Need some tech help here: Is an EV really cleaner than a gas car?

Discussion in 'Nissan/Infiniti Hybrids and EVs' started by Analogkid1958, Sep 4, 2011.

  1. Analogkid1958

    Analogkid1958 Member

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    I test drove a Leaf Friday (really liked it, but it doesn't fit my 110 mile, all-weather interstate commute mission) and am writing a blog post about it and EVs in general. I was testing my hypothesis that the power from the power plant used to charge the EV would be cleaner than the power a gas engine would produce, so I did some research and math...

    "...the power plant emissions per Leaf mile will be far less than the tailpipe emissions of a typical gas-burning car going the same distance. The EPA shows EV mileage a couple different ways, the first being in MPGe – miles per gallon of gasoline equivalents, with the energy content of gasoline being 33.7 kilowatt-hours. According to a US Department of Energy paper US coal-fired power plants typically produce 1.34 pounds of CO2 per kilowatt-hour of generation. A gallon of gasoline produces 19 pounds of CO2 when burned, so:
    19 #CO2 / 33.7 kwH = 0.56 pounds CO2 per kilowatt-hour per gallon of gasoline burned"
    You see my problem - based on average values, burning gasoline in a car is cleaner than burning an energy-equivelant of coal! That said, why would I bother having an EV from a purely environmental point of view?
    Can someone help me with this? Thanks!
     
  2. bisco

    bisco cookie crumbler

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    because, in the future, we can create electricity in environmentally friendly ways and there is no limit to the supply. so, we move ahead with an electric based economy, hoping the powers that be (no pun intended) will lead us in that direction instead of oil/coal/natural gas generating systems.
     
  3. john1701a

    john1701a Prius Guru

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    CO2 is only one type of emission. SMOG is another. Looking at just one type or just energy density doesn't tell the whole story. Then there's the reality that vehicles have different emission systems, some earn much cleaner ratings than others.

    In short, be careful drawing conclusions. The devil is very much in the details.

    For me personally, next year I'll be driving a PHV using electricity from natural-gas and fuel that's a 90/10 blend of gas/ethanol. Combined with the SULEV/PZEV emission rating, it's pretty much the best balance you'll currently find.
    .
     
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  4. SageBrush

    SageBrush Senior Member

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    Pollutants other than CO2 are quite a bit worse if the source is coal compared to petrol.

    To answer OP's question: If you are not producing clean energy to run the EV, it is a poorer choice than a Prius.
     
  5. cwerdna

    cwerdna Senior Member

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    Seems this has been discussed before, such as at http://priuschat.com/forums/environmental-discussion/87022-leaf-c02-versus-prius-c02.html.

    One can read about pollutants from auto emissions at http://www.epa.gov/greenvehicles/Aboutratings.do#aboutairpollution. Until recently, CO2 wasn't even considered as a pollutant by the EPA. As such, it (even now) doesn't count towards a car's air pollution score.

    Unfortunately, I put in a zip code of 47396 into http://www.epa.gov/cleanenergy/energy-and-you/how-clean.html found the OP's area gets 72.9% of its electricity from coal. The OP could get his electricity from clean sources such as via solar panels on his roof.
     
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  6. Corwyn

    Corwyn Energy Curmudgeon

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    Well cleaner than coal anyways.

    The standard offer for my local electric company claims 0.95 lbs per kWh. So for a Leaf that is 0.95 lbs per 3 miles, or 16 lbs per 50 miles versus 19 lbs per 50 miles for a Prius.
     
  7. Zythryn

    Zythryn Senior Member

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    Leaking oil can be quite messy, none of that with an EV.
    But your research does bring to light a big issue, as have many other threads on this topic. Crome a strictly environmental standing, how clean your car is depends on how clean your fuel source is.
    Luckily almost no one is using 100% coal. Unfortunately the national average is still around 55% as I recall.
    When you add things such as national security, national financial health, and simply a more pleasurable driving experience, EVs win hands down (IMHO).

    On the environmental front, we need to clean up our grid. EVs or only one of the reasons, and pretty far down the list ifyou ask me.
    Luckily, as the grid gets cleaned up, EVs will automatically do so as well.

    As a final note, don't forget how much energy is used to refine the oil into gasoline. If you are going to count the emissions from generating the electricity, you should do the same for gas generation to get an apples to apple comparision. If your oil comes in part, or majority, from the tar sands, that has a larger co2 footprint as well.
     
  8. Danny Hamilton

    Danny Hamilton Active Member

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    As has been pointed out already, not all electricity comes from coal. Also, as has already been pointed out, as "the grid" moves to cleaner electricity generation, all the electric vehicles move with it, without having to retro-fit or replace the vehicle. If cleaner energy is really important to you, you also have the option of generating some of your own.

    What hasn't yet been pointed out [this was being written while Zythryn was posting] is that you are comparing tail-pipe CO2 on the gasoline vehicle to processing plant CO2 for the electricity. There is CO2 released in the transportation of that gasoline to your local refueling station, in the processing of the crude into gasoline, in the transportation of the crude to the processing plants, and in the extraction of the crude from the ground. You haven't taken into consideration any of these.

    Of course, there is also CO2 released in the extraction, and transportation of coal as well, so now you need to figure out what the TOTAL ground-to-tailpipe gasoline vs. electric difference is in released CO2. You also need to find a fair way to choose which gasoline vehicle to compare to. Will it be an Insight, Prius, Mustang, Corvette, Escalade, or Hummer?

    Once you've done all that calculation, keep in mind that if the released CO2 ends up breaking even in an area of the country where 72.9% of electricity is coal generated, or even if it is only slightly worse than an equivalent gasoline vehicle, you still have the benefit of your purchase creating a demand that will encourage automobile manufacturers to manufacture more electric vehicles which will then be bought in areas of the country where a much smaller percentage of electricity comes from coal. The increased electric vehicle sales will increase visibility, publicity, and marketability of electric vehicles. So a break-even or even slight increase in CO2 released based on your current source of electricity can be part of a long term decrease in CO2 released overall countrywide.
     
