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How Green is the PIP? Where Do You Live?

Discussion in 'Toyota Prius Plug-in' started by bilofsky, Apr 15, 2012.

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  1. bilofsky

    bilofsky Privolting Member

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    An all-electric vehicle might produce 50% more greenhouse gases than a non-plug-in Prius, according to a study to be released tomorrow by the Union of Concerned Scientists. It depends on the mix of electric energy sources.

    A preview article in today's (April 15) New York Times reports that in Los Angeles a Nissan Leaf would emit the greenhouse gases of a 79 mpg gasoline car. In Denver, where electricity depends on coal generation, the Leaf is as dirty as a 33 mpg gas car.

    The map accompanying the article can tell you whether your PIP will be responsible for more greenhouse gases in EV or HV mode. Better figures might be available when the study is released tomorrow.
  2. richard schumacher

    richard schumacher shortbus driver

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    Thanks. This reminds us of the importance of switching one's household electricity supply to one not fueled by coal. Contact your utility about the available options. It would be silly to buy an electric only to create more CO2 pollution than one would get with a Prius costing thousands less.
  3. bilofsky

    bilofsky Privolting Member

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    Another important factor is the time of day that we charge. Does the utility generate cleaner power at night, when demand is low? Or is it running the cheapest plants, which might be coal, depending on market prices at the time?
  4. evfinder

    evfinder Member

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    The answer is that they run the plants that are hardest to restart if they shut them down. For example if you shut down a nuclear plant it can take you a month to get it restarted so you keep it running. A coal plant typically takes about 4 hours to restart so you keep it running. A gas plant only takes a short time to get back up and running so you shut it down, Hydro takes seconds to come back on line so you shut it down.

    Now, if demand is less than supply the overproduction goes to heating up the grid and causes the wires to sag. If you are in this situation and you have already shut down the plants that can be shut down then you typically bleed steam away from the turbines into the cooling towers to cut production.

    This leads to a very interesting situation if you are charging at night where you might be using energy that would otherwise be thrown away so although you are technically generating CO2 to charge the car the marginal CO2 generated is zero or close to zero since the coal would have been burned anyway.
  5. drinnovation

    drinnovation EREV for EVER!

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    The article ignores the issue that gasoline also have highly varying CO2 production costs. The rocky mountain gas comes mostly from Canadian Tar sands and the production is about 20% higher in GHG production.
    Much of the graph that shows high CO2 also gets their gas from higher CO2 sources. (Our gas is also cheaper.. gas by schools is $3.72 and a month ago it was only $3.25.. but with all the national press I guess they figured they could raise it.)

    More importantly, it ignores the fact that we can choose where to buy our energy. I pay extra for wind-power and its still way cheaper than gas. While at night coal plants tend to dominate in CO, there is a lot of wind, often being idled (i.e. the turn off the turbines) so by purchasing wind can keep them spinning and help the system get greener.
  6. drinnovation

    drinnovation EREV for EVER!

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    There are more costs than just CO2.. what about our national security and the lives of those serving in the military protecting oil interests.

    But yes we should switch.. and switching the house and car to renewables is a much greener choice.
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  7. GrumpyCabbie

    GrumpyCabbie Senior Member

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    So everywhere else in the world it is indicated that electric vehicles use much less fuel and produce significantly less emissions, even running on coal, than if petrol or diesel were used, yet in America with its big oil lobby it is said EV's pollute more? :rolleyes:

    Guys if you believe that then you're doomed to the sidelines of the 21st Century. Carry on with petrol into the next few decades and the rest of the World will laugh at you as we all used to laugh at China using steam engines right up until the year 2000.
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  8. giora

    giora Active Member

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    The study summarized in the article is trying to shade light on one aspect only - emissions of GHGs, and in this aspect - what is true for the US is true everywhere else.
    They are not dealing with (the very important) pailpipe polutants like NOx, particle matter, HC and so on.
  9. bilofsky

    bilofsky Privolting Member

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    Yes, we do have huge industrial lobbies, not to mention a Supreme Court that thinks companies are people (as in "Government of the people, by the people and for the people").

    But the Union of Concerned Scientists is quite a credible organization and I would suggest not disregarding them, even though they are American.
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  10. evfinder

    evfinder Member

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    The Union of Concerned Scientists has had a long history of support for hybrids over other technologies. Personally I want to see the report before passing judgement. I've heard people claim that an EV can run 30 miles on the electricity it takes to produce a gallon of gas. While I am very skeptiacal of that number here in California Oil refineries are the second largest user of electricity after the state's water system and I would like to be sure that their well to wheels calculations actually take that into account.

