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Thread: Carnegie Mellon Study, on EVs and cost / environment

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    Carnegie Mellon Study, on EVs and cost / environment

    I came across an article on a Carnegie Mellon Study that shows that plugin hybrids make more environmental sense than electric vehicles.

    Tesla Motors Pollutes Today for a Greener Tomorrow - TheStreet

    It would be nice to have a solid response to this, by understanding the study and seeing where the holes are, if there are any.

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    Member ToddRLockwood's Avatar
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    Here's a 2010 Swiss study that directly contradicts the Carnegie Mellon Study...

    Contribution of Li-Ion Batteries to the Environmental Impact of Electric Vehicles - Environmental Science & Technology (ACS Publications)

    "The study shows that the environmental burdens of mobility are dominated by the operation phase regardless of whether a gasoline-fueled ICEV or a European electricity fueled BEV is used." In other words, the environmental impact of Li-Ion battery manufacturing is insignificant compared to power plant pollution from charging electric vehicles. And as we already know, even in places that generate electricity exclusively from high-sulphur coal, the environmental impact of the Model S is still less than a gas-powered car driven the same distance.
    Last edited by ToddRLockwood; 2012-11-08 at 06:35 AM.
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    Senior Member dhrivnak's Avatar
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    In looking at the CMU study I found a few flaws. First they compare against the Prius, a great car and low emissions but hardly the average car. They use a battery cost between $625 and $850 and Tesla is under $500. Then I am not sure they are properly accounting for battery production. Here is an excerpt "a materials-based assessment is performed for battery manufacturing, including lead-acid (plastic, lead, sulfuric acid, fiberglass, water), nickel metal hydride (NiMH)". Today's electric cars do not use lead batteries and we know lead is particularly nasty.They use a "the high case assumes all electricity is from coal". Nowhere are we 100% coal and I cannot imagine a case where we will be all coal. The majority of the air pollution costs for the electric vehicle is from SO2, not a good pollution, but it only comes from coal, a power source that is in decline. They also appear to assume battery production is 100% coal powered as half of the pollution cost of the battery is SO2. Again I am unsure making lithium batteries makes that much SO2. Finally they assume $30,000 on battery replacement costs on a BEV that has 150 mile range. I can't imagine that a new battery for Tesla 40 KWH pack would cost $30,000. I am sure they are plenty of other "errors" in the study.

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    Model S VIN P01536 Robert.Boston's Avatar
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    My comment:
    The Carnegie Mellon report states: "We find that, in the base case, plug-in vehicles (PHEVs and BEVs) may produce more damage on average than today’s HEVs. This fact is due in large part to SO2and GHG emissions from coal-fired power plants."
    Clearly, the problem is NOT about EVs; it is about the mix of generation resources on the electric grid. What the authors (both of this article and the Carnegie Mellon piece) ignore is that the grid's sources are becoming much cleaner. In 2007, half of the US's power came from coal; today it's about one-third. Continued advances in displacing high-carbon sources on the grid will continue to make EVs a better choice for environmental reasons. But cars that use gas are stuck, forever, with their high-carbon footprints.

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    Model S P85 (#2817) PureAmps's Avatar
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    A discussion was started on this already in another thread (Anti-Tesla Gibberish), but got side tracked by a discussion on conflict of interest (my fault).

    The main problem with the CMU study (IMHO) is they are attempting to place a dollar value on "environmental damage" of emissions. Unfortunately, this is not something one can easily calculate, but they attempt to anyway. For example, they assign a $6 million value to each statistical (presumably human) life in their morbidity and mortality calculations for various pollutants. They then then use that along with actual measurable costs of raw materials and fuel to calculate a cost associated with the production and operation of a vehicle over 12 years and draw their conclusions. I have questions about their emissions model for battery pack production, but don't really have time to dig into that.

    They have also stacked the deck against the BEV by including only a 240km battery pack which is quite costly compared to the smaller packs in the plug-in hybrids. They are using a vehicle driving range model which favor shorter distances, so 240km is probably too much range for typical use in their model. If they had included a 120km pack similar to the Nissan Leaf, then the Leaf equivalent would have most likely had the lowest costs across the board. Curiously, this additional (and more appropriate) BEV pack size was omitted even though they modeled two battery pack sizes for a plug-in hybrid (20km and 60km).
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    Model S P85 (#2817) PureAmps's Avatar
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    Another comment from Jack Burgess posted on JB's street.com article:

    The cited Carnegie Mellon study was based on the Saft VL41M Li-ion battery cell that has a specific energy after charge of 136 Wh/Kg. All costs of the Li-ion batteries in the study were on a weight basis. The BEV240 case vehicle was modeled with a 66.1 kWh battery pack. So, the weight of the Li-ion cells in the BEV240 would have been (66.1 kWh) * (1000/k) / (136 Wh/Kg) = 486 Kg.
    The Model S's Panasonic Li-ion battery cells have a specific energy after charge of 240 Wh/Kg. Doing similar calculations, the weight of the Li-ion cells in the Model S's 40 kWh battery pack would be 167 Kg; the 60 kWh Battery Pack, 250 Kg; and, the 85 kWh battery pack, 354 Kg. So, the BEV240 case vehicle's battery costs overstated the Model S's 40 kWh battery pack costs by 191%; the 60 kWh battery pack costs by 94.4%; and, the 85 kWh battery pack costs by 37.2%.
    Also, with all of our electronic gadgets, there is an enormous amount of battery R&D at this time. Li-ion battery manufacturers are projecting annual energy density increases of 8-10% for the next several years. If we follow the methodology of the study and base all battery costs on a weight basis, we could possibly see battery costs decreasing fairly rapidly & for the Model S, this is starting from a much better cost basis than BEV240 case vehicle.

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    Completely discredited the CMU study on seeking alpha. If you really read the study and picked it apart, all I have to say too many fudge factors

    Dan Fichana's Instablog - Seeking Alpha

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