same speed &c, and for best results swap drivers in the middle.

Divide gallons used by KWh used, and there's your conversion factor. You can use that to work backwards through the supply chain to get total efficiency.
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Old 05-02-2009, 12:55 AM   #109 (permalink)
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Good idea, James

Hey, good idea, James,

There is an alternative. I can do this comparison analytically. I just put the parameters for each kind of car into the program.

Here are parameters you could consider--

Gasoline engine efficiency.......30% (to the shaft, good for a Prius)

EV efficiency, plug to shaft.....70%

My reasoning on this: charger, 95%; battery, 85%, controller, 95%, motor, 90%........... 0.95 x 0.85 x 0.95 x 0.90 = 0.69, close enough.

Feel free to correct me, either upward or downward.

I usually use 85% for transfer from the motor shaft to the wheels, and would use that for both cars unless you want to adjust it for the EV.

The cars may be about equal weight, or the EV with batteries could be slightly heavier, you can suggest values.

All other design parameters should be the same, like rolling resistance coefficient and drag coefficient. I don't correct for stop-and-go driving effects, making the results more appropriate for comparison of an EV against a hybrid with comparable regen capability.

Okay, if the numbers to be input are agreeable, then I can do a comparison calculation and report back. I will supply the program for others to try if you want.

Ernie Rogers

Quote:
Originally Posted by jamesqf View Post
I think there is a fairly reasonable way to compare: start from the other end and do it experimentally. Find someone (or better, several someones) who've done EV conversion on say a Geo Metro. Find the same model that's unconverted, have them both drive a measured course keeping same speed &c, and for best results swap drivers in the middle.

Divide gallons used by KWh used, and there's your conversion factor. You can use that to work backwards through the supply chain to get total efficiency.
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Old 05-02-2009, 01:17 AM   #110 (permalink)
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I don't *think* I need a program to show me how to multiply by 3/7ths, but thanks anyway Ernie

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