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Discussion in 'News' started by dpeilow, Dec 10, 2010.
Tesla Gets New “Green” Kudos. And Here’s How Prius Beat the Volt and Leaf
Looks like very biased numbers. How can the volt have more tailpipe emmisions than a prius? I say this because there is no accurate way to predict how the volt will be used.
Also there is no way that the fuel related emissions of the Leaf are going to be more than Prius which uses all of it's energy from gasoline.
Where do these people come up with this stuff?
From my understanding Leaf should have ranked 2nd. It has no tailpipe!!
I find the methodology not so clear-cut either.
The calculation includes the pollution due to manufacturing (a fixed, one time thing) but measures it "per year", so I suppose the lifetime of the vehicle should also be factored in. Seems you could tweak these numbers to show whatever you want. For example, is the air delivery of the Roadster gliders from the UK included? If so, how?
A lot of people use the DOE formula, but that is actually very outdated (from ten years ago).
I have done something similar with EIA data for the fuel rated part and it puts the Leaf slightly above the Prius when on the average US grid, instead of below.
The Leaf gets 34kWh/100miles combined.
Transmission losses are 5.872E12 kWh loss/ 100.350E12 kWh disposition = 5.85% as of 2008 (transmission efficiency is 94.15%).
Carbon emissions for the US average grid is 2.269508E9 Metric Tons CO2/3.950E12 kWh = 1.267lbsCO2/kWh (EIA, EPA 2009).
This gives 0.46lbs CO2/mile. Factoring in 19.4lbs CO2/gallon and 0.83 gas transport/refining efficiency, that gives equivalent emissions to a 51mpg gas car.
Hardest part to tell is the manufacturing emissions, that can only be very roughly estimated and when numbers are this close I'm not sure it is fair to be that dependent on it. It would be nice if they provided the tailpipe, fuel related, and manufacturing separately in order to see the bigger picture (and also be sure what kind of assumptions they made).
I wonder how one accounts for the "fuel related" pollution of an electric car without knowing the source of the electricity... And even if you know your source, how do you account for its total impact? For example, if your car is fed entirely by off grid solar panels (during the day, no buffer battery used), do you include the environmental impact of the manufacturing the panels? What about recycling the panels at the end of their life? The same is true for any form of electricity generation from coal plants to wind turbine to nuclear plants.
In short, where do you stop along the chain of manufacturing and energy supply when calculating the effect of a given product on the environment?
I posted the question: Do you consider the environmental impact of petroleum production? on his site at:
His response: Yes:
One of the easiest ways to call BS on the results is to compare the average compact tailpipe emissions to the Prius... The Prius does no better than triple the gas mileage that a standard compact has, if you burn the same kind of fuel and have the same miles traveled, the ratio of tailpipe emissions should be the same. making the priuses tailpipe emissions taller by this amount definitely would push it into third place.