  9. Corwyn

    Corwyn Energy Curmudgeon

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    It should also be noted that, done correctly EVs not only benefit from a cleaner grid, but also contribute to cleaning up the grid.
     
  10. hill

    hill High Fiber Member

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    Yep,
    Plus, one of the points that often gets lost is that when you have (for example) 72.9% coal fired electricity, appx 12kWh's of that electricity is used just to REFINE crude into each gallon of gasoline. So 1st you smoke out people with coal ... then you smoke 'em out with the car's exhaust ... and I'm not even talking about the carbon ... I'm talking all the other acknowledged toxins filtered through our lungs. Meanwhile, if you'd taken that 12kWh's worth of electricity used to refine a gallon of gas, and instead - put the 12kWh's worth of electricity into an EV's batteries, it would have gotten you down the road about 50 miles in an EV ... roughly the same distance as you go on a gallon in a prius ... except you'd have done it just a little closer to being smog free. BUT - if you'd have taken the kWh energy in the gallon of gas, and made THAT into electricity too ... your EV would go an ADDITIONAL 80 or 90 miles.
    :)
    So . . . how come no one talks about cleaning up the grid via hydro, solar, wind geothermal etc, so we can have less dirty electricity to make diesel, gas, road tar, solvents, etc. Not very romantic? Just something to think about
     
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  11. bisco

    bisco cookie crumbler

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    once again, we have a democratic regime who can't get anything significant done on the energy front. al gore redux. if the republicans get back in, you can kiss any thoughts of clean energy goodbye again. oil companies control everything in both parties.
     
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  12. daniel

    daniel Cat Lovers Against the Bomb

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    I think Hill said it best in his post above: The gallon of gasoline that moves your Prius 50 miles, required as much electricity to refine as the Leaf (or Tesla or Xebra) would use to travel the same distance.

    And as others have pointed out, most of us live where a smaller percentage of our electricity comes from coal. Where I live, all my electricity comes from hydro, except for a small part that comes from wind. You might be able to join a program whereby you pay slightly more for your electricity in order to get wind electricity instead, or, depending on your circumstances, you might be able to install PVs on the roof of your home. When you take the national grid as a unit, the CO2 numbers are much lower than coal.

    And finally, as others have mentioned, there are other considerations besides carbon when considering an EV: Other pollutants, balance of trade (oil mostly is imported, where all other energy sources are domestic), the oil-terrorism connection, the political leverage that oil exporting countries have over us with the threat of cutting off our supply, and finally the increasing international competition for a decreasing supply of oil.

    All of these should be taken into consideration, along with carbon footprint, when considering an EV compared with a gasoline car.
     
  13. bac

    bac Active Member

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    THIS!

    -Brad
     
  14. Analogkid1958

    Analogkid1958 Member

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    Thanks, John. I was trying very hard to not draw conclusions but rather just see where the math took me. I realized that there are many ways to slice the data - any of which could be used to make a particular argument.
     
  15. Analogkid1958

    Analogkid1958 Member

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    Thanks for the references! I didn't see that it had been discussed here before.

    Yes - we're heavy into coal here in the Midwest, sadly, though we seem to be growing a lot of wind farms, too. Solar power here in the Midwest is a marginal proposition at best. Paybacks are wayyyyy too long.

    I was trying to deal with the numbers on a "nationwide" "average" basis, realizing that local conditions could swing the decision one way or another.

    But maybe that's the point? Your local conditions and needs SHOULD drive the buying decision!

    I could technically also be carbon neutral just by buying certified carbon offsets. This would promot efficiency because the cost of the offset would be reduced in line with my reduction of consumption.
     
  16. Analogkid1958

    Analogkid1958 Member

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    Thanks, all for all the great feedback and information. I knew most of this intuitively, but you all confirmed it with your good data. By the way, you can read the blog post I was working on that inspired my question here:

    Pacing The Gilded Cage

    Enjoy. cheers!
     
  17. wjtracy

    wjtracy Senior Member

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    Your calcs are correct. I have calc'ed (see other threads - Coal power Volt vs. Gaso Prius) that you have to burn as much as 3-4x more coal than gasoline in a Volt EV mode. Of course, no one is using 100% coal, so my calc is worst case scenario. There is a Motor Trend article posted here with a state map that shows which states Leaf is cleaner than a Prius (based on elec fuel source). You are probably in a red state on that map. Note that Obama admin apparently just yesterday postponed a cleaner grid by deferring ozone regs.

    It is also confusing, since EPA assigns ~100 MPGe to the EV mode, incorrectly suggesting EV mode is energy efficient. The EPA MPGe calc is discussed in some detail on Wiki, but was intended to reflect near-zero gasoline use. The EPA MPGe calc was not intended to account for electricity energy use, which it most certainly does not.
     
  18. ItsNotAboutTheMoney

    ItsNotAboutTheMoney EditProfOptInfoCustomUser Title

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    Plus, the grid is getting cleaner as new power is mainly natural gas. When you're running an EV in 5 or 10 years time national mix will be less than 55%.

    Also, local relative efficiency depends significantly on climate and terrain and personal efficiency depends significantly on the nature of the miles driven.
     
  19. wjtracy

    wjtracy Senior Member

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  20. austingreen

    austingreen Senior Member

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    You are in one of the dirtiest places for EVs and for electricity in general. It would be good to replace the older coal plants with wind and natural gas.


    I would say other pollutants are a bigger problem locally in Indiana than carbon. Can you buy wind with green choice?
     
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