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  1. #1

    Plug-in hybrid: true comparison?

    Has anyone here ever tried (or read of someone trying) to compare the consumption of a traditional hybrid versus a plug-in hybrid or true electric car? In other words, that electricity is coming from somewhere, and what is the comparison between getting that power from your local utility versus burning a minimal amount of gas to do it. As a former mech eng I am famliar with the tradeoffs, etc....but a lot of work would go into such an analysis.

    Has anyone done it?

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  3. #2

    Plug-in hybrid: true comparison?

    Its been done a lot. See:



    http://www.pluginamerica.com/faq.shtml (emissions summary)

    Rough numbers to help you are:

    - Power plant efficiency 60 – 80% (combined cycle gas turbine)
    - Power-line transmission efficiency ~95%
    - Charging efficiency – 90 – 95%
    - Discharge/motor efficiency ~90 %

    Basically, the BEV or plug-in portion of the Plug-in Hybrid are around twice the efficiency of the gas-only hybrid.

  4. #3

    Plug-in hybrid: true comparison?

    I would like to see one from a source that is completely objective.

  5. #4

    Plug-in hybrid: true comparison?

    It's kind of hard to define anyone who is 'truly objective' since something has to motivate someone to do the research. I suggest that if you trust yourself, you need to do your own basic research into each of the steps in the energy chain from well to wheel.

    For the record, Plug-In-America is a non-profit organization composed of people who saw the light and have no financial interest in EV's (except that a lot have wasted a lot of $ buying the few RAV4EV's that exist on the market). EPRI is a government agency FWIW. Tesla Motors are a bunch of guys who have really put their own money where their mouths are to develop affordable, practical EV's.

    You might want to start with some of this analysis that you question and then try to follow up the footnotes and sources to confirm for yourself that the fundamental science is pretty close. Don't worry about too much precision since EV's are so more efficient and clean than their pure ICE counterparts that there is significant tolerance to inaccuracies.

    Happy number crunching.

  6. #5

    Plug-in hybrid: true comparison?

    I would like to see a more independent analysis also. Most power plants are not combined cycle plants, and only get about 35-40% efficiency.

    It is good to lower our dependence on liquid fuels, i.e., those coming from countries that don't like us, but the ecological and health costs of the mercury, sulphur dioxide and particulates coming out of coal plants need to be taken into account also. We don't want to minimize a problem in one area only to increase our costs in another years down the road.

    However, if we consumers just keep trying to buy the highest mpg vehicles we can, then we will do a lot to minimize all these factors.

  7. #6

    Plug-in hybrid: true comparison?

    Me too. Of course, it depends on how you define 'truly objective'. I doubt that anyone with nothing to gain from any outcome will go to the effort of doing the study. You should probably look at the footnotes in the sources provided and see the fundamental sources of the information are believable.
    But then again, you could probably say that I'm not 'truly objective' either since I've done sufficient research and talking with people to have made my mind up about the electric drivetrain being the most efficient/feasible one known today.

  8. #7

    Plug-in hybrid: true comparison?

    I think this comes close to answering the questions. Popular Mechanics did a comparison of fuel costs. Down load the chart from the link at the bottom of this page:
    Plug in electric appears to be about 1/3 the cost of using gasoline for fuel. Most other fuels other than natural gas cost more than gasoline.

  9. #8

    Plug-in hybrid: true comparison?

    I have solar electric panels (about 8KV system) on the roof of my house and generate most of my electric needs. Thus, if I added a few more panels and had a plug in hybrid rather than my hybrid Ford Escape, my hypothetical plug in hybrid would probably be fueled in a significantly more efficient manner than the gas hybrid.

  10. #9

    Plug-in hybrid: true comparison?

    It would take a major investment in solar panels and a low-latitude sunny climate to charge up a plug-in vehicle every night. Current Li-Ion based plug-in designs need a lot of energy to recharge.

  11. #10

    Plug-in hybrid: true comparison?

    Actually Li-ion batteries don't take any more energy to do a day's drive than any other battery type (maybe less since they are lighter).
    For a typical 30 mile day, a Tesla, that can go 250 miles on 50 kWh would consume 50k/250=0.2 kW per mile driven so it would need 30*0.2=6 kWh per day. Assuming 6 hours of sunlight per day, it would take a 1 kW solar array to meet your daily driving needs. This isn't particularly tough except maybe for Helsinki or Fairbanks in December - but it would average out in June.

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