    Noel
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  11. bilofsky

    bilofsky Privolting Member

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    Here's the full report. I look forward to comments from those more knowledgeable than I.
    Edit: "The emissions [from electric sources] include those associated with building the power plant, extracting the fuel and transporting it to the plant, converting the fuel into electricity, and delivering the electricity to the point of use. For example, for electricity produced from coal the total emissions include those associated with mining the coal, delivering it to the power plant, and then burning it there. The small percentage of electricity consumed in the transmission from the coal-fired power plant to the point of use, about 5 to 7 percent, is also taken into account."​
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  12. Biking Maniac

    Biking Maniac Junior Member

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    Here in western Wisconsin buying all-renewable adds about ten percent to our electric bill, so my PIP costs 35 cents to charge, rather than 32. We charge at night, and keep the wind turbines spinning.
  13. TomE

    TomE Junior Member

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    Two words: solar panels.
  14. giora

    giora Active Member

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    And how the Prius PHV fits in?

    The following chart plots the Prius PHV with 30% EV (PIP30%) emissions as a function of the local grid GHG intensity, and as compared to the Leaf and to the 'EPA average Volt' (64% EV).
    The chart is based on the same EPA data as the UCS report.

    [​IMG]


    So, the Prius PHV 30% EV is greener than the Leaf in most regions of USA, Break-even point is around 560 gCO2(e)/kWh (regions that are about 10% cleaner that US average.

    If you drive a Prius PHV and your average EV miles is 30%, then you drive greener than the 'EPA average Volt' in almost all US regions, break-even point is regional grid with 300 gCO2(e)/kWh.

    Attached Files:

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  15. bilofsky

    bilofsky Privolting Member

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    I have solar panels, so it's tempting to feel good by thinking that I'm charging my PIP off clean energy. But feelings aside, these are logically two separate things. I could be green by having the panels without the car, or vice versa. And the charging mostly happens at night. My daytime solar generation mostly goes into the grid.

    (Admittedly, having the solar installation has made me feel less guilty about driving my previous low mpg car. But that just proves my point. I'm definitely not filling that car's gas tank off the solar electricity.)

    Now here is the most interesting point I took away from the whole study. I had not realized that in most regions nighttime electricity is dirtier than day. (See the chart and map on pages 13 and 14 of the report's appendix for the figures for your region.) For example, here in California, electricity between 7 and 10 at night is 22% cleaner than from midnight to 7 am.

    So should I charge in the evening? Drinnovation explains why not:


    This is also true of hydro plants. So charging in the early hours is something we can directly do with our PIPs to increase clean energy generation.

    (Some years ago, I met with PG&E staff to discuss electric rates and their impact on solar energy. An executive made an offhand comment about liking electric cars because they could use all that nighttime wind power. Now I see he wasn't kidding.)

    The report's conclusions are based on regional averages, and don't take time of day into account in considering emissions (but they do with cost). So the green advantage of EVs here in California - with one of the largest time of day variations in electric generation greenhouse emissions - is even greater than the report says.
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  16. Jeff N

    Jeff N Senior Member

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    I really like your graphs, but it would have been more useful to include an "EPA average PiP" (i think it's around 22-25% or something like that) rather than using an arbitrary 30% EV miles number (or at least use an equivalent arbitrary number for the Volt like 70%). It would also be useful to include a higher than average EV utilization entry for the Volt (85%?) to parallel the one you added for the PiP at 50%.
  17. wjtracy

    wjtracy Senior Member

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    This is similar to what I have been trying to say and it's even way less than 33 MPG fossil fuel equivs if you say winter EV getting say 2 mile per KWhr.

    I'll get back to my calcs after taxes but this report makes my point.
  18. wjtracy

    wjtracy Senior Member

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    Noel I am pleased you are skeptical...we have discussed elec use by refineries in ENVIRO and it is a relatively small number . In CA you have a heavier crude tar which does take a little more, but there has been enormous exaggeration by some activists such that Nissan stopped quoting the numbers apparently realizing they were bad numbers

    I know it is important to look at life cycle but too often today people use this as gimmick to say we cannot take numbers at face value. Sometimes face value works fine in fact probably the best place to start.
  19. giora

    giora Active Member

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    Thanks for appreciating my work.
    Agree that it would have been more useful to show 'EPA average PiP' line, however, to date there is no average utility factor for PiP announced by EPA (so it is not 22-25%). My estimate is that it will be (when announced) around 30% and that is why I based it on this utility factor. Of course, it may turn out that I am wrong... time will tell.
    Agree, should have included high utility factor Volt alongside with high utility factor PiP, OK next project.
  20. evfinder

    evfinder Member

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    After reviewing the report I found that there was no explanation I could find for how the CO2 numbers were derived for gasoline, they just appeared to have a single number with no attempt to break the number down by region. The number apparently had about 50% for the amount created by burning the gas tagged on to account for downstream emissions.

    They broke down the emissions from power plants by region but not the emissions from gasoline. The emisisons are not the same. For example California gets a good percentage of its oil from local sources where Colorado gets a good portion of its crude from Canadian oill shale deposits which are much dirtier to refine.

    I also don't know if they took into account things like the CO2 from burning of gasses at both wells and refineries. Here in California I see the refineries flaring gas on a fairly regular basis. Also, they appear to be totally focused on CO2 with nothing about unburned hydrocarbons. The Prius is pretty good at not putting unburned hydrocarbons into the atmospher but most cars are not.

    Noel
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