• Aug 24th 2010 at 2:57PM
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Ford Escape plug-in hybrid – Click above for high-res image gallery

One of the major benefits of plug-in vehicles is the ability to operate without any direct emissions while also diversifying the possible energy sources used for transportation. Unfortunately, that also means that unless you have your own solar or wind power installation, chances are you won't know where your power is coming from.

Unlike solar, wind and hydro power – all renewable and emissions-free – half of all electricity in the United States is generated by burning coal, with the next biggest share going to natural gas. With the fuel mix varying regionally, the net well-to-wheel emissions effect of plug-in vehicles will also differ. In some areas, overall emissions will go down significantly, in others they may actually get worse.

Researchers Michael Wang and Amgad Elgowainy from the Argonne National Lab have expanded the Greenhouse Gases, Regulated Emissions and Energy Use in Transportation (GREET) model to help the evaluate the overall environmental impact of deploying large numbers of plug-in vehicles. In addition to the fuel mix, the model will now be used to examine what happens if plug-in drivers charge their vehicles during the day instead of at night, as most advocates have assumed they will. Night-time charging could be largely accommodated with existing capacity, but extensive plug-in vehicle daytime charging might skew the mix toward even higher emissions. The variables are extensive and the only thing we know for sure at this point about the overall effect of plug-in vehicles is that we don't know all that much.



[Source: Physorg]


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    • 1 Second Ago
  • 15 Comments
      • 5 Years Ago
      All the more reason to phase out aging coal plants and replace them with nuclear power plants.
      • 5 Years Ago
      The GREET model is just a fancy spreadsheet that lets you plug in any numbers/assumptions you want. Last time we had a report like this, I went through and read the report and they listed NONE of the assumptions they used to reach their conclusions. Did they assume coal provided XX CO2 per BTU? Did they include the cost of mining it? For oil/gasoline, did they include the CO2 used from refining the oil into gasoline and the fact that they have to use between 3 and 5 kWh of electricity (depending on the refinery). Did they include the natural gas used to power equipment to drill and pump the oil out of the ground? The natural gas that is "burned off" at site in many cases?
      Did they count the energy used to support militaries to fight over the oil?

      Anyway, back to reality: I hope this one does list the limited assumptions they DID make or it is equally as useless as the last one we debated. Face it, without that data, we're all just picking our favorite and justifying it.

      You want to know the real answer? Ok:
      Oil is bad. Coal is bad. Natural Gas is a little better (unless you are fracking).
      Wind and Solar are expensive and have limitations.
      Nuclear is good/bad depending on what type of tree hugger you are.

      Are we willing to attribute all the cost to oil/coal/natural gas that is really there so we can get a balanced view of the real cost of each compared to renewables? Willing to admit to the military costs? The cleanup cost from their pollution?
        • 5 Years Ago
        Yes, I've looked at GREET and it's underspecified. FWIW this Argonne lab often uses it to prove how great Ethanol is.

        Make your own spreadsheet, put it on Google Docs, share it. And ABG should do some real journalism and interview these scientists and challenge them with your points.
        • 5 Years Ago
        Excellent post.
      Level4
      • 5 Years Ago
      pick your poison, no matter what new tech we develop...in till we clean up the power grid we going in circles..
      • 5 Years Ago
      You guys may not know much - but my friend Brian assured me that every inch of manufacturing of a modern lithium based EV was done under coal power from a plant built around 1800.
      He, based upon this knowledge, assured me that I could drive a hummer and have less environmental impact than an EV does.

      The hummer it seems is built by fairies who live on rainbows, happy thoughts, and cherry flavored candies found in the stool of unicorns.

      But seriously - by the time EVs have a massive impact the grid will have changed a bit I would think.
      Of course the problem is that the adoption rate will not be evenly spread out.
      So some communities will see much higher local adoption rates much earlier.

      I'm sure it will get sorted.
      Let's just hope they have not forgotten to task some engineers to work it out as well as the accountants they have toiling away trying to figure out the best way to rape us on charging prices for this new breed of car.
      • 5 Years Ago
      I thought it would take some time even at a decent adoption rate before the night time load from plug-in charging was anywhere near the amount available.

      When I look at the line of machinery going from the tank in the ground at the local station back to an oil well on another continent, I have a hard time believing power produced relatively locally could be any worse.

      Think about a tanker truck delivering gas to a gas station. Now, consider that this tanker truck is ALSO connected to the end of a chain of equipment going back to an oil well somewhere. Did the study take into account things like taking a tanker truck off of the road and all of that truck's attendant support structure? How far can a plug in travel on the electricity required to refine the fuel that fills the tank of a car? Or the electricity used by a gas pump to pump the 15-20 gallons that fills up the tank of a gas powered car? It seems to me electrical autos remove a LOT of these "middle steps" which themselves add emissions (and cost) to the price of that gallon of gas. Maybe I'm overlooking something, but electrical distribution looks dog simple and efficient compared to the way we get gas into the tank of an automobile.
        • 5 Years Ago
        Another Argonne summary http://www.transportation.anl.gov/pdfs/TA/419.pdf from the same Michael Wang says it takes 0.23 gallons of fossil fuel to make a gallon of gasoline. But I don't know if that includes the fossil fuel to make the electricity for all the other parts of the supply chain that you mention.

