Quote:
Originally Posted by Allch Chcar
...It's only to properly gauge everything else against Gasoline
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How is it "proper" to stack the deck for electricity? Or stay in the mental trappings of mpg and gasoline?
Quote:
Originally Posted by Allch Chcar
..We're comparing energy efficiency here not range per gallon.
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Not exactly. Range is part of the calculation and there is little contention there. main issues are:
1. Information is lost in the conversion to the "dumbed down" mpge figure.
you cannot discern the distinct fuel and electric contributions. This could have major effects on your cost per mile assumptions, or your expected environmental impact based on location specific factors and fuel preferences.
2. MPG was a horrible metric. Mass gives a consistent energy content for a given fuel (what planes use), gallons (volume) does not, we should kill mpg while we can.
3. and not least by any measure, Electricity has undergone it's major heat losses at the plant. It has well to walls efficiency of ~%30, where gasoline (possibly better for other liquid fuels like biodiesel) is considered ~%83 efficient. But electricity has not undergone the major carnot cycle transformations, so the deck is stacked for electricity in MPGe. If I take my "%41" efficient tdi, times %83, I get %34 efficiency out of my engine, whereas a %90 efficient electric motor (if it was plugged directly into the wall) would only be %27 efficient. This appears to be a fundamental flaw in the GREET model, there is not a good way to compare electricity (which has already undergone it's major heat loss conversion) to liquid (or gaseous or solid) fuels without looking at the full lifecyle.