        "How far can a plug in travel on the electricity required to refine the fuel that fills the tank of a car?"
        If it's close to the 40 miles a car travels then that would really help to reduce this endless inconclusive debate, which means oil companies will never 'fess up about their electricity use to allow the calculation.
      • 5 Years Ago
      China is in the middle of a Shutdown-Startup phase of Coal Energy Production.
      - Shutting down old, inefficient plants.
      - Starting up new, much higher efficiency plants.

      Why is it the US is tied to Old Coal Plants. Where is the investment and efficiency that a "Free Market" is supposed to deliver?


      • 5 Years Ago
      "but extensive plug-in vehicle daytime charging might skew the mix toward even higher emissions."

      This is opposite of what the report says ...

      "However, the researchers also considered a different case - one in which many drivers chose to charge their batteries in the middle of the day. In this scenario, the additional electricity would likely originate in different power plants such as natural gas plants - which would result in less greenhouse gas emissions, ..."

      Not surprising given, night electricity comes from baseload generators like coal & nuclear, where as peak almost always comes from NG.
        • 5 Years Ago
        It is strange, isn't it? They also seem to say that charging your plug-in at night - which is what everyone is planning to do - will increase the amount of emissions.

        "... they assumed that PHEV owners would likely charge their vehicles overnight, when they won’t be driving and energy is cheapest. Under this paradigm, more and more fossil-based power plants are brought online to handle the additional demand represented by vehicle charging. For regions with a large share of coal-power generation, the electricity generated for recharging PHEVs could result in greenhouse gas emissions comparable to conventional gasoline-powered vehicles."

        So, it's up to the owner of the plug-in to learn how their local power is generated, and then plug in at the appropriate times:

        Lots of coal power = plug in during the day
        anywhere else = plug in at night
        • 5 Years Ago
        @Paul (somewhat off topic)

        Is it really only a 20% loss of energy to store energy via pumping water? If so, then why isn't pumped water storage used more extensively for wind power?
        • 5 Years Ago
        Excess energy generated at night either goes to waste or is stored via pumped water storage for use during the day. So if you charge during the day you are wasting nighttime generation and forcing natural gas peaker plants to fire up or you are using pumped water storage energy which wastes 20% of the excess energy generation.

        By charging during the day you are also forcing the utility to operate closer to their maximum capacity which on a large scale will either cause grid instability and/or force the utility to build additional peaker plants and transmission lines which will significantly increase electricity rates.

        I pay $5 extra per month for wind power, I know that the grid is powered by a mix of energy sources and not all of my power actually comes from wind, but the money I pay my utility is invested in new wind power projects.

        If we had a smart grid then perhaps utilities and EV owners could collaborate to use power more effectively, for instance your charger could have a priority setting: high(max charge now, full charge in 4 hours), medium(charge depending on available energy in the next 8 hours), low(charge depending on available energy within the next 12 hours). Then the utility could use energy forecasts and weather forecasts and send excess power to vehicles when the wind is blowing strongly and they could limit use of higher cost peaker plants.
        • 5 Years Ago
        The assumption should be that the baseload plants are running anyway. That's the whole point - that it costs so much, in energy and in time, to shut them down that there's no point in doing so. They are generally capable of producing far more power than they actually are called on to generate off-peak, and so are running inefficiently. Much like an ICE vehicle idling, in fact.

        This is likely to mean that the output of those plants could be increased slightly to cover EV charging at night - particularly as initial take-up of EVs will be low, due to low production volume if nothing else - and in doing so actually improve their efficiency. On the other hand if they're already running at peak output, then more of the daytime plants would have to be brought online to cover the demand - so you've lost nothing.

        The profile of how power is used over the day is part of the Meter Point Administration Number which identifies the customer's site to electricity suppliers in the UK. There are charts of the profiles at http://energylinx.co.uk/mpan.htm. 'Economy 7' is a special cheap night rate offered in some areas because the electricity generating companies want to encourage use of electricity outside peak demand hours, and reduce demand within peak.
        • 5 Years Ago
        Actually they are making your choice for you. Everyone is getting smart meters and rates are being varied by time of day. I guarantee you will not want to recharge your EV battery at the high rate. You will recharge at the cheap time of day. There are exceptions to stepped rates that need to be worked out for EV owners as well. For example, filling your electric tank now in LA during the day will quickly push your electricity charges into the "abuser" punishment rates and end up costing you more to recharge for daily use than keeping a tank filled with gasoline.
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